Residential development in Valdelacasa

Situation

The development of the Valdelacasa residential area in Alcobendas (Madrid), Spain, involved the construction of a bridge over a nearby river. The approach ramp to the bridge had to be founded on one side of the river over a 3 m thick layer of clay with low bearing capacity. Sand lies beneath the clay layer. The embankment has a height of 5 m, a base width of 32 m and a slope gradient of 33.7°.

Solution

After evaluating various solutions, it was decided to install geogrids with a tensile strength of 150 kN/m in the longitudinal direction. During installation in August 2007, the geosynthetic sheets were laid at right angles to the dam axis. The design lateral overlap of the individual sheets was 25 cm. Before backfilling the dam, the correct laying of the sheets was checked to prevent creasing in the material.

Advantages

The solution increases the stability of the embankment structure whilst also facilitating construction progress. As the reinforcement sheets could be laid directly onto the soft subgrade, there was no need for excavation and disposal of the existing soil – with a positive impact on the environmental footprint of this construction project.