Construction method of frame bridge under operating line

Abstract

The present invention discloses a construction method for a frame bridge under an operating line, which relates to the field of frame bridge construction, comprising: constructing pile foundations in the roadbed on both sides of the railway track, installing temporary beams on top of the pile foundations to support the railway track; injecting slurry into the roadbed soil to form an arched grouting reinforcement layer; excavating an initial space inward from the roadbed slope, and casting end segments using the inner wall of the grouting reinforcement layer as a template; excavating the working space forward, and casting and burying segments between the inner wall of the grouting reinforcement layer and the template; repeating the excavation and casting until the frame bridge is completed. The method realizes the safe construction of a frame bridge on a large-width roadbed under normal railway operation by integrating grouting reinforcement layer support and segmented cast-in-place, greatly reducing site occupation and avoiding soil disturbance and settlement.

Description

Technical Field

[0001] The present invention relates to the field of frame bridges, and more particularly to a construction method for a frame bridge under an operating line. Background Art

[0002] With the continuous updating of my country's transportation system and transportation network, the number of road construction projects passing under the existing railway subgrade has gradually increased. In the construction of frame bridges, the traditional open-cut method requires the railway line to be shut down, and then the subgrade is excavated on a large scale. This method generally constructs support piles and temporary beam systems on both sides of the railway track to temporarily bear the track load, and then excavates the subgrade soil to the design elevation. Finally, the frame bridge structure is cast as a whole in the foundation pit. After the frame bridge is completed, backfilling is carried out. The open-cut method has many defects. First, the railway line needs to be shut down. Second, it is difficult to fully control the deformation of the soil during the subsequent backfilling, and local settlement is prone to occur, resulting in excessive track settlement.

[0003] In order to solve the above problems, the existing frame bridge construction method adopts the prefabricated frame bridge jacking process. This process excavates a working pit on one side of the railway to prefabricate a box, and uses a jack system to push the box section by section under the roadbed. Although this method reduces the amount of excavation, it still has multiple constraints. First, a jacking working pit and reaction wall with a depth greater than the height of the frame bridge must be set on the side of the roadbed, and the width of the site is often more than twice the height of the bridge body. It cannot be implemented in adjacent buildings or narrow areas. Second, in some railway hub sections, when long-distance jacking is required, the friction between the box and the soil increases significantly, and the jacking force demand increases exponentially, which can easily lead to box axis deviation or even structural cracking. Therefore, the current jacking-type frame bridge construction method is often used in projects with narrow roadbeds. In addition, during the jacking-type construction operation, although the upper track is supported by temporary beams, the weight and speed of the vehicle need to be strictly controlled.

[0004] Therefore, it is necessary to propose a new frame bridge construction method that is suitable for wider roadbeds in transportation hubs, requires a very small construction site, does not affect railway operations, and does not cause significant disturbance to the soil and cause settlement problems during construction. Summary of the Invention

[0005] One object of the present invention is to provide a method for constructing a frame bridge under an operating line, which is suitable for railway roadbeds with a relatively wide width located in a transportation hub environment. Compared with conventional jacking methods, this method requires an extremely small construction site, does not affect railway operations, and the construction does not cause significant disturbance to the soil to cause settlement problems.

[0006] In order to achieve these purposes and other advantages according to the present invention, the present invention provides a method for constructing a frame bridge under an operating line, comprising the following steps:

[0007] S1. On both sides of the designed location of the frame bridge, construct several rows of pile foundations in the roadbed on both sides of the railway track;

[0008] S2. Fixing temporary beams on top of the pile foundations on both sides of the railway track, and installing supporting members for supporting the railway track between the temporary beams on both sides of the railway track;

[0009] S3. Grouting is carried out in the soil of the roadbed to form an arched grouting reinforcement layer on the top and both sides of the design outline of the frame bridge;

[0010] S4. Below the grouting reinforcement layer, complete the construction of the end sections of the frame bridge from the outside of the slope on both sides of the roadbed to the inside of the roadbed. The structural top plate and structural side walls of the end sections located inside the roadbed are cast as one piece with the inner wall of the grouting reinforcement layer.

[0011] S5. Excavating the next working space from the end segment into the roadbed, constructing a buried segment in the working space, and casting the structural top plate and structural side walls of the buried segment into an integral whole with the inner wall of the grouting reinforcement layer;

[0012] S6. Continue to dig out the next working space and complete the construction of the next buried segment. Repeat this step until the entire frame bridge is completed.

[0013] Preferably, step S3 includes the following steps:

[0014] S31. Construct concrete sleeves on the slopes on both sides of the roadbed. The concrete sleeves are formed into a gate shape that matches and is larger than the cross-sectional size of the frame bridge. A plurality of grouting holes are provided at intervals on the concrete sleeves.

[0015] S32, inserting a plurality of horizontal and mutually parallel grouting flower pipes into the roadbed from a plurality of grouting holes on both sides of the roadbed, wherein the tube bodies of the grouting flower pipes are provided with a plurality of grouting holes at intervals;

[0016] S33. Pressure grouting is performed on the grouting flower pipes one by one. The grouting material solidifies with the soil in the roadbed to form a gate-shaped and complete grouting reinforcement layer.

[0017] Preferably, before pressure grouting the grouting flower pipes, a number of exhaust pipes are arranged in a matrix and vertically pressed into the roadbed from above the roadbed. The exhaust pipes are hard pipes that pass through the gaps between adjacent grouting flower pipes from top to bottom, and the bottom of the exhaust pipes is located below the grouting reinforcement layer.

[0018] Preferably, step S4 includes the following steps:

[0019] S41. Excavate an initial space with a cross-section larger than that of the frame bridge from the side slope of the roadbed under the grouting reinforcement layer, with the inner wall of the grouting reinforcement layer serving as the top and two side surfaces of the initial space.

[0020] S42. Complete the construction of the end segment bottom plate of the end segment according to the designed position of the frame bridge;

[0021] S43. Tie steel bars on the bottom plate of the end segment and set up formwork, and cast the end segment. The structural top plate and structural side walls of the end segment located in the initial space are solidified and formed between the formwork and the inner wall of the grouting reinforcement layer.

[0022] Preferably, step S5 includes the following steps:

[0023] S51. Excavate the next working space in the roadbed. The cross-sectional dimensions of the working space are the same as those of the initial space. The top ends of the grouting reinforcement layer in the working space area are supported by the unexcavated soil and the top of the end segment, respectively.

[0024] S52, constructing a buried segment bottom plate of the buried segment in the working space;

[0025] S53. On the bottom plate of the embedded segment, tie the steel bars of the embedded segment and support the formwork of the embedded segment, and inject grout between the formwork of the embedded segment and the inner wall of the grouting reinforcement layer to solidify and form the structural top plate and structural side walls of the embedded segment.

[0026] Preferably, the pile foundation is a cast-in-place concrete pile, the temporary beam includes several beam sections and beam end steel nodes, embedded steel sections are buried on the top of the pile foundation, the part of the embedded steel sections exposed outside the pile foundation is detachably connected to the beam end steel node, and the two ends of the beam section are detachably connected to the beam end steel node.

[0027] Preferably, the grouting flower tubes are arranged in more than one row, and the grouting flower tubes in each row are arranged in a gate shape, wherein the grouting diffusion radius of a single grouting flower tube is R The distance between the central axis of the row of grouting flower pipes closest to the frame bridge and the frame bridge A=R+ a , a is the reserved operation length When pressure grouting the grouting flower pipes, grouting is carried out from the row of grouting flower pipes closest to the frame bridge to the outside row by row. The spacing between grouting flower pipes in the same row and the spacing between grouting flower pipes are less than 2R .

[0028] Preferably, the grouting amount of a single grouting flower tube is ,in, V is the single hole grouting volume, l Length of grouting tube, n is the soil porosity, β is the shrinkage rate of the grouting material, and the strength calculation formula of the grouting reinforcement layer is: ,in σ a is the grouting material strength, σb is the soil strength, σ c The strength of the grouting reinforcement layer.

[0029] Preferably, the maximum excavation depth of the initial space or working space is calculated as follows: ,in L For maximum excavation depth, q is the cover load, E is the elastic modulus of the grouting reinforcement layer, T eq is the equivalent thickness of the grouting reinforcement layer, δ a To allow deflection.

[0030] Preferably, T eq The calculation formula is:

[0031] ;

[0032] in, S The spacing between grouting flower tubes in the same row, S i is the row spacing, μ is the inter-row effect coefficient, when there are two rows μ= 1.8, three-person team μ= 2.5, η The reduction factor is 0.75.

[0033] The present invention has at least the following beneficial effects:

[0034] First, this method constructs rows of pile foundations on both sides of the railway track and installs temporary beams on the top of the piles to support the railway track. This eliminates the need to completely close the railway line during construction, thereby minimizing interference with existing traffic. At the same time, this method combines segmented cast-in-place with a grouting reinforcement layer, which greatly reduces the space required for the construction site compared to the top-push frame bridge construction method. It is particularly suitable for the construction of long-length frame bridges and can effectively reduce the project's occupation and damage to the surrounding environment.

[0035] Second, this method integrates segmented cast-in-situ and grouting, and can be constructed segment by segment under the protection of the grouting reinforcement layer. The grouting reinforcement layer bears the load segment by segment, which effectively protects the construction space below. At the same time, due to the segmented casting construction method, the railway track under construction below can be opened to traffic with limited speed and weight, and the embedded segment that has reached the required strength can independently support the load above. Moreover, since it does not participate in any subsequent processes, the corresponding railway track above it can be opened to traffic normally.

[0036] Third, this method does not require backfilling or secondary construction of the roadbed, and the overall process is improved compared to the currently commonly used jacking operation method.

[0037] Other advantages, objectives and features of the present invention will be reflected in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is an overall schematic diagram of the engineering site in one technical solution of the present invention;

[0039] Figure 2 This is a schematic diagram of the interior of a construction site in a technical solution of the present invention;

[0040] Figure 3 This is a schematic top view of a construction site in a technical solution of the present invention;

[0041] Figure 4 Schematic diagram of the construction process of the end segment in a technical solution of the present invention Figure 1 ;

[0042] Figure 5 Schematic diagram of the construction process of the end segment in a technical solution of the present invention Figure 2 ;

[0043] Figure 6 This is a schematic diagram of the completion of the end segment construction in a technical solution of the present invention. Figure 3 ;

[0044] Figure 7 This is a cross-sectional schematic diagram of a working space before excavation in a technical solution of the present invention;

[0045] Figure 8 This is a cross-sectional schematic diagram of the working space after excavation in a technical solution of the present invention;

[0046] Figure 9 This is a cross-sectional diagram of the bottom plate and steel bars in the working space after completion in a technical solution of the present invention;

[0047] Figure 10 This is a cross-sectional schematic diagram of an embedded segment in a working space before casting in a technical solution of the present invention;

[0048] Figure 11 This is a cross-sectional diagram of a technical solution of the present invention after the embedded segments in the working space are cast;

[0049] Figure 12 This is a schematic cross-sectional view of the front side of the end segment casting in a technical solution of the present invention;

[0050] Figure 13This is a schematic side cross-sectional view of the working space after excavation in a technical solution of the present invention;

[0051] Figure 14 It is a schematic cross-sectional view of the front side of the buried segment casting in a technical solution of the present invention;

[0052] Figure 15 This is a schematic diagram of a buried segment before pouring in a technical solution of the present invention;

[0053] Figure 16 This is a schematic diagram of the buried segment after pouring in a technical solution of the present invention;

[0054] Figure 17 This is a schematic diagram of the installation of a temporary beam and pile foundation in a technical solution of the present invention;

[0055] Figure 18 This is a schematic diagram of a grouting flower tube in a technical solution of the present invention.

[0056] Description of the drawings: 1-roadbed, 10-inner soil, 11-working space, 2-railway track, 3-temporary beam, 31-beam section, 32-beam end steel node, 33-connector, 4-pile foundation, 40-pile hole, 41-embedded steel, 5-grouting reinforcement layer, 51-concrete arch, 52-grouting flower pipe, 520-grouting orifice, 6-end segment, 61-end segment steel bar, 62-end segment formwork, 63-end segment bottom plate, 7-embedded segment, 71-embedded segment bottom plate, 72-embedded segment anti-step, 73-embedded segment steel bar, 8-exhaust pipe, 9-formwork trolley. DETAILED DESCRIPTION

[0057] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can implement the invention with reference to the description.

[0058] It should be understood that terms such as “having”, “including” and “comprising” used herein do not preclude the existence or addition of one or more other elements or combinations thereof.

[0059] It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the structures and components are commercially available unless otherwise specified. In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "set" should be understood in a broad sense. For example, they can be fixedly connected or set, or detachably connected or set, or connected or set as a whole. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances. The directions or positional relationships indicated by the terms "transverse", "longitudinal", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention.

[0060] like Figures 1 to 18 As shown, the present invention provides a method for constructing a frame bridge under an operating line, comprising the following steps:

[0061] S1. On both sides of the designed position of the frame bridge, a number of pile foundations 4 are constructed in rows in the roadbed 1 on both sides of the railway track 2. Specifically, the pile foundations 4 can be concrete cast-in-place piles. The construction personnel first use a total station to accurately lay out according to the overall design drawings of the frame bridge to ensure that the pile foundations 4 in the same row are at the same horizontal distance from the railway track 2, and that the pile positions of all pile foundations 4 are located outside the overhead projection range of the frame bridge to avoid conflicts with subsequent construction. The pile foundations 4 can be vertically drilled with a rotary drilling rig or manually dug. The depth of the pile foundations 4 penetrates the roadbed 1 to reach a stable bearing layer. After the pile holes 40 are completed, concrete is continuously poured through the conduit and vibrated to compact it.

[0062] S2. Temporary beams 3 are fixedly installed on the top of the pile foundations 4 on both sides of the railway track 2, and supporting members for supporting the railway track 2 are installed between the temporary beams 3 on both sides of the railway track 2. Specifically, the temporary beams 3 are finished steel beams in the prior art, and the tops of the pile foundations 4 are fixedly connected to the temporary beams 3. The connection method between the two is designed with reference to the existing steel-concrete nodes. After the temporary beams 3 on both sides of the railway track 2 are fixed, supporting members are installed between the two temporary beams 3. The supporting members are cross beams, which are arranged between the sleepers of the railway track 2. The top of the cross beam supports the bottom of the track and fixes the track through fixing parts. When the train is running on the railway track 2, the overall load transfer path is train wheel load, track, cross beam, and temporary beam 3 in sequence.

[0063] S3. Grouting is carried out in the soil of the roadbed 1 to form an arched grouting reinforcement layer 5 on the top and both sides of the design outline of the frame bridge. Specifically, the grouting reinforcement layer 5 is a continuous cement-soil stone body surrounding a certain distance outside the design outline of the frame bridge. The pipe-roof method can be used to use several spaced grouting pipes to perform pressure grouting into the roadbed 1 to form a complete arched grouting reinforcement layer 5. The strength of the stone body formed by the grouting material and the soil can be controlled to be above 5 MPa. The soil inside the arch of the grouting reinforcement layer 5 is regarded as the inner soil body 10, which is separated from the soil outside the grouting reinforcement layer 5 and is dug out section by section with subsequent construction operations. When the inner soil body 10 is dug out, a space enclosed by the grouting reinforcement layer 5 is formed inside the roadbed 1. Since the railway track 2 and vehicle loads are borne by the pile foundation 4, the grouting reinforcement layer 5 can independently bear the load of the soil layer above.

[0064] S4. Below the grouting reinforcement layer 5, the construction of the end segment 6 of the frame bridge is completed from the outside of the slope on both sides of the roadbed 1 to the inside of the roadbed 1. The structural top plate and structural side walls of the end segment 6 located in the roadbed 1 are cast as one piece with the inner wall of the grouting reinforcement layer 5. Specifically, under the protection of the grouting reinforcement layer 5, an initial space is excavated inward from the slope on both sides of the roadbed 1. The initial space is slightly larger than the outer contour of the frame bridge. The top surface and both sides of the initial space are the inner walls of the grouting reinforcement layer 5. When constructing the end segment 6, first construct the end segment bottom plate 63 according to the design drawings, and then tie the end segment steel bars 61 upward based on the end segment bottom plate 63. The end segment steel bars 61 include side wall steel bars and top plate steel bars, among which the horizontal longitudinal main bars are reserved in length in the subsequent construction direction to facilitate connection with the subsequent The longitudinal main reinforcement in the embedded segment 7 forms an overlapping relationship, and the end segment formwork 62 is supported along with the binding of the end segment steel bars 61. The top plate formwork in the end segment formwork 62 adopts the same support method inside and outside the initial space, and the side wall formwork of the end segment formwork 62 outside the initial space is two formworks, while the wall formwork located in the initial space only needs to be supported once, and the inner wall of the grouting reinforcement layer 5 serves as another formwork. The support measures of the end segment formwork 62 need to be further designed, and traffic space is reserved in the middle to facilitate subsequent construction without removing the formwork. During the concrete pouring process, the structural top plate and structural side wall of the end segment 6 are poured at the same time. Before pouring, the junction of the end segment formwork 62 and the initial space opening needs to be sealed to avoid leakage.

[0065] S5. Excavate the next section of the working space 11 from the end segment 6 into the roadbed 1, and complete the construction of a buried segment 7 in the working space 11. The structural top plate and structural side wall of the buried segment 7 are cast as one body with the inner wall of the grouting reinforcement layer 5. In this technical solution, after the strength of the end segment 6 reaches 75% of the design strength, excavation can continue into the roadbed 1 without removing the support measures of the end segment template 62. The bottom elevation of the working space 11 is equal to or lower than the design bottom elevation of the frame bridge. The two sides and top of the working space 11 reach the inner wall of the grouting reinforcement layer 5 respectively. The grouting reinforcement layer 5 serves as the top and side support of the working space 11. At this time, one end of the grouting reinforcement layer 5 located in the working space 11 section is consolidated into one body with the end segment 6, and the other end is buried in the soil. The soil and materials in the working space 11 are transported inside the segment 6. After the excavation is completed in the working space 11, the buried segment bottom plate 71 is poured. After the buried segment bottom plate 71 reaches 75% of the design strength, a support frame is erected on the segment bottom plate 71 to tie the buried segment steel bars 73. Since the process in the working space 11 is to tie the buried segment steel bars 73 first and then support the formwork, the top plate steel bars can be hung by appropriately installing a hanger on the top plate of the grouting reinforcement layer 5 to avoid the top plate steel bars from deflecting when there is no lower support. After the buried segment steel bars 73 are tied and positioned, a formwork is supported below the buried segment steel bars 73. After a closed space is formed between the formwork-grouting reinforcement layer 5-end segment 6, concrete is poured into the formwork. After solidification, the buried segment 7 is formed.

[0066] S6. After the previously cast buried section 7 reaches the designed strength, continue to dig out the next working space 11 and complete the construction of the next buried section 7. Repeat this step until the entire frame bridge is completed.

[0067] In this technical solution, construction can be carried out symmetrically from both sides of the roadbed 1 toward the inside of the roadbed 1, further shortening the construction period. Compared with any existing frame bridge construction method, this method constructs rows of pile foundations 4 on both sides of the railway track 2, and installs temporary beams 3 on top of the pile foundation 4 to support the railway track 2. It adopts a combination of segmented cast-in-place and grouting reinforcement layer 5, which greatly reduces the space required for the construction site compared to any frame bridge construction method. It is particularly suitable for frame bridge construction in roadbed 1 with large length and height, effectively reducing the occupation and damage of the project to the surrounding environment, and after the construction of this method is completed, there is no need to backfill and reinforce the roadbed.

[0068] In another technical solution, step S3 includes the following steps:

[0069] S31, constructing concrete arches 51 on the slopes on both sides of the roadbed 1, the concrete arches 51 are in a gate shape that matches and is larger than the cross-sectional size of the frame bridge, and a number of grouting holes 520 are arranged at intervals on the concrete arches 51. Specifically, according to the design size of the grouting reinforcement layer 5 and the design spacing of the grouting holes 520, a foundation trench with a width of 1m to 2m is excavated on the slopes on both sides of the roadbed 1, and a steel grid is tied inside the foundation trench and galvanized steel pipes are embedded at intervals as subsequent grouting holes 520. After the gate-shaped template is supported, concrete is poured to form the concrete arches 5. 1. When designing the size of the grouting reinforcement layer 5 and the spacing of the grouting holes 520, it is necessary to first sample the soil in the roadbed 1, and calculate the diffusion radius of the grouting material based on the designed grouting pressure and the existing formula, so as to calculate the size and strength of the stone body formed by a single grouting flower tube 52 after grouting. Then, the number, row spacing, and spacing of the grouting holes 520, as well as the size of the concrete arch 51, are calculated, and the size of the grouting reinforcement layer 5 is strictly controlled to make the inner wall of the grouting reinforcement layer 5 as close as possible to the designed outer contour of the frame bridge.

[0070] S32. Insert a number of horizontal and mutually parallel grouting tubes 52 into the roadbed 1 from a number of grouting holes 520 on both sides of the roadbed 1. A number of grouting holes are spaced apart on the tube wall of the grouting tube 52. The grouting tube 52 is pushed horizontally into the roadbed 1 through the grouting holes 520. The grouting tube 52 is made of seamless steel tube with a wall thickness of more than 5mm. The tube sections of the grouting tube 52 are connected by threaded sleeves. A conical closing head is installed at the front end of the grouting tube 52. After the grouting tube 52 is installed, the outer end is fastened to the grouting hole 520 by flange bolts. All grouting tubes 52 maintain a parallelism deviation of ≤1%.

[0071] S33. Pressure grouting is performed on the grouting flower tubes 52 one by one. The grouting material solidifies with the soil in the roadbed 1 to form a gate-shaped and complete grouting reinforcement layer 5. Cement slurry with a water-cement ratio of 0.8:1 can be used, and the flow rate is controlled at 30L / min. The grouting material penetrates into the surrounding soil from the grouting holes of the grouting flower tubes 52. After the grouting material and the soil solidify, the single grouting flower tube 52 is transformed from a hollow tube into a steel tube concrete beam. At the same time, after the grouting material solidifies, all the grouting flower tubes 52 are consolidated with the surrounding soil to form an integral gate-shaped load-bearing structure.

[0072] In another technical solution, before pressure grouting the grouting flower pipe 52, a number of exhaust pipes 8 are arranged in a matrix and vertically pressed into the roadbed 1 from above the roadbed 1. The exhaust pipe 8 is a hard pipe that passes through the gap between adjacent grouting flower pipes 52 from top to bottom. The bottom of the exhaust pipe 8 is located below the grouting reinforcement layer 5. In this technical solution, since the buried segment 7 is poured with concrete in a closed space, it is necessary to consider exhausting the concrete to make it dense. The exhaust pipe 8 is a galvanized steel pipe. After the grouting flower pipe 52 is arranged, the exhaust pipe 8 is pressed vertically downward from the upper part of the roadbed 1 to the inside of the roadbed 1. When the grouting reinforcement layer 5 is constructed, the pipe body of the exhaust pipe 8 is embedded in the grouting reinforcement layer 5. During the excavation of the initial space and the working space 11, the exhaust pipe 8 is cut off from the inner wall of the grouting reinforcement layer 5. When the buried segment 7 is poured, the gas can be discharged upward, and the slurry leakage at the port of the exhaust pipe 8 on the roadbed 1 can be used to judge whether the buried segment 7 has been poured densely.

[0073] In another technical solution, step S4 includes the following steps:

[0074] S41. Excavate an initial space with a cross section larger than the cross section of the frame bridge from the side slope of the roadbed 1 under the grouting reinforcement layer 5, and use the inner wall of the grouting reinforcement layer 5 as the top surface and two side surfaces of the initial space.

[0075] S42. Complete the construction of the end segment bottom plate 63 of the end segment 6 according to the designed position of the frame bridge. Specifically, complete the construction of the end segment bottom plate 63 according to the design of the frame bridge. The steel bars in the end segment bottom plate 63 are reserved outward according to the specifications to facilitate the subsequent steel bar overlap. After the end segment bottom plate 63 is poured and its strength reaches 75% of the designed strength, the end segment bottom plate 63 can be used as the basis for other structural formwork of the end segment 6.

[0076] S43. Tie the steel bars on the end segment bottom plate 63 and set up the formwork, and cast the end segment 6. The structural top plate and the structural side wall of the end segment 6 located in the initial space are solidified and formed between the formwork and the inner wall of the grouting reinforcement layer 5. In this technical solution, in order to simplify the formwork operation inside the end segment 6, the formwork trolley 9 can be customized according to the design size of the frame bridge and the existing technology. The formwork trolley 9 includes a walking structure and a top formwork and side formwork that can be supported and retracted under the action of the hydraulic structure. The end segment formwork 62 is supported in the end segment 6 outside the initial space according to the existing conventional formwork method. After the end segment formwork 62, the end segment bottom plate 63 and the initial space opening are sealed, the concrete casting of the end segment 6 is completed.

[0077] In another technical solution, step S5 includes the following steps:

[0078] S51. Excavate the next working space 11 in the roadbed 1. The cross-sectional dimensions of the working space 11 are the same as those of the initial space. The top ends of the grouting reinforcement layer 5 located in the working space 11 area are supported by the unexcavated soil and the top of the end segment 6 respectively. Specifically, when the end segment 6 reaches 75% of the design strength, the end node 6 can cooperate with the unremoved support system to play a good supporting role for the grouting reinforcement layer 5, and continue to excavate the working space 11 forward. Since the railway track 2 is directly supported by the pile foundation 4 outside the grouting reinforcement layer 5, the grouting reinforcement layer 5 only bears the load of the soil layer of the roadbed 1 above. Before excavating the working space 11, it is necessary to sample and analyze the thickness and strength of the grouting reinforcement layer 5, and calculate the safe excavation length of the working space 11.

[0079] S52. Construct the buried segment bottom plate 71 of the buried segment 7 in the working space 11. Specifically, the buried segment bottom plate 71 can be cast upward together to form the buried segment anti-step 72 according to the positions of the side walls and partition walls in the cross section of the frame bridge, so as to facilitate the subsequent binding of the buried segment steel bars 73.

[0080] S53. On the embedded segment bottom plate 71, tie the steel bars of the embedded segment 7 and support the formwork of the embedded segment 7. Perform grouting between the formwork of the embedded segment 7 and the inner wall of the grouting reinforcement layer 5 to solidify and form the structural top plate and structural side wall of the embedded segment 7. Specifically, after the embedded segment bottom plate 71 and the embedded segment anti-ridge 72 reach 75% of the design strength, tie the embedded segment steel bars 73. After all the embedded segment steel bars 73 are completed, the formwork trolley 9 releases the support for the previous end segment 6 or the embedded segment 7, and drives into the embedded segment bottom plate 71 in the working space 11 to re-form the formwork and support system for the embedded segment 7. After ensuring the sealing of the formwork system, the embedded segment 7 can be poured with concrete.

[0081] In another technical solution, the pile foundation 4 is a concrete cast-in-place pile, and the temporary beam 3 includes several beam sections 31 and beam end steel nodes 32. The top of the pile foundation 4 is embedded with embedded steel sections 41, and the part of the embedded steel sections 41 exposed from the pile foundation 4 is detachably connected to the beam end steel node 32. The two ends of the beam section 31 are detachably connected to the beam end steel node 32. In this technical solution, the pile position of the pile foundation 4 is first located according to the design coordinates, and a rotary drilling rig is used to drill a hole to the bearing layer. After the hole is cleaned, a steel cage is hoisted, and the concrete is poured and vibrated to be dense and then maintained. The cast-in-place pile is rotary drilled. There is no vibration during hole drilling to avoid affecting the stability of the operating line. The embedded steel 41 is a columnar steel node. Before the pile foundation 4 is poured, the embedded steel 41 is embedded in the end of the pile foundation 4 through external support measures. The upper part of the embedded steel 41 is exposed to the connection part. The beam end steel node 32 includes a downward connection part and connection parts on both sides. The beam end steel node 32 and the embedded steel 41 are connected by a gusset plate and high-strength bolts. The connection parts on both sides of the beam end steel node 32 are connected to the end of the temporary beam 3 through a connector 33 composed of a gusset plate and high-strength bolts.

[0082] In another technical solution, the grouting flower tubes 52 are arranged in more than one row, and the grouting flower tubes 52 in each row are arranged in a gate shape, wherein the grouting diffusion radius of a single grouting flower tube 52 is R The distance between the central axis of the row of grouting flower tubes 52 closest to the frame bridge and the frame bridge is A=R+a , a In order to reserve the operation length, when the grouting flower tubes 52 are pressure grouting, grouting is performed from the row of grouting flower tubes 52 closest to the frame bridge to the outside row by row. The spacing between the grouting flower tubes in the same row and the spacing between the grouting flower tubes 52 are both less than 2R. In this technical solution, since the grouting diffusion radius R cannot be accurately controlled during the grouting operation, a The value should be greater than 100mm, so that the inner wall of the grouting reinforcement layer 5 will not invade the outline of the frame bridge. When excavating the initial space and the working space 11, use the excavator to excavate to the outer outline of the frame bridge and then use manual soil removal to remove the reserved working length. a The soil within the range is cleaned to avoid mechanical impact on the grouting reinforcement layer 5 and thus damage to it, and the residual soil on the inner wall of the grouting reinforcement layer 5 is removed by manual soil cleaning and water guns and other measures.

[0083] In another technical solution, the grouting amount of a single grouting flower tube 52 is ,in, V is the single hole grouting volume, l Length of grouting tube, n is the soil porosity, β is the shrinkage rate of the grouting material, and the strength calculation formula of the grouting reinforcement layer 5 is: ,in σa is the grouting material strength, σ b is the soil strength, σ c is the strength of the grouting reinforcement layer 5, the soil porosity n It represents the ratio of the pore volume to the total volume of the soil in the roadbed 1, which is measured by the ring knife method combined with the pycnometer method. β Depending on the type of grouting material, the value range is 0.05~0.15.

[0084] In another technical solution, the maximum excavation depth of the initial space or working space 11 is calculated as follows: ,in L For maximum excavation depth, q is the cover load, E is the elastic modulus of the grouting reinforcement layer 5, T eq is the equivalent thickness of the grouting reinforcement layer 5, δ a is the allowable deflection, where the maximum excavation depth L is or The purpose is to prevent the two failure modes of the grouting reinforcement layer 5. The compressive strength of the material mechanics is used to prevent the grouting reinforcement layer 5 from collapsing. It is based on the elastic thin plate bending theory to limit the deformation of the grouting reinforcement layer 5. Since the grouting reinforcement layer 5 formed by grouting through a number of grouting flower tubes 52 is not a uniform plate, the thickness cannot be simply considered to be equal to 2R, so the thickness needs to be appropriately corrected.

[0085] In another technical solution, T eq The calculation formula is:

[0086] ;

[0087] in, S The spacing of grouting flower tubes, S i is the row spacing, μ is the inter-row effect coefficient, when there are two rows μ= 1.8, three-person team μ= 2.5, η The reduction factor is 0.75.

[0088] The following is a specific on-site embodiment:

[0089] A project located in a railway hub area requires crossing a double-track electrified railway. The roadbed width is 42m and the average daily train traffic is 120. The frame bridge is designed with a net width of 24m and a net height of 5m. The cover depth above the frame bridge top plate is 7m. According to the geological survey report, the soil layer where the frame bridge is located is silty clay with a porosity of 0.35, and the cover load is 120.6KN / m 2 The grouting flower tube 52 is made of φ120mm×8mm seamless steel pipe. The length of the grouting flower tube 52 is 22m. The grouting material is ultra-fine cement slurry with a water-cement ratio of 0.8. The strength of the grouting material is 22m. σ a =20Mpa, soil strength σ b =0.2Mpa, grouting material shrinkage rate β According to the typical value of cement slurry, take 0.1 ， The strength calculation formula of the grouting reinforcement layer 5 is: , elastic modulus of grouting reinforcement layer 5 E =0.8 Gpa.

[0090] The grouting flower pipes 52 are arranged in a double row plum blossom pattern, and the designed grouting diffusion radius R=0.8m. The spacing between the grouting flower pipes 52 in the same row is S =0.8m ， The row spacing of grouting flower tube 52 S i =0.8m, set a =0.1m, so the distance between the center axis of the row of grouting flower pipes 52 closest to the frame bridge and the frame bridge is A= 0.9m, grouting volume of a single grouting flower tube 52 .

[0091] The concrete arch 51 is set on the slope of the roadbed 1 at the design location of the frame bridge, with a width of 1.2m and a thickness of 0.8m. A φ150mm steel casing is pre-buried as a grouting hole 520. After the concrete arch 51 is cured, a double row of grouting flower pipes 52 are horizontally pushed in, and then grouting is carried out in sequence from the inner row to the outer row.

[0092] Equivalent thickness of grouting reinforcement layer , allowable deflection δ a= 0.02m, maximum excavation depth , with maximum excavation depth L = The initial space and construction space 11 are excavated with a limit of 14.42m.

[0093] It should be noted that although the steps are described above in a specific order, this does not necessarily mean that the steps must be performed in this specific order. In fact, some of these steps can be performed concurrently or even in a different order, as long as the required functions can be achieved. The number of devices and processing scales described here are intended to simplify the description of the present invention. Applications, modifications, and variations of the present invention will be apparent to those skilled in the art.

[0094] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. The construction method of a frame bridge under an operating line includes the following steps: S1. constructing a plurality of pile foundations (4) in rows in the roadbed (1) on both sides of the railway track (2) on both sides of the designed position of the frame bridge; S2. Fixedly installing temporary beams (3) on the tops of the pile foundations (4) on both sides of the railway track (2), and installing supports for supporting the railway track (2) between the temporary beams (3) on both sides of the railway track (2); S3, grouting is performed in the soil of the roadbed (1) to form an arched grouting reinforcement layer (5) on the top and both sides of the design outline of the frame bridge, including the following steps: S31, constructing concrete sleeve arches (51) on the slopes on both sides of the roadbed (1), wherein the concrete sleeve arches (51) are in a gate shape that matches and is larger than the cross-sectional size of the frame bridge, and a plurality of grouting holes (520) are arranged at intervals on the concrete sleeve arches (51); S32, inserting a plurality of horizontal and mutually parallel grouting flower pipes (52) into the roadbed (1) from a plurality of grouting holes (520) on both sides of the roadbed (1), wherein the tube bodies of the grouting flower pipes (52) are provided with a plurality of grouting holes at intervals; S33, pressure grouting is performed on the grouting flower tubes (52) one by one, and the grouting material condenses with the soil in the roadbed (1) to form a gate-shaped and complete grouting reinforcement layer (5). Before pressure grouting the grouting flower tubes (52), a plurality of exhaust pipes (8) are arranged in a matrix and vertically pressed into the roadbed (1) from above the roadbed (1). The exhaust pipes (8) are hard pipes that pass through the gaps between adjacent grouting flower tubes (52) from top to bottom, and the bottoms of the exhaust pipes (8) are located below the grouting reinforcement layer (5); S4. Below the grouting reinforcement layer (5), the end section (6) of the frame bridge is constructed from the outside of the slope on both sides of the roadbed (1) to the inside of the roadbed (1). The structural top plate and structural side wall of the end section (6) located in the roadbed (1) are cast as one piece with the inner wall of the grouting reinforcement layer (5), including the following steps: S41, excavating an initial space with a cross section larger than the cross section of the frame bridge from the side slope of the roadbed (1) under the grouting reinforcement layer (5), with the inner wall of the grouting reinforcement layer (5) serving as the top surface and two side surfaces of the initial space; S42, constructing the end segment bottom plate (63) of the end segment (6) according to the designed position of the frame bridge; S43, tying steel bars on the end segment bottom plate (63) and setting up a formwork, and casting the end segment (6), wherein the structural top plate and the structural side wall of the end segment (6) located in the initial space are solidified and formed between the formwork and the inner wall of the grouting reinforcement layer (5); S5, excavating the next section of working space (11) from the end section (6) into the roadbed (1), completing the construction of a buried section (7) in the working space (11), and casting the structural top plate and structural side walls of the buried section (7) into an integral whole with the inner wall of the grouting reinforcement layer (5); S6. Continue to dig out the next working space (11) and complete the construction of the next buried segment (7). Repeat this step until the entire frame bridge is completed.

2. The construction method of a frame bridge under an operating line according to claim 1, characterized in that: Step S5 includes the following steps: S51, excavating the next working space (11) in the roadbed (1), wherein the cross-sectional dimensions of the working space (11) are the same as the cross-sectional dimensions of the initial space, and the top ends of the grouting reinforcement layer (5) located in the working space (11) area are supported by the unexcavated soil and the top of the end segment (6) respectively; S52, constructing a buried segment bottom plate (71) of the buried segment (7) in the working space (11); S53. On the embedded segment bottom plate (71), the steel bars of the embedded segment (7) are tied and the template of the embedded segment (7) is supported. Grouting is performed between the template of the embedded segment (7) and the inner wall of the grouting reinforcement layer (5) to solidify and form the structural top plate and structural side walls of the embedded segment (7).

3. The construction method of a frame bridge under an operating line according to claim 1, characterized in that: The pile foundation (4) is a concrete cast-in-place pile. The temporary beam (3) includes a plurality of beam sections (31) and beam end steel nodes (32). A pre-buried steel section (41) is embedded in the top of the pile foundation (4). The portion of the pre-buried steel section (41) exposed outside the pile foundation (4) is detachably connected to the beam end steel node (32). Both ends of the beam section (31) are detachably connected to the beam end steel node (32).

4. The construction method of a frame bridge under an operating line according to claim 1, characterized in that: The grouting flower tubes (52) are arranged in more than one row, and the grouting flower tubes (52) in each row are arranged in a gate shape at intervals, wherein the grouting diffusion radius of a single grouting flower tube (52) is R The distance between the central axis of the row of grouting flower pipes (52) closest to the frame bridge and the frame bridge is A=R+a , a In order to reserve the operation length, when the grouting flower tubes (52) are pressure grouting, grouting is performed row by row from the row of grouting flower tubes (52) closest to the frame bridge to the outside, and the spacing between the grouting flower tubes (52) in the same row and the spacing between the grouting flower tubes (52) are both less than 2R.

5. The construction method of a frame bridge under an operating line according to claim 4, characterized in that: Grouting amount of a single grouting flower tube (52) ,in, V is the single hole grouting volume, l Length of grouting tube, n is the soil porosity, β is the shrinkage rate of the grouting material, and the strength calculation formula of the grouting reinforcement layer (5) is: ,in σ a is the grouting material strength, σ b is the soil strength, σ c is the strength of the grouting reinforcement layer (5).

6. The construction method of a frame bridge under an operating line according to claim 4, characterized in that: The maximum excavation depth of the initial space or working space (11) is calculated as follows: ,in L For maximum excavation depth, q is the cover load, E is the elastic modulus of the grouting reinforcement layer (5), T eq is the equivalent thickness of the grouting reinforcement layer (5), δ a To allow deflection.

7. The construction method of a frame bridge under an operating line according to claim 6, characterized in that: T eq The calculation formula is: ； in, S The spacing of grouting flower tubes, S i is the row spacing, μ is the inter-row effect coefficient, when there are two rows μ= 1.8, three-person team μ= 2.5, η The reduction factor is 0.75.

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