Construction method for excavation of oblique tunnel intersection section

Abstract

The application discloses a construction method for excavation of an oblique tunnel intersection section. The method comprises the following steps: excavating and supporting a branch hole according to a design section of the branch hole intersection section until a branch hole working face is parallel to a main hole axis, and a first set distance a is reserved between the branch hole working face parallel to the main hole axis and a main hole standard section excavation section; dividing the main hole intersection section into an excavation driving section and a groove cutting driving section according to upstream and downstream sequences, carrying out a groove cutting driving process in the groove cutting driving section from the branch hole intersection section, and carrying out excavation driving of the excavation driving section along the main hole axis direction by using a main hole intersection section cut out by the groove cutting, until the position of a large included angle side intersection point A of the branch hole and the main hole is passed; and respectively carrying out driving and supporting processes of upstream and downstream working faces of the main hole standard section. The application not only meets the requirement of passing of the branch hole to the small included angle side of the main hole, but also enables the main hole intersection section to be constructed by using the same excavation section, so that the work efficiency of on-site construction is improved.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel construction, and in particular to a construction method for excavating an intersection section of an oblique tunnel. Background Art

[0002] The excavation of the intersection section of the oblique tunnel is a challenging engineering task due to its large span and difficult construction.

[0003] However, the excavation method in the prior art has the following problems:

[0004] First, due to complex geological conditions and other factors, it is difficult to set the angle of the tunnel intersection section to be orthogonal. However, when excavating oblique intersection sections using normal excavation methods, there are often problems such as over-excavation on the side of the intersection section with small angles, which is difficult to retain.

[0005] Second, after entering the main tunnel from the branch tunnel, steel arch frames are often used for reinforced support because the intersection section is a key part. The elevation of the top plate of the main tunnel and the branch tunnel is often inconsistent, resulting in frequent changes in cross-section during blasting excavation, which will cause a certain amount of over-excavation. At the same time, if poor surrounding rock is encountered, the construction safety risk will increase. In addition, the specifications and sizes of the steel arch frames in the intersection section vary due to the different heights of the tunnel sections, which will reduce construction efficiency and increase engineering safety risks. Summary of the Invention

[0006] In response to the shortcomings of the existing technology, the present invention proposes a construction method for excavating the intersection section of an oblique tunnel, which can not only regularize the side excavation of the intersection section with a small angle, but also enable the main tunnel intersection section to be constructed using the same excavation section, unify the steel arch structure size required for support, make the initial support of the intersection section easy to construct, and improve the work efficiency of on-site construction.

[0007] To achieve the above-mentioned object, the present invention provides a construction method for excavating an intersection section of an oblique tunnel, which is particularly characterized in that it comprises the following steps:

[0008] S1) After reaching the branch tunnel intersection section construction stake number, excavate and support the branch tunnel according to the branch tunnel intersection section design section until the branch tunnel face is parallel to the main tunnel axis, and a first set distance a is retained between the branch tunnel face parallel to the main tunnel axis and the main tunnel standard section excavation section;

[0009] S2) dividing the main tunnel intersection section into an excavation excavation section and a groove excavation section in an upstream and downstream order, with the groove excavation section close to the small angle side of the main tunnel and the excavation excavation section close to the large angle side of the main tunnel;

[0010] Enter the groove excavation section from the branch tunnel intersection section and carry out the groove excavation process, and the groove width meets the normal operation requirements of the initial support construction trolley;

[0011] After the groove excavation section is completed, the main tunnel cross section obtained by the groove is used to open the excavation section and excavate along the axis of the main tunnel until it passes through the intersection point A on the side with the largest angle between the branch tunnel and the main tunnel;

[0012] For the groove excavation section and the excavation excavation section, the main tunnel intersection section steel arch construction shall be carried out immediately after each set distance of excavation;

[0013] S3) After step S2) is completed, the excavation and support processes are carried out on the upstream working face of the main tunnel standard section on the large angle side of the main tunnel and the downstream working face of the main tunnel standard section on the small angle side of the main tunnel, and the upstream and downstream working faces of the main tunnel standard section shrink the main tunnel cross section to the main tunnel standard section respectively.

[0014] Furthermore, in S1), a set distance a is retained between the branch tunnel face parallel to the main tunnel axis and the main tunnel standard section excavation section to meet the requirement of small angle side vehicle passing.

[0015] Furthermore, in S1), when constructing the steel arch support of the branch tunnel, in order to avoid construction difficulties at the small angle side of the main tunnel, multiple branch tunnel advance anchor rods are installed in advance on the small angle side of the main tunnel of the third steel arch frame of the branch tunnel, and the external insertion angle of the branch tunnel advance anchor rods is higher than the main tunnel intersection section range.

[0016] Furthermore, in S1), the branch tunnel steel arch frame support of the branch tunnel intersection section adopts a gradual arrangement, from the first steel arch frame 1 of the branch tunnel to the last steel arch frame 3 of the branch tunnel, it gradually changes from being perpendicular to the branch tunnel axis to being parallel to the main tunnel axis.

[0017] Furthermore, in S1), when constructing the branch tunnel steel arch support, the spacing between adjacent steel arches on the small angle side of the main tunnel and the spacing between adjacent steel arches on the large angle side of the main tunnel are arranged according to the size of the angle.

[0018] Furthermore, in S2), the groove excavation section II is divided into a first groove excavation section II1 and a second groove excavation section II2 in sequence according to the groove excavation order, the first groove excavation section II1 adopts an upward top-lifting process, and the second groove excavation section II2 adopts a downward groove excavation process; the excavation excavation section III includes a first excavation excavation section III1 and a second excavation excavation section III2, and the first excavation excavation section III1 is adjacent to the first groove excavation section II1, and the second excavation excavation section III2 is adjacent to the second groove excavation section II2.

[0019] Furthermore, in S2), the main tunnel intersection section steel arch frame includes a plurality of main tunnel steel arch frames 5 arranged at intervals, each of the main tunnel steel arch frame 5 has a main tunnel vertical steel frame 6 extending downward near the side of the branch tunnel, and the connection between the main tunnel vertical steel frame 6 and the last steel arch frame 3 of the branch tunnel is welded.

[0020] Furthermore, in S2), an advance anchor rod 7 is installed within 120° of the top arch of the main tunnel intersection section steel arch frame to prepare for the contraction section in step S3.

[0021] Furthermore, in S3), the downstream working face of the standard section of the main tunnel includes a pilot tunnel section IV1 located in the middle of the working face and excavation sections IV2 located on both sides of the working face. When excavating the downstream working face of the standard section of the main tunnel on the small angle side of the main tunnel, the pilot tunnel section IV1 is excavated first, and then the excavation sections IV2 on both sides are excavated. After excavating to a safe distance, full-section excavation is adopted.

[0022] Furthermore, in S3), before excavating the upstream and downstream working faces of the standard section of the main tunnel, double rows of locking anchor rods 8 are applied to the working faces beyond the standard section range of the main tunnel, and the double rows of locking anchor rods 8 are spaced 0.8 to 1.5 m apart, with an external insertion angle of 15° to 45°, and arranged in a plum blossom shape.

[0023] The advantages of the present invention are:

[0024] 1. The present invention maintains a first set distance a between the branch tunnel face parallel to the main tunnel axis and the excavation section of the standard section of the main tunnel. The purpose of this is to expand the cross-sectional width of the main tunnel. The expansion of the cross-sectional width of the main tunnel not only avoids the problem of irregular excavation on the small angle side, but also meets the turning requirements of vehicles on the small angle side. At the same time, by unifying the excavation section in this way, the frequent changes in the excavation section during the blasting excavation of the intersection section are avoided. Fewer steel arch processing types are used to facilitate construction, greatly improving construction efficiency.

[0025] 2. The present invention welds the vertical steel frame of the main tunnel near the side of the branch tunnel to the last steel arch frame of the branch tunnel. The purpose is to strengthen the arch support of the tunnel intersection section, ensure the stability of the tunnel rock column in the intersection section of the oblique tunnel, and improve the construction quality and engineering safety.

[0026] 3. Before excavating the upstream and downstream working faces of the main tunnel standard section, the present invention applies double-row locking anchors on the working face beyond the main tunnel standard section range, the purpose of which is to strengthen the end wall locking and improve construction safety;

[0027] The present invention is used for the construction method of excavating the intersection section of the oblique tunnel. It adopts the methods of expanding the intersection section width of the main tunnel, strengthening the arch support of the tunnel intersection section, and strengthening the end wall lock. It not only meets the demand of passing vehicles from the branch tunnel to the main tunnel on the side with a small angle, but also enables the intersection section of the main tunnel to be constructed with the same excavation section, unifies the steel arch structure size required for support, makes the initial support of the intersection section easy to construct, and improves the work efficiency, construction quality and engineering safety of on-site construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a construction process diagram of the intersection section of the oblique tunnel in the present invention;

[0029] Figure 2 This is the support axonometric drawing of the intersection section of the oblique tunnel in the present invention;

[0030] In the figure: branch tunnel intersection section I, groove excavation section II, excavation excavation section III, pilot tunnel sections IV1 and IV2;

[0031] Grooving excavation section II includes: first groove excavation section II1, second groove excavation section II2;

[0032] Excavation section III includes: first excavation section III1, second excavation section III2;

[0033] The first steel arch frame of the branch tunnel 1, the third steel arch frame of the branch tunnel 2, the last steel arch frame of the branch tunnel 3, the advance anchor rods 4 of the branch tunnel, the steel arch frame of the main tunnel 5, the vertical steel frame of the main tunnel 6, the advance anchor rods 7, and the double-row locking anchor rods 8;

[0034] First, set the distance a and the intersection point A of the branch tunnel and the main tunnel at the largest angle. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] In the description of the present invention, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the invention.

[0037] The present invention provides a construction method for excavating an intersection section of an oblique tunnel, comprising the following steps:

[0038] S1) Branch tunnel construction: After reaching the construction pile number of branch tunnel intersection section I, the branch tunnel is excavated and supported according to the designed section of branch tunnel intersection section I until the branch tunnel face is parallel to the main tunnel axis, and the first set distance a is retained between the branch tunnel face parallel to the main tunnel axis and the excavation section of the standard section of the main tunnel.

[0039] Specifically, a set distance a is retained between the branch tunnel face parallel to the main tunnel axis and the excavation section of the standard section of the main tunnel to meet the requirements of small angle side vehicle passing.

[0040] The present invention retains a first set distance a between the branch tunnel face parallel to the main tunnel axis and the excavation section of the standard section of the main tunnel. The purpose is to expand the width of the main tunnel intersection section. The expansion of the main tunnel intersection section width not only meets the requirements of vehicle turning at a small angle, but also avoids frequent changes in the excavation section during the blasting excavation of the intersection section, greatly improving construction efficiency.

[0041] The steel arch support of the branch tunnel in the branch tunnel intersection section adopts a gradual arrangement, from the first steel arch 1 of the branch tunnel to the last steel arch 3 of the branch tunnel, it gradually changes from being perpendicular to the branch tunnel axis to being parallel to the main tunnel axis.

[0042] In this embodiment, all the steel arch frames from the first steel arch frame 1 of the branch tunnel to the last steel arch frame 3 of the branch tunnel are I20a steel arch frames.

[0043] Specifically, when constructing the steel arch support for the branch tunnel, the spacing between adjacent steel arches on the small-angle side of the main tunnel and the spacing between adjacent steel arches on the large-angle side of the main tunnel are arranged according to the size of the angle. For example, the spacing between adjacent steel arches on the small-angle side of the main tunnel is 0.8-1.2m, and the spacing between adjacent steel arches on the large-angle side of the main tunnel is 2.5-3.5m. In this embodiment, the spacing between adjacent steel arches on the small-angle side of the main tunnel is 1.0m, and the spacing between adjacent steel arches on the large-angle side of the main tunnel is 3.0m.

[0044] In addition, when constructing the steel arch support of the branch tunnel, in order to avoid construction difficulties at the small angle of the main tunnel where the side circle turns into a square and the subsequent top-picking and grooving construction, the branch tunnel advance anchor rod 4 should be installed in advance when the construction of this section reaches the predetermined heading and there is a certain distance. The external insertion angle of the branch tunnel advance anchor rod 4 should be determined by the height difference and distance between it and the highest construction point of the main tunnel.

[0045] In this embodiment, 12 branch hole advance anchor rods 4 are installed in advance on the small angle side of the main hole of the third steel arch frame 2 of the branch hole, and the external insertion angle of the branch hole advance anchor rods 4 is higher than the main hole intersection range. L=6.0m.

[0046] S2) includes the construction of the branch tunnel along the vertical direction of the main tunnel and the intersection section of the main tunnel.

[0047] The main tunnel intersection section is divided into excavation section III and groove excavation section II in the order of upstream and downstream, with groove excavation section II close to the small angle side of the main tunnel and excavation section III close to the large angle side of the main tunnel;

[0048] Enter the groove excavation section II from the branch tunnel intersection section I, and carry out the groove excavation process, and the groove width meets the normal operation requirements of the initial support construction trolley.

[0049] Specifically, after reaching the construction face of step S1), a groove should be cut along the direction of the vertical main hole on the small angle side, and the width of the groove should meet the requirements of the initial support trolley construction operation. The groove cutting process should be supported by I20a steel arches with a spacing of 1.0 m. After each section of steel arch construction condition is reached, the steel arch installation should be performed and fixed by using the lock foot anchor rod. After the connection is reliable, the next stage of groove cutting construction is performed, and the cycle is repeated until the groove cutting is completed. The lock foot anchor rod uses L=4.5m lock foot anchor rod.

[0050] The groove cutting process should not exceed 2 m per cycle of excavation. If the surrounding rock condition is poor, it can be divided into upper and lower step excavations.

[0051] Specifically, the groove cutting excavation section II is divided into a first groove cutting excavation section II1 and a second groove cutting excavation section II2 in sequence according to the groove cutting excavation sequence. The first groove cutting excavation section II1 uses an upward roof picking process, and the second groove cutting excavation section II2 uses a downward groove cutting process. The excavation section III includes a first excavation section III1 and a second excavation section III2, and the first excavation section III1 is adjacent to the first groove cutting excavation section II1, and the second excavation section III2 is adjacent to the second groove cutting excavation section II2.

[0052] For the groove cutting excavation section II and the excavation section III, the main hole intersection section steel arch is constructed immediately after each excavation is set to a certain distance.

[0053] Specifically, the main hole intersection section steel arch includes a plurality of main hole steel arches 5 arranged at intervals. Each main hole steel arch 5 extends downward near the branch hole side edge and has a main hole vertical steel frame 6. The main hole vertical steel frame 6 is connected to the connection of the last branch hole steel arch 3 by welding. At the same time, adjacent main hole vertical steel frames 6 are connected by welding with steel bars. If the surrounding rock is poor, semi-split I20a steel should be used for welding.

[0054] After the branch hole is grooved into the main hole, the main hole vertical steel frame 6 is used to connect the main hole steel arch 5 and the branch hole steel arch, which can ensure the consistency of the excavation section during the construction of the main hole and improve the construction efficiency.

[0055] In this embodiment, the main hole steel arch 5 and the main hole vertical steel frame 6 are both I20a steel frames.

[0056] After the groove cutting of the groove cutting excavation section II is completed, the main hole intersection section obtained by groove cutting is used to excavate and excavate along the main hole axis direction of the excavation section III until it passes through the intersection A position of the branch hole and the large angle side of the main hole. That is, the branch hole and the large angle side of the main hole will form a certain distance end wall. In this embodiment, within this distance, 2 I20a main hole vertical steel frames 6 and I20a main hole steel arches 5 are connected.

[0057] ​Preferably, the main tunnel intersection section steel arch frame has an advanced anchor rod 7 within the range of 120° of the top arch to prepare for the contraction section in step S3. The advanced anchor rod 7 with L=4.5m is used to prepare for the shrinkage section in the subsequent construction process.

[0058] S3) Excavation of upstream and downstream working faces of the main tunnel standard section: After the step S2) is completed, the excavation and support processes are carried out on the upstream working face of the main tunnel standard section on the large angle side of the main tunnel and the downstream working face of the main tunnel standard section on the small angle side of the main tunnel, and the upstream and downstream working faces of the main tunnel standard section shrink the main tunnel intersection section to the main tunnel standard section respectively.

[0059] The upstream working face of the standard section of the main tunnel on the large-angle side of the main tunnel is excavated and supported according to the designed section. For the excavation of the downstream working face of the standard section of the main tunnel on the small-angle side, in order to avoid the rock pillar on the small-angle side from being destroyed during the blasting process, the following excavation method can be adopted: a pilot tunnel can be excavated for a certain distance first, and then the outline of the main tunnel can be grooved in the direction perpendicular to the axis of the main tunnel, and then normal excavation can be carried out.

[0060] Specifically, the downstream working face of the standard section of the main tunnel is divided into a pilot tunnel section IV1 located in the middle of the working face and an excavation section IV2 located on both sides of the working face. The excavation is carried out by first excavating the pilot tunnel section IV1 and then excavating the excavation sections IV2 on both sides. After excavating to a safe distance, full-section excavation is adopted.

[0061] Preferably, before excavating the upstream and downstream working faces of the standard section of the main tunnel, double rows of interlocking anchors 8 are installed on the working face beyond the standard section of the main tunnel. The external insertion angle of the double rows of interlocking anchors 8 should be determined by the angle between the branch tunnel and the main tunnel. In this embodiment, the double rows of interlocking anchors 8 are spaced 0.8 to 1.5 meters apart and have an external insertion angle of 15° to 45°, forming a plum blossom pattern.

[0062] The end wall at the cross-section change point of the main tunnel (the side with a small angle between the branch tunnel and the main tunnel) is reinforced with double-row lock anchor rods 8, and the pilot tunnel is excavated at the same time, which effectively avoids the destruction of the rock column on the side with a small angle, ensures construction safety and certain economy.

[0063] The present invention is used for the construction method of excavating the intersection section of the oblique tunnel. It adopts the methods of expanding the intersection section width of the main tunnel, strengthening the arch support of the tunnel intersection section, and strengthening the end wall lock. It not only meets the demand of passing vehicles from the branch tunnel to the main tunnel on the side with a small angle, but also enables the intersection section of the main tunnel to be constructed with the same excavation section, unifies the steel arch structure size required for support, makes the initial support of the intersection section easy to construct, and improves the work efficiency, construction quality and engineering safety of on-site construction.

[0064] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A construction method for excavating an intersection section of an oblique tunnel, characterized in that: The steps include: S1) After reaching the construction stake number of the branch tunnel intersection section (I), the branch tunnel is excavated and supported according to the designed section of the branch tunnel intersection section (I) until the branch tunnel face is parallel to the main tunnel axis, and a first set distance (a) is maintained between the branch tunnel face parallel to the main tunnel axis and the main tunnel standard section excavation section; S2) The main tunnel intersection section is divided into an excavation excavation section (III) and a groove excavation section (II) in the upstream and downstream order, with the groove excavation section (II) close to the small angle side of the main tunnel and the excavation excavation section (III) close to the large angle side of the main tunnel; Enter the groove excavation section (II) from the branch tunnel intersection section (I) and carry out the groove excavation process, and the groove width meets the normal operation requirements of the initial support construction trolley; After the groove excavation section (II) is completed, the main tunnel cross section obtained by the groove is used to open the excavation section (III) along the axis of the main tunnel until it passes through the intersection point (A) on the side with the largest angle between the branch tunnel and the main tunnel; For the groove excavation section (II) and the excavation excavation section (III), the main tunnel intersection section steel arch construction shall be carried out immediately after each set distance of excavation; The groove excavation section (II) is divided into a first groove excavation section (II1) and a second groove excavation section (II2) in sequence according to the groove excavation sequence. The first groove excavation section (II1) adopts an upward top-lifting process, and the second groove excavation section (II2) adopts a downward groove excavation process. The excavation excavation section (III) includes the first excavation excavation section (III1) and the second excavation excavation section (III2), and the first excavation excavation section (III1) is adjacent to the first groove excavation section (II1), and the second excavation excavation section (III2) is adjacent to the second groove excavation section (II2). The main tunnel intersection section steel arch frame comprises a plurality of main tunnel steel arch frames (5) arranged at intervals, each of the main tunnel steel arch frames (5) having a main tunnel vertical steel frame (6) extending downward near the side of the branch tunnel, and the main tunnel vertical steel frame (6) is connected to the last steel arch frame (3) of the branch tunnel by welding; S3) After step S2) is completed, excavation and support processes are performed on the upstream working face of the main tunnel standard section on the large-angle side of the main tunnel and the downstream working face of the main tunnel standard section on the small-angle side of the main tunnel, and the upstream and downstream working faces of the main tunnel standard section shrink the main tunnel intersection section to the main tunnel standard section respectively; The downstream working face of the standard section of the main tunnel includes a pilot tunnel section (IV1) located in the middle of the working face and excavation sections (IV2) located on both sides of the working face. When excavating the downstream working face of the standard section of the main tunnel on the small angle side of the main tunnel, the pilot tunnel section (IV1) is excavated first, and then the excavation sections (IV2) on both sides are excavated. After excavating to a safe distance, full-section excavation is adopted.

2. The construction method for excavating the intersection section of an oblique tunnel according to claim 1 is characterized in that: In S1), the set distance (a) between the branch tunnel face parallel to the main tunnel axis and the main tunnel standard section excavation section must meet the requirement of small angle side passing.

3. The construction method for excavating the intersection section of an oblique tunnel according to claim 2 is characterized in that: In S1), when constructing the branch tunnel steel arch support, in order to avoid construction difficulties at the small angle side of the main tunnel where the circle changes to the square, multiple branch tunnel advance anchor rods (4) are installed in advance on the small angle side of the main tunnel of the third branch tunnel steel arch (2), and the external insertion angle of the branch tunnel advance anchor rods (4) is higher than the main tunnel intersection range.

4. The construction method for excavating the intersection section of an oblique tunnel according to claim 3 is characterized in that: In S1), the branch tunnel steel arch support at the branch tunnel intersection section adopts a gradual arrangement, from the first branch tunnel steel arch (1) to the last branch tunnel steel arch (3), it gradually changes from being perpendicular to the branch tunnel axis to being parallel to the main tunnel axis.

5. The construction method for excavating the intersection section of an oblique tunnel according to claim 4 is characterized in that: In S1), when constructing the steel arch support of the branch tunnel, the spacing between adjacent steel arches on the small angle side of the main tunnel and the spacing between adjacent steel arches on the large angle side of the main tunnel are arranged according to the size of the angle.

6. The construction method for excavating the intersection section of an oblique tunnel according to claim 1 is characterized in that: In step S2), an advance anchor rod (7) is installed within 120° of the top arch of the steel arch frame in the main tunnel intersection section to prepare for the contraction section in step S3).

7. The construction method for excavating the intersection section of an oblique tunnel according to claim 1 is characterized in that: In S3), before excavating the upstream and downstream working faces of the main tunnel standard section, double rows of locking anchor rods (8) are applied to the working faces beyond the main tunnel standard section range, and the double rows of locking anchor rods (8) are arranged in a plum blossom shape with a spacing of 0.8 to 1.5 m and an external insertion angle of 15° to 45°.

Images