What is wrong with screw piles: an overview of the main disadvantages

Screw metal piles divided the builders into two opposing camps: some advocate this type of foundation; others are against it. Supporters of screw piles talk about the cheapness of the material, the speed and ease of installation - this is where their arguments end. Opponents of screw-pile foundations have much more serious arguments. Read on for the disadvantages of screw piles.

A bit of history: why and where the screw piles were developed

Screw piles were invented by an English engineer in the early 19th century. Initially, they were used for the construction of berths, and a little later they were adapted for the construction of buildings. In the XX century, their popularity fell due to the development of reinforced concrete production and pile-bit machines.

In the USSR, the military became interested in this technology. They developed frame-screw supports (RVO), which were used for the construction of folding bridges and crossings. A distinctive feature of the RVOs was that they were a temporary solution. Supports on screw piles were quickly assembled, dismantled and transported.

Our scientists and engineers saw the potential of using the pile-screw foundation only for military purposes, where speed and mobility are important. For capital housing construction, these elements were not considered.

But with the advent of modern realities, this solution has become in demand in frame housing construction. Manufacturers unanimously began to declare an almost innovative breakthrough in housing construction, which will significantly reduce the cost of construction.

What is a metal screw pile?

A screw pile is a pipe with a cone at one end and a blade welded slightly above the cone. This product is screwed into the ground manually or mechanically. At the time of her invention, up to 30 workers or several animals were involved to twist one screw pile - this is to understand the difference from modern counterparts.

The screw keeps, like any other - due to the support on dense layers of soil. The supporting part of the metal pile is the blade. And also the stability of the pile element is affected by the expansion and compaction of the soil when screwing. This process can be compared to tightening a self-tapping screw. The rigidity of the pile-screw foundation is given by the binding of the upper part of the piles with a metal channel or a wooden beam. In some cases, the strapping is additionally reinforced with jibs from a corner or profiled pipe. Rigid strapping is necessary because if a slab or strip foundation evenly distributes the load, then the piles are upset each by itself.

What's wrong with screw piles?

The first thing to pay attention to is the absence of a unified state standard (GOST) for these products. This means only one thing: each manufacturer in his enterprise sets its own technical conditions and is guided by them. There is SNiP, which imposes requirements on the foundation of these elements, but the piles themselves are not subject to any regulations.

In the west, there are: Eurocode and American regulations. In Russia, screw piles can be called illegal. Simply put: in a market where there is no control over the production of any product, there is a huge number of parodies - what is sold to the consumer is not known. It looks like a metal screw pile, but in fact... But the manufacturer is the manufacturer, and someone really works according to Western standards.

About durability

The next nail in the coffin lid for the large screws is the corrosiveness of the metal. It is very difficult to protect the pile from corrosion - when screwed into the ground, the protective layers (except for galvanizing) are erased or damaged.

Two more weak points are the welds on the cone and the junction with the blade. This is where rust traditionally appears. In addition, the pipe rusts not only outside, but also inside, and this accelerates the processes of metal destruction and thinning of the pile walls. But this stone is not in every manufacturer's garden, for example, a galvanized pile is excellent against corrosion.

Manufacturers claim that the metal pile will last up to 100 years. But you must admit that it is impossible to guarantee the absence of corrosive processes during such a time; and no one has seen what a Russian-made metal screw pile looks like, which has stood in the ground for at least 20 years.

But skeptics say that this product will last approximately 35 years. This argument is confirmed by one more fact: metal is a good conductor of cold, which increases the freezing of the soil around the pile. Due to regular soil loads that occur during frost heaving of the soil and rust of the joints, the blade can fall off. And without a blade, the pile loses its load-bearing function.

About soils and installers

This type of pile does not work and is used not in all soils. For example: in soil, where the bearing layer is clayey with a viscous consistency; oozy or peaty soil; in soils with a high organic content and soils with PH less than 5.5. In soft soils, the blades simply do not what to catch, and if you order piles with wide blades (special order), this will lead to a rise in cost project. And as we know, the pile-screw foundation is an emphasis on economy. The screw pile will not be installed in rocky soil either, as this is fraught with breakage of the blades.

But even in ordinary soil, a stone can be encountered on the path of the pile - the blade will simply rest against it and stop before reaching the calculated depth. Such obstacles are common. Deviation from the design loads, and even taking into account complex soils, leads to uneven subsidence of the foundation of the house as a whole. But here there is more wine not of the pile itself, but of the specialists who carry out the work.

How do you feel about the pile-screw foundation? Write in the comments!

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