What is a pile screw foundation?
The screw pile foundation is a type of pile foundation with a helix near the pile toe to screw the piles into the ground. The system of this type of foundation is relatively young, but it has already managed to positively recommend itself among builders worldwide.
What determines the quality of pile-screw foundation?
The quality of pile-screw foundation directly depends upon 2 things:
- The qualities of screw piles;
- The quality of the screw pile installation.
It is better to give preference to a reliable manufacturer than to buy cheaper ones from an accident merchant who cannot guarantee that the production cycle of screw piles has not been disrupted. Probably not worth talking about what the consequences can be if the screw blade was welded to the pile stem is not sufficiently reliable… etc.
There is a poor-quality screw pile installation in addition to the poor-quality pile production. Some people install piles by hands or by a low-power equipment. This equipment is often unreliable, as it is not possible to guarantee the desired level of the installation without constant sufficient torque, so it is recommended to use special equipment (such as Iron-Mechanics). During the installation the screw pile must reach the load-bearing layer of the ground, eliminating the possibility of pushing the pile out of the ground by ground heaving forces, or of subsidence of the ground, thus it becomes a reliable foundation element for the future construction.
What equipment to install screw piles?
Screw piles are installed by different ways and even by hand, but we would highlight three main ways:
Each of these methods will let you to install screw piles qualitatively. But there is not always an opportunity to apply one or another method. For example, if you need to install screw piles for the gazebo or outbuilding in a cramped site in the backyard and you wouldn`t like to spoil the lawn, you will choose the Manual ground screw driver. It is a great solution for those proposes. You will install the required number of screw piles gently and quickly.
It is faster and more convenient to use the Self-propelled ground screw machine if the site is large enough and unnecessary delicacy is not required.
If you have a mini excavator we recommend for you the Hydraulic excavator add-on. Excavator superstructure can be used for the installation of screw piles. It is an inexpensive and universal solution.
How to calculate a pile screw foundation?
In order to calculate the screw piles for the foundation, you will need a plan and mass of your future structure. The next step you have to mark the placement of the piles on the plan. Screw piles are always located at the corners of the facility and at the intersection of load-bearing walls with internal partitions. If the project includes an extension and/or a terrace you need to take them into account during the foundation design phase. Then you will add some additional installation points to the plan depending on the configuration of the extension and/or a terrace. The type, number and length of screw piles are selected based on the mass of the structure, as well as the load capacity of the ground and climatic features. At low soil density, piles with a larger support area are used, and in regions with low temperatures you need to determine the depth of freezing of the ground because screw piles are installed below this point to avoid a bulge.
Considering the load of the future structure on the foundation, it is also necessary to determine the optimal distance between the piles, which should not be more than three meters (if the construction is heavy, then the distance can be 2.5 or even 2 meters). After that, the future pile field is marked on the ground.
It is necessary to take into account the differences of heights, as this type of foundation does not imply an excavation, and, accordingly, in lower places you will need piles with a longer length.
How to install a pile-screw foundation?
Screw piles are screwed by the applied marks. During installation it is important to control the verticality of the installation. To do this, you need to use conventional bubble levels with a magnetic sole. The magnetic sole attaches the bubble level to the stem pile during the installation process. The more precise the screw pile is installed, the more evenly the load will be distributed during its operation. The permissible deviations from the vertical, as it turned out, have their own. On average (according to the survey) deviation from the vertical of more than 2 degrees is considered significant and such deviations you should be avoided.
And the most important indicator is the torque at which the screw pile was screwed. The denser the ground, the more resistance it has to the pile during the screwing process. If the screw pile is driven without any resistance, then it has not found a support and you need to continue to drive it until the pile meets the proper resistance in the way.
Installation time depends on the complexity of the object. For example, if you use the hydraulic equipment Iron-Mechanics it will take no more than two days to install piles for a house of 10mx10m (after the pile field has been marked).
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