Soil temperature at depth during the winter months. Winter measurements. Dynamics of temperatures underground, in the subfield and well

Temperature change with depth. The earth's surface, due to the uneven supply of solar heat, either heats up or cools down. These temperature fluctuations penetrate very shallowly into the thickness of the Earth. So, daily fluctuations at a depth of 1 m usually no longer felt. As for annual fluctuations, they penetrate to different depths: in warm countries by 10-15 m, and in countries with cold winters and hot summers up to 25-30 and even 40 m. Deeper than 30-40 m already everywhere on Earth the temperature is kept constant. For example, a thermometer placed in the basement of the Paris Observatory has been showing 11°.85C all the time for over 100 years.

A layer with a constant temperature is observed throughout the globe and is called a belt of constant or neutral temperature. The depth of this belt varies depending on climatic conditions, and the temperature is approximately equal to the average annual temperature of this place.

When deepening into the Earth below a layer of constant temperature, a gradual increase in temperature is usually noticed. This was first noticed by workers in the deep mines. This was also observed when laying tunnels. So, for example, when laying the Simplon tunnel (in the Alps), the temperature rose to 60 °, which created considerable difficulties in work. Even higher temperatures are observed in deep boreholes. An example is the Chukhovskaya well (Upper Silesia), in which at a depth of 2220 m temperature was over 80° (83°, 1), etc. m the temperature rises by 1°C.

The number of meters that you need to go deep into the Earth in order for the temperature to rise by 1 ° C is called geothermal step. The geothermal step in different cases is not the same and most often it ranges from 30 to 35 m. In some cases, these fluctuations can be even higher. For example, in the state of Michigan (USA), in one of the boreholes located near the lake. Michigan, the geothermal stage turned out to be not 33, but 70 m On the contrary, a very small geothermal step was observed in one of the wells in Mexico, There at a depth of 670 m there was water with a temperature of 70 °. Thus, the geothermal stage turned out to be only about 12 m. Small geothermal steps are also observed in volcanic regions, where at shallow depths there may still be uncooled strata of igneous rocks. But all such cases are not so much rules as exceptions.

There are many reasons that affect the geothermal stage. (In addition to the above, one can point out the different thermal conductivity of rocks, the nature of the occurrence of layers, etc.

The terrain is of great importance in the distribution of temperatures. The latter can be clearly seen in the attached drawing (Fig. 23), depicting a section of the Alps along the line of the Simplon Tunnel, with geoisotherms plotted by a dotted line (i.e., lines of equal temperatures inside the Earth). Geoisotherms here seem to repeat the relief, but with depth the influence of the relief gradually decreases. (The strong downward bending of the geoisotherms at Balle is due to the strong water circulation observed here.)

Temperature of the Earth at great depths. Observations on temperatures in boreholes, the depth of which rarely exceeds 2-3 km, Naturally, they cannot give an idea of ​​the temperatures of the deeper layers of the Earth. But here some phenomena from the life of the earth's crust come to our aid. Volcanism is one such phenomenon. Volcanoes, widespread on the earth's surface, bring molten lavas to the earth's surface, the temperature of which is over 1000 °. Therefore, at great depths we have temperatures exceeding 1000°.

There was a time when scientists, on the basis of the geothermal stage, tried to calculate the depth at which temperatures as high as 1000-2000 ° could be. However, such calculations cannot be considered sufficiently substantiated. Observations made on the temperature of the cooling basalt ball and theoretical calculations give reason to say that the value of the geothermal step increases with depth. But to what extent and to what depth such an increase goes, we also cannot yet say.

If we assume that the temperature increases continuously with depth, then in the center of the Earth it should be measured in tens of thousands of degrees. At such temperatures, all rocks known to us should go into a liquid state. True, there is enormous pressure inside the Earth, and we know nothing about the state of bodies at such pressures. However, we have no data to state that the temperature increases continuously with depth. Now most geophysicists come to the conclusion that the temperature inside the Earth can hardly be more than 2000 °.

Heat sources. As for the heat sources that determine the internal temperature of the Earth, they can be different. Based on the hypotheses that consider the Earth formed from a red-hot and molten mass, internal heat must be considered the residual heat of a body that is melting from the surface. However, there is reason to believe that the reason for the internal high temperature of the Earth may be the radioactive decay of uranium, thorium, actinouranium, potassium and other elements contained in rocks. Radioactive elements are mostly distributed in the acidic rocks of the Earth's surface shell; they are less common in deep-seated basic rocks. At the same time, the basic rocks are richer in them than iron meteorites, which are considered fragments of the internal parts of cosmic bodies.

Despite the small amount of radioactive substances in rocks and their slow decay, the total amount of heat resulting from radioactive decay is large. Soviet geologist V. G. Khlopin calculated that the radioactive elements contained in the upper 90-kilometer shell of the Earth are enough to cover the loss of heat of the planet by radiation. Along with radioactive decay, thermal energy is released during compression of the Earth's matter, during chemical reactions, etc.

Here is published the dynamics of changes in winter (2012-13) ground temperatures at a depth of 130 centimeters under the house (under the inner edge of the foundation), as well as at ground level and the temperature of the water coming from the well. All this - on the riser coming from the well.
The chart is at the bottom of the article.
Dacha (on the border of New Moscow and the Kaluga region) winter, periodic visits (2-4 times a month for a couple of days).
The blind area and the basement of the house are not insulated, since autumn they have been closed with heat-insulating plugs (10 cm of foam). The heat loss of the veranda where the riser goes in January has changed. See Note 10.
Measurements at a depth of 130 cm are made by the Xital GSM system (), discrete - 0.5 * C, add. the error is about 0.3 * C.
The sensor is installed in a 20mm HDPE pipe welded from below near the riser, (on the outside of the riser thermal insulation, but inside the 110mm pipe).
The abscissa shows dates, the ordinate shows temperatures.
Note 1:
I will also monitor the temperature of the water in the well, as well as at the ground level under the house, right on the riser without water, but only upon arrival. The error is about + -0.6 * C.
Note 2:
Temperature at ground level under the house, at the water supply riser, in the absence of people and water, it already dropped to minus 5 * C. This suggests that I did not make the system in vain - By the way, the thermostat that showed -5 * C is just from this system (RT-12-16).
Note 3:
The temperature of the water "in the well" is measured by the same sensor (it is also in Note 2) as "at ground level" - it stands right on the riser under the thermal insulation, close to the riser at ground level. These two measurements are made at different times. "At ground level" - before pumping water into the riser and "in the well" - after pumping about 50 liters for half an hour with interruptions.
Note 4:
The temperature of the water in the well can be somewhat underestimated, because. I can't look for this fucking asymptote, endlessly pumping water (mine)... I play as best I can.
Note 5: Not relevant, deleted.
Note 6:
The error of fixing the street temperature is approximately + - (3-7) * С.
Note 7:
The rate of cooling of water at ground level (without turning on the pump) is very approximately 1-2 * C per hour (this is at minus 5 * C at ground level).
Note 8:
I forgot to describe how my underground riser is arranged and insulated. Two stockings of insulation are put on PND-32 in total - 2 cm. thickness (apparently, foamed polyethylene), all this is inserted into a 110mm sewer pipe and foamed there to a depth of 130cm. True, since PND-32 did not go in the center of the 110th pipe, and also the fact that in its middle the mass of ordinary foam may not harden for a long time, which means it does not turn into a heater, I strongly doubt the quality of such additional insulation .. It would probably be better to use a two-component foam, the existence of which I only found out later...
Note 9:
I want to draw the attention of readers to the temperature measurement "At ground level" dated 01/12/2013. and dated January 18, 2013. Here, in my opinion, the value of +0.3 * C is much higher than expected. I think that this is a consequence of the operation "Filling the basement at the riser with snow", carried out on 12/31/2012.
Note 10:
From January 12 to February 3, he made additional insulation of the veranda, where the underground riser goes.
As a result, according to approximate estimates, the heat loss of the veranda was reduced from 100 W / sq.m. floor to about 50 (this is at minus 20 * C on the street).
This is also reflected in the charts. See the temperature at ground level on February 9: +1.4*C and on February 16: +1.1 - there have not been such high temperatures since the beginning of real winter.
And one more thing: from February 4 to 16, for the first time in two winters from Sunday to Friday, the boiler did not turn on to maintain the set minimum temperature because it did not reach this minimum ...
Note 11:
As promised (for "order" and to complete the annual cycle), I will periodically publish temperatures in the summer. But - not in the schedule, so as not to "obscure" the winter, but here, in Note-11.
May 11, 2013
After 3 weeks of ventilation, the vents were closed until autumn to avoid condensation.
May 13, 2013(on the street for a week + 25-30 * C):
- under the house at ground level + 10.5 * C,
- under the house at a depth of 130cm. +6*С,

June 12, 2013:
- under the house at ground level + 14.5 * C,
- under the house at a depth of 130cm. +10*С.
- water in the well from a depth of 25 m not higher than + 8 * C.
June 26, 2013:
- under the house at ground level + 16 * C,
- under the house at a depth of 130cm. +11*С.
- water in the well from a depth of 25m is not higher than +9.3*C.
August 19, 2013:
- under the house at ground level + 15.5 * C,
- under the house at a depth of 130cm. +13.5*С.
- water in the well from a depth of 25m not higher than +9.0*C.
September 28, 2013:
- under the house at ground level + 10.3 * C,
- under the house at a depth of 130cm. +12*С.
- water in the well from a depth of 25m = + 8.0 * C.
October 26, 2013:
- under the house at ground level + 8.5 * C,
- under the house at a depth of 130cm. +9.5*С.
- water in the well from a depth of 25 m not higher than + 7.5 * C.
November 16, 2013:
- under the house at ground level + 7.5 * C,
- under the house at a depth of 130cm. +9.0*С.
- water in the well from a depth of 25m + 7.5 * C.
February 20, 2014:
This is probably the last entry in this article.
All winter we live in the house all the time, the point in repeating last year's measurements is small, so only two significant numbers:
- the minimum temperature under the house at ground level in the very frosts (-20 - -30 * C) a week after they began, repeatedly fell below + 0.5 * C. At these moments, I worked

Soil temperature changes continuously with depth and time. It depends on a number of factors, many of which are difficult to account for. The latter, for example, include: the nature of vegetation, the exposure of the slope to the cardinal points, shading, snow cover, the nature of the soils themselves, the presence of supra-permafrost waters, etc. stable, and the decisive influence here remains with the air temperature.

Soil temperature at different depths and in different periods of the year can be obtained by direct measurements in thermal wells, which are laid in the process of surveying. But this method requires long-term observations and significant expenses, which is not always justified. The data obtained from one or two wells are spread over large areas and lengths, significantly distorting the reality so that the calculated data on the ground temperature in many cases turn out to be more reliable.

Permafrost soil temperature at any depth (up to 10 m from the surface) and for any period of the year can be determined by the formula:

tr = mt°, (3.7)

where z is the depth measured from the VGM, m;

tr is the soil temperature at depth z, deg.

τr – time equal to a year (8760 h);

τ is the time counted forward (through January 1) from the moment of the beginning of the autumn freezing of the soil to the moment for which the temperature is measured, in hours;

exp x is the exponent (the exponential function exp is taken from the tables);

m - coefficient depending on the period of the year (for the period October - May m = 1.5-0.05z, and for the period June-September m = 1)

The lowest temperature at a given depth will be when the cosine in formula (3.7) becomes -1, i.e., the minimum soil temperature for the year at a given depth will be

tr min = (1.5-0.05z) t°, (3.8)

The maximum soil temperature at depth z will be when the cosine takes a value equal to one, i.e.

tr max = t°, (3.9)

In all three formulas, the value of the volumetric heat capacity C m should be calculated for the soil temperature t ° using the formula (3.10).

С 1 m = 1/W, (3.10)

Soil temperature in the layer of seasonal thawing can also be determined by calculation, taking into account that the temperature change in this layer is quite accurately approximated by a linear dependence for the following temperature gradients (Table 3.1).

Having calculated according to one of the formulas (3.8) - (3.9) the soil temperature at the level of the VGM, i.e. putting Z=0 in the formulas, then using Table 3.1 we determine the soil temperature at a given depth in the seasonal thawing layer. In the uppermost layers of the soil, up to about 1 m from the surface, the nature of temperature fluctuations is very complex.

Table 3.1

Temperature gradient in the seasonal thaw layer at a depth below 1 m from the ground surface

Note. The sign of the gradient is shown towards the surface.

To obtain the calculated soil temperature in a meter layer from the surface, you can proceed as follows. Calculate the temperature at a depth of 1 m and the temperature of the daytime surface of the soil, and then, by interpolation from these two values, determine the temperature at a given depth.

The temperature on the soil surface t p in the cold season can be taken equal to the air temperature. During the summer period:

t p \u003d 2 + 1.15 t in, (3.11)

where t p is the surface temperature in deg.

t in - air temperature in deg.

Soil temperature with non-confluent permafrost is calculated differently than when merging. In practice, we can assume that the temperature at the WGM level will be 0°C throughout the year. The calculated temperature of the permafrost soil at a given depth can be determined by interpolation, assuming that it varies at depth according to a linear law from t° at a depth of 10 m to 0°C at the depth of the VGM. The temperature in the thawed layer h t can be taken from 0.5 to 1.5°C.

In the seasonal freezing layer h p, the soil temperature can be calculated in the same way as for the seasonal thawing layer of the merging permafrost zone, i.e. in the layer h p - 1 m along the temperature gradient (Table 3.1), considering the temperature at the depth h p equal to 0 ° C in the cold season and 1 ° C in the summer. In the upper meter layer of soil, the temperature is determined by interpolation between the temperature at a depth of 1 m and the temperature at the surface.

Photo: "NesjavellirPowerPlant edit2" by Gretar Ívarsson / https://commons.wikimedia.org/wiki/ May 25, 2015 / Tags:

In the city of Espoo, Finland's first geothermal power plant will be launched in two years. Finnish engineers plan to use the natural heat of the earth's interior to heat buildings. And if the experiment is successful, then similar heating plants can be built everywhere, for example, in the Leningrad region. The question is how profitable it is.

Harnessing the Earth's energy is not a new idea. Naturally, the inhabitants of those regions where nature itself created “steam engines” first of all took up its implementation. So, for example, back in 1904, the Italian prince Piero Ginori Conti lit four electric bulbs by placing a turbine with an electric generator near the natural outlet of heated steam from the earth, in the region of Larderello (Tuscany).

Nine years later, in 1913, the first commercial geothermal station with a capacity of 250 kilowatts was launched there. The station used the most profitable, but, unfortunately, rare resource - dry superheated steam, which can only be found in the depths of volcanic massifs. But, in fact, the heat of the Earth can be found not only near the fire-breathing mountains. It is everywhere, under our feet.

The bowels of the planet are heated to several thousand degrees. Scientists have not yet figured out what processes our planet stores a huge amount of heat for several billion years, and it is impossible to estimate how many billion years it will last. It is reliably known that for every 100 meters deep into the earth, the temperature of the rocks rises by an average of 3 degrees. On average, this means that there are places on the planet where the temperature rises by half a degree, and somewhere by 15 degrees. And these are not zones of active volcanism.

The temperature gradient, of course, increases unevenly. Finnish experts expect to reach a zone at a depth of 7 km in which the temperature of the rocks will be 120 degrees Celsius, while the temperature gradient in Espoo is about 1.7 degrees per 100 meters, which is even below the average level. And, nevertheless, this is already a sufficient temperature to start a geothermal heating plant.

The essence of the system is, in principle, simple. Two wells are drilled at a distance of several hundred meters from each other. Between them, in the lower part, water is injected under pressure to break the layers and create a system of permeable fractures between them. The technology has been worked out: shale oil and gas are now being extracted in a similar way.

Then, water is pumped from the surface into one of the wells, and vice versa, it is pumped out of the second. Water flows through fissures among hot rocks, and then flows through a second well to the surface, where it transfers heat from a conventional city heating plant. Such systems have already been launched in the United States, and are currently being developed in Australia and the countries of the European Union.

Photo: www.facepla.net (screenshot)

Moreover, there is enough heat to start generating electricity. The priority in the development of low-temperature geothermal energy belongs to Soviet scientists - it was they who solved the issue of using such energy in Kamchatka more than half a century ago. The scientists proposed to use as a boiling coolant an organic liquid - freon12, which has a boiling point at normal atmospheric pressure - minus 30 degrees. Water from a well with a temperature of 80 degrees Celsius transferred its heat to freon, which rotated the turbines. The first power plant in the world to operate with water of this temperature was the Pauzhetskaya geothermal power plant in Kamchatka, built in 1967.

The advantages of such a scheme are obvious - at any point on the Earth, humanity will be able to provide itself with heat and electricity, even if the Sun goes out. Enormous energy is stored in the thickness of the earth's crust, more than 10 thousand times the entire fuel consumption of modern civilization per year. And this energy is constantly renewed due to the influx of heat from the bowels of the planet. Modern technologies make it possible to extract this type of energy.

There are interesting places for the construction of similar geothermal power plants in the Leningrad region. The expression "Peter is standing in a swamp" is applicable only from the standpoint of the construction of low-rise facilities, and from the point of view of "big geology" - the sedimentary cover in the vicinity of St. Petersburg is quite thin, only tens of meters, and then, as in Finland, primary igneous rocks originate . This rocky shield is heterogeneous: it is dotted with faults, along some of which a heat flow rises.

Botanists were the first to pay attention to this phenomenon, who found islands of heat on the Karelian Isthmus and on the Izhora Plateau, where plants grow either with a high reproduction rate, or belonging to the more southern botanical subzones. And near Gatchina, a botanical anomaly was discovered at all - plants of the Alpine-Carpathian flora. Plants exist thanks to heat flows coming from the ground.

According to the results of drilling in the Pulkovo area at a depth of 1000 meters, the temperature of crystalline rocks was plus 30 degrees, that is, on average, it increased by 3 degrees every 100 meters. This is the "average" level of the temperature gradient, but it is almost twice as large as in the Espoo region, in Finland. This means that in Pulkovo it is enough to drill a well to a depth of only 3500 meters, respectively, such a heating plant will cost much less than in Espoo.

It is worth considering that the payback period of such stations also depends on the tariffs for heat supply and electricity for consumers in this country or region. In May 2015, the tariff for apartment buildings without electric heating from Helsingin Energia was 6.19 euro cents per kWh, with electric heating, respectively, 7.12 euro cents per kWh (during the daytime). Compared to the tariffs in St. Petersburg, the difference for those who use electricity and for heating is about 40%, while the fluctuations in rates must also be taken into account. Such a low price for electricity in Finland is due, among other things, to the fact that the country has its own nuclear generating facilities.

But in Latvia, which is forced to constantly buy electricity and fuel, the selling price of electricity is almost twice as high as in Finland. However, the Finns are determined to build a station in Espoo, in a place that is not the most favorable in terms of geothermal gradient.

The fact is that geothermal energy requires long-term investments. In this sense, it is closer to large hydropower and nuclear power. A geothermal power plant is much more difficult to build than a solar or wind power plant. And you need to be sure that politicians will not start playing with prices and the rules will not change on the fly.

Therefore, the Finns decide on this important industrial experiment. If they succeed in carrying out their plan, and at least for a start, warm their inhabitants with heat that will never end (even on the scale of life in general on our planet), this will allow us to think about the future of geothermal energy in the vast Russian expanses. Now in Russia they are warming themselves with the warmth of the Earth in Kamchatka and Dagestan, but perhaps the time of Pulkovo will also come.

Konstantin Ranks

To model temperature fields and for other calculations, it is necessary to know the soil temperature at a given depth.

The temperature of the soil at depth is measured using exhaust soil-deep thermometers. These are planned studies that are regularly carried out by meteorological stations. Research data serve as the basis for climate atlases and regulatory documentation.

To obtain the soil temperature at a given depth, you can try, for example, two simple methods. Both methods are based on the use of reference literature:

1. For an approximate determination of temperature, you can use the document TsPI-22. "Railway crossings by pipelines". Here, within the framework of the methodology for the heat engineering calculation of pipelines, Table 1 is given, where for certain climatic regions, soil temperatures are given depending on the depth of measurement. I present this table below.

Table 1

1. Table of soil temperatures at various depths from a source "to help a gas industry worker" from the times of the USSR

Normative freezing depths for some cities:

The depth of soil freezing depends on the type of soil:

I think the easiest option is to use the reference data above and then interpolate.

The most reliable option for accurate calculations using ground temperatures is to use data from the meteorological services. On the basis of meteorological services, some online directories work. For example, http://www.atlas-yakutia.ru/.

Here it is enough to select the settlement, the type of soil and you can get a temperature map of the soil or its data in tabular form. In principle, it is convenient, but it seems that this resource is paid.

If you know more ways to determine the soil temperature at a given depth, then please write comments.

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