Use of SASW Measurements to Evaluate the Effect of Lime Slurry Conditioning in Drilled Shafts

Abstract

Spectral-Analysis-of-Surface-Waves (SASW) testing was conducted in untreated and treated drilled shafts at the NGES “TXHOUSTO” test site as part of a study on lime-slurry conditioning of soil in drilled shafts for pier foundation construction. Results of SASW testing in an untreated shaft revealed a reduction in shear wave velocity ([Formula: see text]; a measure of small-strain shear stiffness) within an annular zone slightly less than one shaft diameter in thickness. This reduction is attributed to stress relief and soil disturbance during excavation. Results of SASW testing in a treated shaft revealed that [Formula: see text] of the soil surrounding the shaft depended upon whether the measurement was performed above or below the water table. Above the water table, a thin (less than [Formula: see text]) annulus of stiffen cemented soil was created due to the reaction between the lime and the carbon dioxide in the pore spaces of the partially saturated soil. Since the clay was saturated below the water table, there was no carbon dioxide in the pore spaces available to react with the lime, so there was no observed increase in stiffness due to cementation. As a result of these observations, an alternative strategy for the application of lime-slurry conditioning of drilled shafts in the construction of pier foundations has been conceived.