Earthfill Embankment Research Articles

The impact of assumptions on deterministic and probabilistic analyses of earth fill embankments

This paper considers the impact of assumptions made when formulating analytic approaches to deterministic and probabilistic analyses of slope stability. The assumptions reviewed were presented in a paper, Waddell (2023) that presented semi-quantitative stability assessment using survey data, deterministic and probabilistic slope stability analyses of fill embankments constructed from residual soil and weathered bedrock in Western Sydney. A single variable fill strength was adopted, that was obtained from an Infinite Slope analysis assuming fully saturated fill. Rainfall records were used to predict risk of saturation to calculate annual probability of slope failure. The impacts of assumptions used to calculate the strength parameter, factor of safety and predicted failure probability are addressed in this paper. Saturation assumptions, the choice of limit equilibrium model, shape of the probability distribution functions, and spatial correlation of material properties are considered.

Settlement Control Technology of High Filled Soil-Rock Embankment in Alpine and High-Altitude Areas

China's infrastructure has gradually achieved large-scale development, and transportation construction has also shifted from east to west, transitioning from plains to mountainous areas. High-fill embankments of different sizes in mountainous areas are unavoidable, and the settlement of high-fill embankments is usually the most concerned issue in high-fill projects. According to the current research results of highway projects, most of the high embankments in mountainous areas are soil-rock mixed embankments or rock-filled embankments, and their post-construction settlements are directly related to construction technology and filler types. The problems existing in the settlement control of earth-filled embankment and related influencing factors are analyzed in detail. At the same time, the settlement control technology of high-fill embankment in high-cold and high-altitude areas is also discussed, so as to ensure the overall quality of high-fill embankment.

Stability of earth fill embankments constructed from residual soils including impacts of climate change

The paper looks at the stability of fill embankments using data from failed embankments constructed from residual soils in Western Sydney. Semi-quantitative, deterministic and probabilistic methods are used to consider the stability of such fill embankments. A simple, infinite slope model was adopted to carry out deterministic and probabilistic analyses. Climate data was used to assess the likelihood of fill saturation and the impacts of climate change on predictions.

A Study on the Installation of Measuring Instruments for Early Warning of Small-scale Reservoirs

Climate change is causing the collapse of 101 reservoirs due to localized torrential rains and continuous heavy rains. To minimize the damage to human life and property, this article focuses on selecting appropriate local instruments for the efficient maintenance and proper arrangement of these instruments to maximize the efficiency of the early warning and predictive warning systems. In this study, six small-scale reservoirs were studied, and two cases were considered and compared, namely an embankment with a central clay core and a simply earth-filled embankment. The results showed that to predict the collapse of the reservoir by piping, it was considered appropriate to apply 50% of the wetness ratio (<i>l/L</i>) by calculating the wet length (<i>l</i>) on the length (L) of the downstream slope of the embankment. Finally, a methodology was presented for selecting the location of the measuring device.

Mechanical Responses of Soil-Geosynthetic Composite (SGC) Mass under Failure Load

There is an increasing awareness on the major benefits of using soil-geosynthetic composite (SGC) to achieve and maintain the stability of earth-filled embankment. Unlike the mechanically stabilized earth wall, the mechanism of the composite mass is still not fully understood. For examples, current analyses have been limited to an SGC mass with a reinforcement spacing Sv of 0.2 m only; the combined effect of reinforcement and backfill properties is rarely studied; the equation for the estimation of the load-carrying capacity of the SGC mass has only been validated for backfill with maximum particle size dmax between 10 mm and 33 mm and an Sv/dmax ratio between 6 and 20. The consequences of backfill compaction on an SGC mass with different reinforcement spacings are yet to be validated and whether the load-carrying capacity equation would still be applicable for materials with properties falling outside the above ranges. Through the simulation and validation of a field scale SGC mass, this study aims to assess the influence of various reinforcement and backfill parameters on the mechanical responses of a large-scale experimental SGC mass under its working load and failure conditions; the results are presented in terms of the wrapped face lateral displacement, reinforcement axial strain, and load-carrying capacity.

Stability Analysis of the New Section in Raising the Existing Composite Wala Dam Using Finite Element Methods

Jordan is a country with a population that increases steadily but is punctuated by waves of refugees. Henceforth, Jordan will be destabilized with prolonged and potential water shortages. With both climate and population changes, the nation needs to implement comprehensive reform. In many cases, raising the height of an existing dam would help reduce the gap between the sources and water demands. Consequently, the original Wala dam in Jordan with a capacity of 9.3 million cubic meters (MCM) was raised to achieve a capacity of 25 MCM. The Wala dam was raised uniquely and unusually, which raises concerns about its stability and safety. In this paper, a two‐dimensional plane strain model was conducted using finite element modeling (FEM) on the Wala dam to investigate the stability conditions of the raised dam. Several material properties were used in this study. These properties are density, Poisson’s ratio, elastic modulus, and friction angle. Stresses and deformations of the new section within the dam body, dam foundation, and an earthfill embankment are presented and compared with the original dam. Results showed that the stresses after raising the height of the dam body are below 1.5 MPa, and it is within the allowable range. Moreover, the stability analysis showed that the stresses and deformation are minimal and negligible. Also, no failure was observed or reported within the soil. Furthermore, a stability analysis of the slip surface of the new body of the dam structure using the finite element method is introduced. Two potential slip surfaces were examined, and a surface‐to‐surface contact element is modeled to simulate the slip surface. In addition, settlement field observations for 16 months are presented and discussed in this paper.

A levee breach induced by internal erosion in Western Australia

This case study presents a levee breach induced by piping erosion under cyclonic conditions in 2019. The levee is a 2.5 m-high, 500 m-long, mass earth-fill embankment; with no cutoff trench, core or ancillary structures. Located near Port Hedland on the north coast of Western Australia, its purpose is diversionary: to redirect cyclonic surface water away from the nearby Great Northern Highway. The levee was founded directly on alluvium in 1987; it is formed of locally sourced clayey sandy gravel. In 2003, the levee was partially excavated to enable the placement of a buried pipeline through the levee. Following a cyclonic event in 2019, a 27 m length of the levee breached, resulting in significant scour of the foundation and downstream soil. A site visit and investigation were conducted shortly thereafter, where in situ testing and laboratory soil tests on the levee and foundation materials were conducted. Analysis of the site observations and laboratory testing data led to the probable failure mechanism being theorized as having been initiated within the foundation by piping erosion within sand-rich beds of alluvium. The large quantity of water ponding upstream of the levee then caused a progressive washout and breach of the levee. Thematic collection: This article is part of the Role of water in destabilizing slopes collection available at: https://www.lyellcollection.org/cc/Role-of-water-in-destabilizing-slopes

Method for predicting factor of safety and seepage due to variation in dam width and other parameters

Slope stability analysis and seepage analysis are two important aspects of embankment stability. Landslides are a common risk faced by many people in the world, with this risk increased in the case of an earthfill embankment or water reservoir. People living in downstream regions are always at risk if the dam is not designed to achieve full strength. In this work, a pre-defined earthfill dam was analysed to assess its strength with variations of dam width (WD), shear strength of the soil (τ) and dam slope angle (β). The factor of safety was considered as the dependent, with WD, τ and β as independent variables. A pre-defined proposed dam model was analysed using limit equilibrium (LE) methods with the help of the LE software Slide. Linear regression analysis was performed using SPSS (Statistical Package for Social Sciences) software and equations were developed. The computed equations show a very close relation of all the analysed parameters. The coefficient of determination (R2) of all the developed correlations was found to be very high and the equations can thus be used in design analysis of slopes, embankments and earthfill dams.

A Study on Protection Measure for Water Level Fluctuation and Overflow Conditions in Earth-filled Embankment by Centrifuge Model Tests

A Study on Protection Measure for Water Level Fluctuation and Overflow Conditions in Earth-filled Embankment by Centrifuge Model Tests

A Study on Seismic Behaviors of Earth-Filled Embankment with Intact and Deteriorated Core Using Centrifuge Model Tests

Janghyeon dam, located at Gangneung-si with 6.9 m height and constructed in 1947, is modeled at a scale of 1:60 to analyze the seismic behaviors of the dam during seismic loading through dynamic centrifuge model tests. The centrifuge model tests are performed by simulating the field stress conditions and seismic loads. The results of dynamic centrifuge model tests show that the dam with an intact core satisfies the stability criteria against crest settlement. In contrast, a settlement of 1.2% of the dam height suggests that the dam with a deteriorated core does not satisfy the stability criteria. The acceleration amplification ratio from the core base to crest is 1.1–1.6 in the case of the intact dam and is 1.15–2.32 in the case of the deteriorated dam. Thus, it is inferred that the acceleration and settlement responses rely not only on seismic loads but also on the condition of the dam (i.e., intact or deteriorated). The acceleration amplification and settlement in the deteriorated dam are observed to be apparent. This is due to the weakening phenomenon of the dam by water that seeps through the deteriorated core, which increases pore water pressure and saturation level. Thus, the dynamic behaviors of the earth-filled dam, obtained through this study, can be used as primary data for seismic design and reinforcement of dam.

Simulation of Mosul Dam Break Using Finite Volume Method

Mosul dam is an earth-fill embankment located north of Iraq on the Tigris River forming a reservoir with 11.11 km3 water storage capacity which is the largest dam in the country. The dam is built on a rock bed foundation, in which the dissolution process is dynamic in the zone where gypsum and anhydrite layers present. During the construction development seepage locations were found in the dam foundation and the grouting process is in progress until now to control this problem. Therefore, the possibility of the Mosul dam break is highlighted by previous studies. In this research, a FORTRAN code based on the finite volume method is modified to solve the two-dimensional shallow water equations and simulating the Mosul dam break. The computational domain discretized using unstructured triangular mesh. The solver applied Harten lax van leer with contact (HLLC) wave approximate Riemann solver to calculate the cell interface fluxes, and the semi-implicit scheme employed to solve the friction source term. The numerical scheme applied to two benchmark test cases, and the results showed that the presented model was robust and accurate especially in handling wet/dry beds, mixed flow regimes, discontinuities, negative water depths, and complex topography. The results of this study demonstrate that flood waves may reach the center of Mosul city in < 6 h and water depth may rise to 34 m after 7 h of Mosul dam breaking. Finally, the simulation results of the Mosul dam break were used to prepare an emergency action plan.

Investigating the Earth Fill Embankment of the Lotsane Dam for Internal Defects Using Time-lapse Resistivity Imaging and Frequency Domain Electromagnetics

We investigated the internal structure of the Lotsane Dam for zones that may be prone to seepage and internal erosion using the electrical resistivity imaging (ERI) and the frequency domain electromagnetic (FDEM) methods. Time-lapse ERI measurements were also made for a period of 8 months in order to monitor the temporal evolution of defective zones. Results from both the FDEM and ERI measurements show two main layers. The first is an upper conductive layer varying in thickness from 10 to 25 m which is related to the clay core embankment. Situated beneath this upper conductive layer is a highly resistive crystalline basement on which the dam was founded. Furthermore, the ERI and FDEM measurements revealed the presence of fractures and possible zones of weakness within the dam foundation. Time-lapse ERI measurements revealed resistivity increases in the observed possible defective zones, including proximal to the spillway and at the embankment-foundation interface. The long-term resistivity variation may be indicating change in material properties in those portions of the dam, and may evolve to destabilize the structural integrity of the dam and or develop into preferential seepage pathways with time. The identified anomalous zones are good indicators that the embankment integrity is at risk and we suggest continuous geophysical monitoring of Lotsane Dam structure in order to ensure dam safety and integrity on the long term.

Flume study on the effects of microbial induced calcium carbonate precipitation (MICP) on the erosional behaviour of fine sand

Tangential flow-induced interface erosion poses a major threat to a wide variety of engineering structures, such as earth-filled embankment dams, and oil- and gas-producing wells. This study explores the applicability of microbial induced calcium carbonate (CaCO3) precipitation (MICP) by way of the ureolytic soil bacterium Sporosarcina pasteurii as a method for enhancing the surface erosion resistance of fine sand. Specimens were treated with cementation solution concentrations between 0·02 and 0·1 M, and the erosional behaviour examined in a flume under surface-parallel flow and increasing shear stress. Photographs, cumulative height eroded-time series and erosion rates were obtained as a function of specimen height, MICP treatment formulation and calcium carbonate content. Results showed that while untreated specimens eroded primarily in particulate and mass form, MICP-treated specimens were characterised by a block erosion mechanism. Further, erodibility was found to depend on the calcium carbonate content and the cementation solution concentration. To understand this, a systematic study of the calcium carbonate crystal sizes and distributions was undertaken through X-ray computed tomography. Fundamentally, the effectiveness of MICP for erosion control was found to be dominated both by the precipitated calcium carbonate content and microstructural features, with higher contents and larger crystals yielding lower erodibility values. Additionally, crystal growth mechanisms varied depending on the cementation solution concentration.

Micro-topographic assessment of rill morphology highlights the shortcomings of current protective measures in loess landscapes

Due to urban expansion and the rapid development of infrastructure in the loess area of China, artificial earth-fill embankments and excavated slopes are increasingly widespread in recent years. Erosion is typical in such loess slopes; however, quantitative statistical analyses of various counter-measures that affects rill erosion are still lacking. Here, we quantified rill morphology and rill erosion development in two newly constructed slopes with different engineering protection measures. We used high-resolution digital surface models (DSMs) acquired using an Unmanned Aerial Vehicle (UAV) to analyze the case areas during two-time periods. Our results from centimeter accuracy differential DSMs demonstrated that rapid rill erosion is prevalent in the study area, expressed as rill density varying between 2.03 km−2 and 8.81 km−2 at different slope surfaces (viz., erosion protected slopes [EPS], landslide protected slopes [LPS], and unprotected slopes [US]). The slope gradient responsible for rill erosion of the EPS, LPS and US are obviously different, and such information is essential for planning preventive measures in each slope type. At the EPS, the severity of erosion is maximum at the top of the ridges, whereas the gap between reinforced concrete lattice and loess deposits are of serious concern at the LPS. The current engineering measures employed in the study area are thus found ineffective for protection against rill erosion. We therefore propose an improved design by implementing an intercepting drain to the existing design for preventing further erosion.

Dam Breach Size Comparison for Flood Simulations. A HEC-RAS Based, GIS Approach for Drăcșani Lake, Sitna River, Romania

Floods are the most destructive natural phenomenon, by the total number of casualties, and value of property damage, compared to any other type of natural disaster. However, some of the most destructive flash floods are related to dam breaches or complete collapses, that release the large amounts of water, affecting inhabited areas. Worldwide, numerous dams have almost reached or surpassed the estimated construction life span, and pose an increasing risk to structure stability. Considering their continuous degrading state, increasing rainfall aggressiveness, due to climatic changes, technical error, or even human error, there are numerous, potential causes, for which dams could develop breaches and completely fail. This study aims to portray a comparative perspective of flood impact, with real-life consequences, measured by quantifiable parameters, generated from computer simulations of different breach sizes. These parameters include the total flooded surface, water velocity, maximum water depth, number of affected buildings, etc. The analysis was undergone by means of HEC-RAS based 2D hydraulic modeling and GIS, depending on high-accuracy Lidar terrain data and historical hydrological data. As a case study, Drăcșani Lake with the associated Sulița earthfill embankment dam was chosen, being one of the largest and oldest artificial lakes in Romania.

Slope Stability Analysis of the Gbeni Earth Dam (GB3) in Rutile - Sierra Leone

Earth slopes stability analysis is important in the design and construction of earth dams under different loading conditions. Several factors such as difference in water level or rapid drawdown in the reservoir, right after construction, and steady - state seepage may result in instability of Earth Dams for all possible combinations. In this study, three scenarios were evaluated for the Gbeni Earth Dam (GB3) at Sierra Rutile Mining Company in Sierra Leone. It is a zoned earth-filled embankment dam with respective upstream and downstream slopes of 1:3 and 1:2, having a horizontal sand blanket downstream. The upstream slope was subjected to both rapid drawdown in the reservoir of the earth dam and end of construction condition when there is no water present in the reservoir, whilst the downstream slope was assessed for steady seepage and end of construction conditions. The shape of the critical slip surface of both slopes was evaluated using a circular failure surface. The objective of this study was to assess the stability of these slopes under the above conditions using traditional analysis according to the theory of limit states and safety factor in GEO 5 software and its subprograms. The level of water on the upstream and downstream banks, the geotechnical properties of soil materials and boundary conditions of the dam were used as contribution variables and safety factors as the desired output. The study found out that the factor of safety against sliding of the upstream slope marginally drops within the short period after the start of rapid drawdown of water in the reservoir of the dam. Also, the downstream slope was found to be more stable under steady seepage. This accounts for the uncertainties involved in the strength of material, pore pressures in impervious clay core material, and long-term loading condition.

Geophysical Investigation of Oba Earth-Fill Dam Embankment using Electrical Resistivity Method

Geophysical Investigation of Oba Earth-Fill Dam Embankment using Electrical Resistivity Method

Geodetic monitoring of earth-filled flood embankment subjected to variable loads

Abstract The article presents an example of supplementing geotechnical monitoring with geodetic observations. The experimental flood embankment built within the ISMOP project (Information Technology System of Levee Monitoring) was subjected to continuous monitoring based on built-in measuring sensors. The results of geodetic monitoring used for observation of earth-filled flood embankment subjected to external loads are presented in the paper. The tests were carried out on an experimental food embankment forming a closed artificial water reservoir. The observations were carried out for two purposes. The first was long-term monitoring, which was aimed to determine the behaviour of the newly built embankment. The second purpose was to check the reaction of the levee to the simulated flood wave, caused by filling and draining the reservoir. In order to monitor the displacements of the earth-filled embankment, it was necessary to develop the proper methodology. For the needs of research works, an appropriate network of 5 reference points and 48 survey markers has been designed and established. The periodic measurements were carried out using precise robotic total station. The stability of the reference frame was each time checked and displacements of survey markers were determined based on it. The final results allow to reveal the reaction of levee to external loads. The displacement values were referred to the course of the filling and draining experiment to indicate the relationship between them. In the field of long-term monitoring the results clearly imply the dominance of displacements outside the reservoir for points located on the embankment, in contrast to points on the crest and foreground, which do not show significant movements. On the other hand, in the field of testing the embankment reaction to the flood wave, obtaining reliable results was possible thanks to high-accuracy geodetic measurements. Small displacement values, often at the level of their determination errors, were averaged for groups of points with the same height of foundation. A sizable number of points allows to perceive some tendencies and the relation between embankment soaking, hence its movement directions can be noticed. During periods when the levee was still saturated with water, slight movements outside the reservoir were revealed. On the other hand, the following period of drying caused movement in the opposite direction.

SH-Mode Seismic-Reflection Imaging of Earthfill Dams

Abstract Assessing subsurface characteristics and imaging geologic features (e.g., faults, cavities, low-velocity layers, etc.) are typical problems in near-surface geophysics. These questions often have adverse geotechnical engineering implications, and can be especially acute when associated with high-hazard structures such as large earthen flood-control dams. Dam-related issues are becoming more frequent in the United States, because a large part of this major infrastructure was designed and constructed in the early- to mid-twentieth century; these dams are thus passing into the latter stages of their design life, where minute flaws that were overlooked or thought to be insignificant in design/construction are now proving problematic. The high-hydraulic heads associated with these structures can quicken degradation of weak areas and compromise long-term integrity. Addressing dam-related problems solely with traditional invasive drilling techniques is often inadequate (i.e., lack of lateral resolution) and/or economically exorbitant at this scale. However, strategic geotechnical drilling integrated with the broad utility of near-surface geophysics, particularly the horizontally polarized shear-wave (SH-mode) seismic-reflection technique for imaging the internal structural detail and geological foundation conditions of earthfill embankment dams can cost-effectively improve the overall subsurface definition needed for remedial engineering. Demonstrative evidence for this supposition is provided in the form of SH-wave seismic-reflection imaging of in situ and engineered as-built components of flood-control embankment dams at two example sites in the central United States.

Earthquake Rating of Pore Water Pressure Generation – Induced Liquefaction of Earth Fill Embankments by Numerical Simulation

Earthquake Rating of Pore Water Pressure Generation – Induced Liquefaction of Earth Fill Embankments by Numerical Simulation