洞口不良地质段
Tunnel Portal in Unfavourable Geological Section
洞口段施工
Construction of the entrance
Portal construction
Portal section construction
洞口附加钢筋
additional bar around opening
洞口改造
hole mouth transformation
洞口偏压
asymmetrical-loaded portal
洞口施工
Portal construction
Construction of tunnel entrance
construction technology of tunnels entrance