单轴应力状态下石灰岩体静态破碎裂纹演化规律及应用

Crack evolution of limestone induced by static demolition at axial stress and its application

为了研究静态破碎过程中裂纹演化规律,采用真三轴岩石力学试验机对200 mm×200 mm×200 mm的立方体石灰岩试样进行了单轴应力状态下静态破碎试验,并利用声发射空间定位技术对静态破碎过程中裂纹起裂与扩展进行监测。结果表明:单轴应力下裂纹起裂位置为钻孔中下部,并先后形成两组裂纹,每组裂纹沿孔壁对称分布并大致成一直线;两组裂纹的扩展速率均先快后慢,分为快速增长和快速下降两个阶段,并且下降阶段的裂纹扩展速率小于增长阶段扩展速率;先生裂纹的扩展速度大于后生裂纹;每条裂纹的扩展速度具有方向的差异性,即平行孔轴向方向大于与垂直孔轴向方向;基于弹性力学、断裂力学理论,建立了静态破碎剂作用力与裂纹扩展半径的关系,并通过试验结果验证了该模型的合理性。将研究结果应用于某高瓦斯矿实际地质条件下的强制放顶工程中,确定了静态破碎强制放顶的基本参数,获得了良好的工业效果。

In order to study the crack evolution during static demolition,the authors performed the test of static demolition in cubic limestone with the size of 200 mm × 200 mm × 200 mm at axial stress by true triaxial rock mechanics testing machine,and simultaneously monitored the acoustic emission from limestone fracture in the process of static demolition by dimensional location technology. The results are as follows,at axial stress,the crack initiation is located at the lower part of the borehole wall and the newly formed cracks can be divided into two groups according to the initiation time and location of crack. Every group cracks symmetrically appear near the borehole wall along a line. The propagation rate of two group cracks follows a trend of ＂from rapidness to slowness＂. The process of propagation can be divided into rapid increasing phase and rapid decreasing phase and the rate at the rapid increasing phase is higher than that at the decreasing phase. The propagation rate of early formed cracks group is higher than that of late formed cracksgroup. For single crack,its propagation is highly directional that the rate parallel the borehole axis is greater than that perpendicular to the borehole axis. The authors also presented a model based on the theories of elastic mechanics and fracture mechanics which is a relationship between forces from the static demolition agent and crack propagation radius,and the model proved to be applicable by comparing with the test results. In accordance with the actual geological situation of some mines,the basic parameters of manpower manipulated caving with static demolition are determined,which shows a good industrial effects.