Effects of installation methods and polymer support fluids on the lateral load capacity of piled foundations in low to medium permeability soils

Installation of shafts for piled foundations through collapsible soils by auger or drilling means always requires the use of either temporary casings or support fluids such as bentonite or polymers to stabilise the shaft. Whilst the effects of such support fluids on the base and shaft resistance capacity of piles has been well studied (Fleming and Sliwinski, 1991; Lam et.al. 2010), little is known about how the fluids may affect the lateral load capacity and deformation of piles. The current codes of practice in Europe, USA and other parts of the world recognise that the design of piles should consider the potential effects of support fluids however these codes do not give any specific guidelines.

The proposed research project will utilise laboratory techniques and mathematical modelling to simulate different scenarios of model piles installed with support fluids of different properties in soils of different properties. Lateral load tests on piles will be performed in a custom-built chamber accommodating model piles of various materials and dimensions, instrumented with strain gauges, displacement transducers and load cells. The chamber will hold a low to medium permeability soil acted upon by a variable surcharge and instrumented with pore pressure sensors and displacement transducers. All instruments will be monitored on a data logger to facilitate automatic data capture. The load-deformation responses of the piles will be monitored to failure for different cases of support fluids and pile installation method. Numerical simulation will also be performed using a 3D finite element program such as MIDAS or PLAXIS.