【作者】 张百胜；

【导师】 康立勋；

【作者基本信息】 太原理工大学 ， 岩土工程， 2008， 博士

【摘要】 由于成煤条件的不同,煤层的赋存条件各异。煤层厚度从零点几米到上百米,可采层数从一层到数十层,层间距离大小不等,有时还出现煤层局部合并或分岔现象。煤层层间距离不同,相互问开采的影响程度各异。当煤层层间距离较大时,上部煤层开采后对下部煤层的开采影响程度很小,其矿压显现规律,开采方法不受上部煤层开采影响。但是,随着煤层间距离减小,上下煤层间开采的相互影响程度会逐渐增大,特别是当煤层间距很近时,下部煤层开采前顶板的完整程度已受上部煤层开采损伤影响,其上又为上部煤层开采垮落的矸石,且上部煤层开采后残留的区段煤柱在底板形成的集中压力,导致下部煤层开采区域的顶板结构和应力环境发生变化。从而使下部煤层开采与单一煤层开采相比出现了许多新的矿山压力现象。主要表现在下部煤层开采时,极易发生顶板冒漏,严重时造成支架压埋;当与上部煤层采空区沟通,造成工作面漏风,易形成火灾隐患;巷道布置和支护方式盲目性较大,巷道的矿山压力显现十分明显,巷道支护困难。而现有单一煤层开采顶板岩层控制理论和经验,不能很好地解释这种矿压现象及机理。在极近距离煤层开采的过程中,存在许多技术难题。在我国近距离煤层赋存和开采所占比重很大,大多矿区都存在近距离煤层群开采的问题。目前,单一煤层开采围岩活动规律和控制的理论和实践研究已经有了很大进展,然而对近距离煤层开采研究相对较少,特别是极近距离煤层的开采技术的系统研究更少,有关极近距离煤层开采研究主要是实践性和经验性的定性总结。论文以大同矿区下组煤层群开采为主要研究对象,采用现场实测、理论分析、数值模拟计算和工业性试验等方法,对极近距离煤层的定义、极近距离煤层顶板分类、下部煤层开采矿山压力显现规律、工作面顶板控制,合理巷道位置及开采技术保障体系等几方面做了探索性研究。主要研究成果如下:(1)针对长壁工作面开采,运用弹塑性理论、滑移线场理论,结合上部煤层开采顶板垮落特点及应力分布规律推导出上部煤层底板损伤深度,给出了极近距离煤层的定义和判距。并结合大同矿区下组煤层群赋存和开采条件,进行极近距离煤层实例判别。(2)确定了以屈服比作为极近距离下部煤层顶板分类主要指标,对极近距离煤层顶板进行了分类(夹石假顶、碎裂顶板、块裂顶板)。(3)以大同矿区为例,通过现场实测和数值模拟分析的方法,揭示了极近距离下部煤层开采工作面矿压显现的基本特征和规律,为探讨极近距离下部煤层开采覆岩结构形式及采场围岩控制提供可靠的现实和理论基础。(4)针对极近距离煤层开采时顶板的结构特点,构建了下部煤层开采为散体边界条件的“块体—散体”顶板结构模型,运用块体和散体理论,对极近距离下部煤层开采顶板岩层结构稳定性进行分析。揭示了极近距离下部煤层开采顶板易于冒落的机理,并从理论上研究了极近距离下部煤层工作面支架载荷的确定方法。为下部煤层开采采场围岩控制提供了理论基础。(5)运用理论和数值模拟分析的方法,研究了极近距离煤层开采煤柱稳定性和煤柱载荷在底板煤(岩)层中的非均匀应力分布规律;理论分析了巷道在非均匀应力场中,支护体结构更易出现局部过载,产生局部破坏,最终可能导致支护体结构失稳的原因;提出了极近距离下部煤层回采巷道的合理位置确定方法。并通过现场实践进行验证。(6)针对极近距离下部煤层顶板受上部煤层采动损伤影响,顶板破碎,易漏冒顶,严重时造成支架压埋,漏风严重,易形成火灾等不安全隐患问题。采用现场实践的方法确定了顶板加固及漏顶充填技术、巷道合理断面形状与支护参数、工作面初末采空间控制及工艺、工作面超前支护方式以及泄压通风系统、汽雾阻化防火等安全保障体系。形成了一套较为完善的极近距下部煤层开采辅助技术,为实现极近距下部煤层安全回采提供可靠的技术保障。总之,本文通过深入、系统的研究了极近距离煤层开采围岩控制理论与技术,解决了极近距离煤层在煤矿开采中存在的实际问题,为今后极近距离煤层的开采、设计提供科学依据。更多还原

【Abstract】 The coal seams defer significantly in their occurrence: the thickness of coal seams varies from less than one meter to hundreds of meters; the number of useful coal seams ranges from one to tens; the is uneven; and sometimes such changes occur as merging and splitting because of the close spacing between lower and upper seams. Difference in interlamellar spacing between seams, especially extremely small distances affects the mining of adjacent coal seams heavily, and causes side effect on safety and highly efficient production.When the intelamellar spacing between seams is relatively big, the influence of the upper seam after being mined on the lower seam to be mined is actually little; its rule of coal mine pressure and mining method are free from the effect from the upper seam mined. But mining practice shows that with the narrowing of the spacing between two coal seams, especially when the distance between them is ultra close, the interaction between them will increase, and the continuity of the roof of the lower seam will be interrupted and its integral degree will be affected by the upper coal seam mining; on the lower seam is the gangue caved from the upper coal seam extraction, with the remaining pillar in the mining face forming a strong pressure on the underplate. The two factors will lead to changes in roof structure and stress on the part to be extracted in the lower seam. They will further give rise to many new phenomena in mine pressure when the lower seam is mined as is measured against single coal seam mining. The new phenomena are mainly manifested by the following. "When extraction is in process in the lower seam, roof falling and leakage, which at sever level may cause supports to be buried, is very likely to occur; air leakage in the working face, a firetrap, is hard to avoid when connected to the upper seam goaf; the scientific layout of roadway and supporting pattern is out of reach, thus rock pressure appearance becomes obvious and roadway supporting tends to be difficult to proceed. However, the existing theories and experiences on the control of roof strata in single coal seam mining cannot well explain this kind of rock pressure appearance and mechanism. Therefore in extra close seam mining exist many technological puzzles.In China, close seam occurrence and mining takes up great percentage and in almost every mine camp exists problems in mining of close coal seam group. So far, theory and practice research on the acting law and control of surrounding rocks in single coal seam mining has achieved great progress, while research on close seam mining, especially systematic research on ultra-close seam mining technology, is relatively few and far between. Most of the research on ultra-close seam mining is a practical and empirical qualitative summary.This thesis, taking coal seam group occurrence and mining condition in the lower groups of seams in Datong mining area as its object and adopting such methods as field investigation, theoretical analysis, numerical stimulation and industrial test, does some explorative research and comes up with the definition of ultra-close multiple coal seams, engineering classification of ultra-close multiple-seam roofs, law of strata pressure behaviors in lower seam mining, the control of roofs in working face, the rational roadway arrangement and the guarantee system for mining technology. The research achievements are as follows.(1) According to long wall face mining, with the elastic-plastic theory and slip-line field theory, combining roof falling characteristics in mining in the upper seam and stress distribution law, the roof destruction depth in the lower seam is worked out and the definition and estimated criterion of ultra-close multiple seams is obtained. At the same time, the ultra-close multiple seam spacing in the lower groups of seams in Datong mining area is determined with the coal seam group occurrence and mining conditions in the lower groups of seams in Datong mining area.(2) The roofs of ultra-close multiple-seam are divided into 3 types (false roofs, completetely broken roofs and fractured roofs) according to yield depth ratio, the leading parameter to classify the roofs of ultra-close multiple-seam.(3) In the example of Datong mining area, through on-site observation and numerical simulation analysis, the basic features and law of strata pressure behaviors in the working face of the lower seam mining in the ultra-close multiple seams is further disclosed. All these will lay a reliable practical as well as theoretical foundation for further research on the structure of overlying strata and strata control around longwall face in the lower seam mining in the ultra-close multiple seams.(4) In accordance with the roof structure characteristic in the ultra-close multiple seams mining, the "blocky-loosen" roof structure model is constructed with the lower seam mining as the loosen boundary condition; the roof strata structure stability is analyzed in the lower seam mining in the ultra-close multiple seams with the blocky and loosen theory; the roof falling mechanism is expounded in the lower seam mining in the ultra-close multiple seams; determination of the support in working face loading in the lower seam in the ultra-close multiple seams is researched theoretically. All the above provides a theoretical basis for the strata control around longwall face in the lower seam mining.(5) With theoretical analysis and numerical simulation computation, the coal pillar stability and the uneven stress distribution of coal pillar load in the floor seam in the ultra-close multiple seams mining is studied. Theoretical analysis is carried out about the tendency of the support structure to be locally overloaded in the gateway in nonuniform stress field. Local overloading causes local damage, and further leads to support structure destabilization. The method is proposed to determine the rational position of the mining gateway in the ultra-close lower seam. This method is confirmed through on-site observation.(6) Faced with the damaging influence of the upper seam mining on the roof of the ultra-close lower seam with the roof crushing and given to leakage and falling which at severe level may cause supports to be buried, and sever air leakage and become a flretrap, reinforcing technology of fractured roof, sealing and filling technology, parameters for shape and support of the rational section in the gateway, spatial control and techniques in beginning and ending mining, such safety assurance systems as end of mining face, fore support pattern, decompression ventilation and mistretarder fire prevention are determined through on-site observation. A set of perfect aid technology for ultra-close lower seam mining is achieved and provides reliable technical support for safe extraction in the ultra-close lower seam.In short, the thesis researches deeply and systematically into the theory and technology of surrounding rock control in ultra-close seams mining, solves the practical problems existing in ultra-close seams mining, and has scientific reference value to the future ultra-close seams mining, designing, planning.更多还原