双侧壁导坑法施工的大断面隧道的稳定性分析

Stability Analysis on Large Section Tunnel with Double-Side-Drift Method

以沙湾大断面隧道为研究背景,应用ANSYS有限元软件,采用释放荷载法,研究支护封闭的快慢对双侧壁导坑法施工的隧道稳定性的影响。通过对拱顶沉降、边墙中点水平位移、围岩塑形区及初衬应力的分析,得到了支护封闭时间对隧道受力和位移状态的影响,施工中应尽量缩短各开挖面的距离,使支护尽快封闭,有利于隧道稳定。为了进一步改善隧道的受力状态,模拟分析了加固部分围岩后的状态。结果表明加固侧壁导坑临时支护与初衬接触处的围岩能较好的改善隧道的受力条件。在临时钢架支护下端与初衬的接触点附近出现了应力集中现象,受到了很大的拉应力,在设计施工中应引起重视。

Taking Shawan Tunnel as background,the influence of tunnel＇s stability resulting from the time of closing the support in large section tunnel with double-side-drift method is studied by finite element software ANSYS with the load-releasing method.Through analyzing vertical displacement of the vault,horizontal displacement of the middle point of sidewall,plastic zone of surrounding rock and stresses of preliminary lining,the result shows that sealing the primary shoring quickly is favorable to control the stresses and displacements of the tunnel.So in construction process the distance between adjacent excavation faces should be shortened and the speed of closure should be stepped up to achieve stability of the tunnel.The state of reinforcing parts of surrounding rock is simulated in order to further search for some way to improve the stresses of the tunnel.It is shown that reinforcing the surrounding rock near the contact area of the temporary support and preliminary lining will improve the stresses condition of the tunnel.Meanwhile,the contact area of the temporary support and preliminary lining,where a great deal of concentrated tensile stress appears,should be paid attention to in the design and construction process.