Keywords: Fondation ; Mur de soutenement ; Pieux ; Capacite portante ; Ancrage ; Dimensionnement Reference Record created on 2004-09-07, modified on 2016-08-08

Le procede de Compactage Horizontal Statique, mis en œuvre pour la premiere fois aux Etats-Unis dans les annees 1950 par les ingenieurs d’Hayward Baker Inc (Groupe KELLER), a ete developpe considerablement par la suite, de telle sorte que depuis le debut des annees 1990, il trouve egalement une diffusion croissante en Europe (Warner J 1982 “Compaction grouting-the first thirty years” Gr Geotech Eng , ASCE, 1982: P694–707) Alors qu’a l’origine, les applications du procede etaient limitees a la consolidation sous les fondations d’ouvrages susceptibles de subir des tassements, il en existe maintenant beaucoup d’autres Aujourd’hui, les domaines d’application du Compactage Horizontal Statique sont multiples : amelioration et renforcement de sol pour des ouvrages neufs ou des reprises en sous-œuvre mais egalement pour des traitements de vides karstiques Un exemple de chantier vient illustrer une application de ce procede sous des eoliennes en mettant en evidence les avantages de ce procede dans un contexte geotechnique difficile de zones decomprimees et de vides dans la craie jusqu’a des profondeurs de 20 a 45 m Il a egalement ete associe a un autre procede de renforcement de sol par inclusions rigides pour traiter les sols superficiels La detection et la delimitation des zones d’anomalies par des sondages destructifs avec enregistrements de parametres n’ont pas ete possibles en phase projet et ont ete tres compliquees en phase travaux pour garder un delai d’execution court Le retour d’experience de cette operation montre que dans un tel contexte, il y a lieu de prevoir plusieurs mailles : une maille primaire lâche sur l’ensemble de l’emprise de l’ouvrage de maniere a delimiter grossierement les zones a injecter, et une maille secondaire voire tertiaire en intermaille, pour circonscrire precisement la zone d’anomalies

Foundation analysis and design

Compactage Horizontal Statique : retours d'expérience

The estimation of the structural response of civil engineering structures as they are subjected to different combination of loadings is currently done by the use of numerical models, and its effectiveness depends on how boundary conditions are included into the mod- el. In the case of constructions seated on clay soils, a numerical difficulty resides in how to model the soil-foundation interaction as well as the non linear material behavior of soil. In this work a practical engineering solution is presented in which a set of some simplified foun- dation elements is integrated into the conventional analysis of a building. A simplified numer- ical strategy of four steps is proposed in order to include the soil-foundation interaction into the calculations of a global structure. Regarding to the soil-foundation interaction, two super- elements called "Isolated Foundation Element (IFE)" and "Continuous Foundation Element (CFE)" are numerically formulated, being able to take into account the non linear material behavior of a stratified soil -in particular, long term deformability -, the influence of the soil region in the vicinity of the embedded foundation and their effects in the whole structural sys- tem. Both formulations include different criteria for evaluating soil stress distribution (Bous- sinesq, Westergard, Fhrohlich) as well as the evaluation of the volumetric deformation for a stratified soil (Zeevaert semi-empirical criteria). In order to evaluate the robustness of the proposed strategy, some foundation cases are analyzed in the finite element codes ANSYS and GeoStudio, as well as using the IFE/CFE elements: the comparison of the numerical results shows a good performance of the proposal, with a reduced number of calculations and less complexity.

/pdf/a-simplified-finite-element-formulation-of-shallow-founda-5ba70glfbj.pdf

A simplified finite element formulation of shallow founda- tions for civil engineering structures seated on soft clay soil

Osiadanie i obrót ław i stóp fundamentowych posadowionych na piaskach

The Combined Piled Raft Foundation (CPRF) is a modern concept in which the total load coming from the superstructure is partly shared by the raft through contact with soil and the remaining load is shared by piles through skin friction and/or base capacities. A CPRF system is economical compared to the traditional “piled foundation” design where the pile cap is assumed to be sustained by piles only. A “case study” (Basrah elevated water tank project) is studied thoroughly in this work. The 1365 m 3 elevated water tank located at 3 nearby sites was originally designed as a piled foundation with 25 bored piles for each site (0.7m diameter and 24m length). Theoretical analysis reveals that the piles have an allowable capacity of 2245 kN. On the other hand static pile tests were preformed on 17 piles out of 75 piles and it appeared that the allowable capacity demonstrated erratic values below the expected pile capacity. A re-analysis of the pile raft is performed establishing the CPRF concepts. The case study was modeled by STAAD Pro computer package to determine the loads on both piles and soil with the corresponding settlement values. The reliability aspects of behavior of both “piled foundation” and CPRF are investigated. In this approach the influence of autocorrelati on for the stiffness modulus (of both piles and soil) and raft thickness are considered. The safety of both systems is obtained in terms of traditional factor of safety (FS) and reliability index ( β). The results showed that the “piled foundation” system is “unsafe” for 3 criteria for both FS and β. On the other hand, the CPRF is “safe” for the 4 criteria for FS concept while it is “unsafe” for 3 criteria for β.

/pdf/reliability-based-design-of-pile-raft-foundation-vkvm54307i.pdf

Reliability Based Design of Pile Raft Foundation

In order to get the exact response of the structure under the earthquake loading, it is necessary to include the interaction effect in the analysis. It is a very challenging task to include the interaction effect in the analysis as it is very complex and governed by the many factors including impedance, wave propagation, resonance, damping etc (10). In the present study, the 3-story asymmetrical building supported by pile foundation is considered for the analysis. Dynamic analysis is carried out in time domain by applying a Bhuj (2001,0.31g) ground motion and the response of the superstructure is predicted in the form of displacements and stresses. The elastic half space is considered as supporting local soil which included the horizontal stratification with four soil layers. The parametric study has been carried out for a different stratification order with the Mohr-Coulomb material model. For each analysis case the displacement of the superstructure and piles have been estimated using finite element software. The response is compared with the equivalent homogeneous soil strata which shows the average engineering properties of the stratified soil considered in the present study. It has been observed that the response varies with the stratification sequence and more for the granular soil overlaid on the clay. The response with the equivalent homogenous soil strata is found to be greater that other analysis cases and thus study concluded that the stratification plays an important role in the response of the superstructure.

Foundation analysis and design

Citations

Compactage Horizontal Statique : retours d'expérience

A simplified finite element formulation of shallow founda- tions for civil engineering structures seated on soft clay soil

Osiadanie i obrót ław i stóp fundamentowych posadowionych na piaskach

Reliability Based Design of Pile Raft Foundation

Dssi for pile supported asymetrical buildings in a stratified soil

Related Papers (5)

Soil mechanics in engineering practice

Theoretical Soil Mechanics

Pile Foundation Analysis and Design

Principles of Foundation Engineering

Analysis of Ultimate Loads of Shallow Foundations