A thermal insulation and antifreeze structure for high-speed railway tunnels in severe cold regions

Abstract

The present invention discloses a thermal insulation and antifreeze structure for high-speed railway tunnels in severe cold regions, comprising: initial support, which is formed by spraying concrete on the surface of the surrounding rock of the excavated tunnel and solidifying. There are multiple corrugated steel pipes, each of which is concave into a semicircle and consistent with the shape of the cross section of the initial support; multiple corrugated steel pipes are tightly attached to the inner wall of the initial support and arranged in parallel along the longitudinal direction of the tunnel; both ends of each corrugated steel pipe are located at the bottom of the left and right sides of the tunnel. A lightweight concrete layer is formed by spraying lightweight concrete on the inner wall of each corrugated steel pipe and solidifying; a waterproof layer is laid and covered on the inner wall of the lightweight concrete layer; a secondary lining is applied to the inner wall of the waterproof layer and is tightly fitted with the waterproof layer; and an insulation board is laid and covered on the inner wall of the secondary lining. The thermal insulation and antifreeze structure can reduce and alleviate the frost heave deformation of the surrounding rock and the secondary lining, and has a thermal insulation effect; and can prevent the insulation board and the tunnel structure from falling off and affecting driving safety.

Description

[Technical field]

[0001] The invention belongs to the technical field of thermal insulation and anti-freezing damage of tunnel engineering in cold regions, and in particular relates to a thermal insulation and anti-freezing structure for high-speed railway tunnels in severe cold regions. [Background technology]

[0002] Due to the intrusion of cold air in winter, high-speed railway tunnels in high-altitude and cold regions may cause frost damage to the tunnel structure and surrounding rock, such as frost heave, spalling and cracking of the tunnel lining, partial or overall collapse of the tunnel arch and side walls, water leakage under freeze-thaw cycles, and even water gushing. In order to effectively prevent freezing of tunnels in cold regions, it is necessary to insulate and frost-proof the tunnel structure. According to actual engineering experience, simple drainage technology can no longer meet the frost heave resistance requirements of the lining. In view of this, tunnel frost damage treatment requires a technical method that combines drainage and antifreeze insulation layers to ensure that the groundwater behind the lining does not freeze and the drainage system operates normally, effectively avoiding the occurrence of frost heave of the lining.

[0003] Traditional insulation measures mostly use insulation boards. There are two common ways to lay antifreeze insulation boards. One is to lay insulation boards on the surface, that is, to lay prefabricated insulation boards on the surface of the secondary lining of the tunnel; the other is to lay insulation boards in the middle, that is, to lay prefabricated insulation boards on site between the waterproof layer and the secondary lining of the tunnel. These two insulation methods can theoretically achieve the effect of insulation, thereby solving the problem of frost heave disasters in cold-region tunnels, but both laying methods have certain defects. The wind of high-speed railway tunnels is strong. During the operation of the tunnel, the insulation boards laid on the surface of the secondary lining will loosen or even fall off under the action of the train wind, thus affecting the normal operation of the train; and when the insulation board is laid between the secondary lining and the waterproof layer or between the secondary lining and the primary lining, the moisture in the surrounding rock will gather near the insulation board and penetrate into the insulation board, which not only affects the insulation effect of the insulation board, but also the accumulated moisture freezes in winter, causing frost heave and cracking of the lining structure.

[0004] Therefore, a thermal insulation and anti-freezing structure for high-speed railway tunnels in severe cold regions is needed to solve the above problems, which can effectively prevent the insulation board from falling off and affecting driving safety, and ensure the thermal insulation and anti-freezing effect. [Summary of the invention]

[0005] The purpose of the present invention is to provide a thermal insulation and antifreeze structure for high-speed railway tunnels in severe cold regions, which can reduce and alleviate the frost heave deformation of surrounding rocks and secondary linings, has a thermal insulation effect, and can prevent the thermal insulation board from falling off and affecting driving safety.

[0006] The present invention adopts the following technical scheme: a heat preservation and antifreeze structure for high-speed railway tunnels in severe cold areas, including: initial support, which is formed by spraying concrete on the surface of the surrounding rock of the excavated tunnel and solidifying it.

[0007] There are multiple corrugated steel pipes, each of which is concave into a semicircle and consistent with the shape of the cross-section of the initial support; the multiple corrugated steel pipes are tightly attached to the inner wall of the initial support and arranged in parallel along the longitudinal direction of the tunnel; both ends of each corrugated steel pipe are located at the bottom of the left and right sides of the tunnel respectively.

[0008] The lightweight concrete layer is formed by spraying lightweight concrete on the inner wall of each corrugated steel pipe and solidifying it;

[0009] The waterproof layer is a composite geotextile, which is laid and covered on the inner wall of the lightweight concrete layer;

[0010] Secondary lining is applied to the inner wall of the waterproof layer and fits closely with the waterproof layer;

[0011] The insulation board is arranged and covered on the inner wall surface of the secondary lining.

[0012] Furthermore, the inner wall surface of the insulation board is covered with an aluminum plate, the aluminum plate has a shape consistent with the cross section of the insulation board, and is fixed and fitted by a connecting device.

[0013] Furthermore, it also includes a drainage device, which includes an aluminum alloy water collection tank, a vertical drainage pipe, a longitudinal drainage pipe, a transverse drainage pipe and a central drainage ditch;

[0014] There are two aluminum alloy water collecting troughs, each longitudinally arranged at the bottom of the left and right sides of the tunnel, located below the opening of the corrugated steel pipe on the same side and below the invert arch;

[0015] There are two longitudinal drainage pipes, each located below the aluminum alloy water collection tank on one side;

[0016] The central drainage ditch is located below the invert arch, excavated longitudinally at the bottom of the tunnel arch and along the centerline of the tunnel;

[0017] There are multiple vertical drainage pipes, which are vertically connected between the aluminum alloy water collection tank and the longitudinal drainage pipe on the same side, and the multiple vertical drainage pipes are arranged at intervals in the longitudinal direction;

[0018] There are multiple transverse drainage pipes. On the same side, one end of each transverse drainage pipe is connected to the side wall of the longitudinal drainage pipe on the same side and is communicated with the longitudinal drainage pipe; the other end of each transverse drainage pipe extends into the central drainage ditch.

[0019] Furthermore, the lightweight concrete adopts fiber high-strength lightweight concrete, which is made of the following raw materials in parts by weight: 100 parts of silicate cement; 10 parts of high-alumina cement; 0.0576 parts of polypropylene fiber; 0.17 parts of foaming agent; and 30 parts of water.

[0020] Furthermore, the polypropylene fiber has a length of 3 mm, a diameter of 25 to 100 μm, and a density of 0.6 to 0.9 g / cm 3The foaming agent is expandable polystyrene powder with a diameter of 0.75-1.1 mm and a density of 30 kg / m 3 .

[0021] Furthermore, a thickener is added to the lightweight concrete, and the weight of the thickener is 16.5% of the weight of cement in the lightweight concrete; the thickener is composed of the following raw materials in parts by weight: silica fume: 10 parts; polymer emulsion: 5 parts; water reducing agent: 0.0926 parts; expandable polystyrene powder: 2.67 parts.

[0022] Furthermore, the connecting device is a plurality of screws, all of which vertically penetrate the insulation board and the aluminum plate.

[0023] The present invention also discloses a construction method of the above-mentioned high-speed railway thermal insulation and antifreeze structure in severe cold regions, comprising the following steps:

[0024] Step 1: Carry out initial support in the excavated tunnel;

[0025] Step 2: Make semicircular corrugated steel pipes close to the initial support and arrange them in parallel along the longitudinal direction of the tunnel and close to the inner wall of the initial support;

[0026] Step 3: Spray 10 cm thick lightweight concrete toward each corrugated steel pipe to form a lightweight concrete layer;

[0027] Step 4: Lay a composite geotextile waterproof layer on the lightweight concrete layer;

[0028] Step 5: Apply secondary lining on the inner wall of the waterproof layer;

[0029] Step 6: pour concrete foundations on the base, with two foundations arranged along the longitudinal direction of the tunnel;

[0030] Step 7: Lay the insulation board on the inner wall of the secondary lining;

[0031] Step 8. Lay an aluminum plate on the inner surface of the insulation board, penetrate the screws vertically through the aluminum plate, penetrate the insulation board, and fix it to the secondary lining.

[0032] The beneficial effects of the present invention are: 1. Lightweight concrete is used to fill the space between the corrugated steel pipes, and the inner side of the secondary lining is in close contact with the insulation board, which has good drainage, antifreeze and insulation effects.

[0033] 2. The lightweight concrete used is a flexible structure with high compressive strength and elastic modulus, which can effectively reduce and alleviate the frost heave deformation of the surrounding rock and the secondary lining. Since there are a large number of voids inside the lightweight concrete, it can form an air-proof insulation body with a heat preservation effect;

[0034] 3. The insulation board is tightly attached to the secondary lining surface through the aluminum plate, which can effectively prevent the insulation board from loosening and falling off.

Brief Description of the Drawings

[0035] Figure 1 It is a cross-sectional view of the thermal insulation and antifreeze structure of a high-speed railway tunnel in a severe cold region provided by the present invention;

[0036] Figure 2 It is an overall model diagram of the thermal insulation and antifreeze structure of a high-speed railway tunnel in a severely cold region provided by the present invention;

[0037] Figure 3 yes Figure 2 Middle A is an enlarged schematic diagram;

[0038] Figure 4 yes Figure 3 Middle B is an enlarged schematic diagram;

[0039] Figure 5 It is a schematic diagram of the connection between the aluminum plate, the insulation plate and the second lining thread screws of the present invention;

[0040] Figure 6 It is a schematic diagram of the aluminum alloy water collecting tank of the present invention;

[0041] Figure 7 It is the temperature result of the tunnel without insulation and antifreeze structure;

[0042] Figure 8 is the tunnel temperature result after the present invention is applied;

[0043] Fig. 9 It is the result of moisture freezing in tunnels without thermal insulation and antifreeze structures;

[0044] Fig.10 It is the result of freezing of water in the tunnel after the present invention is applied;

[0045] Among them: 1. Initial support; 2. Corrugated steel pipe; 3. Lightweight concrete; 4. Waterproof layer; 5. Secondary lining; 6. Insulation board; 7. Aluminum plate; 8. Aluminum alloy water collection tank; 9. Vertical drain pipe; 10. Longitudinal drain pipe; 11. Horizontal drain pipe; 12. Center drain ditch; 13. Base; 14. Screws; 15. Tee pipe. [Specific implementation method]

[0046] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0047] A thermal insulation and antifreeze structure for high-speed railway tunnels in severe cold regions, such as Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown, it includes: initial support 1, which is formed by spraying concrete on the surface of the surrounding rock of the excavated tunnel and solidifying it.

[0048] There are multiple corrugated steel pipes 2, each of which is concavely folded into a semicircle and consistent with the cross-sectional shape of the initial support 1; multiple corrugated steel pipes 2 are closely attached to the inner wall of the initial support 1 and arranged in parallel along the longitudinal direction of the tunnel; both ends of each corrugated steel pipe 2 are located at the bottom of the left and right sides of the tunnel. Both ends of each corrugated steel pipe 2 are open.

[0049] A lightweight concrete layer 3 is formed on the inner wall of the corrugated steel pipe 2 and the concrete in the gap. The concrete is sprayed toward the corrugated steel pipe 2 by spraying. Concrete is sprayed on the corrugated steel pipe 2 and in the gaps between the corrugated steel pipes. After solidification, a lightweight concrete layer 3 is formed. The waterproof layer 4 is a composite geotextile, which is laid and covered on the inner wall of the lightweight concrete layer 3. The secondary lining 5 is applied to the inner wall of the waterproof layer 4 and is closely attached to the waterproof layer 4; the composite geotextile waterproof layer is closely attached between the lightweight concrete and the secondary lining, and can effectively play a waterproof role.

[0050] The corrugated steel pipe 2 and the lightweight concrete layer 3 work together to have the following functions: multiple corrugated steel pipes 2 form a whole and are fixed, and the steel pipe and the concrete form a whole, separating the secondary lining and the initial support, playing the role of heat preservation and anti-freezing and buffering the deformation of the secondary lining 5.

[0051] Also includes drainage devices, such as Figure 5 and 6 As shown, the drainage device includes an aluminum alloy water collection tank 8, a vertical drainage pipe 9, a longitudinal drainage pipe 10, a transverse drainage pipe 11 and a central drainage ditch 12; there are two aluminum alloy water collection tanks 8, each longitudinally arranged at the bottom of the left and right sides of the tunnel, located below the opening of the corrugated steel pipe 2 on the same side, and located below the inverted arch. There are two longitudinal drainage pipes 10, each located below the aluminum alloy water collection tank 8 on one side; the central drainage ditch 12 is located below the inverted arch, longitudinally excavated at the bottom of the tunnel arch, and along the center line of the tunnel. The vertical drainage pipe 9, the longitudinal drainage pipe 10 and the transverse drainage pipe 11 are connected by a tee.

[0052] There are multiple vertical drain pipes 9, which are vertically connected between the aluminum alloy water collection tank 8 and the longitudinal drain pipe 10 on the same side, and the multiple vertical drain pipes 9 are arranged at intervals in the longitudinal direction. There are multiple transverse drain pipes 11, and on the same side, one end of each transverse drain pipe 11 is connected to the side wall of the longitudinal drain pipe 10 on the same side and communicates with the longitudinal drain pipe 10; the other end of each transverse drain pipe 11 extends into the central drain ditch 12. The corrugated steel pipe 2 also plays a role in guiding water.

[0053] The insulation board 6 is arranged and covered on the inner wall surface of the secondary lining 5. The inner wall surface of the insulation board 6 is covered with an aluminum plate 7, which has the same cross-sectional shape as the insulation board 6 and is fixed to the secondary lining 5 through a connecting device. The insulation board 6 and the aluminum plate 7 are tightly fitted into one with the secondary lining. The connecting device is a plurality of screws, which are vertically penetrated through the insulation board 6 and the aluminum plate 7. The screws are arranged according to a 2m×2m rectangle; the insulation board adopts a 5cm thick polyphenolic foam / polyurethane foam / aluminum silicate fiber material.

[0054] The above-mentioned lightweight concrete adopts fiber high-strength lightweight concrete, which is made of the following raw materials by weight: 100 parts of silicate cement; 10 parts of high-alumina cement; 0.0576 parts of polypropylene fiber; 0.17 parts of foaming agent; 30 parts of water. The length of polypropylene fiber is 3mm, the diameter is 25-100μm, and the density is 0.6-0.9g / cm 3 The foaming agent is expandable polystyrene powder with a diameter of 0.75-1.1 mm and a density of 30 kg / m 3 .

[0055] In order to enhance the solidification of lightweight concrete, a thickener is added to the lightweight concrete. The weight of the thickener is 16.5% of the weight of cement in the lightweight concrete. The thickener is composed of the following raw materials in parts by weight: silica fume: 10 parts; polymer emulsion: 5 parts; water reducer: 0.0926 parts; expandable polystyrene powder: 2.67 parts.

[0056] The above-mentioned construction method of the thermal insulation and antifreeze structure of high-speed railway in severe cold regions comprises the following steps:

[0057] Step 1: Carry out initial support 1 in the excavated tunnel;

[0058] Step 2: a semicircular corrugated steel pipe 2 is made on the initial support 1 and arranged in parallel along the longitudinal direction of the tunnel and close to the inner wall of the initial support 1;

[0059] Step 3: spray 10 cm thick lightweight concrete toward each corrugated steel pipe 2 to form a lightweight concrete layer 3;

[0060] Step 4: Lay the composite geotextile waterproof layer 4 on the lightweight concrete layer 3;

[0061] Step 5: Apply secondary lining 5 on the inner wall surface of waterproof layer 4;

[0062] Step 6: pouring concrete foundations 13 at the bottom of the tunnel. There are two foundations 13, both of which are arranged along the longitudinal direction of the tunnel.

[0063] Step 7: Lay the insulation board 6 on the inner wall of the secondary lining 5;

[0064] Step 8: Lay an aluminum plate on the inner surface of the insulation board 6 , penetrate the screws vertically through the aluminum plate 7 , penetrate the insulation board 6 , and fix it to the secondary lining 5 .

[0065] like Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown, the lower part of the corrugated steel pipe 2 is connected to the aluminum alloy water collection tank 8, which is close to the lower part of the corrugated steel pipe 2 and has a width greater than or equal to the width of the corrugated steel pipe 2. A hole with a diameter of 55mm is drilled every 10m under the water collection tank, and a Φ55PVC pipe is inserted as a vertical drainage pipe 9. The vertical drainage pipe 9, the longitudinal drainage pipe 10, and the horizontal drainage pipe 11 are connected by a reinforced three-way joint, and finally converged in the central drainage ditch 12 directly below the tunnel. The corrugated pipe used is concave into a semicircle with a diameter of 120mm.

[0066] The specific construction method of the present invention is as follows:

[0067] A. After tunnel excavation is completed, initial support 1 construction is carried out, including steel mesh, steel arch frame, anchor rods and primary lining concrete.

[0068] B. Treat the initial support surface and clean the surface dirt.

[0069] C. Make a semicircular corrugated steel pipe 2, arrange it along the cross section of the tunnel and closely along the longitudinal direction of the tunnel. The lower part of the corrugated steel pipe 2 is connected to the aluminum alloy water collection tank 8 with a size of 12cm×10cm. Drill a hole with a diameter of 55mm every 10m under the water collection tank, insert a Ф55PVC pipe as a vertical drainage pipe 9, and use a reinforced three-way joint 15 to connect the vertical drainage pipe 9, the longitudinal drainage pipe 10, and the horizontal drainage pipe 11, and finally collect them in the central drainage ditch 12 just below the tunnel.

[0070] D. Spray 10 cm thick lightweight concrete 3 on the surface of the corrugated steel pipe, and clean the surface of the lightweight concrete 3 until it is flat; the lightweight concrete 3 is prepared according to the following components and raw materials in weight ratio: ordinary Portland cement: 100 parts; high alumina cement: 10 parts; polypropylene fiber: 0.0576 parts; foaming agent: 0.17 parts; water: 30 parts; lightweight concrete thickener is prepared according to the following components and raw materials in weight ratio: silica powder: 10 parts; polymer emulsion: 5 parts; water reducer 0.0926 parts; expandable polystyrene powder: 2.67 parts; the weight of the thickener accounts for 16.5% of the weight of cement in the lightweight concrete.

[0071] E. Lay the composite geotextile waterproof layer 4 close to the surface of the lightweight concrete 3 by screw anchoring method.

[0072] F. Construct the secondary lining 5 of the tunnel, check the surface flatness, and remove dirt from the surface of the secondary lining 5 of the tunnel.

[0073] G. After the secondary lining 5 is cured, the base is leveled and a concrete foundation 13 is poured. The foundation thickness is 35 cm and the width is 1.0 m. There are two foundations 13, both of which are arranged along the longitudinal direction of the tunnel;

[0074] H. After the concrete base 13 is built, the aluminum plate 7 is tightly fixed to the tunnel secondary lining 5 by passing through the insulation board 6 with screws 14. The screws 14 are arranged in a 2m×2m rectangular shape.

[0075] In order to verify the insulation and antifreeze effect of the tunnel insulation and antifreeze structure in this embodiment, numerical simulation and comparison of the temperature field of high-speed railway tunnels with the tunnel insulation and antifreeze structure in this embodiment and without the insulation and antifreeze structure were carried out under severe cold conditions. Severe cold areas refer to areas with the lowest monthly average temperature below -10°C. A tunnel freezing temperature finite element model was established to simulate the tunnel temperature field in the cold season:

[0076] like Figure 7 and Figure 8 As shown, in Figure 7 In the experiment, the inner surface temperature of the tunnel was -3 degrees Celsius, and the freezing depth of the surrounding rock reached about 3 meters. After the thermal insulation and antifreeze structure of the present invention was applied, the inner surface temperature of the tunnel was above 0 degrees Celsius, and there was no freezing and frost heaving of the surrounding rock. Since the surrounding rock of the tunnel will frost heave below the freezing temperature of 0 degrees Celsius, continuous frost heave will cause damage to the surrounding rock. In severe cases, it will cause damage to the tunnel structure, ice on the lining surface and other frost heave damage, and even cause driving safety accidents inside the tunnel. Therefore, by applying the thermal insulation structure of the present invention, the tunnel insulation effect is well achieved.

[0077] like Fig. 9 and Fig.10 As shown, Fig. 9 From the inner surface of the tunnel to the surrounding rock, the amount of frozen water decreases continuously. The amount of frozen water on the inner surface of the tunnel is the largest, indicating that the temperature here is the lowest. The deeper into the surrounding rock, the smaller the amount of frozen water, indicating that the temperature of the surrounding rock continues to rise, until the temperature reaches above 0 degrees Celsius, at which time the surrounding rock will not freeze. Fig.10 This indicates that there is no frozen water in the surrounding rock of the tunnel, and at this time the temperature of the surrounding rock of the tunnel is above 0 degrees Celsius. By applying the heat preservation structure of the present invention, a good heat preservation effect of the tunnel is achieved.

Claims

1. A thermal insulation and antifreeze structure for high-speed railway tunnels in severe cold regions, characterized in that: include: Initial support (1) is formed by spraying concrete onto the surface of the surrounding rock of the tunnel excavation and solidifying it; There are multiple corrugated steel pipes (2), each of which is concavely folded into a semicircular shape and is consistent with the shape of the cross section of the initial support (1); the multiple corrugated steel pipes (2) are closely attached to the inner wall of the initial support (1) and are arranged in parallel along the longitudinal direction of the tunnel; both ends of each of the corrugated steel pipes (2) are located at the bottom of the left and right sides of the tunnel; A lightweight concrete layer (3) formed by spraying lightweight concrete onto the inner wall of each of the corrugated steel pipes (2) and solidifying; The waterproof layer (4) is a composite geotextile, which is laid and covers the inner wall surface of the lightweight concrete layer (3); A secondary lining (5) is applied to the inner wall of the waterproof layer (4) and is closely attached to the waterproof layer (4); A heat-insulating plate (6) arranged and covering the inner wall surface of the secondary lining (5); The inner wall surface of the heat-insulating plate (6) is covered with an aluminum plate (7), the aluminum plate (7) having a shape consistent with the cross-section of the heat-insulating plate (6), and being fixedly attached by a connecting device; It also includes a drainage device, which includes an aluminum alloy water collection tank (8), a vertical drainage pipe (9), a longitudinal drainage pipe (10), a transverse drainage pipe (11) and a central drainage ditch (12); There are two aluminum alloy water collecting troughs (8), each of which is longitudinally arranged at the bottom of the left and right sides of the tunnel, located below the opening of the corrugated steel pipe (2) on the same side, and located below the invert arch; Two longitudinal drainage pipes (10), each located below the aluminum alloy water collecting tank (8) on one side; A central drainage ditch (12), located below the invert arch, is longitudinally excavated at the tunnel arch bottom and along the tunnel centerline; A plurality of vertical drainage pipes (9) are vertically connected between the aluminum alloy water collection tank (8) and the longitudinal drainage pipe (10) on the same side, and the plurality of vertical drainage pipes (9) are arranged at intervals in the longitudinal direction; There are multiple transverse drainage pipes (11), and on the same side, one end of each transverse drainage pipe (11) is connected to the side wall of the longitudinal drainage pipe (10) on the same side and communicates with the longitudinal drainage pipe (10); the other end of each transverse drainage pipe (11) extends into the central drainage ditch (12); The lightweight concrete adopts fiber high-strength lightweight concrete, which is made of the following raw materials in parts by weight: 100 parts of silicate cement; 10 parts of high-alumina cement; 0.0576 parts of polypropylene fiber; 0.17 parts of foaming agent; 30 parts of water; The polypropylene fiber has a length of 3 mm, a diameter of 25-100 μm, and a density of 0.6-0.9 g / cm 3 The foaming agent is expandable polystyrene powder with a diameter of 0.75~1.1mm and a density of 30kg / m 3 ; A thickener is added to the lightweight concrete, and the weight of the thickener is 16.5% of the weight of cement in the lightweight concrete; the thickener is composed of the following raw materials in parts by weight: 10 parts of silica fume; 5 parts of polymer emulsion; 0.0926 parts of water reducing agent; and 2.67 parts of expandable polystyrene powder. The connecting device is a plurality of screws, all of which vertically penetrate the insulation board (6) and the aluminum board (7).

2. The construction method of a thermal insulation and antifreeze structure for a high-speed railway tunnel in a severely cold region according to claim 1, characterized in that: The following steps are involved: Step 1: Provide initial support in the excavated tunnel (1); Step 2: a semicircular corrugated steel pipe (2) is made on the initial support (1), and arranged in parallel along the longitudinal direction of the tunnel and closely attached to the inner wall of the initial support (1); Step 3: spraying 10 cm thick lightweight concrete toward each of the corrugated steel pipes (2) to form a lightweight concrete layer (3); Step 4: Laying a composite geotextile waterproof layer (4) on the lightweight concrete layer (3); Step 5: Apply a secondary lining (5) on the inner wall surface of the waterproof layer (4); Step 6: pouring a concrete base (13) on the base, wherein there are two bases (13) arranged along the longitudinal direction of the tunnel; Step 7: Laying an insulation board (6) on the inner wall of the secondary lining (5); Step 8: Lay an aluminum plate on the inner surface of the insulation board (6), and vertically penetrate the aluminum plate (7) with screws, penetrate the insulation board (6), and fix it to the secondary lining (5).

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