Manh Ngoc Tran
Research project - Installation of suction caissons in dense sand and the influence of the silt and cemented layers
Supervisor: Prof Mark Randolph (UWA)
Associate Supervisor: A/Prof David Airey
Suction caissons have been used in the offshore industry in the last two decades as both temporary mooring anchorages and permanent foundation systems. The study investigates the installation aspect of suction caissons, focusing on the installation in dense sand and layered soils, where sand is inter-bedded by silt and cemented layers. The research was mainly experimental, at both normal gravity and elevated acceleration levels in a geotechnical centrifuge, with some numerical simulations to complement the experimental observations.
The study firstly explored the suction caisson installation response in the laboratory at 1g. The tests were conducted in both homogenous dense silica sand, and in layered sand-silt soil, where caissons were installed using slow and rapid pumping. The mechanisms of heave formation in dense sand and deformation of the silt layer were also investigated using a half-caisson model and particle image velocimetry (PIV) technique.
The installation response at prototype soil stress conditions was then investigated in a geotechnical centrifuge. The installation response was investigated in various types of sand, and comparison with the 1g results was made. The installation in layered soil was also investigated in the centrifuge, including installation in various sand-silt profiles, and uncemented-cemented calcareous soil.
Finite element modelling was performed to simulate key installation behaviour. In particular, it was applied to simulate the sand deformation observed in the PIV tests, and the likely loosening range of the internal sand plug during suction installation in silica sand. The principle underlying the suction response for different combinations of self-weight and wall thickness was identified by investigating the development of hydraulic gradient along the inner wall. FE modelling was also performed to explore the influence of the hydraulic blockage by the silt layer.
- Tran, M.N., Randolph, M.F. and Airey, D.W. (2005). “Installation of suction caissons in sand with silt layers”. Submitted to ASCE Journal of Geotechnical and Geoenvironmental Engineering.
- Tran, M.N. and Randolph, M.F. (2005). “Variation of suction pressure during caisson installation in sand”. Submitted to Géotechnique.
- Tran, M.N., Randolph, M.F. and Airey, D.W. (2005). “Study of sand heave formation in suction caissons using particle image velocimetry (PIV)”, Proc. International Symposium on Frontiers in Offshore Geotechnics - ISFOG, Perth, Australia, 259-265.
- Tran, M.N., Randolph, M.F. and Airey, D.W. (2005). “Study of seepage flow and plug loosening in installation of suction caissons in sand”, Proc. 15th International Offshore and Polar Engineering Conference - ISOPE, Seoul, Korea, 2, 516-521.
- Tran, M.N., Randolph, M.F. and Airey, D.W. (2004). “Experimental study of suction installation of caissons in dense sand”, Proc. 23rd International Conference on Offshore Mechanics and Artic Engineering - OMAE, Vancouver, Canada. Paper: OMAE2004-51076.
Learning and Teaching
- CIVL2410 Soil Mechanics (at USyd)
- GEO 255 2nd year Geomechanics (at UWA)
- GEO 351 3rd year Geomechanics (at UWA)
- GEO 352 3rd year Geomechanics (at UWA)
- CIVIL 213 Statics and Solid mechanics (at UWA)