Seyed Naser Moghaddas Tafreshi

• PhD
• Professor at K. N. Toosi Toosi University of Technology

This paper presents a novel experimental investigation for improving the bearing pressure resistance of medium-dense sand deposits. Model footing tests were performed on similarly prepared sand beds to examine the effects of incorporating one, two and three separate geogrid-reinforced thin densified gravel layers at various depths within the beds....

This paper presents an experimental investigation examining the novel idea of employing curved expanded-Polystyrene (EPS) blocks that arch around the upper section of buried flexible pipes to reduce the pressures acting on them and hence resulting deformation/deflections. Large-scale testing was performed to examine key performance indicators for r...

Huge stockpiles of End-of-Life Tires (ELTs) are of major global concern. This paper investigates and helps to demonstrate the beneficial utilization of ELTs to provide geotechnical seismic isolation (GSI) of machine foundations located on a rubber-soil mixture (RSM). A series of laboratory tests is conducted to extend the understanding of RSM behav...

The response of soil beds reinforced with multi-layer geocell systems that support machine foundations is investigated by laboratory testing that incorporates vertical machine vibrations of a square concrete foundation (400 × 400 mm) resting on soil that is unreinforced or reinforced with single-, double- or triple geocell layers. The tests are per...

The fundamental aim in the proper design of machine foundations is to limit the response amplitude by preventing resonance in all vibration modes. The effects of static and dynamic forces and embedment depths for foundation-induced vertical vibration have been examined, experimentally and analytically using the Cone model. Therefore, various vibrat...

This paper reports on a series of static and cyclic plate loading tests performed on a weak unreinforced sand bed in a test pit. The weak sand was covered by a 160 mm thick layer comprised of one of three compacted soil types which was either unreinforced or geocell-reinforced. The purpose was to investigate the effects of soil density and grain si...

Protecting sensitive and/or valuable facilities is of concern when placing them near a machine foundation. There are methods available and well-studied such as wave barriers to reduce transmitted vibration and noises in the vicinity of a vibration source. Wave barriers are feasible to protect objects that are far enough from the vibration sources b...

Expanded polystyrene (EPS) geofoam is commonly used as lightweight fill materials in wide range of geotechnical engineering applications including protection of buried utilities and pipelines. EPS blocks are usually placed next to buried pipelines to reduce the overburden and traffic-induced pressure on them. In this paper, a new configuration of E...

This study proposes reusing post-consumer soil-filled PET (polyethylene terephthalate) bottles as a novel soil reinforcing element by conducting a laboratory-scale experimental investigation. The concept is that the polymer bottle walls act to confine the interior soil so that the bed behaves somewhat like a brick-built load spreading zone. The soi...

In this study, the efficiency of employing rubber sheets to modify the dynamic response of a concrete machine foundation model of size 400 × 400 mm is explored by conducting a series of steady-state vertical vibration tests. Rubber is a low-cost energy dissipater material having high resistance to erosion which can be used in a form of sheets and s...

The recent increase in the use of Expanded Polystyrene (EPS) geofoam in construction and geotechnical projects has driven researchers to investigate its behavior, more deeply. In this paper, a series of experimental tests to investigate the stress-strain behavior and the mechanical properties of EPS blocks, under monotonic axial loading are present...

This chapter introduces expanded polystyrene (EPS) geofoam as a relatively new material for civil engineering applications. EPS geofoam is significantly lighter that common civil engineering materials (for example, 1%–2% of soil density) and it is available in a wide range of compressive strengths. Therefore it is a suitable material for a large va...

This paper reports full scale experiments, under simulated heavy traffic, of geocell and EPS (expanded polystyrene) geofoam block inclusions to mitigate the pressure on, and deformation of, shallow buried, high density polyethylene (HDPE) flexible pipes while limiting surface settlement of the backfilled trench. Geocell of two pocket sizes and EPS...

With growing populations and continuing urban development, embedding pipes in the ground that are then overrun by traffic is inevitable. This paper describes full-scale prototype tests on high-density polyethylene (HDPE) flexible pipes (of 250 mm diameter), buried at shallow depth, under simulated traffic loading. The paper studies the effect of su...

Expanded polystyrene (EPS) geofoam is often used in below ground applications in geotechnical engineering. A most recent configuration system implemented in roadways to protect lifelines such as buried pipes, electrical cables and culvert systems could be consisted of two EPS geofoam blocks, "posts" placed on each side of the structure, an EPS bloc...

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....

The suitability of geocell reinforcement in reducing rut depth, surface settlements and/or pavement cracks during service life of the pavements supported on expanded polystyrene (EPS) geofoam blocks is studied using a series of large-scale cyclic plate load tests plus a number of simplified numerical simulations. It was found that the improvement d...

Existing studies confirmed that the response of geocell-reinforced beds is directly affected by contributory factors, including soil's grains, geocell's characteristics, and surface loading geometries. In this paper, a series of plate load tests has been carried out for the further understanding of the behaviour of geocell-reinforced soil. Four dif...

Expanded polystyrene (EPS) is a lightweight material commonly used in sensitive geotechnical applications, particularly in transportation applications that often see a confluence of buried utilities and traffic loading. This study investigates the behavior and efficacy of EPS geofoam post-beam (PB) systems as a means of protecting underground utili...

Plate anchors are commonly used to resist static, cyclic, and monotonic post-cyclic uplift loads. Under cyclic loading, progressive sudden failure may occur, characterized by accumulated displacement — even under loads significantly less than the static capacity. Despite extensive usage of geocell materials for increasing cyclic resilience, the inf...

EPS Geofoam is an appropriate material for reducing dead loads of road embankments and hence, mitigating settlements of pavements constructed over poor ground conditions. It has been used successfully in many projects since its appearance in 1960’s, yet, there are still pitfalls regarding its application and design, requiring deeper investigations....

This study introduces a mechanism for initial assessment and future development to improve understanding of expanded polystyrene (EPS) behavior as a super-lightweight material for road construction. Large scale cyclic plate load tests on model pavements were performed. The effect of several factors including thickness of soil, thickness of subseque...

Plate anchors are frequently used to provide resistance against uplift forces. This paper describes the reinforcing effects of a geocell-reinforced soil layer on uplift behavior of anchor plates. The uplift tests were conducted in a test pit at near full-scale on anchor plates with widths between 150 and 300 mm with embedment depths of 1.5–3 times...

Use of geosynthetic reinforcement may improve the performance of many geotechnical systems, including anchors. In this study, the uplift capacity of geocell-reinforced sand is studied based on a series of near largescale experiments and calibrated three-dimensional Finite Element (FE) models. Using the verified FE models, a comprehensive parametri...

With increase in cities' population and development of urbane life, passing buried pipelines near ground's surface is inevitable in urban areas, roads, subways and highways. This paper presents the results of three-dimensional full scale model tests on high-density polyethylene (HDPE) pipe with diameter of 250 mm in geocell reinforced soil, subject...

This paper describes the results of laboratory tests conducted on flexible PVC pipes with diameter of 160 mm, buried in unreinforced and reinforced trench with geogrid layer and expanded polystyrene (EPS) geofoam block. The repeated load with amplitude of 450 kPa and frequency of 0.33 Hz was applied on the trench surface, using plate loading at a d...

This paper presents a set of results of plate load tests that imposed incremental cyclic loading to a sandy soil bed containing multiple layers of granulated rubber-soil mixture (RSM) at large model scale. Loading and unloading cycles were applied with amplitudes incrementally increasing from 140 to 700 kPa in five steps. A thickness of the RSM lay...

This paper presents a numerical study for investigating the effectiveness of geocell reinforcement in reducing pressure and settlement over EPS geofoam blocks in road embankments. A 3-D FEM model of soil and geofoam was created in ABAQUS, and geocell was also modeled realistically using membrane elements. The accuracy of the model was tested by com...

This paper describes the beneficial effects of multiple layers of rubber–sand mixture (RSM). The plate load tests, using circular plate of 300 mm diameter, were performed at an outdoor test pit, dug in natural ground with dimensions of 2000 × 2000 mm in plan and 720 mm in depth to facilitate realistic test conditions. The rubber used in the RSM lay...

In order to investigate the effect of embedment depth on settlement of footing supported by geocell-reinforced bed, a series of cyclic plate loading at a diameter of 300 mm supported by layers of geocell in a test pit of 2000*2000 mm in plane and 700 mm in depth, were performed. The results show that installation of the geocell layers in the founda...

This paper describes a series of reduced scale tests, at unit gravity, performed on circular footings supported by reinforced sand. Reinforcement by multiple layers of geocell was investigated and performance of the footing was compared to one on the same sandy soil containing multi-layered planar geotextile reinforcement. The comparison used geoce...

This paper describes the effect of embedment depth on bearing capacity of footing supported by geocell-reinforced bed, using plate load test at a diameter of 300mm. The embedment depth ratio of the footing was varied from zero to 0.75. The plate load tests were performed in an outdoor test pit dug in natural ground measuring 2000 x 2000mm in plan a...

This paper describes a series of cyclic plate load tests on a circular plate with diameter of 300mm, supported on unreinforced and reinforced beds by one and two layers of geocell. The results show that, as the number of geocell layers increases, the loading surface settlement decreases due, in part, to better load spreading. The optimum depth of t...

In this paper, a series of repeated load tests were carried out on a 150 mm diameter plate simulative of vehicle passes, to demonstrate the benefits of soil-rubber shred mixture in decreasing the soil surface settlement of road embankment. The results show that the efficiency of rubber reinforcement is significantly a function of the rubber content...

Comprehensive results from cyclic plate loading at a diameter of 300 mm supported by layers of geocell are presented. The plate load tests were performed in a test pit measuring 2000 × 2000 mm in plane and 700 mm in depth. To simulate half and full traffic loadings, fifteen loading and unloading cycles were applied to the loading plate with amplitu...

In this paper, a series of repeated load tests were carried out on a 150 mm diameter plate simulative of vehicle passes, to demonstrate the benefits of soil-rubber shred mixture in decreasing the soil surface settlement of road embankment. The results show that the efficiency of rubber reinforcement is significantly a function of the rubber content...

A numerical simulation of laboratory model tests was carried out to develop an understanding of the behaviour of pipes in a trench prepared with 3-Dimensional reinforced (namely geocell-reinforced in the present study) sand and rubber-soil mixtures, under repeated loadings. The study reports overall performance of buried pipes in different conditio...

Multiple layers of geosynthetic reinforcement, placed below foundations or in the supporting layers of road pavements, can improve section performance through several mechanisms, leading to reduction in stresses and deformations. This paper aims to present a new analytical solution, based on the theory of multi-layered soil system to estimate the p...

Piles are frequently used to transfer the heavy compressive loads to strong soil layers located in the depth of bed. In addition, such piles may be subjected to combination of repeated compressive and tensile loads due to earthquake, wind, etc. This paper describes a series of laboratory model tests, at unit gravity, performed on belled pile, embed...

This paper presents a simple solution based on the limit equilibrium of sliding soil wedge of reinforced backfill subjected to the horizontal acceleration in the framework of the pseudo-static method. In particular, contrary to most studies on the reinforced retaining wall, the solution proposed in this study, takes into account the effect of the u...

Sandy soil/aggregate, such as might be required in a pavement foundation over a soft area, was treated by the addition of one or more geocell layers and granulated rubber. It was then subjected to cyclic loading by a 300 mm diameter plate simulative of vehicle passes. After an initial study (that established both the optimum depth of the uppermost...

Service trench provision and maintenance of buried pipes represent major cost items in the utilities industry. The main purpose of the paper is to investigate the behavior of geocell with different opening areas and heights, above the buried pipes under repeated loads. Soil surface settlement, vertical diametric strain of the pipe (as an indication...

The results of plate load tests on a circular footing with diameter of 300 mm, supported on unreinforc ed and multi-layered geocell-reinforced beds are presented. The influences of various parameters are studied including embedded depth of the first layer of geocell, vertical spacing of geocell layers and number of geocell layers below the footing...

This paper describes the reinforcing effects of multiple layers of geocell in combination with rubber-soil mixture layers in sand, and compares their behaviour with that of the multilayered geocell reinforcement alone, using plate loading at a diameter of 300 mm. The plate load tests were performed in an outdoor test pit, dug in natural ground meas...

This paper describes laboratory tests on footing constructed on unreinforced and geogrid-reinforced sand with circular a void subjected to a combination of static and repeated loads. The settlement of the footing was measured for up to 5000 cycles of loading and unloading. The variables examined in the testing program include the number of geogrid...

Heavy traffic loading can produce loss of functionality in pipeline networks, with consequential interference with economic and social impacts in the areas involved in breakage. The consequences of breakage or disconnection of pipelines are technical, economic and social. In the case of a sewer network failure, illness and epidemics might result. I...

In geotechnical engineering, recycled tires are used in lightweight fills, backfill materials, highway embankments, soil reinforcement, and soil-retaining walls. The rubber-soil mixture can exhibit a greater capacity for energy absorbency than soil alone under cyclic loading and tends to decrease the stress and shocks transferred into the ground. T...

Service trench provision and maintenance of buried pipes represent major cost items in the utilities industry. Using recycled material in order to optimize the design of the buried pipe system can lead to significant cost reductions, but only if performance is not degraded. The main purpose of the paper is to investigate the mitigation of strain in...

Footings are frequently subjected to combination of permanently downward loads (weight of the structures) and upward loads (e.g. earthquake, wind tension cables for suspension bridges, marine structures such as floating platforms and tension leg platforms) which may result in pullout forces much greater than the weight of the structure itself. Henc...

This paper describes a series of laboratory model tests on strip footings supported on unreinforced and geogrid-reinforced sand with an inside void. The footing is subjected to a combination of static and cyclic loading. The influence of various parameters including the embedment depth of the void, the number of reinforcement layers, and the amplit...

Reinforced soil wall designed and constructed based on numerous methods for the stability of retaining walls, slops, and embankments have been performed. This paper describes a new simplified pseudo-dynamic method for evaluating the behaviour of reinforced retaining wall under horizontal and vertical seismic accelerations. Stability analyses are co...

Underground voids located in the failure zone of a structure's footing decrease the bearing capacity and increase the settlement of the footing. This paper presents results from laboratory-model tests of strip footings supported by reinforced sand beds above a continuous void to investigate the potential benefits of using a replaced reinforced sand...

Soil reinforcement with randomly-distributed rubber has been used as another type of soil reinforcement over past years. In this paper a series of laboratory, pilot scale tests were performed by placing a square plate of 10 cm in width on the soil bed to evaluate the using of waste rubber as reinforcement to decrease the soil surface settlement und...

This paper describes a laboratory model test carried out on high-density polyethylene (HDPE), small diameter pipes buried in trenches, which subjected to repeated loadings to simulate the vehicle loads. Deformation of the pipe was recorded at eight points on the circumference of the tested pipes to measure the radial deformations and detect cross-s...

This paper describes a series of laboratory model tests performed on strip footings supported on 3D and planar geotextile-reinforced sand beds under a combination of static and repeated loads. Footing settlement due to initial static applied load and up to 20,000 subsequent load repetitions was recorded, until its value becomes stable or failure oc...

This paper describes laboratory tests results on the strip footing supported on the geocell reinforced sand bed under monotonic load. The various parameters studied in this testing program include the reinforcement width (2.1, 3.2 and 4.2 times of footing width) and height of the reinforcement (0.33, 0.66, 1 and 1.33 times of footing width) below t...

In this paper, nonlinear pile-soil-structure interaction under dynamic loads is formulated by using free-field soil analysis and beam on Winkler foundation. The free-field motions are calculated separately through a site response analysis using DYFRA program which was developed by the author to prepare the data in the form of displacement time hist...

Comprehensive results from laboratory model tests on strip footings supported on the geocell and planar reinforced sand beds with the same characteristics of geotextile are presented. The various parameters studied in this testing program include the reinforcement width, the number of planar layers of geotextile and height of the geocell below the...

An appropriate estimation of buried pipe deformation is a major concern to designers in geotechnical, construction and civil engineering and traditional methods are unable to estimate this phenomenon accurately. Numerical methods may be powerful tools to cope with the complexity of this fact. This paper develops a fuzzy set based method for the ana...

This paper presents the numerical analysis of seismic soil-pile-superstructure interaction in soft clay using free-field soil analysis and beam on Winkler foundation approach. This model is developed to compute the nonlinear response of single piles under seismic loads, based on one-dimensional finite element formulation. The parameters of the prop...

The coefficient of elastic uniform compression of soil (C u) is the most important parameter to be determined in designing a machine foundation. This paper presents the results of cyclic-footing-load tests from the laboratory-model tests on square footings supported by a sand bed. The various intensity of cyclic load (loading, unloading and reloadi...

This paper presents a feed forward back-propagation neural network model to estimate the vertical deformation of high-density polyethylene (HDPE) small diameter flexible pipes buried in reinforced trenches and settlement of soil surface (SSS) subjected to repeated loadings to simulate the heavy vehicle loads. The experimental data show that the ver...

This paper describes laboratory tests on small-diameter high-density polyethylene (HDPE) pipes buried in reinforced sand subjected to repeated loads to simulate the vehicle loads. The amplitude of applied stress was 5.5kg/cm2 in all tests. Deformation of the pipe was recorded at eight points on the circumference of the tested pipes to measure the r...