Slope Design with Eurocode 7
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Slope Design with Eurocode 7
Eurocode 7 is a design document that establishes rules and standards for
geotechnical engineering design across Europe (BSI, 2004). Eurocode 7
represents a major change in design philosophy. Traditionally a single,
lumped factor of safety accounts for all of the uncertainties in the
problem. With Eurocode 7, partial factors of safety are applied to different
components of the analysis. The partial factors are applied prior to the
analysis to give design values that are used in the calculation. The final
result is an over-design factor, which must be greater than 1 to ensure
the serviceability limit state requirement is satisfied. For more
information on using Eurocode 7 in geotechnical design, see Smith (2006)
and Bond and Harris (2008).
This tutorial describes how to design a slope to Eurocode 7 specifications
using RocPlane. The focus will be on how different design combinations
are applied in the computation and what they mean.
Topics Covered

Example for Design Approach 1, Combination 2

Example for Design Approach 2

Single Source Principle
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Slope Design with Eurocode 7
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Model
Start the RocPlane program. Once the program is open, maximize the
view if it is not already maximized.
Project Settings
Open the Project Settings dialog from the Analysis menu or the
toolbar.
Select: Analysis  Project Settings
Under the General tab, set the Units to Metric, stress as MPa.
Go to the Design Standard tab. You’ll see that the current “Design
Standard” is “None.” We’ll leave this setting as is, and come back later to
assign different design standards.
Click on “View Partial Factors.” With no design standard applied, you
should see that all partial factors are set to a default of 1, which means
all values used in the calculation are the exact input values.
Click “Cancel” to exit the Partial Factors dialog.
Click “OK” in the Project Settings dialog to finalize the settings.
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Input Data
Let’s use the default model for this example. The default model has a
factor of safety of 1.0.
Let’s add a bolt, using the Bolt Dialog.
Select: Support  Add Bolt
Click on the wedge and the Bolt Properties dialog will appear. Enter the
following bolt specifications:
Select “OK”.
The factor of safety is now 1.05.
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Design Approach 1, Combination 2
Without changing the current input data, let’s go back to the Project
Settings dialog to apply a design standard.
Under the Design Standard tab, select “Eurocode 7 – Design Approach
1, Combination 2” for the Design Standard.
Let’s view the Partial Factors for this Design Standard.
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Applying this set of partial factors means to enlarge unfavorable variable
actions while to ignore favorable variable actions, and to reduce the shear
strength parameters. If bolts are present, then their capacity or the
resistance they provide to stabilize the slope is also reduced.
Click “OK” in the Partial Factors dialog. Click “OK” in the Project
Settings dialog.
The wedge should now have a factor of safety of 0.8368. Notice the
sidebar listing of Strength and Bolt Force information.
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Equivalent Model
We can reproduce the results from Design Standard Approach 1,
Combination 2, without having to use the Design Standard.
Let’s first turn off the Design Standard. Go to the Project Settings
dialog, and under the Design Standard tab, change the “Design
Standard” to “None.” The Factor of Safety has gone back to 1.05.
To simulate the design approach, we need to apply a factor to the
following parameters:
1. Increase variable unfavorable actions by a factor of 1.3 – we do
not need to do anything because there are no external variable
loads.
2. Reduce the effective cohesion and the friction angle (tan(φ)) by a
factor of 1.25. Go to the Input Data dialog, and in the Strength
tab, change Phi(degrees) to 29.256.
Reduced Phi:
Tan-1(Tan(35°)/1.25) = 29.256°
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Click “OK” to close the Input Data Dialog.
3. Reduce the Tensile Capacity of all bolts.
Select: Support  Edit Bolt
Select the bolt and the Bolt Properties dialog will appear. Change
the Capacity to 0.9091 MN (1MN/1.1=0.9091MN)
The Factor of Safety should now be 0.8368, which is exactly the
same as that for Design Approach 1, Combination 2.
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Design Approach 2
We will use the same geometry but remove the bolt.
Select: Support  Delete Bolt
Click on the bolt to delete it.
Set the friction angles back to 35°, and check to make sure that the
Design Standard is still set to None.
We will now add an external force to the model.
Select: Analysis  Input Data
Go to the Forces tab and enter the following data:
Select “OK.”
The Factor of Safety should have decreased to 0.8709. The direction of
the applied load decreases the stability of the wedge.
Let’s now go to the Project Settings dialog. Under the Design
Standard tab, set the Design Standard to “Eurocode - Design
Approach 2.”
Click “View Partial Factors…,” and you should see the following dialog.
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For this design standard, a partial factor is applied to the driving force of
the slope weight (permanent unfavorable action), any unfavorable
external force that is set to be “variable”, the joint shear strength, and the
tensile capacity of any bolts.
Click “OK” in the Partial Factors dialog, and then also click “OK” in the
Project Settings dialog.
The Factor of Safety is now 0.7846. Notice the sidebar listing of External
Forces information:
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Equivalent Model
We will construct a model to replicate the partial factors are applied in
“Eurocode 7 - Design Approach 2.”
Change the Design Standard to “None.” The Factor of Safety should
revert to 0.8709.
To simulate the design approach, we need to apply changes to the
following parameters:
1. Under the Geometry tab in the Input Data dialog, multiply
the Rock Unit Weight by 1.35, to get 0.03645 MN/m3. This
has the same effect as applying a factor of 1.35 to any
permanent unfavorable actions, which in this case is the
driving force due to the slope weight. However, remember
that the weight has both a favorable and unfavorable action
component (stabilizing and driving). We have to adhere to the
“Single Source Principle” and apply only 1 factor to any
actions that come from the same source. Click “Apply” and the
factor of safety changes to 0.8923.
2. Under the Strength tab in the Input Data dialog, we need
to reduce the overall joint shear strength by a factor of 1.1.
This is the equivalent to reducing the Earth Resistance by a
factor of 1.1.
Base Joints Friction Angle:
Tan-1(Tan(35°)/1.1) = 32.48°
Keep in mind that this is different than reducing individual
shear strength parameters. If cohesion is present, then a
factor of 1.1 is applied to the overall shear strength:
Factored Shear Strength =
(Normal Force x Tan(φ) + cohesion)/1.1
Click “OK” in the Input Data dialog. The Factor of Safety
should now be 0.8112.
3. We need to multiply the value of the external force by 1.5, to
get 30MN. We do this because the external force is an
Unfavourable Action, and is considered to be Variable.
The Factor of Safety is now 0.7846, the same as for “Eurocode – Design
Approach 2.”
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References
Bond, A. J. and Harris, A. J., 2008. Decoding Eurocode 7, Taylor &
Francis.
British Standards Institution, 2004. Eurocode 7: Geotechnical design –
Part 1: General rules, BS EN 1997-1, London, UK.
Smith, 2006. Smith’s Elements of Soil Mechanics, 8th Edition, Blackwell
Publishing.
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