As before, this example uses Bishop's Simplified Method and highlights the issues of using software for a Eurocode 7 design. It also demonstrates the requirement for a bearing capacity check for embankments on soft clays.

The box below summarizes the analyses undertaken for this worked example.

Notes on Example 9.5

O The calculated factor of safety in the undrained case for DA1-1 is satisfactory as the calculated factor of safety is greater than the target factor.

© As for other slope stability examples, even in the short term DA1-2 gives a lower factor of safety than DA1-1 and is therefore the governing case. This example implies that the design does not meet the requirements of Eurocode 7.

© For DA2 the same factor of safety as for DA1-1 is calculated.

© The utilization factors for DA1-1 and DA2 are different, since for DA2 a target factor of safety of 1.1 is required. Thus DA2 would indicate that the design does not meet the requirements of Eurocode 7.

© The degree of utilization for the long-term case is less than for the short-term, which is as would be expected for an embankment on soft clay.

Eurocode 7 requires that embankments on soft clays are checked for bearing capacity. As for the stability analysis above, the undrained (short-term)

situation should be the most critical. The thickness of the soft clay is relatively small and therefore a full bearing failure surface cannot develop.

For a simple verification of bearing resistance, an equivalent strip footing 15m wide due to an embankment 3.5m high will be considered with a 10kPa surcharge. A modified bearing capacity formula12 developed for a shallow depth of soft clay overlying stiffer strata will be used:

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