Application of X80 large deflection steel in the pipeline construction in seismic fault zone

Considering the possibility of pipe fracture in the construction of West-to-East Parallel Gas Transmission Pipeline Project passing through the seismic fault zone, X80 large deflection steel was applied in order to offset the fracture. Compared with the traditional method in increasing pipeline wall thickness, the strain-based design method was introduced into the project. The main construction procedures were consisted of "digging trench from one side+ combination welding in ditch + digging the other side". The technique of "RMD root bead + flux-cored wire cosmetic bead" was used in the large deflection welding technology. Results showed that X80 large deflection steel pipe could satisfy the anti-seismic requirements and decreased the project costs. The construction method effectively solved the problems existed in the high slope rate and wide trench. The pass percent of one-round welding reached at 98%.