Modeling of in-situ seismic tests using a laboratory true triaxial box

A laboratory true triaxial box with individually applied stress system is used to model the in-situ cross-hole and down-hole seismic tests, and hence determine the small-strain shear modulus and damping ratio, i.e. G _max and D _min. The method suggested by ISSMGE TC10 in finding the S-wave arrival time is found to yield consistent results when compared with the one obtained by the cross-correlation peak of two receiver signals. The spectral ratio method integrated with the self-healing technique gives similar damping ratios as in resonant column tests under isotropic confinement. Experimental results provide further evidence that shear modulus is only dependent on the principle stresses in the direction of shear wave propagation and polarization. The damping ratio, however, is independent of the principle stress changes, regardless of its direction with respect to the polarization plane. The cross-hole test yields better results than down-hole test in this laboratory modeling.