Hydraulic Tests on Corrugated Metal Culvert Pipes

Abstract

Experimental studies on culverts conducted at the St. Anthony Falls Hydraulic Laboratory of the University of Minnesota, beginning in 1946, included several series of observations on commercial , corrugated metal culvert pipes, The primary purpose of these large-scale tests was to obtain pipe friction and entrance loss coefficients which would be more accurate and dependable than those currently recommended in culvert design literature. A previous paper in this series gives a discussion of the comparison with the results of parallel studies on concrete culverts. The present paper is confined to a discussion of the corrugated pipe culvert test program and an analysis of the results of the studies.

Two types of corrugated metal culverts were tested, namely, the circular and the pipe arch types. In each case, threee different nominal diameter pipe sections were tested--18 in., 24 in., and 36 in., respectively--, making a total of six corrugated metal culverts in the test program. Each pipe was 193 ft long and laid on a slope of 0.20 per cent.

For the pipe arch culverts, the identifying dimensions refer to the diameters of circular pipes having the same length of periphery. For example, the 36-in. pipe arch and the 36-in. circular culvert have equal perimeters although their heights, widths, and areas are unequal. Cross sections of the various pipes, with controlling dimensions, appear in Fig. 1. (Note that the corrugation height in each case is 1/2 in. and that all computations have been based on the inside section, that is on the minimum cross-sectional area.)

Friction and entrance loss coefficients were established for the culverts under the usual conditions of field operation. With this objective in view, each pipe was tested for the following conditions: (a) Full flow with submerged inlet and outlet. (b) Part-full flow at uniform depth.

For each flow condition, several values of head and discharge were used. In addition, five of the culverts were tested with two different entrance conditions; namely, (a) Pipe projecting 2 ft into the headwater pool. (b) Pipe entrance flush with headwall.