Full-scale Embankment Research Articles

Automated localization of dike leakage outlets using UAV-borne thermography and YOLO-based object detectors

Leakage-induced soil erosion poses a major threat to dike failure, particularly during floods. Timely detection and notification of leakage outlets to dike management are crucial for ensuring dike safety. However, manual inspection, the current main approach for identifying leakage outlets, is costly, inefficient, and lacks spatial coverage. To achieve efficient and automatic localization of dike leakage outlets, an innovative strategy combining drones, infrared thermography, and deep learning is presented. Drones are employed for dikes’ surface sensing. Real-time images from these drones are sent to a server where well-trained detectors are deployed. Once a leakage outlet is detected, alarming information is remotely sent to dike managers. To realize this strategy, 4 thermal imagers were employed to image leaking outlets of several models and actual dikes. 9,231 hand-labeled thermal images with 13,387 leaking objects were selected for analysis. 19 detectors were trained using transfer learning. The best detector achieved a mean average precision of 95.8 % on the challenging test set. A full-scale embankment was constructed for leakage outlet detection tests. Various field tests confirmed the efficiency of the proposed leakage outlet localization method. In some tough conditions, the trained detector also evidently outperformed manual judgement. Results indicate that under typical circumstances, the localization error of the proposed method is within 5 m, demonstrating its practical reliability. Finally, the influencing factors and limits of the suggested strategy are thoroughly examined.

Development of a Multiphase Numerical Modeling Approach for Hydromechanical Behavior of Clay Embankments Subject to Weather-Driven Deterioration

Clay embankments used for road, rail, and flood defense infrastructure experience a suite of weather-driven deterioration processes that lead to a progressive loss of hydromechanical performance: micro-scale deformation (e.g., aggregation and desiccation), changes in soil-water retention, loss of strength, and macro-scale deformation. The objective of this study was to develop a numerical modeling approach to simulate the construction and long-term, weather-driven hydromechanical behavior of clay embankments. Subroutines within a numerical modeling package were developed to capture deterioration processes: (1) strength reduction due to wet-dry cycles; (2) bimodality of the near-surface hydraulic behavior; (3) soil-water and soil-gas retentivity functions considering void ratio dependency; and (4) hydraulic and gas conductivity functions considering void ratio dependency. Uniquely, the modeling approach was comprehensively validated using laboratory tests and nine years of field measurements from a full-scale embankment. The modeling approach captured the variation of near-surface soil moisture and matric suction over the monitored period in response to weather cycles. Further, the developed model approach could successfully simulate weather-driven deterioration processes in clay embankments. The model predictions manifested the ability of the modeling approach in capturing deterioration features such as irrecoverable increases in void ratio and hydraulic permeability near surface. The developed and validated numerical modeling approach enables forecasting the long-term performance of clay embankments under a range of projected climate conditions.

Xanthan gum biopolymer-based soil treatment as a construction material to mitigate internal erosion of earthen embankment: A field-scale

Biopolymers, which are naturally produced polymers, exhibit hydraulic and mechanical properties, and have low environmental impact. Therefore, they can be employed as an alternative to conventional civil engineering materials for internal erosion prevention. However, the internal erosion behavior of biopolymer-treated soils in a full-scale embankment is yet to be thoroughly investigated. This study focused on the potential of using xanthan gum biopolymer for internal erosion control in earthen embankments. To this end, both laboratory and full-scale investigations were conducted for analyzing its influence on the prevention of internal erosion. The laboratory tests showed that a 1% xanthan gum treatment demonstrated optimal characteristics for embankment building with enhanced soils’ plasticity and mechanical strength. Full-scale embankments were constructed using both untreated and 1% xanthan gum treated earthen materials with simulated internal erosion beneath the box culvert to test the effect of xanthan gum on mitigating internal erosion. The results revealed that xanthan gum successfully minimized the expansion of internal erosion through particle bonding, enhanced apparent cohesion, and pore-clogging. The untreated embankment eroded rapidly via seepage flow and collapsed within 1,500 s, while the 1%-XG-treated embankment retained its structure without considerable erosion until 2,500 s. Thus, xanthan gum is an environmentally friendly construction material that can achieve sufficient embankment stability with a small weight ratio (1% of total soil).

INFLUENCE OF PREPARATION CONDITIONS ON SOLIDIFIED-CRUSHED SOIL CHARACTERISTICS AND STRENGTH

When the soil generated during road or river excavation work is too soft to be used as a material, it can be improved by the use of solidifiers such as cement and lime. However, if an embankment has excessive strength as a result of solidification, the embankment may be difficult to re-excavate. High-strength embankments may fail if they are constructed on soft ground and are not able to follow the behavior of that ground. For this reason, there is a demand for a material whose strength development can be controlled even when a solidifier is added. As a solution to this issue, we investigated the use of crushed solidified soil. Crushed solidified soil is produced by adding a solidifier to soil and then crushing the soil in the middle of the solidification process. It is considered that the type and amount of solidifier and the timing for crushing have considerable influence on the physical properties and strength of the product. Therefore, we investigated the physical properties and strength of the crushed solidified soil and constructed two types of full-scale embankments on soft ground. We compared the deformation characteristics of these two embankments. We found that the crushed solidified soil had lower strength than the solidified soil and that the physical properties and strength of the material depended on the time elapsed before crushing of the solidified soil. Furthermore, it was found that the embankment by solidified crushed soil follows the deformation of soft ground

Field investigation on thermal characteristics of a slope-cooling structure for permafrost embankment in the Qinghai-Tibet Plateau

A poor cooling effect on warm permafrost (> −1.0 °C) was observed in the crushed-rock revetment embankment (CRRE), which is widely used in the Qinghai-Tibet Railway. The filling of the porous rock layers caused by wind-blown sand and rock-weathering in the Qinghai-Tibet Plateau can further weaken the cooling capacity of the CRRE and may cause instability of the railway vehicles. This study describes a novel slope-cooling structure (NSCS), which combines a CRRE and a slope-warming prevention measure. A full-scale embankment was built using the new design in a warm permafrost region of the plateau. Ground temperatures and air speeds in the pore space of rock layer of the slopes were monitored. The thermal characteristics of the NSCS were evaluated along with its cooling performance. The results indicated that the new slope structure produced an effective cooling process on the side-slopes and the subgrade permafrost. The permafrost table was elevated and the ground temperatures at the embankment shoulders showed a decreasing trend after construction, particularly under the shady side. Asymmetrical convection process, which exhibits a significantly higher air speed and frequency in winters than those in summers, was observed to occur in the rock layers of the new structure. The NSCS decreases the heat absorption during summers and thus is beneficial for the heat-dissipating of the side-slopes. Moreover, the NSCS can reduce the sunny-shady slope temperature difference, which is induced by embankment orientation; therefore, the symmetry of the embankment temperature distribution is maintained. In general, these cooling characteristics contribute to the enhancement of thermal stability of the embankment and confirm the application of the NSCS as an effective method for the design and maintenance of embankments formed on warm permafrost.

Performance of geosynthetic cementitious composite mat and vetiver on soil erosion control

An understanding of how different land covers affect soil erosion caused by rainfall is necessary in mountainous areas. The land cover usually plays an important role in controlling landslide hazards associated with these terrains. This paper presents the results of a field experiment where several types of land covers were placed on a full-scale embankment as erosion control. An 8 m wide, 21 m long, and 3 m high embankment with a 45° side-slope was built with lateric soil. The soil was compacted under a relative compaction of 70% to simulate a natural soil slope. Two sides of the embankment were divided into six land cover areas, with three different areas of bare soil, and one each of a geosynthetic cementitious composite mat (GCCM), vetiver grass, and a combination of GCCM and vegetation. Soil erosion and moisture levels were monitored for each land cover area during six natural rainfall events encountered over the experimental period. Field results were compared with a numerical simulation and empirical soil loss equation. The results revealed that the GCCM gave the best erosion control immediately after installation, but vetiver grass also exhibited good erosion control six months post-construction.

Settlement and Vertical Load Transfer in Column-Supported Embankments

Column-supported embankments (CSEs) with or without a load-transfer platform (LTP) can reduce settlements, improve stability, and prevent damage to adjacent facilities when embankments are constructed on ground that would otherwise be too weak or compressible to support the new load. CSEs function by transferring the embankment load to the columns through stress redistribution above and below the foundation subgrade level. Mobilization of load-transfer mechanisms to the columns requires differential settlement at the base of the embankment between the stiff columns and foundation soils. This paper presents the load-displacement compatibility (LDC) analysis method, which estimates the transfer of vertical loads by (1) arching within the embankment fill, (2) the vertical component of tension developed in the geosynthetic reinforcement within the LTP, and (3) negative skin friction acting along the column. The LDC method incorporates the vertical displacements that accompany load transfer by considering nonlinear consolidation of the soft foundation soil, elastic compression of the columns, out-of-plane deformation of geosynthetic layers, and settlement of the embankment surface in compliance with the differential settlement at the embankment base. This paper also presents recommendations for estimating the critical height of the embankment, which is the minimum embankment height above the columns to avoid poor ride quality resulting from differential settlement at the surface of the embankment produced by differential settlements at the base of the embankment. Estimates of load transfer and reinforcement strain using the LDC method are compared to measurements from 15 full-scale embankments.

Explosive compaction technology for loess embankment settlement control: numerical simulation and field implementation

Loess covers about one-tenth of the world’s land area. While it is often used as embankment fill, loess is not an ideal construction material due to its wet collapsible nature, as it may cause significant embankment settlement and other related problems. Although explosive compaction (EC) technology has been used for many years, the challenges in experimental testing and theoretical analysis hinder its wider application. This paper contributes to the development of a design construction scheme of EC technology for loess embankment improvement through an integrated approach that involves finite element modeling, small-scale experiments, full-scale simulation and field implementation. In this study, a reliable finite element model is developed and validated through a small-scale experiment. The model is developed based on the software ANSYS/LS-DYNA®14.5 and takes into account the coupling between different materials (including soil, explosives, air and pavement). Critical performance factors such as the volume of the explosion cavity, the density of the compacted soil and the soil pressure can be obtained directly from the model. The model is then extended to simulate full-scale embankments. A sensitivity study is conducted to establish the correlations between the design parameters and the abovementioned performance factors. The relationships served as design guidelines for the successful implementation of the EC technique in an embankment section on the Cheng-Chao highway in China. The results demonstrated the feasibility of the EC technique as a ground improvement method for loess embankments, and it illustrated the effectiveness of the numerical method as a tool in design.

Site characterisation and some examples from large scale testing at the Klett quick clay research site

The Klett research site was developed in conjunction with the new E6 developments south of Trondheim, Norway. The site comprises non-sensitive clay to about 6 m to 8 m and quick clay with significant silt lenses below this down to at least 30 m. The materials encountered are typical of the marine clays found in Scandinavia and North America. Classical geophysical and geotechnical techniques such as total soundings, rotary pressure soundings and ERT proved very useful in characterising the quick clay. The material is particularly susceptible to sample disturbance effects and the work showed that it is important to test any samples as soon as possible after sampling. CPTU data proved particularly useful for the determination of some soil properties as well as general soil classification. Several full-scale experiments have been performed at the site. Pile capacity tests showed that significant ageing effects occurred. Lime-cement column tests, as well as laboratory trials, allowed considerable savings to be made in the amount of binder required for foundations and slope improvement. A full-scale embankment test provided very useful data for the calibration of soil constitutive models.

Monitoring of a Full-Scale Embankment Experiment Regarding Soil–Vegetation–Atmosphere Interactions

Slope mass-wasting like shallow slides are mostly triggered by climate effects, such as rainfall, and soil–vegetation–atmosphere (SVA) interactions play a key role. SVA interactions are studied by a full-scale embankment with different orientations (North and South) and vegetation covers (bare and vegetated) in the framework of the prediction of climate change effects on slope stability in the Pyrenees. A clayey sand from the Llobregat river delta was used for the construction of the embankment and laboratory tests showed the importance of suction on the strength and hydraulic conductivity. Sixty sensors, which are mostly installed at the upper soil layer of the embankment, registered 122 variables at four vertical profiles and the meteorological station with a 5 min scan rate. Regarding temperature, daily temperature fluctuation at the shallow soil layer disappeared at a depth of about 0.5 m. There was great influence of orientation with much higher values at the South-facing slope (up to 55 °C at −1 cm depth) due to solar radiation. Regarding rainfall infiltration, only long duration rainfalls produced an important increase of soil moisture and pore water pressure, while short duration rainfalls did not trigger significant variations. However, these changes mostly affected the surface soil layer and decreased with depth.

On the hydro-mechanical behaviour of a lime-treated embankment during wetting and drying cycles

The paper presents some experimental results obtained on samples extracted from a full-scale embankment obtained by compacting a lime-treated clayey soil. A comprehensive test programme was carried out in order to highlight the improvement of mechanical behaviour induced by lime treatment as well as to assess the durability of the improved material, which may be affected by severe seasonal wetting and drying cycles.Direct shear tests, triaxial compression tests, swelling potential measurement and oedometric tests were performed on samples cured in controlled environmental conditions for at least 18 months. Wetting and drying cycles were applied in a very wide range of suction values with different experimental techniques. Test results show that the cyclic variations in total suction in the range 2-110 MPa give rise to significant irreversible deformations of shrinkage, since the material, during the wetting stages, proves to be unable to recover most of the deformations developed in the previous drying stages. However, this volumetric behaviour shows an almost reversible pattern after a few suction cycles. In contrast, saturation after drying implies a strong variation in the mechanical response due to the irreversible pattern of the observed volumetric behaviour. Accumulation of swelling deformation, reduction of the yielding stress, increase of compressibility and loss of shear strength due to softening of bonding, induced by the pozzolanic reaction products, were measured with the increase of the number of wetting and drying cycles. Mercury intrusion porosimetry (MIP) tests, carried out before and after the wetting and drying cycles, highlighted that cyclic suction paths result in a collapse of the structure since the pore size distribution of microstructure changes, its peculiar double-porosity network becoming almost unimodal in type.

The comparison of modelling inherent and evolving anisotropy on the behaviour of a full-scale embankment

The behaviour of a full-scale embankment constructed on a soft soil deposit has been studied using two different anisotropic elasto-plastic constitutive models, namely S-CLAY1 and Sekiguchi–Ohta (SO) inviscid, in order to investigate the influence of modelling (initial) inherent and evolving anisotropy on boundary value level simulations. The initial inherent anisotropy which is generally modelled by a rotated yield surface can also influence the model prediction capability. A Finnish test embankment known as Murro embankment was chosen for finite-element analysis using the two advanced soil models. The predictions of each model were studied and compared with measured field data. For the purpose of model comparison, the influence of evolution of anisotropy was further investigated by using only the inherent anisotropy feature of S-CLAY1 model, by setting the values of rational hardening parameters to zero. Overall, the S-CLAY1 model predictions are in good agreement with the measured data, which is due to the incorporation of a rotational hardening law (evolution of anisotropy) into the model in addition to the consideration of inherent anisotropy. However, the SO inviscid model predictions are less comparable with the measured data due to the consideration of only the inherent anisotropy into the model. The results clearly demonstrate the importance of including soil’s evolving anisotropy in the analysis and how the inherent anisotropy is modelled (i.e. the shape of yield surface).

Arching in geogrid-reinforced pile-supported embankments over silty clay of medium compressibility: Field data and analytical solution

The objective of this study is to improve the understanding of load transfer mechanism of Geogrid-Reinforced Pile-Supported Embankments (GRPS) via a new 3D analytical approach and comprehensive field tests. A full-scale embankment was built over a silty clay of medium compressibility as a part of the Liuzhou-to-Nanning High-speed Railway (LNHR) in China. Six sections of the embankment have been heavily instrumented producing comprehensive data of high quality. Field measurements evidence the existence of soil arching, membrane contribution and ground reaction, phenomena that are all contributing to load transfer mechanism. The new 3D analytical arching model accounts for a triangular arrangement of piles and, unlike existing methods, accounts for all relevant components of load transfer mechanisms. In addition, two key parameters were introduced in the model: an elastoplastic state parameter of soil arching (α) and a coefficient of equivalent uniform stress (β). The former was used to satisfy the load equilibrium in case of partial arching while the latter was adopted to allow possible nonuniform vertical stress acting on the ground surface. The so-called ground reaction method was incorporated in an innovative manner to take into account the reactive support of the subsoil beneath geogrid-reinforced layer when estimating the tension development in the geogrid. Finally, the performance of the proposed model was assessed against several existing models and field measurements. Results showed that the new model presented herein outperforms existing models and satisfactorily predicts both the pile efficiency and tension development within the geogrid.

Comparing overflow and wave-overtopping induced breach initiation mechanisms in an embankment breach experiment

As part of the SAFElevee project Delft University of Technology collabored with Flanders Hydraulics Research, and Infram B.V. in the preperation and execution of a full scale embankment breach experiment in November 2015. This breach experiment was performed on an 3.5m high embankment with a sand core and clay outer layer situated along the tidal river Scheldt in Belgium near Schellebelle. During the experiment a wave overtopping simulator and overflow simulator were used to initiate a breach. Both simulators were placed near the top of the waterside slope. The use of the simulators facilitated comparison between the effects of continueous overflow and the effects of intermittent wave overtopping. This paper presents the data collected during the experiment, describe the development of hypotheses on the failure processes using the latest insights, and comment on the failure initiation process of a grass covered flood embankment with a clay outer layer and a sandy core.

Stability evaluation of full-scale embankment constructed by volcanic soil in cold regions

Stability evaluation of full-scale embankment constructed by volcanic soil in cold regions

Full-scale embankment failure test under simulated train loading

A full-scale embankment failure experiment was conducted in 2009 in Perniö, Finland. A small, extensively instrumented railway embankment on a soft clay foundation was brought to failure by loading over a period of 30 h. Instrumentation consisted of over 300 different measurement points, including 37 piezometers and nine automatically monitored inclinometer tubes. The relatively rapid loading simulated a heavy train coming to a standstill on the embankment. The primary purpose of the experiment was to gather field data of a failure caused by a rapidly applied load, with an emphasis on the pore pressure response in the clay foundation layer. The test was also used to assess the suitability of various instruments for real-time stability monitoring. The embankment failure was an asymmetric bearing capacity mechanism that is hypothesised to have been triggered by an undrained creep rupture. During the last 2 h of the experiment, pore pressure and displacements increased at an accelerating rate while the external load was kept constant. The time-dependency of the pore pressure and displacement responses was a key factor in the experiment. With regards to monitoring of similar in-service train embankments, proper placement of instruments according to predicted failure mechanisms was found to be important.

Three-dimensional finite element modelling of a full-scale geosynthetic-reinforced, pile-supported embankment

The performance of four sections of a full-scale embankment constructed on soft soil is examined using a fully coupled and fully three-dimensional finite element analysis. The four sections had similar embankment loadings but different improvement options (one unimproved, one with pile-support only, one with a single layer geotextile-reinforced platform and pile-support, and one with two layers of geogrid-reinforced platform and pile-support). Like the field data, the numerical results show that the inclusion of piles decreases the settlement at the subsoil surface to 52% of that for the unimproved section, and the addition of a single layer of geotextile reinforcement (J = 800 kN/m) further reduced settlement to only 31% of that of the unimproved section. The effects of geosynthetic reinforcement and multiple layers of reinforcement on the performance of the pile-supported embankment are discussed. The relative load transfer is calculated using eight existing methods and they are compared with the field measurements and numerical results.

Full-scale embankment failure test under simulated train loading

Full-scale embankment failure test under simulated train loading

Experimental investigation of the effects of embankment scenario on railway vehicle aerodynamic coefficients

The embankment is a typical layout for rail infrastructures, and train aerodynamic coefficients for the analysis of cross-wind effects with this scenario are required by the TSI standard. Nevertheless, wind tunnel tests on scale models with the embankment scenario present problems in the reproduction of the end layout conditions, that is the simulation of a “pseudo-infinite” full scale embankment. In this paper, the effect of different end layouts of the embankment model as well as wall proximity effects are analysed.To study these two effects, two wind tunnel campaigns were carried out on a ETR500 train model 1:45 scaled. In the first tests, performed in a 1.5×1m wide wind tunnel section, different embankment end layouts (wall-to-wall, finite length with and without noses, etc.) were reproduced and tests performed with different Reynolds numbers. The second experimental campaign was then carried out in a wider wind tunnel section (4×4m), with a different distance between the end of the vehicle and the walls of the wind tunnel.From the results of the first experimental campaign it was found that, in the 10°–40° range of wind angle, all the configurations with nose are generally equivalent, in terms of aerodynamic coefficients, to the wall-to-wall one, considered as the reference configuration (error range ±10%). Moreover, comparison of the results obtained with the different wind tunnel setups led to the conclusion that the distance from the upstream end of the ground model to the leading edge of the train model is a key parameter for determining aerodynamic coefficients with the embankment scenario, especially around the critical angle where the coefficients reach their maximum values. For this reason, this parameter has to be correctly reproduced to obtain coefficients comparable with full scale values.

Measured and simulated results of a Kenaf Limited Life Geosynthetics (LLGs) reinforced test embankment on soft clay

For the first time, woven Kenaf Limited Life Geosynthetics (LLGs) were used for short term reinforcement of full scale embankment constructed on soft clay and their behavior is presented. The observed data in terms of settlements, excess pore water pressures and deformations or stresses in the reinforcements were compared with the simulated data. Two types of Kenaf LLGs were utilized, namely: coated and not coated with polyurethane. The coating can reduce water absorption and increase their life time. Subsequently, numerical simulations were performed on the behavior of Kenaf LLGs reinforced embankment using 2D and 3D finite element software. The rates of settlement from FEM 2D method overestimated the observed settlements data while the FEM 3D predictions agreed with observed settlements due to the three-dimensional geometrical loading of the embankment with length to width ratio (L/B) of 1.0. Regarding the maximum excess pore-water pressures at the locations of 3 m and 6 m depth, the FEM 2D analyses overestimated while the FEM 3D simulation yielded satisfactory agreement with the observed data. The reinforcement deformations and stresses in both coated and non-coated Kenaf LLGs reinforcement have higher values at the middle portions of the embankment and the predicted results from FEM 3D simulation yielded closer deformations of Kenaf LLGs reinforced than the FEM 2D simulation. Consequently, FEM 3D simulation captured the overall behavior of the Kenaf LLGs reinforced embankment with more reasonable agreement between the field observations and the predicted values compared to the FEM 2D simulation. The behavior of the sections on coated and non-coated LLGs were similar. The Kenaf LLGs can be applied for short term embankment reinforcement in order to improve the stability of embankment on soft clay.