A super-large-span tunnel support structure and excavation method

Abstract

The present invention discloses a super-large span tunnel support structure and excavation method, including a force-bearing part, the force-bearing part is located above the tunnel structure; a guide tunnel, the guide tunnel is arranged on both sides of the tunnel structure and is connected to the tunnel structure; a support part, the support part is connected to the force-bearing part; and a diagonal brace, the diagonal brace is connected between the force-bearing part and the support part, which solves the problem of large overburden load on shallow-buried super-large span tunnels. The advantages of the present invention are: the safety of shallow-buried super-large span tunnels is ensured by prestressing and forming rectangular cross-section beams through supports; the formed combined structure is equivalent to advanced reinforcement of the stratum, on this basis, the excavation section can be increased, and the construction efficiency of the tunnel is greatly improved on the basis of ensuring construction safety; compared with the traditional excavation method, the overall structural force of the excavation method is more clear, and the settlement control of the surface and underground pipelines during construction is better.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnels and underground engineering, and in particular to a super-large-span tunnel support structure and excavation method. Background Art

[0002] In the prior art, for the advance support of shallow buried super-large span tunnels, there are mainly grouting to reinforce the soil, advance small-duct grouting through advance pipe-roof support and other methods. However, due to the large overlying load on shallow buried super-large span tunnels, it will cause problems such as the control of surface settlement and the safety and economy of construction during the construction process. Summary of the invention

[0003] The purpose of the present invention is to provide a super-large-span tunnel support structure and excavation method, which can solve the problem of large overburden load on shallow-buried super-large-span tunnels. In order to achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0004] The present application provides a super-large-span tunnel support structure, comprising:

[0005] The force-bearing part is located above the tunnel structure;

[0006] A pilot tunnel is arranged on both sides of the tunnel structure and is connected to the tunnel structure;

[0007] A supporting part is connected to the force-bearing part; and a diagonal brace is connected between the force-bearing part and the supporting part.

[0008] In the existing technology, some scholars have conducted in-depth research on the excavation of super-large span tunnels, and some have simulated and analyzed the stress field and surrounding rock displacement caused by three construction methods of shallow-buried biased large-span highway tunnels under different levels of surrounding rock conditions, and evaluated the applicable conditions of various methods; some pointed out in the large-span soft surrounding rock step method construction technology of Kunming Gangtou Tunnel that when the surrounding rock of large-span tunnels has a certain self-stabilizing ability, it is possible to try to optimize the traditional CRD method and double side wall method into a step method construction; some use FALC3D simulation to simulate the excavation process of the tunnel portal, and combine the control ability of each construction method on the deformation around the tunnel. Evaluate the advantages and disadvantages of each method; some comparative analyses are conducted on the arch settlement value, surrounding rock horizontal displacement value, plastic zone, and maximum and minimum principal stresses of the tunnel entrance section under the three methods of double side wall pilot tunnel method, CRD method, and three-step seven-step method, and the optimal excavation method is analyzed; however, in the existing technology, for the advance support of shallow buried and super-large span tunnels, there are mainly grouting reinforcement of soil, advance small guide tube grouting and advance pipe shed support, etc. However, due to the large overlying load on shallow buried and super-large span tunnels, there are still some unresolved disputes on the control of surface settlement and the safety and economy of construction during the construction process.

[0009] In summary, the following three methods are widely used in the advanced support of shallow buried and dark excavated super-large span tunnels: pipe shed, pre-cutting groove method, and grouting method. Pipe shed is an effective construction method that can safely excavate, prevent surface subsidence, and protect underground and above-ground structures under harsh conditions, but its construction is more complicated and the project cost is relatively high.

[0010] The present invention combines the advance support method with the excavation construction sequence. The small pilot tunnel can be used as the working surface for constructing steel pipe beams, and the concrete structure under the diagonal support of the structure can be constructed therein, which greatly simplifies the construction process and excavation process and has a better effect.

[0011] In summary, in some possible implementations, the force-bearing part includes a ground beam, tension anchor rods and a steel tube beam; the ground beam is arranged below the ground surface, and the ground beam is connected to the steel tube beam through the tension anchor rods; the steel tube beam passes through the guide hole and is connected to the support part.

[0012] In summary of the technical solutions provided above, in some possible implementations, the steel tube beam includes an anchor head, a tension anchor cable and a steel tube, a plurality of tension anchor cables are arranged inside the steel tube, the anchor head is arranged at both ends of the tension anchor cable, and the anchor head is connected to the support part.

[0013] In summary of the technical solutions provided above, in some possible implementations, the support portion is a vertical guardrail pile, and the guardrail pile is connected to the steel pipe.

[0014] A method for excavating a super-large-span tunnel comprises the following steps:

[0015] S1: excavating ground beams: opening a guide groove underground, and laying the ground beams in the guide groove;

[0016] S2: Driving tension anchor rods: Driving the tension anchor rods on the ground beam to connect the ground beam and the steel pipe beam, wherein the tension anchor rods are arranged every 0.5m-2m;

[0017] S3: excavating a pilot tunnel and constructing retaining piles: excavating the pilot tunnels on both sides of the tunnel by using a step method, and constructing retaining piles on both sides in the pilot tunnel;

[0018] S4: constructing prestressed steel pipes: constructing the steel pipes by pre-tensioning method, injecting grout into the steel pipes, and connecting the grouting steel pipes with the retaining piles through diagonal braces, and then excavating the lower steps after the connection;

[0019] S5: excavating a tunnel and supporting the tunnel;

[0020] S6: Construction of secondary lining of tunnel invert.

[0021] In summary of the technical solutions provided above, in some possible implementations, after the step method is used to excavate the guide tunnels on both sides of the tunnel, the method also includes: performing advance grouting reinforcement with small guide tubes at the arch portion of the guide tunnel, and using the anchor spraying method for support.

[0022] Based on the technical solutions provided above, in some possible implementations, the retaining piles on both sides of the construction in the guide tunnel also include: forming a retaining pile structure by erecting steel bars and pouring concrete.

[0023] In summary, in some possible implementations, the steel pipe is constructed by a pre-tensioning method, and grouting is performed inside the steel pipe, which also includes: drilling a hole on the inner wall of the guide tunnel after excavation, placing a steel pipe with a diameter of 105-110 mm into the hole, inserting a steel bar with a diameter of 26-30 mm in the middle of the steel pipe, fixing the two ends of the steel pipe with an anchor head, applying prestress and grouting into the inside of the steel pipe, and relaxing the anchor heads at both ends after the slurry solidifies.

[0024] Some extensions can be added: The basic principle of the present invention is actually to analyze the upper soil of the shallow buried large-span tunnel and the constructed steel pipe beams and ground beams as a whole, and perform strength, stiffness and stability calculations, so as to design structures such as anchor rods and ground beams.

[0025] The beneficial effects of the present invention are as follows: the present invention adopts a method for excavating a super-large-span tunnel, in which two parallel pilot holes are excavated in advance on both sides of the tunnel top, and after the excavation is completed, a retaining pile structure is constructed inside the pilot hole as a prestressing pedestal and also as a support for the later combined rectangular cross-section beam. A prestressed steel pipe beam is used to connect the two pilot holes, and is connected to the constructed ground beam through a tension anchor rod, and is combined with the soil above the tunnel to form a force mode of an approximately rectangular cross-section beam.

[0026] In summary, after the construction of the ground beam of the steel tube beam and the tension anchor rods connecting the two, the weight of the entire soil formed on the top of the tunnel due to the ultra-shallow burial is no longer applied to the structure as the entire load, but is transmitted through the prestressed and formed rectangular cross-section beams through the supports to ensure the safety of the shallow buried ultra-large span tunnel; the formed combined structure is equivalent to the advance reinforcement of the stratum, on this basis, the excavation section can be increased, and the construction efficiency of the tunnel can be greatly improved on the basis of ensuring construction safety; and full consideration is given to the problem of excessive overburden load on the tunnel caused by the inability of the ultra-shallow buried large-span tunnel to form a natural arch effect, and the overburden load is better converted by optimizing the design of the soil structure above the tunnel; compared with the traditional excavation method, the overall structural force of this excavation method is clearer, and the settlement control of the surface and underground pipelines during construction is better.

[0027] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or be understood by implementing the embodiments of the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 A schematic diagram of a tunnel cross-section structure provided in an embodiment of the present invention.

[0030] Markings in the figure: 1. Ground beam; 2. Tension anchor rod; 3. Anchor head; 4. Tension anchor cable; 5. Steel pipe; 6. Diagonal brace; 7. Retaining piles; 8. First pilot tunnel; 9. Second pilot tunnel; 10. First tunnel; 11. Second tunnel; 12. Third tunnel; 13. Fourth tunnel; 14. Fifth tunnel; 15. Sixth tunnel; 16. Seventh tunnel. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0032] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. At the same time, in the description of the present invention, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0033] Among the existing advance support methods for ultra-large span tunnels constructed with shallow buried tunnels, the following three methods are more commonly used: pipe shed, pre-cutting method or grouting method; and pipe shed is an effective construction method that can safely excavate, prevent surface subsidence, and protect underground and above-ground structures under harsh conditions, but its construction is relatively cumbersome and the project cost is relatively high. The advance support method proposed in the present invention is combined with the excavation construction sequence, and the small pilot hole can be used as the working surface for the construction of steel pipe beams, and the concrete structure under the diagonal brace of the structure can be constructed therein, which greatly simplifies the construction process and excavation process and has a good effect.

[0034] The present invention regards the load-bearing part including the ground beam, the tension anchor rod and the steel pipe beam as a whole, and transmits the load through the support through prestressing and the formed rectangular cross-section beam (the rectangular cross-section beam is actually the load-bearing part), which is equivalent to advanced reinforcement. It can greatly improve the construction efficiency of the tunnel on the basis of ensuring construction safety and make the overall structural force more clear, saving costs and having good economic benefits.

[0035] Embodiment 1:

[0036] like Figure 1 As shown, this embodiment provides a super-large span tunnel support structure, including:

[0037] The force-bearing part is located above the tunnel structure;

[0038] Pilot tunnels are arranged on both sides of the tunnel structure and are connected to the tunnel structure;

[0039] The supporting part is connected to the force-bearing part, and the diagonal brace 6 is connected between the force-bearing part and the supporting part, and the diagonal brace 6 is arranged at an oblique angle to improve the bearing capacity of the prestressed steel beam.

[0040] In some optional implementation schemes, the load-bearing part includes a ground beam 1, a tension anchor rod 2 and a steel pipe beam 5. The ground beam 1 is arranged below the ground surface. In this scheme, the ground beam 1 is spaced 1 to 8 m apart, and the cross-sectional size can be 0.5 m*0.5 m. The ground beam 1 is connected to the steel pipe beam through the tension anchor rod 2; the steel pipe beam 5 passes through the guide tunnel and is connected to the support part; in the present invention, the load-bearing part, that is, the upper soil of the shallow buried large-span tunnel and the constructed steel pipe beam and the ground beam 1 are taken as a whole for load analysis.

[0041] Preferably, the length of the tension anchor rod 2 is determined according to the tunnel burial depth, and the distance between two adjacent anchor rods is 0.5-2 m.

[0042] In some optional implementation schemes, the steel tube beam includes an anchor head 3, a tension anchor cable 4 and a steel tube 5. A plurality of tension anchor cables 4 are arranged inside the steel tube 5. The anchor heads 3 are arranged at both ends of the tension anchor cables 4, and the anchor heads 3 are connected to the support. After the prestressed steel tube beam and the ground beam 1 are constructed, the steel tube 5, the soil above it and the ground beam 1 form a rectangular cross-section beam similar to reinforced concrete. Under the action of the upper load and self-weight, the lower part of the rectangular cross-section beam is tensile and the upper part is compressed. Since the soil at the lower part can hardly bear the tensile stress, the tensile stress is entirely borne by the steel tube beam, and the compressive stress at the upper part is jointly borne by the upper soil and the ground beam 1, of which the ground beam 1 bears the main part. At this time, the design and calculation can be carried out according to the prestressed concrete bending member. The effect of the prestressed steel tube 5 on the concrete beam can be equivalent to two parts, one part is the horizontal pressure Np generated by the prestress on the beam in the anchoring area, and the other part is the upward distributed force ω perpendicular to the center line of the prestressed tendon caused by the curvature of the prestressed steel bar. This distributed force is opposite to the uniform load on the beam and can be used to offset all or part of the load on the beam. In addition, under the action of horizontal pressure, the soil is compressed, which improves the shear strength of the soil.

[0043] In some optional implementation schemes, the supporting part is a vertical retaining pile 7, and the retaining pile 7 is connected to the steel pipe 5. It should be noted that the retaining pile 7 has a diameter of 0.5m-1.0m and a spacing of 1-2m.

[0044] It should be noted that according to the concrete design code, prestressed concrete flexural members are similar to reinforced concrete flexural members. If ξ≤ξ b When the prestressed tendons in the tensile zone of the cross section are damaged, they first reach the yield strength, and then the concrete in the compressive zone is crushed. When the prestressed concrete stress at the point of action of the prestressed tendons in the tensile zone is zero, the stress in the prestressed tendons is σ p0 At the critical failure, the prestressed tendon stress reaches the tensile strength design value f py , according to the plane section assumption, the relative limit compression zone height ξ b It can be determined by the following formula:

[0045]

[0046] In the formula, x c is the height of the neutral axis, h 0 is the effective height of the cross section, ε cu is the ultimate compressive strain of concrete, f py is the tensile strength of the prestressed tendon, σ p0 is the prestressed tendon stress when the normal stress of concrete at the resultant point of the longitudinal prestressed tendons in the tension zone is equal to zero, E s is the elastic modulus of the prestressed tendons.

[0047] When the limit is destroyed, the height of the limit compression zone is xb =β 1 x c , substituting into the above formula, we can get

[0048]

[0049] In the formula, ξ b is the relative compression zone height, x b is the height of the limit compression zone, h 0 is the effective height of the section, β 1 is the ratio of the height of the compression zone to the height of the neutral axis of the rectangular stress diagram, f py is the tensile strength of the prestressed tendon, σ p0 is the prestressed tendon stress when the normal stress of concrete at the resultant point of the longitudinal prestressed tendons in the tension zone is equal to zero, ε cu is the ultimate compressive strain of concrete, E s is the elastic modulus of the prestressed tendons.

[0050] Assume the prestress of the prestressed tendon is σ p , its distance to the edge of the concrete compression zone is h 0 , based on the plane section assumption, the stress of the prestressed tendon can be obtained:

[0051]

[0052] In the formula, E s is the elastic modulus of the prestressed tendon, ε cu is the ultimate compressive strain of concrete, β 1 is the ratio of the height of the compression zone to the height of the neutral axis of the rectangular stress diagram, x is the height of the compression zone, σ p0 It is the prestressed tendon stress when the normal stress of concrete at the resultant point of the longitudinal prestressed tendons in the tension zone is equal to zero.

[0053] The area of ​​the ground beam under compression is A s ′, the area of ​​prestressed steel bars in the tension zone is A p When the bending bearing capacity of the positive section is:

[0054] α 1 f c bx=f py A p -f y 'A s '

[0055]

[0056] In the formula, α 1 is the coefficient, f c is the compressive strength of concrete, b is the width of the rectangular section, x is the height of the compression zone, and f pyis the tensile strength of the prestressed tendon, f y ′ is the compressive strength of the steel bars in the steel tube beam, M is the design value of the bending moment, and M μ is the design value of the bending bearing capacity of the positive section, a′ s It is the distance from the point where the combined force of the reinforcement acts to the edge of the section.

[0057] According to the "Concrete Structure Design Code", "concrete beams should use stirrups as reinforcement to bear shear force". In the present invention, the tension anchor rods are used as stirrups to bear force, and the specific design calculation is as follows:

[0058] The shear force of the section at the edge of the support is the largest, and the maximum value is:

[0059]

[0060] Where V is the shear design value, q is the uniformly distributed load, and l 0 is the beam span value.

[0061] Cross-section verification according to thick web beam:

[0062] 0.25β c f c bh 0 >V

[0063] In the formula, β c -Concrete strength influence coefficient, f c is the compressive strength of concrete, b is the width of the rectangular section, h is 0 is the effective height of the section, and V is the shear force design value.

[0064] If the above formula is met, it means that the cross section meets the requirements and then check whether stirrups are configured.

[0065] 0.7f t bh 0 <V

[0066] In the formula, f t The design value of concrete tensile strength, b is the width of the rectangular section, h is 0 is the effective height of the section, and V is the shear force design value.

[0067] If the above formula is satisfied, it means that stirrups need to be configured according to the calculation, and V = V u

[0068]

[0069] In the formula, A sv1 is the tension anchor area, s is the tension anchor spacing, V is the shear force design value, f t The design value of concrete tensile strength, b is the width of the rectangular section, h is0 is the effective height of the section, f yv Tensile strength of anchor rod

[0070] During configuration, just satisfy That's it.

[0071] According to the above formula, the arrangement of prestressed tendons in steel tube beams and the calculation of the bearing capacity of the entire section can be carried out.

[0072] Embodiment 2:

[0073] A method for excavating a super-large-span tunnel comprises the following steps:

[0074] S1: Excavation of ground beam 1: After the tunnel design burial depth is determined, the size of the rectangular cross-section beam is also determined according to the tunnel design burial depth. Since the ground beam 1 mainly bears the function of the compression zone in the rectangular cross-section beam, according to calculation and construction requirements, the beam needs to ensure limit damage.

[0075] S2: Install tension anchor rods 2: Install tension anchor rods 2 on the ground beam 1 to connect the ground beam 1 and the steel tube beam. Install one tension anchor rod 2 every 0.5m-2m. It should be noted that the tension anchor rods 2 can effectively connect the ground beam 1 and the steel tube beam, and can also play the role of stirrups for rectangular cross-section beams to prevent shear failure of the oblique cross-section. The spacing and stress of the tension anchor rods 2 need to be configured according to the shear calculation method for the oblique cross-section in the above formula.

[0076] S3: Excavate the pilot tunnel and construct the retaining piles 7: The construction method of the pilot tunnel is similar to that of the tunnel with piles. When the ground conditions are poor, the step method can be used for excavation, and the small guide tube can be pre-grouted in the arch of the small pilot tunnel. The excavation cycle advance is determined according to the initial support steel frame spacing. After excavation, the anchor spraying system support is carried out in time to maintain the stability of the small pilot tunnel during the construction stage;

[0077] The arrangement of the retaining piles 7 needs to be based on the construction process requirements of the prestressed anchor cables in the steel tube beam and the transfer load requirements after the steel tube beam is constructed; the small guide holes on both sides are the first guide hole 8 and the second guide hole 9. After the construction is completed, excavation is carried out at the bottom of the first guide hole 8 and the second guide hole 9, and drilling or manual digging is carried out to form the retaining pile 7 structure by erecting steel bars and pouring concrete. The main function of the retaining piles 7 is to bear the load transferred from the steel tube beam.

[0078] S4: Construction of steel pipe 5: The prestressed steel pipe 5 consists of anchor heads 3 at both ends, tension anchor cables 4 and grouting bodies, and is constructed using the pre-tensioning method. A hole is opened on the inner wall of the excavated small pilot tunnel, and a steel pipe 5 with a diameter of 108m is pushed in. During the pushing process, the size is strictly controlled to prevent the steel pipe 5 from being tilted. A 28mm diameter steel bar is inserted in the middle of the steel pipe 5. After the two ends of the steel bar are fixed by the anchor heads 3 at both ends, prestress is applied, and then the steel pipe 5 is filled with grout. After the slurry solidifies to reach the design strength, the anchor heads 3 at both ends are released.

[0079] S5: excavate the tunnel and support the tunnel; the order of excavation in the tunnel structure is: the upper layer of the tunnel, the middle part of the tunnel and the lower part of the tunnel. The excavation should be carried out in steps. The upper step should be excavated first, and the upper step should be excavated to the bottom of the steel pipe beam. The excavation cycle advance is determined according to the initial support steel frame spacing, and the maximum shall not exceed 1.5 meters. After excavation, the connection construction between the lower part of the tension anchor 2 and the steel pipe beam is completed. After the connection is completed, the lower step is excavated: the upper layer of the tunnel is the first tunnel 10 and the second tunnel 11;

[0080] The third tunnel 12 and the fifth tunnel 14 are on the left and right sides of the middle part. The excavation depth should be determined according to the initial support steel frame spacing, which shall not exceed 1.5m at most. The excavation height is generally 3-3.5m, and the steps on the left and right sides are staggered by 2-3m. Immediately after excavation, 3-5cm concrete is sprayed, and support is carried out with spraying, anchoring and net systems in time, and the steel frames are extended. When the initial support strength of the third tunnel 12 and the fifth tunnel 14 reaches the design requirements, the excavation of the fourth tunnel 13 soil is carried out.

[0081] The final excavation of the lower tunnels is as follows: the sixth tunnel 15 and the seventh tunnel 16: the excavation advance length of each cycle should be 2 to 3 m. After excavation, initial support of the invert should be carried out in time. After completing two cycles of tunnel bottom excavation and support, the invert should be constructed in time. The segment length of the invert should be 4 to 6 m.

[0082] S6: Construction of the secondary lining of the tunnel arch: Construction of the secondary lining of the tunnel arch wall to complete the construction of the overall structure of the tunnel.

[0083] In some optional implementation schemes, after excavating the pilot tunnels on both sides of the tunnel by the step method, it also includes: pre-grouting reinforcement with a small guide tube at the arch of the pilot tunnel, and supporting it by the anchor spraying method.

[0084] Preferably, the retaining pile 7 structure is formed by erecting steel bars and pouring concrete.

[0085] In some optional implementation schemes, the steel pipe 5 is constructed by the pre-tensioning method, and grouting is performed inside the steel pipe 5, which also includes: drilling a hole on the inner wall of the excavated guide tunnel, placing a steel pipe 5 with a diameter of 105-110m into the hole, passing a steel bar with a diameter of 26-30mm in the middle of the steel pipe 5, fixing both ends of the steel pipe 5 with an anchor head 3, applying prestress and grouting inside the steel pipe 5, and relaxing the anchor heads 3 at both ends after the slurry solidifies.

[0086] In summary, after the ground beam 1 of the steel tube beam and the tension anchor rod 2 connecting the two are constructed in the present invention, the weight of the entire soil formed on the top of the tunnel due to the ultra-shallow burial is no longer applied to the structure as the entire load, but is transmitted through the prestressed and formed rectangular cross-section beam through the support, thereby ensuring the safety of the shallow buried ultra-large span tunnel; the combined structure formed by the present invention is equivalent to the advance reinforcement of the stratum, on this basis, the excavation section can be increased, and the construction efficiency of the tunnel can be greatly improved on the basis of ensuring construction safety.

[0087] And most importantly, compared with traditional excavation methods, the overall structural force of this excavation method is more clear, and the settlement of surface and underground pipelines can be better controlled during construction; and in terms of construction economy, it saves certain costs compared with pipe curtain method and freezing method, and has good economy.

[0088] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0089] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0091] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A super-large span tunnel support structure, characterized in that: include: A force-bearing portion, wherein the force-bearing portion is located above the tunnel structure; A guide tunnel, which is arranged on both sides of the tunnel structure and is connected to the tunnel structure; A supporting portion, the supporting portion being connected to the force-bearing portion; and An oblique brace (6), wherein the oblique brace (6) is connected between the force-bearing portion and the supporting portion; The force-bearing part comprises a ground beam (1), a tension anchor rod (2) and a steel tube beam; the ground beam (1) is arranged below the ground surface; the ground beam (1) is connected to the steel tube beam via the tension anchor rod (2); the steel tube beam passes through the guide hole and is connected to the support part; The steel tube beam comprises an anchor head (3), a tension anchor cable (4) and a steel tube (5); a plurality of tension anchor cables (4) are arranged inside the steel tube (5); the anchor head (3) is arranged at both ends of the tension anchor cable (4); and the anchor head (3) is connected to the support portion; Wherein, the supporting part is a vertical retaining pile (7), and the retaining pile (7) is connected to the steel pipe (5); The super-large-span tunnel support structure adopts a tunnel excavation method, which includes: S1: excavating the ground beam (1): opening a guide groove underground, and laying the ground beam (1) in the guide groove; S2: Driving the tension anchor rods (2): Driving the tension anchor rods (2) on the ground beam (1) to connect the ground beam (1) and the steel pipe (5) beam, wherein the tension anchor rods (2) are arranged every 0.5 m to 2 m; S3: excavating a pilot tunnel and constructing retaining piles (7): excavating the pilot tunnels on both sides of the tunnel by using a step method, and constructing retaining piles (7) on both sides of the pilot tunnel; S4: constructing the steel pipe (5): constructing the steel pipe (5) by using a pre-tensioning method, injecting grout into the steel pipe (5), and connecting the grouting steel pipe (5) to the retaining pile (7) through a diagonal brace (6), and then excavating the lower step after the connection; S5: excavating a tunnel and supporting the tunnel; S6: Construction of secondary lining of tunnel invert.

2. A tunnel excavation method, comprising the super-large-span tunnel support structure according to claim 1, characterized in that: After the pilot tunnels on both sides of the tunnel are excavated by the step method, the method also includes: performing advance grouting reinforcement of small guide tubes at the arch portion of the pilot tunnel, and using the anchor spraying method for support.

3. The tunnel excavation method according to claim 2, characterized in that: The retaining piles (7) constructed on both sides of the guide tunnel also include: forming the retaining piles (7) by erecting steel bars and pouring concrete.

4. The tunnel excavation method according to claim 2, characterized in that: The steel pipe (5) is constructed by using a pre-tensioning method and grouting is injected into the steel pipe (5), which also includes: drilling a hole in the inner wall of the excavated guide tunnel, placing a steel pipe (5) with a diameter of 105-110 mm into the hole, inserting a steel bar with a diameter of 26-30 mm through the middle of the steel pipe (5), fixing the two ends of the steel pipe (5) with anchor heads (3), applying prestress and injecting grout into the steel pipe (5), and relaxing the anchor heads (3) at both ends after the grout solidifies.

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