Portal section construction
Sealing failure at tunnel portal
Tunnel portal
隧道洞口
隧道门(隧道洞口)
隧道入口
隧道峒口
隧道
洞口
隧道口
horseshoe section tunnel
horse-shoe section tunnel
Large Cross Section Tunnel
poor geological tunnel section
Shallowly embedded big fracture section tunnel
Small Cross Section Tunnel