
The world’s longest spiral tunnel-the left line of Laoyingpan No.1 Tunnel of Xizhao Expressway runs through
Laoyingpan No.1 Tunnel on the Xichang-Zhaotong Expressway, the world’s longest spiral tunnel invested by CREC and China Railway City Development & Investment Group, surveyed and designed by China Railway Eryuan Engineering Group and constructed by China Railway No.2 Group, was…











