Experimental and Numerical Investigation of Void-Induced Load Transfer in Buried Flexible PE Pipes

Localized voids between buried pipes and the surrounding soil, often caused by erosion or leakage, can weaken flexible thermoplastic pipelines by interrupting load-transfer paths and reducing soil confinement. This study investigates how void width and void location affect stress redistribution in a DN400 PE100 pipe. A series of soil-box tests was conducted for a reference case with full pipe–soil contact and for voided cases with localized arc-shaped voids at the invert and springline. The experimental program considered void widths of 100 and 200 mm. A two-dimensional finite-element model developed in ABAQUS version 2025 was validated against the experimental results and then used to extend the analysis to void widths of 50–200 mm and additional void locations, including the crown. The results show that invert voids produce a pronounced load-transfer effect: contact pressure at the voided invert decreases sharply, while stresses in the adjacent soil increase accordingly. By contrast, springline voids mainly reduce lateral confinement on the voided side and promote lateral bulging, leading to greater overall pipe displacement than invert voids. The circumferential strain response exhibits a threshold-type transition with increasing void width, beyond which the affected region expands markedly along the pipe perimeter and additional critical zones develop. Void enlargement also alters the location of stress concentration, indicating a redistribution of structural demand within the pipe–soil system. Comparison with an existing analytical formulation for additional invert load shows good agreement with the numerical results. Within the studied configurations, the influence of void location on structural response follows the order invert > springline > crown. These findings provide a mechanistic basis for defect assessment and targeted rehabilitation of buried municipal polyethylene (PE) pipelines.