S-wave cross-hole logging for stone columns

Abstract

S-wave cross-hole logging was successfully developed to outline the shape of a stone column and to confirm in turn its integrity. The technique is, in conception, quite identical to the Cross-hole Sonic Logging (CSL) for drilled piers. One of the key distinctions is the use of s-wave, which can be conveniently measured using the s-wave logger developed by the authors. The other key feature is that the s-wave velocity profile of the aggregates (Va profile) is required to back-calculate the diameters of the column. Va profile can be evaluated with the internal friction angle and the coefficient of earth pressure at rest of the aggregates. Fortunately, the calculation of the diameters is inherently very rugged against the uncertainty of Va profile. The technique can even detect bottle-neck and gourd-shaped anomalies of the stone column.