RU2647517C1 - Method for erecting embankment from substandard soils on permafrost - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: method for erecting a road embankment on permafrost with increasing permafrost and general stability includes allowing thawing the soil of the active layer at the embankment base (with a reserve for setting) during operation. In the lower part of the embankment, a weakly water-permeable soil is laid in a layer with a thickness determined from the ratio: 1.3≥H_fr/H_th≥1.0 (1), where H_fr and H_th are the depth of freezing and thawing of the embankment and the active base layer (with the moisture of initially unstable soil layers, with a compaction ratio of 0.90), m. The initially unstable layer, in the lower part of the embankment, is arranged from temporarily substandard (overmoistened and/or frozen) soil, mainly, using reinforcing layers (from geosynthetics, geomembranes, geocomposites, etc.), and while reinforcing, the above condition is complied with. After that, the upper stable (working) layer from standard or draining soil is poured out (pushed "from the head" on thawed soil) and compacted. Then, unstable layers are rapidly consolidated by the dynamic action of the traffic flow motion.

EFFECT: increasing the speed and environmental friendliness of constructing road embankments on permafrost with strengthening their permafrost and general stability in conditions of global warming.

2 cl, 2 tbl, 1 dwg

Description

The invention relates to the field of transport construction in areas of permafrost. It is mainly intended for the construction of road embankments on unstable permafrost (taking into account the ongoing global climate warming).

A known method (the first design principle) of the construction of road embankments in the areas of permafrost [SP 34.13330.2012 p. 7.50; p. 7.52 and BCH 84-89 p. 3.9; paragraph 3.11], in which the height of the embankment is prescribed from the condition of ensuring the artificial raising of the natural, natural upper horizon of permafrost soils (VGVMG) not lower than the bottom of the embankment. With its subsequent safety at this level, during the entire period of operation of the road.

The disadvantage of this method is that it is not intended (and does not take into account in its heat engineering nomograms) for use in global warming. This warming in the regions of the north of the Russian Federation is now accompanied by a significant (3-5 ° C) increase in average annual air temperatures (mainly winter), and an increase in the amount (by 10-20%) of warm precipitation. Additional rainfall, as well as earlier and more intense melting of snow, cause off-design flooding. Warm water flows into the lower part of the embankment, mainly covered with water-permeable (rocky, coarse-grained, wood-sandy) soils, as well as condensation of water vapor (with the release of 539 calories of heat from 1 gram of condensed water). These factors heat the frozen base of the embankments from 1.5 to 4.5 ° C. Together with extra-calculated warming, all this leads to the beginning of thawing of the frozen base with a long-term loss of stability of road embankments. Additional disadvantages of this method is the need for the construction of road embankments of increased height and mainly from the normatively recommended during construction, as a rule, scarce (and expensive) rocky, coarse and sandy draining soils. This lengthens the construction time, makes it difficult (due to the range of delivery and the frequent complexity of development) and makes it more expensive. At the same time, long-term thermal (permafrost) and, accordingly, the general stability of the frozen base with road embankments is not provided.

There is also known a method (third design principle) of the construction of the subgrade, mainly in areas of the distribution of intermittent and island high-temperature (unstable) permafrost [SP 34.13330.2012 p. 7.50]. According to this method, the permafrost soils at the base of the embankment are thawed first and the road lane is drained before the construction of the embankment.

The disadvantages of this method are its duration and limited applicability (mainly near the southern border I _z - the southern permafrost subzone with intermittent and island permafrost, insignificant, mainly up to 2.0-2.5 m, thickness). In this case, problems arise with the provision of drainage and compaction of the thawed and, as a rule, waterlogged weak base. This requires the implementation of additional special measures and a long consolidation period, with the presence of threshold loads in the bases of the embankments. The latter is feasible mainly for high embankments. All this limits the application of this method and lengthens the construction time.

The closest in technical essence to the proposed method is the method (second, basic, design principle) [SP 34.13330.2012 p. 7.49, p. 7.50 and p. 7.53 and BCH 84-89 p. 3.9 and p. 3.12]. It allows partial thawing of the soil of the active layer at the base of the road embankment during operation, with limited operational rainfall to acceptable limits (depending on the type of pavement and the staging of its structure).

The disadvantages of the known method (prototype) are all the above disadvantages of the first method (design principle) and it is also not intended for use in global warming. This leads to the subsequent mass (embankment of the BAM railway, the Amur railway station / Chita-Khabarovsk /, Lena, Vilyuy, Kolyma, etc.) and the long-term loss of stability built on it on permafrost road embankments. The disadvantage of this method is the limited permissibility of using it, for filling in the embankment, giving a significant draft, of local, temporarily substandard (waterlogged and / or frozen), clay and other soils, which sharply slows down the pace and degrades environmental friendliness (and therefore economy ) construction. This is due to the prevention in this method of exceeding the limits of permissible (normative) operational precipitation (assigned, by type of d / o, etc.). At the same time, the value of operational sludge is almost completely used (consumed) when calculating the permissible thawing depth (according to the normatively permissible amount of sludge) of the compacting active (seasonally thawing) layer at the base of the embankment. An additional serious drawback of this method is the increased leakage of rain, flood and other warm waters into the sedimentary bowl formed, with this method, in a frozen base. Especially when filling the bottom of the embankment from draining soils. The flow of warm water into the base of the embankment on permafrost is accompanied by the massive development of thermokarst, with the long-term loss of permafrost and general stability of road embankments. [SP 34.13330.2012 p. 7.53 tab. 7.6].

The objective (goal) of the invention is: Increasing the pace and environmental friendliness (economy) of the construction of road embankments on permafrost (constituting 65% of the territory of the Russian Federation) with increasing their permafrost (and general) stability in the context of the ongoing global climate warming.

This is achieved by the fact that in the method of erecting a road embankment on permafrost, including the assumption of thawing of the soil of the active layer at the base of the embankment (with a margin for sediment) during operation, according to the invention, a low-permeable soil is laid in the lower part of the embankment with a layer thickness determined from the ratio:

where N _pr and N _from - the depth of freezing and thawing of the embankment and the active layer of the base (with humidity of the initially unstable soil layers, with a compaction coefficient of 0.90), m

at the same time, the initially unstable layer in the lower part of the embankment is arranged from temporarily substandard (waterlogged and / or frozen) soil, mainly using reinforcing layers (from geosynthetics, geomembranes, geocomposites, etc.), and when reinforcing, the following condition is met:

where S _add and S - permissible (by standards) sludge and sludge of an unstable layer (waterlogged and / or thawed frozen) soil under a given load, m;

- коэффициент армирования; |

- reinforcement coefficient; |

where E and E _a are the deformation modulus of the unstable soil layer before reinforcement and after reinforcement, MPa

after that they pour it (they push it “from the head” onto the thawed overmoistened soil) and compact the upper, stable (working) layer from the conditioned or draining soil, and then the unstable layers are accelerated to consolidate by the dynamic effect of the traffic flow.

Moreover, local clay soils are mainly used as poorly permeable, substandard, and the depth of thawing and freezing of the embankment together with the active layer of the frozen base is determined by the formulas:

- продолжительность годового периода с плюсовыми температурами воздуха, час;Where

- the duration of the annual period with plus air temperatures, hours;

L _ν is the amount of latent heat of the phase transitions of moisture in 1 m ³ , kJ / m ³ or kcal / m ³ ,

,

,

where L _o is the latent heat of ice formation (equal to 334 kJ / kg or 80 kcal / kg);

ρ is the density of the soil, kg / m ³ ;

ρ _d is the density of dry soil, kg / m ³ ;

W _w - unfrozen water content;

- суммарная влажность грунта, дол. ед.;

- total soil moisture, dol. units;

при коэффициенте уплотнения 0,90 ориентировочно составляет:Total soil moisture

at a compaction factor of 0.90, approximately:

;- sandy and silty sandy loam -

;

;- light sandy and silty loam -

;

,- heavy sandy and silty loam, clay -

,

- оптимальная влажность грунта;Where

- optimum soil moisture;

λ _mi is the coefficient of thermal conductivity of the soil in a thawed state, W / (m⋅ ° С) or kcal / (m⋅h⋅⋅ ° C);

Т _max - average monthly air temperature for the warmest (July) summer month (taking into account experimental temperature corrections), ° C;

С _mi - volumetric heat capacity of thawed soil, kJ / (m ³ ⋅ ° С) or kcal / (m ³ ⋅ ° С);

- средневзвешенный коэффициент теплопроводности слоев многослойной конструкции (дорожная одежда, слои насыпи и основания) в мерзлом состоянии, Вт/(м⋅°С) или ккал/(м⋅час⋅°С);Where

- weighted average coefficient of thermal conductivity of layers of a multilayer structure (pavement, layers of the embankment and base) in the frozen state, W / (m⋅ ° С) or kcal / (m⋅h⋅⋅ ° C);

λ ₁ , λ ₂ , ..., λ _n are the coefficients of thermal conductivity of the layers in the frozen state, W / (m⋅ ° С) or kcal / (m⋅h⋅ ° С);

T _s - average air temperature for a period with negative air temperatures (taking into account the predicted winter climate warming by 3-5 ° C in the northern territories of the Russian Federation and experimental amendments), ° C;

τ _s - the duration of the annual period with negative air temperatures, hour;

H _from - the depth of thawing of a multilayer structure, m;

- объемная теплоемкость слоев в мерзлом состоянии, кДж/(м³⋅°С) или ккал/(м³⋅°С).

- volumetric heat capacity of the layers in the frozen state, kJ / (m ³ ⋅ ° С) or kcal / (m ³ ⋅ ° С).

The proposed method for the construction of road embankments on permafrost differs from analogues, prototype, etc. in that it is expanded and direct, the use in the construction of substandard local (waterlogged and / or frozen) soils, as well as increased thermal (permafrost) and general stability of the road embankment on an permafrost basis in it provide the following:

- In the inventive method, for the first time in permafrost road construction, it is proposed to use the natural conditions for the emergence and preservation of natural permafrost, now for the foundation of the road embankment. In permafrost science, this is formulated as follows: the thermal state of the permafrost mass (and for the embankment - its frozen base) is stable if the soil layer thawing in summer (active) completely freezes in winter (i.e., N _pr / N _from ≥1.0). Moreover, according to the generalized data of long-term permafrost observations and studies of prof. V.A. Kudryavtsev et al. (Permafrost department of Moscow State University) established that, based on the existing interannual variability of seasonal thawing, etc., to ensure the stable existence of permafrost, the depth of seasonal freezing should be, on average, 20-30% more than the thawing depth. [Shur Yu.L. The upper horizon of the thickness of frozen rocks and thermokarst. - Novosibirsk “Science”, 1988 - p. 33.]. This also takes into account the constant (year-round) warming effect from below on the permafrost of the geothermal heat flux (on average equal to 0.046 W / m ² ) from the hot bowels of the Earth. This heat flow is dangerous for large areas with unstable permafrost, resulting from global warming, and is not taken into account in analogues and prototype.

A necessary, generalized condition for the natural provision of permafrost preservation at the base of the permafrost embankment can be represented as:

If the lower limit of this ratio is violated, permafrost ceases to form and begins to degrade (thaw). Exceeding the upper limit is naturally (and therefore environmentally) excessive, and leads to the implementation (provision) of additional technical cooling measures. This lengthens the construction time (reducing its pace) and increases its cost, requiring large expenditures of resources, which is technically, economically and environmentally unfeasible. As Newton noted: "Nature herself does nothing in vain and does not achieve with the help of much that can be achieved with the help of little."

This optimized natural condition allows, with the involvement of additional, naturally-occurring cooling mechanisms (effects), to provide the necessary increase in permafrost stability in the foundations of road embankments. As a result, the degree of dynamization (adaptability) of the “embankment-permafrost” system increases to natural conditions, which is the most environmentally friendly and economical.

The use of weakly permeable clay soil with regulation of the thickness of the lower layer of the embankment laid from it provides the following natural, cooling effects: thermodiode, capillary-evaporation, anti-heat-filtration, anti-condensate, etc. This then allows the natural forces to regulate its necessary and sufficient in the frozen base of the embankment cooling. Moreover, in the heat engineering calculations of the proposed method, the moisture content of clay soil, regardless of its moisture during construction, is taken at a compaction factor of 0.90. The latter, according to available permafrost observations in road embankments, is most consistent with subsequent long-term operational humidity. By calculating the regulation of the thickness of the upper layer together with the selection of the necessary reinforcement coefficient (to comply with condition 2 of this method, according to the permissible operational draft), they simultaneously provide for the direct use (without preliminary drainage and / or defrosting) of local, temporarily non-conditional (waterlogged and / or frozen ) soil, giving a significant sediment, for filling the bottom layer. Other well-known methods, quickly and in large volumes (mass) to dry and at the same time compact the clay soils on permafrost, for the needs of road construction, is not possible. In the heat engineering formulas and calculations of the proposed method, when adjusting and assigning the thickness of the lower soil layer, significant (from experimental data) corrections for the thermodiode, capillary-evaporative, anti-heat filter and anti-condensation cooling effects (not taken into account in other methods) are taken into account. The average values of these corrections (determined from field observations and measurements) are given in the guidelines developed by the authors of the ODM “Methodological recommendations for the geocryological forecasting of the stability of road structures in the design, construction and operation of roads” Rosavtodor, 2016 (Table 6.2. Natural factors acting on amplification or degradation permafrost and the approximate degree of their impact). Using the work of natural mechanisms themselves in technical systems is environmentally friendly, economical, and most operational reliable. The basic laws of ecology are: “Nature knows better”, “Everything natural is economical” [Evgeniev I.E., Karimov BB Roads in the environment. - M .: "Transdornauka", 1977 - 285 p.].

The use of natural laws - (1) to maintain permafrost in the foundations of road embankments and engineering structures, in other known technical solutions and sources, on permafrost construction, was not found by the authors.

- By the ratio of (2) The clay soils (sandy loam, loam, clay) most prevalent in the permafrost regions of the North are mainly in very wetlands (with humidity near or exceeding the yield strength) and / or frozen state. [BCH 84-89 "Research, design and construction of roads in the areas of permafrost." - M: "Soyuzdorzhnii", 1990, p. 7, tab. one]. In the frozen and / or excessively waterlogged state, these soils are unsuitable for construction (and normatively prohibited). In practice, it is not possible in large volumes (necessary to ensure mass road construction) to quickly thaw them and / or drain them to regulatory requirements. This is explained by a short warm period and not a rare excess of precipitation over evaporation in permafrost regions. And also, with an average depth of seasonal thawing of 1.5-1.8 m, a close level of permafrost waters, with a capillary rise of water in clay soils of up to 1.6-1.8 m. As a result, gradually thawed overmoistened clay soils in permafrost are constantly in a capillary-backed state. Any evaporation (drainage) of moisture from their surface is immediately compensated by an additional capillary rise (suction) of water through the capillaries. At the same time, waterlogged clay soils strongly adhere and are squeezed out under load, without having the necessary bearing capacity. Driving through them in a waterlogged state (or in a layer of their thawed winter dusting) of wheeled and even tracked construction equipment is extremely difficult or impossible (because it falls through them and sits on the bottom). It is not possible to mechanically compact these soils or squeeze water out of them using conventional construction equipment. In view of the foregoing, it was not possible to use them directly (without thawing and / or drainage) in the construction of road embankments. However, in a thawed and drained (to the required humidity) state, they are suitable for the construction of road embankments. At the same time, clay soils provide the simplest, technologically available and reliable (natural) operational protection of the bases of embankments on permafrost from flowing there, through the lower part of the embankment, (when using skeletal soils) warm surface rain and flood waters. As a result, they provide anti-heat filter and anti-condensation cooling effects. In addition, they create natural cooling thermodiode and capillary-evaporative effects, which is also necessary for independent (natural) enhancement of the conservation of natural permafrost in the bases of road embankments. It was possible to apply these soils more widely without preliminary defrosting and / or draining them during the construction (for example, in a loosened frozen state or partially thawed from side reserves) of road embankments, including when reinforcing them with various geosynthetics. At the same time, a significant (non-normative) value of construction fall can be reduced to the required value by selecting the necessary geosynthetics according to the experimental reinforcement coefficients - K _a and relation (2). As a result of this, direct (without thawing and / or drainage) use of local clay soils temporarily in a substandard condition is achieved in this method. In the conditions of permafrost, thawed, drained and compacted clay soils in a mass volume have not yet succeeded in other ways. At the same time, reinforced embankments according to the proposed method, initially calculated to extinguish significant construction residues, with the usual occurrence of off-settlement sediments in the future (from off-design warming, flooding, under-consideration of geology, miscalculations in predictive design, etc.) will also smooth out their irregularities and reduce their size. As a result, embankments erected using this new method will additionally work in the same way as embankments originally designed to reduce and smooth out (i.e. quench) uneven production sediments on a weak foundation (according to the fourth design principle). It also provides them with subsequent increased overall stability. In the context of the ongoing global warming, this is quite important, in mind, more significantly and rapidly changing, after design studies, permafrost-soil and hydrological conditions in permafrost areas.

- To accelerate the consolidation of the dynamic (micro-shaking) impact of the traffic flow (leading simultaneously to a decrease in the required threshold load - R _o ). Waterlogged (mainly clay, etc.) soils in low (up to 3 m) embankments (comprising up to 98% of all road embankments) practically do not consolidate (i.e. do not self-compact under the influence of their own weight). This is due to the lack of the necessary, ultimate threshold load P _о on the soil, with which the consolidation process begins, due to the structural strength of the soil. [Cm. "Guide to the construction of subgrade road". - M. "Transport", 1982, p. 8.13, table. 8.3].

There is a method of erecting an embankment from frozen, loosened (lumpy) waterlogged clay soils, with the introduction into the intercomplex voids, in the optimal amount (for drainage and stability), of a loose draining material (for example, sand, etc.) and a dynamic (vibrational) compaction effect on the embankment after thawing by the movement of vibratory rollers and technological transport. [Copyright certificate (patent) No. 1615285 E02D 17/18 Method of erection of the embankment on permafrost].

The prior art also knows a method of erecting an embankment, in which when erecting the embankment, after filling the upper, working layer from conditioned or draining soils, with geosynthetic interlayers, it is compacted by the movement of technological transport, and also by the operation of soil compaction agents [Patent RU 2148125 C1, E02D 17/20, 04/27/2000, 9 pp.].

In the inventive new method, the soil is not mechanically compacted by the movement of technological transport or the operation of soil compaction machines and mechanisms. This (as explained above) is either impossible, or will require 1-2 years, technological movement, which is long-term (i.e. will drastically reduce the pace of construction), and not technologically. In the proposed method, using the reinforcement condition (2), reduce the unevenness of the construction draft of the embankment to the size of the unevenness of the permissible operational precipitation, and immediately open the normal (normative) operational movement along the upper working layer of the embankment. The required surface operational strength (deformation modulus, adhesion and angle of internal friction) of the embankment is ensured by its upper, stable (working) layer of normatively compacted, conditioned or draining soil. The residual (excess) construction sediment, lower, unstable soil layers, due to reinforcement according to condition (2) and a strong upper layer, becomes uneven, as from normative permissible (during normal operation) precipitation. This allows you to immediately open on the embankment the usual operational traffic. The accelerated process of consolidation to the density necessary to achieve the normative stability of the lower, unstable, soil layers from the existing operational load gradually occurs already in the process of the (normal) operation of the road embankment itself. At the same time, due to operational dynamic impact (concussion, etc.) from the traffic flow, the required consolidation (compaction) of the lower, unstable soil layers (embankment and foundation) is ensured in low (up to 3 m) road embankments (making up 98% of all embankments ), without which the threshold load necessary for the start of consolidation does not arise - R _o .

Conducted by the authors and other researchers of the Omsk Union in the 80-90s, long-term field observations and laboratory studies (on odometers and a stabilometer) revealed this effect. Waterlogged clay soil laid in the lower part of the embankment, even without the presence of layers of drainage material in it and the absence of the necessary threshold sealing pressure - P _o , began to rapidly consolidate (to be compacted with squeezing out excess water) in the presence of a small (much lower than P _o ) static load and constant slight dynamic (micro shaking) effects. For example, from the movement of vehicles, during field trials, or from the effects of a simulating it rotating, an eccentric on a stabilometer (three-axle soil compression device) under laboratory conditions. This is due to the occurrence of periodic micro-shocks of waterlogged soil. Micro-shocks under load cause microtixotropy (microvibro-dilution), which contributes to constant repacking of soil particles under pressure from above (for example, it is known that resistance to plow movement decreases 10-20 times if the ploughshare vibrates at a certain frequency). As a result of constant dynamic impact, an accelerated console consolidation also occurs (1-2 warm periods, instead of the usual 6-8 years). Moreover, with a load of P _o lower than necessary to ensure normal (static) consolidation. In practice, the latter occurs at a static pressure of even a small thickness (with pressure from its own weight, below the threshold P _o necessary to start consolidation), the topsoil (with a thickness of 0.60-0.80 m instead of 2.5-3 m). Observations of road embankments with unstable layers showed that initially waterlogged and frozen (unconsolidated) clay soil in the lower part of the embankment (usually winter dumping), after 1-2 warm periods of normal operation of the embankment, reaches a compaction coefficient (K _y ) of about or equal to 0 , 90-0.92 (on average - 0.91), even in low (up to 3 m) embankments. [Final report on research for ODM: “Methodological recommendations for the design of subgrade on permafrost using local (substandard - waterlogged and frozen) soils", Omsk, 2011, UDC 624.139: 625.731.1, state No. registration 01201155351, - 319 p.]. This degree of compaction (according to the required normative compaction coefficient K _u ) is already sufficient for normative (usual) operation of previously substandard (unsuitable for moisture) clay soil in the lower part of road embankments [Surveys, design and construction of roads in permafrost areas. BCH 84-89. Alliances. M .: 1990 - 271 p. tab. 8].

The established effect of a decrease in the dynamic effect of the magnitude of the threshold load required to start consolidation — P _o and consolidation acceleration — is not known and is not indicated in other known (including the above) methods.

The new method achieves accelerated with an acceptable operational settlement, dynamic-consolidation compaction (under static load, from the top layer of the embankment, less than the threshold load - P _o required for normal consolidation) reinforced by geosynthetic interlayers of overmoistened clay soil, in the lower part of the embankment, in operation period. This, immediately after construction (dumping), provides regulatory movement along the embankment of the operational traffic flow. Thawed clay in the summer and temporarily excessively moistened clay soil of the lower part of the road embankment on permafrost, with repeated rapid two-sided winter freezing, is usually characterized by a slight (on average up to 2-3 cm), uniform frosty rise, without the formation of deeps. This value of temporary frosty rise and subsequent summer lowering does not exceed the values of permissible normative precipitation. At the same time, poorly permeable clay soil performs important useful functions. It does not allow warm water (rain and flood) to flow into the base of the embankment in the summer, and in winter, it recharges (freezes) with additional cold the frozen base as a “thermal diode”. As a result, an increased supply of cold to the frozen base of the embankment in winter is achieved (due to the fact that the conductive thermal diffusivity of ice in the soil is 8 times higher than that of ground water) and to prevent its summer warming from flowing into the bowl of sediment at the base of the embankment of warm water. The latter is most characteristic of the usual, normative, use of draining (permeable) soils in the lower part of the embankment, with the assumption of their settlement in the base of the embankment, with the 2nd (main) principle / method (prototype) of designing and building permafrost embankments.

In the proposed method, three effects known from the prior art are combined:

- ensuring the optimal sufficient natural conditions for the emergence and maintenance (conservation) of permafrost:

- ensuring a decrease in the size and unevenness of sedimentation of unstable soil layers of the embankment and foundation - S, to the required operational level, by reinforcing, with its regulation according to the experimental reinforcement coefficients K _a , and observing the ratio:

- ensuring (especially for embankments below 3 m that make up 98% of all road embankments) a decrease in the threshold load - P _o (without which the consolidation process does not begin in them) and accelerating consolidation (from 6-8 years to 1-2 years). Due to the dynamic impact of the very operational transport flow directly onto the soil in unstable layers of the embankment and base (with a decrease in the amount of settlement, and therefore its unevenness, to the required standard values).

This previously unknown combination (combination) is not just a sum, but a necessary combination of interrelated and complementary effects, without any of which the purpose of the invention is not provided. This combination creates a new set of useful effects, and is not known in other methods and technical solutions (ie, meets the criterion of "novelty"). It is also not obvious (that is, it has "significant differences" from others and meets the criterion of "inventive step") and provides the purpose of the invention:

1. Increasing the pace and environmental friendliness (efficiency) of the construction of road embankments on permafrost.

2. Provision of expanded and direct (direct) application in the construction of temporarily non-conditioned (waterlogged and / or frozen) local weakly permeable soils, the most common in permafrost regions of the North of the Russian Federation.

3. Strengthening (ensuring) permafrost and general stability of road embankments in permafrost distribution areas (including, taking into account the observed and predicted progress of global climate warming).

In the proposed new technical solution, the inventive law is used to increase the degree of ideality of technical systems (TS). According to him, the technical system, when approaching the ideal, first fights (counteracts) with the forces of nature, then it technically adapts to them and, finally, it itself uses the forces of nature. At the same time, it “automatically” itself and controls them, for the needs of a person, but without his direct intervention (according to the “made and forgot” system). This law is most effectively applied to that element (for example, an embankment on permafrost) that is directly located in the zone of conflict (technical conflict) or itself generates undesirable phenomena. For example, the frequent occurrence of processes of degradation (thawing) of permafrost after the construction of road embankments. At the same time, an increase in the degree of TS ideality is, as a rule, carried out by using previously unused resources (substances, fields, physical effects, etc.) available in the zone of the problem (technical contradiction). According to this law, the farther the resources are taken from the conflict zone, the less is it possible to move towards an ideal solution. In view of this, the provision in the new method of direct use in the construction of local, substandard (frozen and / or waterlogged) weakly permeable (clay) soils, with the involvement and launch of additional (not previously used) natural-natural, self-cooling mechanisms (physical effects), most optimally in advancing to the perfect technical solution.

In addition to the above law, the viability of any system is determined by another main inventive indicator: the degree of dynamization. That is, by increasing the ability of the vehicle to be more mobile, flexible and adapt itself to the external environment.

Reliability and stability of the “embankment-permafrost” system in a dynamic (changing) natural permafrost environment directly depend on its ability to change (adapt). The degree of dynamization (ie, self-adaptability to warming in permafrost and uneven sediment) of the technical system, in the form of "road embankment - permafrost", according to this method increases significantly (compared with analogues and prototype). This is achieved by connecting additional, cooling natural effects, as well as the effect of accelerated dynamic consolidation and ensuring the reduction and smoothing of the unevenness (blanking) of these embankments, and then other, possible, when warming unforeseen and extra-calculated subsidence.

According to claim 2 of the claims:

The Laboratory of Global Energy Problems of Professor V. Klimenko, based on the collection and processing of climatic, geological, glaciological, anthropogenic and other data, constructed model empirical graphs of global climate change and its forecast changes, which are well (adequately) consistent with the data of past and current practical instrumental temperature observations . In accordance with this empirical (experimental) model of global changes in air temperature and climate, in the period 2000-2100. in the regions of the North of the Russian Federation, the average annual air temperature ΔT is predicted to increase by an average of 3-5 ° C (with a simultaneous increase in rainfall by an average of 15-20% or more). In this case, the main warming will occur in the winter. [Nikonov A.P. A history of frostbite in the context of global warming. - M.: Publishing House NTs ENAS, 2007 - 296 p. - (according to the natural science data of the Laboratory of Global Energy Problems under the guidance of Dr. V. Klimenko)].

Additionally, the average calculated air temperatures for summer and winter periods can be reduced directly to the surface temperature of the embankment by introducing empirical (experimental) corrections [tab. 6.2 Natural factors acting on the enhancement or degradation of permafrost and the approximate extent of their impact. ODM Guidelines for geocryological forecasting of the stability of road structures in the design, construction and operation of roads. M .: Rosavtodor, 2016].

In the prototype, in order to avoid exceeding the permissible precipitation, in the second principle (main method) of designing road embankments on permafrost, for filling the body of the embankment it is recommended to use mainly, not rarely (especially in vast tundra and forest-tundra territories), deficient draining soils [Surveys, design and construction of roads in permafrost distribution areas. BCH 84-89. Alliances. M .: 1990 - 271 p. paragraph 3.18].

At the same time, not only the pace of construction is significantly reduced, and its cost increases sharply, but after passing the calculated (permissible by the 2nd principle) precipitation of the base, and immersion in the formed sedimentary bowl of draining soil, warm rain flows almost inevitably into the base from slopes, etc. (since Nature does not tolerate emptiness). As a result, thawing of the frozen soil of the base of the embankment in contact with flowing and filtered warm water significantly (several times) and non-computationally increases [Shur Yu.L. The upper horizon of the thickness of frozen rocks and thermokarst. - Novosibirsk “Science”, 1988 - p. 101].

The extraordinary thawing of the frozen base, then leads to the appearance of long-term uneven precipitation and a long-term loss of stability by road embankments. For example, according to the report of the Chukotavtodor Road Department, road embankments in Chukotka were mainly designed and built according to the second principle (prototype) from conditioned and draining soils. By 2000, such embankments already had a height 2 times lower than what was required by the design and thermal engineering calculation, and 15-20% of such embankments were almost completely immersed in the tundra. This required annual summer refills and maintenance, as well as constant winter clearing of snow drifts. Unscheduled operating costs significantly increased, in the absence of real travel and increased transportation costs (excessive consumption of expensive imported fuel and lubricants in the North, increased wear and tear of vehicles, significant delay and reduced speed of delivery of necessary goods, etc.). A typical example are those built according to the 2nd principle (prototype), permanently off-settlement sediment mounds of the BAM railway, the Amur railway station (Chita-Khabarovsk), the Lena railway station (BAM-Yakutsk), and Kolyma (Yakutsk-Magadan) and many others, due to the subsequent development of thermokarst degradation of permafrost under them. All this is even more aggravated by the ongoing warming and flooding (from an increase in precipitation) of permafrost territories. This causes multibillion-dollar damage, only from the need for constant repairs of road embankments (with the addition of slopes and ballast prisms with the rise of railway tracks or the replacement of railway stations). Significant damage occurs from operational and transportation losses. For example, reducing the average speed of movement, up to its stops, overspending fuels and lubricants and electricity, increased wear of vehicles, slowing down the delivery and transit of necessary goods, etc. [Kondratiev V.G. The experience of organizing an engineering-geological survey and monitoring of the subgrade of the Baikal-Amur Railway. // railway transport. Ser. “Way and track economy”: EI / TSNIITEI MPS. - 1992: - Issue. 5-6. - from. 28-44].

Ensuring the expanded and direct use of substandard local soils is the most environmentally friendly, economical and technological. This follows from the generalized domestic and foreign experience in road construction, as well as from scientific scientific permafrost studies. Extensive experience in economical, mass, and high-speed construction of the necessary (basic) permafrost road network is available in Canada. There 11 thousand km of roads were built in just 5 years, back in 1960-1965 (under the program “Face to the North” and its section “Roads to resources”), mainly from substandard local clay soils (instead of coarse-grained ones used earlier there soil). Local soils in the North of Canada were also mainly represented by highly waterlogged clays and loams (with a natural moisture content of 35-40%) [K.K. Grain Exploration and road construction in northern Canada. Proceedings of the 4th meeting-seminar on the exchange of construction experience in severe climatic conditions. Section of road construction. Vorkuta, 1966]. In pre-revolutionary Russia, the permafrost sections of the Transsib embankments were covered with wheelbarrows from clay soils of lateral reserves. In the process of filling, clay soils layer by layer, manually, were compacted by “pushers” and then, finally, compacted already under operational railway traffic. At the same time, road embankments were built several times more than with all modern equipment in the Soviet era (for example, the construction of the BAM, etc.), and at the same time much faster and cheaper. The permafrost and general stability of the Transsib pre-revolutionary railway embankments from clay soils, in practice, turned out to be much greater. Several times longer and more expensive (more expensive), the constructed road embankments of BAM, Amur, Lena, etc. (designed according to the 2nd design principle) are completely dumped from expensive coarse and rocky soils, but they have been sinking for decades (up to now) ( with a gradual decay of precipitation).

The invention is illustrated in the drawing.

In FIG. 1 shows a transverse profile (section) of a road embankment on permafrost. The embankment includes a top layer 1 of conditioned or drainage soil, sprinkled on a layer of substandard (waterlogged and / or frozen) clay and other soil 2, preferably with interlayers 3, (made of geosynthetic material) on the soil base 4 and on the surface of layer 2, natural soil base 4 may have a mossy cover (MCI) 5 and an active (seasonally thawing) layer 6.

The method is as follows. In the tundra and forest-tundra regions of the North, clay soils are most common, but very waterlogged (W _eats ≥W _fluidity ), and in summer, according to the seasonally thawed layer, there is no passing through of construction equipment. Therefore, in a longer (7-8 months) cold period, at the location of local, temporarily substandard clay (waterlogged and / or frozen) soils closest to the construction site, the frozen soil is loosened (by drilling and blasting or mechanically). Then he is being piled with a bulldozer into a pile. After that, by excavator or loader, the loosened frozen clay soil is loaded from the stack into dump trucks and transported to the embankment. The thickness of the upper and lower layers is preliminarily prescribed (under the condition of ensuring snow tolerance, the volume of available deficient conditioned or draining soils, etc.). The calculation according to condition (1) of this method determines the suitability (admissibility) of the assigned thickness of the upper 1 and lower 2 layers. If conditions (1) of this method are not met, the thicknesses of layers 1 and 2 (mainly layer 2) are adjusted (changed). By controlling the thicknesses of the layers, the fulfillment of condition (1) of this method is achieved. On the base 4 and 5 cleared (from snow, shrubs, etc.), layer 2 is poured, to the thickness established by condition (1). The surface of layer 2 is leveled with a bulldozer and a reinforcing layer 3 of geosynthetic material is appointed according to condition (2) of this method. The upper layer 1 is poured onto interlayer 3, layer 1 from conditioned or draining soil and compacted to the required (according to technical standards) density. After that, the technological and / or operational movement of transport is allowed on the surface of the embankment (the latter, mainly after the construction of pavement).

An example of the selection and appointment of the thickness of the upper 1 and lower layer 2 of the road embankment, with verification of compliance with the ratio (1) of this method:

It is required to carry out the construction of a road embankment in the area of the city of Nadym, if there is permafrost soil in the base, I1 permafrost subzone. The height of the snow-resistant embankment in the Nadym region is estimated to be 1.46 m. The guide (main) height of the embankment is 1.50 m. The thickness of the upper part (layer) of the embankment 1 is 3, on the layer of geosynthetics - 3, taken from the economy of scarce draining soil (sand), at a minimum strength of 0.6 m. The pre-assigned (selected) thickness of the lower part of the embankment is 2, sprinkled from local substandard (frozen and waterlogged) clay soil will be 1.50-0.60 = 0 , 90 m (in compacted, operational condition).

After that, the depth of thawing and freezing of this embankment design in the operational (steady and stable) state is calculated, i.e. with humidity, compacted to a compaction coefficient of not less than 0.90, originally waterlogged clay soil in the lower part of the embankment. In this case, the estimated moisture content of clay soil, (regardless of its initial moisture during construction), is taken, on average, equal to 1.3-1.5 of its optimal humidity, depending on the type of clay soil (according to experimental data from Table B. 12 of the mandatory Appendix B, SP 34.13330.2012 Automobile roads).

The initial data for calculating (checking and assigning) the thickness of layers 1 and 2 by the ratio (1) of this method:

- the average duration of the warm (with air temperature above 0 ° C) period in the region of Nadym is 3264 hours, and the cold period is 5496 hours;

- monthly average temperature for the warmest summer month (July) + 14.7 ° C;

- the average negative temperature for the cold period is 12 ° C (taking into account the predicted warming ΔT, i.e., minus 3 ° C);

- the height of the embankment from the conditions of snow tolerance - 1.46 m, taken equal to 1.5 m;

- the thickness of the upper layer of the embankment from sand is 0.6 m, the lower layer of the embankment from loam is 0.9 m, the mossy cover (MCI) at the base is 0.15 m, the soil of the base is loam;

- bulk density of dry soil: sand - 1720 kg / m ³ , loam of the lower part of the embankment - 1480 kg / m ³ , loam of the base - 1420 kg / m ³ , MCI or peat in the base - 270 kg / m ³ ;

- the estimated moisture content of the sand is 8%, the loam of the embankment is 24%, the loam of the base is 30%, the MCI or peat is 320%;

- coefficients of thermal conductivity W / (m⋅ ° C) and volumetric heat capacity kJ / (m⋅ ° C) of soils in thawed and frozen state:

- sand - λ _m = 1.45; λ _m = 1.65; C _m = 2155; C _m = 1800;

- loam of the embankment - λ _m = 1.35; λ _m = 1.50; C _m = 2765; C _m = 2050;

- loam base - λ _m = 1.45; λ _m = 1.55; C _m = 3015; C _m = 2175:

- MCI or peat -λ _m = 0.95; λ _m = 1.40; C _m = 4145; C _m = 2380;

- the amount of latent heat of the phase transitions of moisture in 1 m ³ , kJ / m ³ :

- sand - 45960;

- loam mound - 118640;

- loam base - 142280;

- MCI or peat - 288580.

To comply with the dimension during thermotechnical calculations, it is necessary to convert the values of the thermophysical characteristics of soils: thermal conductivity coefficient from W / (m⋅ ° C) to kcal / (m⋅h⋅ ° C) by dividing the data by 1.16; volumetric heat capacity from kJ / (m ³ ⋅ ° C) to kcal / (m ³ ⋅ ° C) by dividing the above data by 4.19; latent heat of ice formation from kJ / m to kcal / m divided by 4.19, which will be:

- sand - λ _m = 1.25; λ _m = 1.42; C _m = 518; C _m = 430;

- loam mound - λ _m = 1,16; λ _m = 1.29; C _m = 660; C _m = 489;

- loam base - λ _m = 1.25; λ _m = 1.34; C _m = 720; C _m = 520;

- MCI and peat - λ _m = 0.82; λ _m = 1.21; C _m = 989; C _m = 568;

- the amount of latent heat of phase transitions of moisture during freezing of the soil in 1 m ³ , kcal / m ³ :

- sand - 11008;

- loam mound - 28416;

- MCI and peat - 69120;

The depth of seasonal thawing of the soil layers of the embankment and its base is determined as:

.

.

- Depth of thawing sand:

.

.

- Depth of thawing loam of the lower part of the embankment:

.

.

- Depth of thawing MCI or peat:

- Depth of thawing loam at the base of the embankment:

.

.

The thickness of the thawing of the clay base under the embankment will be:

The total thawing depth of a multilayer system with MCI and clay soil at the base will be:

.

.

The depth of seasonal freezing of a multilayer system of layers of a road embankment and a soil base is determined as:

,

,

Substituting the values of the characteristics in the numerator of the radical expression, we obtain:

;

;

for the denominator we get:

.

.

The freezing depth as a result will be:

Checking the thermal stability of the embankment design with layers 1 and 2, a layer of mossy cover (MCI) 5 and a seasonally thawing (active) layer 6 of loam in the base 4 according to condition (1):

The operational permafrost stability of the embankment with the selected minimum (in terms of snow tolerance and environmental friendliness) height and use in the construction of local, initially substandard (frozen and / or waterlogged) clay soils in the lower part, on partially seasonal thawing frozen ground, is in the optimal range. It is environmentally friendly, economical and provides long-term (taking into account the forecasted global warming for 50-100 years) thermal (permafrost), and accordingly, the overall stability of this road embankment, in view of observing condition (1) for subsequent natural conservation and maintenance of permafrost at the base of the embankment .

An example of calculating the decrease in the volume of settlement of the embankment (and increase its uniformity) by reinforcing with geosynthetic materials, in compliance with the ratio (2) of this method:

From the calculation example (1), the upper part of the embankment, 0.6 m thick, is sprinkled from sand. The lower part of the most common local frozen clay soils. Modules of deformation of an unstable soil layer before and after reinforcement are accepted according to previously conducted experimental definitions of deformation modules or by direct testing of applied soft soil under a stable layer at a design load, with and without reinforcing layer.

According to engineering and geological surveys and compression tests of soil samples lying along the route of the designed road, the deformation modulus of thawing ice-saturated clay soils of the active (seasonally thawing) layer in the thawed state was E _о = 0.62 MPa or 6.2 kg / cm ² .

The deformation modulus of loosened frozen ice-saturated clay soil, poured onto mossy cover (MCI) in the lower part of the road embankment, with an average voidness of the filling layer of 20%, in the first approximation (in view of its direct proportionality to the sediment), will be:

или 5,0 кг/см².

or 5.0 kg / cm ² .

1. Clearing precipitate S _est ldonasyschennogo thawing, ground base mound in sezonnoottaivayuschem under bulk layer is determined by the formula:

where H is the depth of thawing of frozen soil at the base of the embankment (according to the heat engineering calculation), cm;

E _o - the deformation modulus of the weak soil of the base under the design load, MPa (kg / cm ² );

δ _o - the total stress (load) on the seasonally thawing (active) base layer from the weight of the embankment and the moving load, MPa (kg / cm ² ).

where δ _St - stress (load) from the dead weight of the embankment, MPa (kg / cm ² );

δ _mon - voltage (load) from a moving load, MPa (kg / cm ² ).

where ρ is the density (weight) of the soil layers of the embankment, kg / cm ³ ;

h is the thickness of the soil layers of the embankment, see

where δ _a is the magnitude of the normal stress from the impact (wheel) of the moving load at the calculated depth (taken from Table 3), MPa (kg / cm ² );

R _p - pressure in pneumatic tires of a moving load (equal to 0.6-0.8 MPa), in MPa (kg / cm ² );

η is the coefficient of dynamism from the impact of a moving load (accepted, on average 1.5).

The pressure (normal voltage) from the dump truck wheel (with a wheel imprint radius of usually 16-18 cm) on the soil base of the road embankment, according to experimental data (Table 1), will be equal to:

Ψ = 150/16 = 9.4 according to the table. 1, δ _a = 0.025 kg / cm ²

then

δ _pn = δ _a * P _p * η = 0.025 kg / cm ² * 6 kg / cm ² * 1.5 = 0.23 g / cm ²

δ _st = 0.002 kg / cm ³ * 60 cm + 0.0018 kg / cm ³ * 90 cm = 0.28 kg / cm ²

δ _about = δ _sv + δ _mon = 0.28 kg / cm ² + 0.23 kg / cm ² = 0.51 kg / cm ²

S _main = δ _o * N / E _o = 0.51 * 18 / 6.2 = 1.48 cm

отсыпанной из разрыхленных мерзлых (и переувлажненных) глинистых грунтов аналогично составит:2. The estimated draft of the lower part of the road embankment

poured from loosened frozen (and waterlogged) clay soils similarly will be:

Ψ = 60/16 = 3.75 according to the table 1, δ _a = 0.15 kg / cm ²

then

δ _pn = δ _a * P _p * η = 0.15 kg / cm ² * 6 kg / cm ² * 1.5 = 1.35 kg / cm ²

δ _st = 0.002 kg / cm ³ * 60 cm = 0.12 kg / cm ²

δ _about = δ _sv + δ _mon = 0.12 kg / cm ² + 1.35 kg / cm ² = 1.47 kg / cm ²

определяют по формуле:3. Building sediment thawing under load MCI or peat layer at the base of the embankment

determined by the formula:

where e is the relative sediment MCI or peat soil of the base during thawing under the design load; set during engineering surveys (sampling) along the road and the data of their laboratory compression tests (or is taken according to Table 1 of Appendix 7 Calculation of construction sedimentation of soil of the base and body of the embankment, VSN 84-89).

In this example, for the density of dry MCI or peat 270 kg / m ³ and its total humidity of 320%, with the above (calculated) sealing pressure of 0.51 kg / cm ² when interpolating table. 1, e = 0.32,

then:

Note: Building sludge from thawing frozen permafrost cover (MCI) or poorly decomposed peat, it is permissible without calculation, to take from experience 50-50% of the initial layer thickness (according to Note 2 to Table 16, VSN 84-89).

To ensure the operational (after construction) height of the embankment with such a significant draft, during construction it is necessary to immediately pour the lower part of the embankment with a reserve for the total draft.

.For this example, it will be:

.

When adding this stock to the sediment of 35 cm, from frozen, loosened (waterlogged) clay soil, this layer of addition will also give sediment. Its size will be: 35 cm * 26.5 cm / 90 cm = 10.3 cm.

The total value of the construction fill of the lower part of the embankment (with a margin for the subsequent total draft) will be: 35 cm + 10.3 cm = 45.3 cm. The total thickness of the lower unstable layer in the embankment, taking into account the reserve for the construction and operational settlement, will be 45.3 + 90 = 135.3 cm or rounded 1.4 m.

The total draft of 45.3 cm does not allow, under the conditions of the permissible total draft (in accordance with the requirements of Table 7.6 of SP 34.13330.2012 [1]), the device on the surface of this embankment of pavement necessary to ensure operational traffic. It is not allowed to arrange pavement even lower (transitional type). It allows a total settlement of the base and unstable layer of the embankment with a thickness of up to 1.5 m, by no more than 24 cm. To reduce the amount of settlement (and therefore its unevenness) on the surface of the lower part of the embankment, lay a device for a reinforcing layer of woven geosynthetic material of grade 300 in accordance with table. 2

In accordance with condition (2) and table 2, the decrease in precipitation, as a result of this reinforcement will be:

или

or

Reduced precipitation is also not acceptable (according to SP 34.13330.2012 tab. 7.6). To further reduce the total draft, increase the value of the reinforcement coefficient K _a from 1.4 to 1.90 (according to table 2) by additional laying on the surface of the geotextile layer of a volume geogrid, then:

The achieved decrease (due to unevenness) of the total precipitation in accordance with table. 7.6 SP 34.13330.2012, now less than the permissible 24 cm. This is already acceptable for the installation of transitional road pavement and the implementation of consolidating (accelerated re-sealing with permissible draft) operational movement.

If such a decrease in precipitation is insufficient, additionally, a flat geogrid device with a geosynthetic interlayer with K _a = 1.75 is laid in the base for for example from ASG. This provides an additional reduction in the magnitude (and unevenness) of precipitation with the possibility of a device of a higher category d / o, requiring a lower value of permissible operational precipitation (for example, to 12 or 18 cm) in accordance with Table. 7.6 SP 34.13330.2012:

The generalized experimental values of the reinforcement coefficients by various geosynthetic materials of the structural layers of the pavement of their base and subgrade layers according to [ARDS 32-12-08 of the RF Ministry of Defense. Guide to the arrangement of airfield bases and pavement with reinforcing layers of geosynthetics]

Decrease in precipitation due to reinforcement completely by the value of K _a does not occur. However, this, together with relatively close to the K value _{and the} average reduction precipitation is significantly reduced and its unevenness. This is important, since any draft is mainly the most dangerous of its unevenness. A uniform sediment is easily compensated technologically by filling in embankments immediately with a reserve for sediment, with the observed global warming, accompanied by massive degradation of permafrost in vast permafrost territories (65% of the territory of the Russian Federation). Permafrost embankments, initially erected at first with a device for damping construction and operational sludge, will then smooth out and extinguish irregularities, various off-design and unforeseen subsidence as a result of global warming. Reinforcement with geosynthetics also provides road embankments with a subsequent increased general (in terms of slope stability, etc.) operational stability, which allows (according to generalized operating experience) to increase the turnaround time of expensive pavement, pavement or railway tracks by 1.5-2 times.

Claims (32)

1. A method of erecting a road embankment on permafrost with increasing permafrost and general stability, including the assumption of thawing of the soil of the active layer at the base of the embankment (with a reserve for sediment) during operation, characterized in that a low-permeable soil is laid in the lower part of the embankment with a layer of thickness determined by from the ratio:

where N _CR and N _from - the depth of freezing and thawing of the embankment and the active layer of the base (with humidity of the initially unstable soil layers, with a compaction coefficient of 0.90), m, in this case, the initially unstable layer in the lower part of the embankment is arranged from temporarily substandard (waterlogged and / or frozen) soil, mainly using reinforcing layers (from geosynthetics, geomembranes, geocomposites, etc.), and when reinforcing, the following condition is met:

where S _add and S - permissible (by standards) sludge and sludge of an unstable layer (waterlogged and / or thawed frozen) soil under a given load, m; To _a = E _a / E is the coefficient of reinforcement; where E and E _a are the deformation modulus of the unstable soil layer before reinforcement and after reinforcement, MPa; after that they pour it (they push it “from the head” onto the thawed waterlogged soil) and compact the upper stable (working) layer from the conditioned or draining soil, and then the unstable layers are rapidly consolidated by the dynamic effect of the traffic flow. 2. The method according to p. 1, characterized in that local clay soils are mainly used as poorly permeable, substandard, and the depth of thawing and freezing of the embankment together with the active layer of the frozen base is determined by the formulas:

Where

- the duration of the annual period with positive air temperatures, h;

- the amount of latent heat of phase transitions of moisture in 1 m ³ , kJ / m ³ or kcal / m ³ ,

where L _o - latent heat of ice formation (equal to 334 kJ / kg or 80 kcal / kg); ρ is the density of the soil, kg / m ³ ; ρ _d is the density of dry soil, kg / m ³ ; W _w - unfrozen water content; W _tot - total soil moisture, dol. units The total soil moisture content W _tot at a compaction factor of 0.90 is approximately: sandy and silty sandy loam W _tot = 1.6W _opt light sandy and silty loam W _tot = 1.5W _opt heavy sandy and silty clay loam, clay W _tot = 1.3W _opt , where W _opt is the optimum soil moisture; λ _mi is the coefficient of thermal conductivity of the soil in a thawed state, W / (m⋅ ° C) or kcal / (m⋅h⋅ ° C); T _max - average monthly air temperature for the warmest (July) summer month (taking into account experimental temperature corrections), ° C; C _mi - volumetric heat capacity of thawed soil, kJ / (m ³ ⋅ ° C) or kcal / (m ³ ⋅ ° C);

Where

- weighted average coefficient of thermal conductivity of layers of a multilayer structure (road pavement, embankment and foundation layers) in the frozen state, W / (m⋅ ° C) or kcal / (m⋅h⋅ ° C); λ ₁ , λ ₂ , ..., λ _n are the thermal conductivity of the layers in the frozen state, W / (m⋅ ° C) or kcal / (m⋅h⋅ ° C); T _s - average air temperature for a period with negative air temperatures (taking into account the predicted winter climate warming by 3-5 ° C in the northern territories of the Russian Federation and experimental corrections), ° C; τ _s - the duration of the annual period with negative air temperatures, h;

- depth of thawing of a multilayer structure, m; С _mi is the volumetric heat capacity of the layers in the frozen state, kJ / (m ³ ⋅ ° C) or kcal / (m ³ ⋅ ° C).

Images