不同围压巷道开挖应力场演化规律模拟试验研究

Simulation studies on stress field evolution of roadway excavation under different confining pressures

在实验室利用自制模具对模型边界进行约束,采用微机控制电液伺服万能试验机进行加载,采取卸除前约束板模拟煤矿井下煤层巷道开挖,得出了不同应力煤层开挖前后轴向应力变化特征,探讨了低应力、中等应力、高应力条件下巷道围岩开挖前后的应力场变化特征。研究结果表明:在低应力条件下,模型开挖造成应力的重新分布,在开挖面附近形成拉应力区,但模型内应力值较小,整体处于弹性状态,围岩抗开挖扰动能力较强;在中等应力条件下,模型开挖造成围岩浅部拉应力区进一步加大,岩体接近或达到屈服状态,围岩受开挖扰动比较强烈,开挖后应力场开始呈现"拉—压—拉"交替现象;在高应力条件下,围岩出现明显的塑性破坏,模型内部整体处于受拉状态。受到开挖扰动,围岩表面迅速恢复到受压状态,并再次向深部转移,形成明显的动态"拉—压—拉—压"交替现象,围岩破坏深度大、抗扰动能力差,呈现深部开采特征。

A model of mine roadway was constrained on the boundary by home-made mold,loaded by microcomputer control electro-hydraulic servo universal testing machine in laboratory.Thus the coal mime roadway excavation was simulated by unloading the front constraint plate of model.The variation characteristics of axial stress before and after the excavation of coal seam with different stresses were obtained,and also the roadway surrounding rock stress field variation characteristics before and after excavation under low,secondary and high stress conditions were discussed.The results showed that the tensile stress area near the excavation plane was formed under low stress condition,but the internal stress values were small,the whole surrounding rock was in elastic state,the resistance ability of surrounding rock to excavation disturbance was strong.Under the condition of secondary stress,the tensile stress area of surrounding rock in the shallow further expanded,which was caused by model excavation,rock mass reached yield status and the excavation disturbance of surrounding rock was strong,the stress field after excavation began to present ‘pull-pressurepull'alternate phenomenon. Under the high stress condition,the surrounding rock obviously appeared as plastic and the rock mass within the model all appeared in a state of tension.By excavation disturbance,the surrounding rock sur-face rapid returned to compression state and moved to deep again,forming obvious ‘pull-pressure-pull-pressure'dynamic alternation phenomenon,damage depth of surrounding rock was larger,the ability to resist disturbance was poor,appeared deep mining characteristics.