薄壁面板隔墙法在特大断面隧道施工中的力学特征分析

Study on Mechanical Characteristics of Thin Mid-partition Wall Method in Super-large Section Tunnel Construction

以某浅埋暗挖城市地铁车站为工程背景,利用有限元数值模拟方法分析了薄壁面板隔墙法的原理和在施工过程中隧道围岩的变形和力学演化特征。分析结果表明,薄壁面板隔墙法的台阶式导坑开挖主导了隧道结构的应力集中特征和变形特征,施工时特大断面隧道的初衬、锚杆和围岩的应力、应变均沿隧道轴向方向阶段性地出现多个应力集中区和位移剧变区,各区域的分界处基本和隧道先开挖侧各导坑开挖端面平齐。而且,中隔墙和预留核心土的设置有效地改善了开挖对特大断面隧道围岩的扰动,使得隧道围岩塑性区小,隧道的拱脚水平相对净空变化指标和拱顶相对下沉指标均能满足特大断面隧道的稳定性要求。

Based on the construction of tunneling urban subway station, theories of the thin mid-partition wall method is introduced and the transformation and mechanical evolution characteristics are analyzed with the finite element numerical simulation analysis method. The results show that the pilot tunnel excavation dominates the tunnel structure stress concentration and deformation characteristics. The stress and strain of the surrounding rock, initial liner and rock bolt in the super large section tunnel have multiple stress clusters and displacement upheaval zones along the axial direction of the tunnel.The boundaries of different stress clusters and displacement upheaval zones are almost at the end face of the pilot tunnels. Meanwhile, the setting of the middle wall and the reserved core soil effectively improves the excavation disturbance of super large section tunnel surrounding rock, narrowing the plastic zones of the surrounding rocks. The horizontal relative clearance index of tunnel arch foot and the relative sinking index of vault can also meet the stability requirements of the super large section tunnel.