Ali Bouafia | SAAD DAHLEB DE BLIDA (original) (raw)

Papers by Ali Bouafia

European Journal of Environmental and Civil Engineering, May 15, 2020

Pile foundations are usually subjected to cyclic loading which could possibly causes a significan... more Pile foundations are usually subjected to cyclic loading which could possibly causes a significant degradation of the friction mobilised along the pile shaft. Most of the experimental studies devoted to analysing the behaviour of the pile-soil interfaces under cyclic loading tests are performed at a few hundred of cycles. However, a large number of cycles of the order of hundreds of thousands may cause a severe degradation of pile capacity. The present work aims to study the effect of cyclic loading parameters on the evolution of shaft friction of pile subjected to a large number of cycles. The experimental study is based on a physical modelling in a calibration chamber of axial cyclic loading of single pile jacked into sand under a large number of cycles, up to 10 5. It is found that cyclic amplitude, confining pressure and soil density have a significant effect on the evolution of skin friction along the pile shaft at a large number of cycles.

HAL (Le Centre pour la Communication Scientifique Directe), 1996

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

CRC Press eBooks, Jun 9, 2021

Revue française de géotechnique, 1996

Effet de la proximité d'un talus sur un pieu court et rigide chargé horizontalement Résumé L'infl... more Effet de la proximité d'un talus sur un pieu court et rigide chargé horizontalement Résumé L'influence de la proximité d'une pente sur le comportement d'un pieu court et rigide chargé horizontalement a été étudiée à l'aide d'essais sur modèles réduits centrifugés. L'étude des déplacements du pieu a montré que l'effet du talus n'est significatif que si le pieu se trouve en deçà d'une distance limite de la tête du talus. On montre qu'il est possible de prévoir le comportement d'un pieu implanté près d'un talus, en effectuant une correction adéquate des courbes P-Y correspondant à un sol horizontal.

Taylor & Francis eBooks, Jul 12, 2006

Geomechanics and Geoengineering, Apr 29, 2020

This paper proposes a new hybrid artificial neural network and mathematical (ANN-MATH) model to i... more This paper proposes a new hybrid artificial neural network and mathematical (ANN-MATH) model to improve the prediction capability of the load-settlement behaviour of shallow foundations in sandy soils. The hybridisation process is performed by replacing the conventional activation function of the ANN output layer by a new mathematical model. Thereafter, 110 full-scale loading tests of shallow foundations, carried out in sand with the cone penetration test (CPT) results, are used to build and validate the proposed model. In terms of accuracy, the proposed model shows a high correlation between the predicted results and the measured data. In addition, the proposed method was compared to the available methods in the literature. It was found that the proposed model is superior to classical and artificial intelligence-based methods by more than 29% and 35%, respectively, in terms of root mean square error (RMSE). Furthermore, a parametric study was undertaken to assess the robustness of the proposed model and to derive the bearing capacity factor based on the CPT test. The bearing capacity factor was found close to those recommended by the French standard NF P 94-261.

The paper presents lateralloading tests Onsingle piles in sand carri.edout on the LCPC centrifuge... more The paper presents lateralloading tests Onsingle piles in sand carri.edout on the LCPC centrifuge.The two models tested and the devices and instru.mentation are described. From the measured bending moments, the P-Y curves are derived and the subgrade reacrion modulus are compared with values from difjerenI methods (Menard, PHRl). The ejJect of a slope on the behaviour of larerally loaded pitt: was studied and results re/ated to ;".ead displacements and bending moments are presenIed.

Paper No. 1.12 Reduced scale model tests in centrifuge have been carried out for measurement of t... more Paper No. 1.12 Reduced scale model tests in centrifuge have been carried out for measurement of the ultimate horizontal load of a pile driven in dense sand. The construction of thL load-transkr P-Y curves has allowed to analyse the rcsrxmsc of the soil to the large displacements of the pi \c. The comparison hctwccn c:xpcrimcntal results and those predicted by the current methods has shown the insufficiency of the theoretical approaches

Journal of Sustainable Architecture and Civil Engineering, Mar 17, 2014

Confining granular materials still a very benefic practice to achieve civil different engineering... more Confining granular materials still a very benefic practice to achieve civil different engineering works. In this paper, the design and analysis of a wall shaped structure made of technical fabric-confined sand will be exposed. This composite structure, made of local materials, where, Polyvinyl Chloride (PVC) technical fabric constitutes a containing envelope and sand a filler material. Designed wall represents a good sustainable development project (idea) to build single story buildings in hot and humid inaccessible areas (Sahara); alternatively, it may provide many other geotechnical applications as retaining walls etc. An experimental campaign to identify the mechanical and physical properties of the studied structure was conducted. Earlier, and not exposed here, a design and analysis of a 1/5 scale model is achieved to evaluate a bearing ability of the wall under vertical compressive and horizontal flexural loads is done. Test to evaluate energy dissipative power of the wall under impact has been also conducted and discussed.

Arabian Journal of Geosciences

Maǧallaẗ al-abḥāṯ al-handasiyyaẗ, Nov 16, 2022

The objective of this article is to present original research work results on the contribution of... more The objective of this article is to present original research work results on the contribution of the standard penetration test (SPT) to the design and analysis of pile foundations on the basis of the interpretation of a database of full-scale pile loading tests undertaken in sandy soils, with the aim to provide practical recommendations to the designers. The article encompasses three parts, the first one presents a detailed comparative study of 10 currently used methods of design on the basis of the SPT, assessed according to their predictive capability of the axial bearing capacity, within a database consisting of 46 axial pile loading tests carried out in 27 sites in the United Arab Emirates. The second part presents some experimental findings related to the critical (or creep) vertical load, whereas the third part highlights the concept of the reference pile settlement and its application to the limit state design of pile foundations.

Influence of the cyclic loading of very large number of cycles on the pile capacity Influence du ... more Influence of the cyclic loading of very large number of cycles on the pile capacity Influence du chargement cyclique à grand nombre de cycles sur la capacité portante des pieux

Geotechnical and Geological Engineering, 2003

ABSTRACT

Canadian Geotechnical Journal, Apr 1, 1995

This paper presents the results of a static lateral loading test, carried out in a centrifuge, on... more This paper presents the results of a static lateral loading test, carried out in a centrifuge, on the reduced model of a single pile, instrumented with strain gauges, installed near a dense sandy slope. The effect of the proximity of the slope on the behaviour of the pile is studied. P–Y lateral reaction curves are constructed, and the variations of the horizontal subgrade modulus are analyzed. A practical method, based on the correction of the horizontal soil P–Y curves, is proposed to study the behaviour of piles near a slope. Key words : horizontal loading, pile, centrifuge, slope, sand, P–Y curve.

Geomechanics and Geoengineering, Aug 6, 2021

ABSTRACT The results of a series of displacement-controlled cyclic axial loading tests of model p... more ABSTRACT The results of a series of displacement-controlled cyclic axial loading tests of model pile in saturated kaolinite clay, carried out in a calibration chamber, are presented. An instrumented pile-probe was used to investigate the evolution of local skin friction and excess pore water pressure during cyclic loading. After a brief description of the experimental setup and the testing procedure, the tests results are presented concerning the response of the probe during installation, initial monotonic axial loading, cyclic loading up to large numbers of cycles (105 cycles) and post-cyclic monotonic axial loading. During cyclic loading, an initial degradation phase of local skin friction followed by a stabilization phase is observed. Generation of excess pore water pressure occurs during the 60 first cycles followed by a dissipation phase. Parametric study showed that, for initial monotonic loadings, maximum tip resistance and local skin friction are proportional to stress level. Furthermore, excess pore water pressure generated during cyclic loading depends both on initial stress level applied to the clay specimen and cyclic displacement amplitude. A peak value of local skin friction resistance has been observed during post-cyclic monotonic loadings.

Within the scope of an important experimental program of research on piles behaviour, the LCPC (L... more Within the scope of an important experimental program of research on piles behaviour, the LCPC (Laboratoire Central des Ponts & Chaussées, France) carried out static lateral loads on two 915 mm diameter steel tubular piles in order to analyze the load-transfer P-Y curves. Each pile was driven up to 5 m deep into a brown clayey layer of thickness 6.50 m overlying a blue stiff marl. The instrumentation of each pile comprised 12 pairs of strain gauges for the measurement of bending moments along the pile and LVDTs for pile deflections. Process of double differentiation and double integration led to derive lateral soil reaction and pile deflection respectively and therefore to construct P-Y curves along the pile. Lateral reaction modulus as well as ultimate soil reaction were derived and compared to some usual methods in the literature of laterally loaded piles.

Studia Geotechnica et Mechanica, Nov 18, 2022

Static stability of an earth dam can be established by estimating the static safety factor equal ... more Static stability of an earth dam can be established by estimating the static safety factor equal to the ratio of the shear strength to the shear stress along a critical sliding area. In contrast, it is more complicated to evaluate the dynamic stability during an earthquake. The water filling the interstices of the earth dams cannot drain during the short duration of an earthquake. An excess pore water pressure DU develops, and its role is predominant in the destabilisation of the dam. The pore water increase causes a decrease in the soil shear strength. It is, therefore, crucial to evaluate and take into consideration DU in the dam dynamic stability analysis. This research is a contribution to reach this objective. A parametric study was conducted by varying the physical and mechanical soil characteristics constituting the dam, as well as its geometrical values, in order to evaluate their effects on the dynamic safety factor. The dynamic safety factor is calculated using the pseudo-static method, taking into account the excess pore water pressure that develops during cyclic loading into the granular soil of the earth dam upstream face. The results of the parametrical analytical study were also compared to the results of numerical simulations of the dam seismic stability trough pseudostatic method. The numerical simulations were done with three different software: PLAXIS and ABAQUS (based on the finite element method) and GEOSTAB (deals with the problem at the limit equilibrium using the simplified Bishop method). At the end, on one hand, we were able to describe how and at what level of the dam upstream face the sliding occurs, and on the other hand, we were able to underline the adequate combination between the dam geometric parameters and the mechanical soil characteristics which may ensure seismic stability.

MATEC web of conferences, 2018

This paper is aimed to contribute to the analysis of three important aspects of soil-foundation i... more This paper is aimed to contribute to the analysis of three important aspects of soil-foundation interaction, which are not clearly investigated, by means of a detailed parametric study based on a finite elements modelling. The first aspect focuses on the effect of the bedrock proximity on the load-settlement behaviour of a continuous or circular shallow foundation. It was found there exists a threshold distance between the foundation base and the top of the bedrock layer beyond which the foundation behaves as in an infinitely deep medium. The second one deals with the behaviour of shallow foundation on a bi-layered soil where the effect of the underlying layer on the bearing capacity as well as on the settlements depends on the distance between the foundation base and the top of the underlying layer, and beyond a threshold value this effect vanishes. The third aspect studied was the interference between two strip footings installed on saturated clay. It was shown within a threshold distance between these foundations, an important modification of the foundation behaviour may occur. Finally, the numerical results were fitted and interpreted which allowed suggesting simple practical formulae for shallow foundations design.

European Journal of Environmental and Civil Engineering, May 15, 2020

Pile foundations are usually subjected to cyclic loading which could possibly causes a significan... more Pile foundations are usually subjected to cyclic loading which could possibly causes a significant degradation of the friction mobilised along the pile shaft. Most of the experimental studies devoted to analysing the behaviour of the pile-soil interfaces under cyclic loading tests are performed at a few hundred of cycles. However, a large number of cycles of the order of hundreds of thousands may cause a severe degradation of pile capacity. The present work aims to study the effect of cyclic loading parameters on the evolution of shaft friction of pile subjected to a large number of cycles. The experimental study is based on a physical modelling in a calibration chamber of axial cyclic loading of single pile jacked into sand under a large number of cycles, up to 10 5. It is found that cyclic amplitude, confining pressure and soil density have a significant effect on the evolution of skin friction along the pile shaft at a large number of cycles.

HAL (Le Centre pour la Communication Scientifique Directe), 1996

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

CRC Press eBooks, Jun 9, 2021

Revue française de géotechnique, 1996

Effet de la proximité d'un talus sur un pieu court et rigide chargé horizontalement Résumé L'infl... more Effet de la proximité d'un talus sur un pieu court et rigide chargé horizontalement Résumé L'influence de la proximité d'une pente sur le comportement d'un pieu court et rigide chargé horizontalement a été étudiée à l'aide d'essais sur modèles réduits centrifugés. L'étude des déplacements du pieu a montré que l'effet du talus n'est significatif que si le pieu se trouve en deçà d'une distance limite de la tête du talus. On montre qu'il est possible de prévoir le comportement d'un pieu implanté près d'un talus, en effectuant une correction adéquate des courbes P-Y correspondant à un sol horizontal.

Taylor & Francis eBooks, Jul 12, 2006

Geomechanics and Geoengineering, Apr 29, 2020

This paper proposes a new hybrid artificial neural network and mathematical (ANN-MATH) model to i... more This paper proposes a new hybrid artificial neural network and mathematical (ANN-MATH) model to improve the prediction capability of the load-settlement behaviour of shallow foundations in sandy soils. The hybridisation process is performed by replacing the conventional activation function of the ANN output layer by a new mathematical model. Thereafter, 110 full-scale loading tests of shallow foundations, carried out in sand with the cone penetration test (CPT) results, are used to build and validate the proposed model. In terms of accuracy, the proposed model shows a high correlation between the predicted results and the measured data. In addition, the proposed method was compared to the available methods in the literature. It was found that the proposed model is superior to classical and artificial intelligence-based methods by more than 29% and 35%, respectively, in terms of root mean square error (RMSE). Furthermore, a parametric study was undertaken to assess the robustness of the proposed model and to derive the bearing capacity factor based on the CPT test. The bearing capacity factor was found close to those recommended by the French standard NF P 94-261.

The paper presents lateralloading tests Onsingle piles in sand carri.edout on the LCPC centrifuge... more The paper presents lateralloading tests Onsingle piles in sand carri.edout on the LCPC centrifuge.The two models tested and the devices and instru.mentation are described. From the measured bending moments, the P-Y curves are derived and the subgrade reacrion modulus are compared with values from difjerenI methods (Menard, PHRl). The ejJect of a slope on the behaviour of larerally loaded pitt: was studied and results re/ated to ;".ead displacements and bending moments are presenIed.

Paper No. 1.12 Reduced scale model tests in centrifuge have been carried out for measurement of t... more Paper No. 1.12 Reduced scale model tests in centrifuge have been carried out for measurement of the ultimate horizontal load of a pile driven in dense sand. The construction of thL load-transkr P-Y curves has allowed to analyse the rcsrxmsc of the soil to the large displacements of the pi \c. The comparison hctwccn c:xpcrimcntal results and those predicted by the current methods has shown the insufficiency of the theoretical approaches

Journal of Sustainable Architecture and Civil Engineering, Mar 17, 2014

Confining granular materials still a very benefic practice to achieve civil different engineering... more Confining granular materials still a very benefic practice to achieve civil different engineering works. In this paper, the design and analysis of a wall shaped structure made of technical fabric-confined sand will be exposed. This composite structure, made of local materials, where, Polyvinyl Chloride (PVC) technical fabric constitutes a containing envelope and sand a filler material. Designed wall represents a good sustainable development project (idea) to build single story buildings in hot and humid inaccessible areas (Sahara); alternatively, it may provide many other geotechnical applications as retaining walls etc. An experimental campaign to identify the mechanical and physical properties of the studied structure was conducted. Earlier, and not exposed here, a design and analysis of a 1/5 scale model is achieved to evaluate a bearing ability of the wall under vertical compressive and horizontal flexural loads is done. Test to evaluate energy dissipative power of the wall under impact has been also conducted and discussed.

Arabian Journal of Geosciences

Maǧallaẗ al-abḥāṯ al-handasiyyaẗ, Nov 16, 2022

The objective of this article is to present original research work results on the contribution of... more The objective of this article is to present original research work results on the contribution of the standard penetration test (SPT) to the design and analysis of pile foundations on the basis of the interpretation of a database of full-scale pile loading tests undertaken in sandy soils, with the aim to provide practical recommendations to the designers. The article encompasses three parts, the first one presents a detailed comparative study of 10 currently used methods of design on the basis of the SPT, assessed according to their predictive capability of the axial bearing capacity, within a database consisting of 46 axial pile loading tests carried out in 27 sites in the United Arab Emirates. The second part presents some experimental findings related to the critical (or creep) vertical load, whereas the third part highlights the concept of the reference pile settlement and its application to the limit state design of pile foundations.

Influence of the cyclic loading of very large number of cycles on the pile capacity Influence du ... more Influence of the cyclic loading of very large number of cycles on the pile capacity Influence du chargement cyclique à grand nombre de cycles sur la capacité portante des pieux

Geotechnical and Geological Engineering, 2003

ABSTRACT

Canadian Geotechnical Journal, Apr 1, 1995

This paper presents the results of a static lateral loading test, carried out in a centrifuge, on... more This paper presents the results of a static lateral loading test, carried out in a centrifuge, on the reduced model of a single pile, instrumented with strain gauges, installed near a dense sandy slope. The effect of the proximity of the slope on the behaviour of the pile is studied. P–Y lateral reaction curves are constructed, and the variations of the horizontal subgrade modulus are analyzed. A practical method, based on the correction of the horizontal soil P–Y curves, is proposed to study the behaviour of piles near a slope. Key words : horizontal loading, pile, centrifuge, slope, sand, P–Y curve.

Geomechanics and Geoengineering, Aug 6, 2021

ABSTRACT The results of a series of displacement-controlled cyclic axial loading tests of model p... more ABSTRACT The results of a series of displacement-controlled cyclic axial loading tests of model pile in saturated kaolinite clay, carried out in a calibration chamber, are presented. An instrumented pile-probe was used to investigate the evolution of local skin friction and excess pore water pressure during cyclic loading. After a brief description of the experimental setup and the testing procedure, the tests results are presented concerning the response of the probe during installation, initial monotonic axial loading, cyclic loading up to large numbers of cycles (105 cycles) and post-cyclic monotonic axial loading. During cyclic loading, an initial degradation phase of local skin friction followed by a stabilization phase is observed. Generation of excess pore water pressure occurs during the 60 first cycles followed by a dissipation phase. Parametric study showed that, for initial monotonic loadings, maximum tip resistance and local skin friction are proportional to stress level. Furthermore, excess pore water pressure generated during cyclic loading depends both on initial stress level applied to the clay specimen and cyclic displacement amplitude. A peak value of local skin friction resistance has been observed during post-cyclic monotonic loadings.

Within the scope of an important experimental program of research on piles behaviour, the LCPC (L... more Within the scope of an important experimental program of research on piles behaviour, the LCPC (Laboratoire Central des Ponts & Chaussées, France) carried out static lateral loads on two 915 mm diameter steel tubular piles in order to analyze the load-transfer P-Y curves. Each pile was driven up to 5 m deep into a brown clayey layer of thickness 6.50 m overlying a blue stiff marl. The instrumentation of each pile comprised 12 pairs of strain gauges for the measurement of bending moments along the pile and LVDTs for pile deflections. Process of double differentiation and double integration led to derive lateral soil reaction and pile deflection respectively and therefore to construct P-Y curves along the pile. Lateral reaction modulus as well as ultimate soil reaction were derived and compared to some usual methods in the literature of laterally loaded piles.

Studia Geotechnica et Mechanica, Nov 18, 2022

Static stability of an earth dam can be established by estimating the static safety factor equal ... more Static stability of an earth dam can be established by estimating the static safety factor equal to the ratio of the shear strength to the shear stress along a critical sliding area. In contrast, it is more complicated to evaluate the dynamic stability during an earthquake. The water filling the interstices of the earth dams cannot drain during the short duration of an earthquake. An excess pore water pressure DU develops, and its role is predominant in the destabilisation of the dam. The pore water increase causes a decrease in the soil shear strength. It is, therefore, crucial to evaluate and take into consideration DU in the dam dynamic stability analysis. This research is a contribution to reach this objective. A parametric study was conducted by varying the physical and mechanical soil characteristics constituting the dam, as well as its geometrical values, in order to evaluate their effects on the dynamic safety factor. The dynamic safety factor is calculated using the pseudo-static method, taking into account the excess pore water pressure that develops during cyclic loading into the granular soil of the earth dam upstream face. The results of the parametrical analytical study were also compared to the results of numerical simulations of the dam seismic stability trough pseudostatic method. The numerical simulations were done with three different software: PLAXIS and ABAQUS (based on the finite element method) and GEOSTAB (deals with the problem at the limit equilibrium using the simplified Bishop method). At the end, on one hand, we were able to describe how and at what level of the dam upstream face the sliding occurs, and on the other hand, we were able to underline the adequate combination between the dam geometric parameters and the mechanical soil characteristics which may ensure seismic stability.

MATEC web of conferences, 2018

This paper is aimed to contribute to the analysis of three important aspects of soil-foundation i... more This paper is aimed to contribute to the analysis of three important aspects of soil-foundation interaction, which are not clearly investigated, by means of a detailed parametric study based on a finite elements modelling. The first aspect focuses on the effect of the bedrock proximity on the load-settlement behaviour of a continuous or circular shallow foundation. It was found there exists a threshold distance between the foundation base and the top of the bedrock layer beyond which the foundation behaves as in an infinitely deep medium. The second one deals with the behaviour of shallow foundation on a bi-layered soil where the effect of the underlying layer on the bearing capacity as well as on the settlements depends on the distance between the foundation base and the top of the underlying layer, and beyond a threshold value this effect vanishes. The third aspect studied was the interference between two strip footings installed on saturated clay. It was shown within a threshold distance between these foundations, an important modification of the foundation behaviour may occur. Finally, the numerical results were fitted and interpreted which allowed suggesting simple practical formulae for shallow foundations design.

Calcul des Ouvrages géotechniques - Problèmes résolus, 2018

Nombreux sont les livres traitant de l’aspect théorique du calcul des ouvrages géotechniques... more Nombreux sont les livres traitant de l’aspect théorique du calcul des ouvrages géotechniques, mais peu sont ceux présentant des applications pratiques de cet aspect sous forme de problèmes résolus.
Dans cet état des choses, ce livre a pour mission de présenter l’application des méthodes de calcul en se référant dans bon nombre de cas à des exemples issus des projets géotechniques. Il va sans dire que la résolution de tels problèmes est très avantageuse car elle permet d’analyser des "cas d’étude" et d’apprécier la démarche entreprise pour appliquer telle ou telle méthode de calcul.
Ce livre est structuré en trois grandes parties, à savoir : Bases de mécanique des sols, Calcul statique des ouvrages géotechniques, et Calcul dynamique des ouvrages géotechniques.