弱胶结覆岩采动隔水性演变规律与区域水系统响应机制

Finding the optimum solution between coal exploitation yield and water resource bearing capacity is one of key issues in scientific coal mining of western coal. The mechanism of reginal groundwater system responding to underground gob keeping extending under the effect of widely-distributed weak-cement rock water-referred argillization and expansion, in which the mechanism of overlying strata permeability evolution induced by mining is the key. This project is conducted from the permeability evolution of the weak cemented strata in response to its deformation and failure. Through the triaxial permeability tests with full stress and strain and loading-unloading, the stress-strain-permeability relation will be analyzed to reveal the strength degradation and impermeability self-healing effect and to deduce the critical seepage gradient of impermeability performance failure. According to 3D solid-liquid coupling models and the impermeability evolution laws of overlying strata will be analyzed and the effect of mining height, face dimension and gob quantity on the overburden permeability will be studied. A model for assessing the stability of strata flowing system will be constructed. Based on groundwater flowing models, the variation of groundwater flow field and the effect of different gob parameters on the vertical drawdown and the lateral influence radius of groundwater table will be studied. Variance analysis will be conducted to evaluate the effect sensitiveness. The mechanism of reginal groundwater system responding to underground mining is therefore revealed. The results are thought to be helpful for revealing the mechanism of water protection in mining and improving the coalfield planning and mining design on basis of water resource bearing capacity.

寻求煤炭开采量与水资源承载力间的满意解是西部煤炭科学开采中的难题，在西部广泛赋存的弱胶结岩层的遇水泥化膨胀特性作用下，开采空间不断扩大对区域水系统的影响机制是其中的基础课题之一，其核心是采动覆岩隔水性演变规律。本项目以弱胶结岩层变形破坏过程中的渗透率变化为主线，通过三轴全应力应变和加卸载渗透性试验，测试应力-应变-渗透率关系，分析弱胶结岩石强度劣化与隔水性自修复效应，得出隔水性失效临界渗透比降；进而构建三维固液耦合模型，分析单面采动到多面采空过程中覆岩隔水性演变规律，研究采高、工作面尺寸和采空面数量等空间参数对覆岩渗透率的影响特征，依此构建覆岩渗流系统稳定性评判模型；最后基于区域水系统运移模型，研究不同开采空间参数对地下水位垂向降深与侧向影响半径等水流场参数的影响规律及其敏感性，揭示采动区域水系统响应机制。研究成果为进一步揭示保水开采机理、完善基于水资源承载力的矿区规划与开采设计提供依据。

针对西北矿区典型弱胶结地层条件下煤炭大规模开采与地下水系统保护的难题，明确了弱胶结岩石全应力应变过程渗透变化与孔隙率、胶结形式、矿物组分、崩解性等之间的关系，分析了围压、岩性、矿物组分等对弱胶结岩石峰值强度、残余强度及渗透性的影响规律，揭示了弱胶结岩石强度劣化与隔水性自修复机理；基于弱胶结岩石等效表征单元体（REV单元），建立了考虑基质压缩-融合-破裂全过程的弱胶结岩石应力-损伤-渗流耦合方程，得到了以流量、孔隙率、剪切强度等为关键指标的隔水层隔水自修复能力失效临界渗透比降；揭示了三维固液耦合条件下单一工作面及多工作面开采顺序对覆岩渐进破坏与渗透率演化特征，明确了采高、工作面长度、推进距离、采空面数量等开采空间参数对覆岩移动变形、裂隙发育、渗透率变化等的影响规律；从采动覆岩整体阻水性能角度出发，提出了将上覆隔水岩层（组）虚拟为等效阻水层的学术思想，构建了基于岩层厚度、渗透率、孔隙率、煤层-含水层间距等因素的层状岩层渗流系统动力学模型，采用分层、分区组合等效，建立了覆岩垂向等效渗透系数的计算方法，提出了以等效阻水厚度为综合指标的保水开采覆岩渗流系统稳定性评价模型；建立了研究区域地下水系统运移模型，得出了单一工作面及多工作面不同顺序开采等不同开采布局条件下地下水流场演化特征，揭示了采高、工作面长度、推进距离、采空面数量等因素对地下水垂向降深和侧向影响半径的影响规律；建立了开采空间参数各影响因素主效应方差分析模型，得出了开采空间参数对地下水系统的影响敏感性，确定了煤炭开采区域地下水系统主控影响因素，揭示了弱胶结地层地下区域水系统对开采空间变化的响应机制。研究成果解决了弱胶结岩石强度劣化与渗透性演化规律、弱胶结地层保水开采可行性评价、基于地下水系统保护的开采参数选取与布局优化等保水开采理论与技术中的关键科学问题，为西北大型煤炭基地保水开采设计提供了基础依据。

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