This research deals with the problem of interpretation of the results of a particular kind of field soil test. The overall problem involves the difficulty of measuring relevant soil properties for use in the design of foundations for buildings, stability of deep excavations, and other similar problems where shearing stresses develop in the soil. The usual procedures for solving such problems involve withdrawal of soil samples from the ground and performance of relevant tests in the laboratory. Unfortunately, the act of taking the samples results in significant changes in the soil properties, leading to designs which are often uneconomical, but are occasionally unsafe. Efforts to resolve this problem have recently involved development of tools to test the soil in place ("in situ"). Unfortunately, field conditions are much more complex than those in the laboratory and it is often unclear as to how the field data are to be converted into realistic soil properties. The PI's for this project are concerned with field measurements involving the pressing of a flat plate into the soil at a steady rate. They will use, and further develop, a theory originally developed by Baligh at MIT, termed the "strain path method", to predict stresses, strains, and pore water pressures around such a penetrating plate. In addition, they will perform laboratory tests where plates will be penetrated into large-sized soil specimens, and also field tests. The costs of field tests will be greatly reduced through use of a field testing rig at another university, that was funded through an NSF equipment grant. The theoretical work will be funded by the Air Force and the field and laboratory work by NSF. The goals of the research are then to develop a way of converting data on plate penetration into soil properties for use in foundation design, leading to a reduction in testing costs and in the cost of foundations, and to verify the analysis using laboratory and field tests, and case histories.
