Constant-temperature anti-cracking structure for secondary lining concrete of portal section in alpine region

Abstract

The utility model relates to the technical field of tunnel construction in alpine regions, in particular to a constant-temperature anti-cracking structure for secondary lining concrete of a portal section in an alpine region. The constant-temperature anti-cracking structure for the secondary lining concrete of the hole section in the alpine region comprises embedded pipes, and a plurality of axial embedded pipes are embedded in the secondary lining concrete of the hole section; the heating modules are arranged in all the embedded pipes in an inserted mode; and the waterproof structure layer is pre-buried on the outer peripheral surface of the hole section secondary lining concrete. The device can quickly respond to the external temperature change so as to timely adjust the active heating temperature, realizes the constant-temperature anti-cracking of the secondary lining concrete, and also has the advantages of low maintenance cost, no leakage risk and the like.

Description

Technical Field

[0001] This utility model relates to the field of tunnel construction technology in high-altitude and cold regions, specifically to a constant-temperature and crack-resistant structure for secondary lining concrete in tunnel entrance sections in high-altitude and cold regions. Background Technology

[0002] Tunnel entrance sections in high-altitude and frigid regions face extreme low temperatures (typically annual minimum temperatures as low as -10℃ to -30℃) and severe freeze-thaw cycles (50 to 100 cycles per year). Such extreme temperatures and frequent freeze-thaw cycles often cause cracks in the secondary lining concrete, significantly reducing its strength and durability. The secondary lining concrete at the tunnel entrance is the core load-bearing layer of the tunnel structure; its compressive strength and durability directly determine the tunnel's safety and service life. Therefore, it is necessary to take appropriate measures to protect the secondary lining concrete at the tunnel entrance.

[0003] Chinese patent CN202110832058.2 utilizes a heat transfer circulating medium that circulates in a heat exchange pipe circuit to exchange heat with underground rocks and absorb heat. The absorbed heat is then boosted by a first ground source heat pump and a second ground source heat pump, causing the heat transfer circulating medium in the first heating pipe circuit and / or the second heating pipe circuit to reach a certain temperature requirement. The heat transfer circulating medium in the heating pipe serves as the primary lining, secondary lining, and for heating within the tunnel. However, using underground rock as a heat source results in unstable temperatures, and the lower the ambient temperature, the less the underground rock is affected by the ambient temperature. This makes it difficult to sustain this method of insulation when the external ambient temperature is low and higher heating power is required. The circulating medium needs to flow to the underground rock to absorb heat before being pumped to the area to be heated, resulting in a slow response speed. In addition, the heat transfer medium is circulated through pre-buried pipelines. When the heat transfer medium leaks due to pipe aging, loose connections, construction damage, frost heave, or other reasons, repairing or replacing the pipeline requires damaging the lining, which is a lot of work and affects the normal operation of the tunnel. Furthermore, the leaked liquid seeps into the lining structure, which may cause local frost heave, leading to cracks, spalling, or lining deformation. Utility Model Content

[0004] The purpose of this utility model is to provide a constant temperature and crack prevention structure for secondary lining concrete in tunnel sections in cold regions. It can at least partially overcome the above-mentioned technical problems, can quickly respond to external temperature changes and adjust the active heating temperature in a timely manner to achieve constant temperature and crack prevention of secondary lining concrete. In addition, it also has the advantages of low maintenance and repair costs and no leakage risk.

[0005] This utility model provides a constant temperature and crack prevention structure for secondary lining concrete in tunnel sections in cold regions, including pre-embedded pipes, multiple axial pre-embedded pipes are pre-embedded inside the secondary lining concrete in the tunnel section; heating modules are inserted into each of the pre-embedded pipes; and a waterproof structural layer is pre-embedded on the outer circumferential surface of the secondary lining concrete in the tunnel section.

[0006] Furthermore, the constant temperature and crack prevention structure of the secondary lining concrete of the tunnel entrance section in the high-altitude and cold region also includes a thermal insulation layer. The thermal insulation layer is laid on the outer surface of the secondary lining concrete of the tunnel entrance section. For the outer peripheral surface of the secondary lining concrete of the tunnel entrance section, the thermal insulation layer is located between the waterproof structure layer and the outer peripheral surface.

[0007] Furthermore, the heating module includes a housing, an electric heating wire, and a first filler. The electric heating wire is inserted inside the housing and there is a first gap between the heating wire and the housing. The first filler is filled in the first gap and is thermally conductive and insulating. A support frame is provided at intervals outside the heating module. There is a second gap between the heating module inserted in the pre-embedded pipe and the pre-embedded pipe. The second gap is filled with a thermally conductive second filler.

[0008] Furthermore, the heating wire is a nickel-chromium wire; the first filler and the second filler are both selected from one or more of magnesium oxide powder, aluminum oxide powder, and boron nitride powder.

[0009] Furthermore, each of the pre-embedded pipes is evenly distributed circumferentially along the secondary lining concrete of the opening section; for any two adjacent pre-embedded pipes, the two adjacent pre-embedded pipes are connected by multiple heat-conducting rods.

[0010] Furthermore, the distance from each point on the centerline of the heat-conducting rod to the inner circumferential surface of the secondary lining concrete of the opening section is equal; each heat-conducting rod is evenly distributed along the axial direction of the secondary lining concrete of the opening section.

[0011] Furthermore, multiple radial holes are drilled on the inner circumferential surface, and a temperature sensor is installed in each of the drill holes. The gap between the temperature sensor and the drill hole is filled with thermally conductive silicone grease.

[0012] Optionally, multiple mounting cylinders are pre-embedded in the secondary lining concrete of the opening section. The axis of the mounting cylinder is along the radial direction of the secondary lining concrete of the opening section, and the opening side is flush with the inner circumferential surface. Multiple heat-conducting fins extend from the outer circumferential wall of the mounting cylinder, and threads are formed on the inner circumferential wall of the opening section of the mounting cylinder. A temperature sensor is installed in each of the mounting cylinders, and the gap between the temperature sensor and the mounting cylinder is filled with thermally conductive silicone grease. The opening side of the mounting cylinder is sealed by an end cap threaded connection.

[0013] Furthermore, for any temperature sensor, the temperature sensor is located within the grid formed by the embedded tube and the heat-conducting rod, and is located at the intersection of the diagonals of the grid.

[0014] Furthermore, the constant temperature and crack prevention structure for the secondary lining concrete of the tunnel entrance section in high-altitude and cold regions also includes: a control terminal, wherein each of the temperature sensors and each of the heating modules are electrically connected to the control terminal, and the control terminal can adjust the heating temperature of each of the heating modules in response to the temperature signals transmitted by each of the temperature sensors.

[0015] Compared with the prior art, this utility model has the following advantages and beneficial effects:

[0016] 1. The constant temperature and crack prevention structure for secondary lining concrete in tunnel entrance sections in high-altitude and cold regions provided in this embodiment actively heats the secondary lining concrete by inserting heating modules into pre-embedded pipes, thus preventing the secondary lining concrete from becoming too cold and achieving the effect of crack prevention, thereby ensuring the long-term safe operation of the tunnel. By setting a waterproof structural layer on the outer periphery of the secondary lining concrete in the tunnel entrance section, the seepage of molten water caused by heating into the secondary lining concrete in the tunnel entrance section can be prevented, thereby reducing the potential freeze-thaw risk in the secondary lining concrete in the tunnel entrance section. In addition, the waterproof structural layer can also provide a certain buffering capacity, thereby buffering the frost heave force of the surrounding rock and the primary lining structure during freeze-thaw, reducing its impact on the secondary lining concrete in the tunnel entrance section.

[0017] 2. The constant temperature and crack prevention structure for secondary lining concrete in tunnel entrance sections in high-altitude and cold regions provided in this embodiment reduces heat exchange between the secondary lining concrete in the tunnel entrance section and the outside environment (surrounding rock side and tunnel passage side) by setting up a heat insulation structure layer. This can limit the heat provided by the heating module to the interior of the secondary lining concrete in the tunnel entrance section as much as possible, ensuring that the temperature of the secondary lining concrete in the tunnel entrance section is uniform and stable, and also reducing heating energy consumption and lowering operating costs.

[0018] 3. The constant temperature and crack prevention structure for the secondary lining concrete of the tunnel entrance section in high-altitude and cold regions provided in this embodiment of the invention features an integrated heating module, which makes the heating module easy to install and remove, and facilitates replacement after subsequent damage.

[0019] 4. The constant temperature and crack prevention structure for the secondary lining concrete of the tunnel entrance section provided in this embodiment of the present disclosure, by setting up a control terminal and a temperature sensor, uses the control terminal to adjust the heating temperature of the heating module in a timely manner according to the temperature feedback from the temperature sensor, so that the temperature of the secondary lining concrete of the tunnel entrance section can still be maintained at the preset temperature when the external temperature changes, thereby achieving constant temperature and crack prevention. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of the embodiments of the present invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0021] Figure 1 This is a three-dimensional structural diagram of the constant temperature and crack prevention structure of the secondary lining concrete in the opening section, drawn according to an embodiment of the present utility model.

[0022] Figure 2 This is a three-dimensional structural schematic diagram of the heating module according to an embodiment of the present utility model;

[0023] Figure 3 This is a sectional view of the constant temperature and crack prevention structure of the secondary lining concrete in the opening section, drawn according to an embodiment of the present utility model.

[0024] Figure 4 This is another sectional view of the constant temperature and crack prevention structure of the secondary lining concrete in the opening section, drawn according to an embodiment of the present utility model.

[0025] Figure 5 This is another sectional view of the constant temperature and crack prevention structure of the secondary lining concrete in the opening section, drawn according to an embodiment of the present utility model.

[0026] Figure 6 This is a three-dimensional structural diagram of the mounting cylinder according to an embodiment of the present utility model.

[0027] The attached diagram shows the markings and corresponding component names:

[0028] 1-Secondary lining concrete at the opening; 21-Embedded pipe; 22-Waterproof structural layer; 23-Insulation structural layer; 24-Heat-conducting rod; 31-Outer shell; 32-Electric heating wire; 33-First gap; 34-Support frame; 35-Second gap; 41-Drill hole; 42-Temperature sensor; 43-Thermal grease; 44-Mounting cylinder; 45-Thermal fins; 46-End cap. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this utility model clearer, the following detailed description is provided in conjunction with the embodiments and accompanying drawings. The illustrative embodiments and descriptions of this utility model are for explaining the utility model only and are not intended to limit the utility model. It should be noted that this utility model is already in the actual research and development stage.

[0030] Tunnel entrance sections in high-altitude and frigid regions face extreme low temperatures (typically annual minimum temperatures as low as -10℃ to -30℃) and severe freeze-thaw cycles (50 to 100 cycles per year). Such extreme temperatures and frequent freeze-thaw cycles often lead to cracks in the secondary lining concrete, resulting in a significant reduction in strength and durability. (The freezing and expansion of water within the concrete pores creates expansion pressure, causing microcracks; the thawed water then seeps into these microcracks, freezes and expands again, and this repeated freeze-thaw cycle causes the cracks to expand continuously, leading to a substantial decrease in the concrete's strength and durability.) The secondary lining concrete at the tunnel entrance is the core load-bearing layer of the tunnel structure; its compressive strength and durability directly determine the tunnel's safety and service life. Therefore, it is necessary to take appropriate measures to protect the secondary lining concrete at the tunnel entrance.

[0031] Chinese patent CN202110832058.2 utilizes a heat transfer circulating medium that circulates in a heat exchange pipe circuit to exchange heat with underground rocks and absorb heat. The absorbed heat is then boosted by a first ground source heat pump and a second ground source heat pump, causing the heat transfer circulating medium in the first heating pipe circuit and / or the second heating pipe circuit to reach a certain temperature requirement. The heat transfer circulating medium in the heating pipe serves as the primary lining, secondary lining, and for heating within the tunnel. However, using underground rock as a heat source results in unstable temperatures, and the lower the ambient temperature, the less the underground rock is affected by the ambient temperature. This makes it difficult to sustain this method of insulation when the external ambient temperature is low and higher heating power is required. The circulating medium needs to flow to the underground rock to absorb heat before being pumped to the area to be heated, resulting in a slow response speed. In addition, the heat transfer medium is circulated through pre-buried pipelines. When the heat transfer medium leaks due to pipe aging, loose connections, construction damage, frost heave, or other reasons, repairing or replacing the pipeline requires damaging the lining, which is a lot of work and affects the normal operation of the tunnel. Furthermore, the leaked liquid seeps into the lining structure, which may cause local frost heave, leading to cracks, spalling, or lining deformation.

[0032] Therefore, this utility model proposes a constant temperature and crack prevention structure for the secondary lining concrete of tunnel sections in cold regions. It can quickly respond to external temperature changes and adjust the active heating temperature in a timely manner to achieve constant temperature and crack prevention of the secondary lining concrete. In addition, it has the advantages of low maintenance and repair costs and no risk of leakage.

[0033] Example 1:

[0034] like Figure 1 , Figure 3 and Figure 4 As shown, this embodiment provides a constant temperature and crack prevention structure for secondary lining concrete in tunnel entrance sections in cold regions. The structure includes embedded pipes 21, and multiple axial embedded pipes 21 are embedded inside the secondary lining concrete 1 in the tunnel entrance section.

[0035] The heating module is inserted into each of the pre-embedded pipes 21;

[0036] Waterproof structural layer 22 is embedded in the outer periphery of the secondary lining concrete 1 in the opening section.

[0037] It should be understood that the pre-embedded pipe 21 is installed in the casting cavity of the secondary lining concrete 1 of the opening section before the secondary lining concrete 1 is poured, and then it is integrated with the secondary lining concrete 1 of the opening section during the pouring operation; the preferred material is an aluminum alloy pipe with good thermal conductivity, light weight, corrosion resistance, and easy processing. Similarly, before constructing the cavity of the secondary lining concrete 1 of the opening section, the waterproof structural layer 22 is attached to the primary lining structure (not shown in the attached drawings), and then the secondary lining concrete 1 of the opening section is poured. Thus, after the secondary lining concrete 1 of the opening section is poured, the waterproof structural layer 22 is located between the primary lining structure and the secondary lining concrete. Preferably, the waterproof structural layer 22 is a geotextile sandwiched with a waterproof membrane. Specifically, a layer of geotextile is attached to the primary lining structure, followed by a waterproof membrane (commonly PVC, EVA, or HDPE waterproof membranes), and then another layer of geotextile. This prevents groundwater from seeping into the secondary lining concrete and also avoids the waterproof membrane being punctured by the sharp parts of the primary lining structure.

[0038] Accordingly, this embodiment provides a constant temperature and crack prevention structure for the secondary lining concrete of the tunnel entrance section in cold regions. By inserting a heating module into the pre-embedded pipe 21, the secondary lining concrete 1 of the tunnel entrance section is actively heated, which can prevent the temperature of the secondary lining concrete 1 of the tunnel entrance section from being too low, thereby achieving the effect of crack prevention and ensuring the long-term safe operation of the tunnel. By setting a waterproof structural layer 22 on the outer periphery of the secondary lining concrete 1 of the tunnel entrance section, the seepage of molten water caused by heating into the secondary lining concrete 1 of the tunnel entrance section can be prevented, thereby reducing the potential freeze-thaw risk inside the secondary lining concrete 1 of the tunnel entrance section. In addition, the waterproof structural layer 22 can also provide a certain buffering capacity, thereby buffering the freeze-thaw heave force of the surrounding rock and the primary lining structure, reducing its impact on the secondary lining concrete 1 of the tunnel entrance section.

[0039] Specifically, such as Figure 3 and Figure 4 As shown, the constant temperature and crack prevention structure of the secondary lining concrete in the high-altitude cold region also includes a thermal insulation layer 23. The thermal insulation layer 23 is laid on the outer surface of the secondary lining concrete 1 in the tunnel entrance section. For the outer periphery of the secondary lining concrete 1 in the tunnel entrance section, the thermal insulation layer 23 is located between the waterproof structural layer 22 and the outer periphery. Preferably, the thermal insulation layer 23 is XPS board (extruded polystyrene foam board) and / or PU rigid foam board (rigid polyurethane foam board).

[0040] Accordingly, this embodiment provides a constant temperature and crack prevention structure for the secondary lining concrete of the tunnel entrance section in cold regions. By setting up a thermal insulation layer 23, the heat exchange between the secondary lining concrete 1 of the tunnel entrance section and the outside world (the surrounding rock side and the tunnel passage side) is reduced. This can limit the heat provided by the heating module to the interior of the secondary lining concrete 1 of the tunnel entrance section as much as possible, ensuring that the temperature of the secondary lining concrete 1 of the tunnel entrance section is uniform and stable, and also reducing heating energy consumption and lowering operating costs.

[0041] More specifically, such as Figure 2 As shown, the heating module includes a housing 31, an electric heating wire 32, and a first filler. The electric heating wire 32 is inserted into the housing 31 and there is a first gap 33 between the electric heating wire 32 and the housing 31. The first filler is filled in the first gap 33. The first filler is thermally conductive and insulating.

[0042] The heating module is provided with a support frame 34 at intervals on the outside. There is a second gap 35 between the heating module inserted into the pre-embedded pipe 21 and the pre-embedded pipe 21. The second gap 35 is filled with a heat-conducting second filler.

[0043] Preferably, the heating wire 32 is a nickel-chromium wire;

[0044] Both the first filler and the second filler are selected from one or more of magnesium oxide powder, aluminum oxide powder, and boron nitride powder.

[0045] It should be understood that the heating module is a pre-manufactured finished product (similar to an immersion heater) that integrates the outer shell 31, the electric heating wire 32, and the first filler. During installation, it is inserted into the pre-embedded pipe 21. During this process, the support frame 34 ensures that the heating module is centered in the pre-embedded pipe 21. Then, the second filler is filled into the second gap 35 between the heating module outer shell 31 and the inner wall of the pre-embedded pipe 21 (preferably, it can be compacted by vibration with a vibrator, thereby improving the thermal conductivity between the heating module and the pre-embedded pipe 21). Obviously, in order to facilitate the filling of the second filler, the pre-embedded pipe 21 has a certain slope and its open side is higher. In order to avoid filler leakage, the open side of the pre-embedded pipe 21 is sealed (e.g., with a rubber plug, a threaded plug, etc.). It is only necessary to pay attention to the heat insulation performance of the plug to prevent the plug from forming a channel for heat transfer from the pre-embedded pipe 21 to the outside. The connection method between the plug and the pre-embedded pipe 21 is existing technology and will not be described in detail here.

[0046] Accordingly, the integrated heating module is easy to assemble and disassemble, facilitating replacement after subsequent damage (without needing to break the secondary lining concrete 1 structure of the opening section), and has low maintenance and repair costs. Specifically, if the heating module in a certain pre-embedded pipe 21 is damaged, the heating module in the pre-embedded pipe 21 can be extracted, and then the second filler inside the pre-embedded pipe 21 can be removed (e.g., scraped and sucked out), and then a new heating module can be installed, the second filler can be filled, and the opening end of the pre-embedded pipe 21 can be sealed. In addition, it uses an electric heating wire 32 for heating and uses a thermally conductive and insulating solid medium for heat conduction, eliminating the risk of liquid leakage.

[0047] Example 2:

[0048] like Figure 1 , Figure 5 As shown, this embodiment is based on embodiment 1, the difference being that in this embodiment:

[0049] Each of the pre-embedded pipes 21 is evenly distributed circumferentially along the secondary lining concrete 1 of the opening section;

[0050] For any two adjacent pre-embedded pipes 21, the two adjacent pre-embedded pipes 21 are connected by multiple heat-conducting rods 24.

[0051] Preferably, the distance from each point on the centerline of the heat-conducting rod 24 to the inner circumferential surface of the secondary lining concrete 1 of the opening section is equal;

[0052] Each of the heat-conducting rods 24 is evenly distributed along the axial direction of the secondary lining concrete 1 of the opening section.

[0053] It should be understood that the heat-conducting rod 24 is preferably made of aluminum, which has good thermal conductivity, is lightweight, corrosion-resistant, and has a thermal conductivity similar to that of the embedded pipe 21. It is also tightly connected to the embedded pipe 21 to ensure efficient heat conduction. The inner circumferential surface refers to the wall surface of the secondary lining concrete 1 at the tunnel entrance section facing the tunnel's driving side. The centerline of the heat-conducting rod 24 refers to... Figure 5 The central axis of the heat-conducting rod 24, indicated by the dashed line, means that the distance from each point on it to the inner circumference of the secondary lining concrete 1 in the opening section is equal. This means that the distance from any point on the dashed line to the inner circumference of the secondary lining concrete 1 in the opening section is equal (e.g., ...). Figure 5 (As indicated by the arrow in the image) are equal.

[0054] Therefore, the constant temperature and crack prevention structure for the secondary lining concrete of the tunnel entrance section provided in this embodiment forms a mesh-like heating source inside the secondary lining concrete 1 of the tunnel entrance section by reasonably arranging the pre-embedded pipes 21 and heat-conducting rods 24. The heat energy from the heating module is then rapidly and evenly transferred to the mesh-like heating source and then to the secondary lining concrete 1 of the tunnel entrance section, which greatly improves the response speed of the secondary lining concrete 1 of the tunnel entrance section when heated by the heating module. This facilitates timely and accurate temperature control of the secondary lining concrete 1 of the tunnel entrance section, thereby achieving the purpose of constant temperature.

[0055] More preferably, a predetermined proportion of steel fibers are added to the secondary lining concrete 1 of the opening section during the mixing process before pouring. As a result, the secondary lining concrete 1 of the opening section containing steel fibers has better thermal conductivity, which can increase the temperature uniformity of the secondary lining concrete 1 of the opening section when heated by the mesh heat source. Furthermore, the addition of steel fibers can enhance the crack resistance of the secondary lining concrete 1 of the opening section.

[0056] Example 3:

[0057] like Figure 1 and Figure 3 As shown, this embodiment is based on embodiment 1, the difference being that in this embodiment:

[0058] Multiple radial holes 41 are made on the inner circumferential surface, and a temperature sensor 42 is installed in each of the holes 41. The gap between the temperature sensor 42 and the hole 41 is filled with thermal grease 43.

[0059] The constant-temperature crack-resistant concrete secondary lining structure for tunnel entrance sections in high-altitude and cold regions also includes:

[0060] The control terminal is electrically connected to each of the temperature sensors 42 and each of the heating modules. The control terminal can adjust the heating temperature of each heating module in response to the temperature signal transmitted by each of the temperature sensors 42.

[0061] It should be understood that the temperature sensor 42 is a component in existing technologies such as thermocouples that can realize temperature monitoring and output electrical signals; the control terminal can be a commercially available PLC with a thermocouple input module. Both are existing technologies and will not be elaborated here.

[0062] Specifically, when the temperature signals transmitted by each temperature sensor 42 indicate that the current temperature of the secondary lining concrete 1 in the tunnel section is higher than the preset temperature, the control terminal controls each heating module to reduce the heating temperature (i.e., adjust the output power, for example, by adjusting the input voltage or input current of the heating module) until the temperature signals transmitted by each temperature sensor 42 indicate that the current temperature of the secondary lining concrete 1 in the tunnel section is equal to the preset temperature; similarly, when the temperature signals transmitted by each temperature sensor 42 indicate that the current temperature of the secondary lining concrete 1 in the tunnel section is lower than the preset temperature, the control terminal controls each heating module to increase the heating temperature until the temperature signals transmitted by each temperature sensor 42 indicate that the current temperature of the secondary lining concrete 1 in the tunnel section is equal to the preset temperature.

[0063] When the external temperature changes, if a constant heating temperature is used to heat the secondary lining concrete 1 at the tunnel entrance, the actual temperature of the secondary lining concrete 1 at the tunnel entrance will inevitably deviate from the preset temperature, and it may even fall below 0°C. Therefore, this embodiment sets up a control terminal and a temperature sensor 42. The control terminal adjusts the heating temperature of the heating module in a timely manner according to the temperature feedback from the temperature sensor 42, so that the temperature of the secondary lining concrete 1 at the tunnel entrance can still be maintained at the preset temperature when the external temperature changes, thus achieving constant temperature and crack prevention.

[0064] However, in this embodiment, drilling 41 requires the erection of a manual operation support platform on the inner circumference of the secondary lining concrete 1 at the opening section after the secondary lining structure construction is completed, and then the drilling operation is completed by manual operation of the impact drill, which is difficult to carry out and has a high risk factor.

[0065] Example 4:

[0066] like Figure 1 , Figure 4 and Figure 6 As shown, this embodiment is based on embodiment 3, the difference being that in this embodiment:

[0067] Multiple installation cylinders 44 are pre-embedded in the secondary lining concrete 1 of the opening section. The axis of the installation cylinder 44 is along the radial direction of the secondary lining concrete 1 of the opening section, and the opening side is flush with the inner circumferential surface.

[0068] Multiple heat-conducting fins 45 extend from the outer peripheral wall of the mounting cylinder 44, and threads are provided on the inner peripheral wall of the opening section of the mounting cylinder 44.

[0069] A temperature sensor 42 is installed in each of the mounting cylinders 44. The gap between the temperature sensor 42 and the mounting cylinder 44 is filled with thermally conductive silicone grease 43, and the opening side of the mounting cylinder 44 is sealed by an end cap 46 threaded connection.

[0070] Preferably, such as Figure 6 As shown, a hexagonal head is provided on the outside of the end cap 46 for easy disassembly and assembly; the hexagonal head has a hole for threading wires to pass through the signal transmission line of the temperature sensor 42; obviously, an insulation layer 23 should also be provided on the opening side of the mounting cylinder 44 to prevent the temperature of the secondary lining concrete 1 in the opening section from leaking out through the mounting cylinder 44. The mounting cylinder 44 is preferably made of aluminum alloy tube, which has good thermal conductivity, light weight, corrosion resistance, and is easy to process.

[0071] Accordingly, the constant-temperature crack-prevention structure for the secondary lining concrete of the tunnel entrance section provided in this embodiment not only facilitates the adjustment of the heating module's heating temperature to ensure a constant temperature for the secondary lining concrete 1 of the tunnel entrance section, but also allows for the installation of the temperature sensor 42 via a pre-embedded installation cylinder 44. The installation of the pre-embedded installation cylinder 44 can be assisted by the existing trolley used in the secondary lining construction, reducing construction difficulty. Furthermore, the heat-conducting fins 45 structure set on the outer peripheral wall of the installation cylinder 44 ensures a reliable connection between the installation cylinder 44 and the secondary lining concrete 1 of the tunnel entrance section, and increases the heat conduction area between the installation cylinder 44 and the secondary lining concrete 1 of the tunnel entrance section, thereby making the temperature of the installation cylinder 44 more representative of the temperature of the secondary lining concrete 1 of the tunnel entrance section.

[0072] Preferably, such as Figure 1 As shown, for any temperature sensor 42, the temperature sensor 42 is located within the grid formed by the embedded pipe 21 and the heat-conducting rod 24, and is located at the intersection of the diagonals of the grid. More preferably, as Figure 1 As shown, the temperature sensors 42 are arranged in a quincunx pattern.

[0073] Therefore, the temperature signals monitored and fed back by each temperature sensor are more representative of the actual temperature of the secondary lining concrete at the tunnel entrance.

[0074] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this utility model. It should be understood that the above description is only a specific embodiment of this utility model and is not intended to limit the scope of protection of this utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the scope of protection of this utility model.

Claims

1. A constant-temperature crack-resistant concrete secondary lining structure for tunnel entrance sections in high-altitude and cold regions, characterized in that, include: Embedded pipes (21) are embedded in the secondary lining concrete (1) of the opening section, with multiple axial embedded pipes (21). The heating module is inserted into each of the pre-embedded pipes (21); Waterproof structural layer (22) is embedded in the outer periphery of the secondary lining concrete (1) of the opening section.

2. The constant-temperature crack-resistant concrete secondary lining structure for tunnel entrances in high-altitude and cold regions according to claim 1, characterized in that, Also includes: Thermal insulation layer (23) is laid on the outer surface of the secondary lining concrete (1) of the opening section. For the outer circumferential surface of the secondary lining concrete (1) of the opening section, the thermal insulation layer (23) is located between the waterproof structural layer (22) and the outer circumferential surface.

3. The constant-temperature crack-resistant concrete secondary lining structure for tunnel entrances in high-altitude and cold regions according to claim 1, characterized in that, The heating module includes a housing (31), an electric heating wire (32), and a first filler. The electric heating wire (32) is inserted inside the housing (31) and there is a first gap (33) between the electric heating wire (32) and the housing (31). The first filler is filled in the first gap (33). The first filler is thermally conductive and insulating. The heating module is provided with a support frame (34) at intervals on the outside. There is a second gap (35) between the heating module inserted into the pre-embedded pipe (21) and the pre-embedded pipe (21). The second gap (35) is filled with a heat-conducting second filler.

4. The constant-temperature crack-resistant concrete secondary lining structure for tunnel entrances in high-altitude and cold regions according to claim 3, characterized in that, The electric heating wire (32) is a nickel-chromium wire; Both the first filler and the second filler are selected from one or more of magnesium oxide powder, aluminum oxide powder, and boron nitride powder.

5. The constant-temperature crack-resistant concrete secondary lining structure for tunnel entrances in high-altitude and cold regions according to claim 1, characterized in that, Each of the pre-embedded pipes (21) is evenly distributed circumferentially along the secondary lining concrete (1) of the opening section; For any two adjacent pre-embedded pipes (21), the two adjacent pre-embedded pipes (21) are connected by multiple heat-conducting rods (24).

6. The constant-temperature crack-resistant concrete secondary lining structure for tunnel entrances in high-altitude and cold regions according to claim 5, characterized in that, The distance from each point on the centerline of the heat-conducting rod (24) to the inner circumference of the secondary lining concrete (1) of the opening section is equal; Each of the heat-conducting rods (24) is evenly distributed along the axial direction of the secondary lining concrete (1) of the opening section.

7. The constant-temperature crack-resistant concrete secondary lining structure for tunnel entrances in high-altitude and cold regions according to claim 6, characterized in that, Multiple radial holes (41) are made on the inner circumferential surface, and a temperature sensor (42) is installed in each of the holes (41). The gap between the temperature sensor (42) and the hole (41) is filled with thermal grease (43).

8. The constant-temperature crack-resistant concrete secondary lining structure for tunnel entrances in high-altitude and cold regions according to claim 6, characterized in that, Multiple installation cylinders (44) are pre-embedded in the secondary lining concrete (1) of the opening section. The axis of the installation cylinder (44) is along the radial direction of the secondary lining concrete (1) of the opening section and the opening side is flush with the inner circumferential surface. Multiple heat-conducting fins (45) extend from the outer peripheral wall of the mounting cylinder (44), and threads are provided on the inner peripheral wall of the opening section of the mounting cylinder (44). A temperature sensor (42) is installed in each of the mounting cylinders (44). The gap between the temperature sensor (42) and the mounting cylinder (44) is filled with thermal grease (43), and the opening side of the mounting cylinder (44) is sealed by an end cap (46) threaded connection.

9. The constant-temperature crack-resistant concrete secondary lining structure for tunnel entrances in high-altitude and cold regions according to claim 7 or 8, characterized in that, For any temperature sensor (42), the temperature sensor (42) is located within the grid formed by the embedded pipe (21) and the heat-conducting rod (24), and is located at the intersection of the diagonals of the grid.

10. The constant-temperature crack-resistant concrete secondary lining structure for tunnel entrances in high-altitude and cold regions according to claim 7 or 8, characterized in that, Also includes: The control terminal is electrically connected to each of the temperature sensors (42) and each of the heating modules. The control terminal can adjust the heating temperature of each heating module in response to the temperature signal transmitted by each of the temperature sensors (42).

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