生态脆弱矿区煤层顶板水井下储存结构及其稳定性研究

How to realize co-extraction of coal and water resources is particularly important in the arid and semi-arid mining area of western China, whose ecological environment is extremely vulnerable. And it is inevitable that the overlying aquifer will infiltrate downward due to movement of the strata in the process of mining, and may even lead to water inrush accidents in the sections where the aquifer is on-existent or destroyed. Based on these, taking the Jurassic coal seam of arid and semi-arid area in the coal field of northern Shaanxi and Ningdong as an example, this project has studied the spatial structure of underground storage of roof water in ecologically vulnerable mining area during coal mining and its stability by using the following methods, theoretical analysis, experiment of rock and similar simulation, and numerical calculation. Technology principles which realize underground storage of roof water have been put forward by studying the flow law of roof water and its occurrence mode of storage spatial structure in single coal seam when different mining sequences are adopted in the following three conditions, mining district, inner sublevel of strip district, strip; Methods which calculate the load and long-term strength of the boundary coal-pillars that used to protect storage structure have been put forward by studying the characteristics of long-term strength of the boundary coal-rock mass surrounding water storage structure and long-term evolution law of the abutment pressure; Indexes that predict deformation and instability of the boundary coal-rock mass surrounding water storage structure have also been put forward by studying the strength of roof and floor strata and characteristics of acoustic emission of Jurassic typical coal seam under the conditions of different moisture content.

我国西部干旱半干旱矿区，生态环境及其脆弱，如何实现煤炭与水资源共同开采显得尤为重要。煤层开采过程中，上覆含水层随着岩层移动而下渗不可避免，甚至在隔水层缺失或破坏地段发生突水事故。为此，本课题以我国陕北、宁东煤田干旱半干旱地区侏罗系煤层为例，采用理论分析、岩石与相似模拟试验、数值计算方法研究生态脆弱矿区煤层开采过程中顶板水井下储存空间结构及其稳定性。通过研究单一煤层采区/带区内区段/分带不同开采顺序顶板水流动规律及其矿井水储存结构赋存形态，提出实现顶板水井下储存的技术原理；研究矿井水储存结构边界煤岩体水作用下长期强度特征和支承压力的长期演化规律，提出储水结构边界煤柱载荷及其长期强度计算方法；研究不同含水状态下侏罗系典型煤层、顶底板岩层强度、声发射特征，提出储水结构边界煤岩体变形失稳的预测指标。

本课题研究设计了煤岩体无损浸水和力学性质损伤特征实验方法，开发了水-锚固体实验平台、设计了水-锚固剂环形剪切试验；基于以上实验方法和实验平台，研究了典型煤系沉积岩矿物组分、微结构特征，不同含水状态下典型煤系沉积岩/煤-煤岩组合体强度损伤及声发射特征，开展了典型煤系沉积岩吸水、失水试验；研究了不同含水率影响下煤岩体强度损伤演化规律，提出了反映含水率影响的煤岩损伤统计模型；利用弹塑性力学推导出了边界煤岩柱塑性区宽度的计算公式；数值计算研究了水作用下岩石细观参数的变化规律。研究发现：典型煤系沉积岩含水率与浸水时间满足对数函数关系，可大致分为含水率增速较快、含水率增速减慢、含水率增速趋于零三个阶段；典型煤系沉积岩单轴抗压强度与含水率呈负线性关系，峰值应变随含水率呈正线性变化，弹性模量与含水率呈负指数函数关系；峰值应变、单轴抗压强度与浸水次数分别满足正、负二次多项式关系，弹性模量与浸水次数呈负指数函数关系；法向和切向弹性模量及法向和切向粘结强度与含水率呈负线性关系；法向应变能密度在数值上低于切向应变能密度，二者均与含水率呈负线性关系。通过本课题的研究，能够为防水煤岩柱、采空区储水边界煤岩柱等设计提供有益参考。