A thermal insulation and frost protection structure for gravel blind drains in cold regions and its construction method

Abstract

This invention discloses a thermal insulation and antifreeze structure for a gravel blind drain in a cold-region tunnel, comprising an active heating module and a thermal insulation and waterproofing module. The active heating module includes electric heating tubes installed within the gravel blind drain, which are connected in a loop to an electric heating control system. The electric heating control system is electrically connected to a temperature sensor and a temperature controller. The thermal insulation and waterproofing module includes a first thermal insulation and waterproofing structure installed on the side of the initial support adjacent to the gravel blind drain and a second thermal insulation and waterproofing structure installed between the initial support and the secondary lining. This invention also discloses a construction method for thermal insulation and antifreeze of a gravel blind drain in a cold-region tunnel. This invention adopts dual insulation measures, combining active and passive thermal insulation and antifreeze technologies for multi-layer composite insulation, resulting in good thermal insulation and antifreeze effects. The electric heating control system centrally heats the electric heating tubes to actively change the temperature conditions of the tunnel's antifreeze section, enabling real-time monitoring and automatic control of the gravel blind drain temperature.

Description

Technical Field

[0001] This invention relates to the field of tunnel construction technology, specifically to a thermal insulation and antifreeze structure for gravel blind drains in cold regions and its construction method. Background Technology

[0002] With the continuous development of tunnel construction in my country, the number of tunnels in high-altitude and cold regions is also increasing. Due to deficiencies in construction technology, many tunnels in these regions are currently experiencing varying degrees of frost damage, including lining frost heave cracking, spalling, arch icing, and road surface icing. These defects not only severely affect the tunnel structure but also pose a significant threat to tunnel operational safety. Temperature and water flow are important factors contributing to frost damage in tunnels. Domestically and internationally, insulation and frost protection for tunnels in cold regions are mainly achieved by improving the tunnel's temperature environment, water environment, and surrounding rock properties. However, existing construction measures are relatively simple and mostly employ passive insulation and frost protection methods, lacking multi-faceted and multi-layered composite insulation and frost protection construction methods, making it difficult to effectively solve the problem of tunnel insulation and frost protection in complex and harsh environments. To address these issues, research is needed on a new composite insulation and frost protection structure and construction method to prevent frost heave cracking in the tunnel's surrounding rock and solve the tunnel frost damage problem. This research is of great significance for the construction and durability of tunnel insulation and frost protection in cold regions. Summary of the Invention

[0003] To address the shortcomings of the existing technology, this invention provides a composite insulation and frost-proof structure for gravel blind drains in cold regions that reduces frost heave damage, along with its construction method.

[0004] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0005] A thermal insulation and antifreeze structure for a gravel blind drain in a cold region tunnel includes an active heating module and a thermal insulation and waterproofing module. The active heating module includes electric heating tubes installed in the gravel blind drain in a matrix. The electric heating tubes are connected in a loop to an electric heating control system, which is electrically connected to a temperature sensor and a temperature controller. The thermal insulation and waterproofing module includes a first thermal insulation and waterproofing structure installed on the side of the initial support adjacent to the gravel blind drain and a second thermal insulation and waterproofing structure installed between the initial support and the secondary lining. The first thermal insulation and waterproofing structure is composed of rock wool board, geotextile, waterproof insulation layer, heat insulation layer, and waterproof insulation layer in sequence. The second thermal insulation and waterproofing structure is composed of geotextile, heat insulation layer, and waterproof insulation layer in sequence.

[0006] Furthermore, the heating element consists of a spiral heating wire, a heating liquid, and a protective tube. The spiral heating wire and the heating liquid are placed inside the protective tube, and the heating liquid submerges the spiral heating wire. Both ends of the spiral heating wire are connected to a power supply line.

[0007] Furthermore, the waterproof and thermal insulation layer comprises two waterproof boards sandwiching a thermal insulation board, wherein the waterproof boards are EVA waterproof boards and the thermal insulation board is a rigid polyurethane thermal insulation board; and the thermal insulation layer is an aerogel composite thermal insulation layer.

[0008] Furthermore, multiple self-adhesive strips are provided on the front and back of the insulation board to bond and fix it to the waterproof board.

[0009] A method for thermal insulation and frost protection of gravel blind drains in cold regions is described below:

[0010] S1: Excavate a gravel blind ditch, reserve the position for installing a waterproof insulation layer and electric heating pipe, and drill drainage holes;

[0011] S2: Install and fix the steel cage, fixing bars and electric heating tube positioning bars, and then cover with rock wool board as insulation material;

[0012] S3: Arrange the electric heating tubes in a semi-circular array in the blind trench, connect them into a loop and connect to the electric heating control system to start preheating;

[0013] S4: Lay a gravel insulation layer and a nylon mesh at the bottom of the blind drain from bottom to top, and lay geotextile between the initial support and the secondary lining, and on the surface of the initial support.

[0014] S5: Lay two layers of waterproof and heat-insulating layers inside the geotextile on the side of the initial support adjacent to the crushed stone blind ditch, lay an insulation layer between the two layers of waterproof and heat-insulating layers, and lay a waterproof and heat-insulating layer and an insulation layer inside the geotextile between the initial support and the secondary lining to start formal heating.

[0015] S6: Fill with crushed stone, spray concrete to seal the construction and reserve temperature measurement holes; measure and record the temperature regularly, and adjust the heating according to temperature changes to ensure that the surrounding temperature is not lower than 5℃;

[0016] S7: After heating is complete, disconnect the power supply. After the overall structure cools down, finally lay nylon mesh and gravel insulation layer on the top of the blind drain from bottom to top to seal and insulate it.

[0017] S8: After each process passes quality inspection, check whether the heating effect of the electric heating tube and the insulation effect of the insulation layer meet the quality requirements. After each process passes quality inspection, the next cycle begins.

[0018] Furthermore, in step S1, the gravel blind ditch is excavated into a semi-circular arc shape with dimensions of 0.3m wide × 0.5m deep, reserving space for the initial support on both sides for the insulation layer, heat insulation layer, and the installation position of the electric heating pipe in the gravel blind ditch; after excavation, six 4m long and 5cm diameter drainage holes are drilled radially at the top of the blind ditch.

[0019] Further, in step S2, the reinforcing cage uses 16mm threaded steel bars as main bars and 8mm round steel bars as stirrups, and is processed and installed according to the size of the crushed stone blind ditch; the positioning bars are arranged in three rings along the longitudinal direction of the blind ditch inside the blind ditch to position the electric heating tube; then rock wool board is covered as insulation material, and the rock wool board is set on the side of the crushed stone blind ditch close to the initial support.

[0020] Further, in step S3, the heating tubes are arranged in a semi-circular array with a sparse inner layer and a dense outer layer in the blind trench, and all the heating tubes are connected to the electric heating control system through a PVC sheathed cable. The system is equipped with a temperature sensor and a thermostat. The heating tube consists of a spiral heating wire, a heating liquid, and a protective tube. The spiral heating wire and the heating liquid are placed inside the protective tube. The heating liquid submerges the spiral heating wire. Both ends of the spiral heating wire are connected to the PVC sheathed cable.

[0021] Furthermore, in step S4, the gravel insulation layer is made of gravel with a diameter of 0.5 to 5 mm, and the nylon mesh is 150 mesh nylon mesh.

[0022] Furthermore, in step S5, the waterproof and thermal insulation layer comprises two waterproof boards sandwiching a thermal insulation board. The waterproof boards are EVA waterproof boards, and the thermal insulation board is a rigid polyurethane thermal insulation board. The thermal insulation board is laid with a width of 2m, and three self-adhesive strips are respectively provided on the front and back of the thermal insulation board to be bonded and fixed to the waterproof boards.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] This invention employs dual insulation measures, combining active and passive insulation and antifreeze technologies for multi-layered composite insulation, resulting in excellent insulation and antifreeze effects. The invention utilizes an electric heating control system to centrally heat the heating elements, actively altering the temperature conditions of the tunnel's antifreeze section, enabling real-time monitoring and automatic control of the temperature in the gravel drainage ditch.

[0025] This invention effectively improves the water environment while providing thermal insulation. It has significant anti-freezing and thermal insulation effects, is easy to construct, and effectively ensures the efficiency and timeliness of thermal insulation construction of gravel blind drains near tunnel entrances. It greatly reduces the damage caused by frost heave and enables rapid construction of tunnel insulation layers in frigid regions.

[0026] This invention involves laying a composite insulation layer in areas such as gravel blind drains, initial support, and secondary lining. This effectively increases the tunnel's thermal resistance, reduces the temperature sensitivity of the surrounding rock to the external environment, and achieves passive insulation and frost protection. The insulation layer is composed of geotextile, EVA waterproofing board, polyurethane insulation board, and aerogel composite insulation layer, significantly improving waterproofing and insulation performance and effectively preventing damage to the waterproofing and insulation layers caused by improper construction. Furthermore, a gravel insulation layer and nylon mesh are symmetrically laid at the top and bottom of the gravel blind drain, ensuring unobstructed water flow while providing insulation and effectively reducing the freezing depth. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a top view of the tunnel sidewall gravel blind drain structure in this invention.

[0029] Figure 2 This is a front view schematic diagram of the gravel blind drain in the tunnel sidewall of the present invention.

[0030] Figure 3 This is a flowchart of the construction process of the method of the present invention.

[0031] Attached reference numerals: 1-Heating tube, 11-Spiral heating wire, 12-Heating liquid, 13-Protective tube, 14-PVC conduit cable, 2-Gravel blind drain, 3-Electric heating control system, 4-Geotextile, 5-Waterproof insulation layer, 6-Insulation layer, 7-Initial support, 8-Secondary lining, 10-Fixing reinforcement, 15-Positioning reinforcement, 16-Rock wool board, 17-Gravel insulation layer, 18-Nylon mesh, 19-Wire mesh, 20-Gravel, 21-Temperature measuring hole. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0033] This invention proposes a thermal insulation and frost protection structure for gravel blind drains in cold regions, such as... Figure 1 , Figure 2 As shown, the system includes an active heating module and a thermal insulation and waterproofing module. The active heating module includes electric heating tubes 1 installed in the gravel blind ditch 2. The electric heating tubes 1 are arranged in a matrix in the gravel blind ditch 2. The electric heating tubes 1 are connected in a loop to the electric heating control system 3. The electric heating control system 3 is electrically connected to a temperature sensor and a temperature controller. The thermal insulation and waterproofing module includes a first thermal insulation and waterproofing structure installed on the side of the initial support 7 adjacent to the gravel blind ditch 2 and a second thermal insulation and waterproofing structure installed between the initial support 7 and the secondary lining 8. The first thermal insulation and waterproofing structure is composed of rock wool board 16, geotextile 4, waterproof and thermal insulation layer 5, heat insulation layer 6, and waterproof and thermal insulation layer 5 in sequence. The second thermal insulation and waterproofing structure is composed of geotextile 4, heat insulation layer 6, and waterproof and thermal insulation layer 5 in sequence. The heating element 1 consists of a spiral heating wire 11, a heating liquid 12, and a protective tube 13. The spiral heating wire 11 and the heating liquid 12 are disposed inside the protective tube 13, with the heating liquid 12 submerging the spiral heating wire 11. Both ends of the spiral heating wire 11 are connected to a PVC-coated cable 14. The waterproof and heat-insulating layer 5 comprises two waterproof boards sandwiching a heat-insulating board. The waterproof boards are EVA waterproof boards, and the heat-insulating board is a rigid polyurethane heat-insulating board. The heat insulation layer 6 is an aerogel composite heat insulation layer. Preferably, multiple self-adhesive strips are provided on the front and back of the heat insulation board for bonding and fixing to the waterproof boards.

[0034] This invention also proposes a construction method for thermal insulation and frost protection of crushed stone blind drains in cold regions, such as... Figure 3 As shown, the specific steps are as follows:

[0035] S1: Excavate the gravel blind ditch 2, reserving positions for the installation of insulation layers and electric heating pipes, and drilling drainage holes. Specifically, the gravel blind ditch 2 is excavated in a semi-circular arc shape, with dimensions of 0.3m × 0.5m (width × depth), reserving positions for the installation of insulation layers and heat insulation layers on both sides of the initial support 7, as well as for the installation of electric heating pipes in the gravel blind ditch; after excavation, six 4m long, 5cm diameter drainage holes are drilled radially at the top of the gravel blind ditch to ensure unobstructed water flow in the tunnel and prevent freezing.

[0036] S2: Install and fix the steel cage, fixing ribs 10 and electric heating tube positioning ribs 15, and then cover with rock wool board 16 as insulation material.

[0037] First, the steel cage is fabricated and installed according to the dimensions of the gravel blind drain 2. The steel cage uses 16mm threaded steel bars as main bars and 8mm round steel bars as stirrups. Next, the fixing bars 10 and the electric heating tube positioning bars 15 are installed. The positioning bars 15 are arranged in three rings along the longitudinal direction of the gravel blind drain inside the blind drain to position the electric heating tube 1. Then, rock wool board 16 is covered as insulation material. The rock wool board 16 is set on the side of the gravel blind drain close to the initial support 7.

[0038] S3: Arrange the electric heating tubes 1 in a semi-circular array in the gravel blind ditch 2, connect them into a loop and connect them to the electric heating control system 3 to start preheating.

[0039] The heating elements 1 are arranged in a semi-circular array with a sparse inner layer and a dense outer layer in the gravel blind ditch. All the heating elements 1 are connected to the electric heating control system 3 via PVC conduit cables 14. The electric heating control system 3 is electrically connected to a temperature sensor and a thermostat for real-time monitoring and automatic temperature adjustment to start preheating. The heating element 1 mainly consists of a spiral heating wire 11, a heating liquid 12, and a protective tube 13. The spiral heating wire 11 is a double-helix thick wire made of nickel-iron alloy, with both ends connected to the PVC conduit cables 14. The heating liquid 12 is pure water and submerges the spiral heating wire 11. The protective tube 13 is an aluminum alloy protective tube, which has the characteristics of being lightweight, high-strength, and having excellent thermal conductivity and corrosion resistance.

[0040] S4: Lay a gravel insulation layer 17 and a nylon mesh 18 from bottom to top at the bottom of the gravel blind drain 2. Lay a geotextile 4 between the initial support 7 and the secondary lining 8, and on the surface of the initial support 7 on the side of the gravel blind drain 2.

[0041] At the bottom of the gravel blind drain 2, a gravel insulation layer 17 and a nylon mesh 18 are laid sequentially from bottom to top to seal and insulate the bottom. The gravel insulation layer 17 uses gravel with a diameter of 0.5-5mm, and the nylon mesh 18 is 150-mesh nylon mesh. This ensures unobstructed water flow in the gravel blind drain while providing insulation and preventing freezing. Then, geotextile 4 is laid between the initial support 7 and the secondary lining 8, and on the surface of the initial support 7. The geotextile 4 is laid on both sides, and a layer of dense wire mesh 19 is placed on the outermost side of the geotextile 4 closest to the gravel blind drain to prevent the geotextile 4 from being torn by the gravel. Before laying the waterproof insulation layer, the flatness of the initial support must be no less than D / L≤1 / 20, and the flatness of the waterproof insulation layer should also be no less than D / L≤1 / 20.

[0042] S5: Lay two layers of waterproof and heat-insulating layer 5 inside the geotextile 4 on the side of the initial support 7 adjacent to the crushed stone blind ditch 2, lay a heat insulation layer 6 between the two layers of waterproof and heat-insulating layer 5, and lay the waterproof and heat-insulating layer 5 and the heat insulation layer 6 inside the geotextile 4 between the initial support 7 and the secondary lining 8, and start formal heating.

[0043] After the geotextile 4 is laid, a waterproof and thermal insulation layer 5 is laid inside the geotextile 4, and a thermal insulation layer 6 is laid between the two waterproof and thermal insulation layers 5. The waterproof and thermal insulation layer 5 consists of two waterproof boards sandwiching a thermal insulation board. The waterproof board is an EVA waterproof board, and the thermal insulation board is a 5cm thick rigid polyurethane thermal insulation board. The thermal insulation board is laid with a width of 2m and is treated with plastic coating to improve its moisture-proof effect. Three self-adhesive strips are set on the front and back of the thermal insulation board to facilitate bonding with the waterproof board. The thermal insulation layer 6 is an aerogel composite thermal insulation layer. The passive thermal insulation layer adopts a composite multi-layer insulation, which consists of geotextile + waterproof and thermal insulation layer (EVA waterproof board + polyurethane thermal insulation board + EVA waterproof board) + aerogel composite thermal insulation layer + waterproof and thermal insulation layer, which can achieve effective thermal insulation and water stoppage, and good anti-freeze and thermal insulation effects.

[0044] S6: Fill with 20 cubic meters of crushed stone, spray concrete to seal the construction and reserve temperature measurement holes; measure and record the temperature regularly, and adjust the heating supply according to temperature changes to ensure that the surrounding temperature is not lower than 5°C.

[0045] After the insulation layer is constructed, crushed stone 20 is filled in, and sprayed concrete is used to seal the area, with temperature measuring holes 21 reserved. The crushed stone 20 should have a diameter of 2.5-5cm, a surface cleanliness of less than 0.17%, a needle-like / flaky index of less than 20%, and a rock compressive strength of not less than 60MPa under water saturation. The temperature measuring holes 21 are arranged circumferentially at 3m intervals on the outside of the crushed stone blind drain to monitor the surface temperature of the blind drain. During heating, the temperature is measured and recorded regularly, and the heating is adjusted according to temperature changes to ensure that the surrounding temperature is not lower than 5℃.

[0046] S7: After heating is complete, disconnect the power supply. After the overall structure cools down, finally lay nylon mesh 18 and gravel insulation layer 17 on the top of the gravel blind drain 2 from bottom to top for sealing and insulation.

[0047] S8: After each process passes the quality inspection, check whether the heating effect of the electric heating tube 1 and the insulation effect of the insulation layer meet the quality requirements. After each process passes the quality inspection, the next cycle begins.

[0048] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A method for thermal insulation and frost protection of a gravel blind drain in a cold region tunnel, characterized in that: The specific steps are as follows: S1: Excavate a gravel blind ditch, reserve the position for installing a waterproof insulation layer and electric heating pipe, and drill drainage holes; S2: Install and fix the steel cage, fixing bars and electric heating tube positioning bars, and then cover with rock wool board as insulation material; S3: Arrange the electric heating tubes in a semi-circular array in the blind trench, connect them into a loop and connect to the electric heating control system to start preheating; S4: Lay a gravel insulation layer and a nylon mesh at the bottom of the blind drain from bottom to top, and lay geotextile between the initial support and the secondary lining, and on the surface of the initial support adjacent to the gravel blind drain. S5: Lay two layers of waterproof and heat-insulating layers inside the geotextile on the side of the initial support adjacent to the crushed stone blind ditch, lay an insulation layer between the two layers of waterproof and heat-insulating layers, and lay a waterproof and heat-insulating layer and an insulation layer inside the geotextile between the initial support and the secondary lining to start formal heating. S6: Fill with crushed stone, spray concrete to seal the construction and reserve temperature measurement holes; measure and record the temperature regularly, and adjust the heating according to temperature changes to ensure that the surrounding temperature is not lower than 5℃; S7: After heating is complete, disconnect the power supply. After the overall structure cools down, finally lay nylon mesh and gravel insulation layer on the top of the blind drain from bottom to top to seal and insulate it. S8: After each process passes quality inspection, check whether the heating effect of the electric heating tube and the insulation effect of the insulation layer meet the quality requirements. After each process passes quality inspection, the next cycle begins.

2. The construction method for thermal insulation and frost protection of gravel blind drains in cold regions according to claim 1, characterized in that: In step S1, the gravel blind ditch is excavated into a semi-circular arc shape with dimensions of 0.3m wide × 0.5m deep, reserving space for the initial support on both sides for the insulation layer, heat insulation layer, and the installation position of the electric heating pipe in the gravel blind ditch; after excavation, six 4m long and 5cm diameter drainage holes are drilled radially at the top of the blind ditch.

3. The construction method for thermal insulation and frost protection of gravel blind drains in cold regions according to claim 1, characterized in that: In step S2, the reinforcing cage uses 16mm threaded steel bars as main bars and 8mm round steel bars as stirrups, and is processed and installed according to the size of the crushed stone blind ditch; the positioning bars are arranged in three rings along the longitudinal direction of the blind ditch inside the blind ditch to position the electric heating tube; then rock wool board is covered as insulation material, and the rock wool board is set on the side of the crushed stone blind ditch close to the initial support.

4. The construction method for thermal insulation and frost protection of gravel blind drains in cold regions according to claim 1, characterized in that: In step S3, the heating tubes are arranged in a semi-circular array with a sparse inner layer and a dense outer layer in the blind trench, and all the heating tubes are connected to the electric heating control system through a PVC sheathed cable. The system is equipped with a temperature sensor and a thermostat. The heating tube consists of a spiral heating wire, a heating liquid, and a protective tube. The spiral heating wire and the heating liquid are placed inside the protective tube. The heating liquid submerges the spiral heating wire, and both ends of the spiral heating wire are connected to the PVC sheathed cable.

5. The construction method for thermal insulation and frost protection of gravel blind drains in cold regions according to claim 1, characterized in that: In step S4, the gravel insulation layer is made of gravel with a diameter of 0.5 to 5 mm, and the nylon mesh is 150 mesh nylon mesh.

6. The construction method for thermal insulation and frost protection of gravel blind drains in cold regions according to claim 1, characterized in that: In step S5, the waterproof and thermal insulation layer comprises two waterproof boards sandwiching a thermal insulation board. The waterproof boards are EVA waterproof boards, and the thermal insulation board is a rigid polyurethane thermal insulation board. The thermal insulation board is laid with a width of 2m. Three self-adhesive strips are respectively set on the front and back of the thermal insulation board to be bonded and fixed to the waterproof boards.

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