Search

The numerical analysis using finite difference method to study static and dynamic performance of embankment dams is a complex process, in which the materials behavior, soil-dam foundation interaction, hydraulic conditions and saturation effects, should be taken into account. In this study, static and dynamic analysis of Keddara earth dam, located in Boumerdes region (Algeria), is conducted by a numerical analysis using finite difference method (FLAC 3D), with the objective to define its behavior in terms of settlement, strain and pore pressure variation, during its construction and operation. Two stages are considered; the dam construction stage and water filling stage. In this way, two mathematical models are considered for the static analysis; the elastic model and Mohr-Coulomb model. To conduct a coupled dynamic analysis a real earthquake record is used and the interaction between the fluid and solid phases is taken into account.

This paper work is in the frame of the study about the reduction of settlements in the case of floating columns. The prediction of a settlement remains a prickly problem to which geotechnical engineer is confronted. Experience has shown that structural pathologies are caused by the effects of excessive differential settlements before reaching soil bearing capacity. To palliate this problems in the case of soft and compressible soils, we advocate, as an alternative solution, piles or the reinforcement of the soils with stone columns. This strengthening method, introduced in Algeria in 1999, is economical. However, it does not inihilate settlements but it speeds up the time factor. Numerical modelings by finite element method (FEM) have been carried out through interest into all mechanical and geometrical aspects that are inherent in the meshing of floating stone columns. An analytical formulation of a correction coefficent (μβ) and an abacus of the settlement reduction factor (β) has been suggested. On the other way, the monitoring instrumentation of experimental site since 2008 to 2017 at the level of the harbour lowland of Bejaia has been carried out. It concerns important storage structures fonded on a very compressible ground reinforced by floating stone columns. The records of the settlements at the scale of the structures, according to variable loads recorded in real time, have revealed excessive settlements under the effects of variable stresses from 1 to 3 bars. An exhaustive geological, geotechnical and geomechanical analysis has been carried out for the characterization of the grounds, and numerical modelling by finite element method (FEM) has been carried out. The experimental and numerical investigation of the concerned structures at issue allowed us to confront the results with regard to settlement prediction of an environment reinforced with floating stone columns. The result is a perfect matching in relation to the suggested formula.

Landslides are one of the most catastrophic geo-risks observed in northern Algeria, particularly in the regions of mountain ranges (Mediterranean Kabylia), where the processes are spectacular. Over the past decade, the landslides risk has become increasingly amplified in urban space, mainly affecting the economy and human life. This highlights the importance and the need to predict the spatial occurrence of these events in the national territory. In order to better manage this phenomenon, decision-makers must be able to have susceptibility maps, allowing them to identify areas in their region where new landslides will have a higher probability of being triggered in the future and of predefine the damage associated with this phenomenon. However, approaches to assessing landslide sensitivity require a good knowledge of previously observed scenarios and include data collection and management, as well as spatial and statistical analyzes. In this study, a new multivariate statistical approach "PCA" was proposed to produce landslide susceptibility maps of the study area in a GIS system. This study allows the automatic analysis of most of the parameters related to the occurrence of slope failures while reducing the factors not influencing the triggering of landslides, this eliminates the effect of redundancy between the factors studied.

This paper deals with the evolution of the shear modulus G and the damping D as a function of the shear deformation of the soil, using data from field and laboratory tests. The studied experimental site is located in port area of the city of Bejaia (Algeria), which has already been the subject of numerous geotechnical and geophysical investigation campaigns as part of construction of important industrial projects. In a first step, the geological, tectonic and hydrological contexts of the region are described, as well as the results of the geophysical and geotechnical tests. The result of this first step is the development of a database from field and laboratory tests. In a second step, monotonic and cyclic triaxial tests are performed to identify the dynamic properties on a reconstituted silty clayey sand soil in the laboratory with a characteristic relatively close to the ground in place. In a third step, a numerical analysis is carried out using a FLAC2D code. The nonlinear elastic model proposed by Ramberg–Osgood and limited by the Mohr–Coulomb criterion is used. The comparison between the numerical results and the experimental data shows the applicability of the Ramberg–Osgood model to describe the dynamic behavior of muddy silty sand and muddy sands of Bejaia.

The Boumerdes earthquake of May 21, 2003 in Algeria, which widely felt within a radius of ~ 400 km, caused damage in five provinces. Numerous structures have been devastated, others suffered of damages. Keddara rockfill dam which is situated approximately at 20 km from the epicentre was strongly shaken during this seismic event and can undergo significant deformations. In this study, numerical analysis of Keddara rockfill dam under Boumerdes earthquake is performed. It is mainly focus on the seismic amplification at different level of the dam under the main shock with dominant frequency close to the natural frequency of the dam. The low coherence between the input and the structural output indicates the need of nonlinear analysis of the dam under the spatial variation in excitation. Furthermore, the effect of plasticity on the seismic response is investigated by using maximum acceleration which is one of the most important properties selected. The analysis of the dam under stochastic non-uniform excitation is conducted using a 2-D finite difference modeling by using the software Fast Lagrangian Analysis of Continua (FLAC). The final results obtained after successive analyses on the dam configuration incorporating the nonlinear soil properties are presented.

This article proposes a method based on artificial neural networks (ANN) to predict the time history responses at any point on the ground near a shaking table reaction mass (Earthquake Engineering ...

The natural hazard assessment is hampered by many difficulties due to the complexity of the phenomenon and the need to manage simultaneously several natural and/or technological hazards. Such is the case of most unstable urban sites in Algeria. The paper presents a risk analysis study of landslides and their reactivation in Tigzirt coastal city, located in the north of Algeria, which is classified in a moderate seismic zone. The spatial techniques based on geographic information systems are used to assess landslide susceptibility and hazard. Two qualitative studies of landslide hazard assessment are conducted using parameters defining the Algerian landslides context. The hazard is evaluated by performing a combination of the landslide susceptibility and the urban density. Earthquake-induced landslide hazard is assessed taking into account the Algerian seismicity. The study led to determination and mapping of the hazard induced by Tigzirt landslides.

Rainfall-induced slope failure is a major geotechnical disaster and has been frequently reported in many regions worldwide. This work aimed to study the rainfall (climate) influence on slope stability. The climate is represented by precipitations rate, precipitation duration and the stability of this unsaturated slope in natural terrain was evaluated based on a key indicator which is “safety factor”. The finite elements software (PLAXIS2D) was used to analyze the stability of the slope. The factors of safety were evaluated by means of fully coupled flow-deformation analyses and then compared with the various controlling factors: rainfall intensity, rainfall duration, angles and heights of slopes, soil characteristics and hydraulic conductivity of the soil. The results were discussed in this paper and led to confirm the relationship existing between landslide and climate effects considered in this analysis. In fact, this relation is observed for most part of the north Algerian instabilities.

In the assessment of slopes, factor of safety values still remain the primary indexes for determining how close or far slopes are from failure. Limit equilibrium and finite elements methods are among the most popular methods of slope analysis. Both methods were used to analyze homogeneous and inhomogeneous slopes. However, Limit equilibrium methods are relatively simple and suffer from many assumptions compared with finite element analysis. Recently, as computational techniques advance, more and more attention has been paid to the slope stability evaluations using finite element methods (FEM). This article demonstrates a finite element approach to analyze the response of homogeneous and layered slopes. A detailed parametric analysis is presented to study the effect of surcharge (it can be an imposition of building load….etc.) on the stability of the slope. In regard with these results it is seen that the factor of safety increases with increase in soil properties, groundwater depth, slope length, distance from the crest of slope. However, it decreases with increase in surcharge intensity, increase of weak soil layer thickness and increase of slope angle and slope height.

Landslides are one of the most common natural hazards all over the world. In mountainous northern Algeria, the rainy winter climate triggers or reactivates a variety of instabilities, causing major structural and infrastructure damage in several wilayas (provinces). The activation of these instabilities is often related to exceptional weather (such as heavy rain or snow). Tizi-Ouzou region, located in the Mediterranean part of Algeria, is one of the zones most affected by this hazard. Over 50 instabilities, each spanning an area of more than 2 ha, have been identified in various cities and villages of this region. This paper summarizes a study of a landslide that affects Azazga city, located at 20 km east of Tizi-Ouzou city and 117 km east of the capital Algiers. The unstable zone covers an area greater than 260 ha and affects vital structures, such as the regional hospital and polyclinic. Since the winter of 2012, this ground movement has been experiencing significant activity phases related principally to climate effects, such as a reactivation in March 2012 caused by a major snow cover, and a reactivation in 2014 caused by heavy rains. The objective of this paper is to determine the landslide reactivation threshold in terms of the average monthly rainfall and exceptional rainfall using the software PLAXIS2D.

In this study, an experimental investigation carried out to assess the performance of addition of an inert material on stabilization of an expansive soil in order to solve the lifting structures caused by this phenomenon. The results showed that an addition of glass is capable of reducing the actions of swelling. From the global analysis of the porosity using an ultrasonic device, we measure the propagation velocities of ultrasonic pulse through the tested clay samples. This reveals a change occurring in the porosity of the clay when glass is added to it. As a result some interesting conclusions concerning the expansive soil-material amendment are drawn.

The coastal city of Bejaia, located 250 kilometers east of the capital Algiers, Algeria, is characterized by soft soils. The residual grounds encountered on the first 40 meters usually have a low bearing capacity, high compressibility, insufficient strength, and subject to the risk of liquefaction. These unfavorable soil conditions require deep foundations or soil improvement. Since late 1990s, stone columns technique is used to improve the weak soils of the harbor area of the city. A shallow raft foundation on soft soil improved by stone columns was designed for a heavy storage steel silo and two towers. The improvement of 18m depth have not reached the substratum located at 39m depth. The stresses transmitted to the service limit state are variable 73 to 376 kPa. A rigorous and ongoing monitoring of the evolution of loads in the silo and settlements of the soil was carried out during 1400 days that is from the construction of foundations in 2008 to 2012. After the loading of the silo in 2010, settlement occurred affecting the stability of the towers due to excessive differential settlements. Consequently, the towers were inclined and damaged the transporter. This paper presents and discusses the experience feedback of the behavior of these structures. Numerical calculations by finite elements have been carried and the results are compared with the measurements.

This study presents the results of an experimental work carried out to investigate the effects of treatment of fine bentonite clay using various contents of lime. Tests conducted verified substantial changes and significant improvement in physical and mechanical characteristics of the clay. Techniques including ultrasonic tests and unconfined compression were utilized for a series of lime content (0%,2%, 4% and 6%) for variable curing times. The studied clay soils revealed that lime treated clays get changed and improved with regard to particular geotechnical characteristics due to cation exchanges, particle rearrangements and pozzolanic reactions. The analysis of ultrasonic tests and compressive strength showed a process of gradual increase in strength and compactness of the reaction products over time. For an optimum dose and extended curing time, the stabilized soil acts as a rock.

Landslides are one of the most catastrophic geo-hazard all over the world. The study of this phenomenon is hampered many difficulties due to the complexity of the instabilities, the loose of data and the important variability of its causes. Geomorphological mapping of landslide susceptibility is a method that relies to the ability of the investigator to actual and potential slope failure according landslide inventory. The landslide susceptibility and hazard assessment approaches need a good knowledge of the previous observed scenarios and include collecting data, construction of spatial database as well as spatial and statistical analyses. Every year, principally in winter, the North of Algeria is affected by instabilities of greater magnitude causing equipment damage and important costs. This research is focused on the study of Tizi-Ouzou region, located at about 90 km east of Algiers, Algeria. Tizi-Ouzou is a region of Kabylia, with an area of 3568 km2, characterized by a mountainous morphology. This region is characterized by about 84 significant instabilities affecting urban areas. The work aims to make, in the first hand, a spatial and statistical study of instability causes and site sensibility parameters, and in the second hand, the susceptibility assessment and mapping of Tizi-Ouzou region according to the landslide inventory effectuated in this region. The study indicates that the main instability factor is water effect and lets the proposal of Tizi-Ouzou region susceptibility map.

An experimental investigation on the shrinkage and durability of stabilized soil was conducted to examine the effect of the addition of chemical stabilizers such as cement, lime, filler and their combination on the characteristics of clays. Shrinkage was measured on un-stabilized soil and stabilized samples with cement, sand or a mixture of cement and sand. The results show that the shrinkage of un-stabilized soil is proportional to the water content of saturation. The higher the percentage of initial water in the soil, the greater the drying shrinkage. For the stabilized soil, the combination of cement and sand reduces the shrinkage slightly better than when only cement is added. The durability was evaluated by conducting series of wetting-drying cycle tests. The study shows that the durability of earth material can be improved by cement and lime stabilizers.

This paper presents the approach followed for the geological, mineralogical, and geotechnical characterization of swelling marly clays in the Medea region. This investigation is conducted in order to estimate the swelling potential of this marly clay layer. The studied sites, located at about 80 km south of Algiers, Algeria, cover an area of approximatively 400 hectares. Five sites are considered. In the first step, the geological, tectonic, climatic, and hydrological contexts of the region are described. According to the geological map of Medea, most of the formations encountered in the area are composed of Miocene layers represented by marly clays (Fig. 2). This region is characterized by its high and low temperature in summer and winter, respectively, and variable humidity (Fig. 3). In a second step, the results of geotechnical studies, X-ray diffraction tests, chemical analyses, and scanning electron microscope (SEM) observations are presented (Figs. 3, 4, 5, 6, 7, 8, 9). The soils contain quartz (20–26 %), calcium carbonates (11–55 %), kaolinite (8–13 %), illite (6–14 %) and Montmorillonite (18–26 %). The study of their microstructure by means of SEM indicates that these soils are formed by a compact marly clay matrix that is relatively homogeneous and oriented in the dip direction of bedding. A grain size analysis shows that the clay content varies between 17 and 70 %. The water content of all samples varies between 8 and 30 %. The values of the liquidity limit (LL) and plasticity index (PI) vary between 28–76 % and 16–36 % respectively, indicating a highly plastic soil; this is also confirmed by a specific surface varying between 99 and 179 m2/g. The dry density γ d varies between 15 and 19 kN/m3. The swelling potential of the marly clay samples is evaluated firstly using various indirect methods. In literature, a number of empirical classifications are proposed by different authors (BRE 1980; Chen 1988; Komornik and David 1969; Seed et al. 1962; Snethen 1984; Vijayvergiya et Ghazzaly 1973 et Williams and Donaldson 1980). The swelling potential is related to certain physical properties of soils, such as consistency limits, clay content, methylene blue value, etc. In general, these methods indicate that all the tested soils have a high swelling potential, which confirms the results of mineralogical analysis. Secondly, direct measurements of swelling parameters are performed. Swelling tests are carried out using a standard slaved one-dimensional odometer using two methods: free swell and constant volume, according to standard ASTM D 4546-90 and AFNOR (1995). The swell pressure, the swell percentage and the swell index are given in Fig. 16. It is noted that the soils develop very significant swell pressures which vary between 25 and 900 kPa. This is in agreement with the results obtained by empirical methods. This investigation clearly shows that the marly clays of the Medea region have a high swelling potential. Therefore, taking into account the phenomenon of soil swelling in structure design is essential.

This paper presents the results of an experimental study on the durability of stabilized soil. The effect of the addition of chemical stabilizers such as cement, lime, filler and their combination on the durability of clay was examined. The durability of stabilized material was evaluated by conducting series of cyclic wetting-drying and weight loss tests. The study shows that the durability of earth material can be improved by cement and lime stabilizers. These stabilizers provide interesting properties of clays and the durability of stabilized material is greatly enhanced by a combination of these stabilizers.

Views the scarcity of building sites, the urban development on soils with problems such as swelling soils, causes the damage to lightweight structures, as a sewerage networks, shod, etc. These damages are often classified in the low risk category. However, the neglect of these disorders can create geotechnical problems, much more complicated, with high risk, as a land motion. This case of disorders has been recording in several regions in Algeria, as example: Ain Defla, Boumerdes, and Medea, which is the studied case in this paper. The geotechnical study and the swelling tests on undisturbed and remolded samples, indicate the presence of a high swelling clay layer, of about 3–4 m deep. This research focuses on the evolution of the phenomenon of shrinking and swelling under the effect of a set of parameters existing in situ, such as climate cycles (alternating between winter and summer) and the effect of soil saturation mode. In this work, two modes are studied: saturation by infiltration and saturation by capillary. The results analysis shows the remolding of samples structure and the loss of their initial mechanical and physical properties. The test results justify the observed disorder on the site such as the erosion of foundation soils under the effect of the flow of surface water, and landslide triggering, affecting the whole of the site, and endanger the university campus located on this site.

Currently, the composite materials make important great strides, considering their high mechanical properties. The studies relating to the conceptual, technical aspect and modeling of their mechanical behavior are more than desirable. The mechanical properties of the composite material depend on several factors as the nature of fibers, the fiber/matrix ratio, compatibility, homogeneity... In this study, we present the results of an experimental analysis of the behavior of the composite material, under a static and a dynamic loading. The composite material is composed respectively of the glass and metal fiber reinforcement. A various dimensions of the mesh are considering. The resin used is polyester Resow 55 E. The dynamic test ( Knoop test) is carried out on various specimens made up of an polyester resin RESOW 55 E reinforced with varied powder nature. It makes it possible to measure the hardness of composite materials. The analysis of the results shows clearly that the mechanical properties are strongly influenced by the dimensions of the elementary mesh of the fiber grid reinforcement. Based on experimental results, a Weibull modulus has been established for each specimen.

The behaviour of saturated clays under undrained conditions around pressuremeter path is studied by means of a theoretical and a numerical analysis based on the generalised elastoplastic Prager’s model with the Von Mises Criterion which is suitable for these cases of soils and gives a realistic response when unloading is considered. The soil constitutive model is described depending only on three parameters. The model response on pressuremeter path and its identification from experimental data lead to the determination of the undrained cohesion and the initial Young modulus of clays. Comparisons between the undrained cohesions determined with the proposed method and those obtained by other means illustrate the applicability of the method. An application to predict the bearing capacity and the settlement of bored piles using parameters derived from the proposed approach is also presented with a comparison to the measured data. Le comportement des argiles saturees en conditions non drainees sur un chemin pr...

An experimental program carried out in this study seeks to understand the physical mechanisms of stabilization of an expansive soil by adding an inert material (sand) at various forms; mixing and intercalation layers of sand. The first aim of the study is to analyze the effect of stabilization on the variation of soil consistency. The results show a marked improvement in soil consistency. Then a study of the effect of the additives on the variation of the swelling in order to solve the lifting structures caused by this phenomenon is carried out. It can be seen that the addition of sand is capable of reducing the swelling action. We complete the study using an ultrasonic device, measuring the propagation velocities of ultrasonic pulse through the tested clay samples. This shows a change occurring in the porosity of the clay when sand is added to it. As a result some interesting conclusions concerning the expansive soil-material amendment are drawn.

In this paper, a new approach for soil profile characterization is validated. The soil characteristics are calculated by fitting the theoretical amplification functions to those obtained experimentally. The identified characteristics have been observed to agree well with those obtained by in situ and laboratory tests. This new approach uses system identification theory and free field records. It is based on formulation of theoretical soil amplification function for two sites in terms of the different parameters of the soil profile layers (thickness, damping ratio, shear wave velocity and unit weight). The theoretical function is smoothed according to the experimental data (spectral ratios) by means of the least squares minimization technique. The function parameters are determined by solving, numerically, a non linear optimization problem. In this approach, soil profile characteristics of two sites can be identified simultaneously, from only a single soil acceleration record at free surface of each site without need of bedrock or outcropping acceleration records. Strong ground motions data recorded during the Boumerdes earthquake (Algeria) of May 21, 2003, are used for the validation.

An earthquake, with magnitude of 6.8, shocked Keddara rockfill dam on May 21, 2003 in Algeria. Accelerometers array that had been installed on the site recorded the motions at the crest, the abutments and in free field. An analysis of accelerograms recorded during and after the main shock provided the basis for an analysis of the seismic behavior of this dam. The vibrational modes excited during the earthquake were estimated. A spectral analysis indicated that the fundamental mode of the dam excited during the main shock corresponds to a longitudinal mode. In addition, a simulation of the seismic response of Keddara dam to varying earthquake ground motions in the transversal direction is proposed. A space time earthquake ground motion model that account for both coherency decay and seismic wave propagation is used to specify the support motions. Many analyses on seismic behavior of embankment dams have shown the need to consider differential ground motion along the canyon width; this study illustr...

Schist is abundant in the Kabylia region of Algeria and hence its use for civil engineering applications, particularly in pavements, is desirable. The paper reports a study on three of the more common schists to determine the characteristics controlling the mechanical behaviour of these materials. The geological and engineering properties of the schists are described and it is concluded that anisotropy is a more important influence than the mineralogy. Of the three schists studied, the harder minerals present in the mottled schist make this the most applicable for use in pavements.

Cement stabilized soil is usually compacted by different mechanical methods to increase its strength and durability. This paper summarizes the results of an experimental study on the effect of different compaction methods on the performance of stabilized soil. The compaction methods investigated were either static compaction by applying a static pressure using an universal compression testing machine, dynamic compaction by a drop weight method, or static compaction coupled with vibration. All methods were applied on unstabilized soil or cement stabilized soil. The effect of each method of stabilization on compressive strength, shrinkage and water resistance are reported. Dynamic compaction with about 8% of cement content seems to give the best performance for the soil investigated.

The purpose of this paper is to present a stochastical approach, which analyse the torsional ground motion, induced by the spatial variability of seismic motions. For this purpose, a torsional ground motion analytical model is proposed and a normalised differential motion parameter is introduced. The approach regards the seismic motion as the combination of a travelling wave on the site (coherent component) and a zero mean randomizing factor that introduces a loss of correlation effect. The soil parameters as fundamental frequency and damping coefficient are integrating by modeling the coherent component with the commonly used Kanai-Tajimi power spectral density. The parametric analysis of the model shows an increase of the induced torsion with both the soil frequency and the motion scattering parameter, and a decrease with the separation distance, the apparent wave velocity and the correlation length. Finally, in order to test the proposed torsional ground motion model prediction, it is compared to the experimental results recorded by the EPRI LSST array in Lotung, Taiwan (Laouami and Labbe, 2002). The comparison leads to the identification of the model parameters for the Lotung soft site.

Earth construction is widespread in desert and rural areas because of its abundance and cheap labour and could be an alternative construction material for low cost housing in Algeria. However, earth construction suffers from shrinkage cracking, low strength and lack of durability. This paper reports on the Algerian experience on earth construction in housing and gives an extended review of an experimental study to investigate a stabilised soil by either mechanical means such as compaction and vibration and/or chemical stabilisation by cement. Soil used was characterised by its grading curve and chemical composition. Compaction was either applied statically or dynamically by a drop weight method. A mixture of sand and cement was also tried. The effect of each method of stabilisation on shrinkage, compressive strength, splitting tensile strength and water resistance are briefly reported. The experimental results showed that the best method of stabilisation of the soil investigated, which gives a good compressive strength and a better durability at a reasonable cost, could be a combination of a mechanical compaction and chemical stabilisation by cement or sand and cement up to a certain level.

This paper reports on the assessment study conducted by the authors on the new Algiers airport building. The evaluation approach included visual inspection of the concrete, seismic parallel method for piles testing and non-destructive testing of concrete with Schmidt hammer, ultrasonic pulse velocity measurements, cores testing, carbonation tests and also ambient vibrations of the structure. The diagnostic confirmed that the concrete was of low strength and showed many shortcomings such as inappropriate mix design with respect to coarse aggregate size of concrete resulting in honeycombing, construction errors such as lack of cover and the use of low slump concrete, poor placement and inadequate vibration. The repair work involved the application of ready mixed cement based polymer modified sprayed mortar with and without fibers on more than ten thousand square meters of honeycomb concrete, the injection of about five hundred linear meters of cracks and the repair of about one hundred square meters of corrosion damaged concrete at a cost of more than three millions US dollars.

Des desordres ont ete constates dans plusieurs edifices publics dans une ville au sud d’Alger. Cet article presente une description de ces desordres et de leurs causes probables. Les etudes geologique, hydrogeologique et geotechnique ont montre que la region de la ville est geologiquement stable et le sol est de bonne resistance. La cause principale des desordres est liee a l’infiltration des eaux dans les sols argileux provenant des pluies et des reseaux d’assainissement defectueux. La presence d’arbres et arbustes tres proches des constructions ainsi que le manque de dallage peripherique autour des bâtiments ont contribue a l’acceleration de ces desordres.

This paper describes two landslide case histories triggered by rainfall, unfavourable geological, hydrogeological and geotechnical conditions and human interventions. The first one is located about 250 kms South-West of Algiers, at place named Bordj Bounaama in Tissemsilt region. The landslides caused a collapse of a stadium and surrounding wall of the gymnasium and tilting of retaining wall under the earth pressure. The second landslide is one of the most spectacular among the 120 sites affected by landslides since 2000 in Bejaia department, located in Kabylia region. It was occurred at PK 226 + 300 of the National Road RN 24. The landslide caused the collapse of a section of the road of about 120 m, with a main scarp of about 8 m. During the firstly time of the field observation, the landslide mass and the road moved 10 m. Based on extensive geological, geotechnical and hydro-geological investigations, comprehensive of the landslide analyses were made using limit equilibrium and finite element method.

The management of major landslides faces several difficulties especially when important stakes are exposed to risk. The landslide of the city Azazga is one of the most extensive cases observed in Algeria. This is an instability reactivated by specific climate events such as floods of 1974 and snow of 2012. Landslides affect the center town of the region of Azazga situated 20 Km East of Tizi-Ouzou (northern Algeria). They affect a highly urbanized area and endanger vital structures such as the regional hospital. Managing this risk requires the development of an effective management methodology as well as a good knowledge of site conditions, the causes and the extent of the landslide. To better characterize this extensive instability, a geographic information system was created for the study site. This GIS greatly facilitates the interpretation of spatial data.

International audience; This paper describes an efficient methodology for the identification of soil parameters using the combination of the finite element method and the in situ pressuremeter test (PMT). The objective of the procedure applied here is to identify the parameters of generalized Prager model associated with the Drucker and Prager failure criterion from a pressuremeter expansion curve. The approach consists of minimizing the function representing the difference between the experimental curve and the curve obtained by integrating the model along the loading path in the in situ testing. First, both analytical expressions governing the problem of cavity expansion and those related to the finite element modeling are given in detail. Then, a Fortran computer program called "Press-Sim" along with the solution strategy are described and clearly explained. The influence of some model parameters as well as the probe geometry on the computed pressuremeter curves is examined. The paper finishes by presenting some identification examples drawn from real experimental tests for which the targeted parameters are compared with those of other experimental procedures. Results of comparison show a very good agreement.

This paper presents a new method proposed for the prediction of long term settlement of very heavy structures based on a numerical interpretation of long term pressuremeter creep tests. The constitutive model used for the modelling of the soil creep is described. The constants of the constitutive model are determined by fitting a simulated curve, given by a simple Finite Element Method, to the results of a long term pressuremeter creep test. The calculation of long term settlement under nuclear power plants, using the soil parameters defined by this method, is presented and compared with the in situ measured values.

Cet article presente une procedure permettant l'utilisation des resultats de l'essai pressiometrique pour l'identification de parametres intrinseques du comportement d'un sol. La premiere partie de cette etude analyse numeriquement un certain nombre de phenomenes importants pour la qualite de l'identification (non linearite, dilatance, remaniement, drainage, utilisation d'un cycle). La deuxieme partie de l'etude est consacree a la presentation de la methode d'identification a partir du pressiometre qui est proposee. Quelques exemples d'utilisation de cette procedure sont ensuite presentes avec des comparaisons entre previsions et mesures experimentales in situ. (A). (Titre anglais : Use of pressuremeter tests to define the intrinsic parameters of soil behavior).

The morphology of the North Algerian basins characterized by precarious stability constitutes an important issue for the development and the economy of many cities in the region. The landslide affecting the city of Azazga represents one of the most active and dramatic land movements experienced by the region in recent years. The city affected by the movement is situated at about 20 Kms in the East of the Wilaya of Tizi - Ouzou (in northern Algeria); the instability is located in a slope, composed of flysch (Azazga flysch are compounds of two terms of marly clay with small sandstone beds), with an inclination of about 13 °. Several factors have acted to activate this instability. Furthermore, water factor and geological conditions of this region are the main parameters of the susceptibility of the site to landslides.The Geographic Information Systems (GIS) are an effective alternative for the analysis of large-scale instabilities (such as Azazga landslides). GIS made for the site of Azazga allowed better management and interpretation of spatial data as well as good understanding of deformation mechanisms and the extent of this landslide. Geological profile has been defined for this slope using the results of spatial data analysis. Numerical modeling of this slope was then carried out, using the finite element software PLAXIS 2D , with taking in consideration the effect of the water level. Those studies show the important influence of the position of water table on the activity of the landslide and the safety factor.