Bored Pile Capacity by Direct SPT Methods Applied to 40 Case Histories

In these last decades, the in situ tests have known considerable progress caused by the technological development reported in this area, their earlier use were in the foundation design. These technical improvements have permitted more real knowledge of the soils characteristics and/or behavior in different depths.  They became good tools for a geotechnical engineer. Recently, the use of bored piles is multiply around the world because of their moderate bearing capacity suitable in many projects, relatively low cost, easy length adjustments, low vibration, and noise levels during the installation.  An attempt is done in this paper to formulate and calibrated a new method based on the N-value from SPT. Data averaging, failure zone extension, and plunging failure of piles has been noticed in the proposed approach. A data base were collected and analyzed, including 40 full scale static pile load tests through a variety of grounds and stratigraphy around the world. The soil profiles range from soft to stiff clay, medium to dense sand, and mixtures of clay, silt, and sand. The pile embedment lengths range from 2 to 57 m and the pile diameters from 100 to 1220 mm. A performance analysis of the new SPT method is carried out with other prediction methods by using different criteria. The proposed method is suitable tool to practical design of bored piles, due to their consistent results

Study of the mechanical behavior of dune sand treated by hydraulic binders: application in the road geotechnical field

The purpose of this work consists of valorizing a local sand dune which is found in abundance in the region of Djelfa (Algeria); for use in pavement foundations. For this investigation a method of formulation has been proposed, which based on the stabilization of this material using a mixture of two hydraulic binders. Various mixtures were subjected to classification tests, tests grain size distributions, tests of compaction with modified Proctor, shear strength, tests of bearing pressure (CBR unsoaked and soaked), compressive strength and tensile strength. The results obtained have shown that some mixtures are of high mechanical characteristics and could be then used in road foundations. &nbsp

Experimental Characterization of the Hydromechanical Properties of the Gypsum Soil of Sebkha of Oran

This paper deals with hydro-mechanical investigation of salinegypsum soil properties from Sebkha of Oran in respect withtheir impact on the feasibility of the project of the second runwayof the Es-Sénia airport in Oran (Algeria). The geologicaland in-situ geotechnical studies prior to the construction phaseof the airport runway revealed underground cavities supposedto be created from salts and gypsum dissolution in the Sebkhasoil. Standard laboratory experiments are used to determinepermeability coefficient, isotherm curve, shear resistance andelastic parameters of two soils. These ones are affected by thevariation of water table level that varies according to the dryperiod (summer) or the rainy period (winter), creating cyclichydric conditions. The paper presents a comparison of parametersof these two soils in saturated and partially saturatedconditions. The results of tests performed in laboratory arecompared with those performed in situ in order to check theirrepresentativeness before a detailed comparison of the effect ofwater conditions. The two soils have similar behavior highlysensible to water with some particularities

Valorization of dune sand of Djelfa (Algeria) treated by hydraulic binders in pavement foundations

The purpose of this work is the study and the valorization of sand dune which is found in abundance in the region of Djelfa (Algeria); for use in pavement foundations. For this investigation a method of formulation has been proposed, which based on the stabilization of this local material using a mixture of two hydraulic binders. Various mixtures were subjected to classification tests, tests grain size distributions, tests of compaction with modified Proctor, shear strength, tests of bearing pressure (CBR unsoaked and soaked), compressive strength and tensile strength. The results obtained have shown that some mixtures are of high mechanical characteristics and could be then used in road foundations

Transverse Vibration Analysis of Uniform Beams under Various Ends Restraints

AbstractThe beam analysis, based on the assumptions of the Bernoulli-Euler theory, in free vibration has been largely investigated. Many researches focused on the transverse vibrations study, under the application of different boundary constraints where different theories were applied. The considered stiffness and mass matrices are those obtained by assembling the elementary ones resulting from the FEM use The Jacobi method allowed the solution of the eigenvalue problem. These well known concepts were applied to the study of beams with constant geometrical and mechanical characteristics having one to two overhangs with variable lengths. Murphy studied, by an algebraic solving approach, a simply supported beam with two overhangs of arbitrary length, which allows an experimental determination of the E elastic modulus.The advantage of our paper offers a possibility of extending this approach to many interesting problems formed by beams vibrating transversally with various ends restraints

Prediction of axial capacity of piles driven in non-cohesive soils based on neural networks approach

This paper presents an application of two advanced approaches, Artificial Neural Networks (ANN) and Princi­pal Component Analysis (PCA) in predicting the axial pile capacity. The combination of these two approaches allowed the development of an ANN model that provides more accurate axial capacity predictions. The model makes use of Back-Propagation Multi-Layer Perceptron (BPMLP) with Bayesian Regularization (BR), and it is established through the incorporation of approximately 415 data sets obtained from data published in the literature for a wide range of un-cemented soils and pile configurations. The compiled database includes, respectively 247 and 168 loading tests on large-and low-displacement driven piles. The contributions of the soil above and below pile toe to the pile base resistance are pre-evaluated using separate finite element (FE) analyses. The assessment of the predictive performance of the new method against a number of traditional SPT-based approaches indicates that the developed model has attractive capabili­ties and advantages that render it a promising tool. To facilitate its use, the developed model is translated into simple design equations based on statistical approaches

Modélisation numérique du problème du surcarottage : influence de la loi de comportement de la roche

Not availableLa connaissance de l'état de contrainte in situ est indispensable dans les applications rencontrées en mécanique des roches. Plusieurs techniques d'estimation des contraintes in situ ont été élaborées. Parmi ces méthodes, nous nous sommes intéressés en particulier à l'essai de surcarottage. Si le modèle de comportement de la roche est irréversible, l'interprétation de l'essai de surcarottage est délicate. Les relations contraintes-déformations ne sont plus linéaires et dépendent notamment de l'état initial en contraintes et de la totalité du chargement mécanique subi par le matériau. L’analyse exposée dans ce mémoire est consacrée au problème direct. Le but de l'approche est de déterminer les facteurs essentiels au niveau de la rhéologie et de l'état initial de contrainte, influant sur le comportement de la roche lors du surcarottage. Une étude paramétrique a été menée en simulant numériquement la procédure du surcarottage à l'aide du code de calculs aux éléments finis CESAR-LCPC. Plusieurs modélisations sont utilisées : modélisation bidimensionnelle en déformation plane, modélisations axisymétrique et tridimensionnelle prenant en compte l'avancement du carottier. L’analyse bidimensionnelle du problème du surcarottage en terrain élastoplastique montre que la totalité de l'histoire du chargement mécanique subi par le matériau doit être prise en compte et que l'influence de la rhéologie est fortement liée à l'état initial de contrainte. Il a été mis en évidence l'influence des contraintes initiales sur l'apparition des zones plastiques et leurs extensions. Nous avons montré que, la simulation numérique utilisant un modèle élastoplastique peut expliquer certains résultats observés in situ : évolution non monotone de déformation lors du surcarottage, fortes chutes de déformations. L’étude tridimensionnelle a également mis en évidence les effets couples des directions d'anisotropie et de contrainte et de l'intensité de la contrainte déviatorique sur les déformations