Seismic Techniques in the Laboratory

Applications of scaled-down seismic cross-hole and steady-state Rayleigh wave tests to characterize dynamic soil properties in laboratory facilities are described. The nondestructive nature of seismic tests make them highly advantageous in laboratory settings. The major changes in test procedures and equipment to scale-down from field seismic tests are associated with: (1) Size and energy content of seismic source; (2) receiver size and sensitivity; (3) wave speed timing; (4) electronic triggering requirements; and (5) precision of distance or spacing measurements, or both. The seismic cross-hole test proved to be most effective in determining the spacial and temporal variation of elastic soil properties and proved to be a very sensitive indicator of small changes in confining pressure. In addition, a sand bin testing facility which is fitted with air bags to provide surface confining pressure and new torsional cross-hole hammer are described.