加锚岩石力学性质及破坏特征试验研究

采用煤矿煤层顶板岩石作为加锚基体,用钢丝模拟锚杆,对由二者组成的加锚岩石进行了巴西劈裂、单轴压缩和压剪试验研究。结果表明,当加锚试件岩石基体出现塑性屈服裂纹开始扩展后,锚杆逐渐取代岩石基体成为外荷载的承载主体,试件的破坏特征由脆性向延性转变。加锚试件劈裂过程中,圆盘中心出现裂缝后,部分试件仍具有一定的承载能力,其抗拉强度提高了51.1%;另有部份试件则表现为迅速破坏并丧失承载能力,其抗拉强度提高了91.6%。单轴压缩试验中,加锚试件的破坏形式可分为两类:一类为裂纹平行锚杆轴向发展;另一类为裂纹垂直锚杆轴向发展,加锚试件的抗压强度提高了34.6%。加锚试件剪切过程中,其承载能力出现了明显的二次劣化现象,回归试验结果可得加锚试件的内摩擦角基本不变,而凝聚力提高了22.9%。

Test study of mechanical properties and failure characteristics of anchored rock

With rock sample of coal seam roof as matrix and steel wire as bolt, anchored rocks have been experimented by means of uniaxial compression, Brazilian split and pressure-shear test. The results show that: when rock matrix comes up against plastic yielding and certain cracks begin to extend, anchor bolt gradually becomes the main carrier of external load and rock's failure characteristics also change from fragility to ductility. During the process of splitting disk samples, a certain crack in the center of part of samples have no obvious impacts on carrying capacity; its strength increases by 51.1%. A huge penetrating crack turns up in other parts of samples and it quickly loses the carrying capacity; its strength increases by 91.6%. Failure forms of uniaxial compression samples can be divided into two categories. The first is failed with cracks propagating parallel with bolt; and the second is failed with cracks propagating vertically with bolt; the strength of anchored rock increases by 34.6%. In the pressure shear test, the carrying capacity of anchored samples obviously deteriorates once again; and the result shows that its internal friction angle of anchored samples isn't changed while the cohesive force rises by 22.9%.