Field Seismic Testing in Geotechnical Earthquake Engineering

Abstract

Field seismic testing is an active and growing area in geotechnical earthquake engineering. The primary purpose of the field tests is to develop compression-wave velocity (V_p) and shear-wave velocity (V_s) profiles. These profiles are used to represent the stiffnesses of the geologic materials in the small-strain range. Many seismic methods are available for shallow investigations as discussed in the paper. Shallow investigations are defined as profiling to depths less than 75 m. Developments are occurring in profiling to intermediate (75 to 225 m) and deep (greater than 225 m) depths. The seismic methods used for deeper profiling are the downhole, suspension logging, and surface-wave methods. Examples of deeper profiling are presented. In addition, field seismic methods are being developed to perform parametric studies in situ. Examples are presented that show in-situ measurements of the effects of: (1) stress state on V_s and V_p, (2) nonlinear straining on shear modulus, and (3) cyclic loading leading to liquefaction.