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This paper investigates the behavior of EPS geofoam in a true triaxial apparatus using 70mm×70mm×140mm prismatic brick-shaped specimens. The specimens are subjected to different stress paths in the deviator (π) plane by means of stress-controlled loading, in which the axial stress is imposed at a rate of 75kPa/min in the major principal direction. Stress–strain characteristics and volume change behavior have been recorded, and the yield surface has been deduced from the experimental data. The following observations have also been made for the geofoam: (a) it is an elastoplastic hardening material with plastic contractive volume change under compressive loading, (b) it softens stiffness-wise under confining stress, (c) the onset of contractive volume change corresponds quite well to the proportional limit, and (d) yielding is a slightly decreasing function of the intermediate principal stress. The study found that yielding can be represented reasonably well by a Drucker–Prager yield surface.

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... In this study, lifecycle cost and carbon emissions in different measures are calculated and compared. Considering the quantity of materials needed in each abatement method [53][54][55][56][57][58][59][60] is the main factor (which influences the overall cost and carbon footprint), rational engineering assumptions are made before conducting the lifecycle assessments. ...

... The geofoam density is around 1-2% to the soil and ranges from 10-30 kg/m 3 [55]. In this study, the 16 kg/m 3 geofoam is selected for the cost and carbon emission calculations. ...

Noises and vibrations caused by operating transport systems can seriously affect people’s health and environmental ecosystems. Railway-induced vibrations in urban settings can cause disturbances and damages to surrounding buildings, infrastructures and residents. Over many decades, a number of mitigation methods have been proposed to attenuate vibrations at the source, in the transmission path, or at the receiver. In fact, low-frequency or ground-borne vibration is turned out to be more difficult to be mitigated at source, whilst some attenuation measures in propagation path can be applicable. To broaden the mitigating range at the low-frequency band, the applications of meta-materials/structures have been established. In railway systems, periodic structures or resonators can be installed near the protected buildings to isolate the vibrations. Despite a large number of proposed attenuation methods, the sustainability of those methods has not been determined. Based on rational engineering assumptions, the discounted cash flows in construction and maintenance processes are analysed in this study to evaluate lifecycle costs and the quantity of materials and fuels, as well as the amount of carbon emissions. This study is the world’s first to identify the efficacy and sustainability of some transmission path attenuation methods in both normal and adverse weather conditions. It reveals that geofoam trenches and wave impeding blocks are the most suitable methods. Although metamaterial applications can significantly mitigate a wider range of lower frequency vibrations, the total cost and carbon emissions are relatively high. It is necessary to significantly modify design parameters in order to enable low-cost and low-carbon meta-materials/structures in reality.

... This model was developed by the authors (Wong and Leo, 2006) based on experimental results from a series of standard "drained" triaxial tests. It initially adopted the Mohr-Coulomb yield function used widely in soil mechanics but upon further testing with a true triaxial apparatus ( Leo et al., 2008), a Drucker-Prager type yield function was subsequently preferred. This is written as: ...

All classic developments based on irreversible thermodynamics assume implicitly that the process does not deviate significantly from thermodynamic equilibrium. In consequence, despite the fact the system is in evolution therefore in non-equilibrium, the state equation expressing the condition of thermodynamic equilibrium can still be used to reduce the number of independent state parameters by one in complex problems (for example, the density, pressure and temperature of the pore fluid transiting a porous solid is related by a state equation). This is strictly speaking an approximation. Its efficiency can only be assessed a posteriori by the results.
c is a rheological parameter which depends on the initial stress. This is because experimental measurements suggest that the plastic volumetric strain is better represented by the plastic potential given in (97) rather than the yield function of (94). As discussed earlier, this means that the thermodynamics principle in terms of the non-negativity of the dissipation may possibly be violated in some evolutions since the normality rule (plastic strain increment being normal to the yield function) is not being followed. The associative flow rule, however, has been a problem with some geomaterials such as soils and rocks in that it tends to erroneously predict plastic volumetric strain. This is one instance where the insight provided by thermodynamics into post yielding volumetric behavior is seemingly at odds with experimental evidence. In these cases it is widely accepted that the plastic volumetric behavior would be better captured using a non-associative flow rule. These cases also demonstrate that while thermodynamics insights provide useful guidance to help engineers focus on important aspects of the constitutive relationships in continuum mechanics, it is necessary that these insights should ultimately be supported by experimental evidence.

... In addition, other EPS material properties e.g. Modulus of subgrade reaction (Negussey and Huang 2006), Stress-strain relationships (Hazarika 2006), Resilient modulus (Huang and Negussey 2007) and Compressibility (Leo et al. 2008) have also been investigated by several researchers. ...

Expanded polystyrene (EPS) geofoam has been used in a wide range of geotechnical applications since 1960s. These applications involve the use of geofoam either as a lightweight fill material (e.g. in embankments and bridge approaches) or as a compressible inclusion (e.g. in retaining walls and culverts). In these applications, geofoam is placed directly in contact with other construction materials. Therefore, for successful analysis and design of these composite structures, a detailed knowledge of both compression and shear behavior of the geofoam material as well as the strength of the interface are needed. In the present research, an attempt has been made to determine the shear strength parameters of geofoam monoblocks and the interface strength properties of EPS blocks in contact with other construction materials using direct shear tests (DSTs). Test results showed that both the geofoam density and the applied level of normal stress have significant effects on the shear strength of monoblock as well as the interface properties of EPS geofoam.

... The material behaviour of EPS geofoam under various loading conditions such as compression, tension, flexure and shear was reported by Horvath (1994) [18], [32]. Several researchers have done extensive work to determine the material properties of EPS geofoam such as compressibility Leo et al. (2008) [24], modulus of subgrade reaction Negussey and Hsuang (2006) [29] and resilient modulus Negussey and Hsuang (2007) [30], EPS geofoam applications in geotechnical engineering, especially in construction of embankments and pavements Frydenlund and Aaboe (1994) [16], Chang (1994) [10], Duskov (1997a) [11], Duskov (1997b) [12], Duskov and Scarps (1997) [13], Beinbrench and Hillmann (1997) [8], Perrier (1997) [33], Stark et al. (2004) [35], Fransworth et al (2008) [15], Horvath (2008) [20] and Arellano and Stark (2009) [2], centrifuge modeling on EPS embankments Mandal and Nimbalkar (2000) [26], slope stability analysis Jutkofsky et al. (2000) [23], Mandal and Nimbalkar (2004) [27] and Akay et al. (2013) [1]. Experimental investigations and numerical modeling was carried out on EPS geofoam as a compressible inclusion behind retaining walls Horvath (1997) [19], Murphy (1997) [28], Mandal and Nimbalkar (1999) [25], Hatami and Witthoft (2008) [17] and Ertugrul and Trandafir (2013) [14]. ...

It is very difficult to construct any structure on soft foundation soil such as marine clay due to the major issue of poor bearing capacity and excessive settlement. Therefore to decrease the overburden pressure in such condition a simple technique has been suggested to improve the ground by using expanded polystyrene (EPS) blocks. In the present study, the experimental investigation was carried out using expanded polystyrene (EPS) geofoam blocks to improve the bearing capacity of soft foundation soil. In the experimental investigation marine clay was used as soft foundation underlaying EPS geofoam block. Four different densities of EPS geofoam were used in the investigation. The effect of density of material on bearing capacity improvement was studied. EPS geofoam with low density has higher bearing carrying capacity and it decreases with increase in the density of the material. Settlement at failure decreases with increase in the density of EPS geofoam. Finite element analysis was also carried out using PLAXIS 2D professional version to validate the experimental results. The pressure settlement behavior obtained from the finite element analysis is found to be in good agreement with measured experimental values.

... The main purpose of this type of casing is to allow water mass storage without significantly disrupt its propulsion. As pointed out in the literature [3][4][5][6][7][8][9][10], polystyrene exhibits a brittle behavior in tensile loads and a ductile one in compressive tests. Studies on polystyrene response on large strain and thermal stress have been also detailed [11][12]. ...

This study addresses some aspects regarding water jet propulsion during high explosives detonation. A number of theoretical and experimental studies have shown that using Gurney equation and the relationships derived, one can provide fair results regarding initial velocity of metallic fragments for explosively-driven metal casings. However, an investigation on Gurney equations utilization for the prediction of water velocity has not been performed yet. By carrying out simple experimental tests and numerical simulations, water has been investigated in terms of total mass average velocity and tip velocity. Based on the available data, the findings indicate that Gurney equations overestimate the water mass average velocity. For water tip velocity evaluation, further studies should be made.

... Other nonlinear models have been proposed to capture the material response under triaxial loading (e.g. [17][18][19]). ...

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.

... In literature, there are some investigations about the evaluation of stress-strain behavior of EPS. It is found that some factors influence the stress-strain behavior of EPS such as its density, applied confining stresses, time effects, sample size and temperature (among others: Elragi et al. [11]; Hazarika [12]; Leo et al. [13]; Gnip et al. [14]). Furthermore, EPS wetting could affect its stress-strain behavior [15]. ...

Lightweight fill materials have been used in many civil engineering applications throughout the world. A lightweight fill was produced by blending expanded polystyrene (EPS) beads and sands. Such formed granular geomaterials , known as sand-EPS lightweight fills, have potential of being lightweight compared to traditional fills, thus are suitable for many infrastructure works where less overburdens are expected, e.g., utilities trench backfills. This paper examines the static and cyclic behavior of sand-EPS mixtures under direct shear test conditions. Large direct shear tests were conducted on the lightweight fills to observe materials' stress-strain relationships, specifically, the stress-strain variations associated with the mixing ratios of EPS beads. The behaviors of mixtures under cyclic loading are worth to pay much attention on, though there are few relative studies about this at present. Cyclic stress–strain relationships and stiffness degradation curves for sand-EPS mixtures with different mix ratios are also discussed. EPS beads were incorporated into the mixtures based on their mass ratios over sands, i.e., 0.15% and 0.35%. Monotonic Direct shear tests were conducted under 3 different vertical stresses (40, 80, 160kPa) and the cyclic shear behaviors of the sands was tested by considering the normal stress of 50 kPa. The results showed that the inclusion of EPS bead in sand will lead to a decreased shear modulus and damping ratio.

... Other nonlinear models have been proposed to capture the material response under triaxial loading (e.g. Chun et al., 2004;Leo et al., 2008;Ekanayake et al., 2015). Index tests performed on EPS blocks of different densities show that the material exhibited a nonlinear behavior for compressive strains greater than 1%, associated with a reduction in Young's modulus beyond this strain Level (Ertugrul and Trandafir, 2011). ...

The design of subsurface structures associated with transportation and other underground facilities, such as buried pipes and culverts, requires an understanding of soil-structure interaction. Earth loads on these structures are known to be dependent on the installation conditions. To reduce earth pressures acting on buried structures installed under high embankments, the induced trench method has been recommended and applied in practice for several decades. It involves the installation of a compressible material (e.g. EPS geofoam blocks) immediately above the buried structure to mobilize shear strength in the backfill material. A first step towards understanding this complex soil-geosynthetic-structure interaction and accurately modeling the load transfer mechanism is choosing a suitable material model for the geofoam that is capable of simulating compressive testing results. In this study, an experimental investigation is conducted to measure the changes in contact pressure on the walls of a rigid structure buried in granular backfill with an overlying geofoam layer. Validated using the experimental results, finite element analysis is then performed and used to study the role of geofoam density, thickness and location on the load transferred to the buried structure. Conclusions are made regarding the effect of modeling EPS inclusion as a non-linear material and the role of EPS configuration on the earth pressure distribution around the buried structure.

... Expanded polystyrene (EPS) due to its availability and satisfactory performance characteristics is commonly used in building structures where it is exposed to various kinds of stresses [1]. Expanded polystyrene (EPS) Geofoam is a rigid cellular plastic foam that has been used in a wide range of geotechnical applications including rapid construction of embankment over compressible soils, slope stabilization, reduction of static and dynamic lateral loads on retaining walls and bridge abutments [2]. ...

The mechanical properties of Expanded Polystyrene (EPS) Geofoam are important to be investigated. Loading rate dependency and repeated load effects on the EPS stress strain behaviors were studied by performing compression tests. In the present study an investigation was done to simulate the actual working conditions and hence to evaluate the mechanical behavior of EPS under these conditions. A series of loading cycles were applied in accordance with a defined procedure on EPS cubic samples with densities of 0.30 kN/m3 the elastic properties were evaluated at each loading condition (repeated load and different loading rates values). The significant effects of those loading conditions specially rate dependant stress strain behavior were observed. For the repeated load conditions the residual deformations occurs after each load application was the keyword of repeated load effects, where the relative deformation will increases as the load repeated on the same sample. For the loading rates effects when EPS foam is subjected to compressive loading, the entrapped air within the cells is compressed and viscous force is generated. Viscous forces increase with the loading rate. The detailed of this investigation will be discussed in this article.

... Due to its special inherent properties like low density; low permeability and different mechanical behavior, the EPS Geofoam is extensively being used in geotechnical applications. Number of studies has shown that compressive strength of EPS Geofoam depends mainly on material density, strain rate and confining stress (Chun et al., 2004;Hazarika, 2006;Wong and Leo, 2006;Leo et al., 2008;Ossa and Romo, 2009). ...

Expanded Polystyrene (EPS) Geofoam is successfully used as construction material in the field of geotechnical engineering for the last four decades, due to its wide variety of applications such as compressible inclusion in retaining walls and lightweight fill material in embankments. In the present study, an attempt has been made to understand the behavior of EPS Geofoam under triaxial loading conditions. A series of triaxial tests were carried out on EPS Geofoam specimen of size 75 mm diameter and 150 mm height to obtain the shear strength parameters. Four different densities of EPS Geofoam 0.15, 0.20, 0.22 and 0.30 kN/m 3 were used to prepare the specimens for triaxial testing. Shear strength parameters were calculated for three different confining pressures of 50, 100 and 150 kPa. The tests were carried out up to 15% of axial strain. Increase in the EPS Geofoam density showed increase in the value of cohesion, whereas marginal increase in the angle of internal friction was observed. The deviator stress value increased with the increase in the density of EPS Geofoam. Finite element analysis was also performed using Plaxis 2D professional software to visualize horizontal displacement; deviator stress-strain patterns and found reasonably good agreement with experimental study.

... Leo et al. [8] performed triaxial tests on EPS geofoam to determine its mechanical behavior. Their study showed that EPS geofoam was softening stiffness-wise under increasing confining pressure and the elastoplastic hardening material was having plastic contractive volume change under compressive loading beyond the onset of yielding. ...

Expanded Polystyrene (EPS) geofoam has potential benefits in construction industry for its desirable mechanical properties such as extremely light weight and volume contraction under compressive loading. However, the engineering properties and applications of this material are yet to be fully explored. In this paper, a finite element formulation is presented for a plastic hardening model developed for EPS geofoam. Formulation of the model is based on the Drucker Prager yield criterion but additional parameters are used to simulate the hardening behaviour of the geofoam. The finite element model is verified using experimental data from a series of triaxial tests carried out on a variety of EPS geofoam manufactured in Australia.

... Other nonlinear models have been proposed to capture the material response under triaxial loading (e.g. Chun et al., 2004, Leo et al., 2008, Ekanayake et al., 2015. ...

Numerical modeling of soil-structure interaction problems involving flexible or soft geosynthetic inclusions and large deformation is known to be challenging, especially in the presence of nearby structures. This thesis is devoted to developing a numerical modeling framework for the analysis of soil-geosynthetic interaction problems. It reports the results of both 2D and 3D analyses with explicit modeling of the geometry and material behavior of geosynthetics and the surrounding backfill. The numerical results are validated using existing laboratory experimental data. Two types of geosynthetics that are commonly used in geotechnical engineering projects are considered using the proposed numerical framework; EPS geofoam and geogrid. A numerical procedure for modeling the short-term response of EPS geofoam is first developed and validated for three different EPS geofoam materials. To examine the performance of such model in analyzing complex interaction problems, a laboratory experiment that involves a rigid structure buried in granular material with EPS geofoam inclusion is simulated using a series of 2D finite element analysis. The role of geofoam material, geometrical properties, and configuration on the reduction of earth loads acting on buried structures are investigated. Results showed that the introduction of EPS geofoam block immediately above the structure has a significant effect on the contact pressure distribution particularly on the upper wall of the structure. The rest of the thesis is devoted to introducing a numerical framework that is suitable for the three-dimensional analysis of applications involving soil-geogrid interaction. The geogrid response is investigated under both unconfined and soil-confined environments using different loading conditions (e.g. vertical foundation loading and pullout loading). The proposed FE approach has proven to be efficient in capturing the 3D response of the geogrid, the surrounding backfill, and the geogrid-backfill contact interaction.

... The EPS block was used for backfill material of RAMEN Bridge in Norway in 1972 and has been utilized for the reinforcement of soft ground in Europe and Japan. Leo et al. (2008) investigated the behavior of EPS geofoam in a true triaxial apparatus. Stress-strain characteristics and volume change behavior were examined and the yield surface was deduced from the experimental data. ...

Unconfined and triaxial compression tests were carried out to examine the behavior of light-weighted soils (LWS) consisting of expanded polystyrene (EPS), dredged soils, and cement with respect to initial water content. The stress-strain behavior of LWS are analyzed with varying initial water content and silt contents of dredged soils, cement ratio, and confined stress. As initial water contents increase, the compressibility index increases and the preconsolidation pressure was vice versa. As initial water contents increase, the slope of stress-strain curve in elastic zone increases and strain rate at failure decreases and the strain rate at failure was not changed by the being of foams. As initial water contents increase, a compressive strength of LWS decreases. The decrement ratio of compressive strength of LWS with foams increases as cement content increases and initial water contents decreases. The compressive strength increases as silt contents increases.

... Often, the unconfined compression test is used to determine the strength of the EPS geofoam; which implies that the internal friction angle of this material has been officially neglected. However, direct shear and triaxial test results on the specimens cut from the large geofoam blocks indicate that along with the cohesion, the EPS geofoam enjoys a slight amount of internal friction (Leo et al., 2008;Padade and Mandal, 2012a,b;Beju and Mandal, 2017;Khan and Meguid, 2018). Although compressive strength and stiffness per unit weight of EPS geofoam are high compared to conventional construction materials, due to relatively low absolute values of these two parameters in EPS, care must be taken to keep the vertical stress inside the EPS blocks below the elastic limit so as to prevent punching and diminish the immediate subsidence and excessive creep settlement in the long term. ...

In design, internal stability of EPS lightweight fills are provided either by applying load distributing mechanisms
(thick pavements or concrete slabs) or using more strong lightweight material through denser EPS geofoam
blocks. However, unit weight of the EPS geofoam is a limited parameter. As an attempt to improve the mechanical
properties of EPS geofoam, geocell-geofoam composite (GGC) is introduced in this study. Geocell
mattresses were infilled with solidified geofoam beads in the factory to fabricate GGC. The EPS geofoam and GGC
samples were tested using a large-scale shear test apparatus of size measuring 1 m3. Results indicate that inclusion
of the geocell leads to a considerable increase in the shear strength and a great decline in the
compressibility of the geofoam. In comparison with EPS blocks, up to 72% rise in the shear strength and 67%
decline in the vertical displacement were observed in GGC samples at the normal stress of 35 kPa. In addition,
incorporation of the geocell was found to change the resisting mechanism of the EPS geofoam from cohesive to
cohesive-frictional. While there was only 4.5% decline in the cohesion, the internal friction angle of the tested
geofoam increased six-fold due to the involvement of the geocell.

... Characterized by its low density, nearly 100 times lower than that of most soils and at least 10 to 30 times lighter density than other lightweight fill materials, it has been implemented in a variety of geotechnical applications. Examples may refer to the reduction of deformations (Leo et al. 2008;Jamshidi Chenari et al. 2016;Khajeh et al. 2020), the reinforcement of embankments (Miki 1996;Negussey 1998;Athanasopoulos et al. 1999;Farnsworth et al. 2008;Puppala et al. 2019), retaining walls, buried pipes, tunnels, and culverts (Karpurapu and Bathurst 1992;Horvath 1994;Inglis et al. 1996;Horvath 1997;Bathurst et al. 2007;Zarnani and Bathurst 2007;Kim et al. 2010;Ertugrul and Trandafir 2011;Athanasopoulos et al. 2012;De et al. 2016;Witthoeft and Kim 2016;Beju and Mandal 2017;Meguid et al. 2017) as well as its application in slope remediation projects (Arellano et al. 2011;Özer and Akay 2015). EPS block added to a parent soil functions as a seismic buffer or vibration barrier in order to dissipate a considerable amount of energy induced by the seismic vibrations on the specific geo-structures (Stark et al. 2004;Bathurst et al. 2007;Zarnani and Bathurst 2007;Bathurst and Zarnani 2013). ...

Sand-EPS geofoam is commonly used as a seismic buffer in a variety of geotechnical
applications to alleviate damages imposed by seismic vibrations. Evaluation of the properties of the sand-EPS geofoam interface is an essential part of the design and installation of EPS geofoam in direct contact with the parent sand. In this study, a series of laboratory tests are carried out using a large-scale direct shear apparatus to evaluate the monotonic, cyclic and post-cyclic behavior of the sand-EPS
geofoam interface. Adopting the relative density of the parent sand, the density of EPS geofoam, the applied normal stress, the cyclic shear strain semi-amplitude and the number of cycles as the variable parameters, their influence on the response of the sand-EPS geofoam interface is investigated. According to the experimental results, with the increase in the number of cycles, sand relative density, EPS geofoam density and the applied normal stress, the equivalent or secant stiffness of the sand-EPS geofoam interface increases while its damping ratio declines. The results of the monotonic (MDS) and post-cyclic monotonic (CMDS) shearing experiments also show that with an increase in the EPS density and normal stress, which offers greater resistance against sliding, the mobilized shear stresses generally increase.

... EPS geofoams have been used consistently in roads [25] and as a compressible inclusion behind soil retaining structures [26] as well as a method for protecting buried pipelines [27]. It is an elastoplastic hardening material with plastic contractive volume changes under compressive loading [28], whose behaviour is dependent on the density and confining stress. Further, it has been shown that the volumetric strain and axial compression strain have a linear relation [29]. ...

The technique of stone column to improve the performance of soft soil is well established. However, an alternative material to enhance the performance of the soft soil by reinforcing with geofoam materials is suggested. Expanded polystyrene (EPS) geofoam is a superlight weight geosynthetic material used in various geotechnical engineering applications. This study deals with the innovative use of geofoam as a column material in soft soil for improving the bearing capacity. The method was developed in small-scale laboratory tests, and a series of loading tests were carried out on various single floating geofoam columns (normal geofoam and hollow geofoam) with two different diameters and the length-to-diameter ratio of 5. Next, a comparison was made with the results of ordinary stone columns and reinforced stone columns to obtain the benefits of geofoam columns. According to the results and by considering the bearing capacity, geofoam columns could be a good alternative material for improving the bearing capacity of soft soils. It was also found that the efficiency of the geofoam columns is almost similar to that of the ordinary stone columns and the usage of the geofoam is easy and economical. However, encasing the stone columns with geotextile results in further growth in the bearing capacity.

... The backfill soil material was modeled as a purely frictional, elastoplastic material obeying the Mohr-Coulomb failure criterion. This model allows elastic behavior up to yield (Mohr-Coulomb yield point defined by the friction angle).Many researchers studied the properties of Geofoam,Aytekin, (1997); Elragi et al. (2000); Kumruzzaman, et al. (2008); Abd-Elrahman et al, (2008 a& b);Leo, et al. (2008); and Ikizler, et al. (2008). The Normal EPS geofoam material was modeled as purely cohesive elasto-plastic material, obeying the Mohr-Coulomb failure criterion. ...

This document contains all papers presented in ICGE'10 (Hammamet, Tunisia, 23-25 October 2010) including keynote lectures and oral presentations.

... Using the UC test to assess the strength of the EPS geofoam implies that the EPS geofoam is generally assumed as a purely cohesive material. However, the EPS geofoam shows some frictional resistance, though relatively small, as the results of the direct shear and triaxial tests confirm (Leo et al. 2008, Padade and Mandal 2012a, b, Beju and Mandal 2017, Khan and Meguid 2018. Moreover, UC tests on the large blocks (0.6 m cube) of the EPS geofoam showed that using conventional 0.05 m cube specimens, gives rise to substantial underestimation of the elastic modulus and Poisson's ratio of this material (Elragi et al. 2000). ...

The EPS geofoam as a lightweight material has been widely used in recent years to boost the performance of
geotechnical structures. Both the internal and external stability of the fills made by the EPS blocks should be met. Overlying
concrete slabs and thick pavements or applying denser EPS blocks provide internal stability of EPS geofoam lightweight fills by
reducing the internal vertical stress within the EPS blocks. As an alternative way, in this study, new composite material is
introduced by using the polypropylene fiber to reinforce the EPS geofoam in the factory as an attempt to improve the
mechanical properties of the EPS geofoam. The composite material was fabricated in different fiber contents by solidifying the
mixture of fiber and geofoam beads using controlled heat and temperature. Then, the behavior of the composite was studied
using a series of direct shear tests. The results show that including fiber leads to a rise in the shear strength and a significant
decline in the compressibility of the reinforced EPS geofoam. For the geofoam reinforced with 80% fiber content, up to 23.3%
increase in the shear strength and 57.6% reduction in the vertical displacement (Δz) were observed in the laboratory. In addition,
while the change in the composite's cohesion is largely decreased, the friction angle of the composite shows an increasing trend
with fiber content increase. A maximum of 12.6% reduction in the cohesion and 100% increase in the internal friction angle of
the reinforced material were observed in the laboratory.

... Using the UC test to assess the strength of the EPS geofoam implies that the EPS geofoam is generally assumed as a purely cohesive material. However, the EPS geofoam shows some frictional resistance, though relatively small, as the results of the direct shear and triaxial tests confirm (Leo et al. 2008, Padade and Mandal 2012a, b, Beju and Mandal 2017, Khan and Meguid 2018. Moreover, UC tests on the large blocks (0.6 m cube) of the EPS geofoam showed that using conventional 0.05 m cube specimens, gives rise to substantial underestimation of the elastic modulus and Poisson's ratio of this material (Elragi et al. 2000). ...

The EPS geofoam as a lightweight material has been widely used in recent years to boost the performance of
geotechnical structures. Both the internal and external stability of the fills made by the EPS blocks should be met. Overlying
concrete slabs and thick pavements or applying denser EPS blocks provide internal stability of EPS geofoam lightweight fills by
reducing the internal vertical stress within the EPS blocks. As an alternative way, in this study, new composite material is
introduced by using the polypropylene fiber to reinforce the EPS geofoam in the factory as an attempt to improve the
mechanical properties of the EPS geofoam. The composite material was fabricated in different fiber contents by solidifying the
mixture of fiber and geofoam beads using controlled heat and temperature. Then, the behavior of the composite was studied
using a series of direct shear tests. The results show that including fiber leads to a rise in the shear strength and a significant
decline in the compressibility of the reinforced EPS geofoam. For the geofoam reinforced with 80% fiber content, up to 23.3%
increase in the shear strength and 57.6% reduction in the vertical displacement (Δz) were observed in the laboratory. In addition,
while the change in the composite's cohesion is largely decreased, the friction angle of the composite shows an increasing trend
with fiber content increase. A maximum of 12.6% reduction in the cohesion and 100% increase in the internal friction angle of
the reinforced material were observed in the laboratory.

... Softening of EPS geofoam stiffness with increasing confining pressure and plastic volume contraction under compressive loading beyond yielding was observed by Leo et al. (2008) from a series of true triaxial tests. True triaxial test results further confirmed the previous study by Wong and Leo (2006) showing that the EPS geofoam yield surface can be represented by the Drucker Prager yield surface. ...

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.

This paper reports the results of shear resistance tests conducted on geofoam blocks with no connection, blocks connected with barbed connector plates, and blocks connected with polyurethane adhesive. In the first phase, tests were completed in a large direct shear box (430mm L×280mm W) under normal pressures of 14.8kPa, 29.6kPa, and 74.1kPa. In phase II, tests were conducted on 1200mm L×600mm W specimens using a computer controlled actuator under normal pressures of 9.3kPa, 18.1kPa and 26.9kPa. The measured values of the coefficient of friction between blocks were found to be consistent with the values reported in the literature and conservative in terms of commonly used design values. The test results show that the presence of barbed connector plates did not provide additional interface shear resistance; however polyurethane adhesive was successful in bonding the blocks together thus virtually eliminating horizontal sliding between the blocks. Blocks connected with barbed connector plates subject to repeated loading showed signs of decreased shear resistance during reloading, but did reach the peak shear resistance measured during initial loading.

The geometry of low-density, closed-cell, polyethylene and polystyrene foams was modelled with a Kelvin foam having uniform-thickness
cell faces; finite element analysis (FEA) considered interactions between cell pressures and face deformation. Periodic boundary
conditions were applied to a small representative volume element. In uniaxial, biaxial and triaxial tensile stress states,
the dominant high-strain deformation mechanism was predicted to be tensile yield across nearly flat faces. In uniaxial and
biaxial compression stress states, pairs of parallel plastic hinges were predicted to form across some faces, allowing them
to concertina. In hydrostatic compression, face bowing was predicted. The rate of post-yield hardening changed if new deformation
mechanisms became active as the foam strain increased. The effects of foam density and polymer type on the foam yield surface
were investigated. Improvements were suggested for foam material models in the FEA package ABAQUS.

This paper describes an updated and simple EPS constitutive model proposed by the authors for modelling EPS geofoam in geotechnical applications where geofoam-structure as well as geofoam-soil interactions occur. The work is based on an earlier model developed by the authors, which has since been modified to reflect recent experimental results suggesting the admissibility of the Drucker-Prager failure criterion in lieu of the Mohr-Coulumb criterion. The updated model is developed within the framework of classical elasto-plasticity, with the inclusion of strain hardening, a hardening rule defined in terms of equivalent deviatoric plastic strain and a non-associate flow rule. It is simple to calibrate (with 6 independent parameters determined from triaxial tests) and is relatively easy to incorporate into numerical codes. The updated model has been calibrated against results from a series of “drained” triaxial tests performed on the EPS geofoam. The steps required for calibration are described in the paper. It has been also been shown to accurately reproduce the responses of the material under shearing, in particular, of the shear-contraction post yield behaviour typical of geofoam material. The model will be applicable for a variety of geotechnical applications such as for the modelling of EPS geofoam inclusion behind retaining structures and as a buffer material to mitigate against dynamic loading and vibrations.

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.

EPS geofoam blocks underlying compacted soil and structural loads become subjected to multi-axial loading. Effects of confining pressure on the stress-strain behavior of EPS geofoam have been investigated in previous studies. Some studies found increases in confining stress lead to corresponding decreases in both modulus and compressive strength. Increasing confining stress has also been reported to result in higher compressive strength. Regardless of the sense and attributed significance of the effects of confinement on EPS geofoam behavior, the implied effects on performance are generally not considered in practice. A series of triaxial compression tests was conducted on EPS geofoam of different densities and over a range of confining pressures. Results from the investigation indicate increases in confinement lead to decreases in yield stress and post-yield compressive resistances, depending on the EPS density and range of confining pressures. The sense and practical significance of confining stress effects are discussed. An approach for incorporating the more significant effects of confining stress on EPS geofoam behavior is considered.

A small-sized experimental device of thermal insulation system in Chinese traditional residential roof was established to experiment on the combustion characteristics of thermal insulation material called expandable polystyrene (EPS) in various widths. The time when EPS material began melting (shorted as the melting time) and the total ignition time over EPS surface were analyzed to explore the characteristics of flame spread over EPS surface through monitoring the dynamic combustion process by camera. The experimental results show that the melting time doesn't delay with the increasing of specimen width, but the total ignition time increases non-linearly. And the total ignition time over EPS surface can be forecast when EPS material width range is from 10-30 cm in this study.

Рассматриваются вопросы влияния степени армирования грунтов на их прочность и деформируемость. Выполнен анализ применяемых синтетических армирующих материалов и приведены основные методы экспериментальных и теоретических исследований их взаимодействия с грунтом. Представлены результаты экспериментальных и теоретических исследований характера деформирования армированного и неармированного оснований.
Монография подготовлена на кафедре «Геотехника и дорожное строительство» в соответствии с основной образовательной программой «Геотехника» подготовки магистров по направлению 08.04.01 «Строительство» и предназначена для самостоятельной работы бакалавров и магистров строительных специальностей, способствует закреплению и углубленному изучению теоретических знаний, полученных на лекциях, и прививает будущим строителям навыки научно-исследовательского и творческого подхода к проблеме усиления слабых оснований.

Ground vibrations due to human activity can be reduced with the installation of vertical barriers within the soil. The efficiency of the isolation system depends on various parameters such as depth, width, distance from the source, wavelength. A centrifuge parametric study is conducted to examine the influence of the different parameters in some reduced scale models made of Expanded polystyrene (EPS) isolation barriers within Fontainebleau sand in order to determine geofoam isolation efficiency.

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 observed that there was no significant variation in interface friction angle values. However, a slight increase in adhesion Ca was observed with the increase in the density of EPS geofoam.

Initial elastic modulus and compressive strength are the two most important engineering properties for modeling and design of EPS geofoams, which are extensively used in civil engineering applications such as light-fill material embankments, retaining structures, and slope stabilization. Estimating these properties based on geometric and physical parameters is of great importance. In this study, the compressive strength and modulus of elasticity values are obtained by performing 356 unconfined compression tests on EPS geofoam samples with different shapes (cubic or disc), dimensions, loading rates, and density values. Using these test results, the mechanical properties of the specimens are predicted by linear regression and artificial neural network (ANN) methods. Both methods predicted the initial modulus of elasticity (Ei), 1% strain(σ1) , 5% strain (σ5) , and 10% strain (σ10) strength values on a satisfactory level with a coefficient of correlation (R²) values of greater than 0.901. The only exception was in prediction of σ1 and Ei in disc-shaped samples by linear regression method where the R² value was around 0.558. The results obtained from linear regression and ANN approaches show that ANN slightly outperform linear regression prediction for Ei and σ1 properties. The outcomes of the two methods are also compared with results of relevant studies, and it is observed that the calculated values are consistent with the results from the literature. © 2022, The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature.

The standard criteria (Chap. 6) are too simple to approximate real experimental data. The recommended criteria (Sect. 10.4) need a large number of measurements for the parameter fitting. The parameters of these criteria should be restricted for a reliable application. A possible alternative could be sectorial-related applications.

Multiaxial tests are usually intricate and not adapted to each other. In this chapter, some effective ways for material testing with the following comparison of the results are suggested. The most important multiaxial tests for hard foams are proposed and implemented. Based on these tests, recommendations for further improvements of the experiment setups are given. Open questions are listed.

At present, there exist more than 200 different criteria (Lebedev Development of the theories of strength in the mechanics of materials. Strength Mater 42(5):578-592, 2010, [1]; Pisarenko, Lebedev Deformation and Strength of Materials under Complex Stress State (in Russ.: Deformirovanie i prochnost’ materialov pri slozhnom naprjazhennom sostojanii). Naukowa Dumka, Kiev, 1976, [2]; Yu Unified strength theory and its applications. Springer, Berlin, 2004, [3]).This chapter describes selected criteria which are of the significance for the later chapters and for the systematization. These criteria are written in the same manner and generalized subsequently.

Bridgman’s observation that the hydrostatic pressure seems to have no effect on the yield behavior of metals (Bridgman in J Appl Phys 18(2):246–258, 1947 [1], Bridgman in Studies in large plastic flow and fracture with special emphasis on the effects of hydrostatic pressure. McGraw-Hill, New York, 1952 [2]) led engineers to develop a plasticity theory that subtracts the mean stress from the principal stresses (Wilson in J Appl Mech 69(1):63–68, 2002 [3]). The criteria are written in the invariants of the stress deviator ( 1.28) or ( 1.29) and hence are cylindrical or prismatic surfaces aligned along the hydrostatic axis in the principal stress space. They do not restrict the hydrostatic stresses. The equalities ( 5.2) and the equation \(\nu _+^\mathrm {in}=\nu _-^\mathrm {in}=\frac{1}{2}\) are valid.

This book discusses arbitrary multiaxial stress states using the concept of equivalent stress. It highlights the most useful criteria, which can be applied to various classes of isotropic materials. Due to its simplicity and clarity, this concept is now widely used in component design, and many strength and yield criteria based on the equivalent stress concept have been formulated. Choosing the appropriate criterion for a given material remains the main challenge in applications.
The most useful criteria can be applied best when the plausibility assumptions are known. Accordingly, the book introduces fitting methods based on mathematical, physical, and geometrical objective functions. It also features a wealth of examples that demonstrate the application of different approaches in modeling certain limit behaviors.

The new method of soft foundation treatment in continuous exploration, the introduction of lightweight materials to overcome the low bearing capacity of soft soil foundation is considered to have a good prospect. In this article, it is assumed that the lightweight material can be used as the vertical reinforcement in the form of short pile to form the composite foundation with the soft soil, and to bear the overlying load. Firstly, the material parameters of the lightweight pile under the working conditions were calculated by numerical analysis. According to the calculated parameters of the pile body, the feasible materials were selected, EPS (expanded polystyrene) was preferred for further study in materials that meet the parameters. Through centrifugal model test, settlement and stress state of lightweight material pile composite foundation were analyzed, its smooth settlement and ideal working condition shows a good treatment effect. The results of numerical analysis and centrifuge model test show that it is theoretically feasible to treat soft foundation with lightweight pile composite foundation.

Limited by the particle size requirements of testing apparatus, little true triaxial test (TTT) research on rockfill has been conducted. Using a large true triaxial apparatus (TTA) developed independently by the Changjiang River Scientific Research Institute (CRSRI), tests with different intermediate principal stress ratios {Ratio b[=(σ2−σ3)/(σ1−σ3)]} and plane strain tests were carried out on sandstone rockfill. The results show that, with the same Ratio b, the initial slope in stress-strain curves and peak stress increased with rising σ3; with low σ3, volumetric strain first contracted and then transitioned to dilatancy; with high σ3, it continued to contract throughout the deformation process. With stable σ3 but increasing Ratio b, softening and brittle failure after peak stress were obvious and the strain corresponding to peak stress slightly lagged behind the strain bending point in the ε1–εv curves, which reflected deformation and failure of the specimen force chain. The effect of Ratio b in increasing strength was significant, especially in the range 0–0.25, where strength showed significant growth. The Lade–Duncan failure criterion was more suited to revealing strength evolution than were other criteria, but both σ3 and Ratio b induced significant particle breakage. The actual tested strength was always lower than the estimated strength obtained by the Lade–Duncan failure criterion. Under plane strain, when deviatoric stress approached its peak value, Ratio b was around 0.17–0.19 in all tested specimens. The contribution of σ2 in increasing specimen strength was basically reflected. This means that, when test conditions are limited, the plane strain test can be used to make a rough estimate of the strength index of rockfill under complex three-directional stress.

Pavement foundations supported on expanded polystyrene (EPS) geofoam blocks are vulnerable to excessive deformation or even failure owing to truck passage during construction. To investigate this, a series of large-scale static plate load tests, accompanied by numerical analyses, were carried out to determine the effects of overlying soil thickness, EPS geofoam density, and the gap between EPS blocks. Furthermore, the effect of geocell reinforcement on the performance of such pavement systems was evaluated. Test results showed that as the soil thickness increased from 300 to 600 mm, the surface settlement of unreinforced pavement decreased by up to 65%. Low-density EPS geofoam can double or triple surface settlements or cause premature failure in a system. Additionally, reinforcing the overlying soil layer with geocell causes up to a 54% reduction in surface settlements. A series of verified numerical analyses demonstrated that as long as the pressure transferred to geofoam blocks remains below the compressive strength of EPS geofoam, the increase in pavement surface settlement is limited. Furthermore, increasing the gap between EPS geofoam blocks can increase the surface settlement of unreinforced pavements, while geocell reinforcement can help to moderate these settlements. The results of this study can be used to develop solutions to some of the limitations encountered during the construction of EPS geofoam embankments and under static loading conditions.

For analytical comparison of material properties, two dimensionless values d (compression to tension) and k (torsion to tension) are introduced (Sect. 2.1.3). Further values are needed to describe the properties of advanced materials. These values provide a simple way to characterize the limit surfaces too. Several restrictions on the fitting of the strength criteria are introduced on the basis of these values.

ABSTRACT: The paper reports the results of six shaking table tests using reduced-scale model
walls constructed with expanded polystyrene (EPS) panels to reduce dynamic earth loads due to
base shaking. The results are compared with a nominal identical rigid (control) wall constructed
without a seismic buffer. The test results show that dynamic load attenuation increased with
decreasing geofoam stiffness. The test with the highest buffer stiffness resulted in a 15% reduction
in dynamic load and the test with lowest stiffness resulted in a 40% reduction in dynamic load
compared with the control wall. The results of these experiments provide proof of the concept that
EPS panels placed against rigid walls can act as seismic buffers to attenuate dynamic loads due to
ground shaking (e.g. earthquake). Additional quantitative data related to load–deformation–time
response, back-calculated elastic modulus values for the EPS seismic buffer configurations, dynamic
interface shear properties, acceleration amplification in the backfill soil and post-excitation stress
relaxation-creep behaviour are also reported.

The occurrence of failure, mechanisms that create failure, and soil behavior in the vicinity of failure have been investigated. One mechanism is smooth peak failure, in which the soil continues to behave as a continuum with uniform strains, and smooth peak failure is followed by strain softening. Another mechanism is shear banding, whose occurrence in the plastic hardening regime limits the strength of the soil. True triaxial tests have been performed on tall prismatic specimens of Santa Monica Beach sand at three relative densities in a modified version of a cubical triaxial apparatus to study the effect of shear banding on failure in the full range of the intermediate principal stress. The experiments show that the strength increases as b [=(sigma (2) - sigma (3))/(sigma (1) - sigma (3))] increases from 0 to about 0.18, remains almost constant until b reaches 0.85, and then decreases slightly at b = 1.0. Shear banding initiates in the hardening regime for b-values of 0.18-0.85. Thus, peak failure is caused by shear banding in this middle range of b-values, and a smooth, continuous 3D failure surface is therefore not generally obtained for soils.

An innovative construction material, expanded polystyrene blocks (EPS blocks), has been introduced in geotechnical engineering in recent years. Because of its extremely light weight and ease in handling, it provides an alternative to conventional backfill, embankment earth materials, and lightweight fill. It is anticipated that the use of EPS blocks in the construction industry may result in substantial cost savings. New applications of EPS blocks as structural elements are expected to emerge as engineers learn more about this material. A series of laboratory tests were conducted to determine the mechanical properties of EPS blocks. Included are the results of undrained triaxial tests with volume change measurements for the determination of a constitutive relationship, a repeated loading test, punching shear tests, and a long-term creep test. The test results show several distinctive material characteristics, including a bilinear stress-strain relationship and negative Poisson's ratio that are not common in conventional construction materials. The results of this study can readily be incorporated in detailed analyses of various geotechnical engineering structures constructed with EPS blocks.

In recent years, EPS (Expanded Polystyrene) geofoam is gaining worldwide recognition in the construction industry either as lightweight substitution or as compressible inclusion, in reducing the earth pressures against retaining structures. When EPS geofoam is used behind a structure, the structure interacts with the soil via the EPS blocks giving birth to a hybrid interactive system. In this paper, a numerical model is described for the analysis of such a soil-geofoam-structure interaction system. The development of the model focused mainly on the material constitutive law and the interface modeling. Recognizing the fact that there is always a thin layer of interface that participates in the interaction process, a hybrid type interface model was developed. The interface was assumed to be elasto-plastic in its behavior. A constitutive law of geofoam was formulated using an elasto-plastic hardening law. The soil backfill was modeled assuming it as the elasto-plastic hardening and softening material. The developed model was validated through a numerical experiment on a rigid retaining structure. The model offers an improved performance of the normal and shear deformation at the interfaces, which in turn results in a better prediction of the reduced pressure on a retaining structure.

A simple, practical procedure for representing the nonlinear, stress-dependent, inelastic stress-strain behavior of soils was developed. The relationship described was developed in such a way that the value of the required parameters may be derived from the results of standard laboratory triaxial tests. Comparisons of calculated and measured strains in specimens of dense and loose silica sand showed that the relationship was capable of accurately representing the behavior of sand under triaxial loading conditions.

Over the past 30 years, design with geofoam has been based on either factored strength or limit strain approaches. Geofoam parameters for design have been derived from unconfined compression testing of small laboratory samples. Closer examination of performance observations indicate extrapolation of small sample laboratory results can lead to misleading interpretation of field results. The potential for creep deformations is exaggerated and design modulus values are underestimated when based on small sample laboratory tests. Possible reasons for these shortcomings, in reference to field observations, are examined on the basis of creep tests on small samples, uniaxial loading of large samples, compression tests using tactile pressure sensors and review of enlarged images of geofoam surfaces. Creep deformations in geofoams under uniaxial loading remain mainly in primary stages where strain rates continually decrease. Modulus values for design that are derived from small sample laboratory tests are about half of the values that were estimated from field observations. Accordingly, the suggestion is made to increase small sample based modulus values from laboratory tests for design applications.

This paper summarizes the state of knowledge for using expanded polystyrene (EPS) geofoam where the primary geosynthetic function provided by the geofoam is compressible inclusion. In general, a compressible inclusion is any material that compresses readily under an applied stress or displacement compared to other materials in contact with, or in the vicinity of, the compressible inclusion. Geotechnical applications for a compressible inclusion include behind earth-retaining structures; around formation elements;; and above pipes, culverts, and tunnels. Using a compressible inclusion can result in significant reduction of earth pressures under static and dynamic loading. A compressible inclusion can also be used to accommodate ground or structure movement. Using a compressible inclusion can be cost-effective for both new construction as well as rehabilitating or upgrading existing structures. Numerous examples are used to illustrate these applications. Because of the inherent multi-functional nature of EPS, there can be additional benefits such as thermal insulation and concomitant cost-savings when EPS geofoam is used as a compressible inclusion.

Both small- and large-strain applications of expanded polystyrene (EPS) geofoam involve interactions with the surrounding geologic materials. The stress–deformation response of this material, however, differs significantly from those of the adjoining geologic materials. A well-justified constitutive law for EPS is, thus, a prerequisite for reliable solutions for soil-structure interaction problems where such material is used. This paper describes a stress–strain law for EPS geofoam for its large-strain applications based on the incremental theory of plasticity. In the derivation of the constitutive relationship, the geofoam was taken as a von Mises material, and it was assumed that the hardening regime follows a hyperbolic curve. The material parameters of the constitutive model were determined from a series of unconfined compression tests performed on EPS specimens of various sizes, shapes and densities. These parameters are functions of the absolute dimensions of the tested specimens as well as the density of EPS. The validity of the model was confirmed by numerical simulations on the compression testing program of EPS geofoam.

A case history is presented describing the use of expanded polystyrene (EPS) geofoam blocks to treat an unstable roadway embankment slope involving clayey soils. The selection of the geofoam treatment was based upon its ability to be constructed and have the least impact on both the environment and adjacent homeowners. The site subsurface conditions, engineering properties of EPS, design analysis, and construction phases are reviewed. Potential traffic safety problems associated with differential icing of roadways caused by the presence of geofoam blocks beneath the pavements were minimized by using a thicker subbase layer in the geofoam-treated area. Data from an instrumentation program consisting of an inclinometer, extensometers, and thermistors are presented. Pavement temperature readings collected from areas with and without geofoam treatment are compared to investigate potential differential icing on the roadway.

Triaxial tests were conducted to develop a constitutive model of cellular type expanded polystyrene (EPS) geofoam block under short-term (immediate) loading. Specimens of EPS geofoam with densities of 15, 20, 25, and 30kg/m3 were tested under confining stresses of 0, 20, 40, and 60kPa.Test results show that EPS geofoam displays nonlinear major principal stress–strain behavior, which is a function of confining stress and density, and a higher maximum compressive strength with increased density and confining stress. The EPS geofoam exhibits directional deformation along the axis of major principal strain with no dilative shearing, and the generated axial and volumetric strains produce a linear correlation that is a function of density and confining stress.From the test results, a new hyperbolic model simulating the stress–strain behavior of EPS geofoam is proposed. This model includes the major principal stress and strain as well as density and confining stress. Strain-dependent tangent modulus and Poisson’s ratio influenced by the confining stress and density of the EPS geofoam are derived from the model. The model shows the elastic tangent modulus and Poisson’s ratio increase with density and decrease with confining stress. Compared to previous models, the proposed hyperbolic model is shown to give best fit to the measured test data.

A suction-controlled true triaxial apparatus for unsaturated soil was developed from the existing true triaxial apparatus for sand by attaching a device to supply matric suction to specimens. Using the developed apparatus, true triaxial tests (σ1 σ2 σ3; where σ1, σ2, and σ3 are the three different principal stresses) on an unsaturated silty soil were carried out under constant suction using the negative pore-water pressure method (s = uw > 0; ua = 0) for applying the matric suction, s (s = ua uw; where ua is the pore-air pressure and uw is the pore-water pressure). It was found that the true triaxial test results under three different principal stresses are uniquely arranged on the "extended spatially mobilized plane (extended SMP)" for frictional and cohesive materials that is modified from the original SMP for frictional materials by introducing "a bonding stress, σ0 (= c·cot, where c is cohesion and is the internal friction angle)." It was also found that the shear strengths of the unsaturated silty clay obtained by the true triaxial apparatus nearly agree with the extended SMP failure criterion (Î1Î2/Î3 = constant, where Î1, Î2, and Î3 are the first, second, and third invariants of the translated stress tensor). The measured stress-strain-strength behaviour of the unsaturated soil in three-dimensional (3D) stresses can be well simulated by an elastoplastic model with the transformed stress based on the extended SMP criterion and a special hardening parameter.Key words: failure criterion, shear strength, special shear test, suction, stress path, unsaturated soil.

A closed-form solution of deep tunnel subject to an internal pressure and to an axisymmetrical time-dependent temperature field is presented. The material is supposed to have a thermal-softening behavior, the cohesion decreasing with the temperature. The thermal expansion generates plastic zones with face flow and corner flow, which can coexist and interact. The explicit character of the solution allows rigorous demonstrations of the evolution of such plastic zones, as well as other interesting and fundamental properties of the thermoplastic behavior of deep tunnels. On the other hand, the causal relationship between the thermomechanical loading and the structural response (convergence, extension of rupture zones) is rendered transparent, thanks to the simplicity of the analytical solution. The consequence of thermal-softening is clearly shown by comparison with the analytical solution for a constant cohesion previously established. Quantitatively, its importance is illustrated by a restricted parametric study, to which the analytical solution is ideally suited.

Expanded polystyrene (EPS) geofoam is increasingly being used as a construction material of choice in situations where its mechanical properties—such as its extremely low density, volume contraction under deviatoric compressive loading, and existence of post-yielding strain hardening—can be exploited. In this paper, a simple elastoplastic hardening constitutive model of EPS geofoam is formulated to model the mechanistic behaviour of EPS geofoam taking into account the characteristic properties of EPS. The model is based on experimental results from a series of triaxial tests performed on EPS samples for confining pressure ranging from 0 to 60 kPa at room temperature (23 °C). Behaviour under higher temperatures is currently under investigation and will be addressed in a future publication. The model has a total of six independent parameters and can be calibrated from data obtained from triaxial tests. It is shown that the constitutive model is able to correctly replicate the characteristic behaviour of the EPS geofoam under shearing. The model is relatively simple to incorporate into numerical codes for geotechnical analysis.

A simple displacement-type block model is proposed to compute the compression–load–time response of an idealized seismic buffer placed against a rigid wall and used to attenuate earthquake-induced dynamic loads. The seismic buffer is modelled as a linear elastic material and the soil wedge shear surface by a stress-dependent linear spring. The model is shown to capture the trends observed in four physical reduced-scale model shaking table tests carried out with similar boundary conditions up to a base excitation level of about 0.7g. In most cases, quantitative predictions are in reasonable agreement with physical test results. The model is simple and provides a possible framework for the development of advanced models that can accommodate more complex constitutive laws for the component materials and a wider range of problem geometry.

A new true triaxial cell has been designed, fabricated, calibrated, and successfully tested. Its main feature is very high loading capability in all three orthogonal directions, enabling the testing to failure of hard crystalline rocks subjected to large least and intermediate principal stresses. All three principal stresses applied to rectangular prismatic specimens, 19×19×38 mm in size, are servo controlled. The cell was used to conduct an extensive series of tests in Westerly granite. A new true triaxial strength criterion for the rock was obtained that takes into account the effect of the intermediate principal stress. This turns out to be so significant that it raises serious questions about the suitability of criteria such as those named after Mohr, Coulomb, Griffith, and others. Measurements of strain in all three principal directions revealed that the onset of dilatancy relative to the major principal stress at failure rises substantially as the intermediate principal stress increases. The true triaxial tests also demonstrate that for the same least horizontal stress the main fracture dip angle in Westerly granite increases as a function of the intermediate principal stress, suggesting a strengthening effect. Limited thin section and SEM study shows that microcrack propagation, crack localization, and main fracture characteristics are basically similar to those observed in common triaxial tests.

Use of expanded polystyrene (EPS) in flexible pavements on poor subgrades

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Problè mes de me´caniqueme´canique associe´sassocie´s au stockage souterrain

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- R Aaboe

Aaboe, R., 1987. 13 years of experience with expanded polystyrene as a
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Behaviour of EPS geofoam in model test on pavements

- Y Zou
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Zou, Y., Small, J.C., Leo, C.J., 2000. Behaviour of EPS geofoam in model
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A47 Great Yarmouth Western Bypass: performance during the first three years

- D Williams
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Williams, D., Snowdon, R.A., 1990. A47 Great Yarmouth Western
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Mechanical properties of expended polystyrene for applications in road embankment

- J P Magnan
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Magnan, J.P., Serratree, J.F., 1989. Mechanical properties of expended
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Design assessment of the founders/meadows GRS abutment structure

- N M Abu-Hejleh
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- V Elias
- J Watcharamonthein

Abu-Hejleh, N.M., Zornberg, J.G., Elias, V., Watcharamonthein, J., 2003.
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Expanded polystyrene-the light solution

- T E Frydenlund
- R Aaboe

Frydenlund, T.E., Aaboe, R., 1996. Expanded polystyrene-the light
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Proble`mes de me´canique associe´s au stockage souterrain

- P Berest

Berest, P., 1989. Proble`mes de me´canique associe´s au stockage souterrain.
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3D material model for EPS response simulation

- A E Swart
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Building on EPS Geofoam in the 'low-lands' experiences in The Netherlands

- T Van Dorp

van Dorp, T., 1996. Building on EPS Geofoam in the 'low-lands'
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Design parameters for EPS geofoam (invited state of the art paper)

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Temporary overpass bridge founded on expanded polystyrene

- H Skuggedal
- R Aaboe