水平软硬互层偏压隧道施工稳定性分析

Analysis of Construction Stability of Horizontal Soft and Hard Interbedded Tunnel under Unsymmetrical Pressure

以水平层状的砂泥岩互层围岩条件下遂德高速公路中鸡公岭隧道为工程背景,采用有限元分析软件,模拟分析在不同偏压条件下三台阶开挖施工方法中隧道围岩塑性区分布情况及初衬收敛位移、应力场变化情况。结果表明:中部施工对隧道稳定性影响最大,随着偏压角度的增大,塑性区由拱腰向拱脚及拱肩处发展。初衬拱顶及仰拱竖向位移随着施工步序的进行而增大,总体收敛位移及竖向位移最大值均发生在砂泥岩互层交界处。由于施工荷载作用,整个拱圈初衬的初始应力场被破坏,其中隧道中部施工对应力场重分布的作用更明显。随着偏压角度的增大,左右两侧隧道小主应力最大值绝对值的增量均逐渐变大,在偏压角度大于50°后,左侧隧道小主应力最大值绝对值超过右侧隧道的对应值。

Taking the horizontal layered sandstone and mudstone interbedded surrounding rock conditions as the engineering background, the finite element analysis software is used to simulate and analyze the three-step tunnel excavation method under different bias conditions, such as he distribution of the plastic zone of the surrounding rock, the convergence displacement of the initial lining, and the change of the stress field. The results show that the construction in the middle has the greatest impact on the stability of the tunnel. With the increase of the bias angle, the plastic zone is developed from the arch waist to the arch toe and the arch shoulder. The vertical displacement of the primary lining vault and the inverted arch are increased with the progress of the construction sequence, and the overall convergent displacement and the maximum vertical displacement occur at the junction of sand and mudstone interbeds. Due to the construction load, the initial stress field of the initial lining of the entire arch ring is destroyed. The construction in the middle of the tunnel has a more obvious effect on the redistribution of the stress field. With the increase of the bias angle, the absolute value of the minimum principal stress of the left and right tunnels. After the bias angle is greater than 50°, the minimum absolute value of the minimum principal stress of the left tunnel exceeds the right tunnel.