Abstract
Considering the recent developments of deep mining, investigating the rock properties under high ground stress periodic load is highly demanded. Studies show that these characteristics are important factors affecting the long-term steadiness of rock. However, the mechanical properties of rock mass without macro failure after cyclic load should be studied. In the present study, granite in a mine is considered as the research object. A rock pre-damage experiment is conducted with the same cycles under different confining pressures and constant cycle upper and lower limit loads. The pre-damaged rock sample is subjected to a uniaxial compression test, and a high-speed charge couple device camera is used to record the speckle field image of the sample surface during the whole loading process. The digital speckle techniques are used to analyse the image of the pre-damaged sample, the deformation field of the specimen surface, the displacement dislocation value of the localized deformation area and the deformation energy value of the specimen surface. The results show that for the same cycle times, the confining pressure is less than 80 MPa, which has a weakening effect on the rock's axial strength. As the confining pressure approaches 120 MPa, the pre-damaged rock uniaxial peak strength increases. The characteristics of displacement dislocation energy evolution of the localized deformation bound are divided into three stages (pre-peak stage, peak point and post-peak stage). After pre-damage under the same cycle times and different confining pressure conditions, the deformation field evolution of rock is relatively consistent.
Highlights
The mining of mineral deposits and the excavation of large underground chambers and other construction projects have been continued to the deep development
After performing pre-damage based on different confining pressure cyclic loads, the sample is loaded in a uniaxial testing machine
Considering 0 in figure 8 as a reference point, the evolution law of the displacement and deformation field of the rock sample after pre-damage under high confining pressure cyclic load is observed at points 1, 2, 3 and 4
Summary
The mining of mineral deposits and the excavation of large underground chambers and other construction projects have been continued to the deep development. Ge et al [1] carried out real-time meso-CT experiments on the rock fatigue failure using special triaxial loading experimental equipment incorporating a CT machine They established a threshold for the mesoscale rock fatigue damage. They studied the mechanism that the stress value of the cyclic loading affects fatigue failure. Meng et al [4] studied the energy evolution characteristics of the rock failure for different cyclic load experiments. It showed the rule of the energy cumulative and dissipation before the peak. It is very important to understand damage, fracture and instability of the rock through the displacement dislocation law and energy varying of rock deformation bound
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