Geogrid and burial depth effects on buried pipes near erosion voids under cyclic loading

This study examines the system performance of buried HDPE pipes near erosion voids under incrementally increasing cyclic loading, evaluating the effects of geogrid reinforcement and burial depth. Eleven large-scale tests were carried out using a fully instrumented testing rig with pipes buried at 1.5D, 2.0D, and 2.5D. Voids were created at one side of the pipe springlines and layers of geogrid reinforcement were placed in the backfill. Results indicated that the existence of voids near the buried pipes compromised the system stability. Inclusion of one and two layers of geogrid reinforcement effectively reduced footing settlement by up to 40% and 53.1% respectively, for a pipe burial depth of 2D. Furthermore, geogrid reinforcement remarkably decreased both crown and springline strains and deformations. However, the deformation and strains measured at the springline adjacent to the voids remained higher than those experienced at the other side. Increasing the pipe burial depth allowed the system to withstand additional loading cycles without reaching the failure thresholds. The enhanced performance can be attributed to improved redistribution of the stresses around the buried pipes adjacent to the erosion voids. The findings demonstrated that optimising pipe burial depth and geogrid reinforcement is essential to significantly improve the resilience of buried flexible pipe systems.