Evaluation of Statically-Loaded Large Diameter Steel Pipe Embedded with Lime Stabilized Native Clay Soils

Four static soil load tests on a large diameter steel pipe are in progress consecutively at the Center for Underground Infrastructure Research and Education (CUIRE) laboratory at UT Arlington. For all these tests, a steel pipe sample, 19.75-ft long and 73-in. in diameter, is placed inside a concrete load cell and embedded with native clay soils obtained from the Integrated Pipeline (IPL) project site in Texas. The property of native clay soils is the variable in these tests. Although native clay soils are imported from the same project location, variation in soil properties are achieved in this test by strengthening through stabilization by lime or cementitious materials such as cement and flyash planned for future tests. First two tests have been completed and currently preparation for the third test is in progress. Sharma et al. (2011) presented partial results of the first test carried out with untreated native clay soils as embedment. In the second test, lime stabilized native soil was used as bedding and embedment up to springline of the pipe. Untreated clayey backfill soil was placed above the springline and up to one foot above the crown of the pipe. Pea gravel was placed above untreated soil to simulate dead load of cover in actual project conditions. Vertical loads at crown and bottom of the pipe and horizontal loads at the springline of the pipe were recorded. Also, changes in vertical as well as horizontal diameters of the pipe were measured during and after installation of the pipe. This paper presents the complete results of the first test, describes the details of the second test as well as an analysis of the results. The main purpose of the lime stabilized test was to study behavior of the large diameter steel pipe under modified native backfill and calibrate the related Finite Element Model (FEM).