The distance between the screw piles for frame. The distance between the screw piles for the frame house
Foundations on stilts have been known for a very long time. For the first time, piles began to be used in the construction of bridges where reliability and quality were certainly required.
In this article we will consider what distance should be between screw piles at the skeleton.
In ancient Russia, churches were often erected on wooden stilts. The foundation on piles is used for heaving and bulk areas, with an extremely unreliable composition of the upper soil, which contains clay, is very saturated with water, humus, peat, etc. It is used on various ones without worrying that uneven shrinkage can occur.
Rostverk is the most optimal and universal solution for organizing strong, reliable and high-quality foundations for the home, primarily due to the fact that the best performance, pile and, are embodied in this design. Grillages can be arranged on reliefs of any complexity with a wide variety of soil characteristics without restrictions on the type and weight of buildings. The only exceptions are solid rocks, where the development of pits or wells is impossible or economically impractical.
Low grillage arrange on dry, dense and loose soils with minimal impact of flood, rain and melt water.
Increased grillage lay on soils with a low degree of heaving, where significant wetting of the surface soil layer under the influence of storm, flood and melt water is possible.
Tall grillage organize on any soils with medium and high degree of heaving. In this case, the lower edge of the ribbon of the grillage is raised by at least 10-15 cm above the ground level in order to avoid the action of stress forces from the surface swelling of the soil during frosts.
The choice of grillage type depends on the soil condition, local climatic conditions and the weight of the building, taking into account the possible snow load. The determination of the number of columns, the distance between piles and the width of the monolithic tape refers to responsible design indicators. Therefore, it is better to entrust this part of the calculations to specialists. Marking, preparation of pits for poles or laying of piles is carried out using the same technologies as for pile and column foundations, and filling the tape is similar to the device of the strip foundation.
Features of the pile foundation
In the construction of small frame houses pile is recommended. However, when erecting large tall buildings the use of this type of foundation is undesirable, as the structure will be subject to the influence of strong winds, as well as many other factors from outside that can lead to the destruction of the building.
A huge plus of screw piles is that building a house can be done on a slope
Instructions for installing the pile foundation
The first thing to do is to select and mark out the territory for the construction of the house on stilts. In order to exclude possible problems in the future, you should get a plan of underground and power cable networks.
Installation of piles. There are several simple ways. For example, screwing the piles into the ground completely until it stops manually, or we hammer it mechanically. At the designated installation site of the piles, we make a small depression, the so-called guide. Next, the support is erected. The support should be installed strictly vertically.
The lever of the support becomes scrap installed in the hole of the support on which the pipe is installed. It is necessary to initially install the supports strictly vertically, since in the future it will not be possible to fix it. Therefore, when screwing in, carefully monitor the position of the support and, if necessary, adjust it vertically. In some cases, you should manually prepare a recess of up to 50 cm, and maybe more - this problem can occur if there are stones or solid soil fumes.
Pile immersion depth is calculated individually according to the project and should not exceed the level of solid soil.
Rules for working with screw piles
At the end of the installation of the supports, they are aligned in height and, if necessary, trimmed with a grinder, this should be done in order to eliminate the horizontal subsidence of the plates and bars of the base of the house. The height of the screw piles of the foundation above the ground should not exceed 60cm. Further, the structure is poured with concrete in order to obtain the strength and reliability of the foundation of the future home. It is also important to remove excess air from the concrete surface, as this can lead to deformation of the concrete slab in the future. The next step is welding the heads and tying the beam. You can also use metal channels, replacing them with a beam. When using the channel head can be eliminated, which will significantly reduce the future of the house.
Strictly strictly during the construction of the pile foundation is prohibited:
- Extend or fix twisted piles;
- Use damaged piles;
- Immerse piles to a depth of less than one and a half meters from the upper soil level;
- The assumption of a vertical slope of more than 2 degrees;
- When screwing, adjust the piles to the horizontal level.
It is very important to carefully familiarize yourself with the technologies and rules before installing the pile foundation. In the future, this will certainly bring great benefit, and also get a high-quality and durable foundation for the future home.
The base on screw supports is considered universal, since it can be installed even in places where other types of foundations will be meaningless. This design is installed in cases where even the area is swampy. Building pilescrew base under frame house will be the right decision. These elements are of two types, such as: solid and collapsible. If you plan to do the construction of your own hands, it is best to purchase those that can be disassembled. On the bottom side of the pile there is a sharp tip and a blade, due to which the support is screwed into the soil structure. Its size can vary from 150 to 250 millimeters. In the upper part is a special head.
If the frame structure has a small mass, then supports with a small diameter can be used. In order to correctly calculate the basis, it is necessary to adhere to certain rules, such as:
- The mass of the frame building is calculated taking into account furniture;
- The effect of wind is calculated;
- After calculations, all indicators are added up and then rounded. The result is the total mass that the foundation must withstand.
If all the calculations are carried out correctly, then there will be no problems after the construction of the building as a whole.
The construction of the base of screw piles
Before you start construction work, the first step is to draw up budget documentation. With her help, the quantity will be known the necessary material for the construction of the building and its total cost. Only after all calculations will it become known distance between screw piles, which is necessary for erection frame house and not only.
Nowadays, the construction of frame types of houses on screw supports is in great demand, since such a base has a lot of positive properties:
- The use of a screw foundation makes it possible to construction work on soils with any degree of density;
- The foundation device does not require a certain time of the year, so you can perform the construction of the structure in any season;
- Due to the simplicity of the elements, construction work progresses quite quickly;
- An important advantage of this type of foundation is the low cost, which does not negatively affect the quality of the building as a whole.
Scheme of a screw pile
Most people who do not have building experience ask themselves: how is it possible to find out the distance between the supports of the screw type? To simplify the task, you can use the calculator in real time, it can be found on the Internet or contact a construction organization for help. To determine the distance between piles, there are certain requirements that neither the customer nor the construction organization can influence for their own benefit. In case of violation of the rules, the apartment building will not be reliable, which will subsequently lead to its destruction.
How to correctly calculate the distance between the supports
The calculation of the number of piles and the distance between them is the initial stage in the construction of the foundation. Its accuracy will affect the entire course of construction work. Any person can determine the steps between the supports, even without having at the same time building experience. Factors that affect the process of all calculations:
- Foundation form;
- Methods and mass, which will further influence the basis;
- Characterization of the structure of the soil.
Particular attention should be paid to the moment of placement of pile structures under grillages. This step is performed in two options, such as:
- The order is staggered. Visually, the poles are staggered at the construction site. That is, the installation of supports should be performed at each angle of the strapping. In order to make sure that the installation is correct, the diagonal is determined using a cord.
- Inline mounting method of supports. Installation of supports is carried out parallel to the sides of the grillage.
Calculation of the number of supports
If the piles are screwed at too great a distance, the future foundation of the frame method of construction will become unreliable. Therefore, it is necessary to install the supports at the correct distance from each other. Basically, the steps are determined by the total weight of the apartment building. The maximum pitch between the screw pipes must not exceed five diameters of the pile used.
Distance calculation example
As a sample, you can use the foundation for the frame structure of a house from a bar, which has a size of 6 by 6 meters. The total weight of the building depends on the height of the building, taking into account the roof structure. Assume that the construction of the house is a combination of twenty thousand cubic meters. This value must be multiplied by the mass of one cube of timber. In this situation, it is 800 kilograms. As a result, the total weight will be 16 tons. Approximately 2 tons must be added to this mass, that is, the weight of the finish and the roof as a whole. The following should be determined:
- Useful type of load - 36m2 * 150kg / m2, the result will be five and a half tons (5.4);
- The influence of the permissible load from snow accumulation in wintertime - 36m2 * 120kg / m2, will be equal to (4.30) tons.
Screw base on the project
After carrying out the total action, the result is 27.72 tons. This figure should be multiplied by the spare ratio, that is, 1.1. Next, at the time of counting the number of screwed-in elements, we apply the load size (27.72x1.1 \u003d 30.5) In the case of an uneven number, round it. Using a screw support with 89 diameters, which can withstand a mass of 2 tons, (30.5 / 2 \u003d 16). As a result, for the construction of such a house, 16 screw piles are obtained. They are subsequently evenly placed on the construction site. The step between them will depend on the number of elements for the foundation. You can use additional supports for flooring. If you plan to install a house with two floors, the number of piles will double. Each project is calculated individually.
Optimum pitch between piles
Making the right screw base design provides almost 50 percent of the strength and durability of the entire structure. That's because it contains the maximum allowable level of load on the base as a whole. Often all the rules are present in the GOST, but nevertheless, deviations from the legal norms are allowed. Due to this, it becomes possible to save financial resources. But it should be remembered that this should not be abused, since this action can lead to the destruction of the entire building as a whole.
Distance between piles
The draft indicates the acceptable margin of indentation, but in practice it is used in an understated number. Due to this, the possibility of risk formation is reduced. During installation, piles of a larger diameter are sometimes installed, this will also increase the bearing capacity of the foundation.
Dignity
Screw piles is a material that is used to build the foundation. This building has such advantages as:
- It has a long service life;
- Low cost;
- Low weight of elements;
- Ease of installation;
- The base of the screw supports stands firmly on soft soils;
- Can be mounted on slopes.
Practice has proven that the process of destruction occurs in monolithic foundation faster than screw supports. Experts explain this action as follows: the concrete base is subject to a greater degree of shrinkage, in contrast to the screw structure. This factor significantly affects the service life. In the process of destruction, it is necessary to add concrete structure, which requires additional expenses of money.
An important advantage of screw supports is speed and ease of installation. Small foundation, for example: 6 to 6 can be set in just one day. Factors that make work easier:
- Lack of preparatory work with soil;
- No need to hire large construction equipment;
- No need to take time for hardening, as the composition does not include concrete consistency;
- In order to carry out the installation of this type of foundation, you do not need a lot of experience in construction.
Foundation construction on soils with weak properties is allowed only with the use of screw supports. Supports at the time of screwing pass through loose layers and abut against solid rocks of the soil. Due to this, the foundation is firmly standing for a long time. The only place where installation of piles is prohibited is a rock.
We calculate the distance between the screw piles for the frame house
We calculate the distance between screw piles for a frame house. The foundation on screw supports is considered universal, since it can be installed even in places in which others
Determining the distance between piles during the construction of the foundation under private house requires compliance with a methodology that takes into account many factors. They include parameters that describe both the properties of the piles themselves and the specifics of the soil and weather conditions of the area. But the main point is the overall load that the structure exerts on the foundation.
There are techniques for the typical placement of piles, as well as rules indicating the most loaded sections of the building. To determine the exact placement of piles, it is necessary to calculate their number and, following the requirements, arrange the supports in the foundation plan.
Pile placement specifics depending on the type of foundation
To determine the exact distance between screw piles during the construction of frame or timber house some calculations need to be done. Typically, this distance ranges from 1 to 3 meters. During the construction of temporary or small non-essential buildings, it is calculated by eye, which is not allowed when designing permanent buildings.
When finding the exact distance between the piles, the length of the beams of the grillage is taken into account, because they must abut against the heads of the screwed supports at the two ends. This rule applies to both frame and timber houses, but it does not matter if the grillage is cast from concrete. In this case, the beams are simply not used in it.
When using plates as a material for the foundation, the interval between screw piles is determined design documentation, taking into account their weight and structural features. In this case, the calculations become more complicated, but the principles for placing the support beams remain the same - the piles should be installed under the bearing walls, at the entrance portal, under the columns, etc.
Pile placement options and their purpose
Proper placement of piles is the basis for the integrity and durability of the foundation and the entire structure. When placing the supports, according to the load, it is possible to avoid critical areas that threaten subsidence of piles and individual parts of the house. If the building has complex contours, the placement of the supports requires special attention.
To this end, several basic techniques have been developed.
- Single occupancy. Piles are installed under the supports of frame structures, in the corner joints of the walls and under all the supporting elements. Moreover, their interval cannot be more than 3 meters.
- Tape placement.Piles are located under the bearing walls with the difference from the single type, that the interval of their location is noticeably reduced and often is only half a meter. This technique is used if necessary to withstand a large load (for example, a heavy 2-or 3-storey house).
- Shrub placement.This type is necessary to support heavy single or group structures. There is no definite step for this type, since piles are often placed close to each other in a chaotic order corresponding to the load. Their placement directly depends on the calculation of pressure zones. The only condition is that the elements must be present around the entire perimeter and area of \u200b\u200bthe slab foundation for which they are supports.
- Continuous placement or pile field. Supports are installed everywhere under the area of \u200b\u200bthe slab foundation, the step is about 1 meter. This technique is used for massive structures or on soils with weak bearing capacity.
In the construction of standard frame private houses, not differing in huge mass, single or tape placement of piles is almost always used.
Features of the calculation
When calculating the placement interval of piles, certain essential criteria must be taken into account. This will allow not to place the elements too close, wasting money in vain, and not to put them too far, putting the foundation and the whole house at risk of subsidence.
In the calculations of professional builders, the following points are taken into account:
- the mass of the structure (frame, roof, decoration, etc.);
- mass of internal filling (equipment, furniture, things and residents);
- dynamic factors (wind load, weight of snow on the roof in winter);
- bearing capacity of soil;
- technical parameters of screw piles;
- safety factor.
To determine the payload when calculating the interval of pile placement, the corresponding SNiP is used. For example, for a one-story residential building, the load is set at 150 kg per 1 sq. Km. m. area. Wind and snow load indicators are reference values \u200b\u200band are set for each region depending on local weather specifics. The safety factor averages from 1.1 to 1.25.
Before planning the location of piles, it is necessary to calculate their number. It is determined based on the total load on the supports. The total weight is divided by the bearing capacity of one pile, as a result of which the exact number of supports is determined. Then they are placed with an equal interval along the perimeter of the structure and under the supporting structures.
The second option is the arrangement of piles, planned on the basis of determining the load on 1 linear meter grillage. To calculate it, it is necessary to divide the total load of the building by the total length of all load-bearing walls, and then divide by the load-bearing capacity of the selected type of piles. The result is an indicator that determines the required number of supports to maintain 1 meter grillage. After this, the necessary interval for the placement of piles is determined, sufficient to maintain the foundation. This method is used for more massive buildings and is rarely used for low-rise frame houses.
To determine the approximate bearing capacity of piles of a particular type, you need to look at the table with the relevant indicators. More accurate information used in the final calculations is indicated by the manufacturer in the specification for a particular product. It is worth considering that the minimum distance at which the piles for the house and terrace are screwed is 108 cm.
Rules for the location of screw piles under the foundation
To maintain the structure and ensure uniform load, the supports should be located in the places with the highest load according to the established procedure.
The following zones can be distinguished:
- in the corners of the facade walls;
- at the intersection of load-bearing walls and interior partitions;
- near the entrance;
- on the internal area with an interval of not more than 2 meters;
- under the stove or fireplace (from 2 piles or more);
- under the load-bearing wall, on which there is an additional structure such as a balcony or a mezzanine, locally increasing the load on the wall.
After finding the exact number of piles, the stage of the schematic arrangement of the supports in the foundation plan begins. In this case, the above rules for their placement under the bearing elements and at critical points of the structure must be taken into account. The remainder should be evenly spaced between the key supports. This determines the step in the arrangement of screw piles.
Example of calculating the number of piles
Consider the features of the calculation on the example of a square-shaped house with a perimeter of 8x8.
Other structural features include:
- frame type, slate roof, porch;
- foundation dimensions - 8x8, building height - 3 meters;
- the house has 3 rooms, formed by the intersection of a solid wall 8 meters long and partitions 4 meters long;
- the frame is made of timber 150x150, grillage - 200x200;
- the walls are covered with sandwich panels.
Wall area calculation:
- outdoor - 8 * 3 * 4 \u003d 96 square meters. m;
- internal - 8 * 3 + 4 * 3 \u003d 36 sq. m
Calculation of the mass of the walls using table values \u200b\u200bfor the mass of 1 square. m:
- external (bearing) - 50 * 96 \u003d 4800 kg;
- partitions - 30 * 36 \u003d 1080 kg;
- total weight - 4800 + 1080 \u003d 5880 kg.
Calculation of the mass of basement and attic floors using tabular values \u200b\u200bfor the mass of 1 square. m:
- basement - 8 * 8 * 150 \u003d 9600 kg;
- attic - 8 * 8 * 100 \u003d 6400 kg;
- total weight - 9600 + 6400 \u003d 16000 kg.
To determine the mass of the additional load (internal filling of the house: finishing materials, things, equipment), a tabular value of 350 kg / 1 sq. Is used. m. when calculating the load for two-story house the weight of the additional load is multiplied by 2.
8 * 8 * 350 \u003d 22400 kg.
Calculation of the total load on the foundation:
16000 + 22400 \u003d 38400 kg.
Calculation of the number of piles according to the formula K \u003d P * k / S, where:
“K” - reliability coefficient (1.4 in the example);
“S” - maximum load per 1 pile (this value is based on the specifics of the pile, in the example it is a support with a diameter of 300 mm).
Ground resistance is determined by the specifics of the area on which the house is being built. In the example, this is soil with an average density of 3 kg. / cube see, weak freezing 1 meter and deep bedding of groundwater.
38400*1.4/2600=20.6
Based on the calculation, we can conclude that in this case you need to use 21 piles.
The given example shows possible variant computing.It does not take into account the specifics of a particular structure, which may affect the final number of piles and their placement in the foundation plan.
One of the highlights is decoration Materials and other stuffing at home, accounting for about half the load. The table value is based on the average weight of the materials. If massive cladding is used, for example, granite or marble slabs, masonry of stone or brick, etc., the total load indicator can significantly change. In such circumstances, an accurate calculation of the weight of all elements related to the additional load cannot be avoided.
When planning the construction of a new house, many people opt for a pile-screw foundation, as the least costly, reliable and durable. And they are right. When erecting small light frame, wooden, block and panel houses, this is the best option.
The service life of the pile-screw foundation is more than 100 years. To get a solid house “for centuries”, it is important not to make a mistake in calculating the foundation, choosing the number of piles and the distance between them.
What you need to know about screw piles
In fact, this is a pipe 2.5 meters long, to one end of which a cone with a blade in the form of a spiral is welded. The name "screw" reflects the method of deepening piles into the ground. No special equipment is needed for this. All work can be done manually.
Standard diameters of screw bearings in millimeters: 57, 89, 108.133, 159, etc.
With an increase in the diameter of the pipe, its wall thickness and bearing capacity increase:
- 108 mm - wall thickness 4 mm, rated load from 5 to 8 tons. Used for the construction of wooden houses from timber and logs, lightweight buildings from foam blocks.
- 133 mm - wall thickness 5 mm, rated load from 8 to 11 tons. They are used in the construction of brick houses, heavy buildings of complex construction made of foam concrete block, gas silicate, expanded clay, logs and timber.
Bearing capacity also depends on the depth of twisting of the support. Above are the average parameters for a depth of 1.7-2.0 meters in hard plate soils.
The choice of source data for the calculation of the pile foundation
Mass at home
What form will the foundation have? It is necessary to determine the configuration of the house in advance. If possible, mark all necessary dimensions with pegs on the site.
The mass of the house depends on the materials used for construction, on the number of storeys. Attention: screw piles are not recommended for the construction of buildings above three floors. When determining the total mass of the house, one should take into account the load from the furniture, the weight of the snow cover in winter.
To simplify the calculations, let's take statistics into service. The weight of the external walls of the house is about half the mass of the whole house, along with furniture and snow load.
We consider the volume of the external walls: we multiply the height of the walls by their width and total length.
We learn the mass of walls by multiplying the volume by the density of building materials.
For reference: the density of some building materials:
- dry wood - 500 kg / m³;
- brickwork - 1800 kg / m³;
- cinder block - 1200 kg / m³.
We get the mass of the whole house by multiplying the mass of the walls by two. To obtain the mass of frame houses, the weight of the external walls must be increased three times.
If the calculation of the mass of the house was carried out based on the real weight of all the walls, structures of the house, roof and furniture, then it is necessary to lay 30% weight gain. This will create a margin of safety for the building and foundation.
Soil type
Almost all soils, with the exception of silty and rocky, are suitable to build a pile foundation. Silty soils due to fluctuations are not suitable for twisting piles. On rocky soils, the installation of piles will require the use of special drilling equipment.
When calculating, it is necessary to know the bearing capacity of the soil. Invited specialists-geologists will take the necessary samples at the site and in laboratory conditions will be able to determine its value.
To determine the depth to which it will be necessary to screw the piles, in the place of the foundation of the future house, two or three pits should be dug at least two meters deep. You will see the composition of the soil, and at what depth hard rocks (for example, clay) lie. They are most preferred for fixing piles. Do not dwell on sandy layers.
Other nuances
Seismicity is taken into account. For seismically active regions, special coefficients are provided when calculating bearing capacity. But the foundation is the same as for ordinary areas.
If you want to build a house with a complex architectural and planning decision from heavy building materials, or if you have doubts about the composition of the soil at the construction site, it is advisable to contact a specialized design organization. Perhaps you will be offered typical design solutions for buildings on a pile-screw foundation in your area. If necessary, experts will conduct research and perform calculations for your own project.
Julia Petrichenko, expert
In other cases, the developer is quite capable of independently calculating the pile-screw foundation according to a simplified scheme.
Determination of the parameters of the pile foundation
Pile calculation
- We calculate the total area of \u200b\u200bthe base of the foundation according to the formula: S \u003d M / N,
Where S is the sole area (cm²); M is the mass of the house (kg); N– soil bearing capacity (kg / cm²) - data obtained as a result of geological examination of soil samples ..
In the above simplified calculation of the total mass of the house, the weight of the snow cover and the correction for seismicity are taken into account.
- Choose the type of screw piles. Depending on the diameter of the blade, we calculate the sole area of \u200b\u200bone support.
- The total area of \u200b\u200bthe foundation is divided by the area of \u200b\u200bthe sole of one support.
- We get the number of piles necessary for the construction of a pile-screw foundation.
Determining the distance between piles
There was a simple but no less important part of the calculation. The distance between piles is important to choose so that the load is evenly distributed.
The standard permissible distance between the piles of the foundation is determined:
- minimum - 3d (d - diameter of one pile);
- maximum - 5-6 d.
When screwing the piles, the soil around them is compacted. Therefore, placing the supports closer than the minimum allowable distance is not recommended.
When installing inclined piles in steep sections, it is allowed to reduce the minimum distance to 1.5d. But this need must be confirmed by calculations.
It is also possible to increase the minimum allowable distance to 4d on sandy soils. Because due to soil compaction, installation work may be difficult.
The maximum distance between piles is determined by the bearing capacity of the grillage. It is important that the horizontal slabs and beams do not bend under load. In some cases, on stable and durable soils, an increase in the distance to 8d is permissible. But this also requires a preliminary calculation.
Calculating the pile-screw foundation, the distance between piles is set in the interval between the minimum and maximum permissible limits.
Support on the sole of the grillage can be placed in a row (tape) or in a checkerboard pattern.
The pile row is performed with a small number of supports. They are screwed into the ground around the perimeter, or in rows parallel to the lateral sides of the grillage. The gap between the supports and is the distance between the piles.
If you need to install a large number of supports, then it is advisable to arrange them in a checkerboard pattern. In this case, the distance between piles will be considered the diagonal between adjacent supports.
The use of screw piles allows you to perform work of the zero cycle quickly, efficiently, without disturbing the surrounding landscape. In addition, pile-screw foundations are cheaper than others. Savings range from 30 to 60%. But, despite these advantages, common in southern Russia, pile-screw houses can not often be seen in other regions. Perhaps in many places it is customary to build houses according to the traditions laid down by grandfathers and great-grandfathers. Perhaps someone has a house on pipe stilts associated with an unreliable hut on chicken legs.
If you are lucky to live in a house on a pile-screw foundation, and may even participate in its construction, share your impressions.
This solution allows you to get a reliable and efficient support structure on problem or weak bearing soils.
There are many such regions on the territory of Russia, therefore the technologies for creating pile foundations are popular and well studied.
One of the successful structural options are screw piles, which allow quickly and sparing methods to obtain a reliable foundation without undesirable effects on buildings located nearby.
The possibilities of screw piles make them popular and widespread, and the possibility of self-construction only strengthens these qualities.
Consider one of the important working points - the choice of the optimal distance between the supports.
The pitch of screw piles directly depends on their number, which is calculated by the bearing capacity of the unit.
The main factors of influence in this case are:
- Bearing capacity of the soil.
- Barrel diameter and blade size.
- Depth of immersion, the presence of direct contact with dense layers of soil.
- Magnitude of the load.
The distance between the screw piles is determined during the creation of the project, since this is the calculated value on which most of the structural parameters of all the base elements located on the surface depend.
The permissible load on the pile is usually indicated by the manufacturer in the passport, but this value cannot be used in the calculation.
It does not take into account geological features and operating conditions, being a purely information value.
Features of the soil on the site
The strength and reliability of the contact of the trunk and the blades of each pile with adjacent layers largely depend on the soil parameters. According to the requirements of SNiP, for soil analysis it is necessary to carry out test drilling, laboratory studies of the composition and properties of soil layers.
In addition, the installation of reference piles is recommended, which in practice can demonstrate the bearing capacity of piles and the value of resistance to loads. In practice, most studies are limited to trial drilling and visual determination of soil quality.
The depth of the dense layers and their composition are determined by the resistance of the soil when drilling.
NOTE!
An experienced driller is able to assess the condition of the soil no worse than a specialist geologist, however, if it is possible to perform a qualitative analysis of the soil, it should not be neglected.
Load calculation
The load on the base is the total value composed of the following values:
- The weight of the house with all structures, ceilings and other structural elements.
- The amount of snow load on the roof in winter.
The weight of the house is the calculated value that is obtained by adding the weight of the walls, roof, floors and other elements. All the necessary data can be taken from SNiP applications, multiplying specific values \u200b\u200bby the area or volume of existing structures.
This stage of calculations is the longest, it is important not to miss any designs, to take into account all the elements. It is necessary to show maximum care and consistently add up the weight of all parts of the house.
Snow load is determined by multiplying total area roofs by the specific snow pressure (per m2). This value is available in SNiP applications, the corresponding region is selected and the necessary data is obtained.
In the same way, the wind load is determined, a very relevant parameter for some regions.
Operational load is the weight of people, furniture, household appliances and other property located in the house. These values \u200b\u200bshould not be neglected, since they significantly change the total load.
The total estimated load should be increased by 10-15% in order to have some margin of bearing capacity of the base. This can compensate for the possible additional load from the weight of the casing or other elements not previously considered.
Basic layouts on the foundation
There are various layouts for piles.:
- Single.
- Dolphin.
- Pile field.
- Pile tape.
The choice of scheme is determined by the configuration of the building and the order of load distribution. Separate piles are used to create point supports for pillars or other elements of the minimum area.
Pile bushes are used at high loads for more than one, which happens during the construction of high-rise buildings, large hangars, etc. Pile field is used for heavy constructions with uniform load distribution over the entire area of \u200b\u200bthe base.
Installation of supports is carried out either in longitudinal-transverse rows or in a checkerboard pattern. Tapes are necessary when creating structures having an extended structure with a small width (embankments, retaining walls, fences, etc.).
It should be borne in mind that the design configuration of the pile field does not always fully comply with the requirements of SNiP. Often there are situations when the number of supports does not correspond to the load due to the placement.
In such cases, it is necessary to increase the number of piles or slightly adjust the configuration of the pile field, taking into account the specifics of the loads.
How to calculate the distance
There are many different methods for calculating screw piles. Most of them are incorrect and do not give any useful result.. A competent calculation can be done, guided by SP 50-102-2003, which sets out all the necessary formulas and techniques.
The problem is that simple ways doesn’t exist, you will have to make fairly complex calculations with a high probability of error. Therefore, you need to contact specialists or, at least, use online calculators that allow you to get the desired values \u200b\u200bin just a couple of minutes and completely free.
NOTE!
Tackling the foundation on their own, without adequate training and experience, is strongly discouraged due to the high probability of errors and the misuse of various special values.
After that, piles are distributed along the lines of load placement (load-bearing walls) based on their number.
Sometimes, with a uniform distribution of weight across all supports, they do it simply - they calculate the total length of the bearing walls and divide it by the estimated number of piles.
for example:
The weight of the house is 300 tons. The nominal load on the pile is 5 tons (BC-108).
Total number of piles:
300: 5 \u003d 60 pcs.
The total length of the reference lines is 40 m.
Then the distance between adjacent piles will be:
60: 40 \u003d 1.5 m.
Minimum and maximum value between supports
According to the requirements of SNiP, the minimum distance between two adjacent screw piles is the double diameter of the blades. That is, if there are supports with blades of 30 cm, the minimum distance between them will be 60 cm.
It should be noted that this is the distance between the blades, that is, when marking, marking the axis of the piles, it should be considered not 2, but 3 diameters. The maximum distance is determined by the ratio of the weight of the house to the number of piles.
It is necessary to take into account the material and the cross section of the grillage so as not to obtain excessive mobility of the beams in the central part of each span. According to all calculations, the maximum is always determined as 3, in some cases - 3.5 m.
It is impossible to go beyond these values, this will create a threat to the structures of the house.
Optimal value
It is very difficult to clearly indicate the optimal distance between adjacent piles of a screw foundation. It is necessary to take into account a lot of specific factors specific only to this site, construction and other conditions of construction and operation.
However, there are certain limits that limit the minimum and maximum pitch between the screw supports. Logically, the average distance should be the optimal distance, but in reality the situation looks somewhat different.
According to the results of experiments and practical tests revealed that the optimal distance is 2 m. This value is suitable for almost all types and sizes of piles used in individual construction.
The optimal value should not be used as some kind of universal number, suitable in any case. Each project must be calculated individually.
Useful video
In this video you will learn how to calculate the distance between piles in a screw foundation:
Conclusion
The parameters of the screw foundation are a very complex and controversial issue. It is heavily discussed, but discussions are rarely productive, since in each case there are conditions, weight and material of the house, dimensions, type of soil, etc.
A large number of influence factors make it difficult to develop general rulesallowing everyone to accurately calculate the size of the base, the distance between the supports and other nuances.
The solution to this problem is best entrusted to professionals with experience and relevant skills.
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