Numerical Investigation Impact of the Spacing between Vertical Drains on the Diameter of the Influence Zone

Rapid developments of industrial and urban structures and infrastructures necessitate the utilization of remote or unsuitable lands that were not considered for construction in the past. The application of surcharge and prefabricated vertical drains (PVDs) is one the popular methods that is used all around the world as a result of simplicity and high efficiency. One of the issues that may occur in such reclamation projects, is the existence of sensitive infrastructures or structures in the vicinity of the treatment area. There are many variables that affect the diameter of the influence zone such as: the compressibility of weak layers, the height of clay stratums, length of the PVDs and the height of surcharge embankment and so on. In this literature the impact of spacing between PVDs was investigated using finite element modelling. Three test embankments as TS۱, TS۲ and TS۳ were modeled and verified for the study. For TS۱ (PVDs with ۱.۵ m spacing), TS۲ (PVDs with ۱.۲ m spacing) and TS۳ (PVDs with ۱.۰ m spacing) the diameters of the influence zone were ۵۴.۸, ۴۶ and ۴۲.۳ m respectively. As the distance between the PVDs decreases, the influence zone decreases as well and becomes smaller. For the FEM simulation of only surcharge embankment in the absence of PVDs the influence zone after ۴۰۰ days was ۶۴ m in the case that only ۰.۶۵ settlement was reached. It can be seen that the inclusion of PVDs and the utilization of smaller quantities of spacing can be an effective way for the reduction of influence zones where there are concerns regarding adjacent structures or infrastructures.