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Reference:

The effect of the iciness of the soil on the depth of thawing of the road base

Galkin Aleksandr

ORCID: 0000-0002-5924-876X

Doctor of Technical Science

Professor, Chief Researcher of the Melnikov Permafrost Institute SB RAS

677010, Russia, Yakutsk, ul. Merzlotnaya, 36, IMZ SO RAN. Laboratoriya geotermii kriolitozony

afgalkin@yandex.ru
Other publications by this author
 

 
Pankov Vladimir Yur'evich

PhD in Geology and Mineralogy

Associate Professor, Department of Construction of Roads and Airfields, North-Eastern Federal University

677027, Russia, respublika Sakha(Yakutiya), g. Yakutsk, ul. Belinskogo, 58

pankov1956@gmail.ru
Other publications by this author
 

 

DOI:

10.7256/2453-8922.2022.2.38103

EDN:

ENCKQG

Received:

19-05-2022


Published:

25-07-2022


Abstract: One of the important parameters determining technical solutions in the design of highways in the cryolithozone is the depth of thawing of the soils of the road base. The aim of the work was to quantify the degree of influence of the iciness of the soil foundations of roads in the cryolithozone on the depth of their seasonal thawing. For the analysis, the classical formula for calculating the thawing depth for bodies of plane symmetry, obtained by solving the single-phase Stefan problem, was used. The results of calculations are presented in the form of 2D and 3D graphs, which allow us to visually assess the effect of the iciness of the soil and the degree of its change during the operation of the road on the depth of thawing of the road base. It was found, in particular, that the degree of change in the depth of thawing at the same value of the increase in ice content in different ranges (for example, from 10 to 20% and from 30 to 40%) for the considered typical case of the ground base of the cryolithozone decreases by almost 1.3 times. It is shown that the greater the initial iciness of the soil, the degree of decrease in the depth of thawing when the iciness changes by a constant value will be less. A 3D graph was built to determine the depth of thawing of the soils of the active layer of the road base in a wide range of possible changes in ice content during the construction and use of the highway. The availability of a schedule allows to quickly assess possible options for changing the depth of thawing and make a correct, informed technical decision when designing the road. For example, when assessing the need to use a special heat-protective layer in road clothing. Further directions of research in this area should be aimed at studying the effect of humidity (iciness) of dispersed soils on the depth of thawing of road foundations, taking into account the dependence of the density and thermal conductivity of the soil on the iciness.


Keywords:

automobile road, permafrost, forecast, thawing depth, iciness, 3D graph, designing, degree of change, temperature, calculation

This article is automatically translated. You can find original text of the article here.

 

Introduction

The operation of highways in the cryolithozone is complicated by many objective reasons, including the dependence of the strength properties of the foundation soils on the temperature factor and on the natural or man-made humidity (iciness) of the soils of the active layer of the road [1,2,3]. Moreover, as noted in [4,5], it is the technogenic moistening of the soils of the active layer that plays the greatest role. Therefore, when designing highways, it is important to know not only the natural humidity (iciness) of the soils of the road base, but also the degree of their change during the operation of the highway. One of the main parameters of the design of technical objects interacting with the soils (rocks) of the cryolithozone is the depth of thawing [6,7,8]. This also applies to the design of highways in the cryolithozone [9, 10].

The purpose of the research is to quantify the degree of influence of the iciness of the ground foundations of roads in the cryolithozone on the depth of their seasonal thawing.

Methods

To achieve this goal, we will use the well-known formula for determining the depth of thawing of soils [10,11,12] at their initial temperature equal to the melting temperature of ice.

 (1)

Where: ? is the duration of the warm period of the year, s; ? is the thermal conductivity coefficient of thawed soil, W/m· K; t is the average air temperature during the thawing period, 0C; ? is the density of the soil, kg/m3; L is the latent heat of melting ice, J/ kg; ? is humidity (iciness) of soil, D.E.

 

 This formula does not take into account the amount of heat that goes to heat the frozen ground from the natural negative temperature to the melting point of ice. In this regard, in [11] we evaluated the correctness of this assumption when predicting the depth of thawing of rocks in underground structures of the cryolithozone. It is shown that for the majority of practically interesting cases, the application of formula (1) does not lead to an error greater than the error allowed in engineering practice (usually equal to 10%). Therefore, the use of this formula for the purpose pursued in this work will be considered quite acceptable.

For the convenience of analysis, we additionally introduce the parameter "?", which characterizes the degree of change in the depth of thawing of the soils of the active layer of the road base with changes in humidity (ice content) during the operation of the automobile road.

(2)

Where:? i is the humidity (iciness) of the soil, natural (i=1) and man–made (i=2), i.e.

Formula (1) includes time in seconds, which is not very convenient when calculating seasonal soil thawing. Therefore, considering that the latent heat of melting of ice for the case under consideration is a constant value equal to 335.0 kJ/kg, we convert formula (1) to the form

(3)

Where: N is the number of months in the warm period of the year, units.

Results and discussion

 

To achieve the goal, variant calculations were carried out according to the above formulas, the results of which are presented in the form of 2D and 3D graphs in Fig. 1-3. Figure 1 shows the dependence of the thawing depth of a typical cryolithozone soil with a density of 1600 kg/m3 and a thermal conductivity coefficient of 1.4 W/m·K depending on the iciness for different climatic zones, characterized, in this case, by the product of the duration of the warm period by the average air temperature – "Nt", month · o C.

Fig. 1. The depth of thawing of the soil of the road base, depending on the ice content W, (ie) for different values of the complex "Nt" (month ·oWith): 1- 25,0; 2 - 35,0; 3 – 50,0.

 

It can be seen from the graphs in the figure that with an increase in the iciness of the soil (the degree of filling of the pores with ice), the depth of thawing increases throughout the considered range of changes in iciness, regardless of the climatic zone of the road location.  Moreover, the smaller the range of change in iciness, the stronger the dependence of the depth of thawing on the iciness. This is evidenced by both the nature of the curves in Figure 1 and the quantitative analysis. For example, for the case (Nt) = 25 (curve 1 in the figure), when the iciness changes from 0.1 to 0.2 (an increase of 0.1), the depth of the thawing halo increases by 1.4 times. And, when the iciness changes from 0.3 to 0.4 (an increase of 0.1), the depth of the thawing halo increases by 1.15 times. Which is almost 1.3 times less.

Figure 2 shows 3D graphs that clearly demonstrate this pattern (see the blue and brown area in Figure 2).

 

Fig. 2. The depth of thawing of the soil of the road base depending on the ice content W, (ie) and climatic characteristics of the warm period of the year (values of the complex "Nt", month · o S)

 

The conclusion is also confirmed by a simple quantitative analysis of the calculation formula. The results of the analysis are presented in the table.

Table.

The degree of change in the depth of thawing of the soil in a different range

increasing its iciness

The range of increasing iciness

 

0,1 - 0,2

 

0,2 - 0,3

 

0,3 – 0,4

 

0,4 - 0,5

 

0,6 - 0,7

 

0,7 – 0,8

 

0,8 – 0,9

The degree of change in the depth of thawing

 

1,41

 

1,22

 

1,15

 

1,12

 

1,08

 

1,07

 

1,06

 

From the data given in the table, it follows that the greater the initial iciness of the soil, the degree of decrease in the depth of thawing when the iciness changes by a constant amount (in this case, an increase of 0.1) will be less.

Figure 3 shows a 3D graph of the dependence of the parameter "?", which characterizes the degree of change in the depth of thawing of the soils of the active layer of the road base when the ice content changes during the operation of the automobile road.

 

Fig.3.The degree of change in the depth of thawing of the soils of the active layer of the road base when the ice content changes from the value of W1 to the value of W2 during the operation of the motor road.

 

The graph clearly demonstrates not only the previously described patterns, but also allows you to assess the degree of change in the depth of thawing, both with a possible increase in iciness during the operation of the highway, and with a decrease in iciness (for example, due to soil drying). The availability of a schedule allows you to quickly evaluate possible options and make a correct, reasonable technical decision when designing a highway in the cryolithozone. For example, to justify the need to use a special heat-protective layer in road clothing [13,14,15].

Conclusion

The influence of humidity (iciness) of the soil bases of highways in various climatic zones on the change in the depth of thawing in the warm season is investigated. The results of numerical calculations are presented in the form of graphs and tables that allow us to visually assess the effect of the iciness of the soil and the degree of its change during the operation of the road on the depth of thawing of the road base. It was found, in particular, that the degree of change in the depth of thawing at the same value of the increase in ice content in different ranges (for example, from 10 to 20% and from 30 to 40%) for the considered typical case of the ground base of the cryolithozone decreases by almost 1.3 times.  It is shown that the greater the initial iciness of the soil, the degree of decrease in the depth of thawing when the iciness changes by a constant value will be less.  A 3D graph has been constructed to determine the depth of thawing of the soils of the active layer of the road base in a wide range of possible changes in ice content during the operation of the highway. The availability of a schedule allows you to quickly assess possible options for changing the depth of thawing and make a correct, informed technical decision when designing. For example, to justify the need to use a special heat-protective layer in road clothing. Further directions of research in this area should be aimed at studying the effect of humidity (iciness) of dispersed soils on the depth of thawing of road foundations, taking into account the dependence of the density and thermal conductivity of the soil on the iciness.

 

 

References
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Subject of research: according to the author of the article, a quantitative assessment of the degree of influence of the iciness of the soil foundations of roads on the depth of their seasonal thawing in the zone of operation of highways in the cryolithozone is carried out. However, when describing the subject of the study, it would be necessary to identify the objectives of the study from the point of view of the totality of a specific territorial complex. This is due to the regional peculiarities of the depth of thawing, the manifestation of frosts, and meteorological events. Research methodology: The authors position the analysis of information using a mathematical method using reference literature, at the same time they used methods of graphical modeling. The relevance of the problem consists in identifying the tasks and developing the design of highways with natural soil moisture of the road base and the degree of change in the operation of the highway. One of the main parameters of the design of technical facilities interacting with cryolithozone soils is the depth of thawing from the point of view of increasing the efficiency of use. The author of the article does not position the scientific novelty, they analyzed data on the assessment of the influence of humidity (iciness) of the soil foundations of highways in various climatic zones on the change in the depth of thawing in the warm season. A 3-D graph has been constructed to determine the depth of thawing of soils of the active layer of the road base in a wide range of possible changes in ice content during the operation of the highway. Its presence allows you to quickly assess possible options for changing the depth of thawing and make a correct, informed technical decision when designing The style, structure, content the style of presentation of the results is scientific, the structure of the construction and presentation of the material is built quite logically. The authors of the article presented in the article in the form of tables containing digital information obtained during the study, as well as in the form of graphs of various types. However, there are a number of issues, in particular: the author of the article should avoid excessive quoting, which loads the article (For example, to justify the need to use a special heat-protective layer in road clothes [13,14,15]." The author should provide data on the peculiarities of climate in different climatic zones, identify the prospects for changing climatic conditions with a warming trend. However, this does not reduce the author's contribution to the study of the process. The bibliography is extensive, containing mainly both current and classical sources. An appeal to opponents in identifying the problem at the level of available information obtained by the author as a result of analyzing a large number of literary sources and calculations carried out independently based on the analysis of parameters of different climatic zones. Conclusions, the interest of the readership The conclusion given by the author summarizes the content of the article, the conclusions of the article are ascertaining, the prospects for use are indicated, however, there is no explanation of the reasons and the consumer of the information presented in the article is not determined by the authors.
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