Tunnel road transition structure suitable for soft rock roadbed and construction method

Abstract

The invention relates to the technical field of railway roadbed engineering, in particular to a tunnel road transition structure suitable for a soft rock roadbed and a construction method.The tunnel road transition structure comprises a cover plate, an elastic compression layer and a jack, and the cover plate is arranged above the roadbed and connected between a tunnel inverted arch and a roadbed surface layer; the elastic compression layer is arranged between the cover plate and the roadbed; the roadbed is positioned above the soft rock layer; the side edge of one side of the cover plate is rotationally connected with the tunnel inverted arch or the roadbed surface layer, the jack is arranged above the cover plate, and the jack can apply pressure to the cover plate to enable the cover plate to be aligned with the tunnel inverted arch or the roadbed surface layer. The side edge of the cover plate can be always aligned with the surface layer of the roadbed by controlling the pressure applied by the jack above the cover plate, so that slab staggering at the tunnel interface is avoided, and smooth transition of the tunnel interface is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of railway roadbed engineering, and in particular to a tunnel-road transition structure suitable for soft rock roadbed and a construction method. Background Art

[0002] The Sichuan-Chongqing region in my country is dominated by hilly terrain and widespread red-bed soft rock. The construction of high-speed railways in this area inevitably involves the use of cuttings and tunnels. In cutting sections, due to the water-expansion and unloading rheological properties of the red-bed soft rock, the roadbed experiences significant upwarping deformation after excavation. In tunnel sections, however, due to the small unloading volume of the tunnel excavation and the constraints of the surrounding rock mass, the upwarping deformation is relatively small. High-speed railway ballastless tracks require extremely precise and stringent control of differential deformation in transition sections. Due to the different upwarping deformations in cutting and tunnel sections, poor control of differential deformation can easily lead to misalignment at the tunnel-track interface, and in severe cases, even train tripping, threatening the operational safety of high-speed railways.

[0003] The currently widely used tunnel transition type is an inverted trapezoidal transition structure along the longitudinal direction of the line. The filler within the trapezoidal range is graded crushed stone mixed with a small amount of cement. However, this transition structure cannot effectively control the differential deformation of the transition section of the red-bed soft rock tunnel. The differential deformation is concentrated at the tunnel interface, which is very likely to cause misalignment. Therefore, it is not suitable for the transition section of the red-bed soft rock tunnel.

[0004] Therefore, there is an urgent need for a soft rock tunnel transition structure that is simple to construct, low in cost and has a promising prospect for promotion and application to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to overcome the technical problem that the existing tunnel transition structure cannot effectively control differential deformation and is prone to misalignment when used for soft rock roadbed, and to provide a tunnel transition structure and construction method suitable for soft rock roadbed.

[0006] In a first aspect, the present invention provides a tunnel transition structure suitable for a soft rock roadbed, comprising a cover plate, an elastic compression layer and a jack, wherein the cover plate is arranged above the roadbed and connected between the tunnel invert and the roadbed surface, and the elastic compression layer is arranged between the cover plate and the roadbed; the roadbed is located above the soft rock layer; a side edge of one side of the cover plate is rotatably connected to the tunnel invert or the roadbed surface, and the jack is arranged above the cover plate, and the jack can apply pressure to the cover plate to align the cover plate with the tunnel invert or the roadbed surface.

[0007] The present invention provides a cover plate in a tunnel transition section, and allows the side edge of one side of the cover plate to be rotatably connected to the tunnel invert or the roadbed surface, so that the side edge of one side of the cover plate can be aligned with the tunnel invert or the roadbed surface; an elastic compression layer is provided under the cover plate, and the jack above the cover plate can be used to apply pressure to the cover plate and compress the elastic compression layer, so that the side edge of the other side of the cover plate can be aligned with the roadbed surface or the tunnel invert; specifically, if the side edge of one side of the cover plate is rotatably connected to the tunnel invert, the side edge of the other side of the cover plate can be aligned with the roadbed surface or the tunnel invert under the jack. The elastic compression layer is compressed under the pressure of the top to align it with the roadbed surface. The side of the cover plate can be always aligned with the roadbed surface by controlling the pressure applied by the jack, thereby avoiding misalignment at the tunnel interface and ensuring a smooth transition of the tunnel interface. Of course, the side of one side of the cover plate can also be rotatably connected to the roadbed surface, and the side of the other side of the cover plate can be compressed under the pressure of the jack to align it with the tunnel invert arch. The effect of avoiding misalignment at the tunnel interface can also be achieved by controlling the pressure of the jack.

[0008] Preferably, an anchor cable is further included, one end of the anchor cable passes through the cover plate and is connected to the jack, and the other end of the anchor cable is anchored in the stable layer below the soft rock layer.

[0009] By connecting the anchor cable to the jack and anchoring the anchor cable in the stable layer below the soft rock layer, a stable fulcrum can be provided for the jack when pressure is applied to the cover plate through the jack, which can ensure that the jack provides sufficient pressure to the cover plate when applying pressure; of course, in addition to using the anchor cable, the fulcrum of the jack can also be fixed in other ways. For example, a fixed bracket connected to the surface of the roadbed or the tunnel invert arch can be installed above the jack to achieve the same fulcrum effect.

[0010] Preferably, it also includes an anchor pile, which is located below the elastic compression layer and is arranged corresponding to the anchor cable. The anchor pile passes through the soft rock layer, the upper end of the anchor pile extends into the roadbed, and the lower end of the anchor pile extends into the stabilization layer; the anchor cable is passed through the anchor pile.

[0011] In order to enhance the anchoring effect of the anchor cable, anchor piles can be set at the corresponding positions of the anchor cables, and the upper and lower ends of the anchor piles are respectively passed through the soft rock layer into the roadbed and the stable layer, and the anchor cable is passed through the anchor piles, which can significantly improve the anchoring effect and pull-out resistance, thereby increasing the pressure applied by the jack on the cover plate.

[0012] Preferably, the anchor pile is provided with a sleeve, the outer side of the sleeve is wrapped with an elastic isolation layer, and the elastic isolation layer is located in the soft rock layer and the roadbed.

[0013] The upper part of the anchor pile is wrapped with an elastic isolation layer, which can not only reduce the horizontal stress on the anchor pile and avoid the adverse effects of the surrounding soil pressure on the anchor pile and the cover plate above it, but also reduce the upward arch force of the upper stratum on the anchor pile and improve the pull-out resistance of the anchor pile; the elastic isolation layer and the anchor pile body are isolated by a sleeve.

[0014] Preferably, the cover plate is rotatably connected to the tunnel invert, and the transition structure includes two jacks, which are arranged on a side of the cover plate close to the roadbed surface and spaced apart from each other.

[0015] Preferably, the two jacks are both connected to a control base station, and the control base station is used to adjust the pressure applied by the two jacks to the cover plate.

[0016] Here, the jack can be hydraulic, and the hydraulic jack can be adjusted by controlling the base station so that the elevation of the side cover away from the invert arch matches the elevation of the adjacent roadbed surface, avoiding misalignment and achieving a smooth transition between the tunnel and the road.

[0017] Preferably, an expansion joint is formed between the cover plate and the roadbed surface layer.

[0018] An expansion joint is formed between the cover plate away from the tunnel invert arch side and the roadbed surface to prevent the cover plate and the adjacent roadbed surface from being squeezed and deformed due to thermal expansion and contraction.

[0019] In a second aspect, the present invention provides a construction method for a tunnel transition structure suitable for a soft rock roadbed, which is applied to the tunnel transition structure suitable for a soft rock roadbed as described above, and the construction method comprises: S1: excavating the original road cutting and filling the roadbed; S2: erecting a formwork and steel bars above the roadbed, pouring concrete in the formwork to form the cover plate, and rotatably connecting the cover plate to the tunnel invert or the roadbed surface; S3: removing the formwork, lifting the cover plate, and laying the elastic compression layer on the roadbed; S4: Install the jack on the cover plate, and apply pressure to the cover plate through the jack to align the cover plate with the tunnel invert or the roadbed surface.

[0020] Preferably, in S2, the method of rotatably connecting the cover plate to the tunnel invert or the roadbed surface layer includes: S21: Installing a rotating bearing on the tunnel invert or the roadbed surface; S22: before pouring the cover plate, tying the movable end of the rotating support to the steel bar.

[0021] Preferably, in S3, the formwork is removed after the strength of the concrete reaches 70% of the design strength.

[0022] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention provides a tunnel transition structure and construction method suitable for soft rock roadbed. By arranging a cover plate in the tunnel transition section and rotatably connecting the side edge of one side of the cover plate to the tunnel invert or the roadbed surface, the side edge of one side of the cover plate can be aligned with the tunnel invert or the roadbed surface. An elastic compression layer is arranged under the cover plate. The jack above the cover plate can be used to apply pressure to the cover plate and compress the elastic compression layer, so that the side edge of the other side of the cover plate can be aligned with the roadbed surface or the tunnel invert. Specifically, if the side edge of one side of the cover plate is rotatably connected to the tunnel invert, Then, the side of the other side of the cover plate can compress the elastic compression layer under the pressure of the jack so that it is aligned with the roadbed surface. The side of the cover plate can be always aligned with the roadbed surface by controlling the pressure applied by the jack, thereby avoiding misalignment at the tunnel interface and ensuring a smooth transition of the tunnel interface. Of course, the side of one side of the cover plate can also be rotatably connected to the roadbed surface, and the side of the other side of the cover plate can be compressed by the pressure of the jack so that it is aligned with the tunnel invert. The effect of avoiding misalignment at the tunnel interface can also be achieved by controlling the pressure of the jack. 2. The top surface of the cover plate can be flush with the top surface of the tunnel inverted arch and can be connected to the top surface of the tunnel inverted arch using a rotating support, which can avoid misalignment at the tunnel interface and evenly distribute the uneven settlement of the tunnel transition section to the cover plate; 3. An elastic compression layer is provided between the cover plate and the roadbed below. When the roadbed below arches, the elastic compression layer is compressed and deformed. By reserving a certain amount of arch margin, the arch force of the roadbed on the cover plate can be effectively reduced. 4. The anchor piles pass through the roadbed and the upper arch soft rock layer and are embedded in the stable rock layer to enhance the pullout resistance of the anchor piles. The elastic isolation layer is wrapped around the pile body in the roadbed and the upper arch soft rock layer. The elastic isolation layer can be made of asphalt. Asphalt has good waterproof, corrosion-resistant and elastic properties. It can not only reduce the horizontal force on the anchor piles, avoid the adverse effects of the surrounding soil pressure on the anchor piles and the cover plate above them, but also reduce the uplift force of the upper stratum on the anchor piles, thereby improving the pullout resistance of the anchor piles. 5. The cover plate is connected to the anchor piles through jacks. The anchor piles pass through the roadbed and the soft rock layer of the upper arch and are embedded in the stable rock layer. The jacks can be adjusted by hydraulic pumps to match the elevation of the cover plate on the side away from the inverted arch with the elevation of the adjacent roadbed surface, achieving a smooth transition between the tunnel and the road. 6. Anchor cables are installed in the anchor piles. The lower end of the anchor cables can be buried in the stabilization layer and welded to the steel bars at the bottom of the anchor piles. The upper end is anchored on the jack. The hydraulic jack is controlled by the control base station and is operated regularly by personnel. The height of the cover plate is controlled by adjusting the tension of the anchor cables to ensure a smooth connection between the cover plate and the adjacent roadbed surface.

[0023] 7. An expansion joint is formed between the cover plate away from the tunnel invert arch side and the roadbed surface to prevent the cover plate and the adjacent roadbed surface from being squeezed and deformed due to thermal expansion and contraction. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a longitudinal section view of the tunnel transition structure suitable for soft rock roadbed of the present invention.

[0025] Figure 2 It is a top plan view of the tunnel transition structure suitable for soft rock roadbed of the present invention.

[0026] Markings in the figure: 1. Cover plate, 2. Rotating bearing, 3. Elastic compression layer, 4. Anchor pile, 5. Elastic isolation layer, 6. Sleeve, 7. Anchor cable, 8. Jack, 9. Control base station, 10. Expansion joint, 11. Roadbed surface layer, 12. Roadbed, 13. Soft rock layer, 14. Stabilizing layer, 15. Tunnel invert. DETAILED DESCRIPTION

[0027] The present invention will be further described in detail below with reference to specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments, as all technologies implemented based on the present invention fall within the scope of the present invention.

[0028] Unless otherwise specified, in the description of the specific embodiments of the present invention, the terms indicating the orientation or positional relationship, such as "upper", "lower", "left", "right", "center", "inside", and "outside", are based on the expressions of the orientation or positional relationship shown in the accompanying drawings, or are the orientation or positional relationship in which the invented product / device / apparatus is placed when it is conventionally used. These terms of orientation or positional relationship are merely for the purpose of facilitating the description of the scheme of the present invention or simplifying the description of the specific embodiments to facilitate the rapid understanding of the scheme by technicians, and do not indicate or imply that a specific device / component / element must have a specific orientation, or be constructed and operated in a specific positional relationship, and therefore should not be understood as limiting the present invention.

[0029] In addition, if the terms "horizontal", "vertical", "overhanging", "parallel" and the like appear, it does not mean that the corresponding devices / components / elements are required to be absolutely horizontal or vertical or overhanging or parallel, but may be slightly tilted or have deviations. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but may be slightly tilted. Alternatively, it can be simply understood that the corresponding devices / components / elements are set in directions such as "horizontal", "vertical", "overhanging", and "parallel", and can have an error / deviation of ±10% relative to the corresponding direction setting, more preferably an error / deviation within ±8%, more preferably an error / deviation within ±6%, more preferably an error / deviation within ±5%, and more preferably an error / deviation within ±4%. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its role in the solution of the present invention.

[0030] In addition, the expressions “first”, “second”, “third”, etc. in the terms are merely used to distinguish the description of the same or similar components, and should not be understood as emphasizing or implying the relative importance of specific components.

[0031] In addition, in the description of the embodiments of the present invention, "several," "plurality," and "a number" represent at least two. It can also be any number such as two, three, four, five, six, seven, eight, nine, or even more than nine.

[0032] Furthermore, in the description of the technical solution of the present invention, unless otherwise expressly specified, defined, or limited, the terms "disposed," "installed," "connected," "connected," "provided with," "laid," and "arranged" should be understood broadly. For example, they may refer to fixed connections, detachable connections, or integral connections. They may be welded, riveted, bolted, threaded, or other commonly used connection methods in the art. Such connections may be mechanical, electrical, or communicative; they may be direct, indirect via an intermediate medium, or internally connected between two components.

[0033] Example 1 This embodiment provides a tunnel-road transition structure suitable for soft rock roadbed.

[0034] Figure 1 A longitudinal section of a tunnel transition structure suitable for soft rock roadbed according to the present invention; Figure 2 It is a top plan view of the tunnel transition structure suitable for soft rock roadbed of the present invention.

[0035] like Figures 1 to 2As shown in the figure, the tunnel transition structure suitable for soft rock roadbed of the present invention includes a cover plate 1, an elastic compression layer 3 and a jack 8. The cover plate 1 is arranged above the roadbed 12 and connected between the tunnel invert 15 and the roadbed surface 11. The elastic compression layer 3 is arranged between the cover plate 1 and the roadbed 12. By reserving a certain amount of arch margin, the arch force of the roadbed 12 on the cover plate 1 can be effectively reduced; the roadbed 12 is located above the soft rock layer 13; the side edge of one side of the cover plate 1 is rotatably connected to the tunnel invert 15 or the roadbed surface 11, and the jack 8 is arranged above the cover plate 1. The jack 8 can apply pressure to the cover plate 1 to align the cover plate 1 with the tunnel invert 15 or the roadbed surface 11; the cover plate 1 is arranged on the outside of the tunnel entrance and exit inverts, and the cover plate 1 can be cast in situ with reinforced concrete.

[0036] The present invention provides a cover plate 1 in the tunnel transition section, and allows the side edge of one side of the cover plate 1 to be rotatably connected to the tunnel inverted arch 15 or the roadbed surface 11, so that the side edge of one side of the cover plate 1 is aligned with the tunnel inverted arch 15 or the roadbed surface 11; an elastic compression layer 3 is provided under the cover plate 1, and the jack 8 above the cover plate 1 can be used to apply pressure to the cover plate 1 and compress the elastic compression layer 3, so that the side edge of the other side of the cover plate 1 is aligned with the roadbed surface 11 or the tunnel inverted arch 15; specifically, if the side edge of one side of the cover plate 1 is rotatably connected to the tunnel inverted arch 15, the side edge of the other side of the cover plate 1 The elastic compression layer 3 can be compressed under the pressure of the jack 8 so that it is aligned with the roadbed surface layer 11. The side of the cover plate 1 can be always aligned with the roadbed surface layer 11 by controlling the pressure applied by the jack 8, thereby avoiding misalignment at the tunnel interface and ensuring a smooth transition of the tunnel interface. Of course, the side of one side of the cover plate 1 can also be rotatably connected to the roadbed surface layer 11, and the side of the other side of the cover plate 1 can be compressed under the pressure of the jack 8 so that it is aligned with the tunnel invert 15. The effect of avoiding misalignment at the tunnel interface can also be achieved by controlling the pressure of the jack 8.

[0037] In this embodiment, the tunnel transition structure further includes an anchor cable 7 , one end of which passes through the cover plate 1 and is connected to the jack 8 , and the other end of the anchor cable 7 is anchored in the stabilizing layer 14 below the soft rock layer 13 .

[0038] By connecting the anchor cable 7 to the jack 8 and anchoring the anchor cable 7 in the stable layer 14 below the soft rock layer 13, a stable fulcrum can be provided for the jack 8 when pressure is applied to the cover plate 1 through the jack 8, which can ensure that the jack 8 provides sufficient pressure to the cover plate 1 when pressure is applied; of course, in addition to using the anchor cable 7, the fulcrum of the jack 8 can also be fixed in other ways. For example, a fixed bracket connected to the roadbed surface 11 or the tunnel invert arch 15 is installed above the jack 8, which can also achieve the same fulcrum effect; here, the anchor cable 7 can be a steel wire rope.

[0039] In this embodiment, the tunnel transition structure also includes an anchor pile 4, which is located below the elastic compression layer 3 and is arranged corresponding to the anchor cable 7. The anchor pile 4 passes through the soft rock layer 13, and the upper end of the anchor pile 4 extends into the roadbed 12, and the lower end of the anchor pile 4 extends into the stable layer 14; the anchor cable 7 is passed through the anchor pile 4; specifically, the anchor pile 4 is arranged below the side of the cover plate 1 away from the tunnel arch 15, and the cover plate 1 is connected to the anchor pile 4 through the jack 8. The anchor pile 4 passes through the roadbed 12 and the soft rock layer 13 and is embedded in the stable layer 14.

[0040] In order to enhance the anchoring effect of the anchor cable 7, an anchor pile 4 can be set at the corresponding position of the anchor cable 7, and the upper and lower ends of the anchor pile 4 are respectively passed through the soft rock layer 13 into the roadbed 12 and the stable layer 14, and the anchor cable 7 is passed through the anchor pile 4, which can significantly improve the anchoring effect and pull-out resistance, thereby increasing the pressure applied by the jack 8 to the cover plate 1.

[0041] Optionally, the anchor pile 4 is provided with a sleeve 6 , and the outer side of the sleeve 6 is wrapped with an elastic isolation layer 5 , and the elastic isolation layer 5 is located between the soft rock layer 13 and the roadbed 12 .

[0042] An elastic isolation layer 5 is wrapped around the upper pile body of the anchor pile 4. Here, the elastic isolation layer 5 can be made of asphalt material. Asphalt has good waterproof, corrosion-resistant and elastic properties, which can not only reduce the horizontal stress on the anchor pile 4 and avoid the adverse effects of the surrounding soil pressure on the anchor pile 4 and the cover plate 1 above it, but also reduce the upward arch force of the upper stratum on the anchor pile 4 and improve the pull-out resistance of the anchor pile 4; the elastic isolation layer 5 and the pile body of the anchor pile 4 are isolated by a sleeve 6; of course, the elastic isolation layer 5 can also be made of other materials, such as rubber, etc., and the present invention does not make specific limitations on this.

[0043] Optionally, the cover plate 1 is rotatably connected to the tunnel invert 15, and the tunnel transition structure includes two jacks 8, which are arranged on one side of the cover plate 1 close to the roadbed surface 11 and are spaced apart from each other; of course, the cover plate 1 can also be rotatably connected to the roadbed surface 11. Specifically, the cover plate 1 and the tunnel invert 15 or the roadbed surface 11 can be connected through a rotating support 2 to achieve a rotational connection, and the rotating support 2 is similar to a hinge structure; the number of jacks 8 installed above the cover plate 1 is not limited to two, and can be selected separately according to actual needs. The present invention does not make specific limitations on this.

[0044] In this embodiment, both jacks 8 are connected to a control base station 9, which is used to adjust the pressure applied by the two jacks 8 to the cover plate 1; the control base station 9 can be connected to the two jacks 8 at the same time, and can control the two jacks 8 to move synchronously to ensure that the elevation of the cover plate 1 at the two jacks 8 remains consistent.

[0045] Here, the jack 8 can be hydraulic, and the hydraulic jack 8 can be adjusted by controlling the base station 9 so that the elevation of the side cover 1 away from the invert arch matches the elevation of the adjacent roadbed surface 11, avoiding misalignment and achieving a smooth transition of the tunnel.

[0046] Optionally, an expansion joint 10 is formed between the cover plate 1 and the roadbed surface layer 11 .

[0047] An expansion joint 10 is formed between the side of the cover plate 1 away from the tunnel invert 15 and the roadbed surface layer 11, which can prevent the cover plate 1 and the adjacent roadbed surface layer 11 from being squeezed and deformed due to thermal expansion and contraction.

[0048] This structure can not only effectively solve the problems of large differences in structural stiffness, large uneven deformation, and uncontrollable arching in the existing tunnel transition section, but also is easy to construct, low-cost, and has broad application prospects.

[0049] Example 2 This embodiment provides a construction method for a tunnel-road transition structure suitable for soft rock roadbed.

[0050] The construction method of the tunnel-road transition structure applicable to soft rock roadbed of this embodiment is applied to the above-mentioned tunnel-road transition structure applicable to soft rock roadbed. The construction method includes the following steps: S1: Excavate the existing road cutting and fill the roadbed 12; S2: erecting formwork and reinforcement above the roadbed 12, pouring concrete in the formwork to form a cover plate 1, and rotating the cover plate 1 to connect it to the tunnel invert 15 or the roadbed surface layer 11; S3: Remove the formwork, lift the cover plate 1, and lay the elastic compression layer 3 on the roadbed 12; S4: Install a jack 8 on the cover plate 1 and apply pressure to the cover plate 1 through the jack 8 to align the cover plate 1 with the tunnel invert 15 or the roadbed surface layer 11.

[0051] In this embodiment, in the above step S2, the method of rotatably connecting the cover plate 1 to the tunnel invert 15 or the roadbed surface layer 11 includes: S21: Installing the rotating support 2 on the tunnel invert 15 or the roadbed surface 11; S22: Before pouring the cover plate 1, tie the movable end of the rotating support 2 to the steel bar.

[0052] Optionally, in the above step S3, the formwork is removed after the strength of the concrete reaches 70% of the design strength.

[0053] In combination with all the features of the tunnel transition structure in Example 1, the steps of the construction method of this embodiment can be further refined as follows: ① Excavate the original road cutting to the lower surface of the roadbed 12 and level the site; ② Fill the transition section roadbed 12 with the same material as the roadbed 12, and compact the roadbed 12 layer by layer until the density meets the compaction standard requirements; ③ Construct anchor piles 4 by manually digging holes, and lower the sleeve 6 after cleaning the bottom; ④ Lower the steel cage into the sleeve 6 and pour the concrete of the anchor pile 4; ⑤ Fill the outer surface of the sleeve 6 with asphalt to form an elastic isolation layer 5; ⑥ Set up the construction template at the position of cover plate 1, place the steel bars of cover plate 1, tie the end of the hinged support cover plate 1 to the steel cage of cover plate 1, and then pour concrete; ⑦ After the concrete strength of the cover plate 1 reaches 70% of the design strength, remove the side formwork, lift the cover plate 1, remove the bottom formwork, and lay the elastic compression layer 3; ⑧ Install the anchor cable 7 at the center of the anchor pile 4, lower the cover plate 1, and connect the cover plate 1 to the anchor pile 4 through the anchor cable 7 and the jack 8; ⑨ Fine-tune the anchor cable 7 through the jack 8 to make the elevation of the cover plate 1 consistent with that of the adjacent roadbed surface layer 11, and adjust it regularly.

[0054] The elastic compression layer 3 has a lower compression modulus than the soft rock layer 13 and can be made of rubber sheet, SBS modified asphalt, or polystyrene foam board. The thickness of the elastic compression layer 3 ranges from 0.4 to 0.6 m, with a preferred thickness of 0.5 m. The diameter of the anchor pile 4 ranges from 1.4 to 1.6 m, with a preferred diameter of 1.5 m. The diameter of the steel sleeve 6 is 20 to 30 cm smaller than the borehole diameter.

[0055] In summary, the present invention provides a tunnel transition structure and construction method suitable for soft rock roadbed, by arranging a cover plate in the tunnel transition section, and rotating the side edge of one side of the cover plate to connect to the tunnel inverted arch or the roadbed surface, the side edge of one side of the cover plate can be aligned with the tunnel inverted arch or the roadbed surface; an elastic compression layer is arranged under the cover plate, and the jack above the cover plate can be used to apply pressure to the cover plate and compress the elastic compression layer, so that the side edge of the other side of the cover plate can be aligned with the roadbed surface or the tunnel inverted arch; specifically, if the side edge of one side of the cover plate is rotatably connected to the tunnel inverted arch , the side of the other side of the cover plate can compress the elastic compression layer under the pressure of the jack to align it with the roadbed surface. The side of the cover plate can be always aligned with the roadbed surface by controlling the pressure applied by the jack, avoiding misalignment at the tunnel interface and ensuring a smooth transition of the tunnel interface. Of course, the side of one side of the cover plate can also be rotatably connected to the roadbed surface, and the side of the other side of the cover plate can be compressed under the pressure of the jack to align it with the tunnel invert. The pressure of the jack can also be controlled to achieve the effect of avoiding misalignment at the tunnel interface.

[0056] The top surface of the cover plate can be flush with the top surface of the tunnel invert arch, and can be connected to the top surface of the tunnel invert arch using a rotating support, which can avoid misalignment at the tunnel interface and evenly distribute the uneven settlement of the tunnel transition section to the cover plate.

[0057] An elastic compression layer is provided between the cover plate and the roadbed below. When the roadbed below arches, the elastic compression layer is compressed and deformed. By reserving a certain arch margin, the arch force exerted on the cover plate by the roadbed can be effectively reduced.

[0058] The anchor piles pass through the roadbed and the upper arch soft rock layer and are embedded in the stable rock layer to enhance the pull-out resistance of the anchor piles. The anchor piles are wrapped with an elastic isolation layer around the pile body in the roadbed and the upper arch soft rock layer. The elastic isolation layer can be made of asphalt material. Asphalt has good waterproof, corrosion-resistant and elastic properties. It can not only reduce the horizontal force on the anchor piles and avoid the adverse effects of the surrounding soil pressure on the anchor piles and the cover plate above them, but also reduce the arching force of the upper stratum on the anchor piles and improve the pull-out resistance of the anchor piles.

[0059] The cover plate is connected to the anchor piles through jacks. The anchor piles pass through the roadbed and the soft rock layer of the upper arch and are embedded in the stable rock layer. The jacks can be adjusted by hydraulic pumps to match the elevation of the cover plate away from the inverted arch with the elevation of the adjacent roadbed surface, thereby achieving a smooth transition between the tunnel and the road.

[0060] Anchor cables are installed in the anchor piles. The lower end of the anchor cables can be buried in the stabilization layer and welded to the steel bars at the bottom of the anchor piles. The upper end is anchored on the jack. The hydraulic jack is controlled by the control base station and is operated regularly by personnel. The height of the cover plate is controlled by adjusting the tension of the anchor cables to ensure a smooth connection between the cover plate and the adjacent roadbed surface.

[0061] An expansion joint is formed between the cover plate away from the tunnel invert arch side and the roadbed surface to prevent the cover plate and the adjacent roadbed surface from being squeezed and deformed due to thermal expansion and contraction.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A tunnel transition structure suitable for soft rock roadbed, characterized in that: The invention comprises a cover plate (1), an elastic compression layer (3) and a jack (8), wherein the cover plate (1) is arranged above the roadbed (12) and connected between the tunnel invert (15) and the roadbed surface layer (11), and the elastic compression layer (3) is arranged between the cover plate (1) and the roadbed (12); the roadbed (12) is located above the soft rock layer (13); a side edge of one side of the cover plate (1) is rotatably connected to the tunnel invert (15) or the roadbed surface layer (11), and the jack (8) is arranged above the cover plate (1), and the jack (8) can apply pressure to the cover plate (1) to align the cover plate (1) with the tunnel invert (15) or the roadbed surface layer (11).

2. The tunnel transition structure suitable for soft rock roadbed according to claim 1, characterized in that: It also includes an anchor cable (7), one end of which passes through the cover plate (1) and is connected to the jack (8), and the other end of the anchor cable (7) is anchored in the stable layer (14) below the soft rock layer (13).

3. The tunnel transition structure suitable for soft rock roadbed according to claim 2, characterized in that: It also includes an anchor pile (4), the anchor pile (4) is located below the elastic compression layer (3) and is arranged corresponding to the anchor cable (7), the anchor pile (4) passes through the soft rock layer (13), the upper end of the anchor pile (4) extends into the roadbed (12), and the lower end of the anchor pile (4) extends into the stabilization layer (14); the anchor cable (7) is inserted into the anchor pile (4).

4. The tunnel transition structure suitable for soft rock roadbed according to claim 3, characterized in that: The anchor pile (4) is sleeved with a sleeve (6), the outer side of the sleeve (6) is wrapped with an elastic isolation layer (5), and the elastic isolation layer (5) is located in the soft rock layer (13) and the roadbed (12).

5. The tunnel transition structure suitable for soft rock roadbed according to any one of claims 1 to 4, characterized in that: The cover plate (1) is rotatably connected to the tunnel invert (15), and the transition structure includes two jacks (8). The two jacks (8) are arranged on one side of the cover plate (1) close to the roadbed surface layer (11) and are spaced apart from each other.

6. The tunnel transition structure suitable for soft rock roadbed according to claim 5, characterized in that: The two jacks (8) are both connected to a control base station (9), and the control base station (9) is used to adjust the pressure applied by the two jacks (8) to the cover plate (1).

7. The tunnel transition structure suitable for soft rock roadbed according to claim 5, characterized in that: An expansion joint (10) is formed between the cover plate (1) and the roadbed surface layer (11).

8. A construction method for a tunnel transition structure suitable for soft rock roadbed, characterized in that: The tunnel transition structure suitable for soft rock roadbed according to any one of claims 1 to 7, wherein the construction method comprises: S1: excavating the original road cutting and filling the roadbed (12); S2: erecting a formwork and steel bars above the roadbed (12), pouring concrete in the formwork to form the cover plate (1), and rotating the cover plate (1) to connect it to the tunnel invert (15) or the roadbed surface (11); S3: removing the template, then hoisting the cover plate (1), and laying the elastic compression layer (3) on the roadbed (12); S4: Installing the jack (8) on the cover plate (1), and applying pressure to the cover plate (1) through the jack (8) to align the cover plate (1) with the tunnel invert (15) or the roadbed surface (11).

9. The construction method of a tunnel transition structure suitable for soft rock roadbed according to claim 8, characterized in that: In S2, the method of rotatably connecting the cover plate (1) to the tunnel invert (15) or the roadbed surface layer (11) comprises: S21: Installing a rotating support (2) on the tunnel invert (15) or the roadbed surface (11); S22: before pouring the cover plate (1), the movable end of the rotating support (2) is tied to the steel bar.

10. The construction method of a tunnel transition structure suitable for soft rock roadbed according to claim 8 or 9, characterized in that: In S3, after the strength of the concrete reaches 70% of the design strength, the formwork is removed.

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