Soil Velocity Profiles from In-Situ Seismic Tests at Deep-Mixing Sites

Abstract

The spectral analysis of surface wave (SASW) and the downhole P- wave velocity tests were carried out to characterize the treated and untreated soils at two deep-mixing (DM) sites located on the median of an interstate highway in Texas. These tests are part of a research project evaluating the effectiveness of deep-mixing technology as applied to expansive soils to mitigate the pavement distress caused by subgrade soil swell-shrink movements. Ground treatment for the two sites was performed by mixing in-situ soil with cement and lime to produce DM columns. Results from the initial SASW tests conducted shortly after site construction are consistent with those from shear-wave velocity tests on the laboratory specimens. Results from SASW tests performed one year later indicate certain decreasing in shear-wave velocity for both of the two sites. Results from third-year SASW tests are similar to those from the second-year tests except for the saturated near surface portion. By assuming a proper Poisson's ratio, results from P-wave downhole tests are also quite consistent with those for SASW tests.