A tunnel construction method for expanding a small cross-section into a large cross-section

Abstract

The present invention discloses a tunnel construction method for expanding a small cross-section into a large cross-section, which includes the following steps: S1. The large cross-section tunnel is divided into nine areas for construction respectively; S2. A construction temporary passage is excavated on each of the left and right sides of the small cross-section tunnel; the upper left bench and the upper right bench are successively excavated by using the construction temporary passage, and the primary support structure and the temporary support are constructed; S3. The middle upper bench is excavated and the primary support structure is constructed to form the support system for the upper bench; S4. The construction temporary passages on both sides are backfilled and tamped; S5. The small cross-section tunnel is divided into an upper bench and a lower bench, the upper bench of the small cross-section tunnel is expanded into the cross-section size of the central bench, and the temporary supports on both sides are excavated forward and constructed; after the construction of the central bench is completed, the left middle bench and the right middle bench are excavated; S6. The lower bench of the large cross-section tunnel is excavated by using the lower bench of the small cross-section tunnel; the present invention has the advantages of convenient construction, high safety and high construction efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel excavation construction, and particularly relates to a tunnel construction method for expanding a small cross-section into a large cross-section. Background Art

[0002] During the construction of a tunnel, there may be a situation where excavation needs to be expanded. When constructing a tunnel with a large excavation span and strict control over the deformation of the surrounding rock, due to the increase in the excavation area of the cross-section, the self-stabilizing ability of the surrounding rock during excavation becomes poor, the deformation accelerates, the relaxation range increases, and the construction difficulty increases sharply. In particular, higher requirements are put forward for the initial support technology and the face control technology.

[0003] In the prior art, when the tunnel cross-section sizes differ greatly, there will be a problem that it is difficult to construct due to excessive arch height; if the upper bench of the large cross-section tunnel is directly excavated upward using a small cross-section tunnel, the slope and angle will be too large, which easily leads to the abnormal operation of construction machinery and muck transportation. Summary of the Invention

[0004] The purpose of the present invention is to address the problems existing in the prior art and provide a tunnel construction method for expanding a small cross-section into a large cross-section. This solution has the advantages of convenient construction, high safety, and high construction efficiency.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is: A tunnel construction method for expanding a small cross-section into a large cross-section, comprising the following steps:

[0006] S1. Divide the large cross-section tunnel into nine areas for construction respectively; the nine areas include the upper left bench, the middle upper bench, the upper right bench, the left middle bench, the central bench, the right middle bench, the lower left bench, the middle lower bench, and the lower right bench;

[0007] S2. Excavate a construction temporary passage on each side of the small cross-section tunnel; use the construction temporary passage to successively excavate the upper left bench and the upper right bench, and construct the initial support structure and temporary support;

[0008] S3. Excavate the middle upper bench and construct the initial support structure to form the support system for the upper bench;

[0009] S4. Backfill and compact the construction temporary passages on both sides;

[0010] S5. Divide the small cross-section tunnel into upper and lower benches, expand the upper bench of the small cross-section tunnel into the cross-section size of the central bench, excavate forward and construct the temporary supports on both sides; after the construction of the central bench is completed, excavate the left middle bench and the right middle bench;

[0011] S6. According to the excavation steps in step S5, use the lower bench of the small cross-section tunnel to excavate the lower benches of the large cross-section tunnel.

[0012] In the above solution, in step S1, the large-section tunnel is divided into nine regions, which is convenient for excavation in sequence and ensures construction safety. Among them, the upper left bench, the upper middle bench, and the upper right bench are the upper benches, the left middle bench, the central bench, and the right middle bench are the middle benches, and the lower left bench, the lower middle bench, and the lower right bench are the lower benches; in step S2, by setting construction temporary channels on both sides of the small-section tunnel, it is convenient to construct the bench part of the large-section tunnel that is higher than the small-section tunnel, avoiding the problem of inconvenient excavation due to the sudden increase in the tunnel section. The upper left bench and the upper right bench are constructed successively to avoid excessive disturbance to the tunnel soil layer and avoid safety risks. The upper left bench and the upper right bench are excavated and expanded through the construction temporary channels. The expansion span is small, which is convenient for excavation. At the same time, the primary support structure and temporary support are constructed to ensure the structural stability and construction safety of the upper left bench and the upper right bench; in step S3, the upper middle bench is excavated and the primary support structure is constructed to complete the support system of the upper bench; in step S4, after the support system is stable, the construction temporary channel is blocked and backfilled and compacted to ensure the stability of the soil layer; in steps S5 - S6, after the outside of the small-section tunnel is stable, the upper bench is excavated and expanded into the section range of the central bench, and the central bench and the construction support are continuously excavated. After completion, the excavation of the left middle bench and the right middle bench is carried out; after the excavation of the middle bench of the large-section tunnel is completed, referring to step S5, the lower middle bench is excavated and expanded and the lower left bench and the lower right bench are excavated starting from the lower bench of the small-section tunnel, so as to complete the full-section excavation work of the large-section tunnel.

[0013] Furthermore, the minimum clear distance between the left construction temporary channel and the right side of the small-section tunnel shall not be less than 0.5 times the tunnel diameter; the minimum clear distance between the right construction temporary channel and the left side of the small-section tunnel shall not be less than 0.5 times the tunnel diameter.

[0014] By restricting the dimensions and positions of the left and right construction temporary channels, it is ensured that the left and right temporary construction channels will not affect each other during the excavation process.

[0015] Furthermore, the upward excavation slope of the left construction temporary channel shall not be greater than 30°, and the angle to the right along the tunnel excavation direction shall not be greater than 30°; the upward excavation slope of the right construction temporary channel shall not be greater than 30°, and the angle to the left along the tunnel excavation direction shall not be greater than 30°.

[0016] The upward slope of the construction temporary channel does not exceed 30°, and the horizontal inclination angle does not exceed 30°, so as to ensure that the construction machinery can pass smoothly and safely, reduce the excavation distance, and improve the construction efficiency.

[0017] Furthermore, the left construction temporary channel is connected to the boundary between the upper left bench and the upper middle bench, and the right construction temporary channel is connected to the boundary between the upper right bench and the upper middle bench.

[0018] It is convenient to excavate the upper middle bench along the tunnel direction from the construction temporary access road, and it does not affect the support structure.

[0019] Furthermore, in step S5, after the construction of the central bench is completed, a construction access road is respectively set at the tail of the temporary support on the left or right side of the central bench and the head of the temporary support on the other side of the middle bench, and the left middle bench and the right middle bench are excavated by the method of construction from both sides towards each other.

[0020] By respectively setting the left and right construction access roads at the head and tail ends of the central bench and excavating the left middle bench and the right middle bench, the two are carried out synchronously without interference, improving the construction efficiency.

[0021] Furthermore, the width of the construction access road shall not be greater than 5m, and the height shall not be greater than 4m, and additional reinforcement measures shall be taken for the construction access road and monitoring and measurement shall be carried out.

[0022] Limiting the cross-sectional size, taking reinforcement measures, and monitoring and measurement ensure the structural stability of the access road, facilitating the normal operation of construction machinery and muck transportation.

[0023] Furthermore, in step S3, when excavating the upper middle bench of the large-section tunnel, the temporary support in step S2 needs to be retained to ensure the force integrity of the upper bench support system.

[0024] The retention of the temporary support does not affect the construction and ensures the stability of the force of the construction structure.

[0025] Furthermore, in step S4, when backfilling the left and right construction temporary access roads, the original soil is first used for backfilling and tamping. For the areas in the arch part that cannot be backfilled and tamped, the openings of the temporary access roads are closed, and concrete is poured into the arch part.

[0026] Backfilling the original soil and tamping, and pouring concrete into the arch part to fill the voids of the structure ensure the force stability of the soil layer structure.

[0027] Furthermore, in step S2, when excavating the upper left bench and the upper right bench by using the construction temporary access road, the operation platform is first longitudinally excavated, and then it is changed to horizontally excavate the upper left bench and the upper right bench along the tunnel excavation direction.

[0028] The front ends of the upper left bench and the upper right bench are excavated through the construction temporary access road, the expansion span is small, which is convenient for excavation. First excavating the operation platform is convenient for subsequent excavation work, convenient for tool stacking, and the construction is continuous and smooth.

[0029] Furthermore, in step S3, the cross-sectional size of the upper middle bench is excavated and expanded through the left and right construction temporary access roads. After excavating the operation platform, the upper middle bench is horizontally excavated along the tunnel excavation direction.

[0030] First, excavate the cross-section and operating platform of the upper-middle bench, and then construct along the excavation direction to facilitate the stacking of tools and ensure continuous and smooth construction.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] 1. Construct temporary construction channels on both the left and right sides of the small cross-section tunnel to excavate the large cross-section, avoiding the situation of excessive slopes and angles during excavation, meeting the needs of the entry and exit of construction machinery and the transportation of muck during the excavation of the large cross-section tunnel, and solving the problem that it is difficult to construct the arch crown due to the large difference in cross-section sizes when expanding the small cross-section tunnel into a large cross-section tunnel. The construction process is smooth and convenient.

[0033] 2. The present invention respectively opens a temporary construction channel on both the left and right sides of the small cross-section tunnel to excavate the upper bench of the large cross-section. After the excavation of the upper bench is completed, backfill the temporary construction channel, and then use the small cross-section channel to excavate the middle bench and lower bench of the large cross-section tunnel. During the excavation of the large cross-section tunnel, the stability and safety of the surrounding rock and the support structure are guaranteed.

[0034] 3. By adding the number of construction free surfaces through the temporary construction channels, the construction efficiency is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a three-dimensional schematic diagram of the tunnel structure in the present invention;

[0036] Figure 2 is a front view of the temporary construction channel and the small cross-section tunnel in the present invention;

[0037] Figure 3 is a top view of the construction direction of the temporary construction channel and the small cross-section tunnel in the present invention;

[0038] Figure 4 is a construction flow chart of the present invention;

[0039] Figure 5 is a front view of the construction partition in the present invention;

[0040] Figure 6 is a longitudinal section view of the construction partition in the present invention;

[0041] Figure 7 is a longitudinal section view of the excavation of the upper bench in the present invention;

[0042] Figures 8 - 12 is a top view of the construction of the excavation of the upper bench of the large cross-section tunnel in the present invention;

[0043] Figure 13 is a top view of the backfilling of the temporary construction channel in the present invention;

[0044] Figures 14 - 18It is the construction top view of the middle bench for excavating a large cross-section tunnel in the present invention;

[0045] In the figure: 1. Upper left bench; 2. Middle upper bench; 3. Upper right bench; 4. Left middle bench; 5. Central bench; 6. Right middle bench; 7. Lower left bench; 8. Middle lower bench; 9. Lower right bench; 10. Temporary construction access on the left side; 11. Small cross-section tunnel; 12. Temporary construction access on the right side; 13. Large cross-section tunnel; 14. Upper bench; 15. Middle bench; 16. Lower bench; 17. Temporary support; 18. Backfill with original soil. Detailed implementation manners

[0046] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention. In the description of the present invention, it should be noted that the terms "front", "rear", "left", "right", etc. indicating the orientation or position relationship are based on the orientation or position relationship shown in the accompanying drawings, or the orientation or position relationship when the invention product is usually placed. It is only for the convenience of describing the present invention or simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed or operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. Embodiment

[0047] As Figures 1 - 18 shown, a tunnel construction method for expanding a small cross-section into a large cross-section includes the following steps:

[0048] S1. The large cross-section tunnel 13 is divided into nine areas for construction respectively; the nine areas include the upper left bench 1, the middle upper bench 2, the upper right bench 3, the left middle bench 4, the central bench 5, the right middle bench 6, the lower left bench 7, the middle lower bench 8, and the lower right bench 9;

[0049] S2. A temporary construction access is excavated on each of the left and right sides of the small cross-section tunnel 11, and the two temporary construction accesses are respectively connected to the front ends of the upper left bench 1 and the upper right bench 3; the construction of the upper left bench 1 and the upper right bench 3 is carried out successively. The upper left bench 1 is excavated and expanded by using the temporary construction access 10 on the left side, and the primary support structure and the temporary support 17 on the left side are constructed; the upper right bench 3 is excavated by using the temporary construction access 12 on the right side, and the primary support structure and the temporary support 17 on the right side are constructed;

[0050] S3. After the upper left bench 1 and the upper right bench 3 are both excavated, the middle upper bench 2 is excavated, and the primary support structure is constructed to form the support system of the upper bench 14;

[0051] S4. After the deformation and stress conditions of the upper bench support system are stable, backfill and compact the construction temporary channels on both the left and right sides.

[0052] S5. After the surrounding rock deformation outside the small-section tunnel 11 is stable, divide the small-section tunnel 11 into upper and lower benches, expand the upper bench of the small-section tunnel 11 to the cross-sectional size of the central bench 5 of the large-section tunnel 13, excavate forward and construct the temporary supports 17 on both the left and right sides; after the construction of the central bench 5 is completed, excavate the left middle bench 4 and the right middle bench 6.

[0053] S6. After the excavation of the middle bench 15 in the middle of the large-section tunnel 13 is completed, according to the excavation steps in step S5, use the lower bench of the small-section tunnel 11 to excavate the lower bench 16 of the large-section tunnel 13.

[0054] In the above solution, in step S1, the large-section tunnel 13 is divided into nine areas, which is convenient for sequential excavation and ensures construction safety. Among them, the upper left bench 1, the upper middle bench 2, and the upper right bench 3 are the upper bench 14, the left middle bench 4, the central bench 5, and the right middle bench 6 are the middle bench 15, and the lower left bench 7, the lower middle bench 8, and the lower right bench 9 are the lower bench 16; in step S2, by setting construction temporary channels on both sides of the small-section tunnel 11, it is convenient to construct the stepped part of the large-section tunnel 13 that is higher than the small-section tunnel 11, avoiding the problem of inconvenient excavation due to the sudden increase in the tunnel cross-section. The upper left bench 1 and the upper right bench 3 are constructed successively to avoid excessive disturbance to the tunnel soil layer and avoid safety risks. By expanding and excavating the upper left bench 1 and the upper right bench 3 through the construction temporary channels, the expansion span is small, which is convenient for excavation. At the same time, the primary support structure and the temporary support 17 are constructed to ensure the structural stability and construction safety of the upper left bench 1 and the upper right bench 3; in step S3, the upper middle bench 2 is excavated and the primary support structure is constructed to complete the support system of the upper bench 14; in step S4, after the support system is stable, the construction temporary channels are blocked and backfilled and compacted to ensure the stability of the soil layer; in steps S5 - S6, after the outside of the small-section tunnel 11 is stable, the upper bench is expanded to the cross-sectional range of the central bench 5 of the large-section tunnel 13, and the central bench 5 and the construction support are continuously excavated. After completion, the excavation of the left middle bench 4 and the right middle bench 6 is carried out; after the excavation of the middle bench 15 in the middle of the large-section tunnel 13 is completed, referring to step S5, the lower middle bench 8 is expanded and the lower left bench 7 and the lower right bench 9 are excavated starting from the lower bench 16 of the small-section tunnel 11, thereby completing the full-section excavation of the large-section tunnel 13.

[0055] The small-section tunnel 11 corresponds to the position of the central bench 5, which facilitates the excavation of the central bench 5. When excavating the construction temporary access road, support shall be promptly constructed. Support shall be constructed synchronously with the excavation to ensure the safety and stability of the construction temporary access road. The support can be shotcrete with wire mesh and grouting treatment to ensure the stability of the surrounding rock near the access road. The temporary support 17 will be removed later. In S5, construction is carried out after the deformation of the surrounding rock near the crown and the haunches of the small-section tunnel 11 has stabilized.

[0056] A construction temporary access road is excavated on each of the left and right sides of the small-section tunnel 11 to partition the large-section tunnel 13 for construction. At the same time, within the full section, continuous rolling construction is carried out in three layers of benches. The uppermost bench is divided into upper left, middle upper, and upper right pilot headings, and the pilot headings correspond to the bench structure. For tunnel construction using this construction procedure, construction is carried out in an orderly manner from top to bottom. Each bench is relatively independently closed into a ring, and the time for closing into a ring is short, with high construction efficiency. Using the small-section tunnel 11 as the construction temporary access road can reduce the use of construction backfill materials. In the long run, the solution of the present invention is safe, efficient, and has a relatively low long-term cost.

[0057] The present invention proposes a tunnel construction method in which a temporary construction access road is respectively opened on each of the left and right sides of the small-section tunnel 11 to excavate the upper bench 14 of the large section, and after the excavation of the upper bench 14 is completed, the temporary construction access road is backfilled, and then the middle bench 15 and the lower bench 16 of the large-section tunnel 13 are excavated using the small-section access road. Construction temporary access roads are opened on each of the left and right sides of the small-section tunnel 11, and the upper bench 14 of the large-section tunnel 13 is excavated at a relatively small slope and angle.

[0058] The technical solution of the present invention utilizes the opened temporary construction access road, which not only meets the requirements for expanding the small-section tunnel 11 into the large-section tunnel 13, but also improves the safety of the support structure and the stability of the surrounding rock during the excavation of the large-section tunnel 13. The specific construction process is as follows: excavate the left construction temporary access road 10 of the small-section tunnel 11, excavate the upper left bench 1 of the large-section tunnel 13 using the left construction temporary access road 10, excavate the upper right bench 3 of the large-section tunnel 13 using the right construction temporary access road 12, excavate the middle upper bench 2, backfill the construction temporary access roads on both the left and right sides, excavate the middle bench of the large-section tunnel 13 using the upper bench of the small-section tunnel 11, excavate the lower bench of the large-section tunnel 13 using the lower bench of the small-section tunnel 11, and construct the invert and the secondary lining.

[0059] Furthermore, the minimum clear distance between the left construction temporary access road 10 and the right side of the small-section tunnel 11 shall not be less than 0.5 times the tunnel diameter; the minimum clear distance between the right construction temporary access road 12 and the left side of the small-section tunnel 11 shall not be less than 0.5 times the tunnel diameter.

[0060] By restricting the dimensions and positions of the construction temporary access roads on both the left and right sides, it is ensured that the excavation processes of the left and right temporary construction access roads will not affect each other.

[0061] Furthermore, the upward excavation slope of the left construction temporary access road 10 shall not be greater than 30°, and the angle to the right along the tunnel excavation direction shall not be greater than 30°; the upward excavation slope of the right construction temporary access road 12 shall not be greater than 30°, and the angle to the left along the tunnel excavation direction shall not be greater than 30°.

[0062] The upward slope of the construction temporary access road does not exceed 30°, and the inclination angle in the horizontal direction does not exceed 30°, to ensure that construction machinery can pass smoothly and safely, reduce the excavation distance, and improve construction efficiency.

[0063] The left and right construction temporary access roads are mirror - set, and the construction direction of the construction temporary access road inclines towards the small - section tunnel 11, which is convenient for the construction of the upper bench 14.

[0064] Furthermore, the left construction temporary access road is connected to the boundary between the upper - left bench 1 and the middle - upper bench 2, and the right construction temporary access road is connected to the boundary between the upper - right bench 3 and the middle - upper bench 2.

[0065] It is convenient to excavate the middle - upper bench 2 along the tunnel direction from the construction temporary access road without affecting the support structure.

[0066] Furthermore, in step S5, after the central bench 5 is constructed, a construction access road is respectively set at the tail of the temporary support 17 on the left or right side of the central bench 5 and at the head of the temporary support 17 on the other side of the middle bench, and the left - middle bench 4 and the right - middle bench 6 are excavated by the method of construction from both sides towards each other.

[0067] By respectively setting the left - side and right - side construction access roads at the head and tail of the central bench 5 and excavating the left - middle bench 4 and the right - middle bench 6, the two operations are carried out synchronously without interference, improving construction efficiency.

[0068] Furthermore, the width of the construction access road shall not be greater than 5m, and the height shall not be greater than 4m, and additional reinforcement measures need to be taken for the construction access road and monitoring and measurement shall be carried out.

[0069] Limiting the cross - section size, taking reinforcement measures, and monitoring and measurement ensure the structural stability of the access road, facilitating the normal operation of construction machinery and muck transportation.

[0070] Furthermore, in step S3, when excavating the middle - upper bench 2 of the large - section tunnel 13, the temporary support 17 in step S2 needs to be retained to ensure the force integrity of the support system of the upper bench 14.

[0071] Retaining the temporary support 17 does not affect the construction and ensures the stability of the force of the construction structure.

[0072] Further, in step S4, when backfilling the temporary construction access roads on both the left and right sides, first backfill and compact with the original soil. For the areas in the arch part that cannot be backfilled and compacted, seal the openings of the temporary access roads and pour concrete into the arch part.

[0073] Backfilling and compacting with the original soil and pouring concrete into the arch part to fill the voids in the structure ensure the mechanical stability of the soil layer structure.

[0074] The backfilling is carried out in a layered compaction manner, and conditions for secondary grouting are reserved when pouring concrete.

[0075] Further, in step S2, when excavating the upper left bench 1 and the upper right bench 3 by using the temporary construction access road, first longitudinally excavate the operation platform, and then change to horizontally excavate the upper left bench 1 and the upper right bench 3 along the tunnel excavation direction.

[0076] The front ends of the upper left bench 1 and the upper right bench 3 are excavated through the temporary construction access road. The excavation surface has a small span, which is convenient for excavation. Excavating the operation platform first facilitates subsequent excavation work, convenient for stacking tools, and the construction is continuous and smooth.

[0077] Further, in step S3, the cross-section size of the middle upper bench 2 is excavated through the temporary construction access roads on both the left and right sides. After excavating the operation platform, horizontally excavate the middle upper bench 2 along the tunnel excavation direction.

[0078] First, excavate the cross-section and the operation platform of the middle upper bench 2, and then construct along the excavation direction, which is convenient for stacking tools and the construction is continuous and smooth.

[0079] The length of the operation platform is 4 - 6m, which is convenient for construction.

[0080] As Figures 1 - 4 shown, by using the process flow of this construction method, the invention scheme is based on the advantages of the double-side drift method in terms of the stability and safety of the surrounding rock and the support structure during the excavation of the large-section tunnel 13, and uses the temporary construction access road to excavate the large section.

[0081] As Figure 5 shown, when expanding the small-section tunnel 11 into the large-section tunnel 13, due to the large difference in cross-section sizes, there will be a problem of excessive arch crown height. Therefore, a temporary construction access road is respectively opened on both the left and right sides of the small-section tunnel 11 to excavate the upper left bench 1 and the upper right bench 3 of the large section, and at the same time, the large-section tunnel 13 is divided into three benches and nine areas in the upper, middle, and lower parts for construction.

[0082] As Figure 6 and Figure 7As shown, due to the excessively large cross-sectional size of the tunnel, considering the safety of the lining structure during the construction process, the large cross-section is divided into three steps for construction; at the same time, considering issues such as the entry and exit of construction machinery and the transportation of muck during the excavation of the large cross-section tunnel 13, a construction temporary passage is excavated upward at a certain slope and angle to establish a construction temporary passage, and this is used as the construction free face to excavate the upper bench.

[0083] As Figure 8 and Figure 9 shown, the upper left bench 1 is excavated upward through the left construction temporary passage 10, and the primary support structure and the left temporary support 17 are constructed.

[0084] As Figure 10 shown, the upper right bench 3 is excavated upward through the right construction temporary passage 12, and the primary support structure and the right temporary support 17 are constructed.

[0085] As Figure 11 and Figure 12 shown, the middle upper bench 2 is excavated through the left and right construction temporary passages, and the primary support structure and the temporary support 17 system on both left and right sides are retained.

[0086] As Figure 13 shown, the support structure at the intersection of the upper bench and the construction temporary passage is constructed first to form the support system of the upper bench. After the deformation and stress conditions of the upper bench support system are stable, the left and right construction temporary passages are backfilled with in-situ soil.

[0087] As Figures 14 - 18 shown, the middle bench of the large cross-section tunnel 13 is excavated by expanding the upper bench of the small cross-section tunnel 11. A construction passage is established at the tail of the left temporary support 17 and the head of the right temporary support 17 in the middle bench, and the left middle bench 4 and the right middle bench 6 are excavated by the method of constructing from both sides towards each other.

[0088] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A tunnel construction method for expanding a small cross-section into a large cross-section, characterized in that, It includes the following steps: S1. Divide the large-section tunnel into nine areas for construction respectively; the nine areas include the upper left bench, the middle upper bench, the upper right bench, the left middle bench, the central bench, the right middle bench, the lower left bench, the middle lower bench, and the lower right bench; S2. Excavate a construction temporary passage on each side of the small-section tunnel. The upward excavation slope of the left construction temporary passage shall not be greater than 30°, and the angle to the right along the tunnel excavation direction shall not be greater than 30°; the upward excavation slope of the right construction temporary passage shall not be greater than 30°, and the angle to the left along the tunnel excavation direction shall not be greater than 30°. Use the construction temporary passage to successively excavate the upper left bench and the upper right bench, and construct the primary support structure and temporary support; S3. Excavate the middle upper bench and construct the primary support structure to form the support system for the upper bench; S4. Backfill and tamp the construction temporary passages on both sides; S5. Divide the small-section tunnel into an upper bench and a lower bench. Expand the upper bench of the small-section tunnel to the cross-section size of the central bench, excavate forward and construct the temporary supports on both sides. After the construction of the central bench is completed, excavate the left middle bench and the right middle bench; S6. According to the excavation steps in step S5, use the lower bench of the small-section tunnel to excavate the lower left bench, the middle lower bench, and the lower right bench of the large-section tunnel.

2. The tunneling method for expanding a small cross-section into a large cross-section according to claim 1, characterized in that, The left construction temporary passage is connected to the boundary between the upper left bench and the middle upper bench, and the right construction temporary passage is connected to the boundary between the upper right bench and the middle upper bench.

3. A tunnel construction method for expanding a small cross-section into a large cross-section according to claim 1, characterized in that In step S5, after the construction of the central bench is completed, set a construction passage at the tail of the temporary support on the left or right side of the central bench and the head of the temporary support on the other side of the middle bench respectively, and excavate the left middle bench and the right middle bench in a way of construction from both sides towards each other.

4. A tunnel construction method for expanding a small cross-section into a large cross-section according to claim 3, characterized in that , The width of the construction passage shall not be greater than 5m, and the height shall not be greater than 4m, and additional reinforcement measures need to be taken for the construction passage and monitoring and measurement shall be carried out.

5. A tunnel construction method for expanding a small cross-section into a large cross-section according to claim 1, characterized in that , In step S3, when excavating the middle upper bench of the large-section tunnel, it is necessary to retain the temporary support in step S2 to ensure the force integrity of the support system for the upper bench.

6. A tunnel construction method for expanding a small cross-section into a large cross-section according to claim 1, characterized in that , In step S4, when backfilling the construction temporary passages on both sides, first backfill and tamp with the original soil. For the areas in the arch part that cannot be backfilled and tamped, close the opening of the temporary passage and pour concrete into the arch part.

7. A tunnel construction method for expanding a small cross-section into a large cross-section according to claim 1, characterized in that , In step S2, when using the construction temporary passage to expand and excavate the upper left bench and the upper right bench, first longitudinally excavate the operation platform, and then change to horizontally excavate the upper left bench and the upper right bench along the tunnel excavation direction.

8. A tunnel construction method for expanding a small cross-section into a large cross-section according to claim 1, characterized in that , In step S3, expand the cross-section size of the middle upper bench through the construction temporary passages on both sides. After excavating the operation platform, horizontally excavate the middle upper bench along the tunnel excavation direction.

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