Seepage Head Research Articles

An Improved Physics-Informed Neural Network Algorithm for Predicting the Phreatic Line of Seepage

As new ways to solve partial differential equations (PDEs), physics-informed neural network (PINN) algorithms have received widespread attention and have been applied in many fields of study. However, the standard PINN framework lacks sufficient seepage head data, and the method is difficult to apply effectively in seepage analysis with complex boundary conditions. In addition, the differential type Neumann boundary makes the solution more difficult. This study proposed an improved prediction method based on a PINN with the aim of calculating PDEs with complex boundary conditions such as Neumann boundary conditions, in which the spatial distribution characteristic information is increased by a small amount of measured data and the loss equation is dynamically adjusted by loss weighting coefficients. The measured data are converted into a quadratic regular term and added to the loss function as feature data to guide the update process for the weight and bias coefficient of each neuron in the neural network. A typical geotechnical problem concerning seepage phreatic line determination in a rectangular dam is analyzed to demonstrate the efficiency of the improved method. Compared with the standard PINN algorithm, due to the addition of measurement data and dynamic loss weighting coefficients, the improved PINN algorithm has better convergence and can handle more complex boundary conditions. The results show that the improved method makes it convenient to predict the phreatic line in seepage analysis for geotechnical engineering projects with measured data.

Impacts of subsurface hydrologic conditions on sediment selectivity and sediment transport in rills

Sediment size distribution and sediment load are important factors for the estimation of sediment transport processes. Subsurface hydrologic conditions including drainage, saturation, and seepage can affect the sediment selectivity process and sediment transport, given that downward infiltration under drainage and upward exfiltration under seepage can add one more force on surface particles compared to saturation conditions. The aim of this study was to investigate characteristics of sediment selectivity and transport rates under different subsurface hydrologic conditions in small laboratory flume channels. Series of experiments were conducted with an Opal clay soil under four subsurface hydrologic states ranging from free drainage to 10 cm seepage head conditions with water discharge rates from 0.0003 to 0.0008 m2 s−1 at three slope gradients from 4.56% to 12.17%. Results showed that the fraction of coarse-sized particles increased from saturation to 5 cm and 10 cm seepage head conditions. Compared to saturation conditions, the greater proportion of coarse particles leaving in flow in the free drainage experiments may have been caused by infiltration enhancing the deposition processes and regenerating a coarser surface when reaching the dynamic equilibrium. As slope gradients increased, the subsurface hydrologic impacts decreased on the sediment selectivity process. Both the sediment size distribution and the sediment transport rate changed dynamically and spatially before reaching an equilibrium condition. The determination of sediment transport capacity should consider both dynamic and spatial equilibrium conditions. For the Opal soil, the sediment transport capacity values greatly increased from free drainage to saturation conditions, and the differences between these two subsurface hydrologic conditions increased for greater water discharge rates and slope gradients. From saturation to 5 cm and 10 cm seepage head conditions, the sediment transport capacity values increased slightly, and the differences were stable for the slope gradients and water discharge rates studied.

Impacts of subsurface hydrologic conditions on rill sediment transport capacity

Sediment transport capacity (Tc) is the equilibrium sediment transport value under steady-state flow and channel conditions. Given the difficulties in controlling hydrologic parameters close to steady-state in the field, most previous studies measured transport capacity in the laboratory on either non-erodible beds or erodible beds without drainage. However, infiltration under drainage conditions and exfiltration under seepage conditions cannot be ignored in the real world, and their impacts on soil strength and water discharge may affect transport capacity. The objective of this study was to estimate the effects of subsurface hydrologic conditions on rill sediment transport capacity, and the observations are discussed under both detachment-limited and transport-limited conditions. Series of experiments were carried out with a relatively uniform sand using three water discharges on a 4.56% slope flume with four rills from 0.5 to 3.0 m long under four subsurface hydrologic conditions varying from free drainage to 10 cm seepage head. The determination of equilibrium sediment transport capacity was based on the spatial change of sediment transport as slope lengths increased and the elevation change of the erodible surface in rills. Results from 107 runs indicated that there was only one equilibrium sediment transport value for a given surface and subsurface hydrologic condition, given similar observations were obtained under detachment-limited and transport-limited conditions. For the studied sand, observed critical shear stress decreased around 20% from the drainage to the saturation condition, and decreased slightly from the saturation to the seepage condition. Measured transport capacity increased 13% to 15% from drainage to seepage conditions for the studied water discharges, which was the result of decreased soil strength and increased water discharge. The differences in transport capacities between drainage and saturation increased as water discharge increased, but the differences between saturation and seepage were relatively stable for all studied water discharges.

New Structure of Impervious Steel Sheet Pile in Foundation Slab

In view of the poor seepage control effect, slow construction progress and high investment cost of the existing sluice vertical impervious core structure, a new type of anti-seepage steel sheet pile structure for foundation slab is proposed in this paper.The new structure is formed by connecting multiple steel sheet piles, the steel sheet pile is in “U” shape, the steel sheet pile body forms horizontal extension edges on both sides, the two extended edges form two reverse hooks at the end, and the clasp forms an inward inclined plane at the connection opening. The steel sheet pile is used as the vertical anti-seepage body, and the structure of the steel sheet pile is optimized. The connection end is connected by the reverse hook. The gap between the connection end faces is small and the anti-seepage performance is good. The structure reduces the seepage head, reduces the saturation line, and improves the stability of sluice foundation and sluice.

SFPSO algorithm-based multi-scale progressive inversion identification for structural damage in concrete cut-off wall of embankment dam

As an important part of dam seepage system, the quality of concrete cut-off wall is of great importance. In order to obtain effective feedback on the quality of the wall with limited observation data, this paper introduces the idea of multi-scale parameter inversion. Meanwhile, considering the instability of this ill-posed inversion problem, a regularized coefficient is derived to control the reliability of the final solution. Afterwards, we deduce the analytic sensitivity expression of the seepage head, and simplify the expression based on the adjoint state theory, which greatly improves the computational efficiency of the ill-posed multi-scale parameter inversion. Then, EM clustering algorithm, multi-scale data edit and semi-supervised fuzzy particle swarm optimization algorithm (SFPSO) are proposed to optimize and classify the parameter samples. Finally, we can make an effective identification of the damage inside the cut-off wall through clustering ensemble and progressive learning of the previous sample classification. To verify the accuracy and reliability of this method, we compare the calculation results with actual experimental data. The results show that the proposed multi-scale progressive inversion method is in good agreement with the experimental results and can be used to identify the damage of the actual cut-off wall.

Uncertainty Characterization in the Design of FlowDiversion Structure Profiles Using Genetic Algorithm and Fuzzy Logic

Flow diversion head works are constructed across rivers to divert flow into irrigation, navigation, or power generation channels. Hydraulic structures, such as weirs or barrages, are integral parts of these diversion head works. The optimal design of these hydraulic structures is generally obtained by considering the deterministic values of hydrogeological parameters. However, there is a high degree of local soil variability and imprecision in the determination of soil parameters, such as the safe exit gradient. The seepage head also exhibits a high degree of variability, depending on complex hydrological and metrological factors. This work considers the hydrogeological parameters safe exit gradient and seepage head as imprecise or uncertain. An optimization-based methodology is presented to incorporate uncertainty in the safe exit gradient and seepage head in the optimization formulation and obtain the optimum structural dimensions that minimize the total cost. The subsurface flow consideration is embedded in the optimization formulation. The nonlinear optimization formulation (NLOF) solution procedure using a genetic algorithm (GA) is implemented to demonstrate the characterization of uncertainty in design and hence, overall cost from the uncertain safe exit gradient and seepage head. The limited evaluation shows the potential applicability of the proposed methodology.

Analysis of seepage from a pond

A semi-analytical solution has been derived for predicting the time of emptying a pond due to seepage. The time for the seeping water to reach the water table since the pond was initially filled has been calculated applying the Green-Ampt infiltration theory. The recharge rate after the wetting front joins the water table has been computed using a non-linear relationship between seepage head and recharge rate proposed by earlier investigators. The maximum rise in the water table beneath the center of the pond consequent to the time-varying recharge is calculated applying kernel coefficients obtained from solution of the linearized Boussinesq equation. It was observed that a pond with 50-m initial diameter at the water surface and 3-m maximum depth of water is dry after 168 days, where the subsoil is sandy clay. If the subsoil happens to be clay, the depth of water in the pond at the end of 9 months, i.e., after completion of the non-monsoon period, is 0.62 m. The maximum mound heights beneath the pond for constant recharge rate and uniform recharging area calculated from the present solution compare well with existing numerical as well as analytical solutions.

Progressive Failure of Heavily Overconsolidated Clays

ABSTRACT In this study, in order to comprehend the progressive failure of an overconsolidated clay, triaxial compression tests under constant load application for the overconsolidated Kawasaki clay are carried out. These tests show, after a certain period of time, axial strain rate fluctuations with marked peaks until the specimen reaches outright failure. The experimental procedure is then numerically simulated using the soil-water coupled finite element technique. While the numerical simulation for the triaxial compression test under axi-symmetric conditions did not exhibit the same behavior as in the triaxial test (shear band formation and fluctuation of axial strain rate in the axial strain rate vs. axial strain plot), under plane-strain conditions it properly described the fluctuation of axial strain rate as observed in the experiments. Such fluctuations in the axial strain rate are closely related to the progression of the localized shear zones within the specimen. This behavior is attributed to the “non-local” characteristics of saturated clays. Since the pore water supply to the localized shear zone can not always be sufficient due to Darcy’s law which limits the gradient of global seepage head in the soil, the specimen exhibits varying strain rates. Tertiary mudstone pebbles can be idealized as heavily overconsolidated clay. The progressive failure of a heavily overconsolidated clay suggests that the behavior of crushed Tertiary mudstone is due to slaking at the contact points between the pebbles.

Seepage and antiseepage measures in foundations of hydraulic structures

1. Rock foundations of dams are inhomogeneous water-bearing systems, seepage in them has a complex and nonuniform character; for substantiating antiseepage measures the seepage model of foundations maximally corresponding to real conditions can be represented in the form of a three-dimensional piecewise-homogeneous model consisting of a number of structurally homogeneous fragments cut by systems of water-conducting fractures (zones) and confining interlayers. 2. The effective thickness of grout curtains on average is equal to 10–12 m, in zones of large-scale fracturing of the rocks — up to 20 m and more; the head gradients in the grout curtains do not exceed 10–18; the effectiveness of grout curtains depends substantially on the permeability of the surrounding rocks, and therefore the role which the grout curtain and drainage play under particular conditions is different. 3. The actual diagrams of uplift pressure in the foundations of many operating structures are below the design and standard ones. Under favorable hydrogeologic conditions a reduction of the heads by the watertight grout curtain and drainage in rock foundations of structures is not difficult and can be provided to values considerably less than the standard ones according to SNiP. A generalized diagram of the seepage heads is recommended for calculating the stability of dams on rock foundations in the presence of a grout curtain and drainage. 4. Watertight curtains made by the diaphragm wall method have a high effectiveness and economy. Their filler should be selected with consideration of the properties of the surrouding soils, SSS, and seepage strength of the foundation and diaphragm wall.

Combined static and seepage calculations of the Bratsk concrete dam

1. The results of combined static and seepage calculations of the powerhouse section of the Bratsk dam shows a satisfactory agreement with data of on-site observations with respect to the length of opening of the contact joint and diagram of seepage heads in the contact zone, stresses and displacements of the structure, opening of the column joints, and seepage discharges in the foundation. The closest agreement of the calculated and on-site data was obtained with consideration of stages of constructing the dam in the calculations, which corresponds to the real working conditions of the structure. 2. The agreement of the results of the calculations and on-site data confirm the possibility of mathematical modeling of the behavior of real structures on rock foundations with consideration of the complex set of external factors: stages of construction, presence of joints and cracks in the dam and foundation, seepage along fractures, contact joint, and in entire blocks of the rock, elastoplastic behavior of the material, and temperature effects. 3. Calculations of the SSS, strength, and stability of the Bratsk dam with consideration of the real strength and deformation properties of the materials show that the lightweight powerhouse sections are in a satisfactory operating state. The minimum value of the coefficient of stability against shear for the examined calculated cases is 2.21. 4. The picture of the seepage regime of the dam foundation confirms the data of on-site observations of the high effectiveness of the drainage system and possibility of eliminating a grout curtain in low-permeability rock masses. In this case, the diagram of the seepage heads over the base of the structure differs from the standard one. 5. Opening of the contact joint and decompression of the foundation under the upstream face of concrete dams leads to worsening of the scheme of the static behavior of the structure and requires adequate reflection in the practice of designing these engineering structures.

A Simple Automatic Falling Head Permeameter

The usual method of measuring the permeability of a homogeneous soil in the laboratory is a constant head or a falling head test. Of the two methods, the falling head test is more suitable for measuring the permeability of homogeneous clay as very small flow quantities are involved. The proposed method is to keep the conventional falling head test unchanged except to measure the falling head automatically through a very accurate differential pressure transducer. The low pressure end of the transducer is opened to the atmosphere to correct for changes in the atmospheric pressure over the 24 hour duration of a typical permeability test. By means of several repeated falling head permeability tests at different initial heads for the same effective stresses, it is demonstrated that reasonably reliable and repeatable measurements of permeabilities of clay can be made, provided that the applied head difference as a proprtion of the current vertical stress is swelling is induced by the seepage head.

Static behavior of the Sayano-Shushenskoe data in the last stages of filling the reservoir

1. Opening of the concrete-rock contact under the first columns of the channel sections of the dam at an elevation of the upper pool level that had still not reached the normal pool level is a consequence of the fact that the dam annually absorbed the increasing hydrostatic load as a weakened profile having offsetting and zones of ungrouted concrete. The indicated phenomenon, not presently being catastrophic for the structure, requires, however, both careful monitoring of the dam in the final stage of filling the reservoir and further theoretical investigations. 2. Local disturbance of the grout curtain under the channel sections of the dam can be established on the basis of observations of the seepage regime in the rock. 3. Seepage pressure in the body of the dam is observed both in the construction joints extending to the upstream face of the structure and in the massive concrete of the first column. The pressure somewhat decreases with expansion of the concrete, creating an additional reserve of compression near the upstream face. 4. Seasonal opening of joints, observed to a depth of 1.5 m from the downstream face, has a noticeable effect on stresses near this face. The values of the stresses near the downstream face are less than the calculated, since the measurement points specified under the assumption of constructing the dam full profile were in the offset concrete. 5. For a more accurate evaluation of the state of the dam in the last stage of filling the reservoir it is necessary: to equip the monitoring sections of the dam with additional instruments to establish the depth of opening at the concrete-rock contact; to regulate the measurements of the seepage discharges and head for determining the actual diagram of uplift in the dam foundation; to calculate the stress-strain state of the dam with consideration of temperature effects, opening of the contact joint, and actual diagram of uplift in the foundation.

Monitoring of the seepage regime of earth structures

1. Regular observations of the seepage regime of the earth dams of the Dneprodzerzhinsk hydrostation made it possible to conduct a constant analysis of the condition of the dams. 2. Main stabilization of the seepage regime of the earth dams occurred during the first year after filling the reservoir. 3. It was detected by the method of temperature measurements that an increase of the seepage heads on the right-bank abutment is not related to bypass seepage of the reservoir. 4. An increase of the seepage heads in the summer (seasonal fluctuations) is explained by the effect of the temperature regime and it does not affect the reliability of the structure. 5. The low position of the seepage line can be considered a favorable factor.

Components of forces of a reservoir acting on the foundation of high dams

1. Regular waves of an increase-decrease of the seepage head in the stratum of the permeable rock foundation induced by a change in the upper pool level causes elastic compressive-tensile deformations of the blocks composing the rock mass, which is transmitted to the surface and is manifested in seasonal vertical translational movements of dams with a considerable amplitude. 2. The waves of increase-decrease of pressure being transmitted by the reservoir into deep horizons of the rock foundations propagate with a certain velocity which depends on the permeability and elastic properties of the mass, and therefore stabilization of the settlements of dams caused by these waves occurs with a certain, sometimes considerable, lag with respect to stabilization of the upper pool level. 3. The proposed model of deep penetration of a seepage flow into the stratum of rock foundations most completely takes into account the actually observed dynamics of the settlements of dams.

On-site investigations of the effect of external forces on the contact zone of the Bratsk dam

1. The different state of stress and strain of the foundation under the upstream face of the powerhouse and nonoverflow sections of the Bratsk dam determined the different diagrams of the uplift pressure. The seepage heads depend both on the UPL and on the season —the maximum uplift is observed in February-March at a UPL somewhat below the NPL but with a maximum depth of the open joints on the downstream face. 2. The effect of the uplift pressure on a change in the strained state of the contact zone consists in a direct relation between a decrease of the seepage heads and decrease of the tensile stresses or elongation in the region of the contact joint under the upstream face.

Grout curtain in the foundation of the Nurek dam and evaluation of its effectiveness

1. The grout curtain made in the foundation rocks of the dam to a depth of as much as 140 m provided the achievement of its design density over the entire front. 2. The results of on-site observations of the work of the curtain indicate the absence of worsening of its properties with time. 3. The high values of reduction of the seepage head on the stretch before the curtain in the foundation of the central part of the dam make well-founded the suggestion about reducing the number of rows and spacing between holes when constructing grout curtains under analogous engineering-geological conditions.

Seepage regime in the foundation of the Kanev hydroelectric station

1. The watertight and drainage elements of the concrete structures according to the results of on-site observations are operating rather effectively. A large part of the seepage head is reduced on the blanket and sheet piling parts of the underground contour. The residual heads behind the sheet piling under the powerhouse are close to the design. 2. The hydrostatic levels vary almost linearly with variations of the lower pool level. The hydrostatic levels in the backfill of the left-bank abutment due to the difference of geological conditions are 0.6–1.5 m higher than on the right-bank abutment.

Stress-strain state of the Sayano-Shushenskoe dam during filling of the reservoir

1. The results of monitoring by means of long-term on-site observations and inspections indicate the satisfactory state of the gravity-arch dam during its construction and simultaneous staged filling of the reservoir. The change in the main parameters (deformations, stresses, seepage heads and discharges) characterizing the static behavior of the structure is occurring in conformity with the changes in the hydrostatic load, temperature effects, and concreting, and grouting the joints of the dam. 2. Staged construction and loading of the dam substantially affect its stress-strain state. Construction of the dam in an incomplete profile (the long absence of the fourth columns, toothing on the downstream face, zones of unsealed concrete) under conditions of a constantly increasing hydrostatic load leads to a redistribution of arch and cantilever stresses, to a decrease of compressive stresses in the fourth columns, and to an increase in the third. The actual values of the arch stresses in the first column of the dam at an elevation of the upper pool level close to 500 m are commensurate with the calculated at the normal pool level. This is explained by the fact that owing to the toothings existing on the downstream face the arch on the second columns is not closed. A considerable role in the construction and construction-operating periods is played by the temperature and moisture factors, increasing the compressive stresses on the upstream face compared with the design. As a result, the upstream face of the dam in past stages of filling was compressed practically over the entire height [4]. 3. The “curtain-drainage” cutoff system provides an effective reduction of head on the upstream face of the foundation. Zones of an excess head were not found within the main part of the underground contour of the dam. The discharges of the drain devices do not exceed the design assumptions.

Condition of the concrete dam of the Toktogul hydroelectric station according to on-site observation data

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 studies of the concrete dam at the bratsk hydroelectric power plant : Eidelman, S I US Army Cold Regions Research & Engineering Lab translation TL 621, April 1977, 295P

Abstract : A discussion is presented of the results of field observations and studies performed over a nine-year period during the construction, the temporary operation and six years of permanent operation of the concrete dam at the Bratsk Hydroelectric Power Plant imeni 50th Anniversary of the October Revolution. The characteristics of the measuring instruments, the arrangement and placement of them and the methods of installing them are presented. The field data are presented for the general shifts of the dam, its thermal regime and stressed state, the opening of the structural seams of the dam and the effect of cementation on them. The standard thermal stress patterns of concrete and the development of thermal cracks are investigated. By comparison with the first edition, this book has been enlarged using the results of the field studies of the stresses in the casing and the reinforcing of the turbine conduit and data on the seepage heads in the foundation and in the body of the dam. (Author)