Determining soil shear strength parameters from CPT and CPTu data

Determining the soil shear strength parameters, i.e. cohesion (C), internal friction angle () is done by means of laboratory tests and the in situ testing data. The cone penetration tests, CPT and CPTU, are not only quick and economical, but also repeatable and show continuous records of soil parameters with depth. The common approaches for shearing strength parameters determination from CPT data are on the basis of bearing capacity and cavity expansion theories. In this study, dierent methods of soil shear strength parameters determination from CPT and CPTu results, qc, fs and u, were reviewed and investigated. A new method is proposed for C,  prediction on the basis of all quantities, qc, u and fs, from CPTu considering bearing capacity mechanism of failure. One advantage of this method is improved accuracy in the case of erroneous data by using all three outputs of CPTu. The proposed, current and experimental test results of an information bank including 32 CPT and CPTu results were assessed in ve sites. The comparison of predicted and measured C and  angle values indicates good consistency and low scatter for the proposed method. This can be led to more accurate and applicable continuous soil parameters in optimized geotechnical design. c 2013 Sharif University of Technology. All rights reserved.