Twelve sections of culvert pipe were installed under soil cover ranging from 15 to 27 in. And trafficked with a single-tandem gear load cart. The average wheel load was 62, 875 lb on an average measured contact area of 777 sq in. In addition, several sections of reinforced concrete pipe (rcp) were subjected to laboratory load testing to determine actual three-edge bearing strengths. The field test specimens were corrugated steel pipe (csp) and rcp in 12-, 18-, and 24-in. Diameters. Surface rutting progressed to about 1 in. At the end of trafficking. Surface stiffness, as measured by falling weight deflectometer, showed that the backfill around the pipes was less stiff than the undisturbed areas of the test section between pipe trenches. The rcp was stiffer than the csp, except for the cracked rcp, which had a stiffness similar to the adjacent csp. Permanent deformations (set) in the pipes increased only gradually beyond 326 passes of the load cart, even though the static and dynamic deformations causedby both the stationary and moving load cart, respectively, continued to increase. On the basis of these test results, minimum cover requiremetns are presented. They represent minor deviations above and below typical published values for minimum pipe cover under similar loading conditions. This paper appears in transportation research record no. 1231, Analysis, design, and behavior of underground culverts.
Abstract