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Most dam seepage safety analyses evaluate a stable seepage field, infiltration line, and seepage flow. However, under fluctuating drought-flood conditions, the soil surface becomes cracked, making it too complicated to conduct a routine seepage analysis. In this paper, the seepage characteristics of an inclined wall dam under fluctuating drought-flood conditions were studied using a large-scale physical model. The results show that after drought, the permeability coefficient of clay with low crack development was smaller than that of the saturated permeability, but for cracked areas, with high permeability, permeability coefficients were much larger than those of the saturated permeability. As the water level rose, cracks could heal themselves, but this healing was superficial, and the soil could no longer return to its predrought state. After crack healing, the integrity of the dam slope was much less than its original state. In addition, the formation of cracks increased the porosity of the soil and changed the soil permeability, which permanently weakened the antiseepage performance of the clay soil. This study evaluated the seepage flow behavior of an inclined wall dam under fluctuating drought-flood conditions, and results can be used to monitor and protect the weak parts of seepage dams in practical engineering projects.

Numerical simulation of coupled hydromechanical processes is crucial to address many problems in geotechnical engineering. Conventionally, the seepage flow equation in a hydromechanical model is solved by the continuous Galerkin (CG) finite element method. However, the CG method does not ensure mass conservation in a local (element-wise) manner, which may be a critical drawback in a number of situations. Here we introduce an enriched Galerkin (EG) finite element method that allows locally mass conservative simulation of coupled hydromechanical problems. The major advantage of the EG method is that its computational cost is appreciably less than that of the discontinuous Galerkin (DG) method. We describe the proposed method’s key idea and demonstrate its performance and significance through an example simulation of wetting collapse of a heterogeneous unsaturated soil.

As the coastal region is the most developed region in China, an increasing number of engineering projects are under construction in it in recent years. However, the quality of these projects is significantly affected by groundwater, which is influenced by tidal variations. Therefore, the regional groundwater dynamic characteristics under tidal impact and the spatiotemporal evolution of the seepage field must be considered in the construction of the projects. Then, Boussinesq function was introduced into the research to deduce the seepage equation under tidal influence for the coastal area. To determine the spatiotemporal evolution of the deep foundation pit seepage field and the coastal seepage field evolution model, numerical calculations based on changes in the tidal water level and seepage equation were performed using MATLAB. According to the developed model, the influence of the seepage field on the foundation pit supporting structure in the excavation process was analyzed through numerical simulations. The results of this research could be considered in design and engineering practice.

Many failures of earth structures are caused by the internal erosion occurring in these structures and their foundations. Suffusion, one of four internal erosion types, is a selective erosion of fine particles which move through the matrix formed by the coarser particles. In literature, most investigations on suffusion took it as a single erosion process. However, the suffusion is a complex process due to the combination of three processes: detachment, transport and possible filtration of finer fraction. The influence of the local processes on suffusion susceptibility, especially the filtration process, is not well established. The objectives of this study are investigating the filtration process by verifying results of filtration tests with the basic filtration equation and analyzing the influence of spatial scale effects on the filtration process by performing tests with two different-sized devices. The filtration tests results show the consistency with the basic filtration equation on suspended particle concentration. And suffusion tests indicate the significant effect of specimen size on filtration process. The interpretative method based on the energy expended by the seepage flow and the cumulative loss dry mass is more appropriate with filtration process than those based on the geometric shape of the particles.

The problem of modeling the acid treatment of the dolomitic collector of an oil formation bottom-hole zone is considered with account of rock colmatation. Themodeling is performedwithin the framework of mechanics of multicomponent and multiphase flows using the mean values of the reservoir porosity and permeability with account of kinetics of the acid digestion of the dolomitic rock. A mathematical model of the process that allows for liquid seepage flow and the chemical reaction of the acid with the rock matrix proceeding in the kinetic regime is presented. On the basis of the model proposed the motion of an active admixture and the variation in the filtration parameters of the formation in the process of the reactant pumping are investigated. The rock colmatation effect on the acidizing process is estimated. Numerical calculations are performed and the process characteristics are determined.

Suffusion is a selective erosion of fine particles under the effect of seepage flow within the matrix of coarser particles. This complex phenomenon appears as a combination of three process...

Internal erosion involves migration and loss of soil particles due to seepage. The process of fluid&ndash, solid interaction is a complex multiphase, coupled nonlinear dynamic problem. In this study, we used Particle Flow Code (PFC3D, three-dimensional PFC) software to model solid particles, and we applied computational fluid dynamics (CFD) and the coarse mesh element method to solve the local Navier&ndash, Stokes equations. An information-exchange process for the PFC3D and CFD calculations was used to achieve fluid&ndash, solid coupling. We developed a numerical model for internal erosion of the soil and conducted relevant experiments to verify the usability of the numerical model. The mechanism of internal erosion was observed by analyzing the evolution of model particle migration, contact force, porosity, particle velocity, and mass-loss measurement. Moreover, we provide some ideas for improving the calculation efficiency of the model. This model can be used to predict the initiation hydraulic gradient and skeleton-deformation hydraulic gradient, which can be used for the design of internal erosion control.

Losses in agricultural water conveyance and distribution systems are caused by two main reasons: seepage and improper operation of canal structures. This study examined the potential of Automatic Control Systems (ACS) to simultaneously reduce seepage losses and improve the operational performance of structures. To achieve this goal, a seepage model was integrated with an operational simulation model. The former model simulated the seepage flow throughout the main irrigation canal for different operational conditions imposed by the operational model. The ability of the integrated models to simulate reduction in losses was tested for the main canal of an irrigation district in southwest Oklahoma, United States (U.S.). Three combinations of the ACS and seepage model were studied, where ACS included or lacked inline water storage as an operational strategy and the seepage model simulated seepage rate for existing or maximum potential conditions. Three scenarios of reducing target levels in the canal to reduce seepage losses were considered for each combination. The results showed that without inline storage, considerable reduction in operational and seepage losses could be achieved for variable target levels. However, the adequacy indices for all off-takes were poor and proved water delivery process was unreliable and unacceptable. With inline storage, operational and seepage losses were reduced by 8–9% and 3–7%, respectively, while good adequacy indices were obtained, indicating an appropriate water delivery. The same ACS was able to significantly reduce losses while maintaining acceptable water distribution and hydraulic conditions under maximum seepage that can potentially occur in the studied irrigation canal. The control system proposed in this study can be a reliable and practical solution for reducing two main sources of water losses within irrigation districts and thus improving districts-level water productivity.

本研究では，水を吸収すると膨張する吸水性粒子の間隙に浸入する自由液面流れを有限体積法により計算する手法を提案する．吸水性粒子の膨張により，水に接する粒子の固体領域が広がり，その影響を粒子表面の流速と圧力の境界条件として考慮する．この計算手法を用いて非吸水性粒子間隙の lock-exchange 問題や単一の吸水性粒子の膨張問題を計算し，高密度流体側のフロント位置や水の体積保存性について基本的な検証を行った．さらに，複数の吸水性粒子間隙に浸入する dam-break 流れに対する数値実験を行った．その結果，粒子間隙におけるフローパターンは粒子の膨張に大きく影響を受けること，また粒子の吸水速度が大きくなりすぎると粒子間隙へのフロントの進行が阻害され，領域全体の粒子吸水量が低減する可能性があることを示した．A computational method was proposed for the free-surface flows intruding between multiple absorbent particles on the basis of the finite volume method. In the proposed method, the solid area of the particle, which is in contact with water, expands due to the swelling of the absorbent particle. The influences of particle swelling and water absorption on flows are considered with velocity and pressure boundary conditions on the particle surfaces. The proposed method was first applied to the lock-exchange problem in porous media, which consist of multiple non-absorbent particles. Second, the swelling of a single absorbent particle was calculated with the present method in saturated and unsaturated conditions. The basic applicability of the proposed method was confirmed through the discussions about the front position of the heavy current in the first calculations as well as the volume conservation of water in the second investigations. In addition, the proposed method was applied to the dam-break flows in the porous media, which consist of multiple absorbent particles. As a result of the numerical experiments, it was demonstrated that the flow patterns intruding the porous media are largely affected by the swelling particles. In particular, it was found there is a possibility that the total amount of water absorption decreases due to the blocking of the flows by the swelling particles even in case the water absorption speed of the particles is sufficiently high.

ABSTRACT: Lightweight expanded polystyrene (EPS) block geofoam (geofoam block) is commonly used as a replacement of the heavy in situ soil during slope remediation in order to reduce driving forces. The design procedure requires the use of permanent drainage systems to alleviate hydrostatic pressures in geofoam block slope systems. In this study, small-scale laboratory lysimeter experiments investigated the behavior of a stabilized sandy slope with a geofoam block slope system experiencing seepage. An internal drainage system was incorporated by grooving dual drainage channels (weep holes) on the top and bottom side of the geofoam blocks. A lysimeter with dimensions of 60 cm height, 20 cm width, and 200 cm length was constructed in the laboratory. Slopes were constructed by compacting sand. The geofoam blocks (2.5 cm height, 5 cm width, and 15 cm length) were placed on the sandy slope face with an angle of 45° in ‘one row' and ‘two rows' configurations. The experiments were conducted under constant water pressure heads (25-, 38-, and 50-cm pressure head boundary conditions) in the water reservoir located at the opposite end of the lysimeter from the geofoam blocks. In general, the lightweight geofoam blocks could not resist earth and hydrostatic pressures under seepage. The back-slope was not self-stable under seepage conditions, and deep-seated global stability failures were observed, except for the remediated slope at the 25- and 38-cm pressure head boundary conditions. The internal drainage system was ineffective at dissipating piezometric pressures at the higher seepage gradients investigated at this lysimeter scale. Numerical slope stability modeling confirmed these observations, predicting a factor of safety below the critical value for global stability in cases where failure was observed. More elaborate geofoam block configurations and/or drainage systems should be used to increase resistance against global stability failure caused by higher seepage gradients.

Base on the design of seepage control, the three-dimensional non-steady saturated - unsaturated seepage finite element analysis program CNPM3D is used to establish the three-dimentional finite element seepage model of junction area during operating period. The seepage field of dam site area is studied under the different anti-seepage curtain arrangement scheme. Specifically, the seepage gradient and the seepage discharge of the panel, major material zone, foundation curtains and two sides abutment curtains are analyzed to evaluate the stability of the major district of dam area, in order to provide suggestions for choosing the seepage control standard in the next deepen design stage.The calculation results show that the panel and the impervious curtain anti-seepage effect is remarkable.Impervious curtain can greatly reduce the total seepage flow of the dam and its foundation.However the curtain deepened to 1Lu has little effect on seepage discharge. It is showed that the seepage prevention standards of 3 lu should be proposed in the deepen design stage for both security and economic benefit. The achievement and experience of this seepage prevention design should be taken into consideration for other similar projects.

Significant changes in spontaneous potential and exciting currents are observed during water and grout injection in a simulated porous media. Obvious correlations between the seepage flow field and the electric field in the porous media are identified. In this work, a detailed experimental study of geoelectric field variation occurring in water migration was reported by analyzing water and grout injection processes in a simulated porous media. The spontaneous potential varies linearly with the thickness of unsaturated porous media. Very interestingly, the spontaneous potential generated in the second grout injection exhibits some “memory” of previous grouting paths. The decreases in spontaneous potential observed during grout injection is very probably due to that the spontaneous potential variations are primarily caused by electro-filtration potential, as indicated by the far larger viscosity of grout compared to that of water. The geoelectric response can be utilized to effectively identify the grouting paths in water-bearing rocks.

Development of the area is characterized by a natural Yusupov slowdown selection of oil by a significant depletion of reserves and a sharp watering wells partially associated with aging wells, so to ensure the stability of oil production requires the use of technology to block the formation of washed areas to reduce water production and enhanced oil recovery, due to redistribution of filtration flows, as well as technology allows to eliminate casing flows. Currently, there is a huge amount of reagents and technologies for the technology of blocking washed formation zones (BWFZ). These technologies allow to increase the resistance in the high permeability zones layered formation that promotes redistribution of seepage flow directions in the area of low-permeability oil-saturated areas. The main objective in the development of technologies to block the formation of zones of washed and technologies associated with insulation casing flows, include the search and selection of effective compounds insulating compositions. An analysis of the fishing experience of similar works can formulate the basic requirements for blocking composition. The main objective in the development blocking out technologies in highly watered zones and technologies associated with insulation casing flows, include the search and selection of effective compounds insulating compositions. One of the promising technologies blocking formation zones are washed with injection technology gelling compositions based on aluminosilicate "Syenite". Analysis of the pilot testing of the gel-forming composition "Syenite" showed high technological efficiency, but in the analysis were identified disadvantages associated with low technological gelling composition "Syenite" associated with the preparation of these compositions, therefore, proposed a new formulation based on dicalcium silicate (2KS ) for the conditions Yusupov area Arlanskoye field having higher processability as compared to the analyze gelling composition "Syenite" for the new gelling composition based 2KS hydrochloric acid and subsequently composition "CAS", a complex of laboratory experiments. The results of studies of physical and chemical properties of a new gel forming composition «CAS». Established rheological characteristics of the new composition. The possibility and ways of regulating the composition of the gelation time. With filtration tests show that the proposed composition is capable of effectively blocking the highly watered layers.

Stability of sheet-pile walls is often very sensitive to seepage flow. In the presence of seepage flow, the reduction in passive pressure on one side and increase in active pressure on the other side of the wall increase the risk of the instability that may precede instabilities due to piping or ground heaving. In this research the earth pressure behind sheet-pile walls in granular soils is studied. The flow field is computed by the finite-element method and the slip lines (stress characteristics) method is utilised to compute the associated stress field required to compute the effective passive pressure. The same finite-element mesh and interpolation functions are used to solve the flow field and to interpolate the seepage forces in the stress field solved by the stress characteristics method. Comparisons are made to verify the numerical results with those values available in the literature; these show reasonable agreement. The stability of sheet-pile walls is then analysed for a number of different problems with varying geometries and boundary conditions. These different geometries and boundary conditions are expressed in terms of non-dimensional factors and results are plotted.

This paper studies the seepage flow mathematical model of three-area composite reservoir under three kinds of outer boundary conditions (infinite boundary, constant pressure boundary and closed boundary), in which influences of well-bore storage and skin factor are not taken into consideration. On the basic of theory of similar structure of solution of boundary value problem of differential equation, this paper obtain the solution of the seepage flow model of three-area composite reservoir. The study is not only conducive to further analyze the inherent law of the solution and solve corresponding application problems, but also easy to compile corresponding analysis software.

Nile valley quaternary aquifer is in direct hydraulic interaction with Nile River, canals and drains. Therefore, implementation of new Esna barrage leads to enhancement of seepage flow from Nile River toward adjacent agricultural lands, impedance of drainage conditions and increase in the shallow groundwater levels beneath buildings in urban areas. Therefore, Esna city was selected as the study area to assess the impact of the barrage effect on groundwater aquifer and to propose mitigation measures. The most powerful method for studying the problem is developing a groundwater model based on monitored groundwater levels and simulating the effect of the proposed measures. Results indicated that Nile River in reaches upstream the barrage feeds the aquifer. Then, a model is used to test the effect of the mitigation measures on the surrounding settlements. Results also indicated that using cut off drains with depth of 2.5 m is the most effective and safe solution, in terms of direct impact on the buildings without need for operation cost – only maintenance cost will be needed. Also, implementing a sewage network in the city as a long-term solution is recommended. Keywords: Groundwater rise, Surface water/groundwater interaction, Numerical modeling, Esna barrage, Esna city, Upper Egypt

A seepage catalyst packing internal (SCPI) as a good alternative for catalytic distillation internals was investigated in this work. The seepage flow behavior and liquid holdup characteristics of the SCPI have a significant influence on the performance and industrial design of a catalytic distillation column with SCPI, and the present study focused on this issue. Measurements of the seepage flow and liquid holdup of the SCPI were achieved using a 100-mm-diameter plexiglas tube and a 600-mm-diameter Perspex column, respectively. The experimental results were used to develop a series of correlations to predict the liquid holdup of the SCPI. Again, a comparison to the experimental data showed good agreement. It was concluded that the model represents the real process with satisfactory accuracy, although some deviations were observed. Furthermore, compared with two classical catalytic packings, the experimental results show that the SCPI has a much larger liquid holdup, which is advantageous for the reaction....

The bottom friction beneath random waves is predicted taking into account the effect of seepage flow. This is achieved by using wave friction factors for rough turbulent, smooth turbulent and laminar flow valid for regular waves together with a modified Shields parameter which includes the effect of seepage flow. Examples using data typical to field conditions are included to illustrate the approach. The analytical results can be used to make assessment of seepage effects on the bottom friction based on available wave statistics. Generally, it is recommended that a stochastic approach should be used rather than using the rms values in an otherwise deterministic approach. This is a submitted manuscript of an article published by Elsevier Ltd in Applied Ocean Research, 23 July 2014.

The smear zones are usually caused by the installation of vertical drains in fine-grained soil. An analytical solution for contaminant extraction using well injection depth extraction (WIDE) system considering the smear effect was developed. The injection rate was assumed to be equal to the retrieval rate to maintain full saturation and steady-state seepage flow. The results obtained by the proposed analytical solution agree well with those obtained from the finite element method. An illustrative example was presented to show the influence of the smear zones and results reveal that the smear zone can have a great influence on the contaminant extraction from soils. The 500-hour base concentration of acetone in the middle of the contaminated soil increases by a factor of approximately 1.9 when the effect of the smear zone is considered in the model.

The present paper investigates the problem of the stability of the tunnel face under seepage flow conditions based upon the so-called “method of slices”. This computational model improves the limit equilibrium method of Anagnostou and Kovari (1996) by treating the equilibrium in the wedge consistently with the overlying prism, i.e. without an a priori assumption concerning the distribution of the vertical stresses. Furthermore, it shows that tensile failure of the wedge may be more critical than shear failure, if the gradient of the hydraulic head in the ground ahead of the face is high. For an approximate distribution of the hydraulic head in the ground around the tunnel face, we derive a closed-form solution for the necessary face support pressure. In addition, we provide normalized diagrams, which allow for a quick assessment of the stability of the tunnel face.

By numerical calculation, it analyzed the seepage effects of plastic concrete cut-off wall in in construction period. On construction period, the seepage flow from inside of channel to outside at unit length is 0.753m3/h. The seepage flow from under plastic concrete cut-off wall is 0.646m3/h which is 85.79% of total seepage flow. Under certain condition on operation period, the seepage flow from inside of channel to outside at unit length is 0.394m3/h. The seepage flow from under plastic concrete cut-off wall is 0.358m3/h which is 90.86% of total seepage flow. Under another condition on operation period, the seepage flow from inside of channel to outside at unit length is 0.249m3/h. The seepage flow from under plastic concrete cut-off wall is 0.236m3/h which is 94.78% of total seepage flow. In It showed the plastic concrete cut-off wall has obvious effect.

Stress sensitivity plays an important role in the development of a tight low-permeability gas reservoir. With the constant low-permeability reservoir exploitation, formation pressure drop, rock net effective coverage pressure increase, the rock pore is resulted in deformation and the seepage flow of fluid in a low-permeability reservoir no longer followed Darcy flow law. With the further exploitation of reservoirs, reservoir stress sensitivity is enhanced, so evaluation on the stress sensitivity on reservoir development was a burning question. The authors present results of those experiments that simulated the permeability changes via the net confining pressure in the lab and give the influencing factors of stress sensitivity.

Z_SOIL, commercial software based on finite element technique is proposed to simulate the unsteady seepage flow through earth dams, with variable upstream water heads. Experimental work, using Permeability and seepage model is conducted to verify the reliability and the accuracy of the numerical model. The accuracy and reliability of the model are adequate to handle unsteady flow problems with complex conditions. It is also demonstrated that the method of determining the seepage surface through the saturation described is natural, logical and practical in actual applications. The method provides a relatively simple computing scheme, as compared with traditional methods

A finite element model of tailings dam model was used to simulate the steady seepage field and analysis the stability under different working conditions. The head contour, velocity, seepage flow and seepage gradient was analyzed. The stability against sliding in this tailings dam was analyzed with the help of the simplified Bishop method which is based on rigid body limit equilibrium coupled with seepage force. The security coefficient under different working conditions was calculated. The analysis result shows that the safety factor meets the specification requirements, and which provides reference for the stability evaluation of tailings dam.

The mean net bedload sediment transport rate beneath random waves is predicted taking into account the effect of seepage flow. This is achieved by using wave half-cycle bedload sediment transport formulas valid for regular waves together with a modified Shields parameter including the effect of seepage flow. The Madsen and Grant (1976) bedload sediment transport formula is used to demonstrate the method. An example using data typical to field conditions is included to illustrate the approach. The analytical results can be used to make an assessment of seepage effects on the mean net bedload sediment transport based on available wave statistics. Generally, it is recommended that a stochastic approach should be used rather than using the rms values in an otherwise deterministic approach. This is a submitted manuscript of an article published by Elsevier Ltd in Ocean Engineering, 19 March 2014.

Seepage flow renders tailings dams vulnerable to failure during their staged construction. Draining is one of the most effective measures in improving dam stability. In this study, a stepwise-coupled hydro-mechanical model is employed to examine the effect of seepage control on the stability of a tailings dam during its staged construction. The settlement and deformation of the tailings under gravity load are modelled using the Duncan–Chang non-linear elastic E–B model, and the seepage flow through the tailings with drains is characterised by a variational inequality formulation of Signorini’s condition. The Kozeny–Carman equation is calibrated to illustrate the dependence of hydraulic conductivity on the porosity and volumetric deformation of the tailings. The proposed model was applied to assess the performance of the drains designed for the Luogou tailings disposal in Luanchuan County, Henan Province, China. Numerical results show that the stress-induced variation in tailings permeability could be of 1...

With the permeability of reservoirs becoming lower, the non-Darcy flow phenomenon becoming more obvious. The rules of fluid flow in low permeability reservoirs need to be researched through experimental method. The authors get the function relation between the ratio of resistivity and the concentration of solution through core experiments. The authors performed the single-phase fluid displacement experiment in low permeable natural sandstone plate model, then calculated the spreading condition of fluid in the model by recording the change of resistivity between measuring points. The application of resistivity method is verified the feasibility of measuring seepage flow field.

Water losses due to seepage through the body of the dam is something problems that often occur in planning a dam. The purpose of this research to knows the phenomenon of the seepage flow on the soil through the dam body or under the body of landfill dam. The research methods used the Test Laboratory simulations of homogeny Dams model using with three of the soil density (58.20%, 68.27%, and 76.33%) and with the application of the three theories of seepage in dam body (Dupuit, Schaffernak, Cassagrande). The results of this research indicate seepage flow far that the more the long time it takes to perk, the higher the discharge and the father the distance small then the seepage discharge of seepage, and the higher the density of the ground than the lower depths of the seepage

Artificial ground freezing (AGF) is a reliable technique for ground improvement to address adverse geotechnical engineering conditions. The formation of a freezing curtain during the AGF process is crucial as it serves to control groundwater flow and enhances the strength of the soil. However, groundwater flow has a considerable influence on the formation of the freezing curtain because it provides a continuous source of heat. Thus, to investigate the influence of water flow on the freezing process during AGF, a moisture–heat coupling model was proposed considering ice/water phase transition to quantify the temperature distribution in soil during the freezing process. The proposed numerical model was further validated using thorough laboratory tests under various seepage flow conditions. Finally, a numerical simulation of AGF was conducted for the end well of the Harbin metro station in China. Five representative monitoring points on the end well were selected and continuously monitored for 30 days to predict the formation of a freezing curtain. It was observed that the temperature results obtained using the proposed model are consistent with actual field monitoring data.

The objective of this study is to evaluate different fog seal materials, including Tianjin BEST - micro-seal bonding reductant (BEST-MBR), American MasterSeal, and a newly designed bio-oil–modified fog seal with sand (BFSS) using various sand contents. The workability of all materials was tested based on the fluidity test, seepage performance test, and the indoor skid resistance test. A new method to evaluate the surface texture of solidified fog seal with sand (FSS) material was performed based on the aggregate image measurement system II. The test results show that when the seepage flow evaluation index is set to a 1.5-mm seepage width, the seepage flow value should not be less than 0.2, whereas when the width is 2 mm, the flow value should not be less than 0.7. In addition, the surface texture evaluation indicates that some smaller grooves are formed around the sand particles after the BFSS is solidified and the structural depth of the material surface is increased. The BFSS material with 20 % sand content is slightly better than the BEST-MBR in terms of skid resistance, whereas it is still lower than MasterSeal. The addition of bio-oil lowers the need for asphalt binder, leading to energy savings. Thus, BFSS is a relatively desirable FSS material.

Hydrogeological experiments provide an important means to understand groundwater seepage and solute transport problems. Basic hydrogeological parameters can be obtained for use in assessing groundwater resources. In current porous-media research, studies of side-wall flow are in a preliminary and qualitative phase, and lack systematic and comprehensive understanding. Side-wall flow refers to the non-uniform infiltration and solute transport that occurs near the seepage device boundary. Flow dynamics depends on the fluid under the specific hydraulic conditions, physical properties and chemical composition, medium permeability, the roughness of the side wall, geometric features, and physical chemistry. Such phenomena not only occur in indoor water flows and solute transport, but also under natural conditions in the field. Side-wall flow has features both in common as well as distinct from preferential flows. In porous-media experiments, once side-wall flow commences, it affects the groundwater flow field and chemistry field, resulting in parameter values deviating from actual values. Based on a comprehensive analysis of the influence of side-wall flow, a definition of the side-wall flow effect in porous media is given. Three directions of research are identified concerning side-wall flow: the mechanism of the side-wall flows effect, the study of its quantitative impact on seepage flow and solute transport, and the methods and measures that need to be taken in hydrogeological experiments to reduce (or prevent) side-wall flow development.

東日本大震災では津波により多くの防潮堤が崩壊した．防潮堤の崩壊の原因には波力の作用とともに浸透力の作用が指摘されている．同様の崩壊は河川における堰でも河川水位の差によって発生することが報告されている．しかし，津波などの波力に加えて浸透力が作用する土構造物の安定性は，極限平衡法や支持力公式等の既存の設計手法では評価することが難しい．本研究では，地盤材料に関する剛塑性構成式を用いた剛塑性有限要素法ならびに浸透流解析によるハイブリッド解析手法を開発し，浸透力が作用する地盤の極限支持力・破壊形態を合理的に評価できることを明らかにする．, In 2011 off the Pacific coast of Tohoku Earthquake, lots of seawalls were destroyed by Tsunami. By the survey of destroyed seawalls, not only the wave pressure to dyke but also seepage force in ground have been reported to contribute to the instability of seawalls. However, it has been difficult to consider the effect of seepage force in the stability analysis of seawalls. This paper presents the hybrid stability analysis of rigid plastic finite element method and seepage finite element method in order to evaluate the total stability of seawall against tsunami. To simplify the problem, ultimate bearing capacity of caisson is investigated under the specific seepage condition by setting the sea water levels of upstream and downstream of caisson. Through case studies, the effect of seepage force on the instability of seawall is examined by handling the magnitude of seepage force. The effect of embedment of caisson on ultimate bearing capacity is also investigated. The depth of embedment works to the stabilization of seawall from the two aspects. One is the mechanical stabilization of caisson by overburden pressure and the assistance in shear strength of overburden ground. The other is the decrease in seepage force by embedment. The obtained ultimate bearing capacity shows the proposed analysis method well simulated the stability of caisson under the seepage force condition.

In this paper, considering on the real threshold pressure gradient (TPG), the mathematical model for low velocity non-Darcy unstable gas flow was established for the tight gas reservoir. Based on the low velocity non-Darcy unstable gas flow model, the gas flow model in heterogeneity formation was developed, and the analytical solution was obtained on the condition of constant production for inner boundary. Then we calculated the model numerically by Matlab programming. Its analyzed that the pressure distribution and the influencing factors such as production rate, producing time, reservoir thickness and the threshold pressure gradient. We compared the heterogeneity formation with the homogeneous formation by the heterogeneity low velocity non-Darcy unstable gas flow model, which shows great difference and illustrate the significance of research on heterogeneity.

Seepage problem is of great importance to the stability of the soil dams in deep overburden foundation which is composed of coarse-grained soils. With a discussion on the relationship between particle size distribution and seepage law of the coarse-grained soils, Darcy's law was applied to simulate the seepage flow process of the deep overburden foundation of the Wudongde project. The variational inequality approach of the Signorini's type was used to solve the seepage field of the cofferdam site to eliminate the singularity at the seepage points. The result illustrates that the seepage control system composed of a concreted cutoff wall and geo-membrane sloping wall exhibits perfect performance under normal operation conditions. The differences of the seepage field characteristics under different hydraulic conductivities combinations of overburden layers were discussed. Finally, stabilities under different operation situations were evaluated with linear and nonlinear analysis with a consideration of the effects of seepage process.

The study on seepage flow passing through single fractures is essential and critical for understanding of the law of seepage flow passing through fracture networks and the coupling mechanisms of seepage field and stress field in rock masses. By using the fractal interpolation to reconstruct a natural coarse fracture, as well as taking into account the microstructure of the fracture, the numerical simulation of seepage flow passing through the coarse fractures with two distinct vertical scaling factors is conducted based on the MRT-LBM model of the lattice Boltzmann method. Then, after obtaining the length of the preferential flow pathway, the permeability of the two kinds of fractures is estimated respectively. In view of difficulties in locating the preferential flow pathway of natural fracture networks, by numerical tests a transect permeability weighted algorithm for estimating the fracture network permeability is proposed. The algorithm is not specific to one or more particular preferential flow pathways, but considers the contribution of each section to hinder the fluid passing through the medium. In order to apply the new algorithm, by capturing the structure of fracture networks based on the image-processing technique, the numerical simulations of seepage flow passing through two groups of natural fracture networks is carried out, the permeability is forecasted and the partial flows are reproduced for both cases. It is found that the preferential flow pathway emerges at the beginning of evolution, then is strengthened subsequently, and finally reaches a steady status. Furthermore, by using the proposed method some details on local flow can be clearly observed such as backflows and vortices at local branches can exist simultaneously and so forth, suggesting the validness of the proposed method for multiscale simulations of seepage flow.