滚石在平台上的运动特征分析

Study on the Movement Charateristics of Rolling Rock Blocks on Platform

平台对危岩体失稳后运动有很好的减速拦阻作用，是危岩体防治的有效措施。采用运动学和力学的方法推导了滚石与平台碰撞过程的速度计算公式；探讨了滚石在平台上运动的水平距离的计算方法；在此基础上通过现场滚石试验，分析了滚石形状对滚动摩擦系数的影响。结果表明：滚石与平台碰撞后的速度可由法向恢复系数、切向恢复系数和碰撞前滚石的运动速度确定；滚石在平台上运动的水平距离由第一次碰撞前在平台上飞跃的水平距离、两次碰撞之间水平距离和碰撞结束后滚动的距离3部分组成，其值可通过运动学分析确定，法向恢复系数、切向恢复系数和滚动摩擦系数是计算滚石在平台运动水平位移的重要参数；滚石与表面为块碎石的平台的滚动摩擦系数的值在0．19～1．05之间，按长条形、方形、球形和薄片状的顺序逐渐减小，滚石形状与表面为块碎石的平台之间滚动摩擦系数呈良好的直线关系。所得成果为将平台作为危岩体防治对策时确定平台的宽度提供理论依据。对危岩体与落石的防治有指导意义。

Platform has a good function to baffle potential unstable rock masses movement after their falling.. In this paper, using the kinematics and mechanics theoretical theories, the velocity calculation formula of collision process between rolling rock and platform were put forward, and the horizontal movement calculation method of rolling rock moving on platform was studied. Furthermore, the rolling friction coefficient was researched on the basis of the test and the shape analysis of rolling rock. The test result showed that, the rolling rock moving velocity after collided with platform was ascertained by the normal restitution coefficient, tangential restitution coefficient and the rolling rock moving velocity before collided. The horizontal displacements of the rolling rock on platform have three parts： the horizontal span displacement above the platform before collision, the horizontal displacement between two collisions with the platform, and the rolling displacement after final collision. The displacement value can be en- sured with kinematics analysis. The normal restitution coefficient, tangential restitution coefficient and the rolling friction coefficient are the important parameters to calculate the horizontal displacement of the rolling rock movement on platform. The rolling friction coefficient value between rolling rock and platform with rock blocks and detritus and the platform with rock blocks and detritus surface is a good linear relation. The rolling friction coefficient of others shape rolling rock can be confirmed by interpolation method or regression formula. Then the new feasible methods to prevent potential unstable rock masses are put forward. The results help us make out a draft of geohazards prevention.