In thick deposits of soft clay, the time required for consolidation under a surcharge loading may be unacceptably long and foundation instability may be a serious concern. The rate of consolidation of the soft clay foundation layer is a function of its vertical hydraulic conductivity and the vertical depth over which the excess pore water has to flow in order to exit the soft clay foundation. Consolidation may take many years.

TenCate Geosynthetics offers effective ground improvement solutions for the consolidation of soft soils with Alidrain® AD prefabricated vertical drains (PVD). By inserting Alidrain® PVDs vertically into soft clay foundation deposits at calculated intervals, the consolidation time can be significantly reduced and the consequent rate of gain in foundation shear strength increased. The factors that affect the consolidation performance are:

  • The horizontal hydraulic conductivity and stress history of the soft clay foundation.
  • The spacing and geometry of the PVDs and its discharge capacity in the soft clay foundation
  • The extent of the disturbed zone around the PVDs caused by PVD installation
  • The magnitude of the surcharge loading applied on top of the soft clay foundation 

Alidrain® AD prefabricated vertical drains provide a low cost solution to the problem of long term settlements of soft clay foundations by accelerating the increase in undrained shear strength of the soft clay foundation to improve stability. With proper design, foundation settlement times can be reduced to the extent they occur within the time frame of the construction project, thereby avoiding the need for expensive post-construction maintenance.