The practice of jetting, applying a pressurized water jet at the toe of the pile, can greatly facilitate the driving of piles in some instances. The object of jetting is to loosen the soil, thereby reducing the resistance of the toe of the pile. The effectiveness of jetting depends upon the density of the soil and the availability of adequate water pressure.
Low-Pressure Jetting
This method is used in dense noncohesive soils in combination with a vibratory pile driver. Drivers with variable eccentricity are recommended when low-pressure jetting is used. Water pressure providing a pressure of 20 bar (0.42 lb/ft2) with a volume of 120 to 240 L (31.7 to 63.4 gal) per minute will be required; to be delivered through special nozzles.
High-Pressure Jetting
This method employs pressure of 250 to 500 bar (5.22 to 10.44 lb/ft2) and a water volume of 60 to 120 L/min (15.8 to 31.7 gal/min) also to be delivered through special nozzles.
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