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Using one opening (filter) within the floors of hydraulic structures is a known technique to relieve the seepage effects on their floors. In this study, a new method to control seepage flow by using two identical filters instead of one was tackled numerically. A comparative analysis of using one versus two filters was conducted for different thicknesses of the permeable stratum, apron size (b), filter length, and sheet pile wall depths. Results indicate that two filters are considerably more effective than using one where the overall uplift force, the maximum potential head, and the hydraulic exit gradient downstream of the floor are reduced to 42–56%, 42–51%, and 66–76%, respectively, compared to one filter, while slightly increasing seepage flow by 1–7%. Many reasons can lead to horizontal openings (cracks) appearing along the sheet pile walls beneath hydraulic structures. The current study tackled their effects on seepage flow for the first time and examined their impact on the floor. A crack in the upstream sheet pile wall can increase total uplift forces by up to 40%, while a crack in the downstream sheet pile wall can increase the hydraulic exit gradient by up to 230% [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]

To study the stability of open-air slope with fault under seepage, this paper uses FLAC3D numerical simulation technology to establish a mechanical model of the sliding body under fault action, and deduce the expression of the stability coefficient of the longitudinal slope, to simulate the stability of the slope with fault under seepage action. The results show that the sensitivity analysis is carried out on four influencing factors such as elastic modulus of rock mass strength, cohesion, internal friction Angle, and tensile strength of rock mass. By analyzing the displacement, stress, strain and safety factor of slope under different working conditions of these four factors, the sensitivity analysis curve of each parameter is obtained. It can be seen from the sensitivity analysis curve that the cohesion of rock mass has the greatest influence on the slope stability, and the elastic modulus has the least influence on the slope stability. The main influencing factors of slope stability are different at different excavation stages. In the early stage of excavation, the main factor affecting slope stability is fault, which gradually changes to seepage in the later stage. This study provides a scientific basis for the future analysis of open-pit slope stability. [ABSTRACT FROM AUTHOR]

Copyright of Science Technology & Engineering is the property of Chinese Society of Technology Economics 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.)

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]

Copyright of Railway Construction Technology is the property of Railway Construction Technology 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 Mine Water & the Environment is the property of Springer Nature 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.)

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]

Copyright of Advances in Water Science / Shuikexue Jinzhan is the property of Editorial Board of Advances in Water Science 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.)

In the present study, three machine learning methods were applied for predicting seepage flow through embankment dams, namely (i) support vector regression (SVR), relevance vector machine (RVM), and Gaussian process regression (GPR). The three models were developed using seepage flow (Q: L/mn) and piezometer level (Z:m) measured at several piezometers placed in the corps body of the dam. The proposed models were calibrated and validated using a separate subset. Models evaluation and comparison was successfully achieved using various performances metrics, i.e., coefficient of correlation (R), Nash-Sutcliffe efficiency (NSE), root mean square error (RMSE), and mean absolute error (MAE). Experimental results showed that the proposed models are a good alternative to the in situ measured and contributed significantly in overcoming the case of missing measured seepage flow. The best performances were obtained using the RVM model with R and NSE values of ≈0.909 and ≈0.823, followed by the GPR model with R and NSE values of ≈0.891 and ≈0.767, while the SVR model was ranked as the poorest one exhibiting R and NSE values of ≈0.780 and ≈0.600, respectively. While, a growing number of investigations have focused on testing machine learning in terms of their feasibilities to accurately describe seepage flow, as well as providing important support to our understanding of the factors affecting its fluctuation, the present work was demonstrated that the combination of a wide range of variables can help in simulating seepage flow, and enhance their sensitivity which has help in developing new algorithms. [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]

The analysis of water seepage below the model's foundation of hydrotechnical object is conducted in the paper. A physical model of gravitational dam is made with the aim to visualize seepage through the ground below the dam. The model is made at the laboratory of the Faculty of Civil Engineering and Architecture in Osijek. The aim of the paper is to analyze the influence of the hydraulic gradient on seepage domain deformation, as well as to study the effect of different engineering measures on the decrease of hydraulic gradient. Four measurements were conducted which were mutually distinguished by the shape of the dam model, i.e. the foundation sheet. The first part of the paper is based on the assessment of measurement variants, i.e. engineering solutions used for the reduction of the seepage part of the buoyancy and seepage flow. The second part of the paper is dedicated to adoption of different models in the analysis of groundwater seepage below the object. Values related to seepage flow as well as buoyancy and pressure distribution below the foundation sheet were analyzed. Graphical, numerical, and approximate methods of analysis were used. [ABSTRACT FROM AUTHOR]

Copyright of Tunnel Construction / Suidao Jianshe (Zhong-Yingwen Ban) is the property of Tunnel Construction 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.)

This work is motivated to study the face stability of earth pressure balance shield tunnels excavated in the semi-open mode and supported by non-uniform chamber pressure under seepage conditions. Within the kinematic approach of limit analysis, an analytical framework incorporating the seepage effect and linear chamber pressure distribution is developed. The pore pressure distributions are numerically simulated and imported into the three-dimensional (3D) discrete rotational failure mechanism. The work rates caused by the pore pressure and non-uniform support in the semi-open mode are introduced into the work rate balance equation to optimize the critical support pressure. Then, a parametric analysis of three typical soils, including the sand, silt, and clay, is performed to investigate the difference between the semi-open mode and closed mode under seepage conditions. The effects of the muck height and pressure gradient in the chamber, the groundwater levels, and anisotropic permeability are also studied. Finally, several design charts of the normalized critical support are presented. The results show that the difference between considering a linear pressure distribution and a uniform distribution in the semi-open mode is small, with a maximum difference of 3%. Compared to the closed mode, the instability of the tunnel face is significantly higher in the semi-open mode under seepage conditions. [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]

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]

Copyright of Science Technology & Engineering is the property of Chinese Society of Technology Economics 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.)

The roughness and tortuosity of fractures are essential parameters affecting the fluid flow in a jointed rock mass. This paper investigates the influence of fracture roughness and tortuosity on fluid seepage behavior. A rough fracture surface was characterized by means of three-dimensional scanning and three-reconstruction technology, and the roughness and tortuosity of rock fractures were calculated. Hydraulic tests were conducted on deformed sandstone fractures with a self-made fracture seepage device, and the variation in the seepage flow was analyzed in rough fractures. The experimental results showed that the seepage flow of fluid decreased non-linearly with the increase in fracture roughness. Under different normal pressures, the friction resistance coefficient and tortuous resistance coefficient decreased with the increase in the Reynolds number. The friction resistance coefficient model and tortuous resistance coefficient model were used to quantitatively analyze the influence of fracture tortuosity and roughness on fluid flow, respectively. A modified model of the frictional resistance coefficient, considering fracture tortuosity and roughness, was established, which clearly expresses the law that with the increase in fracture tortuosity and roughness, the seepage flow of fluid decreases, and the head loss increases. The results of this research can provide a theoretical and experimental basis for studying fluid seepage behavior in deformed sandstone fractures. [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]

Assuming time-averaged normalized velocity as a random variable, the present work developed a Renyi entropy-based model for deriving one-dimensional and two-dimensional velocity distributions in seepage-affected alluvial channels. The model requires the maximization of Renyi entropy using the principle of maximum entropy, subject to specified constraints. The derived velocity distributions can have maximum velocity on or below the free surface. The velocity distributions were evaluated with laboratory observations and were also compared with theoretical velocity distributions reported in the literature. The Renyi entropy-based 2D velocity distributions satisfactorily agreed with experimental data, and compared well with reported distributions. Also, the Renyi entropy provided more accurate 2D velocity distribution in the near-bed flow of seepage experiments than the other technique. The present paper concluded that the Renyi entropy model can be used to predict the velocity distribution in seepage flows. [ABSTRACT FROM AUTHOR]

Seepage analysis plays a key role in geotechnical engineering and contributes significantly to the success of its infrastructure projects. Several engineers consider the Finite element (FE) method basics when executing calculations for designing hydraulic structures and dams. Numerical methods are used herein to solve the problem of seepage flow of water under concrete dams. The FE method is applied to model the dam structure and water level. The seepage velocity distribution in the porous soil is determined, and the effects of varying multiple parameters on the velocity are studied. The different parameters investigated are the dam dimensions (i.e., width (4,8,10,15 m) and depth (0,2,4,8 m)), upstream water head level (10, 15, 20 m), soil permeability (10, 15, 20 m day−1) and ambient temperature (5 °C and 50 °C). The developed FE models were validated by carrying out comparisons with analytical solutions that showed that they were in good agreement. It was found that the dam width is inversely proportional to the seepage rate and is independent of the water head level where increasing the dam by 1 unit width drops the seepage by 3.7% regardless of the water head levels. The depth of the dam is exponentially related to the distance away from the toe and independent of both the dam's width and water head level. Increasing the dam depth reduces the seepage flow by 73% at shallower depths and the effect minimizes as we increase the depth to 1% reduction in seepage simulating an exponential behavior. Such behavior is typical for the dam depth factor regardless of the dam width and water head level variations used in the study. The water head level was also found to be linearly proportional to the seepage flow rate with an increased effect of about 10% per additional 1-m head level. In addition, the soil permeability is linearly proportional to the seepage rate, and the same increment is obtained regardless of the dam's dimensions and water head level. The effects of ambient temperature on the seepage flow were introduced in this paper and will be further studied in detail in our future simulations. Our study concludes that the developed FE model can predict the seepage flow of water under concrete dams with a reasonable level of accuracy. [ABSTRACT FROM AUTHOR]

This paper proposed a calculation method for bolts reinforcement of tunnel face under the seepage condition. The existence of seepage in tunnel engineering may greatly reduce the stability of tunnel face, and bolts reinforcement technology is widely used in traditional tunnel engineering. In this paper, a 3D rotational failure mechanism is proposed by the kinematics method combined with the discretization technique. The pore water pressure was added in the energy calculation based on the empirical distribution formula of water head. The interaction between soil and bolts is simulated by using a finite thickness interaction region. The method was compared with the published works in order to verify the effectiveness. The influence of the bolt length, the bolt strength, the hydraulic head size, the face height and the soil parameters are given in the form of some graph. [ABSTRACT FROM AUTHOR]

Mammal bioerosion is an emergent threat to the functionality of levees. In the present paper, the problem of assessing the failure probability of levees affected by mammal bioerosion is addressed. A fully bivariate description of peak flow discharge and flood duration is combined with a deterministic unsteady seepage flow model to obtain a suitable model of variably disturbed levee response to the observed natural variability of floods. Monte Carlo analysis is also implemented to evaluate the epistemic uncertainty connected to the description of the river system. The obtained model is tested with respect to a real‐world levee located along the Secchia River in northern Italy, which underwent a disastrous failure caused by mammal bioerosion in 2014. The convex linear combination of two Archimedean copulas is found to fit the empirical dependence structure between peak flow discharge and flood duration. The reliability of the unsteady seepage flow model is tested against detailed numerical simulations of the seepage occurring through the levee body. A limit state function is obtained by comparing the maximum extent of the seepage front to the distance between the den end and the riverside levee slope, and the corresponding levee safety and failure regions are delimited. Results obtained from the developed model reveal a significant impact of mammal dens located near the levee crest in terms of failure probability and related return period. This impact is consistent with failures observed in the study area. Plain Language Summary: Burrowing mammals often find in levees a suitable habitat. Unfortunately, mammal dens can significantly compromise the functionality of levees by creating preferential flow paths for flood water seeping through the levee bodies, and by causing ultimately levee failures due to excessive seepage and internal erosion. In fact, many levee failures have been connected to the levee weakening caused by mammal dens. Mammal bioerosion significantly increases the failure probability of levees and the related flood risk in densely populated floodplains. Estimating the failure probability of levees affected by mammal bioerosion is therefore a relevant societal need. In the present study levee, safety and failure conditions are estimated by combining a fully bivariate statistical description of peak flow discharge and flood duration with a computationally efficient unsteady seepage flow model. The resulting modeling framework incorporates the natural variability of floods and the essential hydraulic properties of disturbed/undisturbed levees. Model results reveal that the return period of levee failure due to excessive seepage reduces from 100 to 9 years, namely of −91%, when the mammal den extends for 84% of levee thickness. These results can be used to inform levee design and maintenance programs for the safety of societies living in floodplains worldwide. Key Points: Fully bivariate analysis of peak flow discharge and flood duration is used to describe the hydrologic forcing to leveesVorogushyn et al.'s unsteady seepage flow model is extended to derive the failure probability of variably disturbed leveesReturn period of levee failure due to excessive seepage reduces from 100 to 9 years when the mammal den extends for 84% of levee thickness [ABSTRACT FROM AUTHOR]

This paper aims to analyze the turbulent structure of flows over beds undergoing downward seepage under clear-water conditions. Laboratory experiments in this regard were carried out in a straight rectangular channel that was 17.20 m long and 1.00 m wide. A sandy bed with median grain size d50 = 0.50 mm and sediment gradation σg = 1.65 (i.e., slightly non-uniform sediment) was used for the channel bed. The 3D instantaneous velocities of water were measured with an Acoustic Doppler Velocimeter (ADV) at the working test section. In the vicinity of the bed surface with seepage, measurements revealed that the flow longitudinal velocities (i.e., velocities in x direction) were higher than those in the case of a bed without seepage. Moreover, the variations inthe Reynolds shear stresses increased for the bed with seepage, indicating a higher exchange of flow energy towards the boundary and vice versa. Therefore, it was found that seepage processes influence the turbulence intensity, with a prominent magnitude in the streamwise and vertical directions. The paper also focuses on the third-order moment (skewness) and the kurtosis of velocity fluctuations and the governance of sweep events within the near-bed flow in cases where seepage was observed. [ABSTRACT FROM AUTHOR]

Silty sand slopes are prone to damage due to seepage or rainfall. A partial reinforcement method using short polypropylene fiber and sand mixtures was proposed to protect silty sand slopes from seepage flow failure. The effects and the reinforcement mechanism were explored. First, triaxial tests were performed on sand samples reinforced with fiber lengths (6 and 12 mm) and contents (0.25 and 0.50%) to verify the reinforcement effect. Then, model tests were conducted on sand slopes under lateral seepage flow and the failure mode with different fiber contents and reinforcement method were examined. The results showed that the cohesion and shear strength of sand were significantly improved with the increase of fiber content and length. The suction of unsaturated sand was also enhanced by the fibers. The change in stress-strain behavior from strain softening to strain hardening indicated that static liquefaction could be effectively prevented. The failure mode and extent of slope damage depended on the fiber content. However, it was noted that the slope surface with small reinforcement range performed similarly to that with large reinforcement range. In conclusion, the partial reinforcement method with short discrete synthetic fibers can be used as an effective alternative for slope reinforcement. [ABSTRACT FROM AUTHOR]

Artificial ground freezing (AGF) technology has been commonly applied in tunnel construction. Its primary goal is to create a frozen wall around the tunnel profile as a hydraulic barrier and temporary support, but it is inevitably affected by two natural factors. Firstly, seepage flows provide large and continuous heat energy to prevent the soil from freezing. Secondly, as a key soil parameter in heat transfer, the soil thermal conductivity shows inherent spatial variability, binging uncertainties in freezing effects and efficiency. However, few studies have explored the influence of spatially varied soil thermal conductivity on AGF. In this study, a coupled hydro-thermal numerical model was developed to examine the effects of seepage on the formation of frozen wall. The soil thermal conductivity is simulated as a lognormal random field and analyzed by groups of Monte-Carlo simulations. The results confirmed the adverse effect of groundwater flow on the formation of frozen wall, including the uneven development of frozen body towards the downstream side and the higher risk of water leakage on the upstream face of the tunnel. Based on random finite element analysis, this study quantitively tabulated the required additional freezing time above the deterministic scenario. Two levels of the additional freezing time are provided, namely the average level and conservative level, which aim to facilitate practitioners in making a rule-of-thumb estimation in the design of comparable situations. The findings can offer practitioners a rule of thumb for estimating the additional freezing times needed in artificial ground freezing, accounting for the seepage flow and spatial variation in soil thermal conductivity. [ABSTRACT FROM AUTHOR]

In recent years, sediment disaster has frequently been caused by heavy rainfall and has cost many human lives and great property losses. To estimate such risks, Wakai et al. [1] proposed a simplified prediction method to calculate the variation of groundwater levels in natural slopes both at the time of rainfall in wide areas and in real time. To calculate the variation of groundwater levels using this method, the slope conditions (such as material constant and initial conditions) must be determined in advance. This study takes the 2017 heavy rainfall in Northern Kyushu as an example to analyze surface layer thickness, one of the slope conditions that most significantly influences slope stability, over wide areas. The findings reveal that the prediction of slope failure distribution differs depending on how the surface layer thickness and sliding surface are determined. [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]

The paper is devoted to the simulation of oil displacement by water and the formation of the Saffman–Taylor instability. The problem is solved in two-dimensional formulation. A circular domain with one injection well and eight production wells located along the contour around the injection well is considered as geometry. To study the patterns of oil displacement by water, hydrostatic pressure, oil and water seepage rates, and oil saturation are calculated. The graphical analysis considers mainly the oil saturation field. The hydrostatic pressure field is calculated by solving the steady-state piezoconductivity equation; the field of the oil-water seepage rate is calculated using the linear Darcy filtration law; and the oil saturation field is calculated from the solution of the advection transport equation. The two-phase nature of the flow considered in the problem lies in the fact that the oil and water phases have their own relative phase permeabilities calculated using the Brooks–Corey model. The equations are solved numerically using the finite volume method. An irregular triangular grid is used to discretize the computational domain. As a result of the simulation, it is established that the type of the Saffman–Taylor instability, due to its randomness, strongly depends on the computational grid. After the production wells are flooded, the displacement front stabilizes. The instability increases as the ratio of dynamic viscosities of oil and water increases. [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]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology 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.)

Solid backfill coal mining technology can be safely and efficiently used to exploit coal resources under aquifers, without causing harm to the water resources and the environment. Nevertheless, the mechanism of fracture development and seepage channel or pathway control in the key aquiclude strata (KAS) in backfill coal mining under fluid–solid coupling have not been studied. Based on the similarity theory of fluid–solid coupling physical simulation, this study involves experimental evaluation of similar materials and characteristics of composite KAS, backfill body, and aquifer. Subsequently, we designed and employed three experimental models for physical simulation, corresponding to backfill materials' compaction ratios (BMCRs) of 0%, 65%, and 80% using the geological conditions of mining face No. 101 under the aquifer in the Wugou coal mine. Fracture evolution laws, mining-induced deformation, and stress distribution characteristics of composite KAS with different BMCRs are studied. The backfill body can effectively weaken the influence of mining stress, such as the maximum subsidence, sinking speed, initial or periodic fracture damage area of the composite KAS, inhibiting the formation of seepage cracks and water inrush channels. The increase in the BMCR plays an important role in the closure and repair of developed fractures. [ABSTRACT FROM AUTHOR]

Field observations of the foundations of high-head dams established the high sensitivity of the fluid to the crack opening and changes in the stress field, which is used for prediction purposes. [ABSTRACT FROM AUTHOR]

The deep-seated failure caused by inadequate shear resistance against the weight of the surrounding soils is often the more probable mode of failure prior to other types of failure. In this research, stability of flexible supported vertical cuts in granular soils against the deep-seated failure, in the presence of the seepage flow, is investigated. First of all, the flow field is computed by the traditional finite elements method. It is then assumed that the soil in the proximity of the bottom of the cut is at the verge of the limiting equilibrium. Once the flow field solution is known as a steady-state solution, i.e., the background solution, the stress field at the limiting equilibrium subjected to this flow field has been calculated. The method of stress characteristics was used to solve the stress field. It is, therefore, possible to estimate the factor of safety against the deep-seated failure and to assess the overall stability of the system. Results reveal that in spite of quite good margin of safety in the absence of the seepage flow, the deep-seated failure becomes most likely to initiate when the seepage flow exists. [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]

Copyright of Yellow River is the property of Editorial Board of Yellow River 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.)

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]

The face stability of tunnel may be decreased significantly due to the presence of seepage flow. In order to investigate effects of seepage flow, an original procedure is presented for face stability of a circular tunnel excavated by a pressurized shied, based on the discretization technique and the nonlinear failure criterion. A discretization technique is utilized to generate the latent failure mechanism by making use of point to point method. The collapsed blocks are decomposed into infinitesimal triangular elements. Each element is consisted of discretized points and adjacent radial to simplify the computed process. The upper bound solutions of retaining force are derived by equating the total rate of external work to the rate of internal energy dissipation. Pore water pressure is incorporated into energy calculation, according to the empirical distribution formula of hydraulic head which is derived by trial and error. The validity of the proposed method has been proved by making comparison with the published works. Agreement shows that the proposed method is effective. A parametric analysis is implemented to discuss the effects of seepage flow and soil nonlinearity on stability of tunnel face, and the concrete results are illustrated for practical use in engineering. [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]

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]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology 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.)

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]

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]

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]

This paper aims at revealing mechanical behavior of volcanic coarse grained soils subjected to seepage flow. In order to accomplish the purposes, a series of upward seepage tests was conducted to grasp piping phenomenon in compacted volcanic soils and to investigate the effects of differences in compaction conditions on its behavior. In the experiments, the movement of soil particles in seepage flow tests was observed using an X-ray CT scanner in detail. The test results showed that destabilization of soil structures due to seepage flow is changed depending on an increase of amount of finer soil particles, and that internal erosion is induced by loss of fine particles with the changes in void ratio. As a result, a significant variation in hydraulic conductivity was generated. Additionally, internal stability of volcanic soils under several geotechnical conditions was elucidated by empirical criterion. In the consideration of the results, it was shown that volcanic coarse grained soil including pumice particles with a low specific gravity was internally unstable. Based on the results, a geotechnical evaluation was discussed for the stability of soil structures such as embankments constructed by volcanic coarse grained soils. [ABSTRACT FROM AUTHOR]

During the installation process of suction caisson in sandy seabed, the applied suction not only produces a downward driving force, but also decreases the penetration resistance to the caisson. In this paper, numerical studies were performed to investigate the characteristics of seepage flow around the caisson as well as its effects on the wall friction and the caisson tip resistance. A simplified approximation method was proposed to predict the reduction of penetration resistance. In particular, for the case of sandy seabed interbedded by a layer of low-permeability soil, the seepage flow will be suppressed with the caisson tip getting closer to the low-permeability layer. The seepage flow around the caisson was first studied, and then a new approximation for the seepage-induced resistance reduction, considering the effect of low-permeability layer, was proposed for the engineering practice. [ABSTRACT FROM PUBLISHER]