The Grain-Based Model Numerical Simulation of Unconfined Compressive Strength Experiment Under Thermal-Mechanical Coupling Effect

Abstract

PFC-GBM (Particle Flow Code-Grain Based Model) is the major and fundamental method to simulate rock behaviors in this paper. Geo-materials are composed of micro-grains, the behavior of these grains and the interface between them influence macroscopic behavior of materials. Traditional PFC simulation method could simulate the integral micro-behavior of material, and PFC-GBM simulation focuses on every different grains and interfaces to simulate micro-heterogeneity of material. In this paper, an attempt is made to investigate the strength of rock masses and the development of micro-cracks under thermal-mechanical coupling effect. For this purpose, a numerical model is established based on mineral analysis and pre-existing mechanical experiments of Granite from one of complex tunnels in Yunnan Province. After establishing the model, the specimen were first heated and then compressed according to test sequence of laboratory experiments. The simulation results are calibrated to match the laboratory test results including thermal behaviors and fracture development. The conclusion of simulations show that both of thermal behaviors and fracture development are depended on the micro-heterogeneity of granite in UCS (Unconfined Compressive Strength) experiment, the characteristics of minerals influence the macroscopic fracture mechanism. The simulation reveals that in a certain range of temperature (40°C ~ 90°C), temperature increasing enhance the brittle damage of granite. The situation of 130°C had the obvious thermal-crack before loading and then exhibited a much lower peak strength and failure strain. This numerical observation may guide the underground construction in complex geo-environment.