地铁大跨度隧道垂直挑顶施工中的围岩力学分析

Analysis of Surrounding Rock Mechanical Behavior of Metro Large-Span Tunnel Vertical Propping Construction

基于深圳地铁2号线新秀站—莲塘口岸站区间隧道工程,提出了一种适用于软弱围岩大跨度隧道垂直挑顶开挖的施工方法,并采用FLAC3D软件对该挑顶施工全过程进行模拟计算,对施工过程中的围岩进行了力学分析,以解决交叉段隧道挑顶开挖过程中围岩变形控制的难题。模拟计算结果表明:挑顶开挖主要影响了拱顶处的围岩应力重分布,斜井开挖使得正洞相邻拱腰处产生压应力集中,正洞开挖顺序造成斜井拱腰处应力分布不对称;落斜井坡道和正洞下台阶时斜井拱腰水平收敛发生突变,这对隧道拱腰应力分布产生了较大影响,应作为施工的重点关注区域;挑顶开挖使正洞和斜井拱顶的围岩塑性区贯通,在落斜井坡道和正洞下台阶时该塑性区进一步扩展,此区段施工时应加强支护,并减缓施工速度。

Based on the tunnel project between Xinxiu Station and Liantang Port Station of Shenzhen Metro Line 2,a construction technology suitable for vertical propping excavation of weak surrounding rock large-span tunnels is proposed,and FLAC3D software is used to simulate and calculate the whole propping process construction,and the mechanical behavior of the surrounding rock during the construction process is analyzed to solve the problem of surrounding rock deformation control during the excavation of the cross-section tunnel.Simulation results show that the propping excavation mainly affects the gravity distribution of the surrounding rock stress at the vault,and the excavation of the inclined shaft induces compressive stress concentration at the adjacent arch waist of the positive hole.The order of the excavation of the positive hole causes asymmetrical stress distribution at the arch of the inclined shaft.The vertical convergence of inclined shaft arch undergoes sudden change when falling shaft slope and positive hole takes lower step,making great impact on the stress distribution of tunnel arch,which should be considered as the focus area of construction.The propping excavation makes the surrounding rock plastic area of the positive hole and inclined well arch penetrate,and when the inclined shaft slope and positive hole takes lower step.The plastic zone is further expanded and should be supported,and construction speed should slow down.