Discrete Element Modeling of Thermally Damaged Sandstone Containing Two Pre-Existing Flaws at High Confining Pressure

An underground coal gasification (UCG) process is strongly exothermic, which will cause thermal damage on rock cap. We proposed a new numerical model based two dimension particle flow code (PFC2D) to analyze the inception and extension of cracks pre-cracked red sandstone, were thermally treated at temperature 25~1000 °C. The results indicated that: (1) value DT obtained by extracting crack area scanning electron microscope (SEM), can be used as an indicator degree sandstone; (2) established replacing flat-joint with smooth-joint DT, this approach properly simulate mechanical behavior failure patterns (3) critical for strength reduction was 750 peak increased pre-treatment from 25 °C then decreased. elastic modulus E1 decreased increasing treatment temperature; (4) micro-scale initiate tip prefabricated fissure, expand along direction finally developing into macroscopic fracture. This has potential enhance predictive capability modeling presents reliable damaged sandstones, thereby offering sound scientific basis utilization space after UCG.