富水区城市公路隧道中隔壁法各开挖步力学特征研究

以深圳东部过境高速公路连接线工程为依托，基于应力场-渗流场耦合的数值模拟方法，研究富水区城市公路隧道中隔壁法各开挖步力学特征。结果表明:中隔壁法各开挖步骤的围岩主应力变化特征明显，隧道目标面围岩总体受压，在隧道两侧拱腰至拱脚处存在较为明显的压应力集中现象，而拱底及掌子面则出现少量拉应力集中；不同开挖步拱脚处初期支护应力最大，拱腰、拱肩和拱顶处应力量值较为接近，而拱底处应力最小；初期支护受力随隧道开挖进程变化幅度较小，初期支护具有一定的安全储备；各径向特征点水压力均呈现从注浆圈外侧至初期支护外侧逐渐减小的趋势，而各环向特征点水压力由拱顶至拱底逐渐增大；对于作用于初期支护上的水压力值，数值计算结果稍大于不考虑开挖影响的理论预测值，表明中隔壁法隧道施工各开挖步对衬砌背后水压力大小及分布规律有一定影响。

Study on Mechanical Characteristics of Each Excavation Step with CD Method in Urban Highway Tunnel in Water-rich Area

Based on the connecting line project of border crossing highway in the east of Shenzhen, this paper studies the mechanical characteristics of the different excavation steps with CD method in the urban highway tunnel in the water-rich area based on the numerical simulation method considering the coupling of stress field and seepage field. The results show that the main stress changes of surrounding rock in the excavation steps with CD method are obvious; the surrounding rock of the target surface is in a state of compression. There is a more obvious stress concentration phenomenon on both sides of the arch waist to the arch foot in the tunnel. But the arch bottom and tunnel face present a little tensile stress concentration phenomenon. The initial support stress of arch foot is maximal at different excavation steps. The values of stress at arch waist, arch shoulder and arch crown are close. The stress at the arc bottom is the smallest. The change of the initial supporting force is small in the process of tunnel excavation. The initial support has a certain safety reserve. The water pressure of each radial feature point presents a gradually decreasing trend from the outside of the grouting circle to the outside of the initial support. The water pressure of each ring feature point is gradually increased from the crown to the arch bottom. For the value of water pressure on the initial support, the numerical results are slightly larger than the theoretical prediction value not considering the influence of excavation. It reveals that the value and distribution of water pressure behind the lining are influenced by the different excavation steps of the tunnel construction with CD excavation method.