Sadok Benmebarek

• Pr
• Université de Biskra

In this paper, the effects of prestressing geosynthetic reinforcement on settlement reduction in embankments overlying locally weak zones are investigated through numerical analyses using the PLAXIS finite element code. The selected case study focuses on the reinforcement of a road embankment spanning approximately 11 km across soft sabkha soils in...

We often face heterogeneous foundation soils in geotechnics, which significantly influence shallow foundations' shape coefficients and bearing capacity factors. The evaluation of these factors introduces significant uncertainties in the thickness of the upper layer is comparable to the width of the rigid footing placed on the soil surface. This amb...

Geosynthetic Reinforced Soil (GRS) walls have become increasingly popular as a result of their numerous advantages. In some cases these structures are constructed in a multi-tiered configuration, which makes their behavior more complicated. Nevertheless, the response of the multi-tiered walls is insufficiently explained by the existing design manua...

Passive earth pressure behind retaining walls under rotational movements has been widely investigated recently. However, the behavior of surcharge loading under rotational movement has not been fully explored in the literature. This paper numerically investigates the impact of different types of wall movement; translation, rotation about the top an...

The bearing capacity of axially loaded embedded foundations has been widely studied using analytical and numerical methods. However, there are many discrepancies in the literature results regarding the bearing capacity factors and depth factors of circular embedded footings proposed by different authors. Terzaghi's hypothesis has been used to asses...

The use of recycled tire shreds as a compressible inclusion behind cantilever retaining wall is an effective method to reduce the seismic earth pressures acting on the wall. A two-dimensional finite element analysis based on PLAXIS 2D was developed to analyze the response of a typical cantilever retaining wall, consisting of compressible tire shred...

In this paper, numerical computations using FLAC code (Fast Lagrangian Analyses of Continua) are carried out to evaluate the passive earth pressure magnitude and distribution against a retaining wall subjected to different wall movement modes: translation (T) mode, rotation about bottom (RB) mode and rotation about top (RT) mode. In agreement with...

Retaining walls in axi-symmetric conditions and in plane strains have been widely treated in the literature using different approaches (limit equilibrium, limit analysis, slip line, and numerical techniques by finite elements or finite differences). The finite element or finite difference method provides more accurate solutions to the problem than...

A two-dimensional finite-element analysis based on PLAXIS 2D was used to study the behavior of connected and unconnected back-to-back mechanically stabilized earth walls under earthquake loading. The numerical model was first validated with the results from the full-scale dynamic centrifuge tests on reinforced soil-retaining walls. The behavior of...

Construction of long tunnels in difficult sites is associated with various risks. Such risks are usually resulted on one hand from the lack of geological and geotechnical studies of the surrounding ground, and on the other hand from the inappropriate support system. On January 1, 2014, the left tube of T1 tunnel located in Constantine (Algeria) col...

Geotechnical engineers often deal with layered foundation soils. In this case, the soil bearing capacity assessment using the conventional bearing capacity theory based on the upper layer properties introduces significant inaccuracies if the top layer thickness is comparable to the rigid footing width placed on the soil surface. Under undrained con...

Raft and pile foundations are combined with the twofold aim of increasing the overall bearing capacity and reduce the average/differential settlements. This results in a complex system and gives rise to significant soil–structure interaction mechanisms. In the last years, both bearing capacity and settlements of piled raft have been usually expecte...

Purpose This paper aims to investigate the pile group efficiency based on the load-settlement response in soft clay conditions, considering several pile configurations using a variable number of piles and pile spacing. The overall objective of the present paper is to provide further insight into the mechanical response of the pile group and aim at...

With the existence of a high groundwater level, the head difference between the inside and outside of an excavation may lead to the loss of stability of the excavation’s surface. Hence, a fundamental understanding of this occurrence is important for the design and construction of water-retaining structures. In some cases, the failure mechanism cann...

The paper presents 3D numerical simulations that investigate the settlement performance for small groups of stone columns under a rigid circular footing. Particular consideration is given to the effects of stone column installation and load level on the optimum length of the stone columns. The results show that taking into account the installation...

This paper presents a three-dimensional numerical analysis using PLAXIS 3D software of geosynthetic-reinforced embankment over locally weak zones (LWZ). The case study considered here is the construction of road embankment reinforced by geosynthetics on soft sabkha soil of Chott El Hodna in Algeria. The construction site of this project presents a...

In this paper, numerical computations using the FLAC code are carried out to investigate of the behavior the bearing capacity of strip footings embedded in sandy soil and under large eccentric vertical load conditions. The study focuses on an evaluation of the non-dimensional reduction factor (RF), which is the ratio between the average bearing cap...

A quadrilateral and a triangular element based on the strain approach are developed for static, free vibration and buckling analyses of Reissner–Mindlin plates. The four-node triangular element SBTP4 has the three essential external degrees of freedom at each of the three corner nodes and at a mid-side node; whereas the quadrilateral element SBQP h...

This paper describes the results of numerical analysis studying the influence of stone column installation on the pressure capacity of reinforced raft with an infinite grid of stone columns. In the first part of this paper, cylindrical cavity expansion was used to evaluate the installation effects of stone column. A numerical model was created with...

This paper presents the results of parametric studies conducted using the explicit finite differences FLAC 2D code (Fast Lagrangian Analyses of continua), to explore the influence of the shape and depth of the liquefiable layer of the soil as well as the significant duration of seismic load on the collapse mechanism of earth dam. The soil behaviour...

La présente communication s’intéresse à l’évaluation des réponses dynamiques de barrages en terre et plus particulièrement des mécanismes de rupture induits par le phénomène de liquéfaction des sols. Des analyses dynamiques non linéaires couplées (MHD), utilisant Flac 2D, un logiciel commercial basé sur la méthode des différences finies (MDF), ont...

In this paper, numerical computations using FLAC code are carried out to investigate the effect of new construction technique combining substitution and reinforcement on the load-settlement of a strip footing on reinforced sand bed. The purpose is to examine numerically the improvement effect of using full wraparound ends of geosynthetic reinforcem...

In this study, a series of nonlinear 2D finite difference analyses were carried out to study the seismic behavior of non-yielding gravity-type earth retaining walls founded in rock site subjected to “Real Near-Fault ground motions”. Numerical analyses were performed by two dimensional explicit FLAC2D finite difference code. Various sets of real dat...

In this paper, numerical analyses using Plaxis 2D code in axisymmetric model are carried out to evaluate the influence of stone column installation effects on the loading–settlement performance of circular footing supported by a small group of columns. First, the column installation inducing lateral expansion is modelled using large displacements a...

In this work, the formulation of a new triangular finite element is presented for static and free vibration of plate bending. The developed element which contains the three essential external degrees of freedom at each of the three corner nodes is based on the Reissner/Mindlin theory and the strain-based approach. This element is based on the linea...

Back-to-back mechanically stabilized earth walls (BBMSEW) are encountered in bridge approaches, ramp ways, rockfall protection systems, earthen dams, levees and noise barriers. However, available literature studies and design guidelines for BBMSEW are limited and not supported by the numerical modeling when back-to-back walls perform interaction. U...

The undrained vertical bearing capacity of embedded foundation has been extensively studied using analytical and numerical methods. Through comparing the results of a circular embedded foundation in the literature, a significant difference between the bearing capacity factors and depth factors is observed. Based on the previous researchfindings, nu...

In this paper, numerical computations using FLAC code are carried out to develop a new practical reinforcement technique using geosynthetic reinforcement to increase the load bearing capacity of shallow foundations on a sand soil. In all previous works, the method of reinforcing soil with layers of individual reinforcements placed horizontally with...

Mechanically Stabilized Earth Walls (MSEW) are cost-effective soil-retaining structures that can tolerate much larger settlements than reinforced concrete walls. Geosynthetic reinforcement has been used successfully in MSEW, and has several advantages compared to other retaining structures. Several MSEW with simple geometries have been built throug...

In this paper, numerical computations using FLAC code are carried out to evaluate the effects of both the ratio of internal radius to external radius ‘ri/ro’ of the ring footing and the embedment ratios up to unity on the undrained bearing capacity factor ‘(Formula presented.)’ for different roughness conditions. It is observed that for both smooth...

Reinforced soil retaining walls with two opposite sides (back-to-back) are commonly used for embankments approaching bridges. This type of walls has complex geometry. The distance between two opposing walls is a key parameter used for determining the analysis methods in the federal highways administration guidelines. The objective of this research...

Back-to-back mechanically stabilized earth walls (BBMSEWs) are encountered in bridge approaches, ramp ways, rockfall protection systems, earth dams, levees and noise barriers. However, available design guidelines for BBMSEWs are limited and not applicable to numerical modeling when back-to-back walls interact with each other. The objective of this...

The stability of shallow tunnels excavated in full face has been a major challenge to the scientific community for a long time. In recent years, new techniques based on the installation of a pre-reinforcement system ahead of the tunnel face were developed to control the deformations and surface settlements induced by the excavation and to ensure th...

The magnitude and the application point of the resultant active earth pressure are two key problems in the design of a variety of civil engineering structures. Experimental results indicate that these parameters are affected by the wall movements. In this paper, series of two- dimensional finite difference analyses have been carried out using the c...

Ring footings are widely used to support structures like silos and storage tanks. Analytical design of safe and economical shallow footings requires the knowledge of the bearing capacity factors N’c and N’γ. The geotechnical design Eurocode 7 provides such factors only for simple geometric shapes like squares, circles or rectangles. Furthermore the...

This paper deals with a finite difference code (FLAC) to study the bearing capacity for ring footings resting on two layers with an upper layer of soft clay and down layer of cohesionless sand. The main objective of this study is to assess the effect of two factors, the clay layer thickness and the ratio of internal radius to external radius of the...

This paper presents the details of a numerical study using the Fast Lagrangian Analysis of Continua (Flac) software. The numerical computations have been conducted to evaluate the ultimate bearing capacity of a strip footing placed over unreinforced and reinforced sand bed where a single horizontal layer of reinforcements. The aim of this study is...

La présente communication s’intéresse à l’estimation du tassement du cas de l’extension de la plateforme du port d’Alger en cours du traitement par des colonnes ballastées. Différentes modélisations numériques ont été effectuées à l’aide du logiciel PLAXIS. Les résultats numériques sont comparés avec ceux des différentes approches analytiques dis...

This paper focuses on the construction technique of road embankment which crosses a section of about 11 km on sabkha soils of Chott El Hodna in Algeria. Due to the poor bearing capacity of sabkha surface and the rising water table over the surface, serious difficulties were encountered during the investigation of the subsurface soil and the constru...

This paper presents a numerical simulation using PLAXIS code of geosynthetic reinforced embankment over locally weak zones. The case study concerns the reinforcement of the road embankment which crosses a section of about 11 km on sabkha soil of Chott El Hodna in Algeria. This salt flat is dry in summer but gets flooded in winter. The site observat...

The design of cofferdams is often dominated by the water flow around the sheet piles. The seepage flow influences the stability of the wall where bulk heave, boiling, liquefaction, or failure by reduction of the earth pressure may occur. Several methods of calculating the stability against seepage failure have been proposed in the literature, leadi...

Natural soils are often deposited in layers. The estimation of the bearing capacity of the soil, using conventional bearing capacity theory based on the properties of the top layer, introduces significant inaccuracies if the thickness of the top layer is comparable to the width of the rigid footing placed on the soil surface. Saturated normally con...

In this paper, numerical computations using FLAC code are carried out to evaluate the soil bearing capacity factors Nγ′ for both smooth and rough ring footings for low and high friction associated and nonassociated Mohr–Coulomb soils. The results indicate a significant decrease in the value of Nγ′ with an increase in the ratio of internal radius to...

The construction of shallow tunnels causes movements that can affect existing structures, inducing unacceptable disorders. These disorders can not only result from settlements but also from horizontal displacements. In the case of tunneling with pressurized face shield boring machines, ground movements are found to be the result of complex interact...

The 2D passive earth pressures acting on rigid retaining walls problem has been widely treated in the literature using different approaches (limit equilibrium, limit analysis, slip line and numerical computation), however, the 3D passive earth pressures problem has received less attention. This paper is concerned with the numerical study of 3D pass...

This paper deals with the effect of seepage flow on the lateral earth pressures acting on deep sheeted excavations in cohesionless soil. The computation of the passive and active earth pressures in the presence of hydraulic gradients is performed using the explicit finite difference method implemented in Fast Lagrangian Analysis of Continua (FLAC)...

Urban development often requires the construction of deep excavations. These might be for deep basements, cut-and-cover tunnels, underground parking or underground transportation systems. The design of deep excavations is often dominated by the water flow around sheet piles or propped walls. The seepage flow influences the stability of the walls wh...

In order to obtain a precise and reliable measurement database for the validation and qualification of simulation tools describing the deformations induced by tunnelling operations, two sites on the Lyon Metro D line extension have been intensively monitored. This paper presents the results of measurements from two experimental transverse tunnel se...

En vue de constituer une base de données expérimentales précise et liable pour la validation et la qualification des outils de simulation des mouvements induits par les opérations ´un tunnelier, deux plots ´essais de ĺextension de la ligne D du métro de Lyon ont été intrumentés intensivement. Dans cet article, on présente les résultats de mesures ´...

RÉSUMÉ : Le béton de ciment constitue certainement un des matériaux de constructions les plus durables. Certains ouvrages demeurent en excellant état après plus d'un siècle d'exposition à des conditions climatiques particulièrement rigoureuses. Il est quelque fois surprenant de constater que certains ouvrages récents présentent une détérioration im...

Numerical approaches offer the possibility to treat complex cases. Therefore, to investigate the effect of layered soil permeability on the stability of a soil mass in front of a retaining wall, we consider, in this paper, the frequent case of a cofferdam driven into a two-layered soil medium where the permeability coefficients of the upper and low...