New Thrust Restraint Technique Using Geosynthetics for Buried Bend

Thrust force is generated at a pipeline bend due to internal water pressure. Commonly, the thrust force is resisted by the passive resistance acting on the pipe bend. In Japanese current design (M.A.F.F. 1998), the passive resistance acting on the pipe bend is determined based on Rankine's earth pressure theory. In this paper, new backfill methods using geogrid and gravel for buried bend were proposed. In the new methods, the geogrid and the gravel were installed in the passive area to improve the strength of the ground. In order to verify the effectiveness of the proposed methods, lateral loading experiments were carried out using a model pipe having a diameter of 114 mm. The passive resistance of the pipe increased in the case using the proposed methods. In addition, numerical analyses using the distinct element method (DEM) were performed to reveal the resistance mechanism of the proposed methods.