Some aspects of pressuremeter test interpretation in clays

This Paper addresses fundamental questions related to the interpretation of pressuremeter data, with emphasis on the self-boring pressuremeter. The state of stresses and mechanism of failure of clays during pressuremeter tests are identified. The generality of the plane-strain condition during expansion of a pressuremeter cavity is shown and conditions where it is far from plane strain are indicated. Experimental data substantiate the theoretical findings. The potential for radial cracking is analysed and shown to be unlikely unless it is due to natural fissures or weaknesses. A method is developed to obtain the friction angle and overconsolidation ratio of stiff clays. A procedure is proposed to evaluate the error associated with initial disturbance due to unloading of the cavity wall caused during insertion of the probe, and corrections of the interpreted strength parameters are given for self-boring pressuremeter tests. The procedure has been verified using model pressuremeter test data.