Under the term "soil heaving" lies a rather complex phenomenon of natural origin, which can lead to serious consequences. During the period when the ground freezes, the foundation rises along with the entire structure. When thawing occurs, the opposite happens - the base drops. But the bottom line is that it's uneven.
As a result, buildings are in an emergency and sometimes threatening state. In some cases, because of this phenomenon, buildings even begin to collapse, and completely.
Feature of a natural phenomenon
The main feature of the heaving process is a significant increase in the volume of water in the soil due to winter freezing. According to GOST 25100-2011, 5 categories are distinguished, which differ among themselves in the degree of heaving (the level of soil expansion is indicated in brackets):
- Excessively heaving soils - more than 12%.
- Strongly heaving soils - no more than 12%.
- Medium heaving soils - up to 8%.
- Slightly heaving soils - approximately 4%.
- Non-rocky soils - does not exceed 4%.
However, the last category should be considered conditional, because in nature there is simply no soil where moisture is completely absent. Only granite and coarse-grained soil rocks should be attributed to this type. However, in our conditions, this type of soil is quite rare.
Stages of a threatening phenomenon
The territory of the Russian Federation runs along the entire northern part of the Eurasian continent. For this reason, the temperature is always below zero in winter. Depending on the specific region, the soil may be in a frozen state for a period of 2 to 9 months.
In this case, several stages of soil heaving can be distinguished:
- I - preliminary. In this case, the soil is cooled to a temperature not yet equal to water crystallization.
- II - based. In this case, the water is already beginning to move into a different state of aggregation, turning into ice. Accordingly, its volumetric expansion is taking place, which, as we know, does not bode well.
- III - hypothermia. Here, under the influence of frost, the soil shrinks. Subsequently, this leads to a sharp decrease in temperature.
Only it is worth considering that the listed states are conditional, since the transition from one stage to another is very slow. At the same time, one more stage can be distinguished in the process of thawing the soil - its subsidence.
Usually a heaving phenomenonobserved mainly in winter. For this reason, this season is not suitable for construction, especially of a massive nature. This is due to a serious danger - there is a very high risk that the erected structure will be destroyed very quickly.
In particular, the force of heaving of the soil should be taken into account by those who live in the Far North. In this area, the lower layers of the soil freeze much more than in other latitudes.
Main provoking factor
At first glance, it seems that the damage from heaving may not be so huge, but it only seems. In order to realize the full threat from such a natural phenomenon, it is worthwhile to clearly understand how this process occurs.
As we now know, the phenomenon is characterized by heterogeneity, which is mainly due to the difference in the height of the earth's surface. As a rule, this is observed in spring - that side of the building, which is located in the south, is well heated. In addition, spring drops contribute. With the onset of evening, a large amount of melt water accumulates in the ground, which then becomes ice.
The mass of this such layer can reach several centners, and this is quite enough to raise the foundation to a certain height. This process takes all night.
During the day, the opposite picture is observed - with an increase in temperature, the ice in the ground begins to thaw. Accordingly, the base begins to subside, and at the same time the earth is again enriched with another portion of water, which then crystallizes again. All thishappens day after day until the temperature normalizes.
During the spring period of the water level difference, the building can sink several centimeters. This is enough to cause serious damage, which will later be very difficult to fix, if at all.
Other causes of soil heaving
The intensity of heaving can be influenced by various factors, among which the following can be mentioned:
- The duration of the winter period and its intensity (severity).
- Snow thickness.
- Soil characteristics.
- Precipitation per season.
- Air humidity level.
- The nature of the terrain.
- Depth of groundwater.
- Location of the area in relation to the south side.
Since buildings can get very serious damage from heaving, the construction of its foundation should be carried out below the freezing depth of the soil. This value is directly dependent on the area where the construction of houses is planned.
It is worth noting that the Mediterranean soil moisture is a fundamental factor that largely affects the intensity of heaving. At the same time, the density of the lower layers of the soil should not be discounted. But a lot also depends on this parameter.
The denser the soil, the less deformation the building will undergo. Otherwise, frost heaving of soilswill be more intense, which does not bode well.
How to determine the degree of soil heaving?
To do this, it is worth considering not only the composition of the soil, but also the level of groundwater. Any owner of suburban real estate may face the need to determine how strong the heaving soil is in the area of \u200b\u200ba private plot. To achieve this goal, it is necessary to dig a hole up to 2 meters deep. This is such a special vertical working of a square, round or rectangular section.
After that, you should wait a few days. If moisture does not appear at the bottom of a dug small pit, you need to drill another 1.5 meters. One has only to appear to the water, the process can be stopped. Now it remains to measure the distance from the water level to the surface.
You can determine the type of soil by visual inspection. Based on these data, we can draw an approximate conclusion regarding the degree of soil expansion during the cold season.
Let's turn to mathematical calculations
Calculation of soil heaving can be done independently, using the formula E=(H-h)/h, where:
- E is the coefficient of the degree of soil heaving.
- H - the height of the soil layer after freezing.
- h is the height of the soil layer before freezing.
Accordingly, you must first perform the necessary measurements. And not only in summer, but also in winter. It is possible to draw conclusions regarding the heaving of the soil based on changes in height. If this parameter is 10 mm or more per 1 meter of freezing, then the coefficient E will be equal to0.01, which already indicates that appropriate measures should be taken to avoid serious consequences.
It is worth recalling once again that the soil, in which there is a high level of moisture, is predominantly susceptible to heaving processes. Turning into ice, it noticeably expands, increasing in volume. Who hasn't frozen water in a plastic bottle by placing it in the freezer of the refrigerator for experimentation or out of need? You can immediately imagine all the power of the water element, collected in a limited volume.
Clay soil, loam and sandy loam are more prone to heaving. And clay, due to the presence of many pores, is able to retain water well.
Ways to minimize damage
Now it is clear to us that the amount of ground heaving should not be underestimated. But how to avoid unpleasant consequences that can pose a serious threat to people's lives? There are several ways to do this. But since heaving of the soil is largely due to the impact on the foundation, most of them involve ways to strengthen or isolate it. Consider the best options for solving such a difficult problem.
Ground replacement procedure
This method works only when laying the foundation - a sand cushion is placed under the foundation. Moreover, it should be noticeably wider than the foundation of the building itself. Then it is well rammed and compacted. Thanks to this pillow, an even distribution of the entire load on the base is ensured. In addition, a layer of heaving soildecreases, therefore, the strength of the natural phenomenon also becomes weaker. In addition, the sand cushion has cushioning properties.
In addition, experts recommend, in order to avoid deformation from heaving of the soil, to cover the area between the formwork after its removal and the soil with non-heaving soil. Such a measure will avoid freezing of the soil to the walls of the foundation.
Only after some time the sand in the backfill (including the pad) can mix with the clay particles, losing their non-rocking properties. To avoid this, the sand bed and backfill should be separated with foil, roofing material or filter cloth.
Building the foundation
This refers to the optimal choice of the type of foundation, which is relevant only at the stage of building a house. If it has already been erected, then another way to solve the problem should be used. Regarding this technique, you can choose between two types of foundation - a slab structure or a pile foundation.
The formation of a slab structure will make the building heavier, which, in turn, will minimize the impact of soil on the foundation. Of course, it will not be possible to completely eliminate the effect of frost heaving on a monolithic slab with a height of more than 200 mm, sunk into the ground. At the same time, as a result of heaving of the soil, the base will simply rise evenly to a low height in winter. With warming, the foundation will return to its original position.
From a technical point of viewthe implementation of the slab foundation is simple. Certain difficulties usually arise during the reinforcement operation. In addition, this method is quite expensive.
The arrangement of the pile foundation will make it possible to get by with little bloodshed. Only this design is applicable only to buildings with low weight (construction using frame technology, the use of sip panels, etc.).
The following options may be suitable for the base:
- Screw piles - they are screwed into the ground just below its freezing level.
- Reinforced structures - you first need to prepare several wells, and then install rods wrapped in roofing material and wrapped in a metal frame.
After the piles are installed, they should be connected with special beams or slabs to evenly distribute the load on the foundation.
Insulation of the perimeter of the house
This method allows you to minimize or completely eliminate soil freezing. Due to the warming of the soil, it is possible to build a shallow foundation due to a decrease in the freezing depth.
Only this option to deal with heaving of the soil is relevant for areas with a positive average annual temperature. The width of the insulation to be laid should be equal to the depth of freezing of the soil. As for the thickness of the material, it all depends on the thermal insulation properties and the nature of the climate.