Study on crack propagation and parameter effects of concrete under hydraulic fracturing

This paper uses acoustic emission and scanning electron microscopy to conduct hydraulic fracturing experiments on concrete, revealing its macroscopic and microscopic fracture characteristics. Existing studies mainly focus on rocks, while the crack propagation behavior of concrete and the effects of related parameters under hydraulic fracturing remain insufficiently understood. Based on the cohesive method, a meso-numerical model for hydraulic fracturing of concrete is established and validated by CT scanning to investigate crack propagation behavior and key parameter effects. Key findings are as follows: (1) Higher concrete strength reduces main crack width but increases the secondary crack number, along with elevated post-fracturing residual stress and the propagation pressure required after crack initiation. (2) The failure process can be divided into five stages: filling, elastic deformation, preliminary damage, crack propagation, and complete failure. (3) Cracks are mainly concentrated in the mortar–interface transition zone, with a small number in aggregates. Hydraulic fractures may bifurcate in the mortar area, leading to simultaneous multi-fracture expansion; the fracture surface is relatively smooth without typical exfoliated particle accumulation or obvious unevenness. (4) Injection flow is positively correlated with fracture length and concrete cracking area, but shows a weak global nonlinear correlation with fracture width. Fracturing fluid viscosity is positively correlated with fracture width, negatively correlated with fracture length, and nonlinearly correlated with cracking area. This study clarifies the crack propagation behavior of concrete under hydraulic fracturing and the effects of key parameters, and it provides a theoretical basis for its engineering application in concrete structure maintenance and demolition.