6. Technological maps and their differences from the work plan (work project)

The main document of the construction process, regulating its technological and organizational provisions, is a technological map (TC). TCs are developed for individual or complex processes. Technological maps provide for the use of technological processes that provide the required level quality of work, combining construction operations in time and space, compliance with safety regulations, it indicates the most rational composition of the working unit to ensure the effective functioning of the technological process, distribution between working operations; work and rest schedules are given, the Labor Code specifies the needs for materials, conditions and tools, technological schemes, cost calculations, requirements for the quality of work, technical specifications, etc.

TC are integral part PPR. There are three types of TCs in the construction: standard, not tied to the object under construction and the local conditions of the construction; standard, tied to the building or structure being constructed, but not tied to local conditions; workers tied to the facility under construction and the local conditions of the building.

TCs should be developed on the basis of progressive technologies, taking into account the achievements of world science and practice; new technical means, industrialization and comprehensive mechanization of processes and should ensure increased labor productivity, improved quality of work and reduced production costs.

5. Roofing technology.

The installation of roofs is the last stage in the construction of the frame of a building or a rough building. Technological process roofing device depends on the type of roofing used roofing material. Roofing work with a low estimated cost (up to 3%) amounts to 10-15% of the total labor intensity. D/B roofs are waterproof, waterproof, frost-resistant and durable, windproof and heat-resistant. They have a service life: roll tiles - 10 years, tiles, metal tiles - 60 years, slate tiles - 30 years

Roll roofs . Base - reinforced concrete slab, solid wooden flooring (humidity<=23%), цементно-песчаные и асфальтные стяжки. Для плоских кровель – цементно-песчаная стяжка – создается уклон; делается полосами шириной 2-4м. Основание для рулонной кровли д.б. просушено, обеспылено и огрунтовано мастикой. Для рулонных материалов наклейка производится на мастики (горячие и холодные); если наплавляется, то кол-во слоев зависит от уклона крыши. Оклейка осуществляется в одном направлении с нахлестом. Оклейка ведется с карнизов и с примыкающих к дыморям воронок (от пониженных участков к повышенным). При уклоне кровли до 15% полотнища наклеивают перпендикулярно, а при уклоне более 15%- параллельно направлению стока воды. На коньке устраивается перепуск (25 см на противоположный скат).

Sheet roofing /tiles, metal profiles/. Lay on the sheathing or flooring in even overlapping rows. The edge of the first row should hang over the cornice board when installed. The roof ridges and ribs are covered with shaped ridge parts, laid in a 100mm overlap.

The tiles are heavy, requiring a large roof slope (at least 45 0); installation starts from the cornice, laid out in rows, gap -2mm. Laying in stripes: 3-4 rows.

Steel sheet roofs: used as galvanized, as well as black. roofing steel. The steel roof is assembled into a pattern and secured with single or double seams. The paintings are secured with strips of roofing steel.

Mastic roofs. The main material is mastic, prepared directly at the place of its installation from paste using a converted mortar mixer. Application using a mortar pump with a nozzle. To increase the adhesion of the mastic to the insulated surface, the base of the coating is pre-primed with cold bitumen primers. The mastic is applied in 3 layers with a thickness of no more than 5mm. The first layer is lime-bitumen paste, the subsequent layers are lime-bitumen mastics. Reinforcement is done with fiberglass or fiberglass mesh. They are joined with an overlap of 5-7 cm at the junction points. Each layer is rolled until the surface takes on a glossy appearance.

Prefabricated roofs. They are made from self-supporting complex roofing panels with a glued waterproofing layer. The roofing panels are manufactured at the factory, and installation is carried out using a crane. In factory conditions the panels are covered with only one layer of insulation, the remaining layers are glued after the panels are installed.

Diesel hammers are used as directional hammers) by impact.

2) explosive method(effective for soil freezing depths of 0.4-1.5 m and large volumes of work; mainly in undeveloped areas). Spanish short-delayed explosions (portions of charges explode at intervals in time; for frozen soils 15-20 milliseconds; it is possible to loosen an area of ​​250 cubic meters with a thickness of up to 2.5 m);

3) Development of frozen soil: Frozen soil is cut into blocks. With small-block cutting, the soil is cut into blocks taking into account the dimensions of the excavator bucket; with large-block cutting, the soil is cut into separate large blocks, then removed from the soil with a fork. The size of the block depends on the lifting capacity of the crane. You can also pull it out of the pit with a tractor.

3. Thawing of frozen soil. It is carried out by thermal methods, which are characterized by significant labor and energy intensity. They are used when the use of other methods is unacceptable and unacceptable (near underground communications and cables; during emergency and repair work; in cramped conditions). Methods: 1) using steam (Fig. 3) (use steam needles; thawing in the radial direction; note If additional soil moisture does not cause negative consequences); 2) defrosting with hot water (using water circulation needles); 3) chemical method (using salt solutions - NaCl, CaCl 2; the solution is poured on the surface of the soil; thawing 20-22 cm per day; low freezing temperature of the soil -15 o C.. -20 o C); 4) electrochemical method (thawing due to a chemical reaction - perforated pipes are lowered or driven into the wells, a solution of salts is supplied into them, the pipes are connected to the electrical network) 5) thawing with ordinary water (ordinary water is poured onto the surface, when When it freezes, it releases heat.) 6) using electricity. There is an electrode method (Fig. 4) (thawing from top to bottom with horizontal electrodes; from top to bottom with vertical electrodes; from bottom to top with vertical electrodes; in all cases, the electrodes are connected to the electrical network, and sawdust moistened with table salt is poured onto the surface); coaxial heaters and electric needles; 7) thawing in greenhouses (a box on top, heating equipment underneath); 8) use of solar energy (a film is laid on the surface, creating a greenhouse effect)

Features of excavation work in winter

In winter, when negative temperatures are established, the soil freezes due to heat loss and the transition of water contained in its pores into ice, accompanied by a change in its physical and mechanical properties (strength, deformability, thermal conductivity, etc.).

Considering that when freezing, the mechanical strength of the soil, and therefore the labor intensity of development, increases sharply, they try to carry out measures to preliminary protect the soil from freezing, ensuring its development in a thawed form. However, the main methods of preparing and developing soils in winter are protecting them from freezing, thermal and chemical thawing, loosening and mechanical development of frozen soils. The factors that determine the choice of methods and methods for winter soil development are the volume of work, soil properties, the type of earthen structure and specific construction conditions.

Soil protection from freezing is carried out long before the onset of cold weather by plowing with harrowing, deep loosening, covering with insulating materials and chemical treatment.

To plow the soil, various plows with a loosening depth of at least 35 cm and rippers with a loosening depth of 50 ... 70 cm are used. Then the soil is harrowed to a depth of 15 ... 20 cm. For deep loosening (to a depth of 1.3 ... 1 .5 m) use single-bucket excavators with a bucket with a capacity of 0.4 ... 0.65 m 3, while the soil is excavated and laid in place of the adjacent (previous) excavation.

Local materials are used as insulation materials: dry leaves, peat, sawdust, straw, reeds, slag, etc.
Posted on ref.rf
Polymer materials, films, foam, etc. can also be used. Sometimes the soil is chemically treated before plowing, ᴛ.ᴇ. impregnation of the surface layer of soil with calcium chloride and sodium, sodium nitrite-nitrate, which lower the freezing point of water in the soil (to - 30°C). Frost-protected soil is developed using the usual mechanized method.

At the same time, when the soil could not be protected from freezing in a timely manner and according to the work schedule, it is extremely important to develop the soil in the winter, ᴛ.ᴇ. in a frozen state, then in this case it is necessary either to thaw them or to develop them in a frozen state using special means and methods.

Methods for thawing frozen soils are based on the fact that due to the heat transferred to the layer of frozen soil, the ice in its pores melts and the soil becomes thawed. Soil thawing is used for small volumes of work, in cramped conditions, hard-to-reach places and in cases where more economical and less energy-intensive methods cannot be used. Thawing of the soil is carried out using both natural heat sources - solar heat, heat from water from natural reservoirs, and artificial ones - through the combustion of solid, liquid or gaseous fuels, the use of steam or electricity. Based on the direction of heat propagation in the soil, the following three basic methods of thawing can be distinguished: from top to bottom (surface); from bottom to top (deep); in the radial direction.

Surface thawing is carried out either using natural heat sources or artificial ones - hot gases (fire method), in greenhouses, reverberatory furnaces, horizontal electrodes, or chemical methods. Chemical thawing involves introducing a solution of sodium chloride into the soil, under the influence of which ice crystals dissolve in the pores of frozen soil.

Deep and radial thawing is carried out using hydraulic, circulating water, steam and electric needles, as well as electrodes.

Loosening and development of soils in a frozen state, it is carried out explosively or mechanically.

Explosive (hole or slot) method is one of the basic methods of preparing frozen soils for excavation. It is especially effective at freezing depths of 0.4 ... 1.5 m or more and with significant volumes of frozen soil development. It is used primarily in undeveloped areas, and in built-up areas using shelters and explosion localizers (heavy loading platforms). When loosening to a depth of 1.5 m, borehole and slot methods are used, and at greater depths, borehole or slot methods are used. Slots at a distance of 0.9 ... 1.2 m from one another are cut with milling-type slot-cutting machines or bar machines. The slits are charged through one with elongated or concentrated charges, after which they are filled with sand on top. Boreholes and wells are placed in a checkerboard pattern.

When loosening the soil using the explosive method (Fig. 4.22, a), the area is divided into grips, where holes are drilled in the first of them, loaded and exploded; the second work is not performed due to safety conditions; on the third, soil development is carried out. The dimensions of the grips are determined based on the shift productivity of the excavator (excavators).

Mechanical loosening of frozen soils is used for freezing depths of 0.4 ... 1.5 m and small-area excavations of pits and trenches. In this case, the frozen layer is crushed or chipped by dynamic or static action of special replaceable working equipment installed on the base machine (tractor, excavator, etc.). Dynamic impact is provided due to impact, vibration or their combined impact using a ball or wedge hammer, diesel hammers, wedge tractor rippers, etc.
Posted on ref.rf
Static impact during the destruction of frozen soil is ensured by introducing into it a working element consisting of one or several (up to 5) teeth while the tractor (tractor) moves simultaneously.

To loosen frozen soil (Fig. 4.28) mechanically when developing pits and trenches, weightless rippers and earth-moving and milling machines are used, as well as bar machines (for cutting frozen soil into blocks), and when planning the site vertically, mounted rippers are used. These machines work in tandem with excavators, which develop both loosened frozen and unfrozen soil.

Rice. 4.28 – Loosening frozen soils when constructing pits

If the soil freezes at a shallow depth, it is loosened using tractor rippers using longitudinal penetrations at an angle of 60°. The loosened soil is moved by a bulldozer to the end of the pit and loaded onto dump trucks by an excavator. Subsequent layers of frozen soil can be developed using a ripper, first with transverse penetrations, then longitudinal and diagonal. The ripper tooth, based on the properties of the soil and the power of the bulldozer, is buried by 0.5 ... 0.8 m.

At large freezing depths, block methods for developing frozen soils are often practiced, when their solidity is first broken by cutting them into blocks (strips) using special machines equipped with circular saws or bars. Usually small- and large-block methods of soil development are used. Small block method(Fig. 4.28, b) are used when digging small pits and trenches at a freezing depth of 0.6 ... 1.4 m. Using longitudinal and transverse slots of a disk milling machine or bars, the frozen layer is cut into blocks measuring from 0.6 x 0 .8 to 1 x 1.1 m, and then an excavator with a straight shovel (bucket capacity 0.65 ... 1 m 3) loads the frozen blocks and develops the thawed soil. Large block method used when developing pits near buildings or structures, when ground shaking, which is inevitable during impact and vibration-impact loosening, is not allowed. Frozen soils are cut into blocks weighing 4 ... 10 tons, followed by their removal from the face using bulldozers (Fig. 4.28, c), cranes (Fig. 4.28, d) or electric winches. When using cranes, the blocks are torn off and moved away from the thawed base with bulldozers, and then, using a pincer grip, they are loaded onto dump trucks with the tailgate removed (Fig. 4.28, d). In this case, the recesses are divided into two grips; on the first, blocks are cut, and on the second, they are removed with a crane and the base is cleaned.

The development of soils in a frozen state can only be carried out with the help of powerful earth-moving equipment, which allows the development of frozen soil without its preliminary preparation (loosening). Hydraulic excavators are used as such equipment. They work especially effectively when using forward and reverse shovels with active buckets, in the bottom of which pneumatic hammers with teeth are mounted, ensuring the destruction of frozen soil.

Trench development methods in winter, the following: development of a trench into a reserve, protecting the soil from freezing, without preliminary preparation, with preliminary loosening. The development of trenches in the reserve (ᴛ.ᴇ. in advance) for the full profile is carried out in the autumn period before the onset of frost. The disadvantage of this method is that the slopes of the trench partially collapse over time, and the soil dump freezes together by the time the pipelines are backfilled, which requires preliminary loosening before backfilling. Methods for developing trenches while protecting the soil from freezing are fundamentally similar to the methods discussed above. Trenches are developed without preliminary preparation in cases where the necessary technical conditions are available. With a freezing depth of up to 0.3 m, trenches can be developed with single-bucket excavators, and in soils with a freezing depth of up to 1.5 m, they can be torn out to the full profile with rotary excavators.

The method of developing a trench with preliminary loosening of the soil by explosive or mechanical means is used when the soil freezes to a depth of more than 0.4 m. Loosening is carried out with blasthole charges or using rippers. The loosened soil is leveled with a bulldozer, and the trench is developed with a single-bucket excavator. It is extremely important to take the length of the section of loosened soil equal to the shifting productivity of the excavator in order to avoid re-freezing of the soil.

It is extremely important to strictly coordinate the pace of excavation work when digging trenches in winter with the pace of insulation and laying work on the pipeline, since if the excavation work is advanced even by 2-3 days, there is a danger of the soil dump freezing. This will require either preliminary loosening of the soil in the dump before backfilling the pipeline (which is not always easy to do), or powdering the pipes before backfilling.

When developing trenches in frozen soils, several types of machines are most often used, each of which prepares the work front for the machines performing subsequent operations. For example, clearing snow from the ground surface with a bulldozer allows you to begin loosening or cutting through the frozen soil with rippers (bar machines), which, in turn, prepare the work front for an excavator, etc. With a freezing depth of up to 1.3 m, trenches and narrow pits can be developed using backhoes with a bucket capacity of 0.65 m 3 or more, with preliminary cutting of slots through 0.4 ... 0.5 m with a bar machine. Moreover, with a trench width of up to 2 m, it is enough to make longitudinal slits along the trenches, and with a width of more than 2 m, transverse slits are made at an angle of 30°, cutting the blocks in the form of diamonds. Wide trenches or foundation pits (up to 8 m wide) are developed using two end drives of an excavator. When developing wide trenches for laying collectors in frozen soils with a significant freezing depth, bar machines, excavators with wedge hammers and backhoes are usually used.

Backfilling trenches with pipelines in winter conditions. If the construction of pipelines is carried out using a combined flow method (the pipeline is laid in a trench immediately after its development), it is backfilled with thawed soil using a bulldozer, as in normal conditions. If the soil in the dump freezes, for example, if the flow is disrupted, the pipeline in the trench is sprinkled with thawed soil to a height of at least 0.2 m above the pipe to avoid damage to the insulation. Further backfilling of the pipeline with frozen soil that does not contain clods larger than 5 ... 10 cm is carried out using bulldozers.

1. SNB 5.01.01-99 Foundations and foundations of buildings and structures. – Mn.: Ministry of Architecture and Construction of the Republic of Belarus, Mn., 1999. – 36 p.

2. SNiP 3.02.01-87. Earthworks, bases and foundations / Gosstroy USSR - M.: CITP Gosstroy USSR, 1988. - 128 p.

3. Manual P11-01 to SNB 5.01.01-99. Geotechnical reconstruction of building foundations and structure foundations. – Mn.: Ministry of Architecture and Construction of the Republic of Belarus, Minsk, 2001. – 120 p.

4. Manual P17-02 to SNB 5.01.01-99. Design and installation of retaining walls and foundation pits. – Mn.: Ministry of Architecture and Construction of the Republic of Belarus, Mn., 2003. – 95 p.

5. Earthworks (Builder's Handbook) / Ed. L.V. Grinshpuna. – M.: Stroyizdat, 1992. – 352 p.

Topic 5. Concrete and reinforced concrete works

Features of excavation work in winter - concept and types. Classification and features of the category "Features of excavation work in winter" 2017, 2018.

Pile classification

Modern construction makes it possible to erect buildings of various designs on almost any soil. Pile classification is carried out according to the method of transferring loads from structures to the ground, the shape of the trunk, cross-section, material and methods of work.

According to the production method, piles are divided into driven and stuffed. Production driven piles carried out in the factory, after which they are transported to the construction site and immersed in the ground using shock or non-impact methods. With a howl turn, cast-in-place piles are formed directly on the construction site in the ground itself.

Based on the material, piles are divided into reinforced concrete and concrete, wood and metal. According to their shape, piles come in round, square and prismatic sections. Along the longitudinal section, the piles can be of the same width, tapering towards the end or, conversely, widening.

Features of excavation work in winter are negative air temperatures, the presence of snow and ice. Freezing of soils complicates their development, transportation, laying and compaction. The increase in construction costs caused by winter work must be compensated. Soils are protected from freezing as follows:
Before the onset of frost, soils to be developed in winter are protected from freezing by laying a layer of material with low thermal conductivity, loosening (ploughing) or treating with salts that lower the freezing point of water;
during the work process, the compacting layer is removed only in an area sufficient in size for the operation of the SCM during a shift, so that the exposed soil does not have time to freeze before its development;
The soil should be developed in the shortest possible work area.

Method of protecting soils from freezing and technology its developments are selected through a technical and economic comparison of various options possible under given conditions. The simplest and most economical way to prevent deep freezing of soils is to preliminary loosen them before the onset of frost, carried out by cross-plowing with tractor plows or trailed rippers to a depth of 25-35 cm. After plowing, harrowing is carried out to a depth of 10-15 cm. The pores of the loosened soil, filled with air, reduce its thermal conductivity.

Freezing of loose soil occurs more slowly than the surrounding dense soil. The frozen layer of loosened soil has low strength and is relatively easy to develop with excavators or bulldozers. The insulating effect of loosened soil increases when snow accumulates on it. Soil insulation by loosening is usually used in areas planned for development during the first third of winter.

One way to protect soil from freezing is to treat it with chemical additives that lower the freezing point of water. The salts CaC12 and NaCl are most often used for this purpose. Soil treatment involves pouring solutions of these salts onto its surface. Penetrating into the soil, salt solutions reduce the freezing point of moisture in the soil, and thereby protect it from freezing. A layer of soil impregnated with salt solutions, in turn, protects the underlying layers from freezing.

Loosening frozen soils using this method should be used when the soil freezing depth h is more than 0.4 m (mainly in undeveloped areas, and in built-up areas - with the use of shelters and explosion localizers).

14 In construction, of the total volume of earthworks, from 20 to 25% is carried out in winter conditions.

At subzero temperatures, the freezing of water contained in the pores of the soil significantly changes the construction and technological properties of non-rocky soils. In frozen soils, the mechanical strength increases significantly, and therefore their development with earthmoving machines is difficult or even impossible without preparation. The depth of freezing depends on the air temperature, the duration of exposure to negative temperatures, the type of soil, etc. Preliminary preparation of soil for development is carried out in one of the following ways : protecting the soil from freezing, loosening frozen soil, thawing frozen soil. Direct development of frozen soils can be carried out using a block method or earth-moving machines with working equipment that destroys frozen soil in its natural occurrence. It is allowed to develop frozen soil with single-bucket excavators, depending on the capacity of the bucket, when the thickness of the frozen layer is from 0.25 to 0.4 m. Explosive loosening is one of the main methods of preparing frozen soils for development with excavators. This method is very effective for freezing depths of more than 1 m and large volumes of work carried out in newly developed areas or far from buildings and structures.

The essence of the explosive method of loosening consists in crushing frozen soil using the energy of explosion of charges placed in cavities previously created in the soil (boreholes, wells, sleeves, boilers, cracks).

Mechanical loosening of frozen soil is used for freezing depths of 0.4 to 1.5 m and small-area excavations of trenches or pits.

The essence of mechanical loosening consists in crushing or chipping the frozen layer by dynamic or static action, which is carried out by replaceable working equipment installed on the base machine (excavator, tractor, etc.). Dynamic impact is carried out using shock, vibration and vibration-impact methods.

In the impact method, a ball hammer or wedge hammer, a diesel hammer, wedge tractor rippers, etc. are used.

By static action, the destruction of frozen soil is carried out continuously by a working element consisting of one or several (up to 5) teeth, embedded in the soil when the tractor (tractor) moves.

Thawing of frozen soils is used for small amounts of work, in cramped conditions, hard-to-reach places and in cases where it is impossible to use more economical and less energy-intensive methods. The essence of the thawing method is that heat transferred to a layer of frozen soil melts the ice in its pores and turns the soil into a thawed state.

15. In this technological map, the following composition of mechanisms is taken as an example: bulldozer DZ-34 with mounted loosening equipment DP-9S and excavator EO-4124 backhoe, equipped with a bucket with teeth with a capacity of 0.65 m 3, intended for the development of loose and cohesive soils of groups I-IV and pre-loosened rocky and frozen soils with pieces no larger than 400 mm in size.

2.5 Along the designated trench route and adjacent to the non-territory in places where pipes are stored and laid out, snow is cleared with a bulldozer if necessary.

2.6 After this, they begin to loosen the frozen soil using a DP-9S mounted ripper along the width of the trench adopted in accordance with clause 3.3SNiP3.02.01-87. Loosening of the soil is carried out layer by layer in two passes. To ensure the front of work for the excavator, the top layer is initially loosened to a depth of 0.4 m and completely removed by a bulldozer to a dump in parts remote from the slaughterhouse. During the second excavation, the soil is loosened to the remaining freezing depth in a section of the trench about 50 m long and (as necessary) a rough leveling of the loosened area is done with moving large blocks of soil to the dump.

The EO-4124 excavator, moving along the leveled surface of the loosened soil along the axis of the trench, develops the soil to a level of minus 2.1 m and loads the soil into dump trucks. The trench is developed by an excavator from low elevations of the longitudinal profile towards the slope. The scheme for developing soil in a trench is shown in Figure 1.

1 - excavator EO-4124; 2 - bulldozer DZ-34S with mounted ripper DP-9S; 3 - dump truck KAMAZ-55111; 4 - inventory fencing; 5 - pole

Figure 1 - Scheme of soil development in a trench

2.7 Further loosening of the second layer of frozen soil is carried out each time to a volume of soil that ensures the operation of the excavator for 2 shifts.

2.8 Cleaning the bottom of the trench to the design mark is carried out with the same excavator using a leveling plow. The shortfall remaining after mechanized cleaning should not exceed 0.05 m.

2.9 The need to perform manual work to clean up the shortfall is determined by linking the map to specific conditions, depending on the purpose of the trench and the type of communications.

2.10 Soil is transported by KAMAZ-55111 dump trucks and others along a planned dirt road for a distance of up to 1 km. Dump trucks approaching for loading are installed on pre-set poles at a distance of at least 2 m from the bottom of the excavation slope.

2.11 A DZ-34S bulldozer is used for the construction and maintenance of roads and soil leveling at the spoil dump.

2.12 The method of restoring foundations damaged as a result of freezing is agreed upon with the design organization.

21. Drainage and lowering of groundwater levels. When constructing excavations located below the groundwater level, it is necessary to drain the water-saturated soil and ensure its development under normal conditions. In addition, it is necessary to prevent groundwater from entering pits, trenches and excavations and during the period of work in them.

An effective technological method for solving such problems is pumping groundwater. Pits and trenches with a small influx of groundwater are developed using open drainage, and if the influx of water is significant and the thickness of the water-saturated layer to be developed is large, then before the start of work, the groundwater level is artificially lowered using various methods of closed drainage, called dewatering.

Open drainage is used to pump out leaking bottoms directly from pits or trenches with pumps. With open drainage, groundwater seeps through the slopes and bottom of the pit and is directed through dug drainage ditches or trays to specially constructed pits in the lower part of the pit, called sumps, from where the water is pumped out by diaphragm or centrifugal pumps of appropriate capacity.

Pumps are selected depending on the flow rate (inflow) of water, and the flow rate itself is calculated using formulas for the steady movement of groundwater.

Drainage ditches are arranged with a bottom width of 0.3...0.6 m and a depth of 1...2 m with a slope of 0.01...0.02 m towards the pits. The pits themselves in stable soils are secured in the form of a wooden frame without a bottom, and in slumping soils they are also secured with a sheet piling wall.

Open drainage is a simple and affordable way to combat groundwater, but it has serious technological disadvantages. Rising flows of groundwater flowing through the walls and bottom of pits and trenches liquefy the soil and carry small particles from it to the surface. As a result of such leaching, this method has a number of significant disadvantages:

■ the natural strength of the excavation base is reduced due to its erosion by running water;

■ the presence of water at the bottom of the excavation makes it difficult to develop the soil;

■ fastening of the walls of the excavations is required, since the movement of water towards the sumps also causes the soil to move;

■ the influx of water into the drainage ditch can cause weakening of the foundations of buildings and structures located next to the facility under construction.

In cases where drainage turns out to be impractical, three changes are made by artificially lowering the groundwater level (water drawdown).

24 . Equipment used for piling work

Driving piles into the ground is a complex process and is carried out in two main ways: 1) using impact pile driving machines; 2) using vibratory hammers. In addition to these methods, for driving piles, pressing and screwing machines are used, as well as mixed-action units - vibrating impact hammers and vibrating pressing machines.

Impact pile driving machines include pile hammers, which are divided according to the type of drive into hammers with internal combustion diesel engines (diesel hammers), single- and double-action steam-air hammers, and mechanical hammers (27.1).

Diesel hammers operate on the principle of diesel engines; steam-air hammers are driven by the force of steam or compressed air directly acting on the impact part of the hammer, and mechanical hammers are driven by a winch connected by ropes through a system of pulleys to the impact part of the hammer.

For dragging and installing piles to the place of deepening, for installing a hammer on a pile, directing the hammer towards the pile during driving, as well as for moving the pile driving unit on a construction site, pile drivers are used. Depending on the purpose, pile drivers are divided into pile drivers for driving vertical piles, rotary pile drivers for driving piles using various driving methods, and pile driver cranes mounted on a crawler-mounted crane or on a single-bucket excavator.

When piles are arranged in clusters in weakly compressible soils, the piles are driven in a spiral pattern, starting from the middle of the row in a spiral direction towards the outer rows of the site. On large areas and dense soils, piles are driven according to a sectional pattern, i.e. they are immersed in sections through a row. Before driving piles, the main axes of the building or structure are first outlined and the shape and dimensions of the pile field are determined to draw up a layout drawing, from which the distances between the axes of the piles and from the walls of the building are transferred to the area.

As a rule, foundation piles are driven one at a time using pile driving machines.

Driving of sheet piles is carried out with hammers of all types using pile drivers and jib cranes. To hold sheet piles and prevent their deviation from the vertical during driving, a guide frame is installed, consisting of lighthouse piles and guide screeds attached to it. To immerse steel sheet piles, guide templates are used, the shape of which is determined by the project

31. . Construction of stone structures in winter conditions

Negative temperatures have a strong impact on the physical and mechanical processes occurring in freshly laid masonry. The hardening of the mortar in the masonry stops due to the transition of the water in the mortar into ice, and the reaction of cement hydration, which began with the laying of the mortar, fades and stops as the temperature of the mortar decreases. When the solution freezes, it turns into a strong mechanical mixture of cement (lime), sand and ice. Water, turning into ice, increases in volume, which leads to an increase in the volume of the solution, as a result of which it loosens, the bonds between its particles are broken, and the strength sharply decreases. An ice film forms on the surface of the stones, and this further reduces the adhesion strength of the mortar to the stone. As a result, with early freezing of masonry, its final strength is at the age of 28 days. turns out to be significantly lower than the strength of normally hardened masonry.

In lime mortar, when frozen, the hardening process also stops, but unlike cement mortar, the hydration process does not resume after thawing.

To perform masonry in winter conditions, the freezing method is used. Its distinctive features are as follows:

■ at a positive temperature after thawing, the masonry will continue to gain strength if the solution has gained strength by the time of freezing critical strength, which is usually more than 20% of the brand strength;

■ the freezing method is not applicable for eccentrically compressed structures with significant eccentricity and structures subject to vibration, as well as in rubble masonry, in rubble concrete walls, in vaults;

■ use only cement and complex mortars, since lime and lime-clay mortars do not retain the ability to harden after thawing;

■ vehicles in which the solution is delivered to the construction site must be insulated, a portion of the solution is supplied to the work site only for 20...30 minutes of work and at a solution temperature not lower than +20°C;

■ a log of control over the execution of brickwork and its defrosting is required, since due to the unequal density of the solution during thawing, uneven precipitation is possible.

34. Depending on the type of stone products, their physical and mechanical properties and design requirements, masonry can be solid, hollow, layered and large-block. Solid brickwork is made from all types of bricks. The solidity of the masonry is ensured by overlapping vertical joints. Along the wall, the masonry is bandaged in each row, and along its thickness - through several rows, but at least every 50 cm. A multi-row bandaging system requires less labor, but the mortar must be of increased strength. When making masonry using the freezing method, as well as when erecting pillars and narrow walls, a single-row dressing system is recommended. Any system of bandaging the seams of solid masonry requires laying bonded rows in the lower (first) and upper (last) rows of the structure, as well as at the levels of the edges of walls, pillars and protruding rows (cornices, corbels, etc.). Masonry made of concrete and natural stones must have at least one row of joints for every three rows of masonry.

Brickwork with a multi-row (a) and single-row (b) ligation system, hollow masonry made of lightweight concrete (c) and ceramic stones (d), layered lightweight (e) and facing (f) masonry: 1-insulation; 2-face brick; 3-metal brackets; 4-light concrete.

Brick pillars, pilasters and piers up to 64 cm wide, as the most important stone structures, should be built only from whole brick. For the walls of damp and wet rooms, solid masonry should be used in all cases, primarily from ordinary clay bricks of plastic pressing. Hollow masonry made of lightweight concrete and ceramic stones with slot-like voids should be performed using a single-row ligation system. Hollow masonry is very effective. It allows you to increase labor productivity and reduce the weight of walls by 30...40%.

Layered lightweight masonry consists of structural and thermal insulation layers connected by rigid or flexible connections. The thickness of the load-bearing layers is determined according to the strength requirements of the masonry. The thermal insulation layer of the wall can be located both inside the masonry and at its inner surface. Its thickness is selected taking into account the results of thermal engineering and economic calculations. Layer connections are rigid only if the distance between the axes of the vertical diaphragms is no more than 120 cm. Flexible connections consist of corrosion-resistant steels, the total cross-sectional area of ​​which is not less than 0.4 square meters. see per 1 sq. m. wall surface.

Lightweight masonry is used for load-bearing walls of buildings up to five floors high and self-supporting walls up to nine floors high. However, in all cases, layered masonry cannot be used if the premises have a high moisture content. Walls consisting of facing brick or stone and embedded or flat facing slabs are also layered. The outer cladding is tied with stone and is carried out simultaneously with the construction of walls and pillars. The leaning thin cladding is attached to the wall using mortar or special mastic and connected to the masonry using steel anchors protected from corrosion. If masonry is plastered, then the seams on its surface are not filled with mortar to a depth of 15 mm in walls and up to 10 mm in pillars and narrow partitions. In rooms with wet production processes, it is necessary to protect the internal surfaces of the walls with facing tiles, waterproof film coatings, etc. In this case, external plastering is not recommended.

38. Conducted marketing research of the construction products market and analysis of literary sources made it possible to identify the following groups of properties that are reflected in construction quality indicators:

• social properties;
• functional properties;
• reliability;
• aesthetic properties;
• regional properties;
• durability;
• ease of use;
• manufacturability;
• maintainability;
• environmental friendliness;
• economic properties.

39 Determination of the volume of excavation work

In winter, it is advisable to carry out the following work: construction of embankments from coarse and sandy soils, development of excavations and reserves in unwatered sand, gravel-pebble and rocky soils, construction of embankments from clay soils with a humidity close to optimal on stable foundations, development in non-waterlogged clayey soils excavations more than 3 meters deep, construction of embankments in swamps, strengthening of embankment slopes. The development of lateral reserves is possible in the absence of soil freezing or at the beginning of winter at temperatures close to zero degrees; in other cases, it is advisable to carry out work from deep concentrated reserves or quarries suitable for excavator work.

The PPR must provide for the organization of systematic snow removal from work areas and transport routes.

Preparatory work.

Before the start of excavation work at sites planned for construction in winter conditions, in addition to general preparatory work, the following special work must be performed: snow-resistant road markings must be installed, drainage provided at work areas on the highway, access roads and skid protection equipment prepared, household premises.

The foundations for the embankments must be prepared in the summer (including removing the vegetation layer), and before starting they must be thoroughly cleared of snow. In the case of erecting an embankment in heavily and excessively heaving areas in areas with a freezing depth of more than 1.5 meters, the lower layers of the embankment should be erected until stable negative temperatures.

In the summer, it is necessary to prepare the surface of concentrated reserves and quarries: constructing access roads, clearing the surface, constructing entrance faces and pioneer trenches, and preventing freezing.

Reserves intended for development in winter conditions must be preliminarily surveyed in the fall. The task of the survey is to determine the density and moisture of the soil; after the onset of frost, the moisture is checked again.

Development of excavations and construction of embankments.

General provisions

When developing excavations or quarries in winter conditions, it is necessary to clear the excavation surface from snow, ice and heating materials, no more than one shift ahead and subsequently as the face advances, immediately before the start of soil development. The cleaning area at temperatures up to - 10 degrees is the daily productivity of the leading machine, below - 10 degrees is the daily productivity of the leading machine.

In case of heavy snowfalls and blizzards, the development of soil and filling of embankments should be stopped, and snow and ice should be completely removed from the embankment before resuming work. During thaws and before the start of spring snowmelt, the upper part of the embankment and the slopes of embankments built in winter should be cleared of snow. The bottom and slopes of excavations should be planned after the soil has thawed.

At the beginning of winter, also when the thickness of the frozen layer is no more than 25 cm, it is possible to develop the soil with a scraper with a bucket volume of more than 6 m 3, subject to their continuous operation.

The development of excavations located on a slope should begin from the downstream side. Separate faces are located to ensure constant drainage. If there are groundwater excavations in the slopes, drainage must be ensured.

In winter, it is advisable to heat dump truck bodies; if not, lubricate the inside at least 2-3 times per shift with a concentrated solution of calcium chloride or oil, fuel oil, waste oil. At the end of the shift, dump truck bodies, scraper and excavator buckets are thoroughly cleaned.

In the part of the embankment located below the groundwater level in swamps with partial or complete peat removal, it is allowed to lay sandy frozen soils, provided that the upper part of the embankment is built from the same but thawed soils.

Cavaliers poured in winter conditions, in comparison with the usual norms, their location should be moved back from the edge of the excavation by 1.5 meters, with a cavalier height of up to 2 meters, and by 0.25 meters with a cavalier height of more than 2 meters.

For the most effective use of earthmoving and transport machines during breaks forced to open reserves, excavations must be insulated by loosening, which allows you to protect the top layer from freezing for 1-3 days.

When constructing embankments, the soil is distributed over its full width, maintaining a transverse slope of at least 50 ‰.

Compaction of soils in winter conditions.

Rollers require a significant amount of work, which is difficult to accomplish in winter, so the skating rink is often operated using a shuttle system.

The total amount of frozen soil in embankments is no more than 20% for road embankments... the size of frozen lumps during the construction of embankments should not exceed 30 cm when compacting soils with tamping machines and slabs and 20 cm when compacting soils with rollers weighing more than 25 tons. Frozen lumps of soil should be laid no closer than 1 meter from the surface of the embankment and slopes, evenly along the embankment; accumulations of soil should not be allowed, especially in the side parts of the embankment. Soil filling in winter should be carried out in thicker layers than in summer, and on shorter sections...

In winter, development should be around the clock. Avoiding the formation of frozen crust between cuttings, taking into account the following values ​​when calculating the maximum distance for transporting soil:

Soil compaction in winter conditions should be done with self-propelled and trailed rollers weighing more than 25 tons, tamping machines and suspended tamping plates. In the presence of frozen clods, it is also advisable to use a lattice roller. The operation of rollers on pneumatic tires with a pressure of up to 0.7 MPa becomes ineffective when the thickness of the frozen crust on the surface is 2-3 cm thick.

The best way to work in winter is compaction, in which you can fill the soil in the thickest layers and place larger pieces of frozen soil into the embankment.

Rollers with smooth rollers and cam rollers are practically ineffective for compacting soil in winter conditions due to the insignificant thickness of the compacted layer and due to the fact that they require a large area of ​​rolling work, which leads to rapid cooling of the soil and the possibility of its freezing. The operation of rollers on pneumatic tires in winter is accompanied by greater tire wear. The use of trailed rollers requires a large scope of work, and this is difficult to implement in conditions of rapid freezing, especially when filling the embankment in thin layers. It follows from this that soil compaction should be done especially carefully, and backfilling should be done with non-waterlogged and thawed soils with an amount of permafrost no more than permissible. Work is carried out on a narrowed front with maximum saturation of it with mechanized means, with minimal interruptions, and with such intensity that the laid layer of soil does not freeze until the next layer is poured...

The surface of the excavation from which it is planned to transport soil to the embankment, before the onset of frost, is protected from freezing by loosening it to a depth of at least 25 cm, followed by harrowing. At the same time, it is necessary to take measures to retain snow, up to filling the surface with snow, so that the thickness of the snow cover is at least 25 cm... When stopping work on laying soil in the embankment, it is necessary to prevent violation of the density and solidity of the laid and compacted soil due to its possible freezing and subsequent thawing, for this the last 2-3 layers of soil are placed in an embankment with a moisture content not exceeding 0.9 of the rolling limit, after which another layer of soil is poured but without compaction...

For filling embankments in winter, the following are allowed: pre-loosened rock, gravel, crushed stone, coarse and medium-sized sand. Non-cohesive soils are laid and compacted in the same way as in the summer, and no additional moisture is required. Clay soils are allowed if their moisture content does not exceed 0.9 of the rolling limit. Shallow and dusty soils are also acceptable.

However, one should focus on the development of non-cohesive soils and low-cohesion soils...

Loose, uncompacted snow is a good insulator!

When constructing a subgrade in winter, special attention should be paid to the stability of the natural foundation; to prevent freezing of the natural foundation, in the summer, you can pour a layer of soil 1.5 meters high with thorough compaction, this work should be carried out before winter; in winter, the main work on filling the subgrade is carried out, and in the summer, after draining the subgrade, fill the last 1-1.5 meters of the top of the embankment (of course, this is effective for high embankments and large volumes of work).

Modern construction involves a continuous and continuous process that is carried out year-round, so there is a need to carry out significant volumes of excavation work in winter conditions.

Carrying out excavation work in winter conditions is directly related to certain difficulties, depending on changes in the physical and mechanical characteristics of the soil during freezing. It is known that the mechanical strength of frozen soil is significantly greater than that of soil in its normal state. The compressive strength is much greater than the tensile strength, so it is easier to destroy frozen soil by chipping than by cutting.

Frozen soil, compared to thawed soil, has high thermal conductivity, but low heat resistance, as a result of which it hardens from freezing faster and thaws more slowly. The depth and speed of soil freezing are determined by its grain composition, average air temperature, thickness of snow cover, humidity, duration of the period with negative temperatures, etc.

The depth of seasonal freezing is taken from information from meteorological services and climate reference books or calculated using empirical formulas.
Various methods of preparing and developing frozen soils are used: developing soil in a frozen state and thawing it, loosening frozen soil, protecting the soil from freezing.

The development of frozen soil in the normal state is carried out by machines, the working element of which destroys the soil by chipping. This method goes through a production validation phase, during which the machine designs are upgraded and their operating capabilities are expanded.

For small volumes of work, it is reasonable to thaw soil in a frozen state. This is done using steam and water needles, electrical heating, chemical, fire and other methods.
Loosening of frozen soil is carried out by explosive or mechanical methods.

The explosive method of loosening is effective for significant volumes of work and deep freezing of soils. For loosening, slot or hole charges with a short delayed explosion are mainly used. Explosive loosening of frozen soils is beneficial, but in urban areas it is used very rarely, because explosions have a seismic effect on nearby buildings and structures.

Mechanical destruction of the frozen soil layer is carried out with a wedge or hammer ball suspended from the boom of a dragline excavator; static and impact rippers mounted on excavators or tractors; diesel hammer equipped with a wedge; vibro rippers, etc.

In modern construction, continuous loosening of frozen soil has been replaced by a more productive development method, which involves cutting a mass of frozen soil into blocks and strips, which are easily separated from the thawed soil using an excavator bucket equipped with a backhoe, bar and disc milling machines. The advantage of this method is the absence of shocks and vibrations that occur during explosive and mechanical loosening of soils.

The soil is protected from freezing by advance mechanical development of the surface: plowing with harrowing or deep loosening, insulation with heat-insulating materials, snow retention, installation of an ice-protective shell; impregnation of the soil with salt solutions, which lower the freezing point of water in the soil; lowering the groundwater level.

This makes it possible to prevent or significantly reduce the depth of freezing and thereby ensure the ability to develop soil with an excavator. It is useful to protect the soil from freezing, provided that the development site is known and the work is planned to be carried out no later than the second month of the winter cycle.

The choice of method for preliminary preparation of frozen soil for development is determined by the type of size of the earthen structure, production conditions and timing of work, as well as the type of soil. From a number of technically appropriate options, the most economical one is preferred.

The peculiarities of earthworks in winter put forward certain requirements for the organization and technology of their execution. It is necessary to avoid freezing of the soil in the excavator face, for which development must be carried out continuously, in a narrow front and to the full depth of the excavation. Cutting and loosening of soil should be carried out outside the excavator’s operating area with a lead time of no more than one shift.

Alexander Maksimchuk, editor-in-chief of the online publication "ATMBud. Construction Bulletin"