When wet soils (clays, loams, sandy loams, fine and silty sands) freeze, heaving occurs. Heaving is a general or local uplift of the surface of the soil or rail track, the cause of which is the freezing of the soil and an increase in the volume (by 19%) of the water freezing in it.
Freezing usually results in more or less uniform heaving over large areas. In some places, the value of the uniform
swelling is broken: these local distortions are called abysses. The abysses can be in the form of abyssal humps, depressions and drops.
The value of uniform heaving is 30-40 mm, uneven - 200 mm or more.
The abysses are divided into ballast and ground (primary), while in ballast abysses the heaving zone is located within the ballast layer, soil abysses - in the subgrade. The height of ballast abysses is 20-25 mm.
To eliminate ballast abysses, the following measures are carried out: cleaning the ditches, replacing or cleaning the contaminated ballast layer, eliminating or draining the depressions in the main subgrade area.
To eliminate soil abysses, they use: replacing heaving soil with draining soil, removing the freezing zone from the soil layer that causes abysses and lowering the horizon ground water in order to get it out of the freezing zone.
Currently, the last two methods are practically used.
The lowering of the groundwater horizon under the subgrade is carried out using one-sided or two-sided drainages, which are laid under ditches or on slopes.
According to the classification proposed by Prof. G.M. Shakhunyants, drainages are distinguished by the coverage of the object being drained and the nature of work on single, group and drainage networks.
A single drainage is an isolated structure that provides drainage of a specific object.
A group drain is a series of separate drains that are not connected to each other in single system but created for the same purpose. Group drainage in comparison with a single one reduces the time of draining the object.
A drainage network is a complex of drainages connected to each other into a single system.
By the nature of the collection and drainage of groundwater, design features and methods of construction, drainages are divided into horizontal, vertical, combined and biological
Horizontal drains are open in the form of trays or ditches and closed. Closed drains are the most common.
Vertical drainages are used as drilling or mine culverts and much less often with water pumping.
Combined drains are various combinations of horizontal and vertical drains.
Biological drainage is a system for draining the soil by evaporating moisture from various plants (planting trees, creating a grass cover).
Drainage is called imperfect if its bottom is located above the aquiclude, i.e. there is an inflow of water from the bottom of the drainage and is perfect if its bottom rests on the aquiclude or is cut into it.
The most widespread are tubular drainages of the horizontal type.
The device of drainages gives a great effect in the fight against abysses with soils that give off water well.
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Hydraulic Drainage Calculation - CyberPedia
Drain selection. Above, the water consumption per 1 linear meter was determined. m of designed drainage. Obviously, when calculating the capacity of a drainage pipe-drain, it is necessary to determine the flow rate throughout the entire length of the considered drainage, and in the case of a drainage network, the inflow of water from other underground drainage systems should also be taken into account. Total calculated water flow for the end section of the drainage route:
Transit consumption of water flowing from associated drains;
l - the length of the drainage, as a catchment area;
The coefficient taking into account the possibility of gradual contamination of the pipe is taken equal to 1.5;
q - drainage flow rate.
The cross section of the drainage pipe is usually determined by the method of successive attempts, i.e., it is first set by a certain section and then the compliance of this section with the required throughput is checked. In most cases, these requirements are met by round pipes with an internal diameter of 150 mm. Therefore, the calculation of the section should be started, given this size of the inner diameter.
After assigning the diameter of the pipes, a verification calculation is made according to the formulas known from hydraulics
The desired water flow in the pipe in m3 / s;
Wetted pipe perimeter in m;
Hydraulic radius of the pipe in m;
Pipe cross-sectional area in m2;
The longitudinal slope of the pipe in the design section, determined depending on the accepted value of the difference, and the incoming and outgoing pipes in the manhole and the projected longitudinal slope of the trench bottom:
The distance between the manholes in m. As part of the course project, you can take 25-50 m.
The value of the drop in the manhole is set within 0.1-0.25 m. When designing, the slope of the bottom of the drainage trench is often assumed to be equal to the slope of the bottom of the cuvette, i.e.
Coefficient C (Chezy coefficient) can be approximately determined by the formula of academician N. N. Pavlovsky
where n = 0.012; y = 0.164 at m and y = 0.142 at m. In most cases, m can be considered.
Hydraulic Radius of Round Pipes
Having established all the calculated values, determine Qnp and compare this flow rate with the calculated QD. The calculation ends on the condition .
If it turns out that , then recalculate with a new, larger pipe diameter.
Drainage calculation example
It is required to design and calculate a drainage 50 m long to drain the soil of the main platform of a double-track subgrade in the excavation at following conditions. The soil is clayey. Estimated freezing depth from the surface of the ballast layer Z10 = 1.7 m. Elevation of the edge of the subgrade Gb = 73. Elevation of the level of non-pressure gravity waters before their decrease Gg.w. = 73. Elevation of the roof of the aquiclude (along the axis of the subgrade) Gw = 65.
The transverse slope of the aquiclude surface was not found during the survey. Soil filtration coefficient k=1.0 cm/h. The average slope of the depression curve Iо = 0.1. Capillary rise of water acc. = 0.7 m. Filtration coefficient of the drainage backfill kd = 0.001 m/s.
The width of the main platform of the subgrade is 12 m. The average thickness of the ballast layer is 0.5 m. The depth of the ditch is 0.6 m. Drainage is designed on a straight section of the track; longitudinal slope of the bottom of the cuvette of the excavation at the site of the drainage device ik = 0.006.
Earthworks for drainage are carried out mechanized using a drainage machine.
We accept for calculation the sub-cuvet bilateral horizontal drainage of the trench type.
The plan and profile of drainage under given conditions are determined by the existing position of the railway line, i.e., the longitudinal axis of the drainage is assumed to be parallel to the railway line, and the longitudinal slope of the bottom of the drainage trench iD, as a rule, repeats the slope of the bottom of the ditch. Thus, in the case under consideration,
Let's determine the depth of the drainage and specify its type in relation to the roof of the aquiclude (see Fig. 3.12).
We accept e = 0.25 m; ho = 0.3 m. For given conditions b=1.25 m. Then
The width of the trench developed by a mechanized method is 2d = 0.52 m. To clarify the type of drainage, we will perform a number of calculations. The mark of the bottom of the drainage at a depth of the cuvette ko = 0.6 m will be
The DG mark is higher than the GW mark. This means that the designed drainage is of an imperfect type.
The thickness of the part of the aquifer above the bottom of the drainage:
The thickness of the aquifer from the bottom of the drainage to the aquiclude:
The depth of the drainage in the lower section is maintained, since the slope of the bottom of the drainage is arranged parallel to the slope of the bottom of the cuvette.
We calculate the flow rate of water flowing to the field wall of the drainage using the formula:
This value according to the table. 3.19 corresponds to . Next, we calculate:
What is more than 3,
Those. in this case T< Тр.
The obtained data give grounds to conclude that in the example under consideration there is a second case of qr calculation, when its value is found by the formula:
To find qr, we define a using the formula:
According to the schedule (see Fig. 3.14) with
Desired water flow qB:
Consumption of water coming from the second half of the bottom of the drainage:
m3/h per 1 line m.
From the interdrainage space through the side wall of the drainage flow comes:
m3/h per 1 line m.
Thus, the total total water consumption per 1 linear meter. m of drainage will be equal to:
m3/h per 1 line m.
Estimated water flow at the lower section of the drainage, taking into account the fact that QТ = 0:
We express the water flow in various dimensions:
QD \u003d 8.75 l / min \u003d 0.15 l / s \u003d 0.00015 m3 / s.
As a drain, we use pipe filters with an internal diameter of mm.
Find the capacity of the pipe. To this end, we define a number of quantities included in the calculation formulas:
Accept ; . Then ;
m/s m/s,
М3/sec, which significantly exceeds QD.
The concept of soil density in road construction differs from that generally accepted in physics. Soil density is the weight per unit volume of the soil skeleton, i.e. weight without taking into account the weight of pore water while maintaining the natural structure (porosity).
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3.3.2. Design and calculation of annular vertical drainage
Vertical drainage - groundwater is pumped out from specially laid drilled wells, for a deeper lowering of the groundwater level. The location of the wells is done areal or linear.
When draining an annular vertical drainage site, the following should be known: the site plan, the maximum groundwater level, the elevation of the aquiclude and the soil filtration coefficient.
With the help of the ground flow N m, the depth of the lowering of the groundwater level in the center of the site will be S m, and the ordinate of the depression curve
1. Design procedure
We determine the radius of action of the drainage according to the formula of I.P. Kusakina
2. According to the formula
determine the radius of the circle xo, equal to the area of the rectangle
F = a ∙ b, (3.19)
where a and b are the sides of a rectangle of equal area.
3. According to the formula
determine the preliminary flow rate of the annular drainage Qprv.
4. Using the formula for determining the gripping ability of a well
gzkv = , (3.21)
where gzkv is the gripping ability of the well;
Vq = 65m/day, (3.22)
we compose two inequalities for n-2 wells:
qzvn > Qprv (3.23)
qsq(n –2)< Qпрв. (3.24)
So, for n wells
gzv = 2, (3.25)
where yn = , (3.26)
and for n-2 wells
gzv = 2, (3.27)
where уn-2 = . (3.28)
We set the radius of the ring.
From inequalities (3.23) and (3.24), by selection we determine an even number of wells and distribute them along the contour of the site.
5. According to the site plan, we determine the distance from the center A to each of the wells x1, x2, ..., xn. According to formula (3.20), we determine the corrected water flow rate of the annular drainage Q.
So, for well 6, symmetrically located with wells 1, 4, 9, they draw up a diagram and calculate the distances from well 6 to other wells: x1, x2, ..., xn. In this case, x6 = r. Using formula (3.29), we determine y6:
In a similar way, the groundwater levels of all wells are determined and depression curves are drawn up.
If the required lowering of the groundwater level at the site is not achieved, then the number of wells and their placement are changed.
2. Calculation of the annular vertical drainage
To lower the groundwater level at the location of one of the plant's workshops, a vertical annular drainage was designed, consisting of a number of tubular wells located along the direct contour of the protected structure 40x60 m in size.
The elevation of the site is on average 131.5m. Aquiclude mark (clay of the Jurassic age) 177.5 m. Alluvial coarse-grained sands lie above the clays, covered from the surface with a layer of loam 1–2 m thick. The filtration coefficient of the sands is 20 m/day. Underground waters lie at around 130m, i.e. about 1.5m below the ground.
In order to avoid flooding of underground basements, the groundwater level should be lowered to approximately 125m.
We accept the radius of the wells r = 0.1 m, the value of the decrease in the water level in the center of the site
S = 130 - 125 = 5m.
The size of the aquifer E \u003d 130m - 117.5m \u003d 12.5m.
The calculation procedure is as follows:
2.1. We determine the radius of action of the drainage according to the formula (3.17)
2.2. The depth of water in the soil in the center of action of the wells is obtained
ya \u003d H - S \u003d 12.5 m - 5 m \u003d 7.5 m.
2.3. The radius of a circle that is equal in size to the protected area will be equal to
2.4. The preliminary flow rate of the annular drainage is determined by the formula (3.20)
Qprv = m3/day
2.5. Using formula (9.5), which determines the gripping ability of the well, we calculate the number of wells n, using these two inequalities
qzkan > Qpra and qzkv(n-2)< Qпра или
2 > 3.14 ∙0.1∙ Vg ∙pack n > 3600 and 2∙ 3.14∙ 0.1 ∙Vgуn-2(n-2)< 3600.
At the same time, Vg = 60= 125.8 m/day.
We set the number of wells n = 10. Then according to the formula (3.26)
According to the formula
Checking accepted number wells n = 10 by two inequalities
2 ∙3.14∙0.1∙ 126.8 ∙5∙10 = 4000 m3/day > 3600 m3/day
2 ∙3.14∙ 0.1 ∙126.8∙ 4.5 ∙8 = 2900 m3/day< 3600 м3/сут.
We distribute these wells along the contour of the workshop.
2.6. We calculate the adjusted water consumption according to the formula (3.20).
To do this, we calculate, according to the plan of the workshop, the distance from its center A to individual wells
x1 = x4 = x6 = x9 = 36m;
x5 = x10 = 30m;
x1 = x3 = x7 = x8 = 22m.
Then Q = m3/day.
2.7. We calculate the levels of groundwater for groups of wells that are in the same conditions.
So, for well 6 (symmetrically located with wells 1, 4 and 9), we draw up a diagram and calculate the distance from well 6 to other wells (Fig. 9c): x1, x2 …..x10.
In this case, x6 = r. Then by formula (3.29) we obtain
9.2.8. Checking the gripping ability of the well
gcq = 2∙3.14 ∙0.1 ∙126.8∙ 6.3 = 540 m3/day > 390 m3/day,
where 390 = = average well flow.
2.9. Let's calculate the groundwater levels for the group of wells 2, 3, 7, 8. Using the same method, we determine
For wells 5 and 10 we get
2.10. We build longitudinal profiles along equal sections of wells and check the necessary lowering of groundwater at the site. If this reduction is not achieved, then change the number of wells and their placement.
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Drainage calculation
Determining the intensity of wastewater inflow
As a rule, the entire volume of incoming wastewater (qi) is formed due to the following factors:
Drainage water volume (qd)
Rainwater volume (qr)
Waste water volume (qs)
The total volume of wastewater (qi) entering the sewer system per unit of time is calculated as follows:
qi = qd + qr + qs (l/s)
Drainage water (qd)
As a rule, in quantitative terms, the amount of drainage water that needs to be pumped out is negligible. If the soil is loose and the drainage system is located below the water table, the nominal volume of drainage water should be determined on the basis of hydrogeological studies. There is a rule of thumb that the following values can be used in the case of soil with normal characteristics (i.e. in the absence of rivers or other waterways in the immediate vicinity, as well as swamps) and if the level of the soil surface is above sea level
Sandy soil:
qd = L x 0.008 [l/s]
Clay soil:
qd = L x 0.003 [l/s]
where L = length of the drainage pipeline.
Rain water (qr)
Rainwater volume is calculated as follows:
qr = i x ϕ x A where i = nominal rain rate (l/s/m2)
ϕ = runoff factor
A = catchment area in m2
The calculation of precipitation intensity should be based on an analysis of the consequences of flooding.
The nominal intensity of rain is not the same in different regions. There are very rough estimates of this parameter:
The most common standards are:
For flat terrain 0.014 l/s/m2
For mountainous terrain 0.023 l/s/m2
The runoff coefficient is a measure of rainfall runoff from a catchment area. The coefficient varies depending on the type of surface and can be determined using the following table:
The catchment area is the area from which water flows into the spillway system.
Waste water (qs)
The calculation of the intensity of sewage inflow from private houses should be based on the number of people living in these houses.
The standard preliminary value for the intensity of wastewater inflow per person per day is considered to be 170 liters.
Important note:
For residential buildings, the sewage flow rate (qs) must be assumed to be at least 1.8 l/s if toilets are connected to the sewer system.
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| Lecture Search The distance between drains - dehumidifiers is determined by the Rothe formula:
where L is the distance between the drainage drains, m; H is the height of the unlowered groundwater level, m; S is the required decrease in the level of groundwater, m;
Rice. 2.4. Calculation scheme of perfect systematic drainage. Table 2.2. Soil filtration coefficient Table 2.3. Soil infiltration coefficient 2.2. Calculation of imperfect horizontal drainage. When the occurrence of the aquiclude is more than 5 m, imperfect systematic drainage is laid in the aquifer (at a depth of 3.5 m.)
Rice. 2.5. Design scheme for imperfect systematic drainage. The distance between adjacent drains of imperfect drainage is determined by the formula of S.F. Averyanov:
where T is the distance from the center of the drain to the aquiclude, m; h2 is the highest point of the depression curve, m; k is the coefficient of soil filtration, m/day, tab. 2.2; p is the coefficient of precipitation infiltration into the soil, m/day, tab. 2.3. The value of B is calculated according to the dependence
where r is the radius of the drain, m, (we accept drains with a diameter of 0.2 m) Drainage pipes are laid according to a pre-designed drainage system plan. The minimum slope of the drainage pipe according to the building code is 0.002 in clay soils, and 0.003 in sandy soils. In practice, for normal water flow, the slope of the pipe is 0.005 - 0.01. On the ground, drains-driers are located in such a way that the pipe runs in the ground parallel to the terrain and, accordingly, the depth of the drain-drier does not change throughout its length. Drains are covered with several layers of permeable materials (for example, geotextiles) - first, washed crushed stone or gravel is placed, then sand, and the previously excavated soil is laid on top. The thickness of the backfill ranges on average from 100 to 300 mm (the less permeable the surrounding soil, the thicker the backfill). In order to prevent silting of drains and clogging of perforations, filters made of geotextiles (when reclamation of sandy and sandy loam soil) or coconut fiber (if clay, loam, peat bogs are drained) are used. Calculate the distance between the dryer drains of perfect and imperfect drainage, build the appropriate design schemes. Select the initial data according to the table. 2.4. Table 2.4. Initial data.
Note: soil type 1 - loam, 2 - sandy loam, 3 - medium sand Scheme vertical layout village with provision of drainage and normal traffic and pedestrians. The vertical layout scheme is developed on the materials of the geodetic subbase and master plan village (city). At this stage of the design of the vertical layout, the main, expedient decisions are determined on the general high-altitude location of all elements of the city, on the organization of surface runoff and measures for the improvement of territories unfavorable for development. The scale of the diagram is taken - 1:2000 - horizontal and 1:200 - vertical. When developing a vertical layout scheme, design (red) marks are determined at the intersection points of the axes of the streets at intersections and in places where the relief changes along the route of the streets and the route of the street itself. Black marks are determined from the topographic plan by interpolation between contour lines. The distance between the marks is taken according to the plan in accordance with the scale. Then, between the intersections, the compliance of the longitudinal slope of the street with the permissible minimum and maximum slopes is checked and the design longitudinal slope is determined by the formula: i - longitudinal slope; h - elevation of marks between intersections, m; L is the distance between intersections, m. Permissible longitudinal slopes are taken -5‰-80‰. On the vertical layout diagram at intersections at the intersection of the axes of the carriageways of the streets or fractures of the slopes, existing and design marks are applied: the arrow shows the direction of the slope of the street, the longitudinal slope is marked above the arrow, and below it is the distance between the intersections of the axes of the streets. The procedure for performing the final linkage planning decision with the relief and clarification of the actual high-altitude organization of the village, the following can be recommended. 1. A general layout plan is applied to the geodetic plan. The streets, along which the design of longitudinal profiles is supposed, are numbered and along their axes the marks of the existing relief are calculated (by interpolation between contour lines) at their intersections and at turns (Fig. 2). 2. Longitudinal profiles are compiled along the axes of the planned main streets, according to the plan in horizontal lines. In the conditions of existing populated areas, where, in accordance with the rules for surveying and compiling geodetic plans, the relief within the street is not shown, the following methods can be used to compile their longitudinal profiles: if the general character of the street does not differ from the relief of the surrounding territory or differs slightly from it, longitudinal profiles are compiled on the basis of a plan in horizontal lines, and on the territory of the streets the latter are carried out conditionally, in relation to the relief of adjacent territories. If the existing street runs in conditions that differ sharply from the terrain of the neighborhoods adjacent to it (in a cut or along an embankment), it becomes necessary to use leveling profiles. In most cases, such profiles are available in cities along almost all significant streets, usually on a scale from 1:2000 to 1:500.
Rice. 3.1. Street numbering and calculation of marks along the axes. The existing leveling profiles, in relation to the scale of the design solution, must be redrawn at a scale of 1:5000. In order not to equip them with unnecessary marks, one should not transfer all the marks from a large scale, but only the main points characterizing the relief of the longitudinal profiles of the streets should be selected. In this case, in addition to the longitudinal profiles, it is desirable to have cross-sections taken every 200-300 m. The design cross-sections will make it possible to judge the height ratio of the street to the adjacent territory and, accordingly, the most advantageous height solution for the longitudinal profile. It should be noted that the leveling longitudinal profiles of streets are also necessary when drawing up a vertical planning scheme in cities with a very weak relief. In this case, the leveling longitudinal profile of the existing street makes it possible to judge its microrelief and, accordingly, facilitates the task of choosing the direction of drainage.
3. The choice of one of the above methods and the identification of either the need to use leveling profiles, or the possibility of doing without them, can be made on the basis of a detailed survey of questionable areas in nature and a thorough study of the geodetic plan. If the reconnaissance survey reveals existing streets with a particularly difficult terrain, the horizontal profile of which cannot be drawn up, and there is no ready-made leveling profile, leveling should be taken care of. Based on the plan in horizontal lines, and, if necessary, on the basis of leveling profiles, approximate directions of slopes and the direction of drainage along the streets are outlined (Fig. 3). 4. Longitudinal street profiles are designed, a design line is drawn, design marks are written out at intersection points, slope changes and in places of significant earthworks (more than 0.50 m), design slopes and distances are written out. The degree of detail of the design solution of the profile is determined by the scale; namely: the design line is applied only in the first approximation, slopes of similar magnitude are generalized, inserts when conjugating slopes of different directions are not projected at all or are outlined in the most general form.
Rice. 3.3. Drawing a design solution on a plan. 5. Final design solution(slopes, distances, marks) are transferred from the profiles to the plan, the design marks are written out at the points of the profile break and the intersection of the axes. In the sections of overpasses and bridges, due to the impossibility, according to graphical conditions, to put a high-altitude solution on the plan, in full, the design data is shown only in the places of approaches. 6. In conditions of complex terrain (flat or with steep slopes), in addition to the profiles along the main highways, a solution is given in the plan for secondary streets, which more fully illuminates the drainage conditions and the high-rise solution for the city as a whole. The same elements are written on the plan: slopes, distances, red and black marks in places where slopes change. In the graphical design of the drawing, it is necessary to show with various conventional signs the solutions carried out according to the profiles and according to the plan (Fig. 4). 7. The contours of areas that require significant backfilling or cutting are identified. The volumes of solid earthworks are calculated in the areas of construction of overpasses, bridges and approaches to them on dams, in sections of streets where the average height of the excavation or embankment exceeds 0.5 m, etc. In addition, the amount of land that will be obtained from the foundation pits of capital buildings with cellars. For individual elements, the calculation of earthworks is carried out as follows: in sections of streets where working marks exceed 0.5 m, the calculation is made according to longitudinal profiles; in areas of continuous filling or cutting at working elevations of more than 0.5 m, the calculation is made according to the method of squares. The volume of land from building pits is calculated by multiplying the area occupied by capital development by the average depth of the pit. The area of capital development is taken according to the data of the general planning project (percentage of development). Based on the calculation of volumes for individual elements, a list of earthworks is compiled. Design a vertical layout plan locality with provision of drainage, normal traffic and pedestrians. The plan of the settlement is to be adopted in accordance with the option according to adj. one. Practical work 4. |
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2.2.3. Hydraulic calculation of drainage pipes
Transit flow rate of water suitable for the upper section of this section:
Qtr = trV (2.11)
For a round pipe: tr=πd2/4, m2 (2.12)
Let's determine the speed of water movement: V=C√RIv, m/s;
χ=πd, m (2.13)
R=tr/χ, m; (2.14)
It is necessary to comply with the condition Qtr1.5 Qadd, where Qadd is the allowable water flow.
2.2.4. Determination of the technical efficiency of drainage and the period of its drainage
The technical efficiency of drainage is determined by the coefficient of water loss m0. The calculation procedure is as follows:
where nГ is the porosity of the excavation soil;
KN/m3; (2.17)
where S is the specific gravity of the soil;
mo=nГ-(1+α)*Wм*γd/γe(2.18)
where is the value of capillary bound water.
Drainage is effective if μ≥0.2
The soil drainage period t0 is the time during which the found drainage efficiency will be realized, i.e. the groundwater depression curves will take their stationary position. The value of t0 is determined by the formula (in seconds, then converted into a day, dividing the results by 86400 seconds):
where m0 - water loss;
L0 is the length of the depression curve projection along the horizons on the right side, m;
Kf - filtration coefficient;
B - coefficient determined by the formula:
a - half-width of the drainage trench;
1, 2 - some dehumidification functions depending on the type of drainage.
For the field side:
For the interdrain side:
where A is a coefficient determined from the tables depending on h0/H.
Bibliography:
1. Railway track. Ed. T.G. Yakovleva - M.: Transport, 2001
2. Calculations and design of the railway track. Ed. V.V. Vinogradov and A.M. Nikonova - M.: Route, 2003
3. Railways gauge 1520 mm, STN Ts-01-95 Ministry of Railways of the Russian Federation, 1995
| INITIAL DATA |
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| Name | Designation | unit | Meaning | ||
| task p.5.2 |
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| Specific gravity of embankment soil | calculation in clause 1.1 |
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| calculation in clause 1.1 |
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| task p.5.4 |
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| task p.5.5 |
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| task p.6.2 |
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| base=0 t.2.embankment | calculation in part 1.1. |
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| task p.6.4 |
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| task p.6.5 |
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| Specific gravity of water | |||||
| GSP Load Width | from directories |
from directories |
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| Train load width | Sleeper length |
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| Cross slope of the terrain | task p.5.8 |
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| task p.8.0 |
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| The slope of the depression curve | |||||
| Height of capillary rise | task p.5.6 |
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| =(s+v*e)/(1+e) |
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| \u003d (s-v) / (1 + e) |
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| =- 0,25* |
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| =(sbase-in)/(1+eobase) |
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| =base - 0.25*base |
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| Specific cohesion of embankment soil in a water-saturated state | Cosn - 0.50 * cosn |
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| according to the formulas in STN-C 95 |
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| Initial data for the calculation of slope stability 1 sheet |
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| INITIAL DATA |
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| Name | Designation | unit | Meaning | ||
| Specific gravity of embankment soil particles | task p.5.2 |
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| Specific gravity of embankment soil | calculation in clause 1.1 |
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| Embankment soil porosity coefficient | calculation in clause 1.1 |
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| The angle of internal friction of the embankment soil | task p.5.4 |
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| Specific cohesion of embankment soil | task p.5.5 |
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| Specific Gravity of Base Soil Particles | task p.6.2 |
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| Stresses at the contact of the embankment with the base (along the axis of the embankment) | base=0 t.2.embankment | calculation in part 1.1. |
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| Base soil porosity coefficient | determined by the compression curve of the base from the stress at the contact of the embankment with the base (along the axis of the embankment) |
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| Base soil internal friction angle | task p.6.4 |
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| Specific cohesion of the base soil | task p.6.5 |
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| Specific gravity of water | |||||
| GSP Load Width | from directories |
from directories |
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| Train load width | Sleeper length |
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| Train load intensity | |||||
| Cross slope of the terrain | task p.5.8 |
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| Water depth at the calculated level (taken with a probability of 0.33%) | task p.8.0 |
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| The slope of the depression curve | |||||
| Height of capillary rise | task p.5.6 |
||||
| The height of the fictitious column of soil from the VSP | |||||
| The height of the fictitious soil column from the train load | |||||
| Weight of soil embankment with water in capillaries | =(s+v*e)/(1+e) |
||||
| Weight of embankment soil suspended in water | \u003d (s-v) / (1 + e) |
||||
| The angle of internal friction of the embankment soil in a water-saturated state | =- 0,25* |
||||
| Specific cohesion of embankment soil in a water-saturated state | |||||
| Weight of foundation soil suspended in water | =(sbase-in)/(1+eobase) |
||||
| The angle of internal friction of the foundation soil in a water-saturated state | |||||
| Specific cohesion of embankment soil in a water-saturated state | |||||
| Permissible stability factor | according to the formulas in STN-C 95 |
||||
studfiles.net
How is drainage calculated?
One of effective ways protection adjoining territory from excessive waterlogging - this is the arrangement of deep drainage.
Timely removal of rain and melt water from the site will provide simpler, budgetary surface drainage.
Right choice drainage system and its installation will effectively protect the foundation of the house and other underground structures from the damaging effects of groundwater.
Important! The efficiency and durability of the drainage system is affected by the correctness of the calculations performed. As a rule, this work is carried out by invited specialists. At the same time, possibilities are being developed for the safe removal of drained water outside the site.
The water collector can be a natural reservoir or a specially equipped drainage well made of plastic or concrete. Underground moisture can be excessively mineralized, and in some regions it can contain undesirable chemical compounds, so it can be used for technical needs after laboratory testing.
When calculating the drainage in without fail the following parameters are taken into account:
- maximum permanent and seasonal groundwater level,
- granulometric composition of the soil base,
- the availability of the necessary components and the cost of the project as a whole.
Tip: do not try to get such data yourself. The required amount of information can be obtained from the Land Resources Administration.
In addition, about unfavorable hydrogeology land plot testifies:
- lack of basements and underground garages in neighboring houses or their periodic flooding,
- excessive soil moisture on which moisture-loving plants, including marsh plants, readily grow.
The complete or partial absence of such signs is not an indication of the absence of a high level of ground moisture. Moreover, undesirable changes in the soil may occur during the construction of houses in neighboring areas. It is not uncommon that after the waterproofing of the pit, the groundwater level in the surrounding areas increased sharply.
Even the most expensive and effective drainage does not eliminate the need for waterproofing the foundation of the house. In the budget option, ring drainage is recommended, with the location of pipes along the perimeter of the foundation and the removal of drained moisture outside the site or into an equipped water collector. The calculation of the ring drainage includes such parameters as:
- foundation depth,
- the possibility of installing pipes with a slope towards the water intake.
Regardless of the material, the pipes are laid below the foundation pad, not less than 300 mm, the slope is within 1 °, which is 1 cm per linear meter.
Here is a simple calculation of the drainage system:
The collector well is located at a distance of 10 meters from the house, the total length of the trench is 25 m. given value we take one percent, which is 25 cm. It is this difference that should be between the structure and the top of the collector well. If, due to the complexity of the terrain, this requirement is not feasible, the problem is solved by using a pump that draws and removes water from the system.
The durability of the drainage system can be increased by using efficient filters made on the basis of needle-punched textiles.
This material is characterized by high selectivity, creating an impenetrable barrier to soil microparticles, which contribute to siltation of the system and reduce its productivity.
Today we told you how the approximate calculation and drainage of the site is performed. If you cannot cope with these works on your own or your house is located in an area with difficult soil, you can order drainage work from our professionals!
Drainage project
Calculation and design
In order for the drainage, equipped on the land plot, to function correctly, to have the necessary throughput, before starting work, it is necessary to draw up a draft of the drainage system.
This is technical documentation, which is compiled taking into account generally accepted requirements and norms of SNiP.
The design begins with hydraulic drainage calculations. They will help determine the amount of material required for the work, as well as its characteristics.
In the course of calculations, you need to determine:
- the degree of permeability of all rocks that make up the soil on the site, as well as the tendency of hard rocks available in this area to crack;
- indicators of resistance of rocks to leaching of mineral particles, which can provoke soil salinization;
- the presence of tectonic disturbances on the site, the quality of the rocks on it;
- the average amount of precipitation falling in a given climatic zone for a certain period of time;
- the level and composition of groundwater at the site;
- features of the location and activity of groundwater sources.
Hydraulic calculation of drainage
Of course, if we are talking about a private plot, then the drainage project in such cases is not always done, usually it is taken as a basis standard scheme systems.
But, if special climatic or geological conditions are observed here, the project is still needed.
Site drainage scheme
In addition to the above calculations, it is imperative to investigate the relief of the site. Determine the place where the largest amount of water accumulates after rain or snow melt. This will help to correctly determine the slope of the elements of the drainage system, to make it more efficient.
Now you can begin to make a project for the drainage system of the site.
It will include:
Site drainage project
- a schematic sketch of the laying of drainage pipes for the arrangement of deep and surface communications;
- design indicators of drainage pipes: length, cross-sectional diameter, slope, laying depth, as well as the distance between several drains;
- dimensions and location of other elements of the drainage system: connecting nodes, wells, water receivers;
- a list of materials that will be required in order to be able to create an effective drainage system.
Having a project in hand, it will be easier to determine the required amount of material, as well as perform installation work.
What rules and regulations are regulated by SNiP
To equip the drainage system of a land plot, you will need to carefully study the norms of SNiP 2.06.15-85 and 2.04.03-85.
It contains all the information you need to successfully complete the job.
First of all, study the rules that govern the SNiP drainage device.
They are as follows:
SNiP norms for drainage
- to create a drainage system, moisture-resistant pipes should be used, preferably ceramic, asbestos-cement or plastic;
- observe the slope of the pipes to the place of collection of water. It should be 0.5-0.7%;
- be sure to equip revision wells - elements that allow you to control the operation of the drainage system, flush and clean it;
- in front of the wall of the basement, vertical drainage must be made to allow water to be diverted from the building into the drainage system;
- place pipes along the walls of the building. If the foundation has an irregular shape, drains can be laid at an increased distance from it;
- lay pipes so that the bottom of the products is located below the edge of the base of the foundation by 20 cm or more. The top edge of the pipes should not protrude beyond the bottom of the foundation base;
- wall drainage should be equipped around the entire perimeter of the building.
Next comes the compilation technical documentation. First, a site drainage project.
When compiling it, you will need the following data:
Project according to the norms of SNiP
- trench dimensions - for open drainage, the depth should be 50 cm, and the width 40 cm, for deep drainage, the depth of the ditch is 70-150 cm, the width is 40-50 cm;
- drainage pipe slope indicators (SNiP) - 2 cm per meter of pipe with clay soil and 3 cm per meter of product with sandy soil;
- pipe diameter - drainage pipes with a diameter of 110-160 mm are usually taken;
- sand cushion height 10 cm;
- the thickness of the gravel layer is from 20 to 40 cm.
Estimate of landscape works
Now an estimate is being drawn up, which will include the calculation of the volume of drainage, the length of the pipes, the amount of geotextile.
How to calculate drainage? For example, there is a house whose walls are 10 x 10 meters long.
The foundation is laid in the ground at 1.2 meters.
The depth of soil freezing is 0.8 m.
Foundation wall drainage
Now consider an example of wall drainage of the foundation, SNiP norms are taken into account here.
First, determine the number of drainage wells. The length of one drainage pipe, given the indentation of 3 meters from the foundation, will be 16 m.
The total length of the drains along the perimeter will be 64 m. If the flow is organized along two parallel drains into one well, then we will get a length of 32 meters.
The top point will be the corner opposite in its placement to the well.
Considering a slope of 1 cm per meter, we get a difference in the height of the collection and drainage points of 32 cm.
If you install two wells on opposite sides of the house, then the length of each section of drains can be reduced to 16 m, respectively, the difference will be 16 cm, so it turns out to reduce the cost of installation work.
Foundation wall drainage
Given that the depth of soil freezing is 0.8 m, and the thickness of the drainage layer itself is 0.5 m, we will need to dig a trench 1.3 meters deep.
Project example
To understand how much it will cost to equip a drainage system on a site, consider an example of a project offered by specialized companies.
This includes:
- site drainage;
- arrangement of a trench with an average depth of 1 meter;
- laying a pipe with a diameter of 110 mm;
- winding the pipe with geofabric;
- laying a layer of sand about 15 cm high;
- crushed stone layer 40 cm;
- backfilling with gravel pipes in geotextiles;
- backfilling with soil.
Drainage calculation project
So, one meter of such a system will cost about 1550 rubles.
If you need to equip the drainage of the site, for example, 15 acres, you will need 200 running meters of drainage. The total price will be about 295,000 rubles.
This includes the design of drainage according to SNiP standards, materials and work.
Site drainage
If you do the work yourself, you will only have to pay for the materials.
The calculation of the drainage system will include:
- pipe with a diameter of 110 mm - 80 rubles per bay (50 meters);
- drainage well with a diameter of 355 mm - 1609 rubles per meter;
- hatch for a well - 754 rubles;
- bottom cover for a well - 555 rubles;
- quarry sand - 250 rubles per cubic meter;
- crushed stone with a fraction of 20-40 mm - 950 rubles per cubic meter;
- geotextiles - 35 rubles per square meter;
- plastic well with a diameter of 1100 mm - 17240 rubles per meter.
Design of drainage systems on the site
Of course, by designing drainage systems on the site, and arranging them with your own hands, you can save money.
But you can do this work yourself only if you have special knowledge and skills.
First, you will need to perform all the necessary measurements and calculations to determine the required amount of materials, and, accordingly, their cost.
In this case, you will not have to pay for the work.
Video
Lower water levels in the center S 0 and contour S c of annular drainage of imperfect type are interconnected by the equation
Gavrilko V.M., Alekseev V.S. Well Filters
where T- pressure on the drainage circuit: for scheme 3 of the table. 19.18 T = h; for scheme 4 of the same table T = yc = H-Sc ;
;
φ 1 ( r/T), φ 2 ( R/T) And F(r/T) are found in Fig. 19.36.
Rice. 19.36. Function values φ 1 ( r/T), φ 2 ( R/T) And F(r/T)
According to equation (19.32), it is possible, with a given decrease in the center of the annular drainage, to determine its required deepening, which is taken equal to the required decrease in the groundwater level at the drainage contour, and, conversely, with the accepted depth of the annular drainage, determine what decrease can be achieved in its center.
Equation (19.32) is solved by numerical selection or graphically.
At a given depth of the annular drainage, the inflow to it is calculated according to the formula (19.1) and schemes 3 and 4 of Table. 19.18. The decrease in groundwater levels at points external to the drainage contour is recommended to be determined by formula (19.16) based on the inflow found by expression (19.1).
When calculating from a given depression at a point at a distance X from the axis of the linear drainage, you should first determine the inflow to the drainage according to the formula (19.1) and scheme 2 of Table. 19.18, and then, using the formulas of schemes 5 and 6 of Table. 19.18, find the required depth of the linear drainage.
TABLE 19.29. FLOW AND VELOCITY OF WATER IN PIPES
| Nominal diameter, mm | Slope, % | Values Q, l/s, and v, m/s, at the degree of filling of the pipeline | |||||||||
| 0,4 | 0,5 | 0,6 | 0,8 | 1 | |||||||
| Q | v | Q | v | Q | v | Q | v | Q | v | ||
| 150 | 0,5 0,6 0,8 1 |
3,69 3,75 4,32 4,83 |
0,56 0,57 0,65 0,73 |
5,39 5,50 6,41 7,17 |
0,61 0,63 0,72 0,81 |
7,19 7,46 8,61 9,63 |
0,65 0,07 0,78 0,87 |
10,3 10,9 12,5 14 |
0,69 0,72 0,83 0,92 |
10,5 11,1 12,8 14,3 |
0,58 0,63 0,72 0,81 |
| 200 | 0,4 0,6 0,8 1 |
6,56 8,04 9,28 10,4 |
0,56 0,69 0,79 0,88 |
9,73 11,9 13,8 15,4 |
0,62 0,76 0,88 0,98 |
13,1 16 18,5 20,7 |
0,66 0,81 0,94 1,05 |
19 23,3 26,9 30,1 |
0,71 0,87 1 1,12 |
19,6 23,9 27,5 30,8 |
0,62 0,76 0,88 0,98 |
| 250 | 0,3 0,6 0,8 1 |
10,3 14,6 16,8 18,8 |
0,56 0,8 0,92 1,03 |
15,3 21,6 25,0 27,9 |
0,62 0,88 1,02 1,14 |
20,5 29,0 33,5 37,5 |
0,67 0,94 1,09 1,22 |
29,9 42,3 48,8 54,5 |
0,71 1 1,16 1,3 |
30,6 43,2 49,9 55,8 |
0,62 0,88 1,02 1,14 |
| 300 | 0,3 0,6 0,8 1 |
16,8 23,7 27,4 30,6 |
0,84 0,9 1,04 1,16 |
24,9 35,2 40,6 45,4 |
0,7 1 1,15 1,29 |
33,4 47,3 54,5 61,0 |
0,76 1,07 1,23 1,38 |
48,6 68,8 79,4 88,8 |
0,8 1,14 1,31 1,47 |
49,8 70,4 81,2 90,8 |
0,7 1 1,15 1,29 |
Note. For the diameters shown in the table, the minimum slopes are given based on ensuring that the pipes are not silted up.
Example 19.9. Determine the depth of the annular drainage and the inflow to it Q with contour dimensions of 20 × 20 m, the required lowering of the groundwater level in the center of the drained area S 0 = 6 m, filtration coefficient k= 10 m/day, bottom layer H= 14 m, drain radius (along the outer layer of backfill) 0.5 m and lowering of the water level above the aquiclude y = H – S 0 = 14 - 6 = 8 m.
Solution. The reduced radius of the annular drainage is determined by the formula (19.5):
m.
The depression radius is calculated by equation (19.3):
We find the drainage depth by graphical solution of equation (19.32). To do this, by specifying successively three values S with equal to 6.25; 6.5 and 7 m, we calculate the corresponding values \u200b\u200bseparately for the left F 1 and right F 2 parts of equation (19.32): the point of intersection of graphs of functions F 1 and F 2 will match the desired value S with. We summarize the calculations in Table. 19.30.
TABLE 19.30. FOR EXAMPLE 19.9
| S c, m | T, m | r/τ | R/T | ψ 1 ( r/τ) | ψ 2 ( R/T) | F(r/τ) | ln(8 r/r h) | F 1 | F 2 |
| 6,25 | 7,75 | 1,42 | 19,35 | 5 | 2,2 | -0,19 | 5,17 | 72,7 | 78,7 |
| 6,5 | 7,5 | 1,47 | 20 | 4,95 | 2,15 | -0,195 | 5,17 | 77,6 | 80,4 |
| 7 | 7 | 1,57 | 21,43 | 4,9 | 2,1 | -0,2 | 5,17 | 87,9 | 83,8 |
Note.
;
Getting the depth S c= 6.71 m by graphical solution of two equations: F 1 (S c) And F 2 (S c) (Fig. 19.37)
Rice. 19.37. To the definition S c
To determine the inflow to the annular drainage, we calculate the values of Φ according to the formulas of scheme 4 in Table. 19.18 at h = (H + y)/2 \u003d (14 + 7.29) / 2 \u003d 10.6 m:
.
Groundwater inflow to the ring drainage is determined by the formula (19.1):
Q\u003d 10 10.6 6.71 / 0.5 \u003d 1430 m 3 / day.
Example 19.10. Determine the inflow to the linear drainage and calculate the depressions in points along the normal to the axis of the drainage when it is laid at depth S c= 5 m in a confined aquifer at h= 10 m, k= 12 m/day, H= 15 m, r h= 0.1 m. The sources of recharge of the aquifer are not defined.
Solution. The radius of the depression of the drainage installation is determined by the formula (19.4):
m.
Filtration resistance is found according to the equation of scheme 5 of the table. 19.18:
.
Groundwater inflow per 1 m of linear drainage on one side is calculated by the expression (19.1):
q\u003d 12 10 5/197 \u003d 3 m / day.
Full inflow per 1 m of drainage from both sides Q\u003d 6 m 3 / day. The lowering of the groundwater level at given points on the line normal to the drainage axis is calculated from formula (19.1) and the equation of scheme 2 in Table. 19.18. Calculations at q/(kh) \u003d 3 / (12 10) \u003d 0.025 we summarize in table. 19.31.
TABLE 19.31. FOR EXAMPLE 19.10
| x, m | R – x, m | S = 0,025(R – x) , m | x, m | R – x, m | S = 0,025(R – x) , m |
| 5 10 20 |
170 165 155 |
4,25 4,13 3,88 |
100 150 175 |
75 25 0 |
1,87 0,62 0 |
Example 19.11. For the conditions of example 19.3, it is required to select a longitudinal slope and determine the diameter of the tubular drain located along the long side of the reservoir drainage. Groundwater inflow to formation drainage Q= 860 m 3 / day = 9.95 l / s.
Solution. We accept the slope of the tubular drain i= 0.004 from the condition of the minimum amount of excavation in the trench and the minimum depth of the drain below the bottom of the pit. The diameter of the tubular drain is selected according to the table. 19.29 based on the maximum inflow to the reservoir drainage, the accepted slope and the degree of filling of the pipeline equal to 0.6.
At Q max = 9.95 l/s, i= 0.004 and h = 0,6 d The minimum pipe diameter is d= 200 mm.
For any construction process, it is very important to follow the rules and established standards. According to the requirements of SNiP, drainage must be located at a certain distance from the building, and its device must meet all technical standards.
What is SNiP?
SNiP is an abbreviation derived from " building codes and rules." According to these codes, the requirements of various organizations for the implementation of sewerage, drainage, various buildings and other engineering structures. The SNiP takes into account ergonomic, economic, architectural, specifications that must be fulfilled.
Why comply with SNiP if sewerage, drainage or any other communication works like this:
- Any construction must be legalized, whether it is the construction of an extension near the house or the laying of a sewer pipeline. If you did not comply with the norms that were announced in the regulatory document, then the project will not be legal. State organizations they can force you to rebuild the pipeline or even fine you;
- SNiP not only helps to build drainage systems correctly, but also contributes to certain savings. The document contains many turnkey solutions for designing a drainage system, the least expensive for the owner;
- Communication performed according to certain standards is more effective and durable. She is less prone negative impact groundwater, seal failure or other factors.
What should be in the project
Before starting any construction, it is necessary to develop a drawing. According to the requirements of SNiP, the foundation drainage project should include:
The resulting scheme will help to calculate the cost of materials, develop estimates and approve the project in certain public institutions. In addition, according to SNiP, wall drainage of the foundation also takes into account the general slope of the site, the amount of average annual precipitation, the level of freezing of the earth and groundwater.
The next step is to install a drainage system according to the scheme.. Regardless of whether a closed or open drainage system is used, the following operations must be performed before installing the drain:
geometric design
Installation of the drainage system is also carried out according to certain rules. The design of the system is controlled not only by SNiP, but also by GOST 1839-80. What is specified in the regulations:
During the installation of drainage, the location of other communications must also be taken into account. With an allowable pipe height of 50 mm, it is necessary that the distance between the underground wire electrical network(if any) or sewage was about 150 mm.
The diversion of groundwater, including flood water, from buildings and soil on the site is one of the most frequent hydrogeological tasks. However, before proceeding with its solution, it is necessary to determine the required throughput of the sewer, and for this, a drainage calculation will be required. How to perform it, what factors are taken into account, and what are the groundwater drainage systems - later in the article.
Attention! It should be taken into account that, depending on the specific conditions, when laying the ring drainage, the distance between the wall of the trench in its upper part and the wall / foundation of the house should be at least 3 m. The filler (gravel and sand) should be backfilled to such a depth as to prevent swelling of the soil when water freezes around the foundation. We should not forget about mandatory organization concrete blind area under the walls, extending at a distance of at least 1 mot of the building.
Ways to organize drainage
It could be:
- simple backfilling of the trench with sand and gravel
- installation of drainage trays
- installation of drainage pipes
- installation of drainage mats
Sand and gravel backfill is attractive for its simplicity, for it it is enough to dig a trench and add filler with a layer of 15-40 cm. As a rule, the rest of the volume is filled from above with previously excavated soil.
But such rather quickly (within 2-3, maximum - 5 years) lose their effectiveness as a result of silting. Filling the space between the aggregate grains does not allow water to flow into the drain.
In the trench, also on a gravel-sand base, concrete or polymer concrete trays can be laid, which are covered on top, for example, with cast-iron gratings. This method is used, as a rule, near garden paths, transport entrances and similar objects.
The most common method now is the laying of drains - a special smooth-walled or corrugated perforated pipe. The advantage of this method is that with proper organization, especially with the use of geotextiles (for wrapping pipes), it ensures a long and reliable operation of the system.
Drainage mats are a three-layer material made from a combination of polymers, which have a high drainage capacity even under high ground pressure.
Mats are laid either in ordinary trays or trenches, or directly on the soil surface, which is used in large and excessively wet areas. In addition to high drainage capacity, mats also create a frost-protective layer that prevents soil heaving.
All these methods are applicable both for the organization of the removal of groundwater from the foundation of the building, and for the drainage of the territory of the land plot itself.
