Surface water drainage. Surface water drainage systems: closed, open and mixed Systems for organizing surface water drainage
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Drainage is considered to be a fairly important hydraulic engineering operation. summer cottage. The easiest way to improve the water balance of the soil must be mandatory, because the moisture ratio in different periods years may change not only due to natural factors. Sometimes even a nearby construction site can upset the balance.
A simple system for draining water from a building
Soil drainage can be done using open trenches or specialized pipes placed in the ground. The first of them are simple in design, but do not look very aesthetically pleasing. In this regard, some developers are creating channels closed type without disturbing the attractiveness of the landscape.
Surface lines
Although the systems surface collection are relatively simple, they allow you to effectively remove moisture from the site in the form of precipitation. Through special trays and depressions, water is directed to a central drain or drain well. The advantages include:
- high construction speed;
- low costs;
- sufficient level of efficiency;
- ease of cleaning.
Helpful advice! If we are talking about how to make drainage on a site with your own hands without unnecessary financial investments, then first of all you should consider the option with a system of open channels.
Closed drainage systems
Systems with deep lines are ideal for draining both stormwater and groundwater located in the immediate vicinity. Most often they are arranged using polymer pipes, which sink into the ground at a certain distance.
In practice, two types of drainage with closed channels are well applicable:
- point (water collection occurs in one place);
- linear (moisture collection is ensured throughout the pipeline through special holes).
Note! Within one site, the presented species can be combined. For example, for drainage system At home, you can use point collection, and for groundwater - linear.
Drainage in a summer cottage: the simplest method of installation for specific conditions
Before making a drainage system on a site, it is necessary to select its type based on operational features. It is worth considering the most optimal options for installing water drainage systems, which are popular under certain conditions.
An example of site drainage with a high groundwater level
When groundwater is close to the groundwater level the best option can be deep system linear type. It will drain moisture from the entire area into a drainage well, ravine or ditch located a level below. It is proposed to use perforated panels as the main elements plastic pipes in the geotextile filter.
One of the simplest methods of drainage in a summer cottage with groundwater located near the surface comes down to the following scheme:
- A trench is dug to the distance where the soil freezes. Its slope should be 2 cm per linear meter towards the liquid collection point. A layer of sand is poured for leveling.
- Geotextiles are spread on the prepared bottom so that its edges overlap the walls of the pit by at least 1-2 m. A small layer of gravel is poured on top.
- Next, plastic pipes are laid, after which they are again filled with approximately the same layer of gravel. The ends of the geotextile are rolled up to form a protective barrier. The rest of the trench is filled with soil.
For your information! Knowing how to properly drainage around a site and on its territory with close groundwater, you can avoid serious problems associated with excess moisture.
Related article:
Installation of open drainage with your own hands on an area with clay soil
For land plots With clay soil, a system with an open channel arrangement is more suitable. At closed system pipelines, water will not be able to seep through such soil and go into specialized sedimentation tanks or other suitable places.
In places where water accumulates, ditches are dug with a depth of at least 50 cm. Their width should increase as they approach the receiving site. It is necessary to make the widest trench that collects water from the ditches adjacent to it. To make draining easier and to protect the edges from collapsing, side walls cut at an angle of 30 degrees.
Because open view spoils the trenches appearance plot, it is necessary to decorate them. It not only improves aesthetic properties, but also strengthens the side surfaces of open lines. In this regard, the operation of the system increases significantly.
Stones of different sizes can be used as material for decorating pits. The largest of them should be placed on the bottom, and the medium and small ones should be placed on top. If you have good financial resources, the surface can be covered with marble chips, which will give the outlet lines a respectable appearance.
If with in cash tight, then ordinary brushwood can be a good option for decoration. It is necessary to find dry branches of any wood species that grow nearby. They should be tied in bunches and placed on special stands installed at the bottom of the ditch.
The thickness of the bundles of brushwood should be no more than 30 cm. It is better to place the branches so that the larger ones lie in the center, and the smaller ones at the edges.
Related article:
Average prices for turnkey plot drainage
Many companies offer professional services for installing drainage systems, but they are not that cheap. During the work, a double-wall pipe with a geotextile filter will be used.
Rules of care
Drainage structures will function properly for many years if the basic rules are followed during operation.
Storm drainage system (storm drainage) is a system that serves to protect the foundations of houses and the territories that surround them from rain and melt water. The main task of the mechanism is to collect rain and melt water in the canal lines. One of the main elements is rainwater inlets that collect water from drainpipes. In general, the system is able to stop the flooding of foundations, which can lead to destruction. Storm drain is a mandatory equipment in engineering country house or garden. Installing a high-quality drain will help you preserve your lawn, flower garden, and most importantly, protect your house from destruction.
To do this, we must answer the question, where does the sedimentary liquid go? Some of the water is absorbed by the earth, but due to the development of civilization most of plots of land turned into asphalt. Now she has nowhere to go. Because of this, rain can destroy our yards and contribute to dampness in our homes. Today, the installation of storm sewers is combating this problem. In most cases they work by gravity.
When choosing technologies, pay attention to the following indicators:
- Relief of the earth;
- Nature of the development
- The amount of precipitation in a given area.
Advantages of storm drainage
50-100 cubic meters - this is how much water flows annually from under a country house. Storm system collects all the water and evenly divides it into areas. If sedimentary water is left uncontrolled, it will cause great harm to the owner of the site. The consequence of this may be destruction of the foundation and rotting of vegetation on the site.
Stormwater has the following advantages:
- Installation work is easy and inexpensive;
- It is much easier to make slopes for such a system;
- 90% are located on the surface, which helps to avoid pipe clogging and facilitates access to repair work;
- The soil layer is almost not disturbed;
- Trays perform two functions: they collect and drain water.
What does a storm drainage system consist of?
The drainage design consists of the following components:
- Gutters;
- Storm water inlets;
- Pipes;
- Supporting parts.
Now let's take a closer look at the functions and features of each.
Gutters collect water resources in places with huge mechanical loads, for example: parking lots and garages. They are used from different materials: plastic, concrete and polymer concrete. The package may include special nozzles made of metal and decorated mesh, which protect them from clogging with large debris.
Storm water inlets work with point collection of water from the surface and roofs of houses, if a connection is established with drainpipes. They are made of plastic and can withstand moving a car. The package may also include: a trash can, a special partition and a cast iron or galvanized grill.
The pipes that make up the gutters are designed to transport water to the collector and are used for outdoor work. Material – polypropylene. When designing systems, as a rule, two options for laying pipes are used:
- Shallow planting. They operate mainly in the summer. In this case, thick-walled brown pipes are most often used.
- Deep. Operate year-round. In this laying system, preference is given to two-layer corrugated pipes.
Important! When choosing a pipe diameter, it is necessary to calculate the expected amount of precipitation. Also, to control storm drains, it is necessary to organize inspections and install inspection wells to clean the wire tubes.
The design of drainage systems may include rain wells, drainage trays, sand traps and underground drains.
Attention buyers! The storm drainage scheme is planned for landscape design and proportionally depends on the vertical structure of the site.
Why is it necessary to install inspection wells?
These structures are installed at turning points of drainage systems, as well as on pipes that are too long, every 25 m. Manholes allow us to carry out an audit and monitor the cleanliness of the drainage system. Previously, they were made by hand from reinforced concrete rings or laid out with bricks. Today it is plastic.
Their advantages include the fact that they:
- Sealed;
- Not subject to corrosion;
- Reliable and durable;
- They are light in weight;
- Easy to install.
Storm sewer classification
Before buying, we need to familiarize ourselves with the classification of gutters. They are divided according to the following criteria: method of drainage and type of drainage.
It is important to know that the drainage and stormwater systems are installed in parallel. They shouldn't unite. Moreover, the stormwater pipeline is laid higher in their parallel.
Types of systems according to the method of water drainage:
- Closed. This is the most complex mechanism. For it to work, it is necessary to carry out detailed hydraulic calculation For suitable diameter pipes Water is collected in special storm inlets or trays and then moved into a pipe system. Then it follows gravity, from which it enters the collector, from where it is transferred outside the site. For example, in bodies of water.
Advice! Installation of closed type systems with big pipes produced on city streets or factories. But in some cases it is ideal for a site if it is a large area.
- Open. This is the simplest option. In this case, precipitation is collected in trays installed in ditches, which are inclined towards the collector. The trays are covered with bars.
- Mixed drainage systems. This system provides for the installation of both types of components, which significantly reduces costs. With this choice, pipes with a diameter of 10-15 cm should be installed.
Types by type of drainage system:
- Point water collection. The principle of operation is the installation of storm water inlets, which are connected by pipes into one network. It needs to be installed in problem areas.
- Linear. This installation is used to collect sediment from large areas, for example, paved areas, etc.
PS: You can get acquainted with each type of water drainage by looking at the photos posted on the Internet.
How to choose a suitable location for the collector?
- Positive or favorable. The terrain is flat or with a slope of no more than 0.005. In this case, drainage areas can reach 150 hectares or less.
- Average. The collector is located at the bottom of the slope. Area – 150 hectares or a little more.
- Unfavorable. Sloping terrain and steep slopes. The area exceeds 150 hectares, and significantly.
Advice. To properly lay a drainage system, you need to choose the most shortcut to the descent point. Drainage and storm water should never be combined!
Stages of preparation for installing a stormwater system
Work should begin immediately after finishing the façade planning and landscaping of the area. You need:
- Perform vertical soil dumping on the site and compact it. This is necessary in order to avoid equipment deformation.
- Installation for drainage of rainfall from roofs outside the site. This helps protect the foundation from getting wet and collapsing.
- Determine the method and place for drainage of sediment. The location must be determined on a case-by-case basis based on the locality. There are two options: drainage ditches and a sewer system.
- Rainwater collection on tile surfaces. They are installed only if there is a slope from the adjacent territory or building.
Advice. The system should consist of linear and point drainage; the kit may also include protective devices against dirt. So before installation, you need to consult with a specialist: after all, any system is selected individually for the area.
Installation procedure
Installation of storm drains plays a big role in its further performance. Correct sequence action will give proper operation and high efficiency. You can find many on the Internet various photos, explaining the principles of installation. We will try to describe it to you below.
So, install the components in the following sequence:
- We fix local points collecting water under pipes;
- We carry out a linear outlet, which is based on trays;
- We connect all components with pipes to the manifold.
Important! Install inspection wells, they will help avoid clogging. The collector must be installed, lowered to a greater depth, so that in frosty weather it does not freeze; if this is not possible, insulate it!
Basic rules and principles for installing drainage systems
- Precipitation from raincoats enters the collector or spillway through pipes;
- A drainage system must be connected from the same system;
- Mainly used for storm drains PVC pipes, diameter 11 cm;
- Corrugated pipes that have a smooth surface inside may also be suitable;
- As a rule, they are installed so that precipitation descends by gravity. To do this, maintain a slope of 1 cm per 1 m of pipe.
- To prevent the system from freezing in the off-season, pipes must be laid below the freezing point of the soil;
- If you cannot place the pipes at depth, then it is worth insulating them.
Attention! If possible, avoid turning pipelines. If you don’t have it, create 90 degree angles.
Built in accordance with all the rules, taking into account the characteristics of the soil and in compliance with construction technology, then only soil and ground moisture will pose a danger to its strength and durability. The integrity of the foundation of the house can be compromised by rain and melt water that enters the soil and cannot be properly maintained due to the seasonal rise in groundwater levels, or if they pass close to the surface.
As a result of such waterlogging of the soil near the foundation, the parts of its structure become damp, and undesirable processes of corrosion and erosion may well begin in them. In addition, dampness is always a prerequisite for damage building structures fungus or other representatives of harmful microflora. Fungal colonies on the walls of premises quickly take over areas, spoiling the finish and negatively affecting the health of the residents of the house.
These problems must be solved at the design and construction stage of the building. The main measures are the creation of reliable waterproofing of structural elements and properly organized drainage of water from the foundation of the house. About waterproofing - a special conversation, but the water drainage system requires careful calculations, selection of appropriate materials and components - fortunately, these days they are presented in a wide range in specialized stores.
The main methods of draining water from the foundation of a building
To protect the foundation of the house from atmospheric and ground moisture, they are used various designs, which are usually combined into one system. This includes blind areas around the perimeter of the house, a storm sewer with a roof drainage system included in it, a set of storm water inlets, horizontal drainage with a set of transportation pipes, inspection and storage wells and collectors. To understand what these systems are, we can look at them in a little more detail.
- Blind areas
The blind areas around the perimeter of the house can be called mandatory element for draining rain and melt water from the foundation. In combination with a roof drainage system, they are able to effectively protect the foundation of the house even without installing a complex storm drainage system, if the amount of seasonal precipitation is within this region– not critical, but groundwater runs deep from the surface.
Blind areas are made from different materials. As a rule, their placement is planned with a slope at an angle of 10–15 degrees from the wall of the house, so that water flows freely into the soil or storm drain gutters. The blind areas are located along the entire perimeter of the building, taking into account that they should have a width of 250÷300 mm larger than the protruding eaves or gable overhang of the roof. In addition to good waterproofing, the blind area also has the function of an external horizontal line for insulating the foundation.
Construction of blind areas - how to do it right?
If you do everything “according to your mind”, then this is very not an easy task. It is necessary to thoroughly understand the design, to know which materials will be optimal for specific construction conditions. The process is outlined with all the necessary details in a special publication on our portal.
- Storm sewer with drainage system
A drainage system is required for every building. Its absence or incorrect planning leads to the fact that melting and rainwater will fall on the walls, penetrate to the base of the house, gradually eroding the foundation.
Water from the drainage system should be directed as far as possible from the foundation of the house. For this purpose it is used whole line devices and elements of storm drainage systems of one type or another - storm water inlets, open gutters or pipes hidden under scrapped earth, sand traps, filters, inspection and storage wells, collectors, storage tanks and others.
Roof drainage system – we install it ourselves
Without right organized collection water from a considerable area of the roof, talking about effective drainage of water from the foundation is simply ridiculous. How to correctly calculate, choose and install on the roof - all this is described in a special publication on our portal.
- Drainage wells
Drainage wells are usually used as independent, autonomous elements of a water drainage system when arranging bathhouses or summer kitchens, not connected to the domestic sewage system.
To build such a well, you can use metal or plastic barrel with perforated walls. This container is installed in a pit dug for it, and then filled with crushed stone or broken stone. The drainage system of the bathhouse is connected to the well by a gutter or pipe, through which water will be drained from the foundation.
This system is obviously extremely imperfect, and in no case should it be combined with storm sewerage, since in case of heavy rain a rapid overflow with a spill of sewage is possible, which, of course, is not very pleasant. However, under conditions country house construction they resort to it quite often.
- Drainage system
Arranging a full-fledged drainage system in conjunction with storm sewerage is a very responsible and labor-intensive process, requiring considerable material investments. However, in many cases it is impossible to do without it.
For this system to work effectively, it is necessary to carry out careful engineering calculations, which are most often entrusted to specialists.
Prices for storm drainage
storm drain
Since this is the most difficult, but at the same time the most effective option drainage of water from the base of the building, and can be performed in different ways, it needs to be considered in more detail.
Drainage system around the house
Is it always necessary to install a drainage system?
By and large, it is highly desirable that drainage be installed around any building. However, in some cases, a water drainage system is simply vital, since there are a number of objective reasons for this, which include:
- Groundwater is located between layers of soil close to the surface.
- There are very significant amplitudes of seasonal rises in groundwater.
- The house is located in close proximity to a natural reservoir.
- The construction site is dominated by clay or loamy soils, wetlands or peat bogs saturated with organic matter.
- The site is located on a hilly area in a lowland area where melt or rainwater can obviously collect.
In some cases, you can refuse to arrange a drainage system, making do with blind areas and properly organized So, there is no urgent need for a full-fledged drainage circuit in the following situations:
- The foundation of the building is erected on sandy, coarse or rocky soil.
- Groundwater passes below floor level basement no less than 500 mm.
- The house is installed on a hill where melt and rain water never collects.
- The house is being built far from bodies of water.
This does not mean that such a system in these cases is not needed at all. It’s just that its scale and overall productivity may be smaller – but this should already be determined on the basis of special engineering calculations.
Types of drainage systems
There are several types of drainage systems that are designed to remove moisture of different nature. Therefore, the choice is made on the basis of geotechnical studies carried out in advance, which determine which of the options are suitable in maximum degree for a specific area.
Drainage can be divided into following types by area of application: internal, external and reservoir. Quite often, installations of all varieties are carried out, for example, to drain groundwater from the basement, it is used internal option drainage, and for soil - external.
- Formative drainage is almost always used - it is installed under the entire structure and is a sand, crushed stone or gravel “pillow” of different thicknesses, mainly 100÷120 mm. The use of such drainage is especially important if the groundwater is located high enough to the floor surface of the basement.
- The external drainage system is installed at a certain depth or placed superficially along the walls of the building and on the site, and is a set of trenches or perforated pipes that are installed with a slope towards the drainage tank. Through these channels, water is drained into a drainage well.
- Internal drainage is a system of perforated pipes that are laid under the floor of the basement of a house, and, if necessary, directly under the foundation of the entire house, and discharged into a drainage well.
External drainage system
The external drainage system is divided into open and closed.
The open part, in essence, is a system for collecting storm or melt water from the roof drainage system and from concreted, asphalted or lined paving slabs areas of the territory. The collection system can be linear - with extended surface trays, for example, along the outer line of blind areas or along the edges of paths and platforms, or point - with storm water inlets connected to each other and to wells (collectors) by a system of underground pipes.
A closed drainage system includes in its design perforated pipes buried in the ground to a depth determined by the design. Very often, open (storm) and closed (underground drainage) systems are combined into one and used in combination. In this case, the drainage contours of the pipes are located below the stormwater ones - the drainage, as it were, “cleans up” what the “stormwater” could not cope with. And their storage well or collector may well be combined.
Closed drainage system
Starting to talk about installation work When it comes to arranging a drainage system, first of all you need to say what materials will be required for this process, so that you can immediately determine the required quantity.
So, to install a closed drainage system, the following are used:
- Bulk Construction Materials– sand, crushed stone, coarse gravel or expanded clay.
- Geotextiles (dornit).
- Corrugated PVC pipes for installation of collector wells, with a diameter of 315 or 425 mm. Wells are installed at all points of change of direction (at corners), and on straight sections - in increments of 20–30 meters. The height of the well will depend on the depth of the drainage pipes.
- Perforated PVC drainage pipes with a diameter of 110 mm, as well as connecting parts to them: tees, corner fittings, couplings, adapters, etc.
- Container for arranging a storage well.
Number of all necessary elements and materials are calculated in advance according to the drawn up design of the water drainage system.
In order not to make a mistake in choosing pipes, it is necessary to say a few words about them.
It is clear that drainage pipes are not used to drain rainwater, since through the holes water will flow under the blind area or to the foundation. Therefore, perforated pipes are installed only in closed drainage systems that drain groundwater away from the building.
In addition to PVC pipes, drainage systems are also assembled from ceramic or asbestos concrete pipes, but they do not have factory perforation, so in this case they are non-functional. You will have to drill holes in them yourself, which takes a lot of time and effort.
Corrugated perforated PVC pipes are the best option, as they are lightweight, highly flexible, and easy to assemble. unified system. In addition, the presence of ready-made holes in the walls allows you to optimize the volume of incoming water. Except flexible pipes PVC, you can find hard versions on sale that have a smooth inner and corrugated outer surface.
PVC drainage pipes are classified according to strength level, have letter markings SN and numbers from 2 to 16. For example, SN2 products are only suitable for contours at a depth not exceeding 2 meters. At a depth of 2 to 3 meters, models marked SN4 will be required. At a depth of four meters it is better to place SN6, but SN8, if necessary, can cope with depths of up to 10 meters.
Rigid pipes are produced in lengths of 6 or 12 meters, depending on the diameter, while flexible pipes are sold in coils up to 50 meters.
A very successful purchase would be pipes that already have a filter layer on top. For this purpose, geotextiles are used (more suitable for sandy soils) or coconut fibers (they show their effectiveness well on clay layers of soil). These materials reliably prevent the rapid creation of blockages in the narrow openings of perforated pipes.
Pipe assembly in common system does not require any special tools or devices - the sections are joined manually using special couplings or fittings, depending on the model. To ensure tight connections, the products are equipped with special rubber seals.
Before moving on to the description of installation work, it is necessary to clarify that drainage pipes are always laid below the freezing depth of the soil.
Installation of a closed drainage system
When starting a description of the arrangement of the drainage system, it is necessary to mention and clearly present the fact that it can be laid not only around the house, but also throughout the entire territory of the site, if it is very wet and requires constant drying.
Prices for geotextiles
geotextiles
Installation work is carried out according to a pre-drawn project, which is developed taking into account all the necessary normal functioning parameter systems.
The schematic location of the drainage pipe looks as shown in this illustration.
| Illustration | Brief description of the operations performed |
|---|---|
 | The first step is to mark the passage of drainage channels on the site according to the dimensions indicated on the project. If it is necessary to drain water only from the foundation of the house, then the drainage pipe is often placed at a distance of about 1000 mm from the blind area. The width of the trench for the drainage channel should be 350÷400 mm. |
 | The next step, following the applied markings, is to dig trenches around the perimeter of the entire house. Their depth should also be calculated based on data obtained after soil surveys. Trenches are dug with a slope of 10 mm for each linear meter of length towards the drainage well. In addition, it is a good idea to provide a slight angle of inclination of the bottom of the trench from the foundation walls. Next, the bottom of the trench must be compacted well, and then laid on it sand cushion 80÷100 mm thick. The sand is spilled with water and also compacted with a manual tamper, respecting the previously formed longitudinal and transverse slopes of the trench bottom. |
 | As the drainage of the foundation of a built house progresses, obstacles in the form of floor slabs may arise along the path of the trench. It is impossible to leave such areas without a drainage channel, otherwise moisture, having no outlet, will accumulate in these areas. Therefore, you will need to carefully dig under the slab so that the pipe is laid continuously along the wall (so that the ring is closed). |
 | In addition to the remote drainage system, in some cases a wall version of the channel for water drainage is installed. It is relevant if the house has a basement or ground floor, under which an internal drainage system was not installed when the house was built. The trench is dug to a depth below the basement floor, without a large distance from the foundation wall, which must be additionally covered with bitumen-based waterproofing material. The remaining work is similar to that which will be carried out when laying pipes running at a meter distance from the wall. |
 | The next step is to lay geotextiles in the trench. If the trench is deep and the width of the canvas is not enough, then it is cut and laid across the pit. The canvases are laid on top of each other with an overlap of 150 mm, and then glued together with waterproof tape. Geotextiles are temporarily secured along the upper edges of the trench with stones or other weights. When installing wall drainage, one edge of the canvas is temporarily fixed on the wall surface. |
 | Next, at the bottom of the trench, on top of the geotextile, a layer of sand 50 mm thick is poured, and then a layer of medium-fraction crushed stone 100 mm thick. The embankment is evenly distributed along the bottom of the trench, and care must be taken to ensure that the previously laid slope is maintained. |
 | In order to embed a coupling into a corrugated pipe of a plastic drainage well, the diameter is outlined on it, and then, using sharp knife the marked area is cut out. The coupling should fit tightly in the hole and protrude into the well by 120÷150 mm. |
 | Drainage pipes are laid on top of the embankment made in the trenches and, according to the design, inspection wells are installed, to the couplings of which pipes intersecting at a given point are attached. |
 | After completing the installation of pipes and wells, the design of the drainage circuit should look something like the one shown in the illustration. |
 | The next step is to backfill large gravel or medium-fraction crushed stone on top of the drainage pipes and around the wells. The thickness of the embankment above the top point of the pipe should be from 100 mm to 250 mm. |
 | Next, the edges of the geotextile, fixed to the walls of the trench, are released, and then they cover the entire resulting “layered structure” from above. |
 | The rolled geotextile, which has completely covered the filter layer of crushed stone or gravel, is used to sand backfill, 150÷200 mm thick, which needs to be slightly compacted. This layer will become an additional protection for the system against subsidence of the soil, which is poured into the trench last top layer and is also compacted. You can do it differently: before starting to dig a trench, the turf layer is carefully removed from the ground, and after completing the installation work, the turf is returned to its place, and the green lawn again pleases the eye. |
 | When setting up a drainage system, it is necessary to remember that all the pipes that make it up must have a slope towards the inspection well, and then towards the storage well or collector, which is installed away from the house. If a drainage version of a water intake is being installed, then it is completely or its bottom part filled with coarse gravel, crushed stone or broken stone. |
 | If you want to completely mask the covers of inspection, drainage or storage wells, you can use decorative garden elements. They can imitate a round log or a stone boulder that decorates the landscape. |
Discharge of storm and melt water
Features of storm drainage
An external drainage system is sometimes called an open drainage system, meaning its purpose is to drain rainwater from the roof drain and from the surface of the site. It would probably be correct to call it a storm drain. By the way, if it is assembled according to the point principle, it can also be located hidden.
Installing such a water drainage system seems to be easier than buried drainage, since installation will require less volume earthworks. On the other hand, elements become important external design, which also requires certain costs and extra efforts.
There is one more thing important difference. The drainage system is designed, as a rule, for constant “even” operation - even if seasonal changes in soil moisture saturation occur, they are not so critical. Storm sewers must be able to very quickly, literally within minutes, drain large volumes of water into collectors and wells. Therefore, increased demands are placed on its performance. And this performance is ensured by correctly selected sections of pipes (or gutters - in a linear scheme) and the slope of their installation for the free flow of water.
When designing storm sewers, the territory is usually divided into water collection areas - one or more storm inlets are responsible for each area. A separate area is always the roof of a house or other buildings. They try to group the remaining fates according to similar external conditions– external coating, since each of them has special characteristics of water absorption. So, you have to collect 100% of the fallen volume from the roof storm water, and from the territory - depending on the coverage of a particular area.
For each area, the average statistical water collection is calculated according to the formulas - it is based on the coefficient q20, which shows the average precipitation intensity for each specific region.
Knowing the required volume of water drainage from a particular area, it is easy to determine the nominal diameter of the pipe and the required slope angle from the table.
| Hydraulic cross-section of pipes or trays | DN 110 | DN 150 | DN 200 | Slope value (%) |
|---|---|---|---|---|
| Volume of collected water (Qsb), liters per minute | 3.9 | 12.2 | 29.8 | 0.3 |
| -"- | 5 | 15.75 | 38.5 | 0,3 - 0,5 |
| -"- | 7 | 22.3 | 54.5 | 0,5 - 1,0 |
| -"- | 8.7 | 27.3 | 66.7 | 1,0 - 1,5 |
| -"- | 10 | 31.5 | 77 | 1,5 - 2,0 |
In order not to torment the reader with formulas and calculations, we will entrust this task to a special online calculator. It is necessary to indicate the mentioned coefficient, the area of the site and the nature of its coverage. The result will be obtained in liters per second, liters per minute and in cubic meters at one o'clock.
LECTURE 3
DISCHARGE OF SURFACE (ATMOSPHERE) WATER
The organization of surface rain and melt water runoff in residential areas, microdistricts and neighborhoods is carried out using an open or closed drainage system.
On city streets in residential areas, drainage is usually carried out using a closed system, i.e. city drainage network (storm sewer). The installation of drainage networks is a citywide event.
In the territories of microdistricts and neighborhoods, drainage is carried out by an open system and consists of organizing the flow of surface water from building sites, sites for various purposes and areas of green spaces into the passage trays, through which the water is directed to the carriageway trays of adjacent city streets. This organization of drainage is carried out using a vertical layout of the entire territory, ensuring drainage created by longitudinal and transverse slopes on all driveways, sites and territories of a microdistrict or block.
If the network of passages does not represent a system of interconnected passages or if the capacity of the trays on the driveways is insufficient during heavy rainfall, a more or less developed network of open trays, ditches and ditches is envisaged in the territory of the microdistricts.
An open drainage system is the simplest system, which does not require complex and expensive structures. In operation, this system requires constant supervision and cleaning.
The open system is used in microdistricts and neighborhoods of relatively small areas with a terrain favorable for water runoff that does not have low drainage areas. In large neighborhoods open system does not always provide surface water drainage without overflowing trays and flooding driveways, so then a closed system is used.
A closed drainage system provides for the development of an underground network of drainage pipes - collectors - on the territory of the microdistrict, with the reception of surface water by water intake wells and the direction of the collected water into the city drainage network.
As possible option a combined system is used when an open network of trays, ditches and ditches is created on the territory of the microdistrict, supplemented by an underground network of drainage collectors. Underground drainage is very important element engineering improvement of residential areas and microdistricts, it meets the high requirements of comfort and general improvement of residential areas.
Surface drainage on the territory of the microdistrict must be ensured to such an extent that from any point in the territory the flow of water can easily reach the trays of the roadway of adjacent streets.
As a rule, water is diverted from buildings towards driveways, and when green spaces are adjacent, to trays or ditches running along the buildings.
On dead-end driveways, when the longitudinal slope is directed towards the dead end, drainless places are formed, from which water has no outlet; Sometimes such points appear on driveways. Water is released from such places using overflow trays, in the direction of passages located at lower elevations (Fig. 3.1).
Trays are also used to drain surface water from buildings and sites for various purposes, in green areas.
Overflow trays can be triangular, rectangular or trapezoidal in shape. The slopes of the trays are taken depending on the soil and the method of strengthening them in the range of 1:1 to 1:1.5. The depth of the tray is not less, and most often not more than 15-20 cm. The longitudinal slope of the tray is taken to be at least 0.5%.
Earthen trays are unstable, they are easily washed away by rain, and they lose their shape and longitudinal slope. Therefore, it is most advisable to use trays with reinforced walls or prefabricated ones made of some stable material.
When there is a significant flow of water, the trays turn out to be insufficient across their entire capacity and are replaced with ditches. Typically, ditches have a trapezoidal shape with a bottom width of at least 0.4 m and a depth of 0.5 m; the side slopes have a steepness of 1:1.5. Strengthen the slopes with concrete, paving or turf. With significant sizes, at a depth of 0.7-0.8 m or more, ditches turn into ditches.
It should be borne in mind that ditches and ditches at intersections with driveways and sidewalks must be enclosed in pipes or bridges must be built over them. It is difficult and difficult to release water from ditches and ditches into driveway trays due to different depths and differences in elevations.
Therefore, the use of open ditches and ditches is permissible only in exceptional cases, especially since ditches and ditches generally disrupt the amenities of modern microdistricts. Trays, with their usually shallow depth, are acceptable if they do not create great inconvenience for movement.
With relatively small areas of green space, drainage can be successfully carried out open method along the trays of paths and alleys.
When paths and driveways are located among green spaces over a relatively short distance, surface water flow can be carried out without installing trays or ditches, directly onto planting areas. In such cases, fencing with edges for paths and driveways is not suitable. In this case, the formation of stagnant waters and swamps must be excluded. Such runoff is especially appropriate when it is necessary to artificially irrigate green areas.
When designing an underground drainage network, special attention must be paid to the drainage of surface water from main roads and pedestrian alleys, as well as from places where visitors gather (main squares of the park; squares in front of theaters, restaurants, etc.).
In places where surface water is discharged from the territory of microdistricts onto city streets, a water intake well is installed behind the red line, and its waste branch is connected to the collector of the city drainage network.
With a closed drainage system, surface water is directed to the water intake wells of the drainage network and enters them through water intake grates.
Water intake wells on the territory of microdistricts are located in all low points that do not have free flow, on straight sections of driveways, depending on the longitudinal slope, with an interval of 50-100 m, at intersections of driveways on the side of the water inflow.
The slope of drainage branches is taken to be at least 0.5%, but optimal slope is 1-2%. The diameter of drainage branches is taken to be at least 200 mm.
The routes of drainage collectors in the microdistrict are laid mainly outside of passages in strips of green spaces at a distance of 1-1.5 m from curb stone or roadway.
The depth of the drainage network collectors in the microdistrict is taken taking into account the depth of soil freezing.
Water intake wells have water intake grates, mainly rectangular shape. These wells are constructed from precast concrete and reinforced concrete elements and only in their absence - from brick (Fig. 3.2).
Manholes are constructed according to standard designs from prefabricated elements.
When choosing a drainage system in a microdistrict, it should be borne in mind that in modern well-maintained microdistricts, the development of a network of drainage collectors is predetermined not only by the collection and disposal of surface water, but also by the use of the drainage network for other purposes, such as, for example, for receiving and discharging water from snow melters and when dumping snow into network collectors, as well as when discharging water into the network when washing roadways and driveways.
It is advisable to install an underground drainage network in a microdistrict when equipping buildings with internal drains, as well as with a system for removing water from the roofs of buildings through external pipes with water discharge into the underground drainage network.
In both of these cases, the flow of water from drainpipes along sidewalks and areas adjacent to buildings is eliminated, and the appearance of buildings is also improved. Based on these considerations, it is considered advisable to develop an underground drainage network in microdistricts.
An underground drainage network in microdistricts is also justified if there are drainage-free places on the territory that do not have a free outlet for rain and melt water collected in them. Such cases are relatively rare, but are possible with complex, rugged terrain and cannot be eliminated by vertical planning due to the large volumes of excavation work.
It is almost always necessary to construct an underground drainage network when the microdistrict is deep and the watershed is 150-200 m away from the nearest adjacent street, as well as in all cases when throughput there are not enough trays on the driveways and the driveways can be flooded during relatively heavy rains; the use of ditches and ditches in residential areas is highly undesirable.
When planning vertically and creating surface water flow, the location of individual buildings relative to the natural topography is very important. For example, it is unacceptable to place buildings across the natural thalweg, thereby creating drainless areas.
Avoiding unnecessary and unjustified excavation work on bedding in places without drainage is possible only by draining water from such places using an underground collector of the drainage network, installing a water intake well at a low point. However, the direction of the longitudinal slope of such a reservoir will be opposite to the topography. This may lead to the need for excessive deepening of some sections of the district's drainage network.
Unsuccessful examples include the arrangement of buildings of various configurations in plan without taking into account the natural topography and water flow from the buildings (Fig. 3.3).
2.187. It is necessary to include permanent and temporary (for the construction period) devices for draining surface water in subgrade designs.
Surface drainage may not be provided for when designing subgrades in sandy areas in areas with arid climates.
The drainage of surface water to low areas of the relief and to culverts should be provided: from embankments and semi-embankments - ditches (upland, longitudinal and transverse drainage) or reserves; from the slopes of recesses and semi-recesses - by ditches (upland and behind-the-bank); from the main platform of the roadbed in excavations and semi-excavations - using ditches or trays.
2.188. A system of structures for collecting and draining surface water from the roadbed at the sites of industrial enterprises should be developed in conjunction with a vertical site layout project, taking into account sanitary conditions and requirements for the protection of water bodies from pollution wastewater and landscaping of the enterprise territory, as well as taking into account technical and economic indicators.
To collect and drain surface water, an open (ditches, trays, drainage ditches), closed (storm drainage system with a network of shallow and deep drainage systems) or a mixed drainage system is used.
2.189. The scope of work on the design of drainage devices includes: determining the volume of flow to the drainage devices of the catchment basin; selection of the type, size and location of the drainage device, allowing the use of earth-moving machines for its construction, as well as for cleaning during operation; the purpose of the longitudinal slope and speed of water flow, excluding the possibility of siltation or erosion of the riverbed with the adopted type of strengthening of slopes and bottom.
2.190. Minimum dimensions and other parameters of drainage devices should be assigned on the basis of hydraulic calculations, but not less than the values given in table. 20.
Cuvettes should be designed, as a rule, with a trapezoidal transverse profile, and with appropriate justification - a semicircular one; In special cases, the depth of the ditches can be set to 0.4 m.
The greatest longitudinal slope of the bottom of drainage devices should be assigned taking into account the type of soil, the type of strengthening of slopes and the bottom of the ditch, as well as the permissible flow rates of water according to App. 9 and 10 of this Manual.
If the maximum permissible longitudinal slope of the drainage device for the given design parameters is less natural slope terrain or longitudinal slope of the roadbed with water flow rates of more than 1 m 3 /s, it is necessary to provide for the installation of rapid flows and differences, designed individually.
Table 20
|
Slope steepness in soils |
Elevation |
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|
Drainage device |
Bottom width after strengthening, m |
Depth, m |
clayey, sandy, coarse-clastic |
silty, clayey and sandy |
peats and peat |
Longitudinal slope, % o |
edges above the design water level, m |
|
Upland and drainage ditches | |||||||
|
Beyond the banquet ditches | |||||||
|
Ditches in swamps: | |||||||
|
*Due to terrain conditions, the slope can be reduced to 3% o . ** In exceptional cases, the slope can be reduced to 1% 0. *** In areas with a harsh climate and excessive soil moisture, the slope is assumed to be at least 3% 0. |
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2.191. Cross section drainage devices should be checked for the passage of the calculated water flow using automated hydraulic calculations in accordance with App. 9 of this Manual. In this case, the probability of exceeding the estimated costs should be taken, %:
for pressure ditches and spillways............................................................ .5
longitudinal and transverse drainage ditches and trays........10
Upland and drainage ditches for railway tracks on the territories of industrial enterprises should be designed for flows with a probability of exceeding 10%.
2.192. On the watershed of two adjacent basins, it is necessary to provide for the construction of a dividing dam with an upper base of at least 2 m with slopes no steeper than 1:2, with its height exceeding at least 0.25 m above the design water level.
2.193. On on-site routes, an open drainage system is allowed only with appropriate instructions from the customer. When draining water by ditches in subsidence, swelling, and heaving soils, it is necessary in the design to include measures against the infiltration of water from the ditches into roadbed by appropriately strengthening them.
If it is necessary to pass water through a path, including for bypassing water from a ditch, inter-sleeper trays are used, and their depth is checked for sufficient depth to pass water at the existing marks of the bottom of the ditch.
2.194. It is not allowed to design the release of atmospheric water from ditches and ditches into:
watercourses flowing within a populated area and having a flow speed of less than 5 cm/s and a flow rate of less than 1 m/day;
stagnant ponds;
reservoirs in places specially designated for beaches;
fish ponds (without special permission);
closed ravines and lowlands prone to waterlogging;
eroded ravines without special strengthening of their channels and banks;
swampy floodplains.
2.195. When rain and melt water is polluted by industrial waste from chemical enterprises, treatment facilities should be provided.
Drainage devices should be placed in the right of way. The distance from the outer edge of the slope of the drainage device to the boundary of the right of way must be at least 1 m.
In places where watercourses exit onto the slopes of ravines and lowlands, drainage devices must be laid away from the roadbed and their strengthening must be provided.
2.196. In areas with groundwater, upland ditches, as well as drainage devices within the excavations, should be developed in conjunction with measures for groundwater drainage. When the groundwater horizon lies at a depth of up to 2 m from the surface, the upland ditch can serve, with appropriate strengthening, to drain water from the subgrade, and when the groundwater lies deeper, deepening the upland ditch below the aquifer is prohibited. In this case, other measures are provided to protect the subgrade from the effects of groundwater.
2.197. With a closed system, water is drained from the enterprise site using storm drains. In this case, water is discharged from drainage trays, ditches and longitudinal drainage pipes into rainwater wells with gratings. In this case, the wells should have settling tanks, and the gratings should have clearances of no more than 50 mm.
2.198. A mixed drainage system in a built-up area is used in the following cases: when the requirements for landscaping the territory and the construction of storm sewers apply only to part of the site, and in the rest of it open drainage is acceptable when wastewater treatment is required.
With a mixed drainage system, the requirements for the installation of open and closed drainage systems must be observed.
2.199. The distance from the rainwater drainage pipelines to the axis of the extreme track of a railway with a 1520 mm gauge should be less than 4 m.
The distance between rainwater wells can be taken according to the table. 21.
