砂岩等岩体内部通常含有节理，当受到外界载荷扰动时砂岩往往沿着节理贯通形成滑移面。砂岩沿着节理面滑动，节理表面凸体不断磨损，导致节理表面粗糙度不断变化，进而影响砂岩滑动的稳定性。利用自制滑动摩擦试验装置对劈裂砂岩节理进行了滑动摩擦试验，采用高分辨率相机、电子分析天平、动态应变仪和激光共聚焦扫描显微镜测量滑动过程中磨损面积、摩擦质量、摩擦因数和表面粗糙度的变化。结果表明:滑动过程分为初始滑动、磨合和稳定滑动3个阶段。在初始滑动阶段，砂岩节理表面的初始粗糙度值较大，磨损面积较小，磨损质量和摩擦因数都较大;在磨合阶段，已磨损区域表面的微凸体不断被剪断、磨平，表面粗糙度降低趋势变缓，新增磨损面积不断减小，但在总磨损面积的占比仍大于10%，磨损质量和摩擦因数出现局部跳动的现象;在稳定滑动阶段，磨损区域与金刚石磨片表面已基本匹配，表面粗糙度趋近于定值，新增磨损面积在总磨损面积的占比小于10%，磨损质量和摩擦因数都逐渐趋于稳定，最终在某一稳定值附近波动。利用激光共聚焦扫描显微镜对砂岩节理表面轮廓进行了测量，选取轮廓的均方根估算了节理粗糙度系数，发现节理粗糙度系数主要受磨损区域面积影响，局部粗糙度对节理粗糙度系数影响较小。建立了以磨损面积为变量的摩擦因数预测模型，模型能够反映滑动过程中砂岩节理摩擦因数的变化，当修正系数a=2.5时，摩擦因数预测值与试验值吻合良好，最小误差为2.89%。

Interior of rock mass,such as sandstone,has joint in general.The sandstone penetrates along joints to form a slip surface when disturbance by external loading.The sandstone slides along the joint surface,the asperities on the surface of joints are constantly worn leading to the constant changes of the roughness of the joint surface,which affects the sliding stability of sandstone.The reciprocating sliding friction test is performed on the split sandstone joints using the self made sliding friction test device.The changes of wear area,wear mass,friction coefficient,and surface roughness are measured through a high resolution camera,electronic analytical balance,dynamic strain gauge,and laser confocal scanning microscope during the sliding process.The results indicate that the sliding process can be divided into three stages,such as the initial sliding stage,the running in stage,and the stable sliding stage.In the initial sliding stage,the initial value of roughness of the sandstone joint surface is relatively large,the wear area is small,and the wear mass and friction coefficient are large.In the running in stage,the asperities on the surface of the wear area are constantly sheared off and ground flat,the decreased trend of surface roughness slows down,the new wear area constantly decreases.The proportion of newly added wear area in total wear area is still higher than 10%,and the wear mass and friction coefficient appear to have a jump phenomenon.In the stable sliding stage,the surface of the wear zone is matched with the diamond lapping,and the roughness of the wear zone tends to be a stable value.The proportion of newly added wear area in total wear area is less than 10%.The wear mass and friction coefficient finally tend to be stable and fluctuate at the surrounding of a stable value.The surface profile of sandstone joints is measured through the laser confocal scanning microscope,and the root mean square of the profile is chosen to evaluate the joint roughness coefficient.It demonstrates that the joint roughness coefficient is mainly affected by the wear area,while the effect of local roughness is small for the joint roughness coefficient.The prediction model of the friction coefficient of a sandstone joint based on the variable quantity of the wear area is established,and the change of joint roughness coefficient during the sliding process can be reflected by the model.The estimated value is in good agreement with the test value when the correction coefficient a=2.5 and the minimum error is 2.89%.

1 砂岩滑动摩擦试验

   1.1 试件准备

   1.2 表面粗糙度及质量的测定

   1.3 试验过程

2 试验结果与分析

   2.1 试验结果

   2.2 滑动过程中表面粗糙度变化规律

   2.3 磨损质量、磨损面积和摩擦因数变化规律

   2.4 节理粗糙度系数的估算

3 滑动过程中砂岩节理摩擦因数预测模型

   3.1 滑动过程中砂岩节理摩擦因数预测模型

   3.2 节理摩擦因数预测模型的修正

4 结论