Soil Embankment Research Articles

Seismic Characteristics of a Geotextile Tube-Reinforced Embankment and Shallow Foundations Laid on Liquefiable Soil

The ground in Saemangeum has a high water level and is mostly composed of silty soil and sand, which makes it susceptible to liquefaction and seepage effects. To investigate the seismic response of a geotextile tube-reinforced embankment and shallow foundations laid on a liquefiable soil, a simple spring type shaking table apparatus was developed. The variation in the response acceleration and shear stress-strain relationship were investigated, and the effect of soil improvement and reinforcement were explored, wherein one of the shallow foundations was laid on a coarse sand layer and reinforced by a polyester geotextile. The results showed that the main cause of damage to the embankment was seepage-induced liquefaction. Excessive surface accelerations were observed in the embankment soil due to lateral spreading, indicating the importance of analyzing the liquefaction potential of soils not only at the site area but also near embankments. Lastly, the inclusion of geotextile reinforcement and soil improvement only resulted in the slight reduction of shallow foundation settlement.

THE EFFECT OF ADDED NICKEL SLAG TO COMPRESSION AND SHEAR STRENGTH ON LATERITE SOIL SOUTH KALIMANTAN

Laterite soil is an embankment soil that is often used because it is easy to find and is widely found in South Kalimantan. However, this land has many shortcomings to be used as embankment soil. This is because the lateritic soil has a clay content and a high Plasticity Index (PI) value. So the quality is still questionable to be used as landfill. To overcome this, it is necessary to improve or stabilize the lateritic soil. In this study, the lateritic soil was stabilized by the addition of slag nickel This study aims to determine the physical characteristics of laterite soil after being given a mixture of nickel slag addition, this study also aims to determine the effect of the percentage of nickel slag on primary consolidation (Sc) of laterite soil. As well as knowing the effect of the percentage of nickel slag on the parameters of shear strength in the form of cohesion (c) and shear angle (f). Consolidation and shear strength specimens were made with 90% of the optimum moisture content. The variations of the nickel slag mixture used in this study were 0%, 5%, 10%, 15%, and 20% of the weight of the soil used. Based on the results of data analysis, the addition of a mixture of nickel slag in each sample variation can reduce the plasticity index value of the lateritic soil. In addition, the addition of nickel slag also affects the value of the primary consolidation settlement value (Sc) of the laterite soil. The addition of the percentage of nickel slag also affects the parameters of the shear strength of the soil, for the cohesion value (c) of the laterite soil experiences a value that decreases with the increase in the percentage of nickel slag. Meanwhile for the shear angle (φ) of the laterite soil, the value increases with the increase in the percentage of nickel slag.Keywords: laterite soil, nickel slag, plasticity index, consolidation of laterite soil, shear strength of laterite soil

Experimental observation and constitutive modelling of the shear strength of a natural unsaturated soil

Increasing frequency and intensity of extreme weather events in the Netherlands is raising attention on the unsaturated response of geo-infrastructures, promoting research projects to provide an overview of the impact of unsaturated conditions on the response of shallow soil layers and embankments, and to better address maintenance and mitigation measures. As part of this effort, we discuss the results of standard laboratory tests performed on initially unsaturated samples retrieved from the field and tested in natural conditions, as well as after controlled drying and wetting. The variation of the “undrained” (i.e. at constant water content) shear strength with the degree of saturation obtained from the laboratory tests aligns well with CPT measurements performed in the field. An elastic-plastic constitutive model with mixed isotropic-rotational hardening developed for saturated soft soils was extended to unsaturated conditions by following a robust approach previously developed for compacted clayey soils. Coupling between the mechanical and the hydraulic behaviour is provided by the water retention curve. The model nicely captures the response observed in the laboratory, until extreme dry conditions, which possibly alter the structure of the soil, the peak stress, and the brittleness after failure. The model is capable of reproducing the effects of the previous hydraulic history on the stress-strain behaviour observed from the laboratory tests over a wide range of degree of saturation.

Finite element modelling of unsaturated soils using a modified version of the Barcelona Basic Model

In this paper, unsaturated soil behaviour is numerically simulated using a modified version of the Barcelona Basic Model. The model has been implemented as a User-Defined Soil Model (UDSM) in the finite element code PLAXIS. Unlike the original formulation based on net stress ([1]), this model isformulated based on the well-known Bishop’s effective stress, with suction as an additional stress variable. Furthermore, a non-associated flow rule and the dependency on Lode’s angle proposed by [2] are incorporated. The Soil Water Characteristic Curve (SWCC) follows the Van Genuchten model ([3]). First, the simulation of laboratory tests along different stress paths and levels of suction are compared againstexperimental data. Then, an unsaturated soil embankment subject to a time-dependent precipitation is simulated by means of a fully coupled flow-deformation analysis. The results show the capability of the model to reproduce the main features of unsaturated soil behaviour both at material point level and inboundary value problems.

Response observation of a full-scale geosynthetic-reinforced pile-supported system to environmental actions

The collected field data from well-instrumented reinforced embankments in the framework of a real project for the extension of the inner-city area at HafenCity in Hamburg is used to study the effect of environmental changes on the load transfer process over the structure lifetime. A particular focus is put to improve the understanding of the load transfer mechanism from the soil embankment to pile foundations through the reinforced geosynthetic layer and to investigate the corresponding long-term settlements. The time-dependent stress and strain distribution of the reinforced load transfer platform has been focused to investigate the process of soil arching on top of the piles and examine the overall settlement of the embankment. Finally, the most common available prediction models in European design guidelines are applied to estimate the loads on structural components and the results are compared with the measurements.

Reducing impact of embankment soils on shore support of bridge on the approaches to bridges

The article defines the reduction of active ground pressure and amplitude-frequency characteristics by theoretical and practical studies on approaches to bridges by driving reinforced concrete piles into the embankment. Reinforced concrete piles were driven into the model of the roadbed, and vibrations were created using a vibrator mounted on piles. The frequency of these oscillations was 50 Hz, and the values of the oscillations were recorded at different points of the roadbed. Processing the obtained results made it possible to determine the distance between piles for different soils on the transition section reinforced with reinforced concrete piles. As a result, some of the vibrations in the roadbed are transmitted to the base using reinforced concrete piles. The amplitude-frequency characteristics (frequency response) of the vibrations of the embankment soils are decreasing.

LABORATORY STUDIES OF EQUIVALENT GEOSYNTHETIC MATERIAL FOR FLUME TESTS

The article presents the results of laboratory research of soils and geosynthetic materials (geogrids) used as reinforcement elements of soil embankments. The strength and deformation characteristics were the estimated parameters of the soil, and the main parameter of selection for geogrid was the axial stiffness of the material, the assessment of which was reduced to measuring the tensile strength of geogrid and its equivalent material.

KAJIAN PENURUNAN TANAH TIMBUNAN PENYEBAB KERETAKAN STRUKTUR RIGID PAVEMENT DENGAN MENGGUNAKAN METODE ASAOKA (Studi Kasus Proyek Pembangunan Jalan XYZ)

<p>Rigid pavement work on the XYZ Road Construction Project experienced a problem, <br />namely the occurrence of cracks in the rigid pavement structure above the box <br />culverts under which soil improvement was carried out using embankment soil. The <br />purpose of this study is to analyze the factors that cause settlement of the <br />embankment that causes the rift of the rigid pavement structure on box culverts built <br />on embankment soil so that the results can be used as a reference for handling or <br />repairing rigid pavement work on box culverts with a structure piled up soil in <br />subsequent segments. From the results of the analysis it can be seen that the process <br />of casting rigid pavement was carried out at two points, namely Point 1 and Point 2 <br />where after casting the rigid pavement, the subgrade beneath it still experienced a <br />decrease of 10 mm and 6 mm. This decline occurred for up to 3 months and caused <br />cracks in the rigid pavement structure above it. This is due to the difference in <br />settlement of the box culvert which was initially assumed not to have decreased <br />again with the surrounding embankment which was still experiencing settlement. In <br />addition, the results of the analysis show that the rigid pavement design uses a <br />single reinforcement so that the capacity of the concrete (Mu) is less than the weight <br />of the concrete itself which causes the concrete to crack.</p>

Expansive Soil Embankment Filling and Cutting Treatment Technology: A Systematic Review

The characteristics of expansive soil, including over consolidation, swelling-shrinkage, fissures, and strength attenuation, can cause potential hazards in road construction, which are mainly manifested as subgrade swelling-shrinkage deformation and slope collapse. Effective treatment can not only ensure long-term subgrade stability but also reduce investment costs and environmental impact. In this review, the current development status of embankment filling and cutting slope treatment technology in expansive soil areas were summarized, and the classification standards of expansive soil filler, moisture retention, and antiseepage technology were described. Then, the utility of chemical, physical, biological, and solid waste modification materials in improving the engineering characteristics of core-filled expansive soil was discussed, and the cost and technical characteristics of these modification technologies were compared and analysed. Next, the application of rigid and flexible support technology in the treatment of cutting slope collapse was analysed, and the advantages and disadvantages of rigid and flexible supports were summarized. Finally, the development direction of expansive soil subgrade treatment technology was discussed. This review includes a summary of the treatment methods of highway subgrade in expansive soil areas and can provide a technical reference for treatment methods of expansive soil subgrade.

Value Coefficient of Polyethylene Fiber Soil Embankment Slope Based on Response Surface Analysis.

The utilization of polymers can strengthen soil, but at a high price. In this study, value coefficients were proposed to evaluate the cost-effectiveness of fiber-reinforced roadbeds, and the effects of embankment-slope-influencing factors on the value coefficients were analyzed by response surface methodology. Ultrahigh-molecular-weight polyethylene fiber (UPEF) was used as the reinforcement material for soil. First, the shear strength parameters of fiber soil with different fiber diameters were obtained from the direct shear tests to set the parameters of the finite element models. Second, three factors, namely filling height, slope angle, and fiber diameter, were selected as input parameters based on the Box–Behnken Design (BBD) experimental design method, and their effects on the value coefficient of the fiber soil embankment slope were investigated. Finally, the design parameters at the maximum value coefficient of the fiber soil embankment slope were determined based on the results of the response surface analysis. The results indicated that the addition of UPEF could effectively improve the cohesion of the soil; the interaction between the filling height and fiber diameter is most obvious. The optimization of design parameters based on the value coefficient of the fiber soil slope is a slope-engineering design method considering comprehensive benefits.

Stability Analysis of Pile-Supported Embankments over Soft Clay Considering Soil Failure between Piles Based on Upper Bound Theorem

Most analytical methods used to analyze the stability of pile-supported embankments are based on shear and bending failure of piles. However, the centrifuge test and practical engineering show that rigid pile-supported embankments have a failure mode of soil sliding around piles. Therefore, the stability analysis method of the pile-supported embankment under the failure mode of the soil sliding around piles based on the upper bound theorem is given in this study. First, the failure mechanism is assumed to be a rigid body and slide along two logarithmic spiral surfaces in the embankment and soft soil. The rate of external work and internal energy dissipation of the failure mechanism are further obtained, wherein the internal energy dissipation rate of piles is obtained based on the limit state of soil sliding around piles. Secondly, according to the equation formed by the upper bound theorem, the optimization model of the safety factor function when the potential slip surface is passing through different pile rows is obtained. Then, the algorithm of solving the model is given and the overall safety factor of the pile-supported embankment is obtained. Compared with other methods, the advantage of this method is that it considers the influence of embankment soil property and the width perpendicular to the two-dimensional plane on the pile load and the influence of the soil internal friction angle on the slip surface. Finally, it can be concluded from parametric analysis that: with the increase of the horizontal distance from piles to the slope toe, the reinforcement effect of piles first increases and then decreases; with the decrease of the embankment height and the increase of the soft soil cohesion and internal friction angle, the overall safety factor of the embankment increases.

Slope stabilisation of railway embankments over loose subgrades using deep-mixed columns

An investigation was undertaken into the stability of railway embankment slopes over soft subgrades stabilised by deep-mixed columns (DMCs). Three 1 : 10 scale laboratory embankments were constructed over unreinforced and reinforced subgrade with DMCs in square and triangle patterns. The load–settlement responses of both embankments and columns were measured. The laboratory embankments were then mathematically modelled and the results were compared. After validation, a comprehensive parametric study was carried out to evaluate the factor of safety (FoS) of the embankment side slopes against sliding. Five embankment soil types from poor to high strength, three heights from 1.5 to 10 m and various DMC improvement area ratios from 0 to 65% were considered. The experimental outcomes indicated an increase of nearly 63% in the bearing capacity of both DMC-supported embankments compared with the unreinforced one. Regarding the parametric study, a minimum required FoS of 1.5 was observed for 1.5 m embankments of all soil types stabilised with a 60% improvement ratio. The greatest safety increase was associated with a 1.5 m height embankment with poor soil type, which showed a 36% increase.

A data-driven approach for forecasting embankment settlement accounting for multi-stage construction

Reliable forecasts of the behaviour of embankments on soft soil are important for safe and efficient infrastructure design. Despite the development of advanced models in the past few decades, recent soft soil embankment prediction exercises revealed that forecasts from these models can be poor due to the subjective judgement required in the parameter selection process. Data-driven approaches, which connect measured soil data directly to a forecasting model, aim to overcome this by eliminating or reducing the subjectivity in assigning parameters. This paper builds on an existing data-driven approach for forecasting the behaviour of embankments on soft soil by including the ability to account for staged embankment construction. The multi-stage method was found to provide a significantly improved match to measured embankment settlements during and shortly after construction. The long-term settlements are similar to the single stage approach and both methods eventually converge to the same settlement-time response.

Modelling ground vibration from a high-speed railway track resting on a periodic pile-plank structure-enhanced embankment

Pile-plank structure-enhanced embankments are used in high-speed railways, mainly for controlling embankment settlement and frost heave. The effect of such embankment on train-induced ground vibration has yet received little attention. In this paper, a model is developed to predict ground vibration from such a high-speed railway. In the model, the track/embankment/ground system is idealised as an infinitely long periodic structure. The periodicity is created by the piles which are arranged periodically in the track direction to support the plank and the track. The fictitious pile method is used to divide the periodic track/embankment/ground system into two systems interacting with each other. One is a structure formed by the track, plank, pure soil embankment and ground, all of which are assumed to be uniform in the track direction. Therefore, this structure is uniform in the track direction and termed the 2.5D track/ground structure. The other is an infinite number of fictitious piles which are arranged periodically in the track direction (termed the fictitious piles). The 2.5D finite element method (2.5D FEM) and the Floquet transform are combined to deal with the interaction between the two systems, making the model a 2D FE mesh based and convenient to consider the moving of a train along the track. The focus of the paper is modelling methodology and therefore only preliminary results are produced from the model. The results show that, the pile-plank structure studied in this paper can largely reduce low frequency ground vibrations, for which other measures of ground vibration mitigation are often difficult to apply, but it may also increase ground vibration at other frequencies, depending on the observation location on the ground surface.

Measurement of Physical Parameters for Transient Seepage Assessment of Levees

Abstract An embankment was instrumented and monitored as part of a multiyear project to assess appropriate pore-water pressure distributions and soil water retention curves for use as initial conditions in transient seepage analyses. The increased use of unsaturated soil mechanics and transient seepage has led to the need for practical methods of assigning accurate properties and initial conditions in these types of analyses. Monitoring results were validated against published pore-water pressure measurements collected from multiple embankment studies. The collected distributions showed nonlinear behavior in near-surface embankment soils due to infiltration and evapotranspiration processes. Seasonal variations in pore-water pressure and the soil moisture deficit were shown to correlate at the monitoring site. The seasonal response of the embankments exhibited a large variation in pressures between summer and winter. Assessment of flood occurrence showed the distribution of pore pressures during flood loading was typically near −10 kPa at a depth of 2 m at the onset of the flood. Laboratory soil water retention testing of undisturbed samples collected from the embankment showed that when compared with field measurements, they overestimated the field response for the considered initial water content and dry density values. Also, comparisons between hydrostatic pore pressures above the phreatic surface showed that at soil moisture deficits greater than 20 mm, the difference between the measured and hydrostatic pore pressures greatly increased. The laboratory and monitoring results were used to provide practical methods of assigning representative pore-water pressure distributions and material properties necessary for performing transient seepage analyses. These results will aid in more accurate transient seepage analyses of flood control embankments.

Seismic probabilistic risk estimation of Japanese railway embankments and risk-based design strength of soil and reinforcement

For the rational seismic design of railway embankments considering seismic risk, high-strength geomaterials and reinforcements should be used in areas with high seismic probability, and low-strength geomaterials and reinforcements should be used in areas with low seismic probability. In this study, a seismic probabilistic risk estimation of Japanese railway embankments was conducted using publicly available information on seismic hazards in Japan and previously estimated seismic-fragility curves for Japanese railway embankments. To determine the required average friction angle of backfill soil and average reinforcement tensile strength for satisfying the prescribed allowable seismic risk, a sensitivity analysis of the railway embankment was conducted by changing the average friction angle of the backfill soil and the average reinforcement tensile strength. Using the sensitivity-analysis results, the required average friction angle of the backfill soil and average reinforcement tensile strength of the railway embankment satisfying the prescribed allowable seismic risk considering the occurrence probability of earthquakes were analytically obtained.

Coupled Large Deformation Finite Element Formulations for the Dynamics of Unsaturated Soil and Their Application

Unsaturated soil is a three-phase medium with three interfaces, and the mathematical equations that represent its behavior must be developed in a fully coupled manner for accurately predicting its hydromechanical behavior. In this paper, a set of fully coupled governing equations was developed for the dynamics of unsaturated soil, considering the interaction among the bulk phases and interfaces. In addition to implementing the complete governing equations, a simplified formulation was developed for practical applications. The derivation of the finite element formulation considering all the terms in the partial differential equations resulted in a formulation called complete formulation and was solved for the first time in this paper. Another formulation called reduced formulation was derived by neglecting the relative accelerations and velocities of water and air in the governing equations. In addition, small and large deformation theories were developed and implemented for both formulations. To show the applicability of the proposed models, the dynamic behavior of an unsaturated soil embankment was simulated using both small and large deformation formulations by applying minor and severe earthquakes. The reduced formulation was found to be computationally efficient and numerically stable. The smaller displacements predicted by large deformation theories show that the results are consistent with the expected behavior. Large deformation theories are considered suitable when the geotechnical system undergoes large deformation and may lead to accurate prediction.

Analysis of mixing construction and demolition waste with soil for embankments

In some countries, there are cases of inadequate destination and even final disposal of construction and demolition waste (CDW), which contributes to environmental degradation and material wastes. The construction sector is a great consumer of natural resources, and CDW can sometimes be useful to minimise the need for natural materials, including embankment filling, which could use a large volume of material. In these cases, the use of CDW can be promising if the embankment quality is not affected; and it will have a great economic advantage. This paper aims to assess experimentally the feasibility and potential benefits of employing CDW mixed with soil in embankments. CDW samples were collected from three recycling facilities in Brazil and mixed with lateritic soil. Compaction tests determined optimum parameters of the lateritic soil, and the soil mixed with 25 and 50% of CDW. The maximum dry densities of the mixtures changed slightly compared to natural soil. The mixtures’ optimum water content increased only 2% in relation to the soil without waste, which means that the compaction of the mixtures will require 10–20% more water, depending on CDW quality. Results show that these materials and proportions can be considered for possible application in embankments.

Calculation and Analysis of Nonlinear Algorithm for Stability of Nanosilica Powder Soft Soil Pile Foundation.

In order to reasonably evaluate the stability of the embankment supported by the rigid pile composite foundation, a nonlinear algorithm calculation and analysis method for the stability of the nanosilica powder soft soil pile foundation is proposed. First, the soft soil foundation reinforced by the composite structure of “piles (prestressed pipe piles, (cement fly-ash gravel, CFG) piles)—pile caps—geotextile pads” is analyzed through the soft soil embankment test section of the Wenfu high-speed railway. Second, the compressive modulus under one-dimensional confining compression is calculated using the layered summation method. Finally, the deep lateral deformation of the pile foundation soil is measured by an inclinometer to evaluate the actual displacement of the pile foundation soil. In the standard method, the empirical coefficient 1.1–1.7 is multiplied on the basis of the calculation result of this method to correct the calculation error. Combined with the test results, it is shown that nanosilica powder can give full play to its excellent characteristics: promoting hydration speed and hydration degree through the reaction of pozzolan refining and consuming Ca(OH)2 crystals produced by cement hydration. Soft soils and modified soft soils: a certain amount of nanosilica powder can significantly improve the strength of soft soil at different ages.

Seismic performance of near-fault geosynthetic-reinforced pile-supported embankment

The seismic performance of embankments is an important consideration for the design and construction of high-speed railways (HSRs) in near-fault areas. Incorporating geosynthetics into embankment soil can improve seismic resistance. However, the effect of different reinforcement methods on the seismic performance of embankments is not well understood. In this study, two 1 : 20 scaled embankment models (full-length-geosynthetic-reinforced pile-supported embankment (FRPE) and turn-back-geosynthetic-reinforced pile-supported embankment (TRPE)) were tested on a shaking table to compare their seismic performance and failure characteristics. The results show that under near-fault bidirectional seismic excitation, the pile foundations of both embankments exhibited bending deformation, with the largest bending moment in the middle of the pile body. The TRPE reduced the vertical dynamic response of the embankment slope but exhibited a more remarkable horizontal dynamic response than the FRPE. Furthermore, the embankment deformation and excess pore water pressure of the TRPE were generally larger than those of the FRPE. Nonetheless, the TRPE has potential application in practical engineering as it ensures earthquake resistance, with higher economic benefits.