Extremely-low-temperature frost crack prevention structure for concrete calandria of superconducting cable channel and construction method of extremely-low-temperature frost crack prevention structure

Abstract

The invention belongs to the technical field of electric power engineering channel structure protection and material application, and relates to a concrete calandria extremely-low-temperature frost crack prevention structure for a superconducting cable channel and a construction method. The extremely-low-temperature frost crack prevention structure of the concrete calandria comprises the concrete calandria, a priming coat, a closed-cell foam buffer layer, a mechanical anchoring part, a flexible sealant and a lining layer. The concrete calandria, the priming coat, the lining layer, the flexible sealant and the closed-cell foam buffer layer are sequentially arranged from outside to inside; the mechanical anchoring part is sequentially connected with the closed-cell foam buffer layer, the flexible sealant, the lining layer, the priming coat and the concrete calandria from inside to outside. And the closed-cell foam buffer layer is arranged around and close to the outer side of the superconducting cable. The structure provided by the invention can ensure that the superconducting cable channel is not damaged due to frost heaving under the condition of liquid nitrogen leakage, so that the safe operation of the superconducting cable is ensured, and the reliability and stability of the superconducting cable channel are improved.

Description

Technical Field

[0001] This invention relates to the field of power engineering channel structure protection and material application technology, specifically to a low-temperature anti-freezing and cracking structure and construction method for concrete pipes used in superconducting cable channels. Background Technology

[0002] High-temperature superconducting cables rely on liquid nitrogen to maintain low temperatures. If the seal fails or external force causes liquid nitrogen leakage, the local temperature inside the concrete pipe channel can drop sharply to below 0 ℃ in a short time, or even to -50 ℃ or close to -120 ℃. This causes the free water inside the channel to freeze and expand in volume, and the resulting radial pressure acts on the inner wall of the pipe, which can easily induce concrete cracks and deterioration of durability.

[0003] Literature studies have shown that cryogenic freeze-thaw cycles induced by liquid nitrogen significantly reduce the ultrasonic wave velocity and compressive strength of concrete. After four freeze-thaw cycles, the wave velocity can decrease by up to 13.6%, and the compressive strength can decrease by more than 28%, accompanied by microstructural deterioration such as increased porosity and enlarged pore size. Furthermore, liquid nitrogen leaks typically occur due to sudden events such as micro-leakage, external force damage, or short-circuit breakdown, which often happen in enclosed or semi-enclosed spaces. To ensure structural safety, an effective "passive energy dissipation + waterproofing" safety boundary is required.

[0004] Therefore, there is an urgent need for a structure and construction method that can prevent freezing and cracking in the event of a sudden low temperature leak caused by liquid nitrogen leakage in a superconducting cable. Summary of the Invention

[0005] The purpose of this invention is to overcome the deficiencies of the existing technology by providing a low-temperature frost-resistant structure and construction method for concrete ducts used in superconducting cable channels. Specifically, this invention addresses the protection against frost heave and cracking of concrete ducts in high-temperature superconducting cable channels (including ducts and / or tunnels) under sudden low-temperature conditions caused by liquid nitrogen leakage; it is also applicable to structural safety protection when superconducting cables and ambient temperature cables are laid in the same channel.

[0006] This invention can be achieved through the following technical solutions: The first objective of this invention is to provide a low-temperature anti-freezing and crack-resistant structure for concrete pipes used in superconducting cable channels, the low-temperature anti-freezing and crack-resistant structure for concrete pipes includes a concrete pipe, a base coating, a closed-cell foam buffer layer, mechanical anchors, a flexible sealant, and an inner lining layer. The concrete pipe, primer, inner lining, flexible sealant, and closed-cell foam buffer layer are arranged sequentially from the outside to the inside. The mechanical anchor is connected sequentially from the inside out to the closed-cell foam buffer layer, flexible sealant, inner lining layer, primer layer, and concrete pipe. The inner lining extends along the inner wall of the concrete pipe to form a circumferential closed cylindrical structure; The closed-cell foam buffer layer is located inside the inner lining layer and continuously or in sections surrounds the superconducting cable along the circumference of the concrete pipe.

[0007] Furthermore, "extremely low temperature" refers to a low-temperature operating condition that poses a threat to the structure of the present invention, typically a temperature range of 0 ℃ or below, preferably around -(40~50) ℃ or below as determined by finite element simulation analysis software, and more preferably an ultra-low temperature operating condition close to -120 ℃ as determined by simulation, in order to cover the operating limit conditions that the high-temperature superconducting cable may encounter when liquid nitrogen leaks or the cooling system malfunctions.

[0008] Furthermore, the concrete pipe is made of concrete, and the concrete strength grade reaches C25 or above. The concrete pipe uses precast concrete materials.

[0009] Furthermore, the concrete pipe is the main load-bearing structure of the entire superconducting cable channel.

[0010] Furthermore, the cross-section of the concrete pipe is rectangular, circular, or other shapes, which can be customized according to engineering needs. It has high compressive strength and impermeability, and can effectively withstand external loads.

[0011] Furthermore, the ultra-low temperature anti-freezing crack structure of the concrete pipe also includes a flow guide channel; the flow guide channel is formed in the concrete pipe; the flow guide channel is used for guiding and draining.

[0012] Furthermore, free water may exist in the channel due to leakage, condensation, or construction residue; when liquid nitrogen leaks or abnormal cooling causes a sudden drop in the local temperature of the channel, the free water freezes and expands in volume, forming radial frost heave pressure.

[0013] Furthermore, the ultra-low temperature anti-freezing and cracking structure of the concrete pipe also includes a support; the support can be made of stainless steel; the support is used to support and position the superconducting cable, so that the axis of the superconducting cable is kept at the designed position of the channel section.

[0014] Furthermore, the support structure possesses excellent corrosion resistance, enabling long-term stable operation under low temperature, high humidity, and harsh environmental conditions. The support structure ensures the structural stability of the superconducting cable channel and effectively distributes and transmits external loads, preventing deformation or displacement of the superconducting cable channel due to external forces. Through proper configuration of the support structure, the safe operation of the entire piping system can be ensured even under extreme conditions such as liquid nitrogen leaks.

[0015] Furthermore, the base coating is an epoxy interface agent or a polyurethane interface agent, used for interface treatment, sealing concrete pores, and enhancing the bond strength between the closed-cell foam buffer layer and the inner wall of the concrete pipe.

[0016] Furthermore, the inner lining is made of one or more of PVC, PP, and HDPE materials, and the inner lining is used for waterproofing and friction protection.

[0017] Furthermore, PVC material possesses excellent chemical stability, preventing damage to the cable caused by chemical corrosion. Simultaneously, PVC's low water absorption and excellent sealing properties enhance the overall waterproofness of the superconducting cable channel, effectively protecting the superconducting cable from external environmental influences.

[0018] Furthermore, the inner lining is made of polymer materials such as PVC (or PP, HDPE, etc.), which has low surface energy and good chemical resistance, effectively reducing frictional resistance during cable laying, protecting the superconducting cable and reducing the corrosive effects of environmental media on the internal structure of the superconducting cable channel.

[0019] Furthermore, the inner lining layer is located inside the concrete pipe and together with the closed-cell foam buffer layer, forms the inner wall of the superconducting cable channel, which is used to indirectly cover and protect the superconducting cable laid in the channel.

[0020] Furthermore, the smooth inner wall of the inner lining layer effectively reduces friction during the laying process, avoiding mechanical damage to the superconducting cable.

[0021] Furthermore, the material of the closed-cell foam buffer layer is one or more of polyethylene closed-cell foam or EVA closed-cell foam; the closed-cell foam buffer layer is used for buffering and absorbing the volume expansion energy caused by freezing under extremely low temperature conditions.

[0022] Furthermore, the closed-cell foam buffer layer maintains a certain compressibility under extremely low temperature conditions, which is used to absorb the radial pressure generated by the volume expansion of water freezing in the superconducting cable channel and reduce the peak stress transmitted to the concrete pipe.

[0023] Furthermore, the polyethylene closed-cell foam is a high-performance engineering material made from polyethylene material through a foaming process. The polyethylene closed-cell foam is one or more of PE, XPE, or IXPE.

[0024] Furthermore, using high-closed-cell polyethylene (PE) foam provides excellent low-temperature toughness, allowing it to withstand temperatures down to -196°C without cracking. The design allowable compressive strain is [value missing]. e allow ≈ 30%~50%, ensuring that the foam can effectively buffer the pressure of frost heave in low-temperature environments.

[0025] Furthermore, the closed-cell foam buffer layer is fixed inside the inner lining layer. The closed-cell foam buffer layer is the core buffer unit, which can absorb the volume expansion energy caused by freezing under extremely low temperature conditions. The closed-cell foam buffer layer serves as a buffer layer to bear the expansion pressure caused by water freezing at low temperatures.

[0026] Furthermore, the closed-cell foam buffer layer is made of polyethylene closed-cell foam board, which has excellent compressibility (compressible by 30%-50%). The closed-cell structure effectively prevents moisture penetration and will not crack at low temperatures, ensuring good elastic deformation capacity when ice expands. The use of this material can significantly reduce the squeezing effect of ice expansion pressure on concrete pipes and reduce the risk of frost heave cracking.

[0027] Furthermore, the superconducting cable is laid in the center of the superconducting cable channel, and its structure includes a copper support core, a superconducting layer, liquid nitrogen, an insulation layer, a shielding layer, a heat insulation tube, and an outer sheath. Liquid nitrogen serves as the cooling medium to maintain the superconducting state. When liquid nitrogen leaks, the temperature drops sharply below zero degrees Celsius, causing a rapid decrease in temperature within the superconducting cable channel, leading to water freezing and creating frost heave pressure. The overall structure must possess excellent low-temperature resistance and mechanical protection performance to ensure safe operation under harsh conditions.

[0028] Furthermore, the mechanical anchor includes an expansion anchor and a gasket. The expansion anchor passes through the closed-cell foam buffer layer, flexible sealant, inner lining layer, and primer layer before connecting to the concrete pipe. The gasket is disposed on the inner side of the closed-cell foam buffer layer.

[0029] Furthermore, the gasket is a force-distribution gasket.

[0030] Furthermore, the expansion anchor penetrates the closed-cell foam buffer layer, flexible sealant, inner lining layer, and primer layer, and is anchored in the concrete pipe.

[0031] Furthermore, the gasket is disposed on the inner side of the closed-cell foam buffer layer. The diameter of the gasket is preferably 2 to 5 times the diameter of the expansion anchor and not less than 30 mm. It is used to disperse the local compressive stress at the anchorage and avoid indentation damage to the closed-cell foam buffer layer and the inner lining layer.

[0032] Furthermore, the flexible sealant is one or more of silicone sealant or MS sealant. The flexible sealant uses low-temperature resistant silicone sealant and / or MS sealant as the sealing material, maintaining good flexibility and sealing performance below -50°C, ensuring sufficient sealing performance even in low-temperature environments.

[0033] Furthermore, the mechanical anchors and flexible sealant are used to ensure the stability and sealing of the overall concrete pipework structure against freezing and cracking at extremely low temperatures.

[0034] Furthermore, the mechanical anchors are made of one or more stainless steel or galvanized components to meet the corrosion resistance requirements in humid and low-temperature environments, ensuring a long-lasting and stable fixing effect in harsh environments.

[0035] Furthermore, the design principle for the stress of the closed-cell foam buffer layer adopts the following formula: E c ·e allow ≥ s design ; Where Ec is the equivalent compressive elastic modulus of the closed-cell foam buffer layer. e allow To allow for an upper limit of compressive strain, the e allow The value ranges from 30% to 50%. s design The design stress for the closed-cell foam buffer layer.

[0036] Furthermore, the above formula ensures that in practical applications, the material of the closed-cell foam buffer layer can play a sufficient buffering role under the action of frost heave pressure, thus avoiding material failure.

[0037] Furthermore, the thickness of the closed-cell foam buffer layer follows the pressure limiting principle ( E c ·e allow ≥ s design The safety factor is set based on the allowable value of the equivalent expansion pressure estimated in the project. Under the premise of satisfying the above relationship, the thickness and material parameters of the closed-cell foam buffer layer are adjusted so that the closed-cell foam buffer layer generates elastic compression under frost heave conditions to absorb expansion energy, thereby limiting the equivalent stress transmitted to the concrete pipe to not exceed its allowable value.

[0038] Furthermore, under normal operating conditions, the liquid nitrogen inside the superconducting cable is kept at a low temperature to ensure its superconducting performance. When a liquid nitrogen leak occurs, the temperature around the superconducting cable drops rapidly, causing the water inside the cable channel to freeze and expand. The increased volume of the expanding water after freezing exerts compressive stress on the concrete pipes within the cable channel, potentially leading to concrete cracking. To avoid this problem, closed-cell polyethylene foam board plays a crucial role as a closed-cell foam buffer layer in this process.

[0039] Furthermore, during ice expansion, the closed-cell foam buffer layer, with its high compressibility (30%-50%), undergoes elastic deformation, absorbing and mitigating frost heave pressure. The closed-cell structure of the foam buffer layer effectively isolates moisture, preventing it from penetrating into the layer and causing performance degradation. Its excellent low-temperature toughness ensures that it does not crack even at extremely low temperatures, maintaining a stable buffering effect over a long period. This structural design significantly reduces the pressure exerted on the concrete pipes by the expansion of ice, ensuring the integrity of the concrete structure and guaranteeing the normal operation and safety of the superconducting cable.

[0040] Furthermore, the composite system of "closed-cell foam buffer layer + inner lining layer" can significantly reduce the equivalent peak stress and stress concentration on the inner wall of concrete pipes, and suppress the generation of concrete cracks caused by frost heave.

[0041] Furthermore, when liquid nitrogen leaks, the temperature drops sharply, water freezes, and the ice expands, generating radial expansion pressure that acts on the inner wall of the concrete pipe. The closed-cell foam buffer layer provides an "energy storage-release" buffering mechanism with its microporous compressible structure, converting the expansion pressure into elastic deformation and diffusing it along the surface; the inner lining layer forms a smooth friction-reducing interface, further dispersing the stress peak.

[0042] Furthermore, when the temperature rises or during maintenance or replacement, the closed-cell foam buffer layer rebounds and re-adheres to the inner lining layer, maintaining the integrity of the protective interface and extending the service life of the structure.

[0043] Furthermore, the closed-cell foam buffer layer and inner lining layer can be replaced equally, provided that they meet the requirements of low-temperature non-brittleness, closed-cell rate and resilience.

[0044] Furthermore, for high-humidity environments, an anti-mildew layer and / or a flame-retardant layer can be added.

[0045] The second objective of this invention is to provide a low-temperature frost-resistant structure for concrete ducts used in superconducting cable channels, the construction method of which includes the following steps: A. Base treatment: Clean the concrete pipework, dry it, level it, and repair any defects to obtain the treated concrete pipework; B. Primer coating: Apply a primer coating to the treated concrete pipework; C. Apply closed-cell foam buffer layer: After applying the primer, apply the closed-cell foam buffer layer in sections along the circumference of the pipe; D. Mechanical anchoring: After attaching the closed-cell foam buffer layer, install mechanical anchors to enhance anti-peeling performance; E. Install the inner lining: After installing the mechanical anchors, assemble the inner lining and apply flexible sealant to the longitudinal and circumferential seams; F. Sealing and finishing: After applying flexible sealant, the joints and ports are sealed using a flexible sealant.

[0046] Furthermore, the construction method includes the following steps: A. Base treatment: Clean the inner wall of the concrete pipe, dry it, level it and repair any defects to obtain the treated concrete pipe; B. Apply primer coating: Apply primer coating evenly to the inner wall of the treated concrete pipe and cure according to the product instructions; C. Apply closed-cell foam buffer layer: After the primer layer has cured, apply the closed-cell foam buffer layer in sections according to the circumference of the concrete pipe, and make the joints of adjacent sections staggered and tightly fitted. D. Mechanical anchoring: After the closed-cell foam buffer layer is pasted and adjusted into place, holes are drilled at the designed intervals, and the closed-cell foam buffer layer is mechanically anchored to the concrete pipe using expansion anchors and stress distribution shims. E. Install the inner lining layer: After the closed-cell foam buffer layer is anchored, assemble the prefabricated inner lining plate or roll material on the inner side of the closed-cell foam buffer layer to form the inner wall of the cable channel, i.e., the inner lining layer; apply flexible sealant to the longitudinal seams, circumferential seams and anchor bolt protrusions of the inner lining layer to seal the gaps. F. Sealing and finishing at nodes and ports: At the connection points (nodes) between concrete pipes and manholes, branch fittings or equipment, and at the openings (ports) at the ends of concrete pipes, flexible sealant is used to seal the cross-sections of the closed-cell foam buffer layer and inner lining layer to ensure continuous sealing and smooth transition.

[0047] Further, after step F, perform the following steps: G. Acceptance testing: Conducting tests on appearance, adhesion, ball passing, and video verification, etc. H. Operation and maintenance linkage: The ultra-low temperature anti-freezing and crack prevention structure of the concrete duct used for superconducting cable channels is linked with the gas and temperature monitoring devices for segmented maintenance in case of abnormalities.

[0048] Furthermore, the operation and maintenance linkage includes the following processes: linkage with the channel gas (including air and nitrogen mixture formed after liquid nitrogen leakage), temperature monitoring and exhaust system; and segmented replacement of closed-cell foam buffer layer and / or inner lining layer in case of abnormality.

[0049] Furthermore, the operation and maintenance linkage specifically includes the following process: monitoring parameters such as oxygen and nitrogen content, temperature, etc. of the gas inside the concrete pipe channel (including air and nitrogen mixture formed after liquid nitrogen leakage); when abnormally low oxygen or abnormally low temperature is detected, coordinating with the exhaust system to carry out forced ventilation or segmented exhaust; when it is confirmed through assessment that the local closed-cell foam buffer layer and / or lining layer are damaged due to frost heave or extremely low temperature, the segmented structure is dismantled and replaced.

[0050] Furthermore, during the construction of the elbow joint, the closed-cell foam buffer layer is assembled using arc-shaped cut blocks with staggered joints.

[0051] Furthermore, during the construction of elbow joints, the inner lining layer is formed using prefabricated bends or rolled materials.

[0052] Furthermore, multiple layers of thickened areas are set in key corner areas, and the gaps are sealed with continuous flexible sealant to ensure a smooth transition, continuous sealing, and prevention of stress concentration.

[0053] Furthermore, during construction, straight pipe sections are lined with rolled material, and elbows and / or joints are made of prefabricated sections; weak points can be stacked in multiple layers or widened and thickened.

[0054] Compared with the prior art, the present invention has the following beneficial effects: 1) The present invention provides a low-temperature anti-freezing and cracking structure for concrete pipes used in superconducting cable channels, which can effectively prevent freezing and cracking after liquid nitrogen leakage of superconducting cables: by setting a closed-cell foam buffer layer inside the concrete pipe, the pressure of water freezing and expansion on the inner wall of the concrete pipe can be reduced under the low temperature caused by liquid nitrogen leakage of superconducting cables, thus preventing concrete cracking.

[0055] 2) The present invention provides an ultra-low temperature anti-freezing and cracking structure for concrete pipes used in superconducting cable channels, which has compressibility and elastic buffering. The high compressibility (30%-50%) of the closed-cell foam buffer layer ensures that the frost heave pressure is absorbed and relieved when the ice expands, significantly reducing the stress on the concrete pipes caused by frost heave.

[0056] 3) The low-temperature anti-freezing and cracking structure of concrete pipe for superconducting cable channel provided by the present invention has excellent low-temperature resistance and chemical stability. The selected materials (such as PVC for the inner lining layer and PE for the closed-cell foam buffer layer) maintain good physical and chemical properties in low-temperature environment, ensuring that the entire superconducting cable channel has long-term stability and durability under the working conditions of superconducting cable.

[0057] 4) The low-temperature anti-freezing and cracking structure of concrete pipe for superconducting cable channels provided by the present invention has strong corrosion resistance and low-temperature environment adaptability. Stainless steel and / or galvanized materials are selected as mechanical anchors to ensure that the low-temperature anti-freezing and cracking structure of concrete pipe has good corrosion resistance and stability in humid and low-temperature environments.

[0058] 5) The ultra-low temperature anti-freezing and cracking structure of concrete pipe for superconducting cable channel provided by the present invention can ensure that the superconducting cable channel will not be damaged by freezing expansion in the event of liquid nitrogen leakage, thereby ensuring the safe operation of the superconducting cable and improving the reliability and stability of the superconducting cable channel. Attached Figure Description

[0059] In this invention, all figures are schematic and not drawn to scale.

[0060] Figure 1 This is a schematic diagram of a superconducting cable channel. Figure 2 This is a schematic diagram of the ultra-low temperature anti-freezing and cracking structure of the concrete pipe for superconducting cable channel of the present invention; Figure 3 This is a construction flowchart of the ultra-low temperature freeze-cracking prevention structure for concrete pipes used in superconducting cable channels according to the present invention. Figure 4 This is a schematic diagram of the construction of the elbow joint of the ultra-low temperature anti-freezing and cracking structure of the concrete pipe for superconducting cable channel according to the present invention. Figure label: 1. Concrete pipework; 2. Primer coating; 3. Closed-cell foam buffer layer; 4. Mechanical anchors; 5. Flexible sealant; 6. Inner lining layer; 7. Superconducting cables; 8. Flow guide channel; 9. Bracket.

[0061] A. Substrate preparation; B. Applying primer; C. Applying closed-cell foam buffer layer; D. Mechanical anchoring; E. Installing inner lining layer; F. Sealing and finishing edges; G. Acceptance testing; H. Operation and maintenance coordination.

[0062] 4a. Arc-cut closed-cell foam buffer layer (staggered assembly); 4b. Prefabricated curved sections or sheet roll forming of inner lining layer; 4c. Multi-layer stacked thickened area; 4d. Continuous flexible sealant at corners. Detailed Implementation

[0063] The present invention will now be described in detail with reference to specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0064] In this invention, the terms "comprising," "including," "containing," "having," or other variations are intended to cover non-closed inclusion, and no distinction is made between these terms. The term "comprising" means that other steps and components may be added without affecting the final result. The compositions and methods / processes of this invention comprise, consist of, and are substantially composed of the essential elements and limitations described herein, as well as any additional or optional components, parts, steps, or limitations described herein.

[0065] The terms "and / or," "or / and," and "and / or" as used in this invention encompass any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected using at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that in this invention, the technical solution undoubtedly includes solutions connected using "logical AND," and also undoubtedly includes solutions connected using "logical OR."

[0066] In this invention, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions that include the listed features.

[0067] In this invention, numerical ranges are involved. Unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed in this invention should be understood to include any and all subranges included therein.

[0068] This invention only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range that is not explicitly stated; and any lower limit can be combined with other lower limits to form a range that is not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range that is not explicitly stated. Furthermore, each individually disclosed point or single value can itself serve as a lower limit or upper limit and can be combined with any other point or single value or with other lower limits or upper limits to form a range that is not explicitly stated.

[0069] Unless otherwise specified, the angles in this invention are allowed to fluctuate within a certain range of manufacturing precision. Fluctuations are permitted within ranges such as ±5°, ±4°, ±3°, ±2°, and ±1°.

[0070] In this invention, "optionally," "optionally," and "optional" mean that they are optional, that is, they are selected from either "with" or "without." If multiple "options" appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "option" is independent.

[0071] In the description of the invention, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0072] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions. Unless otherwise specified, all technical features and optional technical features of the present invention can be combined with each other to form new technical solutions.

[0073] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially.

[0074] In this invention, unless otherwise specified, the relative positions, depths, heights, thicknesses, lengths, and widths of the components shown in the accompanying drawings are merely illustrative, used to express the relative fit and spatial correspondence between the parts. Those skilled in the art can scale these figures up or down proportionally according to actual needs without affecting the essential content of this invention.

[0075] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection achieved by screw fastening, welding, or cooperation with a seal; they can also refer to a direct or indirect connection between components, or an interaction relationship achieved through other elements; they can be a fixed connection, a detachable connection, or an integral part; they can be a mechanical connection or an electrical connection; they can be a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components or the interaction relationship between two components; "upper," "lower," "left," "right," etc., are only used to indicate relative positional relationships, and the relative positional relationship may change when the absolute position of the described object changes. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0076] It should be noted that in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations, nor should they be construed as limiting their quantity, order, priority, or importance. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0077] This invention belongs to the technical field of power engineering channel structure protection and material application, and relates to a low-temperature anti-freezing cracking structure and construction method for concrete ducts used in superconducting cable channels. The low-temperature anti-freezing cracking structure of the concrete duct includes a concrete duct, a primer, a closed-cell foam buffer layer, mechanical anchors, a flexible sealant, and an inner lining layer. The concrete duct, primer, inner lining layer, flexible sealant, and closed-cell foam buffer layer are arranged sequentially from the outside to the inside. The mechanical anchors connect the closed-cell foam buffer layer, flexible sealant, inner lining layer, primer, and concrete duct sequentially from the inside to the outside. The closed-cell foam buffer layer is positioned around and close to the outer side of the superconducting cable. The structure of this invention ensures that the superconducting cable channel will not be damaged by freezing heave in the event of liquid nitrogen leakage, thereby guaranteeing the safe operation of the superconducting cable and improving the reliability and stability of the superconducting cable channel.

[0078] In this invention, any component models, material names, connection structures, control methods, etc., not explicitly stated are considered common technical features disclosed in the prior art.

[0079] Example 1 like Figure 2 As shown, this embodiment provides a low-temperature anti-freezing and crack-resistant structure for concrete ducts used in superconducting cable channels. The ultra-low temperature anti-freezing crack structure of the concrete pipe includes a concrete pipe 1, a base coating 2, a closed-cell foam buffer layer 3, mechanical anchors 4, flexible sealant 5, and an inner lining layer 6. The concrete pipe 1, primer 2, inner lining 6, flexible sealant 5, and closed-cell foam buffer layer 3 are arranged sequentially from the outside to the inside. The mechanical anchor 4 is connected sequentially from the inside out to the closed-cell foam buffer layer 3, flexible sealant 5, inner lining layer 6, primer layer 2, and concrete pipe 1. The inner lining layer 6 extends along the inner wall of the concrete pipe 1 to form a circumferential closed cylindrical structure; The closed-cell foam buffer layer 3 is located inside the inner lining layer 6 and continuously or in sections surrounds the superconducting cable 7 along the circumference of the concrete pipe 1.

[0080] The concrete pipe 1 is made of concrete, and the concrete strength grade reaches C25 or above. The concrete pipe 1 is made of precast concrete.

[0081] The concrete pipe 1 is the main load-bearing structure of the entire superconducting cable channel.

[0082] The concrete pipe 1 has a cross-section that is rectangular, circular, or other shapes, which can be customized according to project requirements. It has high compressive strength and impermeability, and can effectively withstand external loads and frost heave forces.

[0083] In this embodiment, the cross-section of the concrete pipe 1 is circular.

[0084] The ultra-low temperature anti-freezing crack structure of the concrete pipe also includes a flow guide trough 8; the flow guide trough 8 is formed in the concrete pipe 1; the flow guide trough 8 is used for flow guidance and drainage.

[0085] Free water may exist in the passage due to leakage, condensation or construction residue. When liquid nitrogen leaks or abnormal cooling causes a sudden drop in the local temperature of the passage, the free water freezes and expands in volume, forming radial frost heave pressure.

[0086] The base coating 2 is made of one or more of epoxy interface agent or polyurethane interface agent; the base coating 2 is used for interface treatment, sealing concrete pores and enhancing the bond strength between the closed-cell foam buffer layer 3 and the inner wall of the concrete pipe 1.

[0087] The inner lining layer 6 is made of one or more of PVC, PP, and HDPE materials, and serves for waterproofing and abrasion protection. PVC material has good chemical stability, preventing damage to the cable caused by chemical corrosion. Simultaneously, the low water absorption and good sealing performance of PVC material enhance the overall waterproofness of the superconducting cable channel, effectively protecting the superconducting cable 7 from the influence of the external environment.

[0088] In this embodiment, the inner lining layer 6 is made of PVC material.

[0089] The inner lining layer 6 is made of polymer materials such as PVC (or PP, HDPE, etc.), which has low surface energy and good chemical resistance. It can effectively reduce the frictional resistance during cable laying, protect the superconducting cable 7, and reduce the corrosive effect of environmental media on the internal structure of the superconducting cable channel.

[0090] The inner lining layer 6 is located inside the concrete pipe 1 and together with the closed-cell foam buffer layer 3, forms the inner wall of the superconducting cable channel, which is used to indirectly cover and protect the superconducting cable 7 laid in the channel.

[0091] The smooth inner wall of the inner lining layer 6 effectively reduces friction during the laying process, avoiding mechanical damage to the superconducting cable 7.

[0092] The closed-cell foam buffer layer 3 is made of one or more of polyethylene closed-cell foam or EVA closed-cell foam; the closed-cell foam buffer layer 3 is used for buffering and absorbing the volume expansion energy caused by freezing under extremely low temperature conditions.

[0093] The polyethylene closed-cell foam is a high-performance engineering material made from polyethylene material through a foaming process. The polyethylene closed-cell foam is one or more of PE, XPE, or IXPE.

[0094] In this embodiment, the closed-cell foam buffer layer 3 is made of polyethylene closed-cell foam, specifically PE foam.

[0095] Utilizing high-closed-cell polyethylene (PE) foam, it exhibits excellent low-temperature toughness and can withstand ultra-low temperature environments without cracking. The design allowable compressive strain is [value missing]. e allow ≈ 30%~50%, ensuring that the foam can effectively buffer the pressure of frost heave in low-temperature environments.

[0096] The closed-cell foam buffer layer 3 is fixed inside the inner lining layer 6. This layer serves as the core buffer unit, absorbing the energy from volume expansion caused by freezing under extremely low temperatures. It also acts as a buffer layer to withstand the expansion pressure caused by water freezing at low temperatures. The closed-cell foam buffer layer 3 is made of polyethylene closed-cell foam board, possessing excellent compressibility (30%-50% compressibility). Its closed-cell structure effectively prevents water penetration and does not crack under low-temperature conditions, ensuring good elastic deformation capacity during ice expansion. The use of this material significantly reduces the squeezing effect of water expansion pressure on the concrete pipe 1, lowering the risk of frost heave and cracking.

[0097] The superconducting cable 7 is laid in the center of the superconducting cable channel and its structure includes a copper support core, a superconducting layer, liquid nitrogen, an insulation layer, a shielding layer, a heat insulation tube, and an outer sheath. Liquid nitrogen serves as the cooling medium to maintain the superconducting state. When liquid nitrogen leaks, the temperature drops sharply below zero degrees Celsius, causing a rapid decrease in temperature within the superconducting cable channel and creating frost heave pressure. The overall structure must possess excellent low-temperature resistance and mechanical protection performance to ensure safe operation under harsh conditions. The structure of the superconducting cable 7 is not an improvement of this invention; existing superconducting cables 7 can be used.

[0098] The mechanical anchor 4 includes an expansion anchor and a gasket. The expansion anchor passes through the closed-cell foam buffer layer 3, the flexible sealant 5, the inner lining layer 6, and the primer layer 2 before connecting to the concrete pipe 1. The gasket is disposed on the inner side of the closed-cell foam buffer layer 3. The gasket is a stress-distributing gasket.

[0099] The expansion anchor penetrates the closed-cell foam buffer layer 3, the flexible sealant 5, the inner lining layer 6, and the primer layer 2, and is anchored in the concrete pipe 1.

[0100] The gasket is placed inside the closed-cell foam buffer layer 3. The diameter of the gasket is preferably 2 to 5 times the diameter of the expansion anchor and not less than 30 mm. It is used to disperse the local compressive stress at the anchorage and avoid indentation damage to the closed-cell foam buffer layer 3 and the inner lining layer 6.

[0101] The flexible sealant 5 is one or more of silicone sealant or MS sealant. The flexible sealant 5 uses low-temperature resistant silicone sealant and / or MS sealant as the sealing material, which can maintain good flexibility and sealing performance below -50℃, ensuring sufficient sealing performance in low-temperature environments.

[0102] In this embodiment, the flexible sealant 5 is MS adhesive.

[0103] The mechanical anchor 4 and flexible sealant 5 are used to ensure the stability and sealing of the overall concrete pipe structure against freezing and cracking at extremely low temperatures.

[0104] The mechanical anchor 4 is made of one or more stainless steel or galvanized components to meet the corrosion resistance requirements in humid and low-temperature environments, ensuring a long-term and stable fixing effect in harsh environments.

[0105] In this embodiment, the mechanical anchor 4 is made of stainless steel.

[0106] The design principle for the stress of the closed-cell foam buffer layer 3 adopts the following formula: E c ·e allow ≥ s design ; Wherein, Ec is the equivalent compressive elastic modulus of the closed-cell foam buffer layer 3. e allow To allow for an upper limit of compressive strain, the e allow The value ranges from 30% to 50%. s design This is the design stress for the closed-cell foam buffer layer 3. This formula ensures that, in practical applications, the material of the closed-cell foam buffer layer 3 can provide sufficient buffering under frost heave pressure, preventing material failure.

[0107] In this embodiment, the e allow The value is a conservative 30%, which is the calculated value of the equivalent expansion pressure.

[0108] Under normal operating conditions, the liquid nitrogen inside the superconducting cable 7 is kept at a low temperature to ensure the superconducting performance of the cable. When a liquid nitrogen leak occurs, the temperature around the superconducting cable 7 drops rapidly, causing the water inside the cable channel to freeze and expand.

[0109] The increased volume of water upon freezing and expansion can exert compressive stress on the concrete pipe 1 within the superconducting cable channel, potentially causing the concrete to crack. To avoid this problem, polyethylene closed-cell foam board, as a closed-cell foam buffer layer 3, plays a crucial role in this process.

[0110] When ice expands, the closed-cell foam buffer layer 3, with its high compressibility (30%-50%), undergoes elastic deformation, absorbing and mitigating frost heave pressure. The closed-cell structure of the closed-cell foam buffer layer 3 effectively isolates moisture, preventing it from penetrating into the layer and causing performance degradation. Its excellent low-temperature toughness ensures that it does not crack even at extremely low temperatures, allowing it to maintain a stable buffering effect over a long period.

[0111] This structural design significantly reduces the pressure exerted on the concrete pipe 1 by the expansion of water upon freezing, ensuring the integrity of the concrete structure and guaranteeing the normal operation and safety of the superconducting cable 7.

[0112] The composite system of "closed-cell foam buffer layer + inner lining layer" can significantly reduce the equivalent peak stress and stress concentration on the inner wall of concrete pipe 1, and suppress the generation of concrete cracks caused by frost heave.

[0113] When liquid nitrogen leaks, the temperature drops sharply, causing the water to freeze and the ice to expand, generating radial expansion pressure on the inner wall of the concrete pipe 1.

[0114] The closed-cell foam buffer layer 3 provides an "energy storage-release" buffering mechanism with a microporous compressible structure, converting expansion pressure into elastic deformation and spreading it along the surface; the inner liner layer 6 forms a smooth friction-reducing interface, further dispersing the stress peak.

[0115] When the temperature rises or during maintenance and replacement, the closed-cell foam buffer layer 3 rebounds and re-adheres to the inner lining layer 6, maintaining the integrity of the protective interface and extending the service life of the structure.

[0116] Example 2 like Figure 1 As shown, for ease of explanation, the components such as the base coating 2, mechanical anchor 4, flexible sealant 5, and flow guide 8 are not individually labeled or illustrated in the figure; the specific structures of the above components are consistent with those described in Embodiment 1, and are all considered as part of this embodiment. This embodiment provides an ultra-low temperature anti-freezing cracking structure for concrete pipes used in superconducting cable channels. Based on Embodiment 1, this embodiment also includes the following settings: The ultra-low temperature anti-freezing and cracking structure of the concrete pipe also includes a bracket 9; the bracket 9 can be made of stainless steel; the bracket 9 is used to support and position the superconducting cable 7, so that the axis of the superconducting cable 7 is kept at the designed position of the channel section.

[0117] The two ends of the bracket 9 are supported by the inner wall of the concrete pipe 1.

[0118] Support 9 possesses excellent corrosion resistance, enabling long-term stable operation under low temperature, high humidity, and harsh environmental conditions. The support ensures the structural stability of the superconducting cable channel and effectively distributes and transfers external loads, preventing deformation or displacement of the superconducting cable channel due to external forces. By properly configuring support 9, the safe operation of the entire piping system can be ensured even under extreme conditions such as liquid nitrogen leaks.

[0119] Example 3 like Figure 3 As shown (e.g.) Figure 3 (Steps A to H) In this embodiment, a construction method for an ultra-low temperature frost-resistant structure for concrete ducts used in superconducting cable channels is provided. This construction method is used for the construction of the ultra-low temperature frost-resistant structure for concrete ducts used in superconducting cable channels in Embodiment 1 or Embodiment 2. The construction method includes the following steps: A. Base treatment: Clean the inner wall of concrete pipe 1, dry it, level it and repair defects to obtain the treated concrete pipe 1; B. Apply primer coating 2: Apply primer coating 2 evenly to the inner wall of the treated concrete pipe 1 and cure according to the product instructions; C. Adhere closed-cell foam buffer layer 3: After the base layer 2 has cured, adhere the closed-cell foam buffer layer 3 in sections according to the circumference of the concrete pipe 1, and make the joints of adjacent sections staggered and tightly fitted. D. Mechanical anchoring: After the closed-cell foam buffer layer 3 is pasted and adjusted into place, holes are drilled according to the design spacing, and the closed-cell foam buffer layer 3 is mechanically anchored to the concrete pipe 1 by expansion anchors and stress distribution shims. E. Install the inner lining layer 6: After the closed-cell foam buffer layer 3 is anchored, the prefabricated inner lining plate or roll material is assembled on the inner side of the closed-cell foam buffer layer 3 to form the inner wall of the cable channel, i.e., the inner lining layer 6; apply flexible sealant 5 to the longitudinal seams, circumferential seams and anchor bolt protrusions of the inner lining layer 6 to seal the gaps. F. Sealing and finishing at nodes and ports: At the connection points (nodes) between the concrete pipe 1 and the inspection well, branch pipe fittings or equipment, and at the openings (ports) at the ends of the concrete pipe 1, the cross-sections of the closed-cell foam buffer layer 3 and the inner lining layer 6 are sealed with flexible sealant 5 to ensure continuous sealing and smooth transition.

[0120] G. Acceptance testing: Conducting tests on appearance, adhesion, ball passing, and video verification, etc. H. Operation and Maintenance Linkage: The ultra-low temperature anti-freezing and cracking structure of the concrete duct used for superconducting cable channels is linked with gas and temperature monitoring devices for segmented maintenance in case of abnormalities. Oxygen concentration sensors and temperature sensors are installed inside the concrete duct to link ventilation and shutdown. When a sharp drop in temperature or abnormal oxygen concentration caused by liquid nitrogen leakage is detected, segmented shutdown and maintenance are triggered, and damaged closed-cell foam buffer layer 3 and inner lining layer 6 are replaced if necessary. The operation and maintenance linkage specifically includes the following process: monitoring parameters such as oxygen and nitrogen content and temperature of the gas (including air and nitrogen mixture formed after liquid nitrogen leakage) inside the concrete duct 1. When abnormally low oxygen or abnormally low temperature is detected, forced ventilation or segmented ventilation is initiated in conjunction with the ventilation system; when it is confirmed through assessment that the local closed-cell foam buffer layer 3 and / or inner lining layer 6 are damaged due to frost heave or ultra-low temperature effects, the segmented structure is dismantled and replaced.

[0121] Example 4 like Figure 4 As shown, this embodiment provides a construction method for an ultra-low temperature frost-resistant structure for concrete ducts used in superconducting cable channels. This construction method is used for the construction of ultra-low temperature frost-resistant structures for concrete ducts used in superconducting cable channels in Embodiment 1 or Embodiment 2. Based on Embodiment 3, the construction method of this embodiment has the following steps: When constructing the elbow joint, the closed-cell foam buffer layer 3 can be assembled by staggered joints of arc-shaped cut blocks (as shown in 4a).

[0122] When constructing the elbow joint, the inner lining 6 can be formed by prefabricated bends or roll forming (as shown in 4b).

[0123] Key corner areas can be reinforced with multiple layers (as shown in 4c), and the gaps can be sealed with continuous flexible sealant 5 (as shown in 4d) to ensure a smooth transition, continuous sealing, and prevention of stress concentration.

[0124] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A low-temperature anti-freezing and crack-resistant structure for concrete ducts used in superconducting cable channels, characterized in that, The ultra-low temperature anti-freezing cracking structure of the concrete pipe includes a concrete pipe (1), a base coating (2), a closed-cell foam buffer layer (3), mechanical anchors (4), flexible sealant (5), and an inner lining layer (6). The concrete pipe (1), primer (2), inner lining (6), flexible sealant (5), and closed-cell foam buffer layer (3) are arranged sequentially from the outside to the inside. The mechanical anchor (4) is connected from the inside out to the closed-cell foam buffer layer (3), flexible sealant (5), inner lining layer (6), primer layer (2), and concrete pipe (1). The inner lining (6) extends along the inner wall of the concrete pipe (1) to form a circumferential closed cylindrical structure; The closed-cell foam buffer layer (3) is located inside the inner lining layer (6) and continuously or in sections surrounds the superconducting cable (7) along the circumference of the concrete pipe (1).

2. The ultra-low temperature anti-freezing and cracking structure for concrete ducts used in superconducting cable channels according to claim 1, characterized in that, The ultra-low temperature anti-freezing cracking structure of the concrete pipe also includes a flow guide (8). The guide channel (8) is formed in the concrete pipe (1); The flow channel (8) is used for flow guidance and drainage.

3. The ultra-low temperature anti-freezing and cracking structure for concrete ducts used in superconducting cable channels according to claim 1, characterized in that, The concrete pipe (1) is made of concrete, and the strength grade of the concrete reaches C25 or above. The material of the base coating (2) is one or more of epoxy interface agent or polyurethane interface agent; the base coating (2) is used for interface treatment, sealing concrete pores and enhancing the bonding strength between the closed-cell foam buffer layer (3) and the inner wall of the concrete pipe (1).

4. The ultra-low temperature anti-freezing and cracking structure for concrete ducts used in superconducting cable channels according to claim 1, characterized in that, The closed-cell foam buffer layer (3) is made of one or more of cross-linked polyethylene closed-cell foam or EVA closed-cell foam; the closed-cell foam buffer layer (3) is used for buffering and absorbing the volume expansion energy caused by freezing under extremely low temperature conditions. The inner lining (6) is made of one or more of PVC, PP and HDPE materials, and is used for waterproofing and friction protection.

5. The ultra-low temperature anti-freezing and cracking structure for concrete ducts used in superconducting cable channels according to claim 4, characterized in that, The cross-linked polyethylene closed-cell foam is one or more of PE, XPE or IXPE.

6. The ultra-low temperature anti-freezing and cracking structure for concrete ducts used in superconducting cable channels according to claim 1, characterized in that, The mechanical anchor (4) includes an expansion anchor and a gasket. The expansion anchor passes through the closed-cell foam buffer layer (3), flexible sealant (5), inner lining layer (6), and primer layer (2) and is connected to the concrete pipe (1). The gasket is placed inside the closed-cell foam buffer layer (3). The flexible sealant (5) is one or more of silicone sealant or MS sealant; The mechanical anchors (4) and flexible sealant (5) are used to ensure the stability and sealing of the overall concrete pipe structure against freezing and cracking at extremely low temperatures; The mechanical anchor (4) is made of one or more of stainless steel or galvanized components.

7. The ultra-low temperature anti-freezing and cracking structure for concrete ducts used in superconducting cable channels according to claim 1, characterized in that, The design principle for the stress of the closed-cell foam buffer layer (3) adopts the following formula: E c ·ε allow ≥ σ design ； Wherein, Ec is the equivalent compressive elastic modulus of the closed-cell foam buffer layer (3). ε allow To allow for an upper limit of compressive strain, the ε allow The value ranges from 30% to 50%. σ design The design stress for the closed-cell foam buffer layer (3).

8. A construction method for a low-temperature frost-resistant structure for a concrete duct used in superconducting cable channels as described in any one of claims 1-7, characterized in that, The construction method includes the following steps: A. Base treatment: Clean the concrete pipe (1), dry, level, and repair defects to obtain the treated concrete pipe (1); B. Applying a primer coating (2): Apply a primer coating (2) to the treated concrete pipe (1); C. Paste closed-cell foam buffer layer (3): After applying the primer layer (2), paste the closed-cell foam buffer layer (3) in sections according to the circumference of the concrete pipe (1); D. Mechanical anchoring: After pasting the closed-cell foam buffer layer (3), install mechanical anchors (4) to enhance the anti-peeling performance; E. Install the inner lining: After installing the mechanical anchors (4), assemble the inner lining (6) and apply flexible sealant (5) to the longitudinal and circumferential seams. F. Sealing and finishing: After applying flexible sealant (5), the nodes and ports are treated with flexible sealing.

9. The construction method according to claim 8, characterized in that, When constructing the elbow joint, the closed-cell foam buffer layer (3) is assembled by staggered joints of arc-shaped cut blocks; When constructing the elbow joint, the inner lining (6) is formed by prefabricated bends or roll forming.

10. The construction method according to claim 8, characterized in that, When constructing the elbow joint, a multi-layered thickened area is set in the key corner area, and the gap is sealed with continuous flexible sealant (5) to ensure a smooth transition, continuous sealing, and prevent stress concentration.

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