Utilizing HDD and Finite Element Modeling to Achieve Seismic Resilience for the Golden Ears Forcemain River Crossings

Abstract

Metro Vancouver (MV) recently constructed new sewer forcemain crossings under the Fraser River. The river crossings were installed using Horizontal Directional Drilling (HDD) method and forcemains in the north riverbank were installed using open cut and trenchless methods. The new sewer forcemains are classified as essential pipelines for MV which are intended to remain functional and operation during and after a 2,475 year return earthquake. Major seismic hazards consist of soil liquefaction induced permanent ground deformations (PGD) of vertical settlement and lateral spreading movements. To design these essential pipelines to achieve the required resilience performance level under the seismic PGDs, a pipe-soil interaction finite element analysis was completed for the entire forcemain alignment. PGDs were applied at multiple steps to account for the sequential loading stages from the PGDs. Both steel and HDPE pipes were analyzed in the model, and appropriate pipe sections, joints and connections were selected based on the modeling results. Strain based design considering both elastic and plastic behavior were utilized for the steel pipe.