When constructing embankments over soft ground such as peat or clay, there is often risk of foundation failure if the shear strength of the foundation materials is exceeded. Maccaferri provides a range of solutions revolving around the control of the rate of settlement of the embankment. The use of geosynthetic materials can avoid the use of more traditional methods, which may involve excavation and subsequent replacement of these soft soils or a slower staged filling process that extend the construction time out to 10 years.

Embankments over soft soil
Embankments over soft soil can fail as a result of foundation soil failure, lateral extrusion of the foundation soil or excessive settlement. Maccaferri offers a range of high strength reinforcement including both woven geotextiles and polymer geogrids having tensile strengths from 100kN/m to in excess of 1000kN/m that are normally placed at the base of the embankment to improve stability.

Embankments can be constructed and then wait for settlement to occur vertical wick drains can be inserted into the foundation soil to accelerate the settlement time to less than 2 years. The use of Colbonddrain, a vertical wick drain and bidim geotextiles acting as a separator between the drainage blanket and foundation soil together with specialist reinforcing materials is now common practice for highway construction over soft soils in New Zealand.

Embankments over piles
Where there is a need to prevent settlement, piling or inserting stone column can be used to transfer loads down to a firm foundation layer. Both foundation treatments are expensive and by increasing the pile spacing along with the incorporation of high strength woven geogrids spanning across the pile caps to transfer the embankment load onto the piles can offer significant savings.