This type of foundation is used for more than 150 years, it was used for the rapid construction of military bridges in a swampy area, laying power lines, installation of piles, lighthouses, and other structures in areas with weak or frozen ground.
Application screw-pile foundations in residential construction began recently, but the benefits of this type of foundation quickly appreciated developers.Nowadays, many companies are already engaged in the improvement of production technology and the installation of piles, offering new design features screw piles that improve their performance.
One of the main advantages of a screw-pile foundation is a possibility of building on any difficult terrain - watered, marshy, peat, heaving, as well as in areas with difficult terrain.This foundation is very economical, since its construction does not require preparatory earthworks such as digging pits or trenches, and screw the pile can even manually, without the use of special equipment.
With no excavation pile
reliability and durability of such a foundation can also be noted among its advantages.The stock piles bearing capacity - from 4 to 18 tons, while that for the wooden house is enough 2 - 3 tons, and for the brick - 7 - 9. The earthquake-proof foundation is obtained, not subject to the forces of frost heaving, maintainable.
Structurally helical pile is a steel pipe, which is welded to the tip of the blades.In the construction market represented alloy screw piles and helical piles welded.The difference between these piles is a method of manufacturing the pile tip.In the first case, the tip blades are made by precision investment casting, in the second case the blades are welded to the tip of the semi-automatic welding method in a gaseous environment.
Available piles with tips in the form of a cone or an oblique cut at the end.Piles with conical tip is recommended to fill with cement mortar after screwing, and the interior of the pile with an oblique cut at the time of screwing filled with earth, which increases the strength of the pile installation.
Some manufacturers offer piles of original designs, such as three-lobed screw piles fence, in addition to having the blades on the tip, two more blades on the body of the pile.This construction ensures the stability of the fence piles under load in the horizontal direction, i.e. at swinging fence under the influence of wind.
piles covered by a rust inhibitor, also produces galvanized piles.The diameter of the piles varied from 57 to 325 mm, the most popular are piles with a diameter of 108 mm, is widely used in the construction of lumber, frame-panel and log houses.The length of the piles is from 1.5 to 3 meters, if necessary, screwing the pile to a greater depth, it can be extended.
Calculation of screw-pile foundation is carried out in several stages.At the beginning of counting the strength of the material piles and raft foundations, then you need to calculate the bearing capacity of the soil.By making these calculations, it is necessary in addition to the type of soil and the depth of its freezing into account the climatic conditions of the region, which is being built up portion.The final step in the calculation is to determine the bearing capacity of the foundation.At this stage should focus on the design of the house, to take into account its features, the location of the load-bearing structures and so on. To obtain the information needed for more accurate calculations, produce test screwing piles.
Screwing made piles to a depth less than the depth of freezing.If the soil on the site complex, for example, the upper layers of soil - peat piles building up until they reach good soil.Then the pile is cut to the same level and concreted.It is recommended to lay in piles alternately cavity 5cm thick solution and 5 cm of dry mix.In this case, released by the shrinkage of the solution absorbs moisture dry mix.
concreting is necessary to enhance the rigidity of the pile, also achieved an increase in the service life of the foundation.When using a thick-walled pipe (wall thickness of 6-8 mm) can not be applied concreting, although this is undesirable.If used with the walls of the pipe of 4 mm, then concreting is required.
After casting their piles are fastened together, the foundation used for binding channels, I-beams or wooden beams.If the foundation is designed for light construction, such as for a bath, the role of raft foundation can play a lower crown framework.In this case, the upper part of the pile is welded special headroom for distributing the load.The resulting welds must be covered with anti-corrosion compound.
Screw piles can be reused.This is especially useful in the construction of temporary facilities.And structures, and the foundation can be disassembled and moved to another location, using the same pile.In this case, the piles after screwing not concreted.
Often during installation mistakes are reducing the stability and reliability of a screw-pile foundation.One of the most common mistakes is to install piles in advance to dig a hole.This method used by inexperienced builders, if the soil is found too many obstacles.This is unacceptable, because it reduces the horizontal stability of the pile.If you still had to dig a hole, the pile should be screwed into the ground below the steady bottom of the well to 600-800 mm.
Such an error can be tolerated in the case of work on peat soil.Having a peat layer should not stop screwing on the surface of a dense layer and penetration continue to pile on the same 600-800 mm.
other errors that could lead to a lowering of foundation piles for the unscrewing height compensation.The pile may sag to the height and unscrewing the foundation is destroyed.
When installing vertical piles permissible deviation is 1.5 - 2 degrees if the pile of underground obstacles deviates by a large amount, it will lose stability, moreover, it is impossible to increase.
thus producing an accurate calculation and avoid mistakes when driving the pile, you can get the foundation, which is guaranteed to last for 80 - 100 years.