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In this paper, a homogenized multiphase lattice Boltzmann (LB) model is established for parallelly simulating immiscible two-phase flow in both solid-free regions (pore scale) and porous areas (continuum scale). It combines the color-gradient multiphase model with the Darcy–Brinkman–Stokes method by adding a term that includes surface force and drag force of porous matrix to multiple-relaxation-time LB equation in moment space. Moreover, an improved algorithm is proposed to characterize and implement the apparent wettability in the locally homogenized porosity field. Validations and test cases are given to demonstrate the accuracy and robustness of this new model, as well as its applicability for trans-scale fluid simulation of transport and sorption behavior from porous (Darcy flow) area to free (Stokes flow) area. For practicality, the two-phase seepage flow in a composite rock structure with multiscale pores is simulated by this new model, and the effects of viscosity ratio and wettability on the displacement process are discussed. [ABSTRACT FROM AUTHOR]

This study investigates the challenge of borehole instability in shale gas development, focusing on the interactions among temperature, fluid flow, and stress. Using a thermal-hydro-mechanical coupling model of borehole elastic stress combined with a true triaxial rock strength criterion and tensile failure criterion, the research systematically examines the effects of different models on borehole stability in shale formations. The findings reveal that while temperature has a relatively minor impact on the stress distribution and failure zones around boreholes, bottom hole pressure plays a critical role in influencing both the extent of unstable regions and the modes of rock failure. Under varying inclination angles, the unstable zones and failure patterns generally remain consistent, with higher stability observed when drilling aligns with the direction of minimum horizontal stress. Moreover, the study highlights the significance of appropriate drilling fluid density in maintaining borehole stability. Specifically, when the bottom hole pressure ranges from 50.66 to 70.66 MPa, the tensile and shear instability areas are minimized within seven days of contact with the drilling fluid. The research underscores the importance of optimizing drilling fluid density, carefully managing bottom hole pressure, and selecting proper borehole trajectories to enhance stability during shale gas drilling. These findings provide both theoretical insights and practical guidance, contributing to the optimization of shale gas drilling engineering practices. [ABSTRACT FROM AUTHOR]

The article published in the Journal of Earth Science in February 2025 explores how the shape of notches and boundary conditions impact the hydro-mechanical behavior of fractured geomaterials. The study uses the Darcy-Brinkman-Biot approach to analyze the effects of different notch shapes on hydraulic fracturing and surface uplift. Findings suggest that notch shape influences cracking behavior, with multi-corner notches creating multiple fractures, while single-corner notches initiate cracks at corners. The study also investigates the hydro-mechanical response of fractured geomaterials under varying boundary conditions, showing that velocity boundary conditions generate higher pressure at the notch, leading to increased water infiltration and solid deformation. The research provides insights for addressing complex engineering challenges and enhancing engineering resilience and efficiency. [Extracted from the article]

Most of the studies in the literature focus on analyzing water flow within earthen dam under static condition. The objective of this study is to analyze water flow mechanisms within earthen dam under seismic condition. To achieve this purpose, a series of numerical simulations were conducted to model earthen embankment based on a real case scenario based on dam built in eastern province of India (i.e., South 24 Parganas in West Bengal). Further the effect of sheet pile as a seepage cutoff has been evaluated with variations in sheet pile length and location under steady-state settings for both static and seismic conditions. The study was carried out using FLAC2D version 5.0 and SEEP/W version 12.0 for a dam. The results show that pore pressure is high on the upstream side of the sheet pile during continuous seepage and quickly decreases along the sheet pile itself for all sheet pile positions. In seismic instances under steady-state conditions, when pore water pressure increases, the factor of safety decreases by 45% to 50% as compared to similar static cases. This is due to an increase in seepage force. As the sheet pile is cut off, the overall factor of safety increases as compared to the condition with no sheet pile. This study is though simplified; however, it provides insights into water flow pattern within earthen dam that need to be considered for preliminary design in regions, which are subjected to seismic loads. [ABSTRACT FROM AUTHOR]

Coal seam water injection is widely used to reduce dust pollution and mitigate rock burst disasters. Evaluating its effectiveness depends on understanding the water content and distribution within the coal seams. Therefore, understanding the water content and its distribution after injection is crucial for optimizing the injection param. A theoretical model based on hydromechanical interaction and seepage theory was developed to analyze changes in injection pressure, permeability, and water content. Numerical simulation was used to analyze the wetting radius and seepage rates under different injection pressures and axial stresses. The results showed that the effective wetting radius increased with higher injection pressure, which improved the penetration range and effectiveness of water injection. At 4 MPa pore water pressure, the wetting front was 6 m from the borehole and increased to 10 m at 25 MPa. The seepage velocity within the coal seam also increased with higher injection pressures, reaching a maximum of more than 23.75 m/s at 25 MPa, which was about 4.9 times higher than the 4.85 m/s observed at 4 MPa. The application of various axial stresses gradually increased the internal porosity of the coal, which extended the influence of water pressure and improved the effectiveness of water injection. As a result, the moisture content of the coal increased significantly. At 30 MPa axial stress, the wetting range increased by 20% compared to 10 MPa. These results have significant practical value for the design and implementation of coal seam water injection param under field conditions. [ABSTRACT FROM AUTHOR]

The construction of steel sheet pile cofferdams is a systematic project. Simplified construction sequences are widely used to facilitate the numerical modeling of cofferdams, while the mechanical behaviors of cofferdams with different construction sequences have yet to be understood. In the present study, finite element models of steel sheet pile cofferdams with different construction sequences were established, based on the temporary cofferdam of the Shenzhen–Zhongshan Link. The mechanisms of simplified construction sequences on bending moment were revealed by analyzing the displacements and contact press of steel sheet piles. The distribution of bending moment with elevation demonstrates the importance of the layered backfill process in numerical modeling. In addition, a finite element model of the cofferdam considering steady-state seepage was also established. The comparison of the hydrostatic pressure results and the bending moment results obtained by engineering experience and seepage analysis were discussed. The analysis results showed that the empirical method overestimated the maximum bending moment of the inner side of piles, which led to a more conservative design of the cofferdam. This work can serve as a reference for numerical modeling of steel sheet pile cofferdams and contribute to risk assessment in related engineering projects. [ABSTRACT FROM AUTHOR]

The current research focuses on integrating the impact of seepage into the tractive force method for sediment particles situated on porous riverbanks. A formula is developed using the tractive force approach to calculate the critical shear stress acting on sediment particles under steady seepage conditions. The study reveals that the hydraulic gradient influences the critical shear stress, which rises with higher hydraulic gradients. Additionally, application of the derived equation is demonstrated through a hypothetical channel design problem. [ABSTRACT FROM AUTHOR]

The pressure applied to the tunnel face during excavation plays a significant role in ensuring the tunnel face stability. The tunnel face collapses at lower pressure and blasts out at higher pressure. In the present study, tunnel face stability analysis has been carried out under dry and seepage conditions for both φ and c - φ soil. The effects of tunnel geometry, including the tunnel diameter (D = 5.0, 7.5, 10.0) and cover-to-diameter ratio (C/D = 0.5, 1.0, 2.0, 4.0)] as well as the shear strength parameters of soil [Cohesion (c) and angle of internal friction (φ)] have been studied. A linearly proportional relationship has been observed between the face pressure and the tunnel diameter (D). The face pressure has been found to increase linearly with the increase in the value of the (H/D) ratio, irrespective of the soil type. Based on the observation of the parametric study, mathematical models have been developed to compute the stability numbers in dry ( N γ and N c ) and seepage ( N γ ′ and N c ′ ) conditions as a function of the angle of internal friction (φ) of soil. Based on soil types and drainage conditions, appropriate solutions have been proposed to find the face pressure. The face pressure predicted by the present model has also been validated with the experimental studies of previous researchers. Hence, the developed numerical model may find potential application for the assessment of face pressure in φ and c - φ soil under both dry and seepage conditions. [ABSTRACT FROM AUTHOR]

This paper develops a finite element analysis model to investigate the seepage characteristics of cement sheaths, considering the flow properties of their porous medium. The model's applicability under various conditions was evaluated through grid sensitivity tests and model validation, indicating that it effectively captures the seepage behavior of cement sheaths with a reasonable degree of reliability. Key parameters, including cement sheath length, permeability, gap structure, pressure differential, and fluid properties, were analyzed using finite element methods to determine their impact on seepage flow. The findings reveal that crack width, permeability, and cement sheath length significantly influence seepage flow in both liquid and gas media. These insights enhance the understanding and prediction of cement sheath seepage characteristics under diverse conditions. [ABSTRACT FROM AUTHOR]

Accurate estimation of reservoir water level fluctuation (WLF) is crucial for effective dam operation and environmental management. In this study, seven machine learning (ML) models, including conventional, integrated swarm, and ensemble learning methods, were employed to estimate daily reservoir WLF. The models comprise multi-linear regression (MLR), shallow neural network (SNN), deep neural network (DNN), support vector regression (SVR) integrated with homonuclear molecules optimization (HMO) and particle swarm optimization (PSO) meta-heuristic algorithms, classification and regression tree (CART), and random forest (RF). These models were trained and evaluated using in situ data from three embankment dams in Algeria: the Kramis dam, the Bougous dam, and the Fontaine Gazelles dam. Performance evaluation was conducted using statistical indices, scatter plots, violin plots, and Taylor diagrams. The results revealed superior prediction accuracy for the Fontaine Gazelles dam compared to Kramis and Bougous dams. Particularly, the RF, DNN, and SVR-HMO models exhibited consistent and excellent predictive performance for WLF at the Fontaine Gazelles dam with RMSE values of 0.502 m, 0.536 m, and 0.57 m, respectively. The RF model demonstrates remarkable accuracy across all three case studies. This can be attributed to the ensemble structure of RF, as evidenced by the results. This study underscores the significance of considering factors such as seepage flow intensity in understanding WLF variability. Furthermore, the proposed ML models offer promising capabilities in WLF prediction, highlighting their potential utility in enhancing reservoir management practices and addressing the limitations of traditional regression models. Keys words. Embankment dam, Water level fluctuations, Seepage, Artificial neural network, meta-heuristic algorithm. [ABSTRACT FROM AUTHOR]

Seepage accelerates the weathering and destruction of cultural heritage sites, posing a major preservation challenge, while the concealed nature of seepage channels complicates their detection due to noninvasive requirements. In this study, we applied a comprehensive geophysical approach, integrating electrical resistivity tomography (ERT) and self-potential (SP) techniques, to image seepage channels within the Leitai heritage site. These potential seepage channels have already caused a collapse pit measuring 3.1 m × 2.7 m on the site's surface. We began with 2D ERT surveys, which were then combined for 3D inversion to reveal the resistivity structure of the site. Subsequently, SP data were extracted along typical survey lines using interpolation algorithms, and these were inverted to supplement and verify the resistivity structure. The results from both techniques were highly consistent, indicating the presence of internal channels within the site. This comprehensive geophysical approach provides critical insights and references for the subsequent restoration efforts of the Leitai heritage site, ensuring the protection and preservation of this culturally significant landmark. Moreover, the method proposed in this study can be easily applied to the preservation of similar cultural heritage sites elsewhere. [ABSTRACT FROM AUTHOR]

Choosing the reasonable and economical grouting parameters is crucial for controlling the seepage field of surrounding rock and tunnel stability. This paper adopted the fluid–solid coupling theory based on FLAC3D to establish numerous simulations on the stability of surrounding rock and lining structure in karst tunnels under the different grouting conditions. The influences of grouting layer thicknesses and their permeability coefficients on the mechanical behaviors of lining structure, seepage, and stress properties of surrounding rock were investigated. The results show that with the increase of grouting thickness and its ratio of permeability, the maximum flow velocity and flow rate per liner meter in surrounding rock, the bending moments and axial forces, and the horizontal and vertical displacements of the lining structure all exponentially decrease, but safety factors at different positions of the lining structure first rapidly and then slowly increase. The changes in safety factor and uplift displacement at the inverted arch are more significant, and the minimum safety factor occurs at the left arch foot. As the grouting thickness and its ratio of permeability increase, the plastic zone range in surrounding rock decreases and expands, respectively. Through considering the improvement effect and economy of grouting comprehensively, choosing a grouting layer thickness of 7–9 m and a ratio of permeability of 20–50 is an ideal configuration parameter to ensure the stability and safety of karst tunnels under the conditions of this paper. The research results could provide references for choosing the reasonable grouting parameters in karst tunnels. [ABSTRACT FROM AUTHOR]

The construction environment of subsea tunnels is highly complex. Revealing the influencing factors and governing laws of surrounding rock stability as well as ensuring the stability of the surrounding rock during the construction process is crucial for the safe construction of the tunnel. Based on the coupling of peridynamics (PD) with finite element method (FEM) and finite volume method (FVM), the PD-FEM coupling method describes solid deformation and damage, while FVM solves the fluid seepage field. Data exchange is performed through a transition layer to achieve efficient fluid–solid coupling calculations. Using the Shantou Bay Subsea Tunnel as the engineering background, an engineering-scale simulation of the subsea tunnel excavation process was conducted. The results were validated by comparison with COMSOL simulation results and field monitoring data. Furthermore, 15 additional simulations were conducted. Through comparing and analyzing the distribution characteristics of excavation damage zones, displacement fields, and seepage fields in the surrounding rock under various influencing factors, this study unveils the influence patterns of tunnel burial depth (in situ stress conditions), seawater depth (groundwater pressure), rock mass elastic modulus (surrounding rock properties), and tunnel excavation methods on the stability of surrounding rock in Shantou Bay Subsea Tunnel. This provides a scientific basis for predicting the stability of subsea tunnel surrounding rock and ensuring safe construction. [ABSTRACT FROM AUTHOR]

Coalbed gas production contributes to energy diversification and effectively mitigates the risk of mine gas outbursts. However, the complexity and nonlinear characteristics of multifield coupled gas migration in deep coal seams pose significant challenges that traditional prediction and control methods struggle to address. This paper explores the effects of coupled multi-physics fields on gas migration and reviews a numerical simulation method that integrates fractal theory with discrete fracture network modeling, aiming to overcome the limitations of conventional models in capturing the interactions among seepage, heat transfer, stress distribution, and gas adsorption/desorption. The study highlights the interactions between fractures and pores, as well as the coupling effects between fluids flow, heat transfer, and solid mechanics. It further presents a more accurate prediction method to enhance the simulation accuracy of gas migration in deep coal seams. [ABSTRACT FROM AUTHOR]

Fine particle migration is common in loose slopes with wide gradation characteristics under rainfall infiltration conditions. The seepage characteristics and stability of loose soil slopes are affected by the migration of fine particles along them. First, a flume model test was conducted to illustrate the migration law of fine particles under rainfall conditions. It was found that fine particles primarily migrated to two zones of the model slope (i.e., the shallow part of the slope and the toe of the slope) and most fine particles accumulated close to the slope toe. Second, the influence of fine particle migration on the seepage stability of loose soil slopes was also explored. The equation for the unsaturated permeability coefficient was then established considering the influence of fine particle migration. The present equation was further discussed by numerical simulations in contrast to the case where the fine particle migration was neglected. The results show that the fine particle migration along with rainfall infiltration has obvious influence on the seepage field, displacement field, and stability of the slope. [ABSTRACT FROM AUTHOR]

The soil’s creep characteristics significantly impact both the effectiveness of the support system and the enduring stability of the engineering structure. During construction, dewatering is often carried out, which results in seepage within highly permeable soils. To scrutinize the creep behavior of silty fine sand under seepage conditions, triaxial compression tests and triaxial creep tests were conducted on the silty fine sand, subject to three distinct seepage flow rates: 0.5 ml/min, 1.0 ml/min, and 1.5 ml/min. The test results indicate that seepage reduces the maximum stress capacity of the soil and increases its creep deformation. Particularly under relatively high deviatoric stress and seepage flow rates, the specimens exhibit three stages: transient creep, stationary creep, and acceleration creep. Notably, the axial creep deformation rate shows a positive correlation with both seepage flow rates and deviatoric stress. Concurrently influenced by seepage and creep, fine particles within the specimen accumulate in the central and upper regions, whereas the lower section is characterized by larger particles. The progressive increase in pore water pressure, intricately linked to the impeding effect of fine particles on permeation pathways, catalyzes the creep-induced deformation of the specimen. Based on the experimental results, a modified Burgers model has been established. This model takes into account seepage, sliding damage, and particle fragmentation. A comparative analysis, contrasting the modified Burgers model against calculated values derived from the traditional Burgers and Kelvin-Voigt models, underscores the effectiveness of the proposed model. Specifically, the modified Burgers model adeptly captures the transient creep, stationary creep, and acceleration creep stages of silty fine sand, especially under varying seepage flow rates.Highlights: Obtained the creep characteristics of fine silty sand under steady-state seepage. Proposed an improved Burgers model that takes into account the slip damage and particle migration of silty fine sand. Presented a unique micro-creep mechanism of silty fine sand under seepage conditions. [ABSTRACT FROM AUTHOR]

Levees and the beneath foundation ground sometimes cause consolidation settlements. When the consolidation estimation is underestimated in advance, the structures and residents are damaged by consolidation. In addition, levees are subjected to piping and boiling with heavy rainfalls, which often have coarse permeable layers. The seepage is concentrated through coarse permeable layers. Owing to the repetition of regular rainfall and the changes in water levels, internal erosion occurs between a permeable and a finer soil layer. This study aims to reveal the effect of internal erosion on consolidation. Clay, including granular soil, is used to simulate both internal erosion and consolidation. First, long-term seepage is imposed on a soil specimen with a coarse layer. Then, clayey soil samples are obtained from the specimen subjected to seepage, and a consolidation test is conducted. The soil properties related to consolidation are revealed in several experimental cases. A numerical analysis is conducted using the experimentally obtained parameters to simulate the consolidation for embankment construction. Finally, the influence of internal erosion on consolidation is discussed. The soil consolidation behavior is similar to that of the clayey material when the specimen is loosely compacted. However, the behavior of the dense material appears to be sandy; consolidation is rapidly completed. The loosening caused by internal erosion is dissipated, and the consolidation properties approach those of the soil sample with a similar initial compaction degree. Finally, a practical application method for the internal erosion effect is proposed. [ABSTRACT FROM AUTHOR]

Structural failure is one of the maximum essential reasons of collapse inside the embankment dams due to the float of water from the reservoir on the upstream of the dam via the dam segment closer to downstream. In order to keep away from or manage this phenomenon and treat it, we want to investigate the manner of float and calculate the amount of seepage water from the dam's frame via using one of the no longer unusual strategies known, which might be often long and hard and want precise gear. Two mathematical equations have been prepared to discover each the seepage discharge and the intensity of water emerging from the middle in zoned earth fill dams with a willing core without a doubt and quick. Statistical strategies have been used for a database produced by way of numerical approach (finite detail technique) for a fixed formed of two hundred fashions of zoned earth fill dams with two shapes of inclined middle (forward or backward). Observed models were prepared with dimensions and properties in accordance with the recommended safe boundary limits to ensure the safety of stability of slopes or sliding and scouring of the dam in the construction designs of this type of dams. These equations showed high performance in predicting both the seepage discharge amount and the depth of water emerging from the middle while tested and evaluating their consequences with different analysis methods effects with a correlation coefficient r2 equal to 97.3% and 89.5% for each of them, respectively. [ABSTRACT FROM AUTHOR]

In the process of deep mining, the dynamic disasters of coal and rock occur frequently under the action of high stress and high seepage pressure, the essence of which is energy-driven coal rock failure. In order to explore the energy evolution law and damage mechanism of sandstone with intermittent cracks under the coupling effect of stress and seepage, in this paper, by comparing the differences in mechanical characteristics between fractured rock and intact rock, the energy evolution characteristics, crack propagation, and micro-damage mechanism of fractured rock under different confining pressures and seepage pressures are analyzed. The research shows that: (1) The local stress drop phenomenon occurs in the fractured rock during the loading process, and the stress–strain shape is 'bimodal'. At the same time, there is stress concentration at both ends of the fracture. (2) The energy conversion of the fractured rock changes in stages during loading. As confining pressure rises, the energy storage limit and the maximum dissipation energy go up. The increase in seepage pressure reduces the energy storage limit, while the dissipation energy shows an upward trend. The energy consumption ratio curve shows 'concave' evolution during the loading process. (3) Based on the dissipation energy and residual stress, the damage state of the specimen is analyzed, and the proposed damage variable can reasonably explain the whole process of the damage evolution of intermittent fractured rock under stress and seepage. (4) The increase in confining pressure increases the friction between the particles inside the sample and promotes the transformation of the sample from tensile failure to shear failure. The seepage pressure reduces the friction between the particles in the sample through the air wedge effect to deepen the damage degree, thus promoting the tensile failure of the sample. [ABSTRACT FROM AUTHOR]

This study presents a comparative analysis of horizontal and pipe drains in earth dams, focusing on optimizing seepage control and stability. Using the Kreireche dam in Algeria as a case study, we employed GeoSlope software (SEEP/W and SLOPE/W) to conduct numerical simulations across 20 different scenarios, varying drain configurations and hydraulic conditions. Results indicate that pipe drains significantly outperform horizontal drains in managing seepage and enhancing dam stability. Pipe drains with larger diameters (2 m) reduced pore pressure by 15–20% compared to horizontal drains, demonstrating superior seepage control. Optimal drain placement within the range of X/B = 0.2 to 0.4 led to maximum safety factors, highlighting the importance of drain positioning. Statistical analysis using RMS, MAE, and MSE metrics showed that pipe drains consistently provided more reliable seepage and exit gradient control compared to horizontal drains. Increasing pipe drain diameter from 1 m to 2 m improved discharge seepage prediction consistency, reducing normalized RMS and MAE by 18.5% and 17.3%, respectively. Pipe drains exhibited 64.2% lower normalized RMS values for exit gradient predictions compared to horizontal drains, indicating more effective erosion risk mitigation. This study provides important insights for enhancing drainage system design in earth dams, resulting in increased stability and long-term performance of these crucial water management structures. [ABSTRACT FROM AUTHOR]

The establishment of a high-precision piezometric water level monitoring model ensures the safe operation of earth-rock dams. The hysteresis effect of the upstream water level and rainfall should be considered during modeling. In the traditional method, the average factors are used to express this effect, and linear regression modeling is adopted. These factors reduce the accuracy of the model. In this paper, the mutual information (MI) and support vector machine (SVM) algorithms are proposed. MI has a powerful correlation analysis capability, and it is innovatively used to address hysteresis effects. SVM has a strong nonlinear modeling ability, and it is used as a modeling algorithm. During this study, it was found that the lag time of rainfall varied. In view of this characteristic, the concept of an innovative model group, which is an important extension of the traditional single model, is proposed. In the example, the mean square error (MSE) is used as the precision index. Compared with the traditional single model established by linear regression, the MSE of the MI–SVM model group can be reduced by approximately 60.98%–68.75%. Compared with the model group established by linear regression, the MSE of the MI–SVM model group can be reduced by approximately 41.28%–45.45%. The new method effectively improves the accuracy of the model and can precisely monitor the seepage state of the dam. Moreover, it is beneficial for improving the level of dam safety management and can be extended to other fields involving hysteresis effects and nonlinear modeling. [ABSTRACT FROM AUTHOR]

In-channel water treatment systems remove excess nutrients through biological, chemical, and physical processes associated with the hyporheic zone. However, the impact of surface and groundwater interactions on these treatment processes is poorly understood. This research aims to assess the influence of varying groundwater conditions (neutral, drainage water, and groundwater seepage) and different bed sediment hydraulic conductivities on nitrogen and phosphorus dynamics in in-channel treatment systems. A flume containing bed sediment was used to study changes in surface water quality under different groundwater and bed sediment conditions. Compared to inlet and outlet concentrations, dissolved reactive phosphorus (DRP) and ammoniacal nitrogen (NH4-N) levels in the surface water increased by 11–65% and 10–51%, respectively, while nitrate (NO3-N) concentrations decreased by 11% under groundwater seepage conditions. The increase in NH4-N was due to ammonification, while the decrease in NO3-N was due to denitrification and mixing and dilution with the groundwater. The upward groundwater flux through the bed sediment transported both DRP and NH4-N into the surface water. Low hydraulic (LH) conductivity sediment led to greater changes in nutrient concentration than high hydraulic (HH) conductivity sediment (DRP increased by 65% and NH4-N by 51% for LH, compared to 11% and 10% for HH, respectively). However, HH conductivity sediment led to greater variations in pH and Eh values. The findings could assist the design and monitoring of in-channel treatment systems where groundwater and surface water interact. [ABSTRACT FROM AUTHOR]

Critical shear stress and erosion rate are two key factors for the prediction of the incipient motion of sediment and the transport of sediment. Seabed seepage can significantly alter the pore pressure gradient within the soil and the hydrodynamics around the surface of the seabed, further affecting erosion processes. Previous studies attempted to theoretically clarify the effect of the seepage force on sediment incipient motion. In this study, a newly designed erosion–seepage system (ESS) that considers the effect of seepage under steady or oscillatory flow is used to simulate the erosion process. Through the designed ESS, the erosion height per unit time was measured directly on the Yellow River sand, and the upward seepage force was applied at the bottom of the soil sample in the process. Then, the relationship between the erosion rate and seepage was established.The experimental results show that upward seepage reduces the critical shear stress of the sand bed and increases the erosion rate of the soils under both steady flow and oscillatory flow conditions. The erosion coefficients in the erosion models decrease with increasing seepage gradient. The effect of seepage on erosion is more obvious when the flow velocity of the steady stream is large, while the effect of seepage on erosion is relatively small under the oscillatory state with a shorter period. However, when violent erosion of soil samples occurs, seepage under both flow conditions greatly increases the erosion rate. [ABSTRACT FROM AUTHOR]

To study the meso-mechanical characteristics and energy dissipation mechanism of damage and failure of cemented backfill with cracks under seepage-stress coupling, the discrete element numerical test was used to explore the influence of axial stress, seepage water pressure and crack defects on the distribution of particle contact force chain and the development of microcracks in backfill, and the energy dissipation mechanism was expounded. The research shows that: ① With the increase of axial stress, and the particle contact force increases. The more elastic strain energy is released when the sample is destroyed, the greater the damage degree is, and the more cracks are developed. ② With the increase of seepage water pressure, the comparison of the strong and weak force chains is more and more obvious, the degree of stress concentration is intensified, and the cemented backfill specimen is more likely to yield failure. ③ The crack defects change the distribution law of the contact force chain inside the cemented backfill sample during the compression process. The contact force at the end of the crack is more concentrated, and the microcracks are generated, expanded and penetrated at the end of the crack. ④ With the increase of seepage water pressure, the boundary energy, bond energy and strain energy decrease gradually, and the energy absorption and storage capacity of cemented backfill samples decrease, while the friction energy shows an increasing trend. Compared with intact cemented backfill sample, the boundary energy, bond energy and strain energy of the cracked sample are reduced. The research results provide theoretical basis for the stability analysis and instability prediction of filling materials in deep water rich mines. [ABSTRACT FROM AUTHOR]

Eight-node quadrilateral isoparametric elements of the serendipity type have frequently been used in finite-element analyses of two-dimensional seepage problems. The shape functions for these elements are quadratic. Hence, nonlinear variation in the potential and stream function values across each element could be approximated to a high degree of accuracy. This also necessitates a commensurate high-order interpolation function to locate, in a straightforward way, equipotential lines and streamlines. In this paper, a quadratic interpolation algorithm for locating deformation contours is modified to suit flow net generation. The modification lies in the procedure for identifying the pairs of the points of intersection to be joined when there are four, six, or eight points of intersection of the contour segments of the same level and the edges of an element. The original algorithm finds the pairs of intersection points in a local coordinate system by testing all possible cases that may be encountered. The modified algorithm considers that in most, if not all, scenarios, equipotential lines and streamlines extend monotonically from one impervious boundary of the flow domain to another and from an inflow boundary to an outflow boundary, respectively. The intersection points are rapidly paired by converting their local coordinates to global coordinates and sorting the order of the intersection points according to their global coordinates. The modified algorithm eliminates the need for an exhaustive search and complex matching process, enhancing computational efficiency. The modified algorithm is verified against an exact analytical solution to the flow net for a levee under-seepage flow. Excellent agreement is obtained. Two additional illustrative examples are analyzed. One is unconfined seepage through a rectangular dam, and the other is confined seepage beneath unsymmetrical cofferdams. The equipotential lines and streamlines obtained from the modified algorithm are shown to be smoother and more accurate than those obtained using popular commercial software (GeoStudio 24.2.0), especially when a coarse finite-element mesh is adopted. [ABSTRACT FROM AUTHOR]

The permeability characteristics of tailings directly affect the position of the infiltration line of the tailings dam, which is the most critical factor affecting tailings dam failures. In order to fully analyze the essence of its permeability characteristics, computed tomography (CT) technology is used to analyze the structure of different types of tailings from a microscopic perspective and carry out microscopic seepage simulation. The results showed the following findings: (1) The porosity of viscous tailings ranges from 25 to 35%, the distribution of surface porosity along the height is relatively uniform, and the distribution is shown as having a certain discrete nature with the increase in particle size. (2) Compared with silty and sandy tailings, the surface of viscous tailings is smoother and more round, and the shape factor can reach 0.95; (3) The data gap between the simulation and the measurements by CT scanning technology is less than 10%, and the estimation of the permeability characteristics is feasible, with good applicability in the simulation of tailings seepage. (4) In the microscopic pore throat structure, the permeability characteristics of the tailings are more affected by the radius of the throat than the pore radius, and the exponential function relationship between the permeability coefficient and the porosity satisfies a high correlation. In this paper, the relationship between the microstructure and permeability characteristics of tailings is analyzed by CT technology; the permeability is simulated and calculated, and a permeability coefficient prediction model for tailings is proposed in combination with the experiment, which can provide a new idea and method for the study of the permeability characteristics of tailings. [ABSTRACT FROM AUTHOR]

Recent increases in rainfall duration and intensity due to climate change have heightened the importance of levee stability. However, previous studies on levee failure, primarily caused by seepage and overtopping, have mostly examined these causes independently owing to their distinct characteristics. In this study, we conducted lateral overtopping failure experiments under seepage conditions that closely resembled those in experiments conducted in previous studies. Seepage was monitored using water pressure sensors and a distributed optical fiber cable that provided continuous heat for temperature monitoring in the levee. Τhe analysis of levee failure due to lateral overtopping, in the presence of seepage, was conducted using image analysis with digitization techniques and machine learning-based color segmentation techniques on the protected lowland side of the levee, targeting the same area. The results revealed that levee failure occurred more than twice as fast in experiments where seepage conditions were considered compared to the experiments where they were not. Thus, levees weakened by seepage are more vulnerable to overtopping and breaching. Consequently, employing a comprehensive approach that integrates various monitoring and analysis methods for assessing levee stability is preferable to relying on a single method alone. [ABSTRACT FROM AUTHOR]

The deep in-situ environment is often characterized by high pore pressure, which will be released during traditional coring in deep rocks and lead to damage in rock samples. Hence, a novel coring technology has been proposed and systematically investigated for preserving in-situ conditions, including pore pressure, to obtain rock samples with high fidelity to the deep in-situ environment. To theoretically examine the variation in pore pressure after coring and evaluate its influence on rock samples, two kinds of mesoscopic model representing closed-pore and open-pore were established and analyzed by stressflow coupling, in which both seepage in porous matrix and flow in relatively bigger cavities are considered. An elastic-plastic-damage model associated with volumetric dilatation was introduced to reflect tensile damage. The influences of pore pressure after different kinds of coring were simulated by a series of conceptualized models, and the results revealed three kinds of situations: Pore pressure removal, pore pressure release, and pore pressure preservation. During traditional coring, the high pore pressure will neither be sealed completely nor released suddenly because the rock matrix has low permeability. The higher residual permeation pressure in the rock matrix will be caused by lower permeability, larger closed cavities or smaller open cavities. During traditional coring, the coring-induced inner damage arises nearby closed cavities. Both the damage value and the damage zone are increased with decreasing permeability. However, extra tensile damages rarely arise during in-situ pore pressure-preserved coring, which technology can also retain in-situ high pressure. Hence, the in-situ pore pressure-preserved coring technology has great significance for eliminating the distortion effect of coring to the greatest possible extent. [ABSTRACT FROM AUTHOR]

In order to explore the propagation mechanism of fracturing fractures in elastoplastic medium-deep formations, a fully coupled finite element model of seepage-stress in medium-deep formations was established by using the Moore-Coulomb plasticity criterion and the traction-separation law of cohesive units, and a series of numerical simulation studies were carried out on the strength of the temporary plugging agent, the length of the temporary plugging zone, the plastic parameters of the formation, the injection displacement and other influencing factors in the process of temporary plugging and fracturing, and the changes of each factor and the pressure and fracture width required to break through the temporary plugging zone were explored. The numerical simulation results show that with the increase of the length and strength of the temporary plugging zone, the pressure required for fracturing to break through the temporary plugging zone is also greater. Appropriately increasing the injection displacement is conducive to the formation of pressure holding and increasing the crack width. The results show that the lower the cohesion strength, the smaller the internal friction angle, the greater the plastic deformation, the higher the fracture propagation pressure, and the wider the crack width. [ABSTRACT FROM AUTHOR]

Vacuum preloading via prefabricated horizontal drains (PHDs) is an efficient technique to accelerate the consolidation of dredged soft soils. However, this technique lacks a clear and concise theoretical solution to the PHD vacuum consolidation analysis for slurry. To address this issue, this study proposes a novel analytical solution based on a mathematical logical procedure. The governing equations are first derived based on square PHD consolidation unit cells given the assumption of equal strain, taking into account various drainage conditions at the boundaries and the horizontal and vertical spacings of PHD. A seepage direction coefficient, directly determined through PHD spacing without additional identification, is further introduced into the derived formulation to enhance the solution to be more consistent with the results of free strain consolidation analysis. Then, the proposed analytical solution is validated based on three laboratory and field tests. The proposed solution is successfully applied to estimate the consolidation behavior at a site in Aomori Prefecture, Japan, involving PHD vacuum preloading. All results demonstrate that the proposed analytical solution is applicable for the design and management of PHD vacuum preloading construction projects and practically useful for engineers. Furthermore, the influences of the large strain effect, variable hydraulic conductivity, and variable compressibility on the consolidation analysis are discussed. [ABSTRACT FROM AUTHOR]

Fractures serve as the main pathways for the occurrence and transportation of gases within rock layers. Studying the seepage characteristics of fractured rock masses during loading and unloading processes is an essential issue for understanding the mechanism of hazardous gas migration in surrounding rock under tunnel excavation action. Experiments on rock mass seepage under different precast fracture angles and confining pressures during the loading and unloading process were conducted by using a multi-field coupled triaxial testing system. The findings of the tests indicate that the lateral stress, particularly during the unloading stage, induces the volumetric expansion of fracture. However, the influence of the fracture angle on rock mass fracture expansion is greater than that of the confining pressure. Moreover, the effect of the lateral stress on the fracture surface increases the permeability of the rock mass, nevertheless, the permeability decreases with increasing the confining pressure and decreasing the fracture angle. Under the same stress level value, during the loading stage, the permeability of the rock mass linearly decreases with increasing the confining pressure, while during the unloading stage, the permeability of the rock mass decreases nonlinearly with increasing the confining pressure. Based on the test results, a fluid–solid-damage coupling computational model for the fractured rock mass's permeability was established by considering the influence of the lateral stress on the fracture surface. In addition, further analysis related to the evolution process of the damage and the rock mass seepage has been done. The result reveals that the change in χ with increasing confining pressure exhibits logarithmic characteristics. As the fracture angle decreases, the respective variation ranges of χ are: 0.005~0.03, 016~0.17, 0.2~0.22. Highlights: The lateral stress causes volumetric expansion of fracture. The effect of lateral stress on fracture surface increases the permeability of rock mass. Proposed a calculation model for permeability of fractured rock considering the influence of lateral stress on the fracture surface. The change in χ with increasing confining pressure exhibits logarithmic characteristics. [ABSTRACT FROM AUTHOR]

After the anchor is installed, relative slip between the anchor and the surrounding rock will occur in the actual engineering. Based on the proposed nonlinear bond-slip model, a three-dimensional elastoplastic analysis of the strain-softened surrounding rock is performed in this study while considering hydraulic-mechanical coupling. A numerical iterative method of surrounding rock analysis is proposed, which considers the relative slip between the anchor and the surrounding rock. These stresses and displacements of the surrounding rock, as well as the anchor shear stress distribution, can be obtained using the proposed method. Furthermore, the calculation results of the program are compared with the existing field test results and with the calculation results of other methods to verify the accuracy of the proposed method. The results indicate that the calculation results of the proposed method are generally in line with the test results, and the largest slips occurring at the two ends of the anchors. Meanwhile, the proposed method is applied to an actual engineering, and the results agree well with the field data. Finally, the effects of seepage and strain softening of the surrounding rock on the interaction between the surrounding rock and the anchors are investigated by parametric analysis. [ABSTRACT FROM AUTHOR]

Two etching models, the spherical-rod standard pore channel and the pore structure, were used to conduct displacement experiments in the water-gas dispersion system to observe the morphological changes and movement characteristics of microbubbles. Additionally, numerical simulation methods were employed for quantitative analysis of experimental phenomena and oil displacement mechanisms. In the experiment, it was observed that microbubble clusters can disrupt the pressure equilibrium state of fluids within the transverse pores, and enhancing the overall fluid flow; bubbles exhibit a unique expansion-contraction vibration phenomenon during the flow process, which is unobservable in water flooding and gas flooding processes. Bubble vibration can accelerate the adsorption and expansion of oil droplets, and promote the emulsification of crude oil, thereby improving microscopic oil displacement efficiency. Combining experimental data with numerical simulation analysis of bubble vibration effects, it was found that microbubble vibrations exhibit characteristics of a sine function, and the energy release process follows an exponential decay pattern; compared to the gas drive front interface, microbubbles exhibit a significant "rigidity" characteristic; the energy released by microbubble vibrations alters the stability of the seepage flow field, resulting in significant changes to the flow lines; during the oil displacement process, the vast number of microbubbles can fully exert their vibrational effects, facilitating the migration of residual oil and validating the mechanism of the water-gas dispersion system enhancing microscopic oil displacement efficiency. [ABSTRACT FROM AUTHOR]

Considering the adsorption loss of the hydraulic fracturing assisted oil displacement (HFAD) agent in the matrix, a method is proposed to characterize the dynamic saturation adsorption capacity of the HFAD agent with pressure differential and permeability. Coupled with the viscosity-concentration relationship of the HFAD agent, a non-linear seepage model of HFAD was established, taking into account the adsorption effect of high pressure drops, and the influencing factors were analyzed. The findings indicate that the replenishment of formation energy associated with HFAD technology is predominantly influenced by matrix permeability, fracture length and the initial concentration of the HFAD agent. The effect of replenishment of formation energy is positively correlated with matrix permeability and fracture length, and negatively correlated with the initial concentration of the HFAD agent. The initial concentration and injection amount of the high-pressure HFAD agent can enhance the concentration of the HFAD agent in the matrix and improve the efficiency of oil washing. However, a longer fracture is not conducive to maintaining the high concentration of the HFAD agent in the matrix. Furthermore, the fracture length and pump displacement are the direct factors affecting the fluid flow velocity in the matrix subsequent to HFAD. These factors can be utilized to control the location of the displacement phase front, and thus affect the swept area of HFAD. A reasonable selection of the aforementioned parameters can effectively supplement the formation energy, expand the swept volume of the HFAD agent, improve the recovery efficiency of HFAD, and reduce the development cost. [ABSTRACT FROM AUTHOR]

Artificial Ground Freezing (AGF) is a promising method for controlling seepage in permeable strata. However, AGF faces challenges, including difficulties in achieving a frozen barrier in high-flow conditions and concerns about cost-effectiveness. This study optimizes freezing pipe placement in AGF using a simulated annealing algorithm and a coupled hydrothermal finite element model, focusing on AGF system responses under varying seepage velocities. The optimized layout significantly reduces freeze-ring formation time (by 2.5 days) and the overall freezing duration (by 12.5 days). Moreover, it substantially decreases the required frozen soil volume, facilitating drilling and excavation. Across different seepage velocities, the difference in freeze-ring formation time between the optimized and uniform layouts gradually increases with higher seepage velocity, reaching a maximum difference of 5.9 days. Finally, the relationship between freezing time and seepage velocity was quantitatively described using exponential functions. This study underscores the critical role of optimizing freezing pipe placement in AGF, providing a foundation for efficient and cost-effective geotechnical engineering practices. [ABSTRACT FROM AUTHOR]

The grout injection forms a compacted backfill in the separation chamber, and most of the grouting water seeps into the overburden pores. The initial saturation of overlying rock has been found to affect the seepage distribution of effluent in overlying rock. In the actual grouting process, the flow direction of grouting water in overlying rock and the initial saturation of overlying rock may affect whether the bled water will leak to the working face. In order to investigate the influence of initial saturation on the seepage law of isolated overburden grout injection, the present paper studies the saturation change process of bled water seepage at three different initial saturations (Sr = 29%, 51%, 73%). The water leakage of the working face was monitored with the self-developed 3D visual simulation experimental system, without considering the overlying rock of the injection layer. The results show that the bled water flows mainly in the horizontal direction, and the horizontal seepage velocity is about 10 times the vertical seepage velocity. The higher the initial saturation of the overburden, the larger the seepage range of the overburden, and the closer the seepage boundary is to the working face, the easier the bled water will leak into the working face. Therefore, the grouting design and process control can be carried out better. When the thickness of the selected isolation layer is insufficient, the bled water may appear on the working face, so this problem can be improved by increasing the thickness of the isolation layer. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)