开挖卸荷条件下深部软岩巷道应力场演化时效机制及动态补强支护机理研究

Soft rock roadway supporting in deep mines has become the bottleneck problem of mining industry with coal mining reaching greater depth. In light of the long and great deformation of deep soft rock roadway as well as the difficulty in controlling it, dynamic reinforced supporting is a new technology concerned. However, some theoretical problems on the reinforced supporting time, parameters, reinforced supporting mechanism, etc. remain to be resolved. The project studies such scientific issues as the aging mechanism of stress field evolution, the interaction of reinforced supporting and surrounding rock by combining physical modeling technique, computer numerical simulation and field tests, and by adopting the theoretical methods including rock mass mechanics of underground engineering, rheological mechanics and damage mechanics. Based on unloading rheological characteristics of typical deep soft rock, viscoelastic - plasticity of roadway excavation, rheological deformation phase and corresponding constitutive relation, the calculation method of stress field evolution is put forward and the aging mechanism of stress field evolution is revealed. Besides, the interaction mechanism and course of reinforced supporting and surrounding rock are studied to construct coupling mechanics model of reinforced supporting and surrounding rock based on rheological mechanism. Finally, the criterion of optimal time of reinforced supporting is put forward. The research provides the theoretical basis for supporting design of deep soft rock roadway, scientific determination of reinforced supporting time and stable control of surrounding rock.

随着煤矿开采向深部发展，深部软岩巷道支护已成为制约煤矿行业发展的瓶颈，针对深部软岩巷道变形时间长、变形大且难以控制，动态补强支护技术是一项深部软岩控制的新技术，但补强时机、参数及动态补强支护机理等深层次理论问题亟待解决，本项目采用地下工程岩体力学理论、流变力学理论、损伤力学理论相结合的方法，借助物理模拟、计算机数值模拟与现场实测相结合的综合手段，对深部软岩巷道应力场演化的时效特征与补强支护-围岩相互作用关系等关键科学问题展开研究。基于典型深部软岩流变特性与巷道所经历的开挖粘弹塑性、流变变形阶段及其相应的本构关系，提出软岩巷道围岩应力场随时间演化的计算方法，揭示深部软岩巷道围岩应力场演化的时效机制；研究支护与围岩相互作用机制与过程，构建基于流变机制的补强支护与围岩耦合作用的力学模型，提出补强支护最佳时机判据。为深部软岩巷道支护设计、科学确定补强支护时机，实现围岩稳定控制奠定理论基础。

随着煤矿开采向深部发展，深部软岩巷道支护已成为制约煤矿行业发展的瓶颈，针对深部软岩巷道变形时间长、变形大且难以控制，动态补强支护技术是一项深部软岩控制的新技术，但补强时机、参数及动态补强支护机理等深层次理论问题亟待解决，本项目采用地下工程岩体力学、流变力学等理论相结合的方法，借助计算机数值模拟与现场实测相结合的综合手段，对深部软岩巷道应力场演化的时效特征与补强支护-围岩相互作用关系等关键科学问题展开研究。基于软岩分级卸荷蠕变试验，建立了软岩卸荷非线性蠕变本构方程，基于巷道开挖引起应力状态改变与软岩流变特性，分析了围岩应力场演化时效机制，以信湖煤矿典型深部软岩为工程背景，进行了流变影响围岩应力场演变实例分析，给出了应力场演化计算算法，并编制相应程序，进而提出了补强支护时机确定方法。依据巷道围岩应力变化趋势及围岩强度变化，按照深部软岩巷道四线段全应力应变曲线划分围岩次生承载结构为“流动层—塑性软化层—塑性硬化层—弹性层”耦合承载层，塑性软化层、塑性硬化层组成塑性承载区。并根据巷道围岩承载层划分提出动态补强支护方案，结合支护方案特点提出“层-双拱”承载结构力学模型，在极限平衡条件下对“层-双拱”承载结构进行受力分析得到其极限承载强度解析式。在技术方面，提出了包括动态补强时机在内的动态补强支护技术方案，一次支护采用锚网喷支护，在合适补强支护时机进行二次补强，选取浅、深孔注浆锚杆锚索联合支护。工程实践表明动态补强支护后巷道围岩变形趋于平稳，巷道能够保持长期稳定。为深部软岩巷道支护设计、科学确定补强支护时机，实现围岩稳定控制奠定理论基础。