Lubrication performance of pipejacking in soft alluvial deposits

Abstract

Pipejacking technologies has been extensively chosen by many mega cities worldwide to construct their sewer pipelines. Lubrication has been deemed to be the key factor in manipulating the performance of pipejacking works. Inadequate lubrication during pipejacking can lead exaggerated jacking force causing damages to the jacked pipe string and adjoining properties. Due to limited studies, a consensus has not yet reached. This study gives an access of evaluating the lubrication performance via the reduction in the frictional coefficient μ and investigates the impacts of injection type, soil and lubrication natures, and misalignment on the lubrication performance for a pipejacking project in alluvial soil deposits. The effect of misalignment, while ramming through the 8–21 m section of gravel at Drive C, gears up the frictional stress τld to 12.5 kPa (compared to 0.4 kPa of the 2–8 m section of the same gravel) and reduces the reduction to 71%. While traversing through the 24–31 m section of clayey gravel at Drive D, the occasional gravel not being long enough to develop lower face resistance leads the misleading reduction of 60%. These factors have greater influences on the lubrication performance than the injection type. The presented results would be helpful in managing the lubrication performance while pipe ramming for upcoming pipejacking project.