What Is a Screw Pile?
A screw pile is a type of pile used for ground improvement.
Screw piles are driven into the ground while rotating a screw-shaped steel pipe to increase the strength of the ground by integrating the pile with the ground.
Compared to conventional pile driving methods, this method has the advantages of less noise and vibration, and a shorter construction period. It is costly and time-consuming to pour concrete and install a foundation on a large site. However, a strong foundation can be easily installed by driving screw piles while rotating them with heavy machinery.
Compared to the foundation at the time of concrete placement, the accuracy of the screw piles may deviate due to the driving method. For this reason, the mounting holes for the upper flange of screw piles are often long holes. The long holes also allow for fine adjustment during installation of the trestle, which is a feature that makes it easy to work with.
Uses of Screw Piles
Screw piles are mainly used in civil engineering and construction projects. Screw piles can be easily installed in narrow spaces or on slopes where conventional pile driving methods are difficult. Because of this feature, these piles are widely used in outdoor solar panel installation work.
In order to install solar panels in the field, a frame must be installed. If the frame is simply placed on the ground, it will be blown away when a typhoon or gust of wind blows. A sturdy foundation is essential for a strong trestle, and screw piles can be used to lay the foundation inexpensively and in a short period of time.
Screw piles are also used in docks and offshore platforms. Screw piles can be driven into fragile ground such as rivers and seabeds, making them useful for laying foundations for docks and offshore platforms. Screw piles are especially suitable for offshore platforms because of the high durability required for such platforms.
Other applications include small buildings and ground improvement. Screw piles increase the strength of the ground, prevent ground subsidence, and improve the earthquake resistance of buildings.
Principle of Screw Piles
The principle of screw piles is to integrate the pile with the ground by driving a screw-shaped steel pipe attached to the end of the pile into the ground while rotating it.
Screw piles tighten the ground with the rotating screw piles. This increases the density of the ground and the strength of the soil. The screw pile is resisted by the frictional force of the ground, and as the driving progresses, the ground and the pile become one.
Generally, a hydraulic motor is used for driving. Piles of appropriate length and diameter can be selected to suit the ground conditions, allowing for a highly flexible installation. In most cases, they are hot-dip galvanized, so they will not rust or corrode even after prolonged outdoor use.
Types of Screw Piles
There are various types of screw piles. The following are examples of screw pile types
1. Ground Screw Pile
This is a commonly used type of screw pile. It is shaped like a large wood screw and has a spiral projection on about half of its overall length. This type is the least expensive.
It is used especially for lightweight structures such as gardens, playground equipment, and signs. These are relatively small piles, and the diameter of the steel pipe is generally a few dozen centimeters. On the other hand, other screw piles used for building foundations can be as large as one meter or more in diameter.
2. Large Screw Pile
Large screw piles have larger spiral wings than ordinary screw piles. The wider wings provide stronger anchorage to the ground and increase the vertical strength of the pile. They are best suited for use in agricultural land where the ground is relatively weak and soft.
3. Spiral Pile
Spiral piles are more like screws themselves than screw shapes. Leaving the top flange and a single pipe section of several tens of centimeters, all the rest of the pile is formed in the shape of a screw. This shape gives a very high stabilizing effect in any kind of ground.