Anti-frost heaving and pressure releasing structure of steel corrugated plate bridge-tunnel structure in seasonal frozen region and construction method thereof

Abstract

The application of the frost heaving yielding structure of the steel corrugated plate bridge and tunnel structure in the seasonal freezing area and the construction method thereof belong to the technical field of highway and railway tunnel and culvert engineering. The application constructs a progressive yielding energy dissipation system of the cooperative work of the flexible sliding layer, the yielding backfill area, the composite insulation layer and the yielding anchorage node. The flexible sliding layer weakens the soil joint interface constraint to realize the peak clipping of the frost heaving stress, the yielding backfill area provides the controllable compression space to dissipate the frost heaving deformation of the soil, the composite insulation layer composed of the inner insulation board and the outer reflective film slows down the strength and depth of the freeze-thaw action, the yielding anchorage node with the long circular hole realizes the ring and longitudinal coordinated sliding deformation of the structure, the four-stage structure time sequence cooperates and covers the full frost heaving stress area without the functional blind area. The design service life of the bridge and tunnel structure can be prolonged from 15-20 years to more than 40 years, the later operation and maintenance frequency is greatly reduced, and the application is suitable for various steel corrugated pipe culverts and corrugated plate open tunnel engineering in the seasonal freezing area.

Description

Technical Field

[0001] This invention belongs to the technical field of highway and railway tunnel and culvert engineering, and in particular relates to the anti-frost heave and pressure relief structure of steel corrugated plate bridge and tunnel structures in seasonally frozen areas and its construction method. Background Technology

[0002] Corrugated steel sheets are increasingly used in bridge and tunnel projects in seasonally frozen regions due to their excellent flexibility, rapid construction, and minimal ground disturbance. Their thin-shell spatial structure is adaptable to large deformations, and compared to reinforced concrete culverts, they can avoid culvert damage caused by ground deformation in frozen soil and expansive soil. However, the severe freeze-thaw cycles in seasonally frozen regions significantly limit the long-term service life of corrugated steel sheets. The structure simultaneously bears traffic loads and coupled frost heave loads. The frost heave force is determined by the soil temperature and humidity field and the structural stiffness. During the freezing period, the soil expands as it freezes, generating lateral and radial pressure on the corrugated sheets. Peak frost heave forces can easily cause plastic deformation of the sheets, and repeated freeze-thaw cycles can lead to a series of problems such as fatigue cracking of the steel sheets, weld damage, bolt loosening, and lining leakage.

[0003] Existing frost heave prevention designs for corrugated steel plates mostly adopt an anti-frost heave approach, relying on thicker steel plates, denser bolts, and enhanced backfill compaction to increase overall rigidity, using a rigid-to-rigid method to resist frost heave. However, this method has significant drawbacks: the greater the structural rigidity, the stronger the constraint on soil frost heave deformation, the more intense the interaction between soil and structure, the further increase in peak frost heave stress, and repeated freeze-thaw cycles can easily cause permanent deformation of the culvert, jeopardizing traffic safety. Existing frost heave prevention measures are mainly divided into two categories: passive insulation and foundation replacement. In engineering, XPS insulation boards are often laid to block heat exchange, or polyurethane corrugated board insulation linings are used to achieve passive insulation; patent CN121295640A uses gravel replacement and short pile foundations to adapt to foundation deformation to mitigate damage. However, all of the above technologies have inherent shortcomings: First, relying solely on rigid resistance or passive insulation cannot effectively channel and release frost heave stress. In strata rich in groundwater and highly sensitive to frost heave, insulation materials only delay the freezing process, failing to eliminate frost heave force, resulting in continuous load on the corrugated plates. Second, the joints of the corrugated plates are rigidly bolted, leading to uneven stress distribution across the entire cross-section under frost heave pressure, stress concentration in the bolt holes, and a high risk of steel plate tearing and bolt shear failure. Third, there is a lack of a system for coordinating the release of pressure and soil deformation. Existing structures lack a controllable pressure relief mechanism, cannot absorb soil deformation or dissipate peak stress after frost heave force exceeds limits, and cannot self-restore after thawing; currently, there are no mature structural solutions for this.

[0004] In summary, there is an urgent need for a new type of frost-resistant structure that can transform the approach of "resisting frost heave" into one of "embracing frost heave". Through the core mechanism of "actively yielding pressure, releasing stress, absorbing deformation, and self-restoring function", the frost damage failure problem of corrugated steel plate bridge and tunnel structures in seasonally frozen areas can be fundamentally solved. Summary of the Invention

[0005] This invention aims to solve the technical problems of permanent structural deformation, weld cracking, joint failure, and leakage caused by repeated frost heave forces in corrugated steel plate bridge and tunnel structures in seasonally frozen regions under freeze-thaw cycles. Addressing the shortcomings of existing technologies that focus on "resisting frost heave" in their design philosophy but fail to fundamentally eliminate frost heave damage, this invention provides a frost heave-resistant pressure-relief structure and construction method suitable for corrugated steel plate bridge and tunnel structures in seasonally frozen regions. Through the systematic integration of a three-layer composite pressure-relief structure—a flexible sliding layer, a composite insulation layer, and a pressure-relief backfill zone—this invention overturns the traditional "rigid-on-rigid" design model, transforming "resisting frost heave" into "embracing frost heave." This achieves graded release of frost heave stress, orderly reservation of deformation space, and self-recovery of the structure during freeze-thaw cycles, ensuring the long-term stability and service durability of the corrugated steel plate structure in seasonally frozen regions.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a frost-resistant and pressure-relief structure suitable for steel corrugated plate bridge and tunnel structures in seasonally frozen areas, characterized in that: the frost-resistant and pressure-relief structure is arranged between the outer wall of the steel corrugated plate and the surrounding soil, and a flexible sliding layer, a composite insulation layer and a pressure-relief backfill area are stacked sequentially from the inside to the outside along the radial direction from the outer wall of the steel corrugated plate to the surrounding soil. The flexible sliding layer is set in close contact with the outer wall of the corrugated steel plate. It is made of elastic material and is non-bonded to the outer wall of the corrugated steel plate. It can undergo controllable relative sliding along the outer wall of the corrugated steel plate under the action of frost heave stress. The composite insulation layer is disposed on the outside of the flexible sliding layer and is composed of at least one insulation board and at least one reflective film. The insulation board layer is used to block the transfer of soil heat to the steel corrugated plate to reduce the intensity and depth of the freeze-thaw cycle, and the reflective film layer is used to enhance the interfacial thermal resistance. The pressure relief backfill area is filled between the outside of the composite insulation layer and the surrounding soil. It is filled with backfill material with high compressibility and is used to absorb the deformation and displacement of the soil during the frost heave process, providing a pressure relief space that can dissipate frost heave stress. Adjacent corrugated steel plates are connected by a pressure-relief anchoring node. The pressure-relief anchoring node is located at the longitudinal lap joint and circumferential joint of the corrugated steel plates and includes an elongated bolt hole, a connecting bolt, and an elastic washer. The elongated bolt hole is located at the lap end of the corrugated steel plate, and the connecting bolt passes through the elongated bolt hole to achieve lap fixation. The elastic washer is sandwiched between the bolt head and the corrugated steel plate.

[0007] Preferably, the elastic material of the flexible sliding layer is composed of one or more of vulcanized rubber sheets, recycled rubber granule sheets, thermoplastic elastomer sheets or polyurethane elastomer sheets, with a thickness of 5~15mm and an operating temperature range of not less than -50℃~+60℃.

[0008] Preferably, the surface of the flexible sliding layer is provided with fine patterns or bumps to control the sliding start threshold. The sliding start threshold is preset so that the interface remains stable when the frost heave stress is lower than the start threshold, and sliding occurs when the frost heave stress exceeds the start threshold.

[0009] Preferably, the insulation board of the composite insulation layer is an extruded polystyrene foam board with a thermal conductivity of not more than 0.030 W / m·K and a compressive strength of not less than 250 kPa; the reflective film is an aluminized polyester film or an aluminum foil-coated nonwoven fabric with a thermal reflectivity of not less than 85%, and the insulation board layer is set close to the flexible sliding layer, while the reflective film layer covers the outside of the insulation board layer to ensure that the composite insulation layer remains intact under conditions without direct compression.

[0010] Preferably, the material of the backfill area is one or more of EPS particle mixed lightweight soil, slag-fly ash mixture, expanded perlite concrete, or rubber particle mixed soil; the density of the backfill area is 600~1,200 kg / m³, and the compression modulus is 5~30 MPa.

[0011] Preferably, the vertical thickness and horizontal width of the backfill area are designed differently according to the frost heave sensitivity zone, which is divided into a high frost heave sensitivity zone and a frost heave insensitive zone, wherein the backfill size of the high frost heave sensitivity zone is larger than that of the frost heave insensitive zone.

[0012] Preferably, the long axis of the oblong bolt hole of the pressure anchoring node is aligned with the main frost heave stress direction of the corrugated steel plate, allowing the corrugated steel plate to undergo a predetermined amount of relative slippage under frost heave stress. The long axis of the oblong bolt hole is 2 to 5 times the nominal diameter of the connecting bolt, and the reserved slippage amount is not less than the maximum design value of frost heave deformation in the seasonally frozen area. The elastic washer is a disc spring washer or a rubber washer.

[0013] A construction method for using a frost-resistant and pressure-relief structure suitable for corrugated steel plate bridge and tunnel structures in seasonally frozen regions is characterized by the following steps: Step S1: Excavation and foundation treatment of the foundation pit; Excavate the foundation pit for the corrugated steel structure according to the design elevation, remove the loose soil layer on the surface, and level and compact the foundation or replace the foundation according to the design requirements. Step S2: Construction of the lower part of the backfill zone; Within the design range of the bottom and sidewalls of the foundation pit, the backfill material in the pressure relief area shall be filled in layers, and the compaction degree shall be controlled to be no more than 85% in order to retain compressibility; Step S3: Laying the composite insulation layer; After the lower backfill layer has been completed, insulation boards are laid in staggered joints on the surface and the gaps are sealed with expanding foam. A reflective film is then laid on the outside of the insulation boards. Step S4: Laying of flexible slip layer; A flexible sliding material is laid on the inner side of the composite insulation layer, and the sliding layer and the steel corrugated plate are kept in a non-adhesive state. Step S5: Install the corrugated steel plate and connect it to the pressure relief node; The corrugated steel plates were hoisted into place one by one and connected using long oval bolt holes and elastic washers for pressure relief anchoring nodes. Step S6: Allow the backfilling of the upper part and both sides of the compacted backfill area to proceed in layers; Between the corrugated steel sheet and the sidewall of the foundation pit, backfill material for the pressure relief zone is filled in layers according to the design, with each layer having a height of 20-30cm and a compaction degree of less than or equal to 85%. Step S7: Construction of topsoil cover and road surface structure layer; The top of the corrugated steel plate structure is covered with soil according to the design requirements, compacted in layers, and then the upper road structure layer is constructed.

[0014] Preferably, in step S3, the gap between the staggered joints of the insulation boards is no more than 3mm; the overlap width of the reflective film is no less than 10cm, and the overlap seam is sealed with weather-resistant tape; in step S5, the torque of the connecting bolts is controlled according to the design torque value, and the initial compression of the disc spring washer is controlled to be 40%~60% of the design compression range.

[0015] Preferably, the method further includes the step of embedding monitoring sensors at key nodes of the corrugated steel plate, on both sides of the flexible sliding layer, on both sides of the insulation layer, and in the pressure relief backfill area, and establishing an online monitoring system for service life, wherein the monitoring sensors include stress gauges and / or displacement gauges.

[0016] Through the above design scheme, the present invention can bring the following beneficial effects: Existing corrugated steel plate structure designs focus on increasing structural stiffness to resist frost heave. Under this "resistance" mode, greater structural stiffness and stronger constraints exacerbate soil-structure interaction, actually pushing up the peak frost heave force and ultimately leading to permanent deformation of the structure under repeated frost heave stress. This invention transforms the design concept into "frost heave containment." It reduces the constraint stiffness of the soil-structure interface through a flexible sliding layer, absorbs soil frost heave deformation through the backfill zone, and allows for coordinated overall deformation through the anchored joints. This forms a four-stage energy dissipation chain: "elastic sliding to reduce peak stress → backfill energy dissipation → thermal insulation to slow frost heave → synchronous anchoring at joints." This fundamentally solves the core contradiction of permanent structural failure caused by accumulated frost heave stress, representing a revolutionary breakthrough in the traditional frost heave resistance design of corrugated steel plate structures.

[0017] The flexible slip layer transforms the soil-structure interface from a rigid constraint to an elastic slip interface, enabling active slippage under frost heave forces, thus reducing the peak stress transmitted to the corrugated steel plate by 30% to 50%. The backfill zone absorbs frost heave soil deformation through controlled compression, providing dissipable pressure relief space for frost heave stress. The composite insulation layer mitigates the amplitude of freeze-thaw fluctuations, indirectly reducing the frost heave amplitude. The pressure relief anchoring nodes allow the corrugated steel plate to slide freely within the limit range of the elongated bolt holes, achieving overall coordinated deformation in the longitudinal and circumferential directions. The four pressure relief levels form a progressive coordination in time and space—the slip layer first reduces the peak stress in the low-stress stage, the backfill zone plays a major role in energy dissipation in the medium-stress stage, and the node pressure relief provides the final line of defense in the high-stress stage. There is no functional overlap or blind spot between the levels, achieving complete coverage of the entire stress spectrum.

[0018] The core components of this invention—the flexible sliding layer, the composite insulation layer, the pressure-relief backfill zone, and the pressure-relief anchoring node—are arranged in layers from the inside out with clear structural boundaries. The selection of materials, thickness range, and performance indicators of each layer can be differentiated, which facilitates the accurate definition of the scope of protection in the claims and significantly improves the identifiability of the technical solution and the determination of infringement.

[0019] Simulation tests have verified that the corrugated steel plate structure constructed using this invention reduces deformation by more than 75% and joint stress concentration factor by more than 60% under 30 freeze-thaw cycles. It is expected to extend the design service life of corrugated steel plate culverts and open tunnels in seasonally frozen areas from the current 15-20 years to more than 40 years, and reduce maintenance frequency during operation by more than 50%. Attached Figure Description

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments: Figure 1 This is a cross-sectional schematic diagram of the anti-freezing heave and pressure relief structure of the present invention; Figure 2 This is a detailed structural drawing of the pressure-bearing anchor node of the present invention; Figure 3 This is a schematic diagram comparing the deformation of a corrugated steel plate under 30 freeze-thaw cycles between the anti-freeze-heave pressure relief structure of this invention and the existing "anti-freeze-heave" structure. Figure 4 This is a schematic diagram comparing the deformation of a corrugated steel plate under 30 freeze-thaw cycles between the anti-freeze-heave pressure relief structure of this invention and the existing "anti-freeze-heave" structure. Figure 5 This is a process flow diagram of the construction method for the anti-frost heave and pressure relief structure of the present invention. Detailed Implementation

[0021] The present invention will be further illustrated below with reference to specific embodiments, but the embodiments do not limit the present invention in any way.

[0022] like Figures 1-5 As shown, the solution of the present invention is: a frost heave relief structure suitable for steel corrugated plate bridge and tunnel structures in seasonally frozen areas, characterized in that it is set on the outside of the steel corrugated plate and in contact with the surrounding soil, and includes, from the inside to the outside, a flexible sliding layer, a composite insulation layer and a relief backfill area.

[0023] The flexible sliding layer is installed in close contact with the outer wall of the corrugated steel plate, and is made of elastic material with a thickness of 5-15mm. The flexible sliding layer is in a non-bonded state with the outer wall of the corrugated steel plate, and can undergo controllable relative sliding along the outer wall of the corrugated steel plate under the action of frost heave stress. It is used to reduce the constraint stiffness of the soil-structure interface and reduce the peak value of frost heave stress transmitted to the corrugated steel plate.

[0024] Preferably, the flexible sliding layer is one or more composites of vulcanized rubber sheet, recycled rubber granule sheet, thermoplastic elastomer sheet or polyurethane elastomer sheet; more preferably, the surface of the flexible sliding layer is provided with fine patterns or raised structures to regulate the sliding start threshold (sliding is initiated when the frost heave stress exceeds the preset threshold, and remains stable when it is below the threshold).

[0025] The principle of slip direction control in this invention is as follows: the slip layer is in a non-bonded state with the outer wall of the corrugated steel plate and is laid along the tangent direction of the corrugated steel plate to ensure that the slip occurs in the preset direction; the slip amount is controlled by the pressure relief anchoring node: the elongated bolt hole of the pressure relief anchoring node (the long axis direction is consistent with the main frost heave force direction) limits the maximum slip amount (usually 2 to 5 times the bolt diameter).

[0026] The composite insulation layer is disposed outside the flexible sliding layer and consists of at least one insulation board and at least one reflective film, with a total thickness of 5-15 cm. The insulation board layer is used to block the transfer of heat from the soil to the corrugated steel plate to mitigate the intensity and depth of freeze-thaw cycles, while the reflective film layer is used to enhance interfacial thermal resistance. The distance between the insulation board layer and the corrugated steel plate is indirectly separated by the flexible sliding layer, ensuring that the insulation layer remains intact under conditions of no direct compression.

[0027] Preferably, the insulation board is an extruded polystyrene foam board with a thermal conductivity of not more than 0.030 W / m·K and a compressive strength of not less than 250 kPa; the reflective film is an aluminized polyester film or an aluminum foil-coated nonwoven fabric with a thermal reflectivity of not less than 85%.

[0028] The pressure relief backfill zone is located outside the composite insulation layer and is a compressible backfill material area used to absorb soil deformation during frost heave and provide a dissipable pressure relief space for frost heave stress.

[0029] Preferably, the material of the backfill area is one or more of EPS particle mixed lightweight soil, slag-fly ash mixture, expanded perlite concrete, or rubber particle mixed soil; the density of the backfill area is 600~1200 kg / m³, and the compression modulus is controlled within the range of 5~30 MPa. The vertical thickness and horizontal width of the backfill area can be differentiated according to the frost heave sensitivity zones—the backfill layer is thickened in areas with high frost heave sensitivity (such as shallow groundwater levels and silty clay enrichment sections), and appropriately thinned in areas with low frost heave sensitivity.

[0030] Adjacent corrugated steel sheets are lapped together via pressure-relief anchoring nodes. These anchoring nodes are located at the longitudinal and circumferential lap joints of the corrugated steel sheets and include: an elongated bolt hole at the lap end of the corrugated steel sheet; a connecting bolt passing through the elongated bolt hole; and an elastic washer between the bolt head and the corrugated steel sheet. The long axis of the elongated bolt hole is aligned with the main frost heave stress direction of the corrugated steel sheet, allowing for a predetermined amount of relative slippage under frost heave stress.

[0031] Preferably, the major axis length of the oblong bolt hole is 2 to 5 times the nominal diameter of the bolt, and the allowable slippage is not less than the maximum design value of frost heave deformation in the seasonally frozen area; the elastic washer is a disc spring washer or a rubber washer.

[0032] The four components mentioned above function as a whole through the following synergistic mechanism: The flexible slip layer reduces the normal bond strength and tangential constraint stiffness of the soil-structure interface, reducing the peak value of frost heave stress by 30% to 50%. The compressible material in the backfill zone provides space for frost heave deformation of the soil, further reducing the stress transmitted to the insulation layer and corrugated steel plate. The composite insulation layer mitigates the disturbance of temperature fluctuations to the active layer of frozen soil, indirectly reducing the amplitude of frost heave. The frost heave anchoring nodes allow the corrugated steel plate to undergo overall coordinated deformation under non-uniform frost heave forces. This forms a four-stage frost heave energy dissipation chain: "elastic slip peak reduction → frost heave backfill energy dissipation → thermal insulation and frost heave mitigation → node frost heave synchronization," completely realizing the safe release of frost heave stress and avoiding stress concentration and permanent structural damage.

[0033] A construction method for an anti-frost heave relief structure suitable for corrugated steel plate bridge and tunnel structures in seasonally frozen regions includes the following steps: (1) Excavation and foundation treatment of the foundation pit: Excavate the foundation pit of the corrugated steel structure according to the design elevation, remove the loose soil layer on the surface, and level and compact the foundation or replace the foundation according to the design requirements. The compaction degree shall not be less than 93%. (2) Construction of the lower part of the backfill area: Within the design range of the bottom and side walls of the foundation pit, the backfill material of the backfill area is filled in layers, with each layer being 20-30cm thick. Light compaction equipment is used to level the material, and the compaction degree is controlled to be no more than 85%, while preserving the compressibility of the material. (3) Laying of composite insulation layer: On the top surface of the completed lower pressure backfill layer, the insulation board is laid in a staggered manner, the gap of the insulation board is no more than 3mm, and it is sealed with polyurethane foam; a reflective film is laid on the outside of the insulation board (the side away from the steel corrugated plate), the overlap width of the reflective film is no less than 10cm, and it is sealed with weather-resistant tape. (4) Flexible sliding layer laying: Flexible sliding material is laid on the inside of the composite insulation layer (the side that is close to the steel corrugated plate). The sliding layer and the steel corrugated plate are kept in a non-adhesive state and no adhesive is applied. (5) Steel corrugated plate installation and pressure relief node connection: The precast steel corrugated plates are hoisted into place one by one. The circumferential and longitudinal joints are connected by pressure relief anchoring nodes with elongated bolt holes and elastic washers. The bolt torque is controlled according to the design torque value. (6) Layered backfilling of the upper part and both sides of the pressure backfilling area: After the steel corrugated plate is installed and positioned, the pressure backfilling material is filled in layers between the steel corrugated plate and the side wall of the foundation pit according to the design. Each layer is 20~30cm thick and the compaction degree is controlled to be no more than 85%. The material is filled layer by layer to the design elevation. (7) Construction of top soil cover and road structure layer: Soil cover is applied to the top of the steel corrugated plate structure according to the design requirements, and compaction is carried out in layers with a compaction degree of not less than 93%. Then the upper road structure layer is constructed.

[0034] Figure 1 A cross-sectional diagram of the anti-frost heave and pressure relief structure is shown. The blue lines correspond to the flexible sliding layer, the orange lines correspond to the composite insulation layer, and the green dashed lines correspond to the pressure relief backfill area. The thickness of the flexible sliding layer is 5-15mm, the thickness of the composite insulation layer is 5-15cm, and the thickness of the pressure relief backfill area is 1-2m. The flexible sliding layer uses non-bonded rubber sheet / elastic material, the composite insulation layer uses XPS insulation board + reflective film, and the pressure relief backfill area uses EPS lightweight soil / compressible material. The multi-layer combination eliminates the damage to the steel corrugated plate structure caused by frost heave and thermal shrinkage. Figure 2 To provide a detailed structural drawing of the anchoring node, the lower layer is a corrugated steel plate A, and the upper layer is an overlapping corrugated steel plate B with an elongated bolt hole C. The connecting bolts, in conjunction with disc spring washers D, penetrate through the two layers of plates. The elongated hole is reserved for a sliding amount ΔL = (2~5) × bolt diameter. The red arrow indicates the direction of plate sliding during frost heave.

[0035] Example 1: Anti-frost heave project for the open-cut section of a steel corrugated plate tunnel on a highway in the Changbai Mountain area of ​​Jilin Province This embodiment uses a section of a highway tunnel in the Changbai Mountain area of ​​Jilin Province as an example. The project is located in the heart of the Changbai Mountains, a typical high-altitude, cold, and frost-prone region in Northeast China. According to meteorological data, the average annual extreme minimum temperature in this area can reach -37.5℃, with winter temperatures below 0℃ lasting for up to four months, and a standard freezing depth of 1.70m. Engineering geological surveys indicate that the upper strata of the tunnel section consist of a 3-6m thick layer of silty clay, and the lower layer is completely weathered granite. The silty clay layer has a natural moisture content of 24%-32%, a liquid limit of 35%, and a plastic limit of 19%, classifying it as frost-susceptible soil. The groundwater level is approximately 1.8m deep, with ample capillary water replenishment during frost heave. The tunnel structure uses corrugated steel plates for main support, with a single-span diameter of 12m and a rise of 6m. The corrugated steel plates are 6mm diameter galvanized corrugated steel plates with a wave height of 150mm and a wave spacing of 380mm. This embodiment designs and implements an anti-frost heave pressure relief structure for this tunnel section.

[0036] Structural design parameters: Flexible sliding layer: Constructed from a 10mm thick, low-temperature vulcanized rubber sheet with a Shore hardness of 55±5A, an operating temperature range of -50℃ to +60℃, and a permanent compression set ≤15%. The rubber sheet surface features a 5mm spaced diamond pattern to adjust the sliding initiation threshold (calibrated by testing to have a sliding initiation shear stress of 40kPa). The rubber sheet is mechanically clamped to the anchoring bosses on the outer wall of the corrugated steel plate without the application of adhesive.

[0037] Composite insulation layer: 8cm thick extruded polystyrene foam board with a thermal conductivity of 0.025W / m·K and a compressive strength of 300kPa. The insulation boards are laid in a staggered manner, and the gaps are sealed with polyurethane foam. The outer layer is pasted with a 0.2mm thick aluminized polyester film reflective film with an overlap width of 10cm and a measured heat reflectivity of approximately 87%.

[0038] The backfill area for pressure relief uses EPS particles mixed with lightweight soil, with a density controlled at 850~950 kg / m³ and a compression modulus of 12~18 MPa. The EPS particles have a particle size of 3~5 mm and a volumetric content of 45%. The cementing material is 42.5 grade ordinary Portland cement with a water-cement ratio of 0.45. The designed thickness of the backfill area for pressure relief is: 1.0~1.5 m horizontally on the side walls, 1.0 m vertically at the bottom, and 0.5 m at the top.

[0039] Anchoring joint with pressure relief: The circumferential joint of the corrugated steel plate is connected with M20 high-strength bolts. The bolt holes are oblong holes with a major axis length of 80mm (minor axis of 22mm, with reserved sliding space for M20 bolts). The major axis is set along the circumferential tangent of the corrugated steel plate. A disc spring washer is set between the bolt head and the corrugated steel plate. The initial preload is controlled according to the design torque value of 130N·m.

[0040] Construction process: (1) Excavate the foundation pit of the open tunnel section to the design elevation of the base. The silty clay layer is about 4.5m thick and is excavated down to the completely weathered granite layer. The base is repeatedly compacted by a vibratory roller 6 to 8 times to achieve a compaction degree of 94%.

[0041] (2) Construction of the bottom backfill area: First, pour a 10cm thick C20 plain concrete cushion layer as a leveling layer. After curing for 3 days, fill the EPS particle mixed lightweight soil in layers to the designed thickness of 1.0m, with each layer having a filling height of 25cm. Use a plate vibrator to lightly vibrate twice, and control the compaction degree at 83%~85%.

[0042] (3) Construction of the lower part of the side wall pressure backfill area: EPS mixed lightweight soil is filled in layers on both sides of the foundation pit according to the design width, with each layer being 30cm high, and the construction is carried out simultaneously.

[0043] (4) Laying of composite insulation layer: XPS insulation boards are laid in a staggered manner with a gap of ≤3mm between the boards. After the polyurethane foam is used to seal the gap, an aluminum-coated polyester film reflective film is pasted on the outside (the side closest to the soil) and the overlap is sealed with weather-resistant tape.

[0044] (5) Flexible sliding layer laying: The pre-vulcanized rubber sheet is cut and shaped according to the curvature of the outer wall of the steel corrugated plate. The rubber sheet and the steel corrugated plate are fixed by U-shaped grooves pre-welded to the outer wall of the steel corrugated plate to maintain a non-adhesive state and ensure that the sliding layer can slide freely along the tangent direction of the steel corrugated plate.

[0045] (6) Installation and pressure relief anchoring of corrugated steel plates: The corrugated steel plates are hoisted into place one by one. The circumferential joints are fastened with M20 bolts using elongated bolt holes. The compression of the disc spring washers is controlled at 50% of the initial state.

[0046] (7) Construction of the upper and side wall pressure relief backfill area: After the steel corrugated plate is positioned, EPS mixed lightweight soil is backfilled in layers in the reserved gap between the steel corrugated plate and the side wall of the foundation pit, with each layer being 25cm. The horizontal thickness of the side wall pressure relief backfill area is designed differently according to the frost heave sensitivity zone - the thickness is increased to 1.5m in the high-sensitivity section where the silty clay layer thickness is greater than 5m, and the thickness is reduced to 1.0m in the low-sensitivity section where the silty clay layer thickness is less than 2m.

[0047] (8) Top cover: The top of the corrugated steel plate shall be backfilled with ordinary fill in layers according to the designed cover thickness, and the compaction degree shall not be less than 93%.

[0048] (9) Monitoring system deployment: stress gauges and displacement gauges are installed at key circumferential nodes (arch crown, arch shoulder, arch foot), both sides of the flexible slip layer, both sides of the insulation layer, and in the pressure relief backfill area of ​​the corrugated steel plate, totaling 36 monitoring points, to establish an online monitoring network during service life and track the development of structural stress and deformation in real time.

[0049] Implementation results:

[0050] After the structural construction was completed, a control section was set up for an accelerated simulation test of 30 freeze-thaw cycles. Control section A adopted a conventional design (without pressure relief structure), while control section B adopted the structure of this invention.

[0051] Cumulative deformation of corrugated steel sheet (after 30 freeze-thaw cycles) 28.6mm 7.2mm Reduced by 75% Stress concentration factor of joint bolt holes 2.8~3.5 1.2~1.5 57% reduction Crack rate of welded joints 26% (5 nodes cracked / 19 nodes) 0%（0 / 19） Completely eliminate Peak value of frost heave stress (measured value) 480kPa 260kPa 46% lower Structural self-restoring rate (melting period) Unrecoverable 92% — Monitoring data shows that the invention constructs a complete four-stage pressure relief energy dissipation mechanism: the flexible sliding layer initiates sliding in the early stage of frost heave loading (stress below 80 kPa), with a sliding amount of about 2-5 mm, contributing about 15% stress reduction; the pressure relief backfill zone undergoes about 10-20 mm of compression deformation in the middle stage of frost heave (stress 80-200 kPa), and the reversible elastic recovery rate of the EPS lightweight soil compression deformation reaches over 85%, contributing about 55% stress dissipation; the composite insulation layer reduces the frost depth by about 0.6-0.8 m, reducing the frost heave volume. The pressure relief anchoring nodes allow the corrugated steel plate to slide approximately 3-8 mm at the end of the frost heave period (when the stress exceeds 200 kPa), releasing residual stress of approximately 30-50 kPa. The four pressure relief layers work together to gradually reduce the frost heave stress from the initial 480 kPa to approximately 90 kPa, a reduction of 81%. After a complete freeze-thaw cycle, the compression deformation of the pressure relief backfill area elastically recovers synchronously with the thawing of the frozen soil, achieving an overall structural recovery rate of 92%, realizing the self-recovery function of "pressure relief during frost heave + recovery during thaw settlement".

[0052] The above-mentioned implementation results fully verify the effectiveness of the core technical concept of "graded pressure relief + self-recovery" of this invention, indicating that this invention can fundamentally solve the problem of frost heave damage of steel corrugated plate bridge and tunnel structures in seasonally frozen areas and significantly improve the long-term service performance of the structure.

[0053] Example 2: Anti-frost heave project for corrugated steel culverts on a highway in the Changbai Mountain area This embodiment uses a corrugated steel culvert at kilometer marker K85+300 of a highway in the Changbai Mountain region of Jilin Province as an example. This culvert serves as a drainage channel across the highway, with a span of 6 meters and a rise of 4 meters. The engineering geological conditions are similar to those in Embodiment 1, but the foundation consists of an approximately 8-meter-thick layer of silty clay, and the groundwater level is only 1.2 meters deep, resulting in higher frost heave sensitivity.

[0054] This embodiment differs from Embodiment 1 in the following ways: Due to the higher sensitivity to frost heave, the backfill area is thickened: the horizontal thickness of the side walls is increased to 2.0m, and the vertical thickness of the bottom is increased to 1.5m; The flexible sliding layer is replaced with recycled rubber granules (lower cost, 12mm thickness). The insulation layer uses double-layer XPS boards (5cm each, 10cm total thickness), with staggered joints between the two insulation boards and an air barrier layer in between. The thickness of the soil covering the top of the structure was adjusted to 1.5m (originally 1.0m) to enhance the insulation effect.

[0055] On-site monitoring showed that after a complete winter freeze-thaw cycle, the maximum deformation of the corrugated steel plate was 5.8 mm, with no cracks at the joints, no leakage inside the culvert, and the structure remained intact. The frozen soil temperature around the corrugated steel plate was about 2.2℃ higher than the ambient soil temperature, and the frost depth was 0.7m less than the surrounding area, verifying the adaptability of the invention's structure in areas sensitive to high frost heave.

[0056] Example 3: Comparative Test of Performance of Different Pressure-Relief Materials To optimize the material selection for the backfill area, this embodiment conducted comparative tests on three types of backfill materials under laboratory conditions: EPS granules mixed with lightweight soil 850~950 12~18 ≤5% ≥88% ★★★★★ Slag-fly ash mixture 1,000~1,150 8~15 ≤8% ≥82% ★★★★ Expanded perlite concrete 700~900 6~12 ≤10% ≥75% ★★★ Test results show that EPS particle-mixed lightweight soil exhibits the best overall performance in terms of moderate density, controllable compression modulus, freeze-thaw resistance, and elastic recovery rate, making it the preferred material for frost-susceptible conditions in cold regions. Slag-fly ash mixture has a lower cost (approximately 25% lower than EPS lightweight soil) and is suitable for frost-susceptible sections to control project costs.

Claims

1. A frost-resistant structure for corrugated steel plate bridge and tunnel structures in seasonally frozen regions, characterized in that: The anti-frost heave pressure relief structure is arranged between the outer wall of the corrugated steel plate and the surrounding soil. A flexible sliding layer, a composite insulation layer and a pressure relief backfill area are stacked sequentially from the inside to the outside along the radial direction from the outer wall of the corrugated steel plate to the surrounding soil. The flexible sliding layer is set in close contact with the outer wall of the corrugated steel plate. It is made of elastic material and is non-bonded to the outer wall of the corrugated steel plate. It can undergo controllable relative sliding along the outer wall of the corrugated steel plate under the action of frost heave stress. The composite insulation layer is disposed on the outside of the flexible sliding layer and is composed of at least one insulation board and at least one reflective film. The insulation board layer is used to block the transfer of soil heat to the steel corrugated plate to reduce the intensity and depth of the freeze-thaw cycle, and the reflective film layer is used to enhance the interfacial thermal resistance. The pressure relief backfill area is filled between the outside of the composite insulation layer and the surrounding soil. It is filled with backfill material with high compressibility and is used to absorb the deformation and displacement of the soil during the frost heave process, providing a pressure relief space that can dissipate frost heave stress. Adjacent corrugated steel plates are connected by a pressure-relief anchoring node. The pressure-relief anchoring node is located at the longitudinal lap joint and circumferential joint of the corrugated steel plates and includes an elongated bolt hole, a connecting bolt, and an elastic washer. The elongated bolt hole is located at the lap end of the corrugated steel plate, and the connecting bolt passes through the elongated bolt hole to achieve lap fixation. The elastic washer is sandwiched between the bolt head and the corrugated steel plate.

2. The anti-frost heave and pressure relief structure for corrugated steel plate bridge and tunnel structures in seasonally frozen areas according to claim 1, characterized in that, The elastic material of the flexible sliding layer is composed of one or more of vulcanized rubber sheets, recycled rubber granule sheets, thermoplastic elastomer sheets or polyurethane elastomer sheets, with a thickness of 5~15 mm and an operating temperature range of not less than -50℃~+60℃.

3. The anti-frost heave and pressure relief structure for corrugated steel plate bridge and tunnel structures in seasonally frozen areas according to claim 1, characterized in that: The surface of the flexible sliding layer is covered with fine patterns or bumps to control the sliding start threshold. The sliding start threshold is preset so that the interface remains stable when the frost heave stress is lower than the start threshold, and sliding occurs when the frost heave stress exceeds the start threshold.

4. The anti-frost heave relief structure for corrugated steel plate bridge and tunnel structures in seasonally frozen areas according to claim 1, characterized in that: The composite insulation layer uses extruded polystyrene foam board with a thermal conductivity of no more than 0.030 W / m·K and a compressive strength of no less than 250 kPa. The reflective film is made of aluminized polyester film or aluminum foil-coated nonwoven fabric with a thermal reflectivity of no less than 85%. The insulation board layer is set close to the flexible sliding layer, and the reflective film layer covers the outside of the insulation board layer to ensure that the composite insulation layer remains intact under conditions without direct compression.

5. The anti-frost heave relief structure for corrugated steel plate bridge and tunnel structures in seasonally frozen areas according to claim 1, characterized in that: The material of the backfill area is one or more of EPS particle mixed lightweight soil, slag-fly ash mixture, expanded perlite concrete or rubber particle mixed soil; the density of the backfill area is 600~1,200 kg / m³, and the compression modulus is 5~30 MPa.

6. The anti-frost heave relief structure for corrugated steel plate bridge and tunnel structures in seasonally frozen areas according to claim 1, characterized in that: The vertical thickness and horizontal width of the backfill zone are designed differently according to the frost heave sensitivity zone, which is divided into a high frost heave sensitivity zone and a frost heave insensitive zone. The backfill size of the high frost heave sensitivity zone is larger than that of the frost heave insensitive zone.

7. The anti-frost heave relief structure for corrugated steel plate bridge and tunnel structures in seasonally frozen areas according to claim 1, characterized in that: The long axis of the oblong bolt hole of the pressure anchoring node is aligned with the main frost heave stress direction of the corrugated steel plate, allowing the corrugated steel plate to undergo a predetermined amount of relative slippage under frost heave stress. The length of the long axis of the oblong bolt hole is 2 to 5 times the nominal diameter of the connecting bolt, and the reserved slippage amount is not less than the maximum design value of frost heave deformation in the seasonally frozen area. The elastic washer is a disc spring washer or a rubber washer.

8. A construction method for using a frost-resistant and pressure-relief structure suitable for corrugated steel plate bridge and tunnel structures in seasonally frozen regions, characterized in that, Includes the following steps: Step S1: Excavation and foundation treatment of the foundation pit; Excavate the foundation pit for the corrugated steel structure according to the design elevation, remove the loose soil layer on the surface, and level and compact the foundation or replace the foundation according to the design requirements. Step S2: Construction of the lower part of the backfill zone; Within the design range of the bottom and sidewalls of the foundation pit, the backfill material in the pressure relief area shall be filled in layers, and the compaction degree shall be controlled to be no more than 85% in order to retain compressibility; Step S3: Laying the composite insulation layer; After the lower backfill layer has been completed, insulation boards are laid in staggered joints on the surface and the gaps are sealed with expanding foam. A reflective film is then laid on the outside of the insulation boards. Step S4: Laying of flexible slip layer; A flexible sliding material is laid on the inner side of the composite insulation layer, and the sliding layer and the steel corrugated plate are kept in a non-adhesive state. Step S5: Install the corrugated steel plate and connect it to the pressure relief node; The corrugated steel plates were hoisted into place one by one and connected using long oval bolt holes and elastic washers for pressure relief anchoring nodes. Step S6: Allow the backfilling of the upper part and both sides of the compacted backfill area to proceed in layers; Between the corrugated steel sheet and the sidewall of the foundation pit, backfill material for the pressure relief zone is filled in layers according to the design, with each layer having a height of 20-30cm and a compaction degree of less than or equal to 85%. Step S7: Construction of topsoil cover and road surface structure layer; The top of the corrugated steel plate structure is covered with soil according to the design requirements, compacted in layers, and then the upper road structure layer is constructed.

9. The construction method according to claim 8, characterized in that: In step S3, the gap between the staggered joints of the insulation boards shall not exceed 3 mm; the overlap width of the reflective film shall not be less than 10 cm, and the overlap seam shall be sealed with weather-resistant tape; in step S5, the torque of the connecting bolts shall be controlled according to the design torque value, and the initial compression of the disc spring washer shall be controlled to 40% to 60% of the design compression range.

10. The construction method according to claim 8, characterized in that: It also includes the steps of embedding monitoring sensors at key nodes of the corrugated steel plate, on both sides of the flexible sliding layer, on both sides of the insulation layer, and in the pressure relief backfill area, and establishing an online monitoring system for service life, wherein the monitoring sensors include stress gauges and / or displacement gauges.

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