Analysis of wedge penetration in clay

Abstract

A variety of devices designed to penetrate soil is used in soil engineering practice to measure soil properties or to emplace instrumentation, although the mechanics of the steady state penetration process is not well understood. Consequently the two-dimensional problem of steady state wedge penetration is examined. Solutions are obtained for wedge penetration in an ideal rigid plastic medium representing a clay. It is found that the solution requires the presence of a cavity behind the wedge, and the geometry of this cavity is established. A lower limit of the soil/wedge friction coefficient is derived, above which the wedge is considered rough. The force required to push the wedge is calculated as a function of wedge point angle and is shown to reach a minimum for a rough wedge at a point angle of about 67°. For axisymmetric penetration some finite element solutions were obtained and show that cone and wedge penetration mechanisms are similar. The mechanism and patterns of flow movement past the wedge for different point angles are demonstrated. Practical implication of the results and their extension to axisymmetric cone penetration are discussed.