劈裂实验中不同岩石力学行为特征

Mechanical behavior of different rocks in the splitting test

为提高厚煤层开采围岩控制效果,研究了煤、泥岩、砂岩在受拉应力环境中的力学行为特征,结果表明:煤、泥岩、砂岩的平均抗拉强度分别为1.25,3.45,12.85 MPa,抗拉强度变异性系数分别为29.12%,18.67%和11.52%;劈裂裂纹在煤、泥岩、砂岩中的扩展速度依次升高,贯穿用时分别为0.006,0.004,0.001 s;煤中弹性应变能转变为裂纹表面能,泥岩中应变能转变为裂纹表面能、声能,砂岩中应变能转变成裂纹表面能、声能、半圆盘动能;煤体拉伸破坏受原生微裂隙影响,泥岩拉伸破坏受不规则坚硬晶体颗粒影响,砂岩则主要受最大拉应力平面控制;煤、泥岩、砂岩破断面的平均粗糙度分别为18.53,20.60和15.33,岩石劈裂断面粗糙度增大,围岩稳定性增强.

In order to improve surrounding control in mining thick coal seam, mechanical behavior of the coal, mudstone and sandstone was analyzed under tensile stress environment. The results show that tensile strengths of the coal, mudstone and sandstone are 1.25, 3.45 and 12.85 MPa, respectively. The variation coefficients of tensile strength are 29.12%, 18.67% and 11.52%. In the referred three kinds of rocks, propagation speed of splitting fracture shows an increasing trend, which uses 0.006, 0.004 and 0.001 s, respectively, to break through the disk sample. After failure, strain energy of the coal mainly transforms into fracture surface energy. In the mudstone, it transforms into both fracture surface energy and sound energy. In the sandstone, it changes into fracture surface energy, sound energy and kinetic energy of half disks. Tensile failure of the coal is influenced by small pre-existing fractures. Tensile failure of the mudstone is influenced by hard crystal grain with large strength. In the sandstone, tensile failure is controlled by the maximum tensile stress plane. The joint roughness coefficients of fracture plane in the coal, mudstone and sandstone are equal to 18.53, 20.60 and 15.33, respectively. The stability of surrounding rock is strengthened by the larger joint roughness coefficients.