Numerical Prediction of Plastic Behavior of Highly Fractured and Weathered Phyllite Subjected to Pressuremeter Testing

Abstract

Pressuremeter test (PMT) is an in-situ test which serves well as an alternative to characterize highly fractured rock masses. However, complications arise as most of the pressuremeter probes are designed for tests in soils whose strength and stiffness are much lower than rocks. As a result, the pressuremeter probe used cannot apply sufficient pressure to cause significant plastic deformation, which leads to the lack of data points on the plastic behavior of the highly fractured rocks. Coupled with the limited understanding in the stress-strain response of highly fractured rocks subjected to the test, these challenges provide the research motivation to develop a reliable characterization method to generate useful parameters that can accurately describe the physical behavior of highly fractured rocks. This paper presents a numerical approach to predict the plastic deformation of pressuremeter tests in highly fractured rocks through the use of numerical modelling. The results generated from the developed method show good potential to characterize the unload-reload modulus, Eur, effective cohesion, c’ and friction angle, φ’ of the highly fractured rocks that cannot be directly obtained from the measured PMT results from an established case study.