What is the compaction coefficient of sand? What is the compaction coefficient of bulk materials? Sand-gravel mixture compaction coefficient Compaction coefficient pgs during backfilling.

In preparation for development, they conduct special studies and tests to determine the suitability of the site for the upcoming work: they take soil samples, calculate the level of occurrence groundwater and examine other soil features that help determine the feasibility (or lack thereof) of construction.

Carrying out such activities helps to improve technical performance, as a result of which a number of problems that arise during the construction process are solved, for example, soil subsidence under the weight of the structure with all the ensuing consequences. Its first external manifestation looks like the appearance of cracks on the walls, and in combination with other factors it leads to partial or complete destruction of the object.

Compaction factor: what is it?

By soil compaction coefficient we mean a dimensionless indicator, which, in fact, is a calculation from the ratio of soil density/soil density max. The soil compaction coefficient is calculated taking into account geological indicators. Any of them, regardless of the breed, is porous. It is permeated with microscopic voids that are filled with moisture or air. When the soil is excavated, the volume of these voids increases significantly, which leads to an increase in the looseness of the rock.

Important! The density of bulk rock is much less than the same characteristics of compacted soil.

It is the soil compaction coefficient that determines the need to prepare the site for construction. Based on these indicators, sand cushions are prepared for the foundation and its base, further compacting the soil. If this detail is missed, it may cake and begin to sag under the weight of the structure.

Soil compaction indicators

The soil compaction coefficient shows the level of soil compaction. Its value varies from 0 to 1. For a concrete base strip foundation a score of >0.98 points is considered normal.

Specifics of determining the compaction coefficient

The density of the soil skeleton, when the subgrade is subjected to standard compaction, is calculated in laboratory conditions. Schematic diagram research consists of placing a soil sample in a steel cylinder, which is compressed under the influence of external rough mechanical force- impacts from a falling load.

Important! The highest soil density values ​​are observed in rocks with moisture content slightly above normal. This relationship is depicted in the graph below.

Each subgrade has its own optimal moisture content, at which the maximum level of compaction is achieved. This indicator is also studied in laboratory conditions, giving the breed different humidity and comparing compaction performance.

Real data is the final result of research, measured at the end of all laboratory work.

Methods for compaction and coefficient calculation

Geographical location determines high-quality composition soils, each of which has its own characteristics: density, humidity, ability to subsidence. That is why it is so important to develop a set of measures aimed at qualitatively improving the characteristics for each type of soil.

You already know the concept of compaction coefficient, the subject of which is studied strictly in laboratory conditions. This work is carried out by the relevant services. The soil compaction indicator determines the method of influencing the soil, as a result of which it will receive new strength characteristics. When carrying out such actions, it is important to consider the percentage of gain applied to obtain the desired result. Based on this, the soil compaction coefficient is calculated (table below).

Typology of soil compaction methods

There is a conventional system for subdividing compaction methods, groups of which are formed based on the method of achieving the goal - the process of removing oxygen from soil layers at a certain depth. Thus, a distinction is made between superficial and in-depth research. Based on the type of research, specialists select an equipment system and determine the method of its use. Soil research methods are:

• static;
• vibration;
• percussion;
• combined.

Each type of equipment displays a method of applying force, such as a pneumatic roller.

Partially, such methods are used in small private construction, others exclusively in the construction of large-scale objects, the construction of which is agreed with local authorities, since some of these buildings can have an impact not only on a given area, but also on surrounding objects.

Compaction coefficients and SNiP standards

All construction-related operations are clearly regulated by law and are therefore strictly controlled by relevant organizations.

Soil compaction coefficients are determined by SNiP clause 3.02.01-87 and SP 45.13330.2012. The steps described in regulatory documents, were updated and updated in 2013-2014. They describe seals for various kinds soil and soil cushions used in the construction of foundations and buildings of various configurations, including underground ones.

How is the compaction coefficient determined?

The easiest way to determine the coefficient of soil compaction is using the cutting ring method: a metal ring of a selected diameter and a certain length is driven into the soil, during which the rock is tightly fixed inside a steel cylinder. After this, the mass of the device is measured on a scale, and at the end of weighing, the weight of the ring is subtracted, obtaining the net mass of the soil. This number is divided by the volume of the cylinder and the final density of the soil is obtained. After which it is divided by the indicator of the maximum possible density and a calculated value is obtained - the compaction coefficient for a given area.

Examples of calculating the compaction factor

Let's consider determining the soil compaction coefficient using an example:

• the value of the maximum soil density is 1.95 g/cm 3 ;
• cutting ring diameter - 5 cm;
• cutting ring height - 3 cm.

It is necessary to determine the soil compaction coefficient.

With such practical task It's much easier to deal with than it might seem.

To begin with, drive the cylinder completely into the ground, and then remove it from the soil so that interior space remained filled with earth, but no accumulation of soil was noted outside.

Using a knife, the soil is removed from the steel ring and weighed.

For example, the mass of the soil is 450 grams, the volume of the cylinder is 235.5 cm 3. Calculating using the formula, we obtain the number 1.91 g/cm 3 - soil density, from which the soil compaction coefficient is 1.91/1.95 = 0.979.

The construction of any building or structure is a responsible process, which is preceded by the even more important moment of preparing the site to be built, designing the proposed buildings, and calculating the total load on the ground. This applies to all buildings without exception that are intended for long-term use, the duration of which is measured in tens or even hundreds of years.

Sand (K upl) is known not only by specialists working in design organizations, but also by operators whose main activity is construction. It is calculated in order to compare the actual density in a certain area with the value prescribed regulations. The compaction coefficient of bulk materials is important criterion, which evaluates the quality of preparation for the main types of work on construction sites.

What is it?

To compaction characterizes the density that the soil has in a particular area; it refers to the same indicator of the material that has undergone standard compaction under laboratory conditions. It is this figure that is used when assessing the quality of work performed. This coefficient determines how well the soil on the site complies with the requirements of GOST 8736-93 and 25100-95.

At various works sand may have different indicator density. All these standards are prescribed in SNiP 2.05.02-85, table 22. They are also usually indicated in project documents; in most cases this figure ranges from 0.95 to 0.98.

What causes the density coefficient to change?

If you do not understand what sand compaction is, then it is almost impossible to correctly calculate the amount of material during construction. After all, you need to clearly know how various manipulations affected the soil. What coefficient of relative sand compaction we will ultimately obtain may depend on many factors:

• on the method of transportation;
• how long the route was;
• whether mechanical damage has appeared;
• the presence of foreign inclusions;
• moisture ingress.

Naturally, if you ordered sand, you simply must check it on the spot, because late complaints will be completely inappropriate.

Why take into account the relative coefficient when building roads

This indicator for a sand cushion must be calculated, and this is explained by a common physical phenomenon that is familiar to any person. To understand this, remember how loosened soil behaves. At first it is loose and voluminous. But after a couple of days it will settle and become much denser.

The same fate awaits any other bulk material. After all, its density increases in the warehouse under the pressure of its own weight. Then, during loading, it is loosened, and directly at the construction site, the sand is again compacted with its own weight. In addition, moisture affects the soil. The sand cushion will be compacted during any type of work, be it construction road surface, or backfilling the foundation. For all these factors, the corresponding GOSTs (8736-93 and 25100-95) were calculated.

How to use a relative indicator

For any construction work ah, one of the most important stages The preparation of estimates and calculations of coefficients is considered. This is necessary in order to correctly draw up the project. If it is important to find out how much sand will compact when transported in a dump truck or railway car, it is enough to find the required indicator in GOST 8735-88 and divide the required volume by it.

It is also necessary to take into account what kind of work is ahead. Is that what you're going to do sand cushion under the road surface, or backfilling of the foundation. In each situation, compaction will proceed differently.

For example, when backfilling sand, a dug pit is filled. Tamping is done using various equipment. Sometimes compaction is done with a vibrating plate, but in some cases a roller is required. Accordingly, the indicators will be different. Keep in mind that the soil changes its properties during excavation. So the amount of backfill must be calculated taking into account the relative indicator.

Table of compaction coefficient values ​​depending on the purpose of sand.

The compaction coefficient of any bulk material shows how much its volume can be reduced with the same mass due to compaction or natural shrinkage. This indicator is used to determine the amount of filler both during purchase and during the construction process itself. Since the bulk weight of crushed stone of any fraction will increase after compaction, it is necessary to immediately lay down a supply of material. And in order not to purchase too much, a correction factor will come in handy.

The compaction coefficient (K y) is an important indicator that is needed not only for correct formation ordering materials. Knowing this parameter for the selected fraction, it is possible to predict further shrinkage of the gravel layer after loading it building structures, as well as the stability of the objects themselves.

Since the compaction ratio represents the degree of volume reduction, it varies under the influence of several factors:

1. Loading method and parameters (for example, from what height is backfilling performed).

2. Features of transport and the duration of the journey - after all, even in a stationary mass, gradual compaction occurs when it sags under its own weight.

3. Fractions of crushed stone and grain contents of smaller size than the lower limit of a specific class.

4. Flakiness - needle-shaped stones do not give as much sediment as cuboid ones.

The strength subsequently depends on how accurately the degree of compaction was determined. concrete structures, building foundations and road surfaces.

However, do not forget that compaction on the site is sometimes carried out only on the top layer, and in this case calculated coefficient does not quite correspond to the actual shrinkage of the pillow. Home craftsmen and semi-professional construction teams from neighboring countries are especially guilty of this. Although, according to technology requirements, each layer of backfill must be rolled and checked separately.

Another nuance - the degree of compaction is calculated for a mass that is compressed without lateral expansion, that is, it is limited by the walls and cannot spread out. At the site, such conditions for backfilling any fraction of crushed stone are not always created, so a small error will remain. Take this into account when calculating the settlement of large structures.

Sealing during transport

Finding some standard compressibility value is not so easy - too many factors influence it, as we discussed above. The compaction coefficient of crushed stone can be indicated by the supplier in accompanying documents, although GOST 8267-93 does not directly require this. But transporting gravel, especially large batches, reveals a significant difference in volumes during loading and at the final point of delivery of the material. Therefore, an adjustment factor that takes into account its compaction must be included in the contract and monitored at the collection point.

The only mention from the current GOST is that the declared indicator, regardless of the fraction, should not exceed 1.1. Suppliers, of course, know this and try to keep a small supply so that there are no returns.

The measurement method is often used during acceptance, when crushed stone for construction is brought to the site, because it is ordered not in tons, but in cubic meters. When the transport arrives, the loaded body must be measured from the inside with a tape measure to calculate the volume of gravel delivered, and then multiply it by a factor of 1.1. This will allow you to roughly determine how many cubes were put into the machine before shipping. If the figure obtained taking into account the compaction is less than that indicated in the accompanying documents, it means that the car was underloaded. Equal or greater - you can command unloading.

Compaction on site

The above figure is taken into account only for transportation. Under construction site conditions, where crushed stone is compacted artificially and using heavy machines (vibrating plate, roller), this coefficient can increase to 1.52. And the performers need to know the shrinkage of the gravel backfill for sure.

Typically the required parameter is specified in project documentation. But when exact value no need, use average indicators from SNiP 3.06.03-85:

• For durable crushed stone of fraction 40-70, a compaction of 1.25-1.3 is given (if its grade is not lower than M800).
• For rocks with a strength of up to M600 - from 1.3 to 1.5.

For small and medium size classes of 5-20 and 20-40 mm, these indicators have not been established, since they are more often used only when decluttering the upper load-bearing layer of grains 40-70.

Laboratory research

The compaction factor is calculated based on laboratory test data, where the mass is compacted and tested for various devices. There are methods here:

1. Substitution of volumes (GOST 28514-90).

2. Standard layer-by-layer compaction of crushed stone (GOST 22733-2002).

3. Express methods using one of three types of density meters: static, water balloon or dynamic.

Results can be obtained immediately or after 1-4 days, depending on the study chosen. One sample for a standard test will cost 2,500 rubles, and at least five of them will be needed in total. If data is needed during the day, express methods are used based on the results of selecting at least 10 points (850 rubles for each). Plus you will have to pay for the departure of a laboratory assistant - about 3 thousand more. But during the construction of large projects it is impossible to do without accurate data, and even more so without official documents confirming the contractor’s compliance with the project requirements.

How to find out the degree of compaction yourself?

IN field conditions and for the needs of private construction, it will also be possible to determine the required coefficient for each size: 5-20, 20-40, 40-70. But to do this, you first need to know them bulk density. It varies depending on the mineralogical composition, although slightly. Crushed stone fractions have a much greater influence on the volumetric weight. For calculations, you can use averaged data:

More accurate density data for a specific fraction is determined in the laboratory. Or by weighing a known volume of building rubble, followed by a simple calculation:

• Bulk weight = mass/volume.

After this, the mixture is rolled to the state in which it will be used on site and measured with a tape measure. The calculation is made again using the above formula, and as a result, two different densities are obtained - before and after compaction. By dividing both numbers, we find out the compaction coefficient specifically for this material. If the sample weights are the same, you can simply find the ratio of the two volumes - the result will be the same.

Please note: if the indicator after compaction is divided by the initial density, the answer will be greater than one - in fact, this is the material reserve factor for compaction. It is used in construction if the final parameters of the gravel bed are known and it is necessary to determine how much crushed stone of the selected fraction to order. When calculated back, the result is a value less than one. But these numbers are equivalent and when making calculations it is only important not to get confused which one to take.

Why the compaction coefficient of sand is needed, and what importance this indicator plays in construction, is probably known to every builder and those who are directly involved with this non-metallic material. A physical parameter has a special meaning, which is expressed through the purchase value. The calculation parameter is necessary so that it is possible to directly compare the actual density of the material on the spot. a certain area area with the required values, which are prescribed in 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 on the site is assessed construction sites using bulk non-ore substances.

Basic concepts of compaction factor

According to generally accepted formulations, the compaction coefficient of sand is the density value that is characteristic of a specific type of soil on a certain area of ​​the site to the same value of the material that transfers standard compaction modes in laboratory conditions. Ultimately, it is this figure that is used to assess the quality of the final construction work. In addition to the above technical regulations, to determine the compaction coefficient of sand during compaction, GOST 8736-93 is used, as well as according to GOST 25100-95.

At the same time, it must be remembered that in the work 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 corresponding technological regulations SNIP 2.05.02-85 in part of Table No. 22. This indicator is the most important in the calculation, and the main design documentation indicates these values, which in the design calculation range range from 0, 95 to 0.98.

How does the sand density parameter change?

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

• The method of transporting a substance, starting from the starting point;
• Length of 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 the laboratory.

Features of backfill calculation

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

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

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

Any design documentation for a construction project or road construction indicates the coefficient of relative sand compaction, which is necessary for high-quality work. As you can see, the technological chain of delivery of non-metallic material is from the quarry directly to construction site changes in one direction or another, depending on natural conditions, methods of transportation, storage of material, etc. builders know that in order to determine the required amount of sand for a specific job, the required volume will need to be multiplied by the value of the purchase specified in the design documentation. Removing material from a 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.

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

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

“In each design documentation for the implementation of construction and road works, these parameters are mandatory for keeping records and making decisions about the use of sand in the production cycle.”

Compaction parameters during production work

In any working documentation you will be faced with 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 a pit - 0.95 Kupl;
• To fill the sinus regime - 0.98 Cupl;
• For backfilling trench holes - 0.98 Kupl;
• For restoration work everywhere underground equipment utility networks located near the roadway - 0.98 Buy-1.0 Buy.

Based on the above parameters, we can conclude that the compaction process in each specific case will have individual characteristics and parameters, and will involve various techniques and compaction equipment.

“Before carrying out construction and road work, it is necessary to study in detail the documentation, which will necessarily indicate the density of sand for the production cycle.”

Violation of the requirements of the Buyer will lead to the fact that all work will be considered 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 section of production work.

Video. Sand compaction test