Physical Modeling of a Footing on Soft Soil Ground with Deep Cement Mixed Soil Columns under Vertical Loading

Abstract

Deep cement mixing (DCM) technique is a deep in-situ stabilization technique by mixing cement powder or slurry with soft soils below the ground surface to improve their properties and behavior. Some of DCM treated soft soil grounds are approximately in a plane-strain condition; for example, a fill embankment on DCM improved ground. In this study, a plane-strain physical model was created with instrumentation and used to investigate the bearing capacity and failure mode of a soft soil improved by an end-bearing DCM column group. This study focuses on the observed wedge-shaped shear failure of the model ground and attempts to give an account of the failure. Two different methods are used to calculate the bearing capacity of the model ground, and the computed values are compared with the measured ones. It is found that the simple Brom's method gives a better estimate of the bearing capacity of the present model ground. It is also found that measured data of pore water pressures at different locations in the soft soil indicate coupling between failure of columns and consolidation of the soft soil. This study has presented the first time that a wedge-shaped block failure was observed for pattern of DCM treated soil ground.

Keywords:

• bearing capacity
• deep cement mixing
• excess pore pressure
• failure
• physical model
• soft soil

Financial support from The Hong Kong Polytechnic University and a grant from the Research Grants Committee (RGC) of The Government of the Special Administrative Region of the People's Republic of China are gratefully acknowledged.

Notes

Note: ^a The model ground was used by Kitazume et al. (1996, 1999) and Kitazume and Yamamoto (1998).

^b The model ground is studied in the present paper.