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在依据摩尔图解及断裂力学理论对底板卸荷突水破坏分析的基础上,运用损伤断裂力学并结合统一强度理论,建立了考虑渗透水压作用下分支裂纹端部形成的塑性区范围计算方程与岩体发生贯穿破坏时的损伤阀值。将裂纹扩展过程与岩体损伤耦合起来,确定了裂纹的损伤断裂能量计算公式并分析了其影响因素。结果表明:侧压系数λ=0.5时,最大主应力完全卸荷状态下裂纹端部应力强度因子比双轴应力状态下大,岩体易发生破坏。考虑了裂纹端部塑性区的影响,裂纹损伤断裂能量相比于不考虑其影响时偏大,增大了煤层底板突水的危险性。裂纹损伤断裂能量G_1与裂纹半长a、裂纹面连通面积与总面积之比α、裂纹面渗透水压p及最小主应力σ_3呈正相关,与裂纹面摩擦系数f及岩体的弹性模量E呈负相关。分析结果为底板突水破坏机制研究提供了一定的参考依据。
Based on Mohr diagram and fracture mechanics theory, based on the analysis of damage and unloading water inrush of floor, the calculation formula of the plastic zone formed at the end of branch crack considering the effect of seepage hydraulic pressure is established by using the damage fracture mechanics combined with the unified strength theory The damage threshold of the rock mass occurs during failure. Coupling the crack growth process with the rock mass damage, the calculation formula of the damage energy of the crack is determined and its influencing factors are analyzed. The results show that the stress intensity factor at the crack tip is larger than that under biaxial stress when the lateral compressive coefficient λ = 0.5, and the rock mass is easy to be damaged. Considering the influence of the plastic zone at the crack tip, the energy of the fracture damage fracture is larger than that without considering its influence, increasing the risk of water inrush from the coal seam floor. The crack damage energy G_1 and the crack half-length a, the ratio of the area of the crack surface to the total area α, the water pressure p of the crack surface and the minimum principal stress σ 3 are positively correlated, the friction coefficient f with the crack surface and the elastic modulus E Negative correlation. The results provide some references for the study of mechanism of water inrush from floor.