26.03.2020

On a solid foundation

  3.jpgA reliable foundation is responsible for the safe operation of the entire building. Accordingly, the design must be particularly strong and durable. Nevertheless, there are cases when under the buildings, especially erected a very long time ago, the foundation is weakened and deformed. There are also precedents when problems in this area are found under new houses and even with a zero cycle of construction work.

Currently, many modern technologies have appeared that allow you to quickly diagnose the condition of foundations, identify defects and damage. Effective new methods have been developed and used to reinforce and strengthen these structures. Some of them allow you to work without violating the appearance and design features of the building.

At the initial stage

According to Anton Detushev, general director of Ikon Development, if we talk directly about the zero cycle, then most often the strengthening of foundations is necessary in cases where technical errors were made during the survey and design work. It is also required when resuming construction at facilities that were not properly mothballed and protected from external influences. In particular, when irregularities were discovered during the construction of drains, which entailed the formation of voids due to suffusion (leaching of soils from under the base of the foundation) or other technological processes associated with soil movement (subsidence, swelling, weathering, etc.).

Yevgeny Ponomarev, an engineer at Construction Control, gives an example when it is necessary to strengthen a foundation with a monolithic grillage at the zero construction cycle. Such may be needed due to the peculiarity of the soil, which, due to its mobility, can change from the moment of engineering surveys to the start of construction. Based on engineering and geological surveys, the design of the pile foundation is being carried out. The document indicates the length, cross section and pitch of the piles. However, these surveys are not enough - and the design decisions made must be checked during the work. Therefore, when installing a pile foundation, field tests of soils by dynamic loading are carried out, at which a parameter called failure is determined, static tests of piles are carried out, their bearing capacity is determined. If the results of these tests do not meet the design data and regulatory requirements, then a decision is made to strengthen the foundation. In particular, reinforcement technology involves the use of piles with a longer length and / or a larger cross section. It is also possible to use piling doubles, at a certain step from the design, which showed unsatisfactory values ​​during the tests, he says.

Rational choice

Experts note that under different conditions, various methods of reinforcing the supporting structures are optimal. It is necessary to take into account the characteristics of the soil, the nearby objects of real estate and communications, and much more.

According to the chief architect of the KVS group of companies, Nadezhda Virolainen, more often the strengthening of the foundations of existing buildings, rather than those under construction, is required. In particular, such work is carried out at reconstruction facilities where it is necessary to strengthen old structures or where the house is being rebuilt and an increase in static load is expected. Reinforcement of the foundations of old buildings may also be necessary when they were damaged due to a number of other construction works.

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The methods depend on the type of foundation and soil characteristics. For example, additional piles may be immersed (rammed, bored, and others). Local repairs can be performed by self-expanding repair compounds. With insufficient bearing capacity of the elements of the foundations, an increase in the cross section is made by concreting with reinforcement and anchoring of the reinforcement. If necessary, to strengthen the columnar or strip foundations, at some objects, clips from rolled metal profiles and plates are made. When changing the design of the building under reconstruction, new elements can be installed - foundation slabs, beams, etc., says Nadezhda Virolainen.


According to the head of the design department of the Metropolis company Alexei Kushchenko, the most common methods of soil reinforcement can be considered as backing the building onto piles and fixing the soil in the foundation foundation. They are carried out together with the work to eliminate the consequences of the physical deterioration of the foundations in the form of cement injection of the foundation body, the construction of various clips, etc. "An example of such an approach is the work at the cultural heritage site in the center of Moscow. Reconstruction meant an increase in the loads on the foundations with a significant deepening of the underground part of the building. The project provides for the backlash of the supporting columns and walls of the building on cement-cement piles with a diameter of 600 mm, reinforced with steel pipes with a diameter of 140 mm. Piling work was preceded by restoration of the physical integrity of the foundations by repairing damaged areas, injecting the foundations body and, in some places, arranging metal clips, he added.


Both in the case of reinforcing the foundations by simple cementation, and in the case of injection, quality building material is important. Anton Ruzhylo, a technical specialist at TECHNONICOL Corporation, notes that in order to increase the efficiency of the cement hydration process, to create a more dense concrete structure and, thus, improve the structural strength, it is recommended to use special additives. This applies equally to the pouring of a new foundation, and jet cementation. The use of additives has a positive effect on the physical and mechanical properties of concrete and mortar, such as frost resistance, water resistance, strength and workability, the specialist emphasized.


By the way

Injection of foundations can be carried out in cramped conditions. In addition, it is not required to open the site around the building and on the construction site, deepen the pit and make additional trenches.


Read the article on the website of the Construction News AgencyASNinfo.ru