Abstract
Part of the essential infrastructure required to control water run-off in both rural and urban environments, are embedded stormwater reticulation pipes. Underground pipe networks facilitate the transportation and management of surface storm water which when left uncontrolled, could endanger the safety of motorists and cause flooding of hydrologically sensitive surface level infrastructure.
The performance of buried pipes is broadly dependent on the geotechnical condition of the surrounding soil and is measured in terms of permissible deflection and buckling resistance. The root cause of failure is variable ranging from incorrect backfilling material, improper installation, poor bedding to fabrication defects.
This study examines the behaviour of a buried flexible pipe when subjected to the application of overlying soil and light traffic loads. A 7.4m long pipe has been analysed at a short depth (0.52m) relative to the ground surface. Several parameters govern the study which include pipe deformation, circumferential pipe stresses, load dissipation through soil depth and general soil behaviour under various loading conditions. The linear finite element method is used to carry out this investigation using the ABAQUS program. Various assumptions of the surrounding soil and pipe’s mechanical and physical properties have been made respectively.
The results from the FEM study indicate opportunity and potential use of flexible pipes as a substitute for rigid pipes in the transportation of stormwater for civil engineering applications. Results further indicate that flexible pipes have sufficient bearing capacity to self-support against gravitational loads and against applied loads generated from traffic loads. A maximum pipe deformation and stress of 0.117mm and 0.55MPa were determined respectively for four hypothetical loading cases. From this, it was deduced that a flexible pipe would not yield or loose serviceability. Additionally, the FEM study could not make a determination whether serviceability can be maintained over a long period due to secondary loading effects such as mechanical abrasion, creep, soil consolidation and fractures from impact loading during backfilling.