Stress Dependence of Shear-Wave Velocity in Unconsolidated Sand: Implication for New Monitoring Possibilities

We have performed an experiment on an unconsolidated sand sample in a biaxial pressure chamber to observe the effect of horizontal stress on seismic shear-wave velocity. Multi-offset seismic reception was successfully implemented in the laboratory scale. From changes in shear-wave moveout velocity observed in a receiver array we could distinguish the effect of horizontal stress change. The approach appears to be realisable in field. This may lead to a new methodology for in-situ monitoring of horizontal stress change in soil. Further, we found a good match between the observed and the modelled shear-wave velocity change as a function of horizontal stress. This has potential to offer the magnitude of in-situ stress in soil, which has so far remained difficult to estimate in the field. Our observation also reinforces the possibility of implementing the model-based integration of seismic and CPT data, proposed earlier, for obtaining unique estimates of in-situ porosity and horizontal stress.