Withdrawal of surface (atmospheric) water. Devices for the removal of surface water

Water is one of the most common causes damage to earthworks. In addition, if it gets into the pit or excavation a large number of water, their development is very difficult. Therefore, the drainage of water should, as a rule, be carried out before the commencement of earthworks.

Surface water diversion

Withdrawal surface water can be done in the following ways:

1. a device on the upland side near the cuts and embankments of upland ditches that collect water flowing along the slope (Fig. 5b);
2. arranging cuvettes in recesses to divert water falling onto the canvas and slopes of the recess (Fig. 5b);
3. the arrangement of correctly arranged reserves near the embankments (Fig. 5a) and correctly arranged cavaliers near the excavation (Fig. 5b);
4. the correct device for planning a strip of land between an embankment and a reserve or between a cut and a cavalier with a slope of the surface of this strip (berm) away from the structure;
5. a device on the upland side of the roller from the ground when digging a trench;
6. strengthening the slopes of embankments, excavations, dams and other structures.

If a excavation needs to be carried out in a swampy area, then before starting work it is necessary to carry out a series of works to drain the site, sometimes with a whole system (network) of drainage ditches that collect water from the swamp and divert it to the nearest river, stream, lake, etc. etc.

Groundwater drainage

Groundwater can occur at various depths.

For shallow ground water ah and the small thickness of their layer, they can be diverted from the structure by open ditches that collect water.

Sometimes ground waters lie deep, and their layer has a large thickness. Then resort to the drainage device.

Drainage is a narrow closed ditch filled with water-permeable materials. At the bottom of these ditches, pipes are laid that collect groundwater or large gravel material that conducts water well.

The purpose of drainage is different:

1. Water drainage together with an open ditch(subcuvette drainages); in this case, the minimum section is given to the ditch, and the drainage is arranged under the bottom of the ditch. Drainage pipes can be wood, plastic, steel, stone, concrete or pottery (Fig. 35). In order for the drainage not to become clogged through the wells, the latter are closed from above with bars.
2. Lowering of the groundwater level. This depression is strongest near the drain; as you move away from the drainage, the level rises again (Fig. 36). In order to drain a large area, it is necessary to have drainages in several lines at a certain distance from each other in the plan.

Each drainage must have a longitudinal slope (0.0025-0.015). It is necessary to ensure that the water from the drainage has an outlet to a low point in the terrain, an open ditch or other deeper drainage. Drainages are arranged below the freezing line of the soil.

Drainage ditches are dug with special narrow shovels. In the absence of such shovels, digging is carried out with ordinary shovels, and then the width of the ditch has to be given a large one, which increases the amount of work.

If groundwater appears in the pit during work, it is necessary to resort to pumping out groundwater (drainage). In this case, the pit of water into the pit (by tongue and groove fastening).

These two types of work are usually done simultaneously with the excavation itself and are not preparatory, but auxiliary work and are described below.

Preparation of tools and inventory for work, their storage and organization of their repair

Before starting work, all essential tool and inventory (wheelbarrows, grabbars, etc.) according to the number of workers, with a margin in case of breakdown. The tool must be suitable for the soil and the type of work.

Tools, such as shovels, must be prepared with handles of various weights, and crowbars of various weights, so that the worker can select the appropriate tool. Tools and inventory must be attached to a specific team, link or individual worker responsible for their safety and condition.

To store the tool, it is necessary to have pantries at the place of work, and sheds are needed to store wheelbarrows, grabars and trolleys.

Timely repair of tools and all inventory should be provided.

In addition to the above preparatory work before the start of the main work it is necessary:

• provide workers with housing and food at the place of work;
• provide water supply;
• on the spot future work examine soils and accurately determine their category, the presence of groundwater, etc .;
• determine the exact scope of work;
• assign methods of production of work and their organization;
• allocate workers to brigades, links.

Surface water is formed from atmospheric precipitation (storm and melt water). Distinguish between surface waters "foreign", coming from elevated neighboring areas, and "our", formed directly on construction site.

The territory of the site must be protected from the inflow of “foreign” surface waters, for which they are intercepted and diverted outside the site. To intercept water, upland ditches or dikes are made along the boundaries of the construction site in its elevated part (Figure 1). To prevent rapid silting, the longitudinal slope of drainage ditches must be at least 0.003.

"Own" surface waters are diverted by giving an appropriate slope in the vertical layout of the site and by arranging a network of open or closed drains.

Each pit and trench, which is an artificial water collector, to which water actively flows during rains and snowmelt, must be protected by drainage ditches by embanking them from the upland side.

Figure 1. - Protection of the site from surface water ingress

In cases of heavy flooding of the site with groundwater with a high level of the horizon, the site is drained using open or closed drainage. Open drainage is usually arranged in the form of ditches up to 1.5 m deep, cut off with gentle slopes (1: 2) and the longitudinal slopes necessary for the flow of water. Closed drainage is usually trenches with slopes towards water discharge, filled with drainage material (crushed stone, gravel, coarse sand). When arranging more efficient drainage, pipes perforated in the side surfaces are laid at the bottom of such a trench - ceramic, concrete, asbestos-cement, wooden (Figure 2).

Figure 2 - Protection of closed drainage for drainage of the territory

Such drains collect and drain water better, since the speed of water movement in the pipes is higher than in the drainage material. Closed drains must be laid below the level of soil freezing and have a longitudinal slope of at least 0.005

At the stage of preparing the site for construction, a geodetic staking basis should be created, which serves for planned and high-altitude justification when taking out the project of buildings and structures to be erected on the ground, as well as (subsequently) geodetic support at all stages of construction and after its completion.

The geodetic marking basis for determining the position of construction objects in the plan is created mainly in the form of:

construction mesh, longitudinal and transverse axes, determining the position on the ground of the main buildings and structures and their dimensions, for the construction of enterprises and groups of buildings and structures;

red lines (or other building regulation lines), longitudinal and transverse axes that determine the position on the ground and the size of the building, for construction individual buildings in cities and towns.

The building grid is made in the form of square and rectangular shapes, which are divided into basic and additional (Figure 3). The length of the sides of the main grid figures is 200 - 400 m, and the additional ones are 20 ... 40 m.

The construction grid is usually designed at the construction site. master plan, less often - on the topographic plan of the construction site. When designing the grid, the location of the grid points on the construction plan (topographic plan) is determined, the method of preliminary grid breakdown and fixing the grid points on the ground is chosen.

Figure 3 - Construction grid

When designing a building grid, there should be:

Provided maximum convenience for marking work;

The main buildings and structures being erected are located inside the grid figures;

The grid lines are parallel to the main axes of the buildings under construction and are located as close as possible to them;

Direct linear measurements are provided on all sides of the grid;

Grid points are located in places convenient for angular measurements with visibility to adjacent points, as well as in places that ensure their safety and stability.

Altitude substantiation at the construction site is provided by high-altitude strongholds - construction benchmarks. Usually, strong points of the construction grid and the red line are used as construction benchmarks. The height mark of each construction benchmark must be obtained from at least two benchmarks of state or local significance of the geodetic network.

The creation of a geodetic stakeout is the responsibility of the customer. He must, at least 10 days before the start of construction and installation work, transfer to the contractor technical documentation on the geodetic center base and on the points and signs of this base fixed on the construction site, including:

Building grid points, red lines;

Axes that determine the position and dimensions of buildings and structures in the plan, fixed by at least two leading signs for each separately located building or structure.

During the construction process, it is necessary to monitor the safety and stability of the signs of the geodetic center base, which is carried out by the construction organization.

Breakdown of earthworks

The breakdown of structures consists in establishing and fixing their position on the ground. The breakdown is carried out using geodetic instruments and various measuring devices.

The breakdown of pits begins with the removal and fixing on the ground (in accordance with the project) with leading signs of the main working axes, which are usually taken as the main axes buildings I-I and II-II (Figure 4, a). After that, around the future pit at a distance of 2-3 m from its edge, a cast-off is installed parallel to the main center axes (Figure 4, b).

A single-use cast-off (Figure 4, c) consists of metal racks hammered into the ground or dug in wooden poles and boards attached to them. The board must be at least 40 mm thick, have a cut edge facing upwards, and rest on at least three posts. More perfect is the inventory metal cast-off (Figure 4, d). For a pass Vehicle there should be gaps in the cast-off. With a significant slope of the terrain, the cast-off is done with ledges.

Figure 4 - Scheme of laying out pits and trenches: a - scheme of laying out the pit; d - inventory metal cast-off: e - layout of the trench; I-I and II-II - the main axes of the building; III-III - axes of the walls of the building; 1 - the boundaries of the pit; 2 - cast-off; 3 - wire (mooring); 4 - plumb lines; 5 - board; 6 - nail; 7 - rack

The main center axes are transferred to the cast-off and, starting from them, all other axes of the building are marked. All axes are fixed on the cast-off with nails or cuts and numbered. On a metal cast-off, the axes are fixed with paint. The dimensions of the pit on top and bottom, as well as its other characteristic points, are marked with clearly visible pegs or milestones. After the construction of the underground part of the building, the main center lines are transferred to its basement.

Works in this cycle include:

Arrangement of upland and drainage ditches, embankment;

Open and closed drainages;

Surface planning of storage and assembly areas.

Surface water is formed from atmospheric precipitation (storm and melt water). Distinguish between "foreign" surface waters coming from elevated neighboring areas, and "ours", formed directly at the construction site.

The construction area must be protected from the ingress of “foreign” surface waters, for which they are intercepted and diverted outside the site. To intercept the waters suit upland and drainage ditches or embankment along the boundaries of the construction site in its elevated part. Drainage ditches must ensure the passage of storm and melt water to low points in the terrain outside the construction site. Depending on the planned water flow rate, drainage ditches are arranged with a depth of at least 0.5 m, a width of 0.5 ... 0.6 m, with an edge height above the calculated water level of at least 0.1 ... 0.2 m. ditch tray from erosion, the speed of water movement should not exceed 0.5 ... 0.6 m / s for sand, 1.2 ... 1.4 m / s for loam. The ditch is arranged at a distance of at least 5 m from the permanent excavation and 3 m from the temporary one. To protect against possible silting, the longitudinal profile of drainage ditches is made at least 0.002. The walls and bottom of the ditch are protected with turf, stones, and fascines.

"Own" surface waters are diverted by giving an appropriate slope in the vertical layout of the site and arranging networks of open or closed drains, as well as by means of forced discharge through drainage pipelines by means of electric pumps.

With a strong flooding of the site with groundwater with a high horizon, drainage is carried out by drainage systems, which are open and closed types. Drainage systems designed to improve general sanitary and building conditions and provide for lowering the groundwater level.

open drainage used in soils with a low filtration coefficient, if it is necessary to lower the groundwater level to a shallow depth - about 0.3 ... 0.4 m. Drainage is arranged in the form of ditches 0.5 ... 0.7 m deep, on the bottom of which a layer of coarse sand, gravel or crushed stone 10 ... 15 cm thick.

Closed drainage- these are usually deep trenches with wells for system revision and with a slope towards water discharge, filled with drained material (crushed stone, gravel, coarse sand). On top, the drainage ditch is covered with local soil.

When arranging more efficient drainage, pipes perforated in the side surfaces are laid at the bottom of such a trench - ceramic, concrete, asbestos-cement pipes with a diameter of 125 ... 300 mm, sometimes just trays. The gaps of the pipes are not closed, the pipes are covered from above with well-draining material. The depth of the drainage ditches is 1.5 ... 2.0 m and the width on top is 0.8 ... 1.0 m. A crushed stone base up to 0.3 m thick is often laid below the pipe. Recommended distribution of soil layers:

1) drainage pipe laid in a layer of gravel;

2) a layer of coarse sand;

3) a layer of medium or fine-grained sand. The thickness of all layers is at least 40 cm;

4) a layer of local soil up to 30 cm thick.

Such drains collect water from the adjacent soil layers and drain it better, since the speed of water movement in the pipes is higher than in the drainage material. Closed drains should be laid below the level of soil freezing and have a longitudinal slope of at least 0.005%. The drainage device must be completed before the construction of buildings and structures.

For tubular drains last years pipe filters made of porous concrete and expanded clay glass are widely used. The use of pipe filters significantly reduces labor costs and the cost of work. They are pipes with a diameter of 100 and 150 mm with large quantity through holes(pores) in the wall, through which water seeps into the pipeline and is discharged. The design of the pipes allows their machine laying on a previously leveled base.

The removal of surface water and lowering the level of groundwater is carried out to protect construction sites and foundation pits of future structures from flooding with storm and melt water.

Works on the diversion of surface and ground waters include: arrangement of upland and drainage ditches, embankment; drainage device; layout of the surface of storage and assembly sites.

Ditches or trays are arranged along the boundaries of the construction site on the upland side with a longitudinal slope of at least 0.002, and their dimensions and types of fastenings are taken depending on the flow rate of storm or melt water and the limiting values ​​of their non-erosion flow rates.

The ditch is arranged at a distance of at least 5 m from a permanent excavation and 3 m from a temporary one. The walls and bottom of the ditch are protected with turf, stones, and fascines. Water from all drainage devices, reserves and cavaliers is diverted to low places, remote from the erected and existing structures.

With a strong flooding of the site with groundwater with a high level of the horizon, drainage systems of open and closed types are used.

Open drainage is used in soils with a low filtration coefficient, if it is necessary to lower the groundwater level (GWL) to a depth of 0.3–0.4 m. sand, gravel or crushed stone 10-15 cm thick.

Closed drainage is usually deep trenches with wells for system revision and with a slope towards water discharge, filled with drained material. Sometimes pipes perforated in the side surfaces are laid at the bottom of such a trench. On top, the drainage ditch is covered with local soil.

The drainage device must be carried out before the construction of buildings and structures.

Organization of drainage and artificial lowering

Groundwater level

Excavations (pits and trenches) with a small influx of groundwater are developed using open drainage.

With a significant influx of groundwater and a large thickness of the water-saturated layer, the GWL is artificially reduced before the start of work.

Dewatering works depend on the accepted method of mechanized excavation of pits and trenches. Accordingly, the order of work is established both for the installation of dewatering and dewatering installations, their operation, and for the development of pits and trenches. When placing a pit on the shore within the floodplain, its development begins after the installation of dewatering equipment so that the lowering of the ground water level is ahead of the deepening of the pit by 1–1.5 m. dams (bridges). In this case, drainage work consists of removing water from a fenced-off pit and subsequent pumping out of the water that filters into the pit.

In the process of draining the excavation, it is important to choose the right pumping speed, since very fast drainage can cause damage to the cofferdams, slopes and the bottom of the excavation. In the first days of pumping, the intensity of lowering the water level in pits from coarse-grained and rocky soils should not exceed 0.5-0.7 m / day, from medium-grained - 0.3-0.4 m / day and in pits from fine-grained soils 0, 15–0.2 m/day In the future, water pumping can be increased to 1–1.5 m/day, but at the last 1.2–2 m of depth, water pumping should be slowed down.

In an open drain pumping out of incoming water directly from the pit or trenches by pumps is provided. It is applicable in soils resistant to filtration deformations (rocky, gravel, etc.). With open drainage, groundwater, seeping through the slopes and the bottom of the pit, enters the drainage ditches and through them into the pits (sumps), from where it is pumped out by pumps. The dimensions of the pits in the plan are 1 × 1 or 1.5 × 1.5 m, and the depth is from 2 to 5 m, depending on the required immersion depth of the pump intake hose. Minimum dimensions the pit is assigned from the provision condition continuous work pump for 10 min. Pits in stable soils are fixed wooden frame from logs (without a bottom), and in floating logs - with a sheet pile wall and a return filter is arranged at the bottom. Approximately the same way, trenches are fixed in unstable soils. The number of pits depends on the estimated water inflow to the pit and the performance of pumping equipment.

The inflow of water to the pit (or debit) is calculated according to the formulas for the steady movement of groundwater. According to the data obtained, the type and brand of pumps, their number are specified.

Open drainage is an effective and simple way of dehumidification. However, loosening or liquefaction of soils at the base and removal of part of the soil by filtering water is possible.

Artificial lowering of GWL involves the installation of a drainage system, tube wells, wells, the use of wellpoints located in the immediate vicinity of the future pit or trench. At the same time, the GWL sharply decreases, the soil previously saturated with water and now dehydrated is being developed as a soil of natural moisture.

There are the following methods of artificial dewatering: wellpoint, vacuum and electroosmotic.

Methods of artificial dewatering exclude water seepage through the slopes and the bottom of the pit, therefore the slopes of the excavations are preserved intact, there is no removal of soil particles from under the foundations of the nearest buildings.

The choice of the method of dewatering and the type of equipment used depends on the depth of excavation of the pit (trench), engineering-geological and hydrogeological conditions of the site, construction time, structure design and TEP.

Artificial dewatering is carried out when the drained rocks have sufficient water permeability, characterized by filtration coefficients of more than 1–2 m / day; it cannot be used in soils with a lower filtration coefficient due to low groundwater movement rates. In these cases, vacuuming or the method of electro-drying (electroosmosis) is used.

Wellpoint method provides for the use of often located wells with tubular water inlets of small diameter for pumping water from the soil - wellpoints connected by a common suction manifold to a common one (for a group of wellpoints) pumping station. To artificially lower the GWL to a depth of 4–5 m in sandy soils apply light wellpoints (LIU). To drain trenches up to 4.5 m wide, single-row wellpoint installations are used (Fig. 2.1, a), with wider trenches - two-row (Fig. 2.1, b).

To drain the pits, installations closed along the contour are used. When lowering the hydrocarbon to a depth of more than 5 m, two- and three-tier wellpoint installations are used (Fig. 2.2).

In the case of using two-tier wellpoint installations, the first (upper) tier of wellpoints is first put into operation and under its protection the upper ledge of the pit is torn off, then the second (lower) tier of wellpoints is mounted and the second ledge of the pit is torn off, etc. After the commissioning of each subsequent tier of wellpoints, the previous ones can be turned off and dismantled.

The use of wellpoints is also effective for lowering water in poorly permeable soils, when a more permeable layer lies under them. In this case, the wellpoints are buried in the lower layer with their obligatory sprinkling.

Rice. 2.1. Dewatering with light wellpoints: a- one-

in-line wellpoint installations; b– double-row wellpoint installations;

1 - trench with fastening; 2 - hose; 3 - valve; 4 – pump unit;

5 – suction manifold; 6 – wellpoints; 7 - reduced GWL;

8 – wellpoint filter element

Rice. 2.2. Scheme of longline dewatering needle-film

trami: 1 , 2 - wellpoints of the upper and

lower tier; 3 - the final decrease in depression

groundwater surface

In addition to wellpoints, LIAs also include a water collection manifold that combines wellpoints into one water reduction system, centrifugal pump units and a discharge pipeline.

To lower the wellpoint in working position in difficult soils, drilling of wells is used, into which wellpoints are lowered (at depths up to 6–9 m).

In sands and sandy loamy soils, wellpoints are immersed in a hydraulic way, by washing the soil under the milling tip with water with a pressure of up to 0.3 MPa. After the wellpoint is immersed to the working depth, the hollow space around the pipe is partially filled with sagging soil, and partially filled with coarse sand or gravel.

The distances between the wellpoints are taken depending on the layout of their location, the depth of dewatering, the type of pumping unit and hydrogeological conditions, but usually these distances are 0.75; 1.5, and sometimes 3 m.

Vacuum method dewatering is based on the use of ejector dewatering units (EIU), which pump water from wells using water jet ejector pumps. These installations are used to lower the GWL in fine-grained soils with a filtration coefficient of 0.02–1 m/day. The depth of GWL lowering by one tier is from 8 to 20 m.

EIU consist of wellpoints with ejector water lifts, a distribution pipeline (collector) and centrifugal pumps. Ejector water inlets placed inside the wellpoints are driven by a jet of working water injected into them by a pump at a pressure of 0.6–1.0 MPa through a collector.

Ejector wellpoints are immersed hydraulically. The distance between wellpoints is determined by calculation, but on average it is 5–15 m. The choice of wellpoint equipment, as well as the type and number of pumping units, is made depending on the expected groundwater inflow and the requirements for limiting the length of the collector served by one pump.

Electroosmotic dewatering, or electrodrainage, based on the phenomenon of electroosmosis. It is used in poorly permeable soils with a filtration coefficient Kf less than 0.05 m/day.

First, along the perimeter of the pit (Fig. 2.3), at a distance of 1.5 m from its edge and with a step of 0.75–1.5 m, cathode wellpoints are immersed, with inside the contours of these wellpoints at a distance of 0.8 m from them with the same step, but in a checkerboard pattern, immerse steel pipes (anode rods) connected to the positive pole, wellpoints and pipes are immersed 3 m below required level dewatering. When a direct current is passed, the water contained in the pores of the soil moves from the anode to the cathode, while the soil filtration coefficient increases by 5–25 times. The pits usually begin to be developed three days after the electric dehumidification system is turned on, and in further work in the pit can be carried out with the system turned on.

Open (connected to the atmosphere) dewatering wells used at a large depth of lowering GWL, as well as

when the use of wellpoints is difficult due to large inflows, the need for dehumidification large areas and tightness of the area. For pumping water from wells, artesian turbine pumps of the ATN type are used, as well as deep pumps submersible type.

Rice. 2.3. Scheme of electrodrainage of soils:

1 - anode pipes; 2 – wellpoints-cathodes;

3 – pump unit; 4 - reduced GWL

The use of methods for lowering GWL depends on the thickness of the aquifer, the coefficient of soil filtration, the parameters of the earthwork and construction site, and the method of work.

Withdrawal of surface and ground waters.

Works in this cycle include:

■ arrangement of upland and drainage ditches, embankment;

■ open and closed drainage;

■ layout of the surface of storage and assembly sites.

Surface and ground waters are formed from precipitation (storm and melt water). Distinguish between surface waters "foreign", coming from elevated neighboring areas, and "ours", formed directly at the construction site. Depending on the specific hydrogeological conditions, surface water diversion and soil drainage can be carried out in the following ways: open drainage, open and closed drainage, and deep water drawdown.

Upland and drainage ditches or embankments are arranged along the boundaries of the construction site on the upland side to protect against surface water. The territory of the site must be protected from the inflow of “foreign” surface waters, for which they are intercepted and diverted outside the site. To intercept water, upland and drainage ditches are arranged in its elevated part (Fig. 3.5). Drainage ditches must ensure the passage of storm and melt water to low points of the terrain outside the construction site.

Rice. 3.5. Protection of the construction site from the ingress of surface water: 1 - water runoff zone, 2 - upland ditch; 3 - construction site

Depending on the planned water flow rate, drainage ditches are arranged with a depth of at least 0.5 m, a width of 0.5 ... 0.6 m, with an edge height above the calculated water level of at least 0.1 ... 0.2 m. To protect the ditch tray from erosion, the speed of water movement should not exceed 0.5 ... 0.6 m / s for sand, -1.2 ... 1.4 m / s for loam. The ditch is arranged at a distance of at least 5 m from a permanent excavation and 3 m from a temporary one. To protect against possible silting, the longitudinal profile of the drainage ditch is made at least 0.002. The walls and bottom of the ditch are protected with turf, stones, and fascines.

“Own” surface waters are diverted by giving an appropriate slope during the vertical layout of the site and the installation of an open or closed drain network, as well as by forced discharge through drainage pipelines using electric pumps.

Drainage systems of open and closed types are used when the site is heavily flooded with groundwater with a high level of the horizon. Drainage systems are designed to improve general sanitary and building conditions and provide for lowering the groundwater level.

Open drainage is used in soils with a low filtration coefficient, if it is necessary to lower the groundwater level to a shallow depth - about 0.3 ... 0.4 m. Drainage is arranged in the form of ditches 0.5 ... 0.7 m deep, to the bottom which lay a layer of coarse sand, gravel or crushed stone with a thickness of 10 ... 15 cm.

Closed drainage is usually deep trenches (Fig. 3.6) with wells for system revision and with a slope towards water discharge, filled with drained material (crushed stone, gravel, coarse sand). On top, the drainage ditch is covered with local soil.

Rice. 3.6. Closed, wall and girdle drainage: a - common decision drainage; b - wall drainage; c - ring enclosing drainage; 1 - local soil; 2 - fine-grained sand; 3 - coarse sand; 4 - gravel; 5 - drainage perforated pipe; 6 - compacted layer of local soil; 7 - the bottom of the pit; 8 - drainage slot; 9 - tubular drainage; 10 - building; eleven -retaining wall; 12 - concrete base

When arranging more efficient drainage, pipes perforated in the side surfaces are laid at the bottom of such a trench - ceramic, concrete, asbestos-cement pipes with a diameter of 125 ... 300 mm, sometimes just trays. The gaps of the pipes are not closed, the pipes are covered from above with well-draining material. The depth of the drainage ditch is -1.5 ... 2.0 m, the width at the top is 0.8 ... 1.0 m. A crushed stone base up to 0.3 m thick is often laid below the pipe. Recommended distribution of soil layers: 1) drainage pipe laid in a layer of gravel; 2) a layer of coarse sand; 3) a layer of medium or fine-grained sand, all layers are at least 40 cm; 4) local soil up to 30 cm thick.

Such drains collect water from adjacent soil layers and drain water better, since the speed of water movement in pipes is higher than in the drainage material. Closed drains are arranged below the level of soil freezing, they must have a longitudinal slope of at least 0.5%. The drainage device must be carried out before the construction of buildings and structures.

For tubular drainage in recent years, pipe filters made of porous concrete and expanded clay glass have been widely used. The use of pipe filters significantly reduces labor costs and the cost of work. They are pipes with a diameter of 100 and 150 mm with a large number of through holes (pores) in the wall, through which water seeps into the pipeline and is discharged. The design of pipes allows their laying on a previously leveled base by pipelayers.

Engineering preparation of the construction site.

General provisions

Any construction (object or complex) is preceded by site preparation aimed at ensuring necessary conditions high-quality and on time erection of buildings and structures, including engineering training and engineering support.

During engineering training, a complex of processes (works) is performed, in the general case, the most characteristic of which are in technology construction industry are the creation of a geodetic center base, clearing and planning of the territory, diversion of surface and ground waters.

In each case, the composition of these processes and the methods for their implementation are regulated by natural and climatic conditions, the characteristics of the construction site, the specifics of the buildings and structures being erected, the characteristics of the object - new construction, expansion or reconstruction, etc.

Engineering support the construction site provides for the construction of temporary buildings, roads and networks of water, electricity, etc. building materials, tools, temporary workshops, sheds, etc. For these structures, it is advisable to use part of the demolished buildings, if they do not fall into the dimensions of the structure being erected and will not interfere with the normal implementation construction works, as well as inventory buildings of wagon or block type.

For the transportation of goods, the existing road network and only if necessary provide for the construction of temporary roads.

During the preparatory period, temporary water supply lines are being laid, including fire-fighting water supply, and power supply with energy supply to all change houses and installation sites of electrical mechanisms. The foreman's office should be provided with telephone and dispatch communications. At the construction site, a place for repair and parking of earthmoving and other machines and vehicles will be equipped. The site must be fenced or marked with appropriate signs and inscriptions.

Creating a geodetic stakeout

At the stage of preparing the site for construction, a geodetic staking base should be created, which serves for planned and high-altitude justification when the project of buildings and structures to be erected is brought to the site, and also (subsequently) for geodetic support at all stages of construction and after its completion.

The geodetic marking basis for determining the position of construction objects in the plan is created mainly in the form of: a construction grid, longitudinal and transverse axes that determine the position on the ground of the main buildings and structures and their dimensions, for the construction of enterprises and groups of buildings and structures; red lines (or other building regulation lines), longitudinal and transverse axes that determine the position on the ground and the dimensions of the building, for the construction of individual buildings in cities and towns.

The building grid is made in the form of squares and rectangles, which are divided into main and additional (Fig. 1, a). The length of the sides of the main figures of the grid is 100 ... 200 m, and the additional ones - 20 ... 40 m.

Rice. 1 - Construction grid: a - location of grid points; b - removal of the construction grid to the area; 1 - tops of the main figures of the grid; 2 - the main axes of the building; 3 - vertices of additional mesh figures

When designing a building grid, the following should be provided: for the execution of marking work, maximum convenience is provided; the main

buildings and structures are located inside the grid shapes; grid lines are located parallel to the main axes of the buildings under construction and as close as possible to them; direct linear measurements.

Rice. 2 - Permanent geodetic signs: a - from concreted pipe cuts; b - from a steel pin with a concreted head; in - from scraps of rails; 1 - planned point; 2- steel pipe with a cruciform anchor, 3 - concrete head; 4 - steel pipe; 5 - freezing border

The breakdown of the construction grid on the ground begins with the removal of the original direction to nature, for which they use the geodetic network available on the site (or near it) (Fig. 1, b). According to the coordinates of geodetic points and grid points, the polar coordinates S1, S2, S3 and the angles are determined, along which the initial grid directions (AB and AC) are brought to the terrain. Then, from the initial directions on the entire site, the construction grid is broken and fixed at the intersections with permanent signs (Fig. 2) with the planned point. Signs are made from concreted cuts of pipes, rails, etc. The base of the sign (bottom of the sign, sign support) must be at least 1 m below the freezing line.

The red line is transferred and fixed in the same way.

When transferring the main axes of objects under construction to the terrain, if there is a construction grid as a planned layout, the method of rectangular coordinates is used. In this case, the adjacent sides of the building grid are taken as coordinate lines, and their intersection is taken as the reference zero. The position of the point O of the main axes ho - yo will be determined in the following way: if it is given that ho \u003d 50 and; yo \u003d 40 m, then this means that it is at a distance of 50 m from the x line towards ho and at a distance of 40 m from the y line towards the yo line.

If there is a red line as a planned layout, the construction general plan must contain any data that determines the position of the future building, the angle between the main axis of the building and the red line, and the distance from point A to point O of the intersection of the main axes.

The main axes of the building are fixed behind its contours with the signs of the above design.

Altitude substantiation at the construction site is provided by high-altitude strongholds - construction benchmarks. Usually, strong points of the construction grid and the red line are used as construction benchmarks. The height mark of each construction benchmark must be obtained from at least two benchmarks of state or local significance of the geodetic network.

During the construction process, it is necessary to monitor the safety and stability of the signs of the geodetic center base, which is carried out by the construction organization.

Clearing the territory

When clearing the territory, green spaces are transplanted, if they are used in the future, they are protected from damage, stumps are uprooted, the site is cleared of shrubs, the fertile soil layer is removed, unnecessary buildings are demolished or dismantled, underground utilities are shifted and, finally, the construction site is planned.

Green spaces that are not subject to felling or replanting are surrounded by a fence, and the trunks are separated standing trees protect from possible damage, protecting with waste lumber. Trees and shrubs suitable for further landscaping are dug up and transplanted to a protected zone or to a new place.

Trees are felled using mechanical or electric saws. Tractors with skidding and uprooting winches or bulldozers with high blades cut down trees with roots and uproot stumps. Separate stumps that are not amenable to uprooting are split by an explosion. Brush cutters clear the area from shrubs. For the same operation, bulldozers with ripper teeth on the blade, and harvesters are used. The brush cutter is a replacement equipment for a caterpillar tractor.

The fertile soil layer to be removed from the built-up areas is cut and moved to specially designated places, where it is stored for later use. Sometimes it is taken to other sites for landscaping. When working with the fertile layer, it should be protected from mixing with the underlying layer, pollution, erosion and weathering.

Demolition of buildings and structures is carried out by dividing them into parts (for subsequent dismantling) or collapse. wooden buildings dismantled, rejecting elements for their subsequent use. During disassembly, each detachable prefabricated element must first be unfastened and occupy a stable position.

Monolithic reinforced concrete and metal structures are dismantled according to a specially designed demolition scheme that ensures the stability of the structure as a whole. The division into disassembly blocks begins with the opening of the reinforcement. Then the block is fixed, after which the reinforcement is cut and the block is broken off. Metal elements are cut off after unfastening. largest mass reinforced concrete block disassembly or a metal element should not exceed half the lifting capacity of the cranes at the largest hook reach.

prefabricated reinforced concrete buildings dismantled according to the demolition scheme, reverse installation scheme. Before starting the disassembly, the element is freed from bonds. prefabricated reinforced concrete structures, not amenable to element-by-element separation, are dissected as monolithic.

The demolition of buildings and structures by collapse is carried out with hydraulic hammers, jackhammers, and in some cases - excavators with various attachments - ball-women, wedge-hammers, etc. The vertical parts of the structure should be brought down inward to prevent debris from scattering over the area. The collapse is also carried out in an explosive way.

After clearing produce a general layout of the construction site.