Earth Dams Research Articles

Mimicking dam upstream slope scenarios in acrylic tanks for ultrasonic evaluation

Monitoring to support the integrity of structures immersed in water has been a challenge for dam engineers and other construction technicians for decades. In addition, it is known that the planning and execution of these activities are often linked to high costs and risk assessment. Non-destructive methods can act in these tasks with the production of useful information for a more optimized decision making. Ultrasound (US) is a wellknown tool that works with the emission and reception of wave signals. US stands out mainly for providing low radiation to operators, high resolution and flexibility in defining sensor arrays. Data acquisition can be performed even in immersed and tilted geometry environments. This article presents benchtop measurements from an approach focused on the microscale study of upstream slopes of earth dams. The model was developed to simulate the approximate geometry and composition of a dam slope. Traditional ultrasonic acquisition techniques are applied using immersion transducers. The investigations carried out in a model with dimensions of 30 cm, 30 cm and 100 cm, rip rap under 2H:1V inclination, central frequency of the transducer of 2.25 MHz and depth of water for measurement of up to 20 cm, demonstrated the ability to classify the ultrasonic reflection in contact between water and the different types of interfaces that mimic typical dam materials. Lessons learned from this microscale development should be tested in a controlled reservoir model before moving to field applications. The perspective of this study is to generate information capable of composing a database for machine learning and subsequently assist in decision-making for engineering solutions that act in maintenance, safety and predictive interventions in dam bodies.

The handling of tunnel collapse and settlement (case study: Jragung Dam diversion tunnel, Indonesia)

A diversion tunnel is a crucial part of dam construction because of its function to derivate the river during earth dam filling works. The Jragung Dam diversion tunnel is located in the Kalibeng Formation, which is dominated by claystone and sandstone lithology, and passed by an anticline fold structure. The geological conditions provide challenges in tunnel construction. The collapse of rock material in the tunnel overburden and settlement on the slopes hill requires a comprehensive approach and handling by prioritizing factors of safety, cost efficiency, and speed of time. Field observation including rock mass quality analysis, reviewing the design, also monitoring of discharge and deformation was conducted to find the source of collapse. The groundwater flow and deformed soft rock were accused of being the tunnel collapse determinant. The rock mass improvements used pore-filling of sodium silicate mixture and fore-polling. Then dewatering was carried out using drainage pipes and deep wells. Because of the steep rock’s dip in the tunnel, the release wells and observation wells location need to design effectively. Geoelectric investigations correlated with bore log analysis aimed to find effective locations for groundwater control. The settlement was refilled with plastic concrete because of its lightweight and durability.

Stochastic seepage analysis in embankment dams using different types of random fields

Random field theory has become a very popular approach for probabilistic analysis of earth dams. This study performs a stochastic analysis of seepage through an embankment dam to account for the spatial variability of hydraulic parameters. The originality of this study consists in using and comparing three types of Random Fields RFs for the seepage analysis: classical stationary RFs, conditional RFs (to consider the position of available measurements), and non-stationary RFs (to consider the mean variation with depth). The same sample of hydraulic conductivity values is considered to generate the three types of random fields. The hydraulic conductivity RFs are integrated into a Finite Element seepage analysis model to evaluate the flow velocity, hydraulic gradient, pore water pressure, and flow rate. The process is repeated by Monte Carlo simulations to characterize the spatial variability of the seepage results in terms of mean and standard deviation at each point of the studied dam and its foundation. The results show a higher dispersion for the stationary RF case and a lower dispersion for the conditional RF case. For the case study, the results also show that the use of different RFs for modelling the spatial variability of hydraulic conductivity induces differences that can be considered significant for flow velocity, moderate for hydraulic gradient and minor for pore pressure.

Modeling‐based performance assessment of an indigenous macro‐catchment water harvesting technique (Marab) in the Jordanian Badia

AbstractWater resources management is fundamental for rural communities in drylands, where water harvesting technologies (WHT) can be used for intercepting surface runoff and storing water in soils. The so‐called “Marab” WHT was initially developed by Middle Eastern agro‐pastoralists that reside or commute in semi‐arid and arid rangelands. The Marab WHT is a macro‐catchment measure consisting of earth dams and stone spillways along the contours of a lowland depression or floodplain. Dependent on the local context (i.e., climate, soil, management, etc.), the established Marabs show highly variable effectiveness and little scientific evidence is supporting the scaling out of the technology. This study aims at filling the knowledge gap on the Marab performance in different environments by simulating its hydro‐agrological effects for different soils and climatic conditions using the AquaCrop model. A case study performed for a Jordanian Marab over three seasons (2019–2022) confirms its huge improvement potential for barley production. Through Marab‐based farming, barley production reached 8.37 t ha−1on average, versus highly variable 0.34 t ha−1without the WHT. The simulation‐based assessment of soil textures identified that silty soils have the largest potential for producing up to 9.25 t ha−1barley, compared to 6.60 t ha−1produced in clay soils. Assessing different climate scenarios, a slight increase in daily average temperatures (+0.5°C) led to a considerable production decline of 4%–8%, while a significant reduction of precipitation (−20%) decreased biomass production by a similar rate (4%–10%). This underlines the robustness of the “Marab” WHT to rainfall amount variation. However, simulations also highlight the sensitivity of timing and frequency of flood events: removing the last and the first flood event reduced biomass production by approximately 50% and 80%, respectively, while the barley fails to develop if both events were suppressed.

Preparation of Design Charts for Estimation of the Length of an Upstream Impervious Blanket in a Homogenous Earth Dam

Earth dams are constructed mainly from soil. A homogenous earth dam is composed of only one material. The seepage through such dams is quite high. Upstream impervious blanket is one of the methods used to control seepage through the dam foundations. Bennet's method is one of the commonly used methods to design an impervious upstream blanket. Design charts are developed relating the length of blanket, total reservoir head, total base width of the dam (excluding downstream drainage), the coefficient of permeability of the blanket material, blanket thickness, foundation thickness, and coefficient of permeability of the foundation soil, based on the equations governing the Bennet's method for a homogenous earth dam with a blanket of uniform thickness. The length of the upstream impervious blanket can be determined by using the developed charts. The length of the blanket is inversely proportional to the coefficient of permeability of the blanket material. The length of blanket is directly proportional to the total reservoir head, total base width of the dam (excluding downstream drainage), blanket thickness, foundation thickness, and coefficient of permeability of the foundation soil.

Influence of intrinsic variability in anthropic slopes

Anthropic slopes are common in constructing embankments and earth dams and forming open pit mines and fills, among others. However, these slopes artificially built sometimes could fail due to the variability of the soils, lack of expertise in determining the design parameters, and lack of knowledge of the soil’s true behavior and construction methods, among others. To address these problems, physical models were made in a geotechnical centrifuge with similar characteristics to study the effect of variability. Subsequently, Monte Carlo simulations were performed using finite element models (FEM) with random geotechnical parameters for an elastic model with Mohr-Coulomb failure criteria. From these simulations, the influence of geotechnical parameters on the factor of safety and deformations was observed. The results show that the coefficient of variation obtained for the factor of safety was less than the coefficient of variation of the geotechnical parameters taken into account. This means that the coefficient of variation of the factor of safety is not the sum or the average of the coefficients of variation taken in the analysis. However, when the factor of safety is more or less constant, but the coefficient of variation of the parameters increases, the probability of failure may increase. This shows that a slope with a factor of safety greater than one can have a high probability of failure. In addition, low friction angle and low cohesion values tend to present more significant slope crest displacements.

A Review of Stochastic Analysis of the Seepage Through Earth Dams with a Focus on the Application of Monte Carlo Simulation

A Review of Stochastic Analysis of the Seepage Through Earth Dams with a Focus on the Application of Monte Carlo Simulation

Simulating the Hydraulic and Volume Change Behavior of Compacted Highly Expansive Soil under Potential Field Stress and Seasonal Climatic Variation

A sustainable design of some engineering applications, such as earth dam cores, landfill liners, clay barriers, and radioactive waste disposal systems, that utilize compacted expansive soils requires simulation for probable field conditions. This study investigated the hydraulic and volume change (H-VC) behaviors of highly expansive compacted soils in Al-Qatif city under different seasonal climatic variations for a wide range of stress conditions, aiming for more economical and rational design and practices. The extent of the effect of the start cycle condition of the cyclic wetting and drying (W/D) process on the examined properties is examined, as well. Two testing series of the cyclic W/D process, representing the probable seasonal climatic variations, were executed for varied axial stress conditions. The H-VC behaviors of expansive soils are affected by the simulated seasonal variation (i.e., cyclic W/D process), with the first cycle of W/D being the most effective cycle and an elastic state being attained by the third to fourth cycle. Swell fatigue is noted for both testing series, and this is attributed to the initial placement condition. Analysis of results recommends exposure of the compacted expansive soil layers in the field to drying after compaction to reduce their equilibrium wetting potential. As a consequence of the noted shrinkage accumulation, a reduction tendency of saturated hydraulic conductivity (ksat) with repeated W/D cycles is reported for both series under all the stress states applied. Finally, it is recommended for clay barrier projects to be submerged once compacted to obtain barriers with the lowest values of hydraulic conductivity.

Development of Soft Computing Models Based on Wavelet Analysis for Estimating Piezometric Heads in Earth Dams

Development of Soft Computing Models Based on Wavelet Analysis for Estimating Piezometric Heads in Earth Dams

Seepage Simulation of the Proposed Makhool Dam in North Iraq

This study aims to simulate water seepage and identify areas of weakness in the foundations through the right and left sides of the proposed Makhool dam in northern Iraq, using the finite element method by advanced computer software (SEEP/ W, 2012). The earth fill dam is 3670 m long on the Tigris River. Many attempts were made to ascertain the program results on the supposed earth dam and compare the results with those of other analytical methods to verify the program. The results are comparable, showing that the program is suitable for use in the seepage analysis at the proposed Makhool dam. According to the seepage analysis, the quantity of seepage through the left side of Makhool is acceptable within permissible limits; however, the right side has a lot more than the left side because of the presence of cracks, fractures, and cavitations in the stratigraphic sequence of Fatha formation at great depths in the gypsum beds under the diaphragm. The results indicate the need to lower the diaphragm about 6 m extra in the foundation's zone to a level of 49 m.a.s.l until reaching the low permeability clay bed within the foundations' zone. This action will reduce the amount of seepage and flow velocity and avoid using more grouting during the dam life. The design limits of the piezometric head (total head) were also determined, which are supposed to be read by the monitoring devices when operating the dam at the maximum level of the reservoir and the normal operating levels.

Suffusion prediction model based on physical parameters for gap-graded and well-graded soils

Suffusion is one of the four types of internal erosion and accounts for 46% of erosion phenomena in earth dams. Suffusion is an erosion of fine particles inside the soil structure that move out of the voids between coarse particles caused by permeability flow. Identification of internal erosion is necessary to mitigate the loss of humans and property as underground erosion occurs. However, determining suffusion susceptibility in situ is complex and takes a lot of time. This study proposed a fine-grained erosion prediction model based on physical parameters related to the grading curve and the dry density. Using the principal component analysis (PCA) tool evaluated the influence of these parameters on suffusion. The proposed predictive model of the erosion resistance index (ERI) supports stakeholders in quickly determining the extent of erosion and then taking appropriate measures to maintain the earth dams.

Assessment of Foundation Rocks of the Proposed Makhol Dam in the Northern Salah- Alddin, Iraq

This study was done as an assessment of the foundation rocks of the proposed Makhol dam in the northern Salah- Aiddin Governorate, Iraq. This study consists of field, laboratory, and office work. It was noticed in the field that the thirteen (13) different rock mass units comprised along the dam axis. Three rock mass classification systems were adopted (used) in the evaluation: Rock Mass Rating, Dam Mass Rating, and Geological Strength Index. The DMRSTA (RMR related to dam stability) values for the right bank range between 36.97- 73.8. These values indicate good stability of foundation rocks of the right part with the presence of some instability of primary effect (not serious effect) in unit no.3 (Fatha Formation), and the DMRSTA values of the left bank range between 44.97– 61.7 These values indicate no instability for the foundation rocks on the left bank for all rock mass units. The RMRBD89 values range between 37– 73.3. These values reveal that the foundation rocks are desirable and can be excavated for rockfill and earth fill dams, but for the gravity dam, the rock mass unit 3, must be excavated to the desirable RMRBD89 value in the case of a gravity dam, and indicate that the foundation rocks do not require grouting when the type of dam is earth fill. Some rock mass units require grouting (spot grouting), especially for the rock mass unit 3 when the type of dam is Rockfill, and require systematic grouting, especially when the type of dam is Gravity. The Roc Lab software was used for the purpose of determining the mechanical properties of all rock units through the Hook-Brown failure criterion.

Напряженно-деформированное состояние плотины Юмагузинского гидроузла

Introduction. The stone-and-earth dam of the Yumaguzinskiy hydroelectric complex on the Belaya river is constructed in complicated geological conditions on heterogeneous foundation. The results of computational research of stress-strain state (SSS) of the dam, carried out for the variant of an earth dam with the central core are presented. When calculating the deflected mode of dams, the real structure of ground characterized by its relation of elastic and plastic bonds should be taken into account. The change of this structure takes place along with the change in stresses and is reflected in the values of coefficient of relative strength and coefficients of reliability. The values of the safety coefficients can be used to judge the strength state of the dam. Materials and methods. The stress-strain state of the dam was determined on the basis of the energy model of the developed by L.N. Rasskazov. The area of the selected fragment of the dam has been divided into single-type elements; a triangular grid of the finite element method has been adopted, by means of which the structure of the soil dam and the foundation have been described. Results. Numerical calculations have shown that when water level in the reservoir rises to the level of the forced retaining level the character of stress distribution σxx changes. At the base of uppermost buttress prism at the boundary with the core there appears an area with small positive values, the largest of which is obtained in the transition zone. The entire hydrostatic load is transferred to the pressure face of the core and, consequently, the entire work of external forces is transferred to the internal deformation energy of this element, causing a stress concentration in it. The transition zone material is forced to follow the deformations of the core, resulting in the development of tensile stresses in the core. Therefore, increasing the stiffness of the core results in less deformation of the core and correspondingly less tensile stress in the transition zone. The nature of stress distribution σyy is symmetrical. Conclusions. Increasing the rigidity of the core entails elimination of the arch effect, which is particularly noticeable at lower reservoir levels. For this reason the use of skeleton material in the core of the dam is desirable.

Correlations between CBR index, using the modified optimum proctor characteristics and lateritic soils identification parameters

The selection of soils for construction of engineering structures is done on the basic of set number of criteria. In road construction, the criteria used are the value of the CBR index at 4 days imbibition. For earth dams and road embankments where materials should be compacted at their maximum dry density, we will adopt the criterion: the compaction characteristics at its optimum modified proctor. The determination of these criteria are very time consuming and can generate several delays which is inconsistent with the strategies of productivity of Publics Works companies. To reduce these delays, relations permitting us to predict their values from soil identification parameters should be developed. In this context, 1500 laboratory test results obtained from samples collected throughout the Cameroon territory were studied. Correlations which obtained were tested on around thirty results gave a prediction with error lower than 6.02%.

Experimental and numerical evaluation of tire rubber powder effectiveness for reducing seepage rate in earth dams

Abstract Tires waste is an undesirable urban industry surplus that has grown worldwide yearly. Because of its seals, this material may be used in earth dams, one option for disposing of this waste. Since this is the main objective of this study, an experiment on a soil sample with various ratios of rubber powder has been conducted to better comprehend the impact of tire rubber powder (TRP) on the seepage rate in earthen dams. This study used physical and numerical models to investigate seepage through earth dams. Analysis indicates that the plotted seepage line in SEEP/W software was comparable to the observed seepage line in the physical model. TRP was tested at concentrations of 15, 30, and 50%. The research demonstrates that there has been a noticeable improvement in reducing the seepage rate through the dam’s body; seepage was decreased by 11.28% when a 15% ratio was adopted, a far smaller impact than the other percentages. The proportion was consequently raised to 30%. The seepage rate was found to be reduced by 35.6%, and TRP with a 50% ratio showed excellent behavior in lowering the water level (phreatic line) from the core point to the downstream face D/S and reducing the seepage rate by 41.5%, producing significantly better results. The findings in SEEP/W software indicate that the relative error in seepage rate varies, averaging 11.8% for the first model, 12.18% for the second, 1.65% for the third, and 7.63% for the fourth. The first and second physical models’ seepage rate (relative inaccuracy) dramatically increased as a result of the presence of piping.

Seismic behavior and reinforcement mechanisms of earth dam and liquefiable foundation system by shaking table tests and numerical simulation

Earth-rockfill dams suffer from various geotechnical disasters during seismic hazards, and liquefiable foundation will aggravate these damages by reducing the foundation bearing capacity. In this research, a quasi-three-dimensional earth dam and liquefiable foundation model was designed to study the seismic behavior, liquefaction process and reinforcement mechanism. Three typical models, including unreinforced (UR), raft reinforced (RR), and gravel pile reinforced (GPR) models, have been investigated by 1-G shaking table test and numerical simulation. The experiment of model UR was utilized for calibrating the numerical parameters via the inverted method, and two other experiments were set as the simulation targets using the above-mentioned parameters. The experiment and simulation results have shown that uneven settlement and cracks appeared in model UR are mainly caused by foundation liquefaction rather than seismic residual deformation. The raft slab and gravel piles mitigate the uneven settlement and cracking potential significantly by multiple reinforcement mechanisms including the supporting effect, drainage effect, and stiffness improvement effect.

Characterization of a leaky earth dam using integrated geophysical surveys

Early earth dams were mainly constructed using a soil core wall, which is susceptible to a variety of potential risks such as inhomogeneity, poor compactness, and leakage due to multiple fillings and biological damage. To ensure safe operation of the dam, cost-effective geophysical non-destructive testing techniques should be considered during routine maintenance. This paper presents a case study of an earth dam designed for water storage and flood control that experienced a leak problem. To provide a basis for future leakage control, we carried out 2D integrated geophysical surveys utilizing Electric Resistivity Tomography (ERT), Ground Penetrating Radar (GPR), and Surface Wave (SW) methods along the dam axis. In conjunction with the fast attenuation characteristic of GPR signals, the low resistivity anomalies recovered by the ERT provide evidence to reveal the leakage area within the dam structure. Moreover, the shear wave velocity variation retrieved by the SW method helps to determine the distribution of bedrock and soil layers. By integrating the results mentioned above, the interpretation outcome yields a comprehensive understanding of the internal condition of the earth dam. The successful investigation of the dam structure and the mapping of the leakage area demonstrate the effectiveness of integrated geophysical surveys in characterizing earth dams. It also suggests that it is essential to consider the difference between various geophysical results and the underlying reason when integrating them to characterize leaky earth dams.

The impact of seismic waves to evaluate the behaviour of a real case of damaged earth dam

ABSTRACT Many earth dams are damaged by shearing under seismic stresses effect. In Algeria, earthquake of 21 May 2003, of magnitude Mm = 6.9 on Richter scale, considered as the most violent for more than 20 years, occurred about 70 km east of Algiers’s capital, where a large number of structures were damaged in this region. The aim of this article is to present a numerical analysis of an earth dam in the province of Oum-Elboughi. The objective is to show the influence of compressive seismic waves and the effect of foundation deph on dam behavior .The stady was carried out using a 2D finite difference method (FDM) using the FLAC 2D calculation code. In this analysis, a soil nonlinear behaviour is provided by a combined Hardin/Drnevich hysteretic damping behaviour model with Mohr–Coulomb elasto-plastic model. Results that are presented in terms of deformations and shear stresses developed at the dam and dam foundation show that the most critical area is located on the downstream side of the dam. Increasing the foundation depth decreases the value of horizontal stress, while decreasing it increases the dam instability risk.

Dam Deformation Monitoring using Cloud-Based P-SBAS Algorithm: The Kramis Dam Case (Algeria)

This paper presents the application of the Parallel Small Baseline Subset (P-SBAS) algorithm, provided by the Geohazards Exploitation Platform for the precise monitoring of an earth dam's ground deformation using C-band Sentinel-1 data. The test site object of this study was the Kramis dam, located in the Mostaganem State, Western Algeria. Among the multiple advanced DInSAR techniques, SBAS is very adequate for long-term displacement monitoring in areas with changing terrain and vegetation. Ten corner reflectors were installed as a backscattered radar signal amplification tool to reduce the effect of temporal decorrelation and delineate the dam area. Four Sentinel-1 A and B satellite tracks were available (T30, T37, T103, and T110) to measure displacements, in the Line of Site (LoS) direction, for two years since the installation of the CRs in July 2019. The results showed a subsiding area on the left bank of the dam dike, with a velocity of 4mm/yr, and an uplifting rate of 3-4mm/yr in the upper part of the dike. The entire 3-dimensional vector of displacement of the dam vicinity was estimated using the least-squares method, proving a better understanding of the dam's temporal deformation, particularly for dams with a high exposure factor and associated risk.

FIBRADIKE, a novel distributed fiber optic monitoring system for dikes and earth dams

Safety issues related to climate change are one of the major challenges of modern society. One of the most significant risks is represented by extreme flood events which could lead to dike or earth dam breaching with catastrophic consequences for the environment. Despite the relevance of these infrastructure and modern advanced sensing technologies, dike and earth dam safety monitoring is carried out as it has been for centuries with visual inspections. In the best case, traditional point sensors, like piezometers, are installed in some limited sections. In this way it is not possible to early identify problem sections, which can be located many km away from the observation point. In this research an attempt has been made in order to develop a distributed fiber optical sensing system for dike and earth dam safety monitoring. The core of the system is represented by a novel distributed pore water pressure sensing unit, in the form of a specifically designed fiber optic sensing cable.. The development and first promising results of laboratory testing carried out on the industrially produced prototypes of the sensing cable are presented in this paper.