Response of steel pipes buried in compacted fills to seismic fault rupture

抄録

This paper summarises findings of a series of 1-g physical model tests conducted on small-diameter steel pipes buried in compacted partially-saturated, saturated and dry sandy backfill materials of similar grain size distribution and dry density. The main aim of these tests was to measure under carefully controlled laboratory conditions the force that will develop on a rigid pipe buried in different backfills as result of relative vertical upwards or lateral permanent deformation of its surrounding soil, ensuing from rupture of a normal or a strike-slip seismic fault. The presentation focuses on i) exploring how sensitive this reaction force is to matric soil suction, which will develop even in sandy partially-saturated compacted backfills, and ii) documenting the mechanisms through which suction increases the resistance offered by the backfill to relative pipe movements. Analysis of comprehensive data collected during the tests revealed that the failure mechanisms that are formed in partially-saturated backfills during pipe movement features notable differences to the mechanisms that are formed in dry or saturated backfills, where the reaction force on the pipe is grossly lower. Findings of this study have important implications for the analysis of buried steel pipes subjected to fault rupture, even for pipes which backfill has relatively low suction potential.