浅埋煤层不同采—充—留条件下地表沉陷控制研究

发布时间：2018-07-22 13:06

【摘要】：地下开采破坏了覆岩的原岩应力场，并使覆岩变形以某种方式传递到地表。地表沉陷不但会使矿区耕地减少，而且由下沉引起的地表变形会使地表建筑物发生倾斜、开裂甚至倒塌的危险，对于浅埋大采高煤层，这种现象尤为突出。目前，膏体充填开采、条带开采及置换开采是缓解地表下沉、控制沉陷的有效方法。膏体充填不仅是一种有效的减沉方法，而且还可以有效的减少矿区的矸石堆放。膏体充填材料的力学性质、变形性质决定了充填开采对地表沉陷控制效果的优劣。条带开采中合适的采留宽度不但能有效的控制地表变形，还能在保证留设煤柱长期稳定的基础上提高煤炭采出率。基于载荷置换理论的置换开采在合适的充填材料配比下不但能保证置换前后地表变形仍控制在建筑物I级允许值以内，而且能最大化的置换煤柱。论文通过实验室制备具有膨胀变形性质的膏体材料、理论分析各减沉方法的减沉机理以及针对浅埋煤矿中三种减沉方法的数值模拟研究，系统的分析对比了不同材料配比下充填开采、置换开采的减沉效果并与最佳采留条件下的条带开采进行对比。主要内容及结果如下: (1)实验室制备了具有膨胀特性的膏体材料，分析了膏体材料的膨胀率、抗压强度、抗剪强度、抗拉强度、内摩擦角、内聚力随膨润土含量的变化关系。实验表明：在膏体材料中掺入一定比例的膨润土,可以提高充填体的膨胀率，但会降低其单轴抗压强度，，而且较高的膨润土掺量不利于膏体材料的和易性、流动性。当膨润土与水泥质量之比为0.6时，膨胀率达到2.25%，材料28d时的抗压强度为4.85Mpa，材料为最佳配比。 (2)针对山西西部某矿的具体地质条件，采用FLAC3D模拟软件利用不同配比时测得的膏体材料力学参数对该矿18112工作面进行完全充填开采的数值模拟。结果表明：充填体接顶率在控制顶板及地表下沉中的影响大于充填体强度的影响，随着膨润土与水泥质量之比的增加，地表变形减小，覆岩垂直应力减小，覆岩破坏区域减小。当膨润土与水泥质量之比为60%时，充填体完全接顶，覆岩应力场最接近原岩应力分布，此时的地表变形最小，且均在建筑物I级允许值以内。 (3)基于条带煤柱的强度理论设计了不同采留比的条带开采方案，模拟结果表明：采35m留30m时地表没有出现波浪下沉且变形均在建筑物I级允许值以内，煤柱安全系数最大，煤柱能保持长期稳定性，采出率达到53.8%。模型高度方向30m以上区域覆岩处于原岩应力状态，而该区域以下煤柱上方存在应力增高区，采空区上方存在应力降低区，并且留宽越大，原岩应力区范围也越大。留设煤柱两端边缘已破坏，应力为0MPa，从煤柱边缘到距离两端小于5m处煤柱只有残余应力，煤柱承受的最大应力均出现在距边缘5m处，煤柱中部受力最小，煤柱屈服区宽度不随采宽的变化而改变。 (4)基于条带开采的置换煤柱研究表明：当充填高度达到4.5m即充填体可以完全接顶时，可将30m煤柱完全置换，此时地表下沉与置换开采前几乎相等。而当充填体不能完全接顶时，置换后地表变形值大幅增加。当留设煤柱两端各保留5m小煤柱时，充填高度由4.3m增加到4.4m，其垂直应力与置换前的差值逐渐减小，并且应力变化规律与置换前相似，此时地表变形与置换前相比稍有增加，但仍小于建筑物I级允许值，说明留设的小煤柱在充填体接顶前有效的控制了顶板下沉。
[Abstract]:Underground mining destroys the original rock stress field of overlying rock and causes the overlying rock deformation to be transferred to the surface in some way. The surface subsidence not only reduces the cultivated land in the mining area, but also causes the surface deformation caused by the subsidence to cause the slope, crack and even the collapse of the surface of the surface, especially for the shallow and large coal seam. Body filling mining, strip mining and replacement mining are effective methods to mitigate surface subsidence and control subsidence.
Paste filling is not only an effective method of reducing subsidence, but also can effectively reduce the dumping of gangue in the mining area. The mechanical properties of the paste filling material and the deformation properties determine the effect of filling mining on the control of surface subsidence. The suitable mining width in strip mining can not only effectively control the surface deformation, but also guarantee the retention of the ground. On the basis of long-term stability of the coal pillar, the coal recovery rate is improved. The replacement mining based on the load displacement theory can not only ensure that the surface deformation is still within the allowable value of the I level of the building before and after the replacement, but also maximizes the displacement coal column. In this paper, the mechanism of sedimentation reduction and the numerical simulation of three methods for subsurface subsidence in shallow buried coal mine are analyzed theoretically. The analysis and comparison of filling mining under different material ratio and the comparison of the settlement reduction effect of displacement mining with the optimum mining conditions are compared. The main contents and results are as follows:
(1) a paste material with expansion characteristics was prepared in the laboratory. The expansion ratio, compressive strength, shear strength, tensile strength, tensile strength, internal friction angle, and cohesive force with the content of bentonite were analyzed. The experiment showed that a certain proportion of bentonite in the paste material could improve the expansion rate of the filling body, but it would reduce it. The uniaxial compression strength, and the higher bentonite content is not good for the paste material and the fluidity, when the ratio of the bentonite to cement is 0.6, the expansion rate is 2.25%, the compressive strength of the material 28d is 4.85Mpa, and the material is the best ratio.
(2) according to the specific geological conditions of a mine in Western Shanxi, the numerical simulation of full filling mining on the 18112 working face of the mine is carried out by using the FLAC3D simulation software. The results show that the influence of the filling roof rate on the control roof and the surface subsidence is greater than the effect of the strength of the filling body. With the increase of the ratio of bentonite to cement, the surface deformation decreases, the vertical stress of overlying rock decreases, and the failure area of overlying rock decreases. When the ratio of bentonite to cement is 60%, the filling body is fully connected to the roof, and the stress field of the overlying rock is closest to the distribution of the original rock stress, and the surface deformation is minimum at this time, and it is within the allowable value of the I grade of the building.
(3) based on the strength theory of strip coal pillar, the strip mining scheme with different recovery ratio is designed. The simulation results show that there is no wave subsidence and the deformation is within the allowable value of the building I level when the 35m is retained for 30m, the coal pillar safety factor is maximum, the coal pillar can maintain the long-term stability, and the recovery rate reaches the height direction of the 53.8%. model above 30m area. The overlying rock is in the stress state of the original rock, and there is an increasing stress area above the coal pillar below this area. There is a stress reduction area above the goaf, and the greater the width of the area, the greater the range of the stress area of the original rock. The stress of the left side of the pillar has been destroyed and the stress is 0MPa. The coal pillar is only residual stress from the edge of the coal pillar to the distance less than 5m and the pillar is subjected to the coal pillar. The maximum stress appears at 5m from the edge. The stress in the middle of the pillar is the smallest, and the width of the pillar yield zone does not change with the change of mining width.
(4) the study of replacement coal pillar based on strip mining shows that when the filling height is 4.5m, the 30m pillar can be completely replaced, and the surface subsidence is almost equal to that before the displacement mining. When the filling body can not be fully connected to the top, the deformation value of the surface after the replacement is greatly increased. When the retained coal pillar is retained at both ends of the pillar, 5m small coal is retained. In the column, the filling height is increased from 4.3m to 4.4m, and the difference between vertical stress and before replacement gradually decreases, and the variation of stress is similar to that before replacement. At this time, the surface deformation is slightly increased compared with that before replacement, but it is still less than the allowable value of the I level in the building, indicating that the small coal pillar is effectively controlled by the roof subsidence before the filling body is connected to the roof.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TD327

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