An Electro-Vibrocone for Site-Specific Evaluation of Soil Liquefaction Potential

An electric downhole vibrocone has been designed for the site-specific evaluation of soil liquefaction susceptibility in high seismicity regions. The device induces localized cyclic pore pressures while concurrently measuring dynamic tip and friction resistances. Initial versions operated on a pneumatic impulse to generate dynamic forces and showed success in preliminary trials in historic liquefaction sites near Charleston, SC. The latest design couples a dual-element penetrometer with a piezo-actuator shaker and is completely electronic. This vibrocone offers a number of advantages over its predecessors including downhole vertical oscillation, adjustable dynamic displacement, control of excitation frequency from 0 to over 500 Hz, and the simultaneous measurement of porewater pressures at multiple positions including both midface and shoulder locations.