Warming up sand in winter. Development of soil in winter conditions. Than heated inerti
Development of soil in winter conditions.
IN construction of the total land of earthworks from 20 to 25% is carried out in winter conditions, while the proportion of soil developed in a permanent state remains constant -10-15% with an increase in year in the year of the absolute value of this volume.
IN the practice of construction arises the need to develop soils located in a marzline state only in the winter period of the year, i.e. Grounds of seasonal freezing, or throughout the year, i.e. Everworking soils.
The development of easery soils can be made by the same ways as frozen soils of seasonal freezing. However, in the construction of earthen structures in the conditions of permafrost, it is necessary to take into account the specific features of the geothermal regime of the perplexed soils and the change in the properties of the soils during its violation.
Under negative temperatures, the freezing of water contained in the pores of the soil significantly changes the construction and technological properties of non-tight soils. In frozen soils, mechanical strength is significantly increasing, and therefore, the development of their exchanging machines is hampered or impossible without preparation.
The draining depth depends on the air temperature, the duration of the effect of negative temperatures, the kind of soil, etc.
Earthworks in winter are carried out by the following three methods. At the first method, it includes preliminary preparation of soils, followed by their development by conventional methods; With the second - frozen soils are cut to the blocks; For the third method, the soil is developed without their preliminary preparation. Pre-preparation of soil for the development of winter is to protect it from freezing, thawing the frozen soil, preliminary loosening of the frozen soil.
Protecting from frozen. It is known that the presence of daylight
the surface of the thermal insulating layer reduces both the period and the depth of the freezing. After removal of surface waters, you can arrange a thermal insulating layer in one of the following methods.
Ruffle soil. When plowing and harrowing the soil on a plot designed to develop in winter, its upper layers acquire a loose structure with closed voids filled with air, which has sufficient thermal insulation properties. Plowing is led by tractor plows or rippers to a depth of 20 ... 35 cm with a subsequent harrowing to a depth of 15 ... 20 cm in one direction (or in cross-directions), which increases the thermal insulation effect by 18 ... 30%. Snow cover On the instended area, it is possible to artificially increase, raking snow by bulldozers, automatic drivers or by snowstaving with shields. Most often, mechanical loosening is used for insulation of significant areas in areas of land, protection of the surface of the soil with thermal insulation materials. The insulation layer can also be made of cheap local materials: wood leaf, dry moss, peat, straw mats, slag, chips and sawdust. Superficial soil insulation is used mainly for small surroundings.
Soil impregnation with salt solutionsbehave as follows. On the surface
the sand and sampling soil is scattered with a given amount of salt (calcium chloride 0.5 kg / m2, sodium chloride 1 kg / m2), after which the soil plow. In low-filtering grooves (clays, heavy loam), wells are drilled in which the salt solution is injected under pressure. Because of the high labor intensity and the cost of such works, they are usually not effective enough.
Methods for thawing of frozen soilit can be classified both in the direction of heat propagation in the soil and according to the type of heat carrier. On the first sign, the following three methods of thawing soil can be distinguished.
Towing the soil from above down. This method is the least effective, since the heat source in this case is placed in the cold air zone, which causes large heat losses. At the same time, this method is fairly easy and easy to implement, it requires minimal preparatory work, and therefore, often applied in practice.
Soil thawing uprequires minimal energy consumption, as it occurs under the protection of the earthen crust and the heat loss is practically excluded. The main disadvantage of this method is the need to fulfill labor-intensive preparatory operations, which limits its scope.
When thawing the soil by the radial direction heat propagates in the ground radially from vertically installed heating elements immersed in the ground. This method of economic indicators occupies an intermediate position between the two previously described, and for its implementation requires significant preparatory work.
According to the type of heat carrier, the following ways of thawing frozen primers are distinguished
Fire method. For passages in the winter of small trenches, the installation is used (Fig. 1a), consisting of a number of metal boxes in the form of truncated cones cut along the longitudinal axis, from which the solid gallery is collected. The first of the boxes is a combustion chamber in which solid or liquid fuel is burned. The exhaust pipe of the last box provides a craving, thanks to which combustion products pass along the gallery and warm the ground under it. To reduce heat loss, the gallery is sprinkled with a layer of melting soil or slag. The strip of the fatty soil falls asleep with sawdusts, and further depressing deep into the heat of heat is continuing due to the heat accumulated in the soil.
Figure 1. Schemes of soil thawing with firing method and steam needles: A
Firing way; b - steam needles; 1 - Camera combustion; 2 - exhaust pipe; 3 - overpopping with a thawed ground: 4 - steam pipe; 5 - steam valve; 6 - steam needle; 7 - a bored well; 8 - Cap.
Thawing in warm and reflective furnaces . Woolly are open from the bottom of the box with insulated walls and the roof, inside which placed heating spirals, water or steam batteries suspended to the box cap. Reflective furnaces are on top of a curvilinear surface, in the focus of which there is an incandescent helix or emitter of infrared rays, and the energy is spent more economically, and the soil thawing occurs more intensively. Woolly and reflective furnaces feed from the power supply 220 or 380 V. Energy consumption per 1 m3 the fatty soil (depending on its type, humidity and temperature) fluctuates within 100 ... 300 MJ, while the temperature 50 ... 60 ° C is maintained inside the heat.
When thawing the soil with horizontal electrodes on the surface of the ground
ta put electrodes from strip or round steel, whose ends are rejected by 15 ... 20 cm for connecting to wires (Fig. 2a). The surface of the heated area is covered with a layer of sawdust with a thickness of 15 ... 20 cm, which is wetted with a salt solution with a concentration of 0.2 ... 0.5% with such a calculation so that the mass of the solution is no less mass
sawdust. Initially, moistened sawdust is conductive elements, since the freezing soil is not a conductor. Under the influence of heat generated in the sawdust layer, pulls off the top layer of the soil, which turns into the current conductor from the electrode to the electrode. After that, under the influence of heat, it begins to clean up the top layer of the soil, and then the lower layers. In the future, the sawing layer protects the heated area from heat loss into the atmosphere, for which the sawdust layer is covered with polyethylene film or shields.
Figure 2. Electrical soil output circuit: A - horizontal electrodes; b - vertical electrodes; 1 - three-phase electrical network; 2 - horizontal strip electrodes; 3.
Layer sawdust moistened with salted water; 4 is a layer of roofing or rubberoid; 5 - rod electrode.
This method is used with the depth of the soil freezing to 0.7 m, the electricity consumption for heating 1 m3 of the soil ranges from 150 to 300 mJ, the temperature in sawdust does not exceed 80 ... 90 ° C.
Towing the soil by vertical electrodes . Electrodes are rods from reinforcement steel with pointed lower ends. With a depth of freezing more than 0.7 m, they are clogged into a checkered ground to a depth of 20 ... 25 cm, and as the upper layers of the soil are plunged into a greater depth. When thawing from top to bottom, it is necessary to systematically remove the snow and arrange a sawmill, moistened with brine. Warm mode with rod electrodes is the same as at strip, and during the power disconnection, the electrodes should additionally beylmaged by 1.3 ... 1.5 m. After turning off the electricity for 1 ... 2 days, the depth of thawing continues to increase The account of the heat accumulated in the soil under the protection of the sawing layer. The energy consumption in this method is somewhat lower than with the method of horizontal electrodes.
Using heating from the bottom up, before the warming start, it is necessary to drill wells in a chess order to a depth above 15 ... 20 cm of the thickness of the frozen soil. The energy consumption during the heating of the soil from the bottom up is significantly reduced (50 ... 150 MJ per 1 m3), it is not required to apply sawdust layer. When the stem electrodes are gluable into the underlying meal primer, the simultaneous device on the daily surface of the sawing sweeping, impregnated with brine, the thawing occurs from top to bottom and bottom up. At the same time, the complexity of preparatory work is significantly higher than in the first two versions. Apply this method only when it is necessary to urgently utter the soil.
Towing the soil from top to bottom with steam or water registers. Region
the strays are placed directly on the surface of the heated area cleared from the snow and is closed with a heat-insulating layer from sawdust, sand or thao soil to reduce heat loss in space. Registers are thawing the soil with a thickness of frozen crust to 0.8 m. This method is expedient if there are sources of steam or hot water, since the installation for this purpose a special boiler installation is usually too expensive.
Towing the soil with steam needlesit is one of the effective funds, but causes excessive soil moisturizing and increased heat consumption. Steam needle is a metallic pipe with a length of 1.5 ... 2 m, a diameter of 25 ... 50mm. The tip with a hole with a diameter of 2 ... 3 mm is imposed on the bottom of the pipe. Needles are connected to steam pipeline
flexible rubber sleeves with cranes (Fig. 1b). The needles are plugged into the wells, pre-drilled at a depth of 0.7 depth of thawing. The wells are covered with protective caps made of wood, covered with roofing steel with a hole equipped with a gland to pass a steam needle. Steam is fed under a pressure of 0.06 ... 0.07 MPa. After installing the accumulating caps, the warmed surface is coated with a layer of thermally insulating material (for example, sawdust). To save steam, the warm-up mode needles should be intermittent (for example, 1 h - steam supply, 1 h - break) with alternate steam supply to parallel groups of needles. The needles are in a checkerboard with the distance between their centers 1 ... 1.5 m. Steam consumption per 1 m3 of soil 50 ... 100 kg. This method requires more heat consumption than a method of deep electrodes, by about 2 times.
When thawing soil with water circulating needles as a heat
pitel use water heated to 50 ... 60 ° C and circulating on a closed system "Boiler - Running pipes - water needles - reverse tubes - boiler". Such a scheme ensures the most complete use of thermal energy. The needles are installed in well bored for them. The water needle consists of two coaxial pipes, of which the inner has an open at the bottom, and the outer-pointed ends. Hot water enters the needle on the inner tube, and through its lower hole enters the outer tube, which rises to the outlet nozzle, from where the connecting pipe goes to the next needle. The needles are connected sequentially several pieces in groups that include in parallel between the bruises and return pipelines. Towing the soil with needles in which hot water circulates, is much slower than around steam needles. After the continuous operation of water needles for 1.5 ... 2.5 days, they are removed from the soil, the surface is insulated, after which for 1 ...
1.5 days will expand the wax zones due to the accumulated heat. The needles are in a checker order at a distance of 0.75 ... 1.25 m between themselves and is used at the depths of the freezing from 1 meter and more.
Tanning of soil by Tanni (electroagulas) . Tannes are steel
about 1 m long pipes with a length of about 1 m with a diameter of up to 50 ... 60 mm, which are inserted into the well-drilled wells.
Inside the needles mount the heating element, isolated from the tube body. The space between the heating element and the walls of the needle is filled with liquid or solid materials, which are dielectrics, but at the same time it is well transmitted and maintained heat. The intensity of the soil exhaustion depends on the temperature of the electriglé surface, and therefore the most economical temperature is 60 ... 80 ° C, but the heat consumption is at the same time compared to the deep electrodes above 1.6 ...
1.8 times.
When thawing the soil with saline solutions the surfaces are pre-drilled on the depth to be thawed. The wells with a diameter of 0.3 ... 0.4 m are placed in a checker manner in increments of about 1 m. They poured a heated to 80 ... 100 ° C saline, which replenish the wells for 3 ... 5 days. In the sandy soils, a well depth is 15 ... 20 cm deep, as the solution penetrates deep into the soil dispersion. Thus down soils after their development are never fatal.
METHOD OF STRONG STAINING OF ENOUGH MUSS the most appropriate in the spring, when it is possible to use warm air of the surrounding atmosphere, warm rainwater, solar radiation for these purposes. The upper thawing layer of the soil can be deleted by anyshuttle-transport Or planning machines, exposing the frozen layer under it, which in turn thaws under the action of the factors listed above. The soil is cut on the border between the frozen and melted layers, where the soil has a weakened structure, which creates favorable conditions for the operation of machines. In the districts of permafrost, this method is one of the most economical
municipal and common to the development of soil when planning recesses, trenches, etc.
METHOD OF STROND WARNING OF WATER SUPPORTS provides for
before the onset of frosts of the upper layer of soil, underlying the horizon of groundwater. When, under the action of cold atmospheric air, the calculated drainage depth reaches 40 ... 50 cm, proceed to the development of the soil in the excavation in the murzed state. Development is conducted by individual sites, between which jumpers from frozen soil are left with a thickness of about 0.5 m to a depth of about 50% of the thickness of the industrial soil. The jumpers are designed to insulate individual sections from the neighboring water in the case of a breakthrough of groundwater. The development front moves from one section to another, while on the already developed sections the depth of the freezing increases, after which the development of them is repeated. Alternated freeing and development of areas are repeated until the project level is reached, after which the protective jumpers are removed. This method allows you to develop with a murzled state of the soil (without fastening and waterfront) of the recess, significantly superior in their depth the thickness of the seasonal freezing of the soil.
Pre-looping of frozen soil means of small mechanization
change with minor scope of work. For large amounts of work, it is advisable to use mechanical and marzular machines.
Explosive way looseningthe soil is most economical under large volumes of work, a significant depth of freezing, especially if the explosion energy is used not only for loosening, but also for emissions of earth masses in the dump. But this method can be applied only in areas located away from residential buildings and industrial buildings. When using localizers, the explosive method of jams can be used near buildings.
Figure 3. Schemes of loosening and cutting of frozen soil: A - with a wedge-hammer; b - looping diesel-hammer; B is a cutting in the frozen ground of the slots of a multi-volume excavator equipped with cutting chains - bars; 1 - Wedge-hammer; 2 - excavator; 3 - frozen layer of soil; 4- guide bar; 5 - diesel hammer; 6 - cutting chains (bars); 7 - multi-loving excavator; 8 - slits in frozen soil.
Mechanical loosening of frozen soils used with a passage of small pumps and tranches. In these cases, frozen soil to a depth of 0.5 ... 0.7 m loosewedge-hammer (Fig. 3a), suspended to the excavator Arret (Draglain), is the so-called swarming loosening. When working with such a hammer, the boom is installed at an angle of at least 60 °, which ensures sufficient height of the drop of hammer. When using the molot of free falldue to Dynamic overload quickly wear steel rope, trolley and individual machine nodes; In addition, from impact on the soil of oscillations, it can be valid for nearly arranged structures. Mechanical rippers are jerked with a depth of freezing more than 0.4 m. In this case, the soils are fried by chip or cutting blocks, and the labor intensity of the destruction of the soil with a slope is several times less than when the soils are filled with cutting. The number of
the ditch on one trace depends on the depth of the freezing, the group of the soil, the mass of the hammer (2250 ... 3000 kg), the height of the lift, determine its drummer of the roads.
Diesel-hammers (Fig. 3b) can loosen the soil with a depth of frozen up to 1.3 m and on a par with wedges are hinged equipment to the excavator, tractorupochorus and tractor. You can looser with a frozen soil diesel-hammer in two technological schemes. According to the first diagram of the diesel-hammer, frustrated layer, moving the zigzag at points located in a checker, in increments of 0.8 m. At the same time, the spheres of crushing from each working parking is merged with each other, forming a solid loose layer prepared for subsequent development. The second scheme requires the preliminary preparation of the opening wall of the slaughter developed by the excavator, after which the hammer is set at a distance of about 1 m from the problem of the face and apply to them at one place until the chip shaft shall occur. Then diesel hammer move along the brow, repeating this operation.
Impact milling motors (Fig. 4b) work well at low soil temperatures, when it is characteristic of non-plastic, and fragile deformations that contribute to splitting under the action of impact.
Grinding soil by tractor loans. This group includes equipment in which the continuous cutting force of the knife is created at the expense of tractor-tractor-tractor. The machines of this type are undergraduate with a frozen soil, providing a loop depth of 0.3 ... 0.4 m: Therefore, a frozen layer is being developed, pre-bursting with such machines as bulldozers. In contrast to shock rippers, static rippers work well at high soil temperatures when it has significant plastic deformations, and its mechanical strength is lowered. Static rippers can be trailed and mounted (on the back bridge of the tractor). Very often they are used in conjunction with a bulldozer, which in this case alternately loose or develop the soil. In this case, the trailed ripper is unfolded, and attached to the hinged. Depending on the engine power and the mechanical properties of the frozen soil, the number of teeth of the ripper ranges from 1 to 5, and most often use one tooth. For the efficient operation of the tractor ripper on frozle soil, it is necessary that the engine has sufficient power (100 ... 180 kW). The soil is loosened parallel (about 0.5 m) penetrations with subsequent transverse penetrations at an angle of 60 ... 90 ° to the previous one.
Figure 4. Schemes for the development of frozen soils with preliminary loosening: A - Wedge-hammer; B - tractor vibrarin ripper; 1 - Avtoshosmoshum; 2 - excavator; 3 - Wedge-hammer; 4 - Vibraroclin.
An frozen soil, cursed by cross-penetration of a single-suitable ripper, can be successfully developed by a tractor scrap, and this method is considered to be very economical and successfully competes with a drilling process.
When developing frozen soils with pre-cutting blocks in a frozle layer, slots are cut (Fig. 5), separating the soil into separate blocks, which are then removed by an excavator or construction cranes. The depth of the cutting in the frozle layer of the slots should be approximately 0.8 of the drainage depth, since the loose layer on the border of the frozen and melt zones is not an obstacle to the development of an excavator. In areas with ever-frozen soils, where the underlying layer is absent, the block development method does not apply.
Figure 5. Development schemes of frozen soils by block manner: a, b - fine block; in, g - largecloth; 1 - removal of snow cover; 2, 3 - cutting blocks of frozen soil with a steam machine; 4 - Development of small blocks with an excavator or bulldozer; 5 - Development of melting soil; 6 - Development of large blocks of frozen soil by a tractor; 7 - the same, crane.
The distances between the sliced \u200b\u200bslots depend on the size of the excavator bucket (the size of the blocks should be 10 ... 15% less than the width of the groove of the excavator). The blocks ship excavators with buckets with a capacity of 0.5 m and above, equipped mainly in the reverse shovel, as the unloading of the blocks of the bucket of a straight shovel is very difficult. For cutting gaps in the soil, various equipment installed on excavators and tractors is used.
Cut the slits in frozle ground with rotary excavators, whose bucket rotor is replaced by milling discs equipped with teeth. For the same purpose, discoofreser machines are used (Fig. 6), which are mounted equipment to the tractor.
Figure 6. Discoofreve earthy machine: 1 - tractor; 2 - the transmission and management system of the working body; 3 is a working body of the machine (cutter).
Most effectively cut the gaps in frozen ground with bars (Fig. 5), the working body of which consists of a cut chain mounted on the basis of a tractor or trench excavator. Bar machines cut the slit depth of 1.3 ... 1.7 m. The advantage of the chain machines compared to the disk is the relative ease of replacing the most rapid wear parts of the working body - replaceable, inserted into the cutting chain of teeth.
Sale with the delivery of hot sand in Moscow, to warm up in the winter soil or land.
Bulk density: 1.5 (t / m3)Payment on non-cash payments with VAT. Prepay 100%.
Delivery the next day after payment. The time on the way of the dump truck with hot sand ranges from 1 to 3 hours. Delivery in Moscow is carried out in the morning.
Characteristics:
- GOST 8736-93, TU 400-24-161-89
- Class II.
- Module of size: from 1.5 microns to 2.8 MK
- Filtration coefficient: from 2 m / day to 9.5 m / day
- The content of dust and clay particles: up to 10%
- Clay content in lumps: up to 5%
- Color: Brown, Yellow, Light Yellow, Brown, Svetlo-Brown
- Methods: Moscow region, Vladimir region, Kaluga region.
- Bulk density: 1.5 g / cm. Cube. (T / m3)
Origin: Sand careers.
Removing area: To warm up the upper layer of earth ground in the winter period of time when laying and repairing thermal networks, etc.
Method of mining: They produce on sandy careers in an open way, is achieved by heating in production furnaces to a temperature from 180 to 250g Celsius.
Additional information about hot sand in construction:
Hot sand in the winter period serves as an indispensable material for heating the soil or other than the top soil at minus temperatures when laying various communications underground. When using hot sand, the effect of heated soil is achieved and it becomes more convenient for work, especially since the likelihood of damage to the pre-laid communications, for example, thermal networks, etc.
Hot sand - seasonal product, it is relevant only at at minus temperatures. In production, it reaches a temperature of an average of 220g Celsius, and as a result - all moisture evaporates from it and it becomes fully disbanded. Although this sand quality is rather a qualitative indicator for the production of dry mixtures, apply it to hot sand or improve its performance for higher heat transfer cannot be. It is rather the result of heating with high temperatures. Hot sand is a high-quality product, since in addition to the fact that the raw material is high-quality sandary sand 2 class, it is still warm and dried and corresponds to TU 400-24-161-89.
When ordering hot sand in the amount of 10m3, its temperature, at the time of delivery to the application object, it practically does not change and it retains high performance of its qualitative properties. As a rule, the practice of conjunction and the use of hot sand is used on the eve of the day of the work produced, for example, from the evening of the day, followed by work. The ten o'clock is enough to warm up the top layer of the soil and prepare it for further work, while the sand will not freeze in this time.
A significant part of Russia is located in zones with long and harsh winter. However, construction is carried out yearly, in this connection, about 15% of the total earthworks have to be carried out in winter conditions and during the frozle state of the soil. The peculiarity of the engineering of the soil in a frozen state is that when the soil is freezing, the mechanical strength increases, and the development is hampered. In winter, the complexity of the engineering of the soil (hand-held works in 4 ... 7 times, mechanized in 3 ... 5 times) increases significantly, the use of some mechanisms - excavators, bulldozers, scraper, graders, while in the same time removal can be performed without sloping . Water, with a lot of trouble in the warm season, becomes an ally builders in the frozen state. Sometimes there is a need for tongue fences, almost always in waterproof. Depending on the specific local conditions, the following soil development methods are used:
■ Protection of the soil from freezing followed by the development of conventional methods;
■ Towing the soil with the development of it in molding;
■ the development of the soil in a murzed state with preliminary loosening;
■ Immediate development of frozen soil.
5.11.1. Protecting from frozen
This method is based on artificially creating on the surface of the site scheduled to develop in winter, thermal insulation cover with the development of soil in molding. Protection is carried out before the onset of stable negative temperatures, with an advanced tap from a warmed section of surface water. The following methods of thermal insulating coating are used: pre-jamming, plowing and harrowing soil, cross loaf, shelter the surface of the soil with insulation, etc.
Pre-jamming of soil, as well as plowing and harrowing is carried out on the eve of the winter period on a plot designed to develop in winter conditions. When the surface of the ground, the upper layer acquires a loose structure with filled with air closed emptiness with sufficient thermal insulation properties. Plowing is produced by tractor plows or rippers at a depth of 30 ... 35 cm with a subsequent harrowing to a depth of 15 ... 20 cm. Such treatment in combination with naturally generated snow cover is given to the beginning of the primer of the soil by 1.5 months, and for the subsequent period, reduce The general depth of the freezer approximately 73. Snow cover can be increased by the movement of snow to the section by bulldozers or motor riders or installation perpendicular to the direction of the dominant winds of several rows of snow-protective fences from lattice shields in size 2 x 2 m at a distance of 20 ... 30 m row from a row.
Deep loosening produce excavators to a depth of 1.3. ..1.5 M by overwhelming the soil developed on the site where the earth facility will be located.
The cross loaf 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 performed with a lamb to 20 cm. Such processing, including snow cover, moves the start of the frozen of the soil at 2.5 .. .3.5 months, sharply decreases the overall depth of the freezing.
Pre-treatment of the surface of the soil with mechanical loosening is particularly effective in the insulation of these land plots.
Shelter the surface of the soil with insulation. To do this, use cheap local materials - woody leaves, dry moss, peat trifle, straw mats, chips, sawdust, snow. The easiest way is to lay down these insulation layer thickness 20 ... 40 cm directly on the soil. Such superficial insulation is used mainly for small surroundings.
Shelter with air layer. More efficient is the use of local materials in combination with air layer. To do this, on the surface of the soil lay a layer with a thickness of 8 ... 10 cm, hill on them or another brew material - branches, bars, reeds; A layer of sawdust or wood chips with a thickness of 15 ... 20 cm with the protection of them from being blown from being blown on them. Such a shelter is extremely efficient in the conditions of medigated Russia, it actually protects the ground from the freezing throughout the winter. It is advisable to increase the area of \u200b\u200bshelter (insulation) from each side to 2 ... 3 m, which will protect the ground from the freezing not only from above, but also on the side.
With the beginning of the development of the soil, it is necessary to lead it to a rapid pace, immediately at all necessary depth and small sections. The insulation of the layer should be removed only on the area being developed, otherwise, with severe frosts, the frozen crust of the soil will be quickly formed, which makes it difficult to produce work.
5.11.2. The method of thawing soil with its development
Towing occurs due to thermal exposure and is characterized by considerable complexity and energy costs. It is applied in rare cases when other methods are unacceptable or unacceptable - near the existing communications and cables, in cramped conditions, in emergency and repair work.
Waying methods are classified in the direction of heat distribution in the soil and according to the coolant used (fuel combustion, steam, hot water, electricity). In the direction of thawing, all the ways are divided into three groups.
Towing the soil from top to bottom. The heat is distributed in the vertical direction from the daily surface of the soil deep. The method most simple, practically does not require preparatory work, most often applicable in practice, although from the point of view of economical energy consumption is most imperfect, since the heat source is placed in the cold air zone, so significant energy losses in the surrounding space are inevitable.
Towing the soil from the bottom up. The heat spreads from the lower boundary of the frozen soil to the day surface. The method is most economical, since the resting occurs under the protection of the frozen crust of the soil and heat loss in the space is practically excluded. The required thermal energy can be partially saved due to the remaining of the upper cooker in the simply state. It has the lowest temperature, therefore requires high energy costs for resting. But this thin layer of soil at 10 ... 15 cm will be freely designed by the excavator, for this, the power of the machine is quite enough. The main disadvantage of this method in the need to fulfill labor-intensive preparatory operations, which limits the scope of its application.
Radial soil thawing occupies an intermediate position between the two previous methods according to the flow rate of thermal energy. The heat applies to the ground radially from vertically installed warming elements, but in order to install them and connect to work, significant preparatory work is required.
To perform soil thawing on any of these three ways, it is necessary to clean the plot from the snow so as not to spend thermal energy on its thawing and unacceptably replete the soil.
Depending on the coolant used, there are several methods of thawing.
Towing the direct burning of fuel. If in winter it is necessary to dig 1 ... 2 pits, the simplest solution is to do with a simple bone. Helping a fire during a shift will lead to a soil under it for 30 ... 40 cm. Riding a bonfire and well insulated the skewering place with sawdust, pulling the soil inside will continue due to the accumulated energy and per shift can reach a total depth of 1 m. If necessary You can leave the fire again or develop a telly soil and on the bottom of the pit is a bonfire. Apply the method is extremely rare, since only a minor part of thermal energy is consumed productively.
The fire method is applicable for excerpts of small trenches, a link structure is used (Fig. 5.41) from a row of metal truncated boxes, of which the gallery of the required length is easily assembled, in the first of them are organized by the combustion chamber of solid or liquid fuel (firewood bonfire, liquid and gaseous Fuel with burning through the nozzle). Thermal energy moves to the exhaust pipe of the last box creating the necessary traction, due to which the hot gases pass along the entire gallery and the ground under the boxes warms down the entire length. It is advisable to insist on top of the box, a telly soil is used often. After changing the unit, the unit is removed, the strip of the fatty soil falls asleep by sawdues, further rejection continues at the expense of heat accumulated in the soil.
Electrical heating. The essence of this method consists in passing the electric current through the ground, as a result of which it acquires a positive temperature. Use horizontal and vertical electrodes in the form of rods or strip steel. For the initial movement of the electric current between the rods, you must create a conductive environment. Such a medium can be a telly soil if the electrodes are scored to the soil to the melting soil, or on the surface of the soil, purified from snow, pour a layer of sawdust with a thickness of 15 ... 20 cm, moistened with saline with a concentration of 0.2-0.5%. Initially, moistened sawdust are a conductive element. Under the influence of heat generated in the layer layer, the upper layer of the soil is heated, it feels and it becomes the current conductor from one electrode to another. Under the influence of heat, the underlying layers of soil occurs. Subsequently, the propagation of thermal energy is carried out mainly in the thickness of the soil, the sawing layer only protects the heated area from the heat of heat into the atmosphere, for which the sawdust layer is advisable to cover with roll materials or shields. This method is quite effective with a depth of freezing or pulling the soil to 0.7 m. The electricity consumption for heating 1 m3 of the soil fluctuates in the range of 150 ... 300 kWh, the temperature of the heated sawdust does not exceed 80 ... 90 ° C.
Fig. 5.41. Installation for thawing soil with liquid fuel:
a - general view; b - scheme of insulation box; 1 - nozzle; 2 - insulation (sprinkling soil); 3 - box; 4 - exhaust pipe; 5 - the cavity of the fattened soil
Towing the soil with strip electrodes stacked on the surface of the soil, purified from snow and garbage, if possible, aligned. The ends of the strip gland are rejected up at 15 ... 20 cm for connecting to electrical pipelines. The surface of the heated area is covered with a layer of sawdust with a thickness of 15 ... 20 cm, moistened with a solution of sodium chloride or calcium consistency 0.2 ... 0.5%. Since the soil in a frozen state is not a conductor, then in the first stage, the current moves along a moistened solution of solids. Next, the top layer of the soil is heated and the exhausted water begins to carry out an electric current, the process in time goes deep into the soil, the sawdust begin to perform the role of heat shields of a heated area from heat loss into the atmosphere. Speakers from above are usually covered with a tale, pergamin, shields, other protective materials. The method is applicable at a warm-up to 0.6 ... 0.7 m, since at high depths the voltage drops, the soils are less intensively involved in the work, much slower is heated much more. In addition, they are sufficiently impregnated with autumn water, which requires more energy to go to the liner. Energy consumption ranges in the range of 50-85 kWh per 1 m3 of soil.
Towing the soil with rod electrodes (Fig. 5.42). This method is carried out from top to bottom, bottom-up and combined methods. When the soil is thawing with vertical electrodes, the rods from reinforcement iron with a pointed lower end are clogged into a staggered ground, usually using a 4x4 m frame with cruciformly stretched wires; The distance between the electrodes is within 0.5-0.8 m.
Fig. 5.42. Towing the soil in deep electrodes:
and - bottom up; B - top down; 1 - a telly soil; 2 - frozen soil; 3 - electric wire; 4 - electrode, 5 - layer of waterproofing material; 6 - sawdust layer; I-IV - Layers of Towing
When driving from top to bottom, the surface is pre-cleaned from snow and the surface, the rods are clogged into the soil by 20 ... 25 cm, lay the sawdust layer impregnated with salt solid. As the soil warmed, the electrodes are scored deeper into the ground. The optimal will be the warm-up depth of 0.7 ... 1.5 m. The duration of the soil is exposed to an electric current to about 1.5 ... 2.0 days, after that an increase in the depth of the exhaustion will occur due to the accumulated heat for even 1 ... 2 days. The distance between the electrodes 40 ... 80 cm, the energy consumption is reduced by 15 ... 20% and is 40 ... 75 kWh per 1 m3 of soil.
When warm upwards, the wells are drilled and the electrodes are inserted to a depth, which exceeds the depth of the industrial soil by 15 ... 20 cm. The current between the electrodes goes on the thawed soil below the level of the freezing, when heated, the soil warms the overlying layers, which are also included in the work. At the same time, the method is not required to apply sawdust layer. Energy consumption is 15 ... 40 kW / h per 1 m3 of soil.
The third, combined method will occur when the electrodes are heated into the underlying meter and the device on the daily surface of the sawing backfill, impregnated with brine. The electrical circuit will be closed at the top and bottom, the soil thawing will occur from top to bottom and bottom up at the same time. Since the complexity of the preparatory work with this method is the highest, its use can be justified only in exceptional cases when accelerated soil is required.
Towing high frequency currents. This method allows you to drastically reduce the preparatory work, since the simplifying soil maintains conductivity to high frequency currents, therefore, there is no need for a large shutback of the electrodes into the soil and in the sawdust device. The distance between the electrodes can be increased to 1.2 m, i.e., their number is reduced almost twice. The process of thawing the soil proceeds relatively quickly. The limited use of the method is associated with insufficient release of high-frequency current generators.
One of the methods that have currently lost their effectiveness and are ousted more modern, is the thawing of soil with steam or water needles. The day of this requires the presence of hot water sources and steam, with a small, up to 0.8 m in the depths of the soil freezing. Steam needles are a metal tube up to 2 m long and a diameter of 25 ... 50 mm. The tip with a hole with a diameter of 2 ... 3 mm is imposed on the bottom of the pipe. The needles are connected to steam pipeline flexible rubber hoses if you have cranes on them. The needles are plugged into wells that are pre-drilled to a depth, approximately 70% depth of thawing. The wells are closed with protective caps equipped with glands for passing a steam needle. Steam is fed under a pressure of 0.06 ... 0.07 MPa. After installing the accumulated caps, the warmed surface is covered with a layer of thermal insulating material, most often sawdust. The needles are in a checkerboard with a distance between the centers of 1 1.5 m.
Steam consumption per 1 m3 of soil is 50 ... 100 kg. Due to the selection of steam in the soil of hidden heat of vaporization, the heating of the soil is particularly intense. This method requires the flow of thermal energy about 2 times larger than the method of vertical electrodes.
Towing the soil with thermal electrical heaters. This method is based on the transmission of heat with frozen soil with contact method. Electro-mats are used as the main technical means, made from a special thermal conducting material through which the electric current is passed. Rectangular mats, the dimensions of which can close the surface from 4 ... 8 m2, are stacked on a taped area and connected to a source of electricity with a voltage of 220 V. At the same time, the heat-sized heat efficiently 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 the soil freezing and the average is 15-20 hours.
5.11.3. The development of the soil in a murzled state with preliminary loosening
The loosening of frozen soil followed by the development of earthmoving and earthmoving machines is carried out by a mechanical or explosive method.
Mechanical loosening of frozen soil using modern high-power construction machines is becoming increasingly distributed. In accordance with the requirements of the ecology, in front of the winter development of the soil, it is necessary to remove the layer of plant soil with a bulldozer to remove the layer of plant soil with a bulldozer. Mechanical loosening is based on cutting, splitting or chipping soil static (Fig. 5.43) or dynamic exposure.
Fig. 5.43. Loosening of frozen soil with static influence:
a - Bulldozer with active teeth, b - excavator-ripper, 1 - direction of jamming
With a dynamic effect on the ground, it is splitting or chipped by the hammers of free fall and aimed (Fig. 5.44). In this way, the soil breaking is produced by the hammers of free fall (sharp and wedges) suspended on the ropes on the booms of excavators, or by the hammers of the directional action when the loosening is carried out by a soil sole. Ruffle mechanically allows for its development to earthy and earthmoving machinery. The hammers weighing up to 5 tons are discharged from a height of 5 ... 8 m: the hammer in the shape of a ball is recommended to be used when loosening sandy and sampling soils, wedge-hammers - for clay (with a depth of freezing 0.5 ... 0.7 m). Diesel-hammers on excavators or tractors are widely used as a movement hammer. They allow you to destroy the escape ground to a depth of 1.3 m (Fig. 5.45).
Static impact is based on a continuous cutting force in the frozen soil of a special working body - a tooth-ripper, which can be the working equipment of the hydraulic excavator "reverse shovel" or be hinged equipment on powerful tractors.
The liquidization of static rippers on the basis of the tractor implies as a special knife (tooth) hinged equipment (tooth), the cutting effort of which is created at the expense of the tractor's tract.
Machines of this type are calculated on the layer-by-layer soil at a depth of 0.3 ... 0.4 m. The number of teeth depends on the power of the tractor, with the minimum power of the tractor 250 hp Used one tooth. The bursting of the soil is carried out by parallel layers in 0.5 m with subsequent transverse penetrations at an angle of 60 ... 900 to the previous one. The movement of the loose soil into the dump is carried out by bulldozers. It is advisable to mount the equipment directly on the bulldozer and use it to independently move the loosen soil (see Fig. 5.21). The productivity of the ripper 15 ... 20 m3 / h.
The ability of static looser layers to develop a frozen soil makes it possible to use them regardless of the depth of the soil freezing. Modern looser on the basis of tractors with bulldozer equipment due to their wide technological capabilities are widely used in construction. This is due to their high economy. Thus, the cost of the development of the soil with the use of rippers compared with the explosive method of loosening in 2 ... 3 times lower. The depth of loosening by these machines is 700 ... 1400 mm.
Fig.5.45. Scheme of collaboration of diesel-hammer and excavator "Direct shovel"
The loosening of frozen soils by an explosion effectively with significant amounts of development of frozen soil. The method is used mainly in unresolved areas, and limitedly built-up - using shelters and explosion localizers (heavy loading plates).
Depending on the depth of the primer of the soil, explosive work is performed (Fig. 5.46):
■ using the method of buckling and sliding charges with the depth of the primer of the soil to 2 m;
■ method of well and slot charges with a depth of freezing over 2 m.
The sheets are drilled with a diameter of 22 ... 50 mm, the wells - 900 ... 1100 mm, the distance between the rows is taken from 1 to 1.5 m. The slit at a distance of 0.9 ... 1.2 m One of the other is cut by phelette With meat of milling type or bars. Of the three adjacent cracks, an explosive is placed only in the middle, extreme and intermediate slots serve to compensate for the shift of the ground soil during an explosion and to reduce the seismic effect. Charges the slots elongated or focused charges, after which they fall asleep with melting sand. With the qualitative implementation of preparatory work in the process of explosion, the frozen soil is completely crushed, without damaging the walls of the pit or trench.
Fig. 5.46. Methods of loosening of frozen soil explosion:
a - tongue charges; B - the same, well; - the same, boilers; M is the same, small-calming; d, e is the same, chamber; z - the same, slotted; 1 - BB charge; 2 - bottom; 3 - breast of slaughter; 4 - sleeve; 5 - Shurf; b - galley; 7 - working gap; 8 - compensation gap
Basin explosives The soil is developed by excavators or earthmoving machines.
5.11.4. Direct development of frozen soil
Development (without prior loosal) 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 monolithicness of the frozen soil is broken by cutting it into blocks. With the help of hinged equipment on the tractor - the hydroelectric machine, the soil is cut with mutually perpendicular penetrations to blocks of 0.6 ... 1.0 m wide (Fig. 5.47). With a shallow depth of freezing (up to 0.6 m), only longitudinal cuts are enough.
Bar machines that cut the cracks have one, two or three perched chains, hung on tractors or trench excavators. Bar machines allow you to cut into the frozen ground slit 1.2 ... 2.5 m. Use steel teeth with a cutting edge of a durable alloy, which extends their service life, and when wear or abrasion allows you to quickly replace them. The distance between the bars is made depending on the soil through 60 ... 100 cm. Development is produced by the "reverse shovel" excavators with a lattice of a large capacity or a boulder of the soil, the wolves move from the site being developed into dop bulldozers or grants.
Fig.5.47. Block development scheme:
a - cutting the gap of the steam machine; b - the same, with the removal of the blocks by the tractor; B - the development of a pit with the extraction of blocks of frozen soil with a crane; I - layer of frozen soil; 2 - cutting chains (bars); 3 - excavator; 4 - cracks in frozen soil; 5 - sliced \u200b\u200bsoil blocks; 6 - blocks movable from site; 7 - Crane tables; 8 - vehicle; 9 - ticky capture; 10 - construction crane; 11 - Tractor
The mechanical method is based on the power, and more often in combination with a shock or vibrational effect on an array of frozen soil. The method is implemented by using conventional earthmoving and earthmoving machines and machines with specially designed for winter conditions of the working bodies (Fig. 5.48).
Conventional serial machines are used in the initial winter period, when the depth of the primer of the soil is insignificant. Direct and reverse shovel can develop a soil at a depth of freezing 0.25 ... 0.3 m; with a bucket with a capacity of more than 0.65 m3-0.4 m; Dragon excavator - up to 0.15 m; Bulldozers and scrapers are able to develop a precipitated ground to a depth of 15 cm.
Fig. 5.48. Mechanical method of direct soil development:
a - bucket of an excavator with active teeth; b - the development of the soil by the "reverse lopa-ta" excavator and the grip-teschemic device; in - earth-milling machine; 1 - bucket; 2 - Tooth Kov-Sha; 3 - drummer; 4 - vibrator; 5 - grip-tinge device; B - Duck a bulldozer; 7 - hydraulic cylinder for lifting and lowering the working body; 8 - worker (mill)
For winter conditions, special equipment for single-loving excavators - buckets with vibrational active teeth and buckets with a tester-teschemic device are developed. The cost of energy to cut the soil is about 10 times more than on the rocking. Introduction to the cutting edge of the bucket of the excavator of the vibrational mechanisms, similar to the work of the jackhammer, bring good results. Due to excessive cutting efforts, such single-sized excavators may lay aside the array of frozen soil. The process of loosens and soil excavation turns out to be united.
The development of the soil is carried out by multi-domestic excavators specifically designed for trenches in the frozen ground. For this purpose, a special cutting tool is served in the form of fangs, teeth or crowns with solid metal inserts, strengthened on buckets. In fig. 5.48, and shows the working organ of a multi-loving excavator with active teeth for the development of rock and frozen soils.
The layer development of the soil can be carried out by a specialized earth-milling machine that takes off the chips to a depth of 0.3 m and a width of 2.6 m. The movement of the developed frozen soil produce bulldozer equipment included in the machine kit.
When inclusable with the help of the cathodes of the ground section into the electrical circuit, the heating current of 120, 220 and 380 V can be missed through it.
The electrical conductivity of the soil depends on its humidity (Fig. 3, a), state and temperature of moisture, concentrations are in the ground solutions of salts and acids (Fig. 3, b), the structure and temperature of the soil (Fig. 3, c), etc. .
The complexity of the structure of the soil occurring physical phenomena and changes related to power processes, significantly complicates the theoretical side of the soil electrical heating, which is still in the study stage.
Fig. 1. Installation of horizontal (stringed) electrodes on frozen soil with filling sawdust
1 - frozen soil; 2 - horizontal (inkjet) electrodes with a diameter of 12-16 mm; 3 - wires, supplying current; 4 - sawdust moistened with salt solution; 5 - upper insulation (tol, wooden shields, mats, etc.)
Fig. 2. Installation of vertical (rod) electrodes in frozen soil with frighting sawdust
1 - vertical electrodes; 2 - wires supplying current; 3 - sawdust, moistened with salt solution, 4-top insulation (only tol, wooden spits, mats, etc.)
Taning the soil is performed using horizontal (shunt) and vertical (rod and deep) electrodes. When thawing with horizontal electrodes (Fig. 1), the surface of the heated portion of the soil is coated with a 15-25-cm layer moistened with an aqueous solution of salt (sodium chloride, calcium, copper sulfate, etc.) with a purpose only to bring current and heat the upper layer of frozen soil, so As the latter, even at a voltage of 380 in current practically does not miss.
With horizontal electrodes, heat is transmitted initially soil only from the heating layer of sawdust. Only the upper minor thickness of the soil layer adjacent to the electrodes is turned on in the electrical panel and is the resistance in which heat is distinguished.
The distance between the rows of electrodes included in different phases is 40-50 cm at a voltage of 220 V and 70-80 cm at a voltage of 380 V. The use of horizontal electrodes is advisable in heating the frozen bases and a small (up to 0.5-0.7 m) of the depth of freezing, as well as in cases where the vertical (rod) electrodes cannot be applied due to the small electrical conductivity of the soil or the impossibility of driving them into the ground.
When thawing with vertical rod electrodes, wet sawdusts first serve as an initial to warming up the upper layer of soil, which, as it turns on to the electrical circuit, after which the sawdust only reduces the heat loss of the thawed soil. Instead, sawdust can serve solutions of salts poured into the grooves in the ground, punched with chisel between all electrodes to a depth of 6 cm.
When shelting the surface of heated soil with a layer of dry sawdust, as practice shows, the device of such groove gives good results.
The use of vertical electrodes is more efficient at a depth of frozen soil more than 0.7 m, as well as if it is impossible to ensure proper contact between horizontal electrodes and soil. In solid (clay and sandy soils with a humidity of more than 15-20%) electrodes are clogged to a depth of 20-25 cm, and then immersed deeper as the soil is thawed (approximately every 4-5 hours).
The distance between the electrodes is prescribed from 40 to 70 cm depending on the voltage, the nature and temperature of the soil. When thawing to a depth of 1.5 m, it is recommended to have two sets of electrodes - short and long; By thawing the soil to the depth of short electrodes, they are replaced with long. Heated soil to a depth of 2 m and more should be made in several techniques, layered with a periodic removal of the outlined layers when the current is turned off. In order to save electricity and the maximum power use, it should be strive to strive to the end of the exhaustion, the temperature of the soil does not exceed + 5 ° and the maximum + 20 °, and the heating should be partitioned by periodically turning off the current.
Fig. 3. Changing the resistivity of the soil depending
A - from the moisture content of the red clay soil, b - from the contents of NACI in the clay ground with 30% of its humidity (by weight), 8 - from the soil temperature with humidity 18.6%
Installation for thawing soil consists of shields and soffits (4-5 per distribution shield) to connect electrodes to the network.
When using deep electrodes, thawing of frozen soil is produced from the bottom up to its daily surface. For this, the round steel electrodes with a diameter of 12-19 mm (depending on their length and soil hardness) are scored through the entire thickness of the frozen layer by 15-20 cm into a telly soil. At the beginning of the thawing, the electric current extending in the soil mob, heats it and pulls the part of the illuminated layer directly directly. Thus, the heat flux, gradually increasing the thickness of the bottom up, sequentially heats the frozen soil, and almost all the heat released heat is used to yield the frozen layer.
This method of thawing, in addition to reducing heat loss, gives a number of other benefits.
As it is known, excavators can develop without preliminary loosening the frozen crust of the soil with a thickness of up to 25-40 cm, which makes it possible to reduce the depth of the soaked soil. Since the upper layers of the soil are usually the most complex and energy-intensive, then developing them in non-taxable state reduces electricity consumption and accelerates the production of work.
The use of higher voltage makes it possible to increase the distance between the electrodes. The latter at a voltage of 220 V is taken in 0.5 m, and at 380 V is already 0.7 m.
The lower end of the electrode is sharpened, and in the top drill through a hole with a diameter of 3-4 mm, through which the copper bare wire is passed 25-30 cm; One end of the wire is welded to the electrode, and the other join the electrical network with the subsequent alternation of the phases.
In case of difficulty driving electrodes, wells in diameter, which is 1-2 mm less than the adopted diameter of the electrode.
According to the experimental data of Sukhlinka with a humidity of 18% with a depth of 1.5 m and the voltage of the current 220 V is thawing for about 16 hours.
The heated pad is isolated by a portable fence and multiply with warning signals with a categorically prohibition of entering it.
When applying any method of heating the soil, it is necessary to strictly follow the rules set forth in the special "instructions for the use of electrical heating in construction.
Towing high frequency currents. The frozen soil permeates for high frequency currents, and it is heating due to heat allocated in the ground when placing it and the alternating electric field of high frequency.
The high frequency generator consists of an increase in transformer, rectifier, generator lamps, capacitors and an oscillatory circuit. Mobile installation is mounted in the trapper and feeds from a voltage of 220-380 V or from a mobile power station.
The method is possible with a small amount of work, the development of trenches and especially in emergency work, when the deadline for execution is a decisive factor.
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