Effect of grouting on damage and fracture characteristics of fractured rocks under mode I loading

Abstract

Grouting is widely used to improve the mechanical properties of fractured rocks, but its impact on the fracture behavior of fractured rocks remains incompletely understood. This research aims to investigate the effects of grouting on the damage and fracture characteristics of fractured rocks under mode I loading. We used epoxy resin and ultrafine cement to grout granite and sandstone centre-cracked Brazilian disc specimens. We conducted Brazilian splitting tests on intact specimens, as well as specimens with and without grouting under mode I loading. Acoustic emission (AE) and digital image correlation (DIC) techniques were utilized to study the effect of grouting on rock fracture behavior. Furthermore, we employed an improved fracture toughness calculation method to evaluate the anti-fracture capacity of grouted specimens. The results show that grouting positively reinforces fractured rocks by increasing the shear crack ratio, mitigating the stress concentration effect at the crack tip, and fostering a more complete and stable development of the fracture process zone (FPZ). Materials with superior strength and bonding properties can effectively improve the mechanical performance of fractured rocks. Notably, epoxy resin significantly boosts the strength, deformation adaptability, and anti-fracture capacity of the specimens, outperforming ultrafine cement in terms of grouting effect. The entropy change of AE energy during the loading process indicates that the rock system undergoes three stages of order-to-disorder-to-order. The second stage and the abrupt changes in entropy value can serve as precursors to rock damage and fracture. This research enriches our understanding of how grouting influences the damage and fracture behavior of fractured rocks, providing valuable insights for risk assessment and disaster prediction in geotechnical grouting engineering.