黏土砾石地层隧洞开挖压力拱数值模拟研究

Numerical Simulation Research on Pressure Arch Effect of Tunnel Excavation in Clay-Gravel Stratum

为分析黏土砾石层中隧洞开挖时周围土体中拱效应的发展规律,基于离散元的方法研究了不同含石率下土体的位移发展过程,分析了隧洞从开挖到塌方结束过程中应力变化曲线,验证了动态压力拱理论在黏土砾石层中的适用性.结果表明:隧洞顶部的土体位移最大,越靠近隧洞两端越小,受扰动区域的沉降最大值随含石率增加而减小,同时更集中在隧洞顶部;隧洞开挖后,应力变化过程主要分为成拱阶段、坍塌阶段以及稳定阶段,隧洞周围土体的应力呈现环向应力增加、径向应力减小的趋势,在隧洞边墙处出现应力集中现象;通过应力张量十字架来反映土体的应力大小与方向,展示了塌落拱与开挖时步的关系,清楚地显示了拱效应在黏土砾石层中的形态,揭示了拱效应由成型到消失的变化机理,验证了动态压力拱理论在黏土砾石层中的适用性.

To analyze in the clay layer of gravel with tunnel excavation,the surrounding soil arch effect in the law of development,the development process of the surrounding soil displacement under different stone content after the tunnel excavation was studied based on the discrete element method,and the stress change curve of the tunnel from the excavation to the end of the collapse was analyzed.The rationality of the dynamic pressure arch theory in the clay-gravel layer is verified.The soil displacement at the top of the tunnel is the largest,and the closer the soil is to the two ends of the tunnel,the smaller the maximum settlement in the disturbed area decreases with the increase of the rock content,and it is more concentrated at the top of the tunnel.After the tunnel is excavated,the stress change process is mainly divided into arching In the stage,i.e.the collapse stage and the stable stage.The soil around the tunnel shows a trend of increasing hoop stress and decreasing radial stress,and stress concentration occurs at the side wall of the tunnel.The stress tensor cross is used to reflect the stress magnitude and direction of soil,which shows the relationship between collapse arch and excavation step,clearly shows the shape of arch effect in layers of clay gravel,reveals the change mechanism of arch effect from forming to disappearing.The application of dynamic pressure arch theory in clay gravel layer is verified.