ABSTRACT
Using high-frequency shear waves and special processing schemes, we observe on field data that shear wave reflections map in great details the distribution of the shallow subsoil layers, and also correlate with the changes in (CPT) cone resistance (qc) indicative of soil strength change. We have extended the possibility by using shear-wave reflection amplitude as a function of incidence angle at a reflector to obtain the local shear wave velocity (VS) variation information. A subsequent amplitude-versus-scale inversion allows us to characterize the fine-scale nature of the velocity change at an interface. We notice that the fine-scale interfacial nature characterized by VS resembles with that characterized by CPT qc. VS and CPT qc correspond respectively to very different levels of strain and hence to very different properties (elastic rigidity versus strength) of the soil; our observed correlation on shear-wave reflection and CPT data is in conformity with earlier reported empirical relation between VS and qc. The proposed approach will be useful for mapping/detecting crucial lateral variations in soil for safe and efficient design and construction, and will supplement conventional geotechnical investigations in borehole.
