不同侧压力系数下圆形巷道变形破裂规律分析

为研究侧压力系数对巷道周边岩体稳定性的影响,以一条深埋圆形巷道工程为背景,采用离散颗粒元软件PFC3D分析了5种侧压力系数下巷道周边岩体的应力差、位移、破裂分布模式和微裂纹数等,得到了圆形巷道周边岩体应力、变形和破裂随侧压力系数的变化规律。结果表明,1)随侧压力系数增大,巷道顶底部浅部岩体主应力差先增大后减小,深部岩体主应力差逐渐增大;而巷道两帮浅部岩体主应力差变化较小,深部岩体主应力差先减小后增大。这表明在相同埋深情况下,高侧压力系数不一定会对帮部岩体造成更大的破坏,但更容易使顶板产生高剪应力,不利于顶板岩体的稳定。2)侧压力系数越大,巷道顶板岩体竖向位移就越小,且其由拱顶往外平滑递减的规律性也越不明显,而帮部岩体水平位移变化规律与顶板岩体相反。3)巷道顶底部围岩在侧压力系数较大的情况下较易发生破裂,并随侧压力系数增大,其破裂范围越来越大;巷道两帮岩体则在不同侧压力系数下均会发生破裂,且其破裂范围随侧压力系数增大而略减小。4)不同侧压力系数下,巷道岩体总裂纹数都随开挖时间呈指数增长;且当巷道开挖完成后,岩体总裂纹数与侧压力系数呈抛物线关系。

Analysis of the regularity of the displacement and rupture in the circular roadway under different lateral pressure coefficients

The given paper is inclined to disclose the evolutionary regularity of the stress,displacement and rupture to be caused by the different lateral pressure coefficients via a discrete particle element software known as PFC3D,in hoping to uncover the effect of the lateral pressure coefficient on the stability of the deep rocks in the background of a deep circular roadway.The results of our study show that,(1) with the increase of the lateral pressure coefficients,the main stress difference between the shallow rock on the roof or the floor and the deep rock therein tends to increase gradually,which may lead to changes little by little and later the change tends to decrease first and then increase correspondingly.What is said above implies that,at the same burial depth,the high lateral pressure coefficient may not always result in failure in regard to the two sides of the roadway rock,rather,it may cause the rock on the roof subjected to the high shear stress,which is naturally detrimental to the stability of roof rock.(2) The greater the lateral pressure coefficient,the smaller the possibility of the vertical displacement of the roof rock,and the lower the diminishing regularity of the roof rock collapsing from the dome to the outside would be,and,in contrast,the greater the horizontal displacement of the rock on the two sides will be,which seems to the opposite to the rule of vertical displacement.(3) It would be more likely for the roadway roof or the floor rock to get fractured in case the lateral pressure coefficient becomes bigger.And,consequently,the greater the lateral pressure coefficient,the greater the rupture range will be.While roadway rock on the two sides tends to rupture under different lateral pressure coefficients,its rupture range tends to be reduced slightly with the increase of the lateral pressure.(4) With the increase of the different lateral pressure coefficients,the probability of the surrounding rock cracks in the circular roadway tends to grow exponentially in the relation to the excavation time length.And,in turn,the total probability rate of the surrounding rock cracks will turn to be in a parabolic relation to the lateral pressure coefficient from the day when the roadway excavation were completed.