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为研究石灰岩裂隙的摩擦滑动特性,搭建了三轴试验系统,进行了劈裂石灰岩岩芯在湿润和干燥条件下的滑动-控制-滑动试验、速度步长试验和渗透试验。通过滑动-控制-滑动试验和速度步长试验分别研究了石灰岩裂隙摩擦强度的时间依赖性和滑动稳定性,并进一步分析了水对裂隙摩擦强度特性的影响,同时还通过渗透试验观察了裂隙渗透率在滑动过程中的变化。滑动-控制-滑动试验表明:裂隙的摩擦强度具有时间和应力依赖性,裂隙摩擦强度在控制时间内的下降量及重新滑动后的愈合量均与控制时长成正比,而与有效压应力成反比;此外,摩擦强度特性还明显受到水的影响。速度步长试验则表明:石灰岩裂隙摩擦强度随滑动速度的增加而增大,呈现速度强化特性。最后通过不同有效正应力下(介于1?3 MPa之间)的渗透试验发现:裂隙的渗透率不仅随有效应力的增加而急剧下降,而且在各级正应力下亦随滑动而逐渐减小。
In order to study the frictional sliding characteristics of limestone fractures, a triaxial test system was set up. The sliding-controlled-sliding test, velocity step test and permeation test of cleaved limestone core under wetting and drying conditions were carried out. The time dependence and sliding stability of the limestone fracture friction were studied respectively by the sliding-control-sliding test and the velocity step test. The influence of water on the frictional strength of the fracture was further analyzed. At the same time, the fracture penetration was also observed The rate of change in the sliding process. The sliding-control-sliding tests show that the frictional strength of fractures is time-dependent and stress-dependent. The decrement of fracture friction in control time and the healing after re-sliding are both proportional to the control time and inversely proportional to the effective compressive stress In addition, the frictional properties are also significantly affected by water. The velocity step test shows that the frictional intensity of limestone fissures increases with the increase of sliding velocity, which shows the velocity enhancement. At last, through different effective normal stresses (between 1 and 3 MPa), it is found that the permeability of the fractures not only decreases sharply with the increase of effective stress but also decreases with the normal stress .