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THESIS APPROVAL the Abstract and Thesis of Susan L. Bednarz for The THESIS APPROVAL The abstract and thesis of Susan L. Bednarz for the Master of Science in Geology were presented May 29, 2002, and accepted by the thesis committee and the department. COMMITTEE APPROVALS: ____________________________________ Michael L. Cummings, Chair ____________________________________ Georg H. Grathoff ____________________________________ Scott F. Burns ____________________________________ Trevor D. Smith Representative of the Office of Graduate Studies DEPARTMENTAL APPROVAL: ____________________________________ Michael L. Cummings, Chair Department of Geology ABSTRACT An abstract of the thesis of Susan L. Bednarz for the Master of Science in Geology presented May 29, 2002. Title: Influence of Halloysite on the Engineering Behavior of Basaltic Saprolites in Northwestern Oregon and Southwestern Washington. Saprolite is commonly developed on Tertiary basalt in northwestern Oregon and southwestern Washington. Basalt saprolites are often sensitive, in that they release water and lose shear strength when disturbed. Non-sensitive, featureless residual soil mantles sensitive basalt saprolites. Borehole samples of extrusive basalt and intrusive basalt (diabase) saprolites from six study sites in northwestern Oregon were analyzed using X- ray diffraction and scanning electron microscopy (SEM). Clay mineral zonation, observed in borehole samples obtained on Mt. Scott in southeast Portland, Oregon, show that 10Å halloysite is most abundant near the bedrock contact, 7Å halloysite is most abundant toward the middle to upper portions of the saprolite, and kaolinite is most abundant in the residual soil. Zonation of smectite is unclear. Interlayered halloysite/expandable clay is identified in almost all saprolite samples analyzed but not in the overlying residual soil samples. Laboratory and field testing can be used to identify sensitive saprolites prior to construction. Sensitive saprolites have high natural water contents (generally >50%), low dry densities (5.7 to 6.4 kN/m3), Atterberg limits and moisture/density relationships that vary with drying and remolding, and release water when compressed. Engineers have linked soil sensitivity in saprolites to the presence of water-filled, hydrated (10Å) halloysite tubes that are crushed during construction, adversely affecting stripping, placement, and compaction. Although 7Å halloysite is found in all sensitive saprolites analyzed within the study sites, 10Å halloysite is not ubiquitous to these soils. The water released during compression of sensitive soils is stored in boxwork voids (identified by SEM analysis) and not inside individual halloysite tubes. The loss of sensitivity in surficial residual soil is due to the breakdown and collapse of the boxwork voids within the saprolite due to pedogenic processes. INFLUENCE OF HALLOYSITE ON THE ENGINEERING BEHAVIOR OF BASALTIC SAPROLITES IN NORTHWESTERN OREGON AND SOUTHWESTERN WASHINGTON by SUSAN L. BEDNARZ A thesis submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE in GEOLOGY Portland State University 2002 ACKNOWLEDGMENTS Many thanks to the following individuals who provided information, assistance, and advice towards the completion of this research: Michael Cummings, Georg Grathoff, Scott Burns, and Sherry Cady, Portland State University; Jim Maitland and Tim Pfeiffer of Foundation Engineering, Inc.; Derek Cornforth, Charlie Hammond, and Brent Black of Cornforth Consulting; Jim Griffith of the US Army Corps of Engineers; Reka Gabor, Portland, Oregon; Reed Glasmann of Oregon State University; David Rogers of University of Missouri, Rolla; Michael Williams of the Washington Department of Transportation; Clackamas County Department of Transportation and Development; Wayne Isphording, University of South Alabama. I would also like to thank the Clay Minerals Society for providing a grant to fund this research. i TABLE OF CONTENTS ACKNOWLEDGMENTS ........................................................................................ i TABLE OF CONTENTS ........................................................................................ ii LIST OF FIGURES ............................................................................................... vi LIST OF TABLES ................................................................................................ vii INTRODUCTION .................................................................................................. 1 BACKGROUND .................................................................................................... 3 GEOLOGIC SETTING .......................................................................................... 9 LOCAL ENGINEERING CASE HISTORIES ...................................................... 17 Mud Mountain Dam ....................................................................................... 17 Toutle River Sediment Retention Structure .................................................. 18 Trask River Dam Raise ................................................................................. 19 Hills Creek Dam ............................................................................................ 21 Spirit Lake Memorial Highway ...................................................................... 22 H3 Tunnel, Oahu, Hawaii .............................................................................. 23 STUDY SITES .................................................................................................... 24 Monterey Avenue Overcrossing, Southeast Portland, Oregon .................... 24 West Salem Site 1, Oregon .......................................................................... 25 West Salem Site 2, Oregon .......................................................................... 25 Carlton, Oregon............................................................................................. 26 Silverton, Oregon .......................................................................................... 26 South Salem, Oregon ................................................................................... 27 ii METHODS .......................................................................................................... 28 Field Sampling Methods ............................................................................... 29 Field Soil Sensitivity Testing ......................................................................... 30 X-Ray Diffraction Analysis ............................................................................ 30 X-ray Diffraction Analysis of -2μm Material ............................................. 31 X-ray Diffraction Analysis of Bulk Samples ............................................. 33 Toluidine Blue Treatment .............................................................................. 33 Magnetism ..................................................................................................... 34 Scanning Electron Microscopy ..................................................................... 35 Engineering Index Testing ............................................................................ 36 RESULTS ........................................................................................................... 37 X-Ray Diffraction Analysis Overview ............................................................ 37 X-Ray Diffraction Sample Data Summary .................................................... 39 Monterey Overcrossing Borehole BH-3 .................................................. 39 Monterey Overcrossing Borehole BH-7 .................................................. 41 Monterey Overcrossing Borehole BH-10 ................................................ 43 Monterey Overcrossing Borehole BH-18 ................................................ 45 Monterey Overcrossing Borehole BH-27 ................................................ 46 Monterey Overcrossing Borehole BH-43 ................................................ 47 West Salem Site 1 Borehole BH-1 .......................................................... 47 West Salem Site 2 Borehole BH-1 .......................................................... 48 Carlton Boreholes BH-1 and BH-2 .......................................................... 48 iii Silverton Borehole BH-1 .......................................................................... 49 South Salem Borehole BH-2 ................................................................... 49 Magnetism Observations .............................................................................. 50 Field Sensitivity Testing Results ................................................................... 51 Testing for Amorphous Clay (Allophane and Imogolite) ............................... 52 Scanning Electron Microscopy (SEM) Results ............................................. 52 Engineering Index Testing Results ............................................................... 62 DISCUSSION ..................................................................................................... 64 Clay Mineralogy in Basaltic Saprolites and Residual Soil ............................ 64 Clay Zonation .......................................................................................... 64 Mixed-Layered Halloysite/Expandable Clay ........................................... 67 Desiccation of 10Å Halloysite .................................................................. 70 Development of Sensitivity in Basaltic
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