不同应力场软弱围岩隧道施工力学特征的数值分析

Numerical Simulation for Soft-Weak Surrounding Rocks Tunnel Construction Mechanical Characteristics of Different Stress Field

岩体内部的初始应力及隧道开挖后的围岩应力是隧道工程的关键影响因素,为了更全面地了解不同应力场软弱围岩公路隧道施工的力学特征,建立有效的有限元模型,采用不同加载方式,模拟不同应力场,对软弱围岩公路隧道施工过程中隧道围岩位移和应力变化特征及其影响范围进行了详细分析,并对衬砌结构的受力特征进行深入研究。结果表明:不同应力场决定了隧道施工过程中围岩塑性区的大小和位置,这也就决定了隧道施工中重点监控的位置;在不同应力场隧道开挖完成后,拱上20 m水平面围岩竖向位移、拱上中心线围岩竖向位移及仰拱底围岩竖向位移随着侧压力系数的减小而明显增大,拱腰处围岩水平位移则随着侧压力系数的减小而明显减小;应力场对衬砌结构的内力影响很大。

From a great deal of engineering practice, the size and the position of the initial stress have great influence on the design and construction of underground such as tunnel and so on. In order to more fully grasp the construction mechanical characteristics of surrounding rock highway tunnel under different stress field, the process of tunnel excavation in different stress fields are simulated by setting up the FEM model. The characteristics of the stress and displacement in surrounding rocks tunnel due to excavation are studied. The characteristics of the stress and displacement in lining due to excavation are studied also. The result shows that after tunnel excavation, area and location of surrounding rock invalidation are different in different stress fields, so the inspection location are different during tunnel construction; the surrounding rocks vertical displacements at 20 m horizontal and vertical up tunnel increase with the lateral pressure coefficient decreasing, the surrounding rocks horizontal displacement at arch waist decreases with the lateral pressure coefficient decreasing; the lateral pressure coefficient has a great impact on the internal forces of lining.