Experimental and theoretical investigations of ground settlement around submerged defective pipelines

Subsurface settlement is often triggered by soil erosion above underground defective pipelines. However, there is currently insufficient research on calculation methods for estimating ground settlement caused by defective pipeline. In this work, a series of laboratory experiments were conducted to investigate the impacts of the soil particle size, hydraulic gradient, thick-span ratio, and full pipe flow velocity on ground settlement around submerged defective pipelines. A sensitivity analysis was performed to further examine these factors. The experimental results revealed that there are three settlement modes, primarily determined by soil skeleton particle size and the thick-span ratio. The full pipe flow velocity and hydraulic gradient significantly affected the settlement range, with the settlement range increasing as either the flow velocity or hydraulic gradient increased. Additionally, a new calculation model based on Manning’s equation was developed to predict soil settlement. The error between the calculation and experiment results was less than 15%, demonstrating the accuracy and effectiveness of the proposed method.