Thin-Walled, Large-Diameter Steel Pipe Response to Various Embedment Conditions

Abstract

Five tests on large-diameter steel pipe were conducted at the Center for Underground Infrastructure Research and Education (CUIRE) laboratory at UT Arlington. The tests were conducted on a 19.75-ft.-long, 72-in. nominal diameter bare steel pipe with D/t of 230. For each test, the test pipe was placed inside a concrete load cell, embedded in compacted soils, and subjected to surcharge load of cover. The embedment soils included clayey soils obtained from the Integrated Pipeline (IPL) project site in Texas in both natural and lime-treated forms, crushed limestone and their combinations. Clayey soils were compacted by using tamping foot compactors, while crushed limestone was compacted using vibratory plate compactor. Peaking deflections or vertical elongations of steel pipe were observed in each of the tests during embedment construction. Static cover loads of pea gravel were placed over the embedded pipe. Pipe deflections and pipe wall strains were measured during and after placement of cover load construction using convergence meters and strain gages. Lateral earth pressures at pipe springline and load cell wall, and vertical loads at top and bottom of pipe were also measured. This paper presents and compares the results of the laboratory tests. The discussions and comparisons include deflection ratios (ratio of horizontal to vertical deflection), bedding angles, and moduli of soil reaction observed in each of the tests. Comparisons are also made with respect to assumptions in Spangler's soil pipe interaction model that was used to derive the Iowa Equation.