Site-specific consolidation analysis for Newtown (Kolkata) using the Soft Soil Model calibrated with Flat Dilatometer (DMT) test results

¹ Studio Prof. Marchetti, Roma, Italy
² Department of Construction Engineering, Jadavpur University, Kolkata, India

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

Kolkata (22.5744° N, 88.3629° E), the capital city of West Bengal, is undergoing rapid urbanization at an annual rate of 4.7%. This growth has intensified challenges related to the city’s soft subsoil conditions, as much of Kolkata lies along the banks of the Ganges and is predominantly underlain by alluvial deposits rich in fine soil particles. These fines govern the time-dependent response of the ground, leading to consolidation settlement. However, in practice, many projects in Kolkata tend to underestimate this issue, often resulting in premature structural damage due to excessive settlement of foundations before the end of their design service life. This study addresses the problem through advanced in-situ geotechnical investigations using the Dilatometer Test (DMT). Complementary in-situ dissipation tests (DMT-A) were also performed to estimate the in-situ coefficient of permeability of the subsoil at a project site in Newtown, Kolkata. The derived soil parameters were then used to calibrate soft soil constitutive models for the site. These models were implemented in PLAXIS 3D (V20) to perform consolidation analyses of a pile-raft foundation system. The results effectively capture the time-dependent behavior of the system under structural loading, providing valuable insights for developing more sustainable and reliable foundation designs in such challenging ground conditions.