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Ground improvement with PVD at Haldia, West Bengal, India: a case study with numerical validation

Construction of oil storage tank on ground with soft cohesive deposit requires ground improvement for achieving bearing capacity with reduction of large settlement. Haldia, major river port and industrial belt at 22.0667° N latitudes, 88.0698°E longitudes, located near the mouth of the Hooghly River, one of the distributaries of the Ganges. Alluvial deposit of Haldia, being highly impermeable, takes very long time to consolidate. Haldia Energy Ltd was commissioning a Coal based Thermal Power Plant for generation of power. An area of 220 m ×30 m on the proposed Power Plant is designated for Cooling Tower which ground needs to improve. As Installation of PVD increases the drainage path and reduce the settlement time, So, Haldia Energy Ltd adopted the PVD technology to improve the ground. This 220m x 30m part of Power Plant construction area was loaded by fly ash as a first stage loading for 45 days up to 6.5 m and second stage loading for 16 days up to 10.0 m. The proposed site has been treated by Pre fabricated vertical drain @ 1.25m ×1.25m triangular grid to accelerate the process of Pre consolidation. The present study has been carried out to investigate the effect of installation of PVD in soft clay at the project site in respect of the rate of settlement and rate of change of pore water pressure. Further two-dimensional numerical analysis has been carried out by PLAXIS 2D finite element software to investigate and validate the pore pressure development and settlement with field investigation. It has been observed that the rate of settlement and rate of dissipation of pore water pressure have been sufficiently decreased within the soil indicating improvement of the soft clay after an appreciable time.