Settlement Fitting Analysis of Highly Compressible Marine Clay Soil on Offshore Polder Type Reclamation Project using 2D Plane Strain FEM

Abstract

In a polder system reclamation project, the future ground level of both the dike and the land side requires rigorous estimation as the sea water level will eventually be higher than the land side in the course of time. This paper discusses a past project experience of conducting settlement fitting analysis of a reclamation project located in the Jakarta Bay area where significant thickness of marine clay deposits is found at shallow depths. During construction, analytical solution using two-dimensional method was used and fit well with the observed field settlement and pore water pressure readings. This paper aims to find the ratio of soil horizontal permeability (Kh) to plane strain horizontal permeability (Kh;p) which is useful for geotechnical modeling with finite element method (FEM). The investigation is conducted by back analyzing settlement records using equivalent plane strain 2D FEM with soft soil creep model (SSC). Using original soil horizontal to vertical permeability ratio (Kh/Kv) of 1.5, it is found that Kh/Kh;p ≥20 yields the best-fitting result with field settlement data for Jakarta Bay area. By using Kh/kh;p ≥20, it is acceptable for a preliminary design stage under short-term condition regardless of the potential occurrence of Mandel-Cryer effect and it should be used cautiously when applied to different soil conditions, PVD configurations, loading histories, or modelling approaches.