Numerical modeling of the face reinforcement of Djebel El-Kantour tunnel face (highway east-west)

The extension of communication ways (roads, highways, railways) often involves difficult crossings that usually lead to the construction of important structures such as tunnels. Similarly congestion on ground surface in cities necessitates the construction of underground structures (roads and metros). Terrain stability during construction especially in the coalface is one of the major problems related to the construction of these structures. This paper presents numerical modeling of the mechanical behavior of the rock face of the DJebel El-Kantour tunnel (East West Highway) reinforced by fits. In order to minimize on maximum the cost of numerical simulations, the reliability of three methods of homogenization of reinforced soil (improving cohesion, improving the cohesion and angle of friction and ultimately improve the Young's modulus) is tested by comparing the results of numerical simulations to the displacements measured insitu.Résumé :L’extension des voies de communication (routes, autoroutes, voies ferrées) impose souvent des franchissements difficiles qui conduisent généralement à la construction d’ouvrages importants tel que les tunnels. De même l’encombrement de la surface de sol dans les villes rend nécessaire la construction d’ouvrages souterrains (voiries et métros).  La stabilité du terrain pendant les travaux notamment au front de taille est l’un des problèmes majeurs liés à la construction de ces ouvrages. Cet article présente la modélisation numérique du comportement mécanique du front de taille du tunnel Djebel El-Kantour (Autoroute est ouest) renforcé par des fits.  Dans le but de minimiser au maximum le cout des simulations numériques, la fiabilité de trois méthodes d’homogénéisation des sols renforcés (amélioration de la cohésion, amélioration de la cohésion et l’angle de frottement et en fin amélioration du module de Young) sera testée, en comparant les résultats des simulations numériques aux mesures des déplacements insitu.Mots clés : Renforcement, sol, homogénéisation, tunnel, déplacement

Pathology Evaluation and Repair of Bridges in Masonry

The field of repair and rehabilitation of civil engineering works is evolving. Indeed, most of these structures, especially masonry structures, are over 50 years old and many of them require maintenance and repair work due to their deteriorated condition. To achieve this objective, a study was carried out concerning the different pathologies affecting the masonry bridges, but also the ways and means necessary for the evaluation and repair of the affected works. The results of this work have not only helped to carry out the diagnosis and verification of the structural state of the bridge over river Kentra Stora Skikda (North-East of Algeria), on the section of the 3AA National Road Skikda, but also for the proposal of repair solutions best adapted to the disorders observed

Modélisation constitutive du comportement cyclique des sables en condition drainée

Dans cette étude, une modélisation numérique simple du comportement des sables sous chargement cyclique est proposée ; la démarche proposée consiste, en condition drainée, à déterminer les paramètres caractérisant le chemin cyclique moyen du sol sous l’'effet de N cycles dûment caractérisés, et à traduire l'’effet cyclique par une déformation volumique cumulée ainsi que par une variation de module du sol. Dans cette étude on s’'intéresse à des essais triaxiaux cycliques simulés au moyen d’'un calcul en éléments finis utilisant le programme Plaxis. On détermine les paramètres d’'identification du premier cycle (charge-décharge) réalisé pas à pas en prenant, comme modèle de comportement du sol le modèle HSM. Puis le comportement après N cycles (N>1000) est simulé par la formulation proposée comme un pseudo-fluage. La comparaison de la méthode proposée à plusieurs essais triaxiaux cycliques confirme la bonne adaptation du modèle proposé à ce type de problème

Calculating the Dynamic Impedances of Foundations and their Effect on the Seismic Response of Structures: Analytical and Numerical Study

This study evaluates the movement of a frame built on soft soil under seismic excitation taking into account soil-structure interaction. First, the study was evaluated using the finite element method, then, by using a substructure method which modelled the soil using springs and dampers in a linear and nonlinear study. Rheological models were determined using impedance functions, calculated using a numerical program CONAN. These dynamic impedances are shown in the displacement vector of a three-degrees-of-freedom frame, which was calculated on the basis of lateral forces distributed over the structure height using the equivalent static method. In this regard, two different calculation norms were chosen; RPA2003 and UBC97. Finally, a parametric study was carried out, based on the effects of soil densification and the foundation geometry on the response of the RC frame

Numerical Modeling of the Degradation of the Normal Stress Under Large Number of Shearcycles

The evaluation of friction is an important element in the verification of stability and the determination of the bearing capacity of piles. In the case of cyclic stress, the soil-pile interface has a relaxation which corresponds to a fall in the horizontal stress which represents the normal stress at the lateral surface of the pile. This paper presents an explicit formulation to express the degradation of the normal stress after a large number of shear cycles as a function of cyclic parameters. In this study we are interested in the exploitation of the cyclic shear tests carried out by Pra-ai with imposed normal rigidity (CNS) in order to demonstrate the phenomenon of falling of the normal stress. The approach presented in this paper consists in proposing a simple expression for estimating the degradation of normal stress as a function of cyclic shear parameters after a large number of cycles. The validation of this approach is verified by the application of this formulation to a real case where the comparison of the simulations made by this approach with those recorded on site shows the good adaptation of this approach to this type of problems