Dam - Seepage Analysis

By means of a drainage and seepage tank, an experimental flow net system inside the body of a homogeneous earth embankment dam model, formed from Leighton Buzzard Silica sand, was developed and studied in this experimental research paper. Water flow through dams is one of the basic problems for geotechnical engineers. Seepage analysis in an important factor to be considered in the proper design of many civil engineering structures. Seepage can occur in both through the structure itself as the case of earth dams and under foundations of an engineering structure. Successful seepage analysis is achieved on the proper and accurate construction of a flow net. Amongst the various existing methods of seepage analysis, the "Finite Element Method" and the method of "Experimental Flow Nets" are the most widely used ones. Construction of a flow net is mainly used for solving water flow problems through porous media where the geometry makes sometimes analytical solutions impractical. This method is usually used in soil mechanics, geotechnical or civil engineering as an initial check for problems of water flow under hydraulic structures like embankments or dams. As such, a grid obtained by drawing a series of equipotential lines and stream or flow lines is called a flow net. In this procedure the Laplace equation principles must be satisfied. Hence, the construction of a flow net is an important tool in analysing two-dimensional irrotational flow problems and provides an approximate solution to the flow problem by following simple rules, as initially set out by Forchheimer, 1900, and later refined by Casagrande,1937. It can also be very useful tool even for problems with complex geometries, as proven in this experimental research paper. The objectives of this experimental research paper are: • To determine the position and shape of the flow line representing the uppermost free water surface inside the body of a dam by using a drainage and seepage tank, • To conceptualise the flow lines system and to demonstrate that each flow line starts perpendicular to the upstream slope of the dam and that that slope is a boundary equipotential line, • To construct an experimental flow net and subsequently to verify and analyse it by the FEA method, • To calculate the rate of seepage through the dam body, and • To summarise the calculations and experimental findings in a concise and readable format.

This investigation concerns to study the characteristics of phreatic line of seepage
through homogenous earth dam with and without horizontal filter using Hele-Shaw model, which
also named the viscous flow analog.
The constructed and used viscous flow analog was verified by comparing the phreatic line and
unit discharge for different cases of earth dams which were measured from this analog with the
phreatic line and unit discharge which were obtained using computer program SEEP/W (which is
a sub-program of Geo-Studio). The comparison gives a good agreement between the results of
these two methods
Using Hele-Shaw model, Experiments were carried out with three different viscous oils in
order to present three different permeabilities of soil, for each oil there was three downstream
slopes of the dam. Different runs were carried out using different upstream slopes, three variable
filter lengths and three different upstream reservoir heads. For each run the downstream cover,
quantity of seepage and the configuration of top seepage line were determined. Dimensional
analysis was used with helping of the experimental results to develop an empirical equation in
order to determine the most effective filter length which used to eliminate the downstream cover.
Results from the experiments show that the downstream cover is increased with decreasing the
upstream slope angel, downstream slope angel and upstream reservoir head, while it is decreased
when the filter length is decreased. The results indicated that the unit discharge through the earth
dam body increases with decreasing the upstream slope angel, and downstream slope angel, while
it is increase with increasing the horizontal filter length, and the upstream and reservoir head.
Also, the results appear the unit discharge through earth dam body increases with increasing the
hydraulic conductivity, this the unit discharge for earth dam of high hydraulic conductivity
affected strongly by the geometry of this dam, while this affecting is limited for the soils of low
hydraulic conductivity.

Spatial variability of material properties is inherent in both natural soil deposits and earth structures, yet it is often ignored during geotechnical design. With the objective of developing novel methods for assessing the effects of soil variability on groundwater flow, this study presents a stochastic finite element model of seepage through a flood defense embankment with randomly heterogeneous material properties. Stochastic modeling is undertaken by means of a Monte Carlo simulation which involves a large number of finite element analyses, each with randomly varied porosity at element level, which leads to a corresponding random variation of both permeability and water retention properties across the embankment domain. This provides a statistical distribution of responses, such as total flow rate and time to reach steady state, instead of a single deterministic result as in conventional studies of seepage through unsaturated heterogeneous soils. As the degree of heterogeneity increases, water tends to flow along the most permeable paths inside the soil mass, resulting in an irregular shape of the predicted wetting fronts and pore pressure contours. The mean and standard deviation of the computed quantities strongly depend on the statistics of the input porosity field. Simulations are also conducted to compare the statistical variation of flow rate with and without dependency of the water retention curve on porosity. With recent growth in computer speed, stochastic finite element models based on the Monte Carlo approach can become a powerful design tool, especially if a quantitative assessment of geotechnical risks is required. Copyright © 2011 John Wiley & Sons, Ltd.

This investigation concerns to find a new equation for computing the quantity of seepage
through homogenous earth dam with horizontal toe drain. For this purpose the computer
program SEEP/W (which is a sub-program of Geo-Studio) was used. The SEEP/W runs were
carried out with three different downstream slopes of the dam, three different upstream slopes,
three variable horizontal toe drain lengths, three different free boards, three different top widths
and three different heights of the dam. For each run the quantity of seepage was determined.
The results show that the seepage discharge increased with increasing upstream slope,
downstream slope, upstream reservoir water depth and length of horizontal toe drain. Also, the
results show that the seepage discharges decreased with increasing the top width of the dam and
the height of the free board. Using SEEP/W results with helping a dimensional analysis theory,
a new easy and reliable empirical equation for computing seepage discharge through
homogenous earth dams with horizontal toe drain was developed. The analysis of the results by
Artificial Neural Network (ANN) shows that the length of horizontal toe drain (L) is the more
geometrical variable effect on the seepage discharge, while the upstream slope (tanθ) of the
earth dam has a little effect

This study stochastically investigates the rainfall-induced differential settlement of a centrally loaded rigid strip foundation on an unsaturated soil with spatially varying values of either preconsolidation stress or porosity. The differential settlement (between the two foundation ends) is calculated at various times during rainfall via a coupled hydro-mechanical finite element analysis. The Barcelona Basic Model describes the mechanical behaviour of the soil while the van Genuchten relationships describe water retention and permeability. The variability of soil properties is modelled by means of random fields with spatial correlation in the framework of a Monte Carlo simulation. The study demonstrates that the occurrence of rainfall-induced differential settlements can be consistently analysed using concepts of unsaturated soil mechanics and random field theory. Results show that differential settlements can be vastly under-predicted (or even completely missed) if random heterogeneity and partial saturation are not simultaneously considered. The variation of differential settlements and their statistics during the rainfall depend on the magnitude of the applied load and the statistics of soil variability. Moreover, the transient phase of infiltration and a spatial correlation length equal to the width of the foundation pose the highest risk of differential settlement.

World experiences reveal that catastrophic floods are posing a serious threat that comes not only from them as extreme events but also as the result of adaptation measures uncertainty, (i.e. dikes). In particularly old dikes constructed earliest at the north part of Albania, during the last floods demonstrated the high uncertainty and weak spots. In this paper, the significance of the seepage investigation and stability analysis are discussed. As a case study, parts of new dikes constructed last years along the Buna River located in north part of Albania are investigated. Filling materials for these dikes are represented mostly from silt and clay. Finite element method is used to perform seepage analysis while general limit equilibrium method is used to perform slope stability analysis. Both, seepage and slope stability analyses are done for three different scenarios: steady state, rapid filling, and rapid drawdown. Finally, it is concluded that silt-clay materials used in these dike even they have low permeability, are posing serious uncertainty during seepage phenomenon, and threatening the stability of entire dike structure especially during the transient condition (rapid filling and drawdown).

The stability and safety are very important issues for the dam structure which are built in seismic regions. The dam body consist of soil materials that behave nonlinearly need to be modelled with finite elements. In present study, the numerical investigation employs a fully nonlinear finite element analysis considering linear and elastic-plastic constitutive model to describe the material properties of the soil. In this paper, dynamic analysis of a dam is carried out using GeoStudio software. Initially the in-situ stress state analysis has been done before the earthquake established, and then its results are used in the dynamic analysis as a parent analysis. A comprehensive parametric study is carried out to identify the effects of input motion characteristics, soil behaviour and strength of the shell and core materials on the dynamic response of earthen dams. The real earthquake record is used as input motions. The analysis gives the overall pattern of the dam behaviour in terms of contours of displacements and stresses.

The Khun Dan Prakarnchon Dam, the largest RCC gravity dam in Thailand, has been completed since 2005. On the 1 st and 2 nd year of impounding, the pressures under the dam foundation were carefully monitored. For the 1 st impounding, the piezometric heads were activated when the water level has been raised above 25 m above the dam foundation level. The discharges of foundation and dam body drains which were measured by 80 V-Notch weirs in the dam galleries show 50% decreasing from the 1 st to 2 nd year mainly because of self-healing in micro-cracks in the dam body.

The stability and safety are very important issues for the dam structure which are built in seismic
regions. The dam body consist of soil materials that behave nonlinearly need to be modelled with finite elements.
In present study, the numerical investigation employs a fully nonlinear finite element analysis considering linear
and elastic-plastic constitutive model to describe the material properties of the soil. In this paper, dynamic analysis
of a dam is carried out using GeoStudio software. Initially the in-situ stress state analysis has been done before the
earthquake established, and then its results are used in the dynamic analysis as a parent analysis. A comprehensive
parametric study is carried out to identify the effects of input motion characteristics, soil behaviour and strength of
the shell and core materials on the dynamic response of earthen dams. The real earthquake record is used as input
motions. The analysis gives the overall pattern of the dam behaviour in terms of contours of displacements and
stresses.

Large palaeo-landslides with considerable movements have sometimes caused the burial of permeable formations by the landslide mass. The pore pressure regime established in the landslide material where it overlies these permeable formations is strongly non-linear with depth. A close to hydrostatic pore pressure may be maintained down to a considerable depth, followed by a sharp drop upon approaching the base of the landslide material, to reach the pore pressure of the underlying permeable strata. This pore pressure profile is known as underdrainage profile. The paper presents the results of numerical analyses investigating the effect of inhomogeneity and anisotropy of the coefficient of permeability and infiltration from the ground surface. In order for such a non-linear pore pressure profile to exist in landslide materials there must be considerable infiltration from the ground surface and the coefficient of permeability of the landslide material must decrease with depth. This decrease is often due to the increase in vertical stress in the landslide material and also due to the orientation of clay particles along the slip surface, which may be located immediately above the upper boundary of the buried permeable formation.

The safe operation and proper maintenance of dam infrastructure is critical taking into account social and economic impacts in case of a failure. Currently, the assessment of dam structures is based on geodetic and geotechnical monitoring instrumentation. However, the majority of these instruments do not provide repeatable and reliable information about the mechanisms occurring inside the body of dams that could compromise the integrity of the structure. Geophysical methods can provide important information to define the safety level of dam infrastructure. Continuous dam monitoring would also enable early remedial maintenance and repair actions to be carried out improving public safety and reducing costs for dam owners, insurers and maintainers. This study investigates for the first time the condition of Mugdock reservoir dam using two different non-destructive geophysical techniques. Electrical Resistivity Tomography (ERT) arrays were installed on the crest to assess the structural integrity of the dam based on the resistivity signatures. Electromagnetic (EM) sensing was then used as a complementary method to confirm the values obtained with the ERT for the upper soil layers of the dam crest. The analysis of the results obtained from the electromagnetic survey indicated high resistivity superficial soil layers beneath the crest of the dam. The electrical resistivity surveys revealed low resistivity zones that could be influenced by seepage conditions inside the body of the dam. The geophysical results presented in this study provide important baseline measurements which with the integration of future geophysical and geotechnical data will deliver key information about the ongoing performance of dam infrastructure.

Experiments were conducted to investigate the odometric swell behavior of expansive soil specimens mixed independently with two different granular additives: silica sand and granulated tire rubber (GTR). All specimens were prepared with the same global water content. However, specimens that contained sand swelled less than did analogous specimens that contained GTR, regardless of the surcharge stress imposed before inundation. Phase relationship analyses based on " oversize correction " equations derived for mixtures with three solid phases indicate that the specimens possessed clay portions with different dry density and initial water content. Such differences are attributed mainly to the role of additive grain stiffness during specimen preparation. Results from complementary discrete element method simulations indicate that the stiffness of the additive grains may also play a role in mitigating the swell via contact force alterations upon swell.

Pulp and paper mills are categorized as a core sector industry and are one of the largest
contributor to industrial water pollution. For every tonne of paper produced , those mills generate 220-380
cumec of highly coloured and potentially toxic waste water. Those industries utilize a huge amount of
lignocellosic materials and water during Manufacturing process and releases chlorinated lignosulphonic
acids, chlorinated phenol and chlorinated hydrocarbons in the effluent. In waste water these compounds are
estimated collectively as “Adorable Organic Halides” AOX. In this paper the various methods of treating
the waste water generated from those type of industries , both traditional and modern techniques that are
used worldwide are discussed.

If there is no proper control, escape of stored water behind the soil dam by dam foundation can cause serious problems for the dam. The most problems arecaused by increased water output gradient that causes soil particles floating in the dam heel and thus, resulting in the movement of the soil particles. To control the seepage of dam foundation methods should be applied to reduce water leakage. One method to reducing the leakage of foundation is drilling trenches in dam foundation and then filling it with plastic concrete materials. Introduction Plastic concrete is material with low resistance (less than normal concrete) and has higher ductility than normal concrete. Low water-cement ratio is often used in plastic concrete. Plastic concrete in addition to high ability to deformation and low permeability (Soroush, and Mojtahedi, 2002) has proportional shear strength to applied pressure. Seepage control under the dam foundation is done in different ways. Earth layers' material in location of dam foundation, the importance of dam and available executing technology are effective factors in selecting the leakage control methods. Injection membrane, shield waterproof, upstream covering and watertight wall are of the main and conventional methods of seepage control of dam foundations. Waterproof walls have characteristics such as high flexibility, low permeability and compression resistance proportion to applied pressure and thus, are used in areas where the foundation is weak and permeability is high. Sealing walls' construction steps include the construction of guide wall and work platform, trenches drilling, adding drilling mud to walls stability and finally, fill it with suitable materials. The filling materials can be aggregated and mixed with bentonite clay, mixed cement and bentonite as flowing clay or plastic concrete (Saghiri, 2011). Plastic concrete strength is much less than normal concrete with high ductility and low permeability. Plastic concrete is an appropriate material in delta regions with poor soil that needs sealing walls to be flexible and have sufficient strength to withstand stresses of dam loading to control seepage of dam foundation .

Reservoir water leakage is mainly manifested in the body and foundation of a dam. While loss of precious water stored in the reservoir is an issue to be attended to, the migration and subsequent loss of particle of dam results in the compromise of dam safety. Detection of pebble layer in Kanupur Earth Dam (left bank) has necessitated to initiate studies on the spatial extent of pebble layers and consequent compromise on the dam safety. Diagnostic tools in the shape of (i) determining predictive permeability of pebble layers using grain size distribution and compare the values with the observed values; (ii) determine the groutability of foundation materials; (iii) conduct geo-electric resistivity tomography to determine the spatial extent of the seepage layers. On the basis of the diagnostic studies, remedial measures have been suggested to the Project Authority for follow-up-action.

The aim of the present research is studying the efficiency and performance of
Mosul Dam with respect of the seepage. It was depended on the dam field
observations of years 2004, 2003 and 1990. These observations included a
discharge measurements and chemical analysis of seepage water from three points
at the downstream left side of the dam, and the chemical analysis of reservoir
water. Also, the ground water levels of grouting gallery piezometers and opening
piezometers at the downstream right side were measured. All these field
observations were taken with every water level of the dam reservoir.
The results concluded that the dam embankments being a good efficiency with
respect the seepage, however, the efficiency of the dam foundation, which presented by
the grout curtain, is in a good condition in most regions, except the region limited
between section (68) and (70), where the efficiency of this region is equal to
(19.5%), (23.07%) and (25.55%) in years 2004, 2003 and 1990 respectively. Also,
the results indicated that some sections of the grout curtain , such as section (79),
being with not agreeable efficiency in 1990, where Is equal to (45.97%). But
according to a continuous and intensive grouting, the efficiency of this section
increased and become (73.74%) and (73%) in 2003 and 2004 respectively

Overtopping erosion is one of the main factors responsible for the destruction of earthen structures due to floods. Considering the shortage of existing studies and the need for further research to properly understand the processes leading to breaching failure, this study investigates the effect of compaction level (dry density) on the overtopping erosion response of model compacted silty sand dams using a laboratory flume apparatus. From side-view video recordings of the homogeneous earthen dam cross-section, digital image-processing techniques are employed to track and forensically analyse and interpret the initiation and progression of the erosion edge. The results indicate that the overall pattern of initiation and development of overtopping erosion depends on the compaction level, with greater compactive effort (higher shear strength of soil) reducing its progression speed, thereby increasing the time period for the erosion edge to reach the dam's upstream crest (tB) and breaching failure. Artificial neural network and response surface methodology (RSM) approaches are investigated for estimating the experimental tB values, with the RSM-derived third-order polynomial found to produce good predictions for the three compaction levels investigated. Finally, recommendations are given for further research, including employing the experimental setup presented for investigating other types of dam failure.

The primary purpose of this article is to present the concept of quasi-spatial monitoring of seepage and erosion processes and phenomena in the area of georisk, using invasive instrumental measurement methods, including, in particular, linear or quasi-linear measurement sensors. Along with the risk of water overflow over the crest of earth damming hydraulic structures, these processes and phenomena pose the main threats for their safety and are the main causes of their repairs. The proposed solutions seem to be valuable ones and have a high application potential. Taking into account the development of measurement methods and the field of the automatic control of the condition of a structure, they will probably be used increasingly frequently in the damming hydro-engineering constructions.

World experiences reveal that catastrophic floods are posing a serious threat that comes not only from them as extreme events but also as the result of adaptation measures uncertainty, (i.e. dikes). In particularly old dikes constructed earliest at the north part of Albania, during the last floods demonstrated the high uncertainty and weak spots. In this paper, the significance of the seepage investigation and stability analysis are discussed. As a case study, parts of new dikes constructed last years along the Buna River located in north part of Albania are investigated. Filling materials for these dikes are represented mostly from silt and clay. Finite element method is used to perform seepage analysis while general limit equilibrium method is used to perform slope stability analysis. Both, seepage and slope stability analyses are done for three different scenarios: steady state, rapid filling, and rapid drawdown. Finally, it is concluded that silt-clay materials used in these dik...

Strong Form Differential Quadrature Element Method (DQEM) is a non-ubiquitous technique for solving various physical and engineering problems having arbitrary domain configurations and complicated boundary conditions. In the present paper, the DQEM is adopted to simulate 2D steady-state confined seepage using quadrilateral elements unprecedentedly. The method discretizes the studied domain to a number of homogenous isotropic or anisotropic zones/elements. Techniques for defining boundary conditions are presented. The numerical modeling process is implemented in a PYTHON computer code. Various problems are solved in the present paper and the obtained results are compared with the available results of theoretical and numerical methods pre-published in the literature. Numerical results demonstrate the rigor and eligibility of the unfamiliar approach (DQEM) with less computational efforts.

In the conditions of severe climatic changes that are sweeping the world now, causing many problems, of which high surface water levels, torrential rains and floods are among the most dangerous phenomena. Since dams are the most engineering and structural protection means that engineers resort to, to protect against these dangers in such circumstances, not to mention the other important uses of dams such as storing water for irrigation purposes, generating electricity, feeding the underground reservoir, or diverting flow paths for any engineering purpose. Dams are usually classified on the basis of several considerations, including solid dams of different types, and flexible dams. Flexible dams, which are sometimes called earth dams, are of a special nature as they consist mainly of loose materials of a special porous nature and different ratios of interspaces that allow water to pass through them and penetrate the dam body in different proportions, which, if not prevented or avoided, may lead to the collapse of the dam body. In the present study a numerical analysis of seepage through zoned earthen dams is introduced, as they are the most popular type of flexible dams, to clarify the behavior of the streamlines of the seepage water through the body of such type of dams with different types of used soil of filling materials. Decreasing the relative permeability coefficient between the inner and transition zones up to 0.001 caused a significant decrease in the different seepage properties, after that, the effect was minor.

SUMMARY Spatial variability of material properties is inherent in both natural soil deposits and earth structures, yet it is often ignored during geotechnical design. With the objective of developing novel methods for assessing the effects of soil variability on groundwater flow, this study presents a stochastic finite element model of seepage through a flood defense embankment with randomly heterogeneous material properties. Stochastic modeling is undertaken by means of a Monte Carlo simulation which involves a large number of finite ...

World experiences reveal that catastrophic floods are posing a serious threat that comes not only from them as extreme events but also as the result of adaptation measures uncertainty, (i.e. dikes). In particularly old dikes constructed earliest at the north part of Albania, during the last floods demonstrated the high uncertainty and weak spots. In this paper, the significance of the seepage investigation and stability analysis are discussed. As a case study, parts of new dikes constructed last years along the Buna River located in north part of Albania are investigated. Filling materials for these dikes are represented mostly from silt and clay. Finite element method is used to perform seepage analysis while general limit equilibrium method is used to perform slope stability analysis. Both, seepage and slope stability analyses are done for three different scenarios: steady state, rapid filling, and rapid drawdown. Finally, it is concluded that silt-clay material used in these dike structure is posing serious uncertainty during seepage phenomenon by threatening the stability of entire dike structure especially during the transient condition (rapid filling and drawdown).

World experiences reveal that catastrophic floods are posing a serious threat that comes not only from them as extreme events but also as the result of adaptation measures uncertainty, (i.e. dikes). In particularly old dikes constructed earliest at the north part of Albania, during the last floods demonstrated the high uncertainty and weak spots. In this paper, the significance of the seepage investigation and stability analysis are discussed. As a case study, parts of new dikes constructed last years along the Buna River located in north part of Albania are investigated. Filling materials for these dikes are represented mostly from silt and clay. Finite element method is used to perform seepage analysis while general limit equilibrium method is used to perform slope stability analysis. Both, seepage and slope stability analyses are done for three different scenarios: steady state, rapid filling, and rapid drawdown. Finally, it is concluded that silt-clay materials used in these dik...

World experiences reveal that catastrophic floods are posing a serious threat that comes not only from them as extreme events but also as the result of adaptation measures uncertainty, (i.e. dikes). In particularly old dikes constructed earliest at the north part of Albania, during the last floods demonstrated the high uncertainty and weak spots. In this paper, the significance of the seepage investigation and stability analysis are discussed. As a case study, parts of new dikes constructed last years along the Buna River located in north part of Albania are investigated. Filling materials for these dikes are represented mostly from silt and clay. Finite element method is used to perform seepage analysis while general limit equilibrium method is used to perform slope stability analysis. Both, seepage and slope stability analyses are done for three different scenarios: steady state, rapid filling, and rapid drawdown. Finally, it is concluded that silt-clay material used in these dike structure is posing serious uncertainty during seepage phenomenon by threatening the stability of entire dike structure especially during the transient condition (rapid filling and drawdown).