【作者】 刘飞；

【导师】 马占国；

【作者基本信息】 中国矿业大学 ， 岩土工程， 2022， 博士

【摘要】 随着我国能源战略西移,煤炭资源进一步向西部大型煤炭基地的集约高效生产方式发展。我国西部地区厚煤层资源的富集为大型煤炭基地集中开采提供了有利条件,然而,其厚松散层、特厚煤层、薄基岩的典型地质条件易衍生矿压显现剧烈、地表环境破坏严重以及漏风发火时有发生等灾害,给西部大型煤炭基地的安全高效生产提出了严峻挑战。因此,围绕西部浅埋厚松散层特厚煤层综放工作面的围岩变形机理及控制已成为国家亟需解决的重大关键科学问题之一。本文综合运用实验室试验、理论分析、现场实测、相似模拟、数值计算和现场试验等手段,对厚松散层特厚煤层综放工作面矿压显现规律、顶板结构特征、载荷传递机制、结构优化方法和围岩控制技术等科学问题开展了深入研究,主要研究工作和创新成果如下:（1）创建了卸荷煤体本构模型,定量表征了放顶煤过程中的煤体卸荷力学行为,得到了含水率和脆性指数等参数对卸荷煤体应力-应变关系的影响规律。（2）建立了薄基岩厚松散层特厚煤层基本顶结构周期性演化力学模型,推导了顶板沿工作面走向结构突变的多参量临界控制方程,得到了断裂块度、转角、破断角、摩擦因数和角端挤压系数等变量对顶板“回转-滑落”稳定性的影响规律,明确了块度、转角和破断角是顶板结构突变的主控参数。（3）构建了特厚煤层综放面邻近巷道采空侧顶板结构分析模型,确定了采空侧顶板极限平衡状态下“弯曲-破断”失稳准则;求解得到了关键块体C质量和位移、下部破碎煤岩体刚度和阻尼、液压支架刚度和位移多因素作用下支架-围岩耦合动力学平衡微分方程,阐明了顶板滑落失稳时关键块体C、下部破碎煤岩体以及液压支架支承荷载的耦合作用关系。（4）建立了厚松散层特厚煤层综放开采离散元计算模型,分析了厚松散层特厚煤层综放工作面回采过程中顶板“大结构”空间动态演化规律,揭示了不同层位顶板变形特征和弯曲-破断结构转化机制,确定了顶板结构演化与工作面采动影响范围之间的定量关系。在此基础上,提出了厚松散层特厚煤层综放工作面推进过程中顶板结构控制原则。（5）构建了厚松散层特厚煤层综放工作面相似试验模型,研究了厚松散层特厚煤层综放开采工作面端头不放煤段长度对工作面倾向顶板结构的影响规律。得到了邻近巷道采空侧顶板“大结构”悬露长度、破断形态、回转角度等关键参数随工作面端头不放煤段长度的演化规律;明确了顶板“大结构”主动作用下,区段煤柱和端头围岩“小结构”的力学响应规律。提出了厚松散层特厚煤层综放工作面端头预裂切顶的结构优化方法。（6）揭示了厚松散层特厚煤层综放工作面推进过程中,区段煤柱应力动态演化特征、工作面矿压显现规律和顶板载荷传递机制。对FLAC^3D进行二次开发,将创建的本构方程嵌入计算模型,合理描述放顶煤开采卸荷作用下端头围岩力学行为,得到了不放煤段长度、区段煤柱尺寸等参数对煤柱能量密度、端头围岩应力分布和顶板载荷传递路径的影响规律,可作为厚松散层特厚煤层综放工作面端头不放煤段长度和区段煤柱尺寸的优化依据。（7）基于本文理论分析、数值模拟和试验研究得到的关键参数设计原则,提出了以端头全部放煤、顶板定向弱化、工作面后方巷道支护解除、区段煤柱尺寸优化等技术为核心的厚松散层特厚煤层综放工作面围岩控制一体化技术方案。技术方案的成功实施,验证了本文研究成果的合理性和实用性。本论文有图137幅,表23个,参考文献289篇。更多还原

【Abstract】 With the westward shift of China’s energy strategy,coal resources are further developed to the intensive and efficient production mode of large-scale coal bases in the West.The enrichment of thick coal seam resources in Western China provides favorable conditions for the centralized mining of large-scale coal bases.However,the typical geological conditions of thick loose layer,extra thick coal seam and thin bedrock are easy to derive disasters such as severe ground pressure,serious damage to surface environment and frequent occurrence of air leakage and fire pose a severe challenge to the safe and efficient production of large-scale coal bases in Western China.Therefore,surrounding rock deformation mechanism and control of fully mechanized top coal caving face in western shallow buried thick loose seam and extra thick seam have become one of the major key scientific problems to be solved urgently.By means of laboratory test,theoretical analysis,field measurement,similarity simulation,numerical calculation and field test,this thesis makes an in-depth study on the scientific problems of fully mechanized top coal caving face in thick loose and extra thick coal seam,such as ground pressure behavior law,roof structural characteristics,load transfer mechanism,structural optimization method and surrounding rock control technology.The main research work and innovative achievements are as follows:（1）The constitutive model of unloaded coal is established,the unloading mechanical behavior of coal in the process of top coal caving is quantitatively characterized,and the influence laws of parameters such as moisture content and brittleness index on the stress-strain relationship of unloaded coal are obtained.（2）The periodic evolution mechanical model of the basic roof structure of thin bedrock,thick loose layer and extra thick coal seam is established,the multi parameter critical control equation of the structural catastrophe of the roof along the strike of the working face is deduced,the influence laws of the variables such as fracture block degree,rotation angle,breaking angle,friction coefficient and corner extrusion coefficient on the"rotation-sliding"stability of the roof are obtained,and it is clear that the block degree,rotation angle and breaking angle are the main control parameters of the structural catastrophe of the roof.（3）The structural analysis model of gob side roof adjacent to fully mechanized top coal caving face in extra thick coal seam is constructed,and the instability criterion of"bending breaking"under the limit equilibrium state of gob side roof is determined;The coupling dynamic equilibrium differential equation of support surrounding rock under the multi factor action of mass and displacement of key block C,stiffness and damping of lower broken coal and rock mass,stiffness and displacement of hydraulic support is solved,and the coupling relationship between key block C,lower broken coal and rock mass and support load of hydraulic support is clarified.（4）The discrete element calculation model of fully mechanized top coal caving mining in thick loose layer and extra thick coal seam is established,the spatial dynamic evolution law of"large structure"of roof in the mining process of fully mechanized top coal caving face in thick loose layer and extra thick coal seam is analyzed,the deformation characteristics of roof in different layers and the transformation mechanism of bending-breaking structure are revealed,and the quantitative relationship between the evolution of roof structure and the mining influence range is determined.On this basis,the control principle of roof structure in the advancing process of fully mechanized top coal caving face in thick loose seam and extra thick seam is put forward.（5）The similarity test model of fully mechanized top coal caving face in thick loose bed and extra thick coal seam is constructed,and the influence of the length of non caving section at the end of fully mechanized top coal caving face on the inclined roof structure of the face is studied.The evolution law of the key parameters such as the"large structure"hanging length,breaking shape and rotation angle of the roof on the goaf side of the adjacent roadway with the length of the non caving section at the end of the working face is determined;The mechanical response law of"small structure"of section coal pillar and end surrounding rock under the active action of"large structure"of roof is clarified.The structural optimization method of pre splitting and roof cutting at the end of fully mechanized top coal caving face in thick loose seam and extra thick seam is put forward.（6）This paper reveals the dynamic evolution characteristics of section coal pillar stress,ground pressure behavior law of working face and roof load transfer mechanism during the advancement of fully mechanized top coal caving face in thick loose layer and extra thick coal seam.The secondary development of FLAC^3D is carried out,and the constitutive equation is embedded into the calculation model to reasonably describe the mechanical behavior of the surrounding rock at the lower end under the unloading effect of top coal caving mining.The influence laws of the length of the non caving section and the size of the section coal pillar on the energy density of the coal pillar,the stress distribution of the surrounding rock at the end and the load transfer path of the top plate are obtained,It can be used as the optimization basis for the length of non caving section and the size of coal pillar at the end of fully mechanized top coal caving face in thick loose and extra thick coal seam.（7）Based on the design principles of key parameters obtained from theoretical analysis,numerical simulation and experimental research in this thesis,an integrated technical scheme of surrounding rock control in fully mechanized top coal caving face with thick loose layer and extra thick coal seam is proposed,which is centered on the technologies of full caving at the end,directional weakening of roof,removal of roadway support behind the face,optimization of section coal pillar size and so on.The successful implementation of the technical scheme verifies the rationality and practicability of the research results of this thesis.There are 137 figures,23 tables and 289 references.更多还原