基于高压注水试验的断层破碎带渗透特性研究

Permeability characteristics of fracture zone by high-pressure water injection tests

采用现场原位高压注水试验研究了巷道底板不同位置断层破碎带的渗透特性。共布置了3个测试孔,进行了5个轮次的注水试验,试验时一孔注水,其它孔水压监测。采用逐级增、降流量的试验路径,过程中连续记录注水流量、注水压力及监测孔水压值。研究发现:(1)在注水流量增加阶段,断层破碎带注水压力整体呈现"快增→突降→小幅波动"的变化过程,符合典型岩体水力劈裂压力曲线特征;(2)单孔多次高压注水劈裂压力差异较小,断层带劈裂裂隙具有较强愈合能力,重复注水试验产生新劈裂通道;(3)断层带注水劈裂压力、劈裂前初始渗透系数整体分别表现为随着测试点与巷道底板距离减小而减小、增加的趋势;(4)在同等注水流量条件下,流量减小阶段的水力隙宽明显大于流量增加阶段,劈裂后注水会导致了破碎带被冲蚀。把断层破碎带阻水强度与含水层水压的比值定义为断层带防突水安全系数,构建了断层带防突水安全评价方法,提出了断层突水防治措施。

The permeability characteristics in different fracture zones of roadway floor are studied by the high-pressure water injection tests.A total of three boreholes are arranged and five water injection tests are carried out.During the tests,water is injected into one bore hole and the water pressure is monitored in the other bore holes.The step wise increase and decrease of the water injection flow rate is adopted.The flow rates of water injection and the pressures of water injection and monitoring bore holes are recorded.The results show that:(1)At the stage of the increasing water flow rate,the water injection pressure in the fracture zone exhibits the process of"rapid increase,sudden drop and small fluctuation",which conforms to the characteristics of typical hydraulic fracturing pressure curve of rock mass.(2)The difference of fracturing pressure in a single hole is small,the fracture in the fracture zone has strong healing capability,and the repeated water injection tests produce new cracks.(3)The water-injection fracturing pressure and the initial permeability coefficient in the fracture zone decrease and increase with the decrease of the distance between the test point and the roadway floor,respectively.(4)Under the same water injection flow rate,the fracturing width at the stage of the decreasing flow rate is significantly larger than that at the stage of the increasing flow rate,and the water injection after fracturing will cause the fracture zone to be washed gradually.The ratio of water-blocking intensity of the fracture zone to water pressure of the aquifer is defined as the safety factor of water-inrush prevention in the fracture zone,the risk evaluation method for water inrush in the fracture zone is established,and the prevention and control measures for the water inrush in the fracture zone are put forward.