Parameter calibration of a modified hyperbolic model for sands using pressuremeter test data

Abstract

The reduction of shear modulus causes non-linearity before plastic yielding, and this needs to be taken into account in deformation analyses for the performance-based design of geotechnical structures. In this respect, this paper demonstrates the simulations of pressuremeter tests via a non-linear elastic perfectly plastic soil model. A modified hyperbolic model was adopted for the pre-failure part of the stress-strain behaviour, and the Mohr Coulomb soil model was implemented for modelling the post-failure behaviour in FLAC3D. Computed pressure-displacement curves at the cavity wall matched very well with the curves of self boring pressuremeter tests carried out in Thanet sand. A new pressuremeter disturbance correction is used successfully as a means of adjusting and updating the shear modulus. The analysis reveals that this approach is essential for estimating the initial lateral earth pressure coefficient, and is capable of refining the selection of new reduction parameters in the modified hyperbolic model using pressuremeter rebound loops, and of refining values of friction and dilation angles from initial expansion and final contraction curves. Using the modified hyperbolic model in conjunction with pressuremeter test data enables not only calibration, but also optimization of parameters. The simulation of a pressuremeter test enables the engineer to obtain an appropriate combination of soil parameters which can later be utilized to analyze geotechnical structures through the same calibrated model.