Djillali Amar Bouzid
Bio: Djillali Amar Bouzid is an academic researcher from University of Blida. The author has contributed to research in topics: Slope stability & Finite element method. The author has an hindex of 1, co-authored 4 publications receiving 11 citations.
TL;DR: In this paper, a new p-y formulation of the Winkler model for large-diameter monopiles was proposed, driven by the need to enhance the performances of the model when dealing with large-scale monopiles.
Abstract: Driven by the need to enhance the performances of the Winkler model when dealing with large-diameter monopiles, the primary objective of this paper is to propose a new p-y formulation that...
TL;DR: In this paper, the authors proposed solutions for stiffness estimation of double-D shaped caisson foundations embedded in three different types of ground profiles (stiffness variation along the depth): homogeneous, linear and parabolic).
Abstract: This article proposes solutions for stiffness estimation of Double-D shaped caisson foundations embedded in three different types of ground profiles (stiffness variation along the depth: homogeneous, linear and parabolic). The approach is based on three dimensional finite element analyses and is in line with the methodology adopted in Eurocode 8-Part 5 (2004)- lumped spring approach. The method of extraction of various stiffness values from the finite element model is described and followed by obtaining the closed form solutions. Parametric study revealed the nominal effect of embedment length of Double-D caisson and hence only the width and diameter effects are included in the suggested formulations. The obtained closed form solutions are presented in terms of multiplication factors for Double-D caissons. Final stiffness terms for a given width and diameter of a Double-D caisson can be conveniently estimated by multiplying the proposed formulations to the circular shaft solutions available in literature. Applicability of the proposed formulations is demonstrated by considering a typical bridge pier supported by Double-D caissons. The proposed formulations requires minimum amount of input parameters and can be used during the tender design to arrive at the required geometry of such foundations.
TL;DR: In this paper, the assessment of slope stability factor by a FE analysis using the shear strength reduction method (SRM) enjoys several advantages and owns many shortcomings, and a new FE approach is proposed.
Abstract: The assessment of slope stability factor by a FE analysis using the shear strength reduction method (SRM) enjoys several advantages and owns many shortcomings. As an alternative, a new FE approach ...
TL;DR: In this article, a nonlinear analysis method for laterally loaded large-diameter monopiles is presented, which accounts for the effects of pile diameter and soil deformation on the modulus of horizontal subgrade reaction.
Abstract: This paper presents a nonlinear analysis method for laterally loaded large-diameter monopiles. The method accounts for the effects of pile diameter and soil deformation on the modulus of horizontal subgrade reaction by considering a modified modulus of horizontal subgrade reaction. The solution considers the force and moment equilibrium of soil-pile system to calculate the response of the monopile to lateral loads. The influence of the soil side friction reaction on the ultimate horizontal resistance is evaluated considering the degradation of modulus of horizontal subgrade reaction due to large pile displacement. The predictions of the developed method compared favorably with the results obtained from full-scale field tests, centrifuge model tests and laboratory model tests as well as existing analytical methods. The developed analytical method is then applied to study the rigid rotation behaviour of offshore monopiles. The results demonstrated that under lateral loading at the pile head, the depth for rigid rotation point lies within 0.62L–0.73L (L is pile length), and the depth of the rotation point increases as the pile diameter increases. It was also found that the load eccentricity has a significant effect on the depth of the rotation point.
TL;DR: A new design method was presented, based on a hybrid pile-soil interaction concept, which allows the stability of the new hybrid monopiles under lateral load to be assessed in a better way and can be useful for designers and other researchers to enhance the design of offshore wind turbines on monopiles.
Abstract: First, a review of knowledge developed over the previous 50 years was presented, including various simplified methods of analyzing hybrid foundations. To discuss this subject comprehensively, a reference to calculations of piles was also made. On this basis, the author focused in the paper on new aspects of designing the hybrid foundations in serviceability limit states. The know-how review showed that the aspects of hybrid foundation design have been poorly recognized so far. For practical reasons, a simple calculation method for the hybrid foundations, useful for initial decision making, is still needed. A new design method was presented, based on a hybrid pile-soil interaction concept. A general design concept was described, the assumptions were formulated, and the method was explained in detail. A practical application of this method has been demonstrated for a large diameter hybrid pile, previously tested at full scale under lateral load. The calculation results were compared with the well-verified data obtained from the field test. By incorporating the extended knowledge on the mechanism of the pile-soil interaction, a significantly reduced horizontal stress in front of the pile was achieved. The conducted calculations confirmed that the hybrid monopile displacement is 40–70% lower compared to the standard monopile with similar dimensions. This method allows the stability of the new hybrid monopiles under lateral load to be assessed in a better way. The gained experiences can be useful for designers and other researchers to enhance the design of offshore wind turbines on monopiles.
TL;DR: In this paper, a numerical frame for analysis of lateral loaded pile was discussed and then verified on the basis of the field data from Dafeng Offshore Wind Farm in Jiangsu Province, the local scour characteristics of large diameter monopile were concluded.
Abstract: The displacement of monopile supporting offshore wind turbines needs to be strictly controlled, and the influence of local scour can not be ignored. Using p–y curves to simulate the pile–soil interaction and the finite difference method to calculate iteratively, a numerical frame for analysis of lateral loaded pile was discussed and then verified. On the basis of the field data from Dafeng Offshore Wind Farm in Jiangsu Province, the local scour characteristics of large diameter monopile were concluded, and a new method of considering scour effect applicable to large diameter monopile was put forward. The results show that, for scour of large diameter monopiles, there was no obvious scour pit, but local erosion and deposition. Under the test conditions, the displacement errors between the proposed and traditional method were 46.4%. By the proposed method, the p–y curves of monopile considering the scour effect were obtained through ABAQUS, and the deformation of large diameter monopile under scour was analyzed by the proposed frame. The results show that, with the increase of scour depth, the horizontal displacement of the pile head increases nonlinearly, the depth of rotation point moves downward, and both of the changes are related to the load level. Under the test conditions, the horizontal displacement of the pile head after scour could reach 1.4~3.6 times of that before scour. Finally, for different pile parameters, the pile head displacement was compared, and further, the susceptibility to scour was quantified by a proposed concept of scour sensitivity. The analysis indicates that increasing pile length is a more reasonable way than pile diameter and wall thickness to limit the scour effect on the displacement of large diameter pile.
TL;DR: In this paper , a review traces the development history and key findings of viscoelastic soil-pile interaction theory and expounds on the advantages and limitations of various theoretical advances in terms of dynamic design and wave propagation modeling.
Abstract: The dynamic viscoelastic theory of soil–pile interaction dominates the initial impedance calculation during the pile dynamic design and analysis. Further, it provides a firm theoretical ground for the wave propagation simulation, which could be the basis of seismic analysis and some geotechnical testing approaches. This review traces the development history and key findings of viscoelastic soil–pile interaction theory and expounds on the advantages and limitations of various theoretical advances in terms of dynamic design and wave propagation modeling. The review consists of three sub-divisions, which are the longitudinal, horizontal, and torsional viscoelastic soil-pile theories. The development and implement of multi-phase soil constitutive equations, multi-dimensional soil–pile interaction modeling methods, pile–soil–pile mutual interactions in pile groups, and the fluid–structure interaction problems in offshore piles are especially remarked and concluded. Finally, the shortcomings and deficiencies of the present development are pointed out with a view to addressing them in the future.
TL;DR: In this article, the post-driving residual stresses acting on the pile could be large when being driven, and the authors proposed a solution to deal with the residual stresses on the stack.
Abstract: Driven Steel H-piles are commonly used in the deep foundation of being cost-effective and easy in workmanship. The post-driving residual stresses acting on the pile could be large when being driven...