Terrestrial heat three-dimensional heat preservation and ice melting system suitable for high and cold deep-buried highway tunnel cable fire-fighting ditch and drainage ditch

Abstract

The invention belongs to the technical field of tunnel terrestrial heat utilization in alpine regions, and particularly discloses a terrestrial heat three-dimensional heat preservation and ice melting system suitable for a cable fire ditch and a drainage ditch of an alpine deeply-buried highway tunnel. The terrestrial heat three-dimensional heat preservation and ice melting system comprises a terrestrial heat taking subsystem, a terrestrial heat pipe heat preservation result, a heat exchange unit and a heat supply subsystem. The terrestrial heat taking subsystem is connected with the heat exchange unit through a transmission pipeline, the heat supply subsystem is connected with the heat exchange unit through the terrestrial heat pipe heat preservation subsystem, and the terrestrial heat taking subsystem is located in a terrestrial heat source area which is about two kilometers away from a tunnel entrance. The system transmits heat to the cable trench and the drainage ditch through circulating high-temperature fluid, so that the temperature of the regions is always kept above a freezing point, and water in the cable, the fire-fighting pipeline and the drainage ditch is prevented from being frozen. The system has the advantages of being efficient, energy-saving, clean, environment-friendly, convenient to construct and the like, and meets the anti-freezing requirements of tunnel cables, fire-fighting pipelines and drainage ditches in the high and cold environment.

Description

Technical Field

[0001] The invention belongs to the technical field of geothermal energy utilization in tunnels in alpine regions, and particularly relates to a three-dimensional geothermal insulation and ice melting system suitable for cable fire trenches and drainage ditches in alpine deep-buried highway tunnels. Background Art

[0002] In recent years, the construction of highways and railways has gradually extended to the high-altitude western regions. In these areas, deep-buried tunnels have become an important part of transportation infrastructure. However, during construction, deep-buried tunnels not only face complex geological conditions but also need to address the technical challenges of thermal insulation and anti-freezing in cold climates.

[0003] Taking the Tianshan Shengli Tunnel, a key control project of the Wuyi Expressway, as an example, this tunnel is 22.1 kilometers long and is currently under construction. It is one of the longest highway tunnels in the world. Its maximum burial depth reaches 1,112.6 meters. As the burial depth increases, the temperature of the tunnel surrounding rock significantly rises, storing abundant geothermal resources. This characteristic provides ideal conditions for the development and utilization of energy in deep-buried tunnels.

[0004] In alpine regions, as important facilities, cable trenches and drainage ditches in tunnels not only need to prevent cable operation failures caused by too low temperatures or freezing and blockage of the drainage system but also ensure the long-term stability of the tunnel structure. Therefore, effectively utilizing the geothermal resources in the tunnel surrounding rock, providing thermal insulation and heating for the cable trench through geothermal heat exchange technology, and combining anti-freezing measures for the drainage ditch can not only reduce energy consumption but also significantly improve the reliability and economy of system operation. This design provides an important guarantee for the long-term operation of deep-buried tunnels in alpine regions.

[0005] In the prior art, although there has been some research on the development and utilization of geothermal resources, there are still some deficiencies in the thermal insulation and heating systems applied to cable trenches in alpine deep-buried highway tunnels. For example, traditional heating systems generally have the problem of large heat losses. Especially in alpine environments, the heat fluid is prone to reduced thermal efficiency due to insufficient thermal insulation during long-distance transportation. In addition, for ultra-long deep-buried tunnels, the existing systems need to be further optimized in terms of heat exchange efficiency, fluid circulation stability, and construction adaptability.

[0006] Based on the above problems, the invention proposes a three-dimensional geothermal insulation and ice melting system suitable for cable fire trenches and drainage ditches in alpine deep-buried highway tunnels. This system is targeted at the special environment of alpine deep-buried tunnels and combines geothermal heat extraction technology, thermal insulation transportation technology, and the efficient heat exchange function of heat exchange units, which can effectively reduce heat losses and achieve long-term stable thermal insulation of cable trenches. This not only fills the gap in heating technology for alpine deep-buried tunnels but also provides a new solution for the efficient utilization of geothermal resources. Summary of the Invention

[0007] To address the deficiencies in the existing technology, the invention aims to provide a geothermal three-dimensional heat preservation and ice melting system applicable to cable fire trenches and drainage ditches in alpine deep-buried highway tunnels. This system is designed for the alpine deep-buried tunnel environment. By making full use of the geothermal resources stored in the tunnel surrounding rock, it designs an efficient, economical, and easily constructible geothermal utilization system. The system can not only achieve the heat preservation function of the cable fire trench but also provide the ice melting and anti-freezing function for the tunnel drainage ditch to ensure the smooth operation of the drainage system. To further improve the ice melting effect, the system is equipped with three-dimensional ice melting facilities. Through three-dimensional heat release, it enhances the heat coverage in the spatial distribution of the system, ensuring that the water temperature in the cable trench, fire pipeline, and drainage ditch is always above the freezing point, effectively preventing ice formation and freezing. The overall system has good energy-saving and environmental protection characteristics, significantly improving the operational safety and reliability of the tunnel.

[0008] The geothermal heat preservation and ice melting system of the invention includes a geothermal heat extraction subsystem, a geothermal pipe heat preservation subsystem, a heat exchange unit, and a heat supply subsystem. The overall system has the advantages of optimized structure, high thermal efficiency, and small heat loss. The geothermal heat extraction subsystem efficiently extracts the geothermal resources in the tunnel surrounding rock. Through the heat preservation and transportation technology and the efficient heat exchange of the heat exchange unit, the heat is reasonably distributed to the cable fire trench and the drainage ditch. The heat supply subsystem provides stable heat preservation heating for the cable fire trench and transports sufficient heat to the drainage ditch through circulating heat supply to prevent the accumulated water from freezing or refreezing after ice melting, ensuring the reliable operation of the drainage system in the alpine environment.

[0009] This design not only fills the gap in the existing technology but also provides a new solution for the comprehensive development and utilization of geothermal resources in deep-buried tunnels, and at the same time has good economic efficiency and potential for sustainable development.

[0010] The invention is realized through the following technical solutions:

[0011] A geothermal three-dimensional heat preservation and ice melting system applicable to cable fire trenches and drainage ditches in alpine deep-buried highway tunnels, which is composed of a geothermal heat extraction subsystem, a geothermal pipe heat preservation structure, a heat exchange unit, and a heat supply subsystem. The alpine deep-buried highway tunnel is a long tunnel in a high-altitude cold area; the geothermal heat extraction subsystem is connected to the heat exchange unit through a transmission pipeline, and the heat exchange unit is connected to the heat supply subsystem through a transmission pipeline, and the three-dimensional anti-freezing and heat preservation of the cable fire trench and the drainage ditch are realized through circulating heat supply.

[0012] The geothermal heat extraction subsystem is arranged in the geothermal source area about two kilometers away from the tunnel entrance. Drill holes obliquely downward facing the side wall surfaces on both sides of the tunnel. The height of the hole opening is higher than the tunnel road surface. A reasonable spacing is maintained between each drill hole to ensure the stability of the overall tunnel support structure. After the drilling is completed, a U-shaped heat exchange PE pipe is buried in the hole. One branch pipe of the U-shaped heat exchange PE pipe is the outlet water branch pipe of the heat extraction subsystem, and the other branch pipe is the inlet water branch pipe of the heat extraction subsystem. After the U-shaped heat exchange PE pipe is buried, a filler is filled into the hole to enhance the heat conduction performance, and at the same time improve the sealing and stability of the hole. Multiple U-shaped heat exchange PE pipes buried in the holes on both sides of the tunnel side wall are connected in parallel to form a heat extraction unit, and the heat extraction unit is directly connected to the heat exchange unit.

[0013] The outlet water branch pipes of the heat extraction subsystem in each hole are connected in parallel to the outlet water main pipe of the heat extraction subsystem. The outlet water main pipe of the heat extraction subsystem is connected to the water inlet of the heat exchange unit. The inlet water branch pipes of the heat extraction subsystem are connected in parallel to the inlet water main pipe of the heat extraction subsystem. The inlet water main pipe of the heat extraction subsystem is connected to the water outlet of the heat exchange unit. At one end of the outlet water main pipe of the heat extraction subsystem connected to the water inlet of the heat exchange unit, a flow meter, a controllable flow circulating water pump, and an outlet water temperature sensor are installed in sequence to monitor and adjust the flow and temperature of the hot fluid in the system. At one end of the inlet water main pipe of the heat extraction subsystem connected to the water outlet of the heat exchange unit, an inlet water temperature sensor is set to monitor the temperature of the inlet fluid in real time. Through the heat exchange function of the heat exchange unit, the high-temperature fluid cools down after flowing through the heat exchange unit, and then returns to the outlet water branch pipe of the heat extraction subsystem in the hole through the inlet water main pipe of the heat extraction subsystem, extracting geothermal resources to achieve cyclic heat extraction.

[0014] The cable trench U-shaped heat insulation board is laid on the bottom surface of the cable fire trench. The two sides of the cable trench U-shaped heat insulation board are slightly higher than the center. The cable trench heat collection and heat conduction board is arranged in the sunken part in the center of the cable trench U-shaped heat insulation board. The cable trench heat collection and heat conduction board is horizontally laid along the axial direction of the cable fire trench, and the vertical heat collection and heat conduction board is vertically laid on it; the inlet water branch pipe of the heat supply subsystem is arranged inside the cable trench heat collection and heat conduction board and the vertical heat collection and heat conduction board to ensure that the heat is evenly transferred to the entire space of the cable fire trench. The heat insulation cover board is laid at the top of the cable fire trench, and the heat insulation and heat preservation board is laid below it. The drain trench U-shaped heat insulation board is laid on the bottom surface of the drain trench, and an arched support steel frame is arranged in the middle. The drain trench heat collection and heat conduction board is arranged in the sunken part in the center of the drain trench U-shaped heat insulation board. The inlet water branch pipes of the heat supply subsystem are respectively arranged inside the drain trench heat collection and heat conduction board and above the arched support steel frame. The upper part of the drain trench adopts a special structure of the drain trench heat insulation cover board, and vertical slots are opened on both sides of the drain trench heat insulation cover board for the accumulated water in the tunnel to flow into the drain trench through the vertical slots.

[0015] The total length of the heating pipeline is about 1.5 kilometers, and the geothermal pipe insulation structure is used to insulate the transmission pipeline. The fluid pipelines between the heat exchanger unit and the cable fire trench, and the fluid pipelines between the heat exchanger unit and the drainage ditch are wrapped with high-density polyurethane pipes and evacuated to form a vacuum insulation layer to ensure the stable delivery of high-temperature fluids to each heating area.

[0016] The main water inlet pipe of the heating subsystem transports the high-temperature fluid to the water inlet branch pipes of each heating subsystem, and then transfers the heat to the cable trench heat collector and vertical heat collector. After heating, the low-temperature fluid flows into the main water outlet pipe of the heating subsystem through the outlet pipe branch pipe of the heating subsystem, and returns to the heat exchanger unit for heat exchange and temperature rise, and then the next round of heating. An arched support steel frame is set in the middle of the drainage ditch to also form three-dimensional heating.

[0017] Preferably, the heating subsystem's inlet and outlet water pipes use special stainless steel heat exchange corrugated pipes with a diameter of 25mm for heating, and the geothermal heat conductive plate uses a high thermal conductivity polymer composite material (with graphite, metal powder, etc. added); the heat extraction subsystem uses a 25mm PPR water pipe; the high-density polyurethane pipe in the geothermal pipe insulation structure is a 30mm high-density polyurethane pipe, and the U-shaped insulation board uses extruded polystyrene (XPS) material.

[0018] Preferably, the thermal mass in the geothermal three-dimensional thermal insulation and ice melting system is a propylene glycol aqueous solution with a volume ratio of 1:1.

[0019] Because there may be large temperature differences in high-altitude and cold regions, especially under extreme weather conditions, the temperature of the fluid in the heat exchanger unit does not meet actual demand and cannot satisfy heating. At this time, the electric heating module in the heat exchanger unit can be started to heat the fluid so that the fluid temperature meets actual demand.

[0020] The geothermal heat preservation heating and ice melting and antifreeze system and construction method of the present invention can not only efficiently extract and utilize geothermal resources in the tunnel surrounding rock, but also significantly reduce the energy loss in the heating process, and is suitable for deep buried highway tunnels in various high-cold areas. The system is specifically designed for the heat preservation and heating needs of cable fire trenches and the antifreeze and ice melting problems of drainage ditches. By reasonably distributing heat, it provides stable heat preservation and heating for cable fire trenches, while ensuring that the drainage ditches do not freeze or get blocked in low temperature environments, thereby ensuring the overall operational safety and reliability of the tunnel. This design not only fills the gap in the prior art, but also provides a new solution for the comprehensive application of clean energy in transportation infrastructure, with significant economic and environmental benefits.

[0021] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0022] 1. Efficient extraction and utilization of geothermal resources

[0023] Through the design of the geothermal heat extraction subsystem, holes are drilled on both side walls of the tunnel and special U-shaped heat exchange PE pipes are buried to efficiently extract geothermal resources from the surrounding rock of the tunnel. The holes are filled with filling materials with high thermal conductivity, and a parallel connection method is adopted to form an efficient and stable heat extraction subsystem, realizing the efficient development and transmission of geothermal resources and significantly improving the thermal energy utilization rate.

[0024] 2. Multifunctional heating design to improve the operation reliability of the tunnel

[0025] The geothermal heat preservation, heating and ice melting and anti-freezing system of the present invention, through reasonable heat distribution, not only provides a stable heat preservation and heating function for the cable fire trench, but also conveys sufficient heat to the drainage ditch to realize ice melting and anti-freezing, preventing problems such as water accumulation freezing or drainage system blockage. In particular, the system is designed with a three-dimensional ice melting function. By arranging three-dimensional heating facilities in the drainage ditch and cable trench, heat can be evenly distributed from multiple directions, effectively preventing the temperature in local areas from dropping below the freezing point and ensuring the normal operation of all parts of the system in extremely cold environments. In alpine environments, the system not only ensures the temperature stability of the cable trench and drainage ditch, but also improves the overall operation safety and reliability of the tunnel.

[0026] 3. Energy saving, environmental protection and strong adaptability

[0027] By adopting designs such as double-layer vacuum heat insulation pipes, insulation boards and insulation cotton cladding, the present invention significantly reduces the heat loss during the transportation of high-temperature fluids and improves the energy-saving effect of the system. At the same time, an electric heating module is equipped to assist in increasing the fluid temperature under extreme weather conditions to meet the heating demand. This system is not only applicable to deep-buried highway tunnels in alpine regions, but also has good economic performance and sustainable development potential, providing important support for the application of clean energy in transportation infrastructure. Brief description of the drawings

[0028] Figure 1 is a simplified diagram of the operation process of the geothermal three-dimensional heat preservation and ice melting system of the present invention.

[0029] Figure 2 is a top view of the geothermal three-dimensional heat preservation and ice melting system of the present invention, where: 1-branch outlet pipe of the heat extraction subsystem, 2-branch inlet pipe of the heat extraction subsystem, 3-drilling wall, 4-main outlet pipe of the heat extraction subsystem, 5-heat exchange unit; 6-flow meter; 7-circulating water pump with controllable flow, 8-outlet pipe temperature sensor, 9-inlet pipe temperature sensor, 10-main inlet pipe of the heat extraction subsystem; 11-branch inlet pipe of the heat supply subsystem, 12-branch outlet pipe of the heat supply subsystem, 13-main outlet pipe of the heat supply subsystem, 14-main inlet pipe of the heat supply subsystem, 15-high-density polyurethane pipe, 20-tunnel entrance, 21-driving direction, 22-surrounding rock mass, 23-filling material, 24-corrugated pipe.

[0030] Figure 3 It is a cross-sectional view of a cable fire trench and a drainage ditch, where: 16 - heat insulation cover plate, 17 - heat insulation and thermal insulation board, 18 - heat collection and heat conduction plate for cable trench, 19 - fire water pipe, 25 - cable support, 26 - cable, 27 - drainage ditch, 28 - heat collection and heat conduction plate for drainage ditch, 29 - U-shaped heat insulation board for drainage ditch, 30 - U-shaped heat insulation board for cable trench, 31 - heat insulation cover plate for drainage ditch, 32 - arched support steel frame, 33 - vertical heat collection and heat conduction plate.

[0031] Figure 4 It is a side view three-dimensional schematic diagram of the drainage ditch.

[0032] Figure 5 、 Figure 6 It is a three-dimensional schematic diagram of a cable fire trench and a drainage ditch. Specific implementation manners

[0033] To make the technical solutions and advantages of the present invention clearer and more definite, the applicant will hereinafter describe in detail the construction method of the present invention with reference to the accompanying drawings. The following specific implementation manners are intended to illustrate the technical solutions of the present invention and do not constitute a limitation on the protection scope of the present invention.

[0034] Embodiment

[0035] A geothermal three-dimensional heat preservation and ice melting system applicable to cable fire trenches and drainage ditches in alpine deep-buried highway tunnels, as shown in the attached Figures 1-6 of the specification. The system is composed of a geothermal heat extraction subsystem, a geothermal pipe heat preservation structure, a heat exchange unit and a heat supply subsystem. The alpine deep-buried highway tunnel is a long tunnel in a high-altitude cold area; the geothermal heat extraction subsystem is connected to the heat exchange unit through a transmission pipeline, and the heat exchange unit is connected to the heat supply subsystem, and the three-dimensional anti-freezing and heat preservation function of the cable fire trench and the drainage ditch is realized through circulating heat supply. The heat medium in the geothermal three-dimensional heat preservation and ice melting system is an aqueous propylene glycol solution obtained by mixing propylene glycol and water in a volume ratio of 1:1.

[0036] The geothermal heat extraction subsystem is arranged in a geothermal source area at a horizontal distance of about two kilometers from the tunnel entrance, and a construction method of drilling obliquely downward facing the side wall surfaces on both sides of the tunnel is adopted, as shown in the attached Figure 2 and 3As shown in the figure. The drilling layout needs to be determined according to the actual engineering conditions of the tunnel surrounding rock. The height of the hole opening is higher than the tunnel road surface, and the spacing between each drilling hole needs to be reasonably designed to ensure the stability of the overall tunnel support structure. After the drilling is completed, a U-shaped heat exchange PE pipe is buried in the hole. One branch pipe of the U-shaped heat exchange PE pipe is the outlet water pipe branch 1 of the heat extraction subsystem, and the other branch pipe is the inlet water pipe branch 2 of the heat extraction subsystem. After the U-shaped heat exchange PE pipe is buried, filler 23 is filled into the hole to enhance the heat conduction performance, and at the same time improve the sealing and stability of the hole. Multiple U-shaped heat exchange PE pipes buried in the holes on both side walls of the tunnel are connected in parallel to form a heat extraction unit, and the heat extraction unit is directly connected to the heat exchange unit 5.

[0037] Specifically, the outlet water pipe branch 1 of the heat extraction subsystem is connected in parallel to the outlet water pipe main pipe 4 of the heat extraction subsystem. The outlet water pipe main pipe 4 of the heat extraction subsystem is connected to the water inlet of the heat exchange unit 5. The inlet water pipe branch 2 of the heat extraction subsystem is connected in parallel to the inlet water pipe main pipe 10 of the heat extraction subsystem. The inlet water pipe main pipe 10 of the heat extraction subsystem is connected to the water outlet of the heat exchange unit 5. At one end of the outlet water pipe main pipe 4 of the heat extraction subsystem connected to the water inlet of the heat exchange unit 5, a flow meter 6, a circulating water pump 7 with controllable flow rate, and an outlet water pipe temperature sensor 8 are installed in sequence, which are used to monitor and adjust the heat fluid flow rate and temperature of the system. At one end of the inlet water pipe main pipe 10 of the heat extraction subsystem connected to the water outlet of the heat exchange unit 5, an inlet water pipe temperature sensor 9 is set, which is used to monitor the temperature of the inlet fluid in real time. Through the heat exchange function of the heat exchange unit 5, the high-temperature fluid cools down after flowing through the heat exchange unit 5, and then returns to the outlet water pipe branch 1 of the heat extraction subsystem in the hole through the inlet water pipe main pipe 10 of the heat extraction subsystem, extracting geothermal resources to achieve cyclic heat extraction.

[0038] As Figure 3, a cable trench U-shaped heat insulation plate 30 is laid on the bottom surface of the cable fire trench. The two sides of the cable trench U-shaped heat insulation plate 30 are slightly higher than the center. A cable trench heat collection and heat conduction plate 18 is arranged at the sunken part in the center of the cable trench U-shaped heat insulation plate 30. The cable trench heat collection and heat conduction plate 18 is horizontally laid along the axial direction of the cable fire trench, and a vertical heat collection and heat conduction plate 33 is vertically laid thereon; the branch pipe 11 of the water inlet of the heat supply subsystem is arranged in the cable trench heat collection and heat conduction plate 18 and the vertical heat collection and heat conduction plate 33 to ensure that heat is evenly transferred to the entire space of the cable fire trench. At the same time, a heat insulation cover plate 16 is laid at the top of the cable fire trench, and a heat insulation and heat preservation plate 17 is laid below it to further reduce the air convection between the cable fire trench and the tunnel, effectively prevent heat from leaking out, and improve the overall heat preservation performance of the cable fire trench. A drainage trench U-shaped heat insulation plate 29 is laid on the bottom surface of the drainage trench 27, an arched support steel frame 32 is arranged in the middle thereof, a drainage trench heat collection and heat conduction plate 28 is arranged at the sunken part in the center of the drainage trench U-shaped heat insulation plate 29, the branch pipe 11 of the water inlet of the heat supply subsystem is respectively arranged inside the drainage trench heat collection and heat conduction plate 28 and above the arched support steel frame 32, and a drainage trench heat insulation cover plate 31 with a special structure is adopted for the upper part of the drainage trench 27. By vertically grooving on both sides of the drainage trench heat insulation cover plate 31, it is ensured that the accumulated water in the tunnel flows into the drainage trench through the vertical grooves while reducing the air convection heat dissipation between the drainage trench and the tunnel, which not only effectively insulates heat but also does not affect the drainage function.

[0039] The alpine deep-buried highway tunnel in this embodiment is 24 kilometers long in total. The total length of the heat supply pipeline extending from the heat exchange unit to the tunnel entrance is about 1.5 kilometers. The heat supply pipeline transports heat mass over a long distance. Through a variety of carefully designed heat preservation measures for the geothermal pipe heat preservation structure, it ensures the stable operation of the cable fire trench and the drainage trench in the tunnel under alpine environment. The fluid pipelines between the heat exchange unit 5 and the cable fire trench, and between the heat exchange unit 5 and the drainage trench 27 are all wrapped with high-density polyurethane pipes and evacuated to form a vacuum heat insulation layer, minimizing heat loss to the greatest extent and ensuring the stable transportation of high-temperature fluid to each heat supply area. The overall design significantly improves the heat preservation effect of the tunnel and the energy utilization efficiency of the system by reducing heat dissipation.

[0040] The branch pipes 11 of the inlet pipes of each heating subsystem are connected in parallel to the main inlet pipe 14 of the heating subsystem, and the branch pipes 12 of the outlet pipes of the heating subsystem are connected in parallel to the main outlet pipe 13 of the heating subsystem. The main inlet pipe 14 of the heating subsystem transports high-temperature heat medium to the branch pipes 11 of the inlet pipes of each heating subsystem, and then transfers heat to the heat collection and heat conduction plates 18 in the cable trench and the vertical heat collection and heat conduction plates 33, effectively realizing centralized heating inside the cable fire trench. After heating, the low-temperature fluid converges into the main outlet pipe 13 of the heating subsystem through the branch pipes 12 of the outlet pipes of the heating subsystem, and then returns to the heat exchange unit 5 for heat exchange and temperature rise, and then conducts the next round of heating. In order to enhance the heating effect of the cable fire trench, a vertical heat collection and heat conduction plate 33 is arranged in the middle of the cable trench, and the branch pipes 11 of the inlet pipes of the heating subsystem are arranged inside it. During construction, the vertical heat collection and heat conduction plate 33 is closely attached to the fire-fighting water pipe 19 to form a three-dimensional heating form, and can be folded through hinges during maintenance. An arched support steel frame 32 is arranged in the middle of the drainage ditch 27, also forming a three-dimensional heating. In terms of pipeline design, 25mm stainless steel heat exchange corrugated pipes are used for the inlet and outlet pipes, and 25mm PPR water pipes are used for the heat extraction subsystem. The outer heat insulation pipe of the geothermal pipe heat insulation subsystem uses a 30mm high-density polyurethane pipe 15 to ensure the effective transmission and insulation of heat energy. This heating subsystem not only provides continuous heat preservation and heating for the cable fire trench, but also effectively provides anti-freezing and ice melting protection for the drainage ditch, ensuring the stable operation of the system in a cold environment.

[0041] In addition, to ensure the stability of the system operation under extreme climate conditions in alpine regions, in the present invention, the main inlet pipes and main outlet pipes of the geothermal heat extraction subsystem and the heating subsystem are all wrapped with heat preservation cotton to further reduce heat loss. If the temperature of the fluid in the heat exchange unit does not reach the actual heating requirement due to extreme low temperature, the electric heating module in the heat exchange unit can be started to assist in heating the fluid to meet the heating requirement.

[0042] The above construction method clearly describes the technical features of the present invention and its implementation process, effectively realizing the heat preservation, heating and ice melting functions of the cable fire trench and the drainage ditch. The present invention has the characteristics of high efficiency and energy saving at the technical level, and the construction process is simple. It can adapt to the complex geological and climatic conditions of alpine deep-buried tunnels, significantly improving the reliability and economy of the tunnel heating system. The protection scope of the present invention should not be regarded as limited to the above specific implementation manners. Any improvement, replacement or equivalent scheme made within the spirit and principle of the present invention shall be regarded as falling within the protection scope of the present invention.

Claims

1. A geothermal three-dimensional heat preservation and ice melting system applicable to cable fire trenches and drainage ditches of highways in alpine deep-buried tunnels, characterized in that: The geothermal three-dimensional heat preservation and ice melting system is composed of a geothermal heat extraction subsystem, a geothermal pipe heat preservation structure, a heat exchange unit and a heat supply subsystem; the high-cold deep-buried highway tunnel is a long tunnel in a high-altitude cold area; the geothermal heat extraction subsystem is connected to the heat exchange unit through a transmission pipeline, and the heat exchange unit is connected to the heat supply subsystem through a transmission pipeline, and three-dimensional anti-freezing heat preservation of the cable fire trench and the drainage ditch is realized through circulating heat supply. The geothermal heat extraction subsystem is arranged in the geothermal source area two kilometers away from the entrance of the high-cold deep-buried highway tunnel. Drill holes obliquely downward facing the side wall surfaces on both sides of the tunnel. The height of the hole opening is higher than the road surface of the high-cold deep-buried highway tunnel, and a certain distance is maintained between each hole; bury a U-shaped heat exchange PE pipe in the hole. One branch pipe of the U-shaped heat exchange PE pipe is the outlet water branch pipe of the heat extraction subsystem, and the other branch pipe is the inlet water branch pipe of the heat extraction subsystem. After the U-shaped heat exchange PE pipe is buried, fill the hole with a filler; several U-shaped heat exchange PE pipes buried in the holes on the side walls on both sides of the tunnel are connected in parallel to form a heat extraction unit, and the heat extraction unit is directly connected to the heat exchange unit. The outlet water branch pipes of the heat extraction subsystem in each hole are connected in parallel to the outlet water main pipe of the heat extraction subsystem. The outlet water main pipe of the heat extraction subsystem is connected to the water inlet of the heat exchange unit. The inlet water branch pipes of the heat extraction subsystem are connected in parallel to the inlet water main pipe of the heat extraction subsystem. The inlet water main pipe of the heat extraction subsystem is connected to the water outlet of the heat exchange unit; at one end where the outlet water main pipe of the heat extraction subsystem is connected to the water inlet of the heat exchange unit, a flow meter, a circulating water pump with controllable flow and an outlet water temperature sensor are installed in sequence to monitor and adjust the heat fluid flow and temperature of the system; at one end of the inlet water main pipe of the heat extraction subsystem connected to the water outlet of the heat exchange unit, an inlet water temperature sensor is set to monitor the temperature of the inlet fluid in real time; through the heat exchange function of the heat exchange unit, the high-temperature fluid cools down after flowing through the heat exchange unit, and then returns to the outlet water branch pipe of the heat extraction subsystem in the hole through the inlet water main pipe of the heat extraction subsystem to extract geothermal resources and realize circulating heat extraction. Lay a cable trench U-shaped heat insulation board on the bottom surface of the cable fire trench. The two sides of the cable trench U-shaped heat insulation board are higher than the center. A cable trench heat collection and heat conduction board is arranged in the sunken part in the center of the cable trench U-shaped heat insulation board. The cable trench heat collection and heat conduction board is horizontally laid along the axial direction of the cable fire trench, and a vertical heat collection and heat conduction board is vertically laid on it; the inlet water branch pipe of the heat supply subsystem is arranged inside the cable trench heat collection and heat conduction board and the vertical heat collection and heat conduction board, so that heat is evenly transferred to the entire space of the cable fire trench; an insulation cover plate is laid at the top of the cable fire trench, and an insulation and heat preservation board is laid below it; a drainage ditch U-shaped heat insulation board is laid on the bottom surface of the drainage ditch, and an arched support steel frame is arranged in the middle. A drainage ditch heat collection and heat conduction board is arranged in the sunken part in the center of the drainage ditch U-shaped heat insulation board. The inlet water branch pipes of the heat supply subsystem are respectively arranged inside the drainage ditch heat collection and heat conduction board and above the arched support steel frame. A drainage ditch insulation cover plate is installed on the upper part of the drainage ditch. Vertical grooves are opened on both sides of the drainage ditch insulation cover plate, and the accumulated water in the tunnel flows into the drainage ditch through the vertical grooves. The geothermal pipe insulation structure is used for heat preservation of transmission pipelines; the transmission pipelines between the heat exchange unit and the cable fire trench, and the transmission pipelines between the heat exchange unit and the drainage trench are wrapped with high-density polyurethane pipes and evacuated to form a vacuum insulation layer; The main water inlet pipe of the heating subsystem transports the high-temperature fluid to the water inlet branch pipes of each heating subsystem, and then transfers the heat to the cable trench heat collecting and heat conducting plates and the vertical heat collecting and heat conducting plates; after heating, the low-temperature fluid is merged into the main water outlet pipe of the heating subsystem through the water outlet branch pipes of the heating subsystem, and then returns to the heat exchanger unit for heat exchange and heating, and then the next round of heating is carried out.

2. The geothermal three-dimensional heat preservation and ice melting system according to claim 1, characterized in that: The heating subsystem water inlet pipe branch, the heating subsystem water outlet pipe branch, the heating subsystem main water outlet pipe, and the heating subsystem main water inlet pipe all use stainless steel heat exchange corrugated pipes with a diameter of 25 mm.

3. The geothermal three-dimensional heat preservation and ice melting system according to claim 1, wherein: The cable trench heat collecting and heat conducting plate, the drainage trench heat collecting and heat conducting plate, and the vertical heat collecting and heat conducting plate are all made of high thermal conductivity polymer composite materials.

4. The geothermal three-dimensional heat preservation and ice melting system according to claim 1, wherein: The pipelines included in the geothermal heat extraction subsystem all use PPR water pipes with a diameter of 25 mm.

5. The geothermal three-dimensional heat preservation and ice melting system according to claim 1, wherein: In the geothermal pipe insulation structure, the high-density polyurethane pipe is a high-density polyurethane pipe with a diameter of 30 mm.

6. The geothermal three-dimensional heat preservation and ice melting system according to claim 1, wherein: The thermal mass in the geothermal three-dimensional thermal insulation and ice melting system is a propylene glycol aqueous solution with a volume ratio of 1:1.

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