Ecology of life. If every spring, as well as after rain, water accumulates and puddles form, this means that you need to drain water from the area.
Drainage system.
If every spring, as well as after rain, water accumulates and puddles form, this means you need to drain water from the area. Excess moisture in the area can become a source of such major problems as: death of garden plants, reduced service life of foundations, flooding of basements.
The problem may be due to: the low-lying location of the site, improper layout of the house and its construction without taking into account groundwater, clay soil, disruption of the rainwater collection system, etc.
The cheapest way to drain a site is through ditches dug to drain excess water from the cultivated soil into a drainage well, stream or river.
Ditches have a definite advantage on flat, low-lying land. The water collected in the ditches gradually evaporates or enters the reservoir.
If the terrain is flat, a ditch is dug at the top, across the slope, to lower the groundwater level and prevent the possibility of saturation of the lower layers. To intercept and collect water flowing from the slope itself, another ditch is dug at its base, parallel to the first. The upper and lower ditches are connected by an additional ditch or pottery drainage system. From the lower ditch, water flows into a drainage well or stream.
The simplest and one that does not require special financial expenses is brick drainage. One (two) trenches are dug through the site, directing them to the drainage well. The dimensions and slope of the trench correspond to the parameters of the pottery drainage system. It is half filled with broken bricks or rubble stones, covering this layer with gravel and inverted turf, then topsoil is poured. This system drains a medium-sized area quite well, but the main drawback is that it quickly silts up. Very often, brick drainage is used to intercept water from neighboring areas.
Pottery drainage consists of short or long sections of pipes that are laid end to end, usually in a herringbone pattern, and buried in trenches designed to collect and drain the drained water.
Plastic pipes are perforated and elastic, so they can be bent if necessary. In some cases, inexpensive concrete drainage pipes are used.
Masonry and brick drainage systems and ditches are led to a drainage well if there is no more convenient catchment for water drainage.
Dig a hole with a diameter of 1-2 m and a depth of at least 2 m (the total volume of the drainage well is determined by the size of the area to be drained). To strengthen and prevent silting, the walls of the drainage well are lined with bricks that are not cemented together so that water can seep through them.
The well is filled with broken bricks or rubble stones, and geotextiles are placed on top to prevent siltation. Having drainage systems, it is very important to monitor the depth of soil cultivation. Deep digging or plowing can damage them and lead to waterlogging.
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DRAINAGE SYSTEMS AND DRAINAGES
5.19. When designing drainage systems To prevent or eliminate flooding of territories, it is necessary to comply with the requirements of these standards, as well as SNiP 2.06.14-85 and SNiP II-52-74.
5.20. When designing drainage systems, preference should be given to drainage systems with water drainage by gravity. Drainage systems with forced pumping of water require additional justification.
Depending on the hydrogeological conditions, horizontal, vertical and combined drainages should be used.
5.21. The drainage system must ensure the groundwater level regime required by the protection conditions: in the territories of populated areas - in accordance with the requirements of these standards, and on agricultural lands - in accordance with the requirements of SNiP II-52-74.
5.22. The use of a drainage system should be justified by studying the water, and for the arid zone, the salt balance of groundwater.
For single-stage design, it is necessary to carry out calculations and analysis of the causes and consequences of flooding specified in clause 1.6. In a two-stage design, based on geological and hydrogeological survey data and research results obtained at the first stage, taking into account the nature of the development and the prospects for development of the protected area, it is necessary to determine the location of the drainage network in plan, the depth of its location and the interconnection of individual drainage lines with each other.
Hydrogeological calculations for the selected drainage schemes should establish:
the optimal position of coastal, head and other drains in relation to the dam or to the boundaries of foundations based on the condition of minimum values of their flow rates;
required drain depth and distance between them, flow rate drainage water, including those subject to pumping;
position of the depression curve in the protected territory.
5.23. Performing horizontal drainage using open trench and trenchless methods is determined by economic feasibility. In the case of installing open horizontal drainages at a depth of up to 4 m from the ground surface, the depth of soil freezing, as well as the possibility of their overgrowing, should be taken into account.
5.24. In all cases of using vertical drainage, its water receiving part should be located in soils with high water permeability.
5.25. Open drainage channels and trenches should be installed in cases where drainage of large areas with one- and two-story low-density buildings is required. Their use is also possible for protecting ground transport communications from flooding.
The calculation of open (trench) horizontal drainage should be made taking into account its combination with a mountain canal or a drainage system collector. In this case, the trench drainage profile should be selected according to the estimated flow rate of surface water runoff during gravity drainage of the area.
To secure the slopes of open drainage ditches and trenches, it is necessary to use concrete or reinforced concrete slabs or rock fill. Drainage holes must be provided in reinforced slopes.
In closed drainages, sand and gravel mixture, expanded clay, slag, polymer and other materials should be used as a filter and filter bedding.
Drainage water should be drained through trenches or channels by gravity. The construction of drainage reservoirs with pumping stations is advisable in cases where the topography of the protected territory has lower elevations than the water level in the nearest water body, where surface runoff from the protected territory should be diverted.
5.26. The following should be used as drainage pipes: ceramic, asbestos-cement, concrete, reinforced concrete or polyvinyl chloride pipes, as well as pipe filters made of porous concrete or porous polymer concrete.
Concrete, reinforced concrete, asbestos-cement pipes, as well as pipe filters made of porous concrete should be used only in soils and water that are non-aggressive towards concrete.
According to the strength conditions, the following maximum depth of laying pipes with filter filling and backfilling of trenches with soil is allowed, m:
ceramic:
drainage with a diameter of 150-200 mm.................. 3.5
" " 300 " .................. 3,0
sewer "150" ................... 7.5
" " 200 " ................... 6,0
" " 250 " ................... 5,5
" " 300 " ................... 5,0
concrete "200" ................... 4.0
" " 300 " ................... 3,5
The maximum depth for laying drainage from pipe filters should be determined by the destructive load in accordance with the requirements of VSN 13-77 “Drainage pipes made of large-porous filtration concrete on dense aggregates,” approved by the USSR Ministry of Energy and agreed with the USSR State Construction Committee.
5.27. The number and size of water intake holes on the surface of asbestos-cement, concrete and reinforced concrete pipes should be determined depending on the water throughput of the holes and drainage flow rate, determined by calculation.
Around drainage pipes it is necessary to provide filters in the form of sand and gravel sprinkles or wraps made of artificial fibrous materials. The thickness and particle size distribution of fishing line and gravel should be selected by calculation in accordance with the requirements of SNiP 2.06.14-85.
5 .28. The outlet of drainage water into a water body (river, canal, lake) should be located in plan at an acute angle to the direction of flow, and its mouth should be provided with a concrete cap or reinforced with masonry or riprap.
Discharge of drainage water into a storm sewer is permitted if the capacity of the storm sewer is determined taking into account the additional flow of water coming from the drainage system. In this case, back-up of the drainage system is not allowed.
Drainage inspection wells should be installed at least every 50 m in straight sections of drainage, as well as in places of turns, intersections and changes in slopes of drainage pipes. Inspection wells may be used prefabricated from reinforced concrete tracks with a settling tank (at least 0.5 m deep) and concrete bottoms in accordance with GOST 8020-80. Inspection wells on reclamation drainages should be adopted in accordance with SNiP II-52-74.
5.29. Drainage galleries should be used in cases where the required reduction in groundwater levels cannot be achieved using horizontal tubular drains.
The shape and cross-sectional area of the drainage galleries, as well as the degree of perforation of its walls, should be established depending on the required water intake capacity of the drainage.
Drainage gallery filters must be made in accordance with the requirements of clause 5.27.
5.30. Water-reducing wells equipped with pumps should be used in cases where a decrease in the groundwater level can only be achieved by pumping out water.
If a drainage dewatering well cuts through several aquifers, then, if necessary, filters should be provided within each of them.
5.31. Self-flowing wells should be used to relieve excess pressure in confined aquifers.
The design of self-discharging wells is similar to the design of water-reducing wells.
5.32. Water absorption wells and through filters should be installed in cases where underlying soils of high permeability with free-flowing groundwater are located below the aquitard.
5.33. Combined drainages should be used in the case of a two-layer aquifer with a poorly permeable upper layer and excess pressure in the lower layer or with a lateral inflow of groundwater. Horizontal drainage should be laid in the upper layer, and self-flowing wells - in the lower layer.
Horizontal and vertical drains must be located in plan at a distance of at least 3 m from each other and connected by pipes. In the case of drainage galleries, the wellheads should be led into niches arranged in the galleries.
5.34. Radial drainages should be used to deeply lower the groundwater level in densely built-up areas in flooded areas.
5.35. Vacuum drainage systems must be used in soils with low filtration properties in the case of drainage of objects with increased requirements for underground and above-ground premises.
Low filtration of the underlying soil is the cause of excess water in the area. It slowly goes into the lower layers or does not seep out at all. Cultivated plants grow poorly here or do not take root at all, the area becomes swampy, and there is a sense of slush. In such cases, a drainage system is needed, which should be properly organized.
We will explain in detail how to make a site drainage project. A system designed according to our advice will cope with its responsibilities perfectly. Familiarization with the proposed information will be useful for both independent owners and customers of landscape arrangement in a specialized company.
We have presented practical schemes for constructing drainage systems for suburban areas. The article describes in detail the factors that require consideration when designing and constructing drainage. The information offered for consideration is illustrated with photographs, diagrams, and videos.
Reclamation activities, in accordance with the standards (SNiP 2.06.15), are carried out in forest and agricultural lands so that the soil becomes as suitable as possible for cultivation fruit trees, grain and vegetable crops.
To do this, a branched system of open ditches or closed pipelines is formed, the main purpose of which is to drain overly wet areas.
The ultimate goal of collecting water through branches and hoses of various types is artificial or natural reservoirs (if conditions permit), special drainage ditches, or storage tanks from which water is pumped for irrigation and maintenance of the territory.
Often, pipes buried in the ground, if the terrain allows, are replaced with external structures - ditches and trenches. These are open-type drainage elements through which water moves by gravity
Using the same principle, a network of pipelines is designed for summer cottage, regardless of its area - 6 or 26 acres. If an area suffers from frequent flooding after rain or spring floods, the construction of drainage structures is mandatory.
Clay soils: sandy loams and loams contribute to the accumulation of excess moisture, because they do not allow water to pass through, or very weakly, to the underlying layers.
Another factor that encourages you to think about a drainage project is the increased level of groundwater, the presence of which can be found out without special geological surveys.
Image gallery
Excess moisture in the soil is always a danger to the integrity of the foundation of construction projects: houses, bathhouses, garages, outbuildings
Drainage design elements
What is the drainage system? This is a network consisting of various components, the main purpose of which is to drain and collect capillary water contained in the pores of non-cohesive soils and cracks of cohesive rocks.
Image gallery
System of regional regulatory documents
urban planning activities in St. Petersburg
REGIONAL METHODOLOGICAL DOCUMENTS
DRAINAGES IN BUILDING DESIGN
AND STRUCTURES
RMD 50-06-2009 St. Petersburg
Government of St. Petersburg
Saint Petersburg
2009
Preface
1 DEVELOPEDResearch and Design Institute for Housing and Civil Construction (JSC "LENNIIPROEKT") and St. Petersburg State University of Architecture and Civil Engineering (SPb GASU)
2 ENTEREDConstruction Committee of the Government of St. Petersburg
4 APPROVEDfor use in work by order of the State Construction Supervision and Expertise Service of St. Petersburg dated November 26, 2009 No. 105p.
5 AGREEDwith the Committee on State Control, Use and Protection of Historical and Cultural Monuments, with the Committee on Energy and Engineering Equipment, with the State Construction Supervision and Expertise Service of St. Petersburg.
6 PREPARED FOR PUBLICATION CJSC "Engineering Association "Lenstroyinzhservice"
7 DEVELOPED FOR THE FIRST TIME
Introduction
This regional guidance document has been developed to provide an effective system of protection against groundwater buildings and structures being erected and reconstructed on the territory of St. Petersburg.
The document takes into account the features of hydrogeological conditions and the location of modern construction sites:
High level of groundwater of technogenic and natural origin, the presence of pressure water with the formation of springs; regional distribution of groundwater in the city with a violation of the natural regime in its island part;
The presence of a heterogeneous upper layer of weakly permeable soils, alluvial and bulk areas along the banks of rivers and bays, peat-covered soils and buried layers of peat; formation of technogenic layers by dumps of soil, ash, urban and construction waste;
Natural water bodies covered with technogenic soils and canalized; waterlogging, soil suffusion, quicksand phenomena associated with the impact of surface and groundwater;
Placement of construction sites near operating buildings, structures, engineering and transport communications, including near buildings that have defects caused by uneven precipitation.
The methodological document takes into account the capabilities of modern technologies in the field of construction, safety and environmental requirements in the design, construction and operation of water protection systems for objects:
Preservation of the drainage function of canalized or filled-up water natural objects;
Ensuring safety that excludes negative changes in the properties of the soil at the base of the protected object, the neighboring ones being operated, as well as engineering infrastructure structures;
The use of water protection system designs that allow the least influence on the natural regime of groundwater;
Comprehensive solution to the issues of organizing surface and underground drainage, installation of waterproofing protection of the building.
The document eliminates discrepancies that make it difficult to make an effective decision, which still exist in various reference literature on the design and installation of drainage.
This methodological document contains requirements for starting materials, composition and content project documentation on drainage, necessary terms, recommendations for choosing types, systems, schemes and designs of drainages, performing preliminary and filtration calculations.
When compiling this methodological document, we used the experience of design, surveys and surveys accumulated at the institutes LenNIIproekt, LenzhilNIIproekt, PI-1, St. Petersburg State University of Civil Engineering, Spetsproektrestavratsiya, Trust GRII, LenTISIZ, NPO Georekonstruktsiya - Foundation Project and other organizations.
Participating in the development: from St. Petersburg State University of Civil Engineering, Ph.D., Professor G.I. Kliorina (topic leader), engineer I.S. Nefedova; from JSC "LENNIIPROEKT" engineers T.L. Sokolova, T.A. Gribanova, V.V. Tkachuk.
REGIONAL METHODOLOGICAL DOCUMENT
DRAINAGES IN THE DESIGN OF BUILDINGS AND STRUCTURES
1 area of use
This methodological document applies to the design and installation of drainage of buildings and structures during their design, construction and reconstruction in St. Petersburg.
The document does not apply to drainages for special purposes - landslide slopes, subsidence soils and peats, retaining walls and shallow drainages for roads.
2 Normative references
This document uses references to the following regulatory documents:
SNiP 2.04.03-85Sewerage. External networks and structures
SNiP 2.06.14-85Protection of mine workings from ground and surface waters
SNiP 2.06.15-85Engineering protection of territories from flooding and inundation
Reference manual for SNiP 2.06.15-85 Flooding forecasts and calculation of drainage systems in built-up and built-up areas
SNiP 2.07.01-89*Urban planning. Planning and development of urban and rural settlements
SNiP II-89-80Master plans for industrial enterprises
SNiP 12-03-2001Occupational safety in construction, Part 1. General requirements
SNiP 12-04-2002Occupational safety in construction. Part 2. Construction production
SNiP 02/22/2003Engineering protection of territories, buildings and structures from hazardous geological processes. Basic provisions
TSN 50-302-2004Saint Petersburg. Design of foundations of buildings and structures in St. Petersburg
TSN 30-305-2002Saint Petersburg. Urban planning, reconstruction and development of non-central areas of St. Petersburg
TSN 30-306-2002Saint Petersburg. Reconstruction and development of historically developed areas of St. Petersburg
PUE- 7th edition. Rules for electrical installations.
3 Terms and definitions
The following terms and their corresponding definitions are used in this document:
Coastal drainage - linear drainage system to intercept the flow of groundwater from the river.
Head drainage- linear drainage system to intercept the flow of groundwater from a higher area.
Geocomposites- combinations of geofilter and polymer moisture conductors in the form of porous, perforated or profiled slabs and sheets.
Geotextile materials - (geotextiles) - filtering membranes (geofilters), used independently and in various composites.
Geofilters- water-permeable synthetic fabrics that perform separation and filtration functions in the drainage design.
Geotechnical drainage - a set of measures to organize the relief, surface and underground drainage, developed to protect the underground volumes of the building and the area where it is located.
Waterproofing system of the building - a set of elements that protect a building or structure from the effects of water and moisture.
Risk area- the area around the source of adverse impact on neighboring buildings due to water reduction during construction and reconstruction, in which negative changes in the properties of the soil mass and/or structures of existing buildings and structures are possible.
Contour drainage - foundation or circular, have a closed or not closed contour in plan.
Ring drainage - contour drainage used to protect a building or several buildings, laid at some distance from the wall of the protected objects.
Linear drainage- head, shore or a combination thereof.
Dehumidification rate- the smallest depth of the maximum predicted groundwater level from the floor level of the basement of the building or the design surface level, which ensures normal operating conditions of buildings and territory.
Imperfect drainage - a tubular drain is laid in a water-containing soil layer above the aquifer.
Foundation drainage - a contour, linear or combined system with a vertical filter layer on the outside of the protected buried part of the object and a horizontal drain laid under the basement floor or along the outer wall, at a distance sufficient to accommodate inspection wells.
Formative drainage - a filter bed at the base of the building made of large-porous soil material or geocomposite.
Plastic drainage - a geocomposite of a three-dimensional drainage plastic base and a filter membrane (geofilter). It is a two-layer structure made of high-strength polyethylene fabric with molded round spikes and a filtering geotextile membrane made of polypropylene []. Orderly arranged round spikes create thickness of the material and form drainage channels between themselves, through which water enters the foundation drainage and is removed from the protected object. The geotextile membrane protects the fabric from mechanical stress, filters out small soil particles and prevents silting of plastic drainage.
Drainage type- perfect or imperfect depending on the position of the drains in relation to the waterproof layer.
Perfect drainage - a tubular drain is laid on a waterproof layer.
Drainage systems- 1 - contour, linear, combined; 2 - diagrams of the placement of drains in plan in relation to the protected object; 3 - local, general, depending on the created water protection effect, respectively, for the object or site.
Geotechnical drainage systems - drainage and rainwater networks on the building site, external (or internal) drains of the building with drainage devices.
4 Abbreviations
GWL - groundwater level
GW - groundwater
PV - groundwater
PP - polypropylene
HDPE - low pressure polyethylene
PVC - polyvinyl chloride
NDPE - high density polyethylene
5 Basics
5.1 Drainage design is carried out taking into account the requirements of reliability, efficiency and economic feasibility, as well as safety, excluding the negative impact of water reduction on neighboring buildings and preserved structures of the reconstruction object, taking into account the assessment of the geotechnical situation for the protected and existing neighboring buildings and structures in accordance with TSN 50-302-2004 Saint Petersburg, TSN 30-306-2002 Saint Petersburg, TSN 30-305-2002 St. Petersburg, as well as forecasts for the development of negative hydrogeological processes when choosing and installing a particular drainage system according to the recommendations of the reference manuals for SNiP 2.06.15 .
5.2 The drainage project must solve the following main tasks:
Ensuring the required drainage rate by regulating the groundwater level and water flow at the site of the building, excluding the flow of water into underground and buried rooms and the contact of water with the external surface of the structure;
Prevention of soil watering and increased filtration, which can cause negative changes in soil properties, the emergence or activation of dangerous geological processes;
Ensuring the required sanitary conditions at the construction site and maintaining environmental safety.
The drainage rate for buildings with basements and technical undergrounds should be taken as 0.30 m, calculated from the floor level of these rooms and undergrounds.
5.3 Drainage for the protection of buildings is arranged when the floors of basements and technical undergrounds are located:
At elevations below the calculated groundwater level and when they exceed the calculated level by less than 30 cm;
In the area of capillary humidification, when dampness is not allowed to appear in the basement;
In clayey and loamy soils, when they are buried more than 1.3 m from the planning surface of the earth, regardless of the presence of groundwater;
In clayey and loamy soils, when they are buried less than 1.3 m from the leveling surface of the earth;
When the floor is located on a foundation slab, when infiltration in the upper layer of natural or man-made soil layers is possible on the upland side of the building, and also when the building is located in close proximity to the thalweg into which pound water is discharged.
5.4 Drainage should be arranged in cases where the peculiarities of the hydrogeological conditions of the construction site negatively affect the strength properties of soils and the bearing capacity of foundations and can cause settlement of buildings.
5.5 The protection of the building from the negative effects of water and moisture is carried out using a set of geotechnical drainage measures, which are carried out for the buried part of the building and at the site where it is located.
If possible, preference should be given to drainage systems that simultaneously protect the site and the building located on it from flooding.
Drainage should be designed in conjunction with the organization of the relief, taking into account the waterproofing role of waterproofing buried building structures.
5.6 The choice of drainage schemes for the object should be carried out taking into account the peculiarities of the hydrogeological conditions of the territory of St. Petersburg, data from engineering geological surveys, the configuration, dimensions and design of the foundation of the protected object, the deepening of basements, the presence of closely located exploited engineering structures, buildings, their geotechnical category, characteristics designs, requirements.
6 Initial data
6.1 Design is carried out on the basis of initial data about the engineering and geological conditions of the construction site, the protected object, as well as information about the operated buildings and structures located nearby.
6.2. The scope of surveys and surveys in order to obtain the necessary initial data depends on the geotechnical category of the object, the design stage, and the category of complexity of the natural conditions of the construction site.
The composition and volume of these materials for the purposes of reconstruction and construction in urban areas must be determined in accordance with the requirements TSN 50-302-2004 Saint Petersburg.
6.3. To develop a drainage project, the following materials are required:
- technical report on the engineering and geological conditions of the construction site;
Conclusion on the hydrogeological conditions of the construction site (if necessary);
Materials of engineering surveys and surveys of previous years;
Territory plan with existing and planned buildings and underground structures, elevation marks;
Plan for organizing the relief of the development site;
Plans and floor marks of basements and subfloors of neighboring objects and the designed (protected) building, as well as its first floor;
Plans and sections of building foundations, elements built along the external facade (stairs, ramps, pits, etc.);
Plans, longitudinal profiles and sections of underground channels;
Plan and sections of pits (objects of reconstruction or subject to restoration).
6.4 Protection of palace and park ensembles and historical buildings from groundwater should be developed in conjunction with measures to strengthen the foundations of historical buildings, vertical site planning and water protection of park areas.
The composition of additional source materials is determined by specific conditions (the condition of underground structures and waterproofing, historical drainage and discharge systems, near-surface infrastructure, the presence of valuable green spaces, the use of the ensemble, etc.) based on a specially designed research program.
7 Drainage design
7.1 Design of drainage includes the selection of its system and design, determination of its position in plan and depth, method of discharging drainage water, as well as carrying out the necessary calculations, including preliminary ones.
7.2 The drainage project must contain the following materials: drainage plan, list of main works for drainage installation, drain designs.
If the construction site involves filling up water bodies or draining their sections, then project proposals should be developed for:
Preservation of the drainage function of buried objects;
Measures that compensate for water removal from natural drainage;
Arrangement of natural springs.
The construction of longitudinal profiles of local drainage is carried out:
If there are special requirements of departmental services;
In difficult conditions (during reconstruction, developed existing engineering networks, etc.).
In the explanatory note, as part of the project documentation, the decisions made are justified and the estimated drainage water flows are given. When developing working documentation, they are limited to brief information of similar content in the explanations on the drawings.
7.3 For water protection projects of palace and park ensembles and historical buildings, the composition of graphic and text materials is determined taking into account this document, the assignment of the KGIOP, as well as the requirements TSN 30-306-2002 Saint Petersburg.
7.4 Preliminary verification calculations determine:
Safe distance of the drain from the external walls of the designed (or existing) building, structure, utility networks, if their bases are buried above the drainage pipe tray.
For calculation use the formula
Where
b- widening of the foundation, m;
IN- width of the drainage trench, m;
N- drainage depth, m;
h- foundation depth, m;
a- angle of internal friction of the soil, degrees.
Ordinates of the depression curve - the position of the reduced groundwater level as a result of the action of drainage, if there are buildings, structures, engineering Communication, valuable green spaces. The purpose of the calculation is to determine the risk zone to eliminate negative impacts on existing buildings, engineering and near-surface infrastructure. In the event of an undesirable decrease in groundwater level in the existing building area, the drainage route is adjusted.
7.5. If there is a drainage network serving other buildings or structures in the immediate vicinity of the facility under construction, it is necessary to calculate the ordinates of the depression curve of the network in use. The purpose of this calculation is to determine the position of the depression curve of the operated drainage and evaluate its capabilities in relation to the water protection effect for the new facility. If the reduced water level established as a result of the operation of the drainage does not exceed the drainage rate, the drainage installation for the new facility can be abandoned or its planned position can be changed.
7.6 Calculation of the ordinates of the depression curve is performed in accordance with the methodology outlined in section 12 of this document.
8 Drainage systems and types
8.1 There are two type of drainage: perfect and imperfect. The latter does not completely cut through the aquifer, unlike the perfect type of drainage, the base of which reaches the aquifer layer.
Preference should be given to drainages of the perfect type if the water-resistant layer is located at a small depth from the planning surface and does not require unreasonable (taking into account the drainage rate) deepening of drainage pipes.
8.2 According to the configuration in the plan, one should distinguish between contour, linear and combined systems (schemes), according to the created water protection effect - general systems (protection of the site and the building located on it) and local (protection of the building).
8.3 When choosing systems and, the nature of flooding should be taken into account depending on the position of the unloading site and groundwater supply sources:
At the top is infiltration feeding by storm and melt waters;
Below - capillary and groundwater with a free surface during periods of seasonal and annual increases in their level, as well as local pressure waters; the latter are recorded, as a rule, in drilling surveys when passing sand lenses in poorly permeable soils;
On the side - groundwater flowing from elevated areas of the slopes, and water filtering from reservoirs;
Mixed nutrition is a combination of the various above-mentioned breastfeeding nutrition options.
8.4 Depending on the geological structure of the construction site, groundwater supply sources, purpose and location of protection objects, the following drainage systems should be used:
Linear (head, shore);
Contour (basement, ring);
Reservoir drainage (areal and linear);
Combined from linear, contour, layer.
For construction sites composed of weakly permeable soils of a layered structure with atmospheric supply of hot water, as a rule, a foundation drainage device for the recessed rooms of the building and an effective solution to the vertical layout are required.
8.5 Single-line systems in the form of a shut-off head drainage are used with a power source “from the side”, when the ground flow coming from the overlying territory is clearly visible.
Drainage is laid along the upper border of the protected area from the side of the inflow of soil flow. The route is laid taking into account the location of the building, if possible, in places with higher water pressure levels.
8.6 Two-line systems are designed when the installation of one line of the head drainage does not provide the required reduction in groundwater level. The second drainage line is laid parallel to the head drainage. The distance between the two designed lines is determined by calculation based on their joint work, and the calculated position of the reduced water level is compared with the drainage rate.
A two-line drainage system is necessary if the protected area is located between the zones of groundwater recharge and its discharge by the local hydrographic network.
It should be taken into account that when using two-line systems (head and bank drainage), a high drainage effect is achieved only in areas composed of highly permeable soils. In this case, the formation of wide depression craters is possible as a result of the joint work of the head and coastal drainages.
In areas composed of weakly permeable soils, especially those with a layered structure, a two-line combination will not provide the desired reduction in groundwater level. In this case, it is necessary to consider the following options for protecting the site from groundwater:
Recessed parts of the building - with a local contour drainage system;
Landscaping elements and underground communications - associated drainages;
The site has a proper vertical layout and organization of surface runoff, which reduces the infiltration of precipitation into the soil.
8.7 In coastal areas, to reduce the groundwater level caused by the backwater of the water horizon in the river, single-line coastal drainage should be installed. It is laid parallel to the coastline and laid below the horizon of the high waters of the river.
The feasibility of constructing coastal drainage should be justified by the significance of the protected area, since the costs of construction and operation of coastal drainage, especially when pumping large flows of drainage water, are quite high.
8.8 When protecting small areas from flooding, the following options are first considered:
Local increase in surface level marks;
Protecting a building with a deep basement using local contour and linear systems, as well as waterproofing.
Along with this, it is advisable to use planning opportunities, for example, you can “plant” the building at higher elevations in order to reduce the cost of measures to protect against air pollution.
8.9. With a side PV power source combined with precipitation infiltration, drainage is carried out along the entire contour of the protected building. Depending on the engineering and geological conditions of the development site, wall (basement) or ring contour systems are used.
When flooding of basements is caused by a clearly defined one-way influx of hot water (supply from the side), drainage is designed in the form of an open loop system.
8.10 Ring drainage protects the basements of the building in case of mixed groundwater supply and the location of these premises in aquiferous sandy soils.
When groundwater is fed from above under conditions of a homogeneous structure of the aquifer, perfect ring drainage is also effective for a group of buildings. In the latter case, even when the drains are located above the aquitard, the water level is set at elevations close to the water level in the drains.
Ring drainage is also used if there is no supply from above, and the increase in groundwater level is due to the entry of water from below. In the latter case, the dimensions of the drainage circuit should be smaller than with a similar solution in the conditions of groundwater supply sources from above.
When the depth of drains is not sufficient due to the size of the outflow, then intermediate drains - “cuts” – should be installed.
8.11 Basement (wall) drainage is used to protect basements and subfloors laid in clayey, loamy soils and with a layered structure of poorly permeable strata:
As a preventive measure in the absence of breastfeeding;
In the presence of a mixed hot water supply.
The foundation drainage system, unlike the ring one, must be as close as possible to the object of protection at a distance that is regulated by the design of the foundation, the possibility of placing inspection wells, the conditions of work, as well as the requirements.
For large sizes of the protected object, in order to achieve the effect of water protection over the entire area of the basement, imperfect contour drains are supplemented with underground lines or areal reservoir drainage is used.
8.12 When protecting several buildings with one contour, as well as when the width of the protected building is more than 20 m, the depth of imperfect drains must be justified by calculation (see) taking into account the position of the depression curve inside the contour.
8.13 If the drainage is laid below the base of the foundation of the protected and neighboring buildings (structures), the safe distance from the drains to the walls of the building should be calculated in order to prevent the removal, weakening and settlement of the soil under its foundation (see).
8.14 Reservoir drainage should be installed in combination with contour and linear systems in the following cases:
If contour and linear drains are insufficiently effective;
In conditions of the complex structure of the aquifer with changes in its composition and water permeability;
For preventive purposes in clay and loamy soils;
In aquifers of great thickness, with their layered structure, the presence of pressure water.
8.15 When installing reservoir drainage, the following requirements must be taken into account:
Reservoir drainage must be combined with the sprinkling of tubular drains to ensure the necessary conditions removing moisture so that the filter bed does not become an accumulating container for groundwater; if the reservoir drainage is laid below the foundation drainage (for various objective reasons), the filter bed should be placed in the foundation drainage trench to ensure the discharge of hot water into the trench;
If the tubular drainage is laid along the internal contour of the building (under the basement floor), the layer structure must be made in the form of filling the sinuses of the pit along the outer walls of the building and “connecting” the layer structure of the sinuses with the filling of the underground drainage, tilting its base towards the tubular drains (Fig.);
If the volumes of the protected basement have different depths, the layer structure for the deepest basements should be combined with a similar structure for the basement with less depth; the choice of a rational solution for interface nodes depends on the location of particularly buried volumes in the spot of the protected contour, the difference in floor elevations of differently buried rooms and the height position of tubular drains.
Rice. 1 . Scheme of filling the pit sinuses
8.16 It is advisable to use reservoir drainage as an independent water reduction system for the construction period if it is necessary to drain a pit for a large building. In this case, the bottom of the reservoir drainage filter bed should not be lower than the mark of the tubular drainage tray laid to drain hot water.
The reservoir drainage filter bed is used during the construction and operation of the building. Tubular drains that drain groundwater collected by a filter bed cannot always be preserved in a drainage system designed to protect basements during the life of the building.
9 Drainage schemes, longitudinal profile, structures on the network
9.1 Object drainage schemes are formed on the basis of standard systems, taking into account the hydrogeological conditions of the construction site, the characteristics of the protected object, as well as the requirements of this document.
The drainage scheme of the protected object may consist of one or several systems (simple and complicated). In some cases, the scheme is limited to only one system, in others it requires a combination of several systems.
9.2 The choice of scheme depends on:
From the hydrogeological conditions of the construction site and the deepening of the basement;
Foundation structures;
Location and depth of the storm network receiving drainage runoff;
Recesses and foundation structures of protruding volumes along the perimeter of the building;
Planning marks around the perimeter of the building;
Availability of neighboring operated buildings and structures;
Dimensions and configuration of the protected premises.
9.3 The drainage scheme of modern civil buildings, especially with a large area of the protected basement floor and a complex configuration of the facility, are combinations of various sophisticated drainage systems.
9.4 Single-line head system. The optimal drainage scheme is for the route to intersect the groundwater flow in width and bury the drains into the impervious layer (Fig.).
Rice. 2 . Scheme of a single-line perfect type drainage system:
a - plan; b - section; 1 - building with a basement;
2 - drainage route; 3 - direction of drain slope;
4 - site boundary; 5 - inspection wells;
6 - drainage outlets
Therefore, the linear head system is effective in narrow, elongated areas, especially in hydrogeological conditions where perfect drainage can be used.
When the length of linear drainage is less than the width of the underground flow, additional lines are installed along the lateral boundaries of the protected area. This achieves the interception of groundwater entering from the side.
When the aquitard is deep, drains are laid in the water-containing layer, creating imperfect drainage. In this case, the filtration capacity of the permeable layer is of great practical importance, since it affects the position of the reduced groundwater level in the protected area. To determine the position of the reduced groundwater level, the depression curve is calculated (see).
9.5 Traditional (typical) ring drainage schemes - contour and contour-linear with external spurs. Tubular drains are laid at a distance from the walls of the building, taking into account hydrogeological conditions of the territory, safety requirements and work performance. If the building has a complex facade configuration or basements with different depths, the drainage may have external transverse branches - spurs (Fig.).
Legend:
Rice. 3 . Scheme of contour drainage with transverse spurs
9.6 Traditional wall drainage schemes for typical buildings of small width (up to 20 m) and simple configuration (see):
Linear;
Contour with external drains (along the facade) or internal (under the basement floor), closed or open (contour diagram);
Combined in the form of linear or contour with reservoir drainage.
The most commonly used scheme is a closed loop one due to the predominance of mixed groundwater recharge. If there are restrictions at the construction site, it is possible to lay an open loop. Such restrictions arise in most cases during the reconstruction of objects, restoration and reconstruction of historical buildings, as well as cramped conditions of the construction site [, ,].
9.7 The foundation drainage route is tied to the protected building. The distance between the drainage and the wall is determined by the protruding elements of the building foundation structure and the diameter of the inspection wells. It also depends on the depth of the drains.
Wall (contour) and underground (including reservoir) drains are linked to each other in height terms in such a way as to ensure effective removal of water from under the protected premises (see).
9.8 Protection of large-area basements from groundwater is carried out according to the following basic schemes: contour-linear, contour-area, combined (see).
Contour-linear scheme - a drainage system with a contour network (actually foundation drainage) and linear underground (tubular or reservoir) lines.
Contour-area scheme - a drainage system with a contour network and a layered area filter bed.
The combined scheme combines elements of both of the above schemes.
The contour-linear diagram is used when constructing imperfect drainage without any restrictions for objects with a pile foundation. With a strip foundation structure, the distance of the tubular drains from the walls should be calculated if they are buried below the level of the base of the foundation.
If the foundation of the building is constructed in the form of a monolithic reinforced concrete slab, only a tubeless structure of underground drains or a contour-area scheme is used.
Underground drains are usually routed along the short axis of the basement and connected to the foundation drainage.
The position of the drains is determined by the design features of the foundation. The distance between underground drains is chosen in such a way as to remove the overhang of the depression curve inside the protected contour.
With a developed system of underground lines, it will be necessary to deepen the wall drains so that the depth of their placement ensures the gravity removal of the flow of an extensive network of underground drains, therefore, pumping out drainage water is often required from the wall drains.
The contour-area scheme is characterized by the presence of layered areal and foundation drainage. The latter is often laid along the outer (external) contour of the basement. This scheme is used when constructing perfect and imperfect wall drainage. It has no restrictions associated with the design of the building foundation and is widely used when the efficiency of imperfect wall drainage of buildings, the foundation of which is made in the form of a monolithic reinforced concrete slab, is insufficient.
In cramped conditions, a contour-area scheme can be implemented only with the help of internal underground drains or their combination with external wall drains when the building foundation is of a pile or strip type.
9.9 Drainage of large-area objects, especially in difficult hydrogeological conditions, is effective only through the joint work of wall and underground drainage devices, the design of which is taken into account the specific conditions of construction (reconstruction).
9.10 Wall and underground (including reservoir) drains must be subordinated to each other in height terms in such a way as to ensure effective removal of water from under the protected premises and outside the building.
9.11 Drains are designed taking into account general requirements to the placement of underground networks, ensuring safe construction conditions (in accordance with SNiP 12-03, SNiP 12-04), operating efficiency and serviceability water-reducing structures (in accordance with SNiP 2.06.15, SNiP 22-02).
The horizontal distance (in the clear) between drainage and utilities is taken in accordance with regulatory requirements ( SNiP 2.07.01, PUE-7).
In the vertical plane, the position of drains relative to other utility networks is taken taking into account their purpose, methods of carrying out work on drainage installation and its normal operation in accordance with SNiP II-89.
9.12 When designing drainage, you should consider the option of laying it together with the drain - above it or in parallel, preferably in the same trench.
It is preferable to lay drainage and drainage in the same vertical plane. In this case, drainage is laid above the drain and drainage water outlets are arranged into each inspection well of the drain. This option is convenient from the point of view of removing drainage costs, but is not always possible due to the deepening of the drainage below the drain or insufficient distance between them.
The minimum distance between the drain and the drainage laid above it must be at least 5 cm.
9.13 Drainage lines should be connected in plan at an angle of at least 90°; in the vertical plane, the connections of tubular drainage branches can be carried out with or without a differential device, with the installation of inspection wells according to SNiP 2.06.15 clause 5.28. The presence of differences may be due to different depths of drains, as well as the connection of more than three lines in one node.
9.14 Drains are laid with slopes that ensure gravity movement of water at speeds that exclude siltation of pipes and soil erosion, and also taking into account the water abundance of the drained horizon.
The minimum slope of tubular drainage is:
In sandy soils - 0.003;
In clayey ones - 0.002.
It is advisable to arrange drains with minimal longitudinal slopes, since an increase in the slope of the drains leads to an increase in the volume of work.
The minimum slope of the reservoir drainage laid at the base of the protected building should be taken as 0.005 - 0.01, the slope of the accompanying reservoir drainage may coincide with the slope along the route of the protected utility networks, the base of the road pavement, etc.
The maximum drainage slope is regulated by the maximum permissible water flow speed of 1 m/s and is determined on the basis of hydraulic calculation according to the methodology described in the literature.
9.15 The depth of the drainage should ensure the required drainage rate (according to), protection of the drainage structure from destruction by temporary and permanent loads, as well as from freezing. If deepening the drainage below the freezing depth is impossible or impractical, special measures are taken to protect the network at subzero temperatures.
9.16 The longitudinal profile of drainage lines should be formed taking into account the drainage scheme of the facility, the position and number of outlets, the elevations of the receiving network and the floor of the basement, the method of discharging drainage water, ensuring the reliability of the system in normal and emergency mode, as well as uniform loading of pumps for removing drainage expenses.
9.17 On large-area objects, when constructing a longitudinal drainage profile, the following should be taken into account:
Significant length of underground linear and area of layer underground drains;
The need to pump water from wall drains;
The feasibility of gravity discharge of water from underground systems to contour wall systems.
9.18 The choice of the optimal longitudinal profile of underground linear drains is determined by their length, the permissible range of depth of the receiving contour drainage lines, the conditions of work, the ratio of dimensions (length and width) of the basement, the position of the latter in the “building spot”, the difference in planning marks along the facade of the building, the presence of the perimeter of the object of attached volumes.
9.19 The optimal longitudinal profile of wall drains along the facade of a building when there is a difference in elevations of the planning surface is formed due to additional outlets or increasing the depth of the drainage.
If there is a significant difference in the planning marks along the facade of the protected building and a large basement area, when forming a longitudinal profile, one should proceed from the permissible minimum and maximum depth of drains.
With a constant level of the basement floor, it is advisable to increase the number of outlets in order to avoid large deepening of the drainage, if differences in elevations along its route are limited only by the drainage rate or methods of work.
For basements with different depths, as well as with a large area, laying drainage with differences in elevations across sections will also require an increase in the number of outlets, which will make it possible to eliminate backwater in the drainage system in emergency situations.
9.20 Inspection (inspection) wells for monitoring the operation of the system are installed in places where the route turns and where drain slopes change, at drops - at the junction points of pipes with different tray marks, as well as in straight sections of drainage (Fig. ).
Rice. 4 . Layout of drainage wells:
a - turns of the route, differences in elevations of drainage pipes; b - projections of the building;
c - starting sections, d - with a pump in the transit section of the drainage; 1 - building;
2 - drainage; 3 - wells; 4 - the same differential; 5 - the same with the settling part;
6 - plugs; 7 - outlet (transit drainage); 8 - well with pump;
9 - pressure section of transit drainage;
10 - pressure damper well; 11 - inspection well for rainwater drainage
Drainage inspection wells (with a drain diameter of up to 300 mm) are installed at least every 50 m according to SNiP 2.06.15(see 5.28), according to the operating conditions of the drainage network, the optimal maximum distance according to is 40 m.
At turns, drainage inspection wells at the ledges of buildings are not necessary if the distance from the turn to the nearest well does not exceed 20 m. When the drainage makes several turns in the area between the wells, inspection wells are installed after one turn. Starting sections of the drainage network up to 20 m long can be completed without the first inspection well. In this case, it is necessary to provide a plug for the drainage pipe.
9.21 Release device. Water is released from tubular drains into drains or reservoirs. In some cases, discharge is carried out into a common sewer network, ditches and specially constructed containers. In the final inspection wells of the drainage, before discharging water into the public sewerage system, a control inspection well with a flap valve is provided (according to the terms of connection with the State Unitary Enterprise Vodokanal).
The discharge of water from the drainage tubular network is carried out using transit drainage from pipes without perforation and sprinkling. Drainage flows are discharged by gravity or using pumping units or submersible pumps. Then the transit section of the drainage to the damper well is arranged in the form of a pressure network.
Transit drainage and pumping equipment are designed in accordance with the requirements for the rainwater drainage network ( SNiP 2.04.03).
9.22 In areas of the urbanized landscape of palace and park ensembles and historical buildings in the absence of places for receiving drainage water ( sewer networks) or the impossibility of discharging drainage water into water bodies in appropriate hydrogeological conditions, absorption wells (wells) should be used, the design of which should be taken in accordance with the Reference Manual for SNiP 2.06.15, SNiP 2.04.03, as well as carry out other geotechnical drainage measures in accordance with the requirements.
9.23. For reliable operation of the drainage system, mandatory regular cleaning of drainage wells is required in order to prevent siltation of drainage pipes, therefore the need for such operational measures should be indicated in the text and graphic parts of the project.
10 Drainage design
10.1 To protect the buried parts of buildings, traditional and modern horizontal drainage designs should be used:
With filter coating of pipes (or filling of a closed drainage) from loose sorted material (sand, gravel, crushed stone);
With a filter made of geosynthetic (or natural) materials in combination with sand and gravel;
With compositions of drainage materials based on plastics (geocomposites);
With and without geofabric (or natural materials) pipe wraps.
Geotextile materials in drainage construction should be used as:
Filter membranes for separating backfill and sprinkling of tubular drainage, filter layers of the latter;
Pipe wraps.
Geocomposites should be used to improve the efficiency of the drainage network and reduce the volume of percolating soil materials.
10.2 The choice of geotextile membranes and geocomposites should be made taking into account their operating conditions, engineering and geological conditions of the construction and reconstruction site, technical characteristics of materials [, , ,].
The geotextile filter must allow water to pass through and filter out soil, not be excessively deformed and not limit the access of moisture to the drainage structure, have bio- and chemical resistance, and maintain working condition throughout the entire life of the drainage.
Geocomposites must meet wear resistance requirements; bio- and chemical resistance; safety in working order throughout the entire service life and have high filtration properties.
Preference should be given to:
Filtering non-woven geotextile membranes made of endless PP threads, with needle-punched reinforcement;
Three-dimensional geocomposites of drainage plastic (PP) base and filter membrane, which are called plastic drainages. The purpose of the membrane in plastic drainage is to pass water into the moisture conductor (base) and retain particles of the soil being drained. The purpose of the plastic base is to transport water to the foundation system of horizontal drains.
For certain types of plastic drainage, there is a design option with a special cavity (channel) for the drainage pipe.
10.3 Filtering soil fills, depending on the composition of the soil to be drained, should be constructed as single-layer or double-layer. Along with this, provision is made for backfilling part of the trench with sandy soil (Fig.). When constructing a slope trench, such backfill is made in the form of prisms for reasons of saving material.
Rice. 5 . Sprinkling arrangement diagram:
a - rectangular; b - in the form of a trapezoid;
1 - drainage pipe; 2 - crushed stone; 3 - sand with coefficient
filtration of at least 5 m/day; 4 - local soil
The purpose of the prism is to receive water flowing from the sides. The smallest height of the sand prism is 0.6 - 0.7 of the excess of the calculated groundwater level relative to the bottom of the drainage trench, the maximum is 30 cm above the calculated groundwater level; the optimal one is determined by the specific construction conditions.
10.4 Single-layer filter mats are acceptable in gravelly and coarse sands, as well as in medium-sized sands with an average particle diameter of 0.3 - 0.4 mm and larger.
Two-layer fillings should be installed in sandy loams, fine silty and medium-grained sands with an average particle diameter less than specified, as well as in the case of a layered structure of the aquifer.
Soil materials used for filling must meet the requirements for materials for hydraulic structures and comply with current state standards.
The composition of the filter coatings should be selected to eliminate suffusion and clogging of the system, the thickness of one layer sprinkles must be at least 150 mm.
For the inner layer of bedding, crushed stone M1000 - 1200 is used with a fraction size of 3 - 10 mm (depending on the size of the pipe cuts), the outer layer and sand prisms are sand with a filtration coefficient of at least 5 m/day.
Sprinkles are given a rectangular or trapezoidal shape; more complex configurations require special inventory panels. Trapezoidal-shaped pavements are made with slopes of a stable outline, rectangular ones - with the help of shields.
10.5 The choice of tubular drainage design depends on the hydrogeological conditions of the construction site, the characteristics of the protected object, the type and system of drainage, the depth of the basement floor and its purpose (Fig.).
10.6 Formative drainage to protect the buried parts of the building should be carried out in the form of a continuous sand and gravel layer (areal), in the form of prisms (linear) and sloping towards the tubular drain, as well as using geotextile membranes and high-strength geocomposites.
The design of reservoir drainage can consist of one or two layers, depending on the nature of the underlying soils, the width of the protected structure and the influx of water.
Single-layer reservoir drainage is made of crushed stone (gravel), two-layer drainage is made of crushed stone and sand. The sand layer can be replaced with a suitable geotextile membrane. In reservoir drainage, crushed stone with a fraction size of 3 - 20 mm is used (heterogeneity coefficient is no more than 5), as well as medium-grained sand. The requirements for soil filter bed materials for drainage are similar to those for soil filter beds for tubular drainage.
Area reservoir drainage with a single-layer crushed stone bed must have a thickness of at least 300 mm. A two-layer drainage bed is constructed from a crushed stone layer with a minimum thickness of 150 mm, and a sand layer of 100 mm.
To reduce the volume of crushed stone, area reservoir drainage of a buried building can be structurally designed in the form of a layer of sand cut in the transverse direction by crushed stone prisms.
The thickness of linear reservoir drainage with a single-layer bed of crushed stone must be at least 200 mm. Required amount drains (prisms) are determined taking into account hydrogeological conditions, and their position in the plan depends on the design of the foundation of the protected object.
a - imperfect type
b - perfect type
c - perfect type on a conditional aquitard with linear reservoir drainage
g - with drainage-insulating geocomposite
e - with a geotextile layer in the drain liner and geocomposite
g - with a geotextile layer in the filling drains without geocomposite
Rice. 6 . Wall drainage design diagrams
The reservoir drainage filter bed must be matched with the drainage pipe cover in accordance with the requirements. During the work process, reservoir drainage is protected from clogging. Examples of reservoir drainage designs for buildings are shown in the figure.
10.7 When choosing the design of underground drainage lines, special attention should be paid to its reliability.
When internal drainage lines are laid under the basement floor slab, the possibility of access to them is excluded, therefore the installation of crushed stone drainage prisms (with optimal routing and appropriate design parameters) has certain advantages over tubular structures.
10.8 Drainage pipes are selected and designed in accordance with the requirements:
Sufficient water carrying capacity;
Strength when exposed to backfill soil and dynamic loads;
Resistance to aggressive groundwater;
Convenience of installation and operation of drainage.
To the greatest extent, these requirements are met by single-layer and double-layer plastic pipes made of low-density polyethylene (HDPE), polyvinyl chloride (PVC), as well as polypropylene (PP) and high-density polyethylene (HDPE). Depending on the material and design, they belong to different stiffness classes.
10.9 The choice of drainage pipe design is determined by the application conditions and operating requirements.
Node I
Rice. 7 . Reservoir drainage design diagram:
A - buildings; a - two-layer sand and gravel layers;
b - the same with a geotextile filter membrane; c - the same single-layer of crushed stone;
1 - filter bed; 2 - drainage perforated pipe; 3 - crushed stone filter;
4 - sand filter; 5 - backfill; 6 - bypass pipe without perforation;
7 - waterproofing membrane; 8 - concrete preparation;
9 - geotextile filter membrane; 10 - local soil
The dimensions of the water intake openings of the drainage pipes should be selected taking into account the granulometric composition of the soil to be drained [, ,]. This requirement should be taken into account when choosing pipes presented on the modern construction market with various options for drainage slots.
Traditional designs are single-layer pipes with a smooth or (more often) corrugated surface, which increases the strength of the pipe, maintains its flexibility and increases the water-capturing area of the drainage holes. Modern designs- two-layer and even multi-layer pipes. The latter are effective at high dynamic loads and depths of the protected object.
In double-layer pipes, the inner wall is smooth, and the outer shell is corrugated, securely bonded to the inner layer. Thanks to the smooth inner wall, the speed of water flow increases and the conductivity of the pipe increases. The presence of an outer corrugated shell makes the pipe structure resistant to impact deformation, which is especially important when transporting and installing pipes in winter conditions. Such pipes are distinguished by their high water-draining and self-cleaning ability, and they usually “hold” well the small specified slope of the drainage route.
The permissible maximum depth for laying single-layer plastic drains depends on the material of the pipes; the minimum depth for laying pipes is determined by the requirements for their protection from dynamic loads and freezing.
In soft soils with insufficient load-bearing capacity, the drainage pipe must be laid on an artificial foundation.
10.10 Inspection wells. Traditional well designs should be made of reinforced concrete rings with an internal diameter of 1000 mm, wells with pumps - 1500 mm.
Modern compact well designs are made of plastic with a minimum diameter of 315 mm. The latter are manufactured at the factory and delivered ready-made to the construction site or assembled on site from the appropriate elements.
Transit drainage pipes are made without perforation and installed without filter coating. In design and technical characteristics, they are similar to gravity storm sewer pipes.
Preference should be given to plastic manholes made from prefabricated elements installed on site. It is advisable to use wells and plastic pipes of the same system, since in this case all the necessary components are available: for connecting pipes to each other, pipes and manholes, anti-freeze devices, etc.
Such a drainage system is the most effective in terms of operation and durability.
10.11 The design of a prefabricated well consists of three main parts: bottom, vertical and cover or hatch (Fig.). Pipes either cut in place into the lower part vertical design, or it has factory taps. As a rule, the preferred option is to insert pipes on site. The structural elements of wells are made from various materials based on their operating conditions. The upper part - the hatch, depending on the purpose of the territory and the expected loads, is made in various versions. The vertical part of the well can be a single-layer corrugated or double-layer pipe made of various materials (PVC, HDPE, PP), the bottom of the well can be made of PP.
10.12 Wells made of plastic products are installed with a settling part (sand trap) at least 0.5 m deep and cleaned using mechanized means.
In traditional reinforced concrete wells, a sedimentary part with a depth of at least 0.5 m is required in the last inspection well of the network at the starting section of transit drainage, in drop wells, as well as in inspection wells along the drainage route after 40 - 50 m.
If there are requirements from special organizations, structures on the transit drainage network should be carried out in accordance with these requirements.
Rice. 8 . Well design diagrams:
a - plastic, assembled on site with a conical concrete neck;
b - the same with a cast iron hatch and skirt; c - the same with an embedded drainage pipe;
1 - corrugated pipe of the well; 2 - PVC skirt; 3 - bottom made of propylene;
4 - conical concrete neck; 5 - rubber ring; 6 - cover.
11 Calculation of drainage
11.1 In the process of calculating horizontal drainages, two stages should be distinguished:
1) Hydrogeological calculations, with the help of which the flow rate of drains and the position of depression surfaces of groundwater in the protected area are determined.
2) Hydraulic calculations that determine the required throughput of the selected drain parameters at permissible water flow rates in them and the corresponding filling.
Hydraulic drainage calculations are traditionally performed using the selection method. Currently, the solution to this problem is facilitated by the use of special graphs, which, as a rule, are contained in the methodological recommendations of suppliers of modern drainage pipes.
Hydrogeological (filtration) calculations are performed on the basis of special (calculation) schemes to display the main hydrogeological characteristics of the construction site and operating conditions of drains.
11.2 When choosing design schemes, take into account the specific conditions of the construction site:
Drainage system and groundwater supply sources;
Type of drainage (perfect or imperfect);
The structure of the drained massif (the degree of homogeneity of rocks in terms of water permeability) and the filtration properties of its layers;
Hydraulic state of the aquifer (pressure or free-flow water);
Characteristics of groundwater flow (direction, power, slopes).
The boundaries between individual layers are schematically represented in the form of horizontal planes passing through the average marks of the contacting layers. Inclined planes in the area under consideration are replaced by horizontal ones, which is acceptable for slopes of no more than 0.01 [].
The hydraulic state of the aquifer determines the operation of drainage systems under pressure or free-flow conditions. In the first case, drainages solve the problem of removing the piezometric pressure (full or partial) in the aquifer. In the second case, drainage is used to drain the aquifer.
11.3 Options for design schemes:
Single-line (single) horizontal drain (shore, head) with one-way or two-way inflow of groundwater from the overlying territory and/or from the side of the reservoir;
Two-line horizontal drainage (a combination of coastal and head drains) with a two-way influx of groundwater from the overlying territory and from the side of the reservoir;
Contour horizontal system (ring or foundation drainage) when feeding groundwater flowing mainly within the area lying outside the drained contour;
Horizontal drains located on the site at conventionally equal distances (systematic drainage*) and usually operating under conditions of groundwater (or similar) water flow with feeding from above and/or from below;
A filter bed at the base of the protected object (formation drainage) when groundwater enters from the side and/or from below.
_____________
* The system is used, as a rule, only for general water reduction.
11.4 Calculation of horizontal tubular and bed drainage devices operating under steady-state filtration conditions, free-flow water and a homogeneous environment should be carried out using the calculation formulas given below.
The calculated groundwater level should be taken on the basis of the predicted values of the long-term average annual water level at the construction site.
When draining buildings with local systems in combination with formation flow, discharged by transit drainage, is determined only by the flow rate of tubular foundation drains.
11.5 To calculate drains operating under pressure conditions, as well as plastic drains, it is necessary to use additional information available in reference materials [, , ,].
11.6 In the formulas and design diagrams shown below, the following notations are used:
N- the height of the unreduced groundwater level above the aquitard, m;
h- depth of immersion of the drain under the unreduced groundwater level, m;
T- excess of imperfect drainage over aquifer, m;
N X - excess of the reduced groundwater level above the water level in imperfect and perfect drains at a distance X from them, m;
h y - excess of the reduced groundwater level relative to the drain in the center of the contour drainage, m;
N max - maximum height of the reduced groundwater level above the aquitard in the interdrain space of systematic drainage, m;
h high - seepage height - the gap between the water level in the drain and at the contact of the drainage fill with the ground, m;
R- radius of depression, m;
r 0 - reduced radius of the contour, m;
r g - drain radius, m;
a - half the distance between systematic drainage drains, m;
Q- design flow rate, m 3 /day;
Q o - specific consumption, m/day per 1 linear line. m;
W- intensity of precipitation infiltration, m/day.
11.7 The calculation is made based on the hydrogeological conditions of the construction site, the actual design position of the drainage, its system (local or general) and type (perfect or imperfect).
Filtration coefficient TO of drained soils in the absence of experimental data are taken on the basis of reference materials and taking into account local construction experience. The latter is especially important, since reference sources do not always provide the same ranges of filtration coefficient values for the same soil. This is explained by the characteristics of the studied breeds.
With a heterogeneous structure of the water-bearing strata, the weighted average value K avg, calculated by the formula
Where K 1 + K 2 + ... + Kn- filtration coefficient of individual drained soil layers, m/day; T 1 + T 2 + ... + T n - thickness of the corresponding layers, m, which is taken on the basis of the initial data and the calculated drainage scheme.
The scope of use of formula () is limited to the ratio of the filtration coefficient of different layers to no more than 1:20:
|
K n: Kn +1 < 20 |
11.8 The intensity of precipitation infiltration is determined taking into account the nature of the soil, the amount of precipitation and the degree of improvement of the building site.
For the territory of St. Petersburg, the approximate values of the infiltration intensity, according to , should be taken for areas of new construction as 0.00129 m/day, old - 0.00246 m/day.
11.9 Single-line and two-line drainages. Drainage water flows and depression curves of single-line drainages (local and general) are calculated using the formulas below.
For perfect drainages, the design diagram of which is presented in the figure, and the specific flow rate is determined by the formula () for two-way inflow of groundwater and by the formula () - for one-way inflow:
Where R- drainage depression radius, m, which is calculated using the formula () or determined from the figure:
Drainage water flow for a drainage line with a total length L determined by the formula
Drainage systems in dacha and house areas are often designed “by eye”. This is not correct and often leads to flooding and other problems. In order to make a drainage system correctly, it is necessary to follow the requirements of regulatory documents.
The basic document is SP 104.13330.2012 - this is an updated version of SNiP 2.06.15-85 “Engineering protection of the territory from flooding and flooding.” Unfortunately, it contains little useful information regarding drainage systems used to protect low-rise buildings.
There is another document - “Guidelines for the design of drainage of buildings and structures” from the Moskomarkhitektura, published in 2000 (hereinafter referred to as the “Manual”). It contains a lot of useful information, but like any other piece of legislation, the guidance is difficult to read and redundant in places. Therefore, the site brings to your attention a summary that outlines all the most important things from this document.
When is it permissible to install an open drainage system?
According to SNIP, an open drainage system of horizontal ditches can be used to drain areas with one- and two-story low-density buildings, as well as to protect roads and other communications from flooding (clause 5.25). In this case, to strengthen the slopes of the canals, concrete or reinforced concrete slabs or rock fill should be used.
Obviously, this point relates to the general drainage systems of settlements or neighborhoods. In relation to a specific private house on its own plot of land creating an open drainage system cannot be considered appropriate, since a ditch on the site takes up space and poses a potential danger.
What materials can be used as a filter and filter mat in closed drainage systems?
The following can be used as a filter and filter mat in drainage systems:
- sand and gravel mixture;
- slag;
- expanded clay;
- polymer materials;
- Other materials.
What pipes can be used to create drainage systems?
According to SNIP, to create drainage systems it is allowed to use:
- ceramic pipes;
- polymer pipes;
- concrete, asbestos-cement, reinforced concrete pipes and pipe filters made of porous cement can be used in soils and water that are non-aggressive towards concrete;
How to determine the maximum depth of pipes in closed drainage systems?
The depth of pipes in closed drainage systems depends on their material and diameter. Data on the maximum depth of pipe installation are presented in the table.
How to determine the depth of installation of pipe filters made of porous concrete?
The maximum depth of installation of pipe filters made of porous concrete is determined in accordance with VSN 13-77 “Drainage pipes made of large-porous filter concrete on dense aggregates.”
How to determine the size of the hole in drainage pipes and the distance between them?
The size of the holes in the drainage pipes and the distance between them is determined by calculation.
How to determine the thickness of the filter around drainage system pipes?
The filter around the pipes of the drainage system should be in the form of sand and gravel coating or wraps or polymeric water-permeable materials. The thickness of the filter and the composition of the coating are determined by calculation in accordance with the requirements of SNiP 2.06.14-85. “PROTECTION OF MINING WORKS FROM GROUND AND SURFACE WATER.”
Is it possible to discharge drainage water into a storm drain?
SNiP allows the discharge of drainage water into storm sewers, provided that the storm sewer is designed for such a load. In this case, back-up of the drainage system at the points of discharge into the storm sewer is not allowed.
How to determine the maximum distance between inspection wells of the drainage system?
The maximum distance between drainage system wells in straight sections is 50 meters. In addition, wells should be located at turning points, changing angles and intersections of drainage pipes.
What should a drainage system inspection well be made of?
According to SNiP, inspection wells must be prefabricated from reinforced concrete rings. They must be equipped with settling tanks with a reinforced concrete bottom. Sump depth - at least 50 cm
What data is needed to create a drainage system project?
To design a drainage system you need:
- technical report on the hydrogeological conditions of construction (in common parlance “hydrogeology”);
- site plan with existing and planned buildings and structures. The scale of the plan is not less than 1:500;
- plan with floor marks in basements and subfloors of buildings;
- layouts, plans and sections of the foundations of all buildings located on the territory;
- plans and profile sections of underground communications;
What should a hydrogeological report include?
The hydrogeological report consists of several sections:
The section “Characteristics of groundwater” includes the following information:
- groundwater recharge sources;
- reasons for the formation of groundwater;
- groundwater regime;
- mark of the calculated groundwater level;
- mark of the established groundwater level;
- height of the capillary soil moisture zone (if dampness in the basement is unacceptable);
- results of chemical analysis and conclusion about the aggressiveness of groundwater in relation to building structures.
The geological and lithological section includes general information about the land plot.
Soil characteristics include:
- geological sections and soil columns from boreholes;
- bearing capacity of soils;
- granulometric composition of sandy soils;
- filtration coefficient of sandy and sandy loam soils;
- coefficients of fluid loss and porosity;
- angles of natural repose of soils.
Is foundation waterproofing necessary if there is a drainage system?
The Moskomproekt “Manual” clearly requires the use of coating or painting waterproofing of vertical wall surfaces in contact with the ground - regardless of the presence of a drainage system.
Are there other ways to protect buildings from flooding and areas of soil flooding (besides creating drainage systems)?
Such methods exist. The Moscoproject manual for the design of drainage systems also recommends:
- soil compaction during the construction of pits and trenches;
- the use of closed outlets of drainage systems that collect water from the roofs of buildings;
- the use of open drainage trays with open outlets of drainage systems. The size of the trays is not less than 15*15 cm, the longitudinal slope is not less than 1%;
- installation of blind areas around the perimeter of buildings. The width of the blind area is at least 1 m, the slope away from the building is at least 2%;
- sealing of all openings with utility system connections located in external walls and foundations. Simply put, if you output sewer pipe through the foundation or wall, the holes must be sealed tightly;
- creation of a surface drainage system from the territory.