Experimental Investigation of Pipe Soil Friction Coefficients for Direct Buried PVC Pipes

Abstract

Soil friction is an important design factor for restrained buried pipes with internal pressure. Utilizing the bedding soil for thrust restraint eliminates the need for thrust blocks and makes pipe installation simpler. A full scale experimental investigation of soil-pipe friction coefficients was performed for an innovative, direct buried, restrained, PVC pipe under controlled laboratory conditions. The experimental work covered a wide range of soil types, over burden pressures and moisture contents. Measurements included force needed to overcome friction between pipe and its surrounding bedding, total pipe movement along its longitudinal axis, rigid body movement, and elongation of pipe under applied axial force. Based on the experimental data, three approaches are proposed for calculating the friction force of a buried restrained PVC pipe installed using the cut-and-cover method. The values reported in this paper are considered conservative and higher friction coefficient values can be anticipated over time due to consolidation and aging of the bedding soil around the pipe.