Modeling the Fracturing Behavior Transition in Fractured Granite under Thermo-Hydro-Mechanical (THM) Condition

An in-depth understanding of the thermo-hydro- mechanical ( THM) effects on rock fracturing becomes progressively important in natural energy exploitation projects. However, the failure mechanisms of fractured granite under THM conditions are very complex. To investigate the effect of THM treatment on the meso-macro fracturing behavior transition in fractured granite, a coupled thermo-hydro-mesostructure-based DEM ( T-H-MSBM) model was developed to reconstruct rock microstructures and distinguish the THM responses of varying mineral grains, pores and micro-cracks in the fractured granite. Based on the T- H-MSBM, fractured granite was first generated in terms of large damage degree, and the comparisons of numerical compression simulations in the natural and fractured granites were carried out under the coupled conditions of temperature (25-225 degrees C) and pore pressure (0-12 MPa). The interplay of THM treatment and damage degree on the mechanical properties of fractured granite was revealed, and the main mechanisms affecting the varied macro mechanical properties were further discussed insight from the fracturing behavior transition in fractured granite during the THM-uniaxial loading process. The results indicate that both temperature and pore pressure exert the amplified deteriorating effect on the macro mechanical properties of fractured granite with increasing damage degree, while the temperature dependence becomes significantly more pronounced in the fractured granite with low damage degree. The unique distribution of initial cracks controlled by mineral characteristics can lead to large variability in the initiation of THM-induced tensile cracks, and hence to the emergence of multiple fragments in the fractured rock with large damage degree during the compression loading, especially under high pore pressure. The findings can provide important insights into geotechnical applications to achieve engineering safety and economic objectives. For example, during the process of deep resource extraction, we can adjust the reservoir reformation methods in a more reasonable and dynamic manner by considering the variations in the damage degree of fractured rock resulting from excavation disturbance.