Improved Design Procedures for Ground Improvement using Pre- Fabricated Vertical Drains

Background/Objective: Ground improvement for soft saturated clay soil is often achieved by preloading combined with vertical drains. Use of vertical drains gives rise to smear zone and well resistance, which hinders consolidation. However, Indian code of practices doesn’t consider this aspect. Method: Computation of optimum spacing for vertical drains is iterative and tedious procedure. Therefore, an automate procedure using goal seek function of MS Excel is developed which gives optimum spacing instantly. Using developed spreadsheet, effect of smear zone has been studied by comparing field data to that obtained by using theoretical equations. Findings: Time estimates for target value of consolidation required in a project are better predicted by considering smear effects. Based on these findings it has been suggested to incorporate the effect of smear zone in Indian Codes for rational design of PVD. Application/Improvement: Using proposed modifications in Indian code of practices realistic estimate for desired consolidation can be found quickly.