The concept of soil loosening coefficient when developing a pit and the rules for its calculation

Comprehending the characteristics of the soil is essential when getting ready to build on a construction site. The soil loosening coefficient is one of the main ideas in this procedure. This coefficient is crucial for organizing and carrying out excavation operations because it makes predictions about the behavior of the soil after it has been dug up and moved.

The volume change that soil experiences during excavation is referred to as the "soil loosening coefficient." Soil takes up specific volume and is compacted when it is left undisturbed in the ground. Nevertheless, the dirt expands and requires more room after it is dug up. For the excavation process to be properly planned and for materials and space to be used efficiently, this expansion must be precisely calculated.

The soil loosening coefficient must be calculated in multiple steps. First, while the soil is still in the ground, its initial volume is measured. Following the excavation of the soil, its new volume is measured. The soil loosening coefficient is found as the ratio of the original volume to the volume that was excavated. Engineers and construction workers can use this coefficient to calculate how much soil will need to be moved, stored, or compacted once more while building.

Precise computation of the soil loosening coefficient is necessary to prevent issues like excessive or inadequate excavation, unanticipated soil settling, and logistical challenges. It guarantees that the project moves forward smoothly and effectively, conserving resources and time. Construction industry professionals can more effectively manage their projects and produce more dependable outcomes by comprehending and implementing this idea.

The concept of soil loosening coefficient	The rules for its calculation
The soil loosening coefficient measures how much the soil expands when excavated. It helps determine the volume increase from its original compact state to its loose state.	To calculate it, measure the original volume of soil, excavate it, then measure the loose soil volume. Divide the loose volume by the original volume to get the coefficient.

What are the types of soil from a construction point of view??

From a construction perspective, soil can be classified into the following types:

• Cemented (rocky) – stone-like rocks that can only be developed by explosion (using special technology) or crushing. This is due to their increased density and water resistance.
• Uncemented – less dispersible and easier to process. Therefore, development can be carried out using special equipment (bulldozers, excavators) or manually. This category of soil includes chernozem, sand, loam, mixed soil mixtures.

Rocky-originated soils have high-density rocks that protrude to the surface or have a thin layer of soil covering them. Granite, lime, sandstone, dolomite, and basalt are a few of these.

Their high strength qualities make them resistant to harmful outside influences:

• temperature fluctuations,
• exposure to moisture.

This kind of soil is the most dependable for building foundations when compared to other types.

In our nation, only rocky soil is uncommon. It also has some drawbacks that make organizing basements and ground floors very difficult.

Rock splitting is the cause of coarse-grained soil. It does not heave, settle evenly, or succumb to compression. Its natural qualities make it perfect for foundations. However, it is advised to cover it with clay and sandstone.

It is important to consider another kind of soil: sand. It contains grains-sized hard particles.

Sands vary in size and can be:

• gravelly;
• large;
• medium;
• fine;
• powdery.

The size of the particles affects the level of sand subsidence and, thus, the foundation. The finest sand is coarse-grained. It is practically impervious to heaving, less prone to compaction, and is not washed away by water.

Sandstones that are dusty and contain gravel are the most hazardous. Because they are not appropriate for the foundation and are highly mobile, they are also known as "quicksand."

Because the clay soil mixture is made up of small, scaly particles, they stick together tightly. Sand loam is a kind of soil that is in between sand and clay. It has up to 30% loam and 10% clay particles. Such soil’s characteristics are contingent upon the extraction site, composition, and relative humidity. The fluidity increases with increasing moisture saturation.

Organogenic variants:

• vegetative layer;
• organic silt;
• soil from swamps and peat bogs.

This choice is not ideal for laying a foundation. This is due to the fact that the salts in such soil degrade the building materials.

Properties that affect the complexity of digging a hole

Certain qualities of the soil determine how difficult the excavation process will be:

• Humidity – the proportions of the mass of water contained in the soil and solid inclusions. It is expressed as a percentage: less than 5% – the soil is dry, over 30% – wet, 5-30% – normal. The wetter the soil, the more difficult it is to remove. An exception to the rule will be clay – it is more problematic to extract it in dry form.
• Looseness – the property of soil to increase in volume during excavation and development.
• Density – the mass of one cubic meter in its normal state. The densest and heaviest soil is rocky, lightest – sandstones and sandy loams.
• Adhesion – the degree of resistance to shear. Sandy loam and sandy soil has an indicator from 3 to 50 kPa, loams – from 5 to 200 kPa. Hence, it follows that the first type is easier to develop.

What does the concept of loosening coefficient mean?

During construction, not only designers but also builders must consider the soil loosening coefficient. This feature is used to compare the nominal and actual soil density at the construction site.

Naturally, using the material’s weight for accounting would be more trustworthy, but there are several reasons why this is frequently not feasible. Then, you are forced to use volumetric accounting, which does not require any specialized equipment.

We can distinguish between the quantity of soil utilized at the building site, available in the warehouse, and mined in the quarry using this method.

Calculations involving coefficients are necessary because the volumes of land before and after extraction are different. It will be necessary to transport soil.

When compared to its initial compacted state, the coefficient of initial loosening (Kp) indicates an increase in the amount of soil mixture due to development and storage in embankments.

The following table lists the characteristics of the soil:

The table demonstrates how the density has a direct bearing on the initial loosening coefficient. Therefore, after removal, the heavier the soil in its original state, the more space it will occupy. The excavated soil is removed after accounting for this indicator.

A coefficient is also present. residual loosening (Kop): a measure of the amount of soil shrinkage caused by specific factors in an embankment

1. caking,
2. contact with moisture,
3. compaction mechanisms.

This value is considered when dumping soil for destruction and storage, as well as when calculating the quantity of material that must be transported to the construction site.

You must perform the necessary computations in order to determine the cost of excavation work. Determine the soil volume by knowing the planned pit’s dimensions. The initial loosening coefficient is multiplied.

Using specialized machinery, the final value will be created and then taken from the construction site. The cost of development, loading, and transportation for one m3 of soil must be added to the final amount.

There are differences in the loosening coefficients before and after soil development. In the table, they are displayed as percentages:

Initial table based on SNiP

The initial loosening coefficient of soil arrogance and density value for the corresponding categories will be as follows, per the SNIP building codes:

Category	Name	Density, tons/m3	Loosening coefficient
I	Wet sand, sandstone, loam	1.5–1.7	1.1–1.25
I	Loose dry sand	1.2–1.6	1.05–1.15
II	Loam, medium and fine gravel, dry clay	1.5–1.8	1.2–1.27
III	Clay, dense loamy soil	1.6–1.9	1.2–1.35
IV	Wet clay, shale, mixture of loam with crushed stone and gravel, rocks	1.9–2.0	1.35–1.5

Residual table based on SNiP

The following table lists residual loosening coefficients for various soil types based on SNIP:

Type of soil	Initial excess soil volume after development, %	Residual loosening, %
Scrap clay	28-32	From 6 to 9
Gravel+pebbles	16-20	From 5 to 8
Vegetable origin	20-25	From 3 to 4
Soft loess	18-24	From 3 to 6
Dense loess	24-30	From 4 to 7
Sandstone	10-15	From 2 to 5
Rocks	About 50	From 20 to 30
Solonchak (solonetz) soft/hard	20-26/28-32	From 3 to 6/from 5 to 9
Loam light/heavy	18-24/24-30	From 3 to 6/from 5 to 8
Sandy loam soil mixture	12-17	From 3 to 5
peat bog	24-30	From 8 to 10
Chernozem	21-27	From 5 to 7

When excavating a pit, knowing the soil loosening coefficient is essential because it affects both the amount of soil that must be removed and the efficiency of the excavation process. Builders can more precisely plan for how much soil to handle and transport by using this coefficient, which measures how much soil expands when it is disturbed. Accurate computation guarantees that the project remains within budget and time constraints and preserves the stability and security of the excavation site.

Calculation example

If one begins with a geometry course in school, three steps will suffice to determine how many times a truck must transport the excavated soil:

• calculate the volume of land;
• calculate the volume of the dump truck body;
• divide the first quantity by the second.

From this point on, it will be evident how much money you need to spend on transportation.

For instance, a house is being designed with a two-meter foundation depth and a base area of 7 by 9 meters, accounting for the finished basement and laid floor.

After that, multiplying these indicators will give you the amount of soil: 7 x 9 x 2 = 126 m^3. An automobile body typically has a volume of 12–13 m3. This is used to calculate the total number of flights: 126:12, or roughly 10, is 10.

These computations are incorrect because the volume of transported soil that actually occurs differs significantly from the volume that was estimated. The fact that it tends to loosen explains this. This causes the initial volume to rise. Because of this, there is a loosening coefficient that accounts for these modifications.

Assume for the moment that a specific piece of land needs to be developed in order to build a facility. Finding out how much land there will be after preparations are finished is the task at hand.

The parameters listed below are known:

• the width of the foundation pit is 1 meter;
• foundation length – 45 meters;
• pit deepening – 1.5 meters;
• the thickness of the gravel cushion after compaction is 0.3 meters;
• soil type – wet sandstone.

This will be the calculation principle:

1. First, determine the volume of the pit (Vk): Vk = 45x1x1.5 = 67.5 m3.
2. Now look at the average initial loosening of wet sand (in the table). It is equal to 1.2. The formula by which the amount of soil is calculated after its extraction: V1 = 1.2×67.5 = 81 m3. It follows that 81 m3 of excavated soil needs to be removed.
3. Then they find out the final volume of the earthen layer after compacting it under the pillow using the formula: Vp = 45x1x0.3 = 13.5 m3.
4. Using the table, look at the maximum initial and residual coefficient of loosening of gravel and pebbles, convert them into fractions. So, the first coefficient kр = 20% or 1.2, and the second kр = 8% or 1.08. Calculate the volume of gravel that will be required for laying the base: V2 = Vп x kр/kр = 13.5х1.2/1.8 = 15 m3. This means that you will need this amount of gravel for filling.

Although this calculation is imprecise, it provides a general understanding of the loosening coefficient and its necessity in construction. A more intricate method is employed when creating a project for the construction of a residential building. Additionally, a similar plan works well when building a small object (like a garage).

When creating a pit for construction, knowing the soil loosening coefficient is crucial. This coefficient influences the amount of soil that needs to be managed by estimating how much the soil will expand after it has been dug up. You can guarantee the effectiveness and economy of the excavation process by precisely calculating this factor.

Depending on the kind of soil you’re working with, the soil loosening coefficient varies. It’s crucial to understand the unique characteristics of the soil at your location because different types of soil respond to disturbance in different ways. You can more accurately estimate the volume of loose soil and make appropriate transportation and disposal plans by using the right methods and computations.

It is imperative that you adhere to the guidelines when calculating the soil loosening coefficient in order to preserve stability and safety during your building project. An unexpected problem, like the soil collapsing or the need to remove excess material, can be avoided with careful planning. This planning promotes the overall success and safety of the construction site in addition to aiding in resource management.

To sum up, the soil loosening coefficient is an important consideration when excavating. Your construction projects will operate more effectively and efficiently if you comprehend and put this idea into practice. Time savings, cost savings, and a more seamless building process can all be achieved with precise computations and thoughtful planning.

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