Eurocode 7 design
The Eurocode 7 Norm does not include a specific section for the landfill design and therefore the case of the landfill has to be “assimilated” to section 11 and 12 “Overall stability and Embankments”.
This European Norm (EN 1997-1) takes into account 3 steps for the determination of the parameters to use in the slope stability analysis.
- Derived values: geotechnical parameters are derived from in-situ measurements f ex mechanical resistance of the waste
- Characteristic values: involves cautious estimating of geotechnical parameters (mean values, lowest values, statistical values etc.)
- Design values: application of partial factors to the characteristic values
Contrary to the classical analysis, this approach uses partial factors of safety to be applied at the level of the geotechnical parameters or of the actions. The output of the analysis is a factor of safety that must be greater or equal to 1 to guaranty the stability of the slope. Two limit-state cases must be verified:
- SLS (serviceability limit state)
- ULS (ultimate limit state)
The ULS has to be verified (using Design values) if there is an expectancy that the peak design loads applied to an object could cause serious harm or the collapse of that object/surrounding infrastructure.
The Serviceability Limit State (SLS) has to be verified when the deformation of the object won’t cause a serviceability limit state (read “harm and damage”) in structures and infrastructure on or near the deforming object. This verification is less restrictive than the ULS since it uses Characteristic values
The Norm proposes different design approaches based on the combination of partial factors of safety (see figure above). Each European Country choses its DA (Design Approach). Belgium has chosen DA1. The DA1 is further grouped in Combination 1 and 2 (C1 and C2). Basically in C1 the partial factors of safety are assigned to the properties of the material. In C2 the partial factors of safety are assigned to the actions. The designer has to choose which combination to use.