Behavior of a Bend Pipe in the Apporo Pipeline Damaged by the 2018 Hokkaido Iburi East Earthquake

Abstract

In the 2018 Hokkaido Iburi East Earthquake, large diameter pipeline was severely damaged by large seismic ground motions. Seismic countermeasures such as selection of backfill material, high degree of compaction, and anti-floating measures were carried out in the district where the soft ground along the pipeline was deeply deposited. However, pipe detachment and flotation occurred in many places. Especially at the bend pipe, the joint detachment was caused by the large deformation of backfill ground and pipe.

In the present study, two-dimensional Finite Element Method (FEM) analysis was conducted for the purpose of clarify the behavior of bend pipe and the effect of mechanical properties of backfill material of the Apporo pipeline in Hokkaido during the earthquake. Through the FEM analysis, the proposed elasto-plastic dynamic analysis which can represent the reduction of strength for backfill material during earthquake exhibited the satisfactory predictions of the movement of bend pipe. The results of analysis and the damaged bend pipe movement at site were discussed considering the soil pipe interaction.