Small-scale Physical Modelling of Geotextile-Reinforced Sand Fill over Hong Kong Marine Clay Improved by Deep Cement Mixed Soil Columns

Abstract

Deep cement mixing (DCM) technology was introduced in Hong Kong for the first time in the reclamation project of the Third Runway System of the Hong Kong International Airport and has been used in many other projects afterwards to improve the soft marine clay. Load transfer platforms (LTP) with or without geotextile reinforcement are often designed to facilitate the load transfer from the reclamation fills to the seabed. In this study, a small-scale physical model test was conducted on a geotextile-reinforced sand fill over Hong Kong Marine Clay (HKMC) improved by DCM columns, aiming to investigate the load transfer mechanism among DCM, HKMD, and geotextile reinforcement. The load transfer mechanism was examined by looking into the vertical stresses measured by earth pressure cells at different locations. The mobilised tensile strain in the geotextile reinforcement was measured using Fibre Bragg Grating sensors. Efficacy was calculated to assess the performances of DCM on load transfer. Furthermore, commonly used design guidelines were reviewed and applied to determine the load taken by DCM and the maximum tensile strain of geotextile reinforcement. It was found that the results offered by Dutch and FHWA methods agreed well with the experimental data.