Earth Embankments Research Articles

The endemic Cyprus Wheatear (Oenanthe cypriaca) adapts readily to artificial nest sites

Widespread urbanization leads to environmental changes and affects avian populations. We provided artificial nest sites in the form of plastic tubes placed in earth embankments and compared the breeding parameters to those in natural nest sites of the endemic Cyprus Wheatear (Oenanthe cypriaca). We hypothesized that the loss of semi-natural habitats, in which Cyprus Wheatear have coevolved with agriculturists, could be offset by the provision of alternative nest sites. We found that breeding parameters like clutch size (4.7; 95% CL: 4.6–4.9), the number of nestlings (4.0; 3.7–4.3), fledglings (3.5; 3.2–3.9) and overall breeding success (82.2%; 73.7–89.0) did not differ between natural and artificial nest sites. Average occupancy of artificial nest sites was only 6.1% (5.4–6.7) but at present, the Cyprus Wheatear population appears to be resilient with high reproductive output and survival. The study showed that the endemic Cyprus Wheatear readily adapts to alternative, artificial nest sites, and their reproductive output is similar to individuals nesting in natural sites. Considering novel approaches to sustain future populations of endemic species are crucial in the face of a fast-changing world.

Shape Optimization of a Kind of Earth Embankment Type Windbreak Wall along the Lanzhou-Xinjiang Railway

Shape Optimization of a Kind of Earth Embankment Type Windbreak Wall along the Lanzhou-Xinjiang Railway

Innovative uses of thermal imaging in civil engineering

Thermal imaging captures information in the infrared spectrum of light invisible to people, thus it can provide valuable extra information. Innovative use of thermal imaging technology can therefore play an important role in many civil engineering applications. This paper provides insight into thermal imaging technology and its uses in civil engineering. A field example of early leak detection in an earth embankment using thermal imaging technology is presented. With ever-improving thermal imaging technology and decreasing cost of thermal imaging cameras, many future uses of thermal imaging in civil engineering are envisaged – from pipeline leak detection to structural integrity inspections, energy efficiency surveys and pollution monitoring. The small size of the equipment means it can also be carried by drones, offering access to remote or otherwise inaccessible areas.

Reducing the hydraulic erosion of sand using microbial-induced carbonate precipitation

Hydraulic erosion is one of the main causes of failure within earth dams and embankments. Various methods are used to mitigate against such erosion, a common approach being grouting with cement, clay or chemical materials. Biogrouting using the microbial-induced carbonate precipitation technique is a relatively new, cost-effective, technically appropriate and environmentally friendly soil improvement method. Bacteria injected into the soil produce urease enzyme, which converts urea to ammonium and carbonate, causing calcite precipitation that binds soil grains together. In this study, the erodibility parameters of dense silica sand specimens treated with different injection strategies were investigated at bench scale. More effective treatment – in terms of greater and more uniform calcite precipitation over the test-specimen length, and hence greater erosion resistance – was achieved by aeration during solution injections and by incorporating a drained stage between injection cycles. With the latter, calcite precipitated as larger crystals, accumulating extensively over grain surfaces and also formed integrated in the pore voids. The best-performing treatment strategy produced a 95% reduction in erodibility and a five-fold increase in critical shear stress relative to untreated sand. These findings were confirmed by scanning electronic microscopy and calcium carbonate titration tests.

Tension Cracks in a Compacted Clay Embankment

AbstractIn a spirit of adventure, a boring was made and soil moisture contents measured along a tension crack near the crest of an earth embankment. Moisture contents increased linearly with depth ...

Stability Analysis of the Earth Embankments Subjected to Natural Cyclic Processes

The paper brings out the stability analysis of the earth embankments subjected to specific natural cyclic processes such as tides in India and freeze-thaw in Romania. The Sundarban, along the Bay of Bengal, is a low tide-dominated deltaic plain of the Ganga-Brahmaputra-Meghna basin (GBM) spreading over India and Bangladesh around 25,500 sq.km. The 3520km of riverside embankments had been erected to protect the deltaic plain from tidal flooding. The tidal cycle in this region is twice high tide and low tide daily. Presently, the Indian Sundarban Delta is under the threat to embankment failure. The study analyses the stability of an 8 m height embankment in the Gosaba region of Sundarban considering a 2m wide earth filled berm at 6m from the bottom of varying clay core thickness under the transient groundwater flow. Pore pressure, Flow net and Phreatic surface have been obtained by numerical models using FLAC 2D software, thus the factor of safety being analysed. In Romania, built on the of the highway A1 Orăştie-Sibiu section crossing the clayey hills from Aciliu and Apoldu known for their instability, the embankment around the abutment pier from Apoldu broke up at the entry to the Aciliu Viaduct. The layers of permeable soil soaked with water become heavy instead the waterproof layers keep the water above them creating sliding surfaces. The water is channelled to dozens of springs that appear or disappear depending on each micro-slip or fallen water amount. By freezing the water expands on the ground determining additional efforts, the cycle iterating with each rain and freeze-thaw.

DISPERSIVE CLAY STABILISED BY ALUM AND LIME

Dispersion phenomenon can cause erosion problems during hydraulic construction projects such as earth dams, channels, hydraulic installations and embankments. However, aluminum sulfate can be used to stabilize dispersive clay. Tests were done to consider the effects of alum and lime additions on shear strength parameters of clay as secondary effects. Clay for samples was taken from the Mirzakhanluo Dam, located in Tarom County, northwestern Zanjan Province of Iran. In this research, the clay sample was subjected to direct shear testing; the clay was tested with optimum moisture under varying percentages of alum (0, 0.3, 0.6, 1, 3, and 5 as percentage of dry soil weight) for 28 days. Also, unconfined tests were conducted on samples with equal amounts of moisture, alum and lime under the different treatment durations of 7, 14, and 21 and 28 days, separately. Results for the direct shear test indicated that the maximum cohesion was recorded in the sample with 1% alum. Results also showed that the internal friction angle decreased in samples with alum percentage up to the level of 0.6% and at levels higher than that it showed an increase. Generally, results showed that soil shear strength was higher in soil stabilized by alum than in unstabilized soil. Results of the uniaxial test, determined that alum and lime additions to dispersive soil and its treatment, compression strength was not limited and elastic modulus showed an increase. The highest evaluations were determined for amounts of elastic modulus and uniaxial strength in soil with 3% lime or 5% alum on the 28th day of treatment.

Anomaly detection in earth dam and levee passive seismic data using support vector machines and automatic feature selection

We investigate techniques for earth dam and levee health monitoring and automatic detection of anomalous events in passive seismic data. We have developed a novel data-driven workflow specific to our domain, which could be generalized for monitoring other systems with time series data. We use machine learning and geophysical data collected from sensors located on the surface of the levee to identify internal erosion events. In this paper, we describe our research experiments with two-class and one-class support vector machines (SVMs). We use two different data sets from experimental laboratory earth embankments (each having approximately 80% normal and 20% anomalies) to ensure our workflow is robust enough to work with multiple data sets and different types of anomalous events (e.g., cracks and piping). We apply wavelet-denoising techniques and extract nine spectral features from decomposed segments of the time series data. The two-class SVM with 10-fold cross validation achieved over 94% overall accuracy and 96% F1-score. Experiments with the one-class SVM (no labeled data for anomalies) using the top features selected by our automatic feature selection algorithm increase our overall results from 83% accuracy and 89% F1-score to over 91% accuracy and 95% F1-score. Results show that we can successfully separate normal from anomalous data observations.

The use of polymeric and metallic geogrid on a full-scale MSE wall/embankment on hard foundation: a comparison of field data with simulation

A full-scale reinforced earth embankment was designed and constructed by the Department of Highways of Thailand on a hard foundation in Phitsanulok Province, Thailand. Two types of reinforcement were used in the embankment. One side was reinforced with polymeric reinforcement consisting of polyester (PET), polypropylene (PP) and high-density polyethylene (HDPE) and referred to as a reinforced steep slope (RSS), with an angle of 70° from horizontal. On the other side, the embankment was reinforced with metallic reinforcement consisting of metallic strips (MS) and steel wire grids (SWG) combined with vertical segmental concrete facing and referred to as a mechanically stabilised earth wall (MSEW). The behaviour of the reinforced soil slope and the mechanically stabilised earth wall on a hard foundation were observed and compared with predictions from the PLAXIS 3D software. The lateral displacements and settlements were very small in the case of the MSEW with inextensible reinforcement. The corresponding lateral and vertical deformations in the RSS were much larger due to its extensible reinforcing materials. The stiffnesses of the reinforcing materials decrease in the following order: MS, SWG, PP, HDPE and PET. The results obtained from three-dimensional (3D) finite element method simulations (using PLAXIS 3D) were in good agreement with the field measurements in terms of vertical and lateral deformations and strains in the reinforcement.

Combined effect of hysteresis and heterogeneity on the stability of an embankment under transient seepage

The stability of most earth embankments is strongly influenced by the water content of the soil. The water content directly influences the suction or pore pressure in the soil, as well as the mass of material, thereby affecting the stress state and strength, and leading to changes in the stability. These aspects are coupled by the so-called soil water retention behaviour, which is observed to be a hysteretic phenomenon. Moreover, soils are known to be spatially variable or heterogeneous in nature, which can lead to preferential flow paths and stronger or weaker zones. In this paper the behaviour of a heterogeneous earth embankment subjected to cyclic water level fluctuation, including the impact of hysteresis, is investigated. The soil property values governing the unsaturated hydraulic response of the embankment are considered as spatially random variables, with the mechanical property values considered deterministic in order to isolate the impact of the hydraulic behaviour. The Monte Carlo Method (MCM) is used to conduct probabilistic analyses and an assessment of the relative influence of material properties illustrates that the saturated hydraulic conductivity, ksat, plays a dominant role in the slope stability. Moreover, in the initially drying condition, the average factor of safety (FOS) and the 95th percentile FOS of the slope considering hysteresis are smaller than those without considering hysteresis, at all times, while the variability of the FOS considering hysteresis is larger than that when not considering hysteresis. In practice, this means that slopes under seepage conditions, which are assessed to have a low FOS, should be assessed including the hysteretic behaviour to ensure stability.

Static Method to Determine Compaction Characteristics of Fine-Grained Soils

Abstract Engineering projects such as roads, earthen dams, embankments, and trench backfills require soil compacted at higher dry unit weight. In a majority of geotechnical projects, compaction of soils is involved with increasing strength and decreasing compressibility and permeability. The Proctor compaction test forms one of the most popular and important tests in geotechnical engineering practice. The moisture content-dry unit weight relationship of the soil obtained from the standard Proctor test forms the basis for specification and field compaction control. Standard Proctor test, also known as the dynamic compaction test requires considerable time and effort and has few imperfections. This study examined the possibility of determining the equivalent static pressure to the standard Proctor test to obtain the optimum moisture content, OMC, and maximum dry unit weight, of fine-grained soils. For this, a static compaction pressure test was devised in the Proctor mold itself to statically compact the soil at different water contents. The equivalent static pressure so determined will simplify the compaction procedure and will also result in considerable saving of time, money, and effort, especially so when dealing with highway and earth embankment projects.

Safety Assessment of Antiliquefaction Performance of a Constructed Reservoir Embankment. I: Experimental Assessment

AbstractEarthquake-induced liquefaction is a major threat to the safety of earth embankments. This paper presents an experiment-based safety assessment of antiliquefaction performance of a construc...

Determining the Elastic Deformation Modulus From a Compacted Earth Embankment Via Laboratory and Ménard Pressuremeter Tests

Compacted earth embankments are routinely used in dams and many others infrastructure projects in Brazil. It is common to use fine-grained soils for these embankments, which are placed and compacted in the field at specific values of unit weight and water content. Their design is usually performed using geotechnical parameters from laboratory tests on compacted samples, although in situ tests could emerge as an alternative for determining specific parameters, as such tests can be conducted reasonably rapidly and can somewhat account for local inherent conditions of the soil such as confining stress levels, water content and mineralogical variations. Therefore, this paper explores the application of Ménard-type pressuremeter tests to determine the Young’s modulus of compacted soil layers from the side flank of a large-scale earth embankment constructed in the city of Goiânia in the Midwest Region of Brazil. The embankment was compacted under controlled conditions, permitting the extraction of undisturbed soil blocks at distinct levels during its erection. Laboratory tests, such as consolidated isotropic triaxial and oedometer tests, were performed on samples at their natural water content. Young’s moduli were derived from these laboratory tests and compared with the elastic moduli measured using the pressuremeter, either directly under different (external) conditions or at normalized levels of the effective confining octahedral stress. This comparison of results enabled the establishment of preliminary statistical correlations between the average (in situ and laboratory) moduli, which will be useful when using the Ménard pressuremeter for a preliminary design or a post-construction check of compacted earth embankments.

Numerical analysis on seismic behavior of railway earth embankment: A case study

A numerical case study on the seismic behavior of embankment was carried out based on a prototype of earth embankment in Yun−Gui Railway (from Kunming City to Nanning City) in southwest of China. A full-scale model of earth embankment was established by means of numerical simulation with FLAC3D code. The numerical results were verified by shaking table test. The seismic behaviors of earth embankment were studied, including the horizontal acceleration response, the vertical acceleration response, the dynamic displacement response, and the block state of earth embankment. Results show that the acceleration magnification near the embankment slope is larger than that in internal earth embankment body. With the increase of input peak acceleration, the horizontal acceleration magnification presents a decreasing trend. The horizontal acceleration response at the top of embankment is more sensitive to the intensity of ground motion than that at the bottom of embankment. The embankment presents an obvious nonlinear-plastic characteristic when the input horizontal peak acceleration is larger than 0.3 g. The maximum residual deformation occurs in the middle of embankment slope surface instead of at the top of embankment. The upper part of embankment experiences tension failure without shear failure, and area at the bottom of embankment around the symmetry-axis of embankment mainly presents shear failure under the earthquake loading. The tension failure and shear failure repeatedly occur along the slope surface of earth embankment.

Shear Strength Response of a Geotextile-Reinforced Chlef Sand: A Laboratory Study

During the last earthquake that occurred in Chlef (El Asnam 1980, Algeria), a significant decrease in the shear strength has caused major damages to several civil and hydraulic structures (earth dams, embankments, bridges, slopes and buildings), especially for the saturated sandy soil of the areas near Chlef valley. This paper presents a laboratory study of drained compression triaxial tests conducted on sandy soil reinforced with horizontal layers of geotextile, in order to study the influence of geotextile layer characteristics both on shear stress–strain and on volumetric change–strain. Tests were carried out on medium and dense sand. The experimental programme includes some drained compression tests performed on reinforced sand samples, for different values of the geotextile layers number (N g), of confining pressure (\( \sigma_{\text{c}}^{\prime } \)) and relative density (D r). The test results have shown that the contribution of the geotextile at low values of the axial strain (e 1) is negligible, for higher values of (e 1); geotextile induces a quasi-linear increase in the deviator stress (q) and leads to an increase in the volume contractiveness within the reinforced samples. A negligible influence of geotextile layers number (N g) on the stress–strain behaviour and the volumetric change has been shown, when normalized with N g. The results indicate that the contribution of geotextile to the stress–strain mobilization increases with increasing confining pressure, while its contribution to the volume contraction decreases with the increase in the confining pressure.

Experimental Investigation of Compacted Sand-bentonite Mixtures

An experimental investigation was carried on sand-bentonite mixtures, prepared with various proportions of its components. The samples were compacted by Standard Proctor procedure, in order to simulate the in situ placement method employed for earth embankments and landfills base layers. By analysing the results of the compaction tests different structure types are identified depending on the bentonite content. For a small amount of bentonite, the mixture keeps the properties of granular soils, while for higher bentonite contents there is a gradual transition to the typical mechanical behaviour of plastic clays. The interaction between sand and bentonite is investigated by Scanning Electron Microscope. Compressibility and permeability are measured by one dimensional swelling and compression tests.

Time-dependent Reliability Analysis of Flood Defence Assets Using Generic Fragility Curve

Flood defence assets such as earth embankments comprise the vital part of linear flood defences in many countries including the UK and protect inland from flooding. The risks of flooding are likely to increase in the future due to increasing pressure on land use, increasing rainfall events and rising sea level caused by climate change also affect aging flood defence assets. Therefore, it is important that the flood defence assets are maintained at a high level of safety and serviceability. The high costs associated with preserving these deteriorating flood defence assets and the limited funds available for their maintenance require the development of systematic approaches to ensure the sustainable flood-risk management system. The integration of realistic deterioration measurement and reliabilitybased performance assessment techniques has tremendous potential for structural safety and economic feasibility of flood defence assets. Therefore, the need for reliability-based performance assessment is evident. However, investigations on time-dependent reliability analysis of flood defence assets are limited. This paper presents a novel approach for time-dependent reliability analysis of flood defence assets. In the analysis, time-dependent fragility curve is developed by using the state-based stochastic deterioration model. The applicability of the proposed approach is then demonstrated with a case study.

Crack Detection in Earth Dam and Levee Passive Seismic Data Using Support Vector Machines

We investigate techniques for earth dam and levee health monitoring and automatic detection of anomalous events in passive seismic data. We have developed a novel data-driven workflow that uses machine learning and geophysical data collected from sensors located on the surface of the levee to identify internal erosion events. In this paper, we describe our research experiments with binary and one-class Support Vector Machines (SVMs). We used experimental data from a laboratory earth embankment (80% normal and 20% anomalies) and extracted nine spectral features from decomposed segments of the time series data. The two-class SVM with 10-fold cross validation achieved over 97% accuracy. Experiments with the one-class SVM use the top two features selected by the ReliefF algorithm and our results show that we can successfully separate normal from anomalous data observations with over 83% accuracy.

Prediction of Permanent Earthquake-Induced Deformation in Earth Dams and Embankments Using Artificial Neural Networks

This research intends to develop a method based on the Artificial Neural Network (ANN) to predict permanent earthquake-induced deformation of the earth dams and embankments. For this purpose, data sets of observations from 152 published case histories on the performance of the earth dams and embankments, during the past earthquakes, was used. In order to predict earthquake-induced deformation of the earth dams and embankments a Multi-Layer Perceptron (MLP) analysis was used. A four-layer, feed-forward, back- propagation neural network, with a topology of 7-9-7-1 was found to be optimum. The results showed that an appropriately trained neural network could reliably predict permanent earthquake-induced deformation of the earth dams and embankments.

Stability assessment of the Farrokhi earth embankment dam using the pseudo-static and deformation based methods

The behavior of earth dams has particular complexities against dynamic forces and its assessment requiresdetailed and scientific analysis. The Farrokhi earth dam is a heterogeneous type with vertical clay core, built 150 km away from Birjand and 41 km away from Qaen on the Farrokhi River. There are concernsregarding the stability of this dam in the event of a future severe earthquake especially because of itsplacement near the active faults of eastern Iran, a very active seismic area in the country. In this study, thepseudo-static analysis, sliding block model and Singh et al empirical relationships were adopted to evaluate safety of the Farrokhi dam against the design earthquake. Based on the findings of the present study, thestability of the Farrokhi earth dam is not guaranteed and as such, small to large size slope failures are expected especially in the upstream side. The pseudo-static analysis and the Singh et al empirical relationships revealed similar conclusions about the stability condition of this dam, while the sliding block method underestimated the earthquake related deformations.