New Pressuremeter Test Analysis Based on Critical State Mechanics

Abstract

To analyze the pressuremeter test results, the medium around the probe is modeled by a clay hollow cylinder subjected to external and internal uniform pressures. However, assuming that during the test the medium strains around the pressuremeter test cavity are homogeneous results in an oversimplification of the problem. A new analysis method is proposed based on an energy approach concept. The objectives are to determine the outer radius of the clay hollow cylinder that models a normally consolidated clay medium idealized in undrained conditions and to express the clay behavior by the effective stress path and the stress-strain relationship. At the position of three particles across such a cylinder, the developed excess pore water pressures were measured during testing. The analysis showed that the development of greater excess pore pressure than the circumferential stress in compression indicates the critical state and that the testing rate has a negligible influence on the deduced critical state. Thus, the undrained shear strength at the level of testing underground can be obtained.