Introduction

The Eurocode Programme includes a series of European Standards that establish common unified design methods for building and civil engineering works across Europe. There are ten standards in the Eurocodes to cover different design and construction sectors of the civil and building industries. The Eurocodes are based on limit state principles, in which a distinction is made between ultimate and serviceability limit states. Ultimate limit states (ULS) are concerned with the safety of people and the structure, such as loss of equilibrium (EQU), loss of stability (STR), etc. Serviceability limit states (SLS) are concerned with the functioning of the structure under normal use, the comfort of people, and the appearance of the construction works [1].

Eurocode 7 is the document that concerns geotechnical engineering design across Europe (BSI, 2004). Full implementation of the Eurocode 7 Standard has been adopted across Europe since 2010. Eurocode 7 reflects a significant change in design philosophy from traditional geotechnical design practice. In contrast to the traditional single, lumped factor of safety, the Eurocode 7 accounts for, with partial factors of safety, different uncertainties in different components of the problem, for example, different partial factors of safety are applied to characteristic values of the loads, soil strength parameters, etc. to get design values of these parameters. The analysis will be performed based on these design values. The factor of safety obtained with these design values is an overall factor of safety, if this factor of safety is greater or equal to 1.0, then we can say it is safe against failure.

Using Eurocode 7 in PLAXIS 2D / 3D LE

The Eurocode 7 standard is implemented as a feature in both our 2D and 3D versions of PLAXIS LE. Note that this feature does not affect any previous analyses performed using the traditional calculation of factor of safety. The traditional calculation of the factor of safety in the software is still supported. 

In PLAXIS 2D/3D LE, Eurocode 7’s three design approaches and British Standard BS 8006-1:2010 are implemented: Design Approach 1, Design Approach 2, Design Approach 3 and BS 8006-1:2010 Section 7. For Design Approach 1, two combinations are available. Furthermore, PLAXIS LE also enables the user to define their own partial factors set. The choice of different design approaches reflects the Europe-wide adoption of the Standard and offers designers in different nations an approach most relevant to their nations.

To apply a Eurocode 7 approach in PLAXIS LE, open the Model > Settings dialogue, and select the Design Standard tab, then select the Design Standard you would like to apply. The default Design Standard selection is None. The following pre-defined options are available:

• Eurocode 7, Design Approach 1, Combination 1
• Eurocode 7, Design Approach 1, Combination 2
• Eurocode 7, Design Approach 2
• Eurocode 7, Design Approach 3
• BS 8006-1:2010 Section 7 - Reinforced Slopes

Figure 1: Set Eurocode 7 Design Standards.

After the user selects the pre-defined design approach, the corresponding partial factors will be shown on the same page. The user cannot edit the partial factor values for the pre-defined standards. If the user wants to define their own partial factors, select User Defined option, then the user can edit the values on the Partial Factor column.

After the user selects a design approach, the user may need to set Load Action as Permanent or Variable if there are external loads in their model. For 2D models, it is shown as in Figure 2 for Distributed Load. For 3D models, it is shown in Figure 3 for Point Loads.

Figure 2: Set Load Action for 2D Distributed Load with a Eurocode 7 design approach selected.

Figure 3: Set Load Action for 3D Point Load with a Eurocode 7 design approach selected.

Figure 4: The user can view the selected Eurocode 7 design approach's partial factors under Model > View Information.

References

1. Bond, A. J. and Harris, A. J., 2008. Decoding Eurocode 7, Taylor & Francis.
2. British Standards Institution, 2004. Eurocode 7: Geotechnical design-Part 1: General rules, BS EN 1997-1, London, UK.
3. British Standards Institution, 2010. BS 8006-1:2010 Code of practice for strengthened/reinforced soils and other fills.
4. Smith, 2006. Smith's Elements of Soil Mechanics, 8th Edition, Blackwell Publishing.