Unit cell consolidation of a PVD incorporated soft soil: Comparative of 2D axisymmetric and plane strain analysis considering ideal and actual drain

Abstract

Abstract The paper presents two-dimensional (2D) finite element-based study of a surcharge-induced consolidating unit cell model comprising fully saturated soft soil. Radial drainage in the unit cell is ensured through a single prefabricated vertical drain (PVD) along with vertical drainage through the top surface. Finite element based 2D axisymmetric and plane strain modelling has been conducted by considering the smearing of cohesive medium. The PVD is represented by both 1D drain element (ideal drain) and through geometric modelling considering well resistance. The parameters for the ‘Soft Soil’ model for the cohesive medium are adopted from the subsurface data at Krishnapatnam Ultra Mega Power Project (KUMPP), India. Comparative assessment of unit-cell consolidation is carried out between the 2D axisymmetric and equivalent plane strain condition based on Hird’s permeability compatibility approach. The two approaches yielded noticeable disparity in the time rates of consolidation for time factor ≤ 0.4, beyond which the disparity decreases, and the two methods lead to identical results beyond time factor = 4. Further, the influence of permeability of a geometrically modelled PVD and the height of unit cell on the time-rate of consolidation is elucidated, thereby manifesting the importance of well resistance and drainage length in such analyses.