GOST 32824-2014 motor roads for general use. natural sand. technical requirements (edition as amended)

Sand and sand: what are the differences

Sand and sand are different materials. The first contains a large amount of impurities, the second - no more than 5–7% of fine clay and dusty particles. In other words, sand is a much cleaner and more homogeneous material. Different formulations provide different properties and applications.

Sand is much more free flowing compared to sand gravel

The main differences between sand and sand:

• Compared to sand, sandy soil holds its shape much better, it has a higher coefficient of friction - therefore, it is suitable for embankments.
• Due to the inclusion of clay, it has higher binding properties - therefore it is convenient for leveling areas.
• It costs less than sand - it is optimal for filling large areas and filling holes.

However, this material cannot be used as a substitute for sand. Its characteristics are significantly lower not only in comparison with high-quality river and washed sand, but also simple open-pit sand.

Sandy soil is not suitable for creating building mixtures, but is used exclusively for "rough" work. It is indispensable for a large volume of zero-cycle operations, when you need to raise a site or unload a site, as it has a low price.

Similarities between sand and gravel

Fields of application - the only thing in which leveling soil and sandy loam are similar. Both materials are in demand when carrying out earthworks. They fill pits, trenches, use them to level the landscape and create embankments.

If the territory is intended for agriculture, the leveling soil and sandy soil are suitable for filling the site. At the same time, fertile soil is poured on top. Also, materials are used in road construction, when laying routes and arranging dirt roads, in construction for filling foundations. However, it all depends on the percentage of sand and clay, as well as the proximity of groundwater.

Soil properties

The porosity of the soil is the ratio of the volume of the mineral part of the soil to the volume of the pores. The higher the e value, the looser the soil. The mechanical properties of the soil decrease with increasing e. Deeper soil layers have higher density and lower porosity.

Clay soils, such as clay, sandy loam and loam, with an increase in soil moisture, pass into a plastic state. This happens when a certain humidity value is reached. WP

, after which the soil begins to roll out. With a further increase in humidity above the valueWL , the soil becomes fluid. The quantity that determines the degree of plasticity is called the yield indexJL ... The flow rate is a characteristic of the moisture content of clay soil. AtJL ≤ 0 - the soil is dry and hard; at0 the soil is plastic, and atJL ≥ 1 - fluid soil.

Soil porosity and plasticity index are the most important indicators in determining the bearing capacity of the soil. According to SNiP Foundations of buildings and structures, the design resistance of soils is determined as: Design resistance of clay soils

Design resistance of sandy soils

Conclusions from the tables:

• the larger the fraction of sand, the greater its bearing capacity;
• almost all soils decrease their bearing capacity with an increase in moisture, some by 2.5 times, however, this dependence is most pronounced in clay and decreases with an increase in the proportion and size of sand particles;
• compacted soils are more durable than uncompacted soils. This dependence is most pronounced in clays, where compacted soil is almost 2.5 times more hardy than unconsolidated soil.

According to ENiR Е2В1

The difficulty of soil development is determined by:

• for mechanized work - according to table 1 and table 2 of Chapter 1;
• for manual work - according to table 1 of Chapter 2.

General part of ENiR Е2В1

p. 5. Frozen soils include soils that contain ice, which changes their structure and properties inherent in soils before freezing.

p.6. Pebble and sandy soils with a negative temperature, but not consolidated by ice due to their low moisture content, as well as coarse and rocky soils in winter, are normalized as non-frozen soils.

Chapter 1 ENiR Е2В1:

item 1. The rates and prices of this chapter provide for the development of non-frozen soils of groups I-IV in their natural state. Heavy soils, as well as soils with impurities, the development of which is difficult in their natural state, are subject to preliminary loosening. The need to loosen the soil is determined in each case based on local conditions (soil density, nature and amount of impurities, power and condition of the machine).

item 2. The development of previously loosened non-frozen soils by machines is standardized as follows:

when working with excavators - according to the standards for soils one group lower (soils II to I; III to II; IV to III);

when working with scrapers, bulldozers, graders and grader-elevators - on the same groups of soils.

Chapter 2 ENiR Е2В1:

p. 1. The distribution of soils into groups depending on the difficulty of their manual development is given in Table. 1 (Chapters 2).

Differences between planning and sand soils

• Composition and properties. According to the ratio of components, the leveling soil is divided into the following types:
  • Loam. It can contain up to 10% sand and up to 30% clay. The last indicator most of all determines the properties of loam. Due to the high clay content, loamy soils have low water permeability. At the same time, the particles of the material are perfectly connected and form a monolith.
  • Sand soil. Sandy loam, depending on the place of extraction, can contain from 10 to 30% clay particles. Almost all the rest, with the exception of small inclusions, is occupied by sand. Therefore, sandy loam is more permeable to moisture, in contrast to loam. It is also less dense and settles faster.
  • Coarse soil. In the composition of over 50% of stones with a diameter of more than two millimeters. The rest is clay or sand. This is a solid soil that practically does not shrink under the influence of physical exertion. Depending on the filler - clay (less than 30%) or sand (less than 40%) - its heaving is determined. This is the ability to expand in volume when frozen. If clay predominates in coarse soil in addition to rock fragments, it will swell in the frost. If there is sand, the soil will practically not change its volume.
• Extraction. Sandy loam is mined in sand pits. This is a recycled material that remains after the extraction of clean sand. Previously, sandy soil was considered a waste product, so it was taken to a landfill. But now it is a material in demand.

Leveling soil can also be mined in quarries. However, unlike sandy loam, it is also obtained when laying roads, digging pits and trenches, and developing the bottom of reservoirs.

At first glance, sandy loam resembles ordinary sand, but there is a big difference in their compositions.

Classification of soils in construction by the type of structural ties

According to GOST 25100-2011, all bases are divided into three large classes: rocky, dispersed and frozen.Sometimes the species formed as a result of human activity - technogenic - are distinguished into a separate category.

All types of bases can be frozen. The connection between particles is provided not only by structural forces, but also by cryogenic bonds (ice). The strength of such soils is great, but only in a frozen state.

Rocky

Rocky soils are a very solid mass with rigid structural bonds. Bases can be of various origins, physical and mechanical characteristics. Such species are quite rare, they are mainly represented by such soils:

• granite;
• quartzite;
• marble;
• basalt;
• sandstone;
• tuff;
• limestone;
• gypsum;
• shales.

Sandstone occurrence.

Rocky soils do not compress well, do not form voids and cracks. This soil is ideal for the construction of unburied foundations. They practically do not deform, so there is no likelihood of uneven settlement, which is dangerous for buildings and lead to the appearance of inclined cracks on the walls. Depending on the strength, rocky soils can be:

• very strong, strong, medium-strength and low-strength (rocky);
• lowered — strong, with low strength and with very low strength (semi-rock).

Dispersed

These types of bases are the most common. The bonds between soil particles here can be mechanical or water-colloidal. The latter are provided by the interaction of soil and water particles. Almost all of these soils are of sedimentary origin.

The table shows the division of dispersed soils into groups and subgroups.

Peat.

Classification of soils according to the degree of heaving

Frost heaving is one of the most pressing construction problems in cold regions where temperatures drop below freezing in winter. This phenomenon is caused by the simultaneous exposure of the soil to moisture and cold. At the same time, the base increases in size and puts pressure on the sole and the side surface of the foundations.

To avoid negative consequences, it is important to take timely measures to combat heaving. To do this, before the start of construction, it will be necessary to determine which of the groups the types of soil located on the site under the house belong to .. The table below is based on GOST 25100-2011 and SP 243.1326000.2015 (Appendix A)

It shows soils and their tendency to the emergence of frost heaving forces

The table below is based on GOST 25100-2011 and SP 243.1326000.2015 (Appendix A). It shows soils and their tendency to the emergence of frost heaving forces.

The numbers in the type of terrain by the nature of soil moisture are determined according to SP 34.13330.2012 (Appendix B) and mean:

• 1 - in the presence of surface moisture removal from the building and a deep location of the groundwater level (GWL);
• 2 - in the absence of surface moisture removal and the deep location of the groundwater level;
• 3 - in the absence of surface moisture removal and a high GWL location.

Gravel (rounded) and crushed stone (with sharp edges).

During construction, it is important to remember that absolutely non-porous soils do not exist. Swelling appears not because of the base, but because of moisture and freezing temperatures

Any soil in winter with water in it can put pressure on foundations. The group of conditionally non-porous grounds includes those that extremely rarely lead to the occurrence of a dangerous phenomenon. In these cases, special measures to protect the building structures from frost heaving are most often not provided.

Measures to prevent frost heaving forces include waterproofing, insulation, drainage, insulated blind area, storm sewer installation. These measures are provided in a complex for all types of heaving soils:

• slightly puffy;
• heaving;
• strongly bulging;
• excessively bushy.

Density and bearing capacity

Sandy soil of any class compresses quickly and well under load. According to this indicator, it is dense and medium density. Dense is usually located at a depth of more than 1.5 m. Such an arrangement, under the pressure of the overlying layers, for a long time makes it the most dense and suitable base for the foundation.

Medium density soil is one that lies above 1.5 m or is artificially compacted. Its load-bearing qualities are inferior and it is prone to more draft.

In sandy soil, density and bearing capacity are mutually related. In gravelly sand with an average density, the bearing capacity is 5 kg per cm2, with a high density - more than 6 kg per cm2. In a large one with an average density, this capacity is 4 kg per cm2, and at a high density - 5–6 kg per cm2. Medium sand has the following parameters: at high density - 4–5 kg per cm2, at average - 3-4 kg per cm2. Fine or dusty has a maximum bearing capacity in a dense state of 3 kg per cm2, on average - 2.5 kg per cm2.

When saturated with moisture, medium and small reduce the bearing capacity by 2 kg per cm2.

Sand and soil: what are the differences

If we compare sandy soil with soils for landscaping, the difference is obvious. The soils are intended for planting green spaces and contain humus, due to which they are distinguished by their fertility. It is ineffective to use sand soil instead of them; it will not provide the plants with the necessary conditions for growth.

The main field of application of the soil is planting

There are several types of soil for landscaping:

• Milling - for garden trees, shrubs and lawns, contains 70% low-lying peat, vegetable soil, washed sand, organic and mineral additives.
• Fertile - for seedlings, vegetables and flowers, contains top peat, sand and fertile soil.
• Soil - a balanced soil for gardening and landscaping, obtained naturally.
• Vegetable - for landscaping large areas and enriching the soil, used to increase yields.
• Peat and mixtures based on it are rich in organic trace elements and have high moisture permeability, are used to improve the quality of the soil.

The leveling soil is as close as possible in characteristics to sandy soil. Both materials contain sand, subsoil layers of the earth, clay, dust particles and impurities of rocks. The conditions of production and the scope of application of these materials are similar, the main difference is in the composition and properties. The basis of the sandy soil is sand, the soil is the earth.

Leveling soil provides good mechanical adhesion to all types of soil

The leveling soil does not always have a dark color and is similar to black soil; it can be yellow, orange, reddish, depending on the composition. It is usually mined not in quarries, but when laying roads, excavating the bottom of reservoirs, digging pits, canals and trenches.The choice between sand and leveling soil depends on how much a particular composition is suitable for solving the task at hand.

Moisture absorption and retention

Sandy soil, due to its low porosity, from 0.2 to 0.5, does not retain moisture well. This makes it practically unaffected by frost heaving. What is a positive quality in construction. Due to this, it is possible not to calculate its freezing during engineering and construction work, but the bearing capacity of the sand depends on moisture. And this must be taken into account. Thus, with a decrease in the moisture content of the sand and an increase in its density, the bearing capacity increases.

Based on all the above parameters, the best characteristic of sandy soils for the construction of foundations of buildings and structures, in gravelly and large rocks. They almost do not absorb water, because their density does not depend on the amount of moisture. These types have the highest and constant bearing capacity.

Description, composition and properties

Sandy soil is soil, which can contain 50 percent or more grains of sand less than 2 mm in size. Its parameters are quite diverse, since they are formed as a result of tectonic processes and can vary depending on the origin, in what climatic conditions it was formed, on the soil rocks in the composition. Particles in the structure of sandy soil have different sizes. It can include various minerals such as quartz, spar, calcite, salt and others. But the main element is, of course, quartz sand.

The main characteristics influencing the choice of soil.

• Load bearing capacity. This building material is easily compacted with little effort. According to this parameter, it is divided into dense and medium density. The first usually occurs at a depth below one and a half meters. Long-term pressure from a significant mass of other soils compacts it well, and it is excellent for construction work, in particular, the construction of foundations for various objects. The depth of the second is up to 1.5 meters, or it is compacted using various devices. For these reasons, it is more susceptible to shrinkage and its bearing qualities are somewhat worse.
• Density. It is strongly related to the bearing capacity and can vary for different types of sandy soil; for high and medium bearing density, these indicators differ. The resistance of the material to loads depends on this characteristic.
• Sandy soil with large particles very poorly retains moisture and due to this it practically does not deform during freezing. In this regard, it is possible not to calculate the ability to absorb and retain moisture in its composition. This is a great design advantage. With small ones, on the contrary, he intensively absorbs it. This also needs to be taken into account.
• Soil moisture affects the specific gravity, it is important when transporting soil. It can be calculated based on the natural moisture content of the rock and its state (dense or loose). There are special formulas for this.

Sandy soils are also divided into groups according to their granulometric composition. This is the most important physical parameter on which the properties of natural sandy soils or those that appeared during production depend.

In addition to the physical characteristics described above, there are also mechanical ones. These include:

• strength ability - a feature of the material to resist shear, filtration and water permeability;
• deformation properties, they speak of compressibility, elasticity and the ability to change.

How to determine the group of soil during construction

In case of private construction, instead of full-fledged geological research, manual work can be carried out. There are two methods:

• a fragment of pits;
• hand drilling.

Excerpt of pits for visual study of the soil.

In this case, the soil layers are studied visually.To make it clear how to visually determine what type of soil on the construction site, it is recommended to familiarize yourself with the table below.

Loess soils.

Species overview

For the classification of various soils, including sandy, there is GOST 25100 - 2011, it lists all varieties and classification indicators for this material. According to the state standard, sand soil is divided into five different groups according to particle size and composition. The larger the grain size, the stronger the soil composition.

Gravelly

The size of grains of sand and other components is from 2 mm. The mass of sand particles in the soil is about 25%. This type is considered the most reliable, it is not affected by the presence of moisture, it is not subject to swelling.

Large

The size of the grains is from 0.5 mm and their presence is at least 50%. He, like gravel, is most suitable for arranging foundations. You can erect any type of foundation, guided only by the architectural design, soil pressure and the mass of the building.

This type of soil practically does not absorb moisture and allows it to pass further without changing its structure. That is, such soil will practically not be subject to sedimentary phenomena and has good bearing capacity.

Medium size

Particles with a size of 0.25 mm account for 50% or more. If it begins to become saturated with moisture, then its bearing capacity is significantly reduced by about 1 kg / cm2. Such soil practically does not allow water to pass through, and this must be taken into account during construction.

Small

The composition includes 75% of grains with a diameter of 0.1 mm. If the soil on the site consists of 70% or more of fine sandy soil, then when erecting the base of the building, it is imperative to carry out waterproofing measures

Dusty

The structure contains at least 75% of elements with a particle size of 0.1 mm. This type of soil has poor drainage properties. Moisture does not pass through it, but is absorbed.To put it simply, it turns out a mud porridge that freezes at low temperatures. As a result of frost, it changes greatly in volume, so-called swelling appears, which can damage road surfaces or change the position of the foundation in the ground.

Therefore, when building in the zone of occurrence of shallow and silty sandy soils, it is important to pay attention to the depth from the surface of groundwater

Using any kind of sandy soil, the base of the foundation should be made below the freezing level of the soil layers. If it is known that there was a body of water or wetlands at the work site, then a responsible decision would be to conduct a geological study of the site and find out the amount of fine or silty sandy soils.

The factor of soil saturation with moisture must be taken into account during construction work and correctly determine the ability to pass or absorb water. The reliability of the objects erected on it depends on this. This parameter is called the filtration coefficient. It can be calculated in the field as well, but the results of the research will not give a complete picture. It is better to do this in laboratory conditions using a special device for determining such a coefficient.

Clean sandy soils are rare, therefore clay has a significant effect on the composition and properties of this material. If its content is more than fifty percent, then such a soil is called sandy-clayey.