The performance of pipeline systems under seismic loading is an important consideration in regions subject to earthquakes. This paper briefly describes a study to evaluate the vulnerability of a natural gas transmission system to seismic hazards, along with some of the remedial treatment options which are being considered. The study was carried out for BC Gas Utility Ltd. in the Greater Vancouver Region of British Columbia. The results of the study are being used by BC Gas in emergency response planning and remedial treatment activities to limit their risk exposure.
The paper describes the approach used to assess liquefaction and lateral spreading risks, and remedial treatment options which were considered. This involved generation of design seismic ground motions, seismic hazard mapping, geotechnical investigations to determine the subsurface conditions, and geotechnical and structural numerical modeling and analysis to assess pipeline performance and remedial treatment options.
Several different approaches to remediation are described; one involves ground treatment to reduce the risk of unacceptable ground deformations; another involves structural modifications to improve the resistance of the pipeline to seismic motions, while another makes use of directional drilling to re-align the pipe below infirm areas.