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