CN114856616A - A kind of tunnel construction method and reinforcement protection structure - Google Patents

Abstract

Embodiments of the present application provide a tunnel reinforcement protection structure and a construction method using the protection structure. The reinforcement protection structure of the tunnel includes a protection structure and a reinforcement structure, and the protection structure includes an isolation protection pile, a horizontal isolation pipe shed, a tunnel top insert Large pipe sheds, isolation protection piles and horizontal isolation pipe sheds are used to block the horizontal and vertical deformation of the passageway caused by tunnel construction. The large pipe shed inserted on the top of the tunnel is used to ensure the safety of the existing railway facilities on the top of the tunnel and prevent collapse. The reinforcement structure includes supporting piles and D-shaped beams, which are used to support the existing railway facilities above the tunnel to be excavated during the construction process. reinforcement. It has been verified that the above reinforcement and protection structure and construction method can ensure the stability of the soil above the tunnel, and can meet the operational safety of existing municipal roads and railways.

Description

A kind of tunnel construction method and reinforcement protection structure

technical field

The present application relates to the technical field of road and bridge construction, and more particularly, to a tunnel construction method and a reinforcement protection structure.

Background technique

With the rapid development of modern economy, almost all large cities have traffic congestion and backward facilities such as urban supporting pipelines. Their municipal and highway projects and supporting pipelines can no longer meet the growing requirements of local traffic and supporting facilities. , the need for new construction of public transport facilities such as subways, light rails, and municipal highways is very urgent.

However, there are already a large number of existing railway facilities in urban areas, such as urban railway lines and railway-related buildings, etc. It is often inevitable for new municipal railways or highway projects and pipelines to penetrate existing railway facilities. The location should be selected in a location with less interference to the operation of the existing railway facilities, and in order to ensure the safe operation of the existing railway and municipal roads during the tunnel excavation construction process, reliable measures must be taken to make the deformation index caused by the construction. Meet specification and design requirements. When the underground tunnel passes through the existing railway facilities, when the burial depth is relatively deep, reinforcement measures such as grouting can be taken in the tunnel hole, combined with the surface longitudinal beams and 3-5-3 rail reinforcement measures (heavy steel rails plus steel buckles). The parts and bolts are connected to form longitudinal and transverse beams.) It can ensure the deformation requirements of existing railway facilities.

However, the construction of underground tunnels is sometimes limited by road and pipeline planning and terrain, and it is unavoidable to pass under the location where the existing railway facilities are busy, such as the level crossing of the existing railway. The location of this level crossing usually adopts an integral reinforced concrete slab structure. Due to the shallow soil covering of the tunnel, the arch effect cannot be formed, and the deformation indicators of the existing railways and municipal roads cannot meet the operational safety requirements. The existing reinforcement measures such as grouting in the tunnel cavity combined with the surface longitudinal beams and the 3-5-3 rail buckle reinforcement measures cannot ensure the stability of the soil above the tunnel, and cannot meet the operational safety of existing municipal roads and railways.

SUMMARY OF THE INVENTION

In order to solve one of the above technical defects, embodiments of the present application provide a tunnel reinforcement protection structure and a construction method using the structure.

According to a first aspect of the embodiments of the present application, a reinforcement protection structure for a tunnel is provided, which includes a protection structure and a reinforcement structure. The isolation protection pile is arranged on one side or both sides of the tunnel to be excavated, the horizontal isolation pipe shed is arranged on the outer side of the isolation protection pile, and the large pipe shed inserted at the top of the tunnel is arranged on the top of the tunnel to be excavated; the reinforcement structure includes: Support piles and beams, the beams include longitudinal beams and transverse beams, the beams are erected on the support piles, and the beams are set under the existing railway facilities above the tunnel to be excavated. According to a second aspect of the embodiments of the present application, a construction method of a tunnel is provided, and the construction method adopts the reinforcement protection structure of the tunnel as described above, and the specific construction steps include:

Set up a construction shaft, set up a construction shaft at the starting point of the tunnel design, and carry out the construction of high-pressure rotary jet piles and ring beams in the shaft;

The protection structure construction, the step of strengthening the protection structure construction includes carrying out the horizontal isolation pipe shed construction, the tunnel roof inserting the large pipe shed construction and the isolation protection pile construction according to the erection position of claim 1, and the existing railway Below the position where the facility needs to be overhead, the support pile construction in the reinforcement structure is carried out;

Construction of the reinforcement structure, erecting D-shaped beams on the supporting piles to support and reinforce the existing railway facilities;

For tunnel undercover construction, the tunnel is excavated after the reinforcement structure construction steps are performed. The tunnel undercover construction adopts the method of subsection excavation. First, one side of the existing railway facility is excavated, and then the tunnel is to be excavated. Excavation is carried out on the other side of the existing railway facilities above.

The reinforcement and protection structure of the tunnel provided in the embodiment of the present application and the construction method using this structure are used to temporarily guide and reform the existing municipal roads, and pass through in sections, so as to ensure the operation of the existing railway facilities; The measures of isolation protection piles and horizontal isolation pipe sheds are adopted to block the horizontal and vertical deformation of the soil caused by the tunnel construction, so as to ensure the stability and safety of the existing railway facilities. Safety of existing railway facilities to prevent collapse; in addition, the existing railway facilities are strengthened with overhead beams to meet the deformation and stress requirements of existing railway facilities. It has been verified that the use of this reinforced protective structure and construction method can ensure the stability of the soil above the tunnel, and can meet the operational safety of existing municipal roads and railways.

Description of drawings

The drawings described herein are used to provide further understanding of the present application and constitute a part of the present application. The schematic embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation of the present application. In the attached image:

1 is a schematic plan view of the reinforcement and protection structure of a tunnel provided by an embodiment of the present application;

FIG. 2 is a schematic elevational structure diagram of a tunnel reinforcement protection structure provided by an embodiment of the present application;

3 is a schematic flowchart of a tunnel construction method provided by an embodiment of the present application;

FIG. 4 is a schematic flowchart of the construction steps of the reinforcement structure of the tunnel provided by the embodiment of the present application;

FIG. 5 is a schematic flowchart of the construction steps of the tunnel undercover construction of the tunnel provided by the embodiment of the present application;

FIG. 6 is a schematic flowchart of a tunnel cleaning and acceptance step according to an embodiment of the present application.

Reference number:

1-construction shaft; 2-tunnel to be dug; 3-isolation protection pile; 4-horizontal isolation pipe shed; 5-D-type beam; 6-support pile; 7-temporary pier; Tube Shed.

Detailed ways

In order to make the technical solutions and advantages of the embodiments of the present application more clear, the exemplary embodiments of the present application will be described in further detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, and Not all embodiments are exhaustive. It should be noted that the embodiments in the present application and the features of the embodiments may be combined with each other in the case of no conflict.

In the process of realizing the present application, the inventor found that the shallow buried tunnel construction was carried out at the position where the tunnel covering soil was very shallow. Due to the shallow covering soil, the arch effect could not be formed, and the deformation indicators of the existing railways and municipal roads could not meet the operational safety requirements. However, the existing reinforcement measures such as grouting in the tunnel cavity combined with the surface longitudinal beams and the 3-5-3 rail buckle reinforcement measures cannot ensure the stability of the soil above the tunnel, and cannot meet the operational safety of existing municipal roads and railways.

In view of the above problems, the embodiments of the present application provide a tunnel reinforcement protection structure and a tunnel construction method using the protection structure, so as to ensure that the soil body above the tunnel can be ensured when the tunnel is constructed at a position where the tunnel is covered with shallow soil. It can also meet the operational safety of existing municipal roads and railways.

In order to clearly and clearly illustrate the technical solution of the present application, the embodiment of the present application adopts the specific application scenario of a shallow buried tunnel underpassing an existing railway level crossing for illustration, but it is worth noting that the technical solution of the present application is not only applied to This type of application scenario can be applied to all shallow buried tunnel construction scenarios where the overburden is too shallow.

FIG. 1 is a schematic plan view of a reinforced protective structure of a tunnel provided by an embodiment of the application; FIG. 2 is a schematic diagram of an elevation structure of a reinforced protective structure of a tunnel provided by an embodiment of the application. As shown in FIGS. 1 and 2 , the present application The reinforcement protection structure of the embodiment tunnel includes a protection structure and a reinforcement structure, wherein the protection structure is erected before the tunnel construction, and the protection structure includes an isolation protection pile 3, a horizontal isolation pipe shed 4, a large pipe shed 9 inserted on the top of the tunnel, and an isolation protection pile 3 It is arranged on one side or both sides of the tunnel 2 to be excavated, the horizontal isolation pipe shed 4 is arranged on the outside of the isolation protection pile 3 (the side of the isolation protection pile 3 close to the tunnel 2 to be excavated is the inner side), and a large pipe is inserted into the top of the tunnel. The shed 9 is arranged on the top of the tunnel 2 to be excavated, and its cross-sectional shape depends on the needs of the geological structure, and is usually an arc concentric with the tunnel vault; The existing railway facilities are supported and reinforced. The reinforcement structure includes supporting piles 6 and convenient beams 5. The convenient beams include longitudinal beams and transverse beams. The longitudinal beams are erected on the supporting piles 6 and/or the temporary support piers 7. There are railway facilities erected on the frame composed of longitudinal beams and beams.

After the tunnel excavation and unloading, the stress state of the surrounding rock changes again, and the pressure at the bottom of the tunnel decreases, causing the bottom to deform and uplift. At the same time, the deformation of the tunnel support structure causes the tunnel surrounding rock to slide into the tunnel, and the tunnel support structure and the protected building An isolation protection pile is set between the objects, and the pile body is inserted into the stable soil layer at the lower part of the sliding surface, and the thrust of the sliding body is balanced by the resistance of the pile, so as to achieve balance and stability. When the surrounding rock of the tunnel slides into the tunnel, it is resisted by the pile body, so that the sliding body in front of the pile reaches a stable state, which controls the displacement and deformation of the soil body behind the pile, thereby reducing the deformation of the facilities or buildings around the tunnel and protecting it. The role of existing railway facilities and/or buildings.

The pipe shed structure is a kind of advanced support structure. The horizontal isolation pipe shed is on the outer side of the isolation protection pile (the side of the isolation protection pile close to the tunnel main body is the inner side), parallel to the isolation protection pile is located in pre-drilled holes and installed inertial. The thick-walled steel pipe with larger moment further plays the role of advanced support. On the one hand, the horizontal isolation tube shed further improves the overall stiffness of the soil mass on the basis of the isolation protection pile, which can prevent the horizontal deformation of the soil mass. On the other hand, when the tunnel construction disturbs the soil, the soil around the protective isolation pile and the horizontal isolation pipe shed will deform unevenly, causing the soil particles to "wedge" each other, and the soil arching effect will appear in the soil layer in a certain area. It can effectively prevent the horizontal deformation of the soil after the piles. Due to the dense arrangement of the horizontal isolation pipe sheds, the soil arch effect is obvious. With the protective isolation piles, the horizontal displacement of the soil around the tunnel during the construction process can be effectively isolated.

The large pipe shed 9 is inserted at the top of the tunnel is to drill holes in advance and install a thick-walled steel pipe with a large moment of inertia on the buried arc of the lining arch ring of the excavated underground tunnel or structural engineering, which plays the role of temporary advanced support and prevents the Soil collapse and surface subsidence to ensure safe operation of excavation and subsequent support processes.

D-type beam is suitable for the construction of bridges, culverts and tunnels of existing lines or stations. Its biggest advantage is that it can ensure the operation of existing railway facilities during the construction process. For example, use D-type beam to support existing railways or municipal roads. , it can be used for tunnel excavation and construction without interrupting traffic. Due to these characteristics, D-type stool beams have been widely used. In order to save design and production costs, D-type stool beams are preferred in the embodiments of the present application.

The above structure can ensure the stability of the soil above the tunnel and meet the operational safety of the existing municipal roads and railways when the tunnel is shallowly buried and excavated at the position where the tunnel covering soil is very shallow.

The embodiment of the present application also provides a construction method of the tunnel applying the above-mentioned reinforcement and protection structure. FIG. 3 is a schematic flowchart of the construction method of the tunnel provided by the embodiment of the present application. As shown in FIG. 3, the specific construction steps include:

Step 200: Set up the construction shaft 1, set up the construction shaft at the starting point of the tunnel design, and carry out the construction of the high-pressure rotary jet pile and the ring beam of the shaft;

Step 300: Construction of the protective structure. The steps of strengthening the protective structure include the construction of horizontal isolation pipe sheds, the construction of large pipe sheds inserted into the top of the tunnel, the construction of isolation protection piles, and the construction of existing railway facilities according to the erection positions of the above-mentioned tunnel reinforcement and support structures. (such as existing railways) below the position that needs to be overhead, carry out the construction of supporting piles in the reinforcement structure;

Step 400: Constructing the reinforcement structure, erecting D-shaped beams on the support piles to support and reinforce existing railway facilities (such as existing railways);

Step 500: After the reinforcement structure construction step is performed, the tunnel excavation construction is carried out. The tunnel construction adopts the method of subsection excavation. First, excavate one side of the existing railway facilities (such as the existing railway), and then perform the excavation construction. Excavation will be carried out on the other side of the existing railway facilities above the tunnel.

Wherein, before proceeding to step 200, step 100 can be performed: preparation before construction. The steps of preparation before construction include temporary traffic guidance and modification, and divided traffic; Temporary diversion according to the plan, diversion if necessary, and guide trains to pass at different times;

After step 500, step 600: cleaning and acceptance may be performed, that is, the construction site is cleaned, restored and accepted after the construction is completed.

If the construction scene is to pass through the tunnel at the existing railway level crossing, the crossing slab 8 needs to be removed before the tunnel excavation and the erection of the D-shaped beam, and the ballast, sleepers, steel rails, etc. need to be laid. In order to ensure the opening to traffic, the crossing slab 8 The removal needs to be carried out within the skylight point.

FIG. 4 is a schematic flowchart of the construction steps of the reinforcement structure of the tunnel provided by the embodiment of the application. As shown in FIG. 4 , further, the construction steps of the reinforcement structure include:

Step 401: Assembling the facilitation beam, that is, after the longitudinal beam is hoisted in place by a crane, it is connected with the transverse beam to assemble the D-shaped facilitation beam 5;

Step 402: erecting the facilitation beam, after the D-type facilitation beam 5 is assembled, gradually raise the longitudinal beam, so that the D-type facilitation beam 5 and the supporting piles are load-bearing;

Step 403: Inspect and maintain the D-type facilitation beam during the tunnel construction process.

Taking an existing railway level crossing under a shallow buried tunnel as an example, the specific method of assembling the beam is as follows:

1) Use a crane to lift the steel sleeper to both sides of the line. The position of the steel sleeper marked on the line according to the spacing of the steel sleeper (marked on the rail waist). Before the blockade point, the distance between the sleepers should be adjusted by using the interval of the slow running of the train, and the distance between the sleepers should be adjusted properly. The penetration of the steel sleeper should be perpendicular to the line, first in the middle and then on both sides.

2) Hoist the longitudinal beam, park the large-tonnage crane on one side of the line, hoist the longitudinal beam on one side, and then hoist the longitudinal beam on the other side, and the longitudinal beam is hoisted in place. After the connection is completed, other steel sleepers are connected and assembled.

3) After connecting the steel sleeper and the longitudinal beam of the D-type facilitation beam as a whole, gradually raise the longitudinal beam, so that the longitudinal beam is slowly stressed, so that the railway line can bear the load on the longitudinal beam. When the longitudinal beam is raised, the on-site technicians perform leveling control to control the elevation consistency of the four corners of the longitudinal beam and the smoothness of the track line in the construction site.

The embodiment of the present application provides specific operation steps of tunnel undercut construction, and FIG. 5 is a schematic flowchart of the tunnel undercover construction step of the tunnel provided by the embodiment of the present application. As shown in FIG. 5 , the embodiment of the present application provides tunnel excavation construction steps including:

Step 501: Prepare for excavation, and determine the tunnel excavation method in combination with the on-site geological factors.

One or several combinations of the full-section method, the step method, the middle partition method, and the double-side wall guide pit method are adopted;

Step 502 : grouting the roadbed and the foundation. After the grouting of the roadbed and the foundation is solidified, reserve a small conduit for grouting of the roadbed;

Step 503: Tunnel excavation, excavating the tunnel from the construction shaft until the design mileage.

The tunnel excavation steps include the longitudinal construction of the tunnel and the horizontal construction of the tunnel. If the step method is used for construction, the tunnel face in the longitudinal construction of the tunnel shall be staggered by a distance of not less than 3m. The horizontal construction steps of the tunnel include:

Step 504: the initial support construction, after the soil excavation is completed, the construction and erection of the initial support and protection structure are carried out;

Step 505 : waterproof layer construction, after the initial support construction is completed, the waterproof layer is laid.

The construction of the waterproof layer uses geotextile as the buffer layer, and the waterproof membrane is used as the waterproof board, which is laid by the method of double-weld laying;

Step 506 : secondary lining construction, after the waterproof layer construction is completed, the secondary lining construction is carried out.

If the step method is used for construction, the upper step part and the lower step part need to be excavated successively. After the excavation of each part is completed, the initial support construction of this part will be carried out. The waterproof layer construction should be carried out from the bottom to the top. After the foundation is solidified, reserve a small grouting conduit for railway subgrade → excavate the soil at the upper step → carry out the initial support construction of the upper step → excavate the soil at the lower step, and apply the lower initial support to seal Forming a ring → laying the lower waterproof layer → applying secondary lining to the lower step portion → laying the upper waterproof layer and applying the secondary lining to the upper step portion → closing the secondary lining into a ring, backfilling and grouting.

Further, the steps of the initial support construction include:

The initial shotcrete, after the tunnel excavation is completed, the preliminary shotcrete; the preliminary shotcrete needs to be carried out immediately after the excavation is completed, and the excavation surface should be closed and leveled in time to prevent the surrounding rock surface from weathering and peeling off.

The grille steel frame is erected, and the grille steel frame is erected close to the initial sprayed concrete surface after the completion of the initial spraying concrete;

Re-sprayed concrete and re-sprayed concrete after the grid steel frame is erected. The re-sprayed concrete needs to be carried out after the construction of the section steel frame has passed the inspection. The thickness of the concrete is 6-8cm in one injection, and it is sprayed in 3 times to the design thickness.

Further, the grid steel frame is erected by on-site assembly of standard finished units. The finished units are welded together by connecting ribs. The grid steel frame is positioned and anchored by locking foot anchors. The gaps in the concrete surface formed after spraying concrete are filled with concrete blocks.

Further, the steps of the secondary lining construction include: binding of steel reinforcement for the bottom plate, formwork for the bottom support, concrete pouring for the bottom plate, binding of steel reinforcement for the side wall and the vault, formwork for the side wall and the vault, concrete pouring for the side wall and the vault, and secondary lining. Backfill grouting. Each sub-step belongs to the existing mature technology and will not be repeated here.

The above-mentioned bottom formwork, side wall and vault formwork use combined formwork, the backfill grouting step of the secondary lining is carried out after the bottom concrete, side wall and vault concrete reach the design strength, and the backfill grouting step of the secondary lining is carried out with cement grout. .

FIG. 6 is a schematic flowchart of the cleaning and acceptance steps of the tunnel provided by the embodiment of the present application. As shown in FIG. 6 , the cleaning and acceptance steps include the steps of restoring existing railway facilities, and the steps of restoring existing railway facilities include:

Step 601: Treatment of the bottom of the existing railway facilities;

Step 602: Remove the D-shaped toilet beam;

Step 603: Restoring the existing railway facilities;

Step 604: Clean up the site and check the project.

Further, the foundation treatment for the bottom of the existing railway facilities includes hollowing out the bottom of the existing railway facilities according to the design elevation; pouring concrete under the existing railway facilities, using cement mortar for leveling above the concrete and/or pouring concrete under the existing railway facilities first Cushion, reinforced concrete base is poured above the concrete cushion, and the width of the concrete cushion and the concrete base is larger than the width of the existing railway facilities.

Taking the existing railway level crossing under the shallow buried tunnel as an example, the crossing slab and the crossing slab platform need to be re-installed in the cleaning and acceptance steps. The specific operation process is: foundation treatment of the crossing slab and the crossing platform → D type Demolition of the line under the convenience beam 5→Remove the D-type convenience beam 5→install the crossing plate→lay the railway track restoration→lay the crossing platform.

During the foundation treatment of the crossing slab and the bottom of the crossing platform, it is necessary to hollow out the crossing slab and the bottom of the crossing platform according to the design elevation. During this period, the ground railway line (that is, the existing railway facilities) is completely supported by the D-shaped beam 5, which is to be installed. The bottom of the crossing slab is hollowed out and then poured with C15 concrete, and the top is leveled with cement mortar; the C15 cushion is poured under the crossing platform, and the C35 reinforced concrete base is poured above the cushion. Both the cushion and the base are 10cm wider than the crossing platform.

The crossing slab and the bottom of the crossing platform have been processed, and the ground railway line will be removed after the concrete reaches a certain strength. First cut off the original rail and lift it out, then lift out the sleeper.

After the original steel rail is removed, the D-type facilitation beam shall be further removed, and the removal of the D-type facilitation beam shall be carried out in the reverse order of the installation of the steel facilitation beam.

The crossing slab to be installed shall be transported to the site from the prefabrication yard 1 day in advance. The crossing slab shall be installed on the cement mortar cushion according to the design position and elevation with the help of cranes and manually. During installation, the crossing slab shall be flat and free from warping angles and overhangs. Phenomenon.

After the installation of the crossing slab is completed, the railway track is laid and restored, and the 25m/piece 50 steel rail is installed in the groove of the crossing slab and fixed.

After the railway track laying and restoration is completed, the crossing platform is paved on the concrete base, leaving a 3cm gap between the crossing platform and the crossing slab. During installation, pay attention to elevation control to ensure that vehicles can pass smoothly at the junction between the crossing board, the crossing platform and Litian Road.

The final acceptance will be carried out after everything is restored to its original state.

In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", " The orientation or positional relationship indicated by "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. is based on the orientation shown in the drawings or The positional relationship is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the indicated device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the present application.

In addition, the terms "first" and "second" are only used for descriptive purposes, and should not be construed as indicating or implying relative importance or implying the number of indicated technical features. Thus, a feature defined as "first" or "second" may expressly or implicitly include one or more of that feature. In the description of the present application, "plurality" means at least two, such as two, three, etc., unless expressly and specifically defined otherwise.

In this application, unless otherwise expressly specified and limited, the terms "installed", "connected", "connected", "fixed" and other terms should be understood in a broad sense, for example, it may be a fixed connection or a detachable connection It can be a mechanical connection, an electrical connection or can communicate with each other; it can be directly connected, or it can be indirectly connected through an intermediate medium, it can be the internal communication between two elements or the interaction relationship between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific situations.

Although the preferred embodiments of the present application have been described, additional changes and modifications to these embodiments may occur to those skilled in the art once the basic inventive concepts are known. Therefore, the appended claims are intended to be construed to include the preferred embodiment and all changes and modifications that fall within the scope of this application.

Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims (14)

1. A tunnel reinforcement protection structure is characterized in that: the reinforcement protection structure comprises: Protection structure, the protection structure includes isolation protection piles, horizontal isolation pipe sheds, and large pipe sheds inserted at the top of the tunnel. The isolation protection piles are arranged on one side or both sides of the tunnel to be excavated. On the outside of the pile, a large pipe shed is installed on the top of the tunnel to be excavated; The reinforcement structure includes support piles and beams, the beams include longitudinal beams and transverse beams, the beams are erected on the support piles, and the beams are arranged under the existing railway facilities above the tunnel to be excavated. 2. a construction method of tunnel, is characterized in that, the construction method of described tunnel adopts tunnel reinforcement protection structure as claimed in claim 1, and its concrete construction step comprises: Set up a construction shaft, set up a construction shaft at the starting point of the tunnel design, and carry out the construction of high-pressure rotary jet piles and ring beams in the shaft; The protection structure construction, the step of strengthening the protection structure construction includes carrying out the horizontal isolation pipe shed construction, the tunnel roof inserting the large pipe shed construction and the isolation protection pile construction according to the erection position of claim 1, and the existing railway Below the position where the facility needs to be overhead, the support pile construction in the reinforcement structure is carried out; Reinforcing structure construction, erecting beams on the supporting piles to support and reinforce the existing railway facilities; For tunnel excavation construction, the tunnel is excavated after the reinforcement structure construction steps are performed. The tunnel construction adopts the method of segmented excavation. First, excavate one side of the existing railway facilities. Excavation work will be carried out on the other side of the railway facility. 3. The construction method of tunnel according to claim 2, is characterized in that, described reinforcement structure construction step comprises: Assembling the convenient beam, that is, after the longitudinal beam is hoisted in place by a crane, it is connected with the cross beam to assemble the convenient beam; Erection of the facilitation beam, after the facilitation beam is assembled, gradually raise the longitudinal beam to make the facilitation beam and the supporting pile bear the load; Check and maintain the beam during tunnel construction. 4 . The tunnel construction method according to claim 3 , wherein, in the step of erecting the facilitation beam, when the longitudinal beam is raised, the on-site technicians perform leveling control. 5 . 5. The construction method of tunnel according to claim 2, is characterized in that, the step of described tunnel excavation construction comprises: In preparation for excavation, the tunnel excavation method shall be determined in combination with the on-site geological factors, and one or several combinations of the full-section method, the step method, the middle partition method and the double-side wall guide pit method shall be adopted; Grouting of roadbed and foundation, after the grouting of roadbed and foundation is solidified, reserve a small conduit for grouting of roadbed; Tunnel excavation, excavating the tunnel from the construction shaft to the design mileage, the tunnel excavation steps include the longitudinal construction of the tunnel and the transverse construction of the tunnel, and the transverse construction of the tunnel includes: In the initial support construction, after the soil excavation is completed, the construction and erection of the initial support and protection structure shall be carried out; The construction of the waterproof layer shall be carried out after the completion of the initial support construction; Secondary lining construction. After the waterproof layer construction is completed, the secondary lining construction is carried out. 6. The construction method of tunnel according to claim 5, is characterized in that, the step of described initial support construction comprises: Initial shotcrete, after tunnel excavation is completed, the initial shotcrete is carried out; The grid steel frame is erected, and the grid steel frame is erected close to the initial spray concrete surface after the completion of the initial spraying concrete; Re-sprayed concrete and re-sprayed concrete after the grid steel frame is erected. 7. The construction method of the tunnel according to claim 6 is characterized in that: the grid steel frame is erected by adopting the method of on-site assembly of standard finished units, and connecting ribs are used for welding between each finished unit, and the grid steel frame is assembled. The frame is positioned and anchored by locking foot anchor pipes, and the gap between the steel grid frame and the concrete surface formed after the initial shotcrete is filled with concrete blocks. 8 . The construction method of the tunnel according to claim 6 , wherein in the step of re-spraying the concrete, the method of multiple re-spraying is adopted to reach the design thickness. 9 . 9 . The construction method of the tunnel according to claim 6 , wherein the construction of the waterproof layer adopts geotextile as the buffer layer, and the waterproof membrane is used as the waterproof plate, and is laid by the method of double-weld laying. 10 . 10. The construction method of the tunnel according to claim 6, is characterized in that, the step of described secondary lining construction comprises: bottom steel bar binding, support bottom formwork, bottom plate concrete pouring, side wall and vault steel bar binding, support side Wall and vault formwork, side wall and vault concrete pouring, backfill grouting behind the secondary lining. 11. The construction method of the tunnel according to claim 10, wherein the bottom formwork, the side wall and the dome formwork are combined formwork, and the backfill grouting step of the second lining is in the bottom concrete, side wall After the concrete of the vault and the vault reaches the design strength, the backfill grouting step of the second lining is carried out with cement slurry. 12. The construction method of the tunnel according to claim 2, wherein the construction method further comprises the steps: Pre-construction preparation, the pre-construction preparation steps include temporary traffic guidance and reform, and divided traffic; Cleaning and acceptance, that is, cleaning, restoration and acceptance of the construction site after the construction is completed. 13. The tunnel construction method according to claim 12, characterized in that: the cleaning and acceptance steps include a restoration step of existing railway facilities, and the restoration step of existing railway facilities includes: foundation treatment of the bottom of the existing railway facilities, Demolition of convenient beams, restoration of the existing railway facilities, site cleaning, and project acceptance. 14. The construction method of the tunnel according to claim 13, characterized in that: the foundation treatment of the bottom of the existing railway facilities comprises hollowing out the bottom of the existing railway facilities according to the design elevation; pouring concrete under the existing railway facilities, above the concrete Use cement mortar for leveling and/or pour a concrete cushion below the existing railway facilities first, and then pour a reinforced concrete base above the concrete cushion, the widths of the concrete cushion and the concrete base are both larger than the width of the existing railway facilities .

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