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Lightweight expanded polystyrene (EPS) geofoam (geofoam block) is used in slope remediation works as a soil substitute fill to reduce driving forces that can lead to global instability. On the other hand, the presence of seepage flow requires special attention because geofoam block slope systems are vulnerable to seepage-induced lateral forces. In this study, the effect of an internal drainage system on the alleviation of piezometric pressures within the back-slope of a geofoam block slope system was investigated. For this purpose, laboratory experiments were conducted using a small-scale lysimeter with dimensions of 60 cm height, 20 cm width, and 200 cm length. The slope was compacted with sand to obtain an overall dry unit weight of 14 kN/m3. The constant piezometric head boundary conditions of 25, 38 and 50 cm generated the necessary hydraulic energy gradient for the seepage flow directed from the water reservoir of the lysimeter to the 45° angle slope face. The slopes were remediated by using geofoam blocks assembled in an embankment-type configuration at the toe of the slope. The internal drainage system consisted of grooved geofoam blocks that formed the 10, 15 and 22.5 cm high embankments. Deep-seated failures of the non-remediated slope were prevented except for the experiments with 10 and 15 cm high embankments under 50 cm pressure head boundary conditions. In general, the internal drainage system alleviated the piezometric pressure conditions within the back-slope by lowering the phreatic surface using the active drainage channels observed during laboratory experiments. These drainage channels provided a convenient passageway for seepage flow. The coupled numerical variably saturated flow modelling and slope stability modelling predicted the factor of safety for global stability which confirmed the observed physical conditions in the laboratory. The use of the internal drainage system increased the factor of safety of the geofoam block slope system under seepage conditions.

An explosion on the ground surface may cause significant damage to an underground structure, such as a tunnel or a pipeline. The extent of damage would depend on the intensity of blast, the material and configuration of the structure, as well as the nature and geometry of the intervening material. An underground structure may be protected by means of a protective barrier, installed directly above the structure. The effectiveness of using a compressible barrier, made of polyurethane geofoam, to mitigate the effects of surface explosion was investigated. The effects of a surface explosion were studied through a combination of physical model tests and numerical modeling. Reduced-scale (1:70 scale) physical model tests were conducted using a geotechnical centrifuge, where the scaling law for explosions was utilized to model the effects of a large explosion using a relatively small mass of explosives under a high gravitational field (70 g, in this case). The results of the physical model tests were used to calibrate a three-dimensional numerical model in which a fully-coupled Euler–Lagrange solver was utilized to model the explosions. Tunnel configurations with and without protective barriers were studied to assess the mitigation provided by protective barriers. Material properties for polyurethane geofoam barriers were evaluated from laboratory tests. The influence of barrier thickness in reducing the strains, stresses, and pressures on the tunnel induced by an explosion was studied. The beneficial effects of a protective geofoam barrier were found to increase with increasing barrier thickness only up to a certain thickness, beyond which, further increase in thickness did not result in additional reductions. The results will help in design optimization, while planning protection systems for new tunnels, as well as for retrofitting existing tunnels.

Purpose – EPS geofoam has been widely used in embankment construction, slope stabilisation, retaining walls, bridge approaches and abutments. Nevertheless, the potential of EPS geofoam as an engineering material in geotechnical applications has not been fully realised yet. The purpose of this paper is to present the finite element formulation of a constitutive model based on the hardening plasticity, which has the ability to simulate short-term behaviour of EPS geofoam, to predict the mechanical behaviour of EPS geofoam and it is implemented in the finite element programme ABAQUS. Design/methodology/approach – Finite element formulation is presented based on the explicit integration scheme. Findings – The finite element formulation is verified using triaxial test data found in the literature (Wong and Leo, 2006 and Chun et al., 2004) for two varieties of EPS geofoam. Performance of the constitute model is compared with four other models found in the literature and results confirm that the constitutive model used in this study has the ability to simulate the short-term EPS geofoam behaviour with sufficient accuracy. Research limitations/implications – This research is focused only on the short-term behaviour of EPS geofoam. Experimental studies will be carried out in future to incorporate effects of temperature and creep on the material behaviour. Practical implications – This formulation will be applicable to finite element analysis of boundary value problems involving EPS geofoam (e.g. application of EPS geofoam in ground vibration isolation, retaining structures as compressible inclusions and stabilisation of slopes). Originality/value – Finite element analysis of EPS geofoam applications are available in the literature using elastic perfectly plastic constitutive models. However, this is the first paper presenting a finite element application utilising a constitutive model specifically developed for EPS geofoam.

The resilient modulus model of EPS geofoam to be used for a flexible pavement design was developed. In this study, the model was applied to design the flexible pavement and to predict the magnitude of the deformation of EPS geofoam blocks as a subgrade in the flexible pavement structure by using the resilient modulus model of EPS geofoam (RMEG) program. The RMEG program presented how much the EPS geofoam subgrade settled over the designed duration and the AASHTO flexible pavement design equation with the resilient modulus of EPS geofoam noted that how long the flexible pavement endured under traffic loads with 70% reliability for the estimated duration with less than 5mm vertical deformation during 20.6 years without the significant pavement distress as a substitute material for the natural soils.

This paper studies the efficiency of trenches constructed alongside a railway track as mitigation measures for vibrations induced by moving trains. A two-and-a-half-dimensional coupled boundary element–finite element methodology (2.5D BEM-FEM) is used, and the BEM is nurtured with fundamental solutions obtained through the thin-layer method. The procedure for the calculation of the fundamental solutions represents the main difference between this approach and similar methodologies used in the previous works. The conditions at an existing and operational stretch of the Portuguese Railway Network are assumed as the scenario for the investigations in which the behaviors of open, concrete filled and geofoam filled trenches are analyzed for the passage of an Alfa Pendular train.

Geofoam has been widely employed in highway, airport and seaport projects, because of its advantageous properties, i.e. light weight, low cost and high strength. Permeability of geofoam is an important hydraulic property affecting its durability. However, limited experimental data are available on the permeability of geofoam and hence relevant models are absent. In this study, an experimental study was conducted to measure the saturated coefficient of permeability and the volume of open pores of a geofoam. A new equation was proposed to model the saturated coefficient of permeability of the geofoam. The equation was verified by showing good agreement with both experimental data in this study and published results. Two regions (i.e. A and B) can easily be identified for the change of permeability. In region A, the influence of the on the saturated coefficient of permeability was not significant. In region B, the saturated coefficient of permeability increased from 1 × 10−8 to 1 × 10−4 m s−1 as increased fr...

El ambito de aplicación de EPS para diferentes soluciones de cimentación y mejora del terreno cobra cada vez más interés por su versatilidad y precio. Con este trabajo se pretende que el alumno alcance a conocer los campos de aplicación de este material y las técnicas de puesta en obra. El alumno realizará una estancia que le permitirá estar en contactos con expertos a nivel mundial en este campo. Escuela de Ingeniería de Caminos y Minas Universidad Politécnica de Cartagena

This paper presents analysis and interpretation of monitored vertical settlements and pressures of a rehabilitated bridge approach slab located in Johnson County, Texas. Four horizontal inclinometer casings and pressure cells (equipped with thermometers) were installed at the test site during the rehabilitation process. In this paper, collected data from the inclinometers, pressure cells, and thermometers were employed in an attempt, to understand the effect of climate changes on the vertical settlements and pressures of the approach slab. It has been observed that with an increase in temperature, the bridge structure enforced the movements of the geofoam blocks causing vertical settlement. Whereas, the bridge structure movements after a temperature decrease, induced vertical swelling at the top of the geofoam blocks. The pressure cells that were installed at the top and bottom of the geofoam embankment revealed that the stresses observed at the top of the geofoam were significantly reduced. Also, the pressure cells installed at the sides of the bridge and geofoam structure to evaluate the lateral pressure response lost contact and provided negative results. The loss of contact can be a response to the movement of the structure with respect to thermal changes in the structure. This research highlights the important observations of a bridge structure and its approach soil-geofoam embankment movements with respect to temperature and precipitation variations.

The effects of climatic variations on the performance of the bridge infrastructure were not adequately addressed. This paper presents a comprehensive analysis of the effect of seasonal temperature and precipitation variations on a bridge infrastructure located in Johnson County, Texas. This bridge has undergone a rehabilitation process by partially replacing the embankment soil with lightweight expanded polystyrene geofoam (EPS geofoam) to reduce bridge approach slab settlements. Four years of monitored vertical deformation and pressure cell data from the field instrumentation was used to analyze the performance of the bridge slab and adjoining roadway pavement system. From the analysis, it was observed that the vertical pressures and total deformations were increased with an increase in temperature and were decreased with a decrease in temperature. Also, with an increase in the temperature, it was observed that the bridge retaining wall exerted lateral pressure on the geofoam blocks and with a decrease in temperature the pressures decreased considerably. This study highlights the observations made on the bridge approach slab and adjoining roadway pavement vertical deformations with respect to temperature and precipitation variations.

This paper addresses the results of the experimental and numerical studies conducted on 4.2 mm thickness and 110 mm diameter high-density polyethylene (HDPE) pipes buried in fly ash material overlying stone dust beds. The model tests were performed using single and double layers of expanded polystyrene (EPS) geofoam as compressible inclusions. In addition to that, jute geotextile was used as a reinforcement for the infill fly ash along with EPS geofoam inclusion to obtain induced trench condition. The test beds were subjected to loading on the fly ash surface with the help of a rigid steel plate to simulate as a strip footing in different embedment depths of the pipe (1–3 times pipe diameter). The test results revealed that the pressure and strain values in the pipe reduced significantly in the presence of EPS geofoam and jute geotextile related to the location of the pipe. In the case of double layers of EPS geofoam could induce reduction of the pressure up to 87.2% and strain about 63.5% respectively depending on the density and width of EPS geofoam. Whereas, at the same burial depth, in the presence of jute geotextile together with EPS geofoam can be reduced up to 93.8 and 73.4% for pressure and strain respectively depending on EPS geofoam density and number of reinforcement. Moreover, the jute geotextile-EPS geofoam combination of model test results were validated with finite element program. A good agreement was observed on pressure-settlement response and pipe strain between experimental and numerical investigations. The numerical studies show that the jute geotextile distributes stresses in the lateral direction and then the stresses on the pipe significantly reduced.

Lengthy retaining walls are typically required in several geotechnical applications. Compacted soil is the classic backfill behind such walls, yet soil has a high unit weight that imposes large lateral loads and may lead to outsized wall dimensions. Geofoam or foam made of expanded polystyrene (EPS) can substitute the soil backfill due to its light weight and high compressibility and can reduce the lateral static loads imposed on walls. In this paper, EPS mechanical properties were measured in addition to the interface friction between this geomaterial and other materials, such as sand and concrete. A reliability analysis was conducted to develop the partial resistance factors required for the main EPS properties. Using a three-dimensional (3D) numerical analysis, the reliable EPS properties were used in the hardening soil constitutive model to simulate flexible walls with EPS inclusions of various thicknesses. Analysis outcomes were verified against measurements from a physical prototype and were...

A rigid nonyielding retaining structure needs to be dimensioned to have adequate stiffness, such that it can resist mobilized lateral earth pressures. This corresponds to the at-rest condition, as there are, in general, negligible lateral deformations in the backfill. Measures that can mobilize higher soil shear strength and reduce lateral thrust are therefore sought to provide a more efficient design. The present study investigates the possibility of inserting compressible geofoam panels against rigid walls using physical model testing. Controlled yielding is allowed in the backfill with the occurrence of deformations in the geofoam. The mobilized earth pressures vary from the maximum at rest, to the intermediate, and finally to the minimum full active state depending on the magnitude of displacement. The effects of geofoam thickness and stiffness on lateral earth pressure reduction are explored. The measured pressure and displacement distributions form a comprehensive reference for use in calibr...

This paper attempts to describe deformation characteristics of EPS geofoam under cyclic loading conditions within and beyond yield states. The loading pattern on geofoam specimen represented a construction sequence as well as a traffic loading of the bridge approach structure. A large size of EPS block specimens with dimensions of 30 cm high, 30 cm wide and 60 cm long were tested in laboratory with different cyclic loads pattern and wide range densities. From testing results, increase in density of EPS geofoam, yield state as well as overall deformation characteristics of EPS foam decreases. The permanent deformation was significantly observed on a low density of EPS geofoam with a low yield state. A stiffness of EPS significantly decreased with increasing of stress level beyond yield stress of material. The stress-strain mechanism of EPS was hardening without failure behaviors when the stress level being more than its yield stress. The overall cyclic behaviors of EPS can be successfully characterized with its yield state.

One major issue in construction is settlement. Building any structure above compressible soils without proper consideration can lead to considerable damage and maintenance cost. Geofoam is a type of light-fill material in the lightest category. Since the 1970s, geofoam has been used worldwide to address settlement problems. Unfortunately, geofoam has not received much attention in Indonesia, mainly due to its cost compared to traditional fill. This paper covers the application of geofoam for road construction based on real soil conditions in Indonesia. From the analysis conducted, the use of geofoam reduces the compacted fill required by 40%. This saves not only construction time, but also carbon footprint of the road design. When the reduction of time by using geofoam is considered, geofoam becomes a feasible solution economically as well as environmentally.

This study presents the results of experimental tests carried on buried uPVC (unplasticized polyvinyl chloride) pipes with an external diameter of 160 mm. The behavior of buried pipes in unreinforced and reinforced trenches by a single layer of HDPE (high-density polyethylene) geogrid and expanded polystyrene (EPS) geofoam block were investigated. To simulate vehicle wheel loadings, 500 cycles of repeated load respectively with an amplitude and frequency of 450 kPa and 0.33 Hz was applied to a loading plate placed over the trench surface. Pipe behavior under cyclic loadings were assessed using vertical diameter strain measurements, circumferential strains and pressures at the crown and springline. Additionally, settlement at the soil surface was measured throughout testing. The testing program is aimed at evaluating the role of different parameters influencing pipe behavior, such as embedded depth of the pipe, implementation of the EPS block and geogrid layer simultaneously and separately, and density, width and thickness of the EPS blocks. The results illustrate that the rate of changes in the pipe circumferential strain, vertical diameter strain and soil surface settlement, which increase rapidly in initial loading cycles, decreased as loading progressed. Based on the results, the density, width and thickness of implemented EPS blocks have an impact role in improving the behavior of buried pipes. The use of geogrid reinforcement with an EPS block with density of 30 kg/m3, thickness of 60 mm and width of 1.5 times the pipe diameter showed the most benefit when balancing vertical diameter strain, pipe crown strain, and soil surface settlement.

Geothermally heating of bridges is a green and sustainable alternative to deicing chemicals, which are energy-intensive, corrosive to the bridges, and dangerous to the environment. Geothermal bridges harness shallow earth geothermal energy, a readily available all-year-round renewable energy source. However, the existing geothermal heated bridge technology was developed based on embedded hydronic loops, which can be only deployed during the construction of new bridges. As there are more existing bridges in the critical need of deicing, a new attached hydronic loop design was developed in this study for geothermal heating of existing bridges. The hydronic loops are attached to the bottom of a bridge deck and are encapsulated inside an insulation material geofoam. The developed hydronic loop was tested on a lab-scale concrete deck with supplied warm water to evaluate its feasibility for field application. This heated deck system was fabricated and instrumented for the heating performance tests in an environmental chamber. It was first tested under various room temperatures higher than 4.4 °C, the lowest temperature permitted by the environmental chamber. Based on the test results, an empirical prediction equation is presented to estimate deck temperature at given ambient and supplied heating fluid temperatures. The applicability of this equation to freezing temperature was validated in localized freezing tests by placing a cooling box on the test deck. All test results show that this heated bridge deck allows efficient heat transfer, approximately 60% of the supplied heat, to the bridge deck surface. The supplied heat flux to the deck surface ranges from 120 to 270 W/m2 depending on the ambient and heating fluid temperature, which is comparable to the embedded hydronic system. The new hydronic loop design is feasible to be implemented on the existing bridges for deicing and snow removal.

Ground vibrations generated by construction activities can adversely affect the structural health of adjacent buildings and foundations supporting them. Therefore propagation and rate of attenuation of construction induced ground vibrations is important during construction activities, particularly in urban areas where constructions are carried out in the vicinity of existing structures. In practice wave barriers are installed in the ground to mitigate the ground vibration propagation and hence to minimise the effect of ground vibrations on surrounding structures. Different types of fill materials such as bentonite, EPS geofoam and concrete are used in constructing wave barriers. In this study, a three-dimensional finite element model is developed to study the efficiency of different fill materials in attenuating ground vibrations. The model is first verified using data from full scale field experiments, where EPS geofoam has been used as a fill material in wave barriers. Then the same model has been used to evaluate the efficiency of open trenches, water filled wave barriers and EPS geofoam filled wave barriers on attenuation of ground vibrations. EPS geofoam is found to be the most efficient fill material, providing attenuation efficiency closer to open trenches. The efficiency of EPS geofoam and water filled wave barriers can be significantly increased by increasing the depth of the wave barrier.

ABSTRACT: Lightweight expanded polystyrene (EPS) block geofoam (geofoam block) is commonly used as a replacement of the heavy in situ soil during slope remediation in order to reduce driving forces. The design procedure requires the use of permanent drainage systems to alleviate hydrostatic pressures in geofoam block slope systems. In this study, small-scale laboratory lysimeter experiments investigated the behavior of a stabilized sandy slope with a geofoam block slope system experiencing seepage. An internal drainage system was incorporated by grooving dual drainage channels (weep holes) on the top and bottom side of the geofoam blocks. A lysimeter with dimensions of 60 cm height, 20 cm width, and 200 cm length was constructed in the laboratory. Slopes were constructed by compacting sand. The geofoam blocks (2.5 cm height, 5 cm width, and 15 cm length) were placed on the sandy slope face with an angle of 45° in ‘one row' and ‘two rows' configurations. The experiments were conducted under constant water pressure heads (25-, 38-, and 50-cm pressure head boundary conditions) in the water reservoir located at the opposite end of the lysimeter from the geofoam blocks. In general, the lightweight geofoam blocks could not resist earth and hydrostatic pressures under seepage. The back-slope was not self-stable under seepage conditions, and deep-seated global stability failures were observed, except for the remediated slope at the 25- and 38-cm pressure head boundary conditions. The internal drainage system was ineffective at dissipating piezometric pressures at the higher seepage gradients investigated at this lysimeter scale. Numerical slope stability modeling confirmed these observations, predicting a factor of safety below the critical value for global stability in cases where failure was observed. More elaborate geofoam block configurations and/or drainage systems should be used to increase resistance against global stability failure caused by higher seepage gradients.

It is becoming a great challenge for civil engineers to design a foundation which able to minimize the effect of an earthquake. A major earthquake produces a strong ground motion in the subsoil and surface structures supported on the soil mass will be induced to move and absorb the dynamic forces. Seismic retrofit of existing foundations is an alternative. However, the modification of this existing foundation toward earthquake resistances raises issues which are far from being totally resolved. Innovative material such as EPS is widely accepted in structural engineering due to its characteristic to absorb the dynamic force effectively. This EPS material demonstrated the practicality and has been applied for geotechnical engineering for various reasons. Based on this, a research which is related to the application of EPS in mitigating the earthquake forces, particularly for raft foundations was conducted properly in this research. The various types and thickness of EPS located beneath the raft foundation and over the soft soil are studied. A finite element program is utilized to develop the computer simulation models. Based on the results, Expended Polystyrene (EPS) Geofoam, placed beneath the raft foundation is able to produces the minimum settlements when subjected to earthquake loading rather than raft foundation modeled without EPS and increasing the density of EPS will simultaneously decrease the settlement of a foundation.

In this study, the results of 1-g shaking table tests performed on small-scale flexible cantilever wall models retaining composite backfill made of a deformable geofoam inclusion and granular cohesionless material were presented. Two different polystyrene materials were utilized as deformable inclusions. Lateral dynamic earth pressures and wall displacements at different elevations of the retaining wall model were monitored during the tests. The earth pressures and displacements of the retaining walls with deformable inclusions were compared with those of the models without geofoam inclusions. Comparisons indicated that geofoam panels of low stiffness installed against the retaining wall model affect displacement and dynamic lateral pressure profile along the wall height. Depending on the inclusion characteristics and the wall flexibility, up to 50% reduction in dynamic earth pressures was observed. The efficiency of load and displacement reduction decreased as the flexibility ratio of the wall model increased. On the other hand, dynamic load reduction efficiency of the deformable inclusion increased as the amplitude and frequency ratio of the seismic excitation increased. Relative flexibility of the deformable layer (the thickness and the elastic stiffness of the polystyrene material) played an important role in the amount of load reduction. Dynamic earth pressure coefficients were compared with those calculated with an analytical approach. Pressure coefficients calculated with this method were found to be in good agreement with the results of the tests performed on the wall model having low flexibility ratio. It was observed that deformable inclusions reduce residual wall stresses observed at the end of seismic excitation thus contributing to the post-earthquake stability of the retaining wall. The graphs presented within this paper regarding the dynamic earth pressure coefficients versus the wall flexibility and inclusion characteristics may serve for the seismic design of full-scale retaining walls with deformable polystyrene inclusions.

International audience; A numerical investigation on the performance of wave barrier and a developed optimization design method for wave barrier are presented. Firstly, a two-dimensional (2D) numerical model is built in ABAQUS and the results are verified by previous publications. A comparative study of the 2D model and three-dimensional (3D) model is also carried out. Then, an extensive parametric study is committed to investigate the effect of each parameter on the barrier vibration isolation effectiveness, key parameters are identified. Unlike most of the previous work, an optimization design method has finally been developed to find out the barrier which has the best vibration isolation effectiveness. An example of optimization design for barriers made up of expanded polystyrene (EPS) geofoam is shown as well. This suggested method can provide useful guidelines for wave barrier design in practice.

ABSTRACT: Lightweight fill solutions have been used in many civil engineering projects throughout the world. At locations with poor soil conditions, alternative lightweight construction fill materials such as expanded polystyrene (EPS) geofoam, wood chips, and tyre wastes may be used instead of conventional fill materials. These materials are used as an additive for the soil. It is known that the type, aspect ratio and content of the admixtures have an important role in the mechanical properties of the mixtures. The main objective of this study was to assess the feasibility of the potential use of EPS beads in geotechnical applications. The effect of EPS bead gradation on the stress–strain behaviour of lightweight composite materials composed of EPS bead–sand mixtures (EPS–sand) was investigated through a series of triaxial compression tests under three different confining pressures. Three different types of spherical EPS beads with different unit weights (EPS-1, EPS-2, and EPS-3) were mixed with sand with varying EPS bead content. This study has shown that the deviatoric stress of a EPS–sand mixture is not only a function of volumetric EPS bead content but it also depends on EPS bead grain size distribution (EPS bead type). Whereas volumetric EPS bead content increases when all other variables are constant (EPS bead type in EPS–sand), the initial modulus of elasticity decreases linearly. Consequently, EPS bead inclusion did not enhance the maximum deviatoric stress of EPS–sand when compared with that of the sand-only specimen. However, bead addition provides a lightweight aspect to the mixture which can be attractive to use in many geotechnical engineering projects. EPS bead content, confining pressure and EPS bead type-dependent multiple linear regression (MLR) equations were proposed to estimate the initial undrained elastic modulus of EPS–sand to reduce the cost and time involved in conventional laboratory testing of EPS–sand mixtures. Based on the stress–strain behaviour of EPS–sand, these mixtures may be utilised in geotechnical applications as a lightweight fill material.

Using expanded polystyrene (EPS) geofoam (geofoam block) in slope remediation projects has drawn interest from the civil engineering sector for its ease of application and budget saving features. According to design precedence, all slope remediation applications that use geofoam blocks should incorporate permanent drainage systems to prevent instability of the lightweight geofoam blocks due to hydrostatic and seepage pressures. In this study, a new method for slope remediation using geofoam blocks was tested through physical laboratory experiments. For this purpose, a total of 24 lysimeter (dimensions of 60 cm height, 20 cm width, and 200 cm length) experiments (including duplicates) were conducted in which seepage through a geofoam block slope system were generated with three different constant water levels in the water reservoir of the lysimeter. Geofoam blocks (dimensions of 2.5 cm height, 5 cm width, and 15 cm length) were assembled to form embankment type configuration at the toe section of the sandy slopes. This study also included coupled numerical model simulations that were comprised of variably saturated flow modeling and slope stability modeling which could be implemented successfully for the global static failure analysis of the geofoam block slope system comprised of two mediums with different geotechnical characteristics. In addition to global static stability failure analysis, which involved conventional limit equilibrium analysis for the geofoam block slope system, hydrostatic sliding mechanism was investigated which provided insight into using an overburden concept to increase the resistance against horizontal driving forces. Experimental and numerical modeling results showed that the geofoam block slope system was stable even though the phreatic surface was above the bottom of the geofoam block assemblage. For this reason, the embankment type configuration tested in this study can be considered a viable remediation technique where seepage induced deep-seated global stability and hydrostatic sliding failures are a concern.

Reducing ground vibrations using a vibration barrier has shown mixed levels of success in practice. The factors affecting the success are the source frequency, distance of source to area of interest at which vibration is to be reduced, ground type, barrier dimensions, and barrier material. Open trench has been shown to be the most effective vibration barrier but faces practical problems in implementation. To overcome the open trench problem, materials like air-filled cushion, polystyrene/geofoam, composites and piles have been used. One promising material which has not been investigated in the field for use as a vibration barrier is sand-rubber mixture. In this study, field tests using a continuous vibration source at various frequencies were conducted where the vibration amplitudes behind an open trench and two different sand-rubber mixtures barriers were measured. The amplitude ratios for the different vibration barriers were compared. The field tests were also modelled numerically to provide contours of the amplitude ratio around the vibration barrier to better understand the spatial performance of the vibration barrier. The sand-rubber mixture barrier is able to reduce the vibration amplitude by 75% behind the barrier when depth of barrier to Rayleigh wavelength ratio is ≥ 0.7. For a barrier, there is a finite zone behind the barrier where the amplitude ratio is ≤ 0.25. The size of the “effective” zone decreases as the impedance of the barrier increases.

In the present investigation, the interface strength behavior of expanded polystyrene EPS geofoam with EPS geofoam and with various other construction materials such as jute geotextile, geogrid, and fly ash are presented. A series of large direct shear tests were conducted with shear box of dimensions 305mm length, 305mm width, and 175mm height. The experimental investigations were carried out by using four different densities of EPS geofoam blocks, 015, 020, 022, and 030kNm3 under four different normal stresses 25, 50, 75, and 100kPa. The effects of density of EPS geofoam and the applied normal stresses on the interface strength parameters were investigated. The results of the interface strength are expressed in the form of shear stress versus normal stress and the direct shear failure envelopes were found to be linear. The experimental results indicate that the density of EPS geofoam does not have significant effect on its interface strength behavior. For all densities of EPS geofoam, it was obs...

Underground structures are sometimes threatened by ground shocks induced by subsurface detonations. This paper proposes one possible method to mitigate the subsurface blasts by attaching a cladding consisting of a face sheet and cellular solid core to the exterior of the structure; the cellular core is foam made from relatively strong materials, such as metal or concrete, rather than typical geofoam made from polymer. A simplified model is established to distinguish three scenarios to delineate the dynamic behavior of a foam cladding subjected to a ground shock. The model compares the velocity time histories of the face sheet and the surrounding soil, in which the foam crushing velocity is not high and the foam is densified uniformly. Further, the governing equations for possible high-velocity foam crushing are established, with progressive collapse as foam crushing mode when alleviating subsurface blasts.

A series of laboratory tests was carried out to assess the time-dependent creep behaviour of EPS geofoam at room temperature (23°C) and at 40°C. The experimental data were then used to calibrate and to validate mechanical viscoelastic models along with an empirical Power Law model, at these two temperatures. The viscoelastic models examined were the 3-element (Maxwell-Kelvin), the 4-element (Burgers) and the Modified 4-element models. The modified 4-element model and the base case, the empirical power law model, were found to give the best predictions. As anticipated, the experimental results show that creep rate is higher at elevated temperatures. The results, at 23°C and 40°C, offer a means to assess and model creep behavior in geotechnical applications at normal, and at a practical elevated, temperature where use of EPS geofoam in warmer climate may be a concern.

The present study explores the potential application of geofoam in reducing the lateral earth pressures on flexible cantilever walls retaining cohesionless and dry backfills. Results of 1-g physical model tests addressing the behavior of yielding cantilever retaining walls with expanded polystyrene (EPS) and extruded polystyrene (XPS) geofoam compressible inclusions are discussed. The effect of relative flexibility of the wall as well as the characteristics of the cohesionless backfill and geofoam on the active earth pressures were investigated in this context. A finite difference code was validated against the lateral earth pressures and backfill strains observed in the tests. Experimental results indicate that the shape of active pressure distribution diagram behind a cantilever retaining wall is non-linear and varies depending on the wall flexibility and characteristics of deformable layer. Geofoam inclusions provide reduction in lateral earth pressures, however the positive contribution of the compressible buffer decreases as wall relative flexibility increases. Reduction of the lateral earth loads is associated with the formation of a wider, non-linear and more stable failure zone induced from the combined influence of the flexural deformations of the cantilever wall and the arching effect induced at the lower half portion of the cohesionless backfill retained by the flexible wall-deformable panel system. Parametric numerical analyses were performed to extend the predictions of the lateral earth pressure coefficients for various combinations of backfill, deformable inclusion and structural attributes by validated numerical model. Based on the results of the parametric analyses, design charts and regression models were proposed to predict active lateral earth pressure coefficients and point of application of the lateral load on the flexible cantilever earth retaining walls with and without deformable geofoam layers.

Expanded polystyrene (EPS) geofoam (geofoam block) is commonly used as a lightweight fill for many civil engineering applications. However, when used for slope remediation, the behavior of geofoam block for slope systems undergoing seepage flow is not well known. In this study, a total of 36 laboratory lysimeter experiments (dimensions of 60 cm height, 20 cm width, and 200 cm length) were conducted to investigate the behavior of sandy slopes containing geofoam blocks as a lightweight fill material. These experiments were conducted with three different values of constant water pressure in the water reservoir located at one end of the lysimeter. In addition, three different configurations of geofoam block were tested with geofoam blocks placed on the face of the packed sandy slope. The dimensions of the geofoam blocks were 2.5 cm high, 5 cm wide, and 15 cm long to achieve a 1:20 scale corresponding to actual block size that is commonly manufactured. Laboratory physical test results were quantified by coupled seepage flow and slope stability models showing the adverse effect of seepage on the factor of safety (FS). Geofoam block configurations were found to be stable against seepage conditions which would cause a shallow-seated failure of the slope in the absence of the geofoam blocks. This is due to the fact that the geofoam blocks could completely fill the mass of the existing slope material subjected to failure. However, the geofoam block configurations were unstable against seepage conditions that resulted in deep-seated failures of marginally stable, sand slopes.

The paper is a synthesis of previously published work by the authors that is focused on the use of expanded polystyrene (EPS) geofoam buffers for seismic load attenuation against rigid basement and soil retaining walls. The paper begins with a brief description of the first documented field application followed by a description of physical 1 m-high reduced-scale shaking table tests that provided the first “proof of concept”. Next, details of the development and verification of a displacement-based model and a FLAC numerical model are described and simulation results that were verified against the physical shaking table tests presented. The numerical results include simulations using simple linear elastic constitutive models for the EPS buffers and granular soil backfill and more complex non-linear hysteretic models. Finally, the verified FLAC model was used to develop a series of preliminary design charts for the selection of a suitable seismic buffer based on characteristics of the design earthquake accelerogram.

The behavior of the pavement is highly dependent on the deformation and stability of the underlying embankment. To optimize the design of embankment suffering heavy asymmetric traffic load in Shanxi province, China, a series of two-dimensional (2D) numerical analyses were conducted using the finite element software PLAXIS to investigate the deformation and slope stability of the unreinforced, geosynthetic reinforced, and expanded polystyrene (EPS) geofoam reinforced embankments. The results show that the general performance in the geosynthetic reinforced case is thought to be superior compared to that in the EPS geofoam reinforced case taking the slope stability into consideration. As the asymmetric traffic load increases, the embankment deformation increases significantly and obvious decrease of the slope stability safety factor is also observed. Great attention need to be paid to the influence of the heavy asymmetric traffic load.

Extruded Polystyrene (EPS) geofoam is a light weight material used in a wide range of geotechnical engineering applications including embankment construction and bridge approaches to reduce earth loads imposed on the adjacent or underlying soils and structures. EPS is also used as a compressible material above deeply buried culverts to promote positive arching and reduce the load transferred to the walls of the structure. An important step towards understanding the soil-geofoam-structure interaction and accurately model the load transfer mechanism is choosing a suitable material model for the EPS geofoam that is capable of simulating the material response to compressive loading for various ranges of strains. In this study, a material model that is able to capture the response of EPS geofoam is first established and validated using index test results for three different geofoam materials. To examine the performance of the model in analyzing complex interaction problems, a laboratory experiment that involves a rigid structure buried in granular material with EPS geofoam inclusion is simulated. The contact pressures acting on the walls of the structure are calculated and compared with measured data for three different geofoam materials. The developed numerical model is then used to study the role of geofoam density on the earth loads acting on the buried structure. Significant pressure reduction is achieved using EPS15 with a pressure ratio of 0.28 of the theoretical overburden pressure at the upper wall. The proposed FE modeling approach is found to be efficient in capturing the behavior of EPS geofoam material under complex interaction soil-structure condition.

Lightweight fills constructed by the use of expanded polystyrene block (EPS-block) geofoam (geofoam block) is known to be susceptible to horizontal loading since the vertical pressure which enhances the shear resistance along the interface of individual blocks is low. Therefore, research has focused on the methods to increase the interface shear resistance of geofoam blocks. This study investigated the use of interlocking mechanisms by conducting direct shear tests on four different interlock configurations. An interlock configuration utilized a number of ledges and notches to interrupt the continuous horizontal shearing plane in-between geofoam blocks. Two different densities of geofoam blocks (EPS19 with a minimum density of 18.4 kg/m3 and EPS29 with a minimum density of 28.8 kg/m3) were used in order to investigate the effect of material hardness on stress-strain behavior and interface friction properties. The results of this study showed that the interlocking mechanism improved the interface...

The effectiveness of EPS geofoam compressible inclusions in reducing both the seismic earth pressure and displacement increment (i.e., horizontal translation and rotation) of yielding, gravity type, earth retaining walls, was investigated by parametric numerical analyses. The 2-D finite element code PLAXIS was used for analyzing the seismic response of two gravity-type retaining walls (with heights equal to 4 m and 7.5 m) under harmonic excitation at the wall base of varying amplitude (0.1 g to 0.7 g) and frequency (0.3 Hz to 20 Hz). The isolation efficiency of the inclusions (defined as the ratio of displacement or pressure reduction, due to inclusion, to the corresponding values for a non-isolated wall) was studied as a function of the normalized – with respect to wall height – thickness of the inclusion and shaking intensity. The results of the analyses indicate that – as in the case of non-yielding walls – the isolation efficiency, in general, increases with increasing inclusion thickness and also depends on shaking intensity, wall height and excitation frequency. However, in contrast to the case of non-yielding walls, the isolation efficiency of yielding walls increases with inclusion thickness only up to a limiting value which cannot be exceeded with a further increase of inclusion thickness. For the case of EPS 100 (i.e., ρ EPS =20 kg/m 3 ) a compressible inclusion with a relative thickness of 15% to 20%, can reduce the seismic pressure by up to 20%, and the seismic displacement increment of a wall by up to 50%, depending on shaking intensity and height of wall. Finally, it was shown that the excitation frequency as well as its relative value, with respect to the natural frequency of the wall-backfill system, is an important parameter which affects the seismic isolation efficiency of EPS and its dependence on shaking intensity, and particularly the isolation against wall rotation. It is concluded that EPS compressible inclusions can provide an effective means for reducing the permanent seismic displacement and lateral thrust increments for new or existing seismically retrofitted yielding earth retaining structures.

The mitigation of seismic-induced dynamic earth forces by placing a vertical layer of expanded polystyrene (EPS) geofoam buffer between a rigid retaining wall and the backfill soil is a recent geotechnical innovation. In this paper, the influence of an EPS geofoam buffer on the reduction of dynamic wall forces is numerically studied by simulating the results of three reduced-scale models of rigid walls mounted on a large shaking table. Numerical simulations were carried out using the finite element program ABAQUS. The paper shows that the numerical results capture the trend in earth forces with increasing base acceleration for all three models. The quantitative dynamic load-time response from the numerical simulations was also judged to be in good agreement with measured physical test values. The numerical trend of EPS geofoam also is the same as that of measured test data. With the increasing time, the compression of EPS geofoam increases. And softer EPS geofoam produces more compression which takes more vibration energy by its deformation. The numerical results confirm the results of physical tests that demonstrate that EPS geofoam seismic buffers hold great promise to reduce earthquake-induced dynamic loads against rigid retaining wall structures.

This paper summarizes major findings from a laboratory study based on stress-controlled cyclic uniaxial compression tests with initial deviator stress conducted on expanded polystyrene (EPS) geofoam. The experiments involved nonelasticized EPS cylinders of various densities subjected to various static deviator stresses and cyclic loading conditions to provide a detailed description of the geofoam cyclic stress-strain response in the viscoelastic and visco-elasto-plastic domains. Experimental results characterizing the viscoelastic behavior were compiled into a normalized Young’s modulus and damping ratio versus cyclic axial strain amplitude relationships. A unified formulation that can be used to determine the normalized modulus degradation curve for a given static deviator stress level and geofoam density (within 15–25 kg/m3 ) was developed. Examination of the yielding behavior of EPS geofoam under cyclic loading revealed a nonlinear increase in the accumulated plastic axial strain with the increasing n...

Expanded polystyrene (EPS) geofoam panels of low stiffness installed vertically against the rigid nonyielding retaining structure provide additional deformations in the backfill. This behavior will lead to the mobilization of a greater portion of the soil strength, thus decreasing the lateral earth thrust acting on the rigid retaining wall. This study addresses the effect of geofoam compressible inclusion on lateral earth thrust acting on a rigid nonyielding retaining wall by small-scale model tests and numerical analyses. The finite-element code used in the numerical modeling is validated against the stress measurements on a 0.7-m-high wall model. Significant reduction is observed in the lateral earth pressures attributable to deformations concentrated at the lower half of retained soil mass. The effects of compressible inclusion thickness, relative stiffness of the EPS geofoam, and strength parameters of the backfill on lateral earth thrust acting on rigid nonyielding walls are investigated by a series ...

Numerical simulation for dynamic response of EPS geofoam seismic buffers placed behind the rigid retaining walls was carried out with the Fast Lagrangian Analysis for Continuum method (FLAC) .The considerations of setting boundary condition of the numerical model, inputting and correcting the dynamic time series of seismic acceleration, and selecting the proper damping were discussed. The coincidence relations of compression-time for EPS geofoam buffers and the horizontal soil pressure -time for retaining wall were numerically calculated by using the proposed model. The calculating results were compared with the physical testing results. The comparisons showed that there were good agreements between the numerical data and the measured data. The numerical results indicate that EPS panels placed between the rigid retaining wall and the backfill soil have a good effect on reducing horizontal earth force during shaking acceleration and can act as seismic buffers against earthquake. The FLAC model provides a feasible way to analyze the dynamic response of EPS geofoam seismic buffers for further researches.

In this paper, the force against rigid retaining walls from backfill soil under static loads and vibration loads is analyzed within three cases. The first case is an ordinary retaining wall without expanded polystyrene (EPS) geofoam buffer. In the second and the third case, a layer of vertical EPS buffer with different density and elastic modulus is placed between a rigid retaining wall and backfill soil. Numerical simulation results show that the force against the same retaining wall in the treated cases is less than that in the untreated case, under both static loads and vibration loads. Moreover, the compression of different EPS buffer is studied. Under vibration excitation, when the density and elastic modulus of EPS buffer decreases, its compression increases and more wall force is mitigated. Simulation results accord with the physical shaking table test data. Numerical results and physical test demonstrate that EPS geofoam seismic buffers hold great promise to reduce loads against rigid retaining wall structures, especially earthquake-induced dynamic loads.