Active cooling and thermal insulation cushion layer in permafrost areas and preparation method and use method thereof

Abstract

The present invention discloses an active cooling and thermal insulation cushion for permafrost regions, as well as its preparation and use methods. The active cooling and thermal insulation cushion comprises an inner layer and an outer layer for wrapping the inner layer. The inner layer is composed of nitrates and black soil. The active cooling and thermal insulation cushion is disposed between the permafrost layer and the replacement treatment layer. The present invention can cool the permafrost layer, lowering its surface temperature; prevent external heat from entering the permafrost layer, and reduce temperature disturbances to the permafrost layer during roadbed construction in permafrost regions, thereby preventing permafrost degradation and maintaining the stability of the permafrost roadbed.

Description

Technical Field

[0001] The present invention belongs to the technical field of frozen soil roadbed protection, and relates to an active cooling and thermal insulation cushion layer in a frozen soil area, and a preparation method and a use method thereof. Background Art

[0002] Permafrost refers to soil (or rock) that remains frozen for two or more years without melting. China has 2.15 million square kilometers of permafrost, accounting for approximately 22.3% of its land area, making it the third largest country in the world. The primary distribution of permafrost in my country lies in the Greater and Lesser Khingan Mountains in northeastern China, the Qinghai-Tibet Plateau, and the high mountains of western China. Permafrost, due to the presence of ice and unfrozen water, has complex properties and is extremely sensitive to temperature fluctuations. The mechanical strength of permafrost varies significantly with temperature: its strength increases at lower temperatures, but as temperatures rise and the permafrost begins to thaw, its strength is largely lost. Constructing roads in permafrost areas alters the water-heat exchange equilibrium in and around the site, altering the hydrothermal effects within the permafrost roadbed, raising the permafrost temperature and further degrading it. Furthermore, overlying loads can cause road subsidence, tilting, and subsidence, among other problems that impact road safety and operation, severely impacting the effectiveness and lifespan of road projects.

[0003] To address roadbed hazards caused by temperature fluctuations, researchers at home and abroad have developed technologies such as rock layers, insulation layers, heat rods, and ventilation pipes to protect permafrost. While these measures have some protective effects on permafrost, they also have limitations. For example, ventilation pipes are expensive, rock layers have low heat dissipation efficiency, especially during high summer temperatures, heat rods are inefficient and have a limited effective range, and insulation layers are unsuitable for high-temperature permafrost. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide an active cooling and insulation cushion layer in permafrost areas and its preparation method and use method, which can cool the permafrost layer and reduce the surface temperature of the permafrost layer; prevent external heat from entering the permafrost layer, reduce the temperature disturbance of the permafrost layer when building a roadbed in the permafrost area, prevent the permafrost layer from degrading, and play a role in maintaining the stability of the permafrost roadbed.

[0005] To achieve the above object, the present invention is implemented by adopting the following technical solutions:

[0006] An active cooling and thermal insulation cushion layer for permafrost areas, comprising an inner layer and an outer layer for wrapping the inner layer, wherein the inner layer comprises nitrate and macroporous dry soil, and the active cooling and thermal insulation cushion layer is arranged between the permafrost layer and the replacement treatment layer.

[0007] Optionally, the outer layer is a geotextile.

[0008] Optionally, the nitrate is solid potassium nitrate.

[0009] Optionally, the macroporous dry soil is sun-dried or oven-dried black soil.

[0010] Optionally, the thickness of the active cooling and thermal insulation cushion layer is 5 to 10 cm.

[0011] Optionally, the method for determining the mass 𝑚 of potassium nitrate per unit area of ​​the active cooling and thermal insulation cushion layer is:

[0012]

[0013]

[0014] in

[0015]

[0016] Where, is the thickness of the active cooling and insulation pad, is the density of water, is the dry density of black soil, is the porosity ratio of black soil, represents the solubility of potassium nitrate at temperature T, is the molar mass of potassium nitrate, represents the heat of solution of potassium nitrate, It represents the specific heat capacity equivalent of active cooling and thermal insulation padding per unit area after immersion in water. Including the specific heat capacity of water and the specific heat capacity of soil particles ; Potassium nitrate mass for and The smaller of the two.

[0017] A method for preparing an active cooling and thermal insulation cushion layer in a frozen soil region, comprising:

[0018] Mix nitrate and macroporous dry soil in proportion;

[0019] The mixed nitrate and macroporous dry soil are wrapped in an outer layer.

[0020] Optionally, the outer layer wraps the mixed nitrate and macroporous dry soil by stitching.

[0021] A method for using an active cooling and insulation cushion layer in a frozen soil region, comprising:

[0022] When constructing the roadbed, excavate below the replacement treatment layer from the roadbed surface to the ground surface according to the buried depth of the roadbed surface required by the design;

[0023] When digging to the permafrost layer, the active cooling and insulation pad layer will be laid between the permafrost layer and the replacement treatment layer.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention sets an active cooling and insulation cushion layer on the surface of the permafrost, and utilizes the characteristic of potassium nitrate absorbing a large amount of heat when it dissolves in water to reduce the temperature of the permafrost. It can effectively solve the problem of permafrost melting caused by construction disturbance of the permafrost layer.

[0026] The black soil used in the active cooling and thermal insulation cushion has a large porosity, a large proportion of air per unit volume, and a low thermal conductivity, which can effectively prevent heat from above from entering the permafrost. On the one hand, it can actively cool the permafrost layer, and on the other hand, it can effectively prevent heat from being transferred into the permafrost, playing a dual role of cooling and thermal insulation.

[0027] The potassium nitrate used to mix the black soil in the active cooling and insulation cushion layer is relatively stable, and potassium nitrate as a fertilizer has very little harm to the soil environment and can exist in the roadbed for a long time; when the temperature drops, potassium nitrate will precipitate, and when the temperature rises, it will continue to dissolve and absorb heat, and can be recycled to reduce project costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of active cooling and thermal insulation cushion layer in an embodiment of the present invention.

[0029] In the figure: 1. Frozen soil layer; 2. Active cooling and insulation cushion layer; 3. Geotextile; 4. Replacement treatment layer; 5. Upper embankment. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0031] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to form one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

[0032] For the purposes of this specification and the appended claims, unless otherwise indicated, all numbers expressing amounts, percentages or ratios and other numerical values ​​used in this specification and the appended claims are to be understood as being modified in all instances by the term "about." In addition, all ranges disclosed herein are inclusive and independently combinable.

[0033] Example 1

[0034] like Figure 1 As shown, an active cooling and thermal insulation cushion layer for permafrost areas, the active cooling and thermal insulation cushion layer 2 includes an inner layer and two layers of geotextile 3 for wrapping the inner layer, the components of the inner layer include solid potassium nitrate and dry black soil, the active cooling and thermal insulation cushion layer 2 is laid on the surface of the permafrost layer 1, and is arranged between the permafrost layer 1 and the replacement treatment layer 4, and the replacement treatment layer 4 is arranged below the upper embankment 5; the thickness of the active cooling and thermal insulation cushion layer 2 is 5 cm, on the one hand, because when the construction disturbance causes the permafrost surface to melt, moisture accumulates on the upper surface and can penetrate the active cooling and thermal insulation cushion layer 2, so that the mixed potassium nitrate is fully dissolved to achieve the effect of cooling the permafrost; on the other hand, because the active cooling and thermal insulation cushion layer 2 is relatively thin, it is convenient to roll up after prefabrication and can be directly spread out when used, which is convenient for use.

[0035] The method for determining the mass 𝑚 of potassium nitrate added per unit area of ​​active cooling and thermal insulation cushion 2 is:

[0036]

[0037]

[0038] in

[0039]

[0040] Potassium nitrate mass for and The smaller of the two; where is the thickness of the active cooling and insulation pad, take 5cm, is the density of water, is the dry density of black soil, is the porosity ratio of black soil, represents the solubility of potassium nitrate at temperature T, is the molar mass of potassium nitrate, represents the heat of solution of potassium nitrate, It represents the specific heat capacity equivalent of active cooling and thermal insulation padding per unit area after immersion in water. Including the specific heat capacity of water and the specific heat capacity of soil particles ; Mass of potassium nitrate added to active cooling and thermal insulation cushion 2 per unit area Pick and The smaller of the two.

[0041] This represents the maximum mass of potassium nitrate that can be dissolved per unit area within the active cooling and insulation cushion 2 after the active cooling and insulation cushion 2 is saturated with melted permafrost, when the surface temperature of the frozen soil rises to a value greater than zero degrees Celsius (T) due to construction disturbance. This reflects the maximum heat absorption capacity of the active cooling and insulation cushion 2. This calculation method assumes that the dissolution heat absorption of potassium nitrate occurs only between the two geotextile layers. This indicates that the maximum heat absorption capacity per unit area of ​​the active cooling and insulation cushion 2 after saturation is related to the porosity of the dry black soil.

[0042] This represents the minimum mass of potassium nitrate required to actively cool and maintain the permafrost surface to 0°C after measuring the permafrost surface temperature. This reflects the amount of heat required to dissolve potassium nitrate to lower the permafrost surface temperature to 0°C.

[0043] If the temperature of the frozen soil surface is too high due to construction disturbance or other environmental factors, the mass of potassium nitrate required to reduce the frozen soil surface to 0 degrees freezing state is greater than the maximum mass of potassium nitrate that can be dissolved by the active cooling and insulation pad 2 at this temperature. Pick , maximally absorb the heat of the permafrost surface and slow down the degradation of permafrost. Pick .

[0044] Example 2

[0045] Based on the active cooling and thermal insulation cushion layer for permafrost areas described in Example 1, this embodiment provides a method for preparing the active cooling and thermal insulation cushion layer for permafrost areas, comprising the following steps:

[0046] S1, mixing solid potassium nitrate and dry black soil in proportion;

[0047] S2, wrapping the mixed nitrate and black soil between two layers of geotextiles, and wrapping the mixed potassium nitrate and dry black soil with the geotextiles by stitching.

[0048] Example 3

[0049] Based on the active cooling and thermal insulation cushion layer in a permafrost region described in Example 1, this embodiment provides a method for using the active cooling and thermal insulation cushion layer in a permafrost region, comprising the following steps:

[0050] S1, when constructing the roadbed, excavate below the replacement treatment layer 4 from the roadbed surface to the ground surface according to the buried depth of the roadbed surface required by the design;

[0051] S2, when digging to the frozen soil layer 1, the active cooling and heat preservation cushion layer 2 is laid between the frozen soil layer 1 and the replacement treatment layer 4.

[0052] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An active cooling and thermal insulation cushion layer in permafrost areas, characterized by: The active cooling and thermal insulation cushion layer includes an inner layer and an outer layer for wrapping the inner layer. The inner layer is composed of nitrate and macroporous dry soil. The active cooling and thermal insulation cushion layer is arranged between the frozen soil layer and the replacement treatment layer. The nitrate is solid potassium nitrate; the macroporous dry soil is sun-dried or oven-dried black soil. The method for determining the mass 𝑚 of potassium nitrate per unit area of ​​the active cooling and thermal insulation cushion layer is: in Where, is the thickness of the active cooling and insulation pad, is the density of water, is the dry density of black soil, is the porosity ratio of black soil, represents the solubility of potassium nitrate at temperature T, is the molar mass of potassium nitrate, represents the heat of solution of potassium nitrate, It represents the specific heat capacity equivalent of active cooling and thermal insulation padding per unit area after immersion in water. Including the specific heat capacity of water and the specific heat capacity of soil particles ; Potassium nitrate mass for and The smaller of the two.

2. The active cooling and thermal insulation cushion layer for frozen soil areas according to claim 1, characterized in that: The outer layer is geotextile.

3. The active cooling and thermal insulation cushion layer in permafrost areas according to claim 1, characterized in that: The thickness of the active cooling and thermal insulation cushion layer is 5 to 10 cm.

4. A method for preparing an active cooling and thermal insulation cushion layer in a frozen soil region according to any one of claims 1 to 3, characterized in that: include: Mix nitrate and macroporous dry soil in proportion; The mixed nitrate and macroporous dry soil are wrapped in an outer layer.

5. The method for preparing an active cooling and thermal insulation cushion layer in a frozen soil region according to claim 4, characterized in that: The outer layer wraps the mixed nitrate and macroporous dry soil by means of needle and thread overlap connection.

6. A method for using the active cooling and insulation cushion layer in permafrost areas according to any one of claims 1 to 3, characterized in that: include: When constructing the roadbed, excavate below the replacement treatment layer from the roadbed surface to the ground surface according to the buried depth of the roadbed surface required by the design; When digging to the permafrost layer, the active cooling and insulation pad layer will be laid between the permafrost layer and the replacement treatment layer.

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