Study on the evolution law of physical mechanics and abrasion characteristics of granite under high temperature-water cooling treatment

Abstract

During deep geothermal resource development, the estimation of drilling efficiency and tool wear in extremely hard rocks relies primarily on CAI testing. However, the degradation of rocks caused by high-temperature water cooling conditions leads to unpredictable changes in CAI. To address this issue, this study conducted P-wave velocity, hardness, thermal conductivity testing, BTS experiments, CAI testing, and NMR testing on granite samples subjected to water cooling at different temperatures (25–600 °C). The study analyzed the degradation mechanisms of granites under high temperature-water cooling conditions, the relationship between various parameters and the CAI index, and established a dual-parameter fitting model. The results indicate that the degradation of rocks under hightemperature-water cooling conditions is primarily attributed to mineral thermal reactions, thermal expansion effects at high temperatures, and rapid cooling-induced thermal contraction effects. Once the degradation effects exceed the skeleton constraint limit, macroscopic cracks gradually form within the granite. The formation of macroscopic cracks has a mitigating effect on abrasivity. The research findings on the correlation between CAI and various parameters can provide important theoretical support for the application of high-temperature rock breaking engineering.