A diversion tunnel plugging structure

Abstract

This invention relates to the field of hydraulic engineering technology, specifically to a diversion tunnel sealing structure. The sealing structure of this invention comprises several construction layers longitudinally. In each construction layer, a phase change layer and a concrete layer are alternately arranged laterally. The phase change layer and concrete layer in different construction layers are alternately arranged longitudinally. Cooling water pipes are arranged between different construction layers. The raw materials of the phase change layer include cement gel material, fine aggregate, phase change material, coarse aggregate, water, water-reducing agent, and waterproofing agent. The phase change material is a porous material loaded with paraffin wax, and the paraffin wax includes graded paraffin wax with phase change temperatures of 40~45℃, 45~55℃, and 55~60℃. This invention, through the spatially alternating distribution of phase change layers and concrete layers combined with graded phase change material, achieves dynamic adjustment and "peak shaving and valley filling" of the heat distribution inside the sealing structure, effectively eliminating local temperature gradients, significantly reducing the risk of temperature cracks, and ensuring the overall performance of the sealing structure.

Description

Technical Field

[0001] This invention relates to the field of water conservancy engineering technology, specifically to a diversion tunnel sealing structure. Background Technology

[0002] A diversion tunnel is a key tunnel structure used for water diversion in water conservancy and hydropower projects during the construction phase. After the main project is completed, it needs to be permanently sealed to restore the normal water storage operation of the reservoir. The diversion tunnel sealing body is usually a large-volume concrete structure that withstands high water head pressure. Its construction quality is directly related to the safety of the power station's impoundment and long-term operational reliability. It has extremely high requirements for the integrity, impermeability, and crack resistance of the concrete.

[0003] During the construction of large-volume concrete sealing bodies, the cement hydration reaction releases a large amount of heat, causing the internal temperature of the concrete to rise rapidly. Due to the poor thermal conductivity of concrete itself, the heat is not easily dissipated, and internal temperature accumulation is likely to occur. Although the project generally adopts the measure of pre-embedded cooling water pipes to cool down the concrete, the cooling radius of the cooling water pipes is limited, the water temperature gradient along the pipes exists, and the heat dissipation conditions at the structural boundary are uneven. As a result, the internal temperature field of the concrete is still difficult to achieve a completely uniform distribution, and there are still significant temperature gradients and temperature differences in local areas. The resulting temperature stress is one of the main causes of through cracks in the sealing body.

[0004] Therefore, how to further optimize temperature control during the construction of large-volume concrete, effectively reduce internal temperature unevenness, and minimize the risk of cracking due to thermal stress has become a pressing technical problem in this field. This invention aims to provide a novel construction structure and method that can improve the temperature field distribution of concrete and suppress thermal stress, thereby solving the problem that existing temperature control methods are unable to eliminate local temperature gradients. Summary of the Invention

[0005] The purpose of this invention is to provide a diversion tunnel sealing structure to solve the technical problem of large local temperature gradients and easy temperature cracks caused by uneven distribution of hydration heat and blind spots in cooling water pipes during the construction of large-volume concrete diversion tunnel sealing bodies.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a diversion tunnel sealing structure, wherein the sealing structure includes several construction layers in the longitudinal direction of the diversion tunnel, and in each construction layer, a phase change layer and a concrete layer are alternately arranged in the transverse direction, and the phase change layer and the concrete layer in different construction layers are alternately arranged in the longitudinal direction to form a cross-sectional and interlocking composite structure; cooling water pipes are arranged between different construction layers.

[0007] Furthermore, the phase change layer and the concrete layer are arranged in a concentric ring or grid pattern alternatingly in a certain construction layer.

[0008] Furthermore, the raw materials for the phase change layer include cement gel material, fine aggregate, phase change material, coarse aggregate, water, water-reducing agent, and waterproofing agent; the phase change material is a porous material loaded with paraffin.

[0009] Furthermore, the mass ratio of the cement gel material, fine aggregate, phase change material, coarse aggregate, water, water-reducing agent, and waterproofing agent is 1:1.3~1.8:0.2~0.5:2.5~3.5:0.35~0.45:0.01~0.03:0.02~0.05.

[0010] Furthermore, the paraffin wax includes a first paraffin wax, a second paraffin wax, and a third paraffin wax, with phase transition temperatures of 40~45℃, 45~55℃, and 55~60℃, respectively.

[0011] Furthermore, the mass ratio of the first paraffin wax, the second paraffin wax, and the third paraffin wax is 1:0.5~1.5:0.5~1.5.

[0012] Furthermore, the porous material is one or more of expanded perlite, expanded vermiculite, or diatomaceous earth.

[0013] Furthermore, the fine aggregate includes natural sand and vitrified microspheres.

[0014] Furthermore, the mass ratio of natural sand to vitrified microspheres in the fine aggregate is 1:0.1~0.3.

[0015] The beneficial effects of this invention are:

[0016] 1. This invention constructs a synergistic temperature control system of "active cooling + passive heat storage" by dividing the sealing body into alternating phase change layers and concrete layers in the longitudinal and transverse directions, and arranging cooling water pipes between different construction layers. The phase change layer utilizes the latent heat absorption and release of the phase change material to spatially cut off the continuous heat transfer path, reconstructing the severe temperature gradient with a parabolic distribution inside traditional large-volume concrete into multiple gentle "small temperature difference" regions. In terms of time, the stepped phase change material (40~60℃) achieves "peak reduction" of the hydration heat temperature rise peak and "valley filling" of the cooling rate through relay heat absorption. This structure fundamentally eliminates the drawbacks of the limited cooling radius and temperature control blind spots of traditional cooling water pipes, making the temperature field distribution inside the sealing body more uniform and significantly reducing the risk of penetrating cracks caused by temperature difference stress.

[0017] 2. This invention introduces vitrified microspheres as a fine aggregate component, which, by utilizing their low elastic modulus, effectively buffers the volumetric deformation stress generated during the paraffin phase change process, avoids interfacial debonding or microcracks caused by the volume change of the phase change material, and improves the integrity and ultimate strain capacity of the sealing structure.

[0018] 3. Compared to the stringent layered and segmented pouring, complex water cooling, and long-term curing measures adopted in traditional large-volume concrete construction to control temperature, this invention reduces the reliance on external forced cooling methods through the inherent temperature control capabilities of the structure. The alternating structure of the phase change layer and the concrete layer allows for continuous operation with a larger construction layer thickness, reducing the number of construction joints and the interval period. While ensuring project quality, it simplifies the temperature control process, helps to shorten the construction period, reduce construction costs, and provides a more reliable technical guarantee for the permanent sealing of high-head, large-section diversion tunnels. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall state of the sealing structure of the present invention; Figure 2 This is the present invention. Figure 1 Schematic diagram of the first state of the AA section in the middle; Figure 3 This is the present invention. Figure 1 Schematic diagram of the second state of the AA section in the middle; Figure 4 This is the present invention. Figure 1 A schematic diagram of the state of the BB cross section.

[0020] The names corresponding to each mark in the diagram: 1. Rock mass; 2. Diversion tunnel; 3. Sealing structure; 31. Phase change layer; 32. Concrete layer. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0022] like Figure 1-4 As shown, the sealing structure of this invention is used to seal the diversion tunnel in the rock mass structure. The sealing structure of this invention includes several construction layers in the longitudinal direction. In each construction layer, a phase change layer and a concrete layer are alternately arranged in the transverse direction. The phase change layer and the concrete layer in different construction layers are alternately arranged in the longitudinal direction. Cooling water pipes are arranged between different construction layers.

[0023] By staggering and interacting with the phase change layer and the concrete layer in space (longitudinal and transverse), dynamic regulation of the heat distribution inside the sealing structure can be achieved, which helps to "stagger and fill the temperature valleys" and eliminate local temperature gradients, making the overall heat distribution inside the sealing structure more uniform, thereby significantly reducing the risk of temperature cracks and ensuring project quality.

[0024] For the phase change layer, the raw materials include cementitious gel material, fine aggregate, phase change material, coarse aggregate, water, water-reducing agent, and waterproofing agent. The mass ratio of cementitious gel material: fine aggregate: phase change material: coarse aggregate: water: water-reducing agent: waterproofing agent is 1:(1.3~1.8):(0.2~0.5):(2.5~3.5):(0.35~0.45):(0.01~0.03):(0.02~0.05); wherein, the particle size of the fine aggregate is 0.15~4.75mm, including natural materials. The mixture consists of natural sand and vitrified microspheres in a mass ratio of 1:0.1~0.3; coarse aggregate with a particle size greater than 4.75mm, including crushed stone; and a phase change material consisting of a porous material loaded with paraffin wax, including primary, secondary, and tertiary paraffin waxes with phase change temperatures of 40~45℃, 45~55℃, and 55~60℃, respectively, corresponding to a mass ratio of 1:0.5~1.5:0.5~1.5. The porous material includes expanded perlite, expanded vermiculite, and diatomaceous earth, with a particle size of 0.15~4.75mm.

[0025] Phase change materials with stepped phase change temperatures are more conducive to heat regulation inside the sealing structure. Appropriate addition of vitrified microspheres, with their low elastic modulus, helps to compensate for the volume change of paraffin material during phase change, eliminates phase change stress, and improves the ultimate strain capacity of the sealing structure, ensuring the stability of the sealing structure's performance.

[0026] The core of the construction process of the diversion tunnel sealing structure proposed in this invention lies in the construction of a composite structure in which the phase change layer and the concrete layer are interlocked through alternating pouring in space.

[0027] Construction begins with foundation treatment and surveying. The bottom of the diversion tunnel bedrock must be thoroughly cleaned, and the bedrock surface of the sealing section roughened. Once the main pouring stage begins, the core of the process lies in strictly adhering to the principle of "alternating horizontally and staggered vertically." Within a construction layer, using removable templates arranged in a concentric ring or grid pattern ("large opening inside small opening"), workers alternately pour the phase change layer and concrete layer horizontally, ensuring they cover the entire cross-section side-by-side. After the layer is poured, the baffle is removed and the concrete is vibrated evenly. Cooling water pipes are then laid and fixed on the surface. After verifying the sealing is satisfactory, the next layer is constructed. At this point, the arrangement of the next layer must be longitudinally staggered with the first layer; that is, where the phase change layer is in the first layer, the corresponding position in the second layer is filled with concrete, and vice versa. This achieves a staggered distribution of the phase change material in three-dimensional space.

[0028] In the material preparation and casting process of the phase change layer, paraffin wax with three phase change temperatures distributed in a stepped manner needs to be loaded and adsorbed through porous materials (vacuum impregnation, etc.) to form a shaped composite phase change material. Then, it is mixed evenly with cement, coarse and fine aggregates, water and admixtures in proportion. During the casting process, special attention should be paid to controlling the synchronous rising speed of the two materials to prevent the height difference from affecting the stability of the template. At the same time, it is necessary to ensure that the vitrified microspheres are not excessively broken so that the phase change material is evenly distributed inside the structure.

[0029] After pouring, the cooling water pipes are immediately circulated. Utilizing the high heat storage characteristics of the phase change layer, the cooling range is effectively extended beyond the cooling radius of traditional water pipes, achieving synergistic temperature control through "active cooling" and "passive heat storage." After all the sealing materials have been poured and fully moisturized (usually for no less than 28 days) and the concrete temperature has stabilized, all cooling water pipes are finally pressure-grouted and sealed. Joint grouting is also performed at the contact surface between the sealing material and the rock mass, forming a complete, dense, and permanently sealed structure with excellent crack resistance. During the curing process, the concrete layer itself acts as a good seal, effectively preventing the leakage of paraffin material. After curing, the paraffin material returns to a solid state, permanently sealing within the sealing structure.

[0030] Example 1 This embodiment uses the diversion tunnel sealing construction in a water conservancy project as an example to describe in detail the diversion tunnel sealing structure and construction method provided by this invention. The diversion tunnel has a city gate-shaped cross-section with dimensions of 12m (width) × 14m (height), a sealing section length of 25m, and a designed water head of 120m.

[0031] In this embodiment, the sealing structure is divided into 5 construction layers in the longitudinal direction of the diversion tunnel, each with a thickness of 2.5m to 3.0m. Within each construction layer, a phase change layer and a concrete layer are alternately arranged in the transverse direction. The width of the phase change layer and the concrete layer is 1 to 1.5m. Between adjacent construction layers, the positions of the phase change layer and the concrete layer are staggered in the longitudinal direction, forming a composite structure of interlocking longitudinal and transverse directions. For the arched part, the radial structure along the direction of the diversion tunnel remains unchanged during construction, while the transverse structure is correspondingly reduced. Cooling water pipes are pre-embedded between different construction layers. The cooling water pipes are made of high-density polyethylene pipes with a diameter of 32mm and a horizontal spacing of 1.0m, arranged in a serpentine pattern.

[0032] In this embodiment, the concrete layer uses conventional C40 high-performance concrete, with a specific mix proportion of (kg / m³). 3 : Cement (PO 42.5) 320, fly ash 80, sand 720, crushed stone (5~20mm) 1080, water 160, high-efficiency water-reducing agent 4.0.

[0033] The raw materials for the phase change layer are prepared according to the following mass ratio: cement gel material: fine aggregate: phase change material: coarse aggregate: water: water-reducing agent: waterproofing agent = 1:1.5:0.3:3.0:0.4:0.02:0.03, where the cement gel material is PO 42.5 Ordinary Portland cement, fine aggregate is a mixture of natural sand and vitrified microspheres at a mass ratio of 1:0.2, with a particle size range of 0.15~4.75mm, and coarse aggregate is continuously graded crushed stone with a particle size of 5~20mm; the phase change material is a porous material loaded with paraffin wax, the porous material is expanded perlite with a particle size of 1~3mm, loaded with paraffin wax mixture using vacuum impregnation adsorption method, the paraffin wax mixture is compounded by first paraffin wax, second paraffin wax and third paraffin wax at a mass ratio of 1:1:1, the phase change temperatures of the three are 42.5℃, 51.2℃ and 57.6℃ respectively, and loaded according to the mass ratio of paraffin wax mixture to expanded perlite of 0.6:1; in addition, polycarboxylate high-performance water-reducing agent and organosilicon waterproofing agent are also added to the phase change layer.

[0034] During the actual construction, the foundation treatment and surveying were carried out first. The bottom rock foundation of the diversion tunnel was cleaned down to the fresh rock surface. The bedrock surface of the sealing section was roughened and washed clean with high pressure water. The boundary lines of each construction layer, phase change layer and concrete layer were accurately marked on the tunnel wall and bottom.

[0035] During the pouring of the first construction layer, detachable formwork is installed, and the cross-section of the diversion tunnel is divided into multiple alternating annular areas according to a concentric ring layout of "large opening inside small opening," achieving a transverse alternation between the phase change layer and the concrete layer. When pouring the phase change layer, compound paraffin wax and expanded perlite are first mixed to form a shaped composite phase change material, which is then uniformly mixed with cement, coarse and fine aggregates, water, and admixtures according to the specified ratio, and poured into the designated area using a pump. Simultaneously with the pouring of the phase change layer, the adjacent concrete layer is poured to ensure that the pouring surfaces of the two materials are basically level. After pouring, the formwork is removed and the concrete is vibrated evenly. The surface is then leveled and roughened. Subsequently, serpentine cooling water pipes are laid and fixed on the surface. After checking the pipe sealing with water and confirming it is qualified, the next layer of construction can proceed.

[0036] During the pouring of the second construction layer, the transverse arrangement of the phase change layer and the concrete layer is completely staggered from that of the first construction layer. That is, the concrete layer is poured at the corresponding position of the phase change layer in the first layer, and vice versa. The phase change layer and the concrete layer are poured alternately in the same material ratio and pouring process as the first layer. The above steps are repeated to complete the pouring of the remaining three construction layers, ensuring that the phase change layer and the concrete layer are staggered and interlocked in both the longitudinal and transverse directions among all construction layers.

[0037] Immediately after pouring, start the cooling water circulation system, with a flow rate of 1.5~2.0m³. 3The water temperature is controlled within 20℃ from the internal temperature of the concrete, and the water supply time is maintained for 14 days, dynamically adjusted according to temperature data. After the entire sealing body is poured, it is covered with geotextile and watered for moisturizing and curing, with a curing time of no less than 28 days. Once the concrete temperature has dropped to a stable state, i.e., the temperature difference with the tunnel environment is less than 5℃, all cooling water pipes are pressure grouted and sealed, and the contact surface between the sealing body and the rock mass is grouted to form a complete and dense permanent sealing structure.

[0038] During construction, the internal temperature of the sealing body was monitored in real time and compared with that of the traditional "cooling water pipe + conventional concrete" scheme.

[0039] The results show that the highest internal temperature of the sealing body using the structure of this embodiment occurs in the core region of the phase change layer at 58.5℃, which is 8.7℃ lower than the 67.2℃ of the comparative example. The maximum temperature difference inside the sealing body is 12.8℃, significantly lower than the 24.5℃ of the comparative example. The temperature field as a whole shows a gentle "small temperature difference" gradient distribution, without any drastic parabolic temperature gradient. After demolding and during the curing period, the sealing body was visually inspected and subjected to ultrasonic non-destructive testing. No penetrating temperature cracks were found, indicating good structural integrity. After 28 days of curing, the compressive strength of the phase change layer core sample was 39.2MPa, meeting the design requirements. Furthermore, the phase change material was effectively sealed between the porous material and the concrete layer after multiple phase change cycles, with no leakage.

[0040] This invention is not limited to the preferred embodiments described above. Anyone can derive other forms of products under the guidance of this invention. However, regardless of any changes made in their shape or structure, any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A diversion tunnel sealing structure, characterized in that: The sealing structure includes several construction layers in the longitudinal direction of the diversion tunnel. In each construction layer, a phase change layer and a concrete layer are alternately arranged in the transverse direction. The phase change layer and the concrete layer in different construction layers are alternately arranged in the longitudinal direction to form a cross-sectional and interlocking composite structure. Cooling water pipes are arranged between different construction layers.

2. The diversion tunnel sealing structure according to claim 1, characterized in that: The phase change layer and the concrete layer are arranged in a concentric ring or grid pattern alternatingly in a certain construction layer.

3. The diversion tunnel sealing structure according to claim 1, characterized in that: The raw materials for the phase change layer include cement gel material, fine aggregate, phase change material, coarse aggregate, water, water-reducing agent, and waterproofing agent; the phase change material is a porous material loaded with paraffin.

4. The diversion tunnel sealing structure according to claim 3, characterized in that: The mass ratio of the cement gel material, fine aggregate, phase change material, coarse aggregate, water, water-reducing agent and waterproofing agent is 1:1.3~1.8:0.2~0.5:2.5~3.5:0.35~0.45:0.01~0.03:0.02~0.

05.

5. The diversion tunnel sealing structure according to claim 3, characterized in that: The paraffin wax includes a first paraffin wax, a second paraffin wax, and a third paraffin wax, with phase transition temperatures of 40~45℃, 45~55℃, and 55~60℃, respectively.

6. The diversion tunnel sealing structure according to claim 5, characterized in that: The mass ratio of the first paraffin wax, the second paraffin wax, and the third paraffin wax is 1:0.5~1.5:0.5~1.

5.

7. The diversion tunnel sealing structure according to claim 3, characterized in that: The porous material is one or more of expanded perlite, expanded vermiculite, or diatomaceous earth.

8. The diversion tunnel sealing structure according to claim 3, characterized in that: The fine aggregates include natural sand and vitrified microspheres.

9. The diversion tunnel sealing structure according to claim 8, characterized in that: The mass ratio of natural sand to vitrified microspheres in the fine aggregate is 1:0.1~0.3.

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