IntroductionThe design of retaining walls in day-to-day practice is currently based on different calculation methods. If classical methods considering specific modes of failure, the elastic line and the equivalent beam are still employed for certain types of walls, it is mainly the subgrade reaction and the numerical methods which are most frequently adopted. The subgrade reaction method or spring method is rather well mastered and uncertainties mainly rely in the choice of the coefficient of subgrade reaction [1], [2]. The numerical methods have the advantage of taking into account more accurately the soil behavior, the soil-wall interface and also the ability to consider multiple hydraulic conditions and various options for modeling support conditions. However, the results obtained by these methods still require to be validated by engineer judgment or others experimental results (physical model in centrifuge for example) or measured in-situ. The main objectives of this study were to define the influence factors of the commonly used design methods and the resulting uncertainties encountered by the practitioners. This paper focuses on numerical modeling and analysis the behavior of a free standing diaphragm wall, made of reinforced concrete, embedded in sand, by the subgrade reaction method using the K-Rea software and by the numerical method based on finite elements with Plaxis 2D-v8.5 software. For both methods, different simulations have been performed with non-loaded supported soil. For the first method, we are interested in analyzing the influence of the main factors affecting soil movement and instability of the retaining wall. These factors mainly concern the wall rigidity, the construction sequence and mechanical parameters of the soil. One key step of this method is the difficulty in evaluating the coefficient of subgrade reaction Kh on a rational basis. Concerning the finite element method, the soil is homogeneous and dry; its behavior is described by linear elastic perfectly plastic model Mohr-Coulomb (MC) and nonlinear hardening soil model (HSM). The diaphragm wall is modeled by "beam" elements. The simulations were performed with different mesh sizes and reduction factors of the soil-wall interface. For both methods, the analyses are focuses on wall deformation,
Abstract. It is obvious that for geotechnical knowledge of soil properties namely, suction-water content and water content hydraulic-conductivity relationship is essential to solve the problems associated with flow in unsaturated soils. The best way to evaluate these properties is to make direct measurements. However, the hydraulic-conductivity water content and suction-conductivity relationship are complex and it is often very difficult to measure for practical reasons, economic and spatial variability. Indeed, the used equipment is expensive and the tests are slow. Of more over the spatial variability of this property that makes the steps number necessary to characterize a site is relatively large. Furthermore, when this relationship is determined, usually it has only limited information and it is always desirable to extrapolate the experimental curve. Facing these difficulties, this given research targets computer tool to assess this relationship from other measurable parameters. In this paper, we used the software "flow line temperature" to achieve numerical and graphical simulations of the water flow in a soil initially unsaturated non-deformable modeling the evolution of the water content and suction in function of depth. The use of this software allowed us to make comparison with the experimental results [18] as well as a qualitative assessment of the drought penetrating in an unsaturated soil.
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