大倾角煤层长壁开采顶板结构时空演化特征

Space-time evolution characteristics of roof structure in longwall mining of steeply dipping coal seam

为了明确大倾角煤层走向长壁开采顶板结构时空演化规律,采用物理相似模拟、数值模拟、现场实测综合互馈的研究手段,对采空区矸石的非均匀充填特征、顶板结构空间展布形态、围岩主应力大小渐变与方向偏转的演化过程和支架工作阻力的区域性特征进行研究。结果表明:随着推进距离的不断增大,底板上矸石堆积范围增大,在支架后方采空区开始往复出现倒三角的临空面;在深部采空区,矸石堆砌与水平面之间夹角沿倾向下部至上部不断减小;顶板位移呈现出“增大-稳定”的演化趋势,峰值位置由工作面倾向中上部区域向倾向中部迁移;顶板应力传递拱壳呈典型的非对称分布特征,拱壳内部岩体受力状态由双向受压转为单、双向受拉,主应力方向由x轴正向转为负向;顶板变形破坏的非对称性使得工作面支架工作阻力呈现倾向中上部较大、离散程度高,倾向中下部较小、离散程度低的区域特征。研究结果可为大倾角煤层长壁采场顶板稳定性控制提供一定的参考与指导意义。

The clarifying of space-time evolution law of roof structure is the key to safe and efficient longwall mining of steeply dipping coal seam.The comprehensive research methods of the physical similarity simulation experiment, numerical simulation and field measurement methods are adopted to explore, the non-uniform filling characteristics of gangue in gob, spatial distribution form of roof structure, the evolution law of principal stress value and direction deflection of surrounding rock and the regional characteristics of mining pressure in working face.The results show: with the advancing distance increasing, the accumulation range of gangue expands, and the inverted triangle airspace begins to appear repeatedly in the gob behind the support.In the deep gob, the angle between the gangue pile and the horizontal plane decreases continuously from the lower part to the upper part along the inclined direction.The displacement of roof shows an evolutionary trend of “increase-stability”.The peak displacement position moves from the upper part to the middle part of the working face, which is located at the hinge point between the broken block and the failure envelope surface.The stress transfer arch shell of roof is characterized by typical asymmetric distribution.The stress state of the rock mass inside the arch shell changes from two-way compression to one-way and two-way tension, and the stress direction changes from x-axis positive to negative.Asymmetric characteristics of roof deformation and failure make the working resistance of working face show regional characteristics of large tendency in the middle and upper part with high dispersion degree, small tendency in the middle and lower part with low dispersion degree.The research results provide certain reference and guiding significance for the stability control of longwall stope roof in steeply dipping coal seam.