浅埋大断面黄土隧道大变形特性及其控制措施研究

INITIAL SUPPORT DEFORMATION AND CONTROL MEASURES OF LARGE CROSS-SECTION TUNNEL IN SUPER-SHALLOW LOESS STRATUM

依托银西客运专线某浅埋大断面隧道,基于数值计算和现场监测等手段对隧道变形特性进行分析,结果表明浅埋大断面黄土隧道拱顶沉降量大、变形时间长,初支封闭成环后变形速率变缓,但在二衬施作前隧道变形速率依旧较大,围岩未达到稳定状态。隧道施工过程中会在拱脚和墙脚形成塑性区,围岩塑性变形导致地层的不均匀沉降使围岩受到的拉应力或剪应力大于土体的强度,极易形成可见的地表裂缝。采用袖阀管注浆+洞内超前中管棚的控制措施能有效控制浅埋大断面隧道变形,保证施工安全。

In this paper,the deformation characteristics of a shallow-buried large-section tunnel on Yinxi passenger dedicated line are deeply analyzed by means of numerical calculation and on-site monitoring.The results show that the settlement of the arch roof of shallow-buried large cross-section loess tunnel is large and the deformation time is long,and the deformation rate slows down after the initial support is closed into a ring,but the deformation rate of the tunnel is still large before the second lining is put into operation,and the surrounding rock has not reached a stable state.During tunnel construction,plastic zone will be formed at arch foot and wall foot.The plastic deformation of surrounding rock leads to uneven settlement of stratum,which makes the tensile stress or shear stress of surrounding rock greater than the strength of soil,and it is easy to form visible surface cracks.The control measures of sleeve valve pipe grouting and advanced middle pipe shed in the tunnel can effectively control the deformation of shallow-buried large cross-section tunnel and ensure the construction safety.