承压水上开采沿工作面倾向底板力学破坏特征

Mechanical failure characteristics of mining floor along working face inclination above confined water

为了研究承压水上开采沿工作面倾向底板应力分布规律和变形破坏特征,运用弹性力学理论,建立考虑沿工作面倾向支承压力分布和承压水共同作用的底板应力计算模型,结合初次和周期来压特点,理论推导计算底板应力分布和破坏形态,并利用FLAC3D数值模拟和原位测试技术进一步探讨开采后沿工作面倾向底板力学破坏特征和应力分布特点。研究表明:(1)理论计算采后底板呈"倒马鞍形"破坏形态,且剪切应力呈"反向对称螺旋状"分布,近似一对正负剪切力偶,易沿边界产生剪切滑移破坏,这与数值模拟得到的塑性区及应力分布特点相吻合;(2)应力集中程度最大值位于弹塑性交界附近,初次和周期来压支承压力系数之比与最大垂直应力集中系数比值近似相等;(3)模拟表明,开采后孔隙水沿底板递进导升,易从工作面端部斜下方涌入工作面,形成突水现象,与实际突水部位相吻合;(4)理论计算、数值模拟和现场实测底板最大破坏深度分别为12,12.875和13.75 m,三者结果大致相当。所构建力学模型计算结果与数值模拟所得有较好的一致性,更加符合现场实际破坏形态,其研究成果可为承压水上开采底板破坏机制提供一定的理论依据,对矿井防治水具有指导意义。

In order to study the stress distribution and mechanical failure characteristics of mining floor along the inclination of the working face above confined water,mechanical models of floor rock were constructed considering the combined action of supporting pressure and confined water along the inclination of the working face respectively.The stress distribution and failure form of floor were theoretically calculated considering the characteristics of initial and periodic pressure.The mechanical failure characteristics and stress distribution of mining floor based on numerical simulation of FLAC3D and in-situ testing technology were further discussed.The failure tendency of mining floor along the inclination of the working face has an＂inverted saddle shape＂.The corresponding shear stress is distributed in＂reverse symmetry spiral＂,which approximates a pair of positive and negative shear couple and is easy to produce shear failure along the boundary.This is in accordance with the failure zone and the stress distribution from numerical simulation.The maximal value of concentration level is located at the boundary of the elastic and plastic junction.The ratio of the supporting pressure coefficient under the initial and periodic pressure is approximately equal to that of the maximum vertical stress concentration coefficients.The simulation shows that the pore water is progressively promoted along the floor and easy to pour into the working face from the underneath part of its two ends,forming a water inrush phenomenon,which is in accordance with the actual water inrush position.The maximum failure depths from theoretical calculation,numerical simulation and field measurement are 12,12.875 and 13.75 m respectively,and the three results are quite close to each other.The results obtained from the mechanical model are in good agreement with one from the numerical simulation,and are consistent with the actual failure mode.