The vertical drains are a technical improvement of soils with poor mechanical and hydraulic characteristics (clay, silt etc ...).

They are two families of drains that have benefits (or sometimes achieved to varying degrees) include:

* The sand drains that contribute to reduced soil compaction and often offer a line of variable depth, it is not possible to achieve with prefabricated drains.

* The prefabricated drains that are rapid and can greatly accelerate the consolidation.