Anti-frost heaving structure of cable trench of substation in permafrost region

Abstract

The utility model discloses a frozen earth area substation cable trench anti -frost heaving structure, including the concrete wall body of cable trench both sides and the bottom plate of lower part, the inside concrete wall body includes the rigid framework of double -layer reinforcement setting from inside to outside, buffer framework, the outside of concrete wall body is provided with the heat preservation layer, and the top cover of concrete wall body is connected with a plurality of cover plates through sealing batten connection, and the longitudinal interval of concrete wall body is provided with omega type expansion joint assembly, and the utility model discloses through setting the rigid framework and buffer framework of double -layer reinforcement, the heat preservation layer of outside, sealing cover plate connection structure and omega type expansion joint assembly, can effectively resist frost heaving force, prevent wall body and crack and bottom plate on the vault, and automatic drainage system can discharge accumulated water in time, prevent base soil frost heaving, has the advantages such as stable structure, long service life, low construction cost.

Description

Technical Field

[0001] This utility model relates to the field of cable trenches, specifically to a frost-resistant structure for cable trenches in substations located in permafrost regions. Background Technology

[0002] Cable trenches in substations located in permafrost regions face severe risks of frost heave damage. In northern regions, the freezing depth of silty soil reaches up to 1.84 meters. When the soil freezes in winter, moisture migration forms ice lenses, generating frost heave forces as high as 500-800 kPa, leading to a series of problems such as cracking of cable trench walls, arching of the base plate, and failure of expansion joints. Although the flexible joint sealant boards (such as polyethylene foam boards) used in existing technologies can buffer some of the frost heave force, they have the fundamental flaw of not being able to block the moisture migration channels, and are prone to compression failure under the high stress environment of silty soil.

[0003] Traditional replacement methods require placing the foundation below the frost depth, resulting in excavation depths exceeding 3 meters. This not only increases construction costs by over 40% but also compromises the stability of the original foundation. Under freeze-thaw cycles, conventional reinforced concrete structures experience accelerated steel corrosion and spalling of the concrete cover, shortening the structural lifespan to 10-15 years. In particular, existing technologies lack systematic solutions to secondary frost heave caused by water seepage and freezing at cable trench cover joints, and frost heave of the foundation soil due to poor drainage in the base slab. These problems seriously threaten the structural safety and service life of cable trenches in substations in permafrost regions, necessitating the development of frost-heave-resistant structural systems with multiple protective functions. Utility Model Content

[0004] To address the aforementioned problems, this utility model provides a frost-resistant structure for cable trenches in substations located in permafrost regions.

[0005] This utility model is achieved through the following technical solution:

[0006] This application provides a frost-resistant structure for cable trenches in substations in permafrost areas. The technical solution is as follows: it includes concrete walls on both sides of the cable trench and a bottom slab at the bottom. The interior of the concrete walls includes a rigid skeleton with double-layer reinforcement from the inside out and a buffer skeleton. An insulation layer is provided on the outside of the concrete walls. The top of the concrete walls is covered with several cover plates connected by sealing strips. Ω-shaped expansion joint components are arranged longitudinally at intervals in the concrete walls.

[0007] Furthermore, this application also proposes that the rigid frame and the buffer frame be connected and fixed by S-shaped tie bars.

[0008] Furthermore, this application also proposes that the insulation layer includes a polyurethane foam board bonded and fixed to the outside of the concrete wall, and an EPDM rubber buffer layer is fixed to the outside of the polyurethane foam board.

[0009] Furthermore, this application also proposes that the sealing strip includes an M-shaped metal strip and a rubber strip connected to its lower part, with the two sides of the M-shaped metal strip snapped into grooves opened on the top of two adjacent cover plates, and the rubber strip set inside the joint between the two adjacent cover plates.

[0010] Furthermore, this application also proposes that the Ω-shaped expansion joint assembly includes an open expansion ring and bent portions at both ends, the bent portions being fixedly connected to pre-embedded connectors in the adjacent concrete wall.

[0011] Furthermore, this application also proposes to install an embedded rubber waterstop at the junction of the concrete wall and the base slab.

[0012] Furthermore, this application also proposes that an automatic drainage system be provided under the base plate, the automatic drainage system including a gravel drainage layer laid under the base plate, a plurality of perforated corrugated pipes for drainage being buried in the gravel drainage layer, and seepage holes being spaced longitudinally on the base plate.

[0013] Compared with existing technologies, the advantages of this utility model are: by setting up a rigid skeleton and buffer skeleton with double reinforcement, an outer insulation layer, a sealing cover plate connection structure and an Ω-shaped expansion joint assembly, this utility model can effectively resist frost heave force, prevent wall cracking and base plate arching, and at the same time, the automatic drainage system can drain accumulated water in time to prevent the foundation soil from freezing heave. It has the advantages of stable structure, long service life and low construction cost. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of this utility model;

[0015] Figure 2 This is a schematic diagram of the cover plate connection in this practical application;

[0016] Figure 3 This is a top view of the cable trench expansion joint connection in this practical application.

[0017] In the diagram: 1. Concrete wall; 101. Embedded connector; 102. Expansion ring; 103. Bending part; 2. Rigid frame; 3. Buffer frame; 4. Base plate; 5. Rubber waterstop; 6. Insulation layer; 7. Crushed stone drainage layer; 8. Seepage hole; 9. Perforated corrugated pipe; 10. Cover plate; 11. M-shaped metal strip; 12. Rubber strip. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments:

[0019] like Figure 1-3As shown, this application proposes a frost-resistant structure for cable trenches in substations in permafrost areas, including concrete walls on both sides of the cable trench and a bottom slab at the bottom. The concrete walls include a rigid skeleton with double-layer reinforcement from the inside out and a buffer skeleton. An insulation layer is provided on the outside of the concrete walls. Several cover plates connected by sealing strips are attached to the top of the concrete walls. Ω-shaped expansion joint assemblies are arranged longitudinally at intervals in the concrete walls.

[0020] The concrete walls utilize C35 frost-resistant concrete (frost resistance grade F300). The inner rigid framework is constructed with Φ16@150mm longitudinal reinforcement and Φ12@200mm transverse reinforcement tied together, while the outer buffer framework consists of Φ14@200mm longitudinal reinforcement and Φ10@250mm transverse reinforcement tied together, forming a dual-layer load-bearing system of "rigid framework + flexible buffer." The two layers of reinforcement are spaced 50mm apart and connected by S-shaped tie bars (Φ8@600mm) to enhance overall bending stiffness. This design increases the wall's crack resistance by 40% and allows it to withstand 800kPa frost heave. The insulation layer preferably uses materials with a density ≥40kg / m³. 3 The rigid polyurethane foam board, 100mm thick, is bonded to the concrete wall using polyurethane adhesive. The sealing strip can be made of 1.5mm thick 304 stainless steel with an M-shaped cross-section, and the lower connecting rubber strip is made of neoprene rubber with a Shore hardness of 60±5. The expansion ring of the Ω-shaped expansion joint assembly is cold-bent from 3mm thick 316 stainless steel plate, with an opening width of 15mm. The bent part is fixed to the pre-embedded connector by welding.

[0021] This technical solution maintains structural stability through a rigid frame and dissipates frost heave stress through a buffer frame; the combined effect of these two components can resist frost heave shear forces of up to 800 kPa. The insulation layer effectively blocks cold energy conduction, keeping the frost depth within 1.2 m. The sealing strip structure of the cover plate allows for ±5 mm of horizontal displacement without compromising the seal. The Ω-shaped expansion joint absorbs 15 mm of longitudinal deformation, preventing temperature stress concentration. Compared with existing technologies, this composite structural system achieves graded dissipation of frost heave force, solving the problem of cracking and failure of traditional structures under frost heave cycles, and extending the structural lifespan to over 30 years. Specifically, the synergistic effect of the rigid and buffer frames allows the structure to maintain overall stability while dissipating energy through plastic deformation when subjected to frost heave force; this is the key innovation in solving frost heave damage.

[0022] Furthermore, this application also proposes that the rigid frame and the buffer frame be connected and fixed by S-shaped tie bars.

[0023] S-shaped tie bars can be made of cold-rolled ribbed steel bars or hot-rolled plain round steel bars, with a bending radius preferably 5-8 times the diameter of the steel bar. As a preferred embodiment, the spacing between the crests and troughs of the S-shaped tie bars is controlled within the range of 80-120mm to ensure sufficient deformation capacity. Specifically, connection and fixing methods include, but are not limited to: welding both ends of the S-shaped tie bars to the transverse steel bars of the rigid frame and the buffer frame respectively using resistance spot welding; or mechanically anchoring the S-shaped tie bars to the two layers of frame using special clamps; or binding them with wire before concrete pouring. The spacing of the S-shaped tie bars can be adjusted according to the magnitude of the frost heave force; in areas where the frost heave force is greater than 600kPa, the spacing can be increased to 400mm.

[0024] This technical solution utilizes the elastic deformation characteristics of S-shaped tie bars to allow a relative displacement of 5-15mm between the rigid and buffer skeletons under frost heave force, effectively releasing stress. Compared to traditional straight bar connections, the geometry of the S-shaped tie bars provides better ductility and fatigue performance, maintaining elasticity even at -30℃. Test data shows that with this connection method, the crack width in the concrete wall under 800kPa frost heave force can be controlled within 0.2mm, and no significant damage was observed at the connection points after 50 freeze-thaw cycles. The resulting graded frost heave resistance system maintains the structural integrity while avoiding brittle concrete failure caused by completely rigid connections.

[0025] Furthermore, this application also proposes that the insulation layer includes a polyurethane foam board bonded and fixed to the outside of the concrete wall, and an EPDM rubber buffer layer is fixed to the outside of the polyurethane foam board.

[0026] Polyurethane foam boards can be bonded and fixed through spray foaming or prefabrication. Spray foaming allows for a seamless bond between the foam and the concrete wall, while prefabrication uses a special polyurethane adhesive. The thickness of the EPDM rubber buffer layer is preferably 10-20mm, and it is bonded to the polyurethane foam board using neoprene rubber adhesive. Its Shore hardness is controlled at 50-60HA to balance buffering performance and durability. As a preferred embodiment, the surface of the EPDM rubber buffer layer can be textured to enhance frictional resistance with the external backfill soil.

[0027] This technical solution utilizes the closed-cell structure of polyurethane foam board to block moisture migration pathways, achieving a thermal conductivity below 0.024 W / (m·K) and maintaining elasticity even at -30℃. The EPDM rubber buffer layer absorbs freeze-thaw deformation using its over 300% elongation at break, dissipating stress waves through entropic elasticity of the molecular chains. The resulting rigid-flexible composite structure ensures that when the insulation layer is subjected to 800 kPa of freeze-thaw force, the polyurethane foam board compression rate does not exceed 5%, and the EPDM rubber layer can offset over 90% of the freeze-thaw stress through a 15% deformation in the thickness direction. Compared to single polyethylene foam board, this structure maintains intact interfacial adhesion after 50 freeze-thaw cycles, with an insulation performance degradation rate of less than 3%, solving the technical problem of compression failure of traditional flexible materials under high stress environments.

[0028] Furthermore, this application also proposes that the sealing strip includes an M-shaped metal strip and a rubber strip connected to its lower part, with the two sides of the M-shaped metal strip snapped into grooves opened on the top of two adjacent cover plates, and the rubber strip set inside the joint between the two adjacent cover plates.

[0029] Specifically, the M-shaped metal strip can be made of 304 stainless steel or galvanized steel sheet, with a preferred thickness of 1.2-2.0 mm. The M-shaped opening angle is controlled within the range of 90-120 degrees to ensure sufficient elastic deformation space. The rubber strip can be made of neoprene rubber or EPDM rubber, with a preferred trapezoidal or semi-circular cross-sectional shape to enhance the fit with the joint. As a preferred embodiment, the metal strip and the rubber strip are chemically bonded through a vulcanization process. The cover plate groove depth is designed to be 8-12 mm, and the groove width is 1-2 mm wider than the strip flange to allow for thermal expansion and contraction.

[0030] To address this, the technical solution utilizes a rigid interlocking structure with an M-shaped metal strip to resist vertical displacement caused by frost heave, while simultaneously compensating for horizontal displacement differences between the cover plates using the elastic deformation of the rubber material. The composite structure of metal and rubber forms a dual sealing mechanism: the metal strip prevents overall dislocation through mechanical locking, while the rubber strip maintains a seal at the joint through continuous elastic pressure. The M-shaped cross-section design causes the strip to generate a downward component force when subjected to frost heave, enhancing its interlocking effect with the cover plates. Compared to traditional single-material seals, this structure maintains stable sealing performance within a temperature range of -40℃ to 60℃ and can withstand more than 200 freeze-thaw cycles without failure. Experimental data shows that under simulated frost heave conditions, the water seepage rate of this sealing structure is less than 0.01 L / (min·m), and the displacement compensation capacity reaches ±5 mm.

[0031] Furthermore, this application also proposes that the Ω-shaped expansion joint assembly includes an open expansion ring and bent portions at both ends, the bent portions being fixedly connected to pre-embedded connectors in the adjacent concrete wall.

[0032] The open expansion ring can be made of stainless steel with a wall thickness of 3mm, a wave height of 50mm, a wave pitch of 80mm, and an expansion / contraction range of ±50mm. The open design of the expansion ring allows for lateral displacement and can absorb lateral deformation caused by frost heave. The fixed connection between the bend and the embedded connector can be welded; the embedded connector is a 10mm thick steel plate with a weld strength of not less than 200MPa. As a preferred embodiment, the expansion ring and the bend can be integrally molded to ensure structural integrity. An Ω-shaped expansion joint is installed every 15m along the longitudinal direction of the cable trench, effectively absorbing 80% of the frost heave deformation.

[0033] This technical solution combines metal components with specific geometric shapes and fixing methods to provide sufficient deformation margin while ensuring structural continuity. The open design of the expansion ring absorbs lateral deformation, while the rigid connection between the bend and the embedded part maintains the longitudinal structural integrity. Together, they achieve effective expansion and contraction compensation under frost heave deformation. Compared with existing technologies, this solution avoids cracking caused by stress concentration, improving the reliability and durability of the expansion joint. Specifically, by precisely controlling the geometric parameters and material properties of the expansion joint, the structural functional integrity can be maintained under frost heave deformation conditions.

[0034] Furthermore, this application also proposes to install an embedded rubber waterstop at the junction of the concrete wall and the base slab (300mm wide, 60±5 Shore A hardness), with the joint using hot vulcanization to ensure that the joint is leak-proof.

[0035] Furthermore, this application also proposes an automatic drainage system installed under the base plate, which includes a gravel drainage layer laid under the base plate, a plurality of perforated corrugated pipes for drainage buried in the gravel drainage layer, and seepage holes spaced longitudinally on the base plate.

[0036] The crushed stone drainage layer can use graded crushed stone, preferably with a particle size range of 5-20mm and a thickness of 200-400mm, with 300mm being a typical implementation thickness. The crushed stone layer must meet the technical requirement of a permeability coefficient greater than 1×10-2cm / s. Perforated corrugated pipes can be made of HDPE material, with pipe diameters of DN80-DN120, with DN100 being the preferred specification, and an opening ratio of 2%-5%, preferably 3%. The corrugated pipes are laid with a slope of 0.3%-1%, with 0.5% being a typical slope value. The diameter of the seepage holes should be 20-50mm, spaced 1-2m apart, arranged in a quincunx pattern. The drainage layer can be wrapped with a composite geomembrane, made of 200g / m³. 2 The system is composed of geotextile and 0.5mm thick HDPE membrane, with seams welded by hot-melt welding. The drainage system is connected to the substation drainage network at its terminal, with a pipe diameter of not less than DN150.

[0037] This technical solution addresses frost heave by constructing an active drainage system. The crushed stone drainage layer forms highly permeable channels, and when combined with perforated corrugated pipes, it increases drainage efficiency to more than three times that of conventional structures, with a measured drainage volume of 0.8 L / (s·m). Infiltration holes allow water accumulated on the foundation slab to be quickly diverted into the drainage layer, controlling the water level to 200 mm below the foundation slab, effectively eliminating the source of moisture for frost heave. A composite geomembrane blocks external moisture infiltration, reducing soil saturation to below 85%. Freeze-thaw cycle tests have verified that this structure reduces frost heave force by 60%-70%, and controls the camber on the foundation slab to within 5 mm, a reduction of more than 80% compared to traditional structures. Compared to the replacement method, the construction depth is reduced by 50%, the project cost is reduced by 35%, and the stability of the original foundation structure is maintained.

[0038] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed utility model. The scope of protection of this utility model is defined by the appended claims and their equivalents.

Claims

1. A frost-resistant structure for cable trenches in substations located in frozen soil areas, comprising concrete walls (1) on both sides of the cable trench and a base plate (4) at the bottom, characterized in that: The concrete wall (1) includes a rigid frame (2) with double reinforcement from the inside to the outside and a buffer frame (3). The concrete wall (1) is provided with an insulation layer (6) on the outside. The top of the concrete wall (1) is covered with several cover plates (10) connected by sealing strips. The concrete wall (1) is provided with Ω-shaped expansion joint assemblies at longitudinal intervals.

2. The frost-resistant structure for cable trenches in permafrost areas according to claim 1, characterized in that: The rigid frame (2) and the buffer frame (3) are connected and fixed by S-shaped tie bars.

3. The frost-resistant structure for cable trenches in permafrost areas according to claim 1, characterized in that: The insulation layer includes a polyurethane foam board that is bonded and fixed to the outside of the concrete wall (1), and an EPDM rubber buffer layer is fixed to the outside of the polyurethane foam board.

4. The frost-resistant structure for cable trenches in permafrost areas according to claim 1, characterized in that: The sealing strip includes an M-shaped metal strip (11) and a rubber strip (12) connected to its lower part. The two sides of the M-shaped metal strip (11) are engaged in the grooves opened on the top of two adjacent cover plates (10), and the rubber strip (12) is set inside the joint of two adjacent cover plates (10).

5. The frost-resistant structure for cable trenches in permafrost areas according to claim 1, characterized in that: The Ω-shaped expansion joint assembly includes an open expansion ring (102) and bent portions (103) at both ends, wherein the bent portions (103) are fixedly connected to the pre-embedded connectors (101) of the adjacent concrete wall (1).

6. The frost-resistant structure for cable trenches in permafrost areas according to claim 1, characterized in that: An embedded rubber waterstop (5) is installed at the junction of the concrete wall (1) and the base plate (4).

7. The frost-resistant structure for cable trenches in permafrost areas according to claim 1, characterized in that: An automatic drainage system is provided at the bottom of the base plate (4). The automatic drainage system includes a gravel drainage layer (7) laid at the bottom of the base plate (4). Multiple perforated corrugated pipes (9) for drainage are buried in the gravel drainage layer (7). The base plate (4) has longitudinally spaced seepage holes (8).

Images