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publicatie: Design Guideline Basal Reinforced Piled Embankments
Chapter 1 Introduction
Chapter 1 Introduction
Worldwide, more and more basal reinforced piled embankments are being constructed for transport infrastructure. A basal reinforced piled embankment (Fig.1.1, Fig.1.2) consists of a reinforced embankment on a pile foundation. The reinforcement consists of one or more horizontal layers of geosynthetic reinforcement (GR) installed at the base of the embankment. In use, these structures exhibit little or no residual settlement.
The force transfer in the reinforced embankment is determined by arching. This is the phenomenon where loads are transferred preferentially to the stiffer elements in the ground, in this case the piles.
The pile caps are preferably positioned with their tops above the groundwater level.
All possible pile systems may be used for piled embankments, providing that the difference in stiffness between the piles and the surrounding soil is sufficiently great; see Table 4.2, boundary condition 8. Important points in the structural design are the calculation of the piles’ bearing capacity, for which the regulations in force for the design of piles are used, and the dimensioning calculation for the geosynthetic reinforcement itself.
The design process for a basal reinforced piled embankment proceeds as indicated in Table 1.1. The steps 1 to 3 may be seen as the preliminary design. In these steps, the pile arrangement including pile type and GR strength are determined. Step 4 may be seen as the final design, in which additional calculations are done to determine for example bending moments in the piles, with the help of numerical calculations.
The following are considered in this publication:
- requirements for the reinforced embankment;
- requirements for the piles and pile caps and recommendations for pile and pile cap design;
- design of the reinforced embankment, including calculation examples;
- evaluation of pile moments with numerical calculations (finite element method, FEM);
- transition zones;
- construction and maintenance of the piled embankment.
|2||Calculation of the bearing capacity of the piles||
|3||Design of the reinforced embankment||
|4||Checking the settlement and stability||
This 2016 publication update has been brought into conformity with the requirements of the European Eurocode. Table 1.2 gives an overview of the Eurocodes applied.
|NEN-EN 1990+A1+A1/ C2:2011 ||National annex to NEN-EN 1990+A1+A1/C2: Eurocode: Basis of structural design|
|NEN-EN 1991-1-4+A1+C2:2011 ||National annex to NEN-EN 1991-1-4: Eurocode 1: Loads on structures|
|NEN-EN 1992-1-1+C2:2011/NB:2011 ||National annex to NEN-EN 1992-1-1+C2 Eurocode 2: Design of concrete structures - Part 1-1: General rules and rules for buildings|
|NEN 9997-1+C1:2012 ||Geotechnical design of structures - Part 1: General rules|
|NEN-EN-ISO 22477-1:2006 ||Geotechnical investigation and testing - Testing of geotechnical structures - Part 1: Pile load tests by static axial compression|
* as valid and in force on date of this 2016 edition of this publication
The European standards mainly concern the structural design of buildings. The requirements specified in them do not always apply to other civil engineering structures, such as embankments, bridges and viaducts.