Inspection of a monolithic foundation
The main load from all ground parts of buildings and structures is borne by the foundation, which is the main bearing element of the entire structure, distributing its weight evenly over the entire base. For this reason, especially durable materials (stone, concrete, wood) are used for its manufacture.
The choice of material depends on the seismicity of the zone, the soil of the area, the architectural design of the structure. If a large building is being erected, then a tape, pile, columnar, slab or glass type of foundation is chosen, and low buildings are placed with a slight deepening.
Due to the structural features of this part of the buildings, their sensitivity to the action of groundwater, vibration loads, soil mobility, it is necessary to periodically inspect the foundations. Such measures make it possible to determine their real technical condition, the degree of wear and tear, and the ability to withstand excess loads.
Complex studies of foundations and soils of foundations should be trusted only by professional experts who have permits for appraisal activities. The specialists of the Constructor company, who have extensive experience in this area, will carry out an examination, help determine the cause of deformations and develop recommendations that will solve all your difficulties.
Why is it important to inspect foundations
Various deformations in the foundation and base of objects can manifest themselves at different times - both during its construction and during the operation of the building. This usually happens if the construction was carried out with violations of standards, which were not recorded in time, and the causes of damage were not eliminated.
Foundations and foundation soils belong to the hidden part of structures. The inability to visually observe their condition and the lack of concern of building owners about the inspection of these important parts of the structure leads to the appearance of various defects in them and even the destruction of the entire object for these reasons. Therefore, it is important to examine the components of the foundation on time, especially if reconstruction of buildings is planned, for example, when additional floors are built on them.
Such surveys are carried out with the involvement of specialists from an independent expert organization. The customer of this service should determine to what volume of research the foundation and the soil base on which it is located will be subjected. He prepares terms of reference for independent experts, where he indicates for what purpose he is going to conduct them. Most often, studies are ordered in connection with the planned overhaul of a building or its reconstruction, as well as in the event of a danger of an emergency or in connection with the discovery of any damage.
The TK specifies the list of examinations required to be carried out at this facility, provides links to regulations, according to which the survey of the specified facility should be conducted. At the end of the assignment, the experts are instructed to make a conclusion on the results of the research and give recommendations on how to eliminate the problems found.
Preparatory stage of the survey
After signing the contract for the provision of the "foundation survey" service with the customer, the experts carry out it in stages, starting with preparatory work, external inspection, instrumental verification and ending with conclusions about the actual state of the specified structure.
At the preliminary stage, experts carry out the following activities:
- consider the design and executive documents of the investigated structure;
- study materials on previous surveys (engineering-geological, hydrogeological);
- review reports related to geophysical and seismological studies;
- study technical diagnostics with information about the various deformations of the building;
- analyze information related to utilities, planning of facilities, the results of previous studies of the foundation and soil.
Foundation expertise
Special pits are made near the foundations to be examined, the depth of which is about half a meter below the level of the sole. The number of pits and their sizes depend on the parameters, the shape of the structures, soil conditions, and the survey task. If there are basements in this building, pits are made from its inside to reduce the amount of work with the soil. First, a visual inspection of the foundations is carried out.
During it, fixation is performed:
- dimensions, type of foundation, depth of its soil immersion;
- gaps between the edge of the bottoms and the foundation;
- deformations of the concrete surface in the form of cracks, chips;
- violations of the protective concrete layer due to corrosion processes in the reinforcement;
- displacement of reinforced concrete blocks from their location relative to the axis of the building;
- various subsidence, faults, deformations of the base soil.
At this stage, the terrain that surrounds the structure, as well as its ground structures, is examined. Waterproofing is checked, or its absence is noted, the level is estimated groundwater... These inspections make it possible to find the cause of the damage, and by the type of ground structures to reveal the nature of the foundation defects. At the end of the visual inspection, a report is made indicating the damage to reinforced concrete structures with their detailed description and location.
After that, a survey of the foundations is carried out using special tools. The strength of concrete is determined by ultrasonic or sclerometric methods (non-destructive testing). In the course of instrumental research, concrete is checked for water resistance, frost resistance, and the degree of corrosion. The valve and its parts are checked for damage. And also all loads are calculated that affect the edge of the foundation, including the dead weight of structures along with technological equipment.
Base soil survey
In the pits prepared during the study of the foundation, an inspection is also carried out subgrade... To assess its condition, exploratory wells are drilled in them, after which samples of soil and groundwater are taken to determine their main characteristics in laboratory conditions.
Expert opinion
After conducting surveys in various ways of the foundation with soil, the information that was obtained during the work is processed and systematized. An expert opinion is drawn up. It is a statement with a detailed report on all types of damage to these building components. An assessment of the main characteristics of the foundation and soil is given, data from instrumental studies are presented.
This survey is performed to assess the technical condition of the foundation and soils of the base of operating buildings, as well as, in the case of an increase in the load on the foundation and the base from the built-up floors, replacement of floors, an extension to the existing building of additional volume. It is also mandatory to inspect the foundations in the presence of defects in the building structures, indicating subsidence, uneven settlement of the building. In the case of a new building being built next to a single existing building, or next to a group of buildings.
When examining foundations and foundations it is obligatory to study the materials previously performed by engineering and geological studies in this or in the neighboring area (if any). Study of the results of previous surveys about the technical condition, the depth of the foundations, the repair work performed.
Directly a pit is being opened at the facilityin the vicinity of the foundations, to study the current state of the foundation, samples of soil and groundwater are taken under the base of the foundation, the soil is tested by static loads. The type, design and depth of the foundations, the degree of improvement and the condition of the building blind area are determined. Instrumental control determines the physical and mechanical characteristics of materials, fixes foundation defects, the state of waterproofing. The correspondence of the current characteristics of the engineering-geological state of the basement soils and the level of groundwater to the archive data is determined.
Based on the survey results measures are determined for the need to strengthen the foundations. In the event of an increase in the volume of a building due to an additional load and in the event of detection of defects, the bearing capacity of the foundation soils is determined by a verification calculation to accommodate the existing and additional load.
The main provisions for the survey of foundations are contained in section 5, GOST R 53778-2010 “Buildings and structures. Rules for inspection and monitoring of technical condition. "
An example of a survey of the foundations of a building.Determination of the state of the foundation for the existing load.
When conducting a survey the foundation of the building was examined, its structure and condition were determined. Soil samples were taken from the pits for examination in the laboratory. To determine the loads on the base, the structure and composition of floors, building walls, roof structures, and roofs were determined. On the basis of examinations in the laboratory, the physical and mechanical properties of soils were determined.
Measurements of structures were made, in some places, probes were made to determine the structure and composition of floors and floors on each floor, the loads from rafter system and roofs. According to the results of the survey, design resistance base, a verification calculation of the base under the base of the foundation for the perception of the existing load has been determined, maximum draft grounds. Based on the results of the survey and verification calculations, it was determined that the bearing capacity of the foundation was provided for the perception of the load transmitted from the base of the foundation. Draft within the limits of norms SNiP.
Based on the survey results of the technical condition of the foundation structure, it was established that the foundation has defects in the form of washing out the destructed mortar from the masonry joints. Horizontal waterproofing does not provide protection against moisture capillary intake from the soil. The blind area, in places, is destroyed, the slope of the layout, in places, is directed towards the building, surface water penetrates to the foundation.
The findings of the inspection are:
- The bearing capacity of the foundation for the perception of the existing load is ensured, reinforcement is not required, but, due to unorganized drainage from the foundation of the building, soil soaking can lead to uneven settlement of the building.
- It is necessary to take measures to eliminate the penetration of surface water to the foundation and base of the building. To do this, it is necessary to arrange a blind area with drainage trays at the locations of drainpipes, to replace drainpipes with new ones, with the organization of the direction of discharge from the drainpipes to the trays of the building blind area.
- In view of the identified defects in the foundation of the building, the bearing capacity of the foundation will be ensured only after measures to strengthen brickwork foundation. It is recommended to make reinforcement, by injection or by means of a reinforced concrete frame.
- Produce a shut-off device horizontal waterproofing along the perimeter of the building, at a height of at least 150mm, from the top of the building blind area.
- Impact on the technical condition of the foundation
- Survey of the foundations of private houses
- How is a home base survey carried out
- Survey stages
- Natural, laboratory and office examinations
- Draft observations
The survey of foundations and foundations is carried out by specialized companies and research institutes that carry out independent examinations, the conclusions of which are a fundamental factor in making decisions about the structure.
The foundation survey includes the following stages: preparatory, full-scale, or it is also called field, laboratory, office.
Such companies have special equipment, construction and soil laboratory with modern tools. In addition, such work requires SRO approvals and accreditation. Inspection of the foundations of buildings is carried out in several cases, such as, for example, in order to identify defects, before the proposed reconstruction with the possibility of increasing, and for a planned technical examination. Inspection of any foundation is aimed at determining the actual technical state of the foundation, its operational properties, assessing the reliability of the foundation, calculating the residual life, to identify the reasons for the decrease bearing capacity.
Impact on the technical condition of the foundation
Instrumental examination of the foundation of a house is a complex undertaking. Assessment of the state of the foundation of the building is carried out as follows: by digging a pit along the structure, the core is taken from the foundation body; determine the diameter of the laid reinforcement; an examination of the geometric parameters of the foundation is carried out; identify and fix defects. In addition, samples are taken from the soil at home for testing in laboratories. Based on the data received from the laboratory of the surveyed object, as well as analysis, taking into account the current situation, archival data, calculation of the bearing capacity of the foundation soils under the foundation, and other calculations on the terms of reference, a technical report is prepared with conclusions, conclusions and recommendations.
As you know, the foundations of houses are used underground. The foundation absorbs loads and forces from the structure of the house, and transfers them to the surface of the subgrade. The foundation soil, in turn, also affects the foundation. As a result, the technical system between the ground and the structure is in balance. If this equilibrium is violated, deformation and gradual destruction of the structure occurs. In the calculations, when designing, predominantly force factors are taken into account. And during the operation of a structure, its foundation is influenced by a variety of other physical processes, such as, for example, temperature drops (seasonal and daily); wandering currents; fluctuations in groundwater; heterogeneity different types soils of their physical properties. Such factors are taken into account using a system of special coefficients.
In certain cases, foundations experience special effects, mainly associated with vibrations during earthquakes, underground workings, etc. The impacts of this kind are seismic. At the same time, they are taken into account by dynamic calculations, involving the determination of frequencies and modes of vibration of the system from the building to the ground.
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Survey of the foundations of private houses
Owners of private houses most often turn to experts with a request to survey the foundations and foundations of their buildings. To get the correct answer to each of the questions that arise, it is necessary to do again an instrumental examination of the foundation. An assessment of the foundation of a house can be obtained after determining and analyzing the parameters and properties:
- soils in;
- their geometric parameters (depth of the foundation, its width and length);
- the presence of reinforcement in the foundation and its location;
- concrete strength;
- loads on the foundation and base;
- inspection of the house itself in case it is already built.
Based on the results obtained after research data, it is possible. As a result, on the basis of the analyzed survey data, the cause of defects in the foundation of built houses is determined, the possibility of its further operation is determined, and a technical conclusion is drawn up with conclusions and recommendations about the state of the foundation at the current moment. There are times when there is a need for a software project. Such a need may arise in the following cases:
- if it is planned to increase the loads, due to the construction of additional floors;
- if you plan to install technological equipment;
- if, due to physical wear and tear, the strength of the base material of the foundation is significantly reduced and reinforcement, strengthening of the foundation is necessary.
Such a survey will help the designers develop the optimal project under the given conditions, according to which the construction team will be able to carry out the necessary work with accuracy.
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How is the survey of the foundation of the house carried out?
Experts conduct an engineering survey of the technical condition of the foundation. Inspection of the bases begins with fragments of pits. The need for these actions is that it is necessary to identify the strength of concrete in its underground part. In addition, soil samples should be taken in order to perform laboratory tests. It is for this purpose that a pit is dug to a depth below the base of the foundation. The foundation can be of the following types: solid and discontinuous tape; columnar - glass; pile; solid - slab under the entire building. If serious defects are detected during the examination, an instrumental examination is performed. This means that core tests are performed that are selected from the structures in order to determine the strength characteristics of the structures. In addition, non-destructive testing is carried out, and in case of detection, the width of their opening is determined, and the reasons for their occurrence are established.
The most significant value in the examination of foundations is the actual strength of concrete in the structures of the foundation, therefore, its strength is necessarily determined.
Methods for examining concrete to determine its strength can be as follows:
- non-destructive testing;
- ultrasonic method - using an ultrasonic tester;
- elastic rebound method;
- shock impulse;
- chipping method;
- using press tests of selected samples from the foundation structure itself;
- in the selection of soil samples in order to determine their foundation by laboratory tests.
The technical conclusion based on the results of the examination includes:
- defective statement of the state of the foundation;
- information about deformations and;
- laboratory test results;
- indicators of the conducted instrumental examinations;
- assessment of the strength characteristics of the base;
- conclusions and recommendations.
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Survey stages
The foundation survey includes the following steps:
- preparatory;
- full-scale, or it is also called field;
- laboratory;
- cameral.
To work preparatory phase relate:
- preparation of project documentation;
- development of materials for engineering and geological studies, hydrogeological and other materials that reflect the characteristics of the surveyed object;
- compilation of logs of observations of rolls, cracks, settlements, deformations and deflections of foundations;
- engineering activities that are carried out within and near the work site;
- in parallel, an external inspection of the structure is carried out in order to establish the general condition of the structures, determine the location of openings and possible workings of foundations, the zone of greatest damage and deformations structural elements buildings, places of geodetic benchmarks and signs.
The work of the preparatory stage helps to determine the need and feasibility of opening the foundations. If there is a development of suffusion processes in urban development with the manifestation of sedimentary properties of the bases, then the opening of the foundations can lead to irreparable damage load-bearing structures buildings. Therefore, when it turns out that there are external signs of sedimentation in places of technogenic long-term operation, in such cases a decision is made that corresponds to GOST 19912-2001, SP 11-105-97, SNiP 2.02.03-85 on static sounding of clay and sandy soils.
