斜井盾构掘进时富水围岩变形特性模拟分析

A study of the rich-water ground rock deformation features as shield tunneling along with inclined shaft

在富水软岩地层中进行盾构掘进施工过程时,围岩应力状态会发生变化。准确掌握其变化规律,有利于采取合适的处置方法,避免发生斜井垮塌涌水和卡盾抱箍等工程事故。以往研究一般只考虑盾构、斜井和软岩中的一个或两个条件,也未对有无渗流两种工况进行对比,并较少涉及不同埋深条件下坡度的影响。文章采用有限元计算模型研究盾构在富水软弱地层中掘进过程中围岩的力学特性,通过选择若干观测断面进行监测,得出软岩整体呈现“横鸭蛋式”椭圆形变化趋势,且顶部比两侧和底部更容易受到施工扰动,在渗流条件下该趋势得到加强;设定5种埋深和5种斜井坡度条件,模拟盾构在掘进过程中不同条件下顶部和侧向监测点的位移,结果显示:盾构洞周拱顶竖向位移一般大于两侧水平位移;当斜井纵坡坡度<4°时,盾构顶部监测点竖向位移与侧向监测点水平位移相差较小,但均随斜井埋深的增大而增大;坡度超过4°后,盾构掘进引起的顶部竖向位移与侧向水平位移间差值随着埋深的增加而逐渐增大。

During shield tunneling in water-rich soft rock strata,the stress state of surrounding rock will change.Accurate grasp of its changing law is conducive to the adoption of appropriate disposal methods to avoid engineering accidents such as inclined shaft collapse,water gushing and clamping hoops.Previous studies generally considered only one or two conditions of shield,inclined shaft and soft rock,and did not compare the two conditions with or without seepage,and less involved in the influence of slope under different burial depth conditions.In this paper,the mechanical characteristics of surrounding rock during shield tunneling in water-rich soft strata are studied by using finite element model.Through monitoring several observation sections,it is found that the whole soft rock presents a trend of“cross-duck-egg”elliptical deformation,and the top is more susceptible to construction disturbance than both sides and bottom.The trend is strengthened.Five kinds of burial depth and five kinds of slope conditions are set to simulate the displacement of top and lateral monitoring points under different conditions during shield tunneling.The results show that the vertical displacement of arch roof around shield tunnels is generally larger than the horizontal displacement on both sides.When the slope of inclined shaft is less than 4 degrees,the vertical displacement and lateral displacement of the monitoring points on top of shield tunnels are simulated.The difference in horizontal displacement between monitoring points is small,but it increases with the increasing depth of inclined shaft.When the slope is more than 4 degrees,the difference between vertical displacement and lateral horizontal displacement caused by shield tunneling increases with the increaseing buried depth.