Urban underground pipeline aging and leakage can result in soil erosion and ground collapse, constituting a major threat to urban public safety. To investigate this disaster mechanism, this present study established a two-dimensional numerical model based on the computational fluid dynamics–discrete element method (CFD–DEM) two-way fluid–solid coupling approach, simulating and reproducing the entire process from soil erosion, soil arch evolution to ground collapse caused by underground pipeline leakage in water-rich sand layers. The simulation shows that under the action of seepage pressures, soil particles are eroded and lost, forming a cavity above the pipeline defect. As soil continues to be lost, the disturbed zone expands toward the ground surface, causing ground settlement, and in water-rich sand layers, a funnel-shaped sinkhole is eventually formed. The ground collapse process is closely related to the groundwater level and the thickness of the overlying soil layer above the pipeline. Rising groundwater levels reduce the effective stress and shear strength of the soil, significantly exacerbating seepage erosion. Increasing the thickness of the overlying soil layer can enhance the confining pressure, improve soil compactness, and promote the formation of soil stress arch, thereby effectively slowing down the rate of ground collapse. This study reproduces the process of ground collapse numerically and reveals the mechanism of ground collapse induced by underground pipeline leakage in water-rich sand layers.

Multiscale responses of gap-graded soil under the combined effect of train vibration and seepage erosion

Abstract Leakage of tunnel can induce particle loss, leading to significant safety risks on ground collapse and continuous damage to tunnel structures. Although previous studies have addressed seepage-induced deformation, experimental methods have faced challenges in reproducing realistic stress conditions and capturing localized interactions. This study proposes a centrifuge modeling approach and its detailed testing procedure, to investigate seepage-induced particle migration and associated ground deformation under properly scaled stress conditions. Layered ground conditions from three representative tunnel sites were modeled, incorporating site-specific geotechnical and hydraulic properties. Test results revealed that seepage erosion significantly increased surface settlement above tunnel openings. Comparative analysis across the test cases and with numerical simulations confirmed that the proposed centrifuge modeling effectively captured complex soil-fluid interactions, including transient seepage, particle migration, and localized erosion near the tunnel opening, consistent with prior observations. Notably, the simultaneous monitoring of flow rate, surface settlement, and pore pressure enabled the quantitative identification of repeated formation and collapse of soil arches driven by soil–water leakage. These findings demonstrate that centrifuge modeling offers a practical and scalable experimental framework for evaluating seepage-induced deformation and provides valuable insights for assessing and mitigating tunnel leakage risks in layered ground conditions.

Abstract Mars' landscapes offer enigmatic clues about a once wetter climate. Particularly puzzling are hourglass landforms, distinguished by two small (10–100 s km2) branching ridge systems connected by a narrow neck. This geometry resembles a source‐to‐sink fluvial system, but occurs on relatively flat terrain without a clear drainage direction. Here, we characterize 13 hourglass landforms and branched ridge networks that occur near the crustal dichotomy boundary and compare them with flume experiments and terrestrial analogs. We find that hourglass landforms are composed of branching and sinuous fluvial ridges, indicating that they are ancient river deposits exposed in positive relief due to substantial differential erosion. Typically, one side of the hourglass is composed of a ridge network with larger and more distinct ridges (type 1), whereas the other network has smaller cross‐cutting ridges (type 2). In some cases, a remnant crater rim divides the two sides, with the type 1 network eroded into the crater wall, indicating a drainage network, and the type 2 network bounded by the crater, indicating an alluvial fan. Results indicate hourglass landforms are eroded remnants of small catchment‐fan drainage systems that have experienced major climate change. They formed following impact cratering in a wet climate by runoff or seepage erosion where the crater breached the groundwater table. Subsequent wind erosion in a dry climate created ridge networks and completely removed the antecedent catchment‐fan topography. Our findings on the distinction between different types of hourglass networks may help differentiate distributary from tributary networks in fluvial ridge systems elsewhere on Mars.

Fluvial, estuarine, and marine deposits record landscape development and relative sea-level (RSL) change since 15 Ma in the Pine Barrens region of the New Jersey Coastal Plain. Coastal deposits that aggraded to an elevation of +60 m record rising RSL from 20 Ma to 15 Ma, and sequentially inset fluvial plains and offlapped coastal sequences record RSL decline to −5 m at 5 Ma. Coastal deposits record RSL highstands in the Pliocene (+20 m) and middle and late Pleistocene (+20 m at marine isotope stage [MIS] 11 or 9, and +10 m at MIS 5e). Denudation after 15 Ma was accomplished by successive river incisions in response to RSL declines accompanied by widening of valleys by seepage erosion, producing terraces and pediments and theater-like valley heads. Denudation from the incision-seepage process can be quantified by reconstructing the topography of a 2400 km2 region at five time periods (11 Ma, 7 Ma, 2 Ma, 125 ka, and 15 ka) based on the extent of surficial deposits of those ages and then subtracting successive reconstructions. This method yields an overall denudation rate of 3.9 m/m.y. (3.1−5.5 m/m.y. uncertainty range), which resolves spatially (as 60 × 60 m grid cells) to a range of <1 m/m.y. on upland remnants of the oldest fluvial plain to 110 m/m.y. during MIS 2 in stream channels connected to the Hudson shelf valley. These rates are at the low end of those measured in areas of higher relief in the Appalachians, indicating that seepage erosion is an effective denudational agent in low-relief coastal plains.

Landslide dams are naturally formed dams with loose structures and poor stability. Whether and how landslide dams break after formation is directly affected by the upstream inflow conditions. In this study, different erosion patterns of landslide dam were achieved by controlling the water level through inflow conditions. Failure processes and characteristics of landslide dams with different erosion patterns were investigated by a series of physical model tests. The tested results showed that the failure process of landslide dam undergoing coupled erosion with seepage and overtopping included piping, slope erosion, settlement, breach evolution, large-scale scouring and formation of armor layer. With the increase in seepage duration before overtopping, the slope scouring and internal erosion were more serious. Headward erosion in coupled erosion occurred earlier and had a faster maximum erosion rate than that of rapid overtopping. When a landslide dam has been subjected to serious piping before overtopping, the peak discharge would increase, the emerging time of the flood peak would be early and the breaching duration would be short compared with that of rapid overtopping and failure triggered by seepage, respectively. The coupled erosion resulted in the smallest volume ratio of residual dam, the largest volume ratio of downstream alluvium and the longest transport distance. Failure processes and characteristic of landslide dams were influenced by seepage erosion that would alter the internal stress conditions and cause migration of fine particles to result in soil deformation. The results indicate that the coupled erosion is more harmful and is not conducive to risk assessment and timely rescue.

Simulation of landslide dam failure due to seepage erosion considering vertical soil particles distribution

Summary Driven by groundwater, defective pipelines can cause soil erosion and pose significant risks to the surrounding infrastructure. In this study, the evolution and collapse characteristics of formation stress caused by defective pipelines were considered not only under the constant groundwater level condition that previous studies have focused on but also under rainfall or flood scenarios (the groundwater level rises briefly and then quickly returns to its original height). This study developed a large-scale 3×2×2 m 3D physical model experimental setup to simulate the process of seepage erosion and collapse within the strata induced by groundwater. The results showed that groundwater seepage provided power for the migration of soil in the stratum, and the defects of pipelines offered migration space for the soil. When soil migration induced by groundwater into the defective pipeline caused the overlying strata to lose bearing capacity, surface subsidence occurred. Compared with the condition of constant groundwater level, the collapse volume under variable groundwater level decreased by 3.48%, but more irregular sinkholes appeared on the surface, which posed a greater threat to regional infrastructure and human activities. The increase in the height of the constant groundwater level not only prolonged the erosion process but also induced a larger erosion cavity and expanded the collapse volume. The increase in overburden thickness intensified the stress change in the stratum, resulting in a larger reduction in in-situ stress and enlarging the scale of erosion and collapse. This study uncovers the critical mechanisms by which rainfall and flooding trigger surface collapse around defective pipelines, offering valuable insights for pipeline design, maintenance, and risk assessment in the petroleum industry.

The seepage erosion of underground defective pipelines can negatively affect the structure and stability of the surrounding strata, leading to severe urban ground collapses. Revealing the failure mechanism and mechanical characteristic is crucial for their prevention and mitigation. A large-scale physical modeling experiment was carried out and a coupled Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) numerical model was proposed. The microscopic soil–water interactions during the seepage erosion process were researched, and the effects of groundwater, overlying strata thickness, defect size, and particle size were evaluated. Results showed that the groundwater seepage would promote soil movement, and the defective pipeline provided sufficient space. The seepage erosion rate increased with the flow velocity, and when it exceeded the threshold (Vmax), the disintegration of the strata occurred. The thickness of the overlying strata was positively correlated with the time when the cavity reached the surface, and it had little effect on the erosion rate before the defect was exposed. Defect size and particle size had minimal effect on the erosion area. The findings of the mechanistic analysis indicated that the effects of seepage erosion on the stress–strain characteristics occurs mainly during the cavity development stage.

To evaluate the seepage erosion during the installation of suction caissons, this study developed a seepage erosion-interface shear test system to simulate the erosion phenomena. First, a parametric analysis was conducted to systematically investigate the effects of main factors (consolidation pressure, particle size distribution, and inhomogeneous pressure) on sand erosion characterization, vertical deformation, seepage characterization, and the interface strength of suction caisson. Following this, interface shear tests were performed to compare and analyze the changes in caisson–sand interface strength before and after soil erosion. It is indicated that the soil erodibility initially increases and then decreases when increasing fine particles. Seepage channels form first at the bottom and become dominant near the caisson wall, enhancing the sand hydraulic conductivity. In addition, the soil inside the caisson is less stable under smaller consolidation pressure. After the erosion, changes in sand particle distributions significantly reduce the caisson–sand interface strength with the maximum reduction of approximately 50%. This study emphasizes the influence of seepage erosion on caisson in-service capacity, which needs more attention in practice.

Experimental and numerical investigation of seepage erosion in sandy cobbles under coupling hydraulic and dynamic load

From manual to UAV-based inspection: Efficient detection of levee seepage hazards driven by thermal infrared image and deep learning

The vast majority of geological disasters in loess-covered areas are caused by seepage erosion in loess. Therefore, this study focuses on the microscopic mechanism of loess seepage erosion and constructs a loess microstructure model based on particle “core + coat”. On this basis, the scanning electron microscope (SEM) photos are imported into COMSOL to simulate the micro-scale seepage in the pore domain. Through the actual permeability test, combined with the micro-quantitative information obtained by Image-Pro-Plus and Arcgis, the micro-factors affecting loess permeability are quantitatively analyzed by grey relational analysis. The results show that the dry density affects the porosity of loess and ultimately determines the permeability of loess. Different pore types and proportions lead to different seepage erosion of loess. The erosion process mainly occurs at the junction of pores. The sudden increase of velocity, pressure drop, and maximum shear rate at the throat indicate that this area is the main action area of loess seepage erosion. The research results of this study provide an important theoretical basis for the research and prevention of geological disasters and engineering diseases related to seepage deformation and failure in loess area.

Changes in the Stability of a Superhigh-Deposit Slope Considering the Influence of Seepage Erosion

Leakage from buried pipelines can lead to an increase in the water content of the subgrade soils and a rise in the water table, leading to soil loosening, erosion and ultimately the formation of hidden voids and roadway collapses. This study presents a discrete-element method and validates its accuracy by utilising cavity data from model experiments. It investigates the mechanism of seepage erosion resulting from pipe leakage and analyses the development of the soil arch effect. Furthermore, it discusses the influence of sand void ratio and particle size on sand seepage erosion. The results indicate that the erosion area is primarily affected by the void ratio and particle size. In comparison to soil particles ranging from 0.1 to 5 mm and from 2 to 5 mm, those with sizes between 0.1 mm and 2 mm generate areas of erosion and loosening that are approximately 40% larger. The proposed model offers a precise analysis of the developmental process and the extent of seepage erosion, thereby contributing to the prediction of potential road cavity areas based on dynamic changes in key factors such as subgrade soil type and groundwater level.

By using the principles of porous media seepage mechanics and solute transport theories, a seepage–erosion theory model was developed to uncover the dynamics of mud and water inrush in fault rupture zones during the construction of tunnels. This model consists of a mass conservation equation, a flow transformation equation, a porosity evolution equation, and a permeability evolution equation. These components illustrate the interaction between seepage–erosion particle loss and the transformation of seepage flow patterns throughout the mud and water inrush evolution in the fault fracture zone. This model proves to be effective in illustrating the catastrophic process of mud and water inrushes within tunnels located in fault rupture zones. To address the spatial and temporal variations, the implicit difference and Galerkin finite element schemes were utilized, and the Newton–Raphson iteration method was applied to handle the nonlinear attributes of the equations. The theoretical model underwent further development and numerical simulations were performed using COMSOL multi-field coupling software. A comparison with existing indoor water inrush mud model test results validated the effectiveness of our model. The theoretical model was then applied to the Yong Lian tunnel scenario within the fault rupture zone. This computational analysis exposed the sequence of flow pattern transformations and the instability in seepage–erosion evolution within the fault rupture zone, ultimately leading to the emergence of mud and water inrush disasters. The findings of this study offer valuable insights for addressing tunnel engineering challenges related to underwater inrush disasters.

Leakage in underground structures, especially tunnels, may cause seepage erosion in the surrounding soil, which in turn leads to ground subsidence, posing a great threat to urban safety. The current literature mainly focuses on seepage erosion in the sand but lacks a systematic study on the development process of seepage erosion induced by tunnel leakage in different strata. To investigate the different seepage erosion modes induced by tunnel leakage in different stratum types, a series of reduced-scale model tests were carried out. A coupled fluid–solid numerical model was further established to analyze the fine-scale characteristics of different seepage erosion modes. The results show that (1) the soil seepage erosion modes can be divided into three categories: no soil cave, unstable soil cave, and stable soil cave; (2) the adopted coupled fluid–solid numerical model based on DEM, which takes into account the degradation of clay during seepage erosion, can effectively simulate the erosion process of soil with different seepage erosion modes; (3) the phenomena of the three erosion modes are different in the process of erosion development; and (4) the micro-mechanisms of the three seepage erosion modes are different, which are manifested in the erosion range, soil arching effect, and displacement.

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 P1=ρ2[2λ(γs−γw)a2B2/(9μ(B2−b2))] ; 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.

Loess is widely distributed in Northwestern China and serves as the preferred engineering construction material for anti-fouling barriers. Heavy metal contamination in soil presents significant challenges to the engineering safety of vulnerable loess structures. Hence, there is an urgent need to investigate the impact of heavy metal ions on their percolation performance. In order to investigate the effectiveness of microbially induced carbonate precipitation (MICP) using Sporosarcina pasturii (CGMCC1.3687) bacteria in reducing internal seepage erosion, a saturated permeability test was conducted on reshaped loess under constant water head saturation conditions. The response of loess to deionized water (DW) and ZnCl2 solution seepages was analyzed by monitoring changes in cation concentration over time, measuring Zeta potential, and using scanning electron microscopy (SEM). The results indicate that the hydrolysis of Zn2+ creates an acidic environment, leading to the dissolution of carbonate minerals in the loess, which enhances its permeability. The adsorption of Zn2+ ions and the resulting diffusion double-layer (DDL) effect reduce the thickness of the diffusion layer and increase the number of free water channels. Additionally, the permeability of loess exposed to ZnCl2 solution seepage significantly increased by 554.5% compared to loess exposed to deionized water (DW) seepage. Following the seepage of ZnCl2 solutions, changes in micropore area ratio were observed, decreasing by 48.80%, while mesopore areas increased by 23.9%. MICP treatment helps reduce erosion and volume shrinkage in contaminated loess. Carbonate precipitation enhances the erosion resistance of contaminated loess by absorbing or coating fine particles and creating bridging connections with coarse particles. These research results offer new perspectives on enhancing the seepage properties of saturated loess in the presence of heavy metal erosion and the geochemical mechanisms involved.

With the increasing complexity of the three-dimensional cross-distribution system of pile foundations and tunnels in the urban underground space, the stability of the pile foundation caused by tunnel seepage erosion becomes more and more prominent. However, the current research mainly focuses on the mechanism of erosion induced by defective tunnels, and little on its interaction with the adjacent pile foundation. Thereby, based on the seepage erosion mechanism revealed by the physical model test, the erosioninduced stratum form is quantitatively characterized by establishing the critical fine particle content expression. Subsequently, a multi-zone eroded strata model is simulated by the random and quantitative removal of fine particles in the DEM domain, and then the erosion response characteristics of the foundation under different positions, loads, sinking methods and types are analyzed. The results show that the pile foundation has different degrees of subsidence under different erosion conditions, and tilts to the eroded area under the drive of unbalance force on its eroded position. After the erosion-induced reduction, the pile-tip resistance increases gradually with the subsidence, but the loss of lateral frictional resistance is basically unrecoverable. In addition, the changing mode of displacement and resistance of the pile is basically the same under different sinking methods and loads, only different in the changed amount. Compared with the single pile, pile group foundation has a better erosion resistance.