Technological map for the layout and compaction of the pgs. What is the crushed stone compaction coefficient? Sand gravel natural compaction coefficient

Crushed stone is a common building material that is obtained by crushing hard rock. Raw materials are extracted by blasting during quarrying. The rock is crushed into the appropriate fractions. In this case, the special coefficient of crushed stone compaction is important.

Granite is the most common, since its frost resistance is high, and water absorption is low, which is so important for any building structure. Abrasion and strength of crushed granite meets the standards. Among the main fractions of crushed stone can be noted: 5-15 mm, 5-20 mm, 5-40 mm, 20-40 mm, 40-70 mm. The most popular is crushed stone with a fraction of 5-20 mm; it can be used for various works:

construction of foundations;
production of ballast layers for tracks and railways;
additive in building mixtures.

Compaction of crushed stone depends on many indicators, including its characteristics. Should be considered:

The average density is 1.4-3 g / cm³ (when compaction is calculated, this parameter is taken as one of the main ones).
The flakiness determines the level of the plane of the material.
All material is sorted into fractions.
Frost resistance.
The level of radioactivity. For all works, crushed stone of the 1st class can be used, but the 2nd class can only be used for road work.

Based on these characteristics, a decision is made which material is suitable for a particular type of work.

Types of crushed stone and technical characteristics

Crushed stone for construction can be used different. Manufacturers offer different types of it, the properties of which differ from each other. Today, according to the type of raw material, crushed stone is usually divided into 4 large groups:

gravel;
granite;
dolomitic, i.e. limestone;
secondary.

For the manufacture of granite material, the corresponding rock is used. This is a non-metallic material that is obtained from solid rock. Granite is a solidified magma with great hardness, its processing is difficult. Crushed stone of this type is manufactured in accordance with GOST 8267-93. The most popular is crushed stone, which has a fraction of 5/20 mm, as it can be used for a variety of jobs, including the manufacture of foundations, roads, sites, and more.

Gravel crushed stone is a building bulk material that is obtained by crushing rocky rock or rock in quarries. The strength of the material is not as high as that of crushed granite, but its cost is lower, as is the background radiation. Today it is customary to distinguish between two types of gravel:

crushed variety of crushed stone;
gravel of river and sea origin.

By fraction, gravel is classified into 4 large groups: 3/10, 5/40, 5/20, 20/40 mm. The material is used for the preparation of various building mixtures as a filler, it is considered indispensable when mixing concrete, building foundations, paths.

Limestone crushed stone is made from sedimentary rock. As the name implies, the raw material is limestone. The main component is calcium carbonate, the cost of the material is one of the lowest.

The fractions of this crushed stone are divided into 3 large groups: 20/40, 5/20, 40/70 mm.

It is applicable for the glass industry, in the manufacture of small reinforced concrete structures, in the preparation of cement.

Secondary crushed stone has the lowest cost. Make it from construction debris e.g. asphalt, concrete, brick.

The advantage of crushed stone is its low cost, but in terms of its main characteristics it is much inferior to the other three types, therefore it is rarely used and only in cases where strength is not of great importance.

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Compaction factor: purpose

The compaction factor is a special standard number determined by SNiP and GOST. This value shows how many times the crushed stone can be compacted, i.e. reduce its external volume during ramming or transportation. The value is usually 1.05-1.52. According to existing standards, the compaction factor can be as follows:

sand and gravel mixture - 1.2;
building sand - 1.15;
expanded clay - 1.15;
crushed gravel - 1.1;
soil - 1.1 (1.4).

An example of determining the compaction coefficient of crushed stone or gravel can be given as follows:

It can be assumed that the mass density is 1.95 g/cm³, after compaction has been carried out, the value has become 1.88 g/cm³.
To determine the value, it is necessary to divide the actual density level by the maximum, which will give the crushed stone compaction coefficient 1.88 / 1.95 = 0.96.

At the same time, it should be taken into account that the design data usually indicate not the degree of compaction, but the so-called skeletal density, i.e. during calculations, it is necessary to take into account the level of humidity, other parameters of the building mixture.

Why the sand compaction coefficient is needed, and what significance this indicator plays in construction, probably every builder and those who are directly connected with this non-metallic material know. The physical parameter has a special meaning, which is expressed through the value of Buy. The calculation parameter is necessary in order to be able to directly compare the actual density of the material on the spot. certain area plot with the required values, which are prescribed in the regulations. Thus, the sand compaction coefficient according to GOST 7394 85 is the most important parameter, on the basis of which the required quality of preparation for work at construction sites with the use of bulk non-ore substances is estimated.

Basic concepts of compaction factor

According to generally accepted formulations, the sand compaction coefficient is the density value that is characteristic of a particular type of soil in a certain area of \u200b\u200bthe site to the same material value that is transferred by standard compaction modes in laboratory conditions. Ultimately, it is this figure that is used in assessing the quality of the final construction works. In addition to the above technical regulations, GOST 8736-93, as well as GOST 25100-95, are used to determine the sand compaction coefficient during tamping.

At the same time, it must be remembered that in the working process and production, each type of material can have its own unique density, which affects the main technical indicators, and the sand compaction coefficient according to the SNIP table is indicated in the relevant technological regulation SNIP 2.05.02-85 in part of Table No. 22. This indicator is the most important in the calculation, and these values \u200b\u200bare indicated in the main project documentation, which range from 0.95 to 0.98 in the project calculation range.

How does the sand density parameter change?

Having no idea what the required sand compaction factor is, it will be difficult to calculate during the construction process required amount material for a specific technological process work. In any case, you will need to find out how the state of the material was affected by various manipulations with non-metallic matter. The most difficult calculation parameter, as the builders admit, is the sand compaction coefficient during the construction of the SNIP road. Without clear data, it is impossible to do quality work in road construction. The main factors that affect the final result of material readings are:

Method of transportation of the substance, starting from the starting point;
The length of the sand route;
Mechanical characteristics affecting sand quality;
The presence of third-party elements and inclusions in the material;
Ingress of water, snow and other precipitation.

Thus, when ordering sand, you need to thoroughly check the sand compaction coefficient in a laboratory way.

Features of backfill calculation

To calculate the data, the so-called “soil skeleton” is taken, this is a conditional part of the structure of matter, with certain parameters looseness and moisture. The calculation takes into account the conditional volume weight considered "soil skeleton", the calculation of the ratio of the volumetric mass of solid elements is taken into account, where water would be present, which would occupy the entire mass volume occupied by the soil.

In order to determine the compaction coefficient of sand during backfilling, it will be necessary to carry out laboratory works. In this case, moisture will be involved, which in turn will reach the necessary indication criterion for the condition optimal humidity material at which the maximum density of the non-metallic substance will be achieved. When backfilling (for example, after a dug pit), it is necessary to use tamping devices that, under a certain pressure, allow you to achieve the required sand density.

What data is taken into account in the process of calculating the Purchase?

In any design documentation for a construction site or the construction of a roadway, the coefficient of relative sand compaction is indicated, which is necessary for high-quality work. As you can see, the technological chain for the delivery of non-metallic material - from the quarry directly to the construction site, changes in one direction or another, depending on natural conditions, methods of transportation, storage of material, etc. builders know to determine the amount required required volume sand for a specific job, the desired volume will need to be multiplied by the value of the Purchase specified in the project documentation. The extraction of material from the quarry results in the material having loosening characteristics and a natural decrease in weight density. This important factor will need to be taken into account, for example, when transporting a substance over long distances.

Under laboratory conditions, a mathematical and physical calculation is made, which will ultimately show the required sand compaction coefficient during transportation, including:

Determination of the strength of particles, caking of the material, as well as the size of the grains - the physical and mechanical method of calculation is used;
With the help of a laboratory determination, the parameter of relative humidity and the maximum density of non-metallic material is revealed;
Under conditions of natural location, the bulk density of a substance is determined empirically;
For transportation conditions, an additional method for calculating the density coefficient of a substance is used;
Climatic and weather characteristics are taken into account, as well as the influence of negative and positive parameters of the ambient temperature.

“In each project documentation for the implementation of construction and road works, these parameters are mandatory for keeping records and making a decision on the use of sand in the production cycle.»

Compaction parameters during production work

In any working documentation, you will come across the fact that the coefficient of the substance will be indicated depending on the nature of the work, so below are the calculation coefficients for some types of production work:

For backfilling of the pit - 0.95 Kupl;
For backfilling of the sinus regime - 0.98 Kupl;
For backfilling trench pits - 0.98 Kupl;
For restoration work everywhere underground equipment engineering networks located near the carriageway of the roadway - 0.98 Kupl-1.0 Kupl.

Based on the above parameters, we can conclude that the tamping process in each case will have individual characteristics and parameters, while various equipment and ramming equipment.

“Before carrying out construction and road works, it is necessary to study in detail the documentation, where in without fail the density of the sand for the production run will be indicated.”

Violation of the requirements of the Purchase will lead to the fact that all work will be recognized as of poor quality, and will not comply with GOST and SNiP. In any case, supervisory authorities will be able to identify the cause of the defect and poor quality of work, where the requirements for sand compaction were not met during a specific area of production work.

Video. Sand compaction test

The compaction factor must be determined and taken into account not only in the narrowly focused areas of construction. Specialists and ordinary workers performing standard procedures use of sand, are constantly faced with the need to determine the coefficient.

The compaction factor is actively used to determine the volume of bulk materials, in particular sand,
but also applies to gravel, soil. Most exact method definition of compaction is a weight method.

wide practical use I did not find it due to the inaccessibility of equipment for weighing large volumes of material or the lack of sufficiently accurate indicators. An alternative option for deriving the coefficient is volumetric accounting.

Its only drawback is the need to determine compaction at different stages. This is how the coefficient is calculated immediately after extraction, during storage, during transportation (relevant for road transport deliveries) and directly at the end consumer.

Factors and properties of construction sand

The compaction coefficient is the dependence of the density, that is, the mass of a certain volume, of the controlled sample to the reference standard.

It should be borne in mind that all types of mechanical, external seals can only affect upper layer material.

The main types and methods of compaction and their effect on the upper layers of the soil are presented in the table.

To determine the volume of material to be backfilled, the relative compaction factor must be taken into account. It is related to the change physical properties excavation after sand excavation.

When pouring the foundation, you need to know correct proportions sand and cement. By clicking on familiarize yourself with the proportions of cement and sand for the foundation.

Cement is a special bulk material, which in its composition is a mineral powder. about different grades of cement and their applications.

With the help of plaster, the thickness of the walls is increased, which increases their strength. find out how long the plaster dries.

P \u003d ((m - m1) * Pv) / m-m1 + m2-m3, where:

m is the mass of the pycnometer when filled with sand, g;
m1 is the weight of an empty pycnometer, g;
m2 is the mass with distilled water, g;
m3 is the weight of the pycnometer with the addition of distilled water and sand, and after getting rid of air bubbles
Pw - water density

In this case, several measurements are carried out, based on the number of samples provided for verification. Results should not differ by more than 0.02 g/cm3. In the case of large received data, the arithmetic mean is displayed.

Estimates and calculations of materials, their coefficients are the main component of the construction of any objects, as it helps to understand the quantity required material and, accordingly, costs.

For a correct estimate, it is necessary to know the density of the sand, for this, information provided by the manufacturer, based on surveys, and the relative compaction factor upon delivery are used.

Because of what the level of the loose mixture and the degree of compaction change

Sand passes through a rammer, not necessarily special, perhaps in the process of moving. It is quite difficult to calculate the amount of material obtained at the output, taking into account all variables. For accurate calculation it is necessary to know all the impacts and manipulations carried out with sand.

The final coefficient and degree of compaction depends on various factors:

method of transportation, the more mechanical contact with irregularities, the stronger the seal;
route duration, information is available to the consumer;
the presence of damage from mechanical influences;
the amount of impurities. In any case, foreign components in the sand give it more or less weight. The cleaner the sand, the closer the density value to the reference;
the amount of moisture that has entered.

Immediately after purchasing a batch of sand, it should be checked.

What samples are taken to determine the bulk density of sand for construction

You need to take samples:

for a batch of less than 350 tons - 10 samples;
for a batch of 350-700 tons - 10-15 samples;
when ordering more than 700 tons - 20 samples.

Take the obtained samples to a research institution for examinations and comparison of quality with regulatory documents.

Conclusion

The required density is highly dependent on the type of work. In general, compaction is necessary for the formation of the foundation, backfilling of trenches, creating a pillow under the roadbed, etc. It is necessary to take into account the quality of tamping, each type of work has different requirements to seal.

In construction highways a skating rink is often used; in hard-to-reach places, a vibrating plate of various capacities is used.

So, to determine the final amount of material, it is necessary to lay down the compaction coefficient on the surface during tamping, this ratio is indicated by the manufacturer of tamping equipment.

Is always the relative index of the density coefficient is taken into account, since soil and sand tend to change their performance based on the level of humidity, type of sand, fraction and other indicators.

Everything Construction Materials, especially mixtures, have a number of indicators, the value of which plays an important role in the process of construction work and largely determines the final result. For bulk materials, such indicators are the size of the fraction and the compaction coefficient. This indicator fixes how much the external volume of the material decreases when it is compacted (rammed). This factor is most often taken into account when working with building sand, however, both sand and gravel mixtures and just gravel itself can also change their value during compaction.

Why do you need to know the compaction factor of a sand-gravel mixture?

Any loose mixture, even in the absence of mechanical action, changes its density. This is easy to understand by remembering how a mountain of sand that has just been dug out changes over time. The sand becomes denser, then, when re-treated, it returns to more loose appearance by changing the amount of space occupied. How much this volume increases or decreases is the density coefficient.

It fixes not the volume lost during artificial tamping (for example, during the construction of the foundation under the foundation, when the mixture is rammed with a special mechanism), but the natural changes that occur with the material during transportation, loading and unloading. This allows you to determine the losses incurred during transportation and more accurately calculate the required volume of delivery of the sand and gravel mixture. At the same time, it should be noted that the size of the compaction coefficient of the sand-gravel mixture is influenced by many indicators, such as the size of the lot, the method of transportation, and the initial quality of the sand itself.

In construction work, information about the volume of compaction is used in the calculation and preparation for construction. In particular, based on this parameter, certain indicators are set for the depth of the trench, the thickness of the backfill for future pillow from a sand and gravel mixture, the intensity of tamping and much more. Among other things, the season is taken into account, as well as climatic indicators.

The size of the sand/gravel compaction factor may vary for different materials, each type of bulk mixture has its own standard indicators that guarantee its quality. It is believed that the average size of the compaction coefficient for a sand-gravel mixture is about 1.2 (these data are indicated in GOST). It should be borne in mind that the same indicator, but separately for sand and gravel, will be different, from 1.1 to 1.4, depending on the type and size of the fractions.

The crushed stone compaction coefficient is a dimensionless indicator that characterizes the degree of change in the volume of material during tamping, shrinkage and transportation. It is taken into account when calculating the required amount of filler, checking the mass of products delivered to order and when preparing bases for bearing structures along with bulk density and other characteristics. The standard number for a particular brand is determined in the laboratory, the real one is not a static value and the same depends on a number of inherent properties and external conditions.

The compaction factor is used when working with bulk building materials. Their standard number varies from 1.05 to 1.52. The average value for gravel and granite crushed stone is 1.1, expanded clay - 1.15, sand and gravel mixtures- 1.2 (read about the degree of sand compaction). The actual number depends on the following factors:

Size: the smaller the grain, the more efficient the compaction.
Flakiness: gravel needle and irregular shape compacted worse than cuboid filler.
Duration of transportation and type of transport used. The maximum value is achieved with the delivery of gravel and granite stone in dump trucks and railway wagons, the minimum - in sea containers.
Conditions for backfilling in a car.
Method: with manual it is more difficult to achieve the desired parameter than with the use of vibration equipment.

In the construction industry, the compaction factor is taken into account primarily when checking the mass of the purchased bulk material and backfilling of foundations. The design data indicates the density of the structure skeleton. The indicator is taken into account in combination with other parameters of building mixtures, humidity plays an important role. The degree of compaction is calculated for crushed stone with a limited volume of walls; in reality, such conditions are not always created. A prime example serves as a backfilled foundation or drainage cushion (fractions go beyond the interlayer), an error in the calculation is inevitable. To neutralize it, gravel is purchased with a margin.

Ignoring this coefficient when drawing up a project and carrying out construction work leads to the purchase of an incomplete volume and deterioration performance characteristics erected structures. With a correctly selected and implemented degree of compaction, concrete monoliths, building and road foundations withstand the expected loads.

The degree of compaction on the site and during transportation

The deviation in the volume of crushed stone loaded and delivered to the end point is a well-known fact, the stronger the vibration during transportation and the further the distance, the higher its degree of compaction. To check the compliance of the amount of material brought in, an ordinary tape measure is most often used. After measuring the body, the resulting volume is divided by a coefficient and compared with the value indicated in the accompanying documentation. Regardless of the size of the fractions, this indicator cannot be less than 1.1; with high requirements for the accuracy of delivery, it is negotiated and prescribed separately in the contract.

If this point is ignored, claims against the supplier are unfounded, according to GOST 8267-93, the parameter does not apply to mandatory characteristics. The default for crushed stone is taken equal to 1.1, the delivered volume is checked at the receiving point, after unloading the material takes up a little more space, but over time it shrinks.

The required degree of compaction in the preparation of the foundations of buildings and roads is specified in the project documentation and depends on the expected weight loads. In practice, it can reach 1.52, the deviation should be minimal (no more than 10%). Ramming is carried out in layers with a thickness limit of 15-20 cm and the use of different fractions.

The road surface or foundation pads are poured onto prepared sites, namely, with leveled and compacted soil, without significant level deviations. The first layer is formed from large gravel or crushed granite, the use of dolomite rocks must be allowed by the project. After preliminary compaction, the pieces are cleaved in smaller fractions, if necessary, up to the filling of sand or sand and gravel mixtures. The quality of the work is checked separately on each layer.

Compliance of the obtained ramming result with the design one is evaluated using special equipment- density meter. The measurement is carried out under the condition that the content is not more than 15% of grains with a size of up to 10 mm. The tool is immersed by 150 mm strictly vertically with the necessary pressure, the level is calculated from the deviation of the arrow on the device. To eliminate errors, measurements are taken at 3-5 points in different places.

Bulk density of crushed stone of different fractions

In addition to the tamping factor, to determine the exact amount of material required, you need to know the dimensions of the backfilled structure and specific gravity placeholder. The latter is the ratio of the mass of crushed stone or gravel to the volume they occupy and depends primarily on the strength of the original rock and size.

Type	Bulk density (kg/m3) at fraction size:
Type	0-5	5-10	5-20	20-40	40-70
granite	1500	1430	1400	1380	1350
Gravel		1410	1390	1370	1340
			1320	1280	1120

The specific gravity must be indicated in the product certificate, in the absence of accurate data, you can find it yourself empirically. This will require a cylindrical container and scales, the material is poured without tamping and weighed before and after filling. The quantity is found by multiplying the volume of the structure or base by the value obtained and by the degree of compaction indicated in the design documentation.

For example, to fill 1 m2 of a pillow 15 cm thick from gravel with a fraction size in the range of 20-40 cm, 1370 × 0.15 × 1.1 = 226 kg will be needed. Knowing the area of the formed base, it is easy to find the total volume of the aggregate.

Density indicators are also relevant in the selection of proportions during cooking. concrete mixtures. For foundation structures, it is recommended to use crushed granite with a fraction size in the range of 20-40 mm and a specific gravity of at least 1400 kg/m3. Compaction in this case is not carried out, but attention is paid to flakiness - for the manufacture of concrete products, a cube-shaped aggregate with a low content of irregularly shaped grains is required. Bulk density is used when converting volume proportions to mass proportions and vice versa.