不同加载模式煤体爆炸荷载作用下损伤和裂隙演化研究

Evolution of coal body damage and crack under blasting load in different loading mode

为研究不同开采深度自重地应力对煤体爆炸荷载作用下损伤和裂纹演化的影响,针对煤层中深孔控制爆破技术的特点,在实验室搭建了爆破模拟试验系统,设计了不加载、加载为5t和10t三组模型。利用相似材料配比加工制备爆破实验模型试件,通过超动态应变仪监测煤体的应变信号,利用高像素数码相机记录爆破后模型试件表面宏观裂纹的变化规律,利用电法仪CT反演爆破前后及爆破后一定时间内电阻率变化规律。根据不同加载煤体爆炸荷载作用下的实验结果,对比分析了其损伤和裂纹演化的特征。结果表明:煤体在爆炸荷载作用下损伤和裂纹演化主要是由爆炸应力波、卸载波和控制孔形成的拉伸波等共同作用形成的,近炮孔区,压缩波形成放射状的压剪裂纹;远炮孔区,压缩波和卸载波共同作用下产生拉剪裂纹;加载对煤体爆炸荷载作用下损伤和裂纹演化的抑制作用。

In order to study the influence of in-situ stress on the damage and crack evolution of coal under blasting load, according to the characteristics of medium deep hole controlled blasting technology in coal seam, a blasting simulation test system was built in the laboratory. Three groups of models were designed, including no loading, loading force of 5 t and 10 t, and the blasting experimental model specimens were prepared using similar material proportion processing. The strain signal of coal body is monitored by ultra dynamic strain gauge, the change rule of macro cracks on the surface of model specimen after blasting is recorded by high pixel digital camera, and the change rule of resistivity before and after blasting and within a certain time after blasting is inversed by electrical instrument CT. According to the experimental results of coal explosion under different loads, the characteristics of damage and crack evolution are compared and analyzed. The results show that: the damage and crack evolution of coal under explosion load is mainly formed by the combined action of explosion stress wave, unloading wave and tensile wave formed by control hole;near the blast hole area, the compression wave forms radial compression and shear cracks;far from the blast hole area, the compression wave and unloading wave form tension and shear cracks;the loading depresses the damage and crack evolution of coal under blasting load.