Pile driving equipment has been assisting construction firms in the development of massive projects in the modern area for over 150 years. Though the concept of driving piles into the ground for the purpose of creating a stable and reinforced foundation has not changed, the evolution of the machinery utilizing different power sources and techniques is a credit to the intelligence of engineers and designers who constantly look to improve processes.
In the rudimentary stages of early pile driving, piles were driven into the ground with the use of blunt force. This can be traced back nearly 5,000 years ago to the development of man-made island in the moors of Scotland. The challenge to the early process was ensuring that the structural integrity of the pile was not compromised when it encountered resistance. Any compromise of the pile would result in the weakening of the pile; therefore making the pile useless in the stabilization of the structure to be built upon it.
Through the development of steam pile drivers in the 19th century, piles were driven into the ground with the use of energy transfer. The hammer portion of the pile driver was evolved into a piston. The use of suddenly pressurized steam inside of the chamber/cylinder above the pile resulted in the creation of energy; which was transferred to the pile, thereby driving it into the ground. Diesel pile drivers improved on the process.
Diesel hammers seized on the concept of pressure to drive the piles, and added the element of burning fuel to create additional force. The piston concept was evolved with the piston creating hot compressed air which was brought to the temperature point where diesel fuel is flammable. By introducing diesel fuel into the chamber at a certain moment, the mixture of air and fuel creates a significant amount of energy. The energy is then transferred down to the pile to drive it into the ground.
Interestingly, with the need to rebuild older structures, the need for a machine that could remove piles that had been previously embedded into the earth came to the market. Attempting to pull previous driven piles out of the earth proved extremely difficult with direct upward force due to the friction that existed. The result is a machine known as a vibratory pile driver/extractor.
A vibratory pile driver/extractor utilizes high amounts of vibration to loosen the pile and reduce the skin friction between the pile and the surrounding soil. The machine’s appearance is much different that of a conventional pile driving equipment. The machine is hoisted above the pile and held in place by a crane. The vibration is created by rotating weights that are powered by hydraulic motors. Interestingly, the motors create vibrations in all directions; however, because the rotating weights are eccentric and are connected in a specific manner with gears to maintain a predetermined synchronization, the horizontal vibration is cancelled. This results in only vertical vibration.
The vertical vibration is then transferred to the pile. The pile absorbs the vibration and then transfers that vibration to the soil around it. Some machines produce as much as 1600 vibrations per minute (over 25 vibrations per second). The process works equally well for both driving of piles and the extraction of piles.