State-of-the-Art for Assessing Earthquake Hazards in the United States. Report 22. Mapping the Extent and Thickness of Liquefiable Soil Layers at Engineering Sites

摘要

This study addresses the problem of mapping the subsurface extent and thickness of potentially liquefiable layers in a dam foundation. Accurate delineation of such materials is essential to evaluation of dam safety in seismic regions. Existing techniques for mapping liquefiable sediments are evaluated. Economics, limitations, and usefulness of each method in delineating soil layering are outlined. Case histories are examined which demonstrate the usefulness of each technique under field conditions. For most sediments, the cone penetrometer was found to be the most useful and economical technique for subsurface delineation of liquefiable soil layers. To gain understanding concerning the minimum thickness of liquefiable layer which would be of concern to dam stability (and, thus, must be detected in subsurface investigation), experts in earthquake engineering were surveyed. Several field studies are reviewed to compare the usefulness, advantages, and disadvantages of the several exploratory techniques considered herein.