The progress of failure of mining developed cavern and its influence on the ground surface

从矿山安全与环境保护的角度出发，探讨什么条件会使开采发育的洞室破坏影响地表，什么条件会导致洞室大规模破坏，防止这种破坏的最小充填体积是什么。为此，在岩石力学的基础上，我们提出了一种基于有限元法的弹塑性分析方法，假设洞室已经存在很长时间，岩石强度已经足够低。然后，我们将该方法应用于某矿山的大型洞室。结果表明，洞室的破坏将向洞室上方推进约100米，但不会影响地表。接下来，为了清除上述条件，我们将此方法应用于平坦表面下的许多均匀分离的洞穴。在此分析中，考虑了通过改变洞室深度、矿柱宽度和水平方向与垂直方向应力比设置的8种情况。因此，下列事项获得批准。当洞室深度大于洞室高度的2倍、矿柱宽度大于洞室宽度的2倍时，破坏的进展对地表没有影响。当应力比大于3且矿柱宽度大于洞室宽度的2倍时，很少发生大规模破坏。这些结果仅来自对8个病例的分析。因此，为了得到更普遍的结果，我们必须研究更多的案例。

From the standpoint of safety and environment keeping in a mine, it is important to discuss what conditions make the failure of mining developed caverns affect the ground surface, what conditions induce large-scale failure of the caverns and what is the minimum volume of filling to prevent such failure. To do this based on rock mechanics, we proposed an elasto-plastic analysis method using FEM assuming that the caverns have passed very long time and the strength of rock has been lower enough. Then, we applied this method for the large caverns of a mine. As the results, it was cleared that the failure of the caverns will progress about 100m upper to the caverns but will not affect the ground surface. Next, in order to clear the conditions as mentioned above, we applied this method for the many equally separated caverns under a flat surface. In this analysis, eight cases set by changing the depth of the caverns, the width of pillars and the stress ratio of horizontal direction to vertical direction were considered. Consequently, the followings were cleared. The progress of the failure does not affect the surface when the depth of caverns is deeper than the twice of caverns' height and the width of the pillars is larger than the twice of caverns' width. Furthermore, the large-scale failure rarely occurs when the stress ratio is as large as three and the width of the pillars is larger than the twice of caverns' width. These results were derived from the analysis only for eight cases. Therefore, in order to get more general results, we must study for much more cases.