基于波速测试和扫描电镜试验的煤系砂岩损伤特性研究

Study on the Damage Characteristics of Coal-Bearing Sandstone Based on Wave Velocity Test and Scanning Electron Microscope Test

摘要: 为探究荷载下砂岩的损伤特性，采用MTS 816岩石测试系统和声波测试系统对岩石单轴加载过程的声波脉冲信号进行实时采集、处理，引入能耗比η量化岩石试件损伤演化程度。并通过SEM扫描电镜试验，从细观角度分析其破裂特性，并揭示其裂隙机制。研究结果表明：在单轴持续加载破坏过程中纵波波速变化经历“平稳→线性减小→台阶波动→台阶突降”4个阶段。岩石试样受载应力为92.1% σ_max~96.1% σ_max时，纵波波速出现变化点。能耗比η为0~1时，纵波波速出现线性减小，当η > 1时，纵波波速出现台阶波动和突降。在单轴循环加卸载破坏过程中纵波波速变化经历“台阶波动→波动下降→台阶突降”3个阶段。岩石试样受载应力为38.8% σ_max~43.9% σ_max时，纵波波速值降低。能耗比η为0~0.65时，纵波波速出现“台阶”波动，当η > 0.65时，纵波波速出现台阶突降。基于波速测试和扫描电镜试验的煤系砂岩损伤特性研究，具有重要的工程意义，可为地球物理勘探提供参考。

Abstract: In order to explore the damage characteristics of sandstone under load, the MTS 816 rock test system and the acoustic wave test system were used to collect and process the acoustic wave pulse signals in the uniaxial loading process of rock in real time, and the energy consumption ratio η was introduced to quantify the degree of damage evolution of rock specimens. And through the SEM scanning electron microscope test, its fracture characteristics were analyzed from a microscopic perspective, and its crack mechanism was revealed. The research results show that the change of longitudinal wave velocity in the process of uniaxial continuous loading failure goes through four stages: “stable → linear decrease → step fluctuation → step sudden drop”. When the rock specimen is loaded with a stress of 92.1% σ_max~96.1% σ_max, the longitudinal wave velocity has a change point. When the energy consumption ratio η is 0~1, the longitudinal wave velocity decreases linearly. When η > 1, the longitudinal wave velocity fluctuates and drops suddenly. During the uniaxial cyclic loading and unloading damage process, the change of longitudinal wave velocity experienced three stages: “step fluctuation → fluctuation decrease → step sudden drop”. When the rock sample was loaded with a stress of 38.8% σ_max~43.9% σ_max, the longitudinal wave velocity value decreased. When the energy consumption ratio η was 0~0.65, the longitudinal wave velocity showed “step” fluctuations, and when η > 0.65, the longitudinal wave velocity showed a step sudden drop. The study of the damage characteristics of coal-bearing sandstone based on wave velocity test and scanning electron microscope test has important engineering significance and can provide a reference for geophysical exploration.