Professor of civil engineering, Portland State University, Portland, OR
Associate professor of civil engineering, Brigham Young University, Provo, UT
An introduction to soil mechanics limitations, testing concerns, and deposition of collapsible soil from the arid western states in the U.S. is presented. Laboratory evaluation of their properties for routine foundation engineering bearing capacity and settlement is of limited use. In situ testing is shown to be practical and successful in a wide range of soil types from uniform fine-grained soils to silty-sandy gravels. The hydraulic, monocell, prebored pressuremeter is proposed as an in situ test to establish dry, wet, and dry-wet geotechnical parameters for design by three testing procedures. Each procedure is given a detailed description, typical results are presented for collapsible debris fan deposits, and application of the procedures to routine foundation design is discussed. Simple collapse categories are introduced based on the pressurementer stiffness change from dry to wet conditions. Two minor modifications to the commercial pressuremeter probe end shoe and top support collar are recommended to ensure uniform radial water migration. Estimates of the depth of collapse from subsurface soil beneath existing foundations undergoing excessive settlement are also possible.
Paper ID: GTJ11416J