Performance evaluation of revere fault-crossing buried pipeline with super-absorbent-polymer concrete as trench backfill

Abstract

Geological and topographical challenges in fault zones pose significant risks to the structural integrity of buried pipelines. Previous studies have shown that continuously buried pipelines using loose sand as backfill material experience severe damage under active fault displacement. This study proposes the use of super-absorbent-polymer concrete (SAPC) as an alternative trench backfill to mitigate structural damage in buried pipelines subjected to reverse fault movement, as opposed to conventional backfill with loose sand. This study begins with the preparation of lightweight porous concrete containing large super-absorbent-polymer aggregates, followed by mechanical property testing to establish a constitutive model of SAPC. The SAPC is then employed to backfill the trench of a fault-crossing pipeline. A finite element model is developed to analyze the pipeline-SAPC trench-soil interaction and evaluate the performance of the pipeline when the trench is backfilled with SAPC. Critical parameters such as SAPC backfill length, overlying thickness, and elastic modulus are also examined for their effects on the performance of a buried pipeline. The numerical results indicate that compared with conventional backfill with loose sand, the critical reverse fault displacement of the pipeline can generally be increased by over 100 % after using SAPC as the backfill material. Optimal pipeline performance is observed when the SAPC backfill length is approximately 60 times the pipeline diameter. Besides, a thinner overlying SAPC thickness will generally enhance the performance of buried steel pipelines under reverse fault movement. Additionally, by adjusting the sand-cement ratio and SAP volume fraction, a SAPC with a higher elastic modulus can slightly improve the performance of the fault-crossing pipeline.