Soft soil, a soil which is considered as poor soil as it has low shear strength,
low permeability, and time-dependent settlement causing consolidation
phenomena, currently exist in major parts of unused land. In order to solve
consolidation problem in soft soil, ground improvement method called vertical
drain has been developed. One of the better methods of ground improvement is
called Prefabricated Vertical Drain (PVD), as it could resist shear load from the soil
and considered cheaper compared to other alternatives. However, in practice, the
installation of PVD is still producing high amount of overall construction cost,
which may raise it up to 30%. Thus, in order to minimalize the fluctuation of cost
in construction cost, optimization of PVD is being researched in this Study.
Optimization in construction is a method that consider the optimum
performance of structure, indicated by fulfilling design criteria needed for the
structure, while producing least cost possible for the project. In this study, the
optimization performed is exact optimization solution for PVD installation. The
optimization used PVD dimension length and spacing to determine the minimum
cost as optimization target, with design criteria of Degree of consolidation reaching
≥95% in one year period. The process of optimization will then be coded using
MATLABR2013a, using data from previous study regarding optimization of PVD.
The result of the optimization in this study is an economic model of PVD
modelled in MATLAB software, with the dimension of length = 33 m and spacing
= 2 m, resulting in 95.2% of Degree of Consolidation in half year period.
Furthermore, sensitivity study is also being performed, to determine which soil
properties affect PVD installation cost, in order to choose the most optimum soil
treatment for other projects. The sensitivity study determines that the soil properties
affecting PVD installation cost the most comes from soil Coefficient of Volume
Change (Mv) and Vertical Coefficient of Permeability (kV).