Using CPT and CPTu Results for Determination of Soil Shear Strength Parameters Consideration with 16 Practical Cases

The most common method for determining soil shear strength parameters is using laboratory tests and Mohr-Coulomb criteria. These methods have some limitations such as preparation of undisturbed samples, samples size, modeling of real in-situ stresses in laboratory condition, discontinuity of data. According to the repeatability and continuous measurements in CPT and CPTu, these tests results used for determination of soil strength parameters in geotechnical engineering. Most studies in fine soils focused on determination of undrained shear strength while in geotechnical design long-term bearing capacity is considered. Thus, in this paper a new method has been suggested for determination of c and φ in drained conditions by using all data (qc,fs,u) of CPT and CPTu in various soil types.The Proposed analytical model composed of bearing capacity theory and shear stress equation at rupture surface. Instead of total bearing capacity (qt), effective bearing capacity (qE) has been used and the shear stresses have been related to sleeve resistance (fs). Assessment and comparison of results of suggested method with current analytical approaches and laboratory tests obtained from five sites shows that results have a good agreement with measurements and predictions. Therefore, by using of all cone penetration test data, the prediction of soil shear strength parameters can be done with better accuracy