Technical operation of basement foundations in adjacent areas. Repair and strengthening of foundations of buildings and structures

The technical operation of foundations and foundations includes measures for the maintenance of adjacent areas. To protect the foundations from moisture, the yard area must have a slope from the building of at least 001 towards the drainage trays or storm sewer intake wells; the drainpipes must be kept in constant repair.

Foundations and basement walls located next to faulty pipelines of the water supply, sewerage, and heat supply systems, at places where they intersect with building structures, must be protected from moisture.

Excavation work near a building is permitted if there are projects that provide for the protection of bases and foundations from moisture and deformations caused by changes or redistribution of loads.

If cracks appear in the walls due to ground settlement, it is necessary to place beacons and observe them for 15-20 days.

If a crack does not appear on the lighthouse during the observation period, it means that their formation and uneven sedimentation have stopped. The destruction of the beacons means continued settlement of the soil, so it is necessary to conduct a more thorough study of the deformation and repair the crack only after eliminating the causes that caused it.

Sources of basement moisture can be moisture entering through pits. The walls of the pits should rise 10-15 cm above the sidewalk, the surfaces of the walls and floors of the pits should be free of cracks, the floor of the pits should have a slope away from the building with a device for draining water from the pit. Cracks and crevices at the junction of the pit elements and the basement walls are filled with bitumen or sealed with asphalt.

If there is unorganized drainage, it is necessary to protect the pits from precipitation.

Basements and technical undergrounds must have temperature and humidity conditions in accordance with established requirements. In unheated basements and technical undergrounds, the temperature and humidity conditions must be maintained, in which the air temperature is maintained at least 5°C and the relative humidity is no more than 60%. In heated basements, the temperature and humidity conditions that prevent condensation from forming on the surface of the enclosing structures are set depending on the nature of the use of the room.

Basements and underground spaces must be regularly ventilated using exhaust ducts from ventilation openings in windows, basements or other devices, ensuring at least one air exchange.

If condensation occurs on the surface of the structure or mold appears, it is necessary to eliminate sources of air humidification and ensure intensive ventilation of the basement or technical underground through windows and doors, installing door leaves and window sashes with grilles and blinds in them.

In basements and crawl spaces with blank walls, if necessary, at least two ventilation holes should be punched in the basement in each section of the building, placing them in opposite walls and equipped with louvered grilles and exhaust fans.

In buildings with heated floors on the ground floor, the vents in the basement are kept open. In buildings with cold floors, the vents are closed when cold weather sets in.

The area of the vents should be approximately 1/400 of the area of the basement or technical underground.

In order to protect structures from the appearance of condensation and mold, it is necessary to organize regular through ventilation, opening all vents, hatches, and doors. Ventilation of the underground should be carried out on dry and not frosty days.

It is not allowed to arrange warehouses of flammable and explosive materials in basements, or to place other household warehouses if the entrance to these premises is from common staircases. Rodent protection nets must be installed on all openings, channels, and technical underground openings.

When thaws occur, it is necessary to regularly remove snow from the walls of the building over the entire width of the blind area or sidewalk, take measures to speed up the melting of snow by loosening, scattering and chipping ice, drain gutters and inlet hatches for water drainage to be periodically cleaned. Plants pose a danger to the foundations, so they are planted no closer than 5 m from the walls of the building.

3 8 ..

Lecture 8

Technology for repairing foundations of buildings and structures

1. Organizational measures for strengthening foundations.

Before starting work on repairing and strengthening foundations, it is necessary to establish the cause of damage to the foundations and eliminate it.

To identify the reasons that caused damage to the foundations, as well as during their reconstruction, they collect information on the history of the building or structure, and also carry out a technical inspection of the above-ground and underground parts of the building and the surrounding area. This is especially true for older buildings. Collecting information on the history of the building makes it possible to determine the date of construction; original appearance; changes that occurred during operation (superstructures, extensions, redevelopment); emergency conditions.

If there are deformations and cracks in the walls, drill holes must be made in places of suspected damage to the foundation. They are torn off 0.5 m below the level of the base of the foundation. In plan, the pit has the shape of a rectangle, with its larger side 1.5...3 m long adjacent to the foundation. The strength of foundations and basement walls is determined by known non-destructive methods, for example, acoustic, radiometric, mechanical, etc.

The settlement of the building is controlled instrumentally, and the opening of cracks is controlled using beacons installed across the cracks on the wall of the building (Fig. 1). Lighthouses are arranged in the form of a bridge with a length of 250...300, a width of 50...70 and a thickness of 15...20 mm. The place where the lighthouse is being built is cleared of plaster, paint, and cladding. Two beacons are installed on each crack: one at the point of greatest opening, the other at its beginning. If cracks do not appear on the lighthouses within 15...20 days, then we can assume that the deformations of the building have stabilized. Lighthouses are made of plaster, metal or glass.

2. Characteristic types of foundation deformations.

The study of the main types of damage to foundations made it possible to systematize them according to the nature of the development of cracks in the foundations and walls of the building:

1. Settlement of the middle part of the building. Main reasons: weak foundation in the middle part of the building; subsidence of subsidence foundation soils; karst voids in the middle part of the building

2. Settlement of the extreme part of the building (left or right). The main reasons: weak foundation under the extreme part of the building; soil subsidence due to soaking; karst voids; fragment of a pit or trench next to a building; shift of a nearby retaining wall; basement flooding

3. Settlement of both extreme parts of the building. Main reasons: similar reasons indicated in the previous paragraph, but operating in both parts of the building; placement under the middle part of a large inclusion (boulder, old foundation, etc.)

4. Buckling and curvature of walls in vertical and horizontal planes. The main reasons: expansion of the rafter system; horizontal forces from guy wires attached to the building; eccentric load transfer from floors; dynamic loads from equipment located in the building; seismic movements

3. Preparatory work for strengthening foundations

Before starting work on repairing and strengthening foundations, the causes of uneven settlement or destruction must be eliminated. If deformations of the foundation caused corresponding deformations of the walls and ceilings, then the work is carried out in the following sequence: strengthening (hanging) the ceilings; strengthening walls in places of deformation; repair and strengthening of foundations; wall repair; ceiling repair.

The main work on repairing and strengthening foundations includes: strengthening foundations and foundations; widening the base of foundations; increasing the depth of placement; their complete or partial replacement.

Unloading foundations.

Before starting work, it is necessary to take measures to ensure the stability of the building and protect structures from possible deformations, i.e. perform partial or complete unloading of foundations.

Partial unloading is carried out by installing temporary wooden supports, as well as wooden and metal struts.

To install temporary wooden supports (Fig. 2), support pads are laid in the basement or on the first floor at a distance of 1.5...2 m from the wall, a support beam is placed on them, on which wooden posts are installed. An upper purlin is laid along the top of the racks, which is attached to the racks using brackets. Then wedges are driven between the racks and the lower support beam, thereby turning the racks into operation, and the load from the floor is partially removed from the walls and transferred to temporary supports. Supports on floors must be installed strictly one above the other. To increase the stability of the structure, the racks are braced with braces.

Complete unloading of foundations is carried out using metal beams (rand beams) embedded in the masonry of the wall, as well as transverse metal or reinforced concrete beams. Rand beams (Fig. 3, a) are installed above the edge of the foundation into grooves previously punched on both sides of the walls onto a bed of cement-sand mortar. The grooves must be punched under the bonded row of brickwork. Temporary fastening of the rand beam in the groove is carried out using wedges. In the transverse direction, after 1.5...2 m, the beams are tightened with bolts with a diameter of 20...25 mm. The space between the temporarily fixed beam and the wall is filled with cement-sand mortar with a composition of 1:3. The joints of the rand beams along the front are connected by electric welding overlays. In this case, the load is transferred to adjacent sections of the foundation.

Ministry of Education and Science of the Russian Federation

South Ural State University

Faculty of Architecture and Civil Engineering

Department of Urban Planning

ABSTRACT

at the rate: “Introduction to the specialty” for specialty 290503

on the topic of: "maintenance and repair of foundations"

Completed : student

AS-107 group

Nadtochy Denis

Checked: head Departments

"Urban planning"

Kutin Yu. F.

Chelyabinsk

2004

1. INTRODUCTION………………………………………………………………………………2

2. MAINTENANCE AND REPAIR OF FOUNDATIONS……6

3. REFERENCES…………………………………………………….....10

1. INTRODUCTION

Buildings and structures play an important role in the life of modern society. It can be argued that the level of civilization, the development of science, culture and production are largely determined by the quantity and quality of buildings and structures constructed.

The life and everyday life of Soviet people is determined by the presence of the necessary buildings and structures, their suitability for their purpose, and technical condition.

The Communist Party and the Soviet government pay constant attention to construction, thus realizing their main concern about raising the material and spiritual standard of living of the Soviet people.

Construction in our country is carried out on a very large scale. Only more residential buildings are being erected in the Soviet Union than in all Western European countries combined. Every year, 2.1 million apartments are put into operation and more than 10 million Soviet citizens improve their living conditions, dozens of new cities appear on the map of our Motherland. That is why construction in our country is the third largest sector of the national economy after industry and agriculture.

During the years of Soviet power, more than 1,200 cities were built in the USSR and more than 3.8 billion m 2 of living space were put into operation. Currently, there are about 65 million apartments in use, with more than 80% of families living in separate apartments. Such a large scale of construction is a characteristic feature of a developed socialist society.

The components of construction as a branch of the national economy, its goals, basis, quality assessment criteria and tasks of construction science are summarized in Table. IN 1.

Each building or structure is a complex and expensive object, consisting of many structural elements, engineering equipment systems that perform specific functions and have established performance qualities.

Construction in our country is characterized not only by high quantitative indicators, but also changes qualitatively and structurally: the layout of apartments is improving, building structures and engineering equipment systems are being improved, and the comfort of the housing stock is increasing. Suffice it to say that for heating, ventilation and hot water supply of cities, "/b of all types of fuel and energy resources are spent. Saving only 1% of these resources will save about 2 billion rubles annually in operating costs and capital investments. The practice of operating buildings shows that automatic methods for regulating heat consumption can bring savings up to 10%.

It should also be taken into account that buildings currently under construction will serve in the 21st century, when the level of comfort will become even higher.

Designed and constructed buildings, in accordance with the defining operational requirements, must:

have high reliability, i.e., perform the functions assigned to them under certain operating conditions for a given time, while maintaining the values of their main pairs of lines within the established limits;

be convenient and safe to operate, which is achieved by rational planning of premises and the location of entrances, stairs, elevators, fire extinguishing equipment, and for the repair and replacement of large-sized technological equipment in buildings, hatches, openings and fastenings must be provided;

be convenient and easy to maintain and repair, i.e. allow it to be carried out in as many areas as possible, have convenient approaches to structures, inputs of utility networks without dismantling and disassembling for inspection and maintenance with extremely low costs for auxiliary operations, should allow apply advanced labor methods, modern means of automation and mechanization, prefabricated devices for servicing hard-to-reach structures, and also have devices for fastening cradles, power sources, etc.;

be maintainable, i.e. their designs must be adapted to perform all types of maintenance and repair without destroying adjacent elements and with minimal labor, time, and materials;

have the maximum possible and close equivalent service life between repairs for all structures;

be economical during operation, which is achieved by using materials and structures with an increased service life, as well as minimal costs for heating, ventilation, air conditioning, lighting and water supply;

have an external architectural appearance that corresponds to their purpose, location in the building, and is also pleasant to view, and the interior painting of buildings should not tire people, should not become dirty if possible and can be easily cleaned and restored.

Depending on the purpose of the building, its design, in accordance with the standards, provides for the necessary dimensions, strength, tightness, heat-insulating and other performance qualities, which are then materialized during construction and maintained during operation.

The use of buildings for their intended purpose is usually called technological operation. In order for buildings to be used effectively, they must be in good condition, i.e. walls, coverings and other elements, together with heating, ventilation and other systems, must allow maintaining the required temperature and humidity conditions in the premises, and water supply and sewerage systems, lighting and air conditioning - to ensure the desired comfort. The processes involved in maintaining buildings in good condition are called technical service living And repairs or technical operation; they are the subject of our consideration.

Buildings constructed and put into operation are subject to various external (mainly natural) and internal (technological or functional) influences. Structures wear out, age, and collapse, as a result of which the performance qualities of buildings deteriorate, and over time they cease to meet their purpose. However, premature wear and tear is unacceptable, because it violates the working and living conditions of the people using these buildings. In addition, buildings represent great material value, which must be protected in every possible way.

Maintenance and repair (technical operation) of buildings is a continuous dynamic process, the implementation of a certain set of organizational and technical measures for supervision, care and all types of repairs to maintain them in good condition, suitable for their intended use during a given service life.

By the nature of the tasks and methods of solving them, maintenance and repair differ significantly from design and construction, although they are part of the construction industry, since they:

are carried out for a very long time compared to the duration of design and construction - tens, hundreds of years, which requires a clear vision of the future and continuity in the activities of the operational service;

have a cyclical nature with a frequency of different activities from one to three years for routine repairs and from six to thirty years for capital repairs, which complicates the planning and execution of work;

are (in particular, repairs) largely random, probabilistic in nature in terms of location, volume and time of work, which complicates their planning and requires managers and performers to be prompt in adjusting plans during their production;

affect the interests of the entire population and each person individually at home and at work, require their participation in repairs (inside apartments), i.e. they are social in nature and influence people’s mood; are associated with large expenditures of effort and money, increasing over time, which is due, on the one hand, to the aging of the building stock and the ever-increasing costs of repairs, and on the other, to its annual replenishment, which requires the attraction of new forces and means for its maintenance and repair;

for particularly important buildings and structures (for example, the Hermitage in Leningrad) they are distinguished by a strict wear prevention system that prevents their failure within a specified period, which is associated with the ability to calculate wear and tear and plan preventive work in place, volume and time, providing their production with materials, mechanisms and labor resources.

All this confirms the importance and complexity of the tasks of maintenance and repair of buildings and structures.

The operation of buildings nationwide is regulated by the Regulations on preventive maintenance systems, and a new edition of the Regulations on the maintenance and repair of buildings is being prepared. They define the principles of organizing the operation of the main types of buildings and structures, all of them are classified into groups and for them the average service life, types, frequency of inspections and repairs, as well as work related to current and major repairs are established.

Of primary importance in the operation of buildings is timely monitoring of their technical condition, checking the serviceability of building structures and engineering equipment. Such regular, not only visual, but (if necessary) instrumental monitoring prevents premature failure of buildings and allows for reasonable planning and implementation of preventive measures to save them.

Each building or structure is designed and constructed to carry out a certain process in it and therefore must have specified performance qualities. It is specific operational qualities that distinguish a residential building from a dining room, mechanical workshops, a club, a garage, etc.

The broad concept of “building construction” includes their design, construction and technical operation. Each of these three stages has its own range of tasks, but they all have a common goal - ensuring the performance of a particular building. Solving problems at each stage is interconnected - how the building is designed and constructed, these are the conditions and problems of its operation. In turn, the experience of using and maintaining constructed buildings, i.e., the experience of their operation, must be studied to improve the design and construction of new buildings.

Let us note another important feature of modern construction and operation of buildings: the novelty of the tasks and problems faced by builders and operators in connection with scientific and technological progress, the development of the northern, eastern and other regions of the country, little studied in construction terms, with special climatic and hydrogeological conditions, strongly influencing the nature of construction and operation of buildings.

In Fig. V.2, b graphically displays the relationship between costs and time for the indicated three stages of construction - between design, construction and operation. Design in modern conditions lasts a month (or months) depending on the complexity of the object and costs approximately 1-2% of the construction cost; the construction of a building, depending on its complexity, usually lasts months (sometimes years); operation, i.e. maintaining the building in good condition, lasts for tens or even hundreds of years, and in terms of costs it annually amounts to 2-3% of the replacement cost for the construction part and 4-5% for the maintenance of engineering equipment. It follows from this that approximately every 12-13 years the costs of operating buildings are equal to the costs of their construction. It is therefore important that operating costs are kept as low as possible.

An essential point in increasing the efficiency of maintenance and repair of buildings is their transfer to a design basis: now they are solved at the design stage in a special section of the project and estimate.

The design, construction and operation of each building are united by the use of uniform performance parameters; they are the core around which all scientific and practical work in the field of construction of buildings and structures is carried out.

When designing a building, performance qualities are determined by the choice of materials, structural calculations, space-planning solution, engineering equipment in accordance with the purpose of the building, Building Codes and Regulations (SNiP) and allocated appropriations.

During the construction of buildings, the values of performance parameters adopted in the project are materialized, their reliability is checked with instruments and, based on their numerical values, the buildings are accepted for operation. It is in this way that it can be confirmed that the constructed building corresponds to what was planned in the project.

When operating buildings, the main task is to maintain the performance qualities envisaged by the project and materialized during construction at a given level. They must fully comply with the purpose of the building (for example, in mechanical workshops the air temperature should be 12 ° C, and in a kindergarten building - 20-22 ° C), which is ensured by certain building structures and engineering equipment.

Thus, by setting the values performance parameters(PEC) and the development of instructions for technical operation, the design of buildings is completed, with the help of the PEC developed in the project, their construction is controlled; Based on the compliance of the actual PEC values with the design ones, buildings are accepted for operation and by maintaining the PEC at a given level, their technical operation is carried out during the established service life.

If all work during operation is carried out on the basis of comparison of actual PEC values with standard or calculated values, then such operation is scientifically justified. Unfortunately, subjective (only visual) control of the technical condition of structures is often still carried out and, based on this, the time, place and amount of work to maintain buildings in good condition is determined. Naturally, in such cases, the volume of work is accepted with a large margin, which excludes the possibility of carrying out regular work at other facilities, since the available forces and means have already been spent.

At each stage of construction, great attention should be paid to the performance parameters of a given building, which will ensure coordinated actions between designers, builders and operators based on the numerical values of PEC, i.e., it will allow organizing all construction on a scientific basis.

The efficiency of operation and its cost-effectiveness depend on many factors, in particular, to a large extent, on the professional training of the persons carrying it out, on their ability to build operation on a scientific basis.

With the growth of cities, the construction of multi-storey and high-rise buildings, their engineering equipment has become more complex, the costs of its maintenance have increased, and the entire structure of operation of the housing stock has changed. It was necessary to integrate and provide automated control of elevators, staircase lighting, establish control over water temperature in central heating systems, hot water supply, gas pollution in basements, entrances to basements, attics, other uninhabited rooms, etc.

Then all building management was consolidated into volume unified control centers(ODP), in united dis petting service(ODS) on a microdistrict scale or comprehensive dispatch service(KDS) of the microdistrict, depending on the amount of equipment installed at these points. Standard dispatching objects for residential areas have already been implemented, allowing to receive information about the operation of elevators, temperature and pressure in hot and cold water supply systems, heating, fire extinguishing, voltage at electrical inputs, lighting of entrances, alarm signals about the opening of basements and other uninhabited premises. At the entrances there is also a loudspeaker connection with the dispatcher for urgently calling specialists to eliminate malfunctions, including those on building structures, for example, roof leaks, etc. There is also a telephone connection at the ODS.

Many cities have created housing maintenance trusts maintenance and repair departments, carrying out planned repairs of buildings. They include a dispatch service with operational teams to eliminate emergency situations. However, most of the existing buildings - many residential, all service and industrial buildings - are operated by independent teams; This is a multimillion-strong army of specialists ensuring the good technical condition of buildings and structures.

Maintenance and especially building repairs, although they belong to a broad branch of construction, have specific features. Particularly complex is a comprehensive overhaul, which differs primarily in the technology of work - new construction begins from the zero cycle and is usually carried out from the bottom up by installing ready-made structures, and repair work is carried out in the cramped conditions of the existing building, when it is difficult to accommodate ancillary enterprises, cranes, and material warehouses. The desire to make fuller use of old materials and structures in repairs is associated with a labor-intensive assessment of their technical condition, since their wear varies in different parts. It is very difficult to plan such repairs, since the results of dismantling the structure, the useful yield of materials, etc. are unknown.

Persons involved in the operation and repair of buildings must have a good knowledge of their structure, operating conditions of structures, technical standards for materials and structures required for repairs. With the help of instruments, as well as by appearance and signs, they must be able to at least approximately assess the technical condition of the building and its individual structures, be able to identify vulnerable spots from which its destruction may begin, choose the most effective ways and means of preventing and eliminating it, not violating, if possible, the intended use of the building.

The theory of building operation is intended to contribute to the solution of such a vast and complex set of issues. It is she who scientifically substantiates the need and timing of operational measures, as it is based on:

knowledge of the values of performance parameters (PEC) that need to be maintained at a given level; establishing patterns of influence of external and internal factors, identifying characteristic defects, damage and prescribing methods for their elimination;

choosing methods for monitoring PEC and methods for finding defects, damage and malfunctions;

determining the methods and procedures for the most rational restoration of buildings' environmental protection standards; assigning the frequency of repairs and volumes of work; rational solution to issues of staffing structure, number and qualifications of operating personnel.

Modern complex buildings and structures can only be operated well and efficiently by professionally theoretically and practically trained specialists; Such specialists require knowledge in three main areas:

knowledge of the structure of operated buildings and their structures, their operating conditions, operational requirements for them, their structures in accordance with their purpose, as well as the purpose and size of the building; the ability to find vulnerable spots where structural destruction may begin;

understanding the mechanism of wear, corrosion and destruction of building structures under the influence of various factors and, on this basis, the effective use of methods and means of their rational protection:

possession of practical techniques and skills in using various materials and devices that allow one to successfully solve everyday problems of maintaining buildings in good condition.

Based on this, the book is divided into three sections, corresponding to the mentioned three areas of necessary knowledge:

section one - description of the design features of the three main types of buildings and structures: residential and public, industrial and special - buried, their structures, operational requirements for them; determination of goals, objectives, scientific foundations and content of operation;

section two - a presentation of the theoretical foundations of the destruction mechanism and methods of protecting building structures under typical conditions, i.e., without emphasis on the specificity of the processes occurring in buildings (since there are extremely many of them), as the basis for solving practical problems of operation and repair of buildings or structures;

section three - consideration of examples of restoring the operational qualities of three main types of buildings and structures: civil, industrial and special buried with the aim of accumulating knowledge and instilling skills in solving practical problems of their maintenance and repair.

In a book of small volume it is impossible to describe all the diversity of buildings and structures in use, to reveal all the features of the factors affecting them, all the damage and methods for restoring their performance. Therefore, of course, each section sets out the basics, the most important information, having mastered which you can practically solve the problems of operating buildings, using (if necessary) also the literature given at the end of the book.

2. Technical service And repair foundations

To effectively maintain foundations, specialists need to know the regulatory operational requirements for them, specified in SNiP, and their possible design solutions (according to textbooks), as well as the characteristics of the building’s foundations according to its design. All this information can be summarized in several groups:

about real impacts on foundations - about the magnitude and nature of loads, about the structure, strength and moisture content of foundations, about precipitation and groundwater, their depth and aggressiveness, about the danger of soil heaving, as well as about requirements for the depth of foundations;

about the features of specific solutions for foundations - strip, columnar, solid, pile, etc. in relation to given hydrogeological and climatic conditions;

on the operational requirements for foundations - their strength, stability, depth taking into account loads, bearing capacity of soils, groundwater level and freezing depth, as well as measures to protect foundations from precipitation and groundwater, especially if they are aggressive, from frost heaving;

about the elements of foundations that meet the operational requirements imposed on them - about the load-bearing element, which must be buried taking into account the strength of the soil, the magnitude of the loads, the presence of groundwater and the depth of freezing, as well as the presence of waterproofing, blind areas, etc.

It is necessary to be able to ultimately construct a structural diagram of the foundation in general form (see Fig. 1) with all the influencing factors indicated on it and a combination of structural elements.

Rice. 1. Structural diagram of the foundation

Impacts on foundations: 1- soil and groundwater; 2 - freezing and heaving; 3 - atmospheric precipitation; 4 - loads

Structural elements of foundations: / - horizontal waterproofing; // - load-bearing elements; III - vertical waterproofing and its protection; IV -- horizontal waterproofing in the floor and foundation; V- drainage; VI- foundation (natural or artificial)

It is also necessary to study the characteristics of soils and the design solution of the foundation of the building in use, taking into account hydrogeological, climatic and other features. Using the listed information about foundations, the person responsible for the operation of the building carries out a qualified examination and gives a technical assessment of “his” foundation. It must reveal to what extent the latter meets its purpose, to what extent the design and construction correctly and comprehensively take into account the operational requirements presented to the foundations and how they are implemented: how rationally the type of foundation, its material, dimensions, depth are chosen, and also how effectively it is solved protecting it from precipitation and groundwater.

If the results of such an analysis are positive, it means that the foundation was designed and built taking into account all the requirements presented to it and local conditions and is in good condition. If shortcomings and errors are identified in the design or during the construction of a building, then they must be carefully studied in order to be eliminated or eliminated in a timely manner.

prevent their development.

During operation, it is necessary to constantly maintain the foundations: avoid cutting or adding soil around the building; maintain the blind area in good condition; exclude accumulation of water near the building, and even more so flooding of the foundation; carry out other measures provided for in the operating instructions. Excessive watering of green spaces near buildings (without organized water drainage) is especially dangerous, because this often leads to an increase in the groundwater level and a change in the operating conditions of the foundation, and subsequently

behind it and the foundation.

The safety of foundations must be ensured if excavation work is being carried out next to them, when constructing a new building nearby or constructing pits for other purposes. To prevent one-sided lateral soil pressure on the foundation and its destruction, it is necessary to protect it, for example, with a sheet pile wall. For the same reason, heavy equipment and materials should not be stored near the walls of the building.

When opening a structure in connection with repair work, if there are heaving soils under the foundations, it is necessary to prevent their freezing and heaving by temporarily insulating the foundations. Experience shows that violation of the conditions for the safety of foundations leads to the destruction of buildings after many years of their normal service.

If necessary, it is necessary to carry out routine repairs to protect the foundations from destruction or put the building under major repairs to strengthen them.

Often the cause of deformation of foundations and overlying parts of a building is the forces of frost heaving, which can occur under certain conditions both during the construction period and many years after the buildings are put into operation. These conditions can and should be excluded: cutting off the soil around buildings, replacing it with easily freezing material, such as stone material, concrete, moistening the soil around buildings and under foundations.

The forces of frost heaving are divided into tangential forces, which arise when heaving soil freezes with the walls of the foundation, and normal, which arise when heaving soil freezes under the base of the foundation and acting on it from the bottom up; they are caused by the forces of ice crystallization during the transition of water into ice. Only wet soils increase in volume, and, as is known, dusty soils also retain moisture.

Therefore, under frost heaving of soils is understood as their property (under a certain combination of hydrogeological conditions within the seasonal freezing layer) to increase in volume under the influence of the forces of ice crystallization during phase transformations of the water contained in the soil and additionally sucked into the ice crystals. This property manifests itself in the uneven rise of soil and foundations due to the formation of ice inclusions. Buckling of building foundations during their operation is explained by the following factors:

freezing of soil in the foundation area; the presence of moisture in the soil;

excess heaving forces over the pressure of the overlying parts of the building;

improper foundation design - failure to implement anti-heaving measures during construction (anchor-free foundation design, lack of coating to prevent freezing of the soil with the foundation walls, etc.).

When the soil freezes, three layers can be distinguished: on top - freezing soil, below - thawed soil and between them - a transitional, dynamic layer. During the cold season, this system is in motion and changes depending on the influx of cold from above. In the second - transitional - layer, phase changes in water occur and frost heaving forces arise, which are dangerous for foundations. Lowering the freezing zone below the base of the foundation is even more dangerous, since the load on the base of the foundation from the frozen zone is determined by the area limited by 45° lines.

Normal heaving force N H acting on the base of the foundation is determined by the formula

N a = nRfhu

Where P- overload coefficient of normal heaving forces equal to 1.1; R- an empirical coefficient taken for highly heaving soils equal to 0.006-10 N/cm 3, this is a quantitative indicator of the heaving of the foundation with a specific normal force per 1 cm 2 of the base with an increase in the thickness of the freezing layer by 1 cm; f- area of the foundation base, cm 2; hi- height of the frozen soil layer, cm.

Example. Determine the normal strength of frost heaving N a on a foundation with an area of 240-240 = 57,600 cm 2 with a freezing depth of 30 cm, overload coefficient "= 1.1, empirical coefficient R= 0.006*10 N/cm 3 and a load on the shoe (base plate) equal to 80-10 kN.

N H = 1.1 *0.006*57*600*30 =114*10 kN.

The load-bearing capacity of a column (foundation rack), which absorbs the normal forces of frost heaving of the foundation, with a concrete strength of 10.8 MPa and a rack cross-section of 30x30 cm, is:

30*30*108 =97.2*10 kN,

that the greater the load on it is 80 * 10 kN, therefore, the rack will be lifted by frost heaving forces exceeding the bearing capacity of the foundation rack and the load on it:

80 < 97,2 < 114*10 кН.

An important anti-heaving measure is to protect the foundations and the soil surrounding the foundation from excessive moisture and freezing: the soil moisture should not be allowed to increase in a zone of 5 m around the building, and conditions should not be created (for example, cutting the soil around the building) conducive to freezing of the foundation. Maintenance workers need, especially in the autumn and winter, to monitor the serviceability of drainage devices, to prevent stagnation of water near foundations and leakage from engineering systems, especially before the soil freezes, etc. Repair work carried out near buildings should not interfere with the flow of atmospheric and melt water and influence the depth of soil freezing. Blind areas and heat-insulating slag cushions that protect the soil around the building from freezing must always be in good working order. Damage to foundations can be caused by a number of reasons:

deformation of the base and uneven foundation settlements;

foundation overload;

errors in the design of the foundation and in the selection of materials for it;

exposure to an aggressive environment on the foundation material.

Strengthening foundations can be carried out by strengthening their masonry, increasing their dimensions - width and depth, as well as transferring the load to the underlying layers of soil (Fig. 2). Examples of damage and restoration of plinths, blind areas and entrance platforms are shown in Fig. 3.

The mentioned methods of strengthening foundations are not equivalent and each of them can be used in certain conditions. It should be borne in mind that work to strengthen foundations is not only complex and time-consuming, but also very responsible. They must be carried out by specialized teams very carefully, using grips (usually no more than 2 m) so as not to damage adjacent areas

Rice. 2. Methods of strengthening foundations

A- cladding when the foundation is damaged by aggressive waters; b- injection of solution into the gap during frost heaving; V - by placing piles; d, e, f, g, h, i- widening of the sole using reinforced concrete tides and steel ties; k, l, m - under-

1 shotcrete; 2- insulation; 3 and 4.-protective wall; 5 - foundation rupture 6 - injector; 7 - compacted soil; 8 And 9- beams; 10 - piles; 11- reinforced concrete tides; 12 -steel rod, 13 - transverse beam; 14 And 15 - longitudinal beams; 16 - piles; 17 - additional foundation; 18 - base for beams

and the overlying parts of the building. To carry out such work, projects are drawn up and technological maps are developed.

In some cases, in particular if there are cracks in the walls, as a result of a technical inspection and feasibility study, it may be advisable to

Rice. 3. Examples of damage and restoration of the base (a, b, c), blind area (d, e) and entrance platform (f, g, h)

simple strengthening not of the base or foundation, but of the walls by installing metal strands with prestressing, ring grips along the internal main walls at the floor level on the outside of the building. Moreover, thanks to the prestressing of the ties installed along the length and height of the building, its entire frame is given high rigidity, eliminating local deformations of the bases or foundations. The experience of the Moscow Housing Project on strengthening buildings in this way (for more details, see the next paragraph) confirms its economic efficiency under certain conditions.

Bibliography

1. Boyko M . D .

Maintenance and repair of buildings and structures. Textbook for universities. L.: Stroyizdat, Leningrad. department, 1986.-256 p.

Rip G.A.

Technical maintenance of buildings. M.: Stroyizdat, 1982

Technical exploitation of foundation soils, foundations and basements of buildings

Methods for strengthening the bearing capacity of foundations

Technical exploitation of foundation soils, foundations and basements of buildings

The foundation carries the load from the building and transfers it to the base (natural or artificially compacted soil).

Base – a layer of soil that takes the load from the building and is in a stressed state. Soils can be in a naturally dense state and artificial - soils that have been strengthened to increase their bearing capacity. The following types of soils are distinguished: rocky, coarse-grained (gravel, crushed stone), sandy, clayey (loam and sandy loam), loess soils and organic sediments (peat, other products of human activity).

When studying soils, their bearing capacity and hydrological regime are taken into account, i.e. standing level and aggressiveness of groundwater, load from the constructed building.

Rocky and coarse soils are considered soils with strong bearing capacity. Clay soils are susceptible to freezing and heaving. Clay soils, as well as sands and organic soils, are considered weak soils.

Artificial foundations are soils that have been strengthened or hardened in one of the following ways: backfilling, pumping out groundwater by installing a drainage system, driving anchors to fasten steeply dipping soil layers, electrochemical compaction, resinization, cementation, silicatization and firing of clay soils.

In this textbook, these methods are not discussed in detail, since the preparation of the territory and strengthening of the soil precede the construction of the building. In the discipline being studied, the work performed at the stage of operation of the building is considered.

Technical maintenance of the foundations consists of monitoring the settlement of the building, the presence and nature of cracks in the walls, the serviceability of the drainage system, and compliance with the design layout of the area around the building. In particular, it is prohibited to add soil around the building above the blind area, to dig pits and carry out other excavation work closer than 10 m from the building, to plant or cut down trees without special permission.

Foundations are made from materials that are highly frost-resistant and moisture-resistant, so they are constructed from well-fired clay bricks, rubble stone or reinforced concrete structures.

Most often in the construction of residential buildings the following foundation structures are used: strip, pile, columnar and a foundation in the form of a box-section slab.

Strip foundations (ruble or brick, or made of prefabricated reinforced concrete blocks, reinforced concrete panels) are a solid wall mounted on a cushion. Columnar foundations are pillars mounted on a cushion. The load from the walls is collected on a rand beam, which is placed on the foundation pillars. Strip and column foundations are used in low-rise buildings up to 5 floors, built on soils with high bearing capacity.

Pile - are piles driven into the ground or filled by pouring cement into a mold directly in the ground. The load from the building is transferred to the pile grillage. Pile foundations, as well as foundations in the form of a box slab, are used during the construction of multi-story buildings on soft soils.

The foundation structure and basement floor form the underground part of the building (basement), the structure of which is shown in Fig. 1.1.

ABOUT platform - a concrete or asphalt-concrete meter-long strip closely adjacent to the base to protect against the penetration of melt water and precipitation from the roof into the basement. It is installed on the outside along the perimeter of the building 15 cm above the roadway, with a slope of 0.03 from the building. Settlements and cracks in blind areas must be sealed with bitumen, asphalt, mastic or other material from which it is made.

The presence of cracks on the walls, curvature of masonry rows, separation of external walls from internal ones, the presence of moisture on the surface of underground or basement walls are the cause of malfunctions in the foundations or base of the building.

The main reasons for deformation of soil foundations are: exceeding the design loads on the foundation; external dynamic loads (seismic, explosive, traffic, etc.); shallow foundation depth; errors during geotechnical surveys; design errors, etc.

Minor and uniform deformations (settlements) are not dangerous for buildings, large and uneven deformations (settlements) can lead to the formation of cracks, structural failure, and accidents of buildings and structures.

Significant precipitation, uniform along the entire perimeter of buildings, does not cause serious deformations and does not interfere with the normal operation of the building. Uneven precipitation is dangerous.

Buildings are classified according to sensitivity into low-sensitive and sensitive. Low-sensitive buildings are those that sag as a single spatial whole either evenly or with a roll, and buildings whose elements are hinged.

Buildings with rigidly connected elements, the displacement of which can lead to significant deformations, are sensitive to uneven precipitation.

The maximum differences in settlement of individual parts of the foundations of columns or walls of buildings should not exceed 0.002 of the distance between these parts.

Limit values for average settlement of building foundations:

large-panel and large-block - 8 cm;
with brick walls - 10 cm;
frame - 10 cm;
with a solid reinforced concrete foundation - 30 cm.

Depending on the nature of the development of uneven settlement of the foundation and the rigidity of the building, the following forms of deformation are distinguished: rolls, deflections, bends, distortions, torsion, cracks, faults, etc.

Misalignment occurs when sudden uneven settlement develops over a short section of a building. Deflection and camber are associated with the curvature of the building. Torsion occurs when there is unequal roll along the length of the building, in which it develops in different directions in two sections of the building. The maximum roll value should not exceed 0.004 of the building height. Deflections for large-panel buildings should not exceed 0.0007 of the length of the section on which the deflection is checked, for brick and block buildings - 0.00013.

From the influence of various factors, precipitation can develop due to changes in the structure of the soil, which can be disrupted due to the influence of groundwater, meteorological influences, freezing, thawing and drying.

If the structure is damaged and the bearing capacity of the foundation is lost during operation, various methods of strengthening the soil are used: compaction, consolidation, replacement.

The second basis of the building is the foundations, the work of which takes place in difficult conditions. They are subject to external force and non-force influences. Power - these are loads from overlying structures, soil pressure, heaving forces, seismic shocks, vibration, etc.; non-force influences - temperature, humidity, exposure to chemicals, etc.

All these impacts can lead to stress and destruction in the foundations and disruption of the operating conditions of the building.

To ensure the necessary operating conditions for buildings, foundations must meet a number of requirements: strength, durability, resistance to overturning, slipping, and be resistant to groundwater and aggressive water.

The operational properties of foundations are influenced by the design design.

When accepting a building for operation, it is necessary to carefully check the quality of the waterproofing of foundations and basements.

The main reason for physical wear and tear and a decrease in the bearing capacity of foundations is the destructive effect of ground and surface waters, therefore it is necessary to take measures to drain surface water and lower the groundwater level.

To protect the soil near the building foundation and basement walls from being moistened by surface water, a blind area of at least 0.8 m wide is arranged with a slope from the building of 0.02-0.01 for asphalt and 0.15-0.1 for cobblestone blinds.

Sidewalks should be constructed with a waterproof coating (asphalt, concrete) with a slope from the building walls of 0.01-0.03; in waterproof soils, preparation for sidewalks is carried out over a layer of rich clay.

The technical operation of foundations and foundations includes measures for the maintenance of adjacent areas. To protect the foundations from moisture, the yard area must have a slope from the building of at least 0.01 towards the drainage trays or storm drainage wells; the drainpipes must be kept in constant repair.

Excavation work near a building is permitted only if there are projects that provide for the protection of bases and foundations from moisture and deformations caused by changes or redistribution of loads.

If cracks appear in the walls due to settlement of the foundation soil, it is necessary to place beacons and observe them for 15-20 days.

If there is unorganized drainage, it is necessary to protect the pits from precipitation by installing canopies.

Basements and technical undergrounds must have temperature and humidity conditions in accordance with established requirements.

In unheated basements and technical undergrounds, the temperature and humidity conditions must be maintained, in which the air temperature is maintained at least 5 ° C and the relative humidity is not more than 60%. In heated basements, the temperature and humidity conditions that prevent condensation from forming on the surface of the enclosing structures are set depending on the nature of the use of the room. Basements and underground spaces must be regularly ventilated using exhaust ducts from ventilation openings in windows, basements or other devices, ensuring at least one air exchange.

In buildings with heated floors on the ground floor, the vents in the basement are kept open. In buildings with cold floors, the vents are closed when cold weather sets in.

The area of the vents should be approximately 1/t area of the basement or technical underground.

Entrance doors to the technical underground, basement must be locked (the keys are kept in organizations for the maintenance of the housing stock, the community service organization, the janitor, workers living in these houses), a special inscription is made on the door about the storage location.

If transit engineering communications pass through the rented premises, the tenant is obliged to provide access to them to representatives of the relevant organizations for servicing the housing stock and city utilities at any time of the day.

The housing maintenance organization must regularly (according to the recommendations of sanitary authorities) carry out deratization and disinfection to destroy rodents and insects in common areas, basements, and technical undergrounds.

Foundations and basement walls become wet due to damage in piping systems; in case of detection of basement flooding leaks, it is necessary to establish the causes and take appropriate measures: install and disconnect the damaged section of the pipeline, eliminate faults in the pipeline, blind area, drainage system, and correct damaged waterproofing.

To prevent premature wear of individual parts of the building and engineering equipment, eliminate minor damage and malfunctions, routine repairs are provided.

The duration of effective operation of the building before the next routine repair of the foundations, depending on the structure, ranges from 15 to 60 years.

During routine repairs of foundations and basement walls, the following basic work must be performed:

sealing and filling out joints, seams, cracks, restoration in places of the cladding of foundation walls from basements and plinths;
elimination of local deformations by re-lining and strengthening walls;
restoration of individual waterproofing sections of basement walls;
punching (sealing) holes, sockets, grooves;
strengthening (arrangement) of foundations for equipment (ventilation, pumping);
changing individual sections of strip, columnar foundations or chairs under wooden buildings, buildings with walls made of other materials;
installation (sealing) of ventilation ducts, pipes, repair of pits, entrances to the basement;
replacement of individual sections of blind areas along the perimeter of buildings;
sealing entrances to the basement and technical underground;
installation of beacons on walls to monitor deformations.

During major repairs of foundations and basements

perform the following work:

strengthening the foundations of stone buildings, not related to the superstructure of the building;
partial replacement or strengthening of foundations under external and internal walls, not related to the superstructure of the building;
strengthening foundations for engineering equipment, repairing brick lining of foundation walls on the basement side in some places;
relaying brick plinths;
partial or complete relocation of pits near basement and ground floor windows;
installation or repair of waterproofing of foundations in basements;
restoration or installation of a new blind area around the building;
restoration or installation of a new drainage system.

ABSTRACT

Technical exploitation of foundation soils, foundations and basements of buildings