Thermal-insulation waterproof frost heaving-prevention structure for existing railway roadbed in deep seasonal frozen soil region and construction method of thermal-insulation waterproof frost heaving-prevention structure

Abstract

The invention relates to the technical field of railroad bed structures, and discloses a deep season frozen soil area existing railroad bed heat preservation, water insulation and frost heaving prevention structure and a construction method of the deep season frozen soil area existing railroad bed heat preservation, water insulation and frost heaving prevention structure. The invention relates to a heat-insulating waterproof frost heaving-preventing structure for an existing railroad bed in a deep seasonal frozen soil region. The overall cross section of the existing railroad bed is of an axial symmetry structure along the center line of the railroad bed; the existing railway subgrade foundation bed is sequentially provided with a first gravel cushion layer, a waterproof geotechnical cloth layer, a second gravel cushion layer, a geogrid layer and a closed railway ballast layer from bottom to top. Polyurethane heat preservation layers are arranged on side slopes on the two sides of the existing railroad bed. A polyurethane heat preservation layer and a waterproof geotechnical cloth layer are sequentially arranged on the road shoulders on the two sides of the existing railroad bed from bottom to top. A drainage channel is arranged at the slope toe of the existing railroad bed; a polyurethane heat preservation layer is arranged on the connecting section of the slope toe of the existing railroad bed and the drainage channel. The thermal-insulation waterproof frost heaving prevention structure for the existing railroad bed in the deep seasonal frozen soil region can be suitable for treatment and maintenance of frost heaving disasters of the existing railroad bed in the deep seasonal frozen soil region, and has a good engineering application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of railway roadbed structures, and in particular to a thermal insulation, water-proofing and frost-heaving prevention structure of an existing railway roadbed in a deep seasonal frozen soil area and a construction method thereof. Background Art

[0002] Frozen soil refers to soil or rock with a temperature below 0°C and containing ice. According to the length of time that frozen soil exists, China's frozen soil can be divided into perennial frozen soil and seasonal frozen soil. Perennial frozen soil refers to soil or rock that does not melt all year round. It is mainly distributed in the Greater and Lesser Khingan Mountains in Northeast China, the Qinghai-Tibet Plateau, the Qilian Mountains, the Tianshan Mountains, etc., accounting for about one-fifth of China's land area; seasonal frozen soil refers to soil or rock that freezes in winter and melts in summer. It is widely distributed in northern and western China, accounting for more than half of China's land area.

[0003] With the rapid development of China's railway construction, especially in permafrost areas, the construction of railway transportation facilities has entered a large-scale implementation stage. However, due to the existence of a large number of permafrost areas, many railway subgrades in deep seasonal permafrost areas have suffered a series of disasters such as frost heave and thaw, mud and mud, and subsidence. Existing railways in high-cold permafrost areas, such as the Qinghai-Tibet Railway, Lanzhou-Xinjiang Railway, Harbin-Dalian Railway, and Shuohuang Railway, have been severely affected by frost heave disasters. Frost heave has become one of the key factors restricting the safe operation of railways in permafrost areas.

[0004] The main mechanisms of frost heave and thaw settlement are as follows: In a cold winter environment, the soil in the railway embankment is affected by temperature changes and heat transfer occurs. When the embankment temperature drops to freezing point, the moisture and gaseous water in the soil pores condense to form ice crystals. This phase change causes the soil particles to be squeezed and rearranged, causing the soil volume to expand, which manifests as frost heave. Due to the expansion caused by the ice-water phase change process, the top layer of the soil will flip over, causing the embankment to move and deform, forming a frost heave disaster. As the temperature rises in spring and summer, the solid ice begins to melt, but the frozen soil layer below is still frozen, forming an aquiclude to prevent the infiltration of melted water from the upper layer. At the same time, due to the cracks formed by frost heave, precipitation can penetrate into the embankment, resulting in a sharp increase in the local water content of the embankment. Under the combined action of deadweight and external dynamic loads, the embankment suffers from thaw settlement.

[0005] As early as the mid-18th century, MB Lomonosov first proposed the formation mechanism of frozen soil in a review of the causes of frozen soil. In the mid-20th century, the Alaska airport design team in the United States buried polystyrene insulation layer in the road fill for the first time, achieving significant anti-frost heave effect; in the 1970s, Canada conducted research on gravel road insulation layer in frozen soil areas; during the same period, when the Soviet Union built the Siberian Railway, foam boards were used as insulation layers under the ballast and on the slopes of some sections. In recent years, geosynthetics have been widely used in the treatment of railway subgrade diseases in frozen soil areas in China. For example, when studying the treatment of road slurry with geosynthetics, Huo Kaicheng et al. used its isolation, drainage, reinforcement and anti-seepage functions to propose some effective treatment methods. Liu Deren and others conducted experimental research on the anti-frost heaving and mudslipping effect of block stone interlayer roadbed in frozen soil areas, analyzed the mechanism of frost heaving and mudslipping, and proposed a composite roadbed structure combining permeable geotextile, waterproof geotextile and crushed stone layer, which effectively reduced the moisture content of the soil and thus significantly improved the prevention and control effect of frost heaving and mudslipping.

[0006] However, the current control technology for railway subgrade frost heave is still not perfect, especially in solving the problem of subgrade displacement during freezing and thawing. There are still great challenges and the control effect is limited. Further technological innovation and optimization are urgently needed. Summary of the invention

[0007] The purpose of the present invention is to provide an existing railway subgrade thermal insulation, water-proofing and anti-freezing heave structure and a construction method thereof in deep seasonal frozen soil areas. The existing railway subgrade thermal insulation, water-proofing and anti-freezing heave structure has good water-proofing and heat-insulating effects, obvious anti-freezing heave and settlement effects, simple construction and low cost, and does not damage the original subgrade structure. It can be used for the management and maintenance of frost heave disasters on existing railway subgrades in deep seasonal frozen soil areas.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] One of the technical solutions of the present invention:

[0010] A thermal insulation, water-proof and frost-heaving prevention structure for an existing railway subgrade in a deep seasonal frozen soil region, wherein the overall cross-sectional form of the existing railway subgrade is an axisymmetric structure along the center line of the subgrade; the subgrade bed of the existing railway subgrade is provided with a first gravel cushion layer (1), a waterproof geotextile layer (2), a second gravel cushion layer (4), a geogrid layer (5) and a closed ballast layer (6) in sequence from bottom to top; the side slopes on both sides of the existing railway subgrade are provided with a polyurethane thermal insulation layer (3); the shoulders on both sides of the existing railway subgrade are provided with a polyurethane thermal insulation layer (3) and a waterproof geotextile layer (2) in sequence from bottom to top; a drainage channel (7) is provided at the foot of the existing railway subgrade; and a polyurethane thermal insulation layer (3) is provided at the connection section between the foot of the existing railway subgrade and the drainage channel (7).

[0011] Furthermore, the central axis of the first gravel cushion layer (1), the waterproof geotextile layer (2), the second gravel cushion layer (4) and the geogrid layer (5) is raised, and both sides are flush with the road shoulders, and the slopes formed on both sides are both 4%.

[0012] Furthermore, the thickness of the first gravel cushion layer (1) and the second gravel cushion layer (4) is 5 cm, and the material is gravel. The gravel used is round granular gravel with a particle size of 2 mm to 10 mm, good gradation, and the muddy particle content is not more than 5%.

[0013] Furthermore, the thickness of the waterproof geotextile layer (2) is 1 mm, and the material is waterproof geotextile. Two adjacent rolls of waterproof geotextile are overlapped in an alternating manner, and the overlap is sealed with a sealant (8), and the overlap length is not less than 15 cm.

[0014] Furthermore, the thickness of the geogrid layer (5) is 2.5 mm, and the material is geogrid. The geogrid used is a steel-plastic geogrid composed of cold-drawn carbon spring steel wire and polyethylene resin, and the mesh specification is 80×80 mm (±10). Two adjacent rolls of geogrid are overlapped in an alternating manner, and the overlap is tied with a plastic strapping tape, and the overlap length is not less than 30 cm.

[0015] Furthermore, the thickness of the closed ballast layer (6) is 30 to 50 cm, and the material is ballast crushed stone after the gaps are filled with foam glue. The foam glue used is a polyurethane foam sealant, and the ballast crushed stone used is ballast crushed stone particles with a particle size of 20 mm to 50 mm. The amount of foam glue used is sufficient to fill the gaps in the ballast crushed stone.

[0016] Furthermore, the thickness of the polyurethane insulation layer (3) is 8 cm to 10 cm, and the material is a polyurethane insulation board. Two adjacent polyurethane insulation boards are overlapped in a staggered manner, and the overlap is sealed with a sealant (8), and the overlap length is not less than 5 cm.

[0017] Furthermore, the horizontal straight-line distance between the drainage channel (7) and the foot of the existing railway embankment slope is 2 to 3 m.

[0018] The second technical solution of the present invention:

[0019] The construction method of the existing railway subgrade thermal insulation, water-proofing and anti-freezing expansion structure in deep seasonal frozen soil areas comprises the following steps:

[0020] A. Explore the sections of existing railway subgrades in deep seasonal frozen soil areas where freezing damage has occurred;

[0021] B. Dispatch machinery and equipment, prepare construction materials as needed, clean and level the slopes, shoulders and areas near the foot of the existing railway embankment on both sides of the section where frost damage occurs, prevent sharp objects from being present, and start construction during the railway operation window period;

[0022] C. removing the original ballast, excavating a paving space for the first gravel cushion layer (1) on the surface of the existing railway subgrade bed below the ballast, and laying the first gravel cushion layer (1);

[0023] D. Laying a polyurethane insulation layer (3) on the shoulders of the existing railway embankment, the side slopes on both sides, and the connection section between the slope foot and the drainage channel (7), and applying a sealant (8) to the overlap of two adjacent polyurethane insulation boards;

[0024] E. Lay a waterproof geotextile layer (2) on the first gravel cushion layer (1) and the polyurethane insulation layer (3) on the shoulders on both sides, and apply a sealant (8) to the overlapping parts of two adjacent rolls of waterproof geotextile;

[0025] F. Laying a second gravel cushion layer (4) on the top of the waterproof geotextile layer (2);

[0026] G. Laying a geogrid layer (5) on the upper part of the second gravel cushion layer (4);

[0027] H. Laying ballast gravel on the top of the geogrid layer (5), and then injecting foamed glue into the gaps between the ballast gravel to form a closed ballast layer (6).

[0028] Furthermore, in step D, the polyurethane insulation layer (3) is laid in sequence from the shoulders on both sides of the existing railway embankment to the connection section between the slope foot and the drainage channel (7) from top to bottom.

[0029] Furthermore, in step G, the geogrid layer (5) is laid specifically as follows: laying from one shoulder to the other shoulder, and leaving 20 cm on each shoulder, and then rolling the remaining geogrid on both sides of the shoulder into the second gravel cushion layer (4) by reverse laying, and fixing it with U-shaped nails.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention provides an existing railway subgrade thermal insulation and water-proof anti-freezing and swelling structure in deep seasonal frozen soil areas, which has good water-proof and heat-insulating effects, obvious anti-freezing and swelling and settlement effects, is easy to construct and has low cost, and does not damage the original subgrade structure. It can be used for the management and maintenance of frost heave disasters of existing railway subgrades in deep seasonal frozen soil areas, and has good engineering application prospects.

[0032] Compared with the existing thermal insulation, water-proof and frost-heaving prevention structure of existing railway subgrade in frozen soil areas, the thermal insulation, water-proof and frost-heaving prevention structure of existing railway subgrade in deep seasonal frozen soil areas provided by the present invention blocks the channel for external moisture such as environmental rainfall and surface runoff to penetrate into the interior of the railway subgrade by setting a gravel cushion layer and a waterproof geotextile, thereby effectively reducing the moisture content in the subgrade; under rainfall conditions, the change in moisture content of the railway subgrade before and after water-proof treatment for 7 days was determined by an indoor model test, and it was found that the change in moisture content of the subgrade treated by the water-proof method of the present invention before and after the application of rainfall conditions was less than 2%, which indicates that: under rain and snow conditions, the method for treating the railway subgrade by using a structure of a gravel cushion layer and a waterproof geotextile can effectively reduce the infiltration of external rainwater, reduce the moisture content of the subgrade, and improve the water-proof and frost-heaving resistance of the existing railway subgrade;

[0033] Compared with the existing thermal insulation and water-proof anti-freezing and swelling structure of existing railway subgrade in frozen soil areas, the thermal insulation and water-proof anti-freezing and swelling structure of existing railway subgrade in deep seasonal frozen soil areas provided by the present invention can insulate the existing railway subgrade by setting a closed ballast layer and a polyurethane insulation layer; in a cold environment, the convection heat exchange channel between the external environment and the inside of the subgrade is blocked, the loss of heat energy inside the subgrade is reduced, the freezing of water in the subgrade soil is prevented, and the thermal insulation and anti-freezing performance of the existing railway subgrade is improved;

[0034] The waterproof geotextile used in the thermal insulation, water-proofing and anti-freezing heave structure of an existing railway subgrade in a deep seasonal frozen soil area provided by the present invention is a geotechnical anti-seepage synthetic material composed of a plastic film and a non-woven fabric, and its main components are various high-molecular polymers such as polyvinyl chloride (PVC) and polyethylene (PE); the waterproof geotextile has many advantages such as excellent water-proofing and anti-seepage performance, simple processing and manufacturing, can be cut into any shape according to requirements, simple on-site construction and layout, convenient transportation, low cost, long service life, etc., and has good prospects for engineering application and promotion; the thermal conductivity coefficient of the rigid polyurethane thermal insulation material used is only 0.018-0.024W / (m·k), and the heat preservation and heat storage performance is good; the closed porosity of the material is greater than 90%, and it is a hydrophobic material with moisture-proof and waterproof performance; it has a long service life and strong deformation resistance and crack resistance; it is light in weight and easy to transport and install, and can be cut into any shape according to requirements;

[0035] The thermal insulation, water-proofing and anti-freezing heave structure for existing railway subgrade in deep seasonal frozen soil areas provided by the present invention has good water-proofing and thermal insulation effects on the subgrade and obvious anti-freezing heave effect without changing the overall structural strength of the subgrade and ensuring the safe and normal operation of railway trains. The structure is suitable for the management and maintenance of frost heave disasters on existing railway subgrades in deep seasonal frozen soil areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0037] Figure 1 It is a cross-sectional structural schematic diagram of the existing railway subgrade thermal insulation, water-proofing and anti-freezing expansion structure in deep seasonal frozen soil areas of the present invention;

[0038] Figure 2 It is a three-dimensional structural schematic diagram of the existing railway subgrade thermal insulation, water-insulating and frost-heaving prevention structure in deep seasonal frozen soil areas of the present invention;

[0039] Figure 3 It is a cross-sectional structural detail diagram of the existing railway subgrade thermal insulation, water-insulating and anti-freezing expansion structure in deep seasonal frozen soil areas of the present invention;

[0040] Figure 4 Schematic diagram of a straight plate and a curved plate of the polyurethane thermal insulation board of the present invention, wherein A is a straight plate and B is a curved plate;

[0041] Figure 5 It is a schematic diagram of overlapping of the polyurethane thermal insulation board of the present invention;

[0042] Figure 6 It is the overlap diagram of the waterproof geotextile of the present invention;

[0043] Figure 7 It is the dimension diagram of the existing railway subgrade model of the present invention;

[0044] Figure 8 It is a cloud map of the temperature field of the original roadbed of the existing railway of the present invention;

[0045] Fig. 9 It is a temperature field cloud map of the roadbed after the existing railway is treated in the present invention;

[0046] Fig.10 The temperature variation relationship diagram of the existing railway subgrade domain point probe of the present invention;

[0047] Fig.11 It is a cloud map of the moisture distribution of the original roadbed of the existing railway of the present invention;

[0048] Fig.12 It is a cloud map of the moisture field of the roadbed after the existing railway is processed according to the present invention;

[0049] Fig.13 It is a displacement field cloud map of the original roadbed of the existing railway of the present invention;

[0050] Fig.14 It is a cloud map of the displacement field of the roadbed after the existing railway is processed according to the present invention;

[0051] Fig.15 A displacement change relationship diagram of a probe at a point in the existing railway subgrade of the present invention;

[0052] In the figure, (1) the first gravel cushion layer, (2) the waterproof geotextile layer, (3) the polyurethane insulation layer, (4) the second gravel cushion layer, (5) the geogrid layer, (6) the closed ballast layer, (7) the drainage channel, and (8) the sealant. DETAILED DESCRIPTION

[0053] Now, various exemplary embodiments of the present invention are described in detail, and this detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention. It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0054] In the description of the present application, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0055] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0056] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0057] Combination Figures 1 to 6The present embodiment discloses a thermal insulation, water-proof and anti-freezing expansion structure for an existing railway subgrade in a deep seasonal frozen soil region, wherein the overall cross-section of the existing railway subgrade is an axisymmetric structure along the center line of the subgrade; the subgrade of the existing railway subgrade is provided with a first gravel cushion layer (1), a waterproof geotextile layer (2), a second gravel cushion layer (4), a geogrid layer (5) and a closed ballast layer (6) in sequence from bottom to top; the side slopes on both sides of the existing railway subgrade are provided with a polyurethane thermal insulation layer (3); the shoulders on both sides of the existing railway subgrade are provided with a polyurethane thermal insulation layer (3) and a waterproof geotextile layer (2) in sequence from bottom to top; a drainage channel (7) is provided at the foot of the existing railway subgrade; and a polyurethane thermal insulation layer (3) is provided at the connection section between the foot of the existing railway subgrade and the drainage channel (7);

[0058] In a specific embodiment of the present application, the central axis of the first gravel cushion layer (1), the waterproof geotextile layer (2), the second gravel cushion layer (4) and the geogrid layer (5) is raised, and the two sides are flush with the road shoulder, and the slopes formed on both sides are 4%;

[0059] In a specific embodiment of the present application, the thickness of the first gravel cushion layer (1) and the second gravel cushion layer (4) is 5 cm, and the material is gravel. The gravel used is round granular gravel with a particle size of 2 mm to 10 mm, with good gradation, and the content of muddy particles is not more than 5%;

[0060] In a specific embodiment of the present application, the thickness of the waterproof geotextile layer (2) is 1 mm, and the material is a waterproof geotextile (a "two-cloth-one-film" composite waterproof geotextile). Two adjacent rolls of the waterproof geotextile are overlapped in an interlaced manner, and a sealant (8) is used to seal the overlapped portion, and the overlap length is not less than 15 cm;

[0061] In a specific embodiment of the present application, the thickness of the geogrid layer (5) is 2.5 mm, and the material is geogrid. The geogrid used is a steel-plastic geogrid (GSZ80-80 steel-plastic bidirectional geogrid of Shandong Lianxiang Geogrid Factory) composed of cold-drawn carbon spring steel wire and polyethylene resin, and the mesh specification is 80×80 mm (±10). Two adjacent rolls of geogrid are overlapped in an interlaced manner, and the overlap is tied with a plastic strapping tape, and the overlap length is not less than 30 cm;

[0062] In a specific embodiment of the present application, the thickness of the closed ballast layer (6) is 30 to 50 cm, and the material is ballast crushed stone after the gaps are filled with foam glue. The foam glue used is a polyurethane foam sealant, and the ballast crushed stone used is ballast crushed stone particles with a particle size of 20 mm to 50 mm. The amount of the foam glue used is sufficient to fill the gaps in the ballast crushed stone.

[0063] In a specific embodiment of the present application, the thickness of the polyurethane insulation layer (3) is 8 cm to 10 cm, and the material is a polyurethane insulation board (density 35 to 40 kg / m 3 The rigid polyurethane insulation board is a polyurethane insulation board, wherein two adjacent polyurethane insulation boards are overlapped in an alternating manner, and the overlap is sealed with a sealant (8), and the overlap length is not less than 5 cm;

[0064] In a specific embodiment of the present application, the horizontal straight-line distance between the drainage channel (7) and the foot of the existing railway embankment slope is 2 to 3 m;

[0065] In a specific embodiment of the present application, the construction method of the existing railway subgrade thermal insulation, water-proofing and anti-freezing expansion structure in deep seasonal frozen soil areas comprises the following steps:

[0066] A. Explore the sections of existing railway subgrades in deep seasonal frozen soil areas where freezing damage has occurred;

[0067] B. Dispatch machinery and equipment, prepare construction materials as needed, clean and level the slopes, shoulders and areas near the foot of the existing railway embankment on both sides of the section where frost damage occurs, prevent sharp objects from being present, and start construction during the railway operation window period;

[0068] C. removing the original ballast, excavating a paving space for the first gravel cushion layer (1) on the surface of the existing railway subgrade bed below the ballast, and laying the first gravel cushion layer (1);

[0069] D. Laying a polyurethane insulation layer (3) on the shoulders of the existing railway embankment, the side slopes on both sides, and the connection section between the slope foot and the drainage channel (7), and applying a sealant (8) to the overlap of two adjacent polyurethane insulation boards;

[0070] E. Lay a waterproof geotextile layer (2) on the first gravel cushion layer (1) and the polyurethane insulation layer (3) on the shoulders on both sides, and apply a sealant (8) to the overlapping parts of two adjacent rolls of waterproof geotextile;

[0071] F. Laying a second gravel cushion layer (4) on the top of the waterproof geotextile layer (2);

[0072] G. Laying a geogrid layer (5) on the upper part of the second gravel cushion layer (4);

[0073] H. laying ballast gravel on the top of the geogrid layer (5), and then injecting foamed glue into the gaps between the ballast gravel to form a closed ballast layer (6);

[0074] In a specific embodiment of the present application, in step E, the laying of the waterproof geotextile layer (2) is specifically: laying from one shoulder to the other shoulder, and leaving an appropriate expansion margin;

[0075] In a specific embodiment of the present application, in step D, the polyurethane insulation layer (3) is laid in sequence from the shoulders on both sides of the existing railway embankment to the connection section between the slope foot and the drainage channel (7) from top to bottom;

[0076] In a specific embodiment of the present application, in step G, the geogrid layer (5) is laid as follows: it is laid from one shoulder to the other shoulder, and 20 cm is left on each shoulder on both sides, and then the geogrid remaining on both sides of the shoulder is rolled into the second gravel cushion layer (4) by reverse laying, and fixed with U-shaped nails.

[0077] In order to verify the insulation and water-proofing and anti-freezing heave treatment effect of the insulation and water-proofing and anti-freezing heave structure of the existing railway subgrade in deep seasonal frozen soil areas described in the present invention, a two-dimensional steady-state coupling model of water, heat and force three fields of the existing railway subgrade in deep seasonal frozen soil areas is established, and the water field, temperature field and stress field in the subgrade are simulated and calculated by finite element software, and the parameters such as the temperature, unfrozen water content and displacement of the existing railway subgrade in the frozen soil area are obtained, and the calculation results of the untreated existing railway subgrade and the calculation results of the existing railway subgrade treated by the present invention are compared and analyzed;

[0078] The model size diagram of the existing railway subgrade is as follows: Figure 7 As shown, the roadbed consists of roadbed filling layer, natural surface layer, silty clay layer and weakly weathered rock layer from top to bottom. The specific thermal parameters are shown in Table 1.

[0079] Table 1 Roadbed thermal parameters

[0080]

[0081] The roadbed boundary conditions are set as follows: Figure 7 As shown in the figure, the HG boundary is a fixed non-displacement boundary, the ABCDEF displacement boundary has a horizontal displacement of 0 in the x direction and a vertical displacement boundary in the y direction (the recharge effect of groundwater on the frost heave layer is not considered), the AH and FG segments on the left and right sides are set as thermal insulation boundary conditions, and the heat source flux of the bottom HG boundary is 0.08w / m 3 , the maximum temperature of the external environment is 20℃ and the minimum temperature is -10℃. The surface of the ground, shady slope, sunny slope and roadbed are set as periodic temperature boundary conditions for 360 days;

[0082] Comparative analysis of the temperature field cloud map of the original railway subgrade and the treated subgrade Figure 8 and Fig. 9 As shown;

[0083] Depend on Figure 8 and Fig. 9It can be seen that after adopting the existing railway subgrade thermal insulation, water-proof and frost-heaving prevention structure and construction method in deep seasonal frozen soil areas of the present invention, the original subgrade freezing line (0°C line) moves up to the upper part of the silty clay layer, so that the temperature of the subgrade frost-heaving layer is kept above 0°C, and the overall temperature field of the subgrade is evenly distributed, which is conducive to reducing the uneven frost heaving degree of the subgrade; in addition, the existing railway subgrade thermal insulation, water-proof and frost-heaving prevention structure and construction method in deep seasonal frozen soil areas of the present invention are also conducive to reducing the yin-yang slope effect caused by the influence of solar radiation, so that the overall temperature change of the subgrade is more stable;

[0084] Extract the temperature variation data of domain point probe α and domain point probe β in the temperature field cloud map before and after the existing railway subgrade treatment. The relationship diagram of domain point probe temperature variation over time is shown in the figure Fig.10 As shown, A is a temperature variation diagram of the domain point probe α over time, and B is a temperature variation diagram of the domain point probe β over time;

[0085] Depend on Fig.10 It can be seen that the temperature of the probes at different points of the treated roadbed is higher than the original roadbed temperature, and the temperature of the treated roadbed changes little within a year;

[0086] Comparative analysis of the moisture field cloud map of the original railway subgrade and the treated subgrade Fig.11 and Fig.12 As shown;

[0087] Depend on Fig.11 and Fig.12 It can be seen that after adopting the existing railway subgrade insulation, water-insulating and anti-freezing heave structure and construction method in deep seasonal frozen soil areas of the present invention, the moisture content of the original subgrade is reduced to below 8% as a whole, and the water field distribution of the subgrade is more uniform, which is conducive to reducing the uneven degree of frost heave of the subgrade;

[0088] Comparative analysis of the displacement field cloud diagram of the original railway subgrade and the treated subgrade Fig.13 and Fig.14 As shown;

[0089] Depend on Fig.13 and Fig.14 It can be seen that after adopting the existing railway subgrade thermal insulation and water-proof anti-freezing heave structure and construction method in deep seasonal frozen soil areas of the present invention, the vertical displacement of the subgrade is greatly reduced, and the frost heave displacement of the subgrade is reduced from 30 mm to less than 5 mm, eliminating the uneven frost heave effect under the influence of solar radiation, which is conducive to solving the frost heave damage problem of the subgrade and improving the stability of the theoretical subgrade structure;

[0090] Extract the displacement change data of the domain point probe α in the displacement field cloud map before and after the existing railway subgrade treatment. The displacement change relationship diagram of the domain point probe is as follows: Fig.15 As shown;

[0091] Depend on Fig.15It can be seen that the vertical displacement of the probe point α of the treated roadbed is much lower than the frost heave vertical displacement of the original roadbed, and the annual variation of the overall displacement of the treated roadbed is small, which is beneficial to improving the stability of the roadbed.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A thermal insulation, water-proof and frost-proof structure for existing railway subgrade in deep seasonal frozen soil areas, characterized in that: The overall cross-sectional form of the existing railway subgrade is an axisymmetric structure along the center line of the subgrade; the subgrade bed of the existing railway subgrade is provided with a first gravel cushion layer, a waterproof geotextile layer, a second gravel cushion layer, a geogrid layer and a closed ballast layer in sequence from bottom to top; the side slopes on both sides of the existing railway subgrade are provided with a polyurethane insulation layer; the shoulders on both sides of the existing railway subgrade are provided with a polyurethane insulation layer and a waterproof geotextile layer in sequence from bottom to top; a drainage ditch is provided at the toe of the existing railway subgrade; and a polyurethane insulation layer is provided at the connecting section between the toe of the existing railway subgrade and the drainage ditch.

2. The existing railway subgrade thermal insulation, water-proof and frost-swelling prevention structure in deep seasonal frozen soil areas according to claim 1, characterized in that: The central axis of the first gravel cushion layer, the waterproof geotextile layer, the second gravel cushion layer and the geogrid layer is raised, and both sides are flush with the shoulders, and the slopes formed on both sides are both 4%.

3. The existing railway subgrade thermal insulation, water-proofing and anti-freezing expansion structure in deep seasonal frozen soil areas according to claim 1, characterized in that: The thickness of the first gravel cushion layer and the second gravel cushion layer is 5 cm. The material is gravel. The gravel used is round grain gravel with a particle size of 2 mm to 10 mm, good gradation, and the content of muddy particles is not more than 5%.

4. The existing railway subgrade thermal insulation, water-proofing and anti-freezing expansion structure in deep seasonal frozen soil areas according to claim 1, characterized in that: The thickness of the waterproof geotextile layer is 1 mm, and the material is waterproof geotextile. Two adjacent rolls of waterproof geotextile are overlapped in an alternating manner, and the overlap is sealed with a sealant, and the overlap length is not less than 15 cm.

5. The existing railway subgrade thermal insulation, water-proofing and anti-freezing expansion structure in deep seasonal frozen soil areas according to claim 1, characterized in that: The thickness of the geogrid layer is 2.5 mm, and the material is geogrid. The geogrid used is a steel-plastic geogrid composed of cold-drawn carbon spring steel wire and polyethylene resin. The mesh specification is 80×80 mm (±10). Two adjacent rolls of geogrid are overlapped with each other in an staggered manner, and the overlap is tied with plastic strapping, and the overlap length is not less than 30 cm.

6. The existing railway subgrade thermal insulation, water-proofing and anti-freezing expansion structure in deep seasonal frozen soil areas according to claim 1, characterized in that: The thickness of the closed ballast layer is 30 to 50 cm, and the material is ballast crushed stone after the gaps are filled with foam glue. The foam glue used is a polyurethane foam sealant, and the ballast crushed stone used is ballast crushed stone particles with a particle size of 20 mm to 50 mm. The amount of foam glue used can fill the gaps in the ballast crushed stone.

7. The existing railway subgrade thermal insulation, water-proofing and anti-freezing expansion structure in deep seasonal frozen soil areas according to claim 1, characterized in that: The thickness of the polyurethane insulation layer is 8cm to 10cm, and the material is a polyurethane insulation board. Two adjacent polyurethane insulation boards are overlapped in a staggered manner, and the overlap is sealed with a sealant, and the overlap length is not less than 5cm.

8. The existing railway subgrade thermal insulation, water-proofing and anti-freezing expansion structure in deep seasonal frozen soil areas according to claim 1, characterized in that: The horizontal straight-line distance between the drainage channel and the foot of the existing railway embankment slope is 2 to 3 meters.

9. A construction method for the existing railway subgrade thermal insulation, water-proofing and anti-freezing expansion structure in deep seasonal frozen soil areas as claimed in any one of claims 1 to 8, characterized in that: The following steps are involved: A. Explore the sections of existing railway subgrades in deep seasonal frozen soil areas where freezing damage has occurred; B. Dispatch machinery and equipment, prepare construction materials as needed, clean and level the slopes, shoulders and areas near the foot of the existing railway embankment on both sides of the section where frost damage occurs, prevent sharp objects from being present, and start construction during the railway operation window period; C. Remove the original ballast, excavate the paving space of the first gravel cushion layer on the surface of the existing railway subgrade bed under the ballast, and lay the first gravel cushion layer; D. Lay polyurethane insulation layer on the shoulders, side slopes, slope toe and drainage channel connection sections on both sides of the existing railway embankment, and apply sealant at the overlap of two adjacent polyurethane insulation boards; E. Lay a waterproof geotextile layer on the first gravel cushion layer and the polyurethane insulation layer on the shoulders on both sides, and apply sealant at the overlap of two adjacent rolls of waterproof geotextile; F. Lay the second gravel cushion layer on the top of the waterproof geotextile layer; G. Lay a geogrid layer on top of the second gravel cushion layer; H. Lay ballast gravel on the top of the geogrid layer, and then inject foam into the gaps between the ballast gravel to form a closed ballast layer.

10. The construction method according to claim 9, characterized in that: In step D, the polyurethane insulation layer is laid in a specific manner: from the shoulders on both sides of the existing railway roadbed to the slope foot and the connection section with the drainage channel from top to bottom; in step G, the geogrid layer is laid in a specific manner: from one shoulder to the other shoulder, and 20 cm is left on each shoulder on both sides, and then the geogrids remaining on both sides of the shoulders are rolled into the second gravel cushion layer by reverse laying, and fixed with U-shaped nails.

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