HYDRAULIC LOADING IN CULVERT INLETS

Flexible corrugated metal pipes are commonly used as an alternative to concrete bridges for small and medium sized streams. If these flexibl e culverts are improperly designed they can fail dramatically. One cau se of failure is uplift at a submerged inlet. With the pipe flowing pa rtly full, the weight of the pipe and the net force due to the interna l water pressure may be less than the buoyant force acting on the subm erged pipe; this may result in an upward bending moment. This paper de scribes an experimental study of the hydraulic forces inside culvert i nlets. The tests were carried out on a plexiglass pipe with projecting and flush inlets. The effect of the flow separation on the pressure f luctuation at the inlet was investigated in this study. The internal p ressures for the case with a headwall were found to be significantly h igher than for the projecting inlet. The formation of a scour hole at the upstream end of the inlet increased the uplift potential. Internal pressure profiles were integrated to determine the internal load dist ributions on culverts with different inlet treatments.