|Budget Amount *help
¥2,700,000 (Direct Cost : ¥2,700,000)
Fiscal Year 1999 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 1998 : ¥2,000,000 (Direct Cost : ¥2,000,000)
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.