【作者】 徐学锋；

【导师】 窦林名；

【作者基本信息】 中国矿业大学 ， 采矿工程， 2011， 博士

【摘要】 煤层巷道底板冲击是冲击矿压灾害的一种,许多矿井发生过底板冲击现象。由于底板冲击发生位置的特殊性,很难采取针对性的防冲措施,造成的危害较大。论文在大量调研资料的基础上,采用理论分析、相似模拟试验、数值模拟和工程实践等手段,对煤层巷道底板冲击矿压发生的影响因素、开挖卸荷过程中底板应力变化规律、底板冲击的孕育过程、动载扰动下底板冲击显现规律进行了研究。在此基础上建立了底板冲击危险的力学模型和底板冲击危险的判别准则,提出了底板减冲和支护控制的技术,并在现场进行实践应用。相似模拟和数值模拟研究了底板冲击矿压的影响因素和冲击发生前的孕育过程。巷道底板冲击受煤层埋深、顶底板条件、巷道施工布置方式等多方面影响。在上覆巨厚坚硬岩层作用下,本工作面开采增加了相邻工作面的应力水平,在厚煤层中沿顶板布置巷道留底煤时,巷道开挖后,巷道底板煤层中的水平应力升高,垂直应力降低,增加了煤层失稳破坏的有利条件;巷道开挖卸荷过程中,底板的塑性区范围大于两帮,并在塑性区变化过程中产生了明显的拉伸破坏,容易使底板成为冲击破坏的突破口。对微震监测记录的冲击矿压波形进行分析,波形的频谱特征表明动力扰动是冲击矿压发生的重要条件。采用FLAC2D软件的Dynamic模块模拟研究了动载扰动作用下底板冲击显现的规律,研究结果表明处于极限应力状态下的底板煤体在动应力波扰动作用下,水平应力、垂直应力、应力差先上升后瞬间大幅度降低,随后底板煤体拉伸破坏的层裂破坏范围和垂直位移瞬间增加。在此过程中,底板水平应力集中现象逐渐消失。理论分析了底板冲击破坏的原因,建立了巷道底板冲击危险的力学模型。认为巷道底板发生破坏与巷道埋深、巷道宽度、巷道底板易发生层裂破坏的结构厚度、底板煤岩层的弹模、泊松比、水平构造应力及巨厚坚硬老顶等因素有关。提出了底板冲击危险性系数Kfb,建立了底板冲击危险的判别准则,即当Kfb≥1时,巷道底板煤岩层容易发生破坏。根据底板煤层冲击破坏的临界厚度和跃进煤矿发生冲击矿压的实例,将底板冲击矿压危险性分为三类:无底板冲击危险、弱底板冲击危险和强底板冲击危险。对底板冲击矿压的防治,数值模拟和现场实践研究认为,采用爆破法对巷道两帮煤体进行强度弱化,可间接减小底板水平应力,起到了诱冲为主、减冲为辅的作用,而采用断底爆破对底板煤体进行强度弱化能明显降低底板的高水平应力,是底板冲击危险解危的有效方法。为了控制巷道底板冲击灾害,设计了锚网+“O”型棚联合支护形成的封闭柔性支护结构,通过数值模拟分析和现场实践表明,该支护结构虽然不能从根本上消除冲击危险,但具有抑制底板冲击显现规模和程度、降低冲击灾害的作用。根据以上研究成果,对冲击严重的跃进煤矿23130面下巷和25110面下巷采取了针对性的控制措施,取得了明显效果,验证了煤层巷道底板冲击机理和控制理论对防冲实践具有较好的指导性。本论文有图90幅,表13个,参考文献115篇。更多还原

【Abstract】 Floor burst is one kind of the rock bursts, and it often seriously happens during the coal seam excavation and roadway driving in some coal mines. As the special burst position and no prevention measures are used, floor bursts have caused seriously damages. According to lots of research data and excavation and mining conditions of Yuejin Coal Mine, theory analysis, numerical simulation, similar simulation and industry practice are used to research the influence factors, the stress and physical and mechanical parameters preparatory process of floor burst during excavation, floor burst appearing laws under dynamic loads, floor burst hazard discriminatory, intensity weakening measures and support structures. The research results are applied to burst control practice in order to verify correctness of the theory.Through numerical simulation and similar simulation methods, the influence factors and preparatory process are researched. The results show that the conditions have great influence on floor burst, such as mining depth, roof condition and roadway drifting and layout ways.On the influence of the heave hard roof, the mining of working face will increase the stress of adjacent coal seam of working face. In high coal seam, roadway is cut along roof of the coal seam, so the floor is coal seam. After roadway is cut, there are areas of vertical stress rising and horizontal stress reducing in the floor, and this raises the burst hazard of floor failure. During the roadway is cutting, the plastic zone of floor is bigger than the two sides, and tensile failure zone distributes in the floor obviously, and this is the sally port of floor burst.Fourier transform is used to analyze the frequency spectrum characters of microseismic signals of rock bursts induced by dynamic disturbance , the results show that dynamic disturbance is necessary condition for rock bursts. The dynamic module of FLAC2D soft is used to analyze the rock burst appearing laws under dynamic loads. The results show that the stress and physical mechanical parameters have changed greatly under dynamic loads. In the dynamic loads process, horizontal stress ,vertical stress and stress difference increase in a small extent and decrease substantially, and the floor velocity and accelerate change rapidly soon after. At the same time, the plastic zone expands, and tensile failure zone appears obviously in the floor with the vertical displacement increases subsequently. After the process, horizontal concentrated stress disappears, and this is the floor burst process under dynamic loads.According to the theory analysis and characteristics of floor burst, a mechanical model is set up, and the dangerous coefficient of floor burst is also initially given. The research results show that the depth, the elastic modulus of rock, the thickness of soft rock in the floor, the horizontal tectonic stress, and the heave hard roof are seriously relevant to the floor burst. The dangerous coefficient of floor burst Kfb is also initially given to evaluate the floor burst hazard .As the dangerous coefficient of floor burst is more than or equal to 1, the floor failure will happen. Based on the critical thickness of floor failure and floor bursts data of Yuejin Coal Mine, floor burst hazard is classified into three categories: no floor burst dangerous, weak floor burst dangerous and strong floor burst dangerous.According to numerical simulation, the two sides intensity weakening can indirectly decrease the horizontal stress of floor. In practical application, the two sides blasting can weaken floor burst dangerous indirectly, and can induce floor burst directly. Based on the numerical simulation results and field application, the floor intensity weakening can remove the horizontal concentrated stress, and it is an effective method to weaken the floor burst dangerous.In order to solve the support technique of floor burst of coal seam roadway, theoretical analysis and numerical simulation is used to research the control function of closed compressible supporting structure made up of anchor net and“O”type shed on floor burst. The research results show that closed flexible supporting structure can not remove shock hazard entirely, however, it can reduce the rock burst extent. The results provide theoretical foundation for roadway support in the same coal mine conditions.According to the research results, the appropriate measures for floor burst prevention are applied in the lower gateway of 25110 coal face and 23130 coal face in Yuejin Coal Mine, and has gained good effect, and this proves the theory of mechanism and controlling technology of floor burst in coal seam roadway is correct.更多还原