Combined support structure and construction method for deep buried tunnels in clastic schist strata

Abstract

The present invention discloses a combined support structure and a construction method for a deep buried tunnel in a clastic schist stratum. The combined support structure comprises an advance support, a tunnel steel arch frame and an anchor-sprayed mesh joint support; the advance support comprises a plurality of face fiber anchor rods vertically driven on the face, a plurality of sections of advance small conduit support and a grouting reinforcement area, the plurality of face fiber anchor rods completely cover the face, each section of the advance small conduit support is composed of a plurality of advance small conduits and the overlap length along the tunnel excavation direction is not less than 1m or 1 / 4L 导管 Each section of the advance small pipe support is a plurality of advance small pipes set within 120° on the arch of the tunnel face, and the grouting reinforcement area is the area where the fiber anchor rods and the surrounding rock of the tunnel face in the area where the advance small pipes are set are grouting. The invention effectively ensures the stability of the tunnel face, prevents the excavation face from sliding and collapses, and effectively controls the combined support structure of the support deformation, ensures construction safety, and improves construction efficiency.

Description

Technical Field

[0001] The invention relates to the field of tunnel support structures, in particular to a combined support structure suitable for deep-buried tunnels in clastic schist strata and a construction method thereof. Background Art

[0002] The surrounding rock of the clastic schist stratum is broken, has low cohesion and extremely poor self-stabilizing ability. If the support is improper after excavation, the excavation face and heading face will easily collapse and slide. The support deformation will be too large and the support structure will become unstable, which will seriously affect the construction quality and operational safety of the tunnel.

[0003] At present, deep tunnels buried in clastic schist still use the traditional initial support form of "advanced support + steel arch frame + shotcrete + anchor rods", and there is no targeted support parameter determination and calculation method. This support structure often cannot guarantee the stability of the excavation face and the heading face in actual construction, and phenomena such as landslides and excessive support deformation often occur, threatening construction safety and greatly reducing construction efficiency. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a combined support structure suitable for deep buried tunnels in clastic schist strata and its construction method, which can effectively ensure the stability of the heading face, prevent the excavation face from sliding and collapsing, and effectively control the support deformation, thereby ensuring construction safety and improving construction efficiency.

[0005] The technical solution of the present invention is:

[0006] The invention is applicable to the combined support structure of deep buried tunnels in clastic schist strata, including advance support, tunnel steel arch frame and anchor-sprayed mesh joint support; the advance support includes a plurality of face fiber anchors vertically driven on the face, a plurality of advance small conduit support and a grouting reinforcement area, the face fiber anchors and the advance small conduit are driven in the surrounding rock area of ​​the tunnel to be excavated behind the face, and a plurality of face fiber anchors completely cover the face, each section of the advance small conduit support is composed of a plurality of advance small conduits and the overlap length along the tunnel excavation direction is not less than 1m or 1 / 4L 导管 , the L 导管 is the length of the conduit, each section of the advance small conduit support, i.e., multiple advance small conduits are driven within 120° on the arch of the tunnel face, the grouting reinforcement area is the area formed by grouting the face fiber anchors and the face surrounding rock in the area where the advance small conduits are set, the grouting slurry is injected into the surrounding rock, and the grouting pressure is used to diffuse the slurry into the cracks of the surrounding rock to form the grouting reinforcement area; the spacing between adjacent face fiber anchors is 200mm, the face fiber anchor driving length is L, H is the excavation height of the tunnel face, To calculate the friction angle, is the surrounding rock friction angle, c is the surrounding rock cohesion, p is the vertical stress of the surrounding rock excavated by the tunnel, the annular spacing between adjacent advance small pipes is 200 mm, and the external insertion angle, that is, the angle between the advance small pipe and the horizontal plane is greater than 0° and less than The upper end surfaces of the flange plates of the tunnel steel arch frame close to the surrounding rock are welded with arc-shaped steel pads. The arc-shaped steel pads have the same curvature as the flange plates and are welded tightly to the upper end surfaces of the corresponding flange plates. The width of the arc-shaped steel pads is greater than the width of the flange plates.

[0007] The palm face fiber anchor rod is an ultra-long fiber anchor rod with a diameter of 22 mm.

[0008] The advanced small conduit is a φ42mm hot-rolled seamless steel pipe with a length of L 导管 ,in, k is an empirical coefficient. According to the construction experience in clastic schist formations, the value of k ranges from 2.0 to 3.0.

[0009] The width of the arc-shaped steel pad is 2-4 times the width of the steel arch flange plate.

[0010] A through hole is provided on the portion of the arc-shaped steel pad that exceeds the width of the flange plate, and the ends of the plurality of leading small guide tubes penetrate into the through hole of the arc-shaped steel pad and are welded to the arc-shaped steel pad.

[0011] The anchor-sprayed mesh joint support includes a system anchor rod, a sprayed concrete layer and a metal mesh. The steel arch frame and the metal mesh are both arranged in the sprayed concrete layer. The system anchor rod adopts a hollow grouting anchor rod. The spacing between adjacent system anchor rods is 1-1.2m. The system anchor rod adopts a plum blossom arrangement. The actual length of the system anchor rod is L 锚杆 , L 锚杆 =(1.5-2)l 锚杆 , l 锚杆 To calculate the anchor length theoretically, r0 is the tunnel excavation radius, is the friction angle of surrounding rock, and p is the surrounding rock pressure.

[0012] The sprayed concrete layer is a C25 sprayed concrete layer, and the thickness of the sprayed concrete layer is 27 cm.

[0013] The diameter of the steel bars of the metal mesh is 6-12 mm, and the spacing between the steel bars is 200-400 mm.

[0014] The construction method for the combined support structure of a deep-buried tunnel in clastic schist strata specifically comprises the following steps:

[0015] (1) First, the face fiber anchors are installed in the surrounding rock area of ​​the tunnel to be excavated behind the face to exceed the limit damage range of the face. The face fiber anchors are installed vertically on the face and arranged in a plum blossom shape on the face to ensure the stability of the surrounding rock in front. Then, a section of advanced small guide tube support is installed within 120° on the tunnel arch.

[0016] (2) The end of each small advance guide tube is inserted into the perforation of the arc-shaped steel plate and welded to the arc-shaped steel plate, so that the surrounding rock, the small advance guide tube and the steel arch frame of the excavated tunnel form a whole and bear the force synergistically;

[0017] (3) During the installation of the fiber anchors and the advanced small guide tubes, the surrounding rock of the face is reinforced by grouting. The grouting pressure is not less than 1 MPa. The grouting slurry is injected into the surrounding rock through the drilling hole. The grouting pressure makes the slurry diffuse into the cracks of the surrounding rock, so that a reinforcement belt is formed in the surrounding rock, thereby improving the integrity of the surrounding rock.

[0018] (4) During tunnel excavation, a steel arch frame is constructed. The steel arch frame is formed by welding I-beams. An arc-shaped steel pad is welded on the upper end surface of the flange plate on the upper part of the I-beam to better protect and stabilize the surrounding rock and ensure construction safety.

[0019] (5) Assemble the anchor-sprayed mesh combined support. The metal mesh and shotcrete layer of the anchor-sprayed mesh combined support can effectively control the falling of stones between the anchor rods of the anchor-sprayed mesh combined support system.

[0020] Advantages of the present invention:

[0021] (1) The present invention adopts the face fiber anchor, advance small pipe and grouting reinforcement technology to carry out advance support for the face. The advance support forms a circumferential protection for the cavern and the face, which can not only stabilize the stability of the surrounding rock of the current excavation face, but also combine the high tensile strength and easy shearing characteristics of the face fiber anchor to ensure the excavation efficiency of the next cycle of the face.

[0022] (2) The present invention uses an arc-shaped steel pad to widen the flange plate of the steel arch frame, so that the contact area between the steel arch frame and the surrounding rock is larger, and the wrapping and supporting force of the broken surrounding rock in the broken surrounding rock environment is stronger, which helps to stabilize the surrounding rock and ensure the safety of tunnel construction. Perforations are reserved on the arc-shaped steel pad. The perforations on the arc-shaped steel pad can be used as a construction platform when setting up the advance small guide tube and anchor rods to ensure the installation angle. After the installation is completed, the surrounding rock, the advance small guide tube and the steel arch frame of the excavated tunnel can form a whole to ensure their coordinated force.

[0023] (3) The present invention adopts the calculation formula of the face limit anchor, the advance small guide tube and the system anchor driving length, which can adjust the support parameters in real time according to the actual monitoring data and surrounding rock conditions, and provide a theoretical basis for the realization of information-based construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of the combined supporting structure of the present invention.

[0025] Figure 2 It is a schematic diagram of the advanced support structure of the present invention.

[0026] Figure 3 yes Figure 2 Enlarged cross-sectional view of AA in the figure.

[0027] Figure 4 The present invention is a structural schematic diagram of a steel arch frame flange plate welded with an arc-shaped steel pad. DETAILED DESCRIPTION

[0028] 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.

[0029] See Figure 1-Figure 4 , suitable for combined support structures of deep buried tunnels in clastic schist formations, including advance support, tunnel steel arch frame and anchor-sprayed mesh joint support;

[0030] The advance support includes multiple face fiber anchors 2 vertically driven on the face 1, multiple sections of advance small pipe support 2 and grouting reinforcement area. The face fiber anchors 2 and advance small pipes 3 are driven in the surrounding rock area of ​​the tunnel to be excavated behind the face 1, and multiple face fiber anchors 2 completely cover the face 1. Each section of the advance small pipe support is composed of multiple advance small pipes 3 and the overlap length along the tunnel excavation direction is not less than 1m or 1 / 4L 导管 , L 导管 is the length of the conduit, each section of the advance small conduit support, i.e., multiple advance small conduits 3 are set within 120° on the arch of the tunnel face 1, and the grouting reinforcement area is the area formed by grouting the surrounding rock of the face where the fiber anchor rods 2 and the advance small conduits 3 are set. The grouting slurry is injected into the surrounding rock, and the grouting pressure is used to diffuse the slurry into the cracks of the surrounding rock to form the grouting reinforcement area;

[0031] The face fiber anchor 2 uses an extra-long fiber anchor with a diameter of 22 mm. The spacing between adjacent face fiber anchors 2 is 200 mm. The face fiber anchor 2 is set to a length of L. H is the excavation height of the tunnel face, To calculate the friction angle, is the surrounding rock friction angle, c is the surrounding rock cohesion, and p is the surrounding rock vertical stress after tunnel excavation;

[0032] The circumferential spacing between adjacent leading small ducts 3 is 200 mm, and the external insertion angle, that is, the angle between the leading small duct 3 and the horizontal plane is greater than 0° and less than The leading small conduit 3 is a φ42mm hot-rolled seamless steel pipe with a length of L 导管 ,in, k is an empirical coefficient. According to the construction experience of clastic schist formation, the value range of k is 2.0-3.0;

[0033] The upper end surface of the flange plate of the tunnel steel arch frame 4 close to the surrounding rock is welded with an arc-shaped steel pad 8, the arc-shaped steel pad 8 has the same curvature as the flange plate of the steel arch frame 4 and is welded closely to the upper end surface of the corresponding flange plate, the width of the arc-shaped steel pad 8 is 2-4 times the width of the flange plate of the steel arch frame 4, and a perforation 9 is provided on the portion of the arc-shaped steel pad 8 that exceeds the width of the flange plate of the steel arch frame 4, and the ends of the multiple advance small guide tubes 3 are inserted into the perforations 9 of the arc-shaped steel pad and welded to the arc-shaped steel pad 8;

[0034] The anchor-sprayed mesh joint support includes a system anchor rod 5, a sprayed concrete layer 6 and a metal mesh 7. The steel arch 4 and the metal mesh 7 are both arranged in the sprayed concrete layer 6. The sprayed concrete layer 6 is a C25 sprayed concrete layer. The thickness of the sprayed concrete layer 6 is 27 cm. The diameter of the steel bars of the metal mesh 7 is 6-12 mm. The spacing between the steel bars is 200-400 mm. The system anchor rod 5 adopts a hollow grouting anchor rod. The spacing between adjacent system anchor rods 5 is 1-1.2 m. The system anchor rod 5 adopts a plum blossom arrangement. The actual length of the system anchor rod 5 is L 锚杆 , L 锚杆 =(1.5-2)l 锚杆 , l 锚杆 To calculate the anchor length theoretically, r0 is the tunnel excavation radius, is the surrounding rock friction angle, and p is the surrounding rock pressure.

[0035] The construction method for the combined support structure of a deep-buried tunnel in clastic schist strata specifically comprises the following steps:

[0036] (1) First, the face fiber anchor 2 is driven into the surrounding rock area of ​​the tunnel to be excavated behind the face 1 to exceed the limit damage range of the face. The face fiber anchor 2 is driven vertically on the face 1 and arranged in a plum blossom shape on the face 1 to ensure the stability of the surrounding rock in front. Then, a section of advanced small guide tube support is driven within 120° on the tunnel arch;

[0037] (2) The end of each small advance pipe 3 is inserted into the through hole 9 of the arc-shaped steel pad 8 and welded to the arc-shaped steel pad 8, so that the surrounding rock, the small advance pipe 3 and the steel arch frame 4 of the excavated tunnel form a whole and are subjected to force in a coordinated manner;

[0038] (3) During the installation of the fiber anchor bolts 2 and the advance small guide tube 3 on the tunnel face, the surrounding rock of the tunnel face 1 is simultaneously reinforced by grouting. The grouting pressure is not less than 1 MPa. The grouting slurry is injected into the surrounding rock through the drilling hole. The grouting pressure causes the grouting slurry to diffuse into the cracks of the surrounding rock, so that a reinforcement belt is formed in the surrounding rock, thereby improving the integrity of the surrounding rock.

[0039] (4) While the tunnel is being excavated, a steel arch frame 4 is constructed. The steel arch frame 4 is formed by welding an I-beam. An arc-shaped steel pad 8 is welded on the upper end surface of the flange plate on the upper part of the I-beam. The widened flange of the steel arch frame 4 has a larger contact area with the surrounding rock, which can better protect and stabilize the surrounding rock and ensure construction safety.

[0040] (5) Assemble the anchor-sprayed mesh combined support. The metal mesh 7 and the sprayed concrete layer 6 of the anchor-sprayed mesh combined support can effectively control the falling of stones between the anchor rods 6 of the anchor-sprayed mesh combined support system.

[0041] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. It is applicable to the combined support structure of deep buried tunnels in clastic schist strata, and is characterized by: It includes advance support, tunnel steel arch frame and anchor spraying net combined support; the advance support includes multiple face fiber anchors vertically set on the face, multiple sections of advance small pipe support and grouting reinforcement area, the face fiber anchors and advance small pipes are set in the surrounding rock area of ​​the tunnel to be excavated behind the face, and multiple face fiber anchors completely cover the face, each section of the advance small pipe support is composed of multiple advance small pipes and the overlap length along the tunnel excavation direction is not less than 1m or 1 / 4L 导管， The L 导管 is the length of the conduit, each section of the advance small conduit support, i.e., multiple advance small conduits are driven within 120° on the arch of the tunnel face, the grouting reinforcement area is the area formed by grouting the face fiber anchors and the face surrounding rock in the area where the advance small conduits are set, the grouting slurry is injected into the surrounding rock, and the grouting pressure is used to diffuse the slurry into the cracks of the surrounding rock to form the grouting reinforcement area; the spacing between adjacent face fiber anchors is 200mm, the face fiber anchor driving length is L, H is the excavation height of the tunnel face, To calculate the friction angle, is the surrounding rock friction angle, c is the surrounding rock cohesion, p is the vertical stress of the surrounding rock excavated by the tunnel, the annular spacing between adjacent advance small pipes is 200 mm, and the external insertion angle, that is, the angle between the advance small pipe and the horizontal plane is greater than 0° and less than The upper end surface of the flange plate of the tunnel steel arch frame close to the surrounding rock is welded with an arc-shaped steel pad, the arc-shaped steel pad has the same curvature as the flange plate and is welded closely to the upper end surface of the corresponding flange plate, and the width of the arc-shaped steel pad is greater than the width of the flange plate; The advanced small conduit is a φ42mm hot-rolled seamless steel pipe with a length of L 导管 ,in, k is an empirical coefficient. According to the construction experience of clastic schist formation, the value range of k is 2.0-3.0; The anchor-sprayed mesh joint support includes a system anchor rod, a sprayed concrete layer and a metal mesh. The steel arch frame and the metal mesh are both arranged in the sprayed concrete layer. The system anchor rod adopts a hollow grouting anchor rod. The spacing between adjacent system anchor rods is 1-1.2m. The system anchor rod adopts a plum blossom arrangement. The actual length of the system anchor rod is L 锚杆 , L 锚杆 =(1.5-2)l 锚杆 , l 锚杆 To calculate the anchor length theoretically, r0 is the tunnel excavation radius, is the surrounding rock friction angle, and p is the surrounding rock pressure.

2. The combined support structure for deep tunnels in clastic schist strata according to claim 1 is characterized by: The palm face fiber anchor rod is an ultra-long fiber anchor rod with a diameter of 22 mm.

3. The combined support structure for deep tunnels in clastic schist strata according to claim 1 is characterized by: The width of the arc-shaped steel pad is 2-4 times the width of the steel arch flange plate.

4. The combined support structure for deep tunnels in clastic schist strata according to claim 1 is characterized in that: A through hole is provided on the portion of the arc-shaped steel pad that exceeds the width of the flange plate, and the ends of the plurality of leading small guide tubes penetrate into the through hole of the arc-shaped steel pad and are welded to the arc-shaped steel pad.

5. The combined support structure for deep tunnels in clastic schist strata according to claim 1 is characterized by: The sprayed concrete layer is a C25 sprayed concrete layer, and the thickness of the sprayed concrete layer is 27 cm.

6. The combined support structure for deep tunnels in clastic schist strata according to claim 1 is characterized by: The diameter of the steel bars of the metal mesh is 6-12 mm, and the spacing between the steel bars is 200-400 mm.

7. The construction method of the combined support structure for deep buried tunnels in clastic schist strata according to claim 1 is characterized by: The specific steps include: (1) First, the face fiber anchors are installed in the surrounding rock area of ​​the tunnel to be excavated behind the face to exceed the limit damage range of the face. The face fiber anchors are installed vertically on the face and arranged in a plum blossom shape on the face to ensure the stability of the surrounding rock in front. Then, a section of advanced small guide tube support is installed within 120° on the tunnel arch. (2) The end of each small advance guide tube is inserted into the perforation of the arc-shaped steel plate and welded to the arc-shaped steel plate, so that the surrounding rock, the small advance guide tube and the steel arch frame of the excavated tunnel form a whole and bear the force synergistically; (3) During the installation of the fiber anchors and the advanced small guide tubes, the surrounding rock of the face is reinforced by grouting. The grouting pressure is not less than 1 MPa. The grouting slurry is injected into the surrounding rock through the drilling hole. The grouting pressure makes the slurry diffuse into the cracks of the surrounding rock, so that a reinforcement belt is formed in the surrounding rock, thereby improving the integrity of the surrounding rock. (4) During tunnel excavation, a steel arch frame is constructed. The steel arch frame is formed by welding I-beams. An arc-shaped steel pad is welded on the upper end surface of the flange plate on the upper part of the I-beam to better protect and stabilize the surrounding rock and ensure construction safety. (5) Assemble the anchor-sprayed mesh combined support. The metal mesh and shotcrete layer of the anchor-sprayed mesh combined support can effectively control the falling of stones between the anchor rods of the anchor-sprayed mesh combined support system.

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