The base is sandy for pipelines thickness. TTK. Establishment of a base of soft soil along the bottom of the trench and backfilling from above before backfilling the main pipeline
GOSSTROY USSR
ALL-UNION PROJECT ASSOCIATION FOR WATER SUPPLY
AND SEWERS
SOYUZVODOKANALPROEKT
STATE ORDER OF LABOR RED BANNER
DESIGN INSTITUTE
SOYUZVODOKANALPROEKT
BENEFITS
NETWORK DESIGN
WATER SUPPLY AND SEWERAGE
IN DIFFICULT GEOLOGICAL ENGINEERING CONDITIONS
(to SNiP 2.04.02-84 and 2.04.03-85)
DIRECTOR OF THE INSTITUTE |
Yu.N. ANDRIANOV |
|
CHIEF ENGINEER |
A.N. MIKHAILOV |
|
RESPONSIBLE EXECUTOR CHIEF SPECIALIST |
L.V. YAROSLAVSKY |
MOSCOW, 1990
When designing foundations and foundations for buildings and structures, it is necessary to take into account the presence of collectors and pressure pipelines near them.
1.5. Network designs should provide for methods and places for discharging water from pipelines in the event of flushing, cleaning or repairing networks, excluding soaking of foundations in the building area.
1.6. To facilitate monitoring of the condition of pipelines and repair in areas where possible, provision should be made for above-ground laying. pressure pipes wires.
In buildings and structures, the laying of pipelines for this purpose should be carried out above the floor level of the basement or technical underground. Below the floor level, the laying of pipelines is allowed in waterproof channels with the removal of emergency water from them.
1.7. The complex of water protection measures also includes: the layout of the general plan, the layout of the built-up area, high-quality backfilling of the sinuses of pits and trenches, the device around hatches, wells and blind areas, the laying of external networks in cases provided for in this manual, on pallets, in channels or tunnels.
1.8. When developing master plans, the preservation of natural conditions for the removal of rain and melt water should be ensured.
Capacitive structures and water-bearing networks should be located, if possible, in areas with a drainage layer and with a minimum thickness of subsidence, swelling and saline soils. If this recommendation is followed, the leakage water will be removed by the drainage layer, which will prevent its penetration into the underlying layers of subsiding, saline or swelling soils. It is necessary to follow the course of drainage layers in order to avoid stagnation and accumulation of water on the site, especially in the area of networks, buildings and structures. If such a hazard is possible, it is necessary to combine natural drainage layers with artificial drainage devices.
1.9. When pipe laying conditions require an increased degree of compaction of the backfill soil, it is necessary to ensure the compaction of the backfill soil up to the compaction factor Kupl. ³ 0.93.
Assignment of technological parameters of compacted soils (thickness of soil layers, humidity, recommended mechanisms and number of passes during compaction) should be carried out in accordance with SNiP 3.02.01-87 “Earthworks. Foundations and Foundations" with the recommended appendix to this "Manual".
1.10. Projects of water supply and sewerage networks, except for technological, planning (general plan and vertical planning) and constructive measures developed in accordance with SNiP 2.02.01-83, 2.04.02-84 and 2.04.03-85 and this Manual, must contain requirements for the production of construction work (clauses ,) and operation. The latter provision is implemented in a note placed on the “General data” sheet with the following content: “The operation of networks (water supply, collector) and structures on them is carried out, guided by the“ Recommendations for the operation of buildings, structures and engineering networks erected on subsidence soils ”, developed by the Central Research Institute of Industrial Buildings , NIIOSP im. Gersevanov and Rostov Research Institute of ACS named after. Pamfilova in 1984
II. SLOWING SOILS.
2.1. When designing foundations composed of subsiding soils, it must be taken into account that when the humidity rises above a certain level, they give additional deformations of subsidence from the external load and (or) the own mass of the soil.
2.2. When planning the site with a cut, the possible amount of subsidence is significantly reduced, therefore, type II soil conditions in terms of subsidence can turn into type I.
With a vertical layout in an embankment, a significant increase in subsidence of soils from their own weight during soaking is possible, i.e. I type will pass into II.
So, when constructing an embankment with a height of 5–6 m, the amount of subsidence can increase by more than 2 times.
Thus, when planning territories with soil filling, it is necessary to ensure, before the start of construction, the elimination of subsidence of the base with residual possible precipitation from the weight of the structure no more than 5 cm.
2.3. Backfilling during territory planning, backfilling of pits and trenches should be carried out from local clay soils. The subsidence properties of these soils must be eliminated when they are laid in the embankment. The use of sandy and coarse-grained soils, construction debris and other drainage materials for planning embankments and backfilling of pits and trenches at sites with type II soil conditions in terms of subsidence is not allowed.
Trench backfill soil should have a plasticity number JL£ 0.1 and backfilled at optimal moisture content in layers with compaction of each layer to the required density (specified soil compaction coefficient or dry soil density) controlled by metrological means of construction laboratories. The required soil density is assigned depending on the material of the pipes, the depth and method of their laying, and also depending on the load on the surface of the compacted soil (table). The density of compacted dry soil should be at least 1.6 - 1.7 t / cu. m and be assigned depending on the results of the experimental compaction, recorded in the relevant acts.
for sewerage systems - reinforced concrete pressure, asbestos-cement, plastic. In areas with a working pressure of more than 0.9 MPa (9 kg / sq. cm), it is allowed to use steel pipes. At the same time, on subsiding soils of type II, the use of asbestos-cement pressure pipes with CAM couplings is not allowed.
2.6. For pressure pipelines in type II soil conditions with a possible drawdown of more than 20 cm:
for water supply systems of I and II categories of water supply availability, water conduits and networks should be designed from welded (steel or plastic) pipes, the use of socket pipes is not allowed;
for water supply systems of the III category of water supply security and pressure sewerage networks, socket pipes with flexible butt joints are allowed. For this purpose, rubber sealing cuffs should be used to seal the joints of reinforced concrete, cast iron and plastic (PVC) pipes.
In areas with a working pressure of more than 0.6 MPa (6 kg / sq. cm), only steel pipes should be used.
2.7. For gravity pipelines, reinforced concrete, asbestos-cement pressure and ceramic sewer pipes should be used.
Asbestos-cement pipes are allowed to be used only after a selective check of the compliance of the main dimensions of the butt joint (outer diameter of the turned pipe ends and inner diameter of the couplings) with the requirements of GOST 539-80.
Table 2.1.
Diameter in mm |
Gap size, mm |
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Asbestos-cement |
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Reinforced concrete pressure |
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non-pressure |
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Ceramic |
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Cast iron on rubber rings |
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For reinforced concrete non-pressure pipes of the type TB, TS, TBP and TSP, manufactured in accordance with GOST 6482-88, for pressure pipes, manufactured in accordance with GOST 125860-83 and pressure pipes with a steel core, manufactured in accordance with GOST 26819-86, - rings according to TU 381051222-88; For cast-iron pressure pipes, rubber cuffs are used as seals according to GOST 21053-75. Rubber rings for sealing joints must be supplied complete with pipes. For ceramic pipes, bituminized or tarred hemp strand is used as a sealing material. The design of butt joints of pipes should be carried out taking into account the "Manual for the laying and installation of cast iron, reinforced concrete and asbestos-cement pipelines for water supply and sewerage (to SNiP 3.05.04-85)", Stroyizdat, 1989. Dk, cm, is the compensation capacity of the butt joint, determined by the formula: In this formula kω - coefficient of working conditions, taken equal to 0.6; lsec- length of the section (link) of the pipeline, cm; e - the relative value of the horizontal movement of the soil during its subsidence from its own weight; D TN - outer diameter of the pipeline; R gr - conditional radius of curvature of the soil surface during its subsidence from its own weight, m. The value of relative horizontal displacements e, is determined by formula 133, and the conditional radius of curvature of the soil surface R gr. according to the formula 139 "Manuals for the design of the foundations of buildings and structures" (to SNiP 2.02.01-83). The maximum value of the bending moment and shearing force arising at the edges of the subsidence lens, to check the strength of pipes when they are bent and to calculate the reinforced concrete foundations of pipelines and channels, are determined by the formulas (3) where µ is the length of the curved section of soil subsidence from its own weight, calculated by the formula 131 of the Manual to SNiP 2.02.01-83; EJ- rigidity of the cross section of the calculated structure (pipe, pallet, channel). 2.21. If it is impossible to comply with the distances indicated in Table. , as well as at the inlets of pipelines of publications and structures, the laying of pipelines in soil conditions of type II in terms of subsidence should be provided for objects of classes I and II and responsibility in watertight channels or tunnels, and for objects of III class of responsibility and on sewer outlets on pallets with mandatory release emergency water into control wells. In soil conditions of type I - on compacted soil of the foundation for objects of II class of responsibility, on pallets for objects of I class of responsibility and without subsidence - for objects of III class of responsibility and on sewer outlets Table 2.2.
Table 2.3.
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The choice of material for pipes and collectors is made taking into account construction, technological and economic requirements. Construction requirements are to ensure the strength and durability of structures and the possibility of industrialization of construction.
The strength of the pipe material is dictated by the impact on them of external loads, which can be permanent and temporary. Permanent loads are due to the weight of the soil located above the pipelines and depend on the type of soil and the depth of laying. Live loads arise from vehicles moving on the surface of the earth, and depend on the type of transport, soil properties and the depth of the pipeline.
Since pipes and collectors are constantly under the influence of external as well as internal loads resulting from blockages, the action of groundwater and sewage can reduce the service life of pipes. In addition, the aging of the material also affects the durability of the pipes. Therefore, the pipe material must be selected taking into account some optimal durability of structures.
The construction of pipelines and collectors must be carried out with maximum industrialization. Therefore, the manufacture of pipes of a certain length or prefabricated elements for collectors should be carried out at the enterprises of the construction industry. The device of pipelines and collectors is carried out by assembling pipelines from individual pipes or individual elements. In this case, the maximum mechanization of construction work of all types is achieved.
Technological requirements are to ensure water tightness and maximum bandwidth pipes and manifolds, as well as the exclusion of their abrasion and corrosion. The capacity of pipes and collectors is inversely proportional to the roughness of the inner walls. Roughness can be reduced by using an appropriate material, as well as by applying special coatings to the walls. The implementation of these coatings is especially advisable if they simultaneously increase the water resistance and abrasion of the walls of pipes and collectors, which occurs due to the presence of high-density inclusions in wastewater (sand, slag, broken glass, etc.). Since wastewater as well as groundwater can be aggressive, the material of the pipes and collectors must be resistant to corrosion. In this case, the composition and properties of waste and groundwater are decisive when choosing a material.
Economic requirements are to ensure the minimum cost of materials and the expenditure of a minimum amount of non-deficient materials.
The stated requirements are more satisfied with ceramic, asbestos-cement, concrete, reinforced concrete and plastic pipes.
CERAMIC PIPES
Ceramic pipes for the installation of non-pressure networks are produced with a diameter of 150-600 mm; plastic sintering refractory refractory clays are used for their manufacture.
Pipe production includes the following main operations:
* preparation of clay masses;
* forming pipes from these masses;
* drying and coating pipes with raw glaze;
* pipe burning.
Ceramic pipes are made with a socket at one end. The inner surface of the socket and the outer surface of the smooth end are made with corrugations (cuts - grooves) and are not covered with glaze. In this case, a better adhesion of the pipes to the joint sealing material is provided.
Coating the outer and inner surfaces of pipes with glaze increases their resistance to abrasion, water resistance, and reduces the roughness of the walls.
Ceramic pipes must meet the following requirements:
* withstand internal hydraulic pressure of 0.15MPa;
* withstand external loads of at least 20-30kN/m;
* have a water absorption of no more than 8%.
Ceramic pipes are sufficiently strong and resistant to the action of slightly aggressive waters and temperature effects, are waterproof, have relatively smooth walls, and are durable. The disadvantages of these pipes include their short length and the possibility of destruction upon impact.
Connections of ceramic pipes are made by inserting the smooth end of one pipe into the socket of the other, followed by sealing the joint. The sealing of the joint is performed as follows. First, the annular gap between the walls of the smooth end and the socket at 1/3 - 1/2 of the depth of the socket is filled with a resin hemp strand or rope and sealed with a special tool - a caulk without the use of a hammer. In this case, the joint is sealed. Filler (lock) is introduced into the rest of the annular gap to increase the strength of the joint. As a filler, asphalt mastic, asbestos-cement or cement mortar is used. Asphalt mastic is made from three parts natural asphalt and one - two parts of hydron or BN bitumen -III. Mastic is poured into the annular gap in a heated state using a special form (formwork). The asphalt joint is hermetic, well resists the action of aggressive underground waters, and is relatively elastic. However, when the wastewater temperature is above 40 0 C and the content of solvents in them, the asphalt joint is not recommended. The joint of the asbestos-cement lock is made of 70% by weight of grade 300 cement and 30% of asbestos fiber. A mixture of these materials is moistened with water in an amount of 10%, introduced in layers into the gap and compacted with a special tool - chasing. The cement joint lock is made from a mixture of cement and sand in a ratio of 1: 1 by weight. Sealing of a joint is made also as asbestos-cement. The cement joint is rigid and does not allow pipe displacement. It is used when laying pipes on an artificial base.
Ceramic pipes are also connected using rings made of rubber and polyvinyl chloride resin (plastisol).
ASBESTOS CEMENT PIPES
Non-pressure asbestos-cement pipes are made with a diameter of 100-400mm, for the manufacture of pipes 80-90% of Portland cement and 10-20% (by weight) of asbestos are used. The production of pipes includes the following operations: asbestos processing (kneading and fluffing), preparation of asbestos-cement slurry, pipe forming, hardening and mechanical processing. Pipe molding is carried out on special molding machines.
Asbestos-cement non-pressure pipes are made with smooth ends, and special couplings are produced for their connection. When testing, pipes and couplings must withstand a hydrostatic pressure of at least 0.4 MPa. Asbestos-cement pipes are waterproof, have a smooth surface, are light and have little thermal conductivity, and are relatively resistant to aggressive environments.
However, asbestos-cement pipes are brittle and have little resistance to sand abrasion.
When connecting asbestos-cement pipes, asphalt, asbestos-cement and cement joints are used, which are performed in the same way as when connecting ceramic pipes.
CONCRETE AND REINFORCED CONCRETE PIPES
Concrete non-pressure pipes are made with a diameter of 100 to 1000 mm. The most important pipe manufacturing operations are: preparing the concrete mixture, forming the pipes and compacting the concrete mixture, keeping the pipes after demoulding to ensure the necessary strength. Concrete pipes are formed, as a rule, in a vertically standing formwork. The concrete mixture is compacted by vibrocompression, radial pressing, tamping.
Reinforced concrete non-pressure pipes are manufactured with a diameter of 400 to 1400 mm. According to the method of connection, reinforced concrete pipes are divided into socket and folded pipes, and according to the cross-sectional shape, they are divided into round and round with a flat sole. Socket pipes are connected using sealant, rubber rings, tarred strand with a cement mortar or asphalt mastic lock. Seam joints of pipes with a diameter of 1000 mm or more are additionally reinforced with cement reinforced belt from the outer surface of the pipes.
PLASTIC PIPES
Plastic pipes include polyethylene, fluoroplastic, fiberglass, high-strength vinyl plastic and others.
Polyethylene pipes made of polyethylene low pressure are issued with a diameter of 63-1200 mm. and x it is recommended to use for the installation of pressure pipelines transporting water of various aggressiveness. The pipes are connected by welding.
Fiberglass pipes are made in diameters 1200, 1400, 1600, 2000 and 2400 mm with smooth ends and diameter 2400 with a socket. These pipes are recommended for transporting aggressive wastewater.
Faolitic pipes and fittings for them are made from acid-resistant faolitic mass by injection, molding and pressing with a diameter of 32-350mm. These pipes are recommended for transporting acidic chemically aggressive wastewater that does not contain oxidizing agents at temperatures up to 120 0 C, depending on the concentration of pollutants.
collectors
To pass significant wastewater flows, large cross-section pipelines are used, which are made of several elements in cross section. Such pipelines are called collectors. They can be built from clinker bricks. Their cross-sectional shape is different, but more often - round or ovoid. Brick collectors are reliable and durable, but they cannot be built by industrial methods.
For construction, prefabricated reinforced concrete is currently widely used (Fig. 26), construction is carried out in an open way.
Fig.26. Collectors made with an open construction method.
a) - semicircular shape; b) - round shape (combined); c) - round shape from pipes.
1. Preparation; 2. Concrete base; 3. Bitumen; 4. Reinforced concrete slab; 5. Plaster; 6. Vault; 7. Concrete belt for sealing joints; 8. Reinforced concrete belt for fastening base blocks; 9. Reinforced concrete pipe; 10. Concrete chair.
Semi-circular and round collectors consist of two elements in cross section, laid on a base of crushed stone or lean concrete. The most important requirement for the assembly of such collectors is the location of the joints of different elements in a run. The pipe collector is the most promising, as it has high strength, water resistance and durability. In addition, in the practice of building collectors in an open way, rectangular collectors are often used. With a closed method of construction (shield penetration), the design of collectors of a round cross-section is used. The inner surface of the collectors is either plastered with iron or lined with bricks, ceramic blocks, plastic plates. When transporting acidic effluents, concrete collectors are lined with bricks on a solution of acid-resistant cement or plastic plates.
Foundations for pipelines
The design of the base depends on the type of soil, its bearing capacity, the material and diameter of the pipeline, as well as the depth of its laying.
Ceramic and asbestos-cement pipelines in sandy and clay soils with a normal resistance of 0.15 MPa or more are laid on a natural base, however, for pipes with a diameter of 350-600 mm, the base must be profiled according to the shape of a pipe with a coverage angle of 90 0 (Fig. 27a).
Fig.27. Foundations for pipelines.
a) Natural profiled; b) Monolithic concrete; c) pile.
1.Pipe; 2. Sandy soil; 3. Concrete chair; 4.Reinforced concrete slab; 5.Piles.
eIf the base soil has a normal resistance of 0.1-0.15 MPa, then ceramic and asbestos-cement pipes are laid on a monolithic concrete base, profiled according to the shape of a pipe with a wrapping angle of 90 0 (Fig. 27b).
andreinforced concrete pipes with a diameter of 400-1200 mm in soils with a normal resistance of more than 0.1 MPa can be laid on a natural or artificial base, similar to ceramic pipes. In weak soils with a normal resistance of less than 0.1 MPa, reinforced concrete pipes are recommended to be laid on a pile foundation.
When laying pipelines in water-saturated soils, an artificial sand and gravel, crushed stone or concrete base is arranged. The base for pipes in rocky soils must be leveled with a layer of sand or soft compacted soil at least 0.1 m high above the protruding irregularities of the trench bottom.
Manholes
Manholes are arranged on drainage network to inspect and monitor the operation of pipelines, as well as to perform various operational activities on the network.
Wells are linear, rotary, nodal, differential, control and flushing. Linear manholes are arranged on straight sections of the network at a distance from each other:
d= 150mm-l= 35m;
d= 200 - 450mm-l= 50m;
d= 500 - 600mm-l= 75m;
d= 700 - 900mm-l= 100m;
d= 1000 - 1400mm-l= 150m;
d= 1500 - 2000mm-l= 200m;
d> 2000- l= 300m.
andx are also satisfied when changing the diameters of pipelines and their slopes. Any manhole consists of a base, a tray part, a working chamber, a neck and a hatch (Fig. 28). Wells can be made from various materials: precast concrete elements, bricks, rubble and other local materials. Wells are arranged in terms of round, rectangular or polygonal.
Fig.28. Lookout well.
1.Crushed stone preparation; 2. Bottom plate; 3. Tray part; 4.Working chamber; 5. Floor slab; 6. Neck; 7.Hatch; 8. Staples.
The base of the well consists of a concrete or reinforced concrete slab laid on a crushed stone base. The main technological part of the manhole is the flume part.
The tray is made of monolithic concrete M 200 using special formwork templates, followed by grouting the surface with cement mortar and ironing. The pipeline in the well passes into the tray, the waste liquid flows through it, which determines the peculiarity of the tray device. In linear wells, the trays are straight, the surface of the tray in the lower part repeats the inner surface of the pipe, in the upper part it is vertical. The total height of the tray must not be less than the diameter of the larger pipe. Shelves (berms) are formed on both sides of the tray. The shelves are given a slope towards the tray 0.02. Shelves serve as platforms on which workers are placed when performing operational activities. The working chamber of the well should have the dimensions of the location of the worker in it, the height should be 1800 mm, and the diameter, depending on the diameter of the pipes: 1000 mm with a pipe diameter of 600 mm, withd = 800 - 1000mm - 1500mm and at d = 1200mm - 2000mm. Dimensions in terms of rectangular wells are taken depending on the diameter of the largest pipe: with d 700mm - 10001000mm; at d >700mm length (along the axis of the pipeline) - d +400mm, width d+500mm.
GThe orlovina of wells should be taken with a diameter of 700 mm. with a diameter of pipelines of 600 mm or more in wells located at a distance of 300-500 m, the size of the necks should be taken sufficient to lower the cleaning devices (balls and cylinders). Working chambers and necks are equipped with brackets or hinged ladders for descending into the well. The transition from the working chamber to the neck can be carried out using a special conical part or a reinforced concrete floor slab. At ground level, the neck ends with a hatch with a lid, which is heavy and light. Heavy is installed on the carriageways. The installation of hatches is provided at the level with the surface of the carriageway - with an improved road surface, 50-70 mm above the ground - in the green zone, and 200 mm above the surface - in an undeveloped area. When wells are located in an uncovered area around the hatch, a blind area is arranged to drain surface water.
In wet soils, it is necessary to waterproof the bottom and walls of wells 0.5 m above the groundwater level. The scheme for sealing pipes in the tray part of the well for dry and wet soils is also different (Fig. 29).
Fig.29. Joint sealing schemes.
a) - in dry non-sagging soils; b) - in wet non-sagging soils.
1. Cement mortar; 2. Asbestos-cement mortar; 3. Resin strand; 4. Waterproofing.
Withthe manhole installed at the turn of the pipeline route is called a turning well, at the side branches attached to them - a nodal one. Their designs are similar to those of a linear one, with the difference that the diameter of the working chamber is determined from the condition of placing curved turns inside the well. The radius of rotation of the axis of the tray in the well must be at least the diameter of the pipeline. Side branch connection trays in nodal wells are also curvilinear with the same turning radius in the direction of the waste fluid flow (Fig. 30). on large collectors with a diameter of 1200 or more, the turning radius must be at least five diameters, and manholes are provided at the beginning and end of the turning curve.
Fig.30. Manhole trays.
Drop wells are arranged to reduce the depth of pipelines, to dampen the speed when it decreases in subsequent sections in order to avoid exceeding the maximum allowable speed, when crossing with underground utilities and when rainwater is flooded into the reservoir. Structurally, drop wells are made with a riser, in the form of a weir of a practical profile, a shaft type, and others.
Fig.31. Drop well with riser.
1.Riser; 2. Water cushion; 3.Metal plate; 4. Reception funnel; 5. Staples.
On pipelines with a diameter of up to 500 mm inclusive and a drop height of not more than 6.0 m, drop wells with a riser in the well are used (Fig. 31). the diameter of the riser is assumed to be equal to the diameter of the supply pipeline. In the upper part of the riser, a receiving funnel is arranged, under the riser there is a water cushion, under it metal plate. For a riser with a diameter of up to 300mm, it is allowed to install a guide elbow with a water-breaking wall instead of a water-breaking cushion.
Fig.32. The design of the overflow well in the form of a spillway of a practical profile.
1. The mouth of the well; 2. Supply pipeline; 3.Water drain; 4.Water-breaking part;
5. Outlet pipeline.
With a pipeline diameter of 600 mm and above with a difference of up to 3.0 m, a differential well is used in the form of a spillway of a practical profile (Fig. 32). The drop well consists of a curvilinear weir and a water well at the base. The device of the water well ensures the flooding of the hydraulic jump, as a result of which the energy of the flow is extinguished.
Fig.33. Design scheme overflow well.
The calculation of a drop well in the form of a weir of a practical profile is reduced to determining the depth and length of the water well. The calculation is made using the following dependencies. Compressed section is determinedh With downstream at the base of the weir:
, where
Specific consumption per unit width of the weir, which is assumed to be equal to the diameter of the supply pipeline;
Speed coefficient equal to 0.95-0.99;
T 0 - average specific energy of the flow, determined by the formula:
T 0 \u003d P + H +, where
P - drop height;
H - filling in the supply pipeline;
d To- depth of the water well.
Next, the second conjugate depth is determinedhII provided that the first conjugate depth (before the jump) is equal to h I = h C:
, where
h KR- critical depth, determined by the formula:
.
The required depth of the water well is found from the condition:
hII < t + d К + z , where
z = - the difference in water levels when it leaves the water well.
Average velocities, respectively, in the discharge pipeline during fillingtand in a water well.
The length of the water well is recommended to be calculated by the formula:l VK \u003d l P ,
Coefficient equal to 0.6-0.7,L P- hydraulic jump length,
.
With large diameters of pipelines and a drop height of more than 3.0 m, shaft drops can be used, Fig. 34 shows the design of a shaft well with multi-stage drops. The well has a shaft blocked by steps alternating along the entire height in a checkerboard pattern. The distance between the steps is recommended to be taken equal toz \u003d (0.52) V, for a rectangular section of the mine and z =(05 2) dwith a round section. The calculation of the differential well is carried out for the limiting flooded state. You can use the following formula to determine performance:
, where
Flow rate;
= BL/2 - cross-sectional area of the hole;
z 1 - water pressure over the hole, which is equal to z;
0,57 + 0,043(1,1- n), where
n\u003d a / - the degree of narrowing of the mine.
The velocity coefficient in the shaft openings is 0.89.
The drop well can be made of prefabricated or monolithic reinforced concrete. Increased requirements are imposed on the arrangement of steps, since they perceive the impact of a water flow that has a large kinetic energy. The shape of the shaft in the plan can be rectangular or round. There are also a number of designs of shaft-type differential wells.
Fig.34. Two-section differential shaft shaft type
with multi-stage transitions.
1. Supply manifold; 2.Shiber; 3. Sections of overflow well; 4.Difference steps; 5. Outlet manifold.
rainwater inlets
To receive rain and melt water into the drainage network, special structures are used - storm water inlets, which are recessed chambers covered with gratings. The designs of storm water inlets are divided into two groups: without a sedimentary part and with a sedimentary part (Fig. 35). To receive sewage into the rain drainage network, storm water inlets without a sedimentary part are mainly used. The bottom of such storm water inlets should have a smooth outline. Grates of storm water inlets can be rectangular and round, installed in the plane of the carriageway. To increase the throughput of the gratings, they are placed 20-30 mm below the carriageway tray. For reception big expenses with a street slope of more than 0.03, it is advisable to install two gratings.
If the runoff area has a paving or cobblestone coating, then it is allowed to install storm water inlets with a sedimentary part. Rainwater inlets on a common alloy network are also equipped with hydraulic gates with a height of at least 10 cm. The depth of the sedimentary part is assumed to be 0.5-0.7 m.
dzhdepriniks are located in low places, at crossroads in front of pedestrian crossings and on long sections of descents (ascents). The distance between the storm water inlets is determined hydraulic calculation street tray, provided that the width of the flow in the tray in front of the grate does not exceed 2.0 m.
Fig.35. Stormwater structures.
a) a storm water inlet without a sedimentary part; b) a storm water inlet with a sedimentary part and a hydraulic shutter
PIf the width of the streets is less than 30 m and there is no runoff from the territory of the quarters, the distance between the storm water inlets is taken according to Table 4.1.
Table 4.1.
Distance between storm water inlets.
Street slopes |
Distance between storm water inlets, m |
up to 0.004 0,004-0,006 0,006-0,01 0,01-0,03 |
PNote: if the width of the streets is more than 30 m or if the longitudinal slope of the streets is more than 0.03, the distance between the storm water inlets should be no more than 60 m.
PThe storm water inlet is connected to the drainage network by a 200 mm pipeline laid with a slope of 0.02. The length of the connection should not exceed 40 m, while it is allowed to install no more than one intermediate storm water inlet.
Storm drains and separation chambers
Storm drains are used to discharge part of the wastewater mixture into water bodies in a common water disposal system. storm drains are installed on the collectors of sewerage basins, in front of pumping stations and treatment facilities. Separation chambers are installed on the rain network of a complete separate system and on a semi-separate network.
Separation chambers on the rain network of a complete separate system ensure the discharge of part of the rainwater into the reservoir when directed to treatment facilities, as well as the separation of the entire flow of rainwater, if necessary, to be sent to treatment facilities with different degrees of purification.
In a semi-separate system, separating chambers are installed on the rain network before connecting it to the combined collectors for discharging part of the rainwater during heavy rains into the reservoir, in front of the treatment plant for temporarily discharging part of the wastewater mixture into control tanks during heavy rain for subsequent supply to the treatment plant.
PThe principle of operation and design of storm drains and separation chambers are similar. According to the principle of operation, they can be divided into the following types: with discharge devices in the form of spillways, with a bottom drain, with a siphon spillway, with a cyclone-type spillway, etc.
Rice. 36. Downspout with side straight spillway
with unilateral release.
1.Livneotvod (discharge pipeline); 2. Outlet pipeline; 3. Weir comb; 4. Supply pipeline.
A storm drain with a lateral straight weir with a one-sided discharge consists of a tray, one side of which is a weir (Fig. 36). Weir crest lengthbit is recommended to determine by the formula:
b= 0.75, where
q SBR- consumption of wastewater discharged through a storm drain, m 3 / s, N 0 - full head on the spillway, equal to H 0 \u003d H + 0.5 .., where
H - static head on the spillway, m (H=h 1 - p; h1- depth of water in the supply pipeline, m; p is the height of the spillway sill, m);
The speed of movement of water in the supply pipeline.
The height of the weir threshold should be equal to the depth of water in the flume when the maximum non-dischargeable flow is passed. The length of the distribution chamber should be taken equal to the length of the crest of the spillway, and the width B K,
V K 1.5N +d sbr + 0.2 , where
d sbr - diameter of the storm drain (discharge pipeline), meter.
A storm drain with lateral straight weirs with a double-sided discharge consists of a tray, both sides of which are weirs (Fig. 37).
Fig.37. Storm drain with lateral straight weirs
with double sided release.
1 and 2. Pipeline, respectively inlet and outlet; 3. Waste pipeline; 4. Ridges of weirs.
Weir crest length is calculated using the formula above, withq sbr /2.
A storm drain with a lateral curvilinear spillway (central angle = 90 0) consists of a curved flume, the outer side of which is a spillway (Fig. 38).
Fig.38. Livnespusk with lateral curvilinear spillway.
1. Supply pipeline; 2. Weir threshold; 3. Waste pipeline (storm drain); 4. Outlet pipeline.
RThe flow of water through the spillway is equal to:
, m 3 / s, where
d 1 - diameter of the supply pipeline;
m- flow coefficient equal to atq c br/ q r >0,5 - m \u003d 0.48, withq sbr / q r <0,5 - m=0,7;
q r - the flow coming to the storm drain.
.
Parameter B depends on the ratioR/d 1
R/d1 |
... |
1,5 |
2,5 |
|||
... |
2,57 |
2,17 |
1,91 |
1,73 |
1,6 |
Weir threshold height: P =h1+ , where
The speed of water movement at the maximum non-resettable flow. The discharge pipeline should be designed for full filling. The shelyga of the storm drain (discharge pipeline) and the crest of the spillway must be at the same level.
A storm drain with a bottom drain is a slot in a rectangular tray or a round pipe (Fig. 39).
Fig.39. Downspout with a bottom drain and a threshold behind the gap.
1. Supply pipeline; 2.Threshold; 3.Livneotvod (discharge pipeline); 4. Outlet pipeline.
The storm drain can be without a threshold or with a threshold behind the gap. The calculation of the storm drain consists in determining the width of the slot and the total length of the storm drain chamberS. The height of the threshold is assigned based on local conditions, but not less than 0.1 m. When flowing from a round pipe, the width of the slot is assumed to be equal to the distance of departure of the outer generatrix of the jet a, which is determined by the formula: , m, where
i- slope of the supply pipeline;
A is the value determined by the formula:
, where
Critical depth at limiting (non-resettable) flowq lim equal to:
.
The total length of the chamber should be:S = S 1 + a + S 2 + S 3, where
S 1 = (4-5)h 1 (cr) ;
Critical depth in the supply pipeline at the estimated flow rate;
15 0 - 22 0 ;
S 3=S2/2.
A storm drain with a side spillway and a semi-submerged shield consists of a tray, the outer wall of which is a spillway and an additional tray with a semi-submerged shield (Fig. 40).
Fig.40. A storm drain with a side spillway and a semi-submersible shield.
1.Water drain; 2. Semi-submersible shield.
The semi-submerged shield ensures the retention of floating substances. This design of the storm drain is recommended for use in sewage systems of industrial enterprises, the wastewater of which contains floating substances (oil, etc.).
Crossing gravity pipelines with obstacles
Gravity pipelines often cross natural and man-made obstacles. Natural obstacles include rivers, streams, ravines, dry valleys, artificial ones: roads and railways, pedestrian underpasses, etc.
The crossing can be performed in the form of siphons, siphons, overpasses, in the form of gravity pipelines laid in a case.
If the pipeline and the obstacle are located approximately at the same level according to the marks, then the intersection is made in the form of a siphon (Fig. 41). The siphon consists of the following main elements: pressure pipelines, upper and lower chambers. Pressure pipelines are made of at least 2 lines of steel pipes with reinforced anti-corrosion insulation. Pipe diameter not less than 150mm. Both threads must be working. It is allowed at low costs to install a siphon with one working and one reserve thread. The siphon is laid in a trench along the bottom of the channel. The angle of inclination of the ascending part of the siphon must be at least 20 0 . Depthh1should be taken at least 0.5 m, and on navigable rivers within the fairway at least 1.0 m. The distance is at least 0.7-1.5m. An emergency outlet can be laid from the upper chamber of the siphon or from the nearest well in front of it. Its device is coordinated with the bodies exercising control over the protection and use of the reservoir.
Fig.41. The device of the siphon across the river.
1. Supply gravity pipeline; 2. Shield shutters; 3. Gate valves; 4. Emergency release, 5. Pressure pipelines; 6.Upper chamber; 7.Lower chamber.
The upper chamber of the siphon consists of two compartments: wet and dry. These compartments are separated by a waterproof partition. In the wet section, the gravity pipeline passes into open trays equipped with shield gates (gates). Pipes with valves are located in the dry section. Each section of the siphon has a neck with a hatch and a lid. The excess of the hatch of the chambers above the high water level in the reservoir should be at leasth2= 0.5m.
The lower chamber of the siphon is arranged in the form of one compartment, where pressure pipelines pass into open trays, at the beginning of which shield gates are installed.
The chambers of the siphon are placed in a non-flooded area, even at a high water level in the reservoir. The siphon pipelines are laid perpendicular to the riverbed to ensure the minimum length of pressure pipelines.
The pipe diameter is determined based on a self-cleaning speed of 1.0m/s:
M where
q- estimated wastewater consumption, m 3 / s,
n- the number of working threads.
Difference of water level marks (z 1 - z 2) in the tray of the upper and lower chambers is equal to the head loss in the siphon. - number of withdrawals.
Siphons can also be arranged at the intersection of a gravity pipeline with roads and railways, if they are in recesses. In this case, the pipelines are laid in cases or they are concreted. Otherwise, the design of such siphons is carried out in the same way as siphons across rivers.
At the transition of a gravity pipeline through transport routes, siphons can be used (Fig. 42). the use of siphons may be required when it is impossible to stop the transport and the need to carry out work in a short time. In addition, siphons can be used when crossing rivers in the presence of large bridges, to which the siphon pipeline can be attached. To charge the siphon, a vacuum device is provided, connected to the highest part of the siphon. The height of the siphon H is determined by calculation, usually it does not exceed 5-7m. The calculation of the siphon is reduced to determining its diameter by the flow rate, based on the estimated speed of 1.0 m/s. the difference in the level marks of wastewater in the inlet and outlet pipelines is determined as the sum of the pressure losses along the length of the pipeline and local resistances.
Fig.42. Siphon device.
1. Supply pipeline; 2.Vacuum pump; 3. Siphon pipe; 4. Outlet pipeline.
If the gravity pipeline is located significantly below the obstacle on the marks, then the crossing is carried out in the form of a gravity pipeline from reinforced steel or reinforced concrete pipes laid in cases, as well as in impassable and through tunnels (Fig. 43).
Fig.43. Scheme of crossing a gravity pipeline under the railway on an embankment.
1.Case; 2. Gravity pipeline; 3.4. Contours of the pit for the construction of the receiving and working, respectively.
Cases and tunnels are designed to protect the pipeline from the loads that occur when vehicles move along the road. At the same time, the cases prevent the destruction of the road from erosion in the event of an accident on the pipeline. The diameter of the case and the dimensions of the tunnels depend on the method of work, for example, with an open method, the diameter of the case should be taken 200 mm larger than the outer diameter of the pipeline. The length of the case is determined based on the size of the obstacle. The cases are protected from corrosion by insulation (shotcrete reinforcement, bitumen-rubber, polymer coatings) and cathodic polarization with tread installations.
The space between the walls of the case and the pipeline is filled with concrete. Manholes with disconnecting devices are arranged before and after the crossing.
If the pipeline is located much higher than the obstacle (when crossing ravines, dry valleys), then the crossing is carried out in the form of a gravity pipeline laid along an overpass or an existing bridge. An overpass is a bridge on supports that can be used as a pedestrian bridge. A gravity pipeline made of metal, reinforced concrete and asbestos-cement pipes is laid along the overpass in an insulated box. Before and after the overpass, it is desirable to install wells with disconnecting devices. In front of the flyover, revisions are arranged at distances equal to the distance between the wells.
Network ventilation. Protection of pipelines from the aggressive action of waste and ground water
Water vapor and gases are emitted from wastewater during their movement through pipelines: hydrogen sulfide, ammonia, carbon dioxide, methane. If industrial wastewater is discharged into the drainage network, other gases may also be released, as well as vapors of gasoline, kerosene, etc. The gases released make it difficult to operate the network, a mixture of some gases with air (vapors of petroleum products, methane, hydrogen sulfide, etc.) can explode. Hydrogen sulfide, carbon dioxide and other gases cause corrosion of concrete. All this causes the need for ventilation of the drainage network.
Natural ventilation is used to ventilate the network, and the exhaust is carried out through risers in buildings. The top of the risers is displayed through the attic space outside the buildings.
PThe air flow is carried out through the leaky fit of the covers to the manholes of the manholes. In places of emission or accumulation of a large amount of gases, supply pedestals can be arranged. The action of supply and exhaust ventilation is based on the difference in densities of the outside air and the air in the risers of buildings, due to different temperatures.
Concrete and reinforced concrete pipes and structures are subject to the strongest impact of aggressive gases, sewage and groundwater. The destruction of concrete occurs due to leaching and exposure to acids.
To protect concrete from the action of aggressive sewage and groundwater, the following measures can be taken: use cements that are not subject to corrosion, increase the density and water resistance of pipe walls, cover concrete surfaces with insulation. For the manufacture of pipes and structures, it is recommended to use pozzolanic, sulfate-resistant and other cements with hydraulic additives. The density of concrete is increased by the use of rigid concretes and compaction by tamping, vibrating, evacuating and centrifuging.
Insulation of concrete surfaces can be rigid and bituminous. Rigid insulation includes cement plaster with ironing, shotcrete plaster, facing with ceramic or plastic tiles. Bituminous insulation can be coating, plastic and gluing. Coating insulation is performed by applying 2-3 layers of bitumen in a heated or cold state. To liquefy bitumen in a cold state, solvents are added to it: gasoline, benzene, solvent. Plastic insulation is made of mastic, which includes 40% bitumen and 60% aggregate (ground chalk, fine sand, clay).
Pasting insulation is made of rolled insulating materials (roofing felt, glassine) glued with bitumen and mastics on the insulated surfaces.
In recent years, the use of polymer coatings has become widespread.
Construction of a drainage network
The laying of the drainage network is carried out in an open and closed way. The most common is the open method, i.e. trench digging method. The closed method is used when laying deep-laid pipelines of large diameter, as well as when arranging crossings through highways when it is necessary to keep traffic moving. The construction of the pipeline in the plan is determined by the laying route, and in the vertical plane - by the longitudinal profile.
The transfer of the design axis of the pipeline from the plan to the terrain is carried out by moving rotary and nodal wells, in the centers of which stakes are hammered. Then, between the wells, the direction of the axis of the pipeline is hung and the places of the linear wells are marked on it with stakes. The width of the trench is also marked with stakes, setting a distance from the axis equal to half the width of the trench. Trenches are developed by mechanisms, allowing a shortage of soil by 0.1-0.2 m for cleaning the bottom, as well as developing pits for sockets and couplings immediately before laying pipes.
Fig.44. Laying pipes with the help of sights.
1. Cast off; 2.Shelf; 3. Fixed sight; 4.Plummet; 5. Running sight; 6. Line of sight; 7. Wire; 8. A peg in the center of the well.
To lay pipes in a straight line and along a given slope above the center of each well, perpendicular to the trench, a cast-off is installed, which is a board firmly nailed to two pillars placed on the sides of the pit (Fig. 44). on the cast-off from the downstream side in the direction of water movement, a shelf with a smoothly planed upper edge and a level determine the mark of the upper edge strictly horizontally. A T-shaped fixed sight is nailed next to the shelf, also installed horizontally. A peg is driven in under the cast-off at the bottom of the well and a screw is screwed into it so that the mark of the top of the screw is equal to the mark of the pipe tray in this well. The same peg with a screw is hammered in the upper well. Then a movable (running sight) is made with a height H equal to the vertical distance from the top of the screw to the upper face of the fixed sight. A cast-off with a sight is installed above the pit of the well and on the upper side of the pipeline section, maintaining the distance H from the top of the screw to the top of the fixed sight.
By installing a movable sight at any point of the trench between the fixed sights, they look through the line of sight along three sights. Thus, the depth of the developed trench and the correct laying of each pipe are checked.
Pipes between wells begin to be laid from the lower well with sockets against the current. The straightness of the pipes being laid in the plan is checked by a plumb line suspended from the wire (Fig. 44). And in height - running sight. The first pipe is laid with a smooth end on the previously laid base of the well, it is tightly embedded in the wall of the well. Depending on the design of the butt joint, two or three turns of a resin strand are put on the smooth end of the second pipe and inserted into the socket of the laid pipe, slightly knocking the strand with a caulk. After that, with the help of sights, the axis of sight is checked. If the movable sight protrudes above the axis of sight, then the pipe is laid higher than required, so it is upset, if lower, then sandy soil is knocked under the pipe. Laying pipes on uncompacted freshly poured soil is not allowed, as sedimentation may occur. After re-checking the correctness of the pipe laying, the joint is finally sealed.
Before backfilling the trench, the correctness of the pipe laying is checked by light. To do this, a light source (lantern) is installed at one end of the section, and a mirror at the other. The correct light disk should be reflected in the mirror. The displacement of the light disc indicates the curvature of the axis of the tubes. After laying the pipes, the manhole trays are stuffed and they are installed.
The closed methods of laying pipelines include horizontal drilling, punching, puncture, adit and shield penetration. The description of these methods is quite fully given in the educational and technical literature.
Hydraulic testing of pipelines
All pipelines are subjected to a hydraulic test before backfilling the trenches and commissioning. The tightness of gravity pipelines is checked:
· in wet soils with a groundwater level above the pipe line of 2.0 m or more - for water inflow into the pipeline;
· in dry soils - for water leakage from the pipeline;
· in wet soils with a groundwater level above the pipe line of less than 2.0 m, also for water leakage from the pipeline.
Tests for the flow of water into the pipeline are carried out by measuring the inflow of groundwater at the spillway installed in the tray of the lower well. The water flow at the spillway should not exceed the normative values specified in the reference literature.
In dry soils, the test is carried out in two ways (Fig. 45).
Fig.45. Scheme of hydraulic testing of drainage networks.
a) After the installation of wells; b) e about the device of wells.
1. Strut; 2. Plug; 3. Water level during testing; 4. Portable tank; 5.Hoses; 6.Support for attaching the hose.
According to the first method, two adjacent sections of the network with three manholes are simultaneously tested. In the end wells, plugs are installed in the pipes, and through the middle well, the pipelines are filled with water to a certain level. Then, an external inspection of the network for leaks is carried out and a constant level in the well is maintained for 30 minutes. at the leakage of water from pipelines is estimated by the amount of water added, it should not exceed the standard values. Joints that have leaked are cleared, dried and sealed again. After the defects are corrected, the pipeline is subjected to a secondary test.
According to the second method, a hydraulic test is carried out before the installation of wells. The ends of the pipeline are closed with plugs, to which two rubber hoses are attached. The hose on the top side of the pipeline serves to release air. The downstream hose is connected to a portable metal tank installed at a height of 4.0 m above the pipe tray. The tested pipeline is filled with water through the tank and the required water level in the tank is set along the water gauge. As the water level in the tank decreases, it is added to the required level. By the amount of water added within 30 minutes, the leak is determined and compared with the standard values. Large collectors laid on an undeveloped area are allowed to be tested selectively in one area.
Pressure pipelines and siphons are tested before the pipeline is backfilled in sections of no more than 1 km. Steel pipelines are tested for a pressure of 1 MPa, the underwater part of the siphon for a pressure of 1.2 MPa. Cast iron pipelines are tested for a pressure equal to the working pressure plus 0.5 MPa, VT6 asbestos-cement pipes - for a pressure exceeding the working one by 0.3 MPa, and VT3 grade pipes - for a pressure exceeding the working one by 0.5 MPa. The tightness of pressure and gravity pipelines is checked 1-3 days after they are filled with water.
TYPICAL TECHNOLOGICAL CHART (TTK)
SOFT GROUND FLOORING DEVICE ON THE BOTTOM OF THE TRENCH AND PACKING ON THE TOP BEFORE BACKBACKING THE MAIN PIPELINE
I. SCOPE
I. SCOPE
1.1. A typical technological map (hereinafter referred to as TTK) is a comprehensive regulatory document that establishes, according to a specific technology, the organization of work processes for the construction of a structure using the most modern means of mechanization, progressive designs and methods of performing work. It is designed for some average working conditions. The TTK is an integral part of the Work Execution Projects (PPR) and is used as part of the PPR in accordance with MDS 12-81.2007.
1.2. The TTK provides a diagram of the technological process, outlines the optimal solutions for the organization and technology of work when constructing a foundation along the bottom of a trench (bed) and powdering the pipeline with soft soil, provides data on quality control and acceptance of work, industrial safety and labor protection requirements in the production of work.
Design features for the construction of the foundation along the bottom of the trench (bed) and the powdering of the pipeline with soft soil are decided in each specific case by the Working Design. The composition and level of detail of materials developed at the TTK are established by the relevant construction contractor, based on the specifics and scope of work performed.
1.3. The regulatory framework for the development of technological maps are:
- working drawings;
- building codes and regulations (SNiP, SN, SP);
- factory instructions and specifications (TU);
- norms and prices for construction and installation works (GESN-2001 ENiR);
- production norms for the consumption of materials (NPRM);
- local progressive norms and prices, labor costs norms, material and technical resources consumption norms.
1.4. The purpose of the creation of the TC is to describe solutions for the organization and technology of work on the installation of a foundation along the bottom of the trench (bed) and powdering the pipeline with soft soil in order to ensure their high quality, as well as:
- cost reduction of works;
- reduction of construction time;
- ensuring the safety of work performed;
- organization of rhythmic work;
- rational use of labor resources and machines;
- unification of technological solutions.
1.5. On the basis of the TTK, Working Technological Maps (RTK) are being developed for the implementation of certain types of work on the construction of a foundation along the bottom of the trench (bed) and the pipeline powdering with soft soil, tied to local conditions. Working technological maps are developed for the specific conditions of a given construction organization, taking into account its design materials, available production, labor and material resources. Working technological maps regulate the means of technological support and the rules for the implementation of technological processes in the production of work. Working technological maps are considered and approved as part of the PPR by the head of the General Contractor Construction Organization.
1.6. TTK is intended for engineering and technical workers of construction organizations, foremen, foremen and foremen, employees of the technical supervision of the Customer, who carry out supervisory functions over the technology and quality of work, in order to familiarize (train) with the rules for the production of work on the construction of the foundation along the bottom of the trench (bed ) and powdering of the pipeline with soft soil using the most modern means of mechanization, progressive materials, methods of performing work and is designed for specific conditions of work in the III temperature zone.
II. GENERAL PROVISIONS
2.1. The technological map has been developed for a set of works on laying the foundation along the bottom of the trench (bed) and powdering the pipeline with soft soil.
2.2. Works on the installation of the foundation along the bottom of the trench (bed) and the powdering of the pipeline with soft soil are carried out in one shift, the working time during the shift is:
Where 0.06 is the coefficient of decrease in working capacity due to the increase in the duration of the work shift from 8 hours to 10 hours, as well as the time associated with preparing for work and conducting ETO, breaks associated with the organization and technology of the production process and rest for construction machine operators and workers - 10 minutes every hour of work.
2.3. The scope of work performed when laying the foundation along the bottom of the trench (bed) and powdering the pipeline with soft soil includes:
- development of soft soil in a quarry with an excavator, transportation to the site;
- development of soft (overburden) soil by an excavator in the right of way;
- backfilling of soil to the bottom of the trench and powdering of the pipeline;
- compaction of the sinuses of the pit with vibrorammers.
2.4. The technological map provides for the performance of work by an integrated mechanized unit consisting of: vibrorammers TSS-HCR60K
(60 kg) and excavator Komatsu PC-400
(backhoe bucket with 1.7 m teeth) as a driving mechanism.
Fig.1. Vibrorammer TSS-HCR80K
Fig.2. Excavator Komatsu PC-400
2.5. For the construction of the embankment is used quarry soil
Group III, average density in natural occurrence 1600 kg/m, 1.0 m/day. Soil classification corresponds to GESN-2001, Collection N 1, PM, Table 1-1, name of soils - sands, N 29
.
2.6. Work on the construction of the foundation along the bottom of the trench (bed) and powdering the pipeline with soft soil should be carried out in accordance with the requirements of the following regulatory documents:
- SP 48.13330.2011. Organization of construction;
- SNiP 3.01.03-84. Geodetic works in construction;
- SNiP 3.02.01-87. Earthworks, foundations and foundations;
- SNiP III-42-80
- VSN 004-88. Construction of main pipelines. Technology and organization;
- SNiP 2.05.06-85 *. Main pipelines;
- RD 11-02-2006. Requirements for the composition and procedure for maintaining as-built documentation during construction, reconstruction, overhaul of capital construction facilities and the requirements for certificates of examination of work, structures, sections of engineering and technical support networks;
- RD 11-05-2007. The procedure for maintaining a general and (or) special journal for recording the performance of work during construction, reconstruction, overhaul of capital construction projects.
III. ORGANIZATION AND TECHNOLOGY OF WORK PERFORMANCE
3.1. In accordance with SP 48.13330.2001 "Organization of construction", prior to the start of construction and installation work at the facility, the Contractor is obliged to obtain from the Customer, in the prescribed manner, project documentation and permission to perform construction and installation work. Work without permission is prohibited.
3.2. Prior to the start of work on laying the foundation along the bottom of the trench (bed) and powdering the pipeline with soft soil, it is necessary to carry out a set of organizational and technical measures, including:
- appoint persons responsible for the quality and safe performance of work, as well as their control and quality of performance;
- briefing the members of the safety team;
- place the necessary machines, mechanisms and inventory in the work area;
- develop schemes and arrange temporary access roads for traffic to the place of work;
- provide communication for operational and dispatching control of the production of works;
- establish temporary inventory household premises for storing building materials, tools, inventory, heating workers, eating, drying and storing work clothes, bathrooms, etc.;
- provide workers with tools and personal protective equipment;
- prepare places for storing materials, inventory and other necessary equipment;
- fence the construction site and put up warning signs illuminated at night;
- provide the construction site with fire-fighting equipment and signaling equipment;
- draw up an act of readiness of the object for the production of work;
- obtain permits for the performance of work from the technical supervision of the Customer.
3.3. The device of the foundation along the bottom of the trench (bed) and the powdering of the pipeline with soft soil is carried out after the completion of all installation and finishing works and is carried out in accordance with the project.
Before starting work on the installation of a base from soft soil (bed), it is necessary to check:
- design position of the open trench;
- the geometric dimensions of the trench.
Before starting work on powdering the pipeline with soft soil, it is necessary to check:
- design position of the pipeline;
- integrity of the insulating and heat-insulating coating of the pipeline;
- presence of ballast weights on the pipeline;
- perform work to protect the insulating coating from mechanical damage during ballasting.
The completion of the preparatory work is recorded in the General Journal of Works (The recommended form is given in RD 11-05-2007).
3.4. The device of the foundation along the bottom of the trench (bed) and the powdering of the pipeline with soft soil is carried out to ensure the safety of the pipes and the insulation coating, as well as the tight fit of the pipeline to the bottom of the trench.
3.5. In the absence of soft soil, backfill and powder can be replaced by a continuous lining of wooden slats or straw, reed, foam, rubber and other mats. In addition, backfilling can be replaced by laying bags filled with soft soil or sand on the bottom of the trench at a distance of 2-5 m from one another (depending on the diameter of the pipeline) or by installing a foam bed (spraying the solution before laying the pipeline).
3.6. After the development and acceptance of the finished trench by the representative of the technical supervision of the Customer, a layer of soft soil (bed) is arranged along the bottom of the trench.
Bed
- a layer of loose, usually sandy soil (10-20 cm thick above the protruding parts of the base), poured onto the bottom of the trench in rocky and frozen soils to protect the insulation coating from mechanical damage when laying the pipeline in the trench.
3.6.1. The bed is made from imported or local overburden soft soil that does not contain construction waste, stones and slag.
3.6.2. The soil brought by dump trucks and dumped next to the pipeline (from the side opposite to the dump from the trench) is placed and leveled at the bottom of the trench using shovel excavator Komatsu PC-400
equipped with a backhoe. With a sufficient width of the trench (for example, in the areas of ballasting the pipeline or in the sections of the turn of the route), leveling the backfilled soil along the bottom of the trench can be carried out by small-sized bulldozers.
3.6.3. To make a bed from local soil single bucket excavator
Komatsu PC-400
, equipped with a backhoe, which develops soft overburden located on the strip next to the pipeline trench, near the roadway, and dumps it on the bottom of the trench.
3.6.4. Upon completion of work on the arrangement of soft soil bedding, the finished bed must be presented to the representative of the technical supervision of the Customer for inspection and documentation by signing the Concealed Work Inspection Report, in accordance with Appendix 3, RD 11-02-2006 and obtain permission to carry out subsequent work on laying the pipeline in a trench.
Fig.3. The device "bed" on the bottom of the trench from soft soil
3.7. After laying the pipeline in a trench, the pipeline is powdered on the bed made of soft soil.
Powder
- a layer of soft (sandy) soil, poured over a pipeline laid in a trench (20 cm thick), before filling it with loosened rocky or frozen soil to the design level of the earth's surface.
The type of foundation is chosen depending on the hydrogeological conditions, the size and material of the pipes to be laid, the design of the butt joints, the laying depth, traffic loads and local conditions.
In order to avoid unacceptable settlements during pipe laying, the base must have sufficient strength to balance all active forces, i.e. external loads acting on the pipe.
The Soyuzvodokanalproekt institute provides the following types of foundations for pressure reinforced concrete pipelines (album 3.901.1/79):
flat ground base with a sand cushion and without a sand cushion;
profiled subgrade with 90° wrap angle with and without sand cushion
concrete foundation with 120° wrap angle with concrete preparation
Backfilling is provided by local soil with a normal increased degree of compaction.
Prefabricated reinforced concrete bases from separate blocks are used for laying non-pressure pipelines of large diameters (1400 mm and above). The device of such bases has the following advantages:
reduction of pipeline commissioning time due to prefabricated construction and comprehensive mechanization of assembly
95% exclusion of wet processes, which is especially important when performing work at low temperatures;
reduction of labor costs in the construction of the foundation.
Prefabricated bases are divided into two types: curved reinforced concrete blocks manufactured at reinforced concrete factories, and reinforced concrete road slabs with subsequent subconcrete of the chair.
Prefabricated bases are laid on a leveled sand, crushed stone or gravel cushion 15-20 cm thick. To evenly support the pipe on the tray, leveling layers of cement-sand mortar are laid.
With a settlement value of up to 40 cm, the base soil is compacted to a depth of 0.2-0.3 m. In this case, emergency water is drained from the drainage layer to control devices.
When laying pipes in water-saturated soils, an artificial sand and gravel, crushed stone or concrete base is arranged on sand, gravel or crushed stone preparation, depending on the natural state of the soil.