人工矿柱-覆岩耦合作用过程力学特性及其失稳机理研究

Underground mining disturbs original stress balance of the surrounding rock and induces the deformation and failure of overburden strata above goaf. It’s an important measure to achieve the stress balance of mining environments by artificial structures to ensure the safe production of mine. Though artificial concrete pillar is widely applied in metal mines to control overburden strata stability, mechanical mechanism of coupling action between artificial pillar and overburden strata is seldom studied, resulting in theoretical research lag behind the engineering application. The project aims at the study of the coupled mechanical properties between artificial pillar and overburden strata with theoretical analysis, numerical simulation, model experiment and on-site tests from the viewpoint of mining environmental reconstruction. Stability characteristics of artificial pillar and overburden strata, coupling mechanics evolution mechanism and system instability mechanism are studied. The deformation mechanism of system load balance and coordination interaction is discussed. On the basis of catastrophe theory, mechanical model of coupling action between artificial pillar and overburden strata under the action of tectonic stress and gravity stress is estabilished and the criterion of catastrophe theory is proposed. Meanwhile, the overburden strata stability safety factor is determined with the application of material strength reserve concept to the safety discrimination of overburden strata in the goaf of metal mine. The strength reduction procedure prepared in dichotomy to solve safety factors that meet the condition of convergence, the calculation method of safety factor is proposed,and to determine the critical failure discriminating standard for overburden strata. The results can provide the basic theoretical basis for the similar metal mines to control overburden strata movement and prevent geological disasters by building artificial pillar.

矿山地下开采打破了围岩原有应力平衡，引起采空区覆岩变形和破坏，采取人工构筑物使采矿环境重新达到应力平衡是保障矿山安全的重要措施。人工矿柱被广泛应用到金属矿山控制覆岩稳定，其让压支护的特点不同于原生矿柱，目前对人工矿柱-覆岩耦合作用过程力学机制研究滞后于工程应用。本项目通过室内试验、理论分析、模型试验和数值模拟方法研究人工矿柱-覆岩耦合作用过程力学特性，对各构件稳定性、耦合作用过程力学演化机制及系统失稳机理进行研究，寻求耦合过程中系统载荷平衡和协调变形机制。以突变理论为基础，在集中应力、构造应力和自重应力作用下，构建人工矿柱-覆岩耦合作用空间力学模型，从势能角度，建立覆岩失稳突变模型，得出其失稳突变理论判据；将材料强度储备概念应用到覆岩的安全判别，对覆岩稳定安全系数进行定义，提出安全系数的计算方法，确定覆岩破坏依据。研究成果可为金属矿山利用人工矿柱控制覆岩移动及预防地质灾害提供理论研究依据。

矿山地下开采打破了围岩原有应力平衡，引起采空区覆岩变形和破坏，采取人工构筑物使采矿环境重新达到应力平衡是保障矿山安全的重要措施。当前对人工（尾砂胶结）矿柱-覆岩耦合作用过程力学机制研究滞后于工程应用。本项目开展了协调承载过程人工矿柱及覆岩力学特性、人工矿柱-覆岩耦合作用下破坏模式和不同弹性模量人工矿柱支撑作用下覆岩临界破坏机理等3个方面内容的研究。研究协调承载过程中在开采集中应力、自重应力和构造应力条件下人工矿柱及覆岩的力学特性。分别就不同弹性模量人工矿柱在开采集中应力与覆岩载荷组合作用下的强度及变形特性，覆岩在人工矿柱支撑下的应力响应特征，建立了人工矿柱-覆岩协调承载过程应力-应变本构模型。在考虑构开采集中应力、自重应力和构造应力条件下，建立基于“四周固支板”的人工矿柱-覆岩耦合作用空间力学模型，对其受力情况和边界条件进行分析。根据采空区覆岩的应力分布及协调变形规律得到覆岩势能，基于突变理论建立人工矿柱-覆岩耦合作用过程覆岩失稳破坏突变模型，得出了覆岩失稳破坏的突变理论判据。研究了覆岩在不同弹性模量人工矿柱支撑下的稳定性及其与人工矿柱的最佳匹配。首先，对耦合作用下覆岩稳定性安全系数进行定义：覆岩实际剪切强度和抗拉强度与折减之后临界破坏的剪切强度和抗拉强度分别之比，以两者中偏安全的系数作为覆岩稳定性最终安全系数；其次，采用损伤力学理论建立不同弹性模量人工矿柱支撑下覆岩损伤本构方程；最后，采用二分法，编写了针对金属矿山不同弹性模量人工矿柱-覆岩耦合作用下覆岩的强度折减程序，提出了人工矿柱-覆岩耦合作用下覆岩稳定性安全系数的计算方法，并确定出覆岩破坏依据。揭示人工矿柱-覆岩协调承载过程中系统载荷平衡、协调变形机理。通过本项目的研究，为阶段矿房嗣后充填法矿房、矿柱结构参数设计及优化提供基础研究依据，为采取尾砂胶结充填人工矿柱控制覆岩变形破坏提供理论指导。