3-D FEM of laterally loaded short shafts in soil

Jinyuan Liu

Dans les comptes rendus d’articles de la conférence: GeoVancouver 2016: 69th Canadian Geotechnical Conference

Session: INFRASTRUCTURE - 1 Highways & Bridges

ABSTRACT: A non-linear three-dimensional (3-D) finite element method (FEM) is used to investigate the behaviour of laterally loaded shafts. The field tests performed by Helmers (1997) are used to calibrate the modelling method and validate the numerical results. The FEM results agree well with field tests in terms of ultimate load and deflection curves. Two theoretical formulas in estimating lateral capacity of piles are also compared with the FEM results. It is found that cohesionless soils has underestimated the lateral load capacities, and Brinch-accurate estimation. The embedded pile model In summary, 3-D FEM is able to accurately simulate the behaviour of laterally loaded drilled shafts in soil.

RÉSUMÉ: Un programme du méthode des éléments finis (FEM) non linéaire en trois dimensions (3-D) est utilisé pour étudier le comportement des arbres chargés latéralement. L'essai sur le terrain effectué par Helmers (1997) sont utilisées pour étalonner la méthode de modélisation et de valider les résultats numériques. Les résultats FEM concordent bien avec les essais sur le terrain en termes de courbes de charge et de déviation ultimes. Deux formules théoriques pour estimer la capacité latérale de pieux sont également comparés avec les résultats FEM. On constate que la théorie de Broms (1964b) pour les sols cohésifs a sous-estimé les capacités de charge latérale, et la théorie de Brinch-Hansen (1961) fournit une estimation plus précise. Le modèle de pile intégré est capable de modéliser une pile avec une surface "rugueuse". En résumé, FEM tridimensionelle est capable de simuler avec précision le comportement des puits forés chargés latéralement dans le sol. 1 INTRODUCTION The most effective method to mitigate roadway, railway, and industrial noise sources is constructing a noise barrier wall. For noise barrier walls, drilled shafts are the most popular foundation types. Larger diameter short shafts are also used to support other structures such as transmission towers, advertisement posts, overhead catenary systems in railway networks, and water towers. These types of structures are capable of withstanding significant lateral loads and overturning moments. It is important to analyze the load system when a noise barrier wall foundation is designed. The noise wall may be considered to present the low magnitude dead load if the light weight material is used. Normally, the wind load is taken as the main structural load, which is a lateral load on the structure and a consequent lateral load on the foundation. The interaction between the shaft and the soil governs the behavior of shafts subjected to lateral loads. Analysing and designing of a shaft under lateral loading is a complex soil-pile interaction problem (Sun, 1994). In addition, this is a non-linear three-dimensional (3-D) soil-structure interaction problem. There are numerous methods available in the geotechnical literature for designing of foundations subjected to horizontal loads. The design guidelines for the foundations of noise barrier walls are provided in general by the agencies like FHWA (2000). However, the available theories are based on many simplifications, which may lead to improper design of foundations. Therefore, it is essential to analyse the problem using a non-linear 3-D finite element method (FEM). The commercial FEM program, Plaxis 3D, is used to investigate real field studies by analysing various variables involved in the design of laterally loaded shafts. The data Polytechnic Institute and State University, United States is used to analyse the problem. Field load test results and the soil properties from five different sites such as Prices Fork, Salem, Fairfax County, Suffolk, and Roberts Road are used to perform the numerical analysis. Ultimate lateral load capacities are also calculated using the conventional empirical theories proposed by Broms (1981) and Brinch-Hansen (1961). The results obtained from numerical analyses, experimental studies, and conventional theories will be compared to each other. The most appropriate theory can be recommended by comparing with FEM results. 2 CURRENT DESIGN OF NOISE BARRIER WALLS There are many theoretical approaches available to predict the lateral capacity of a deep foundation (Tomlinson & Woodward, 2008). The first theories on the subject of the ultimate load design for horizontally loaded foundations These theories are: > 0, friction = 0)

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