基于DP准则的巷道围岩塑性区影响因素分析

Analysis of influencing factors of roadway surrounding rock plastic zone based on Drafcker-Prager criterion

围岩塑性区的扩展是巷道事故频发的根本原因,确定塑性区影响因素及其发展规律对煤矿的安全生产至关重要。基于DP准则推导出非均匀场下的围岩塑性区边界方程,对非圆形截面巷道进行当量半径折算,分析不同侧压系数下塑性区形态,采用单因素法分析不同DP准则的塑性区影响因素。研究结果表明:当侧压系数在0.6~1.5范围时,塑性区呈椭圆形分布;当侧压系数小于0.6或大于1.5时,塑性区呈蝶形分布。巷道地压和围岩岩性显著影响了塑性区的形态及范围,根据工程实际合理选取巷道位置,能够有效降低巷道支护的难度及成本。中间主应力对巷道围岩塑性区范围的影响有着强烈的区间性。巷道支护可以通过注浆来改善岩体的黏聚力、内摩擦角,进而减小塑性区范围,但这一作用效果有限。塑性区半径随着支护阻力的增大而线性减小。根据不同DP准则计算出的塑性区半径有所差异,合理运用DP屈服准则既能够保证煤炭生产的安全性,又能够降低工程造价。

The expansion of plastic zone in surrounding rock is the fundamental cause of frequent roadway accidents.Based on DP criterion,the boundary equation of plastic zone in surrounding rock under non-uniform field is derived,equivalent radius is converted for non-circular section roadway,plastic zone morphology under different lateral pressure coefficients is analyzed,and the influencing factors of plastic zone under different DP criterion are analyzed by single factor method.The results show that when the lateral pressure coefficient is in the range of 0.6-1.5,the plastic zone is elliptic.When the lateral pressure coefficient is less than 0.6 or more than 1.5,the plastic zone presents a butterfly distribution.Roadway pressure and surrounding rock lithology significantly affect the shape and scope of the plastic zone.Reasonable selection of roadway location according to the actual engineering can effectively reduce the difficulty and cost of roadway support.The influence of intermediate principal stress on the plastic zone of roadway surrounding rock has strong interval.Roadway support can improve the cohesive force and internal friction angle of rock mass through grouting,and then reduce the plastic zone,but the effect is limited.The radius of plastic zone decreases linearly with the increase of supporting resistance.The plastic zone radius calculated by different DP criterion is different.Reasonable application of DP yield criterion can not only ensure the safety of coal production,but also reduce the cost of engineering.