INTERNATIONAL SOCIETY FOR SOIL MECHANICS AND GEOTECHNICAL ENGINEERING

This paper was downloaded from the Online Library of the International Society for Soil Mechanics and Geotechnical Engineering (ISSMGE). The library is available here: https://www.issmge.org/publications/online-library

This is an open-access database that archives thousands of papers published under the Auspices of the ISSMGE and maintained by the Innovation and Development Committee of ISSMGE. 8 SUB- SECTION I b GEOLOGY AND SOIL MECHANICS

I b 1 ENGINEERING USES AND LIMITATIONS OF PEDOLOGY FOB REGIONAL EXPLORATION OF SOILS HANS F. WINTEBKOBN

SUMMARY. The field of pédologie science is defined and briefly described. It is indicated how the store of knowledge acquired and organized by this science can be of direct usefulness to the engineer engaged in regional aoil exploration and in the engineering use of data obtained in such exploration. Specific reference is made to the methodique employed for this purpose by the State Highway Departments o f Michigan and M issouri, re sp ectively. Detailed description of the indicated use is found in the references given. Pedology for the purpose of this paper vironment. 11). Glioke 3) employed the term is conceived in its widest sense as the "forces" in a transcendental sense, rather science which concerns itself with: than in accordance with the physical meaning assigned to this term in the exact natural 1. Soil formation or the characteriza­ sciences. This, of course, is to be expected tion of soil systems as functions of: in pioneering work, but must give way to more (a) climate symbol: (cl) exact formulations. (b) organisms " (o) As a result, of the prevailing, somewhat (c) topography " (r) confused situ a tio n , Jenny 4) one of the most (d) parent material " (p) astute and impartial scholars in this field, (e) time " (t) despairs of the possibility of a causal cor­ 2. Classification of soil systems within relation between a particular soil-type and the broad frame of climatic influences, the independent soil forming factors, and but on the pragmatic basis of the soil contents himself with a purely functional cor­ type as a specific observable unit: relation, expressing the relation of any or all properties (s) of a particular soil type 3« Mapping of S o il areas in accordance to those factors as: with a pragmatic classification, such as the U.S. Soil Survey system. s = f (cl, o, r, p, t....) Of these three phases, the second and Jenny's approach, though logically jus­ third are of most direct value to the soils tified, is sterile at least as far as the en­ engineer, because of their pragmatic basis. gineer's problem is concerned. The engineer The first, because of its scientific complex­ must be able to understand or at least to ity, is in a very unsettled condition, and a picture what is going on. Logical understand­ great diversity of opinion rules among the pe­ ing or even picturing of any function of five dologists themselves, not only concerning the independent variables is impossible, especial­ meaning of the phenomena involved, but even ly if the independent variables may range from concerning the proper approach to the problem. the complexity of climate to the fundamental 4) sim p licity of tim e. The problem must be sim­ Because of this situation, the soil en­ plified until the phenomena can be pictured, gineer may receive little direct help from even if a succession of pictures be necessary the professional students of soil formation; instead of but one. A more logical approach on the other hand, he should be vitally in­ to the problem is as follows: terested in the problem itself because the same or closely related factors, which form 1. Benouncing the attempt of bringing the soils, act on the surfaces of exposed structur­ whole world of s o ils in to one formula , es or even throughout the entire structure as and concentration instead, on the forma­ in pavement b a se -so il systems. For th is reason tion of the most important soil types. the problems confronting the student of soil 2. Seduction of the so-called soil-forming genesis will at least be formulated at this factors to something that, can be visualized p lace. and expressed in terms of physics and The work of many scholars of d iffe re n t chemistry. specific interests and leanings has resulted in the recognition that specific soil proper­ Soil formation represents primarily a ties, as well as their integration to soil chain of chemical reactions. In chemical reac­ types, are functions of the above named five tio n one is in terested in soil-forming factors which may vary independ­ 1. Total energy involved in changing initial ently of each other. Becognition of these fac­ to final material. tors leads to the next step, concerning the reason and mechanism of th e ir functioning. 2. Bate of reaction, as influenced by environ­ Joffe 5) differentiates between active mental factors, positive and negative cata­ and passive soil formers: the passive ones lysis, concentrations, etc. concerned with the mass and the source of the The total energy change involved can be mass, the topography and the age, and the ac­ ascertained experimentally by means of calori- tive ones supplying the energy that acts on metric determination of the difference of the the mass. The latter include the elements of heat of solution of the parent material nnfl the biosphere, atmosphere and, partly of the the soil under consideration, respectively,in hydrosphere. Joffi's basic intention is good a suitable acid, in a similar way as the hydra­ but the association of the respective factors tion rate of concrete is checked by determina­ is illogical. tion of heats of solution. To Vilensky and other Bussian workers, Bates of reaction are influenced by tem­ soil-forming factors are synonymous with en­ perature, concentration and catalysis. In 9

TABLE 1. ITEMS GIVEN IH SOIL ENGINEERING DATA AMD RECOMMENDATIONS IN THE FIELD MANTTAL OF THE MICHIGAN STATE HIGHWAY DEPARTMENT

Soil Series Name :

n o •H Brief Description of typical profile : -P 00 1.) adapted to winter grading : yes or no •HU 0> 2.) normal depth to water table s in feet *po CÚ 3 .) subject to wind erosion yes or no A o

recommended location of grade line with respect to natural ground: protection of slopes recommended: No or type estimated percent of boulders (rock excavation) 0) stabilization of subgrade recommended for flexible su rfaces: »d yes or no, or percent <0 removal of topsoil recommended: yes or no, remarks, & estimated lineal feet of frost heave excavation per 1000 fe e t of cut below natural ground elevation: estimated lineal feet of open joint sewer per 1000 fee t of cut below natural ground elevation: a © 0

Source of borrow: yes or no, extent recommended method of restoring borrow pits where necessary, percent of shrinkage method of construction:

o sand-gravel material : yes or no « source of suitable stabilizing material: yes, no, type o possible source of gravel: yes, no o source of topsoil: no, poor, feir, good, excellent. (0 ® «

dividing climate into its temperature and micro-climate is taken into account, topogra­ moisture components, we obtain the temperature phy, as such, ceases to be an independent fac­ and concentration factors influencing the tor in our equition, except for its bearing reaction. The pattern of climate specially on erosion. with respect to the moisture content of the For the picture as a whole, it is impor­ soil, indicates whether the reaction rates tant that plants utilizing solar energy may, are primarily determined by slow molecular depending upon their type and by means of and ionic diffusion processes (uniform moist­ their root system, return elutriated materials ure pattern) or by faster convection proces­ to the reaction system. Thus, a dynamic equi­ ses (non-uniform desiccation and flooding pat­ librium in the soil properties may be reached terns). Topography by controlling amount of at a point where the potential chemical energy precipitation loss is important only as far involved in further decomposition, equals that as the relationship between macro-and micro­ fraction of the solar energy utilized by the climate (i.e. temperature and moisture condi­ plants in counteracting natural depleting tion actually present in the system and not processes. somewhere in the surrounding atmosphere 2)) This picture, of course, gives only a is involved. If, as should be done, only the general scheme, but i t i s thought to be su f­ 10 TABLE 2.

ENGINEERING PROPERTIES SUGGESTED BY THE NAME OF CLARKSVILLE GRAVELLY LOAM 9)

00 o (1) Consists of 3 horizons p CQ (2) Horizon No. 1 - gravelly silt loam - normally 5 to 8 inches in •H u thickness. 0) Horizon No. 3 - gravelly silty clay - normally 20 to 30 inches -p (3) o in thickness. cd (4) Horizon No. 5 - gravelly clay - widely variably in thickness. a ■C o (5) Pockets of very active stone-free red clay are common and are H chiefly responsible for subgrade failures in the region. cd (6) Contains much clay with a lower liquid limit above 65 which is

(7) Backslopes in horizons 1 and 3 will stand at 1 to 1. (6) To prevent backslope slides in deep cuts involving horizon 5 they should be laid back at 2 to 1.

(9) Embankments of Clarksville, ordinarily lying on dolomite beds Slopes in an area of f a ir ly rugged r e li e f must be c a re fu lly drained to prevent slides if constructed on inclined surfaces.

(10) Horizons 1 and 3 compact to high weights per cubic fo o t at low optimum moisture contents, No. 3 being the highest and most a sta b le . •H •P (11) Horizon 5 compacts to a low weight per cubic foot at a high op­ O cd timum moisture content. Standard compaction tests must be made Pi in four l i f t s . Such m aterial must be compacted in very th in so layers in the fill and care must be exercised not to exceed the o optimum moisture content.

(12) Unless on inclined rock surfaces, if properly drained, the Clarksville gravelly silt loam provides form fill foundation. Foundation

ficient to indicate a way for understanding usefulness to the engineer, the following and for scientific treatment of the dynamics treatment is restricted to the soil classific­ of soil formation. As previously pointed out, ation system of the U.S. Soil Survey 8),. The understanding of these dynamics is of more basic physical unit of this system is the soil direct importance to the engineer than to the type. Marbut 6 ). 7) l i s t s the follow in g fe a ­ general soil scientist. tures as essential to the definition of a soil unit: number, color, texture, structure, thick­ PEDOLOGIC SYSTEM OF SOIL CLASSIFICATION. ness, chemical composition and relative arrange­ D ifferen t methods of pedological c la s­ ment of the horizons, and geology of the parent sification have been employed in different m aterial. countries. Because the U.S. have made the The soil type always has at least 2 names: greatest qualitative and quantitative effort, a SERIES NAME and a CLASS (textu re) NAME. and because it appears to be of greatest direct Example: Sassafras Loam 11 TABLE 3

Soil Categories 6)

Category VI Pedalfers (VI-I) Pedocals (VI-2)

S o ils from m echanically com­ Soils from mechanically minuted m aterials. comminuted m aterials. S o ils from e i a l l i t i c decompo­ Category V sition products. S o ils from a l l i t i c decomposi­ tion products.

Tundra Chernozems Podzols Dark brown s o ils Cray-brown podzolic soils Brown s o ils Category IV Red s o ils Gray s o ils Yellow soils Pedocalic soils of Arc­ Prairie soils tic and tropical re­ Lateritic soils gions. Laterite soils

Groups of mature but related Groups of mature but r e ­ soil series lated soils series Swamp s o ils Swamp s o ils G lei s o ils Glei soils Rendzinas Rendzinas Category III Alluvial soils Alluvial soils Immature s o ils on slopes Immature s o ils on slopes Salty soils Salty soils Alkali soils Alkali soils Peat s o ils Peat s o ils

Category II Soil series Soil series

Category I Soil Units or types Soil units or types.

THE SOIL SERIES: 6. Loamy sand 16. S ilt y clay loam All soils having identical properties 7. Loamy fin e sand 17. Clay loam with respect to the items listed below are 8. Loamy very fine sand 18. Sandy clay classified in the same soil series. 9. Coarse Sandy loam 19. S ilt y clay 1) Parent material: (a) solid rock - igneous, 10. Sandy loam 20. Clay sedimentary, metamor- phic. If a soil contains considerable gravel, (b) loose rock - gravels, shale or stone the term gravelly, shaly or sands, clays. stony is added to designate the soil type. It is obvious that the ability to re­ 2) Special features of parent materials, resi­ cognize a soil in the field as belonging to dual or transported by wind, water or ice. a certain type and series, make available 3) Topographic position: rugged to depressed. automatically a tremendous store of knowledge concerning the respective soil. It is of 4) Natural drainage: excessive to poor. greatest practical importance that for such 5) Profile characteristics. recognition in the field only few tools are required, and the most important of these are The different series usually- carry geo­ the five senses. On the other hand, this re­ graphic names in d icatin g the location where cognition is an art and can only be taught they were first recognized and described. and learned in the f ie ld . "The engineer must learn his soils". 10) THE SOIL CLASS (TEXTURE). The pedologic classification being of a Considerable d e ta il i s employed in naming qualitative rather then of a quantitative the various soil classes viz: character, can, of course, not give all the data which the engineer likes to have, such 1. Coarse sand 1 1. Fine sandy loam as maximum density and optimum moisture con­ 2. Sand 12. Very fin e sandy tent of compaction, susceptibility to differ­ 3. Fine sand 13» Loam /loam ent types of stabilization, required spacing 4. Very fin e sand 14. Silt loam of drainage t i l e s , e tc . However, once these 5. Loamy coarse sand 15. Sandy clay loam additional properties have been determined 12 for a certain soil type by engineering tests ty, alcalinity, chemical composition of clay and (or) from experience, they continue to be fraction, presence or absence of a lime accu­ of value for any future encounter with the mulation zone, etc., are also general indices respective soil type. Especially in soil of the subceptibility of soils to different stabilization, many phenomona which cannot be types of stabilization. It should be mentioned explained by the results of the standard engi­ in this connection, that a one-million dollar neering tests, can be correlated with, if not airport concrete pavement is desintegrating at explained by the soil type. the present time for the sole reason that the A truly splendid example of engineering engineer-in-charge neglected to utilize avail­ use and supplementation of the pedologic soil able pedologic knowledge with respect to a classification is presented by the Michigan high sodium and magnesium su lfa te content of State Highway Department 1). The Field Manual the underlying soil. Because of this potential of Soil Engineering of this Department is the role of the higher categories of soil classif­ best available guide for practical application ication as warning signs and as guiding posts of pedology. Among other features, this man­ for country or continent wide planning the ual contains descriptions in sufficient detail higher categories in the pedologic system are of the profile characteristics (with schematic listed in Table 3» presentation) of the 104- important soil series found in the State of Michigan. Also in a CONCLUSIONS. rather extensive table, for each cf these 104 soils, 19 specific engineering items are list­ From the evidence presented in this paper . ed under the respective headings given in and in the references given it is obvious that Table 1. pedology in itp three phaseB can be of great The Michigan experience shows that the usefulness to the highway and airport engineer only limit in the practical use of the pedolo­ or in general to the engineer who deals with gic classification for highway and airport shallow foundations. This helpfulness may be engineering is the capacity and willingness (a) direct and immediate in reconnaissance and of the engineer to learn and use this method. soil survey, and (b) indirect but no less im­ Another pioneer in the use of the pedologic portant in country and continent wide planning system of c la s s ific a tio n amalgamated with en­ for spotting potential trouble areas and for gineering experience and testing is the State in d icatin g most probable types of required s o il Highway Department of Missouri 9)* The Mis­ treatment for economic highway and airport souri way is presented in Table 2. More re­ construction. cently, the States of Indiana, North-Carolina, New York, New Jersey and others have entered actively into the utilization of pedological REBJ|RENCES. knowledge for highway construction purposes. 1) "Field Manual of Soil Engineering", Michi­ For most of the counties of the United gan State Highway Department, Lansing, States, soil survey maps are available. These Mich. 1946 serve for the first orientation of the soils 2) Geiger, Rudolf: "Das Klima der bodennahen engineer; however, since no general map can Luftschicht" Die Wissenschaft, 78. Braun­ ever be made in all the detail necessary for schweig, Vieweg 1927 construction purposes, the soil engineer must 3) Glinka, K: "Die Typen der Bodenbildung , make his own detail map based on his ability ihre Klassifikation und geographische Ver­ to recognize soil types. Of course, the soil breitung", Gebr. Borntraeger, Berlin 1914. survey party will also take soil samples; but 4) Jenny, Hans; "Factors of Soil Formation". this samples w ill rather be taken whenever a Mc-Graw-Hill Book Co. Inc. New York and variation in soil type is recognized. This London, 1941. helps to cut down considerably the number of 5) Joffe, J.S. "Pedology", Rutgers University samples which must be taken and tested per Press, New Brunswick, N.J. mile. For detailed description of soil survey 6) Marbut, C.F. "The Contribution of Soil procedure and reporting, reference is made to Surveys to Soil Science. Soc. Prom. Agr. the respective soil manuals of Michigan and M issouri. Sei. Proc. 41, 116 - 142 (1920) 1921. While pedologic knowledge is most useful 7 ) Marbut, C.F. "A scheme fo r s o il c la s s if ic ­ in the exploration of highway and airport ation. Proc. First Int. Congr. Soil Science, sites, Wooltorton 12) has shown that cracking 4, 1-31, 1928. of light buildings in Burma could be correlat­ 8) Marbut, C.F. Soils of the United States, ed with certain soil types. In Missouri, the Atlas of American Agriculture, Part. Ill, same phenomenon was observed in rather drastic Washington D. C. 1935« forms during the long drought in the Thirties 9) S o ils Manual, D ivision o f Geology and on Buildings up to three and more stories high S o ils , Missouri S tate Highway Department, founded on Putnam soil. In a less drastic form Jefferson City, Mo. 1941. opening and closing of cracks of a chapel at 10) Stokstad, 0. "Get Acquainted with your Concord, Mo; founded on the same soil* paral­ Soils". "Better Roads"., July 1941, 15 - leling desiccation and wetting, has been ob­ 17,3 1. served and recorded for more then thirty years. 11) Vilensky, D.G. "Concerning the principles So far, utilization of pedology has been of genetic soil classification. Contribu­ treated only with respect to the soil type and tions to the study of soils of Ukraina, soil series. In the pedologic system, higher 6s 129 - 151» Kharkov, U.S.S.R. 1927. categories of classification exist. The higher 12)—Wooltorton, D. "A preliminary investig­ the category, the less the number of actual ation into the subject of foundations in properties which can be indicated by the place the blackcotton" and "Kyatti" soils of the of the soil in the higher category."But, it so Mandelay d is t r ic t , Burma". Proc. In t. Conf. happens, th at the in d ices employed fo r place­ 5.M. &. F.E. I ll: 242-256, Harvard Univers­ ment in the higher categories, such as salini­ it y , 1936.

- 0-0-0- 0-0-0-