What Is a Pile Driver?
A pile driver is a construction machine used for driving foundation piles into the ground and digging pile holes.
They are used for a wide range of applications, from foundation piling for large buildings to ground improvement. They are also indispensable construction equipment for infrastructure development. There are various types of pile drivers, including large heavy equipment with a driver’s seat, those installed in the back of a truck, and small machines that can be used manually. In the case of large heavy machines, it is also possible to produce custom-made machines according to the purpose.
Uses of Pile Drivers
Pile drivers are construction machines that can drive foundation piles into the ground or dig pile holes, and are used in the construction of foundations for buildings and piers. The role of piles is to connect the foundations of large structures such as roads, buildings, factories, and railroads to the stratum of the ground, called the support layer.
Because the support layer for large structures is tens of meters deep underground, only heavy equipment can work in this area. Another feature is that the pile driver alone cannot complete the pile driving work. The work is done by several pieces of heavy equipment, including a plant that produces cement solution to prevent the pile holes from collapsing inside, a crane truck to transport and lift the existing piles, and an excavator to be used when sludge is generated.
Principle of Pile Drivers
Pile drivers look like crane trucks, and the self-propelled and caterpillar types are transported to the site on trailers. To begin with, piles are divided into two types: ready-made piles and cast-in-place piles.
Precast piles are piles that have been pre-made in several sections and brought to the site, where they are joined together and installed. Piles can be driven into the ground by dropping a large hammer equipped with a pile driver or by a hydraulic press in.
In the case of cast-in-place piles, a hole is dug, a cylindrical reinforcing bar is inserted, and concrete is poured directly into the dug hole. It is necessary to use different types of heavy equipment depending on the pile and construction method used.
Types of Pile Drivers
As mentioned above, pile drivers can be broadly classified into two types: ready-made piles and cast-in-place piles.
1. Ready-Mixed Piles
Embedding Method
After digging a pile hole, a cement solution is poured into the hole, and the existing pile is sunk. There are three types of pile driving methods: pre-boring method, jet method, and rotary pile method.
Driving Method
There are drop hammer and diesel hammer methods, which use the strong impact force of a hammer to drive a pile. Since the hammering force is used, the method is characterized by its high working speed during installation. There is also a method that uses up-and-down vibration to loosen the ground for driving.
Press-in Method
This method uses a load mounted on a press-in machine to drive a pile into the ground using the force of hydraulic pressure as a reaction force, and the resistance force generated when pulling the pile out is used as a reaction force to drive the pile into the ground continuously. Compared to other methods, this method generates less vibration and noise and reduces the amount of sludge generated.
2. Location-Driven Piles
The heavy equipment used for place-driving piles is an “earth auger. While digging deep into the ground with an earth drill, a viscous cement solution is poured into the pile hole to prevent it from collapsing. The earth auger also has a crane function and can complete pile driving with a single machine, making it suitable for narrow sites where multiple heavy machines cannot enter.
In addition, piles larger than 1 m in diameter, which cannot be driven by existing piles, can be driven in place with an earth auger.
Other Information on Pile Drivers
1. Pile Erection Truck
Foundation work is also involved in the construction of detached houses and is known as “column improvement”. The heavy equipment used in this method, which is similar to piling, is a pillar truck, a 3-ton truck with a drill installed in the bed of the truck, which pours a liquid called cement milk into the hole while digging. The foundation is then supported by the cement milk as it hardens into a cylindrical shape.
Some of these trucks are equipped with crane functions and are used for purposes other than columnar improvement. For example, when installing utility poles, a hole is first dug with a pole erector, and then a crane is used to erect the poles.
When installing steel pipe poles to support golf driving range nets, holes are dug in the same manner, and large tow trucks are used to erect the steel pipe poles.
2. Hydraulic Pile Driver
Smaller pile drivers that can be used manually also exist. Hydraulic pile drivers are used to drive single pipes as piles to firmly support protective walls called temporary enclosures at construction sites; they are large enough to be carried by one person, yet hydraulically powered, making driving faster and easier than using a hammer.