Technical News
Use of Piezo Drive Cone for evaluation of subsoil settlement
induced by seismic liquefaction
Shun-ichi Sawada, OYO Corp. Ikuo Towhata, University of Tokyo
INTRODUCTION
Cone penetration test is one of the most important and convenient tools for subsoil investigation and many efforts have been made in the recent decades to extend its application to a variety of field of geotechnical engineering. The present paper addresses a new development of dynamic cone penetration with pore water pressure measurement in the course of impact. The validation test results indicate that this newly developed equipment is highly useful for mitigation of liquefaction-induced problems due to earthquakes.
MECHAMISM OF DYNAMIC CONE PENETRATION WITH PORE PRESSURE MEASUREMENT
Figure 1 illustrates the overall structure of the new CPT device. The device penetrates into soil by means of dynamic impact which employs 35cm falling of a drop hammer that measures 300N in weight using the mini-RAM device. This device is characterized by the monitoring of pore pressure change during impact near the cone tip. The detailed design of the cone tip is shown in Fig. 2. The transient change of excess pore water pressure in the course of dynamic penetration is measured and recorded near the cone tip through porous stones. Note that the cone tip is covered and protected by a disposable coverage that remains underground upon removal of the device after penetration.
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