砂卵石地层盾构开挖面稳定性分析  

Face Stability Analysis of Shield Tunneling in Sandy Cobble Stratum

作　　者：白永学[1] 漆泰岳[1] 吴占瑞[1] 

机构地区：[1]西南交通大学土木工程学院,成都610031

出　　处：《土木建筑与环境工程》2012年第6期89-96,共8页Journal of Civil,Architectural & Environment Engineering

基　　金：国家自然科学基金资助项目(50879049)

摘　　要：分析了成都砂卵石地层工程地质和水文地质条件,通过大型三轴试验对砂卵石层力学特性进行了研究。针对砂卵石层粘聚力低、离散性强的特点,选用颗粒离散元法作为数值计算工具,通过对大型三轴试验的数值模拟,对砂卵石层的细观参数进行了标定。研究了支护压力对开挖面变形、地表沉降、开挖面的最大位移和土层应力的影响。研究结果表明:1)开挖面土体破坏形状和砂土的离心试验模型相符;2)当支护压力较小时,开挖面前方土体颗粒接触力很低,颗粒流动趋势明显,因此容易引起超挖,从而导致盾构施工后形成地层中的空洞;3)开挖面前的上方土体成拱作用明显,即使土层内部形成空洞也不会立刻引起地面塌陷,这是目前成都盾构施工引发地面滞后沉降的主要原因。When shield crossed the sandy cobble stratum in Chengdu metro line 1, ground subsidence reached as high as dozens of times. The losing stability of excavation face caused excessive ground loss. Conditions of engineering geology and hydrogeology about sandy cobble stratum in Chengdu were analyzed. Mechanical characteristics of sandy cobble were obtained via large-scale triaxial test. According to the low cohesion and heavily discrete characteristics of sandy cobble, numerical computation was conducted by discrete element method. Based on numerical simulation of the large scale triaxial test, the micro parameters of the sandy cobble were calibrated. The influence of support pressure on shield excavation face deformation, surface settlement, max horizontal displacement and stress of soil was analyzed. The results show that： 1） Collapse pattern of excavation face by numerical simulation coincides with result of centrifuge model test in sand. 2） When supporting pressure is small, contact forces of particle in front of excavation face is low. The tendency of particle flow is apparent. Since over-excavation is easily brought out, cavity in the ground is caused after shield tunneling. 3）Soil arching effect in shield construction is obvious. Shield excavation forms cavity in deep ground and obvious earth surface collapse is not observed. This is main reason for lagged settlement phenomena of shield tunneling in Chengdu.

关 键 词：砂卵石地层 颗粒离散元 开挖面稳定性 土拱效应 

分 类 号：U451.2[建筑科学—桥梁与隧道工程]