Protection of flexible pipes from dynamic surface stresses by geocell-reinforced sand backfill

Abstract

Underground conduits or utility pipelines are buried at shallow depths in trenches with the help of flowable fills. These pipes are subjected to deformations and damage due to application of dynamic traffic loads or heavy static loads from the vehicles. This study presents the results of a pipe model installed in geocell reinforced and unreinforced sand. A PVC pipe of 110 mm diameter and 1.4 mm wall thickness was installed in a rigid tank to simulate buried pipe. Different types of instrumentation such as earth pressure cell and vibration meter were used to measure the vertical transmitted pressure and displacement amplitude on the pipe crown, respectively. Different factors that affect the performance of pipes installed in sand bedding and backfill were investigated. The factors included state of compaction of bedding and backfill, magnitude of the applied surface dynamic pressure, and the load frequency. The results of this study were presented in terms of the vertical transmitted pressure on the crown of the pipe, surface soil settlement, the displacement amplitude of the pipe crown. It was concluded that the performance of the buried pipe depends on the state of compaction of sand bedding and backfill. When the relative density of the sand increases from 30% to 60%, the vertical pressure on the pipe crown, surface settlement, and the amplitude of displacement, decrease by about 30 %, 40 % and 15 %, respectively. When the relative density of the soil increases from 30% to 60%, more than 40% reduction was recorded in the surface settlement for unreinforced model while this reduction is about 25% for model reinforced with geocell.

Keywords

• geocell-reinforcement
• displacement
• dynamic stress
• sand backfill
• relative density