The design of a laboratory facility for evaluating the structural response of small-diameter buried pipes

The design of a new laboratory facility for evaluating the structural response of small-diameter buried pipes (e.g., leachate collection pipes in landfills) is presented. The pipe is tested within a 2.0 m wide, 2.0 m long, and 1.6 m high prism of soil, subject to large vertical pressures (1000 kPa), with only minimal roughness and deflection of the lateral boundaries. Results from finite element analyses are presented to examine the effect of proximity, roughness, and stiffness of the lateral boundary on the soil and pipe response and how reasonable the laboratory idealizations are relative to the deep burial conditions expected to prevail in the field. Shear stresses arising from the roughness of the lateral boundaries alter the stresses acting around the pipe and reduce the proportion of the applied surcharge reaching the pipe. Outward deflection of the lateral boundaries also alters the stress state around the pipe, predominantly resulting from decreases in horizontal stresses within the soil. Reducing boundary friction to less than 5° and limiting the boundary deformation to less than 1 mm at a vertical surcharge of 1000 kPa provide a good idealization of field conditions for a deeply buried pipe.