大倾角采场覆岩结构及矿压显现特征分析

Analysis of overlying strata structure and strata behavior characteristics of stope in steep coal seam

针对大倾角煤层采场顶板受力特点建立了非均布载荷作用下顶板的固支梁模型,分析了顶板受力特征,并且结合工作面倾向覆岩运动特征分析了大倾角煤层开采时的矿压显现规律。研究结果表明:大倾角采场顶板压应力最大值位于下端头处梁的下表面,其值比上端头高36%左右,而最大拉应力位于梁上端头的上表面,其值比下端头上表面处拉应力高26%左右,梁的不均衡受力特征以及岩石抗压不抗拉的特性导致工作面上部首先破断失稳造成较早来压;上端头梁的较早受拉破坏以及煤层倾角的影响导致沿倾向由下至上可分为密实充填段、不均匀充填段和动载影响段。密实充填段内覆岩结构主要为受垮落矸石支撑的长悬臂梁,来压强度最小,动载影响段主要表现为短悬臂梁,支架载荷平时较小,动载特征明显。现场支架工作阻力监测结果验证了顶板受力分析和倾向覆岩移动假设的合理性。

Aiming at the mechanical features of stope in steep coal seam,the clamped beam model of roof subjected to non- uniform load is established,the stress characteristics of roof are obtained and the mine pressure behavior during steep coal seam mining are analyzed combining with the motion features of overlying strata along the dip. The results show that the max compressive stress in steep stope locates at the lower surface of the lower beam and its value is about 36% larger than the upper. The max tensile stress locates at the upper surface of upper beam and its value is 26% larger than the lower. The non- uniform stress of beam and the rock characteristics of higher compressive resistance but lower tensile strength lead early failure in the upper roof and cause roof weighting. Considering the early failure of upper beam and dip angle of coal seam,the work face can be divided into solid filling zone,non- uniform filling zone and dynamic load zone.The structure of overlying strata in solid filling zone is mainly long cantilever beam supported by caved gangue,and its weighting intensity is the smallest of all zones. The dynamic load zone shows short cantilever beam structure,and the load of supports is usually smaller but larger at roof weighting,which shows obvious features of dynamic load. The monitoring results of supports＇ working resistance have verified the rationality of mechanical analysis of roof and the hypothesis about strata movement along inclination.