Project Description
All over the construction area from –10m to –30m a soft clay layer is subject to consolidation phenomenon when over loaded resulting in potential drag down forces on piled foundations systems, and post construction settlements on surface foundation areas.
The soft clay characteristics lead to estimated settlements up to 3 m under the project final loads and an estimated stabilization time of 20 years
Menard designed the drain spacing and surcharge characteristics for each construction zone taking into account the following parameters:
- Time allowed for soil improvement
- Final load and foundation type
- Thickness of clay layer
The design is based on Pre-consolidation of the soft clay using vertical drains and fill surcharge up to stress higher than final loads.
This pre-consolidation can be designed to allow surface foundations for most of the structures and a large reduction of the negative skin friction on the piles to be installed under the heaviest structures of the power plant.
Menard has installed the appropriate instrumentation consisting of:
- 150 surface settlement plates,
- 30 pore pressure sensors,
- 10 inclinometers and extensometers
and performed monitoring in order to check fill stability during its construction and to determine loading time required to meet the soil improvement targets.