Mode I fracture behaviour of sandstone after heat treatment

Abstract

The stability of rock in engineering applications, such as exploiting geothermal resources and underground coal gasification, is seriously affected by its fracture behaviour during or after high-temperature exposure. Three-point bending (TPB) tests on sandstone samples with different pre-existing crack lengths after heat treatment were conducted to investigate the influence of temperature and crack length on the mode I fracture properties. As the temperature increased, the fracture toughness first increased and then decreased gradually, reaching a peak value at 200°C. While the a/h (the ratio of the crack length to the height of the sample) was between 0·29 and 0·37, the crack length had no detectable effect on fracture toughness. The crack initiation load, critical tensile strain and the propagation process of mode I cracks were obtained based on the uniqueness of the crack propagation path under TPB and maximum strain theory.