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A modified triaxial shear test apparatus was used to investigate the factors influencing the onset of suffusion (migration of fine particles from soil without a change in volume) and suffosion (migration of fine particles from soil with a change in volume or a local collapse of the soil structure). A new criterion was developed to predict the seepageincited internal instability phenomena of suffusion or suffosion. A flexible wall permeameter, a seepage flow control system, and volume change measurement instrumentation were designed and manufactured for the study.

This work experimentally investigates the turbulent flow characteristics of developing and fully-developed flows over a rough bed channel that is subjected to downward seepage. Instantaneous 3D velocities were collected using an acoustic Doppler velocimeter (ADV) in the developing and fully-developed flow regions, along the channel centerline, to analyze different turbulent statistics. Observations revealed that the streamwise and vertical velocities were higher in developing flows, whereas the Reynolds shear stresses, and turbulence intensities, were smaller. The downward seepage would affect the velocity distributions and flow depth in both the developing and fully-developed regions. Therefore, new equations to represent the distribution of the turbulence intensities were proposed, and a comparison with the current literature is provided. The investigation of the Reynolds stress anisotropy tensors concludes that the degree of anisotropy in fully-developed flows is lower than for developing flows.

There are many studies on the nonlinear relationship between seepage velocity and hydraulic gradient in coarse granular materials, using different approaches and variables to define the resistance formula applicable to that type of granular media. On the basis of an analysis of the existing formulations developed in different studies, we propose an approach for comparing the results obtained by some of the most important studies on state-of-the-art seepage flow in coarse granular media.

International audience; Surface and subsurface flows interact at different spatial and temporal scales through the development of saturated areas occurring when the aquifer reaches the surface. While this interaction exerts a strong control in the partitioning of water between base flow, seepage flow and overland flow, its quantification remains a challenge. Here, we propose a novel modeling approach based on two equivalent hillslopes to capture spatial and temporal variabilities of the main processes. We calibrate their subsurface hydraulic properties based on the temporal dynamics of stream discharge. The model is tested on two pilot catchments located in Brittany (France). For both catchments, the model is successfully calibrated on 40 years of stream discharge data. The results demonstrate that contrasted hydraulic properties are required, with: (1) a relatively low conductive hillslope (conductivities between 3x10–8 m/s and 2x10–6 m/s) enhancing overland flows during recharge periods while also sustaining low flows in the late recession period through slow aquifer discharge, and (2) a highly diffusive hillslope (diffusivity between 5x10–3 m2/s and 3x10–1 m2/s) dominantly shaping the event- to seasonal-scale streamflow recession behavior. The strong contrast of the two hillslopes reveals the fundamental role of heterogeneity in controlling groundwater storage-discharge functions, ruling out any homogeneous equivalent at the catchment scale. Low flows appear to be a non-obvious combination of the contributions of the two hillslopes, the less diffusive hillslope catching up to the more conductive one by the end of the low flow period. Catchment-scale responses integrate complex interactions between recharge, groundwater and overland flows through the volume of subsurface storage and the extent of the saturated area..

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 analysi...

The multi-physical processes during embankment breaching due to overtopping are complex and known to depend upon seepage flow through the embankment. A numerical breach model for progressive embankment breaching is proposed, taking the seepage flow into account including its influence on slope stability due to apparent cohesion effects. Overtopping and embankment surface erosion are computed using finite-volume methods applied to the 2D shallow-water and the Exner equations. The seepage flow is modelled using a Lattice–Boltzmann approach solving the 3D Richards’ equation. The modules are executed in a coupled manner with dynamically adapted boundary conditions. The breach side wall failures are considered using a geometrical approach based on critical failure angles. This approach is enhanced to account for apparent cohesion effects by dynamically adapting the critical failure angles as a function of the water saturation in a heuristic way, as a major enhancement compared to previous approaches. T...

Sediment transport is a geophysical phenomenon in which sediment particles are driven to move in streamwise and vertical directions by various forces. Almost all existing formulas of sedime...

Silty sand is a kind of typical marine sediment that is widely distributed in the offshore areas of East China. It has been found that under continuous actions of wave pressure, a mass of fine particles will gradually rise up to the surface of silty sand seabeds, i.e., the phenomenon called wave-induced soil erosion. This is thought to be due to the seepage flow caused by the pore-pressure accumulation within the seabed. In this paper, a kind of three-phase soil model (soil skeleton, pore fluid, and fluidized soil particles) is established to simulate the process of wave-induced soil erosion. In the simulations, the analytical solution for wave-induced pore-pressure accumulation was used, and Darcy flow law, mass conservation, and generation equations were coupled. Then, the time characteristics of wave-induced soil erosion in the seabed were studied, especially for the effects of wave height, wave period, and critical concentration of fluidized particles. It can be concluded that the most significant soil erosion under wave actions appears at the shallow seabed. With the increases of wave height and critical concentration of fluidized particles, the soil erosion rate and erosion degree increase obviously, and there exists a particular wave period that will lead to the most severe and the fastest rate of soil erosion in the seabed.

Suffusion is a typical form of the internal erosion, which leads to worldwide failures of embankment dams. Extensive investigations have been carried out to characterize suffusion process. However, less research has been focused on the lasting heterogeneity development by suffusion physically and quantitatively, despite the phenomenon been found in literatures. This paper proposes a vertical layered theoretical model based on the force balance of movable particles under one-dimensional upward seepage on gap-graded specimens. In the model, the finer particles loss was deduced respectively in every layer, combined with the coupled calculation including the seepage flow, the soil particles movement and the soil structures changes. The model was verified with experiments and showed a good consistency in the critical hydraulic gradient, layered water head, seepage velocity, finer particle loss and hydraulic conductivity. Finally, suffusion induced soil grading changes and the implications to the suffusion development are discussed quantitatively. The results indicate that the theoretically modeled soil heterogeneity changes are consistent with the suffusion phenomenon and the experimental observations. The outlet and inlet are more sensitive to suffer suffusion under upward seepage, as the two layer have more violent fine particles loss and soil grading coarsening. The layered model can theoretically simulate the development of suffusion with the sequential changes of the soil structures and serves as a new approach to understand the process in cohesionless soil.

Biofilm growth can impact seepage flow properties in the porous media, thereby affecting the performance of the infiltration systems. To better understand and characterize the biofilm distribution and its effect on seepage flow fields in the porous media with different morphologies, two-dimensional transparent flow cells were developed using X-ray images of zeolite, gravel, and ceramsite columns to study the effect of biofilm development and the pore structure on seepage flow properties. The results revealed that the filter morphology and biofilm growth significantly impacted the seepage flow field in porous media. With biofilm growth, a preferential flow pathway was more likely to be formed in angular filter cells (zeolite-shaped cells) than spherical filter cells (ceramsite-shaped cells). It was also found that microbial growth rate was closely related to seepage flowrate in 2D porous media cells. The biofilm grew faster in the areas with higher seepage flowrate. The biofilm accumulation did not seem to affect the location of the preferential seepage flow, probably due to the high permeability of the biofilm in the large pore throats. Although the water head loss of ceramsite-shaped cells was larger than that of two others due to its relatively smaller size of pore throat, the ceramsite-shaped cells presented small dead zone and short-circuiting, which means that ceramiste filter media had higher hydraulic efficiency.

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 mechanis...

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.

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

This paper reports laboratory experiments and numerical simulations of river embankment failure due to overtopping flow for different sediment sizes and different saturation conditions of embankment body. The effects of saturation and sediment size of embankment materials on the erosion process are discussed based on the results of the laboratory experiments. A numerical model is proposed to simulate the erosion process of embankments by overtopping flows. The proposed model considered the effects of infiltration process and resisting shear stress due to suction of unsaturated sediment. To simulate the embankment erosion phenomenon, the numerical model consists of four modules: two-dimensional (2D) shallow-water flow, seepage flow, sediment transport using a non-equilibrium model framework, and 2D slope stability. The validity of the developed model is tested using experimental data on embankment erosion. The numerical results on progressive embankment erosion agree well with the results of the sandy river embankment experiments.

The sheet piles are used below hydraulic structures to reduce seepage flow rate and hydraulic gradients at the outlet of such structures that are rested on the permeable foundations. Up to now, for analysis of seepage under hydraulic structures, a number of research works have been conducted in the form of numerical models. However, less field and laboratory works have been done to study the boiling phenomenon for the evaluation of the numerical models. In the present research work, a laboratory model was made to simulate seepage flow and its behavior downstream of a sheet pile under vertical and inclined configurations. The model consisted of a flume 2.2 m long, 0.8 m deep, and 0.4 m wide, in which vertical and inclined sheet piles were provided by cast acrylic sheet. The flume was made of steel frame and Perspex as well as thick glass sheets. Fine clean sand was used as an alluvial foundation and then compacted to a uniform density at the bottom of 40 cm of flume. Perspex sheets were used as she...

Die Berechnung variabel gesattigter Stromungen durch Dammbauwerke ist von groser technischer Bedeutung. Es existieren zahlreiche numerische Ansatze zur Losung der stark nicht-linearen Richard-Gleichung basierend auf Finite-Differenzen- (FDM) oder Finite-Elementen-Methoden (FEM). Vor kurzem wurde ein neuer Modellierungsansatz vorgestellt und validiert, welcher auf der Lattice-Boltzmann-Methode (LBM) basiert. Die LBM besitzt dabei einige vorteilhafte Eigenschaften, welche die Methode zu einer attraktiven Alternative insbesondere in Hinblick auf komplexe Geometrien und gekoppelte Simulationen machen konnen. In dieser Arbeit wird die LBM auf die 2-D- und 3-D-Richard-Gleichung auf strukturierten Gittern angewandt. Verschiedene Schreibweisen der Gleichung, basierend auf der effektiven Sattigung und der Porendruckhohe, unter Einbeziehung zweier Retentionsmodelle nach Brooks-Corey und Van Genuchten werden angewandt. Die Anwendbarkeit des Verfahrens wird in Hinblick auf idealisierte Testfalle und kleinskalige sowie grosskalige Dammbauwerke untersucht. Die Ergebnisse werden aufgezeigt und mit anderen ausgewahlten analytischen, experimentellen und numerischen Resultaten verglichen. An accurate determination of variably saturated seepage flow through earth embankments is an important engineering task. Numerous approaches exist solving the highly non-linear Richard's equation for this task, typically based on Finite Element or Finite Difference formulations. Recently, a modeling approach using the Lattice Boltzmann method (LBM) for the Richards equation was presented and validated on simple test cases. Models based on the LBM have advantageous characteristics concerning simplicity, complex geometries, parallel efficiency and the possibility to easily extend the model framework to other flow processes, making it suitable for coupled simulations. In this work the LBM is applied for the Richard's equation in 2D and 3D on structured meshes. Different formulations of the Richard's equation based on the moisture content and the pore pressure are used. Two types of retention models after Brooks-Corey and Van Genuchten are implemented. The applicability of the approach is investigated using idealized test cases and scenarios concerning small-scale and large-scale embankments. The results are compared to selected analytical, experimental and numerical results.

A strict hydromechanical solution is given to the problem of free seepage from watercourses (rivers, canals, water bodies, industrial and agricultural ponds) for a family of smooth and complex curvilinear profiles with the use of conformal mappings and with the representation of the flow domain as the basis of the water-course profile in the Zhukovski complex domain. All necessary parameters of the flow are determined, including the outline of the curvilinear profile of the watercourse, depression curves and constant pressure lines (isobars), seepage flow, etc. For the particular case of a circular base of the watercourse profile, the results of obtained solution coincide with the known exact solutions derived by V.V. Vedernikov and N.N. Pavlovskii. Specific numerical examples of calculations for watercourses with different relative widths are given.

Seepage flow through alluvial channel bed can affect significantly the Manning's roughness coefficient, n. Both downward seepage (suction) and upward seepage (injection) through the alluvial channel bed can either increase or decrease Manning's n when compared to its no-seepage value. Such variations in Manning's n due to seepage are presented quantitatively so as to bring awareness among design engineers and researchers that seepage should be considered as a parameter while estimating the value of Manning's n even for a given size of bed material.

Characteristic features are presented for the construction of deeply embedded sections of structures, for example, the erection of pit enclosures. Problems with the building of sheet-pile walls using cast-in-place piles screwed into predrilled hole under conditions whereby the natural seepage flow is retained are examined. New procedures are discussed for the installation of distributive and bracing bands for sheet piling. Conclusions concerning the expediency of use of the technical solutions under consideration, which are based on construction experience, are drawn.

There is an unknown risk potential related to the uncontrolled wastewater infiltrations from damaged sewers into soils affecting groundwater quality. The possible transformation processes during subsurface migration of pollutants are not well understood in their interactions under field conditions. In order to quantify the water and mass fluxes from single sewer leaks to groundwater mainly the hydraulics of water and mass transport in the unsaturated soils were investigated by experimental and numerical methods. The recently developed numerical code WTM (Water and Transport Model) was applied to different scenarios, including a two-dimensional experimental set-up simulating the water content and concentration development from a leaking pipe. Fine-grained soils because of their hydraulic parameters as well as high infiltration rates lead to a wider spreading of the seepage flow. Residence times related to unsteady infiltrations have been more depending on the initial water content than on infiltration rates. Analyses of the pore size distribution in soil columns exposed to long-term wastewater infiltration indicated clogging effects due to chemical or microbial transformation processes. Beurteilung von Abwassereinwirkung auf das Grundwasser mittels hydraulischer Bodenuntersuchungen Es gibt ein unbekanntes Gefahrdungspotential im Zusammenhang mit unkontrollierter Abwasserinfiltration aus schadhaften Kanalen in den Boden, wodurch die Grundwasserqualitat beeintrachtigt wird. Die moglichen Umsetzungsprozesse wahrend der Untergrundpassage von Schadstoffen sind in ihrem Zusammenwirken unter realen Feldbedingungen bislang nicht gut verstanden. Um die Wasserflusse und Stofffrachten aus einer einzelnen Leckage eines Abwasserkanals zum Grundwasser unter Berucksichtigung der Transformationsprozesse zu quantifizieren, wurde im Wesentlichen die Hydraulik des Wasserand Stofftransports in der ungesattigten Bodenzone mit experimentellen und numerischen Methoden untersucht. Das vor kurzem entwickelte numerische Modell WTM (Wasser-Transport-Modell) wurde auf mehrere Szenarien, einschlieslich eines zweidimensionalen Versuchsaufbaus, angewandt, um die Entwicklung des Wassergehalts und der Konzentrationen ausgehend von einer Rohrleckage zu bestimmen. Feinkorniges Bodenmaterial sowie hohe Infiltrationsraten fuhren zu einer breiteren Ausdehnung der Sickerstromung. Die Aufenthaltszeiten bei instationaren Infiltrationen sind eher abhangig vom Anfangswassergehalt als von der Infiltrationsrate. Die Auswertung der Porengrosenverteilungen in Bodensaulen, die uber einen langeren Zeitraum mit Abwasser beschickt wurden, zeigte Kolmationseffekte aufgrund von chemischen oder mikrobiologischen Umsetzungsprozessen.

While Darcy's equation is applied for laminar seepage flow problems, quadratic form of Forchheimer's equation is widely used in non-linear flow conditions. Many equations relating the coefficients of Forchheimer equation with characteristics of porous and fluid media have been proposed. This paper presents results of experiments carried out in a parallel flow permeameter with 2.7, 3.7, 5.3 and 8.0 mm size porous media. Applicability of Forchheimer's equation for a wide range of velocity of flow is studied and the drawbacks have been brought out. Reliability of application of earlier equations relating Darcy parameter and non-Darcy parameter of Forchheimer's equation with size of the media without specifying the limitations applicability is investigated and found that these equations have limited applicability.

The soil particle movement under seepage flow is one of the predominant mechanisms responsible for incidents and failures of dams and streambanks. However, little attention has been paid to the critical hydraulic gradient under two-dimensional (2-D) seepage flow. In this study, a theoretical model was established under 2-D seepage flow to predict the critical hydraulic gradients for soil particle movement. In this model, the sediment particle rolling theory was used, while taking into account the relative exposure degree of the soil grains and the seepage direction. The model was validated through qualitative analysis and comparison with previous data, and showed considerable superiority over Terzaghi's model. In addition, the effect of the soil internal instability, implying that the critical hydraulic gradient of unstable soil is lower than that of stable soil, was discussed. Various parameters of the model were also analyzed. The results showed that the seepage direction angle was positively related to the critical gradient, whereas the void and the mean diameter of the soil were negatively related to it. Finally, the model proposes a calculation method for the particle movement initiation probability, which is regarded as a key parameter in the sediment transport model.

A subsidiary weir is proposed to be constructed downstream of each of the existing barrages on the Nile river in Egypt to secure its stability, which might have been affected after the construction of the Aswan High Dam. The present paper is intended to investigate the characteristics of seepage flow beneath two structures with an intermediate filter. The downstream structure (the proposed weir) has a slopping middle apron and two flat aprons in the upstream and downstream sides and is also provided with upstream and downstream cutoffs. The upstream structure (the existing barrage) has upstream and downstream cutoffs. A conformai mapping technique is used to solve the problem. Equations to calculate the uplift pressure distribution acting on both the existing barrage and the suggested weir are obtained; also equations to calculate the values of exit gradient along the intermediate filter and the downstream bed are derived. The seepage flows which seep into and/or drained f r om the intermediate filter are...

Analytical solutions exist for the problem of determination of seepage loss from polygonal sections such as a triangle, a rectangle, and a trapezoid. In this investigation, seepage from circular and exponential sections has been calculated by a finite-difference-based numerical solution of the differential equation governing the seepage flow. The phreatic boundaries of the flow domain were described in terms of two parameters that are estimated by a minimization process. Such seepage computations were performed for a large number of independent dimensionless variables of the section geometry. Subjecting the computed seepage to regression analyses explicit equations for seepage loss from canals having circular and exponential cross sections have been obtained. Using these seepage-loss equations, the design variables for minimum seepage loss of circular and exponential canal sections have been obtained. The use of the design equations has been illustrated by design examples.

Transient, three-dimensional flux equations are solved by neglecting capillary forces in the first half of the paper, and in the second the steady-state seepage, where the capillary forces are significant, is treated. The following conclusions can be drawn by analysis of solutions for the cases of no capillary effects in unsaturated, anisotropic, layered slopes: (1) The seepage flow for these cases depends on the anisotropy of the soil. It further depends on the slope of the principal axis of the conductivity tensor. The seepage flow is completely independent of the slope of the soil surface. These findings make possible a new description of lateral flow mechanisms in slopes. Thus, the surprising result is that soil can possess a kind of “hydrological memory.” This is because the conductivity tensor can stay unchanged while the soil surface is altered. (2) Based on these findings, when a land fill cover is being designed, it is possible to obtain an optimal angle to minimize infiltration. Solutions for th...

1. A new phenomenon of activation of unloading deep zones under the effect of a large dam and deep reservoir is observed in rock masses of foundations of certain superhigh concrete, mainly arc, dams. The process of technogenic unloading of the natural stress state of the mass leads to its extremely deep decompression, substantially changing the conditions of interaction of elements of the dam — foundation — reservoir system.

1. It is necessary to revise urgently SNiP 2.06.05-84x with respect to the designs of dams being constructed in the northern construction-climatic zone, i.e., to remove all vagueness in understanding the basic design principles. 2. The top of watertight zones of dams should exceed the elevation of the HFL by amounts specified by SNiP. When necessary, in connection with seasonal freezing and thawing of the upper part of the core, additional measures should be provided for ensuring local static stability and seepage strength. 3. Large dams should be evaluated under the aegis of the National Committee on Large Dams, whose role in this matter must be increased. It is necessary to establish legislatively the procedure of changing the designs of dams after approving the projects. 4. A coordination center processing all information on construction and operation should be created for large dams and dams being constructed in the northern construction-climatic zone. The best solutions should be recommended for implementation. 5. It is necessary to reconstruct the upper part of the dams of the Kureika hydrodevelopment, using above the NPL soils of an analogous composition for the entire zone of the core with provision of its seepage strength by an additional filter layer of sorted sand of fractions 0–10 mm. Reconstruction of the dam crests will make it possible not only to obtain additional power production due to the prism of the reservoir between the NPL and HFL within 150–200 million kWh/yr.

Harnessing small and medium rivers is important for the maximum use of the potential of local water resources. When assessing the possibility of constructing earth dams as part of small hydrodevelopments, especially in remote, difficultly accessible regions, it is important to be able to use local natural materials and technological schemes in which the construction of the bulk of the shoulders and watertight elements can be done independently. Of interest under such conditions is the use of the infilling method for reducing the permeability coefficient in the shoulders and foundations of dams composed of coarsefragmental soils. Insignificant volumes of fine-grained materials in the form of sediments or clay and sandy loam deposits can be used for this without the use of scarce building materials and complex technologies [1, 2]. The results of investigating the infilling process in interrelation with the temporal change in the permeability coefficient and parameters of the seepage flow on the basis of a probabilistic model are given below. This makes it possible to most completely take into account the characteristics of the particle-size distributions of the soils of the dam body and infilling material and their change during filling of pores. A variant of a rockfiU dam proposed for small Pamir hydrostations is examined as an example. Infilling is carried out after constructing the dam with complete or partial filling of the reservoir by delivering material to the upstream slope from floating pipelines. Calculation Method. The process of filling the soil pores of the dam and foundation with finer material (infiller) occurs in the form of movement of the particles of this material along the pores. The sizes of an individual particle and of the pore encountered by it have a random character. The mathematical condition under which the infiller particle is retained in the soil pores is written in the following form

When designing and constructing thawed earth—rock and earthfill dams in the northern construction—climatic zone it is necessary to specify the following measures for providing reliable and safe operation of the dams. 1. To construct heated drainage in the downstream shoulder for possible formation of seepage paths from the first moment of operation of the dam and elimination of the possibility of an increase of head in the frozen downstream shoulder. 2. To provide conditions of preventing removal of material of the second layer of the reversed filter into the rock fill, for which a transition rock layer of the appropriate size distribution and density is placed.

1. The main problems when designing pressure tunnels are the maximum use of the bearing properties of the enclosing soil mass and prevention of leakage of water from the structure into the mass. The first condition is fulfilled completely in the case of using unlined tunnels, but here the second problem is not always solved. The optimal solution satisfying both requirements in high-head tunnels is the use of a combined lining consisting of an inner steel lining and outer concrete ring. 2. The length (boundary) of the steel lining in a pressure tunnel is determined on the basis of two criteria: the bearing capacity of the rock mass; the size and length of the seepage path from the tunnel into “dry” underground workings or to an open slope. 3. The criteria of the bearing capacity of the rock mass is characterized by two main parameters: deformation-strength characteristics and height of the stratum covering the tunnel. 4. The criterion of the size and length of the seepage path is determined by the seepage strength of the rock mass and stability of the underground workings an open, slopes located in the zone of the seepage flow issuing from the tunnel. 5. At present there is no unified method of determining the boundaries of a steel lining in pressure tunnels. This problem is solved in each particular case with consideration of the engineering-geologic, topographic, technological, operating, and economic conditions.

1. As shown by the experience of long-term operation of earth structures of the cascade, on dams (embankments) being constructed by the method of dumping soil into water, when designing the slopes of these structures it is necessary to impose more stringent requirements with respect to determining the steepness of these slopes to increase their reliability, as is done for structures constructed dry. 2. To organize successful monitoring of seepage processes in the investigated structures having substantial anisotropy of the soil, special recommendations on the efficient disposition of piezometers under such specific conditions should be worked out. Recommendations on the disposition of piezometers under conditions of a noticeable effect of the groundwater regime of the surrounding territory on the seepage regime of the hydro development should be worked out accordingly. 3. Since the calculations made in the work, as a result of which instability of many slopes was detected, are not always confirmed by practice (there are examples of failure-free operation of slopes whose stability factors are considerably less than unity), it is advisable to correct the method of such calculations with consideration of the characteristics of the formation of the seepage flow in the downstream shoulder of dams with pronounced anisotropy of the soil.

1. In certain cases of constructing dams salt-containing soils serve as their foundation. 2. Under these conditions reliable operation of the structures can be provided only by developing special engineering measures to control dissolution. 3. All existing methods of protecting saliferous foundation soils of hydraulic structures from dissolution can be divided into passive, active, and combined. 4. The combined methods should be considered the most effective for preventing removal of salts from foundation soils by the seepage flow. 5. Large-scale field investigations of the work of the combined method of protecting saliferous foundation soils of the planned Lower Kafirnigan hydro development showed its high effectiveness even in the case of complex engineering-geological conditions at the construction site. 6. Individual elements of the set of dissolution protective measures investigated under field conditions can be used in hydrotechnical and hydropower construction practice.

An impermeable boundary of the grout cutoff has been found that maximizes the seepage flow for a specified grouting volume. The shape of a trench has been defined that maximizes the quantity of fluid entering the ground-water flow from the trench. The seepage characteristics of the grout cutoff and the trench which have arbitrary shapes are estimated in terms of the derived exact analytical solutions of variational problems.

The presently existing methods or calculating seepage in inclined ASEs have a limited area of use and often give substantial deviations from the actual values. At the same time, no analytical relations are known for calculating Iex in the backwater zone of the LP. The formulas proposed in the article permit determining all main parameters of the seepage flow, including separately for the zones of effluent seepage and backwater of the LP, with an accuracy sufficient for engineering calculations.

1. A method was developed and the similarity criteria were obtained for modeling turbulent seepage flows in cavityfree drainage. 2. A graph was obtained for determining the depth of water in the mouth of cavity-free drains with free flow from them as a function of the specific inflow to the drain, coefficient of turbulent seepage flow of the filling, and width and slope of the drain.

1. The observations and installed control-measurement instruments on the whole ensured the required control conditions for the rock-earth dam of the Hoabinh hydraulic development and the carrying out of analyses of its state. 2. An analysis of the structure behavior performed using data from instrumental observations showed that the stress-strain conditions of the dam are favorable and correspond to the requirements intended to ensure its reliable operation. The development and distribution of the stress-strain conditions of the dam conform to the design assumptions. Earthquakes in the hydraulic-development region did not affect the process of development of the measurable deformations. 3. The results of observations of the seepage regime of the dam and the base indicate normal operating conditions. The hydraulic gradients on the curtain and the base do not exceed the allowable values. The antifiltration curtain effectiveness is uniform along the front and is stable with time. 4. An analysis of the full-scale observation results performed when construction of the structure was completed showed that the dam body settlements are in the attenuation phase, that the pore pressure dissipation process has been practically completed, and that the parameters of seepage flow in the dam and the base are below the allowable values. The structure state indices permit giving an optimistic prediction of reliability of the dam under rise of the reservoir water elevation to the NPL.

Analytical solutions describing the concentration distribution along one-dimensional unsteady seepage flow through adsorbing saturated finite porous medium have been obtained. An exponential function concentration is enforced at the source of the dispersion, while the change in the concentration is zero at the other boundary. A new time variable has been introduced to solve the unsteady flow problem and the solution is illustrated.

A new resonant stage is identified in the laboratory during the complex process of soil fluidization by water waves. Massive fluidization failure is consistently observed following internal resonance events inside the silt bed. The weakening effect of this resonance is observed to endure long periods of consolidation. A wave reloading, following such a consolidation period, on a preresonated soil usually results in a recurrence of a similarly massive fluidization failure. Analysis of pore pressure records indicates that the resonance events are localized in space and the associated wave modes are short in wavelengths. It is proposed that these resonant events are a consequence of a strong channeling of the seepage flow within the silt bed.

1. For the first time in Soviet engineering practice retaining earth embankments were constructed on a thick stratum of inhomogeneous rock-free made ground of the inner spoil heap of an operating opencut mine and were put into operation in 1975. 2. Construction of the embankments on a thick stratum of rock-free made ground is possible when the following measures are taken: flooding and overloading the foundation, construction of drainage intersecting the seepage flow in the embankment body and foundation, equipping the structures with a special system of monitoring instruments, and organization of constant supervision of construction and operation. 3. The design and construction of retaining embankments on made ground should be preceded in each case by full-scale investigations of the deformations of the foundation and change in its physical and mechanical properties under the effect of flooding and overloading and by establishment of the flooding time and necessary degree of overloading.

1. The general condition of the dam meets the requirements determined by the criteria of safe and reliable operation. The dam is in a satisfactory state. The increase, compared with the design, of tensile stresses on the faces caused by deviation of the temperature regime of the concrete does not pose a danger for the structure. 2. The absence of substantial disturbances of the solidity of the structure indicates a high level of observance of the specifications when constructing the dam and substantiation of the adopted sizes of the concreting blocks, and also the effectiveness of the cooling and monitoring means being used. 3. The grout curtain, consolidation grouting of the foundation, and developed drainage system under the dam and in the wall abutments of the foundation at the heads attained on the structure provide effective reduction of the seepage heads in the foundation and absence of escape of the seepage flow onto the canyon walls near the downstream face. 4. The settlements of the dam, which at present have relatively stabilized, are less than the calculated in absolute value. Slowing of the increase of settlements is noted during filling of the reservoir compared with the predicted settlements from the weight of the dam, which is related to uplifting of the rock mass in the upper pool; a rise of the foundation was recorded in the lower pool; the tilt of the dam toward the lower pool is 0.01%. 5. Opening of the joints in the dam is not undergoing changes, on the whole the process of deformation of the joints after grouting has stabilized.

Field observations of the behavior of the dam during accumulation of a mudflow, geological investigations, and laboratory investigations lead to the following conclusions. 1. When designing mudflow-retaining dams made from the rock, construction of watertight elements on the upper pool side is practically useless, since the mud deposits themselves successfully form a facing and impervious blanket. 2. The seepage flow through the dam comes from a comparatively small layer of water accumulated on top of the mud deposits due to the river runoff following the mudflow. The mud deposits themselves contribute negligible seepage. 3. When placing earth in the dam by the combined method (blasting and filling) it is necessary to take into account the difference in the seepage properties of the zones constructed by the different methods. When earth is placed by heavy-duty trucks the permeability is considerably lower than in the case of an embankment constructed by blasting. 4. In view of the absence of experience in operating mudflow-retaining dams (excluding the 1973 mudflow) increased requirements must be imposed on the design of drains and discharges, provided the dam is not calculated for brief discharge of the water that seeped along the downstream slope. 5. Retention of the disastrous mudflow by the Medeo dam proved that it is possible to control this menacing natural phenomenon. 6. The insignificant settlement of the dam crest (about 10 cm) following rapid flooding of the dam soils indicates high operating qualities of the embankment constructed by the massive blasting method. 7. The construction of mudflow-retaining structures does not eliminate the need for other measures of controlling mudflows (lowering of the levels of morainal lakes, forest-improvement and channel-regulating measures, etc.). Only a combined approach will create a reliable protection system.

1. The seasonal variations of the discharge and piezometric heads noted in the results of the on-site observations indicate the presence of seasonal deformations of the seepage medium, which with the course of time, evidently, can lead to changes in the state of the contact zone of the dam foundation. 2. The results of measuring the temperature of the seepage flow make it possible to distinguish weakened areas of the foundation subject to special monitoring and to estimate the degree of influence of the lower pool on the drainage discharge. According to an approximate evaluation, the inflow from the lower pool does not exceed 10% of the total discharge. The data of the temperature measurements confirm the overall effectiveness of the vertical drainage system for discharge of the flow in the dam foundation. 3. The wells of the vertical drainage system, accessible for measuring the discharge and water temperature and also for conducting experiments with tracers, can serve as a means of reliable monitoring of the state of the watertight and drainage devices in the foundations of concrete structures and can give additional valuable information about the development of seepage processes in the foundation of the structure.

1. The complex natural conditions and characteristics of the operating regime of the Charvak reservoir determined the duration and complexity of the process of the formation of the hydrogeological (hydrodynamic, temperature, hydrochemical) regime in the dam foundation and abutment. 2. The process of restructuring of the natural hydrogeological conditions, which began with the start of the staged filling of the reservoir in 1970, developed in subsequent years with a variable intensity, determined by the values of the annual increase and drawdown of the head on the dam, and originally had an unsteady cyclic character in which a recurrence of the main characteristics of the seepage flow was not observed from cycle to cycle at comparable elevations of the upper pool level. The extent and rate of the changes that occurred gradually decreased. 3. By the end of the period under consideration, after 10 years of permanent industrial operation of the dam at high reservoir levels, relative stabilization of the hydrodynamic, temperature, and hydrochemical regimes of the subsurface waters in the stretch of the hydro development with approach to a steady cyclic type is observed. 4. The process of a gradual increase of the difference of heads and the general nonunformity of its reduction on the curtain also, apparently, stabilized at the attained level. No substantial change in the established picture of the distribution of heads is expected. The curtain is gradually limiting seepage in the foundation and abutments of the dam, which is indicated by the relative stability of the discharge of the drainage devices of the hydro development. The general hydrogeological conditions that have formed after 10 years of operation of the Charvak dam are evaluated as normal, do not at present arouse apprehension, but require constant checking and continuous systematic observations of the seepage processes.

Unsteady seepage flow in a two-dimensional water-table aquifer is analysed for recession/accretion due to a sudden rise or fall of water level in the adjoining river. Limiting solutions for long—thin and short—thick aquifers are deduced from the complete solution. The long—thin aquifer solution is similar to the usual one-dimensional solution. At small values of time, the complete two-dimensional solution is recommended for use because the one-dimensional solution usually gives inaccurate results due to neglect of vertical motion (implicit in the Dupuit assumptions upon which the one-dimensional solution is based).

1. Above-water sluicing of coarse-fraction riprap with sand is characterized by radial spreading of the mixture and partial filling of the pore channels by the seepage flow at the contact with the filled-in body. 2. For the indicated conditions a relation is proposed for determining the gradient of the filled-in body, using data of laboratory experiments, which showed a satisfactory agreement with the results of full-scale measurements during sluicing of the rockfill dam of the Shirokov station. Knowledge of the magnitude of this gradient will help determine the rational disposition of sluicing points. 3. In the case of steep gradients of the filled-in body the seepage flow is in a energetically turbulent state. The transition of seepage to a tranquil state is accompanied by the occurrence in the riprap of an incomplete hydraulic jump, compacting the sand in the rock voids during sluicing.

The wave‐induced seepage flow in a porous seabed in the neighborhood of a gravity structure is solved exactly by two‐dimensional potential flow theory. The distribution of the hydrodynamic pore‐water pressure along the base of the structure and the wave‐induced vertical force on the structure are computed from the integral solutions. The effects of the thickness of the porous seabed and the width of the structure are examined. Results obtained from the exact theory are compared with experimental data and there is reasonable agreement.