Performance of Steel Pipelines Backfilled with Controlled Low-Strength Material (CLSM) under Seismic Wave Propagation and Reverse-Slip Fault Rupture

Abstract

Seismic events may drastically damage buried pipelines affecting economy and public safety. Traditionally, buried pipelines are bedded and backfilled with compacted soils, which is labor intensive, time consuming, and could be a safety hazard to workers. Many studies have shown that achieving a proper compaction level around pipelines can be a difficult task. Improper compaction can greatly reduce performance of the pipelines under loads. Controlled Low-Strength Materials (CLSM) is a group of cementitious materials that can be used as an alternative to compacted soils to backfill pipelines. These mixtures are highly flowable in their fresh state and are solid in the final state providing a uniform support around pipelines. Although there is considerable research about the advantages of using CLSM to backfill pipelines from construction point of view, there is no research on the performance of pipelines embedded in CLSM subject to seismic loads. In this research, 3D FEA was conducted using ABAQUS software to determine the performance of buried steel pipes backfilled with CLSM when subjected to seismic wave propagation and reverse-slip fault rupture. Under seismic wave propagation, the study started by evaluating the ASCE guidelines and its design limitations. Then, several FE model parameters were evaluated for their effects on FE model results. After setting the model parameters to match the predicted stresses by the ASCE guidelines, the developed FE model was used to evaluate the pipe seismic performance with various soil and CLSM backfill materials. Both linear and non-linear material behavior were considered in this study. Under seismic fault rupture, the study developed a 3D FE model matching results from a full-scale testing performed by others. Various FE model parameters were also evaluated. Then, the developed FE model was utilized to determine the pipe seismic performance of CLSM mixture compared to compacted soil backfill. Results indicated that for 3D FEA pipe seismic analysis, FE model parameters can have a significant effect on the results. In addition, with a proper design buried steel pipe embedded in CLSM backfill with all its inherent advantages can perform as well as or better than soils in seismic prone areas.