采场底板围岩应力壳力学特征研究

发布时间：2019-01-27 14:43

【摘要】：采场底板围岩三维力学特征是有效防控煤层底板采动灾害的理论基础。为此,本论文采用综合研究方法,系统深入研究了采场底板围岩三维力学特征。研究发现,在工作面推进过程中,采场底板部分岩层区域富集着高于邻域的高应力束,形成了采场底板围岩应力壳,采场底板矿压显现受控于底板应力壳的存在和其时空演化。煤层回采后,采场底板围岩中最大主应力方向发生偏转,壳体高应力决定采场底板围岩是否扩展,最大主应力偏转方向决定采场底板岩体的破坏趋势,这正是采场底板围岩由整体连续渐变为宏观断裂的力学本质。破坏场发育在底板应力壳作用下的低应力区内,在采场底板围岩应力壳保护下的低应力区是最大位移区,底板岩层移动形态类似开口向上的抛物线状。壳基高应力是引起采场底板岩层采动应力场的主要力源,煤壁前方壳基高应力在底板岩层中形成高垂直应力,高垂直应力受控于壳基高应力,两者呈正相关性,煤壁前方底板垂直应力随离煤层距离的增而降低,且呈现出降低趋势变缓现象,采动水平应力高度集中于采场底板浅部岩层。在采场底板围岩应力壳保护范围内的采空区下伏岩层出现卸压现象,卸压范围呈倒“八”字型收敛状。采场底板围岩由整体连续渐变为宏观断裂呈现出时间效应,大致经历三个阶段：壳基高应力作用下岩体原始裂纹起裂、采场底板围岩最大主应力的集中与偏转引起裂纹进一步发育、损伤达到或超过损伤阈值后宏观断裂。初采期间,采场底板围岩应力壳力学特征参数受控于工作面推进距离,推进距离达到或超过工作面斜长后,决定采场底板围岩应力壳力学特征参数的主要因素为工作面斜长,表现出短边依赖效应。采场底板岩层赋存状态对采场底板围岩应力壳力学特征有显著影响。基于采场底板围岩应力壳力学特征及时空演化规律,遵循适当的时间、合理的空间、适中开采强度的原则,提出了与开采环境相适应的煤层群工作面协调同采方法。
[Abstract]:Three-dimensional mechanical characteristics of surrounding rock in stope floor are the theoretical basis for effective prevention and control of mining disasters in coal seam floor. Therefore, the comprehensive research method is used to study the three-dimensional mechanical characteristics of the surrounding rock of the stope floor. It is found that in the process of working face advance, the high stress beam is enriched in some strata of the floor of the stope, and the surrounding rock stress shell of the stope floor is formed, and the rock pressure of the stope floor is controlled by the existence of the stress shell of the floor and its space-time evolution. After coal seam mining, the direction of the maximum principal stress in the surrounding rock of the stope floor is deflected, the high stress of the shell determines whether the surrounding rock of the stope floor is extended, and the direction of the maximum principal stress deflection determines the failure trend of the rock mass of the stope floor. This is the mechanical nature of the rock mass of the stope floor from the whole continuous gradual transformation to the macroscopic fracture. The failure field is developed in the low stress zone under the action of the bottom stress shell. The low stress zone under the protection of the surrounding rock stress shell of the stope floor is the maximum displacement zone, and the moving form of the bottom rock layer is similar to the parabolic shape of the upward opening. The high stress of shell foundation is the main force source to cause mining stress field of stope bottom rock. The high stress of shell foundation in front of coal wall forms high vertical stress in bottom rock layer, and the high vertical stress is controlled by high stress of shell foundation, which is positively correlated with each other. The vertical stress of the floor in front of the coal wall decreases with the increase of the distance from the coal seam, and the downward trend becomes slower, and the horizontal stress of mining is concentrated on the shallow strata of the floor of the stope. The pressure relief phenomenon appears in the underground strata of goaf in the protection range of surrounding rock stress shell of stope floor, and the pressure relief range is convergent in the shape of inverted "eight" shape. The surrounding rock of the stope floor changes from the whole continuous gradual transformation to the macroscopic fault and presents the time effect, which generally goes through three stages: the initial crack initiation of rock mass under the action of high stress of shell foundation, The concentration and deflection of the maximum principal stress in the surrounding rock of the stope floor lead to the further development of the crack and the macroscopic fracture after the damage reaches or exceeds the damage threshold. During the initial mining period, the mechanical characteristic parameters of surrounding rock stress and shell of stope floor are controlled by the distance of the working face, and the main factor determining the mechanical characteristic parameters of the surrounding rock stress and shell of the stope floor is the inclined length of the working face after the advance distance reaches or exceeds the inclined length of the working face. It shows short edge dependence effect. The occurrence of stope floor rock layer has a significant influence on the mechanical characteristics of surrounding rock stress shell of stope floor. Based on the mechanical characteristics and space-time evolution law of surrounding rock stress and shell of stope floor, following the principle of proper time, reasonable space and moderate mining intensity, this paper puts forward a coordinated mining method of coal seam group working face suitable for mining environment.
【学位授予单位】：安徽理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TD32

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