Concrete Bedding Effect on the Behavior of Buried Concrete Pipe: Experimental Investigation

Concrete pipes both reinforced and unreinforced still serve as efficient subsurface infrastructure, especially when used as culverts and sewer lines. In which its structural performance greatly affected by pipe-soil interaction through installation types. In this study the effect of concrete bedding on the behavior of buried unreinforced concrete pipe is investigated through full-scale experimental testing program which the concrete pipes are embedded in gravelly sand soil that is loose and dense. With thickness of 30 cm over pipe crown and subjected to different surface loadings. Seven standard 300 mm internal diameter precast unreinforced concrete pipes were evaluated in a lab soil box test facility. Two loading conditions are used, namely earth fill that simulated by a uniform loading platform, and wheel load that simulated using a patch loading platform with dimensions of $254\times 508{\mathrm{mm}}^2$ ($10\times 20{\mathrm{in.}}^2$), which is used by AASHTO to mimic the wheel load of an HS20 truck. The results demonstrated that controlled installation utilizing dense compaction granular backfill could achieve 70% of the pipe strength acquired by employing the typical concrete bedding of the indirect design approach. For concrete bedding under patch loads, the greatest bedding factor (ratio between the supporting strength of buried concrete pipe to the three-edge bearing test strength) obtained is 4.53. The failure loads of pipes with concrete bedding is greater than pipes with compacted soil bedding by 30% for uniform loading and 43% for patch loading.