A statement on the stress field of pipe-soil structure

In this study, stress analyses of buried flexible pipes were carried out using a newly designed experimental setup for the method of photoelasticity. Several universal tests using a Dynamical Mechanical Analyzer and the parallel plate test in a polariscope were performed to obtain the mechanical and optical properties of a ring that is made from a thin plate of optically sensitive Araldite, which modeled the pipe cross section. Additionally, the mechanical properties of soil used in the experiment have been determined by unconsolidated-undrained triaxial compression tests and specifically developed photoelastic tests. This test method, which provided satisfactory results for estimating the coefficient of lateral earth pressure, can be used as a fast method to obtain this coefficient for general cases. From the buried ring experiment, the distributions of the circumferential stresses along the inner surface and the absolute value of the Tresca stresses along the outer surface of the ring were calculated by some precise photoelastic measurements. Comparing the results with those from the parallel plate test, the lack of design criteria were clarified. The buried ring experiment clarified that the pipe-soil structure keeps the field of elastic stress-strain that is due to a loading until a higher load is applied. The distributions of stresses were compared to those obtained from the finite element analysis of a half ring under the loads determined by Michell’s formulation.