PHPA for Bored Piling

Bored Piling is one of the common and modern-day techniques for building a solid pile foundation for construction of various building types and structures. Bored Piling is a process whereby steel circular casings are installed into the ground by the simultaneous process of drilling and soil removal. This is then followed by the concreting of the piles, which then forms a strong pile foundation for the structure. This process is usually required when soil replacement instead of soil displacement is required.

In many of today's rapidly-developing cities, redevelopment and new construction works commonly require the use of bored piles. This is usually the case when surrounding site conditions, especially adjacent structures require minimal vibration and noise. This method also offers considerable flexibility in pile length, ground and soil conditions, without the hassle of large excavations and subsequent backfill of soil.

PHPAs are water-soluble synthetic polymers which carry a negative charge on the molecules. PHPAs now used in the foundation industry have a high molecular weight, so that when dissolved in water they form a non-Newtonian solution which may be used in replacement of bentonite slurry for excavation support. Unlike bentonite, polymer fluids do not form a gel when left undisturbed (nonthixotropic) and have negligible yield stress, although they can still have very high viscosity, up to 105  MPa⋅s at low shear rates. Polymer fluids have been found to offer many benefits such as smaller site footprint, ease of fluid mixing, and better concrete–sand interface resistance.