CN111877073B - Protective heat protection structure and method for frozen soil roadbed - Google Patents
Protective heat protection structure and method for frozen soil roadbed Download PDFInfo
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- CN111877073B CN111877073B CN202010726927.9A CN202010726927A CN111877073B CN 111877073 B CN111877073 B CN 111877073B CN 202010726927 A CN202010726927 A CN 202010726927A CN 111877073 B CN111877073 B CN 111877073B
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
- E01C3/00—Foundations for pavings
- E01C3/06—Methods or arrangements for protecting foundations from destructive influences of moisture, frost or vibration
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Abstract
The invention relates to a protective heat protection structure and a method for a frozen soil roadbed, wherein the heat protection structure is a multilayer structure formed by alternately overlapping two materials A and B with larger heat conductivity coefficients, is arranged under the roadbed in an auxiliary mode and covers the frozen soil roadbed to be protected. The roadbed material for the frozen soil roadbed thermal protection can effectively control the heat conduction direction according to the properties of the thermal super-structure material. When the temperature changes and rises, the heat conducted by the pavement structure can flow away, the heat is prevented from entering the interior of the frozen soil roadbed, the heat entering the frozen soil roadbed in warm seasons is reduced, the freeze thawing of the frozen soil is relieved, and the upper limit degradation of the frozen soil is avoided; the invention can improve the strength of the roadbed by adopting partial metal. The metamaterial has simple components, simple preparation process and low cost.
Description
Technical Field
The invention belongs to the technical field of high-speed rail frozen soil road subgrade thermal protection, and particularly relates to a frozen soil subgrade thermal protection structure and method.
Background
The frozen soil is various rocks and soils with ice content below zero centigrade, and can be divided into seasonal frozen soil and perennial frozen soil according to the freezing duration, and China is the third frozen soil kingdom in the world. Since ice plays a role in cementing in frozen soil, the physical and mechanical properties of frozen soil are closely related to temperature. When the ice inside the frozen soil changes phase, the engineering characteristics of the frozen soil will change greatly. According to the statistics of disease causes of the Qinghai-Tibet highway, 85% of diseases are caused by thawing and sinking of frozen soil, including cracking of roadbed slopes, roadbed sinking, collapse and the like, and the frozen soil frost heaving causes other 15% of disasters.
In order to cope with roadbed disasters caused by temperature, domestic and foreign scholars develop technical measures such as hot sticks, rock blocks, ventilation pipes, heat insulation layers and the like to protect the frozen soil, however, although the technical measures have certain frozen soil protection effect, a plurality of problems exist at the same time, such as: the heat rod technology has low working efficiency, small effective working range, high cost of the ventilating pipe and low heat dissipation efficiency of the stone layer and heat insulation layer technology.
Disclosure of Invention
The invention aims to provide a frozen soil roadbed protective heat protection structure and a method for relieving the occurrence of freezing and thawing of the frozen soil roadbed and avoiding the degradation of the upper limit of the frozen soil.
The purpose of the invention is realized by the following technical scheme:
a thermal protection structure for protecting a frozen soil roadbed is laid under the roadbed and covers the frozen soil roadbed to be protected, the thermal protection structure is a multilayer structure formed by alternately overlapping two materials A and B with large heat conductivity coefficients, the flow direction of thermal conduction in the materials can be modulated by the thermal protection structure, and heat flow does not flow through the protected frozen soil roadbed and is not disturbed by the heat flow, so that the occurrence of freezing and thawing of the frozen soil roadbed is relieved, and the upper limit degradation of the frozen soil is avoided.
Preferably, the two types of material a and material B having a large difference in thermal conductivity are alternately overlapped to form a "cloak" structure.
Preferably, the "cloak" shaped structure is circular in cross-section, such as circular or elliptical ring shaped.
Preferably, the thermal conductivity of the material A is different from that of the material B by more than 300 times.
Preferably, the material a is a heat conductive material having a thermal conductivity of 10 or more, and the material B is a heat insulating material having a thermal conductivity of 0.5 or less.
Preferably, the material a is a metal material selected from stainless steel, aluminum, copper, and the like.
Preferably, the material B is an extruded polystyrene board, a rubber and plastic heat insulation board, a polyethylene wood material, a vacuum heat insulation board, an aerogel heat insulation material, a foam glass heat insulation board and the like.
Preferably, the material a and the material B are alternately overlapped by 5 to 15 layers, preferably 10 layers.
A thermal protection method for protecting a frozen soil roadbed is characterized in that a thermal protection structure is laid on the frozen soil roadbed to be protected, and the specific method comprises the following steps: and alternately paving the material A and the material B on the frozen soil foundation to form an arc hopper-shaped cover which covers the frozen soil foundation.
Based on a metamaterial theory and an equivalent medium principle, according to material characteristics, a concentric ring with large difference of thermal conductivity of a plurality of layers of anisotropic materials is superposed to form a thermal protection structure. According to the properties of the thermal metamaterial, the multi-layer anisotropic thermal protection structure changes the transfer path of heat flow in frozen soil, so that the heat flow flows around from the inside of the annular thermal metamaterial in the transfer process, and the heat conduction direction is effectively controlled. Based on this, the lower frozen soil that is wrapped by this thermal protection structure does not have the temperature field distribution, avoids the frozen soil to receive the disturbance. In addition, the strength of the roadbed can be improved due to the adoption of partial metal; the metamaterial has simple components, simple preparation process and low cost.
Compared with the prior art, the invention has the beneficial effects that:
1. the anisotropic composite thermal protection material disclosed by the invention contains the characteristic of internal thermal stealth streaming in the material, and can bypass through heat flow conduction, for example, when the temperature changes and rises, the heat conducted by a pavement structure can flow away, the heat is prevented from entering the interior of a frozen soil roadbed, the heat entering the frozen soil roadbed in a warm season is reduced, the freeze thawing of frozen soil is relieved, and the upper limit degradation of the frozen soil is avoided.
2. The subgrade filling in the frozen soil area is mostly poor soil, and after the invention adopts various anisotropic composite thermal protection materials, the strength of the subgrade can be improved and the stability of the subgrade is improved due to the metal contained in the subgrade.
3. The roadbed thermal protection material has simple components, simpler process and low cost.
4. The invention actively modulates the heat conduction flow direction from the source, can prevent the temperature inside the frozen soil roadbed from increasing, effectively relieves the freeze-thaw cycle of the frozen soil, can reduce roadbed frost heaving or thaw disaster caused by the freeze-thaw cycle of the frozen soil, and ensures the pavement service quality.
Drawings
FIG. 1 is a geometric model diagram of a frozen earth roadbed;
FIG. 2 is a schematic diagram of railway roadbed thermal protection construction based on thermal super-structural material;
FIG. 3 is an enlarged partial view of the thermal metamaterial of FIG. 2;
FIG. 4 is a 0 ℃ line profile for example 1;
FIG. 5 is a 0 ℃ line profile for example 2;
FIG. 6 is a 0 ℃ line profile for example 3.
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments.
In the embodiment, the height of a geometric model of the frozen soil foundation is 10m, the height of a roadbed model is 4.2m (the upper 0.4m is a graded crushed stone layer; the lower 3.8m is an A/B group soil layer), and the total height of the geometric model is 14.2 m; the width of the frozen soil foundation is taken to be 48m, the width of the upper surface of the roadbed is 13.4m, the width of the lower bottom surface is 26m, and the slope gradient is 1: 1.5, as shown in fig. 1. The thermal protection method for protecting the frozen soil roadbed can adopt an arc-shaped laying mode, as shown in figures 2 and 3, according to the geometric model size of the frozen soil roadbed, the outer diameter of the arc-shaped thermal stealth cloak is 14m, and the inner diameter of the arc-shaped thermal stealth cloak is 13.8 m. Lay hot protective structure above the bed top layer, hot protective structure is the multilayer structure who overlaps in turn and form by two kinds of material A and material B that the coefficient of heat conductivity differs great, and this heat preservation effectively alleviates railway roadbed frost heaving effect, and the stability and the durability of reinforcing heated board effectively avoid the deformation of circuit.
Example 1
A thermal stealth cloak with a 10-layer structure was used as a study object, and the thickness of each layer was 2cm and the total thickness was 0.2 m. The cloak is formed by alternately overlapping and arranging two materials with larger difference of heat conductivity coefficients, wherein the materials are stainless steel (15.1) and extruded polystyrene board (0.041), and the heat conductivity coefficient of the materials is in brackets. Covering the constructed thermal stealth cloak above the roadbed, adding a temperature boundary condition which periodically changes along with seasons, and carrying out hydrothermal coupling finite element simulation on frozen soil. Wherein the position of the 0 ℃ line at the moment when the soil layer reaches the maximum freezing depth is shown in fig. 4. The analysis shows that: the cloak has good thermal protection effect, the soil in the protection area is not frozen, the 0 ℃ line of the axis position is increased to 13.857m, and the 0 ℃ line of the shoulder of the road is increased to the position of 12.129 m.
Example 2
Based on example 1, other materials with significantly different thermal conductivity were replaced, such as aluminum (237) + extruded polystyrene board (0.041), each layer still having a thickness of 2cm and a total thickness of 0.2 m. Covering the constructed thermal stealth cloak above the roadbed, adding a temperature boundary condition which periodically changes along with seasons, and carrying out hydrothermal coupling finite element simulation on frozen soil. Wherein the position of the 0 c line at the moment the soil layer reaches the maximum freezing depth is shown in fig. 5. The analysis shows that: the thermal stealthy cloak has a good thermal protection effect, can effectively relieve freeze thawing of a frozen soil roadbed, and avoids degradation of the upper limit of frozen soil. The 0 ℃ line at the position of the center axis is increased to 13.878m, and the 0 ℃ line at the shoulder of the road is increased to the position at 12.152 m.
Example 3
Based on example 2, the relationship of the thermal conductivity of material A and material B was further increased by selecting copper (401) + extruded polystyrene board (0.041), each layer still having a thickness of 2cm and a total thickness of 0.2 m. Through finite element simulation calculation, when the soil layer reaches the maximum freezing depth, the position of the 0 ℃ line is shown in fig. 6, the 0 ℃ line of the axis line position is increased to 13.878m, and the 0 ℃ line of the shoulder of the road is increased to the position of 12.153 m.
The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.
Claims (3)
1. A thermal protection structure for protecting a frozen soil roadbed is paved under the roadbed and covers the frozen soil roadbed to be protected, and is characterized in that the thermal protection structure is a multilayer structure formed by alternately overlapping two types of materials A and B with larger differences of heat conductivity coefficients, and the materials A and B are alternately overlapped by 5-15 layers;
the two types of materials A and B with larger heat conductivity coefficient difference are alternately overlapped to form a 'cloak' -shaped structure, and the cross section of the 'cloak' -shaped structure is in an arc shape;
the heat conductivity coefficient of the material A is different from that of the material B by more than 300 times, the material A is a heat conduction material with the heat conductivity coefficient of more than 10, and the material B is a heat insulation material with the heat conductivity coefficient of less than 0.5;
the material A is a metal material selected from stainless steel, aluminum or copper, and the material B is an extruded polystyrene board, a rubber and plastic heat insulation board, a polyethylene material, a vacuum heat insulation board, an aerogel heat insulation material or a foam glass heat insulation board;
the thermal protection structure modulates the flow direction of thermal conduction in the material, so that heat flow does not flow through the protected frozen soil roadbed, the frozen soil roadbed is not disturbed by the heat flow, the occurrence of freezing and thawing of the frozen soil roadbed is relieved, and the upper limit degradation of the frozen soil is avoided.
2. The thermal protection structure for frozen earth roadbed protection as claimed in claim 1, wherein said material A and material B are alternatively overlapped by 10 layers.
3. A thermal protection method for protecting a frozen soil roadbed, which is characterized in that the thermal protection structure according to claim 1 or 2 is laid on the frozen soil roadbed to be protected, and the specific method is as follows: and alternately paving the material A and the material B on the frozen soil roadbed to form an arc hopper-shaped canopy which covers the frozen soil roadbed.
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| CN210458824U (en) * | 2019-06-14 | 2020-05-05 | 湖南高速公路配套设施有限公司 | Roadbed structure based on EPS insulation board |
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2020
- 2020-07-26 CN CN202010726927.9A patent/CN111877073B/en active Active
Patent Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
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| SU841418A1 (en) * | 1979-12-14 | 1991-02-23 | Омский Филиал Государственного Всесоюзного Дорожного Научно-Исследовательского Института | Method of erecting embankment in permafrost environment |
| CN102084064A (en) * | 2009-12-31 | 2011-06-01 | 中交第一公路勘察设计研究院有限公司 | Method for protecting roadbeds in frozen soil area and pavement structure |
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