基于能量耗散的弱胶结巷道围岩流变破坏机理研究

The shallow coal measure strata in western China is mainly soft strata with characteristics of bad cementation, low strength and easy-soften. The problem of rheological failure gets more and more serious, which greatly affects the safety mining in western mines. The comprehensive research method, including theoretical analysis, laboratory test, numerical simulation and in-situ investigations, will be adopted to make the innovative researches on three aspects. Firstly, by carrying out the X ray diffraction, CT scanning and rheological test, quantitative characterization of mineral constituent and meso-crack can be obtained. Then the influence of mesoscopic structure of the rock on the crack propagation and accumulation and dissipation of rheological deformation energy will be studied. Secondly, based on the correlation between dissipation of deformation energy and the rheological failure, the damage characterization method reflecting the dissipation of rheological deformation energy will be put forward, and then the rheological damage constitutive relation considering the energy dissipation will be established. Thirdly, the instability and failure with the accumulation of deformation energy damage of weak-cemented roadway surrounding rock is to be revealed. Using the regulation of energy release of surrounding rock and the energy absorption of support structure as reference, the deformation-support energy coupling model based on energy balance will be built. Finally, a design method of deformation and failure control for weak-cemented surrounding rock will be proposed. Research results of this project could provide a theoretical support and scientific basis for the long-term stability control of the weak-cemented roadway in western China.

我国西部浅埋煤系地层多为胶结性差、强度低、易软化的松软岩层，巷道围岩流变破坏问题日益突出，严重制约了西部矿区安全开采。本项目拟采用理论分析、室内试验、数值模拟与现场探测相结合的手段，开展以下创新性研究：①采用X射线衍射、CT扫描和流变试验手段，获得弱胶结岩石矿物组分、细观裂纹的定量表征，揭示细观组构对弱胶结岩石裂纹扩展、流变形变能积聚与耗散的影响规律；②从探究弱胶结岩石形变能耗散与流变破坏之间的联系出发，提出反映弱胶结岩石流变形变能耗散特征的损伤表征方法，构建考虑能量耗散的流变损伤本构关系；③揭示弱胶结巷道围岩随形变能损伤累积的失稳破坏规律，以调控围岩释放能量与支护结构吸收能量为出发点，建立基于能量平衡的围岩变形-支护能量耦合模型，提出弱胶结巷道围岩流变破坏控制设计方法。本项目研究成果可为西部弱胶结巷道长期稳定性控制提供理论支持与科学依据。

针对弱胶结巷道围岩易流变破坏、控制难度大的问题，本项目采用理论分析、室内试验、数值模拟、相似材料和现场监测的综合研究方法，获得了弱胶结岩石细观结构特征，揭示了弱胶结围岩流变破坏规律及能量演化特征。通过本项目研究，主要得到如下结论：（1）通过X-射线衍射和SEM电镜扫描，确定了弱胶结试样内部颗粒以薄膜式胶结为主，部分粒间孔隙被黏土矿物填充，通过与花岗岩等硬岩进行对比揭示了弱胶结岩石的松散特性；（2）获得了弱胶结岩石蠕变力学特性及不同蠕变阶段的能量演化规律，相同围压下弱胶结泥岩试样各蠕变应力水平明显低于脆性煤岩，弱胶结岩石压缩总能量和耗散能增长速率受围压影响较大，而应变能增长速率受围压影响较小；（3）构建了基于能量分析的弱胶结软岩蠕变损伤本构方程，并在西原体力学模型的基础了对建立的基于能量分析的蠕变损伤本构模型进行二次开发，通过数值模拟对比验证了构建模型可较好地表征弱胶结软岩蠕变特性；（4）开展了基于弱胶结岩石力学特征的相似材料配比试验，结合相似材料和数值模拟研究获得了弱胶结围岩巷道变形破坏特征，并依据围岩弹性集中程度量化岩体变形破坏程度，提出了基于能量平衡的围岩变形-支护设计方法。本项目研究成果为弱胶结巷道围岩长时稳定控制提供了一定的理论指导。