Prevention and control technology of collapse and slide disasters inducted by coal mining
1. Introduction
The mountainous area in Southwest China has an intense geological structure and huge topographic gap, and is a region prone to geological disasters such as landslide, collapse and debris flow in China. Fa’er Coal Mine, located in the west of Guizhou Plateau, is an important production mine of Yankuang Group Guizhou Nenghua Co., Ltd. In 2007, mining works began at district 3 of wellblock 1 in Fa’er Coal Mine. In the process of mining, the overlying rock mass was deformed discontinuously, resulting in a large number of mining cracks and geological disasters such as cracking and collapse, which threatened the production and life of villagers around the mining area. It is planned to develop coal resources in district 5 of wellblock 1 as the replacement of the third mining area. The terrain of district 5 is steep, and the surface drop is more than 800m. The upper part of the slope body is the huge thick limestone of Yongningzhen Formation (T1yn) of the Lower Triassic, and the bottom part is the sand mudstone of Feixianguan Formation (T1f), which is a geological structure with poor stability of “harder at top and softer at bottom”. Due to the stoping works of underground coal resources, the intense adjustment in slope stress field will induce large-scale surface deformation and movement. Once the slope becomes unstable, it will block and threaten the tributary of Beipanjiang River to form a dammed lake, and at the same time form a high-level remote landslide disaster, seriously threatening power plants, villages and towns, schools and roads.
Figure 1 Damage to Mountain after mining works in district 3 | Figure 2 High and steep mountains in district 5 |
2. Solution
The existing geological disaster investigation, engineering geological mapping and joint crack statistics were carry out in the district 5 to find out the structural characteristics of rock mass; using engineering geological analogy analysis and numerical simulation methods, the deformation and failure mode and influence range of collapse disaster in high and steep hillside were studied, and the stability and harmfulness of mining-induced collapse were evaluated by optimizing key mining technical parameters such as mining range, mining sequence and working face setting in district 5 to realize the coordinated mining of coal seams in district 5.
Figure 3 Solutions
3. Construction situation
The numerical calculation models of 10 typical sections were established, 100 groups of indoor simulation tests were carried out, and the surface movement deformation parameters such as surface subsidence value, horizontal deformation value and horizontal movement value under different mining schemes were obtained. Two stability calculation models of mining slope were established, and the stability analysis of high and steep mountains under mining conditions was realized.
Figure 4 Diagram of horizontal displacement before coordinated Mining | Figure 5 Diagram of longitudinal displacement before coordinated Mining |
4. Achieved Accomplishment
By optimizing the key mining parameters such as mining sequence, working face layout and mining time interval, the planar range, depth and scale of collapse of high and steep mountains became smaller, and the whole collapse-instability of mountain changed into shallow and local collapse and slide. Safe and efficient mining of coal resources in District 5 has been realized.
Figure 6 Diagram of horizontal displacement after coordinated mining | Figure 7 Diagram of longitudinal displacement after coordinated mining |
Table 1 Comparison of surface movement and deformation of slope before optimization
Maximum Subsidence Value (mm) | Maximum Horizontal Deformation Value (mm | Maximum Inclination Value (mm/m) | |||||||
Before optimization | After optimization | Rate of decrease | Before optimization | After optimization | Rate of decrease | Before optimization | After optimization | Rate of decrease | |
Upon completion of mining in coal mine 1 | 1.1 | 1.1 | 0 | -8 | -8 | 0 | -3/4 | -3/4 | 0 |
Upon completion of mining in coal mine 3 | 2.5 | 1.4 | 44% | -11.5 | -4 | 65% | -8/9 | -3/2 | 62% |
Upon completion of mining in coal mine 5-2 | 3.9 | 1.5 | 62% | -15.0 | -3 | 80% | -15/18 | -5/3 | 67% |
Upon completion of mining in coal mine 5-3 | 5.2 | 1.1 | 78% | -23.5 | -2.5 | 88% | -21/28 | -3/2 | 86% |
Upon completion of mining in coal mine 7 | 7.1 | 2.0 | 72% | -27 | -4 | 85% | -24/42 | -7/4 | 71% |
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