露天边帮煤井工长壁综放开采工作面顶板压力计算

受露天矿剥离和内排回填的影响,采用井工长壁采煤法回采露天矿边帮煤的采煤工作面的顶板结构、覆岩活动规律、矿山压力显现规律与常规井工矿井地层条件下的工作面相比存在显著差别,因此,顶板压力计算方法也需要根据露天矿边帮煤特殊的顶板覆岩结构特点和应力场环境进行理论和实验研究。以黑岱沟露天矿一采区西帮和南帮煤为研究对象,分析其边帮煤层顶板覆岩结构特点。对于经过内排回填,且剥离较多的低台阶处煤层仅保留较薄且强度较低的基岩顶板,其上覆盖厚层的松散排土。这种软弱薄基岩厚松散覆盖层的顶板本质上不存在关键层,露天矿台阶下保留的软弱薄基岩仅仅作为井工长壁工作面的直接顶提供有限的保护作用。由于厚层的松散排土载荷作用,软弱薄基岩的破碎也较为严重。按照传统的矿山压力理论,这种不存在关键层的软弱薄基岩厚覆盖层的顶板压力应当按照支架上方全部岩层重量进行计算。然而,根据相似材料实验结果显示,支架实际受压比其上方岩层重量小得多。实验证明在没有关键层的顶板岩层中仍然存在某种保护结构。根据实验观察和矿山压力理论分析,结合放矿理论,提出了软弱薄基岩厚覆盖层的椭球拱结构和直接顶自承能力相结合混合力学模型。在露天矿边帮下煤层还存在另一种未进行内排回填的薄基岩无覆盖层的顶板覆岩类型。对于这种顶板覆岩类型,提出了薄基岩无覆盖层的台阶式悬臂梁结构和直接顶自承能力的混合力学模型。本文总结了露天矿边帮煤层3种顶板覆岩类型,推导建立了露天边帮煤井工长壁开采工作面3种顶板结构条件下的顶板压力计算解析公式。按照软弱薄基岩厚覆盖层的椭球拱结构和直接顶自承能力相结合混合力学模型计算的顶板压力与相似材料实验结果相吻合。考虑了直接顶自承能力计算的顶板压力比传统不考虑直接顶自承能力的顶板压力小约14%。采用实验和理论分析方法,对露天边帮煤井工长壁工作面开采过程顶板垮落、覆岩活动,顶板压力计算等矿山压力问题进行了系统研究。

Calculation of roof pressure in longwall fully mechanized top coal caving face with open-pit slope mine

Under the influence of open-pit mine stripping and internal backfill,there is a significant difference between the roof structure,overburden rock activity law and mining press show rule in longwall mining face of open-pit slope mine,which is different from the conventional formation condition working face.Therefore,calculation method of roof pressure also needs to be studied theoretically and experimentally according to the special roof overburden structure characteristics and stress field environment of the open-pit mine slope coal.The west side slope and south side slope coal seam in heidaigou open pit No.1 mining area is research background.The characteristics of the side slope coal seam roof overburden structure are analyzed.The coal seam at the low open-pit bench is internal backfill,and the stripping is more.This thinner and lower strength bedrock roof is covered with massive loose dumping.There is essentially no key stratum in the roof of the thick loose overburden of the weak thin bedrock.The weak thin bedrock under the bench of open-pit mine only provides a limited protective effect as immediate roof of longwall mining face.The crushing of weak the thin bedrock is also more serious because of the thick loose dumping loading.According to the traditional underground pressure theory,the roof pressure calculation of the thick loose overburden of the weak thin bedrock with no key stratum should be calculated according to the weight of all rock stratum above the support.However,according to the experimental results of similar materials,the actual pressure of the support is much smaller than the weight of the rock stratum above it.Experiments show that some protective structures still exist in roof strata with no key stratum.Based on the experimental observation and the analysis of underground pressure theory,combined with drawing theory,a hybrid model of the thick loose overburden of weak thin bedrock is proposed.The model is composed of the ellipsoid arch structure and the self-stability of immediate roof.In the open-pit mine slope coal,there are also another with no internal backfill roof overburden types of thin bedrock without overburden.For this roof overburden type,a hybrid model of thin bedrock without overburden is proposed.The model is composed of step cantilever beam structure and the self-stability of immediate roof.This paper summarizes the types of three roof overburden in the open-pit slope coal,and deduces and establishes an analytical formula for calculation method of roof pressure under the condition of three roof structures in longwall mining face of open-pit slope mine.According to the hybrid model of the thick loose overburden of weak thin bedrock,that is,the roof pressure calculated by the hybrid mechanical model combining ellipsoid arch structure and the self-stability of immediate roof is consistent with the result of similar materials experiment.Considering the self-stability of immediate roof of the calculation of the roof pressure than the traditional do not consider the self-stability of immediate roof of the roof pressure is about 14% less.Using experimental and theoretical analysis methods,the problem of ground pressure,such as roof caving,overburden strata movement,roof pressure calculation and so on,is systematically studied in longwall mining face mining process of open-pit slope mine.