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University Microfilms International 300 N. ZEEB ROAD, ANN ARBOR, Ml 48106 18 BEDFORD ROW, LONDON WC1R 4EJ, ENGLAND 8015904
Mast , V erno n Amos
DISTRIBUTION AND ENGINEERING PROPERTIES OF LANDSLIDE SUSCEPTIBLE SOILS IN SOUTHEAST OHIO
The Ohio State University Ph.D . 1980
University Microfilms
International300 N. Zeeb Road, Ann Arbor, MI 48106 18 Bedford Row, London WC1R 4EJ, England PLEASE NOTE: In all cases this material has been filmed in the best possible way from the available copy. Problems encountered with this document have been identified here with a check mark v' .
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Intematicml
300 N Z=== RD.. ANN ARBOR Ml .18106 '3131 761-4700 DISTRIBUTION AND ENGINEERING PROPERTIES OF LANDSLIDE SUSCEPTIBLE SOILS IN SOUTHEAST OHIO
DISSERTATION
Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University
by
Vernon A. Mast, B.S., M.S.
*******
The Ohio State University
1980
Reading Committees Approved by
C.A. Moore W.E. Wolfe O.W. Mintzer Advisor, H.D. Colson Department of Civil J.M. Bigham Engineering ACKNOWLEDGMENTS
The author wishes to express his gratitude to Professor Charles A. Moore for the initial invitation to study under his leadership and his subsequent guidance and encouragement throughout the course of this work. The arrangement of financial help and the sub sequent suggestions for the field mapping phase of the investigation by Professor Olin W. Mintzer are appreciated. Gratitude is extended to Professor Jerry M. Bigham for his assistance in the X-ray diffraction analysis portion of the study. Special gratitude to Karen S. Miller for her patience, understanding, encouragement, and aid in accomplishing this work. For all this assistance, the writer wishes to express his most sincere appreciation. VITA
February 25. 1938...... Born, Coatesville, Pennsylvania 1956...... Diploma Lancaster High School Lancaster, Pennsylvania
1963...... B.S., Natural Science E. M. College Harrisonburg, Virginia I963-I966...... Tehcher Montevideo High School Penn Laird, Virginia 1966-I96 7 ...... M.S., Chemistry University of Pennsylvania Philadelphia, Pennsylvania 1967-1969 ...... Instructor Blue Ridge Community College Weyers Cave, Virginia 1969 (summer}...... Certificate, Applied Ecology Oak Ridge Associated Universities Oak Ridge, Tennessee 1970 (summer)...... Certificate, Soil Mechanics Northwestern University Evanston, Illinois 1971 (summer) ...... Certificate, Polymer Science University of Akron Akron, Ohio 1970-1973 ...... Assistant Professor Blue Ridge Community College Weyers Cave, Virginia 1973 (evenings)...... Visiting Instructor University of Virginia Charlottesville, Virginia VITA (continued)
1973-1975...... Graduate Research Associate Department of Civil Engineering The Ohio State University Columbus, Ohio
1975-1978...... Civil Engineer U.S. Department of the Interior Geological Survey Reston, Virginia (in residence at The Ohio State University)
1978-1979...... University Dissertation Year Fellow Department of Civil Engineering The Ohio State University Columbus, Ohio TABLE OP CONTENTS Page
• • ACKNOWLEDGMENTS...... 11 VITA ...... iii LIST OF TABLES...... viii
LIST OF FIGURES...... xi INTRODUCTION...... 1 CHAPTER I. GEOLOGICAL ASPECTS...... 3 1.1 Overview of Ohio Geology...... 3 1.2 Geology of Southeast Ohio ...... 8 1.3 Landslide Susceptible Geologic Formations in Southeast Ohio...... 12
1.3-1 The Cuyahoga-Logan formation 1.3*2 The Allegheny-Pottsville formation 1.3*3 The Conemaugh formation 1.3.^ The Monongahela formation I.** The Study Area...... 28 II. THE MAPPING OF LANDSLIDE SUSCEPTIBLE TERRAIN ...... 33 2.1 United States Geological Survey Specifications ...... 33 2.1.1 Requirements of the position. 2.2 Data Acquisition Methods...... 36 2.2.1 Airphoto interpretation of landslide susceptible terrain
v TABLE OF CONTENTS (continued) Page
2.2.2 Classification of landslide types 2.2.3 Acquisition of ground truth 2.3 Results of the Mapping...... 58 2.4 Relationship of Landslide Density and Type to Geology...... 59 III. SOIL SAMPLING...... 64 3.1 Selection Processes for Soil Field Sampling...... 64
3.2 Sampling...... 66 3.2.1 Sampling site locations 3.2.2 Site descriptions 3.2.3 Soil sample descriptions IV. LABORATORY TESTING...... 80 4.1 Rationale for Types of Tests Chosen...... 80 4.2 Atterberg Consistency Limit Tests... 86 4.2.1 Liquid limit test 4.2.2 Plastic limit test 4.2.3 Plastic index 4.2.4 Flow index 4.2.5 Toughness index 4.2.6 Liquidity index 4.2.7 Unified Classification 4.2.8 Dry strength, dilatancy, and toughness tests 4.2.9 Discussion 4.3 Mechanical Analysis...... 113 4.4 Shear Strength Tests...... 118 4.4.1 Ultimate shear strength 4.4.2 Sensitivity 4.4.3 Angle'of internal friction and cohesion intercept
vi TABLE OF CONTENTS (continued) Page
4.5 X-ray Diffraction Tests...... 146 V. RELATIONSHIP BETWEEN TEST DATA AND GEOLOGY 157 5.1 Clay Mineralogy...... 157 o 5.1.1 Illite (10A) peak predomination 5-1.2 Vermiculite dominant (14a) peak 5.1.3 Vermiculite/smectite dominant (14a) peak q q 5.1.4 Broad band between 10A and 14a ang long-spacing between 24a and 28A o 5.1.5 Smectite (17£) peak 5.1.6 Kaolinite (7A) peak 5.1.7 Summary 5.2 Atterberg Consistency Limits...... 177 5.3 Mechanical Analysis...... 183 5.4 Shear Strength...... 184
VI. SUMMARY AND CONCLUSIONS...... 189 BIBLIOGRAPHY...... 206
vii LIST OF TABLES
TABLE P a g e
1.1 List of counties in southeast Ohio...... 9 1.2 Soils formed from glacial deposits in the Allegheny Plateau...... 18
1.3 List of 7i minute quadrangles within the Columbus 15 minute topographic map within the study area...... 30 1.4 List of minute quadrangles within the Huntington 15 minute topographic map within the study area...... 31 2.1 Advantages and limitations of aerial photography as a tool in landslide investigations...... 40
2.2 List of the pattern elements and their description...... 41
2.3 Key to landforms and their susceptibility to landslides in southeast Ohio...... 42 2.4 Indicators of landslide susceptible terrain on 1/64,000 scale photography...... 45 2.5 Classification of landslides...... 46 2.6 USGS landslide mapping designations...... 48 2.7 Landslide classification scheme...... 49
3-1 Topographic listing of the sampling sites in the Cuyahoga-Logan area...... 70 3.2 Topographic listing of the sampling sites in the Conemaugh(Allegheny-Pottsville) area.... 71
3.3 A comparison of terrain conditions from which the soil samples were obtained...... 74
viii LIST OF TABLES (continued) Page
TABLE 3.4 A comparison of general landslide types from which the soil samples were obtained.. 7^ 3-5 Munsell color vs. geologic formation...... 77 3.6 General plasticity characteristics of the soil samples within the geologic formation area...... 79 4.1 Atterberg limit tests results...... 89 4.2 Normalization of w-, values from Table 4.1 in intervals of 5 *0$ ...... 92 4.3 Normalization of wp values from Table 4.1 in intervals of 2 .3$ ...... 95
4.4 Normalization of Ip values from Table 4.1 in intervals of 2.5$...... 97 4.5 Plastic Index Soil Classification...... 97 4.6 Normalization of If values from Table 4.1 in intervals of 1 .5$ ...... 100 4.7 Normalization of If values from Table 4.1 in intervals of 0.15 ...... 1°3 4.8 Normalization if Ij, values from Table 4.1 in intervals of 0 . 4 ...... 105 4.9 Summary of the Unified Classification 110 4.10 Summary of observed plasticity character istics...... 112 4.11 ASTM grain size designations...... 114 4.12 Grain size distribution in 5*0$ intervals.. 117 4.13 USDA textural triangle name designation.... 119 4.14 Summary of the USDA classification...... 120 4.15 Direct shear test specifications...... 122 4.16 Ultimate shear strength test data for ov = 6.83 psi...... 126 ix LIST OF TABLES (continued)
TABLE Page 4.17 Ultimate shear strength test data for
' 4.18 List of occurrences of r values from Tables 4.16 and 4.17 in intervals of 1.0 psi 132 4.19 Normalization of S-t values from Tables 4.16 and 4.17 in intervals of 0.25...... 13© 4.20 0 and c test data...... 138 4.21 Normalization of
x LIST OF FIGURES
FIGURE Page 1.1.1 Outcropping geologic systems in Ohio...... ^ 1.1.2 Surficial glacial deposits in Ohio...... 5 1.1.3 Landslide severity of the United States.... 7 1.2.1 Geographic position of the counties in southeast Ohio...... 10 1.3*1 The Cuyahoga-Logan geologic formation 13 1.3*2 Outcrop belt of the Cuyahoga-Logan formation in Ohio...... 15 1.3*3 Thick outcrop of thinly bedded Cuyahoga shale just west of Bourneville, Ohio. 16 1.3*^ Logan formation just east of Chillicothe, Ohio showing interbedded shale and sandstone...... 16 1.3*5 Teays drainage system in Ohio...... 19 1.3*6 Material identified as apparent Minford silts along SR 50 east of Chillicothe, Ohio...... 20 1.3*7 The Allegheny-Pottsville geologic formation...... 21 1.3*8 Massive Allegheny-Pottsville sandstone out crop along the Ohio River beside SR 5 3 ..... 22 1.3*9 The Conemaugh geologic formation...... 2k 1.3*10 Scene showing break in slope with.sliding materials below in the Conemaugh formation north of Athens, Ohio...... 26 1.3*11 The Monongahela geologic formation...... 27 1.^.1 The study area showing the approximate positions of the geologic formations...... 29
xi LIST OF FIGURES (continued)
FIGURE Page
1.^.2 The ?i minute topographic quadrangles as they are positioned within the study area. 32 2.2.1 Flow diagram showing the method of data acquisition for each 7i* topo...... 37 2.2.2 Earth slump...... 50 2.2.3 Earth flow ...... 50 2.2.k Semi-active slide...... 51 2.2.5 Rock fall...... 52 2.2.6 Rock slide...... 52
2.2.7 Hummocky hillside...... 53 2.2.8 Creep...... 5^ 2.3.1 A "Landslide and Disturbed Ground Map".... 60 2.^.1 A landslide susceptible terrain density map of the study area...... 61 3.1.1 Landslide susceptible terrain density map showing the field soil sampling route..... 65 3.2.1 Scene showing the isolation of a soil sample pedestol...... 6? 3.2.2 The selection of a sampling site within that portion of a slump where exposed soil is evident...... 68 3.2.3 Hummocky terrain with creep extending into the roadside ditch...... 68 ^.1.1 Outline of the laboratory procedure...... 81 k.2.1 Histogram of probabilities for liquid limit data of Table ^.2...... 93 k.2.2 Kolmogorov-Smirnov test for normality for the data of Figure ^.2.1...... 93 LIST OF FIGURES (continued)
FIGURE Page 4.2.3 Histogram of probabilities for plastic limit data of Table 4.3...... 96 4.2.4 Kolmogorov-Smirnov test for normality for the data of Figure 4.2.3...... 96 4.2.5 Histogram of probabilities for plastic index data of Table 4.4...... 99 4.2.6 Kolmogorov-Smirnov test for normality for the data of Figure 4.2.5...... 99 4.2.7 Histogram of probabilities for:flow index data of Table 4.6...... 101 4.2.8 Kolmogorov-Smirnov test for normality for the data of Figure 4.2.7...... 101 4.2.9 Histogram of probabilities for toughness index data of Table 4.7...... 1°4 4.2.10 Kolmogorov-Smirov test for normality for the data of-Figure 4.2.9...... 104 4.2.11 Histogram of probabilities for liquidity index data of Table 4.8...... 107 4.2.12 Kolmogorov-Smirov test for normality for the data of Figure 4.2.11...... 107 4.2.13 Plastic index vs. liquid limit cumulative test results...... 108 4.3*1 Mechanical analysis laboratory procedure.. 115 4.4.1 Normalized histogram of undisturbed shear strength values where a = 6.83 psi 133 t » 4.4.2 Normalized histogram of undisturbed shear strength values where ay = 4.63 psi 133 4.4.3 Normalized histogram of remolded shear strength values where a = 6.83 psi 134 4.4.4 Normalized histogram of remolded shear strength values where ay = 4.63 psi 134
xiii LIST OF FIGURES (continued)
FIGURE Page 4.4.5 Normalized histogram of sensitivity values...... 143 4.4.6 Kolmogorov-Smirov test for normality for the data of Figure 4.4.5...... 1^3 4.4.7 Normalized histogram of undisturbed angle of internal friction values...... 144 4.4.8 Kolmogorov-Smirov test for normality for the data of Figure 4.4.7...... 144 4.4.9 Normalized histogram of remolded angle of internal friction values...... 145 4.4.10 Kolmogorov-Smirov test for normality for the data of Figure 4.4.9...... 145 o 5.1.1 Illite (10A) peak predominance with no/trace o 14a peak...... 161 o 5.1.2 Illite (10A)Qpeak predominance with increased 14A peak...... 162 o o 5*1.3 Illite (10A) peak and 14a peak as in Fig ure 5 .1.2 but with increased interstra tification range intensity...... 163 o o 5.1.4 Similar 10A and 14a peak areas with vermi- culite-illite interstratification...... 164 o 5.1.5 Vermiculite dominant (l4A)peak...... 167 o 5*1.6 Vermiculate/smectite dominant (14a ) peak.. 168 0 o 5.1.7 Broad 10A and 14A peak area with long-spacing from 24A to 28A...... 170 o 5.1.8 Smectite (14A) dominating peak...... 173 0 5.1.9 Kaolinite (7A) dominant peak...... 175 5.2.1 Histogram of the plastic limit data as related to geology...... 179
xiv LIST OF FIGURES (continued)
FIGURE Page 5.2.2 Histogram of the liquid limit data as related to geology...... 179
5.2.3 Histogram of the plastic index data as related to geology...... 180 5.2.4 Histogram of the liquidity index data as related to geology...... 180 5.2.5 Histogram of the flow index data as related to geology...... 181 5.2.6 Histogram of the toughness index data as related to geology...... 181 5*4.1 Histogram of the undisturbed angle of internal friction values as related to geology...... 186 5.4.2 Histogram of the remolded angle of internal friction values as related to geology 186
5.4.3 Histogram of the undisturbed cohesion values as related to geology...... 187 5-4.4 Histogram of the remolded cohesion values as related to geology...... 187
xv INTRODUCTION
The prediction of landslide susceptibility on a - -
regional basis defines those areas where special engineering attention or landuse control is most needed. The cost of landslide repairs to highway departments, railroads, and dwellings on a national level is well documented. Chassie (1976) reports on a Federal Highway Administration Survey which shows the U.S. spending $50 million annually to repair "major" landslides on the Federal-aid highway system. He estimates the total annual cost for all land slides to exceed $100 million. The prime reason for this expenditure is that "...little or no investigation is made prior to construction. Many potential slide areas could have been located with minimal observation and appropriate design measures taken." In Ohio, it is estimated that about $1 million is spent annually in landslide related repairs on the State Highway System (Fisher, 1968). A 1976 survey of county highway engineers (written communication) within the study area shows that a significant amount of their annual budget is spent on landslide repair. To this would be added the costs incurred by the interstate and township road systems, and the losses to private and commercial
1 owners of land and buildings. In recent years, several large slides in southeast Ohio have caused considerable damage to highways and property. These include the Dexter City slide along 1-77, "the Portsmouth slide along SR 23, and the slide affecting the Montecello Village Apartment complex. Property damage ranges from very serious in relatively few cases to minor in very frequent cases, such as slumping at the edge of a lawn or highway shoulder. Since many land slides are caused by man's modification of sensitive slopes, he can also control or prevent them, actively by engineering or passively by judicious engineering landuse planning. The taking of preventive measures by site planners of engineering projects will be the most economical in the end. A study area was chosen in southeast Ohio passing through three different geologic formations and the landslide susceptible terrain was mapped topographically. Soil samples were then taken from selected landslides or unstable slopes and laboratory tests were performed. The results were analyzed and compared with an emphasis on noting the differences in soil properties as related to geologic area. The purpose was to identify similarities and differences in soil properties inherent to the land slide susceptible soils within the study area. CHAPTER I GEOLOGICAL ASPECTS
1.1 Overview of Ohio Geology Between the Appalachian region on the east and the Rocky Mountains on the west, the entire central portion of the United States is plain or plateau. This wide section of country is underlain by stratified formations lying almost horizontally, dipping slightly to the east until near the Appalachian Mountain region where the strata exhibits a more pronounced dip. In Ohio, this begins to occur in the middle portion of the state and progressively younger geologic systems are encountered as one proceeds eastward (Figure 1.1.1). Several glaciations have passed through the region and in Ohio the Kansan, Illinoian, and most recently the Wisconsin stages have affected the topography. Kansan and Illinoian surficial glacial deposits are in evidence only in the south-southwest part of Ohio, whereas the Wisconsin glacial retreat left behind a till plain that covers about 2/3 of Ohio (Figure 1.1.2). Bounding this glacial region along Ohio's eastern side are the Appalachian Plateaus, a somewhat elevated area which forms a belt extending from north to south for iTiTT7i1TfiWTiTWi^^^^a^ W lijiiililljlMillilii i i ^ ! T i S PRECAMBRIAN
LEGEND
•Permian Age sa» Pennsylvanian Age Devonian Age SSS& Mississippian Age Silurian Age e u d Ordovician Age Figure 1.1.1.--Outcropping geologic systems in Ohio (adap ted from •;Geologic Map and.Cross Section of Ohio , Ohio Div. of Geological Survey). 5
LEGEND Wisconsin age fvr'ffi Illinoian age H M I Kansan age □ Unglaciated
Figure 1.1.2.--Surficial glacial deposits in Ohio (adapted from J. A. Brownocker, "Geologic Map of Ohio"). " 6 almost the entire width of the country. The unglaciated Allegheny Plateau is a division of the Appalachian Plateau and covers much of western Pennsylvania, West Virginia, eastern Ohio, and eastern Kentucky. The western edge of the Allegheny Plateau in eastern Ohio is about 1100 to 1200 feet above sea level and has a local relief usually not greater than about 400 feet. The Allegheny Plateau escarpment is underlain by horizontally bedded sedimentary rock with a very gentle synclinal structure of both marine and fresh water origin. The bedrock is composed of alternating layers of sandstone, shale, limestone, and coal along with clay and claystone. The beds dip to the southeast at about 30 feet per mile and strike northeast-southwest.
All of the Ohio uplands have a rough topography with almost no level land. Hillsides are gently sloped in zones of soft, easily eroded clays, and steeply sloped in zones of more resistant material, giving a benched or stepped appearance to many hillsides. The rough, deeply dissected terrain has developed by weathering, erosion, and frequent landsliding. Baker (1961) has identified this region of Ohio as having a landslide problem of major severity (Figure 1.1.3), and the area was the focus of this investigation. iff! n
MAJOR SEVERITY
/. MEOLM SEVERITY
BLANK AREAS LANDSLIDE PROBLEM NO N -EX ISTEN T
Figure 1.1.3 .--Landslide severity of the United States. The area in question is marked with an * . (from R. F. Baker, "Regional Concept of Landslide p. 3.) 1.2 Geology of Southeast Ohio The area under consideration is that part of the Allegheny Plateau from its western boundary east along the Ohio River and extending north to about Zanesville. The minimum and maximum elevations in the western sector are about 700 feet and 1200 feet, respectively; whereas in the eastern sector they are about 650 feet and 1000 feet above sea level. The area includes all or parts of the Ohio counties listed in Table 1.1 and shown in Figure 1.2.1.
In this area the Allegheny Plateau is drained by the tributaries of the Ohio River drainage system. Within these tributaries can be found flood plains, filled valleys and terraces. Glacial materials, lacustrine and loess deposits can be found along the western boundary along with gravelly and sandy outwash in some valleys. Illinoian age materials are found in the Scioto River valley and here is also found the Teays buried river system from the pre-Kansan glacial era. The sedimentary process that formed the alternating layering bedrock system was varied and the classification scheme based upon age and stratigraphy was given in Figure 1.1.1. In the western sector is found the Mississippian age system with its outcropping Cuyahoga and Logan formations of marine origin. The Cuyahoga formation is composed of thick shales which undergo a 9
TABLE 1.1 LIST OF COUNTIES IN STUD*.AREA
Fairfield Vinton Pickaway Meigs Muskingum Ross Guernsey Belmont Noble Pike Morgan Scioto Perry Jackson Washington Gallia Athens Lawrence Hocking Adams 10
GLACIAL BOUNDARY
MUSKINGUM RIVER
HOCKING RIVER
SCIOTO .MUSKING- GUERNSEY BELMONT RIVER V UM
PERRY NOBLE MONROE
HOCKING ROSS VINTON ATHENS
PIKE JACK MEIGS SON
SCIOTO GALLIA, ADAMS
IWRENCEl OHIO RIVER
Figure 1.2.1.--Geographic position of the counties in southeast Ohio. 11 facies change to sandstone. The overlying Logan formation is composed of interbedded shales, sandstones, and lime stone. Moving eastward the next youngest system is of Pennsylvanian coal bearing age with its outcropping Allegheny and Pottsville formations. These are charac terized by thick massive sandstones with successions of coal, clay, shale, sandstone, and limestone. The Cone- maugh formation is also of Pennsylvanian age and overlies the Allegheny-Pottsville formation. This formation is composed of bedded marine shale, coal, sandstone, and limestone in the lower part of the formation whereas the upper part contains only non-marine strata, including abundant red calcareous claystones. The Monongahela formation is the youngest of the Pennsylvanian system and is of fresh water origin. Its depositional sequence is similar to the Conemaugh and also includes the presence of red shales. The Permian system is found along eastern Ohio and has a fresh water origin. In Ohio, it is composed primarily of thin sandstone and shales, with some limestone and coal. Within these different formations the strata of shale, claystone, and clay are of varying thickness and composition. In some cases, fluvial, glacial, aeolian, or lacustrine materials have been deposited upon them. Some of these formations are more susceptible to landslid-
ing than others and the identification of these materials 12 is important in the identification of landslide suscepti ble terrain.
1.3 Landslide Susceptible Geologic Formations in Southeast Ohio The description of each formation will focus on that stratigraphy which might be expected to be landslide susceptible or to be the parent material for the formation of landslide susceptible soils. The formations are listed in order of decreasing age (west to east) across the Allegheny Plateau, with each succeeding formation over- lying the preceeding. The stratigraphic profile is included in each case.
1.3.1 The Cu.yahoga-Logan formation This formation, shown in Figure 1.3.1, extends from the central part of Licking County south to the Ohio River. Its length is about 100 miles and its width about 45 miles, it is of marine origin of Mississippian age.
The Cuyahoga section may be made up largely of shales in one area, but of sandstones or conglomerates in adjacent areas. The Black Hand sandstone facies is at times indistinguishable where the Cuyahoga exists as sandstone. These massive sandstones are present in the Hocking Valley and can be several hundred feet thick. Slope instability is seldom a problem, The Fairfield Rushvllle Claystone
Vinton Sandstone, Siltstone and Shale t-\V'C-vr\
Allensvillo Sandstone
Byer Sandstone and Siltstone
Berne Conglomerate and Pebbly Sandstone
Black Hand Sandstone and Cuyahoga Facies
Figure 1.3.1.-- The Cuyahoga-Logan formation (from G. Johnson, Stratigraphic Column of the Mississippian System of Ohio) 14- County Engineer reported that they have not had a land slide related project on their highway system for the past thirty years(written communication, 1976). The sandstones are again predominant along the Ohio River near Vanceburg and these form a belt extending northward with an increase in shale content in that direction. These sandstone areas are shown as the stippled portion in Figure 1.3*2. Thick beds of Cuyahoga shales are found along the Scioto River valley (Figure 1.3*3) and outcrop south to the Ohio River. Landslides have been reported in these shales just north of Portsmouth (Wu, 1977). East of the Scioto River, the shales are overlain by the Logan section which is composed primarily of interbedded sand stone and shale (Figure 1 .3 .4-). The presence of numerous thin sandstone layers will result in a more landslide resistant slope. The Logan formation outcrops in an area shown to the east of the dashed line in Figure 1 . 3 . 2. From Figure 1.2.1 it is noted that glaciation has infringed upon the outer limits of the Allegheny Plateau, especially in Ross County. This has been verified by Soil Survey of Ross County (1967) and more recently by Quinn (1974-). This Illinoian glaciation covered all but the southeastern part of the county. At its most southerly extension, the glacier had sufficient thrust Figure 1.3.2.--Outcrop belt of the Cuyahoga-Logan forma tion in Ohio (that area within the diagonal lines). The dashed line represents the probable boundary of the Logan and Cuyahoga sections with the dotted line representing the maximum probable exposure of the Logan to the west. The stippled area is sandstone, (from Jesse E. Hyde, "Missis sippian Formations of Central and Southern Ohio", p. *0 Figure 1.3*3*--Thick outcrop of thinly tedded Cuyahoga shale just west of Bourneville, Ohio.
Figure 1.3*^.--Logan formation just east of Chillicothe, Ohio, showing intertedded shale and sandstone. 17 to override about half of the area of the higher Allegheny
Plateau in Ross County. The Wisconsin age glacial depos its are also found but are confined to the lower elevations in the form of sandy outwash in terraces, and lacustrine deposits in the valleys. Table 1.2 lists those soils identified by the Soil Conservation Service (1967) as being formed from glacial deposits in the Allegheny Plateau. Of the seven associations listed, five consist of soils that developed in glacial material of Wisconsin age. These soils are on uplands, flood plains, outwash terraces, and in basins of former lakes. The other two associations are made up of soils that developed in glacial deposits of Illinoian age. Those fine-grained soil associations which are found on steep, poorly drained slopes are subject to mass wasting and are identified by the Soil Conservation Service as being severely eroded. The buried Teays River valley system (Figure 1.3*5) exists within most of the Scioto River valley from Chillicothe to Portsmouth. An ancient glaciation from the north blocked its northern passageway resulting in a lake being formed and lacustrine deposits being laid down. These so-called Minford silts (Stout, 1931) are layered gray and tan in appearance (Figure I.3 .6 ) and have been associated with landsliding in cut and fill embankments in the Scioto River Valley (Rogers, 1929; Webb, 1967). 18
TABLE 1.2
SOILS FORMED FROM GLACIAL DEPOSITS IN THE ALLEGHENY PLATEAU
Soil Association Description
Parke-Rainsboro-Negley-Pike Deep soils on glacial ter races of Illinoian age. Cana-Rossmoyne-Latham Soils of uplands in the Illinoian glacial area. Miami-Celina Deep, gently sloping to steep, well drained and moderately well drained soils on uplands developed in calcareous glacial till of Wisconsin age. Genesee-Fox Nearly level to steep soils on flood plains and outwash terraces of Wisconsin age. Cana-Miami Deep soils in the Wisconsin glacial area of the uplands, underlain hy material weather ed from acid shale. Alexandria-Fox Soils of uplands in the Wisconsin glacial area in Paint Valley. Bartle-Pekin-Markland Soils on glacial lacustrine terraces of Wisconsin age*
(from Soil Survey of Ross County, Ohio, Soil Conservation Service, 1967 ) 19
Qlaolal Limit
50
Seal* in Mllaa
Figure 1.3»5*--Teays drainage system in Ohio (from D. K. Webb, "Geological Aspects of a Recent Landslide in Vinton County, Ohio", p. 66). 20
Figure 1.3*6.--Material identified as apparent Minford Silts along SR 35*
Within the Cuyahoga-Logan formation geographic region, those specific materials especially subject to mass wasting are* 1. The Cuyahoga shales; 2. Glacial age materials deposited on uplands; and 3* Glacial age lacustrine materials deposited on lowlands.
1.3*2 The Allegheny-Pottsville formation This formation, shown in Figure 1.3*7, was deposited during the Pennsylvanian period when the area of deposi tion was in shallow brackish or fresh water conditions Figure 1.3*7.--TheFigure
POTTSVILLE ALLEGHENY f the Pennsylvanian System ofOhio").System Pennsylvanian fthe "Stratigraphic Jphnspn,Column 0.from G. he Allegheny-Pottsville geologicformation he Allegheny-Pottsville JWFFTTi v' I Jv 't ' W W WTv i? V andusen S a n d s to n e a n d S h ale ale h S d n a e n to s d n a S andusen V oal C andusen V ng Sandstone e n o t s d n a S g in s s e n e u q o n n o C oal C rd fo ed B toy oal C nthony A onest t hale S d n a e n sto d n a S ta s e n io T own Sandstone e le a h S d n a e n o t s oal d C n a S rry e b n le k w c u to H r e 2 k No. a u al o Q C n w rto e k a u Q al o C un R ear B b 3 No. oal C sta e n io T B rookville C oal No. 4 No. oal C rookville B dl Mecr N. 3 No. le a h S l d a n o a C e n ercer M to s d n a iddle S M ercer M pper U o r re Sandst and Shale a h S d n a e n to s d n a S ercer M er Low al o C idge R t lin F 3 No. oal C ercer M r e p p U ale h S and e n sto d n a S aron Sandsone a e le a h S d an e n sto d n a S n rio la C L ow er M ercer C o al No. 3 No. al o C ercer M er ow L oal C n a oal g C O rs te in W bow er K lttanning C oal No. 6 6 No. oal C lttanning K er bow oe Kltnig ndsone nd Shale a h S d an e n sto d an S lttanning K Lower aron Col o 4a 4 No. oal C oal C n rio la 8 C s ra g b ru c S oal C rence aw L tabr Coal Strasburg prKltnigCoal C lttanning K pper U ideKtann a Na66 a N oal C Klttanning Middle prKltn gSa t n ale h S and e n sto d an S ng lttanm K pper U oe Fra t oal C rt o reap F Lower oal C olivar B o rFr tSandsone n ale h S and e n sto d n a S rt o p a re F er Low le a h S and andstone S rt o p a re F pper U 7 a N oal C rt o p e re F pper U le a h S d n a 21
22 and plant life flourished resulting in an abundance of coal deposits. The Pottsville is the basal member of this period and contains 12 named coal beds whereas the overlying Allegheny has 13* The formation outcrops in a longitudinal belt extending from the Ohio River north through all or parts of Lawrence, Scioto, Gallia, Jackson, Pike, Hocking, and Fairfield counties. The rocks were deposited in a layered cyclic series of alternating coal-to-coal intervals including coal, shale, sandstone, conglomerate, and limestone. The shales and sandstones intergrade each other and the clays are thinly bedded. The sandstone and conglomerates are often exposed as thick massive outcrops (Figure 1.3-8).
Figure 1.3.8.--Massive Allegheny-Pottsville sandstone outcrop along the Ohio River beside SR 53- The slopes in this formation are generally stable and present the fewest landslide problems (Fisher, 1968). The Vinton County Engineer reported that they have few landslip problems along their highways (written com munication, 19?6). The Jackson County Engineer reported that they have had some landslide problems which have necessitated the driving of wood piling, ditch cleaning, and replacing sections of asphalt pavement (written communication, 1976); however, no major regional landslide susceptible terrain problems were expected within this formation.
1*. 3• 3 The Conemaugh formation The Conemaugh formation, shown in Figure 1.3»9> is of Pennsylvanian age with much of the lower part being of marine origin. It outcrops in a broad band, 10 to 20 miles wide from the Ohio River north through all or parts of Lawrence, Gallia, Jackson, Meigs, Vinton, Athens, Hocking, Perry, Morgan, Muskingham, Noble, and Guernsey counties. The formation consists mostly of sandstone, sandy shale and clay, much of which has a reddish brown color. These "red beds" have been identified as being landslide prone. Coal and limestone beds are generally few and thin. Fisher (1968) reported the Round Knob red shale,. Clarkesburg red shale, and the Connellsville sandstone 2k
Pittsburgh Limestone and Shale
Upper Little Pittsburgh Coal Bellaire Sandstone and Shale Lower Little Pittsburgh Coal Summerfield Limestone and Shale
Shale
Connellsuille Sandstone and Shale
Clarksburg Coal , ^ Clarksburg Limestone and Shale Morgantown Sandstone and Shale
Elk Lick Coal Birmingham Shale Duquesne Coal S hale Gaysport Limestone
Ames Limestone
Harlem Coal Round Knob Shale
Barton Coal
Cowrun Sandstone and Shale
Anderson Coal
S hale
Wilgus Coal
Buffalo Sandstone and Shale
Brush Creek Limestone and Shale
B rush C reek Coal M ason Coal Upper Mahoning Sandstone and Shale Mahoning Coal
Lower Mahoning Sandstone and Shale Figure conemaugn geologic formation (from G.O. Johnson, "Stratigraphic Column of the Penn sylvanian System of Ohio")* 25 horizons as "being landslide susceptible. Wu (197?) reported landsliding in the Round Knob, Connellsville, and Birmingham shales. As early as 1912, Condit reported that "Landslips are very common at the Round Knob hori zon; hence the soft red clay becomes distributed over a great vertical range, thus giving an appearance of considerable thickness". The Athens County Engineer reported considerable landslide problems along their highways. Some of the major ones have persisted for over 30 years (written communication, 1976). The Conemaugh contained a significant amount of landslide susceptible terrain, usually associated with the red shales and clays. The slopes upon which these beds were found were often gentle, with breaks in slope occurring at those elevations where more resistant material was encountered (Figure 1.3.10).
1.3*^ The Monongahela formation The Monongahela formation, shown in Figure 1.3.11. is the youngest of the Pennsylvanian age deposits and has a fresh water origin. It outcrops over a narrow belt 5 to 15 miles in width from the Ohio River north through all or parts of Lawrence, Gallia, Meigs, Athens, Guernsey, Noble, Muskingum, Morgan, and Washington counties. The bedrock is composed of beds of shale, sandstone, limestone, clay, and coal; but the shale, sandstone and 26
Figure 1.3.10.--Scene showing break in slope with sliding materials below in the Conemaugh formation north of Athens, Ohio. limestone make up about 95 per cent of the group. Again, red shales are present, and Fisher (1968) has identified the Uniontown and Tyler red shale horizons along with the closely associated Mannington shale in the Washington formation of Permian age to be landslide prone.
The Monongahela formation was not extensively examined in this investigation due to the practical limits imposed on the size of the study area by the United States Geological Survey.
* Figure
MONONGAHELA I ! \ 1.3*11*--The Monongahela formation 1.3*11*--The Monongahela O'/s? R ed sto n e “P om eroy" C oal oal C eroy" om “P e n sto ed R dsone mesone le a h S d n a e n sto e im L e n sto ed R P itts b u r g h S a n d s to n e an d S h ale ale h S d an e n to s d n a S h g r u b itts P le a h S d n a e n sto d n a S tckley Sew P itts b u rg h C o al No. 8 No. al o C h rg u b itts P spt metn a ale h S d an estone im L lshpot F 9 No. oal C reek C eigs M le a h S d n a e n sto e im L rnoldsburg A oal C rnoldsburg A W aynesburgs C oal No. 11 No. oal C aynesburgs W n o Li soe nd Shale S d an estone im L ood enw B llno Sandsone a ale h S d an e n sto d n a S n llnlontow al o C aynesburgs W ittle L ofOhio"). the System Pennsylvanian "StratigraphicofColumn (from Johnson,G.O.
28 1. 4 The Study Area The selected study area extends directly south from
Zanesville to the Ohio River, west along the Ohio River to Vanceburg, and then proceeds north-northeast following the western edge of the Allegheny Plateau to Linnville, and then east to Zanesville. This represents approximately 6,300 square miles. It passes through the Cuyahoga-Logan, Allegheny-Pottsville, and Conemaugh geologic formations as shown in Figure 1.4.1. The Monongahela formation caps the uplands in the eastern portion of the sector. The study area includes that portion of the Allegheny Plateau in Ohio found within the Columbus and Huntington 15 minute (1/250.000 scale) topographic series and includes a total of 108 minute (1/24,000 scale) topographic quadrangles. The list of 7i minute quadrangles is given in Tables 1.3 and 1.4, and their specific positions within the study area are shown in Figure 1.4.2. 29
CUYAHOGA ALLEGHENY CONEMAUGH LOGAN POTTSVILLE FORMATION FORMATION FORMATION
FAIRFIELD PERRY
MORGAI HOCKING
/ ROSS ATHENSVINTON
MEIGS PIKE JACKSON
GALLIA SCIOTO MONONGAHELA \ FORMATION
LAWRENCE
Figure 1.4.1.--The study area showing the approximate positions of the geologic formations. 30
TABLE 1.3
LIST OF 7h MINUTE QUADRANGLES WITHIN THE COLUMBUS 15 MINUTE TOPOGRAPHIC MAP WITHIN THE STUDY AREA
Quadrangle ft Name Quadrangle # Name Co -H-14 Glenford Co-C-11 Ratcliffburg Co-H-15 Gratiot Co-C-12 Allensville Co -H-16 Zanesville W. Co-C-13 Zaleski Co -G-14- Somerset Co-C-1^ Mineral Co-G-15 Fultonham Co-C-15 The Plains Co -G-16 Crooksville Co-C-16 Athens Co-F-12 Lancaster Co-B-5 Rainsboro Co-F-13 Bremen Co -B-6 Bainbridge Co-F-1^ Junction City Co-B-7 Morgantown Co-F-15 New Lexington Co-B-8 Summithill. Co-F-16 Deavertown Co-B-9 Waverly North Co-E-11 Clearport Co-B-10 Richmond Dale Co-E-12 Rockbridge Co-B-11 Byer Co-E-13 Logan Co-B-12 Hamden Co-E-1^ Gore Co-B-13 McArthur Co-E-15 New Co-B-14 Vales Mills Straitsville Co-E-16 Corning Co-B-15 Albany Co-D-7 Frank fort Co-B-16 Shade Co-D-8 Andersonville Co-A-5 Sinking Spring Co-D-9 Kingston Co-A-6 Byington Co-D-10 Hallsville Co-A-7 Latham Co-D-11 Laurelville Co -A-8 Piketon Co-D-12 S .BloomingvilleCo-A-9 Waverly South Co-D-13 New Plymouth Co-A-10 Beaver Co-D-1^ Union Furnace Co-A-11 Jackson Co-D-15 Nelsonville Co-A-12 Wellston Co -D-16 Jacksonville Co-A-13 Mulga Co-C-6 South Salem Co-A-14 Wilkesville Co-C-7 Bourneville Co -A-15 Rutland Co-C-8 Chillicothe W. Co-A-16 Pomeroy Co-C-9 Chillicothe E. Co-C-10 Londonderry 31 TABLE 1.4- LIST OF 7h MINUTE QUADRANGLES WITHIN THE HUNTINGTON 15 MINUTE TOPOGRAPHIC MAP
Quadrangle # Name Quadrangle # Name Hu-H-5 Peebles Hu-F-7 Pond Run Hu -H-6 Jaybird Hu-F-8 Friendship Hu-H-7 Rarden Hu-F-9 Portsmouth Hu-H-8 Wakefield Hu-F-10 Wheelersburg Hu-H-9 Lucasville Hu-F-11 Pedro Hu-H-10 Stockdale Hu-F-12 Sherritts Hu-H-11 Petersburg Hu-F-13 Waterloo Hu-H-12 Oak Hill Hu -F-14 Mercerville Hu-H-13 Rio Grande Hu-F-15 Apple Grove Hu -H-14- Vinton Hu -E-6 Vanceburg Hu-H-15 Addison Hu-E-7 Garrison Hu -H-16 Cheshire He-E-10 Greenup Hu-G-5 Lynx Hu-E-11 Ironton Hu -G-6 Blue Creek Hu-E-12 Kitts Hill Hu-G-7 Otway Hu-E-13 Aid Hu -G-8 W . Portsmouth Hu -E-14 Athalia Hu-G-9 New Boston Hu-E-15 Glenwood Hu-G-10 Minford Hu-D-11 Ashland Hu-G-11 S . Webster Hu-D-12 Catlettsburg Hu-G-12 Gallia Hu-D-13 Huntington Hu-G-13 Patriot Hu -D-14 Barboursville Hu -G-14 Rodney Hu-G-15 Gallipolis Hu-F-5 Concord Hu -F-6 Buena Vista I ^ I— VANCEBUbl lSW-'-'i",
10 11 12 13 14 15 16 Figure lJ*.2.--The 7s minute topographic quadrangles as they are positioned within the study area. CHAPTER II THE MAPPING OF LANDSLIDE SUSCEPTIBLE TERRAIN
2 •1 United States Geological Survey Specifications The landslide mapping phase was sponsored hy the United States Department of the Interior, Geological Survey Eastern Headquarters, Reston, Virginia. The project was part of a long range program studying landslide problems in the Appalachian Mountain Range in the eastern portion of the United States. The study was divided into', the following phases. Phase 1» Mapping the landslide susceptible terrain within the Range completed on October 1, 1978. Phase 2: Research into the causes of landslides within the Range to be completed in 1980. Phase 3: The prediction of landslides within the
Range (no termination date has been set). Phase ki Correction and prevention of landslides (no termination date has been set). The Allegheny Plateau in northeast and east Ohio was mapped by field investigators traveling from the USGS head quarters in Reston, Virginia; whereas southeast Ohio was mapped by this investigator. The work in southeast Ohio began in August, 1975. and was completed in August, 1978.
33 34
2.1.1 Requirements of the position The individual first reviews the literature and determines the status of current investigative efforts in the field of engineering pertaining to soil mechanics, soil genesis, and rock weathering, and their relation to slope stability. He then independently develops techniques for the identification of landslides and landslide prone regions within his study area from the available resources. He plans and performs technical work for the production of maps of landslides and landslide areas based on remote sensing materials, geological and engineering observations and on-site studies. The work was performed for the United States Geological Survey, Branch of Eastern Environmental Geology, Reston, Virginia. The general work plan and mapping procedures were independently determined by the investigator working within the time limits dictated by the USGS. Since land slide susceptible terrain mapping methods vary according to terrain conditions, distance from the field, accessibility to the field, etc., he was responsible for developing techniques which best suited his study area and for the completeness, applicability, breadth, and appropriateness of conclusions.
Initially, articulation with other field investigators included: 35
1. Traveling through the study area for a general analysis of the terrain; 2. Meeting in the Pittsburgh, Pennsylvania, and McMachan, West Virginia region for field sessions on the identification of landslide susceptible terrain in-and-around those areas; 3* Traveling in northeast and east Ohio to review the landslide problems unique to those areas. The area as described in Section 1.4 was selected for study. The USGS supplied three duplicate copies of minute topographic quadrangles on which the data is com piled. Two were used as work copies and the third was a final draft copy. Black and white 1/64,000 scale photography was supplied for stereo viewing. The data compilation was based on topographic map interpretation, aerial photo interpretation, geologic reports, soils reports, published reports, field check, and personal knowledge. Ground field checks were conducted using a GSA issued vehicle and aerial flights were performed to view remote areas inaccessible on the ground. 3 6 2•2 Data Acquisition Methods The techniques used to map landslide susceptible ter rain on a regional basis are varied but are generally related to such factors as the accessibility of an adequate mode of transportation for field check, distance to and from the study area, and the recentness and scale of the aerial photography. Alfoldi (197*0 has mapped eastern Ontario using only black and white 1/10,000 to 1/20,000 scale aerial photog raphy with little/no field check. His technique involved the inventorying of individual landslides from the photo graphs, the creation of a landslide density map, and the subsequent formation of a regional landslide susceptibility map. Drennon's (1975) techniques were similar in mapping the Rapid City, South Dakota area. He used 1/4,150 scale photography, inventoried individual landslides, produced a landslide density map, and in conjunction with a geologic and a slope map, constructed a landslide susceptibility map. He also made little/no use of the field check. The USGS does not recommend the use of aerial photog raphy alone. The photography they supply is small scale and frequently outdated. They encourage sufficient field check to give the most accurate and recent data. The decision as to the amount of field check necessary is made by the individual investigator. The flow chart in Figure 2.2.1 gives the order in 37
eologic Stratigraphic Soil Stereo Map Profile Map Photographic Study Study Study Study
Information Transferred to a ?&' topo
Field Study
Stereo Study of Photography
Compilation of Data
Draft "Landslides and Disturbed Ground Map"
Figure 2.2.1.--Flow diagram showing the method of data acquisition for each 7i' topo. 38 which the data is compiled for each area represented by a 7s minute quadrangle. The first phase of the study is performed in-house. First, the geology of the area is determined and a speculation is made concerning the sandstone, clay, and shale outcrops which might be present along with the approximate elevations that these might occur in the field. Second, county soil maps are consulted in an effort to identify those soils which are erodable and at what elevations they exist. Modern soil reports are available at present only for Ross and Fairfield counties within the study area. Adams, Scioto, Vinton, Athens, and Meigs counties have early soil surveys but these generally are not detailed enough to give site specific information. The Soil Conservation Service's 1975 "Soil Mapping Status of Ohio Counties" lists Jackson, Gallia, and Lawrence counties as not having a soil survey taken to date. There fore, specific background information regarding soils is limited in most of southeast Ohio. Third, a stereo aerial photographic survey is made with the emphasis placed upon identifying the specific geologic outcrops, contour inter vals, and pattern elements. A stereo photo interpretation is then made to determine the presence of landslide indi cators. The information that has been accumulated to this point is compiled along the margins of a 7h minute quadrangle. 39 2.2.1 Airphoto interpretation of landslide susceptible terrain The use of aerial photography as part of a landslide investigation is widely accepted. The advantages and limitations of using airphotos in the study of landslides are given by Liang and Belcher (1958) as summarized in Table 2.1. An important advantage not listed here is the ability to study that portion of the terrain that is inaccessible on the ground. Due to factors such as short field season, difficult weather conditions, dense cover, long slopes, impassable roads, lack of roads, the field observor at times cannot view much of the terrain and must rely on photo interpretation to analyze these areas. In the initial stereo photo survey, the pattern elements are identified. These are listed and described in Table 2.2. The landform analysis is especially important in that it can be directly keyed to landslide potential. Those specific landforms applicable to south east Ohio are listed in Table 2.3. An effort was made to identify on the photographs those landforms associated with clay shales and flat-lying sedimentaries showing a sharp break in slope. The break in slope is often associated with sliding clay beds lying below a more resistant sandstone, a situation common in the Conemaugh formation.
A drainage and erosion pattern showing closely spaced bo TABLE 2.1 ADVANTAGES AND LIMITATIONS OF AERIAL PHOTOGRAPHY AS A TOOL IN LANDSLIDE INVESTIGATIONS Advantages 1. Airphotos present an over-all perspective of a large area When examined with a pocket or mirror stereoscope, over lapping airphotos give a three-dimensional view. 2. Surface and near-surface drainage channels can be traced. 3. Important relationships in drainage, topography, and other natural and manmade elements that seldom are correlated properly on the ground become obvious in airphotos. A moderate vegetative cover seldom blankets details to the photointerpreter as it does to the ground observer. 5. Soil and rock formations can be seen and evaluated in their "undisturbed" state. 6. Continuity or repetitions of features are emphasized. 7. Routes for field investigations and program for surface exploration can be planned. 8. Recent photographs can be compared with old ones to ex amine the progressive development of slides. 9- Airphotos can be studied at any time, in any place, and by any person. Limitations 1. The interpretation is only as good as the interpreter^ knowledge of the study area. 2. The photographic scale should be larger than 1/30,000. 3. Photography is of little use where man has altered the terrain. Should not be used alone without ground investigation.
(Summarized from Liang and Belcher, "Airphoto Interpreta tion", pp. 69-70.) 4 1
TABLE 2.2
LIST OF THE PATTERN ELEMENTS AND THEIR DESCRIPTION
1. landform - A geologic deposit which is identified by its topography on an aerial photo graph . 2. regional drainage and erosion pattern - indicates the regional dip, type of soil or rock material, and depth of the soil mantle. 3* photo tones - indicates variations in soil moisture and color. 4. vegetation - type gives information concerning soil moisture content, natural or man- influenced ground patterns. 5* special or man-made features - strip mines, sink holes, farm ponds, roads, railroads, etc., gives information concerning soils and geology. 42
TABLE 2.3 KEY TO LANDFORMS AND THEIR SUSCEPTIBILITY TO LANDSLIDES IN SE OHIO Landslide Photographic expression Landform potential* I. Level terrain A. Not elevated* Flood plain c B. Elevated: Terrace, Lake b bed II.Hilly Terrain A. Surface drainage not well Limestones c integrated: B. Surface drainage well inte Flat-lying b grated with branching sedimentaries ridges, dendritic drain age, and banding on slopes: C. Surface drainage well inte Clay-shale grated with branching ridges, dendritic drain age, with no banding on the slope. Moderately to highly dissected ridges, uniform slopes: D. Random ridges or hills with Clay-shale dendritic drainage. Low rounded hills with mean dering streams:
(a) susceptible to landslides (b) susceptible to landslides under certain conditions (c) not susceptible to landslides except in dangerous locations
(modified from: Belcher, et al. "Photo Interpretation in Engineering", p. 417.)
I 43 channels with U-shaped gullies generally indicates an impermeable silt-clay-shale system, whereas widely spaced channels with V-shaped gullies indicates a more permeable sandy soil material. The photo gray tone indicates the soil moisture con ditions. Dark tones indicate a high soil moisture con dition, whereas light tones indicate a lower moisture con tent.
The identification of vegetation types reveals important aspects of the terrain. Farm crops and orchards are generally planted on gentle, well drained slopes. Pasture lands are usually not suited for farming because of steeper slopes, the presence of rock outcrops, or landsliding. Cedar trees often indicate limestone bedrock. Large mature deciduous hardwoods in woodlands generally indicate stable slopes; whereas dense undercover, shrubs, ever greens, immature hardwoods, often indicate unstable slopes. Following the pattern element study, the photography was examined in greater detail for the presence of specific landslides and landslide indicators. It was only possible to detect large landslides at the 1/64,000 scale photography used in this investigation. In general, photographs at scales smaller than 1/9,600 are not suitable for small slide details, and the 1/2,400 scale is optimum for a de tailed description. The landslide indicators which were 44 found to be applicable at the 1/64,000 scale are given in
Table 2.4. The most easily observable were numbers (1),
(3)> (7)» and (2) if the hummocky surface is sufficiently large. Generally more than one of these indicators will be expressed in a landslide susceptible area and a general qualitative judgment is made concerning the landslide potential within a 72 minute quadrangle based upon the combined pattern element and landslide indicator study. The topographic area was now ready for field study at which time the landslide susceptible terrain was mapped directly on the topo sheet along with the individual landslide types.
2.2.2 Classification of landslide types The classification of landslides has been variously proposed. Generally the schemes resemble Sharpe's (1938* i960) classification with variations. With some modifi cations, this general scheme is given in Table 2.5* Classification schemes are based on the mechanisms in volved in the landslide movements. The three basically different actions are falls, slides, and flows. In falls, the primary mechanism is free fall after a loosening of the material. Slides are shear failures in which the mass moves as a unit or block, retaining most of its original volume and shape. Flows are also shear failures, but the moving mass does not retain internal continuity and may TABLE Z.h
INDICATORS OF LANDSLIDE SUSCEPTIBLE TERRAIN ON 1/6^,000 SCALE PHOTOGRAPHY
1. Sharp Break in slope. 2. Hummocky surfaces. 3. Appearance of light tones indicative of Bare soil conditions. Elongated dark tones indicating undrained depressions on hillsides or along roadsides. 5. Changes in vegetation types indicative of changes in moisture and slope conditions. 6. Closely spaced drainage channels. 7* Unnatural cirque or spoon shapes in the topography. 46
TABLE 2.5 CLASSIFICATION OF LANDSLIDES with increasing Rate of Movement General Classification water content
Imperceptible Creep Solifluction
Slow to rapid Earth flow Mud flow
FLOW Debris avalanche
Slow to rapid Slump Debris slide Rock slide SLIDE Rock fall
(modified from Sharp, "Landslides and Related Phenomena", and Fisher, "Landslides in Southeastern Ohio".) or may not have a clearly marked, continuous, shear surface.
Much interparticle movement will take place, especially during soil creep. The USGS had originally specified that the field investi gator differentiate between and map the landslide types as given in Table 2.6. This investigator found that much time is spent in the field in an effort to determine the mechanism of failure, especially where a combination of types is evident within a single slide. Remembering the comments of Terzaghi (1950) who stated, "A phenomenon in volving such a multitude of combinations between materials and disturbing agents opens unlimited vistas for the classification enthusiast. The result of the classification depends quite obviously on the classifier's opinion regarding the relative importance of the many different aspects of the classified phenomenon", the classification scheme as shown in Table 2.7 was adopted. Included are the symbols used to map the slopes showing conspicuous soil movement. Active landslides are recently occurring earth slumps (Figure 2.2.2) and flows (Figure 2.2.3) which have not had sufficient time to be overgrown with vegetation. These generally are longitudinal in shape, extending upslope for several hundred feet in the case of large landslides. Semi-active landslides are formerly active slides that have apparently reached some level of stability, and are becoming overgrown with vegetation (Figure 2.2.^). ^8
TABLE 2.6
USGS LANDSLIDE MAPPING DESIGNATIONS
Landslide type Mapping symbol rock fall rf rock slide rs debris flow df debris avalanche da earth or soil flow ef block slump bs
prehistoric P (creep, hummock)
mud flow mf 4-9
TABLE 2.7 LANDSLIDE CLASSIFICATION SCHEME
Landslide type Topographic expression active <9 semi-active
prehistoric 50
j$arth slump along US 50.
Figure 2.2.3.--Earth flow along SR 35. 51
i
Figure 2.2.4.--Serai-active slide along 1-77 •
Falls include both rock falls (Figure 2.2.5) and rock slides (Figure 2.2.6). Rock falls are found on steep slopes where competent sandstone is overlying a more easily weathered material such as shale or an indurated clay. As the weathered material erodes away, the overlying sandstone is stressed to failure and blocks of sandstone break away. Rock slides are defined as broken masses of rock, usually shale or combinations of shale and sandstone, which exist on steep slopes, and move downslope on a surface that underlies the deposit with the speed of motion being essentially that of a free fall. Prehistoric landsliding is an all encompassing term which is defined as that part of the terrain which has at any time 52 .
Figure 2.2.5 .--Rock fall along US 52.
Figure 2.2.6.--Rock slide along Lower Twin Road. The arrow marks -the former slide surface. in the past -undergone movement downslope. The landslide types named above are often the symptoms that this type of terrain is present. Hummocks (Figure 2.2.7) and creep (Figure 2.2.8) are good indicators of this landslide type. This evidence is often associated with specific landslide susceptible strata and may express itself topo graphically for many miles. The most difficult part of the mapping operation is to define the' topographic limits of prehistoric landsliding in the field.
Figure 2.2.7.--Hummocky hillside along Langdon Road. ■54
Figure 2.2.8.--Creep along alternate US 50*
2.2.3 Acquisition of ground truth The field check is considered to be the most important phase of the investigation. The preliminary in-house preparation was used as a guide in mapping the route to be traveled. Generally every passable road including inter state, state, county, and township roads was driven* Many times new roads have been built since the topographic map was drawn or updated. Logging and mining roads are being built daily in southeast Ohio. Many times these as well as other private roads are inaccessible to the public, and the previously mapped route had to be altered in the field. A general route was chosen with changes made as necessary in 55 in the field. Some of the factors involved in choosing a route are t 1. Gentleness of the terrain. There are those areas in southeast Ohio that are almost level and landsliding is obviously not a problem.
These areas are passed through quickly and not every road is traveled. Usually, however, this is not the case and an attempt is made to view every slope. 2. Ability to view the entire slope. County and township roads which go up-and-down the slope are sought so that the stratigraphic profile can be observed. Mapping the topographic interval is made much easier when the upper and lower limits of the sliding strata can be observed along the roadside. Often the roads themselves give clues by failing within these limits. 3. Ability to view the terrain with a minimum of backtracking. Backtracking is impossible to avoid when each road is being traveled and where this becomes necessary, the terrain is rechecked. k. Season of the year. This becomes a critical factor in the heavily forested portions of southeast Ohio. In these areas it is impossible to view the slopes during the summer months when 56 the leaf cover is thick. In the spring of the year it is often impossible to travel the dirt roads either because of wet spring conditions or because of ruts which have developed by traffic during a winter or spring thaw. Heavy snows com pletely halt the field effort. Because of these reasons, many times the mapping effort on a given topo was delayed until another season and the effort moved to another area. It was found that the optimum time to view the forested slopes is during the months of November and December, and in the winter months when there is a very light snow cover. The primary problem in the autumn months was that the fallen leaves often cover exposed soil in landslides. The white snow gives an excellent background in mountain ous terrain but here again, exposed soils were covered. Geologic formation boundaries. The field mapping is expedited if specific geologic strata can be identified and traced in the field. Sandstone outcrops are often good "marker beds." Routes were chosen in a north-south orientation and each formation was mapped as a unit. The important thing to remember in the field is that when traveling from west to east, the beds eventually 57 disappear underground and new "marker beds"
must be sought. The minute topographic work sheet is taken to the field with the data compiled along its margins and a route drawn. A set of aerial photography, a stereoscope, a set of geologic maps, and a camera are also taken. The specific task is to map the landslides and landslide susceptible stratigraphic intervals directly on the topo work sheet at the proper position and elevation. This is done via a GSA vehicle moving at speeds usually not exceeding 25 mph when one person must drive and map simultaneously. About every one mile a parking place is found and each slope is reviewed and mapped. Only those slopes which can be seen are mapped. If the topographic expression indicates that the same terrain exists around the slope or on adjacent slopes, that interval is drawn in as dashed lines. It is difficult to map very small slides because of the topo map scale. The map is drawn with 20 foot contour intervals so that landslides of about 5 foot radius or less cannot be mapped by any symbol larger than a dot. The other field difficulties are linked to the ability to view the full extent of any given slope, especially where stratigraphic facies changes are occurring, and one is faced with the dilemma of being either up or down slope and not being able to see between. The aerial photography can be of help during these times and considerable effort 58 is spent in stereo photo interpretation of the area. The time required to field map an individual quadrangle varies. If little mapping effort is required due to the stability of the terrain, the 8.61 mile X 6.76
mile quadrangular area can be studied in less than a day. The effort may take a week or more in those areas where landsliding is severe. This time estimate includes re checking when seasonal difficulties or foilage density problems are encountered. Portions of the Conemaugh forma tion were rechecked during different flights via a small swept wing aircraft.
2.3 Results of the Mapping The final compilation of data was performed in-house. A final stereo photo interpretation was made in order to make a decision concerning the landsliding potential of those areas which were inaccessible in the field. The factors governing this decision include the combination of the following factors: 1. The ground truth data for similar or surrounding slopes; 2. Similar topographic expression; and 3. Similar photographic features. The information was transferred to a clean 7i minute topographic quadrangle with the completed "Landslide and Disturbed Ground Map" sent to the USGS headquarters in 59 Reston, Virginia. There the following disclaimer is attached. Information shown is intended as a general guide to ground conditions as of the date of field check. Additional active slides should be anticipated in all map units. The map unit depicts the dominant condition in the area delineated and variations in slope sensitivity may occur at any point in the unit. Field check of data was limited. This map cannot be used as a substitute for detailed geologic and engineering investi gations for establishing design and con struction criteria of specific sites. Some categories in the legend may not be depicted on this map. The information is stored by the USGS on open-file and is available for public inspection. An example of an individually mapped "Landslide and
Disturbed Ground Map" is given in Figure 2.3-1.
2.4 Relationship of Landslide Density and Type to Geology Figure 2.4.1 gives a summary of the mapping on a regional basis. This map was prepared by forming a grid which overlaid each 7i minute topographic quadrangle. The grid is composed of 154 squares each representing approxi mately 1000 meters X 1000 meters of ground surface. The degree of susceptibility was considered to be high if the grid square contains 25 per cent or more landslide suscep tible terrain incidence rate. Where this was the case, the corresponding square on the landslide density map was darkened. . . UNITkD STATES STATE OF OHIO JACKSONVILLE OUAORANOLE DEPARTMINT OF HIOHWAYI OHIO *5* C OEPAHTMENT OF TH8 INTERIOR DEPARTMENT OF NATURAL RMOURCM 71 MINUTI BIRIM (TOPOOAAPHJC) AT > OCOIOQICAL SURVEY OlVlilON---- - OF 'V OBOLOOICAlm>:h~------tURVRV *• *. "i .,'1 V ' v'- AV ’’A , A J f
< , \ •"'• ' '*v ^ V.i -va tourf* ' t < b * l 1 !<'"•<. j \ |? \
I K f % ■ joCa> i*. J A .u
w '
^ * :i /,ALr~->V 'v'\r>v *» T M 7 . W Hi ' !j . •'T' Vi:> i( JV» i V > S r t ' . • T * • I
* ** y v's • -,?<- •
Co-D-lfe JACKSONVILLE, OHIO
Figure 2.3.1.--A typical Landslide and Disturbed'Ground Map. 61
Figure 2.4.1.--A landslide susceptible terrain density map of the study area. 62 It is noted that the landslide susceptible terrain
pattern forms two bands appearing in a northeast- southwest orientation. These bands correspond to the Cuyahoga-Logan formation to the west and the Conemaugh formation to the east. The Allegheny-Pottsville formation between shows little comparative susceptibility except perhaps just north of the Ohio River. Comparing Figures 1.3*2 and 2.^.1, it is noticed that the sandstone outcropping areas in the Cuyahoga-Logan formation show little landsliding. The landslide density along the Scioto River north of and along the Ohio River just southeast of Portsmouth, are mostly within the Cuyahoga shales whereas sliding along the western boundary is likely a combination of Cuyahoga shale and glacial materials. The sliding at low elevations, especially along new road cuts, is in fine-grained soils, probably of glacial lacustrine origin. The Allegheny-Pottsville formation shows few landslide dense areas. Those few places where landsliding does occur are at low elevations and may be in lacustrine deposits. The Conemaugh formation has some areas where the density is sparse, associated with sandstone predomination or gentle terrain. The landslide dense areas in most cases contain soils which are reddish-brown in color. These are likely to be the red beds common to the formation. The common type of landsliding in the Cuyahoga shale 63 regions is the shale rockslide, and the soils which develop on these slopes show a debris/earth flow mode of failure. Rockfalls involving sandstone blocks are common along the Ohio River, and within the Allegheny-Pottsville and Conemaugh formations. The landslide susceptible terrain in the Conemaugh formation is characterized by slumps and creep, resulting in many hummocky hillsides. Few hummocky areas are in evidence in the Cuyahoga-Logan formation. CHAPTER III SOIL SAMPLING
3•1 Selection Processes for Soil Field Sampling The sites for soil sample extraction were determined inhouse. The landslide susceptible terrain density map given in Figure Z.k.l was used to determine those areas where landsliding was most persistent and to assure a wide geographic sampling area. An emphasis was placed on choosing landslide sites which show different terrain and soil conditions and which have not been documented in previous studies. The common factor used in the determina tion was that the site be mapped as an active slide within a landslide susceptible slope. Several hundred such sites were selected and marked on the 7~k minute topographic work sheets used in the field mapping phase of the investigation. The final site selection was made in the field where such factors as landslide type, accessibility to the slope, private ownership of land, distance from the last sampling site, and differences in soil texture and appearance influenced the decision. A route was chosen (Figure 3«1»1) so that each of the landslide dense areas was traveled and each
6k 65
Figure 3-1.1.--Landslide susceptible terrain density map with the final soil sampling route mapped between the dual lines. The topographic identi fication key is given in Figure 1.^.2. geologic region sampled separately. The Cuyahoga-Logan area was sampled first, followed by the Conemaugh area. Samples were taken from the landslide sparse Allegheny- Pottsville region while traveling to these other areas. Sampling each area as a unit helped in the recognition of similar soil types and facilitated the keying, storing, and subsequent laboratory identification process. Two days were set aside for sampling the Cuyahoga-Logan area, and three days for the Conemaugh region with the goal being the collection of about 100 total samples. It was felt that this number of samples, gathered in a variety of landslide conditions, was sufficiently large to adequately cover the study area and to give a representative distribution of soil types. The fall of the year (October) was chosen for field sampling in that it is an ideal time to perform field work (see Section 2.2.3). Days were chosen when rainfall had occurred several days prior to the field trip so that the soil moisture conditions were representative for sampling, i.e., neither exceptionally wet nor exceptionally dry.
The landslide susceptible soils exist in the field in a disturbed state. Their structure, texture, and stress conditions had been altered so that the normal precautions and sampling procedures used to obtain undisturbed soil specimens were not appropriate. A shovel was used to isolate an approximately one cubic foot block of soil (Figure 3-2.1) with as little disturbance to the soil fabric as possible. Woodland soils presented a problem in this respect in that they contained more rocks and plant material. An attempt was made to procure the sample in that portion of the landslide showing exposed soil represen tative of the material found within the total mass (Figure 3.2.2). Hummocky terrain was also a problem in this respect in that most cases no exposed bare soil is evident. Here, samples were taken by cutting back into the slope where the hummock was well exposed (Figure 3-2.3)- Often these samples contain a high percentage of small grass root fibers.
Figure 3-2.1.--Scene showing the isolation of a soil sample pedestol. Note that the sur rounding plant material has been removed. Figure 3.2.2.--The selection of a sampling site within that portion of a slump where exposed soil is evident.
f P ® § - '-ftVd'.
Figure 3.2.3.--Hummocky terrain with creep extending into the roadside ditch. The sampling area is on the ditch side of the leaning fence posts. • 69 Following the extraction of a soil sample, it was wrapped in Saran Wrap or aluminum foil until it was air tight. It was labeled, the top of the sample marked, and it was transported with the top oriented upward and stored in a humid room to await laboratory testing.
3.2.1 Sampling site locations Table 3*1 summarizes the sampling effort within the Cuyahoga-Logan geologic region along the Scioto River valley, its tributaries, and the western escarpment of the Allegheny Plateau. On field trip one, 31 samples were gathered from within 12 different quadrangles west of the Scioto River and south to the Ohio River. The least number of samples taken from within any single quadrangle was one whereas the most was four. Samples (9-12) were taken within about one mile of each other on the severely sliding new cut embankment along SR 32. On field trip two, 12 samples were gathered from within five different quadrangles in an area extending east and west from the town of Chillicothe giving a total of ^3 samples from the Cuyahoga-Logan area. Table 3-2 summarizes the sampling effort for the Cone maugh area. Field trip three was spent collecting 19 samples around and north of Athens within five different quadrangles. The red beds were encountered for the first time in the uplands just east of Burr Oak Reservoir in the 70
TABLE 3-1 TOPOGRAPHIC LISTING OF THE SAMPLING SITES IN THE CUYAHOGA-LOGAN AREA Total # of Quadrangle Key Sample #'s samples Chillicothe West Co-C-8 1 , 2 2 Morgantown Co-B-7 5. 6 , 7 3 Summithill Co-B-8 3, 4, 8 3 Piketon Co-A-8 9 , 10, 1 1 , 12 4 Latham Co-A-7 13 1 Byington Co-A-6 14. 15 2 Jaybird Hu-H-6 16, 17, 18, 19 4 Rarden Hu-H-7 20 1 Blue Creek Hu-G-6 21, 22 2 Buena Vista Hu-F-6 23. 24, 25 3 Pond Run Hu-F-7 26 1 Friendship Hu-F-8 27, 28 2 Wakefield Hu-H-8 29, 30, 31 3 Total - Field Trip One 31 Chillicothe West Co-C-8 32 1 Bourneville Co-C-7 33, 34 2 Bainbridge Co-B-6 35, 36, 37 3 Byer Co-B-11 38, 39, 40 3 Londonderry Co-C-10 41, 42, 43 3 Total - Field Trip Two 12
Total - Cuyahoga-Logan area 43 71
TAB US 3-2 TOPOGRAPHIC LISTING OF THE SAMPLING SITES IN THE CONEMAUGH (ALLEGHENY-POTTSVILLE) AREA
Total # of Quadrangle Key Sample #'s sample s Gore Co-E-14 1 New Straitsville Co-E-15 ^5 1 Corning Co-E-16 ^6 , k7, ^8 , 4-9, 50, 10 51, 52, 53, 54, 55 Athens Co-C-16 59. 60, 61, 62 Jacksonville Co-D-16 56, 57, 58 3 Total - Field trip three 19 Wellston Co-A-12 63, 6/f 2 Gallipolis Hu-G-15 65, 66, 67 , 68, 69 5 Addison Hu-H-15 70, 71, 72, 73. 7^ 5 Rutland Co-A-15 75, 76, 77 3 Albany Co-B-15 78 1 Total - Field trip four 16
Rodney Hu-G-14 79 1 Mercerville Hu -F-14 80, 81
00 00 2 Waterloo Hu-F-13 82, 83, Aid Hu-E-13 86 1 Huntington Hu-D-13 87, 88 2 Catlettsburg Hu-D-12 89 1 Pedro Hu-F-11 90, 91, 92, 93 4 South Webster Hu-G-11 94 1 Total - Field trip five 16
New Concord Ch-H-3 95 1 Old Washington Ca-A-5 96, 98 2 Macksburg Ch-F-5 99, 100 2 Athens Co-C-16 101 1 97 1 Total - C onemaugh 5^ Total - Allegheny- 4 Pottsville 72 Corning quadrangle where ten samples were collected.
Samples (^-^5) were collected in the Allegheny- Pottsville area in lowland, probable lakebed sediments. On field trip four, 16 samples were collected in a belt extending from Gallipolis northward toward Athens within five different quadrangles. Samples (63-6*0 were taken in the Allegheny-Pottsville area, again in lowland lakebed sediments. On field trip five, 16 samples were collected in a belt extending from Gallipolis south to the Ohio River, northwest along the river to Ironton, and then north to Jackson. Samples (90-9*0 were collected on the Allegheny- Pottsville/Conemaugh geologic western boundary but were included in the Conemaugh list because they were taken from the uplands at high elevations where the Conemaugh formation caps the ridges. Samples (95-100) were collected from areas just east of the study area within the landslide susceptible Connellsville and Round Knob shales. To summarize the sampling effort, *1-3 samples were taken from the Cuyahoga-Logan, *1 from the Allegheny-Potts ville, and 5**- from the Conemaugh area. Each specific sampling position is topographically specified in a technical report stored in OSU's Engineering Library. 73 3.2.2 Site descriptions The specific terrain conditions where landsliding occurs can generally be grouped into upland and lowland woodlands, pastures, hillsides with dense undercover, and road cut embankments. The landslide types were generally hummocks, slides, and flows. Tables 3*3 and 3*^ summarize the terrain types and the general landslide types encountered. It is seen that the majority of samples were taken in flows and slides from woodlands and cut embankments in the Cuyahoga-Logan area. A more even distribution of terrain types was sampled within the Conemaugh formation with a higher percent of specimens being taken from hummocks in pastures and hillsides with dense undercover. These comparisons reflect the differences in the terrain and mode of land- sliding between these geologic areas.
3*2.3 Soil sample descriptions An initial soil description was made to obtain general information concerning the physical appearance and con sistency of the samples and the presence of extraneous materials. Those specific factors which were described include: 1. The type, shape, softness, and color of rock fragments; 2. The predominating Munsell soil color along with 74 TABLE 3.3 A COMPARISON OF TERRAIN CONDITIONS FROM WHICH THE SOIL SAMPLES WERE OBTAINED
Cuyahoga-Logan Allegheny-Pottsville Conemaugh ' formation formation formation woodland 19 11 dense under- 6 12 covered hillside pasture 2 2 18 cut embankment 16 2 13
Total 43 4 54
TABLE 3.4 A COMPARISON OF GENERAL LANDSLIDE TYPES FROM WHICH THE SOIL SAMPLES WERE OBTAINED Cuyahoga-Logan Allegheny-Pottsville Conemaugh formation formation formation hummock 7 2 25 (prehistoric) slides 17 2 19 flows 19 10
Total 43 k 54 the colors associated with mottles and streaks; 3- The plasticity associated with a wet/dry, sticky or crumbly material; and The presence of roots and decaying organic matter. These factors were helpful in characterizing and predicting the behavior of the soil and identifying any precautions which might be necessary in subsequent sample preparation or in the performing of a given laboratory test. Most of the 101 samples contained some soft angular shale fragments, ranging in amount from a few pebbles to the entire sample where red bed shales were encountered. The woodland soils were generally higher in rocks and organic material. The samples extracted from grassy and densely covered hillsides often contained small fibrous roots. Many of the samples associated with failures in roadcuts, especially those at low elevations (probable river valley fill deposits) are homogeneous and fine grained, often containing gray mottles. The colors of the samples were determined using the Munsell color chart. Because the value of the Munsell varies according to the moisture content of the soil, the soil color name was determined for a dried, crushed to a powder, fine grained fraction. Sometimes the soft shale fragments differed in color from the fine grained fraction. This is perhaps due to the mixing of stratigraphic materials during landsliding. In other cases weathering may have affected color. The soil sample colors are grouped into the general categories as given in Table 3* 5* The majority of the samples, 79/101, were found on the hue 10YR page where the colors range from gray to brownish yellow. Of these, 28 are grayish to grayish brown in color and in most cases are from samples taken in low lands along river valleys. Webb (1967) has identified the ancient Teays River drainage system deposits to be light gray, Munsell 10YR 6/2 to 10YR 7/2 and tan, Munsell 10 YR
7/3 to 10YR 7/5- Twenty-four of the samples are within this light gray range and 22 within the tan range. Most of the gray samples were taken along the Scioto River valley tributaries whereas many of the tan samples were found in tributaries along the Ohio River. The Teays River system at one time drained much of the study area (Figure 1.3*5)» but whether these particular soil samples contain the materials referred to by Webb cannot be determined by Munsell color alone. The brown samples are generally associated with woodlands and cleared hillsides at varying elevations. The color of the samples containing red bed materials is found in the 2.5YR and 5YR color charts. The 8 reddish brown samples identified on the 2.5YR page were brighter in hue than the 14- more subdued reddish brown samples 77 TABLE 3*5 MUNSELL COLOR VS. GEOLOGIC FORMATION
Cuyahoga- Allegheny- Munsell color Logan Pottsville Conemaugh Total
10YR 7/1,7/2 13 7 20 light gray 10YR 6/2 3 1 4 light brownish gray
I 10YR 6/1 3 3 gray 10YR 5/2 1 1
10YR 7/3. 7 A 9 4 9 22 very pale brown g 10YR 6/3 11 6 17 5 pale brown
10 10YR 6 A 3 9 12 light yellowish brown
5YR 6/3, 6A 9 9 light reddish brown 5YR 6/2 4 4 g pinkish gray
| 5YR 5/3, 5A, 4/3, 1 1 1 reddish brown Tt £ 2. 5YR 5A, 4/4 7 7 reddish brown 2.5YR 6/3, 6/4 1 1
Total 101 78 identified on the 5YR page. Each of these 22 samples contains Conemaugh red bed materials. The plasticity characteristics of the samples as related to the intactness or crumbliness of a sample were in most cases associated with the amount of rocks and decaying vegetable matter present. It is seen in Table 3*8 that the intactness of a sample is not associated with any specific geologic area. The samples extracted from woodland soils were usually crumbly, whereas the fine grained samples were usually intact. Small grass roots can have the effect of holding the sample together. A general soil description is given for each sample and these are given in a technical report stored in OSU's Engineering Library. 79
TABLE 3-6 GENERAL PLASTICITY CHARACTERISTICS OF THE SOIL SAMPLES WITHIN THE GEOLOGIC FORMATION
General Cuyahoga- Allegheny- Plasticity Logan Pottsville Conemaueh Total intact sample 25 3 31 59 crumbly sample 18 1 23 kz
Total 101 CHAPTER IV
LABORATORY TESTING
^ 1 Rationale for Types of Tests Chosen
It is desirable to determine a number of different engineering properties for these soils in order that com parisons can be made relative to regional differences in soil type. Studies determining these properties range in sophistication from empirical observations of the soil material to macromolecular descriptions. Because of the large number of samples being studied (101) over a wide study area exhibiting a variety of ter?- rain conditions, tests were chosen which gave a quantity of data for comparative purposes as opposed to a detailed analysis of individual slopes. The testing program in cludes a natural water content determination, identification tests, shear tests, and clay mineralogical tests. The outline of the laboratory testing program is given in Figure 4.1.1.
The determination of the natural water content of a landslide susceptible soil gives a comparative indication of its texture relative to its surroundings and to other
80 81
SOIL SAMPLE
t Soil description
♦ Direct shear test (undisturbed) I Natural water content
t Mechanical analysis
T t Atterberg limits Direct shear test (remolded) t X-ray diffraction
Fig. 4.1.1--Outline of the laboratory procedure. 82 landslide susceptible soils. Clays are usually saturated, whereas silts and sands can be moist, wet or saturated. It can also generally be stated that in the case of a land slide which has attained a level of stability, the water content will likely be lower than was the case when the active condition existed. Seasonal, temperature, and rainfall variations will, of course, affect this parameter, especially near the ground surface. The liquidity index is calculated for each sample. This value gives an indication as to the tendency of the soil to flow as a viscous material at the natural water content.
Identification tests were performed in order to assign the soil a quantitative designation which will give an estimate as to its probable behavior in the field. First, Atterberg limit tests were performed. The determination of these limits is important in the study of landslide susceptible soils in that they reveal the effect of varying the water content on the strength of a given soil. The addition of water to a soil has the effect of decreasing the attractive forces between soil particles with a resulting decrease in strength. The gradual addition of water will result in the soil passing from the solid state to one in which it deforms and can be remolded, the so- called plastic state. The soil finally reaches the liquid state where it has practically no strength and flows under its own weight even on gentle slopes. 83 In this investigation the plastic state was studied with the following limits determined* 1. Liquid limit - that water content above which the soil possesses no cohesion and behaves as a liquid; 2. Plastic limit - that water content below which the soil becomes hard and incapable of being remolded. Those parameters which can be correlated directly with the limits such as the plasticity, flow, toughness, and liqudity indices were also determined. Using the Atterberg limits, the soils were classified according to the Unified Classification System developed by the Bureau of Reclamation and the Corp. of Engineers in 1952. The system makes use of Casagrande's plasticity chart to classify fine grained soils based upon their liquid limit and the difference between the liquid and plastic limits (the plastic index). The liquid limit vs. plasticity index value was plotted for each soil. According to the position of the plotted point on the chart, the soil was classified as a silt or clay, of high or low plasticity. The Atterberg limits identify a soil with respect to its plasticity characteristics, but were performed on the less than 0.^2 mm grain size fraction of the soil. It is also important in the study of a landslide susceptible soil 84 to determine its texture. The water retention and permea bility characteristics of a soil are determined by the relative amounts of sand, silt, and clay present within the soil mass. A second identification test was made by performing a mechanical analysis on each sample. The American Society for Testing Materials (1958) grain size designations were used. The gravel and sand sizes were retained on the #10 and #200 U.S. Bureau of Standards sieves, respectively. The silt/clay fraction which passed the #200 sieve was further separated by centrifugation. This method of separation was chosen because of the need to isolate the clay fraction for subsequent x-ray diffraction. A grain size distribution curve was drawn for each sample. The abscissa represents the logarithm of the grain size whereas the ordinate represents the percentage by weight of grains smaller than the size denoted by the abscissa. The more uniform the grain size, the steeper was the slope of the curve.
The soils were named according to the United States Department of Agriculture system of nomenclature, based on the percentage of sand, silt, and clay present within the sample. The name, gravelly, was attached if the sample contained more than 20 percent of greater than 2 mm sized coarse fragments. Those samples showing a high percentage of the fine grained fraction, especially clay sized, would be expected to be associated with slope instability. The understanding of the mineralogical composition of a material is fundamental to the understanding of that material's behavior. In the case of soils, those com ponents which most effects its physical and chemical properties and hence its engineering behavior are the clay minerals. The weathering of sedimentary rocks, especially shale, results in an abundance of the so-called 2 si clay minerals within the clay mineral component of a soil. Included in this group are expanding members which exhibit shrink-swell characteristics upon changes in water content. The identification of these members is especially important in the study of a landslide suscep tible soil. The most common tool used today for this purpose is x-ray diffraction. Its advantage is that it is able to directly measure that property which makes one clay mineral distinct from another: the basal spacing between particles. Another type of test performed was the direct shear test whose purpose is to obtain information concerning the strength of the soil as it exists in the field. The ability to duplicate the field conditions at failure is an impossible task to accomplish in the laboratory. Land- sliding usually occurs when moisture conditions are optimum. Therefore, a shear test which is rapid to run and does not permit water drainage may best simulate the 86
in-situ condition. Such a test can be conducted using the direct shear test on cohesive soil as described by Lambe (1951)* Since some drainage does occur during this test, it would best be described as a slightly consolidated, quick shear test. This type of test is applicable for landslide soils in that in the field drainage is possible but, since the soils are usually fine grained and imper meable, failure can occur before water has drained from the voids. The results of the tests were plotted on a shear stress vs. sample displacement graph. The highest shear strength test value was chosen to be the ultimate shear strength for the soil in any given test and these were then used in drawing Mohr diagrams for both the remolded case and the undisturbed case where applicable. From these diagrams the angle of internal friction,
4.2 Atterberg Consistency Limit Tests The Atterberg consistency limits give an indication of the behavior of a soil upon changes in water content and delineates that water content range over which the soil will behave plastically. The limit tests were 87 performed and the soils were classified according to the Unified Classification system based upon their plasticity characteristics. A statistical evaluation of each parameter was made in which the mean, n (l/n) S X., 1 1 and the standard deviation, T n ri1/2 a = (l/n-1) s (x± -m)2 ,
were computed, wheres
M = mean, # a - standard deviation, n = number of test samples, and X^ - test parameter.
A normalized frequency histogram is presented along with the Kolmogorov-Smirnov goodness-of-fit evaluation in a graphical manner. This evaluation was performed so that any abnormal variation or anomaly in the test data could be identified and explained. In no case have any test values been altered or discarded. This particular goodness- of-fit test was chosen because very large deviations of the larger and smaller test values must occur before they can be considered improbable. With the number of test samples, n, being large, the hypothesis of normality at the significance level of 5# is tested with the critical 88 statistic = 1.36/*Jn7 The hypothesis of normality at this significance level is accepted for each Atterberg limit test parameter except the liquidity index. The Atterberg limit test results and their calculated associated parameters are given in Table 4.1. The natural water contents are listed for comparison and in calculating the liquidity index.
4.2.1 Liquid limit (w^ ) test The liquid limits were determined using a standard Casagrande liquid limit device and the tests were per formed according to Lambe (1951) on the less than 0.42 mm sized fraction (passed a #40 sieve). Three tests were performed on each sample at varying water contents and the liquid limit determined to be that water content which requires 25 blows to close the groove in the sample. The test results are listed in Table 4.1 and normalized in intervals of 5$ in Table 4.2. The histogram of proba bilities and the goodness-of-fit test are given in Figures 4.2.1 and 4.2.2, respectively. The mean of 42.7 and standard deviation of 8.5 place most of the samples into the range of liquid limits (35-50) identified by Kezdi (1974) as being associated with soils high in silt/clay of medium plasticity. 89
TABLE 4.1 Atterberg limit test results
Sample w {%) w x(^) wp ($) I p W *1 # 1 34.1 38.7 29.6 9.1 10.6 0.9 0.5 2 22.2 38.1 22.3 15.8 9.0 1.8 0.0 3 31.0 43.7 21.3 22.4 10.4 2.0 0.4 4 23-9 42.7 25.2 17.5 10.1 1.7 -0.1 5 22.9 4 6.7 29.4 17.3 11.1 1.6 -0.4 6 20.0 39.8 22.9 16.9 9.4 1.8 -0.2 7 32.0 46.4 32.0 14.4 12.7 1.1 0.0 8 22.5 44.5 29.5 15.0 12.1 1.2 -0.5 9 20.3 43.3 24.0 19.3 11.8 1.6 -0.2 10 27.5 50.1 29.1 21.0 13.7 1.5 -0.1 11 21.0 43.5 25.0 18.5 11.9 1.6 -0.2 12 21.4 43.2 25.6 17.6 11.8 1.5 -0.2 13 24.5 52.4 31.9 20.5 14.3 1.4 -0.4 14 20.6 43.6 24.3 19.3 11.9 1.6 -0.2 15 25.7 49.4 31.1 18.3 13.5 1.4 -0.3 16 23.0 35.9 21.8 13.6 9.8 1.4 0.1 1? 22.0 37.0 21.3 15-7 10.1 1.6 0.1 18 24.5 46.1 27.2 18.9 12.6 1.5 -0.1 19 21.6 28.2 21.5 6.7 7-7 0.9 0.0 20 25.5 34.0 23.1 10.9 9.3 1.2 0.2 21 27.0 4 5.6 26.3 19.3 10.8 1.8 0.0 22 18.7 37.8 22.4 15.4 8.9 1.7 -0.2 23 23.1 45.5 26.2 19.3 12.4 1.6 -0.2 24 23.6 45.3 26.0 19.3 12.4 1.6 -0.1 25 24.6 42.1 23.7 18.4 11.5 1.6 0.0 26 21.3 35-0 24.1 10.9 9.6 1.1 -0.3 27 25.2 43.9 29.0 14.9 12.0 1.2 -0.3 28 20.8 35.5 26.2 9.3 9.7 1.0 -0.6 29 21.8 44.2 25.9 18.3 12.1 1.5 -0.2 30 19.3 26.7 22.0 4.7 7.3 0.6 -0.6 31 20.4 13.3 26.4 16.9 11.8 1.4 -0.4 32 24.2 38.0 23.8 14.2 10.4 1.4 0.2 33 20.1 33.8 27.5 6.3 9.2 0.7 -1.2 34 26.0 30.1 22.7 7-4 8.2 0.9 0.5 35 23.5 36.8 26.5 10.3 10.0 1.0 -0.3 36 23.2 38.9 26.1 12.8 10.6 1.2 -0.2 37 19.4 31.4 22.1 9-3 8.6 l.l -0.3 38 28.2 33-9 25.0 8.9 9-3 1.0 0.4 39 40.9 53.5 27.0 26.5 14.6 1.8 0.5 4o 18.6 36.5 30.5 6.0 10.0 0.6 -2.0 41 16.8 49.3 35.1 14.2 13.5 1.1 -1.3 90
Table 4.1 (continued)
Atterberg limit test results
Sample W (fo) wx(^) I p W . wp (#) xt *1 # 42 26.0 36.6 25.0 11.6 10.0 1.2 0.1 43 30.0 35-3 22.5 12.8 9.6 1.3 0.6 ii4 29.4 40.3 24.2 16.1 11.0 1.5 0.3 45 24.3 60.0 29.2 30.8 16.4 1.9 -0.2 46 39-5 55.0 32.3 22.7 15.0 1.5 0.3 47 33-5 45.8 28.5 17.4 12.5 1.4 0.3 48 36.6 52.3 29.9 22.4 14.3 1.6 0.3 49 29.9 29.3 18.7 10.6 8.0 1.3 l.l 50 26.1 46.1 26.1 20.0 12.6 1.6 0.0 51 27-3 48.1 26.7 21.4 13.1 1.6 0.0 52 38.0 66.8 37.0 29.8 18.2 1.6 0.0 53 24.2 37.3 25.8 11.5 10.2 1.1 -0.1 54 22.8 43.9 29.0 14.9 12.0 1.2 -0.4 55 34.4 45.0 27.5 17.5 12.3 1.4 0.4 56 25.4 40.9 24.1 16.8 11.2 1.5 0.1 57 31.1 51.1 29.2 21.9 14.0 1.6 0.1 58 25.7 27.6 27.6 24.3 14.2 1.7 -0.1 59 18.1 41.5 27.1 14.4 11.3 1.3 -0.6 60 36.9 49.9 31.1 18.8 13.6 1.4- 0.3 61 27.5 36.0 22.1 13.9 9.8 1.4 0.4 62 25.7 45.5 25.9 19.6 12.4 1.6 0.0 63 28.6 39.3 23.5 15.8 11.0 1.5 0.3 64 37-3 45.6 26.3 19.3 16.4 1.9 0.0 65 34.7 46.4 28.7 17.7 12.7 1.4 0.3 66 26.1 43.3 28.0 15.3 11.8 1.3 -0.1 67 24.9 42.8 17.8 17.8 11.7 1.5 0.0 68 25.4 42.4 29.1 13.3 11.6 1.5 -0.3 69 35.4 59.1 35.4 23.7 16.1 1.5 0.0 70 17.2 39.3 25.7 13*6 10.7 1.3 -0.6 71 27.7 51.2 27.0 24.2 14.0 1.7 0.0 72 29.8 45.5 27.4 18.1 12.4 1.5 0.1 73 32.5 59.0 34.1 24.9 16.1 1.6 -0.1 74 26.1 44.8 28.8 16.0 12.2 1,3 -0.2 75 35.1 52.3 30.4 21.9 14.3 1.5 0.2 76 32.7 55.6 28.4 27.2 15.2 1.8 -0.1 77 28.4 51.9 30.1 21.8 14.2 1.5 0.1 78 24.9 44.3 23.4 20.9 12.1 1.7 0.2 79 24.4 40.1 28.4 11.7 9.5 1.2 -0.3 80 28.2 62.1 34.3 27.8 17.0 1.6 -0.2 81 19.2 41.5 22.1 19.4 11.3 1.7 -0.1 82 30.1 57.5 30.3 27.2 15.7 1.7 0.0 91
Table 4.1 (continued) Atterberg limit test results
Sample W (fo) W ^fo ) wp ($) I p W J1 # 83 25.0 58.0 29.9 28.1 15.8 1.8 -0.2 84 17.5 35.9 24.1 11.8 9-8 1.2 -0.6 85 32.1 53.2 33.0 20.2 14.5 1.4 0.0 86 23.7 48.3 29.8 18.5 13.2 1.4 -0.3 8 7 18.7 34.8 19.6 15.2 9.5 1.6 -0.1 88 17.O 53-0 30.9 22.1 14.5 1.5 -0.3 89 23.5 39-9 22.3 17.6 10.9 1.6 -0.3 90 16.8 23.3 15.4 7.9 6.4 1.2 0.2 91 26.5 39-7 26.3 13.4 10.8 1.2 0.6 92 16.7 50.0 30.1 19.9 13.7 1.5 -0.7 93 32.6 40.9 25.4 15.5 11.2 1.4 0.5 94 18.7 28.3 16.7 11.6 7.7 1.5 0.2 95 10.3 40.3 22.8 17.5 11.0 1.6 -1.7 96 9.4 36.4 19.5 16.9 9-9 1.7 -1.6 97 9.3 33.7 23.6 10.1 9-2 1.1 -2.4 98 9.8 37.2 22.8 14.4 10.2 1.4 -1.9 99 9.7 28.7 21.0 7*7 7-8 1.0 -2.5 100 4.2 27.1 18.3 8.8 7.4 1.2 -2.6 101 3-8 32.0 21.0 11.0 8.7 1.3 -2.6 92
"I- Table 4.2 Normalization of values from Table 4.1 in intervals of 5-0$
Interval # of tests Normalized # (Kolmogorov-Smirnov test) ______of tests f (w-^)
<19-9 0 0 0 20.0 - 24.9 1 0.01 0.01 25.0 - 29.9 7 0.07 0.08 30.0 - 34.9 8 0.08 0.16 35.0 - 39.9 23 0.23 0.39 4-0.0 - 44.9 24 0.24 0.63 4-5.0 - 49.9 18 0.18 0.81 50.0 - 54.9 11 0.11 0.92 55.0 - 59.9 6 0.06 0.98 So.o - 64.9 2 0.02 0.99 S5 .0 - 69.9 1 0.01 1.00 > 70.0 0 0
number of tests = n = 101 mean = n = 42.7$ * standard deviation = a =8.5$ 0.20
CM g* 0.15 VI 5i 0.10 •— i r—I
0.05
1 1 * ‘ V * * 1 y » J 20.0 30.0 40.0 50.0 60.0 Liquid limit (#) Fig. 4.2.1.--Histogram of probabilities for liquid limit data of Table 4.2.
A 99*9 99.0 90To 50' . 0 1 - f(w^), percent 70.0
60.0
50.0
40.0
30.0
20.0 /
10.0
0 0.01 0.1 1.0 10.0 50.0 84.1 99.9 f(w-,), percent Fig. 4.2.2.— Kolmogorov-Smirnov test for normality for the data of Figure 4.2.1. 94 4.2.2 Plastic limit ( w ) test Jr The plastic limit was also found according to Lambe (1951) on the less than 0.42 mm sized fraction. Three samples were rolled down to an approximately 1/8 inch diameter thread each until the thread crumbled. The water content on each thread was determined and the plastic limit was taken to be the average. The test results are listed in Table 4.1 and norma lized in intervals of 2.5% in Table 4.3* The histogram of probabilities and the goodness-of-fit test are given in
Figures 4.2.3 and 4.2.4 respectively. Using the scheme given by Kezdi (1974), the range of plastic limits from (20-35) are described as being associated with silt/clay soils of medium plasticity. Most of the cases in this study (92/101), are within this range with the mean = 26.2 .
4.2.3 Plasticity index (Ip)
The plasticity index is defined as the arithmetic difference between the liquid limit and plastic limit test values and is the water content range through which a cohesive soil has the properties of a plastic material. The amount of plasticity is directly proportional to the plasti city index. The calculated test results are listed in Table 4.1 and normalized in intervals of 2.5$ in Table 4.4. The histogram of probabilities and the goodness-of-fit test are 95
Table 4.3
Normalization of wT\ values from Table 4.1 in intervals of 2.5?°
# of Normalized (Kolmogorov-Smirno’v Interval tests # of tests test) f(w)
<14.0 0 0 0 15.0 - 17.4 2 0.02 0.02 17.5 - 19.9 5 0.05 0.07 20.0 - 22.4 13 0.13 0.20 22.5 - 24.9 17 0.17 0.37 25.0 - 27.4 26 0.26 0.63 27.5 - 29.9 21 0.21 0.84 30.0 - 32.4 11 0.11 0.95 32.5 - 34.9 3 0.03 0.98 35.0 - 37-4 3 0.03 1.00 >37.5 0 0
number of tests = n = 101
mean = n = 2 6 .2%
standard deviation = 0 = 4.2$ CM 0.30 ft
0.20 ft
0.10
Plastic limit (fo) Figure 4.2.3 - Histogram of probabilities for plastic limit data of Table 4.3*
99'9 99.0 90
wp W
o.oi o.i l.o 10.0 50.0 84.1 99.9 f(Wp)» percent Figure 4.2.4 - Kolmogorov-Smirnov test for normality for the data of Figure 4.2.3 97
Table 4.4 Normalization of I values from Table 4.1 in intervals of 2.5f« # of Normalized (Kolmo^gorov-Smirnov Interval tests # of tests test r f t v
<3. 9 0 0 0 4.0 - 6. 4 3 0.03 0.03 6.5 - 8. 9 6 0.06 0.09 9.0 - 11. 4 10 0.10 0.19 11.5 - 13. 9 11 0.11 0.30 14.0 - 16. 4 17 0.17 0.47 16.5 - 18. 9 21 0.21 0.68 19.0 - 21. 4 15 0.15 0.83 21.5 - 23. 9 8 0.08 0.91 24.0 - 26. 4 3 0.03 0 .9^ 26.5 - 28. 9 5 0.05 0.99 29.0 - 31. 4 2 0.02 1.00 >31 .5 0 0
n = # of tests = 101
V = mean = 16.7% * a = standard deviation = 5-5?o
Table 4.5 Plastic Index Soil Classification
soil type # of cases 1 p (fo) w plasticity
0 none sand 0 0-7 low silt 4 7-17 medium silty clay 48 clayey silt >17 high clay 49 98 given in Figures 4.2.5 and 4.2.6, respectively. A classification scheme for soils based on the plastic index is adapted from Kezdi (197*0 and others and is summarized in Table 4.5 along with the number of tests which fall into each category. According to this scheme, the land slide susceptible soils are either silt/clay or clay of medium to high plasticity.
4.2.4 Flow index (Ij)
In the liquid limit test, when one plots the number of blows and the corresponding moisture content on semiloga- rithmic graph paper, the best fit to the plot is called the flow curve and the flow index is defined as the slope of this curve. Its numerical value is the difference in water content intercepted by the flow curve in one cycle of the logarithmic scale of number of blows. In general, the higher the flow index, the lower the strength of the soil in that fewer blows are required to close the groove in the liquid limit test.
The calculated test results are listed in Table 4.1 and normalized in intervals of 2.5$ in Table 4.6. The histogram of probabilities and the goodness-of-fit test are given in Figures 4.2.7 and k.2.8, respectively. Most of the test cases (80/101 fall within the range 1^ = (9-0 - 15.0). f . r ' 1 " I 1 I I I '"I" r --T-— r-ffi" 0.20
/■— V CM ft H 0.15 VI ft H 0.10 VI H 0.05 ft H
' f t 0 I I , I, .. I , I. 4.0 9.0 14.0 19.0 24.0 29.0 3^.0 Plastic index (fo)
Figure 4.2.5 - Histogram of probabilities for plastic index data of Table 4.4.
99-9 99.0
0.01 0.1 1.0 10.0 50.0 8471 f(Ip), percent Figure 4.2.6 - Kolmogorov-Smirnov test for normality for the data of Figure 4.2.5* 100
Table 4.6
Normalization of 1^ values from Table 4. 1 in intervals of 1.50
Interval # of Normalized (Kolmofjorov-Smirnov tests # of tests test. f(If)
< 5.9 0 0 0 6.0 - 7.4 3 0.03 0.03 7.5 - 8.9 8 0.08 0.11 9.0 - 10.4 23 0.23 0.34 10.5 - 11.9 24 0.24 0.58 12.0 - 13.4 18 0.18 O .76 13.5 - 14.9 15 0.15 0.91 15.0 - 16.4 7 0.07 0.98 16.5 - 17.9 2 0.02 0.99 18.0 - 19.4 1 0.01 1.00 > 19.5 0 0
n = # of tests = 101
H = mean = 11.6
* a = standard deviation = 2.4 101
0.20
0 . 10
ft 0* 12. 6* i^. o' i8. 0 21. 0 Flow Index Figure 4.2.7 - Histogram of probabilities for flow index data of Table 4.6 99*9 9^.0 9o!o 5o'.o 1 - f(lf ), percent 22.5 19-5 16.5 13.5 If W 10.5 7.5 4.5 / 0 .010,1 1.0 10 >0 50.0 8 5 7 1 997V percent Figure 4.2.8 - Kolmogorov-Smimov test for normal ity for the data of Figure 4.2.7. 102 4.2.5 Toughness index (I-j-) The toughness of a soil is an expression of its consistency as it approaches the plastic limit. The tougher the soil, the higher the resistance to crumbling at the plastic limit. The toughness index is defined as the ratio of the plastic and flow indices. In general, the higher the clay content of a soil, the higher the toughness index. The calculated test results are listed in Table 4.1 and normalized in intervals of 0.15 in Table 4.7* The histogram of probabilities and the goodness-of-fit test are given in Figures 4.2.9 and 4.2.10, respectively. Most of the test cases (87/IOI) fall within the range 1^.= (1.05 - 1.80). 4.2.6 Liquidity index (Ij^) The relative softness of a soil is indicated by the nearness of the natural water content to the liquid limit. It is defined as the ratio of the difference between the natural water content and the plastic limit, and the plasticity index. If the natural soil is at the liquid limit, the liquidity index is 1.05 if at the plastic limit, 0.0. In general, when IL is 1) >1, the soil is in a liquid state. 2) 0 < 1^ < 1* the soil is in a plastic state. 3) < 0, the soil is in a solid state. The calculated test results are listed in Table 4.1, normalized in intervals of 0.40 in Table 4.8, and the 1 0 3 Table 4.7 Normalization of I. values from Table 4.1 in intervals of 0.15 # of Normalized (Kolmogorov-Smirnov Interval tests # of tests test) < 0.59 0 0 0 o.6o - 0.74 3 0.03 0.03 0.75 - 0.89 2 0.02 0.0 5 0.90 - 1.04 5 0.05 0.10 1.05 - 1.19 8 0.08 0.18 1.20 - 1.34 16 0.16 0.34 1.35 - 1.49 21 0.21 0.55 1.50 - 1.64 29 0.29 0.84 1.65 - 1.79 13 0.13 0.97 1.80 - I.79 3 0.03 0.99 1.95 - 2.09 1 0.01 1.00 >2.10 0 0 n = # of tests = 101 M = mean - 1.42 a Q* 0 • 3 0.20 0.10 0.05 Toughness index Figure ty.2.9 - Histogram of probabilities for toughness index data of Table 4.?. 90'. 0 50.'0 1 - f(I+), percent 2.1 1.8 1.5 1.2 0.9 0.6 0.3 0 1070i 50*70 99.9 f(l+)» percent Figure ^-.2.10 - Kolmogorov-Smirnov test for nomal- ity for the data of Figure ^.2.9* 105 Table 4.8 Normalization of 1^ values from Table 4.1 in intervals of 0.40 # of Normalized (Kolmo*;orov-Smirov Interval Tests # of tests test,' f(IT) Jj <-2.81 0 0 0 -2.80 - (-)2.41 3 0.03 0.03 -2.40 - (-)2.01 1 0.01 o.o4 -2.00 - (-)1.61 3 0.03 0.07 -1.60 - (-)1.21 2 0.02 0.09 -1.20 - (-)O.81 1 0.01 0.10 -0.80 - (-)0.41 8 0.08 0.18 -0.40 - (-)O.Ol 43 0.43 o.6i 0.00 - 0.39 32 0.32 0.93 o.4o - 0.79 7 0.07 0.99 0.80 - 1.19 1 0.01 1.00 >1.20 0 0 n = # of tests = 101 M = mean = -0.22 * o = standard deviation = 0.68 106 histogram of probabilities given in Figure 4.2.11. The hypothesis of normality at the significance level of 5% is not accepted from Figure 4.2.12. This lack of normality can be attributed to the low natural water content of several samples which were composed primarily of shale fragments. The resulting high negative values for these samples are in evidence in Figure 4.2.11. From Table 4.8 it is noted that 75/101 of the cases fall within the range, I-jj = ((-) 0.40 - 0.40), indicating that most of the soils are at or near the plastic limit. Thus, increasing the natural water content only slightly will in many cases place the soil in the plastic range. As the liquid limit is approached, the greater is the tendency for the material to flow. 4.2.7 Unified Classification Figure 4.2.13 illustrates the use of the plasticity chart with the plastic index vs. liquid limit results plotted. Generally the soils plot close to the A-line which is characteristic of materials containing a mixture of silt and clay. The higher the point on the plot, the higher is the plasticity. The position of this point for each sample is given in a technical report stored in OSU's Engineering Library. The A-line on the plasticity chart is the arbitrary boundary between the inorganic clays (CL and CH) which are above the line and the inorganic silts (ML and MH) which are below. The organic clays also fall below the line but none 107 0.4 CM f-3 H 0.3 VI 1-3 H 0.2 VI T“”I Hi M 0.1 ' f t 0 Liquidity index Figure 4.2.11 - Histogram of probabilities for liquidity index data of Table 4.8. r ■■ ■¥'" ...... ■■"■I1" -r f 99-9 99.0 90.0 50.0 0.1 1 - f(IT), percent 1.6 0.8 0.0 - 0.8 - 1.6 -2.4 . / -3.2 0.01 0.1 1.0 10.0 50.0 84.1 99-9 f(IL), percent Figure 4.2.12 - Kolmogorov-Smimov test for normal - ity for the data of Figure 4.2.11. Plastic index (fo) 50 30 60 20 10 0 Figure *L.2.13Figure -Plasticindexvs. liquidlimit L C cumulativetestresults LiquidLimit (%) ML CH MH 108 109 of the soil samples have been so-classified in this investiga tion. The CL and CH, ML and MH groups are further subdivided according to their liquid limit. The CH and MH classification are attached to those soils which have a liquid limit greater than 50 and are considered to possess high plasticity characteristics. Between the liquid limit range of (30-50) is found the CL and ML categories including inorganic clay and silt of medium plasticity. Low plasticity is associated with those materials with a liquid limit less than 30. Table 4-. 9 summarizes this classification scheme as applied to this investigation and it is noted that 78/101 of the samples are in the ML and CL categories characteristic of silt/clays of medium plasticity. ^.2.8 Dry strength, dilatancy, and toughness tests These tests are largely empirical observations perform med as the consistency limits were being determined. The dry strength is the resistance of the air dried material to crumbling under finger pressure. Those materials high in silt (ML and MH) generally crumbled readily with little finger pressure whereas the clays generally showed medium dry strength (CL) or high dry strength (CH) in which case the material can be broken with the fingers but cannot be crumbled. The higher the dry strength of the material, the higher is its plasticity. For the dilatancy test a pat of dry soil was wetted until it was soft, placed in the palm of the hand, shaken 110 Table 4.9 Summary of Unified Classification # of Above the A-line Symbol Soil type cases w1 > 50 CH inorganic clay of 7 high plasticity 30 < w1 < 50 CL inorganic clay of 46 medium plasticity Wj < 30 CL inorganic clay of 1 low plasticity < 30, and CL-ML inorganic silt/clay 2 of low plasticity 4 -< I p - < 8 Below the A-line > 50 MH inorganic silt of 12 high compressibility 30 < Wj < 50 ML inorganic silt of 32 medium compressibility w1 < 30 ML inorganic silt of 1 low compressibility Ill horizontally and struck against the palm of the other hand several times. A fine-grained soil which has little to no plasticity quickly shows free water on the surface while being shaken. Rapid reaction is typical of materials high in sand and silt. The reaction decreased as the clay content of the soil increased. An extremely slow reaction or no reaction is characteristic of members of the CL and CH groups whereas the members of the ML and MH groups which have a higher silt content have a slow reaction. The toughness of the material was observed after the thread had crumbled in the plastic limit test. The CL and CH members high above the A-line have stiff threads when crumbled whereas those near the A-line have stiff threads as the plastic limit is approached but crumbled when kneaded below the plastic limit and are considered to be medium- tough. The members of the ML and MH groups form a weak thread and difficulty is encountered in lumping the soil into a mass below the plastic limit. Table 4.10 summarizes the results. It is noted that most of the materials show medium to high dry strength, a slow to no reaction to shaking, and medium to high toughness. This is characteristic of materials high in silt and clay of medium to high plasticity. 112 Table 4.10 Summary of observed plasticity characteristics Dry strength high medium low # of cases 30 66 5 Dilatancy fast slow none # of cases 5 47 49 Toughness high medium weak # of cases 20 69 12 113 4.2.9 Discussion The consistency limits for the most part indicate these slide prone soils to be mixtures of silt and clay of varying proportions with plasticities ranging from low to high but with most being of medium plasticity. The Unified Classification scheme also indicates this to be the case. Some caution must be exercised before one too vigorously relates the consistency limit data to the in-situ soil condition. Although the soil samples were collected in sites showing considerable disturbance, the soil material had not been subjected to the remolding process exhibited in the lab. The bonding between particles as well as the particle fabric is likely altered in sample preparation. The procedure of air-drying the sample may also have an adverse effect on the expanding clay minerals, montmorillonite and vermiculite (Moore, 1970 ). 4.3 Mechanical Analysis The mechanical or grain size analysis was performed using the ASTM grain size designations as given in Table 4.11. The detailed laboratory procedure is given in Figure 4.3-1- About 100 grams of representative soil sample was washed through the #10 and #200 U.S. Bureau of Standards sieves which retain the gravel and sand sized particles respectively. These fractions were oven dried at 110° C and weighed. 114 Table 4.11 ASTM grain size designations Diameter of soil Soil fraction Method of separation particle• in mm name #10 sieve 2.00 gravel #200 sieve 0.?4 to 2.00 sand Centrifugation at 1000 0.002 to 0.0?4 silt rpm for 2 minutes Decantate from silt 0.002 clay separation 115 SOIL S A M P L E Gravel * particles retained on a No. 10 sieve fo gravel determination Sand- p articles retained on a No. 200 sieve fo sand determination Silt and Clay particles passing a No. 200 sieve centrifuge at 1000 rpm I for 2 minutes w /trace wash, centrifuge at 1000 rpm for 2 mi^ p 18^ ^ air dry J Calculate amount of L I clay in Silt Clay suspension w /trace Clay t - wash, settle by X-ray gravity for 2k diffraction hours fair dry I f air dry Silt Clay ~ T Z ] f silt determination * f> clay determination Figure k.J.l - Mechanical analysis laboratory procedure. 116 The silt/clay slurry which passed the #200 sieve was centrifuged to separate the clay fraction. The separation was successful in settling the silt sized particles. At the interface however, a thin clay layer was observed and two washings were needed to achieve separation. The first washing of the silt/trace clay fraction was followed by centrifugation which again separated the silt sized particles. However, a thin clay layer still remains. The second wash ing of the silt/trace clay fraction was allowed to settle over a 2k hour period and a satisfactory separation was achieved. The settled silt fraction was oven dried and weighed. The decantates from the washings containing clay suspension were oven dried and weighed. This weight is added to the weight of the clay calculated to be present in suspension following the initial centrifugation for the percent clay determination. The composition of each fraction is calculated and grain size distribution curves drawn for each sample. These are given in a technical report stored in OSU's Engineering Library. The curves in most cases are not steeply sloped indicating that the grain size is non-uniform. This is also indicated in Table A.12 which summarizes the mechanical analysis data. Here it is seen that only six samples contained more than 75$ of a single grain size type. In most samples, no more than 50$ of any single grain size fraction is present. From the mean it is seen that the 117 TABLE 4.12 GRAIN SIZE DISTRIBUTION IN 5* INTERVALS No. of occurrences Interval Gravel Sand Silt Clay 0.0 - 4.9 21 18 3 7 5-0 - 9-9 18 16 3 9 10.0 - 14.9 6 16 4 19 15.0 - 19.9 9 15 5 14 20.0 - 24.9 9 8 9 15 25.0 - 29.9 7 9 8 11 30.0 - 34.9 6 7 13 8 35.0 - 39.9 6 4 11 6 40.0 - 44.9 3 2 13 0 45.0 - 49.9 4 1 7 4 50.0 - 54.9 1 0 6 3 55.0 - 59.9 4 2 3 0 6o.o - 64.9 2 0 4 0 65.0 - 69.9 0 1 5 1 70.0 - 74.9 0 0 2 0 75.0 - 79-9 0 0 2 1 80.0 - 84.9 0 0 1 1 85.0 - 89.9 1 0 0 0 90.0 - 94.9 0 0 0 0 95.0 - 99.9 0 0 0 0 Mean Standard deviation fo gravel 21.5 20.3 * sand 17.9 13.7 fo silt 38.0 18.0 fo clay 22.7 15.3 118 samples are higher in silt content than the other grain sizes. The clay sized fraction is next highest in percent com position followed in decreasing order by the gravel and sand sized fractions. The USDA system of nomenclature also indicates this lack of uniformity. This system names the soils according to their percentage composition as summari zed in Table 4.13. It is noted that this classification does not include the gravel sized fraction. In determining the USDA percentage composition, the percentage gravel was subtracted from 100$ and new percentage sand, silt, and clay values were calculated in order to determine the position of the soil within the USDA textural triangle. The results of this study are summarized in Table 4.14. It is apparent from the nomenclature that the grain size is distributed non- uniformly in that 81/99 soils have the word "loam" designated as part of the name, denoting a mixture of the different grain sizes. It is concluded from the mechanical analysis that the majority of the landslide susceptible soils are non-uniform in grain size, high in silt/clay, but slightly higher in percentage silt. 4.4 Shear Strength Tests The shear strength of the soil was determined experimently by the direct shear test. The purpose of this test was to obtain the soils ultimate shearing strength, r , 119 Table 4. 13 USDA textural triangle name designation fo clay range % silt range % sand range USDA name 55 - 100 0 - 40 0 - 45 clay 4o - 60 40 - 60 0 - 20 silty clay 27 - 40 60 - 73 0 - 20 silty clay loam 35 - 55 0 - 20 45 - 65 sandy clay 27 - 40 15 - 53 20 - 45 clay loam 20 - 35 0 - 28 45 - 80 sandy clay loam 0 - 12 80 - 100 0 - 20 silt 0 - 27 73 - 88 0 - 50 silt loam 7 - 27 28 - 50 23 - 52 loam 15 - 20 0 - 50 50 - 70 sandy loam 10 - 15 0 - 30 70 - 85 loamy sand 0 - 10 0 - 15 85 - 100 sand Table k.lk Summary of the USDA classification USDA name No. of cases silt loam 21 silty clay loam 18 loam 17 clay loam 11 sandy loam 11 silty clay 9 clay 7 loamy sand 3 sand 1 silt 1 121 its cohesion, c, and its angle of internal friction, A four square inch by one inch thick brass frame mold, corresponding to the shear box dimensions and the desired sample thickness was used to assure proper sample size and shape. The sample was removed from the humid room, unwrap ped, oriented upward as sampled in the field, and in the case of an intact specimen several inches were trimmed by a wire saw or knife and discarded. A representative portion of the sample was chosen and, avoiding rocks where possible, a four square inch pedestol was isolated by a wire saw. The top and bottom sides of the pedestol were carefully trimmed until a one inch thick "undisturbed" specimen was obtained. The sample was then placed in the shear box and a vertical load applied. A remolded sample was prepared by again selecting a representative portion of the sample, remolding it with the fingers, packing it into the brass mold, and transferring it into the shear box. A new sample was prepared for each test 122 Table 4. 15 Direct shear test specifications Test condition Specification Proving ring # 4472 0.32^7#/0.0001 inch calibration factor deflection Sample area 4 in^ Sample thickness 1 inch Sample shearing distance 0.4 inch Applied vertical stresses 4.63 psi and 6.83 psi Time allowed for sample 10 - 15 minutes to reach equilibrium Rate of shear 0.07 inch/minute Time required for shear 5.7 minutes 123 because of water content changes. It was found that some drainage occurs during the test and the remolded sample was sheared at a lower water content when the same specimen was used for each test. This is not desirable since the shear strengths are altered by water content changes. The applied normal stress of 6.83 Psi was chosen as a maximum stress that the landslide soils had been subjected to in-situ. This corresponds to the geostatic stress on the soil at an approximate depth of 10 feet. It was reasoned that the landslides sampled did not have failure planes exceeding this depth. Initially tests were also performed after applying vertical stresses of 1 .20, 8 .39» and 12.39 psi. It was found that in the higher cases water begins to drain from the specimen and soil squeezes out of the shear box. In the lower case expansion of the sample and distortion of the upper shear box occurred. After applying the normal stress, the sample was allowed to adjust itself to the shape of the shear box and to reach equilibrium for about 10 to 15 minutes. When the vertical dial gauge became steady, the test was performed. Proving ring readings were taken at every 0.02 inches of horizontal displacement for the first 0.1 inch and there after every 0,05 inches until a total displacement of 0.4 inches was accomplished. Peak strength generally occurred at about 0.10 to 0.15 inches of horizonal displacement and the 124 proving ring values usually leveled off or decreased. The shear test was performed at a rate of 0.07 inches per minute. The total time required for a test was about 45 minutes which included sample preparation, establishment of equili brium within the shear box, running the test, removal of the specimen from the shear box, weighing the specimen and placing it in the oven for water content determination, and cleaning the shear box for subsequent testing. In the case of intact samples, five different tests were performed: undisturbed at the specified vertical stresses, two remolded at the same vertical stresses, and one on a remolded specimen in which the water content was increased during the remolding process. The affect of the increased water content on the shear strength was then observed. The results were plotted and the shear stress, r , versus displacement curves were drawn. These graphs are given for each sample in the "Soil Sample Properties" section of the Appendix. As was the case for the evaluation of the consistency limits data, a statistical evaluation of each parameter was made in which the mean and standard deviation were determined. A normalized frequency histogram is presented for each case along with the Kolmogorov-Smirnov goodness-of-fit evaluation of the sensitivity and angle of internal friction parameters. The hypothesis of normality at the significance level of 5% was accepted for each test parameter tested. 125 ^•^•1 Ultimate shear strength ( r ) The ultimate shear strength was taken to be the maxi mum shear stress attained in a given test. The shear stress vs. deformation curves sometimes exhibit a peak. This peak was usually associated with samples which were either coarse grained or were low in water content. When a peak is evident, it generally existed for both the undisturbed and remolded cases. The ultimate shear strength test results are given in Tables 4.16 and 4.1? along with the associated water contents. In the case where a test was not performed (usually because of the inability to obtain an undisturbed specimen) the designation NA (not available), is inserted. Table 4.18 gives the listing of occurrances of the ultimate shear strength values in intervals of 1.0 psi and and are summarized in Figures 4.4.1, 4.4.2, 4.4.3» and 4.4.4, respectively. The shear strengths were not significant ly altered by the remolding process and it is of interest to note that identical mean values were obtained for both the disturbed and remolded conditions for each of the different normal stress conditions! 5.0 psi for cry = 6.83 psi, and 4.3 psi at av = 4.63 psi. However, it is noted that the undisturbed tests were performed at a higher mean water contents. The approximately one percent water content difference may have a significant effect. It is noted that in the av = 4.63 psi remolded cases where one test was (text continues on p. 135) TABLE 4M 6 ULTIMATE SHEAR STRENGTH TEST DATA FOR c - 6 .8;) psi Undisturbed Remolded Sample- # r w r w it' 1 NA NA 4.0 28.6 NA 2 4.4 25.1 4.9 25.1 0.9 3 2.9 29.0 2.2 20.0 1.3 4 3.2 25.4 5.1 25.4 0.6 5 NA NA 6.5 23-9 NA 6 6.9 22.3 6.7 22.3 1.0 7 NA NA 4.2 26.9 NA 8 NA NA 8.0 22.2 NA 9 NA NA NA NA NA 10 4.2 28.6 5-1 28.6 0.8 11 12.4 20.6 10.4 20.6 1.3 12 5-9 22.3 10.1 22.3 0.8 13 4.2 24.9 5-5 24.9 0.8 14 NA NA 4.1 28.7 NA 15 8.1 26.0 10.4 26.0 0.8 16 9-7 16.4 10.1 16.1 1.0 17 3-8 22.7 3.5 22.7 1.1 18 NA NA 4.7 23.7 NA 19 12.2 16.5 10.4 16.5 1.2 20 NA NA 5-1 . 22.1 NA 21 NA NA 6.1 28.2 NA 22 5*4 18.3 5-3 19-2 1.0 23 3.2 27.0 3-2 27.0 1.0 24 3-7 2 7*7 3.7 27.7 1.0 25 7.2 21.8 4.6 21.8 1.6 26 NA NA 6.4 22.3 NA 27 4.8 22.6 8.1 2 2.6 0.6 28 NA NA .7.8 19.3 NA 29 6.3 21.8 6.9 21.8 1.0 30 NA NA 6.6 18.8 NA 31 6.4 22.0 8.6 22.0 0.7 32 5.6 24.0 4.6 24.0 1.2 33 NA NA 7-5 21.0 NA 34 9.9 18.1 9-3 18.1 1.1 35 NA NA 5-3 23.1 NA 36 NA NA 7-1 21.8 NA 37 NA NA 6.3 20.0 NA 38 4.8 27.0 4.7 27.0 1.0 127 TABLE 4k 16 continued ULTIMATE SHEAR STRENGTH TEST DATA FORQy, = 6.83 psi Undisturbed Remolded Sample # r V r w St 39 1.2 42.4 1.2 42.4 1.0 40 8.4 29.0 6.2 29.0 1.4 41 NA NA 6.1 27.1 NA 42 NA NA 3.7 23.9 NA 43 2.1 33-6 1.6 33.6 1.3 44 NA NA 2.7 25.6 NA 45 3.9 31.1 5-2 31.4 0.8 46 2.6 35.3 2.6 38.4 1.0 47 NA NA 3.6 28.4 NA 48 2.4 37.2 2.9 35-4 0.8 49 NA NA 3-9 20.3 NA 50 5.3 24.4 4.2 25.6 1.5 51 NA NA 3.6 26.3 NA 52 1.8 41.5 2.5 38.2 0.7 53 7.3 18.5 7.9 19.9 0.9 54 NA NA 5.4 24.0 NA 55 3-3 29.2 3.6 30.6 0.9 56 2.8 27.1 2.9 25.1 1.0 57 3.4 30.4 3.1 30.0 1.1 58 3.7 31.1 2.7 38.2 1.4 59 NA NA 7.4 16.4 NA 60 1.8 34.8 2.8 29.2 0.6 61 NA NA 3.7 28.9 NA 62 3-7 26.1 3-5 27.6 1.1 63 4.9 28.9 3.7 28.9 1.3 64 2.0 39.0 3.7 39.0 0.6 65 1.5 33.2 1.1 33.2 1.3 66 NA NA 2.7 28.2 NA 67 4.6 25.5 3.6 25.5 1.3 68 NA NA 4.1 25.0 NA 69 NA NA 2.8 35-3 NA 70 NA NA 7-3 17.2 NA 71 5.4 25.2 6.1 26.3 0.9 72 4.5 26.2 3.5 26.2 1.3 73 3.1 33.9 4.3 32.9 0.7 74 4.7 25.9 4.4 25.9 1.1 75 1.6 32.9 2.1 32.9 0.7 TABLE 4.16 continued 128 ULTIMATE SHEAR STRENGTH TEST DATA FOR o,v = 6.83 psi Undisturbed Remolded Sample # T w r w St 76 4.5 38.0 3.4 38.0 1.3 77 NA NA 2.2 36.7 NA 78 2.5 28.3 2.8 28.3 0.9 79 NA NA 6 . 6 21.8 NA 80 6.3 25.7 8.8 25.7 0.7 81 NA NA 5.7 22.7 NA 82 2.6 30.2 4.4 28.1 0.6 83 NA NA 5-9 28.4 NA 84 6.5 20.0 7.2 20.0 0.9 85 4.7 3^.5 4.3 3^.5 1.1 86 2.8 31.9 3.4 31.9 0.8 87 5.8 20.4 4.4 19.2 1.3 88 8.4 25.2 9.2 25.2 0.9 89 9.8 19.4 10.6 19.4 0.9 90 NA NA 4.8 17-6 NA 91 NA NA 3.6 27.2 NA 92 6.4 24.8 5.6 24.8 1.2 93 NA NA NA NA NA 94 9.0 17.0 7-1 18.0 1.3 95 NA NA 2.9 15.8 NA 96 NA NA 2.9 15.9 NA 97 NA NA 3-2 14.6 NA 98 NA NA 3.0 14.0 NA 99 NA NA 2.7 17.1 NA 129 TABLE 4.17 ULTIMATE SHEAR STRENGTH TEST DATA FOR dy = 4.63 psi Undisturbed Remolded SAMPLE # r w r w r w St 1 NA NA 3.6 28.6 NA NA NA 2 b. 2 25.1 4.2 25.1 3.2 28.8 1.0 3 2.8 29.0 1.9 29.0 1.5 31.0 1.5 4 2.9 25.4 3.9 25.4 NA NA 0.8 5 NA NA 5.7 23-9 NA NA NA 6 6.4 22.3 6.3 22.3 4.4 26.0 1.0 7 NA NA 3-3 26.9 NA NA NA 8 NA NA 6.9 22.2 4.0 23.6 NA 9 NA NA NA NA NA NA NA 10 3-8 28.6 4.6 28.6 3.4 32.1 0.7 11 10.4 20.6 8.1 20.6 2.4 31.6 1.3 12 5.8 22.3 6.5 22.3 4.7 26.7 0.9 13 3-9 24.9 4.9 24.9 2.7 27.5 0.8 14 NA NA 2.9 28.7 2.9 28.7 NA 15 6.9 26.0 8.9 26.0 4.8 29.1 0.8 16 7-9 16.2 9.3 15.8 4.5 21.9 0.9 17 3.8 22.7 3.6 22.7 3-2 24.8 1.1 18 NA NA 4.5 23.7 2.7 27.2 NA 19 10.6 16.5 7.2 16.5 4.4 22.6 1.5 20 NA NA 4.4 22.1 4.4 23.3 NA 21 NA NA 4.4 28.2 2.1 34.7 • NA 22 NA NA 4.4 28.2 2.1 34.7 1.2 23 3.1 27.0 2.6 27.0 1.5 28.7 1.1 2b 3.6 27.7 3-5 27.7 2.7 29.0 1.0 25 5-9 21.8 4.1 21.8 3-9 23.3 1.4 26 NA NA 5.0 22.3 4.9 22.4 NA 27 4.6 22.6 7.6 22.6 4.4 27.2 0.6 28 NA NA 6-7 19.3 4.6 21.1 NA 29 6.0 21.8 6.4 21.8 3.7 25.7 0.9 30 NA NA 5-6 18.8 5.0 21.2 NA 31 5.2 22.0 7.3 22.0 4.5 23.7 0.7 32 4.6 24.0 3.9 24.0 2.7 28.2 1.2 33 NA NA 6.0 21.0 4.9 25.5 NA 3b 7.4 18.1 7.1 18.1 5.1 21.3 1.0 35 NA NA 3-8 23.1 3.1 26.9 NA 36 NA NA 6.7 21.3 3.5 26.1 NA 37 NA NA 5-3 20.0 NA NA NA 38 4.1 27.0 3.7 27.0 3.3 28.6 1.1 130 TABl!E 4.17 continued ULTIMATE SHEAR STRENGTH TEST DATA FOR = 4.63 psi Undisturbed Remolded Sample 4 r w r w r w St 39 1.1 42.4 0.9 42.4 NA NA NA 4o 8.3 29-0 5-4 2 9 .O 2.9 31.0 0.7 41 NA NA 4.5 NA 4.3 32.4 0.9 42 NA NA 2.7 NA 2.7 25.8 NA 43 3.2 33-6 1.1 33-6 NA NA 1.0 44 NA NA 2.4 NA NA NA 1.0 45 1.5 33-5 5.1 30.3 4.3 32.3 1.3 46 2.0 34.4 2.0 37.8 1.9 38.4 1-5 47 NA NA 2.6 28.4 NA NA NA 48 2.2 34.7 2.7 37.8 2.4 40.5 0.8 49 NA NA 2.8 20.3 1.8 23.1 NA 50 3.6 26.3 3-4 26.3 1.5 30.6 1.1 51 NA NA 3.5 27.4 1.7 29.1 1.5 52 1.6 41.0 2.4 41.4 1.1 48.8 0.6 53 5.8 18.3 6.1 20.1 4.7 25.8 1.3 54 NA NA 4.6 23.9 3-9 25.7 NA 55 3*3 30.7 3.4 30.6 2.6 31-7 1.3 56 2.4 26.1 2.4 28.1 NA NA NA 57 2.7 33-3 2.4 34.9 3.0 34.4 NA 58 3-6 35.6 2.5 34.7 1.5 38.5 NA 59 NA NA 7-6 15.7 5-1 20.4 0.7 6o 1.5 33-1 2.0 28.9 2.0 28.9 1.5 61 NA NA 3-6 28.5 NA NA 0.7 62 2.6 25.6 2.4 24.6 2.4 27.4 0.9 63 4.7 29-1 3-2 28.3 3.2 22.3 0.9 64 1.9 39-0 3-2 39.0 1.5 48.1 1.2 65 1-3 33.2 1.0 33.2 1.0 23.2 1.5 66 NA NA 2.5 28.2 NA NA NA 67 3-3 25-5 2.7 25.5 2.5 29.9 NA 68 NA NA 3.8 25.0 2.2 26.8 1.3 69 NA NA 2.0 35-3 2.1 35.3 NA 70 NA NA 6.0 17.2' 4.2 26.1 0.6 71 4.4 24.8 6.1 26.5 4.2 28.2 1.0 72 4.0 26.2 2.7 26.2 2.4 30.4 NA 73 3-1 34.2 4.3 33.2 3.3 35.5 0.8 74 3*6 25-9 4.1 25.9 4.1 29.1 NA 75 1.3 32.9 1.5 32.9 2.9 33.5 1.1 131 TABLE 4.17 continued q ULTIMATE SHEAR STRENGTH TEST DATA FOR a = 4.63 psi Remolded Undisturbed s Sample # r w r w r w 76 4.2 38.0 3.1 38.0 NA NA 1.3 NA 77 NA NA 2.1 36.7 NA NA 78 2.5 28.3 2.7 28.3 1.5 31.4 0.9 NA 79 NA NA 6.3 21.8 3.6 28.3 80 4.8 25.7 7.6 25.7 4.4 28.5 0.6 81 NA NA 4.9 22.7 2.4 25.9 NA 82 2.4 29.9 4.1 28.2 2.2 33.6 0.6 83 NA NA 5.3 26.4 3.0 31.3 NA 1.0 84 5-9 20.0 6.1 20.0 4.7 22.5 1.1 85 4.6 34.5 4.1 34.5 2.8 33.6 86 2.0 31.9 2.4 31.9 NA NA 0.8 87 4.7 20.5 3-3 19.8 NA NA 1.5 88 7.8 25.2 8.1 25.2 5-1 30.1 1.0 0.8 89 8.1 20.3 9.5 19.3 5-1 23-2 90 NA NA 4.1 17.7 3.7 18.9 NA 91 NA NA 2.5 27.2 2.5 27.2 NA 92 5-5 24.8 5.3 24.8 4.6 29-0 1.2 93 NA NA NA NA NA NA NA 94 7-3 17.4 5-5 17.4 3-5 19-4 1.3 95 NA NA 2.3 17.1 NA NA NA 96 NA NA 2.3 12.9 2.3 17.5 NA 97 NA NA 2.5 15.6 2.0 18.8 NA 98 NA NA 2.7 14.9 2.1 19.5 NA 99 NA NA 2.4 17.8 2.2 20.3 NA TABLE 4 .18 132 — LIST OF OCCURRENCES OF r VALUES FROM TABLES 4.16 4.17 IN INTERVALS OF 1.0 psi cfv =» 6.83 psi av = 4.63 psi ^ of cases # of cases psi r r r r r Interval undisturbed remolded undisturbed remolded remolded o.o-o.9 0 0 0 0 1 l.o-l.9 5 2 7 4 10 2.0-2.9 9 17 10 26 27 3.0-3-9 10 21 12 18 16 4.0-4.9 11 15 11 16 21 5-0-5.9 6 11 7 9 6 o .0-6.9 6 11 3 13 0 7.0-7.9 2 9 4 5 0 8.0-8.9 3 4 2 3 0 9.0-9.9 4 2 0 2 0 10.0-10.9 0 5 2 0 0 11.0-11.9 0 0 0 0 0 12.0-12.9 1 0 0 0 0 13.0-13.9 1 0 0 0 0 14.0 0 0 0 0 0 £ 5. 0 psi 5-0 p 3i 4.3 psi 4.3 p si 3*2psi * cr 2.7 psi 2.3 p si 2.2 psi 2.0 p 3i 1.2psi n 58 97 58 97 81 Water content £ 26.9% 25-50 27.0# 25.6$ 27 • 7% ■it er 6 .3% 6.1% 6.2% 6.2% 6.1% n 58 97 58 97 81 133 o.6o c\j 0.40 ' 0.20 VI 0.08 C* 0.06 ft 0.04 0.02 (psl) Figure 4.4.1 - Normalized histogram of undisturbed shear strength values where cr * 6.83 psi 0.60 0.40 V| °*20 •* 0.10 VI 0.08 0.06 ft o.o4 0.02 0 r (psi) Figure 4.4.2 - Normalized histogram of undisturbed shear strength values where crv = 4.63 psi. 134 "i i , i , i , . | , —T—ii.,.- T. ^ 0.60 • c\i . *« o.4o Jl 1 vl 0.20 ■ 1 1 • 1 1 ^0.08 1 0.06 1 : : h ft ■ | 1 o.o4 1 1 0.02 • i! 1! 1 • >ii 0 1.0 3.0 u-^7TAf T — U'"J— ^ (psi) Figure 4.4.3 - Normalized histogram of remolded shear strength values where crv = 6.83 psi. • • I I I I I I I 1 ■ I I I | |...| o.6o j^o.4o VI 0.20 •* 0.10 vl 0.08 *>ho.o6 L n 0.04 0.02 0 — i i I .-.O.. i— i i . 1 , 1, . i i 11I „I,, I ,,-1,1.. 1,1 ,1 1.1 Jfp, TTo 370 5.0 7.0 9.0 li.O’ 13.0 T (psi) Figure 4.4.4 - Normalized histogram of remolded shear strength values where crv = 4.63 psi. 135 performed after addition of extra water during remolding, an approximately two percent higher mean water content re sulted in an approximately one psi lower mean ultimate shear strength value. Water content differences apparently result from drying during the remolding phase of sample preparation. The higher shear strength values are associated with samples containing hard shale fragments or having low water content. The lower values are associated with homogeneous fine grained, high water content specimens. 4.4.2 Sensitivity (S^) The sensitivity of a specimen, generally associated with soils high in clay content, is defined as the ratio of the peak shear strength of an undisturbed sample to the maximum value of the remolded shear strength of the same sample. The sensitivity was determined for a soil sample where applicable for both the a' = 6.83 psi and the ay = 4.63 psi test conditions as was given in Tables 4.16 and 4.17. In Table 4.19 is given the normalization of these values in intervals of 0.25* It is noted that the mean value is 1.0 for both test conditions although the standard deviation of approximately 0.25 indicates that some of the soils gained strength on remolding whereas others lost strength. Since most of the values are close to one, it is deduced that the remolding process had 126 TABLE 4-. 19 NORMALIZATION OF St VALUES FROM TABLES 4.16 and 4.17 IN INTERVALS OF 0.25 for a = 6.83 psi: V Normalized # of Kolmogorov-Smirov Interval # of tests tests test <0.49 0 0 0 0.50-0.74 10 0.17 0.17 0.75-0.99 15 0.26 0.43 1.00-1.24 18 0.31 0.74 1 .25-1.49 12 0.21 0.95 1 .50-1.74 3 0.05 1.00 > 1.75 0 0 n = 1.0 * a = 0.25 n = 58 for crv = 4.63 psi: ■ Normalized # of Kolmogorov-Smirov Interval # of tests tests test <0.49 0 0 0 0.50-0.74 10 0.17 0.17 0.75-0.99 15 0.26 0.43 1.00-1.24 18 0.31 • 0.74 1.25-1.49 8 0.14 0.88 1.50-1.74 7 0.12 1.00 >1.75 0 0 f* = 1.0 a* = 0.27 n = 58 137 little effect on the shear strength of these soil samples. This is due either to the disturbed state of the landslide susceptible soil as it exists in the field or to disturb ances which occurred during soil sampling and/or laboratory specimen preparation. 4.4.3 Angle of internal friction (0) and cohesion (c) ~~ Since the shear test is being performed as a quick, slightly consolidated, undrained test, a portion of the normal stress is being carried by the pore water. The greater the degree of consolidation, the greater will be the intergranular stress. To some degree therefore, the amount of internal friction and cohesion within the soil mass will be affected by the amount of undissi pated pore water pressure present in a particular test situation. The 0 and c parameters were determined by plotting the ultimate shear strength values vs. the applied normal stress values. The angle of internal friction, 0, is the slope of this curve and the cohesion coefficient, c, is the value of the y-intercept. This graph is given for each sample in a technical report stored in OSU's Engineering Library. The values of c and 0 are tabulated in Table 4.20. The values for 0 are normalized into intervals of 5-0° in Table 4.21, and the normalized histograms and 138 TABLE 4.20 0 AND c TEST DATA Undisturbed Remolded Sample 0 c 0 c 1 NA NA 10.6 2.7 2 10.8 3.4 18.1 2.6 3 4.2 2.4 3-8 1.6 4 6.0 2.5 18.4 1.4 5 NA NA 20.2 4.0 6 12.6 5-4 8.5 5.6 7 NA NA 21.1 1.5 8 NA NA 27-0 4.6 9 NA NA 14.3 3-4 10 10.1 3.0 14.3 3-4 11 53-8 4.1 50.8 2.7 12 10.6 4.7 16.5 4.7 13 9.0 3.1 16.5 3.5 14 NA NA 29.0 0.4 15 28.8 4.3 33.6 5.9 16 39.1 4.1 20.4 7.5 17 0.0 3.8 4.4 3-1 18 NA NA 6.7 3-9 19 38.2 6.9 55.1 0.6 20 NA NA 18.8 2.8 21 NA NA 37.5 0.8 22 2.1 5.2 24.0 2.2 23 2.1 2.9 6.2 4.5 24 4.2 3.2 13.3 3-0 25 31.1 3.0 32.7 3.0 26 NA NA 32.7 2.1 27 6.7 4.0 13.5 6.5 28 NA NA 25.3 4.6 29 8.3 5.3 11.6 5.6 30 NA NA 24.3 3.4 31 28.8 2.6 30.4 4.6 32 23.4 2.6 19.5 2.2 33 NA NA 33-8 2.9 34 48.4 2.2 43.8 2.2 35 NA NA 33.8 0.0 36 NA NA 10.1 5-9 139 TABLE 4.20 continued Sample 0 c 0 c 37 NA NA 26.1 3.0 38 18.4 2.6 24.0 1.7 39 4.2 0.7 7-1 0.3 40 2.3 8.1 21.3 3.6 41 NA NA 3^.3 1.4 42 NA NA 24.2 0.7 43 16.5 0.1 12.6 0.1 44 NA NA 8.5 1.7 45 18.3 1.6 4.5 7.2 46 16.5 0 .6 14.5 0.8 47 NA NA 23.^ 0.6 48 4.2 1.9 2.2 5.2 49 NA NA 25.7 0.6 50 37.9 0.0 20.4 1.7 51 NA NA 2.3 3.3 52 6.5 1.1 4.4 2.0 53 35.2 2.5 39.0 2.3 54 NA NA 20.2 2.9 55 1.8 3-1 4.4 3.0 56 9.6 1-7 14.3 1.2 57 18.4 1.4 16.0 1.2 58 1.8 3.4 6.5 1.9 59 NA NA 16.5 5.4 6o 14.0 0.4 20.2 0.3 61 NA NA 4.2 3-2 62 25.5 0.2 25.5 0.2 63 4.7 ^.3 12.3 2.2 64 4.2 1.5 12.8 2.1 5.5 0.8 3.2 0.7 & NA NA 4.2 2.2 67 29.4 0.7 22.0 0.8 68 NA NA 6.2 3.3 69 NA NA 19.3 0.5 70 NA NA 29.6 3-^ 71 25.7 2.2 0.0 6.1 72 12.6 3.0 20.2 0.7 73 0.0 3.1 0.0 4.3 7^ 26.6 1-3 6.2 3.6 140 TABLE 4.20 continued tf> AND c TEST DATA Undisturbed Remolded Sample 0 c 0 c 75 7-3 0.7 15.3 0.2 76 6.7 3-7 3.4 2.4 77 NA NA 3.4 1.8 78 1.3 3.6 1.0 2.6 79 NA NA 9 ‘? 5.5 80 35-0 1.6 27.4 5.2 81 NA NA 20.2 3.2 82 6. 5 1.8 3.6 6.2 83 NA NA 16.5 3.9 84 15-7 4.6 27.6 3.7 85 4.2 4.2 4.2 3-8 86 19.3 0.4 23.8 0.4 87 25.5 2.5 27-2 0.9 88 14.8 6.6 25.5 5-9 89 43.8 3.6 25.5 7-3 90 NA NA 18.4 2.5 91 NA NA 26.4 0.2 92 10.1 4.7 9-0 4.5 93 NA NA NA NA 94 37.7 3.7 35.0 2.3 95 NA NA 15.0 1.1 96 NA NA 16.5 0.9 97 NA NA 18.4 1.0 98 NA NA 8.5 2.0 99 NA NA 7.8 1.8 l4l—i TABLE 4.21 NORMALIZATION OF 0 VALUES FROM TABLE 4.20 IN INTERVALS OF 5.0 DEGREES undisturbed: Normalized # Kolmogorov-Smirov Interval # of tests tests test 0 .0-4.9 15 0.26 0.26 5.0-9.9 10 0.17 0.43 10.0-14.9 8 0.14 0.57 15.0-19.9 7 0.12 0.69 20.0-24.9 1 0.02 0.71 25.0-29.9 7 0.12 0.83 30.0-34. 9 1 0.02 0.85 35.0-39.9 6 0.10 0.95 40.0-44.9 1 0.02 0.97 45.0-49.9 1 0.02 0.99 50.0-54.9 1 0.02 1.00 55.0 0 0 £ = 16.3° * _ 0 * - 13.7 n = 58 remolded: Normalized # Kolmogorov- Smir o-v Interval # of tests tests test 0.0-4.9 18 0.19 0.19 5-0-9.9 13 0.13 0.32 10.0-14.9 11 0.11 0.43 15.0-19.9 14 0.14 0.58 20.0-24.9 14 0.14 0.72 25.O-29.9 16 0.17 0.87 30.0-34.9 5 0.05 0.94 35.0-39.9 3 0.03 0.95 40.0-44.9 1 0.01 0.98 45.0-49.9 0 0.00 0.98 50.0-54.9 1 0.01 0.99 55.0-50.9 1 0.01 1.00 ^ = 17-7 ‘k ( O =11.5 n = 97 142 goodness-of-fit tests given in Figures 4.4.7» 4.4.8, 4.4,9» and 4.4.10, respectively. For both the undisturbed and remolded cases, the mean value for is approximately 17°. The magnitude of c is dependent on the angle of internal friction, , and on the magnitude of the ulti mate shear strength. The mean values of 5-0 psi a n d '4.3 psi ultimate shear strengths at the two different normal stresses, combined with the mean value of 16.3° for , gave a mean value of 3*° psi for c, the cohesion coefficient in the undisturbed case. For the remolded case, the same mean ultimate shear strength values combined with a mean value of 17.4° for 0.2 0.1 0 0.5 l.o 1.5 2.0 Fig. 4.4.5«--Normalized histogram of sensi tivity values. 1.00 o.oi o. l.o io.o 50.0 84.1 99 . 9 ' percent Fig. 4.4.6.--Kolmogorov-Smirov test for normali ty for the data of Figure 4.4.5. JL 0.2^ CM R 0.21 0.18 VI P 0.15 -e.*3 0.12 VI 0.09 Q P 0.06 -©■ 'p 0.03 T-- 1-1 0 I n ■ I ■ I. ■■I J - 10.0 20.0 30.'o W o 50. 0 *o.o 9UD Fig. ^.4-. 7 . --Normalized histogram of undisturbed angle of internal friction values. T A 99.*9 99! 0 90?o 5oio 0.1 1 - f (^UD)* percent 55.0 50.0 ^5.5 H-o.o 0 U D 3 5 . 0 30.0 25.0 20.0 15.0 10.0 5.0 / 0.01 0.1 1.0 10.0 50.0 84TT" 99-9' f(0U D ). percent Fig. 4.^.8.--Kolmogorov-Smirov test for normality for the data of Fig. 4 .4 .7 . 1 45 0.20 0.15