采动应力偏转诱发回采巷道顶板断层活化风险评估

Risk assessment of roof fault activation induced by mining stress deflection in mining roadway

针对采动影响下回采巷道顶板断层易发生活化和顶板变形失稳问题,以瑞能煤矿201工作面回风巷顶板穿断层破碎带为工程背景,综合采用理论分析、数值模拟和现场实测等研究方法,研究采掘活动诱发主应力偏转对断层活化风险的影响、工作面前方采动应力偏转特征、巷道顶板断层面主应力偏转特征及顶板稳定性。研究结果表明:采动应力偏转引起断层面应力莫尔圆与强度曲线的相切状态过渡到相割状态,增加断层结构面滑移失稳的风险;经理论推导得到涵盖正应力与切应力比值关系的断层面活化风险评判系数k;工作面超前扰动影响范围为25 m,工作面前方2 m内和巷道煤壁侧方4 m内主应力偏转明显,偏转角度大于60°;巷道顶板上覆2 m以内浅部断层面主应力偏转受工作面回采扰动影响较为显著,且随着与工作面距离的增加显著性减弱;沿断层倾向在巷道顶板上覆浅部(k>1区域)属于活化风险区,深部(k<1区域)属于稳定区,沿断层走向随着与工作面距离增加活化风险区的风险性呈指数型减小趋势,工作面前方5 m内属于高风险区、5~20 m内属于一般风险区、20~25 m内属于低风险区;工作面回采阶段断层活化风险对巷道顶板变形影响显著,随着与工作面距离增加,顶板变形有:高活化风险区>一般活化风险区>低活化风险区。基于断层活化风险性和巷道顶板的稳定性给出了工作面回采期间的补强支护方案。

Aiming at the problem that the roof fault of the mining roadway is prone to activation and roof deformation under the influence of mining.With the background of the roof crossing fault fracture zone of return laneway in 201 working face of Ruineng Coal Mine.Theoretical analysis,numerical simulation and field measurement were used in this study.Which contains the influence of principal stress deflection induced by mining activities on the risk of fault activation,the characteristics of the mining stress deflection in front of working face,the principal stress deflection characteristics of the roadway roof fault plane and the roof stability.The results showed that the mining stress deflection caused the transition from the tangent state to the secant state of the stress Mohr circle of the fault plane and the rock strength curve,which increased the risk of slip instability of the fault plane.The risk evaluation coefficient k of fault plane activation covering the ratio of normal stress to shear stress was obtained by theoretical derivation.The influence range of advance disturbance of working face was 25 m,the principal stress deflected obviously in the range of 2 m in front of the working face and 4m on the side of the coal wall of the roadway,and the deflection angle was greater than 60°.The principal stress deflection of shallow fault plane within 2 m of roadway roof was significantly affected by the mining disturbance of working face,and the significance decreased with the increase of distance from working face.The shallow part(k>1)of the overlying roof of the roadway along the fault dip belonged to the fault activation risk area,and the deep part(k<1)belonged to the stable area.The risk of fault activation risk zone decreased exponentially with the increase of distance from working face along fault strike.Within 5 m in front of the working face,it belonged to the high risk area.Within 5-20 m,it belonged to the general risk area.Within 20-25 m,it belonged to the low risk area.The risk of fault activation in the mining stage of working face had a significant influence on the deformation of roadway roof.With the increase of distance from working face,roof deformation in high risk area>general risk area>low risk area.Based on the risk of fault activation and the stability of roadway roof,the reinforcement support scheme during mining was given.