Dynamic Centrifuge Experiments on Thrust Restraint for Pipe Bend Using Consolidation Method for Backfill Material

Abstract

The liquefaction of backfill materials induced by earthquake shaking may cause the movement of pipe bend resulting in joint separation. Thus, in order to prevent the movement of pipe bend buried in the site where only backfill material is liquefied, we propose a thrust restraint using soil-cement produced by grouting or mixing cement with sand as a backfill material. Dynamic centrifuge tests were conducted to validate the restrain method. The test results indicate the followings: (1) When only the backfill material is liquefied, the pipe moves mainly within the range of the backfill material and the original ground is barely deformed; and (2) placing the soil-cement as the backfill material around the sides of the pipe along the direction of thrust force can significantly reduce the pipe movement during an earthquake. Even if the excess pore water pressure generated in the sand―which is the backfill material―is transmitted to the soil-cement, which can resist the thrust due to its adhesive force.