The usual design solution for buried trunk pipeline while crossing active fault zone is to make a trapezoid-like trench with flat slopes and using a backfill with special properties. The aim of this trapezoid-like trench is to reduce strains in pipeline under the action of active fault displacement by enhancing the pipeline capability for relatively free lateral and upward movement. Due to soft backfill these movements not limited to trench borders and gives pipeline a capability of free aboveground deformation. In most cases sand with special properties is used as backfill for the trapezoid-like trench in active fault zones. However, over the years backfill sand is compacting and its mechanical properties become closer to undisturbed soil. In current paper the investigation of pipe-soil interaction under active fault displacement for a number of pipeline lifetime periods were carried out. The influence of backfill properties changing on pipeline stress-strain state under the fault displacement action is shown. For simulation the special finite-element model of pipe-soil interaction is used. Pipeline was simulated by plastic finite elements. Pipe-soil interaction in trench was simulated by nonlinear spring finite elements.
Temis, M. 2017. Influence of backfill compaction in time on buried trunk pipeline behavior under active fault displacement, Proceedings of the 16th World Conference on Earthquake Engineering, Santiago Chile, January 9th to 13th 2017, Paper N° 4909