Optimal Rehabilitation of Gas Distribution Pipelines in Liquefiable Soils Considering Seismic Reliability

Abstract

Continuous functioning of gas distribution networks (GDNs) is important in the aftermath of an earthquake. Liquefaction has been found to cause a majority of the damages to buried pipeline infrastructure during an earthquake. A model for quantifying the seismic reliability of city-level GDNs is presented in this study. The seismic reliability model was used to select optimal rehabilitation alternatives for buried gas pipelines. Cured-in-place lining (CIPL) and replacement of aging pipelines with high-density polyethylene (HDPE) pipelines using the pipe bursting method were considered as rehabilitation alternatives in the study. A synthetic GDN was designed appropriately using the land-use pattern of the peninsular region of Charleston, South Carolina for demonstration purposes, and the 1886 Charleston earthquake was selected as the representative seismic hazard. Serviceability of the GDN was adopted as the basis for the reliability assessment using the Monte Carlo simulation approach, and a computationally efficient gas-flow model was developed to quantify the serviceability. For the selected seismic hazard, the reliability of the GDN in the study area was found to be 16.78%, and it increased to 18.62% after CIPL lining of all the pipelines. Replacement of all aging pipes with HDPE increased the reliability further to 26.94%. The optimization results informed the optimal selection of the rehabilitation alternative for each pipeline to maximize seismic reliability of the GDN at the cheapest possible cost. The proposed seismic reliability assessment approach and its use for rehabilitation planning will aid gas pipeline operators in their capital improvement works.