A modified approach to determine over consolidation ration from piezocone penetration tests in soft clays
ZHANG Yaguo1，LI Jingpei2，HU Zhiping1
(1. School of Civil Engineering，Chang?an University，Xi?an，Shaanxi 710061，China；2. Department of Geotechnical
Engineering，Tongji University，Shanghai 200092，China)
Abstract：Determination of over consolidation ration(OCR) from piezocone penetration tests(CPTU) can not only avoid the sample disturbance in laboratories but also provide the continuous profiles of OCR of soil with depth. The penetration of piezocone is taken as the ultimate internal pressure required in expanding a spherical cavity. Assuming the normal and shear stresses on the cone face to be the friction at the cone-soil interface and the ultimate expansion pressure respectively，a modified approach to determine the OCR from CPTU was proposed using the solution of a spherical cavity expansion described with the modified cam clay. Two CPTUs in lightly and heavily over-consolidated clays are selected to verify the general validity of the proposed method. Comparisons between the predicted and measured results show that the presented method is more reliable than the existing approaches because more factors such as the cone roughness and cone penetration rate are taken into account. The presented method is also applied to Lianyungang marine clay for OCR prediction，and the result shows that the layer is consolidated or lightly over consolidated.
2017, Vol. 36 
