Support system and construction method for flat single-span five-lane highway tunnel

Abstract

The present invention provides a support system for a flat single-span five-lane highway tunnel, comprising an initial support structure, a prestressed anchor cable assembly, a secondary lining, an invert filling layer, and an advance support structure. The initial support structure is a double-layer structure, and the prestressed anchor cable assembly comprises a crown prestressed anchor cable, a left waist prestressed anchor cable, a left foot prestressed anchor cable, a right waist prestressed anchor cable, and a right foot prestressed anchor cable. The present invention also provides a construction method for a support system for a flat single-span five-lane highway tunnel. Prestressed anchor cables are symmetrically applied at the crown, waist, and foot positions of the tunnel for tensioning and locking, to bear the loose load of the surrounding rock, strengthen the self-bearing capacity of the surrounding rock, and achieve the purpose of support and span reduction; the support system adopts double-layer initial support and prestressed anchor cables based on the active support concept, which can effectively ensure the safety of the tunnel surrounding rock during the construction and operation stages, the support system has high integrity and stability, and the support effect is safe and reliable.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel support, and in particular to a support system for a flat single-span five-lane highway tunnel and a construction method thereof. Background Art

[0002] At present, research on super-large cross-section highway tunnels has achieved certain results, and the research objects are basically single-span four-lane tunnels. There has been no research on single-span five-lane highway tunnels, and there is not much engineering experience to learn from, which brings great troubles and challenges to the design and construction of such projects. Support structure design is an extremely important part of tunnel engineering. Choosing appropriate support forms and support parameters can effectively ensure the stability and safety of tunnel construction and operation. Therefore, research on the support system of single-span five-lane highway tunnels is imminent, which has positive significance for promoting the construction of highway tunnels with larger cross-sections. Summary of the invention

[0003] The purpose of the present invention is to overcome the defects of the prior art and provide a support system and a construction method for a flat single-span five-lane highway tunnel. The present invention at least solves some of the problems in the prior art.

[0004] The present invention is achieved in that:

[0005] The invention provides a support system for a flat single-span five-lane highway tunnel. The excavation section of the tunnel comprises an upper left pilot tunnel, a lower left pilot tunnel, an upper right pilot tunnel, a lower right pilot tunnel, an upper rock wall and a lower rock wall. The support system for the tunnel comprises an initial support structure, a prestressed anchor cable assembly, a secondary lining arranged inside the initial support structure, an inverted arch filling layer located at the bottom of the tunnel, and an advanced support structure for performing advanced support on the tunnel. The initial support structure comprises a first layer of initial support, a second layer of initial support and a system anchor rod arranged at an arch wall position of the tunnel, the second layer of initial support is located between the first layer of initial support and the secondary lining, the prestressed anchor cable assembly comprises an arch crown prestressed anchor cable, a left arch waist prestressed anchor cable, a left arch foot prestressed anchor cable, a right arch waist prestressed anchor cable and a right arch foot prestressed anchor cable, the left arch waist prestressed anchor cable and the right arch waist prestressed anchor cable are symmetrically arranged, and the left arch foot prestressed anchor cable and the right arch foot prestressed anchor cable are symmetrically arranged.

[0006] Furthermore, the first layer of initial support includes a steel frame and a steel mesh, and the second layer of initial support includes a grating steel frame and a steel mesh. The steel frame, grating steel frame and steel mesh are all arranged in the shotcrete. The first layer of initial support, the second layer of initial support and the secondary lining all provide full-section support for the tunnel.

[0007] Furthermore, along the longitudinal direction of the tunnel, two adjacent steel frames are fastened together by multiple longitudinal connecting steel bars.

[0008] Furthermore, the longitudinal connecting steel bars are arranged horizontally and along the longitudinal extension direction of the tunnel.

[0009] Furthermore, along the longitudinal direction of the tunnel, the spacing between two adjacent steel frames is the same as the spacing between two adjacent grid steel frames.

[0010] Furthermore, the support system for the flat single-span five-lane highway tunnel also includes a left arch foot locking anchor pipe and a right arch foot locking anchor pipe, and the left arch foot locking anchor pipe and the right arch foot locking anchor pipe are both 3 to 5 meters higher than the top of the tunnel invert filling layer.

[0011] Furthermore, the advance support structure includes a plurality of small grouting conduits for performing advance support on the tunnel arch portion from back to front along the longitudinal extension direction of the tunnel.

[0012] Furthermore, a small grouting duct is arranged in the range of 100-120° in the tunnel arch portion.

[0013] Furthermore, the arch crown prestressed anchor cables are provided with four, and the left arch waist prestressed anchor cables, the left arch foot prestressed anchor cables, the right arch waist prestressed anchor cables, and the right arch foot prestressed anchor cables are each provided with two.

[0014] The present invention also provides a construction method for a support system of a flat single-span five-lane highway tunnel, including S1, construction preparation and advanced geological forecast; S2, application of advanced support; S3, tunnel excavation, tunnel construction adopts a continuous arch excavation method; S4, application of initial support and prestressed anchor cables; S5, secondary lining construction and invert backfilling; S6, construction completion.

[0015] The present invention has the following beneficial effects:

[0016] The invention proposes a support system suitable for an ultra-large flat single-span five-lane highway tunnel, comprising an advance support structure, an initial support structure, a secondary lining structure, an invert filling layer and a prestressed anchor cable; the advance support structure comprises a plurality of advance small duct grouting support structures for performing advance support on the tunnel arch portion from rear to front along the longitudinal extension direction of the tunnel; the initial support is a double-layer structure, the first layer is composed of shotcrete and a steel frame, the second layer is composed of shotcrete and a grid steel frame, and longitudinal connecting steel bars are arranged between two adjacent steel frames, so as to effectively enhance the strength and rigidity of the initial support structure and control the deformation of the surrounding rock; based on the active support concept, prestressed anchor cables are symmetrically applied at the positions of the tunnel arch, arch waist and arch foot for tensioning and locking, so as to bear the loose load of the surrounding rock, enhance the self-bearing capacity of the surrounding rock, and achieve the purpose of support and span reduction; the support system adopts double-layer initial support and prestressed anchor cables based on the active support concept, which can effectively ensure the safety of the tunnel surrounding rock during the construction and operation stages, the support system has high integrity and stability, and the support effect is safe and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 A schematic diagram of an excavation method provided by an embodiment of the present invention;

[0019] Figure 2 A schematic cross-sectional view of a support system provided by an embodiment of the present invention;

[0020] Figure 3 A schematic diagram of advanced support provided by an embodiment of the present invention;

[0021] Figure 4 A partial schematic diagram of double-layer initial support provided by an embodiment of the present invention;

[0022] Figure 5 A schematic diagram of the longitudinal connection of a steel frame provided in an embodiment of the present invention;

[0023] Figure 6 A construction flow chart provided for an embodiment of the present invention.

[0024] Markings in the figure: 1-first layer initial support; 2-second layer initial support; 3-system anchor rod; 4-arch crown prestressed anchor cable; 5-left arch waist prestressed anchor cable; 6-left arch foot prestressed anchor cable; 7-right arch waist prestressed anchor cable; 8-right arch foot prestressed anchor cable; 9-left arch foot locking anchor pipe; 10-right arch foot locking anchor pipe; 11-secondary lining; 12-inverted arch filling layer; 13-small grouting duct; 14-sprayed concrete; 15-steel frame; 16-grating frame; 17-longitudinal connecting steel bars. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] like Figure 1-Figure 6Embodiment 1 of the present invention provides a support system suitable for an ultra-large flat single-span five-lane highway tunnel, wherein the excavation section of the tunnel includes an upper left pilot tunnel, a lower left pilot tunnel, an upper right pilot tunnel, a lower right pilot tunnel, an upper rock wall, and a lower rock wall. The support system for the tunnel includes an initial support structure, a prestressed anchor cable assembly based on an active support concept, a secondary lining 11 arranged on the inner side of the initial support structure, an inverted arch filling layer 12 located at the bottom of the tunnel, and an advance support structure for performing advance support on the tunnel. The secondary lining 11 is a steel frame concrete structure, and the inverted arch filling layer 12 is a plain concrete structure, which is arranged above the bottom of the secondary lining 11. The initial support structure of the tunnel and the secondary lining 11 both perform full-section support on the tunnel, such as Figure 2 The initial support structure includes a first layer of initial support 1, a second layer of initial support 2 and a system anchor rod 3 arranged at the tunnel arch wall. The second layer of initial support 2 is located between the first layer of initial support 1 and the secondary lining 11. A waterproof layer is provided between the second layer of initial support 2 and the secondary lining 11. The system anchor rod 3 adopts a grouting small conduit, and the system anchor rod 3 is arranged in a plum blossom shape. Figure 2 The prestressed anchor cable assembly includes a vault prestressed anchor cable 4, a left arch waist prestressed anchor cable 5, a left arch foot prestressed anchor cable 6, a right arch waist prestressed anchor cable 7, and a right arch foot prestressed anchor cable 8. The left arch waist prestressed anchor cable 5 and the right arch waist prestressed anchor cable 7 are symmetrically arranged, and the left arch foot prestressed anchor cable 6 and the right arch foot prestressed anchor cable 8 are symmetrically arranged. Based on the active support concept, prestressed anchor cables are symmetrically applied at the vault, arch waist and arch foot of the tunnel for tensioning and locking to bear the loose load of the surrounding rock, strengthen the self-bearing capacity of the surrounding rock, and achieve the purpose of support and span reduction. Figure 2 There are four prestressed anchor cables 4 for the arch crown, and two prestressed anchor cables 5 for the left arch waist, two prestressed anchor cables 6 for the left arch foot, two prestressed anchor cables 7 for the right arch waist, and two prestressed anchor cables 8 for the right arch foot.

[0027] like Figure 3 The advance support structure includes a plurality of grouting small ducts 13 for performing advance support on the tunnel arch from back to front along the longitudinal extension direction of the tunnel. The grouting small ducts 13 are arranged in the range of 100-120° of the tunnel arch. The circumferential spacing of the grouting small ducts 13 is 50 cm, and the overlap length is greater than 1.0 m.

[0028] like Figure 4 The first layer of initial support 1 includes a steel frame 15 and a steel mesh, and the second layer of initial support 2 includes a grid steel frame 16 and a steel mesh. The steel frame 15, the grid steel frame 16, and the steel mesh are all arranged in the shotcrete 14. The first layer of initial support 1, the second layer of initial support 2, and the secondary lining 11 all provide full-section support for the tunnel. Along the longitudinal direction of the tunnel, the spacing between two adjacent steel frames 15 is the same as the spacing between two adjacent grid steel frames 16.

[0029] like Figure 5 Along the longitudinal direction of the tunnel, two adjacent steel frames 15 are fastened together by multiple longitudinal connecting steel bars 17, which effectively strengthens the strength and rigidity of the initial support structure and controls the deformation of the surrounding rock. The longitudinal direction is the length direction of the tunnel. The longitudinal connecting steel bars 17 are arranged horizontally and along the longitudinal extension direction of the tunnel.

[0030] like Figure 2 The support system for a flat single-span five-lane highway tunnel also includes a left arch foot locking anchor pipe 9 and a right arch foot locking anchor pipe 10, which are 5 meters long. The left arch foot locking anchor pipe 9 and the right arch foot locking anchor pipe 10 are both set at the tunnel arch foot, and their positions are determined according to the specific excavation height, which is roughly 3 to 5 meters higher than the top of the tunnel invert filling layer. The locking anchor pipe is tangentially at a 45° angle to the steel frame.

[0031] The support system is suitable for super-large flat single-span five-lane highway tunnels with large excavation sections, and is suitable for Class III, Class IV, and Class V surrounding rocks.

[0032] like Figure 6 The second embodiment of the present invention provides a support system and construction method suitable for a super-large flat single-span five-lane highway tunnel, and the construction steps are: construction preparation → advanced geological forecast → application of advanced support → tunnel excavation, tunnel construction adopts the arch excavation method → ​​application of initial support, prestressed anchor cable → secondary lining construction and invert backfill → construction completion. The construction steps of the prestressed anchor cable are: pre-tensioning → secondary compensation tensioning and locking → sealing and grouting.

[0033] The tunnel construction adopts the multi-arch excavation method:

[0034] like Figure 1, the excavation section of the tunnel is set as follows: the upper left pilot tunnel is the first excavation part 101, the lower left pilot tunnel is the second excavation part 102, the upper left pilot tunnel and the lower left pilot tunnel constitute the left excavation part; the upper right pilot tunnel is the third excavation part 103, the lower right pilot tunnel is the fourth excavation part 104, the upper right pilot tunnel and the lower right pilot tunnel constitute the right excavation part, the upper rock wall is the fifth excavation part 105, and the lower rock wall is the sixth excavation part 106; it also includes a first support part 1011, a second support part 1022, a third support part 1033, a fourth support part 1044, a fifth support part 1055, a sixth support part 1066, and a seventh support part 107 7, wherein the first supporting part 1011 is the initial support of the left arch corresponding to the first excavation part and the spraying layer on the left side of the upper rock wall, the second supporting part 1022 is the initial support of the left side wall corresponding to the second excavation part, the third supporting part 1033 is the initial support of the right arch corresponding to the third excavation part and the spraying layer on the right side of the upper rock wall, the fourth supporting part 1044 is the initial support of the right side wall corresponding to the fourth excavation part, the fifth supporting part 1055 is the initial support of the arch corresponding to the fifth excavation part, the sixth supporting part 1066 is the initial support of the inverted arch corresponding to the sixth excavation part, and the seventh supporting part 1077 is the secondary lining;

[0035] Excavation construction is carried out on each excavation section in sequence according to the numerical order, and initial support and prestressed anchor cables are applied. During the entire excavation process, the second excavation section 102 lags behind the first excavation section 101, the third excavation section 103 lags behind the second excavation section 102, the fourth excavation section 104 lags behind the third excavation section 103, the fifth excavation section 105 lags behind the fourth excavation section 104, and the sixth excavation section 106 lags behind the fifth excavation section 105.

[0036] The advance support is to carry out advance grouting reinforcement for the grouting small pipe 13, such as Figure 3 The advance support structure includes a plurality of advance small duct grouting support structures (grouting small ducts 13) for providing advance support to the tunnel arch from the back to the front along the longitudinal extension direction of the tunnel. The structures of the plurality of said advance small duct grouting support structures are the same, and the overlap length between two adjacent advance small duct grouting support structures is greater than 1.0m. Figure 3 The grouting range of the grouting small conduit 13 for advanced support is 100°~120° along the arc line of the arch. The grouting small conduit 13 adopts a hot-rolled seamless steel pipe with a diameter of Φ42mm and a wall thickness of 3.5mm, and the length of the grouting small conduit 13 is 3.5m~4.0m.

[0037] The initial support is a double-layer structure, including the first layer of initial support 1 and the second layer of initial support 2. The initial support is composed of a steel frame 15, a steel mesh, a system anchor 3, a grid steel frame 16 and shotcrete 14. A longitudinal connecting steel bar 17 is set between two adjacent steel frames 15 to effectively enhance the strength and rigidity of the initial support structure and control the deformation of the surrounding rock. The system anchor 3 is set at the arch wall of the tunnel. The system anchor 3 adopts a 5m long Φ42 grouting small pipe, with a circumferential × longitudinal spacing = 1.2 × 1.0m, and a plum blossom arrangement.

[0038] The steel frames 15 are evenly arranged along the longitudinal extension direction of the tunnel. The front and rear adjacent steel frames 15 are fastened together by multiple longitudinal connecting steel bars 17. The longitudinal connecting steel bars 17 are arranged horizontally and along the longitudinal extension direction of the tunnel. The multiple longitudinal connecting steel bars 17 are arranged along the contour line of the full-section steel frame. The circumferential spacing of the longitudinal connecting steel bars is 1.0~1.5m, and the longitudinal connecting steel bars 17 are Φ25 hot-rolled steel bars.

[0039] The first layer of initial support 1: the thickness of the shotcrete 14 is 26cm, and a steel frame 15 and a steel mesh are provided therein; the second layer of initial support 2: the thickness of the shotcrete 14 is 20cm, and a grid steel frame 16 and a steel mesh are provided therein; the longitudinal spacing between the steel frame 15 and the grid steel frame 16 is the same, and the steel frame 15 and the grid steel frame 16 are evenly arranged along the longitudinal direction of the tunnel, with a spacing of 0.6~1.2m, which is determined according to the actual engineering conditions. The grade of the shotcrete 14 is C25, the steel frame 15 uses I20b I-beam, and the grid steel frame 16 uses Φ28 grid steel frame.

[0040] A waterproof layer is provided between the initial support structure and the secondary lining 11. The secondary lining 11 is made of C35 cast-in-place concrete with a thickness of 60 cm. The invert filling layer 12 above the bottom of the secondary lining is made of C30 plain concrete.

[0041] Prestressed anchor cables are symmetrically installed at the tunnel vault, arch waist and arch foot for tensioning and locking to bear the loose load of the surrounding rock, strengthen the self-bearing capacity of the surrounding rock, and achieve the purpose of support and span reduction. Figure 2 , 4 prestressed anchor cables are set at the arch position, and 2 prestressed anchor cables are set at other positions. The prestressed anchor cables use 7φ15.2 steel strands with a designed maximum prestress of 1100kN. In actual construction, the length is 10~12m, the prestress value is 800~1000kN, the circumferential spacing is 1.5m, and the longitudinal spacing is 1.0m. The construction steps are: pre-tensioning → secondary compensation tensioning and locking → sealing and grouting.

[0042] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A support system for a flat single-span five-lane highway tunnel, characterized in that: The excavation section of the tunnel includes an upper left pilot tunnel, a lower left pilot tunnel, an upper right pilot tunnel, a lower right pilot tunnel, an upper rock wall, and a lower rock wall. The support system for the tunnel includes an initial support structure, a prestressed anchor cable assembly, a secondary lining arranged inside the initial support structure, an invert filling layer located at the bottom of the tunnel, and an advanced support structure for advanced support of the tunnel. The initial support structure includes a first layer of initial support, a second layer of initial support, and a system anchor rod arranged at the arch wall of the tunnel. The second layer of initial support is located between the first layer of initial support and the secondary lining. A waterproof layer is provided between the second layer of initial support and the secondary lining. The system anchor rod adopts a grouting small conduit, and the system anchor rod is arranged in a plum blossom shape. The prestressed anchor cable assembly includes a prestressed anchor cable for the arch crown, a prestressed anchor cable for the left arch waist, a prestressed anchor cable for the left arch foot, a prestressed anchor cable for the right arch waist, and a prestressed anchor cable for the right arch foot. The prestressed anchor cables for the left arch waist and the right arch waist are symmetrically arranged, and the prestressed anchor cables for the left arch foot and the right arch foot are symmetrically arranged. The prestressed anchor cables are symmetrically applied at the positions of the tunnel arch crown, arch waist and arch foot for tensioning and locking; the first layer of initial support includes a steel frame and a steel mesh, and the second layer of initial support includes a grille steel frame and a steel mesh. The steel frame, grille steel frame and steel mesh are all arranged in the shotcrete. The first layer of initial support, the second layer of initial support and the secondary lining all provide full-section support for the tunnel; The excavation section of a given tunnel is as follows: the upper left pilot tunnel is the first excavation section, the lower left pilot tunnel is the second excavation section, and the upper left pilot tunnel and the lower left pilot tunnel constitute the left excavation section; the upper right pilot tunnel is the third excavation section, the lower right pilot tunnel is the fourth excavation section, the upper right pilot tunnel and the lower right pilot tunnel constitute the right excavation section, the upper rock wall is the fifth excavation section, and the lower rock wall is the sixth excavation section; it also includes a first supporting section, a second supporting section, a third supporting section, a fourth supporting section, a fifth supporting section, a sixth supporting section, and a seventh supporting section, wherein the first supporting section is the initial support for the left arch corresponding to the first excavation section and the sprayed layer on the left side of the upper rock wall, the second supporting section is the initial support for the left side wall corresponding to the second excavation section, and the third supporting section is the initial support for the left side wall corresponding to the second excavation section. The protecting part is the initial support of the right arch part and the right spray layer of the upper rock wall corresponding to the third excavation part, the fourth supporting part is the initial support of the right side wall corresponding to the fourth excavation part, the fifth supporting part is the initial support of the arch top corresponding to the fifth excavation part, the sixth supporting part is the initial support of the invert arch corresponding to the sixth excavation part, and the seventh supporting part is the secondary lining; each excavation part is excavated and constructed in sequence according to the numerical order, and the initial support and prestressed anchor cables are applied. During the entire excavation process, the second excavation part lags behind the first excavation part, the third excavation part lags behind the second excavation part, the fourth excavation part lags behind the third excavation part, the fifth excavation part lags behind the fourth excavation part, and the sixth excavation part lags behind the fifth excavation part.

2. The support system for a flat single-span five-lane highway tunnel according to claim 1, characterized in that: Along the longitudinal direction of the tunnel, two adjacent steel frames are fastened together by multiple longitudinal connecting steel bars.

3. The support system for a flat single-span five-lane highway tunnel according to claim 2, characterized in that: The longitudinal connecting steel bars are arranged horizontally and along the longitudinal extension direction of the tunnel.

4. The support system for a flat single-span five-lane highway tunnel according to claim 1, characterized in that: Along the longitudinal direction of the tunnel, the spacing between two adjacent steel frames is the same as the spacing between two adjacent grid steel frames.

5. The support system for a flat single-span five-lane highway tunnel according to claim 1, characterized in that: It also includes a left arch foot locking anchor pipe and a right arch foot locking anchor pipe, both of which are 3 to 5 meters higher than the top of the tunnel invert filling layer.

6. The support system for a flat single-span five-lane highway tunnel according to claim 1, characterized in that: The advanced support structure comprises a plurality of small grouting conduits for performing advanced support on the tunnel arch portion from rear to front along the longitudinal extension direction of the tunnel.

7. The support system for a flat single-span five-lane highway tunnel according to claim 1, characterized in that: A small grouting duct is set within the range of 100~120° in the tunnel arch.

8. The support system for a flat single-span five-lane highway tunnel according to claim 1, characterized in that: The arch crown prestressed anchor cables are provided with four, and the left arch waist prestressed anchor cables, the left arch foot prestressed anchor cables, the right arch waist prestressed anchor cables, and the right arch foot prestressed anchor cables are each provided with two.

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