New vibratory cone penetration device for in-situ measurement of cyclic softening
A new type of vibratory cone penetration device has been developed to improve the geotechnical in-situ methods for evaluating the dynamic and cyclic properties of the soil. The new device controls displacement amplitudes in real time and is designed to test various cyclic loads that cover different configurations of vibratory pile installation and different magnitudes of earthquakes. Some soil layers reacted strongly to the induced cyclic loads with high reduction ratios RR of the cone resistance, while other layers did not react to cyclic loading. It was also found that even a distance of 50 cm does not guarantee a good correlation between CPT and Vibro-CPTu. Therefore two or more pairs of CPT and Vibro-CPTu should be conducted at close distances in order to minimize misinterpretations of the data, which are caused by small scale geological structures, such as the presence of inclined layers, cross bedding, or other heterogeneities.