大尺度单裂隙介质应力–渗流耦合试验台架及其渗透系数测试研究

PERMEABILITY MEASURING OF LARGE SCALED SINGLE FRACTURED MEDIA WITH A SEEPAGE-STRESS COUPLING TESTING APPARATUS

针对裂隙介质渗透特性的试验及理论进展,结合裂隙介质渗流诱发的工程问题,详细介绍自主研发的裂隙介质渗透试验台架;该台架可实现裂隙介质在法向、切向的同步、异步加载,其最大加载位移均为100 mm,最大加载荷载均为1 000 k N。密封技术是决定裂隙渗流试验成败的关键技术,通过相关调研及研究,针对试验所用的大尺度岩样,提出全新的密封试验技术(岩石表面内外放置密封圈),采用此技术实现了大尺度裂隙介质渗透试验的密封。同时,基于渗流达西定律及立方定律,得到适用于该试验台架的裂隙介质渗透系数计算方法。进一步地,利用该渗透台架,采取岩石表面黏贴细砂的方法模拟岩石表面的粗糙性,初步开展大尺度单裂隙花岗岩的渗透试验。并基于流量平衡原则,剔除无效试验数据,获得该单裂隙花岗岩渗透系数的变化规律,其随着渗透时间的增加,渗透系数逐渐增大,并稳定至某个数值。深入分析渗透系数变化的影响因素,认为裂隙介质表面黏贴的细砂对其渗透性有着决定性的影响。同时进行裂隙介质的表面为光滑、无黏贴细砂状态下的渗透试验,与之相对比,验证了裂隙表面的粗糙性是影响裂隙介质渗透系数的重要因素。渗透试验结果表明:此渗透试验台架采用该计算测试方法获得的参数是准确可信的,可以应用于地下核废料处置、水利水电地下硐室、水下隧道、采矿等工程有关问题的研究中,为能源的开发利用提供有效的研究手段。

A system for measuring seepage characteristics of the fractured rock with the water flow developed in-house is described in the paper. The normal and shear loads can be applied synchronously and asynchronously to the medium. The maximum loading is 1 000 k N and the maximum displacement is 100 mm. A new method of sealing was employed with the sealing ring set on the rock surface. The calculation of the permeability of the system was recommended according to the Darcy′s law and the Cubic law. Fine sands were stick onto the rock surface to simulate the roughness of the rock surface. The seepage tests were carried out using the system to the large size granite sample with a single fracture. The permeability was found to increase with the time until it reached a stable value. The seepage test was carried on the smooth(without fine sands) rock surface. The factor influencing the permeability was analyzed and the fine sands on the rock surface were found to be crucial. The testing results showed that the parameters obtained with the system were creditable.