Numerical Modeling of Buried PVC Pipes Subjected to Sinkholes

Sinkholes pose a significant threat to buried pipelines, necessitating an in-depth investigation of the factors influencing pipeline behavior under such conditions. This study employs Midas GTX NX software to develop 81 numerical models, analyzing key parameters including the length and width of the sinkhole area, pipe burial depth, and surcharge effects. The study evaluates their impact on the stress ratio at the pipe crown, vertical relative deflection, pipe crown deflection, settlement of the ground surface center, and soil arching in the crown of the midsection of the pipe. Findings indicate that increasing the burial depth (from H/D=1 to H/D=3) of the pipe reduces the stress ratio at the crown (by up to 32%), the soil arching ratio (by up to 33%), and vertical relative deflection (by up to 53%). Notably, when the relative burial depth (H/D) exceeds 2, the deflection decreases significantly, mitigating sinkhole impacts on the pipeline. Conversely, according to the results of this study, increasing the sinkhole width from 50 mm to 150 mm led to a larger unsupported area beneath the pipe, tripling the pipe’s relative vertical deflection and stress ratio at the crown. Initially, vertical deflection at the pipe’s bottom is greater than at its crown; however, as the sinkhole width expands from 50 mm to 150 mm, crown deflection surpasses bottom deflection. Increasing the sinkhole length from 250 mm to 350 mm reduces vertical relative deflection (by up to 20%) and arching ratio (by up to 30%) while slightly increasing soil surface settlement (by up to 23%). In addition, a fourfold increase in the sinkhole area results in a more than 2.5-fold expansion of the affected surface area. Flexible pipes exacerbate surface settlement, and sinkhole-induced deformation may disrupt gravity-fed fluid transfer systems. The results suggest that increasing pipe burial depth can mitigate sinkhole risks, while sinkhole width exerts a more significant influence than length.