Disturbance effects in pressuremeter tests in clay

Abstract

This paper analyzes the effect of borehole disturbance, caused by installation of pressuremeter probes in clays, on the derived stress-strain curves. Both overpushing-and overcutting-induced disturbances are considered. It is shown that overpushing results in underestimation of the undrained shear resistance. In general, the degree of underestimation cannot be determined. As for overcutting, the derived stress-strain curves are characterized by high peak strengths. The degree of overestimation of the undrained shear strength may reach 100% for the case of a strainhardening material. Determination of the strain that corresponds to the peak shear strength allows determination of the true stress-strain curve from the expansion test. Analysis of four well-documented case histories serves to illustrate the proposed approach.

Statistical and numerical analyses of pressuremeter tests in glacial tills

“…The stress strain behavior of the cohesive soil is assumed to follow either a linear elasticity relation (Gibson and Anderson (1961) and Silvestri ( 2003)) a hyperbolic elastoplastic relation (Silvestri (2004)) or a power law (Bolton and Whittle (1999)).…”

A pressuremeter-based evaluation of structure in London Clay using a kinematic hardening constitutive model

“…The two-dimensional axisymmetric idealised geometry of the self-boring pressuremeter was constructed with approximately 110 15-node triangular elements in order to avoid mesh-dependent results [56]. To avoid the influence of the external boundaries, the geometry was extended 30 times the initial cavity radius a 0 [21,53,62]. Simulation took place assuming fully undrained conditions.…”

“…The SBP was also conceived as an instrument that will cause minimal disturbance in the soil during installation [4,6,11]. However, later research has shown that the insertion of a SBP into the ground is not always perfect [2,17,33,35,46,53]. Installation defects such as overdrilling, underdrilling and partial pushing may all take place as the instrument is advanced into the soil.…”