It has long been no secret that the correct choice of the base for the house and the quality of construction determine the service life and comfort of life in it. It is necessary to calculate screw piles for the foundation even at the project development stage, since without this information it is not possible to prepare an estimate, purchase tools and materials.
Design Features
Metal screw piles for foundations, due to their versatility, have earned wide application among developers.
What are the features of piles?
- Design. This is a welded pipe with a sharp end, on which blades in the form of a screw are welded - a fixing element that does not allow the pile to move from its seat when the soil swells, stably holding the entire building.
- Installation. Installation is carried out with a clear control of the verticality of the pipe, mechanical or manualway. The main requirement is that drilling occurs to a stable layer of soil. Piles are driven regardless of the season and precipitation.
Indicators affecting the calculation
Calculation of screw piles for the foundation will require determining the total load on the foundation of the house, which consists of:
- The masses of the building, installed on the foundation. When designing a house, mass is a calculated indicator, it is determined by the materials used in the design.
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Additional load including snow, furniture, equipment and people. Information for calculating the loads on the foundation must be taken from the approved regulatory documents SNIP No. 2.01.07-85. The payload in the form of people and furniture is assumed to be an average of 150 kg per m2.
- Soil density. To determine, it is necessary to conduct engineering and geodetic studies, since without these works the object will not pass the state examination. The calculation is carried out in accordance with SNIP No. 2.02.03-85. For private construction of houses up to 3 floors, you can perform research on your own.
After performing the calculation of nominal loads, it is necessary to take into account the safety factor equal to 1, 2.
Types of piles
It is impossible to calculate the foundation of screw piles for a house without first selecting their type. Each standard size is calculated for a specific type of object being built.
| Pipe diameter,mm | Load, t | Destination |
| 57 | to 1 | Under the supporting pillars of various types of fencing. |
| 76 | to 3 | For light country houses. |
| 86 | 3÷4 | Heavy fences, one-story frame-type houses, gazebos, verandas. |
| 108 | to 10 | Buildings with 2 floors of frame type, as well as wooden buildings made of timber. |
| 133 | 9÷14 | Under the houses of medium gravity from foam blocks. |
| 219 | 10 | For heavy brick structures and two-, three-story houses. |
| 325 | More than 10 | Seldom used for residential buildings, more for industrial facilities. |
The choice of length depends on:
- Horizontal construction site: if there are significant differences in height, it is possible to choose piles of different lengths.
- The nature of the soil. Reliable installation involves screwing to a stable ground and below the freezing level of the soil by 25÷40 cm. In this case, the pile part should go into the ground no higher than 1500 mm.
Length standardized:
- Short: 1.65÷2.5 m.
- Long: up to 11.5 m (500 mm pitch).
Calculation of the number of screw piles for the foundation: steps
You will need:
- Plot to scale on which the planned base with center lines is to be applied.
- Tie to communication lines: sewer pipe from sanitary rooms and from the kitchen, with drawing diameters.
- Results of engineering and geological research.
Location:
- Single - point supports for light structures or country houses.
- Tape - sequential arrangement with a certain step.
- Custom - for heavy houses with many partitions and for each support in a frame building.
Calculation of screw piles for the foundation is carried out taking into account the features of the layout:
- The distance between the support points must be at least 2500 mm.
- The pile should be installed in places of peak loads, which are concentrated in the center of the intersection of perpendicular lines, namely:
- In the corners of the building.
- At the junctions of load-bearing walls and partitions.
- Intermediate supports should be installed evenly, including along the diagonals of the main cells of the building.
- The size of piles and blades is determined depending on the type of load and soil characteristics.
Influence of soil on calculation
Whatever screw piles are chosen for the foundation, load calculation is impossible withoutdetermination of the bearing capacity of the soil. So, the soil does not always have the necessary composition to withstand the building without subsidence.
Important! The selected pile must not exceed the load bearing capacity of the soil.
To determine the bearing capacity of soils, the composition of the soil is first determined and then compared with the characteristics shown in the table.
| Type of soil | View | Soil resistance kg/cm2 for a pile lowered by 2m (SNIP 2.02.03-85) | |
| Medium | Tight | ||
| Sand | Large | 12 | 13 |
| Medium | 11 | 12 | |
| Small, wet | 4 | 5 | |
| Small, wet | 2 | 3 | |
| Sandy loam | Dry | 4 | 5 |
| Wet | 2 | 3 | |
| Loams | Dry | 3 | 4 |
| Wet | 1 | 3 | |
| Clay | Dry | 2, 5 | 6 |
| Wet | 1 | 4 | |
In order to calculate the screw piles for the foundation, you need to determine the type of soil:
- Sand coarse fraction: 2, 5÷5 mm one grain of sand, up to 2 mm - medium. Does not change its size.
- Sandy loam is obtained by mixing sandy with a small percentage (10%) of clay rock.
- If the clay content is up to 30%, you will get loam. When wet, the mixture does not spread, but can be rolled into a ball, but cracks appear when pressed.
- If a lump of wet soil does not crack under pressure, but is plastically crushed, the clay composition is above 30%.
Pay attention! The higher the clay content, the higher the swelling of the soil.
Peat - soft and airy composition does not imply bearing loads
The proximity of groundwater and the degree of moisture resistance is determined by drilling a well to the depth of lowering the pile. If water has formed in a standing pit, then there is a moisture-saturated soil with a close location of the aquifer.
Screw piles for the foundation: customer reviews
Pile reviews depend on where the buyer purchased the product, as many complain about poor manufacturing, including poor anti-corrosion treatment. Praise the design in most cases, the owners of houses oncomplex water-saturated soils, since a pile for such an area is the cheapest and most reliable type of foundation. Also, do not forget about the speed and high quality of installation of such buildings in any weather, this is a plus that many developers note.
Total
Whether or not to use a pile as a foundation for construction depends largely on the location and installation conditions. Knowledge of calculation rules and data sources is desirable even in cases where the calculation is performed by a construction company.
