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The large deformation and strong rheological characteristics of the underground rock body under complex geological conditions have led to the failure of the support system and even the instability of tunnels from time to time. Based on the theory of groundwater seepage, the elastic solution of the mechanical model of the tunnel anchorage support system under seepage is solved, which reveals the influence of seepage on the peripheral rock and the support parameters of the anchorage support system; the viscoelastic solution is solved according to the corresponding principle of elasticity—viscoelasticity, which analyses the influence of seepage on the rheological process of the anchorage support system; and the model is simulated with the help of finite element software, which analyses the agreement and discrepancy of the numerical solution and the theoretical solution. The results show that the analytical and numerical solutions are basically consistent. This study can provide important guidance for controlling long-term stability of water-rich tunnel rocks. [ABSTRACT FROM AUTHOR]

In the process of development and utilization of mine resources, the damp-heat environment has always been a difficult problem for mining. An enormous amount of research effort has gone into analyzing the underground operating environment. By summarizing the existing research theories on the damp-heat environment in the mine, this paper analyzed the influence of the wall rock, wind flow parameters, groundwater seepage, and other factors on the damp-heat environment and summarizes the determination of heat transfer coefficient (h) and mass transfer coefficient (m), which provided the theoretical basis for the improved technology of the damp-heat environment of mines. The field synergy theory (FST) reveals the essence of enhancing heat transfer performance and mass transfer performance and has been widely applied in engineering practice; based on the commonality between the research model of the FST and the damp-heat environment of the mine, we put forward a novel approach by using the FST to study the mine's damp-heat problem and gave the research models based on the FST under the form of bifurcation and turning wall rock, which can be used to guide the design and layout of the mine wind flow deflector. Finally, considering the actual economic benefits of mine engineering, the FST and ventilation system power consumption are used as comprehensive evaluation indicators to guide the design of ventilation systems, which provided fresh concepts and approaches for improving the subterranean damp-heat environment. [ABSTRACT FROM AUTHOR]

The low permeability sandstone reservoir has poor development effect and serious gas channeling in the block W of Zhongyuan oilfield, Sinopec. In order to investigate the influence of rock surface roughness, pore distribution uniformity and homogeneity on porous media of the reservoir. Based on the theory of petro physics, fractal and seepage mechanics, laboratory experiments were carried out. Box dimensions of porous media were calculated by Frac Lab and Frac Lac software respectively, based on Gaussian distribution, Fourier analysis, power law and least square regression. The results show that the porous media of block W reservoir is of fractal characteristics, fractal dimension is about 2. 58, coarse porous media surface, complex pore structure, more micro pores, serious irregular heterogeneity and high flow resistance. The fractal dimensions obtained by Frac Lab and Frac Lac software have good consistency. The results provide strong basic support for enhancing oil recovery, oil and gas seepage law and porous transport properties, in a low permeability sandstone reservoir has excellent practical significance. [ABSTRACT FROM AUTHOR]

The early stages of particle‐scale filtration in idealised granular soils were investigated using coupled Computational Fluid Dynamics and Discrete Element Method. Filtration simulations were conducted for assemblies of finer base particles underlying coarser filter particles with upward seepage flow perpendicular to the base‐filter interface. A wide range of size ratios that covered the complete spectrum of filtration behaviours were considered, along with different ramping accelerations for seepage flow to investigate the combined influence of geometric characteristics and hydraulic loading. The influence of flow conditions and size ratios on the time‐dependent infiltration depth of transported base particles was observed to be universal with respect to a newly proposed dimensionless time parameter. The susceptibility to filtration during the early stages was quantitatively investigated with the number of infiltrating base particles and the filling degree of pores within the filter. The susceptibility during the early stages was shown to have a strong correlation with pore space geometry at the filter boundary, which was also reflected by the maximum pore filling degree of the filter. While filter susceptibility has been conventionally evaluated by the size ratio of the assembly, the consideration of the pore space geometry at the filter boundary provided an alternate approach of evaluating local filter susceptibility. [ABSTRACT FROM AUTHOR]

The occurrence of water inrush accidents in most mines is related to geological structures, especially faults. The influence of mining and confined water on floor fault activation and aquitard stability was analyzed theoretically using mechanical models to study the mechanism of water inrushes caused by mining above confined water under a fault structure. In addition, the stress distribution and seepage characteristics of the floor during mining were simulated and studied by COMSOL Multiphysics. We found that a fault is easier to activate when its dip angle is closer to 45° plus half of the fault's internal friction angle. Fault activation becomes more likely with decreased fault cohesion, friction angle, and minimal principal stress. The instability and failure of the key aquitard occur when: the maximum failure depth of the floor exceeds the distance to the aquitard, and the actual confined water pressure exceeds the critical water inrush pressure. A water inrush point occurred at the floor of the working face 35 m from the fault during mining, where the peak seepage velocity reached 0.22 m/s. The seepage velocity within the fault positively correlated with the initial confined water pressure. This study provides a criterion for fault activation and aquitard failure and improves our ability to predict fault-induced mine water inrushes. [ABSTRACT FROM AUTHOR]

Sediment incipient motion is the first step in sediment resuspension. Previous studies ignored the effect of seepage flow on the mobility of sediment particles and simplified the seabed surface as a rigid boundary. A flume experiment was designed to innovatively divide the seabed into two parts to control the dynamic response of the seabed and control the seepage conditions. In the experiment, the seabed sediments and the amplitude of internal solitary waves (ISWs) were changed to compare and analyze the impact of seepage flow on the sediment resuspension by shoaling ISWs. Moreover, parametric research and verification were carried out. Results indicate that seepage flow can greatly influence fine sand, promote sediment resuspension, and increase the amount of suspension by two times on average. However, seepage flow had a little effect on the suspension of clayey silt and sandy silt. Besides, seepage force was added to the traditional gravity, drag force, and uplift force, and the parameterization of threshold starting shear stress of coarse-grained sediments was developed. The results of this parameterization were verified, and seepage force was critical to parameterization. The threshold starting shear stress was reduced by 54.6% after increasing the seepage force. The physical mechanism of this process corresponded to the vertical reciprocating transient seepage in and out the seabed interface caused by the wave-induced transient excess pore water pressure. This quantitative study on seepage flow for shear stress of coarse-grained sediments induced by ISWs is critical to geohazard assessment. [ABSTRACT FROM AUTHOR]

Tidal channels migrate frequently under the combined actions of coastal dynamics and bank collapse, significantly affecting the stability of tidal network systems. However, existing studies mainly focus on in-channel flow erosion during flood tides, while less efforts are devoted to bank retreat driven by seepage erosion during the ebb tides. It is thus urgent to understand the underlying mechanism of bank collapse that driven by seepage. This study investigates the impact of seepage head height on bank collapse through physical experiments, including bank collapse modes, bank line variations and bank retreat rate. Results show that the process of bank collapse is related to seepage head height. We observe a transition of bank collapse mode from cantilever failure to tension failure, with increased seepage head height. A positive correlation between bank retreat rate and seepage head height is found. Overall, this research reveals the mechanism of bank collapse driven by seepage, and explains the distinct failure process of bank collapse over ebb tides, which is of great significance to the study of tidal channel evolution. [ABSTRACT FROM AUTHOR]

This paper focuses on the influence of permeability anisotropy of seepage flow on the face stability for a shied tunnel. An analytical model has been proposed to present the hydraulic head distribution around the tunnel face in the anisotropic ground, considering the difference of permeability coefficient in the horizontal direction and the vertical direction. The rationality of the proposed model is verified by a series of numerical simulations. Then, an analytical model of face stability for a tunnel under the anisotropic seepage has been established based on the limit analysis upper bound method. Comparisons of the analytical solutions and the numerical simulations are conducted, and the limit support pressure of the two methods is consistent. The effect of permeability anisotropy and water pressure on the stability of the tunnel face is analyzed through the three-dimensional analytical solution. Anisotropy of permeability has a significant impact on the stability of the tunnel face, and its impact gradually decreases. It can also be found that the water pressure coefficient of the tunnel face has a significant effect on the limit support pressure and the failure area when the ratio of the horizontal permeability to the vertical permeability is large. [ABSTRACT FROM AUTHOR]

• Governing equations for thermal-hydro-salt-mechanical (THSM) coupling model are presented. • The THSM coupling model is used to analyze the artificial freezing process in the sand-marine clay layers under seepage flow conditions. • The average degree of artificial freezing at a given time is proposed to qualitatively analyze the effects of the artificial freezing. In this paper, the general governing equations for thermal-hydro-salt-mechanical (THSM) coupling consider the effects of adsorption salt on the surface of soil particles, the mushy zone at the phase-change interface, molecular diffusion and crystal growth, the compressibility of liquid and solid matrices, nonlinear high-salinity groundwater, non-convective flux and thermal permeability. The THSM coupling is used to analyze the artificial freezing process around freeze pipe installed in the sand-marine clay layers under seepage flow conditions. The good agreement between the calculations of the theoretical model and experiment models in the literature. Parametric studies were conducted to investigate the effects of seepage velocity and freeze pipe installation patterns on the effectiveness of artificial freezing which was evaluated using a new definition called the degree of artificial freezing. The average degree of artificial freezing DF at a given time is proposed to qualitatively analyze the effects of the artificial freezing. The lower the flow velocities of groundwater and the spacing of the freeze pipes, the more quickly the formation of the freeze curtain reaches DF =100 %. The freeze curtain with DF =100 % can be earlier formed in the sand layer with freeze pipes installed in rectangular pattern than those installed in triangular pattern. [ABSTRACT FROM AUTHOR]

In open channel flow, the velocity distribution is required to analyze the flow parameters such as discharge, energy and momentum correction factors, and scour depth. Though the existing technique can simulate the velocity distribution practically sound, the hypothesis on the cumulative distribution function of velocity is difficult to track and restricted by several factors that it holds. The paper aims to extend the entropy-based 1-D velocity distribution to rectangular seepage channels, considering the cumulative distribution function based on channel geometry. The present work developed a Tsallis and Shannon entropy-based model for proposing 1-D velocity distributions in seepage-affected alluvial channels. The velocity distributions were evaluated with laboratory observations and were compared with Shannon and Tsallis entropy-based velocity distributions equation. The Shannon and Tsallis entropy-based 1D velocity distributions agreed with experimental data satisfactorily and compared well. However, based on the regression analysis, Tsallis-based velocity distribution performed better than the Shannon-based entropy model. [ABSTRACT FROM AUTHOR]

This paper presents a unified semi-analytical solution to investigate the passive earth resistance of unsaturated soils retained by a rigid wall in the framework of limit-equilibrium approach based on a rotational log-spiral failure mechanism. Coupled influences of unit weight and suction stress changes in unsaturated soils under different steady vertical flow conditions have been considered to provide a more realistic solution. The impact of different parameters such as effective internal friction angle soil, inclination of backfill surface and wall back face, surcharge pressure, height of wall, location of water table, and soil–wall interface friction has been explored by performing a parametric study. It has been found that the changes in the suction stress and unit weight of unsaturated soils under different input parameters have a greater effect on modifying the critical slip surface, and magnitude and point of application of passive earth resistance on the retaining walls. The results obtained from the present study compare reasonably well with the solutions in the literature. [ABSTRACT FROM AUTHOR]

The permeability prediction for fractured rock mass is the basis for analyzing permeability problems such as oil and gas exploitation, pollutant migration, and so on. In this paper, the in-house sub-element program was used to solve the steady-state Navier-Stokes equation for incompressible viscous flow. The periodic boundary conditions (PBC) were introduced to eliminate the error induced by choosing only a small section of fracture and ignoring the extension length of fracture in the previous numerical simulation. This method was applied to explore the effects of joint roughness coefficient (JRC), fracture width and mutual dislocation of two surfaces of fracture on permeability. The results show that the influence of JRC value on permeability decreases as the fracture width grows; the permeability of fractures cannot be accurately evaluated by using JRC values only. [ABSTRACT FROM AUTHOR]

To evaluate hydraulic head distribution in front of a shield tunnel in a saturated soil layer, theoretical analysis and numerical simulations are carried out in this study. Based on the partial differential equilibrium equation of seepage flow, a three-dimensional (3D) theoretical analytical model of the shield tunnel face and the seepage field in front of it is established using the eigenfunction and the Fourier series expansion methods, and the hydraulic head calculation formula is derived. Combined with engineering cases, the theoretical analysis results and the 3D numerical simulation results are compared and analyzed. The effect of the water pressure of the tunnel face on the hydraulic head distribution is also analyzed. The results of the proposed analytical solution are in agreement with those of the numerical simulation solutions; moreover, the proposed analytical solution requires less time to calculate the seepage hydraulic head than the numerical simulation. The ratio of the initial water table to the diameter (D) of tunnel face has a more significant impact on the hydraulic head distribution at a position 0.5D above the tunnel vault. When the water pressure on the tunnel face is not considered, the values of the hydraulic head are significantly underestimated. [ABSTRACT FROM AUTHOR]

• A stabilised SPH model in the u-w-p formulation for internal erosion is proposed. • A modified constitutive model is formulated for the erodible soils. • Extensions of a boundary treatment are proposed for the erosion-transport process. • A novel artificial damping term is established to mitigate numerical instabilities. • Groundwater flow, erosion-transport-deposition, and soil deformation are modelled. This paper presents a stabilised multi-phase smoothed particle hydrodynamics (SPH) model applicable to seepage-induced internal erosion and the resulting deformation in soils. Based on the continuum mixture theory, a new single-layer SPH model in the u - w - p formulation is derived for the mathematical description of the erodible porous material. A new modified constitutive model is formulated to account for the influence of erosion on the mechanical behaviour of soils. Extensions of a first-order consistent boundary condition as well as the diffusion algorithm for hydro-mechanical coupling in SPH are also proposed to accommodate the analysis of erosion-transport process. A novel viscous dissipation term is designed to mitigate the numerical instability commonly encountered in coupled problems. In contrast to existing stabilisation terms in the SPH literature, which operate on both the bulk component and shear component, this new stabilisation term offers the possibility to increase the dissipation of unphysical oscillation due to the shear deformation. The proposed method is validated through a series of benchmark tests. The results demonstrate the effectiveness of the proposed approach in addressing the coupled problem in porous materials involving multi-phase flow, phase interaction/transfer, and large deformation with enhanced accuracy, stability, and robustness. [ABSTRACT FROM AUTHOR]

Suction-induced seepage flow can significantly reduce the soil resistance during the installation of suction buckets, thereby ensuring their intended penetration depths and the designed in-service capacities. However, the lack of analytical models describing seepage flow behavior in the literature poses a significant challenge, primarily due to the complexity of seepage boundary conditions and the anisotropy and spatial variation of soil permeability. This paper addresses this gap by presenting a novel analytical solution for analyzing suction-induced seepage flow around buckets, with a particular focus on the general multilayered soil profile featuring anisotropic permeability. The method of separation of variables is used initially to derive general solutions, and the final solutions are subsequently obtained by combining continuous conditions with the orthogonality of Bessel functions. The accuracy of the solutions is confirmed through comparisons with the results obtained from finite element analysis. Furthermore, this study discusses the seepage flow behavior in several typical scenarios, including permeability anisotropy, increased permeability within the bucket, and the presence of an overlying low-permeability layer. The analytical solutions presented in this paper provide a rapid and accurate method for the analysis of suction-induced seepage flow during suction-assisted installations across a wide range of complex soil permeability conditions. [ABSTRACT FROM AUTHOR]

Understanding the pipeline scour mechanism under different conditions is essential for protection measures. The computational fluid dynamics (CFD) and discrete element method (DEM) are coupled for the simulations. To reduce the computational effort, the coarse-grained method is applied, and the Darcy-Forchheimer porous model is used to replace the far field elements. Both of the porous medium and particles-fluid interaction model are validated by comparison between simulation results and theories. The scouring simulation results show a good agreement with the experiments conducted with single-diameter spherical particles under different current-wave conditions. Further, the flow around the pipeline, the seepage in the sediment bed and the force acting on the particles are analyzed. The vortex shedding exists downstream under current but the vortex moves around under waves. The seepage depends on the pressure, influenced by the pipeline and the water depth, and the variation of the seepage is discussed. The force acting on the particles is not uniform along bed and the distribution is analyzed. This paper provides an insight into scour mechanics from the aspects including seepage and flow-particle interaction. Different methods are used for modification, giving a reference for the usage of CFD-DEM model in the analysis of scour process. [ABSTRACT FROM AUTHOR]

Maintaining the stability of the tunnel face during the construction of the submarine shield tunnel is the prerequisite for safe construction. A series of face instability model tests under saturated strata were carried out. The earth pressure, the evolution of the soil arch area and the amount of soil entering the soil groove caused by the instability of the tunnel face under different face water pressure conditions were studied. A series of numerical simulations were carried out to analyze the effects of tunnel face water pressure. The results show that the vertical earth pressure and horizontal earth pressure at different positions show a gradual decrease with the increase of the baffle backward distance, and the smaller the water pressure ratio, the more obvious this law is. According to the test results, the decrease of the water pressure ratio of the tunnel face can significantly increase the soil intake of the soil tank, which indicates that the collapse range above the tunnel face is large. The trend of instability region obtained by numerical simulation is consistent with the test monitoring results. This provides a reference for the construction of submarine shield tunnels. • Geomechanical model tests are carried out. • The pore water pressure and earth pressure are studied. • The evolution process of the soil arch area and the soil inflow volume of soil tank are investigated. • The failure areas is analyzed. [ABSTRACT FROM AUTHOR]

Suffusion is a grave threat leading to accidents in embankment dams across the world. The process has been widely studied experimentally and numerically with gap‐grading cohesionless soil. One of the direct observations in the studies is the finer particle loss of the soil. However, the movement of the finer particles in the numerical models is commonly predicted with an empirical law. This paper proposes a theoretical particle movement model based on the force balance of soil particles and a probability distribution of the soil pores under one‐dimensional upward seepage flow. In the proposed model, the velocity and the critical movement state of soil particles were deduced, and a method to predict the critical hydraulic gradient was established. The finer particle movement rate was estimated theoretically using the particle movement velocity and probability. The model was verified with several experiments and showed a good consistency in the critical hydraulic gradient, seepage velocity, finer particle loss and hydraulic conductivity. Finally, the changes in the soil parameter during the suffusion process, the effects of the hydraulic gradient and initial porosity and the model applicability are discussed quantitatively. The results indicate that the modelled soil parameter changes match well with the movement characteristics of the finer particles observed in the experiment. The particle movement process is very sensitive to changes in the hydraulic gradient and soil initial porosity. The theoretical model provides a new method to assess the suffusion process for internal unstable cohesionless sand soil. Highlights: A evaluation model of the suffusion‐induced soil particle movement was proposedThe model was established based on force equilibrium of soil particlesThe model was credible in varied factors based on experiment dataThe model evaluated suffusion process, variables affects and model applicability were discussed [ABSTRACT FROM AUTHOR]

A tractable analytical solution for steady-state two-dimensional seepage from a trapezoidal channel in a homogeneous, isotropic porous medium of considerable depth is presented. The analysis is performed by applying the method of inversion and the Schwarz-Christoffel transformation accounting for the capillary action. Because the right half-seepage domain is a mirror image of the left half-seepage domain about the vertical axis (on either side of the channel central plane) owing to the axisymmetric channel, a solution is sought for the right half-seepage domain. The results show that an increase in channel bottom width boosts seepage flux. On the other hand, an increase in channel side slope also amplifies seepage flux. In addition, capillarity plays a subtle role in augmenting the seepage flux from a channel. The analysis suggests that the dynamic capillary rise (i.e., the vertical rise of seepage water along the side slope owing to capillary action) is always less than the static capillary rise. The analysis also presents the relation for the seepage velocity distribution along a channel perimeter. The equations of seepage line coordinates yield the seepage line initially curving downward with a significant lateral shift and eventually becoming vertical at a great depth. Particular solutions for the triangular and rectangular channels and the vertical slit, which is a channel with vertical sides and negligible top width, can be obtained from the generalized solution for the trapezoidal channel. Therefore, this study provides insight into the hydraulics of seepage from a trapezoidal channel, including its particular cases, revealing some new features. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to present a new numerical model for the simulation of water flow through porous media of anisotropic character, based on the network simulation method and with the use of the free code Ngspice. Design/methodology/approach: For its design, it starts directly from the flow conservation equation, which presents several advantages in relation to the numerical simulation of the governing equation in terms of the potential head. The model provides very precise solutions of streamlines and potential patterns in all cases, with relatively small meshes and acceptable calculation times, both essential characteristics when developing a computational tool for engineering purposes. The model has been successfully verified with analytical results for non-penetrating dams in isotropic media. Findings: Applications of the model are presented for the construction of the flow nets, calculation of uplift pressures, infiltrated flow and average exit gradient in anisotropic scenarios with penetrating dams with and without sheet piles, being all this output information part of the decision process in ground engineering problems involving these retaining structures. Originality/value: This study presents, for the first time, a numerical network model for seepage problems that is not obtained from the Laplace's governing equation, but from the water flow conservation continuity equation. [ABSTRACT FROM AUTHOR]

The inrush of groundwater impairs heating efficiency during oil shale in situ pyrolysis mining, and it also increases oily waste-water production. Artificial ground freezing (AGF) is an ideal method to block the adverse groundwater infiltration, while the poor freezing performance and high energy consumption of the current AGF pattern are the biggest obstacles, even failing at high-velocity seepage flow. This study proposed and investigated a novel pattern of AGF through cold gas convection (GC) for oil shale in situ reservoir, this pattern have the potential to enhance the freezing performances, especially when encounters the high-velocity seepage flow. In this study, a coupled hydro-thermal-solid model was developed and numerical simulations were performed, the enhancement mechanism of freezing performances and energy conversion have been analyzed to reveal the superiority of the GC-AGF. The results indicated that the maximum freezing rates were twice the current AGF. With seepage flow, the shape of the frozen zone developed elliptically perpendicular to the seepage flow direction, and the effective radius of the frozen zone formed by GC-AGF decreased only by 10%–20 %, even at a higher-velocity seepage flow. The analysis showed that the gas-water two-phase zone was a barrier to the direct heat exchange between the infiltrated groundwater and the frozen zone, which was the enhancement mechanism of GC-AGF. Correspondingly, the specific energy consumption reduced from 8.0 × 107 to 3.8 × 107 J/m at a higher-velocity seepage flow. The results showed that the proposed GC-AGF method significantly enhanced the freezing performance with low energy consumption. [ABSTRACT FROM AUTHOR]

The method of smoothed particle hydrodynamics (SPH) has been recently developed to study the coupled flow-deformation problems in porous material and considerable success has been achieved comparing to traditional mesh-based method, especially for treating large deformation and post-failure. However, computational challenges remain for the hydro-mechanical boundary treatment as well as the accuracy and stability of the numerical scheme. It is shown that the use of conventional SPH operator for the solution of the coupled problem can lead to several issues including numerical instabilities, inaccuracies and unphysical particle clumping as well as particle disorders near the boundary. To address these issues, a general SPH scheme with enhanced accuracy for saturated/unsaturated porous material is proposed in this paper. An improved SPH formulation for seepage analysis is proposed to allow an accurate prediction of liquid flow in porous material. A new stabilisation technique that combines the use of a density diffusion term, a modified particle shifting algorithm, and a new viscous damping term is developed to further improve the accuracy, stability and robustness of the proposed method. The implementations of stress boundary conditions and hydraulic boundary conditions in SPH, such as confining stress, hydraulic head, infiltration/evaporation, and potential seepage face, using either wall boundary particles or free-surface domain particles, are discussed in detail. A range of benchmark examples is adopted to verify the validity of the present coupled framework. The proposed model is finally applied to simulate the failure process of embankment dam due to rapid drawdown. Results indicate that the methodology proposed herein can be a promising tool for the analysis of the coupled hydro-mechanical process in porous material involving large deformations. [ABSTRACT FROM AUTHOR]

When earth-rock dams are built on deep overburden layers, the seepage prevention effect of dam body and dam foundation is directly related to the safety of dam. According to the geological conditions of an earth-rock dam in the southwestern region of China, the dam body adopted the asphalt concrete core wall to prevent seepage, and the deep overburden layer adopted the suspended concrete anti-seepage wall scheme, focusing on the depth of hanging concrete cutoff wall for 6 kinds of scheme comparison and analysis and determining that when the depth of the cutoff wall was 22 m, the annual seepage flow and seepage ratio drop of the dam and dam foundation met the requirements. On this basis, a number of working conditions were checked and analyzed. The calculation results show that the anti-seepage system based on the asphalt concrete core wall and impervious wall effectively reduces the height of the internal seepage line of the dam, and the saturation line dips at the asphalt concrete core wall, and the internal pore water pressure of the downstream dam slope is relatively small, the maximum dam height where the saturation line falls to the drainage layer and the downstream exit point is located in the lower part of the downstream drainage body. The seepage ratio drop of asphalt concrete core wall and concrete cutoff wall is less than the allowable value of 80 and the seepage ratio drop of the dam filling material and the natural gravel layer is within the allowable percolation drop range. The seepage in the dam body and the dam foundation is stable and no seepage damage will be occurred. [ABSTRACT FROM AUTHOR]

Soil arching effect, which relates to the load transfer and stress redistribution in a soil mass, exists commonly in various geotechnical situations. Many researchers have conducted trapdoor tests and theoretical analyses to study the soil arching and its development in recent years. However, little attention has been paid to the interaction between soil arching and seepage flow, both occurring during the tunnelling of a seabed tunnel. To study the influence of the seepage flow on soil arching, a series of two-dimensional trapdoor tests were carried out considering different fill heights and water level heights. Two subvertical slip surfaces were observed during the tests using the PIV technique. It was found that seepage flow increased the displacement of the particles and the effective vertical stress acting at the top of the trapdoor. However, there was little difference in the development of slip surfaces between the seepage condition and the saturated/no-seepage condition. In addition, a nonuniform distribution of vertical stresses at the top of the trapdoor was observed. The effective earth pressure measured along the centreline of the trapdoor was larger than that on the two edges of the trapdoor. But this nonuniformity decreased with an increasing water level height in the test chamber. [ABSTRACT FROM AUTHOR]

The scouring of seabed beneath an unburied pipeline under regular waves was investigated in a large wave flume. Sands and silts were employed for the contrast experiment and the results obtained were compared with data from literature. It was found that the standard formula of Sumer and Fredsøe was best at predicting scour depth of sands while underestimating that of sandy silts; time evolution of sand-scour depth better followed traditional exponential curves than did those of sandy silts; an empirical formula in the form of T * = 0.0066 θ − 3.034 is suggested for predicting the non-dimensional time scale of the scour process beneath pipeline in the Yellow River delta. The underestimated scour depth of silts was related to the wave-induced pore pressure responses not found in sands. It was wave-forced seepage flows that promoted the normal scour process during the initial period by exerting an uplifting seepage force on the surface particles. [ABSTRACT FROM AUTHOR]

High groundwater flow velocity is a major challenge in many artificial ground freezing (AGF) projects, especially in groundwater control projects. That condition may be unfavorable for the formation of a frozen body. This study aims to understand the effect of seepage flow on the heat transfer behavior and hydraulic conductivity variation of sand during the freezing process in AGF projects by using a vertically buried freezing pipe. The authors conducted a small-scale laboratory experiment that combined a flow test, freezing process, and infrared thermograph observations of thermal distribution. The authors prepared saturated Toyoura sand and a Toyoura-silica sand layer combination as the heat-transfer medium. The thermal distribution and hydraulic conductivity behavior were investigated by two series of freezing experiments with different sand layers and flow scenarios. Infrared thermograph observation results showed how water affects the thermal distribution characteristic, whereas flow test results showed the relation between hydraulic conductivity and frozen-body development. [ABSTRACT FROM AUTHOR]

• The newly developed Lagrange-Lagrange coupling model allows simulating sediment transport under complex moving boundary conditions. • A seepage effect on sediment transport is particularly found around the tip of uprush /backwash waves. • An important role of the DEM-base granular model to evaluation of the bottom shear stress is indicated. Interactions between the uprush and backwash waves around a swash zone cause a complex water surface with wave breaking. Infiltration and exfiltration on a permeable beach face produce significant effects on the bottom shear stress. Abrupt changes of the bottom shear stress induced by uprush waves onto a dry bed have a significant impact on the estimation of sediment flux. In order to simulate, with a high degree of accuracy, a violent flow with wave breaking and complex moving bed boundaries along the on-off shore direction, wave motions are solved by using an enhanced particle method based on the MPS (Moving Particle Semi-implicit) method, while the DEM (Discrete Element Method) is used for a movable bed simulation. Consequently, the high potential of a MPS-DEM coupling model to simulate the swash beach process is clearly demonstrated by comparison with previous experimental results. Furthermore, the significance of the seepage flow in the swash beach process is shown with referring the Nielsen's modified Shields number. [ABSTRACT FROM AUTHOR]

Behaviour of granular soils subjected to internal erosion involves complex coupling between solid–fluid interaction, skeleton deformation and microstructural evolutions. This paper presents a micro–macro investigation on suffusion in idealized gap-graded and well-graded soils using the coupled computational fluid dynamics and discrete element method. The interaction between soil particles and seepage flow is modelled via momentum exchange between two phases. The progressive loss of fine particles subjected to upward seepage flow at various hydraulic gradients is investigated. The fines content, volumetric contraction and void ratio are monitored to identify the changes of macroscopic states of the soil skeleton. In addition, the microstructural evolution is tracked via particle-scale descriptors such as coordination numbers and force chain statistics. Several clogging–unclogging events which are responsible for the sudden changes of fines content and skeleton response are observed during suffusion. A parametric study indicates that the initial fines content and the hydraulic gradient significantly affect the kinetics of suffusion. Microstructural analyses reveal that the removal of fines is accompanied by the reduction in weak contact pairs and particles with low connectivity. [ABSTRACT FROM AUTHOR]

The suction anchor becomes more popular for offshore oil and gas industry in deeper water. For suction anchor–soil interaction, the prediction of hydraulic conductivity of porous materials is a long-standing problem in offshore engineering. To investigate the hydraulic characteristics, an upward seepage flow through saturated sands is considered in this study. A numerical approach, which is able to describe the fluid–particle interaction at particle scale, has been employed to analyse fluid flow in sands. This approach is constructed by adopting a coupled discrete element method and computational fluid dynamic approach (CFD-DEM numerical model). The coupled CFD-DEM approach is first benchmarked by a classic geomechanics problem where analytical solutions are available, and then employed to investigate the characteristics of upward seepage flow in coarse sand columns. Through numerical modelling, the predicted relation between hydraulic gradient and flow velocity is obtained and it is compared with the classical analytical correlation. The effect of several bulk and micromechanical parameters including packing porosity, particle size combination and inter-particle rolling resistance on the flow characteristics is numerically examined. The results show that the particle polydispersity and packing porosity have significant effect on the hydraulic conductivity in the seepage flow. The introduction of inter-particle rolling resistance can change initial packing structure of particle assembly in some extent rather than the hydraulic conductivity from the particle shape effect perspective. A further development of numerical model, in which the effect of non-spherical particles on the seepage flow, will be carried out later. [ABSTRACT FROM AUTHOR]

Abstract In this study, a new shape-dependent fluid-particle drag model for irregularly shaped particles is integrated into the fluid dynamic program CFD-DEM and used to analyse the behaviour of calcareous sand particles in liquids. The new drag model had been correlated by pervious settling experiments of calcareous sand particles in a static Newtonian Liquid. The new drag model defines the particle-fluid drag coefficient as a function of both the fluid regime and particle shape characteristics which can evaluate how the particle shape deviates from a regular sphere. This study is a follow-up work of the authors' previous experimental research, focusing on the numerical modelling of sand particle-fluid interaction. To validate the integration of the new drag model in program CFD-DEM, the code has been used to reproduce the calcareous sand particle settling and seepage experiments. The comparison with simulations using the existing drag models without considering particle shape effect demonstrates that, by means of the new drag model, a significant improvement in the capability of CFD-DEM program to predict the terminal falling velocity of irregularly shaped particles is obtained. With this implementation, CFD-DEM program is used to simulate seepage flows within calcareous sand sample in which particles are significantly different from regular spheres, as is usually the case of environmental and geological fluid-particle flows. Graphical abstract It presents the images of settling of a typical calcareous sand particle taken from the experiment and numerical simulations together with the numerical predictions of terminal fall velocity by new drag model; and the numerical model of seepage flow in cylindrical calcareous sand sample and the relationship between flow velocity and hydraulic gradient obtained by the experiment and numerical simulations. Unlabelled Image Highlights • New shape-dependent drag law for irregular particle is implemented in CFD-DEM model. • The CFD-DEM model predicts the settling of calcareous sand particle in liquid well. • The seepage flow in calcareous sand sample is accurately simulated by CFD-DEM model. • The model with new drag law is useful for hydro-mechanical analysis of natural particles. [ABSTRACT FROM AUTHOR]

Dike failures due to overtopping frequently occur during floods, causing serious damage to settlements and the environment. For risk management, it is of great importance to understand the mechanisms of dike failure and predict this process accurately. In this study, a three-dimensional numerical model is developed to simulate both overtopping and seepage flows during dike breaching. The governing equations describing the free water flow are extended and applied to simulate also the filtration through porous media. A non-equilibrium sediment transport model is utilized for simulation of the bed deformation. The numerical model is firstly applied to flows over a solid embankment in order to validate the flow part of the model, and then the dike breaching is simulated such that the bed deformation model is also incorporated. By comparison with the experimental results, it is shown that the developed model reproduces overflow and the dike failure processes reasonably well. [ABSTRACT FROM AUTHOR]

• Fracture-matrix model considering free/seepage flow and roughness effects. • Non-Darcy coefficient is obtained from 284 seepage tests. • Porosity, permeability, aperture, and roughness are the main factors. • Friction factor reveals critical flow regimes and Reynolds number. The friction factor plays a crucial role in evaluating pressure gradient loss for water flow through fracture-matrix systems (FMS). This study presents a theoretical model for the FMS friction factor, incorporating viscous and inertial terms based on Forchheimer's law. The model considers the coupled effects of free flow, seepage flow, and roughness. The non-Darcy coefficient in the inertial term is determined by fitting 284 sets of FMS seepage test data. To validate the derived friction factor, COMSOL simulations are conducted using the coupled free and porous media flow module, considering two relative roughness values. The proposed model demonstrates higher accuracy compared to existing models and experimental data, with 101 fewer missed prediction points and a 21.4% improvement in accuracy. Additionally, this study examines fluid flow regimes and critical Reynolds numbers for various matrix porosities, permeabilities, fracture apertures, and relative roughness values. The findings reveal that FMS with low matrix permeability, high roughness, and small apertures exhibit larger friction factors and are more prone to nonlinear deviations from Darcy flow. [ABSTRACT FROM AUTHOR]

Abstract It is known that the seepage force has a significant impact on the mobility of bed particles. To assess the effect of seepage force on the sediment transport around a suspended pipeline, a series of numerical tests have been carried out utilising the commercial software Comsol. In the simulation, the shear-stress transport turbulence model was used to simulate the upper turbulence flow field and the porous medium model was adopted to describe the dynamic response of the underlying seabed. Both the fluid flow and the seepage flow within the seabed were modelled. The effect of the vertical seepage force on the Shields number was investigated. The simulation results indicate that seepage plays a vital role in the process of tunnel scour, but becomes quite weak with the form of a scour hole beneath the pipeline. With an increase in scour depth, vortices shed from the pipe lead to a fluctuating fluid pressure, inducing significant upward seepage, and thus influencing the stability of bed particles. If sagging of the pipeline appears, the fluctuation of fluid pressure becomes weak and the seepage effect is minor. Highlights • The seepage effect on the Shields number is studied through numerical simulation. • The vortex shed onto the seabed can induce upward seepage flow due to the negative pressure inside it, which will promote the sediments scour. • Study seepage effect on shields number around fixed and sagging pipeline by coupling numerical simulations with experiments. [ABSTRACT FROM AUTHOR]

Abstract Sediment incipient motion is the first step of the whole process of sediment transport. However, previous numerical works simplified the seabed surface as a type of impermeable and rigid boundary, and ignored the effect of seepage flow on the mobility of bed particles. In this paper, to reveal the physics behind sediment incipient motion around a free spanning pipeline, an integrated numerical model, coupling the SST (Shear-Stress Transport) turbulence model with the porous seabed model, was proposed. Numerical studies showed that with the periodic formation and shedding of vortices around the pipeline, both the oscillatory and residual excess pore-pressures developed within the seabed. In some cases, the vertical gradient of excess pore-pressure (seepage force) had a significant impact on the mobility of bed particles around the pipeline. It was found that lower saturation degree and seabed permeability would remarkably increase both the oscillatory and residual seepage forces, and thus enhance bed particle mobility. While for a sandy seabed with smaller soil shear modulus, the oscillatory seepage force was only slightly reduced, but a high residual seepage force would be generated with time. This could lead to obvious decrease in the submerged weight of bed particles, making them more easily dragged away from the seabed. Highlights • Propose an integrated numerical model to couple the turbulent flow and porous seabed models. • Study the excess pore-pressure responses in the seabed beneath the suspended pipeline. • Quantify the effect of seepage flow on the mobility of bed particles. • Study the effects of seabed parameters on the flow-induced seepage force. [ABSTRACT FROM AUTHOR]

This paper presents the case study of a collapsed riverbank protection structure, located in the curvature of the watershed along the Pasak river in Saraburi province, Thailand. Although efforts have been made to twice rehabilitate this collapsed structure, the rebuilt protection structures were unstable to prevent progressive collapse damage and the causes of their failure remained elusive. The project team was engaged to carried out the site investigation and finite element analysis prior to providing the remedial approach on the collapsed structure. The outcome from this study reveals that the natural disaster events were the main causes of the structure failure. During the rainy season, water flowed into the river from upstream farmlands by crossing the backfill of the riverbank protection structure. Seepage forces were thus developed in the direction of inflows, which resulted in reduced stability of the riverbank protection structure. Furthermore, the strong currents in the river continuously scoured the banks, undermining the natural slope in front of the riverbank protection structure, resulting in soil erosion in the passive zone and instability of the protection structure. Based on these two causes of failure, a remedial solution was devised using a new bored pile riverbank protection structure with the usage of geocomposites and ripraps. Geocomposites and ripraps were installed at the back and front of the bored pile walls to relieve the structure from seepage forces and to prevent soil erosion, respectively. An adequate factor of safety against the external and internal failure of the new riverbank protection structure was verified by finite element modeling and the results confirmed that the structure was safe. [ABSTRACT FROM AUTHOR]

Extreme weather events, such as floods, are becoming more frequent in future with all consequences concerning the safety especially of water retaining structures, in particular, levees used as technical flood protection. The knowledge and correct consideration of coupled hydro-mechanical processes influencing the failure and post-failure behaviour of water saturated soils are of paramount significance for the assessment of hydraulically loaded geotechnical structures. This study focuses on the modelling of the processes governing the behaviour of water saturated soils using Smoothed Particle Hydrodynamics (SPH) on the example of a homogeneous embankment under different loading conditions. This paper aims to improve available SPH framework in order to enhance soil-water interaction in this method for geotechnical engineering investigations. To achieve this goal, the suggested approach is validated intensively by various well-known problems. Finally, the verified tool is used to investigate the hydro-mechanical behaviour of homogeneous embankments under simultaneous hydraulic and mechanical loading. The simulation results prove that the suggested approach is capable of simulating relevant hydraulic and mechanical processes governing the deformation behaviour of hydraulically loaded structures beyond the failure point allowing the detailed analysis of the post-failure behaviour characterised by large deformations. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is to extend the scaled boundary radial point interpolation method (SBRPIM), as a novel semi-analytical scheme, to the analysis of the steady state confined seepage flows.Design/methodology/approach This method combines the advantages of the scaled boundary finite element method and the BRPIM. In this method, only boundary nodes are used, no fundamental solution of the problem is required, and as the shape functions constructed based on the RPIM satisfy the Kronecker delta function property, the boundary conditions of problems can be imposed accurately and easily.Findings Three numerical examples, including seepage flow through homogeneous and non-homogeneous soils, are analyzed in this paper. Comparing the flow net obtained by SBRPIM and other numerical methods confirms the ability of the proposed method in analyzing seepage flows. In addition, in these examples, the accuracy of the SBRPIM in modeling the velocity singularity at a sharp corner is illustrated. SBRPIM accurately models the singularity point in non-homogeneous and anisotropic soil.Originality/value SBRPIM method is a simple effective tool for analyzing various kinds of engineering problems. It is easy to implement for modeling the velocity singularity at a sharp corner. The proposed method accurately models the singularity point in non-homogeneous and anisotropic soil. [ABSTRACT FROM AUTHOR]

• A new method was proposed for determining the maximum paste coating thickness. • Digital models of pervious concrete were created. • Influence of maximum paste coating thicknesses on the pore characteristics and seepage flow was investigated. • An empirical formula was proposed to determine the Kozeny–Carman constant. The determination of the maximum paste coating thickness on aggregate (MPCT) without void clogging is essential for effectively controlling the permeability of a pervious concrete (PC). The main objective of this study is to investigate the influence of varying MPCTs on the pore characteristics and seepage flow of PC. A new method was proposed for determining the MPCT of PC, and the relationships between the MPCT and the rheological properties of cement paste were established. Subsequently, digital models of PC with varying MPCTs were created, and the connected pore was extracted for analysis of pore characteristics. Seepage flow simulations were conducted to analyze the permeability characteristics of PCs under varying MPCTs. The results indicate that the pore characteristics are directly influenced by the MPCT, in which the effective porosity, specific surface, and tortuosity show linear correlations with the MPCT. When the MPCT ranges from 0.44 to 0.99 mm, the pore size of the PCs exhibits a single-peak distribution ranging from 1.4 to 13.5 mm, while the coordination number of the pores is distributed within the range of 1 to 14. Additionally, the permeability coefficient of PC decreases as the MPCT increases. When the MPCT exceeds 0.85 mm, the permeability coefficient drops to less than 1 mm/s, and the rate of decrease slows down. An empirical formula was proposed to determine the Kozeny–Carman (KC) constant, which improves the accuracy of the KC equation in predicting the permeability of PC. The findings presented in this study serve as a reference for the design of mixture proportions and the optimization of permeability in PC. [ABSTRACT FROM AUTHOR]

Carbon foam was utilized to develop corrugated structured packing in distillation for the first time. The hydrodynamics and mass transfer performance of CFP-400X and CFP-500W with 60 and 75° corrugation angle were determined by total reflux experiments. The results indicate that increasing the corrugation angle will improve the capacity but decrease the mass transfer efficiency. Comparisons among CFP-400X, SCFP-500X, BX-500, and B1-500X were made with respect to the performance of hydrodynamics and mass transfer. CFP-400X shows advantages in terms of capacity and efficiency compared with the other two metal packings. SCFP-500X exhibits a higher mass transfer efficiency than CFP-400X because of its superior wettability of test liquid which is supported by the liquid flow behavior experiment. [ABSTRACT FROM AUTHOR]

Underestimation of raw material reserves contained in gold mining waste dumps results in tense socio-economic situation in gold mining regions. Efficient management of gold mine waste is only possible with the new and sound technologies of waste preparation and deep conversion with a view to recovering valuable components. Aimed at creation of such technology, the large-scale theoretical and experimental research has been undertaken in order to study the nature and rate of influence exerted by basic process factors on migration and concentration of gold particles in gold mine waste. [ABSTRACT FROM AUTHOR]

Fractured seepage is an important factor affecting the interface stability of rock mass. It is closely related to fracture properties and hydraulic conditions. In this study, the law of seepage in a single fracture surface based on modified cubic law is described, and the three-dimensional discrete element method is used to simulate the dam foundation structure of the Capulin San Pablo (Costa Rica) hydropower station. The effect of construction joints and developed structure on dam stability is studied, and its permeability law and sliding stability are also evaluated. It is found that the hydraulic-mechanical coupling with strength reduction method in DEM is more appropriate to use to study the seepage-related problems of fractured rock mass, which considers practical conditions, such as the roughness of and the width of fracture. The strength reduction method provides a more accurate safety factor of dam when considering the deformation coordination with bedrocks. It is an important method with which to study the stability of seepage conditions in complex structures. The discrete method also provided an effective and reasonable way of determining seepage control measures. [ABSTRACT FROM AUTHOR]

The authors introduce an experimental method that focuses on the flowthermal relation and the visual observation of heat distribution around a cooling pipe in sand under the flow condition. This experiment aims to understand the effect of seepage flow on the heat transfer behavior of sand under cooling and freezing conditions due to a vertically buried heat exchanger pipe. This method combines a flow test, cooling or freezing processes, and the visual observations of temperature profiles with saturated Toyoura sand as the heat transfer medium. Avertical copper pipe inserted into the sand medium is used as the thermal exchanger, while an infrared thermograph is used to measure and visualize the surface-temperature profile of the specimen. The heat transfer distribution behavior is investigated by conducting a series of cooling and freezing experiments on the specimens with variation of the flow rate condition, initial condition, and pipe depth. The thermograph observation results show how water flow obviously affects the shape and intensity of the heat distribution. [ABSTRACT FROM AUTHOR]

The artificial freezing in the clay-sand stratum under seepage flow conditions involves the hydro-ice-salt-crystalline-thermal-mechanical coupling process. A theoretical model is derived to investigate the influences of water seepage on the freezing process in the clay-sand stratum. The good agreements between the results from the theoretical model and laboratory tests in the literature verified the accuracy of the proposed model. Parametric studies are conducted to investigate the influences of the seepage velocities and temperature gradients on the spatial distributions. It is found that the ice contents, crystalline salt contents and adsorbed salt contents distribution profiles in the clay-sand stratum are nonlinearly distributed with a cliff distribution curve existing on their interface. The crystalline salt contents in the clay layer are higher than those in the sand layer due to the influence of water seepage and heat transfer. The adsorbed salt contents in the frozen area account for 2% of the total salt contents, but those in the unfrozen area account for 8% of the total salt contents. Due to the volume expansion caused by the soil skeleton deformation, thickness of fractional ice, ice frost heave deformation and salt swelling deformation, the soil deformation distribution curves in the clay-sand stratum are in a bilinear shape. • Theoretical model is derived to investigate the influences of water seepage on artificial freezing along clay-sand interface. • The components spatial distributions under different seepage velocities and temperature gradients in the clay-sand stratum are analyzed. • The proposed model is capable to calculate the artificial and seasonal frozen in the non-uniform soil stratum. [ABSTRACT FROM AUTHOR]

Interfacial seepage on soil-structure interface is common in water-related engineering, such as dam, culvert, water tunnel, foundation pit, etc. As a weak part in the project, seepage failure on soil-structure interface has caused many project accidents. However, there are few studies on the seepage mechanism analysis of soil-structure interface. In this paper, a series of numerical tests of interfacial seepage are carried out using CFD-DEM coupling method. The seepage mechanism and characteristics of different soil layers in the seepage device are analyzed and a formula for calculating the critical hydraulic gradient of the interface is discussed. The main conclusions are as follows: (1) The seepage flow on soil-structure interface will go through three stages: stability stage, transition stage and particle erosion stage; (2) The porosity and flow velocity of soil on the interface are greater than those in the far-field soil at the beginning of seepage flow; (3) The particle erosion on the soil-structure interface occurs earlier and the erosion degree is more serious than that of the far-field soil; (4) The critical hydraulic gradient of the interface rises nonlinearly with the increase of the degree of soil compaction; (5) The formula for calculating the critical hydraulic gradient of the interface could predict the numerical test results well. [ABSTRACT FROM AUTHOR]

Most of the current studies on the bearing capacity of rock foundations follow the Hoek-Brown (HB) criterion, but all adopt the generalized tangent technique or the multi-tangent approach, which does not reflect the essence of the nonlinear dependence of the Hoek-Brown criterion. Therefore, a modified unilateral failure mechanism is proposed in the paper, using which the bearing capacity of shallow strip footings considering seepage and seismic forces is evaluated. Use of a statics-like approach for seepage condition and a modified pseudo-dynamic method for seismic condition. The comparison with the results of other literature confirms the feasibility and effectiveness of the study in the paper, while the parametric analysis shows that a smaller upper bound solution is yielded based on the failure mechanism proposed in this paper, and the horizontal gradient ratio, the horizontal factor of seismic acceleration, the normalized frequency, the geological strength index, the disturbance coefficient, and the rock type-dependent parameter all have significant effects on the bearing capacity of rock foundations. In addition, the analysis of the working conditions considering both seepage and seismic forces confirmed the dominance of seismic forces. The results of the superposition treatment between different working conditions are inaccurate, which will underestimate the foundation bearing capacity and cause a waste of cost. This paper develops a more accurate method of assessing the bearing capacity of rock foundations and gives a table of coefficients that can be adopted in engineering practice. [ABSTRACT FROM AUTHOR]

• A widely used mapping in water waves problems is newly applied to seepage flows. • The proposed σ -mapping transforms the time-dependent water table into a fixed boundary. • Steady and unsteady seepage problems are analyzed, with and without recharge. • The method is in excellent agreement with the exact Polubarinova-Kochina solution for the dam problem, and with other solutions in the literature. Regional groundwater flow forecasting is frequently accomplished using model equations based on Darcy's law, the continuity equation, and kinematic and dynamic boundary conditions for a time-dependent water table, to predict hydraulic heads and fluxes. For homogeneous and isotropic aquifers, the model reduces to Laplace's equation for the hydraulic head and a transient non-linear free surface boundary condition. These equations are solved in the literature and in computer packages by a variety of numerical methods, including finite difference, finite element, and boundary element methods. The solution of this model is not simple and subject to instability problems. Computations in a vertical plane using finite-difference methods are not easy due to the irregular mesh needed near a highly curved water table, frequently involving smoothing of the numerical results to ensure stability. A technique to avoid the complications related to mesh generation near a curved boundary and its tracking entails using mappings to produce transformed domains. However, this is not so frequent to compute unsteady seepages. In particular, the so-called sigma mapping is widely used to model irrotational water waves; it applies to any flow involving a time-dependent free surface boundary. This mapping transforms the domain into a rectangle, so that the free surface becomes static in the transformed plane. There is close similarity between the mathematical model describing irrotational water waves and that of unsteady seepage flow, e.g., both are governed by Laplace's equation involving relevant boundary conditions at the moving boundary. Both moving free surfaces are different in character, e.g., the seepage is dissipative whereas the water wave is dispersive. However, it is possible to transfer mathematical approximations between both fields of research. This transfer is exploited in this work and the sigma mapping is newly and successfully applied to seepage flows involving both a steady and unsteady water table either receiving, or not, a recharge from rainfall or an artificial source. [ABSTRACT FROM AUTHOR]

• A physical model test based on cross passage freezing was conducted. • A hydro-thermal coupling model of AGF was proposed. • The effect of four indicators on formation of frozen wall was investigated. Artificial ground freezing is an environmentally friendly and reliable method for ground improvement during subway cross passage construction under variable hydrological conditions. However, natural or induced seepage flow influences significantly the closure of frozen wall, as it supplies a substantial source of heat. In this study, a physical model test was conducted based on the freezing project of a subway cross passage in Beijing Subway Line 19. A series of thermistors were installed in some representative locations to measure the temperature distribution and further calculate power demand. Besides, a hydro-thermal coupling model of freezing process under seepage conditions was derived to consider the variations of physical and thermodynamic parameters of the porous media and the latent heat of ice/water phase transition. The numerical approach was validated by the experimental results. Furthermore, four crucial indicators affecting the closure time during AGF process were quantitatively evaluated. The results showed that the closure time at seepage velocities of 0, 25.6 and 51.2 m/d were respectively 60, 110 and 441 min. Nevertheless, it was impossible to form continuous frozen bodies at 76.8 m/d. Among these indicators, the seepage velocity had the greatest effect on the thickness and shape of frozen body, while seepage temperature had the least impact. [ABSTRACT FROM AUTHOR]

Centrifugal model testing has been widely used to study the stability of levees. However, there have been a limited number of physical studies on levees where the velocity of increasing water levels was considered. To investigate the behavior characteristics of reservoir levees with different velocities of increasing water levels, centrifugal model tests and seepage-deformation coupled analyses were conducted. Through this study, it was confirmed that increasing water levels at higher velocities induces dramatic increases in the displacement, plastic volumetric strain and risk of hydraulic fracturing occurring in the core of the levee. Hence, real-time monitoring of the displacement and the pore water pressure of a levee is important to ensure levee stability. [ABSTRACT FROM AUTHOR]

On a gabion stepped chute, the steps contribute to the dissipation of turbulent kinetic energy, free-surface aeration may be intense, and there are complex interactions between the free-surface flow and seepage motion. Detailed measurements were conducted in a relatively large gabion stepped spillway model. Using a combination of high-speed movies and phase-detection probe measurements, the air--water flow properties in the step cavities and in the gabions were documented. Strong air--water exchanges between seepage and stepped cavity flows were observed. The data showed a complex bubbly seepage motion in the gabions associated with a high level of interactions between seepage and free-surface flows, leading to a modification of the step cavity recirculation and lesser flow resistance. [ABSTRACT FROM AUTHOR]

Artificial ground freezing is an environmentally friendly technique to provide temporary excavation support and groundwater control during tunnel construction under difficult geological and hydrological ground conditions. Evidently, groundwater flow has a considerable influence on the freezing process. Large seepage flow may lead to large freezing times or even may prevent the formation of a closed frozen soil body. For safe and economic design of freezing operations, this paper presents a coupled thermo-hydraulic finite element model for freezing soils integrated within an optimization algorithm using the Ant Colony Optimization (ACO) technique to optimize ground freezing in tunneling by finding the optimal positions of the freeze pipe, considering seepage flow. The simulation model considers solid particles, liquid water and crystal ice as separate phases, and the mixture temperature and liquid pressure as primary field variables. Through two fundamental physical laws and corresponding state equations, the model captures the most relevant couplings between the phase transition associated with latent heat effect, and the liquid transport within the pores. The numerical model is validated by means of laboratory results considering different scenarios for seepage flow. As demonstrated in numerical simulations of ground freezing in tunneling in the presence of seepage flow connected with the ACO optimization algorithm, the optimized arrangement of the freeze pipes may lead to a substantial reduction of the freezing time and of energy costs. [ABSTRACT FROM AUTHOR]