The Analysis of Weak Rock Using the Pressuremeter

The pressuremeter is a versatile in situ testing instrument capable of testing a large range of materials from very soft clay to weak rock. Due to limitations of other testing devices, the pressuremeter is one of the few instruments capable of capturing stiffness and strength properties of weak rock. However, data collected is only useful if the material tested is properly modeled and desirable material properties can be obtained. While constitutive models with various flows rules have been developed for pressuremeter analysis in soil, less research has been directed at model development for pressuremeter tests in weak rock. The result is pressuremeter data collected in rock is typically analyzed using models designed for soil. The aim of this study was to explore constitutive rock models for development into a pressuremeter framework. Three models were considered, with two of those three implemented for pressuremeter analysis. A Mohr-Coulomb model with a tensile cutoff developed by Haberfield (1987) and a Hoek-Brown model initiated by Yang et al (2011) and further developed by the author were implemented and calibrated against a data set of pressuremeter tests from 5 project test sites including a total of 115 pressuremeter tests in a number of different rock formations. Development of a multiscale damage model established by Kondo et al (2008) was explored. However, this model requires further development to be used for pressuremeter data analysis.