平顶山矿区首次采用下保护层岩石工作面开采方式来解放深部受瓦斯突出威胁的己组煤炭资源，但由于岩石工作面开采深度近千米，承压水头高、煤岩层距寒武系灰岩顶部近、地温高，一旦发生底板水害，抢险工作难度大。为客观评价深部采场受寒武系灰岩水害威胁程度，需对深部岩石工作面开采底板扰动破坏规律展开系统性研究。本文采用理论分析、相似模拟、数值模拟及现场实测等多种手段，对保护层开采过程中底板隔水岩层塑性破坏特征、应力场和位移场演化规律进行深入研究，主要结论如下：

（1）在单一岩层底板塑性滑移线场理论基础上，建立了多层结构底板塑性滑移线场理论模型，推导得出复合底板最大破坏深度理论解析解，并给出了滑移破坏形态；考虑底板扰动和承压导升双重影响，建立了非充分采动状态下底板隔水岩层组整体稳定性力学模型，推导得出单、双层结构底板水压与采面推进度关系理论解及极限水压力表达式，并提出了底板隔水层稳定性判别准则，结合临界开采尺寸分析了实际工况下最小极限水压力。

（2）通过自主设计研发承压水反力实验平台，首次实现了承压水压力与地层压力协同工作共同承载，即弹簧模拟孔隙水压力、千斤顶模拟地层有效应力。采用新型实验材料模拟分析了非充分采动及充分采动期间采场顶底板裂隙从萌生、扩展至贯通破坏的演化全过程，得出了下保护层工作面开采引起的底板变形和破坏规律。

（3）通过建立实际开采工况数值模型，分析了不同推进度下顶底板岩体应力场和位移场演化规律、塑性变形特征以及采场底板支承压力分布形态，动态再现了底板岩层开采渐进破坏过程，给出了顶底板塑性破坏区范围。

（4）采用振弦式应力计和应变计分别实时监测了岩石工作面煤岩体支承压力和底板岩体变形量，得到了超前工作面和下帮煤岩体支承压力采动变化规律以及底板扰动发育形态，确定了底板实际最大破坏深度值，实测数值与相似模拟和数值模拟分析结果相吻合，验证了多层结构底板塑性滑移线场理论的科学性。

Pingdingshan mining area for the first time adopts the mining method of rock working face in the lower protective layer to liberate the deep coal resources threatened by gas outburst. However, the buried depth of the rock working face is nearly 1000 m, with high confined water pressure at the bottom, the distance between the mining layer and the top of Cambrian limestone is close, and the ground temperature is high. Once the water inrush from the floor, the rescue work is difficult. To objectively evaluate the threat degree of deep stope affected by Cambrian limestone water disaster, it is necessary to carry out systematic research on the disturbance and failure law of floor in deep rock mining face. This paper adopts theoretical analysis, similar simulation, numerical simulation and field measurement to discuss the plastic failure characteristics, stress field and displacement field deformation law of the floor aquifuge during the protection layer mining. The main conclusions are as follows:

(1) Based on the theory of plastic slip line field of single rock floor, the theoretical model of plastic slip line field of multi-layer structure floor is established for the first time, the theoretical analytical solution of maximum failure depth of composite floor is derived, and the slip failure mode is given. Considering the dual effects of floor disturbance and confined water uplifting, a mechanical model of the overall stability of floor aquifuge under the condition of not full mining was established. The theoretical solution of the relationship between the floor water pressure of the single and double-layer structure and the advancing progress of the mining face and the expression of the limit water pressure are derived, and the criterion for judging the stability of the floor aquifuge was put forward. Finally, the minimum ultimate water pressure under actual working conditions was analyzed in conjunction with the critical mining size.

(2) Through the self-designed confined water simulation experiment platform, the confined water pressure and formation pressure are jointly carried, i.e. the spring simulates the pore water pressure and the jack simulates the effective stress of the formation. By using new experimental materials, the evolution process of the roof and floor cracks from initiation, expansion to through failure during the period of not full mining and full mining is simulated and analyzed, and the deformation and failure law of floor caused by the mining of lower protective layer rock working face is obtained.

(3) Through the establishment of the numerical analysis model of the actual mining conditions, the evolution law of the stress field and displacement field of the roof and floor rock mass, plastic deformation characteristics, and the distribution of the abutment pressure of the stope floor are analyzed. The progressive failure process of floor rock under the mining condition is reproduced dynamically, and the range and depth of plastic failure area of roof and floor are given.

(4) Vibrational chord stress gauge and strain gauge are used to monitor the abutment pressure of coal and rock mass and the deformation of floor rock mass, respectively. The mining variation law of abutment pressure of advanced working face and lower wall coal and rock mass and the development form of floor disturbance is obtained, and the actual maximum failure depth of floor is determined. The measured values are consistent with the results of similar simulation and numerical simulation analysis, and the scientific validity of the theory of plastic slip line field of multi-layer structure floor is verified.

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