Experimental study on fracture behaviour of three‐flawed sandstone specimens after high‐temperature treatments

Abstract

The crack coalescence of rocks significantly affects the stability of rock engineering, and extensive studies have been performed on preflawed rock specimens without thermal treatment. However, the fracturing behaviour of preflawed specimens after thermal treatment has not been investigated comprehensively. In this study, three‐flawed sandstone specimens with different flaw inclinations after high‐temperature treatments were tested under uniaxial compression. Photographic, acoustic emission and digital image correlation techniques were used to investigate the crack initiation, propagation and coalescence behaviour. Experimental results show that the peak strength, elastic modulus and peak strain of the three‐flawed specimens were lower than those of intact specimens and that they gradually recovered with increasing flaw angle. The peak strength and elastic modulus first increased and then decreased, whereas the peak strain increased with temperature. Noncoalescence, indirect coalescence and direct coalescence were three patterns observed between the two adjacent pre‐existing flaws. Finally, the mechanism of high temperature in alteration of the mechanical properties of sandstone was revealed through microobservations.

Compression‐induced crack initiation and growth in flawed rocks: A review

“…To investigate the crack coalescence mechanism of pre-flawed rocks after high-temperature treatments, uniaxial compression tests on three-flawed sandstone specimens heated to high temperatures were performed by Huang et al 97 During the testing, the photographic, AE, and DIC techniques were used to investigate the crack initiation, propagation, and coalescence behaviors. Huang et al 98 further investigated the effects of thermal shock on the strength and cracking behavior of preflawed granite specimens under uniaxial compression. The experimental results demonstrated that strain concentration bands were first emanated from the flaw tips and developed with a continuous increase of external stress, followed by the propagation and coalescence of macrocracks.…”

Model Analysis of Sandstone Tunnel Cracking Based on Fracture Mechanics Theory and Sensor Testing Technology Research

“…In confined pore spaces, damage can occur due to ice pressure that breaks the skeleton of the rock particles. However, the volume expansion theory has been questioned by other scholars as rocks under natural conditions are more likely to have connected pores [7]. The hydrostatic pressure theory was proposed in the study of concrete freeze-thaw damage due to the connectivity of pores within the rock.…”

Theoretical characterization of the temperature‐dependent mode I fracture toughness of rocks

“…However, the difficulty and large cost of testing for the fracture toughness of rocks at real-time high temperatures have forced researchers to study the fracture characteristics by testing heat-treated rocks that cooled to room temperature. [24][25][26] However, the effect of thermal damage caused by temperature on the fracture toughness at room temperature is quite different from that at high temperatures. The research on heat-treated rocks cannot fully reflect the mechanical behaviors of rocks in practical engineering.…”