Investigation on directional rock fracture mechanism under instantaneous expansion from the perspective of damage mechanics: A 3-D simulation

With developments in geotechnical engineering, directional rock-breaking technology has been applied in large quantities. As a novel non-explosive rock-breaking technology, Instantaneous Expansion with a Single Crack (IESC) has been studied and applied to some extent in the past few years. IESC uses expansion gas to fracture rock mass in the predetermined direction by a special energy-gathering tube, which has the advantages of high safety, strong directional ability, and easy to operate. At present, there is a lack of in-depth investigation on the directional fracture mechanism of rock under the action of IESC. According to damage mechanics, the fundamental reason for rock fracture is due to the initiation, expansion, and penetration of internal cracks. In this study, a 3-D numerical model based on the theory of progressive failure is established to study the directional rock fracture mechanism of IESC, while a Conventional Expansion (CE) model without energy-gathering tube is established for comparative research. The maximum tensile stress criterion and unified strength criterion are used to identify damage failure of the element. The evolution processes of four key parameters are simulated, the types and degrees of tensile/compressive damage of the unit are analyzed, which aims to decipher the model's directional fracture mechanism under IESC loading. The established 3-D numerical models are validated by comparing with experimental results. The research results can contribute to further understanding the directional rock fracture mechanism of IESC and provide a theoretical basis for the application of IESC in the field.