An Efficient Tool to Determine Undrained Shear Strength of Soft Soils

Abstract

Disturbance encountered when testing soft soils both in laboratory and in-situ conditions makes the determination of the undrained shear strength, S_u, very challenging. This paper introduces a new tool called “Cylindrical Penetrometer” (CP) to measure the undrained shear strength of soft soils. Description of this tool is given, and the related shear test procedure is detailed. The proposed tool offers the advantage to avoid the disturbance of soft soils before the commencement of the CP test. From recorded measurements and based on considerations of the existing shear tests, a specific method of determination of Su is proposed. The experimental program included laboratory tests by using two sizes of the CP. The recorded results from CP tests, performed on a reconstituted Tunis soft clay, were compared with those obtained from direct shear tests, vane tests, and a consolidated undrained triaxial test. A fair agreement was found between the Cylindrical Penetrometer results with those obtained from the current shear tests.