For the first time the foundation on screw piles was used in the construction of a lighthouse in Meplin Sands on flooded soils of the seabed in the estuary. Thames in 1838. The idea of using a screw piles was an Irish engineer Alexander Mitchell (1780-1868), who in 1848 was elected a member of the Institution of Civil Engineers (ICE) and received a medal for it Telford invention. The construction of the Soviet science in the early 20th century. engineer Vladislav Karlovich Dmohovsky (1877-1952) conducted research in the field of pile foundations (theory of conical piles). He proved that the screw piles have a great advantage in the application to the device, if necessary, precast foundation in permafrost conditions, or when dealing with weak and watered soils. Currently, screw piles are widely used for all types of buildings and structures, due to the high speed setting, the lack of vibration during immersion and the ability to carry out work in the winter.
Recently, are widely used as screw piles with an increased load capacity, as well as two-bladed screw piles. Studies have shown that both types of screw piles have high load-bearing capacity and are able to withstand heavy loads in compression and pulling, which also leads to a reduction in material consumption, and hence to save on the foundation. Some manufacturers used in the manufacture of screw piles thick-walled seamless pipes with wall thickness of 6-10 mm (standard 4 – 4.5 mm) and use the steel grade 30HMA. Due to the higher performance of strength and deformability, they are used for a more extensive list of buildings and structures, compared to the same piles, made of ordinary steel 3.
The calculation for the design of pile foundations using screw piles is performed by SP 24.13330.2011 The updated edition of SNIP 2.02.03-85 “Pile foundations” -Vintovye piles.
Installation is made by means of hydraulic mechanisms of various construction vehicles, or in some cases – by hand. Pile sinking into the ground like a screw, screwed into a tree. In the presence of hard rock or permafrost – Dive leader made well. Correct installation methods are of paramount importance for the calculation of bearing capacity of the foundation.
In order to reduce internal corrosion of the pile shaft, as well as better resistance to screw piles bending loads at great length of the trunk, especially in soft ground, the trunk of the screw piles concreted. In the case of long piles further reinforced.
In order to increase the carrying capacity of screw piles, especially in soft ground, the builders also used the technology of injection solution through the barrel of the screw piles. This technology allows to increase stiffness and density okolosvaynogo array that provides a reduction in the load on the screw piles.
Screw piles are used:
- For low-rise housing (base on the marshy ground, construction, time-limited)
- As a foundation for the transmission lines and towers
- For frame buildings (hangars, warehouses)
- Lightweight constructions (fences, billboards)
- Waterworks on flooded soils (piers, bridges)
- To strengthen the slopes
- In terms of reconstruction, which is necessary to eliminate vibration during burial in the ground (foundations for the equipment in existing buildings, construction of close cultural and historical monuments)
- As grounds for temporary structures, with the possibility of dismantling (trade pavilions, amusement facilities)
- As an anchor for braces
- Screw piles reinforce a monolithic foundation with complex subsidence or flooded soils. (eg slab on screw piles, tape on screw piles)
- As the foundation of industrial greenhouses
- As the foundation of noise screens
- Increasingly in Ukraine are used as the foundation of capital facilities, based on the successful experience of the North American and other builders
Classification of screw piles:
Types of screw piles:
1. Widely Blades piles are metal structure, consisting of the trunk and one or more of the blades from one to one and a half turns:
1.1. Single blade. Developed by the Soviet designer Victor Kolesnikov. An old type used by most manufacturers.
It is recommended for use only under light construction and load-bearing walls of houses.
1.2. Multiblade with two or more blades. In order to increase the bearing capacity in compression and pulling at least 50% and improve the perception of the horizontal loads, the blade of constant width is located on the stem of the pile.
Used construction sites under the responsibility of bearing walls, fences, piers, sheds, houses over 2 floors under construction, being built on the slopes, as well as the strengthening of the slopes.
2. Uzkolopastnye piles are metal structure, consisting of the barrel and a multi-turn vane.
Multiturn pile – pile shaft and molded tip with blender. The connection with the tip of the barrel – welded.
The number of turns of the blade – two or more.
Suitable for soils:
– Very tight, rocky, man-made, coarse;
– Seasonal freezing and permafrost.
Applications: light house, flagpoles, fences, modular buildings in permafrost areas, mountainous terrain.
- Fast installation foundation. The object shall be 15-30% faster than the concrete foundation.
- Ability to use in marshy soils, soils with a high level of groundwater, soil subsidence.
- The ability to completely abandon the excavation and leveling of land.
- Ability to conduct work in the vicinity of underground utilities, trees or in dense urban areas.
- Screw piles after screwing immediately prepared to accept full design load.
- Utilities can be designed in parallel with the construction of the house.
- The work can be done at any time of the year.
- High maintainability.
- The ability to re-use screw piles.
- The absence of vibrations during burial.
- All the work, if necessary, can be performed manually.
- The probability of damage when installed in rocky ground (scratch protection layer, the risk of corrosion). The most effective method of corrosion protection – an increase of the wall thickness of the pile and the blades depending on the desired lifetime.
- High probability of occurrence of corrosion processes in the presence of stray currents in the soil.
- Screw piles are often made artisanal, which leads to a serious loss of quality and reliability. Improper performance of welded joints on a cheap equipment leads to deformation of the tip or the separation of the blades when screwing in the ground.
- The probability of deviations from the design calculations in the case of self-installation of piles.
- The need for quality control of welds, such as ultrasound or X-ray.