Analytical interpretation of dilatometer penetration through saturated cohesive soils

A three-dimensional numerical solution to the problem of penetration of a flat plate dilatometer through saturated cohesive soil is presented. Axisymmetric stream functions are used with those corresponding to a uniform velocity field to approximate the geometry of the stream lines during penetration. After the source strengths have been determined, velocities and strains are computed. The computed strain fields are compared with those for axisymmetric and plane strain penetrations to show the need to use a threedimensional analysis. Effective stresses are computed from the strains based on assumed constitutive response (in this case an anisotropic bounding surface model) and total stresses are computed based on equilibrium considerations. The method provides computed horizontal stress indices that compare favourably with field data. The effect of penetration on the horizontal stress index measured by the dilatometer is evaluated. This index is shown to be most sensitive to changes in overconsolidation ratio and at-rest earth pressure coefficient, which reflect the initial in situ stresses.