高应力层状裂隙岩体卸荷力学时效特性及围岩控制研究

Coal strata has the significant features of layered structure. Engineering rock mass stability of mining activities and a mechanical aging characteristics of high stress layer fractured rock mass unloading is closely related, and unloading mechanics timeliness of layered rock mass under the condition of high stress is more obvious. The complexity of itself and rock unloading failure mechanism need further study. The project will be used by the means of theoretical analysis, mechanical experiment, similar simulation, numerical simulation and field test to form the theoretical system and technical methods, and these theories, such as rock mechanics, the theory of nonlinear rheological mechanics and fracture damage mechanics. The discontinuous characteristics of the high stress unloading layered fractured rock mass will be analyzed. Macro and micro failure mechanism of high stress layered rock unloading will be revealed. The relationship between the mechanical parameters and unloading time of layered rock high stress will be explored. The creep characteristics and aging strength of layered rock unloading will be studied. The fissure fractal model, equation of creep damage and destruction timeliness strength theory and stability criterion of high stress unloading layered rock will be established. Analysis on engineering rock deformation damage evolvement laws of high stress layer fractured rock mass validate the theoretical results, and make the necessary correction. The technical basic study will make a solid theoretical foundation for a mechanical aging characteristics of high stress layer fractured rock mass unloading, which can provide theoretical basis and technical foundation to long-term control of engineering surrounding rock in high stress layered rock.

煤系地层具有显著的层状构造特征，采掘活动形成的工程围岩稳定与层状裂隙岩体卸荷力学时效特性密切相关，且大埋深条件下的高应力层状围岩的卸荷力学时效性更明显，深部煤系地层本身及其卸荷破坏机制的复杂性需进一步研究。本项目拟采用理论分析、力学试验、模拟试验与现场实测相结合的研究方法，综合运用岩石（体）力学、非线性流变力学和损伤断裂力学等理论，分析高应力卸荷层状裂隙岩体断续特征，揭示高应力层状裂隙岩体卸荷破坏的宏、细观机理，探索高应力层状裂隙岩体卸荷的力学参数和时间关系，研究层状裂隙岩体卸荷的蠕变特性和时效强度，建立高应力卸荷层状岩体的裂隙结构模型、蠕变损伤方程及破坏时效性强度理论和判据，结合高应力层状岩体工程围岩变形破坏时效演化规律分析，对所得理论成果进行验证，并做必要的补充修正，形成高应力层状裂隙岩体卸荷的力学时效特性基础理论，给高应力层状裂隙岩体的工程围岩控制提供理论依据与技术基础。

采掘活动形成的工程围岩稳定与层状裂隙岩体卸荷力学时效特性密切相关，且大埋深条件下的高应力层状围岩的卸荷力学时效性更明显，深部煤系地层本身及其卸荷破坏机制的复杂性需进一步研究。通过对卸荷作用下围岩应力调整重新分布下巷道围岩力学特征及承载结构稳定性进行了研究，提高深部高应力层状裂隙岩体的工程围岩控制效果。课题研究获得的主要结论：1）煤岩样的单轴压缩、单面卸荷和孔洞煤样试验显示：煤岩样均有裂隙压密，弹性，屈服，残余强度的四个阶段；强度依次为单面卸荷、孔洞煤样、单轴压缩；单面卸荷的煤体呈现剪切和张拉复合破坏，卸荷面附近岩体由压致拉，向卸荷面扩容，越靠近卸荷面破坏越剧烈；孔洞煤样以孔为中心的“X”型共轭剪切破裂。2）建立深部高应力围岩的巷道开挖力学模型，揭示了开挖时空效应对围岩应力释放及承载结构影响；研究了主动采取卸压、加固施工来改善围岩应力分布时效状态，优化围岩承载结构调整；揭示了采取卸压、加固施工对围岩破坏变形及应力分布的控制作用和岩石破裂发展状态对围岩承载结构的调整机理。3）卸压施工优化巷道空间开挖轴比，两帮加固区为承载结构着力区，且两帮部峰值至巷帮距离与顶、底板峰值至开挖空间距离之比与侧压系数相等，围岩破坏形态为开挖卸荷空间的长轴方向与原岩最大主应力方向一致，而加固措施促使围岩形成“Ω”形承载结构。4）模拟实验显示：开采过程中，工作面顶板冒落表现为直接顶、老顶、2煤及上部岩层整体剪切性冒落推进方向顶板岩层的垮落角度为50°-55°，老顶、2煤及上部岩层垮落岩块形成新的砌体梁结构，工作面上部直接顶和老顶悬臂梁、砌体梁和冒落拱三种结构形式交替出现。5）现场巷道卸压围岩变形实测显示：巷道围压变形与迎头距离有一定的关系，距离的增加顶板下沉量也在逐渐减小，并趋于稳定；底板释放压力后在4d内的底臌量最大，巷道断面的应力没有达到平衡，使得底鼓继续增加；巷道右帮煤柱比左帮实体煤位移量严重。