深部采场覆岩应力路径效应与失稳过程分析

针对深部采场上覆岩层三向采动应力变化规律不清晰、采动应力变化与上覆岩层破断失稳过程之间的关系不明确等问题,提出基于应力状态与强度变化关系的三向采动应力扰动系数计算方法,揭示深部采场上覆岩层采动应力的时空演化特征与破断失稳过程。基于莫尔–库仑强度准则分析不同加卸载条件下主应力的变换形式,提出以最大、最小主应力差值与莫尔应力圆圆心到强度曲线距离之比作为三向采动应力强扰动判别指标,推导得出三向采动应力扰动系数;基于弹塑性力学理论,采用3DEC数值模拟方法,分析深部采场沿工作面推进方向、工作面长度方向上覆岩层的三向采动应力大小、方向变化规律,得出工作面前方上覆岩层的采动应力扰动系数与扰动强度分区,揭示深部采场上覆岩层的采动应力时空演化特征;基于深部采场上覆岩层破断过程的采动应力与位移变化关系,将顶板岩层的破断过程细分为采动应力增加、离层、断裂失稳、顶板上部岩层断裂失稳、上覆岩层压实稳定等5个阶段,分析上覆岩层断裂过程中采动应力的变化规律,揭示垂直应力、水平应力在上覆岩层断裂失稳过程中的作用机制。以口孜东煤矿千米深井长工作面开采实践为工程背景,采用上述研究成果较好地解释了口孜东煤矿千米深井大采高长工作面矿山压力显现频繁、来压强度不大等现象。

Stress path effect and instability process analysis of overlying strata in deep stopes

In order to reveal the three-direction mining stress variation law and the relationship between the mining stress variation and the overlying strata instability,a method for calculating the disturbance coefficient of three-direction mining stresses was proposed,and the temporal and spatial evolution characteristics of mining stresses and the process of fracture instability of overlying strata in deep stopes were studied. The transformation forms of the principal stress under different loading and unloading conditions were analyzed based on the Mohr-Coulomb strength criterion. The ratio of the maximum and minimum principal stress difference to the distance from the center of the molar stress circle to the intensity curve was proposed as the criterion for determining the intensity disturbance of three-direction mining stresses,and the disturbance coefficient of three-directions mining stresses was deduced. Based on the elastic-plastic mechanics theory,the change rules of the magnitude and direction of the three-direction mining stresses in the overlying strata along the working face advance and the working face length directions in the deep stope were analyzed using 3 DEC simulation. The mining stress disturbance coefficient and disturbance intensity partition of the overlying strata in front of the working face were obtained,and the spatial-temporal evolution characteristics of mining stresses in overlying strata were revealed in deep stopes. Based on the relationship of the mining stress and the displacement of overlying strata in the process of breaking,the breaking process of roof strata were subdivided to five stages of mining stress increase,bedding separation,fracture instability,fracture instability of upper roof strata and compaction stability of overlying strata. The variation rule and action mechanism of mining vertical and horizontal stresses in the process of overlying strata breaking were revealed. The research results were applied in the mining practice with 1 000 m buried depth of coal seam,and the phenomena of frequent occurrence of mine pressure and low compressive strength were better explained.