断层内破碎岩石渗透性的实验研究

断层破碎带岩石的渗透性是影响地下工程中由渗流失稳而引发灾害事故的重要影响因素之一。利用一种专门的破碎岩石压实渗透仪,在MTS815.02岩石力学伺服试验系统上测试了取自断层内的破碎灰岩、破碎砂岩、破碎泥岩的渗透系数,得到并分析了轴向压力、岩样粒径、水流速度与渗透系数的关系曲线。研究表明:破碎岩石渗透系数与其压实状态密切相关,随着轴压的增加,渗透系数都相应降低;在相同的轴向压力状态下,岩样粒径越小,其渗透系数也越小,因此,挤压程度和充填程度都较低的小断层导水性好,容易导致突水;破碎岩石的渗透系数随着水流速度的增大呈减小趋势,但水流速度对破碎岩石渗透系数的影响程度有限;在相同的压力、粒径情况下,破碎泥岩的渗透系数比破碎灰岩、破碎砂岩的要小1～2个量级,说明当断层上下盘为坚硬岩石时,断层带渗透性好、易导水。研究结果可为采动过程中评价断层的导水性提供参考。

Experimental Study of Permeability of Broken Rock Sampled from Strata Containing Faults

Permeability of broken rock sampled from strata containing faults is one of important factors involved in seepage disaster in underground engineering. Using a special instrument for compacting broken rock and a rock mechanics servo experimental system MTS 815.02, permeability coefficient of broken limestone, broken sandstone and broken mudstone was tested, respectively. Relation curves among axial stress, grain size, rate of water flow and permeability coefficient were obtained. Results show that 1) permeability coefficient of broken rock is closely related to its compaction state and decreases with axial stress increase for above 3 kinds of broken rocks ; 2) under the same axial stress, permeability coefficient of broken rock with small grain size is smaller than that of broken rock with large grain size. Small fault has advantage of hydraulic conductivity therefore easily leads to water inrush due to its low compaction and filling; 3) permeability coefficient of broken rock decrease with the increasing of water flow rate, but the effect of water flow rate on permeability coefficient is not obvious; 4) under the same axial stress and with the same grain size, the permeability coefficient of broken mudstone is lower than that of both broken limestone and sandstone nearly 1~2 orders of magnitude. So the fault surrounded by solid rock has better permeability and hydraulic conductivity. Above results may provide reference for evaluating fault hydraulic conductivity in mining.