A protective structure for anti-buoyancy and scour protection of riverbed tunnels

Abstract

A protective structure for anti-buoyancy and scour protection of a riverbed tunnel includes a riverbed tunnel, a reinforcement layer, a protective layer, and a backfill layer. The reinforcement layer is installed along the extension direction of the riverbed tunnel, with its bottom extending into the arch of the tunnel and its width exceeding the two arches of the tunnel. The protective layer is installed above the reinforcement layer along the extension direction of the riverbed tunnel, and the backfill layer is installed above the protective layer, with its upper surface flush with the original riverbed elevation. The protective layer includes a protective plate and structural beams. The protective plate extends along the extension direction of the riverbed tunnel and its width is greater than that of the reinforcement layer. The structural beams are located on both sides of the bottom of the protective plate and embedded in the riverbed cushion layer. The riverbed tunnel is constructed from special tunnel segments, in which the diameter of the main reinforcing bars is larger than that of ordinary tunnel segments in other tunnel sections. This invention reinforces the riverbed soil and increases soil pressure, achieving anti-buoyancy and anti-scour capabilities during the construction and operation of the riverbed tunnel, ensuring safety.

Description

Technical Field

[0001] This utility model relates to the field of shield tunneling technology, and in particular to an anti-buoyancy and anti-scour protection structure for riverbed tunnels. Background Technology

[0002] Underground space, as a vital urban resource, serves as a crucial vehicle for implementing green development, enhancing urban resilience, ensuring urban safety, and realizing urban vitality. The coordinated development of underground space zones, resulting in underground spatial structures, has become an important component in promoting urban development. In recent years, with rapid economic development and urban construction, the urban population has grown rapidly, leading to increasingly severe urban traffic conditions. To address traffic problems, my country's infrastructure construction has made leaps and bounds, especially in cities, gradually developing towards a three-dimensional space encompassing the air, ground, and underground. Among these developments, a key focus is the design and construction work surrounding urban rail transit projects crossing existing waterways.

[0003] Rivers often have complex conditions, including intricate embankment structures, numerous surface pipelines, and poor geological conditions. Therefore, ensuring river safety places high demands on the construction and protection of subway tunnels crossing them. As a major urban transportation facility, the safety of tunnels during construction and operation must be considered. Effective protection technologies must be implemented before urban tunnels crossing existing rivers can proceed. Current regulations stipulate that the settlement limit for river sections underpasses is 15mm, and the safety control value for existing rail transit structures should not exceed 15mm.

[0004] Because tunnel boring machines (TBMs) cause soil displacement during excavation, which can adversely affect the safety of riverbanks, it is essential to monitor the safety of riverbanks and implement practical protective measures during TBM tunneling. With the rapid pace of urban development and the widespread existence of waterways, the number of TBM tunnels crossing river channels is increasing. According to current regulations, the minimum required overburden thickness for a TBM tunnel should not be less than three times the outer diameter of the equipment or 8 meters below the maximum scour line of the river; or the TBM should be excavating outside the river management area. However, tunnel depth and route are subject to various constraints, making arbitrary design and alteration difficult. Furthermore, the difficulty of river rerouting is evident, often resulting in insufficient overburden thickness when tunnels cross existing river channels. When shield tunnels are constructed in areas with shallow overburden, the soil pressure above the tunnel and the tunnel's own weight may not be able to overcome buoyancy, significantly impacting construction safety. Furthermore, during tunnel operation, the scouring effect of the riverbed causes changes in the load above the tunnel, and these changes accumulate gradually over time, also seriously affecting operational safety. Therefore, necessary measures are required to ensure the safety of both the river and the shield tunnel during construction and operation when crossing rivers at close range. Shield tunneling under rivers is a key technology in underground space development and is crucial for the successful implementation of projects. Ensuring river safety while considering the construction and operational safety of the tunnel itself necessitates an economically feasible ground protection plan. Utility Model Content

[0005] The purpose of this utility model is to overcome the shortcomings of the prior art and provide a simple, easy-to-construct and easy-to-maintain anti-buoyancy and anti-scour protection structure for riverbed tunnels, ensuring the safety of the tunnel boring machine and the riverbed during construction and operation.

[0006] This utility model is achieved through the following technical solution: An anti-buoyancy and anti-scour protection structure for riverbed tunnels is disclosed, used for anti-buoyancy and anti-scour protection during the construction and operation of riverbed tunnels. It includes a riverbed tunnel passing beneath the riverbed, a reinforcement layer, a protective layer, and a backfill layer. The reinforcement layer is installed along the extension direction of the riverbed tunnel, with its bottom extending into the arch of the tunnel and its width exceeding the two arches of the tunnel. Both ends of its extension cover both ends of the riverbed tunnel. The protective layer is installed above the reinforcement layer along the extension direction of the riverbed tunnel, serving to isolate the tunnel from direct river water scour and to provide support during grouting of the reinforcement layer. The protective layer can also further increase the anti-buoyancy counterweight above the tunnel segments. The backfill layer is installed above the protective layer, with its upper surface flush with the original riverbed elevation, and serves to protect both the protective layer and the riverbed.

[0007] Furthermore, the protective layer includes a protective plate and structural beams. The protective plate extends along the direction of the riverbed tunnel and its width is greater than the width of the reinforcement layer. The structural beams are located on both sides of the bottom of the protective plate and extend along the direction of the protective plate, and are embedded in the riverbed soil to strengthen the fixation between the protective plate and the riverbed soil. The protective plate is supported on the riverbed by the structural beams, and the protective plate and structural beams form the riverbed structure, providing effective resistance to deformation and bearing capacity for routine dredging operations and other activities on the riverbed.

[0008] Furthermore, it also includes a cushion layer set on the riverbed surface, with two cushion layers laid along both sides of the reinforcement layer, and each cushion layer is provided with a groove adapted to the structural beam, through which the structural beam is embedded into the bottom soil layer of the river channel.

[0009] Furthermore, the protective plate is a reinforced concrete slab, and the distance between each side of the protective plate and the two sides of the reinforcement layer is 3m, that is, the two sides of the protective plate extend outward by 3m relative to the two sides of the reinforcement layer. The structural beam is a reinforced concrete beam.

[0010] Furthermore, the riverbed tunnel is constructed from special segments, in which the diameter of the main reinforcing bars is larger than that of ordinary segments in other tunnel sections. This increases the weight and deformation resistance of the segments, and helps them resist the effects of insufficient buoyancy and large fluctuations in the superstructure load.

[0011] Furthermore, the reinforcement layer extends outward by 3m on each side in its width direction towards the arch of the riverbed tunnel.

[0012] Furthermore, the reinforcement layer extends obliquely downward and outward at a 45° angle from the junction of the reinforcement layer and the river channel to the location of the river tunnel in its extension direction.

[0013] Furthermore, the reinforcing layer is a concrete structure. The reinforcing layer can be filled by grouting through a sleeve valve pipe.

[0014] Furthermore, the backfill layer uses riprap with a particle size of 10-30 cm, which is more compact, reduces silt accumulation and water erosion, and the riprap density is between 23-27 kN / m³, improving the tunnel's anti-buoyancy capacity and making the riprap system more stable under external forces such as water flow. Riprap with a large internal friction angle is selected whenever possible to further improve overall stability.

[0015] This invention reinforces the soil space between the riverbed and the tunnel by setting up a reinforcement layer, a protective layer, and a backfill layer at the riverbed, providing erosion protection for the riverbed surface. It also reinforces and weights the tunnel segments themselves at the riverbed, achieving improved buoyancy and erosion resistance during construction and operation of the river-crossing tunnel, ensuring safety. This invention offers valuable insights for tunnels that cannot be deeply buried across riverbeds. The reinforcement layer employs conventional grouting and concrete pouring, simplifying construction. The reinforcement layer extends outward relative to the tunnel, ensuring safety and controllability. The protective layer uses concrete protective slabs and structural beams as its main components. The protective slabs extend outward relative to the reinforcement layer, minimizing soil erosion under their weight and providing excellent erosion resistance. This reduces subsequent maintenance work on the interlayer soil between the protective slab and the tunnel, and also improves the tunnel's buoyancy resistance through their own weight. The overall construction speed is fast, and the grouting, concrete pouring, and riprap replacement processes are all simple and effective, resulting in significant economic benefits. Attached Figure Description

[0016] Figure 1 This is a plan view of the overall layout of an embodiment of the present utility model.

[0017] Figure 2 This is a plan view of an embodiment of the present utility model.

[0018] Figure 3 This is a cross-sectional schematic diagram along the direction of the river tunnel in an embodiment of the present invention.

[0019] Figure 4 This is a cross-sectional schematic diagram of an embodiment of the present invention in the direction perpendicular to the river tunnel.

[0020] Attached reference numerals: 1-Tunnel; 2-Riverbed Tunnel; 3-River Channel; 4-Protective Plate; 5-Reinforcement Layer; 6-Structural Beam; 7-Backfill Layer; 8-Subbase Layer. Detailed Implementation

[0021] Because the overburden thickness of tunnel 2 is relatively thin and the soil and rock properties at the bottom of the river are poor, coupled with the disturbance of shallow geology during shield tunneling, the riverbed soil and rock are prone to erosion, which will adversely affect the buoyancy resistance of tunnel 1. This utility model adopts grouting reinforcement of the riverbed to improve the poor soil and rock properties of the original riverbed, increase the self-weight and mechanical properties of the shallow overburden, and ensure the stability of the shield tunneling and operation, as well as the safety of the river channel 3.

[0022] A protective structure for preventing buoyancy and scour in a riverbed tunnel, used for buoyancy and scour resistance during the construction and operation of the riverbed tunnel 2. Figures 1 to 4The structure includes an underwater tunnel 2 passing beneath the riverbed, a reinforcement layer 5, a protective layer, and a backfill layer 7. The reinforcement layer 5 extends along the direction of the underwater tunnel 2, with its bottom extending into the arch (the widest part of the tunnel) of the underwater tunnel 2. Its width exceeds the arches on both sides of the underwater tunnel 2, and its two ends cover both ends of the underwater tunnel 2. The protective layer is positioned above the reinforcement layer 5 along the direction of the underwater tunnel 2. It is used to isolate the tunnel from direct scouring by river water and to provide support during the grouting and filling of the reinforcement layer 5. The protective layer can also further increase the anti-buoyancy counterweight above the tunnel segments. The backfill layer 7 is positioned above the protective layer, with its upper surface flush with the original riverbed elevation. The backfill layer 7 protects both the protective layer and the riverbed.

[0023] Specifically, in this embodiment, the range of the reinforcement layer 5 is as follows: the reinforcement layer 5 extends outward by 3m on both sides towards the arch position of the riverbed tunnel 2 in its width direction; at the same time, the reinforcement layer 5 extends outward at a 45° angle from the junction of the reinforcement layer 5 and the river to the position of the river tunnel in its extension direction.

[0024] The reinforcement layer 5 is a concrete structure, which can be reinforced by segmented grouting using sleeve valve grouting. Ordinary Portland cement with a strength grade of 42.5, possessing filling and gelling properties, can be used. The water-cement ratio of the cement grout is 0.6-1 (cement:bentonite:water) of 1:2:2.5. The grout is injected into the stratum between the protective plate 4 and the tunnel arch using a matching grouting machine. After gelling and hardening, it fills and seals the voids in the stratum, reducing the permeability coefficient of the grouting area and the leakage during tunnel excavation. It also consolidates weak and loose rock masses, improving the stratum strength and self-stabilizing ability.

[0025] Due to the disturbance caused by shield tunneling, especially in areas with shallow overburden, after the tunnel ring separates from the shield tail, the pressure and weight of the upper part cannot resist buoyancy, easily causing Tunnel 1 to float. Moreover, the shallow riverbed changes over time, resulting in large variations in the load on the upper part of the shield segments. To reduce the impact of these load variations on the buoyancy resistance of the riverbed tunnel 2, the riverbed tunnel 2 is constructed using special segments. The diameter of the main reinforcing bars in these special segments is larger than that of the main reinforcing bars in the ordinary segments of other tunnel sections.

[0026] The selection of tunnel segments requires comprehensive consideration of various factors, including engineering geological conditions, tunnel cross-sectional dimensions, construction technology level, economic costs, and load-bearing requirements. Simultaneously, attention should be paid to the production quality and construction process of the segments to ensure that the selected segments meet engineering requirements and have good performance. In this embodiment, the main reinforcing bars of ordinary segments in other tunnel sections 1 are HRB400 grade steel bars with a diameter of 20mm. For riverbed tunnel section 2, considering various factors, and taking into account that the segments are located in a shallow overburden section of the riverbed, the steel bar grade is increased from HRB400 20 to HRB400 grade steel bars with a diameter of 28mm to improve the segment's counterweight and deformation resistance, and reduce the impact of insufficient buoyancy resistance and large fluctuations in the upper load. To achieve continuous construction procedures, modified special segments need to be prepared in advance.

[0027] When the tunnel boring machine (TBM) passes close to the riverbed, the construction will cause subsidence, deformation, and damage to the river channel and riverbanks above. Furthermore, the cumulative erosion and load changes on the riverbed over time will also affect the safety of the TBM during operation. To control the stability of the riverbed structure, in this embodiment, the protective layer includes a protective plate 4 and structural beams 6. The protective plate 4 extends along the direction of the riverbed tunnel 2, and its width is greater than the width of the reinforcement layer 5. The structural beams 6 are located on both sides of the bottom of the protective plate 4 and extend along the direction of the protective plate 4. The structural beams 6 are embedded in the bottom soil layer of the riverbed 3 to strengthen the anchorage between the protective plate 4 and the riverbed soil. The protective plate 4 is supported on the riverbed by the structural beams 6. The protective plate 4 and the structural beams 6 form the riverbed structure, providing effective resistance to deformation and bearing capacity for routine dredging operations and other activities on the riverbed.

[0028] The protective plate 4 is a reinforced concrete slab. In this embodiment, the distance between each side of the protective plate 4 and the two sides of the reinforcement layer 5 is 3m, that is, the two sides of the protective plate 4 extend outward by 3m relative to the two sides of the reinforcement layer 5. The structural beam 6 is a reinforced concrete beam. The protective plate 4 and the structural beam 6 isolate the riverbed from the tunnel lining segments, which can not only isolate the river water from the direct scouring of the tunnel lining segments and the soil above, but also further increase the anti-buoyancy counterweight above the tunnel lining segments. Because of the installation of the protective plate 4 and the structural beam 6, a riverbed structure can be formed, providing effective resistance to deformation and bearing capacity for conventional dredging operations and other activities on the riverbed.

[0029] To ensure the stability of the structural beam 6, a cushion layer 8 is also installed at a corresponding position on the riverbed. Two cushion layers 8 are laid along both sides of the reinforcement layer 5, and each cushion layer 8 has a groove adapted to the structural beam 6. The structural beam 6 is embedded into the bottom soil layer of the river channel 3 through the groove. The cushion layer 8 can be a C20 concrete cushion layer 8. After excavating to the design elevation at the location on the riverbed where grouting reinforcement and the laying of the protective plate 4 are required, and draining the river water, the construction of the C20 concrete cushion layer 8 is carried out. After the cushion layer 8 reaches the design strength, the binding and pouring of the protective plate 4 and the reinforcement of the structural beam 6 are carried out.

[0030] The backfill layer 7 uses riprap with a particle size of 10-30 cm, which is more compact, reduces silt accumulation and water erosion, and the density of the riprap is between 23-27 kN / m³, improving the tunnel's anti-buoyancy capacity and making the riprap system more stable under external forces such as water flow. After the protective plate 4 is poured with concrete and reaches a certain strength, the riprap can be backfilled to the design elevation of the riverbed. Riprap with a large internal friction angle should be selected as much as possible to further improve overall stability.

[0031] The construction procedure of this utility model is as follows: (1) Segment Improvement: Special segments for the riverbed tunnel 2 were prefabricated in advance, and the main reinforcement of the special segments was increased from HRB400 20 to HRB400 28. By strengthening quality control during segment production, the quality of the segments was improved: the selection of high-quality cement, aggregates, water and other raw materials, as well as an appropriate water-cement ratio, can improve the concrete strength and ensure the optimization of various concrete properties. Strengthening the control of production processes such as pouring, vibration and curing reduces internal defects in the concrete and affects its strength.

[0032] (2) Construction of cofferdams: To ensure that the water flow of the riverbed is not affected during the construction phase, cofferdams will be constructed in three stages during the dry season for each riverbed section. Each stage will enclose 1 / 3 of the riverbed section, and the measures for each tunnel to pass under the riverbed will be completed in three stages. 9m steel sheet piles will be used as temporary cofferdams, which will be about 1m higher than the river water level during construction. After construction, the steel sheet piles will be removed in a timely manner and the trench walls will be backfilled.

[0033] The specific steps are as follows: 1) The planar layout of the cofferdam sheet pile support should be as straight and neat as possible, avoiding irregular corners, to facilitate the use of standard sheet piles. Based on the design cross-sectional width requirements of the trench excavation, the sheet pile driving position lines should be measured and marked.

[0034] 2) Organize the arrival time of steel sheet piles according to the construction schedule or site conditions to ensure that the construction of steel sheet piles meets the schedule requirements. The stacking location of steel sheet piles should be dispersed along the support line according to the construction requirements and site conditions to avoid concentrated stacking and secondary handling.

[0035] 3) Inspection of steel sheet piles: Steel sheet piles are generally inspected for material quality and appearance in order to correct any non-compliant steel sheet piles and reduce difficulties in the pile driving process.

[0036] A. Visual Inspection: This includes checking for surface defects, length, width, thickness, end rectangle ratio, straightness, and lock shape. Note: (a) Welded components that affect the driving of sheet piles should be removed; (b) Holes and cross-sectional defects should be reinforced. (c) If the sheet piles are severely corroded, their actual cross-sectional thickness should be measured. In principle, all sheet piles should be visually inspected.

[0037] B. Material Inspection: A comprehensive test is conducted on the chemical composition and mechanical properties of the sheet pile base material. This includes chemical composition analysis of the steel, tensile and bending tests of the components, interlock strength tests, and elongation tests. At least one tensile and bending test is performed for each specification of sheet pile; two specimen tests are required for every 20–50 t sheet pile.

[0038] 4) Steel sheet piles should be stacked in layers, with each layer generally containing no more than 5 piles. Sleepers should be placed between each layer, with a spacing of 3 to 4 meters between the sleepers. The sleepers between the upper and lower layers should be on the same vertical line, and the total height of the stack should not exceed 2 meters.

[0039] 5) Two-point hoisting is recommended for loading and unloading sheet piles. During hoisting, the number of sheet piles lifted at one time should not be excessive, and care should be taken to protect the interlocking joints from damage. Bundles are typically lifted using steel cables, while single sheet piles should be lifted using specialized lifting equipment.

[0040] 6) In the construction of sheet piles, in order to ensure the correct position of the pile axis and the verticality of the pile, control the driving accuracy of the pile, prevent the buckling deformation of the sheet pile and improve the penetration capacity of the pile, a rigid and sturdy guide frame should be set up.

[0041] 7) The construction of Larssen sheet piles is related to water sealing and safety. The following construction requirements should be noted during construction: a) Before driving Larssen sheet piles, it is essential to be familiar with the underground pipelines and structures, and to carefully mark out the accurate centerline of the piles.

[0042] b) Before piling, each sheet pile shall be inspected and any sheet piles with severe rust or deformation at the connection lock shall be removed. Only sheet piles that have been repaired and are deemed qualified shall be used. Sheet piles that are still not qualified after repair shall be prohibited from use.

[0043] c) Before driving the piles, grease can be applied to the interlocks of the sheet piles to facilitate driving and pulling them out.

[0044] d) During the driving of sheet piles, the inclination of each pile should be measured and monitored to ensure that it does not exceed 2%. If the inclination is too large and cannot be corrected by aligning, the pile must be pulled out and driven again.

[0045] e) Ensure the sheet piles are tightly fastened and closed smoothly. In particular, corner sheet piles should be used at the four corners of the manhole. If such sheet piles are not available, use old tires or rags to seal the gaps to prevent water leakage from carrying away mud and sand and causing ground subsidence.

[0046] f) During the trench excavation process, observe the changes in the sheet piles at any time. If there is obvious overturning or bulging, immediately add symmetrical supports to the overturned or bulging parts.

[0047] 8) Before removing sheet piles, the removal method, sequence, timing, and treatment of the soil holes should be carefully studied. Otherwise, the vibration caused by pile removal and the excessive soil carried by the piles may lead to ground settlement and displacement, which may harm the underground structures that have already been constructed and affect the safety of nearby existing buildings and structures.

[0048] 9) The pile holes left after pile extraction must be backfilled in a timely manner. The backfilling method shall be the filling method, and the materials used for the filling method shall be stone chips or medium-coarse sand.

[0049] (3) Excavation of riverbed soil: Excavate at the corresponding position of reinforcement layer 5, excavate to the design elevation, and after the bottom of the pit is excavated, promptly pump out the river water in the cofferdam and prepare C20 concrete cushion layer 8.

[0050] (4) Construction of protective layer: After the foundation layer 8 reaches the design strength requirements, the protective plate 4 and the bottom structural beam 6 are tied together and concrete is poured.

[0051] (5) Backfilling with riprap: After the concrete of the protective plate 4 and the structural beam 6 reaches a certain strength, riprap can be backfilled to the design elevation of the riverbed to form the backfill layer 7.

[0052] (6) Sleeve valve grouting: Ordinary Portland cement with a strength grade of 42.5, which has filling and gelling properties, is used. The water-cement ratio of the cement grout is 0.6-1 (cement: bentonite: water) of 1:2:2.5. The grout is pressed into the stratum between the protective plate 4 and the tunnel arch waist using the matching grouting equipment. After gel hardening, it fills and blocks the voids in the stratum, forming a reinforcement layer 5. This can reduce the permeability coefficient of the stratum in the grouting area and the leakage during tunnel excavation, and can consolidate weak and loose rock masses to improve the strength and self-stabilizing ability of the stratum. To ensure reliable reinforcement effect, grouting should be carried out in sections, 3-4 times. Reinforcement range: 3m outward on both sides of the tunnel, and 45° inclined soil reinforcement at the boundary between the tunnel and the river.

[0053] (7) Shield tunneling: After the riverbed treatment measures are completed and stabilized, the shield tunneling will proceed. During the passage, monitoring of the tunnel segments themselves and the river channel 3 will be strengthened. Grouting will be carried out on the 10 rings of tunnel segments before and after passing through the riverbed to improve the stability and airtightness of the section passing under the river.

[0054] Before construction, the deformation of the shield tunnel under shallow overburden crossing the riverbed was theoretically simulated, and the results are shown in Table 1. Theoretically, it is proven that this scheme can meet the specified requirements.

[0055] Table 1. Results of riverbed settlement and deformation after simulated tunnel excavation.

[0056] During actual construction, the surface settlement during the tunnel boring machine's passage was monitored in real time. The monitoring results are shown in Table 2. Practice has proven that the monitoring data is stable and within the specified range, demonstrating the feasibility of the proposed solution.

[0057] Table 2. Monitoring results of shield tunneling across the riverbed

[0058] The above detailed description is a specific description of a feasible embodiment of the present utility model. This embodiment is not intended to limit the patent scope of the present utility model. All equivalent implementations or modifications that do not depart from the present utility model should be included in the patent scope of this case.

Claims

1. A river bottom tunnel anti-floating and anti-scouring protection structure for anti-floating and anti-scouring during construction of a river bottom tunnel crossing a river bottom and during operation, characterized in that, The structure includes a riverbed tunnel passing beneath the riverbed, a reinforcement layer, a protective layer, and a backfill layer. The reinforcement layer is installed along the extension direction of the riverbed tunnel, with its bottom extending into the arch of the riverbed tunnel. Its width exceeds the two arches of the riverbed tunnel, and both ends of its extension cover both ends of the riverbed tunnel. The protective layer is installed above the reinforcement layer along the extension direction of the riverbed tunnel to isolate it from direct scouring by river water and to provide support during grouting of the reinforcement layer. The backfill layer is installed above the protective layer, and its upper surface is flush with the original riverbed elevation.

2. The anti-buoyancy and anti-scour protection structure for riverbed tunnels according to claim 1, characterized in that, The protective layer includes a protective plate and structural beams. The protective plate extends along the direction of the riverbed tunnel and its width is greater than the width of the reinforcement layer. The structural beams are set on both sides of the bottom of the protective plate and extend along the direction of the protective plate. The structural beams are embedded in the bottom soil layer of the river channel to strengthen the fixation between the protective plate and the riverbed soil.

3. The anti-buoyancy and anti-scour protection structure for riverbed tunnels according to claim 2, characterized in that, It also includes a cushion layer set on the riverbed surface, and two cushion layers are laid along both sides of the reinforcement layer. Each cushion layer is provided with a groove that matches the structural beam, and the structural beam is embedded into the bottom soil layer of the river through the groove.

4. The anti-buoyancy and anti-scour protection structure for riverbed tunnels according to claim 2, characterized in that, The protective plate is a reinforced concrete slab, and the distance between each side of the protective plate and the two sides of the reinforcement layer is 3m. The structural beam is a reinforced concrete beam.

5. The anti-buoyancy and anti-scour protection structure for riverbed tunnels according to claim 1, characterized in that, The riverbed tunnel is constructed from segments, and the diameter of the main reinforcing bars in the segments is larger than that of the main reinforcing bars in ordinary segments in the tunnel section.

6. The anti-buoyancy and anti-scour protection structure for riverbed tunnels according to claim 1, characterized in that, The reinforcement layer extends outward by 3m on each side of its width toward the arch of the riverbed tunnel.

7. The anti-buoyancy and anti-scour protection structure for riverbed tunnels according to claim 1, characterized in that, The reinforcement layer extends obliquely downward and outward at a 45° angle from the junction of the reinforcement layer and the river channel to the location of the river tunnel in its extension direction.

8. The anti-buoyancy and anti-scour protection structure for riverbed tunnels according to claim 1, characterized in that, The reinforcement layer is a concrete structure formed by grouting.

9. The anti-buoyancy and anti-scour protection structure for riverbed tunnels according to claim 1, characterized in that, The backfill layer uses paved stones with a particle size of 10-30 cm and a density of 23-27 kN / m³.

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