Study on the influence of water supply and drainage pipeline damage on urban silt ground collapse

Abstract

Underground drainage pipelines play crucial roles in urban construction and development. Over time, these pipelines may incur damage and leakage due to aging and changes in surrounding loads. Ruptures and leaks in pipelines can lead to water seepage through cracks, resulting in erosion of surrounding soil layers and the formation of underground cavities. The loss of support in the soil above these cavities can lead to structural instability and eventual ground collapse. Such collapses can disrupt urban transportation systems, leading to significant social and economic consequences. This study specifically investigates ground collapse phenomena resulting from damage to drainage pipelines in silty soil within the Yellow River flood area in Zhengzhou City. By considering the influence of seepage velocity at the damaged pipeline section, the study differentiates between seepage erosion and scour erosion, conducting theoretical analyses and calculations for each scenario. The results show that ① when the surrounding area of the pipeline is damaged and the slow seepage rate causes a change in the critical groundwater level ΔH ≥ (Lσt )/((1 – n)γw), the soil around the pipeline will be damaged by seep erosion; ② when the water flow velocity at the damaged area of the pipeline is reached V 0 = 2λ(γs – γw )a 2 B 2/(9μ(B 2 – b 2)), the water flow impacts the soil and causes erosion damage. The critical pressure within the pipeline can be derived from the stress state where the pipeline is damaged P 1 = ρ 2 [ 2 λ ( γ s − γ w ) a 2 B 2 / ( 9 μ ( B 2 − b 2 ) ) ] ; ③ the underground cavity formed by water flow erosion is assumed to be an “soil arch.” The stress analysis on it obtains the critical span of the “soil arch” when the “soil arch” is damaged 2b = [2c(H + h) + Kaγ(H + h)2 tan φ – P]/(H + h/3). This study provides a theoretical basis and technical support for the management of silty ground collapse in the Yellow River flood area.