Comparative performance of the international piezocone and China CPT in Jiangsu Quaternary clays of China

Abstract

The cone penetration test (CPT) and piezocone penetration test (CPTU) with measurement of pore pressure are one of the more powerful site investigation tools especially for soft clay. Most of the correlations with geotechnical data were developed based on 10cm2 international CPT and CPTU results, but in China there are 15cm2 and 20cm2 CPT devices. However, little has been reported on the effects of size of device, both diameter and area of friction sleeve, on the measured results. Firstly, the difference between the Chinese CPT and the international modern multifunctional digital CPT techniques are compared. Results are presented comparing various sizes and configurations of China double bridge CPT and international CPTU in Jiangsu clays of China. According to the CPT and CPTU tests at five sites, parameters measured by the 10cm2 CPTU are presented and compared to China double bridge 15cm2 CPT equipments. The effects of the increased penetration rate on the measured qt and fs resistances showed some overall decrease while the pore pressures were significantly increased. Cone tip resistance qc or qt and sleeve friction fs measurements were similar for 10 and 15cm2 penetrometers at the standard rate of 20mm/s. The findings give us the added confidence to the use of 10cm2 international piezocone penetrometers in China geotechnical engineering practice.