Observation on Consolidation Settlement of Ground Improved by Sand Compaction Pile and Prefabricated Vertical Drain Applied to Dhaka MRT Line 6

Abstract

Consolidation acceleration and liquefaction mitigation works were carried out on the construction site of the MRT Line6 depot in Dhaka, Bangladesh in 2016-2018. Sand Compaction Pile (SCP) was adopted in order to mitigate liquefaction of upper granular soil layer and accelerate consolidation settlement of cohesive soil layers. A combination of Prefabricated Vertical Drain (PVD) and Dynamic Compaction were also adopted for the same purposes as SCP. Settlement was monitored after raising the embankment. Settlement records of SCP and PVD area indicate the following: 1) Settlement in the SCP areas are smaller than those in PVD areas (0.8 times on average), and 2) Consolidation speed of improved ground shows that the speed in the SCP areas was approximately twice that of the PVD areas (almost equal to the estimated speed).