受煤层倾角影响，大倾角综放采场顶煤采动力学行为沿倾斜方向的非对称性显著，综放开采时倾向各区域顶煤的劣化进程与破碎程度不一，“支架-围岩”系统稳定性沿倾斜方向区化，控制难度加剧。实现大倾角条件下顶煤由相对完整的拟连续介质向破碎松散的非连续介质过渡的时空界限划定，对预判采场“支架-围岩”系统稳定性以及顶煤冒放性至关重要。顶煤由拟连续到非连续这一过渡状态实质上可等效为极限平衡状态。据此，量化表征大倾角综放采场顶煤极限平衡区边界空间形态，揭示边界空间形态演化机制，可为指导该类采场“支架-围岩”稳定性控制实践提供科学依据。

以甘肃某矿1123工作面为工程背景，采用物理相似模拟实验、理论分析、数值模拟、现场监测相结合的研究方法，对大倾角煤层综放采场顶煤极限平衡区边界空间形态演化机制进行系统研究。开展了以下工作并得到相应研究结果：

基于极限平衡理论与岩石强度准则相结合的研究视角，构建了宏观尺度条件下顶煤极限平衡边界处应力状态分析模型，给定了沿走向顶煤极限平衡区边界应力状态表征方法，并结合物理相似模拟实验测定了1123工作面顶煤极限平衡区边界的垂直应力，进一步实现了对极限平衡区边界位置（极限平衡区边界距煤壁的水平距离）的解析。计算结果表明：1123工作面顶煤上边界极限平衡区边界距煤壁1.30m，下边界距煤壁3.85m，沿煤层层厚方向，顶煤极限平衡区边界距煤壁的距离呈现出自上而下递增的关系。

基于弹性力学分析方法，给定了倾角影响下煤层法向应力与最大、最小主应力的相关关系，揭示了顶煤极限平衡区边界应力状态对煤层倾角的响应机制。结合极限平衡理论分析与数值模拟计算，实现了不同煤层倾角条件下顶煤极限平衡区边界位置表征。结果表明，当煤层倾角介于35°-55°范围内，顶煤极限平衡区边界空间形态呈现以下特征：①沿工作面倾向，顶煤极限平衡区在层厚方向的边界呈现“非对称性圆弧拱”形分布，拱顶位于工作面中上部；②沿工作面倾向，不同区域顶煤上下边界极限平衡区边界位置错距不一；③沿工作面走向任意截面，顶煤极限平衡区边界位置距煤壁的距离均呈现出沿层厚方向自上而下逐步递增的规律；④在三维空间内，顶煤极限平衡区边界空间形态呈“非对称扭曲圆弧带状曲面”。随煤层倾角增大，顶煤极限平衡区边界非对称弧顶位置沿走向前移，沿倾向向上端头迁移，边界展布形态的“非对称性”更加明显。

随着工作面推进，顶煤受到的法向应力呈“初采阶段逐渐增长-采动充分后趋于稳定”的演化规律，顶煤极限平衡区边界位置相应呈现出“初采阶段距煤壁水平距离逐步增加-采动稳定后距煤壁水平距离趋于恒定”的演化过程。顶煤极限平衡区边界空间形态随采动的演化规律总体上呈：“不规则扭曲带状”-“非对称扭曲圆弧带状曲面”-“非对称扭曲圆弧带状曲面”加剧（弧顶位置持续向推进方向前移并向工作面倾向上部迁移）-稳定的“非对称扭曲圆弧带状曲面”。同时，随着煤层倾角的增大，顶煤极限平衡区边界空间形态的演化进程加快。

构建了支架稳定性与顶煤极限平衡区边界之间的间接联系，通过1123工作面现场监测得到了顶煤漏冒次数和支架工作阻力的分布规律。结果表明：顶煤端面漏冒次数和支架平均工作阻力沿倾向具有显著的区化特征，具体表现为：工作面中上部顶煤破碎漏冒最严重，支架接顶不实，平均工作阻力最低，上部和中下部次之，下部最弱。定性的角度上，以上矿压显现间接表明了顶煤极限平衡区边界空间形态“非对称”分布是客观存在的。基于此，提出了“控制放煤量+优化支架结构”的支架稳定性控制对策，可为综放采场“支架-围岩”系统稳定性控制实践提供理论借鉴。

Influenced by the dip angle of coal seam, the mining-induced stress of top coal in fully mechanized top coal caving stope with steeply dipping coal seam was obviously asymmetric along the dip direction, and the deterioration process and crushing degree of top coal were different along the dip direction of working face. The stability of “support-surrounding rock” system along the dip direction of working face appears regionalization characteristics, and the control difficulty was intensified. It is very important for predicting the stability of the “support-surrounding rock” system and the caving property of top coal to delimit the time-space boundary of the transition from a relatively complete quasi-continuous medium to loose discontinuous medium under the condition of steeply dipping coal seam. The transition state of top coal from quasi-continuous to discontinuous can be equivalent to the limit equilibrium state. Accordingly, the quantitative characterization of the boundary space form of the top coal limit equilibrium zone in the fully mechanized caving stope with steeply dipping coal seam，and the revealing of the evolution mechanism of the boundary space form can provide a scientific basis for guiding the stability control practice of “support-surrounding rock in this kind of stope.

Taking the 1123 working face of a mine in Gansu Province as the engineering background, the physical similarity simulation experiment, theoretical analysis, numerical simulation and field monitoring were used to systematically study the evolution mechanism of the boundary space form of the top coal limit equilibrium zone in the fully mechanized caving stope of the steeply dipping coal seam. The following work was carried out and the corresponding research results were obtained:

(1) Based on the research perspective of the combination of limit equilibrium theory and rock strength criterion, the stress state analysis model at the limit equilibrium boundary of top coal under macro-scale conditions is constructed, and the stress state characterization method of the limit equilibrium boundary of top coal along the strike is given. Combined with the physical similarity simulation experiment, the vertical stress of the limit equilibrium boundary of top coal in 1123 working face is measured, and the analysis of the limit equilibrium boundary position (the horizontal distance between the limit equilibrium zone boundary and the coal wall) is further realized. The calculation results show that the upper boundary limit equilibrium zone boundary of top coal in 1123 working face is 1.30 m from the coal wall, and the lower boundary is 3.85 m from the coal wall. Along the thickness direction of the coal seam, the distance between the boundary of the top coal limit equilibrium zone and the coal wall shows a decreasing relationship from top to bottom.

(2) Based on the elastic mechanic analysis method, the correlation between the normal stress and the maximum and minimum principal stresses of the coal seam under the influence of the dip angle is given, and the response mechanism of the limit equilibrium boundary stress state of the top coal to the dip angle of the coal seam is revealed. Combined with limit equilibrium theory analysis and numerical simulation calculation, the boundary position of limit equilibrium zone of top coal under different coal seam dip angles is characterized. The results show that when the coal seam dip angle is in the range of 35°-55°, the boundary space form of the top coal limit equilibrium zone presents the following characteristics :①Along the working face tendency the boundary of the top coal limit equilibrium zone in the thickness direction presents an “asymmetric circular arch” shape distribution, and the vault is located in the middle-upper part of the working face.②Along the working face tendency, the boundary positions of the upper and lower boundary limit equilibrium zone of the top coal in different regions are different.③Any section along the strike direction of the working face. the distance between the boundary position of the top coal limit equilibrium zone and the coal wall presents a law of gradual decrease from top to bottom along the thickness direction;④In the three-dimensional space, the boundary space form of the top coal limit equilibrium zone is “asymmetric twisted arc strip surface”. As the dip angle of the coal seam increases, the asymmetric arc top position of the top coal limit equilibrium zone moves forward along the strike, and migrates upward along the tendency, and the “asymmetry” of the boundary distribution pattern is more obvious.

(3) With the advance of the working face, the normal stress of the top coal shows the evolution law of “gradually increasing in the initial mining stage-becoming stable after full mining”. The boundary position of the limit equilibrium zone of the top coal shows the evolution process of “the horizontal distance from the coal wall gradually increases in the initial mining stage and tends to be constant after the mining is stable”. The evolution law of the boundary space shape of the top coal limit equilibrium zone with mining is as follows: “irregular twisted strip”- “asymmetric twisted arc strip surface”- “asymmetric twisted arc strip surface” whose arc top position continuously moves forward in the advancing direction and tends to move to the upper part of the working face-stable “asymmetric twisted arc strip surface”. At the same time, with the increase of coal seam dip angle, the evolution process of the boundary space form of the top coal limit equilibrium zone becomes faster.

(4) The indirect relationship between the stability of the support and the boundary of the limit equilibrium zone of the top coal is constructed. The distribution law of the top coal leakage times and the working resistance of the support is obtained through the field monitoring of the 1123 working face.The results show that the times of top coal leakage and the average working resistance of supports have obvious regionalization characteristics along the tendency, which are as follows: the top coal in the middle-upper part of the working face is the most seriously broken, the stability of supports is insufficient, and the average working resistance is the lowest, the upper and middle-lower parts are the second, and the lower part is the weakest.In a qualitative way, the above ground pressure appearance indirectly shows that the “asymmetric” distribution of the boundary space shape of the top coal limit equilibrium zone is objective. Based on this, the countermeasures of “active control of coal caving quantity-passive optimization of support” are put forward, which can provide theoretical reference for the stability control of “support-surrounding rock” system in stope.