Theoretical DMT Interpretation in Sensitive Clays

摘要

Closed-form solutions are deduced in the present article for the stresses and displacements generated during installation of the flat dilatometer blade in undrained clay, by assuming that the soil behaves ideally elastic first and elastic-plastic second. In the first case, the installation of the dilatometer is modeled as the expansion of a long elliptical cavity, commencing from a vertical line crack under uniform internal pressure. Computations indicate that the horizontal tangential stress may reach very high negative or tensile values in areas located along the edges of the elliptical cavity. In these areas, the maximum shear stresses also attain very high levels. As a consequence, either fractures or plastic deformations would be expected to develop in such areas. In the second case, the installation of the dilatometer is modeled as the expansion of a long cylindrical cavity, in which the applied pressure is transmitted through an internal hydrostatic core. Outside the core, the clay behaves as a linearly elastic perfectly plastic (Tresca) material. The computed ultimate radial pressures compare well with published data obtained by means of finite element analyses. Finally, the theoretical solutions are applied to field tests carried out in a sensitive clay deposit of eastern Canada. The results show that the clay suffers severe remolding following the insertion of the dilatometer.