浅埋小净距偏压隧道合理开挖顺序探讨

运用ANSYS有限元程序，研究浅埋偏压小净距隧道在不同的偏压角度、间距、埋深条件下，先开挖深埋侧和先开挖浅埋侧2种不同的开挖顺序下的受力和变形特性，对比分析了围岩最大拉应力、围岩洞周最大位移、中岩柱水平位移和竖向应力。研究结果表明：随着角度的增加，先开挖深埋侧较先开挖浅埋侧隧道及中岩柱更加安全；当间距小于0．5倍洞径时，先开挖深埋侧较先开挖浅埋侧安全；当间距大于0．75倍洞径时，先开挖浅埋侧对于隧道受力更加有利；当埋深在1倍洞径以下，先开挖深埋侧隧道整体稳定性及受力更加安全，当埋深大于1．5倍洞径时，先开挖浅埋侧隧道受力更加安全。

Study on the reasonable excavation sequence of shallow- embedded bias tunnels with small clear distance

Based on the conditions of different bias angles, different clear distances and different burial depths, the mechanical and deformation characteristics of tunnels were studied under two different excavation sequences with the ANAYS finite element program. A comparative analysis of the maximum tensile stress, the maximum displacement around the tunnel, the horizontal displacement and vertical stress of the middle rock pillar were car- ried out. The results show that the surrounding rock and middle rock pillar are safer with the deep side of tunnel excavated earlier than that with shallow one excavated first with the increase of the unsymmetrical loading angle. It is safer to excavate the deep side of tunnel earlier when the spacing is less than 0.5 times of the diameter of the tunnel. However, it is advantageous to the stress of the tunnel if the shallow side of tunnel is excavated first when the spacing exceeds 0.75 times of the diameter of the tunnel. Moreover, the stability and stress of the tunnel are safer if the deep side of tunnel is excavated earlier while the burial depth is less than 1 times of the diameter of the tunnel. Whereas excavating the shallow side of tunnel earlier is safer when the burial depth exceeds 1.5 times of the diameter of the tunnel.