Our country is located in northern latitudes. The winter period with negative temperatures takes a lot of time from builders. However, you don’t have to stop capital construction if you warm up the soil. This procedure is becoming increasingly popular. In this article we will talk about the main methods of heating the soil.

Why is soil heating needed in winter?

When construction is carried out within the city, it becomes dangerous to remove frozen soil using demolition equipment. You can easily damage underground communications, of which there are so many in the city: cable lines, water pipes, gas pipelines. In such places, soil often has to be removed manually. In winter, frozen soil cannot be removed from the trench with shovels. Therefore, order heating of the soil immediately before starting construction work. At the same time, heating of the concrete after pouring the foundation is ordered to ensure its hydration and proper hardening.

What are the different ways to warm up the soil?

There are many ways to warm the ground at a construction site. They differ not only in costs, but also in efficiency. We list the main ones:

1. Warming up with hot water. This method is suitable for defrosting small plots land. Labyrinths of flexible hoses are laid over the area, which are covered with polyethylene or any heat insulator. Water heated to 70-90 degrees Celsius is released through the sleeves. For this, a heat generator or pyrolysis boiler is used. The defrosting speed is no more than 60 cm per day. Disadvantages - high cost of equipment and low speed warming up.
2. Warming up with steam and steam needles. Wells from one and a half to two meters deep are drilled at the site for special metal pipes with a diameter of up to 50 mm. These so-called needles have holes at the ends no larger than 3 mm. The pipes are staggered every 1-1.5 meters. Saturated water vapor is supplied to the needles (temperature - more than 100 degrees Celsius, pressure - 7 atmospheres). This method is used only for deep pits - more than 1.5 meters. Disadvantages are complex preparatory work, the release of large volumes of condensate and the need for constant monitoring of the process.
3. Warming up with heating elements. This method is similar to the steam needles used as a tool. Pipes with a length of 1 meter and a diameter of up to 60 mm are also used. They are installed in drilled wells at the same distance. Inside the pipes there is a liquid dielectric with high thermal conductivity. The heating elements are connected to the electrical network. Electricity consumption per 1 cubic meter meter of land - 42 kWh. Disadvantages: high costs.
4. Warming up with electric mats. The method involves the use of infrared mats, which work on the principle of similar mats for “warm floors”. Electromats heat the soil to a temperature of 70 degrees. The heating depth is no more than 80 cm in 32 hours. Electricity consumption - 0.5 kWh per 1 square meter. Disadvantages - fragile material, need for constant monitoring.
5. Heating with ethylene glycol using a Waker Neuson unit. The equipment runs on diesel fuel. From this point of view, it is autonomous and does not depend on communications (electricity). A hose is laid out like a snake across the area of ​​the site, through which heated ethylene glycol will circulate. This liquid has the highest thermal conductivity and a higher boiling point than water. The hoses are covered with thermal insulation mats. One installation allows you to defrost 400 square meters to a depth of up to 1.5 meters in 8 days.

Our company offers soil and concrete heating services using the Waker Neuson installation. This method is considered the most effective in terms of cost per area and defrosting time.

The labor intensity of extracting frozen soil is extremely high due to its significant mechanical strength. In addition, the frozen state of the soil complicates the task of excavating it due to the inability to use certain types of earthmoving and earthmoving-transport machines, reduced productivity and accelerated wear of the working parts of the equipment. And yet, frozen soil has one advantage - it is possible to dig pits in it without installing slopes.

There are four main ways to carry out excavation during the cold season:

• protection land plot works against freezing with the further use of conventional earth-moving machines;
• preliminary loosening and excavation of frozen soil;
• direct development of soil in a frozen state, i.e. without any preparation;
• bringing to a thawed state and subsequent removal.

Let's look at each of the above methods in detail.

Protecting soils from freezing

Protection from low temperatures is provided to the soil by loosening the top layer, covering it with insulating materials and pouring aqueous salt solutions.

Plowing and harrowing of the land plot is carried out in the sector of further work on soil extraction. The result of such loosening is the input large quantity air into the soil layers, the formation of closed air voids that prevent heat transfer and maintain a positive temperature in the soil. Plowing is carried out with rippers or factor plows, its depth is 200-350 mm. Next, harrowing is carried out in one or two directions (crosswise) to a depth of 150-200 mm, which ultimately increases the thermal insulation properties of the soil by at least 18-20%.
The role of insulation when covering the site of future work is performed by cheap local materials - dry moss, sawdust and shavings, fallen tree leaves, slag and straw mats, you can use PVC film. Bulk materials placed on the surface in a 200-400 mm layer. Insulation of the soil surface is most often carried out on small plots of land.

Frozen soil - loosening and excavation

To reduce the mechanical strength of winter soil, methods of mechanical and explosive processing are used. The extraction of the soil loosened in this way is then carried out in the usual way - using earthmoving machines.

Mechanical loosening. During its implementation, the soil is cut, chipped and split due to static or dynamic loads.

Static loads on frozen soil are carried out metal tool cutting type - tooth. A special hydraulically driven design, equipped with one tooth or more, is carried out along the work site while being placed on a crawler excavator. This method allows you to remove soil layer by layer to a depth of up to 400 mm for each pass. During the loosening process, the installation equipped with a tooth is first pulled parallel to the previous passes with a distance of 500 mm from them, then it is carried transversely to them at an angle of 60 to 90 degrees. The volume of frozen soil excavation reaches 20 cubic meters per hour. Layer-by-layer static development of frozen soil ensures the use of loosening installations at any depth of soil freezing.

Impact loads on soil areas can reduce the mechanical strength of frozen ground due to dynamic effects. Hammers are used free fall, providing splitting and loosening, or hammers with a directed action for loosening by splitting. In the first case, a hammer in the form of a ball or cone is used greatest mass 5 tons - it is secured with a rope to the boom of an excavator and, after being lifted to a height of five to eight meters, it is dropped onto the work site. Ball hammers are best suited for sandstones and sandy loams, clay soils Conical hammers are effective, provided that the freezing depth does not exceed 700 mm.

Directed action on frozen soil is carried out by diesel hammers mounted on a tractor or excavator. They are used on any soil provided the freezing depth is no more than 1300 mm.

Reducing the strength of frozen ground by explosion is most effective - this method allows for winter excavation at a depth of 500 mm and when significant volumes need to be extracted. In undeveloped areas, open blasting is carried out, and in partially built-up areas, it is necessary to first install shelters and explosion limiters - massive slabs of metal or reinforced concrete. The explosive is placed in a crack or hole (with a loosening depth of up to 1500 mm), and if it is necessary to excavate soil at greater depths, in cracks and wells. Drilling or milling machines are used to cut slots; the slots are made at a distance of 900-1200 mm from each other.

The explosive is placed in the middle (central) slot, and the slots located nearby will provide compensation for the explosive shift of frozen soil and dampen the shock wave, thereby preventing destruction outside the work area. An elongated charge or several short charges at once are placed in the gap, then it is filled with sand and compacted. After the explosion, the frozen soil in the work sector will be completely crushed, while the walls of the trench or pit, the creation of which was the purpose of the excavation, will remain intact.

Development of frozen soil without its preparation

There are two methods of direct soil development in low temperature conditions - mechanical and block.

The technology for mechanical development of frozen soils is based on force, in some cases including shock and vibration. During its implementation, both conventional earthmoving machines and those equipped with special tools are used.

At shallow freezing depths, conventional earth-moving machines are used to extract soil: excavators with a direct or reverse bucket; draglines; scrapers; bulldozers. Single-bucket excavators can be equipped with special attachments - buckets with gripping jaws and vibration-impact teeth. Such equipment allows you to influence frozen soil through excessive cutting force and carry out its layer-by-layer development, combining loosening and excavation in one working operation.

Layer-by-layer soil extraction is carried out with a special earth-moving and milling installation, which cuts off layers 2600 mm wide and up to 300 mm deep from the work site. The design of this machine includes bulldozer equipment that ensures the movement of cut soil.

The essence of block mining is cutting frozen soil into blocks and then removing them using a tractor, excavator or construction crane. The blocks are cut by sawing through the soil with cuts perpendicular to each other. If the ground is frozen shallow - up to 600 mm - then to remove the blocks it is enough to make cuts along the area. Slots are cut to 80% of the depth to which the soil is frozen. This is quite sufficient, since a layer with weak mechanical strength located between the frozen soil zone and the zone maintaining a positive temperature will not interfere with the separation of soil blocks. The distance between the slits should be approximately 12% less than the edge width of the excavator bucket. Extraction of soil blocks is carried out using backhoe excavators, because... It is quite difficult to unload them from the bucket of a straight shovel.

Methods for thawing frozen soil

They are classified according to the direction of heat supply to the ground and the type of coolant used. Depending on the direction of supply of thermal energy, there are three ways to defrost the soil - upper, lower and radial.

The top supply of heat to the ground is the least effective - the source of thermal energy is located in the air space and is actively cooled by air, i.e. a significant amount of energy is wasted. However, this method of thawing is the easiest to organize and this is its advantage.

The thawing procedure, carried out from underground, is accompanied by minimal energy expenditure, since the heat spreads under a strong layer of ice on the ground surface. Main disadvantage this method- the need to carry out complex preparatory measures, so it is rarely used.

The radial distribution of thermal energy in the soil is carried out using thermal elements vertically recessed into the ground. The effectiveness of radial thawing is between the results of upper and lower soil heating. To implement this method, somewhat smaller, but still quite high amounts of work on preparing the heating are required.

Defrosting the soil in winter is carried out using fire, electric thermoelements and hot steam.
The fire technique is applicable for digging relatively narrow and shallow trenches. A group of metal boxes is placed on the surface of the work site, each of which is a truncated cone cut in half. They are placed with the cut side on the ground close to each other and form a gallery. Fuel is placed in the first box, which is then ignited. The gallery of boxes becomes a horizontal exhaust pipe - the exhaust comes from the last box, and combustion products move along the gallery and heat the ground. To reduce heat loss from contact of the box body with air, they are covered with slag or melted soil from the area where work was carried out previously. The strip of defrosted soil formed at the end of heating must be covered with sawdust or covered with PVC film so that the accumulated heat contributes to further thawing.

Electrical heating of frozen soil is based on the ability to heat materials when an electric current is passed through them. For this purpose, vertically and horizontally oriented electrodes are used.

Horizontal thawing is carried out using electrodes made of round or strip steel laid on the ground - in order to connect electrical wires to them, the opposite ends of the steel elements are bent by 150-200 mm. The heated area with the electrodes placed on it is covered with sawdust (layer thickness - 150-200 mm), pre-moistened with a saline solution (salt concentration - 0.2-0.5%) in an amount equal to the initial mass of sawdust. The task of sawdust soaked in saline solution is to conduct current, since frozen soil will not conduct current at the initial stage of work. The top layer of sawdust is closed PVC film. As the upper soil layer warms up, it becomes a conductor of current between the electrodes and the intensity of thawing increases significantly - first the middle layer of soil is thawed, and then those located below. As the layers of soil are included in the conduction of electric current, the layer of sawdust begins to perform a secondary task - the conservation of thermal energy in the work area, for which it is necessary to cover the sawdust wooden shields or roofing felt. Thawing of frozen soil with horizontal electrodes is carried out to a freezing depth of up to 700 mm, the energy consumption when heating a cubic meter of earth is 150-300 MJ, the sawdust layer is heated to 90 o C, no more.

Vertical electrode defrosting is carried out using rods made of reinforcing steel and having one sharp end. If the freezing depth of the soil is 700 mm, the rods are first driven in to a depth of 200-250 mm in a checkerboard pattern, and after the top layer has thawed, they are sunk to a greater depth. In the process of vertical defrosting of the soil, it is necessary to remove the snow that has accumulated on the surface of the site and cover it with sawdust soaked in saline solution. The heating process proceeds in the same way as with horizontal thawing using strip electrodes - as it thaws upper layers it is important to periodically immerse the electrodes further into the ground to a depth of 1300-1500 mm. At the end of the vertical thawing of the frozen soil, the electrodes are removed, but the entire site remains under a layer of sawdust - for another 24-48 hours the soil layers will defrost on their own thanks to the accumulated thermal energy. Electricity costs for vertical defrosting are slightly lower than for horizontal defrosting.

For electrode heating of soil from bottom to top, preliminary preparation of wells is necessary - they are drilled 150-200 mm deeper than the freezing depth. The wells are located in a checkerboard pattern. This method is characterized by lower energy costs - about 50-150 MJ per cubic meter of soil.

The electrode rods are inserted into the prepared wells, reaching the unfrozen layer of the earth, the surface of the area is covered with sawings soaked in saline solution, and a plastic film is laid on top. As a result, the thawing process occurs in two directions - from top to bottom and from bottom to top. This method Thawing of frozen soil is carried out rarely and only when it is necessary to urgently defrost an area for excavation.

Steam defrosting is carried out using special devices- steam needles made of metal pipes with a diameter of 250-500 mm, through which hot steam is introduced into the soil. The lower part of the steam needle is equipped with a metal tip containing many 2-3 mm holes. A rubber hose equipped with a tap is connected to the upper (hollow) part of the needle pipe. To install steam needles, wells are drilled in the ground (checkerboard pattern, distance 1000-1500 mm) with a length of 70% of the required thawing depth. Metal caps equipped with seals are placed on the holes of the well, through which a steam needle will be passed.

After installing the needles through the hose, steam is supplied to them under a pressure of 0.06-0.07 MPa. The surface of the thawed area of ​​land is covered with a layer of sawdust. Steam consumption for heating a cubic meter of soil is 50-100 kg; in terms of thermal energy consumption, this method is 1.5-2 times more expensive compared to heating with buried electrodes.

The method of thawing frozen soil using contact electric heaters is externally similar to steam defrosting. Heating elements with insulation from the metal body of the needle are installed in hollow metal needles, about 1000 mm long and no more than 60 mm in diameter. When the power supply is connected, the heating element transfers thermal energy to the body of the needle-pipe, and it transfers heat to the layers of the soil. Thermal energy during heating it spreads radially.

Winter time is traditionally considered an unfavorable period for work in the construction industry. However, the use of thermoelectric machines will help you achieve an advantage over competitors by switching to a year-round work schedule, regardless of weather conditions and the presence of wind, you can avoid work stoppages and sending your workers on forced leave. We will help you become the strongest company on the market!

Flexible heating mats are installed in areas that need to be defrosted, heated, or require frost protection. Installation and dismantling of mats takes very little time! The heating element of thermomats releases heat directly into the ground.

Heating temperature thermoelectromat 70 o C. Thanks to the built-in reflective material, the heat flow is directed only to the heating zone,
for maximum heat transfer and to reduce heat loss. The thermomat heats up and effectively thaws the soil to a depth of 30 - 40 cm per day, depending on the condition of the soil.

The thermomat functions independently of the operator until the task is completed.

Using a mat with our heating and defrosting concept will help you achieve competitive advantage before other players in the market. You will be able to continue
work while others wait for the frozen ground to naturally thaw. The thermomat has already attracted great interest in the construction industry.

Efficient, easy to use and low maintenance mats have set a new standard in warming up the concrete and defrosting frozen soil in cold climates.

This is the future!

The scope of application is intended for consumers requiring frost-resistant materials or soil for year-round performance of work in accordance with established specifications and quality requirements. In addition to defrosting, preventing freezing and increasing frost resistance, the thermomat can also be used for heating concrete, heating pipelines, tanks, sand masses, masonry and other non-standard heating tasks.

Examples of equipment application

Defrosting soil and territories:

• Water supply and sewerage systems
• Cable trenches
• Shafts, plinths and areas for flooring
• Roofs and coverings
• Ice and snow removal

When freezing:

• Areas intended for cladding
• Sand masses, jigging sand
• Bulk masses
• Pipeline lines
• Turnout switches
• Floating piers

Pre-heating of soil or concrete:

• Grounds before foundation is laid
• Formwork and equipment for concrete work
• Increasing the degree of hardening of concrete and lightweight concrete slabs

Warming the earth with its warmth... (Part 1)

Equipment and methods for heating frozen soils during excavation work

As is known, in winter time The soil sometimes freezes so much that even an excavator and hydraulic hammer cannot reach it. Moreover, in populated areas There are underground communications in the ground that can be damaged by impact impacts on the ground. Therefore, frozen soil must be pre-warmed. There are a number of ways to warm up frozen soil. Each of them has its own advantages and disadvantages.

Methods for thawing frozen soil are classified according to the direction of heat supply to the soil and the type of coolant used.

Thawing from top to bottom. This method is the least effective, since the heat source in this case is located in the cold air zone, which causes large heat losses. At the same time, it is quite easy and simple to implement; it requires minimal preparatory work, and therefore is often used in practice.

Defrosting from bottom to top involves drilling wells into which heat sources are lowered. Energy consumption in this case is minimal, since due to the soil layer there is practically no heat loss. Some experts even believe that it is not necessary to insulate the treated area on top with a layer of sawdust and other materials. The main disadvantage of this method is the labor-intensive preparatory operations, which limits the scope of its application.

Defrosting in a radial direction. In this case, heat spreads in the ground perpendicularly from energy sources vertically immersed in the ground. In terms of economic indicators, this method takes intermediate position between the two previously described, and implementation also requires significant preparatory work.

Regardless of the method adopted, the heated surface is first cleared of snow, ice and top layers of the base (asphalt, concrete).

Thermoelectric mats

Thermoelectric mats (thermomats) are infrared heaters, multifunctional and environmentally friendly auxiliary construction equipment; they allow you to effectively heat soil and hardening concrete with little energy consumption, maintain a set temperature automatically, and some models can be used to melt snow and ice. The design of thermomats includes a heating film that emits heat in the infrared range, with thermal insulation, which is a multilayer “sandwich” of polypropylene or polyethylene foam 6–10 mm thick, limiters to maintain a constant temperature and a dirt- and water-resistant PVC shell with hermetically sealed seams, resistant to adverse conditions. atmospheric influences. They are produced in the form of rectangular panels of various sizes and rolls of considerable length.

Possibilities of thermomats. Many Western and domestic experts believe that heating the soil with thermoelectric and thermal insulation mats is the optimal technology for thawing large areas frozen ground and ice. They can operate from single-phase power sources with a voltage of 220 V. They work better than the sun on a spring day - 24 hours, 7 days a week. They are capable of heating soil to temperatures 50–80 °C above ambient temperature and warming up heavily frozen soil to a depth of 450–800 mm in 20–72 hours of operation, depending on the air temperature and soil properties. Snow and ice turn into water, which is absorbed into the soil and thaws the underlying layers of soil. They are capable of defrosting frozen sewer pipes at a depth of up to 2.5 m. Permissible temperature The operating temperature of thermomats can be down to –35 °C. The specific power emitted by thermomats can reach several hundred watts per 1 m2. Due to the penetrating properties and directed action of infrared radiation, as well as contact heat transfer from the surface of the thermomat, soil heating occurs with high efficiency simultaneously to the entire freezing depth.

Company "Thermal systems"(Moscow), part of the AKKURAT Group of Companies, is engaged in the development, testing and production of TEM thermoelectric mats to accelerate the hardening of concrete and to warm up the soil. In addition, thermomats are also used to perform other tasks, for example, heating containers, heating masonry, etc.

Thermoelectric mats are manufactured according to our own patent using high-quality infrared film Marpe Power 305 with increased power (400, 600 and 800 W/m2), which is produced by the South Korean company Green Industry Co. Supply voltage 220 V/ 50 Hz. Operation is allowed at ambient temperatures from –60 to +40 °C and relative humidity up to 100%.

The main condition for proper operation of thermomats is a tight fit of the working surface of the thermomat to the heated object (concrete or soil). The time to gain critical strength (70%) for a concrete slab with a thickness of 200 mm is about 12 hours; Warming up time for frozen soil is from 20 to 36 hours.

Test results. The technical literature provides descriptions of tests of one of the models of thermomats with dimensions of 1.2x3.2 m and a power of 800 W/m 2. The experiment was carried out at the end of winter, during the period of greatest soil freezing. Heating of the soil by thermomats occurred automatically at an air temperature of –20 °C, an initial soil temperature of –18 °C, the top 20 cm layer of soil consisted of a mixture of clay, sand and slag, followed by pure clay. The area was cleared of snow, the surface was leveled as much as possible, and plastic film was laid on it. Next, the thermomats were placed one next to the other without overlap and connected to the power supply using a “parallel” circuit. In the first hours, all the released heat was absorbed by the soil, and the thermomats worked without turning off, then, as the soil surface warmed up to 70 °C, the thermomats began to turn off, and when the temperature of the thermomat dropped to 55–60 °C, it turned on again. The warming up time is influenced by the initial conditions (air and soil temperature) and soil properties (thermal conductivity, humidity). Tests have shown that to warm up this soil to a depth of 600 mm, it takes from 20 to 32 hours.

Thermal mats create a stable heat flow, which is a necessary condition high-quality hardening of concrete in winter and summer and eliminates the appearance of temperature cracks. Branded concrete gains the strength in 11 hours that it would have acquired in 28 days under natural conditions. A high speed of concrete setting is achieved due to the penetration of infrared rays into the thickness of the concrete mass.

Application. The mats are rolled out from rolls and connected to a power source. To increase the efficiency of their operation, it is recommended to lay thermal insulating protective mats on top to retain heat and protect from wind. To avoid overheating and burning out of the thermomat, it is necessary to ensure a tight fit of the thermomat to the heated surface. It is not allowed to place any heat-insulating materials between the mat and the heated object that would prevent the transfer of heat to the object.

LLC "Plant "UralSpetsGroup"(Miass) offers thermomats with built-in temperature limit sensors for heating concrete and soil with a power of 400 and 800 W/m2, respectively. Thermal mats can consist of several independent sections. Each section has its own thermostat-limiter and maintains the heating temperature in a certain range.

Due to the uniform distribution of heat on the heated surface and automatic temperature control, the growth of concrete strength is significantly accelerated. The curing time for concrete to reach grade strength ranges from 10 hours to 2 days. The heating temperature of the mats is not higher than +70 °C. Operating conditions: ambient temperature from –40 to +40 °C, relative humidity up to 100%.

Advantages of thermomats. The equipment does not require preliminary preparation and is completely ready for use; relatively low cost; ease of setup and maintenance; light weight and ease of use, no special skills are required from workers; high efficiency and low energy consumption, for example, 0.5 kWh per 1 m 2. Thermoelectromats are completely safe. Each segment of the thermomat has a temperature limiter; the temperature will not rise above the set value. The equipment does not pollute the environment. At the customer's request, thermomats can be produced with individual power parameters and dimensions.

Disadvantages of thermomats. The need to provide power supply and constant monitoring of equipment operation; lack of anti-vandal protection, relative instability to damage.

Hydraulic stations for soil heating

If you need to warm up the soil over a large area in winter, for example, to install a concrete pad of 400 m2 or more, using conventional methods - thermomats, infrared emitters, heat guns, it is unlikely that it will be possible to heat such a mass of earth in such an area. Most likely, the technology of warming the earth using the greenhouse effect, which is created by hydraulic stations, will be effective here. Currently, Western companies widely use the technology of defrosting soils using hydraulic stations in winter for excavation and concrete work. Compact hydraulic stations for heating the soil appeared on the global construction equipment market about 15 years ago.

Installation design and operation. The installation itself is a mobile mini-boiler room. The trailer on which the hydraulic station is located is installed as close as possible to the area that is to be warmed up.

The heated surface is cleared of snow. Thorough cleaning will reduce the defrosting time by 30%, save fuel, and get rid of dirt and excess melt water, which complicates further work. The boiler is turned on, in which the coolant is heated. Water is most often used as a coolant, but in the West a water-glycol or propylene-glycol mixture is also used. The maximum heating temperature of the coolant in modern installations (depending on the manufacturer) is in the range of 75–90 °C. The digital thermostat allows the operator to simply adjust the temperature of the coolant. The heating boiler is equipped with a burner that runs on gas or diesel fuel. The coolant heated to a given temperature enters a thermally insulated container. From the container, the coolant is pumped into the heating hoses using a pump.

The heating hoses are unwound from the reel. It is recommended to lay them in a “snake” pattern in 2–4 rows, depending on the intensity of heating required. The smaller the distance between the turns (for example, 450 mm), the less time it will take to warm up the surface. Depending on the inter-hose distance, the required area and heating rate can be achieved. The inlets and outlets of the hoses are connected to the distribution manifold of the station so that the coolant circulates through them in a closed circuit. In principle, hoses can be laid in any pattern; there are also no restrictions on the shape and topography of the heated surface.

Diesel station for soil defrosting and concrete heating SRGPB.SI.350 produced JSC "SI"(Moscow city). Thermal power– 31 kW/h. Thermal efficiency is 85%. Can operate continuously for 120 hours. The volume of the coolant system is 190 liters. Working temperature heating systems: 37–82 °C. Working pressure in the heating system: 4.7–6.2 bar. Heating hose length – 360 m. Productivity circulation pump– 1010 l/h. The defrosting and heating area is from 104 to 210 m2. The defrosting area with an additional enlarged hose storage reel and pump is from 310 to 620 m2. Allows you to warm up soil up to 400 mm in depth in 24 hours. Mounted on a single-axle trailer chassis. The weight of the unit, filled with fuel, is 1402 kg.

The hoses are reinforced with synthetic fiber and have exceptional flexibility and tensile strength. The serviceability and readiness of the equipment for operation is monitored by built-in sensors. The hoses and the heated area must be covered with a vapor-proof or overlapping polyethylene film (especially important when working with concrete) and heat-insulating mats (insulation) in order to create a “greenhouse effect” and reduce heat loss into the surrounding air. The more thoroughly the heated surface is insulated, the less time it will take to warm up the soil. The film will not allow the heated water to evaporate. Melt water will melt the ice in the lower layers of the soil.

Preheating time only takes about 30 minutes. The tap opens and the heating starts! In hydraulic stations of some manufacturers, it is possible, if necessary, to increase the nominal heating area of ​​the soil several times by connecting an additional pump and additional hoses. Frozen soil is heated in a relatively short time - 20–30 hours, but if necessary, continuous operation of such installations is possible for up to 60–130 hours. Such an installation has efficiency. up to 94%, that is, almost all the heat generated by the installation goes to warming the soil. The average rate of soil defrosting using this method is 300–600 mm in depth per day. However, with more dense laying of the heating hoses and careful thermal insulation, the rate of defrosting can be increased.

Other possible applications. Soon after the use of this technology began, it turned out that hydraulic stations also help speed up the hardening process of concrete in winter, preventing moisture in concrete from turning into ice even at temperatures from -30 to -40 ° C. Concrete requires heat to harden: the warmer the concrete, the sooner it will harden. optimal temperature for hardening from +20 to +25 °C. In severe frost, concrete will harden for a very long time and lose quality. In addition, heating hydraulic stations can be used to heat greenhouses and flower beds, heat rooms, prevent icing of football fields, etc.

In Russia, hydraulic installations for heating the soil are widely used for work on large sites. Wacker Neuson E350 And E700, HSH 700G. The units are certified in Russia and do not require special permits for the operator.

Hydraulic station for surface heating Wacker Neuson HSH 350 has a mass (with fuel) of 1500 kg. Heater capacity (gross) 30 kW. At ideal conditions efficiency can reach 94%. Hose length – 350–700 m.

The HSH series unit can defrost frozen soil and also treat concrete even when negative temperatures Oh. Possibility of continuous operation - up to 63 hours. When using additional equipment, it is possible to ensure thawing of soil up to 300 m2 and warm up to 612 m2 of concrete. The HSH device is trailer mounted.

Advantages and disadvantages. The advantages of this technology over other methods are: the ability to heat large areas of soil; ease of operation, maintenance and storage of equipment; the use of equipment does not require specific knowledge, skills and long-term training of personnel; autonomy, mobility and versatility of equipment; stability of results during work; minimal labor and material costs for preparing the heated surface; environmental friendliness and safety - there is no danger of electric shock or hot coolant, does not create magnetic fields, the heating hoses are completely sealed.

Disadvantages include the high cost of equipment (2–3 million rubles), the need for the constant presence of an operator during work.

If a hydraulic station is required for a one-time use or not often, you can rent it. Thanks to the above advantages, the money spent on rent will pay off very quickly. Usually, as soon as a company tries to use such a hydraulic station once, it becomes an adherent of the technology of hydraulic soil heating.

Warmhouse/tent and heating equipment

Warming up with hot air. A fairly simple and affordable method of heating the soil - using hot air - allows you to defrost the soil in the coldest time. Snow must first be removed from the heated area. A temporary structure is erected above the site - a greenhouse or a tent. Teplyak is a temporary frame-tent construction shelter for hydro- and thermal insulation. Used when performing construction work. A diesel, gas or electric heat gun, gas burner or stove is installed inside. The air in the greenhouse/tent can heat up to 50–65 °C. The walls and roof of the greenhouse/tent can be covered with existing heat-insulating materials or even spruce branches from the forest.

In our country, heat guns are produced under the brand Hyundai. For example, Hyundai heat gun H-HG7-50-UI712 with heating element heating element with a power of 4.5 kW. The unit has operating modes: ventilation, intensive and economical heating. The air temperature at the outlet compared to the inlet increases by 32 °C. Productivity – 420 m3/h of air. Duration of operation/pause – 22/2 hours. There is an overheat protection sensor.

Advantages. Constructing such a temporary room or deploying such an installation is much simpler and requires less labor than other types of soil heating equipment. Simultaneously with defrosting, this installation dries the soil, and it becomes easier to dig. Western manufacturers of such equipment claim that their installations heat and dry the soil twice as fast as when using hydraulic stations with hoses through which hot coolant circulates.

Flaw. Weak thermal insulation, hence large heat losses; air heat guns transfer only about 15% of thermal energy to the ground.

Italian company Master Climate Solutions(part of the Dantherm Group) produces air heaters under the brand at a plant in Italy MASTER. Diesel heat guns with direct and indirect heating, as well as gas and electric heat guns. Some of the guns with diesel heating are equipped with a special socket thermostat TN-1, which is installed directly on the product, or with a TN-2 thermostat, which is connected using a cable. The units are capable of continuously operating for a long time with almost 100% efficiency.

For example, direct heating diesel heat gun MASTER B 150 CED with a power of 44 kW, it develops an air flow of 900 m 3 / h, fuel consumption is 3.7 kg / h, the air outlet temperature is 300 ° C, and the installation weight is 30.3 kg. Operates without refueling for 13 hours. Equipped with a device automatic control combustion with photocell and burner and heater safety system. The outer casing of the heater remains cold.

Open flame. The use of an open flame to defrost soil, or the “fire method,” is based on thawing the soil by burning solid or liquid fuel in a unit consisting of a gallery of metal boxes in the shape of a semicircle or truncated cones.

Boxes can be made from sheet steel 1.5–2.5 mm thick or from improvised materials, for example, cut to length metal barrels. The first of the boxes acts as a combustion chamber in which any solid or liquid fuel is burned. For example, a gas burner (nozzle) is installed in the combustion chamber, connected by a hose to a gas cylinder. The gas burner used for this purpose can simply be a piece of steel tube with a diameter of 18 mm with a flattened cone. The exhaust pipe of the last box provides draft, thanks to which combustion products pass along the gallery and heat the soil located underneath it. To reduce heat losses, the gallery is insulated with a layer of thawed soil up to 100 mm thick, slag or other materials.

There are many modern burners on sale now. For example a burner Giersch RG 20-Z-L-F(Germany) with two-stage power regulation 40–120 kW. Operates on natural and liquefied gas. Power supply – 220 V, maximum current consumption – 2.6 A. Electric motor power – 180 W. Built-in sound insulation, there is an air pressure control sensor. Can also be installed in a vertical position.

With a box length of 20–25 m, the installation makes it possible to heat the soil at a depth of 0.7–0.8 m per day. Experts provide the following data: diesel fuel consumption for heating 1 m 3 of soil is 4–5 kg. Heating with a flame is recommended to be carried out for 15–16 hours. Then, after dismantling the boxes, the strip of thawed soil is covered with sawdust so that thawing continues deeper due to the transfer of heat accumulated in the soil.

Flaws this technology: bulky, inconvenient equipment for transportation; the method can be used to excavate only relatively narrow and shallow trenches, since it allows only small areas to be heated. Heating a large area with such burners will be very expensive. The defrosting process takes a long time. It is necessary to carry out auxiliary work on the arrangement (and disassembly) of the structure. It is necessary to constantly monitor the process and compliance with safety regulations. Large heat losses, low efficiency fuel use. Harmful emissions from burned fuel, resulting in a ban on the use of this method in cities

Advantages. There are not many of them. You can assemble such an “installation” from scrap materials and heat it with construction waste - scraps of boards, flammable garbage. The advantages of using gas compared to diesel burners are lower price and less harmful emissions and smoke.

Universal gas burner Roca CRONO-G 15G(Spain) runs on liquefied and natural gas, maximum safety in operation. Before ignition, the combustion chamber is purged with air. Single-stage, two-stage or modulating power control is possible. Power – 65–189 kW. Fuel consumption – 6.5–18.9 kg/h. Electric motor power – 350 W. Electrical power – 220 V. Weight – 15 kg.

Reflective furnaces. As experience has shown, when repairing municipal utility networks, the most convenient and fastest method is to warm frozen soil with reflective stoves, which are suspended from the inside to the roof of the greenhouse - a box open at the bottom with insulated walls and roof.

Reflective furnaces have a parabolic-shaped reflector on top made of aluminum, duralumin or chrome-plated steel sheet 1 mm thick. At the focus of the parabola, which is located at a distance of 60 mm from the reflector, there is a source of heat rays: an electric incandescent coil, a water or steam battery. The reflector focuses heat rays on the underlying area of ​​the ground, due to which energy is spent more economically, and the soil thaws more intensively than when heated by warm air. The top of the furnace is covered with a steel casing that protects the reflector from mechanical damage. There is a layer of air between the casing and the reflector, which improves the thermal insulation of the furnace. The incandescent spiral is made of nichrome or fechral wire with a diameter of 3.5 mm, wound in a spiral on an insulated asbestos steel pipe. Nichrome (Ni-Cr and Ni-Cr-Fe) received its name from the nickel (“ni”) and chromium (“chromium”) in its composition, and fechral (Fe-Cr-Al) is named after the first letters of the main elements (“fe ", "hr", "al"). On modern market fechral is at least 3–5 times cheaper than nichrome. However, nichrome can withstand a greater number of on-off cycles heating elements before they burn out.

The use of heaters and reflectors. When using reflex furnaces, it is necessary to ensure safe working conditions. The heating area must be fenced, the contact terminals for connection by wire are closed, and the leak spirals must not touch the ground.

Hothouses and reverberatory furnaces can be powered from a 380 or 220 V electrical network. If the heating elements are powered from a three-phase electricity source, the heating elements are connected in groups of three according to a “star” or “delta” circuit, depending on the voltage of the power source and voltage for which the heating elements are designed (“triangle” - if the heating elements are designed for a voltage of 380 V, “star” - if for 220 V). To operate a complex of three installations, a source of electricity with a capacity of about 20 kW/h is required. Experts say that the energy consumption for thawing 1 m 3 of soil for a period of 6–10 hours (depending on its type, humidity and temperature) is in the range of 100–300 MJ or 50 kWh, while the temperature inside the greenhouse is maintained at 50 –60 °C.

Flaws of this method: effective thermal insulation of furnaces is impossible due to the risk of overheating and failure, for this reason these heating devices have low efficiency; In addition, the area of ​​the defrosted area is small, and a powerful source of electricity is required to power the equipment; in addition, when the electrical contacts of the heating elements overheat, there is a high probability of electric shock to unauthorized persons; therefore, fencing and security of the area are required while the installation is operating. Due to these inconveniences and operational dangers, some companies refuse to use this heating method.

The arrangement of steam and water batteries is even more complicated; a steam or water boiler is required, etc.

Advantages . Fast and uncomplicated delivery to site and preparation for operation of equipment. Relatively short defrosting period – up to 10 hours.

A significant part of Russia's territory is located in areas with long and severe winters. However, construction is carried out year-round, in this regard, about 15% of the total volume of earthworks has to be carried out in winter conditions and when the soil is frozen. The peculiarity of developing soil in a frozen state is that when the soil freezes, its mechanical strength increases, and development becomes more difficult. In winter, the labor intensity of soil development increases significantly ( handmade 4...7 times, mechanized 3...5 times), the use of some mechanisms is limited - excavators, bulldozers, scrapers, graders, at the same time, excavations in winter can be carried out without slopes. Water, which causes many problems in the warm season, becomes an ally of builders when frozen. Sometimes there is no need for sheet piling, and almost always for drainage. Depending on specific local conditions, use following methods soil development:

■ protection of soil from freezing with subsequent development conventional methods;

■ thawing of soil with its development in a thawed state;

■ development of frozen soil with preliminary loosening;

■ direct development of frozen soil.

5.11.1. Protecting the soil from freezing

This method is based on the artificial creation of a thermal insulation cover on the surface of the area planned for development in winter with the development of soil in a thawed state. Protection is carried out before the onset of stable negative temperatures, with advance removal from the insulated area surface waters. Apply following methods thermal insulation coating devices: preliminary loosening of the soil, plowing and harrowing of the soil, cross-loosening, covering the soil surface with insulation, etc.

Preliminary loosening of the soil, as well as plowing and harrowing is carried out on the eve of the attack winter period on a site intended for development in winter conditions. When loosening the soil surface, the top layer acquires a loose structure with air-filled closed voids that have sufficient thermal insulation properties. Plowing is carried out with tractor plows or rippers to a depth of 30...35 cm, followed by harrowing to a depth of 15...20 cm. This treatment, in combination with the naturally formed snow cover, delays the onset of soil freezing by 1.5 months, and for the subsequent period reduces the total freezing depth is approximately 73. Snow cover can be increased by moving snow onto the site with bulldozers or motor graders, or by installing several rows of snow fences made of lattice panels measuring 2 X 2 m perpendicular to the direction of the prevailing winds at a distance of 20...30 m row from row.

Deep loosening is carried out with excavators to a depth of 1.3. ..1.5 m by transferring the excavated soil to the area where the earthen structure will subsequently be located.

Cross loosening of the surface to a depth of 30...40 cm, the second layer of which is located at an angle of 60...900, and each subsequent penetration is carried out with an overlap of 20 cm. Such treatment, including snow cover, delays the onset of soil freezing by 2.5.. .3.5 months, the total freezing depth decreases sharply.

Preliminary treatment of the soil surface by mechanical loosening is especially effective in insulating these areas of the ground.

Covering the soil surface with insulation. For this, cheap local materials are used - tree leaves, dry moss, peat fines, straw mats, shavings, sawdust, snow. The simplest way is to lay these insulation materials with a layer thickness of 20...40 cm directly on the ground. Such surface insulation is used mainly for small-area recesses.

Shelter with air gap. It is more effective to use local materials in combination with an air gap. To do this, lay beds 8...10 cm thick on the surface of the ground, on them are slabs or other available material - branches, twigs, reeds; a layer of sawdust or wood shavings 15...20 cm thick is poured on top of them, protecting them from being blown away by the wind. Such a shelter is extremely effective in the conditions of central Russia; it actually protects the soil from freezing throughout the winter. It is advisable to increase the area of ​​the shelter (insulation) on each side by 2...3 m, which will protect the soil from freezing not only from above, but also from the sides.

Once soil development begins, it must be carried out at a rapid pace, immediately to the entire required depth and in small areas. In this case, the insulating layer must be removed only on the area being developed, otherwise when severe frosts A frozen crust of soil will quickly form, making work difficult.

5.11.2. Method of thawing soil with its development in a thawed state

Thawing occurs due to thermal effects and is characterized by significant labor intensity and energy costs. It is used in rare cases when other methods are unacceptable or unacceptable - near existing communications and cables, in cramped conditions, during emergency and repair work.

Thawing methods are classified according to the direction of heat propagation in the ground and the coolant used (fuel combustion, steam, hot water, electricity). According to the direction of thawing, all methods are divided into three groups.

Thawing of the soil from top to bottom. Heat spreads in the vertical direction from the day surface deep into the soil. The method is the simplest, practically does not require preparatory work, it is most often applicable in practice, although from the point of view of economical energy consumption it is the most imperfect, since the heat source is located in the cold air zone, therefore significant energy losses into the surrounding space are inevitable.

Thawing of soil from bottom to top. Heat spreads from the lower boundary of the frozen soil to the day surface. The method is the most economical, since soldering occurs under the protection of the frozen crust of the soil and heat loss into the space is practically eliminated. The required thermal energy can be partially saved by leaving the top crust of the soil in a frozen state. She has the most low temperature, therefore requiring large amounts of energy for soldering. But this thin layer of soil of 10...15 cm will be easily developed by an excavator; the machine’s power is quite enough for this. The main disadvantage of this method is the need to perform labor-intensive preparatory operations, which limits the scope of its application.

Radial soil thawing occupies an intermediate position between the two previous methods in terms of thermal energy consumption. Heat spreads radially in the ground from vertically installed heating elements, but in order to install them and connect them to work, significant preparatory work is required.

To carry out thawing of the soil using any of these three methods, it is necessary to first clear the area of ​​snow, so as not to waste thermal energy on thawing it and it is unacceptable to over-wet the soil.

Depending on the coolant used, there are several defrosting methods.

Defrosting by direct combustion of fuel. If in winter you need to dig 1...2 holes, the simplest solution is to make do with a simple fire. Maintaining a fire during a shift will lead to thawing of the soil underneath it by 30...40 cm. Having extinguished the fire and well insulating the heating area with sawdust, thawing of the soil inward will continue due to the accumulated energy and during a shift can reach a total depth of up to 1 m. If necessary, You can light the fire again or develop thawed soil and build a fire at the bottom of the pit. The method is used extremely rarely, since only a small part of the thermal energy is spent productively.

The fire method is applicable for excavating small trenches; a link structure is used (Fig. 5.41) from a number of truncated metal boxes, from which a gallery of the required length is easily assembled; in the first of them, a combustion chamber for solid or liquid fuel is installed (a fire made of wood, liquid and gaseous fuel combustion through a nozzle). Thermal energy moves to the exhaust pipe of the last box, which creates the necessary draft, thanks to which hot gases pass along the entire gallery and the soil under the boxes warms up along its entire length. It is advisable to insulate the top of the box; thawed soil is often used as insulation. After the change, the unit is removed, the strip of thawed soil is covered with sawdust, and further soldering continues due to the heat accumulated in the soil.

Electric heating The essence of this method is to pass an electric current through the soil, as a result of which it acquires a positive temperature. Horizontal and vertical electrodes in the form of rods or strip steel are used. For the initial movement of electric current between the rods, it is necessary to create a conductive environment. Such a medium can be thawed soil, if the electrodes are driven into the ground until the soil thaws, or on the surface of the soil, cleared of snow, a layer of sawdust 15...20 cm thick, moistened with a saline solution with a concentration of 0.2-0.5%, is poured. Initially, the wetted sawdust acts as a conductive element. Under the influence of heat generated in the sawdust layer, the top layer of soil heats up, melts and itself becomes a conductor of current from one electrode to another. Under the influence of heat, the underlying layers of soil thaw. Subsequently, the distribution of thermal energy occurs mainly in the soil thickness; the sawdust layer only protects the heated area from heat loss into the atmosphere, for which purpose it is advisable to cover the sawdust layer roll materials or shields. This method is quite effective at a depth of soil freezing or thawing of up to 0.7 m. Electricity consumption for heating 1 m3 of soil ranges from 150...300 kWh, the temperature of heated sawdust does not exceed 80...90 °C.

Rice. 5.41. Installation for thawing soil with liquid fuel:

a - general view; b - diagram of the insulation of the box; 1 - nozzle; 2 - insulation (sprinkling with thawed soil); 3 - boxes; 4 - exhaust pipe; 5 - cavity of thawed soil

Thawing of soil with strip electrodes placed on the soil surface, cleared of snow and debris, leveled if possible. The ends of the strip iron are bent upward by 15...20 cm for connection to electrical wires. The surface of the heated area is covered with a layer of sawdust 15...20 cm thick, moistened with a solution of sodium chloride or calcium with a consistency of 0.2...0.5%. Since soil in a frozen state is not a conductor, at the first stage the current moves through sawdust moistened with the solution. Next, the top layer of soil is heated and the thawed water begins to conduct electric current, a process with time goes by deep into the soil, sawdust begins to act as a thermal protection for the heated area from heat loss into the atmosphere. Sawdust is usually covered with roofing felt, glassine, shields, and other protective materials. The method is applicable at a heating depth of up to 0.6...0.7 m, since at greater depths the voltage drops, the soils are put into operation less intensively and heat up much more slowly. In addition, they are sufficiently saturated with water since the fall, which requires more energy to transition to a thawed state. Energy consumption ranges from 50-85 kWh per 1 m3 of soil.

Thawing of soil using rod electrodes (Fig. 5.42). This method is carried out top-down, bottom-up and combined methods. When thawing the soil with vertical electrodes, reinforcing iron rods with a pointed lower end are driven into the ground in a checkerboard pattern, usually using a 4x4 m frame with cross-tensioned wires; the distance between the electrodes is within 0.5-0.8 m.

Rice. 5.42. Thawing of soil with deep electrodes:

a - from bottom to top; b - from top to bottom; 1 - thawed soil; 2 - frozen soil; 3 - electrical wire; 4 - electrode, 5 - layer of waterproofing material; 6 - layer of sawdust; I-IV - thawing layers

When warming up from top to bottom, the surface is first cleared of snow and ice, the rods are driven into the ground 20...25 cm, and a layer of sawdust soaked in a salt solution is laid. As the soil warms up, the electrodes are driven deeper into the soil. The optimal heating depth will be within 0.7...1.5 m. The duration of soil thawing under the influence of electric current is approximately 1.5...2.0 days, after which the increase in thawing depth will occur due to accumulated heat for another 1 ...2 days. The distance between the electrodes is 40...80 cm, energy consumption compared to strip electrodes is reduced by 15...20% and amounts to 40...75 kWh per 1 m3 of soil.

When heating from bottom to top, wells are drilled and electrodes are inserted to a depth exceeding the depth of the frozen soil by 15...20 cm. The current between the electrodes flows through the thawed soil below the freezing level; when heated, the soil warms the overlying layers, which are also included in the work. With this method, a layer of sawdust is not required. Energy consumption is 15...40 kW/h per 1 m3 of soil.

The third, combined method will take place when the electrodes are buried in the underlying thawed soil and a sawdust backfill impregnated with a saline solution is placed on the day surface. The electrical circuit will close at the top and bottom, and the soil will thaw from top to bottom and bottom to top at the same time. Since the labor intensity of preparatory work with this method is the highest, its use can be justified only in exceptional cases when accelerated thawing of the soil is required.

Defrosting with high frequency currents. This method makes it possible to sharply reduce preparatory work, since the frozen soil remains conductive to high-frequency currents, so there is no need for large penetration of electrodes into the soil and for the installation of sawdust backfill. The distance between the electrodes can be increased to 1.2 m, i.e. their number is reduced by almost half. The process of soil thawing proceeds relatively quickly. The limited use of the method is due to the insufficient production of high-frequency current generators.

One of the methods that has now lost its effectiveness and has been replaced by more modern ones is thawing the soil with steam or water needles. On this day, it is necessary to have sources of hot water and steam, with a shallow freezing depth of up to 0.8 m. Steam needles are metal pipe length up to 2 m and diameter 25...50 mm. On bottom part pipes are fitted with a tip with holes with a diameter of 2...3 mm. The needles are connected to the steam line with flexible rubber hoses if they have taps. The needles are buried in wells that have been previously drilled to a depth approximately equal to 70% of the thaw depth. The wells are closed with protective caps equipped with seals for the passage of a steam needle. Steam is supplied under pressure of 0.06...0.07 MPa. After installing the accumulated caps, the heated surface is covered with a layer of thermal insulation material, most often sawdust. The needles are placed in a checkerboard pattern with a distance between centers of 1-1.5 m.

Steam consumption per 1 m3 of soil is 50... 100 kg. Due to the release of latent heat of vaporization by steam in the soil, heating of the soil is especially intense. This method requires approximately 2 times more thermal energy consumption than the vertical electrode method.

Thawing of soil using thermal electric heaters. This method is based on the transfer of heat to frozen soil by contact method. The main technical means are electric mats made of a special heat-conducting material through which an electric current is passed. Rectangular mats, the dimensions of which can cover a surface of 4...8 m2, are laid on the thawed area and connected to a 220 V source of electricity. In this case, the generated heat effectively spreads from top to bottom into the thickness of the frozen soil, which leads to its thawing. The time required for thawing depends on the ambient temperature and the depth of soil freezing and averages 15-20 hours.

5.11.3. Development of frozen soil with preliminary loosening

Loosening of frozen soil with subsequent development by earth-moving and earth-moving machines is carried out using the mechanical or explosive method.

Mechanical loosening of frozen soil using modern high-power construction machines is becoming increasingly widespread. In accordance with environmental requirements, before winter excavation it is necessary to autumn period Use a bulldozer to remove a layer of plant soil from the area planned for development. Mechanical loosening is based on cutting, splitting or chipping frozen soil by static (Fig. 5.43) or dynamic action.

Rice. 5.43. Loosening frozen soil by static action:

a - a bulldozer with active teeth, b - an excavator-ripper, 1 - direction of loosening

With dynamic impact on the soil, it is split or chipped with free-fall and directional action hammers (Fig. 5.44). In this method, loosening of the soil is carried out using free-fall hammers (ball and wedge hammers), suspended on ropes on the booms of excavators, or with directional hammers, when loosening is carried out by chipping the soil. Loosening mechanically allows for its development by earth-moving and earth-moving and transport machines. Hammers weighing up to 5 tons are dropped from a height of 5...8 m: a ball-shaped hammer is recommended to be used when loosening sandy and sandy loam soils, wedge hammers - for clayey ones (with a freezing depth of 0.5...0.7 m). Diesel hammers on excavators or tractors are widely used as directional hammers; they allow the destruction of frozen soil to a depth of up to 1.3 m (Fig. 5.45).

The static impact is based on the continuous cutting force in the frozen soil of a special working body - a ripper tooth, which can be the working equipment of a hydraulic backhoe excavator or be an attachment on powerful tractors.

Loosening with tractor-based static rippers involves quality attachments a special knife (tooth), the cutting force of which is created due to the traction force of the tractor.

Machines of this type are designed for layer-by-layer loosening of soil to a depth of 0.3...0.4 m. The number of teeth depends on the power of the tractor, with a minimum tractor power of 250 hp. one tooth is used. Loosening of the soil is carried out by parallel layer-by-layer penetrations every 0.5 m with subsequent transverse penetrations at an angle of 60...900 to the previous ones. Loose soil is moved to the dump using bulldozers. It is advisable to attach attachments directly to the bulldozer and use it to independently move loosened soil (see Fig. 5.21). Ripper productivity is 15...20 m3/h.

The ability of static rippers to develop frozen soil layer by layer makes it possible to use them regardless of the depth of soil freezing. Modern rippers based on tractors with bulldozer equipment, due to their wide technological capabilities, are widely used in construction. This is due to their high efficiency. Thus, the cost of developing soil using rippers is 2...3 times lower compared to the explosive method of loosening. The loosening depth of these machines is 700...1400 mm.

Fig.5.45. Scheme of joint operation of a diesel hammer and a straight shovel excavator

Explosion loosening of frozen soils is effective for significant volumes of frozen soil development. The method is used mainly in undeveloped areas, and in limited areas - with the use of shelters and explosion localizers (heavy loading plates).

Depending on the depth of soil freezing, blasting operations are performed (Fig. 5.46):

■ using the method of hole and slot charges at a soil freezing depth of up to 2 m;

■ by the method of borehole and slot charges at a freezing depth of over 2 m.

Holes are drilled with a diameter of 22...50 mm, holes - 900...1100 mm, the distance between the rows is taken from 1 to 1.5 m. Slots at a distance of 0.9... 1.2 m from one another are cut with a slitting machine. Milling-type molds or bar machines. Of the three adjacent slits, explosive is placed only in the middle one; the outer and intermediate slits serve to compensate for the displacement of frozen soil during an explosion and to reduce the seismic effect. The cracks are charged with elongated or concentrated charges, after which they are covered with melted sand on top. If the preparatory work is carried out with high quality during the blasting process, the frozen soil is completely crushed without damaging the walls of the pit or trench.

Rice. 5.46. Methods for loosening frozen soil by explosion:

a - blasthole charges; b - the same, well; c - the same, boiler; g - the same, small-chambered; d, f - the same, chamber; g - the same, slotted; 1 - explosive charge; 2 - stope; 3 - face chest; 4 - sleeve; 5 - pit; b - adit; 7 - working slot; 8 - compensation slot

The soil loosened by explosions is developed by excavators or earth-moving machines.

5.11.4. Direct development of frozen soil

Development (without preliminary loosening) can be carried out by two methods - block and mechanical.

The block development method is applicable for large areas and is based on the fact that the solidity of frozen soil is broken by cutting it into blocks. Using attachments on a tractor - a bar machine - the soil is cut with mutually perpendicular penetrations into blocks 0.6...1.0 m wide (Fig. 5.47). For shallow freezing depths (up to 0.6 m), it is enough to make only longitudinal cuts.

Bar machines that cut slits have one, two or three cutting chains mounted on tractors or trench excavators. Bar machines allow you to cut cracks 1.2...2.5 m deep in frozen soil. They use steel teeth with a cutting edge made of a durable alloy, which extends their service life, and when worn or abraded, allows you to quickly replace them. The distance between the bars is taken depending on the soil at 60... 100 cm. Development is carried out using backhoe excavators with a large-capacity bucket, or blocks of soil are dragged from the excavated site to a dump using bulldozers or grantors.

Fig.5.47. Scheme of block soil development:

a - cutting slots with a bar machine; b - the same, with the blocks being removed by a tractor; c - development of a pit with the removal of blocks of frozen soil using a crane; I - layer of frozen soil; 2 - cutting chains (bars); 3 - excavator; 4 - cracks in frozen soil; 5 - chopped soil blocks; 6 - blocks moved from the site; 7 - crane tables; 8 - vehicle; 9 - pincer grip; 10 - Construction crane; 11 - tractor

The mechanical method is based on force, and more often in combination with shock or vibration effects on frozen soil. The method is implemented using conventional earthmoving and earthmoving-transport machines and machines with working parts specially designed for winter conditions (Fig. 5.48).

Conventional production machines are used in initial period winters, when the depth of soil freezing is insignificant. A forward and backhoe can excavate soil at a freezing depth of 0.25...0.3 m; with a bucket with a capacity of more than 0.65 m3-0.4 m; dragline excavator - up to 0.15 m; bulldozers and scrapers are able to develop frozen soil to a depth of 15 cm.

Rice. 5.48. Mechanical method of direct soil development:

a - excavator bucket with active teeth; b - development of soil with a backhoe excavator and a gripping and pincer device; c - earth-moving and milling machine; 1 - ladle; 2 - bucket tooth; 3 - drummer; 4 - vibrator; 5 - gripping and pincer device; b - bulldozer blade; 7 - hydraulic cylinder for raising and lowering the working body; 8 - working body (mill)

For winter conditions, special equipment has been developed for single-bucket excavators - buckets with vibro-impact active teeth and buckets with a gripping-pincer device. Energy consumption for cutting soil is approximately 10 times more than for chipping. Installing vibration-impact mechanisms, similar in operation to a jackhammer, into the cutting edge of an excavator bucket brings good results. Due to the excessive cutting force, such single-bucket excavators can develop frozen soil layer by layer. The process of loosening and excavating the soil turns out to be one and the same.

Soil development is also carried out using multi-bucket excavators, specially designed for digging trenches in frozen soil. For this purpose, a special cutting tool is used in the form of fangs, teeth or crowns with hard metal inserts, mounted on buckets. In Fig. 5.48, and shows the working body of a multi-bucket excavator with active teeth for the development of rocky and frozen soils.

Layer-by-layer development of soil can be carried out with a specialized earthmoving and milling machine, which removes shavings up to 0.3 m deep and 2.6 m wide. The developed frozen soil is moved using bulldozer equipment included in the machine.