Evaluation of dilatometer penetration in saturated clays.

摘要

The purpose of this research is to evaluate results of dilatometer tests using numerical methods such that a theoretical basis can be established for determining soil properties with this test in saturated cohesive soils. In particular, this research represents an effort to develop a better understanding of the mechanisms governing the development of soil and pore water pressures during dilatometer penetration.;The dilatometer penetration model is based on the strain path method and is used to compute strain and stress fields around a dilatometer during penetration. The model simulates penetration of an indenter using a series of spherical point sources in a uniform flow field. Both plane strain and three dimensional representations of the dilatometer are considered. The effective stresses are computed using a three dimensional anisotropic boundary surface model. The total stresses and excess hydrostatic pressures are computed using equilibrium analysis.;The model is used to compute the horizontal stress index. Computed values are compared to those measured at the Northwestern lakefill and the Italian sites reported by Marchetti. The results of the model show good agreement with the measured horizontal stress index and indicate that the plane strain simulation is not a good approximation to describe the three dimensional field around the dilatometer. Results also support Marchetti's correlation and confirm that the change in membrane pressure during penetration in slightly overconsolidated clays is mainly due to the creation of excess hydrostatic pressure. In highly overconsolidated clays, the change in the horizontal stress index is dependent not only on the coefficient of earth pressure at rest but also the overconsolidation ratio, friction angle, recompression index and elastic parameters such as Poisson's ratio.