Tunnel primary support steel frame and channel steel joist combined type anchoring connection structure
By using a composite anchoring connection structure of I-beams and channel steel beams, combined with early-strength concrete cushion layers and inclined anchor pipes, the problem of insufficient foundation bearing capacity in traditional tunnel initial support structures is solved, achieving efficient, safe, and long-life tunnel initial support.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-25
- Publication Date
- 2026-03-03
AI Technical Summary
Traditional tunnel initial support structures suffer from insufficient foundation bearing capacity due to steel frame joint design, leading to settlement problems and safety hazards.
A composite anchoring connection structure of I-beams and channel steel beams is adopted, combined with early-strength concrete cushion layer, inclined anchor pipes and longitudinal locking anchor pipes to form a three-dimensional anchoring network, which enhances the coordinated deformation capacity of the surrounding rock and the support body, and improves the shear bearing capacity of the base through drainage and mechanical interlocking.
It significantly improves the coordinated deformation capacity of the surrounding rock and the support structure, increases the shear bearing capacity of the base by 30%, reduces the risk of steel frame settlement, simplifies the construction process, extends the structural life, and adapts to complex geological conditions.
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Figure CN223964483U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of initial support technology for soft rock tunnels, specifically a composite anchoring connection structure of initial support steel frame and channel steel support beam for tunnels. Background Technology
[0002] Initial support for soft rock tunnels often experiences significant settlement. Many factors contribute to this settlement, with insufficient bearing capacity of the foundation at the toe of the support being a major one. The reasons for insufficient foundation bearing capacity include:
[0003] The surrounding rock at the base is loose. The looseness of the support base is due to the traditional steel frame joint design. Traditional steel frame joints are designed as flange plate joints connected by bolts. In order to facilitate the connection between the upper and lower unit steel frames, it is necessary to protect the flange plate of the upper unit steel frame joint from being covered by shotcrete. On site, the joint is usually buried by loosely piling up. This results in the initial tunnel support structure composed of steel frame and shotcrete not being in full contact with the foundation, and the soft foundation of the support posing quality and safety hazards.
[0004] The bearing capacity of the foundation is lower than the stress at the base of the steel frame. The low bearing capacity of the soft rock foundation coupled with the high stress at the base of the steel frame leads to initial support settlement.
[0005] The excavation at the lower part of the tunnel caused the foundation of the initial support steel frame above to be suspended in the air. Summary of the Invention
[0006] To address the problem of initial support in soft rock tunnels, this utility model provides a composite anchoring connection structure of a tunnel initial support steel frame and a channel steel support beam.
[0007] This utility model adopts the following technical solution: a composite anchoring connection structure of tunnel initial support steel frame and channel steel support beam, comprising:
[0008] The parallel I-beams, the transverse channel steel beams that run through the adjacent I-beams, and the early-strength concrete pad layer that fills the bottom of the channel steel beams.
[0009] The bottom end of the I-beam frame is vertically welded to the center of the top surface of the channel steel support beam. Two vertical anchor pipe holes are symmetrically opened on both sides of the channel steel support beam. The vertical anchor pipe is inserted into the vertical anchor pipe holes and is obliquely inserted into the surrounding rock.
[0010] The two ends of the channel steel support beam extend to 1 / 2 of the distance between adjacent I-beams and are bolted to the adjacent channel steel support beams through longitudinal support beam connecting plates.
[0011] The bottom 30cm height of the I-beam frame is wrapped with a peelable plastic film, and anchor pipe connecting plates with double holes are welded to both sides of its web. The transverse locking foot anchor pipes are inserted through the double holes.
[0012] In some embodiments, a connecting sleeve with internal threads is welded onto the channel steel support beam, and the angle between the axis of the connecting sleeve and the axis of the steel frame is ≤5°.
[0013] In some embodiments, the longitudinal support beam connecting plate is a trapezoidal steel plate, with its bottom welded to the flange of the channel steel support beam. Two rows of staggered bolt holes are opened at the bottom, and adjacent support beam connecting plates are connected by connecting bolts.
[0014] In some embodiments, the transverse anchor pipe includes two sets of Φ42×4mm seamless steel pipes, which are driven into the surrounding rock at a 20° elevation angle for 3.5m. The ends of the transverse anchor pipes are welded and fixed to the web of the I-beam through anchor pipe connecting plates.
[0015] In some embodiments, the early-strength concrete cushion layer is 25cm thick, with internally embedded steel mesh, and the concrete has a 3-day compressive strength ≥25MPa.
[0016] In some embodiments, the plastic film is made of 0.5mm thick polyethylene, and the wrapping area extends 30cm upward from the base of the I-beam frame, with the top secured by cable ties.
[0017] In some embodiments, a Φ50mm drainage hole is opened in the web of the channel steel support beam, and a water-permeable hose is embedded in the hole, with the hose outlet connected to the tunnel drainage ditch.
[0018] In some embodiments, the inner wall of the connecting sleeve is coated with a graphite lubricating layer, and the matching bolt rod is machined with a guide taper with a taper angle of 3-5°.
[0019] In some embodiments, shear studs are welded to the bottom surface of the channel steel support beam in an array. The shear studs are 12mm in diameter and 50mm in height, and are arranged in a quincunx pattern with a spacing of 30cm. The shear studs are embedded in the early-strength concrete pad to form a shear-resistant interlocking structure.
[0020] In some embodiments, stiffening ribs are provided circumferentially in the welding area between the I-beam and the channel steel support beam. The stiffening ribs are rectangular steel plates that are symmetrically welded along the front and rear sides of the I-beam to form a local bending stiffness enhancement zone.
[0021] Compared with the prior art, the present invention has the following beneficial effects:
[0022] A spatial force transmission system is formed by the grid connection of the I-beam frame and the channel steel support beams. Combined with the transverse anchor pipes (20° elevation angle) and vertical anchor pipes, a three-dimensional anchoring network is created, significantly improving the coordinated deformation capacity of the surrounding rock and the support structure, and suppressing eccentric deformation of the steel frame. The bottom of the channel steel support beams is welded with studs in a staggered pattern (Φ12×50mm) that interlock with the early-strength concrete cushion layer (3-day strength ≥25MPa), increasing the shear bearing capacity of the foundation by more than 30% and effectively preventing steel frame settlement.
[0023] The longitudinal support beam connecting plate adopts a staggered bolt hole design, enabling rapid alignment and installation of adjacent channel steel support beams and reducing on-site welding. A peelable polyethylene film is wrapped around the bottom 30cm of the I-beam frame to prevent concrete adhesion and simplify the steel frame cutting process during the secondary lining stage. Permeable hoses are pre-embedded in the web of the channel steel support beams for directional drainage, reducing water pressure erosion. The graphite lubricating layer on the inner wall of the connecting sleeve mates with the tapered bolts (3-5°), reducing thread engagement wear and extending the life of the anchoring system.
[0024] Symmetrical stiffening ribs are welded to the bottom of the I-beam frame to form a zone of enhanced bending stiffness, reducing the risk of weld cracking caused by stress concentration. The axial angle error of the connecting sleeve is ≤5°, allowing for fine-tuning of the anchor pipe angle during construction, adapting to complex geological conditions such as fault fracture zones.
[0025] This structure integrates mechanical anchoring, concrete interlocking, and drainage functions to achieve lightweight support system and high construction efficiency, making it particularly suitable for water-rich and soft surrounding rock tunnel projects, thus improving the overall safety factor. Attached Figure Description
[0026] Figure 1 This is a structural diagram of the present utility model;
[0027] Figure 2 Here is a cross-sectional view of section AA in section 1;
[0028] In the figure, 1-channel steel support beam, 2-connecting sleeve, 3-longitudinal support beam connecting plate, 4-transverse locking foot anchor pipe, 5-vertical locking foot anchor pipe, 6-anchor pipe and steel frame connecting plate I, 7-anchor pipe and steel frame connecting plate II, 8-early strength concrete cushion layer, 9-plastic film, 10-connecting bolt, 11-I-beam steel frame. Detailed Implementation
[0029] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions in the embodiments of this utility model will be clearly and completely described below. Obviously, the described embodiments are some embodiments of this utility model, but not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.
[0030] like Figure 1 , 2 As shown, a composite anchoring connection structure of tunnel initial support steel frame and channel steel support beam includes:
[0031] The parallel I-beam frame 11, the transverse channel steel support beam 1 that runs through the adjacent I-beam frame, and the early-strength concrete pad 8 that fills the bottom of the channel steel support beam;
[0032] The bottom end of the I-beam frame 11 is vertically welded to the center of the top surface of the channel steel support beam 1. Two vertical anchor pipe holes are symmetrically opened on both sides of the channel steel support beam 1. The vertical locking foot anchor pipe 5 is inserted into the vertical anchor pipe holes and obliquely inserted into the surrounding rock.
[0033] The two ends of the channel steel support beam 1 extend to 1 / 2 of the distance between adjacent I-beams and are bolted to the adjacent channel steel support beams through the longitudinal support beam connecting plate 3.
[0034] The bottom 30cm height range of the I-beam frame 11 is wrapped with a peelable plastic film 9, and anchor pipe connecting plates with double holes are welded on both sides of its web plate. The transverse locking foot anchor pipe 4 is inserted into the double holes.
[0035] Specifically, a rigid skeleton is formed by vertical welding of the I-beams and channel steel support beams and horizontal through-beam design, which enhances the continuity of the overall support; the early-strength concrete cushion layer provides uniform base reaction force to suppress the settlement of the steel frame; the obliquely inserted vertical anchor pipes and horizontal anchor pipes form a spatial anchoring system to improve the collaborative bearing capacity of the surrounding rock and support.
[0036] A connecting sleeve 2 with internal threads is welded onto the channel steel support beam 1. The angle between the axis of the connecting sleeve 2 and the axis of the steel frame is ≤5°. Controlling the angle between the internal thread of the connecting sleeve and the axis (≤5°) ensures the accurate installation direction of the anchor pipe, reduces stress concentration caused by construction deviations, and enhances the connection strength between the anchor pipe and the steel frame through thread engagement, thereby improving the pull-out resistance of the joint.
[0037] The longitudinal support beam connecting plate 3 is a trapezoidal steel plate, welded to the flange of the channel steel support beam 1 at the bottom. Two rows of staggered bolt holes are opened at the bottom, and adjacent support beam connecting plates 3 are connected by connecting bolts 10. The design of the two rows of staggered bolt holes of the trapezoidal longitudinal support beam connecting plate enables rapid alignment and splicing of adjacent channel steel support beams, reducing the amount of on-site welding by more than 50%, and allowing for slight displacement adjustment to adapt to the dynamic deformation of the surrounding rock.
[0038] The transverse anchor pipe 4 comprises two sets of Φ42×4mm seamless steel pipes, driven obliquely into the surrounding rock at a 20° elevation angle for 3.5m. The ends of the transverse anchor pipe 4 are welded and fixed to the web of the I-beam frame 11 via anchor pipe connecting plates. The transverse anchor pipes, driven into the surrounding rock at a 20° elevation angle for 3.5m, form an oblique support force to counteract horizontal ground pressure; the double-hole anchor pipe connecting plates fix the ends of the anchor pipes to prevent slippage and improve the overturning stability of the steel frame.
[0039] The early-strength concrete foundation layer is 25cm thick and has an internally embedded steel mesh. The concrete has a 3-day compressive strength of ≥25MPa. The early-strength concrete foundation layer (3-day strength ≥25MPa) shortens the foundation curing period to 1 / 3 of the original construction period; the built-in steel mesh enhances crack resistance and, in synergy with shear studs, increases the shear bearing capacity of the foundation by 35%.
[0040] The plastic film 9 is made of 0.5mm thick polyethylene and extends 30cm upwards from the base of the I-beam steel frame 11, with the top secured by cable ties. The peelable plastic film isolates the concrete at the base of the steel frame, preventing concrete damage during the secondary lining stage when the steel frame is cut, reducing rework and saving 20% on labor costs.
[0041] A Φ50mm drainage hole is opened in the web of the channel steel support beam 1, and a permeable hose is embedded in the hole. The outlet of the hose is connected to the tunnel drainage ditch. The drainage hole in the web of the channel steel support beam and the permeable hose form a directional drainage channel, reducing the risk of water pressure seepage in the foundation, avoiding the strength reduction of the steel frame due to water erosion, and extending the structural life by more than 10 years.
[0042] The inner wall of the connecting sleeve 2 is coated with a graphite lubricating layer, and the matching bolt rod is machined with a guide taper with a taper angle of 3-5°. The graphite lubricating layer of the connecting sleeve reduces the thread friction coefficient by 30%, and together with the taper bolt (3-5°), it enables the anchor pipe to be screwed in quickly, improving installation efficiency by 40% and reducing connection failures caused by thread wear.
[0043] The bottom surface of the channel steel support beam 1 is welded with an array of shear studs 12, each 12mm in diameter and 50mm in height, arranged in a quincunx pattern with a spacing of 30cm. The shear studs 12 are integrally embedded in the early-strength concrete pad 8 to form a shear-resistant interlocking structure. The quincunx-shaped shear stud array (30cm spacing) increases the mechanical interlocking force at the interface between the concrete and the steel beam, increasing the interface slip resistance coefficient to 1.5 times, effectively transferring shear loads.
[0044] Stiffening ribs are provided circumferentially in the welding area between the I-beam frame 11 and the channel steel support beam 1. The stiffening ribs are rectangular steel plates, symmetrically welded along the front and rear sides of the I-beam frame to form a local bending stiffness enhancement zone. The stiffening ribs at the bottom of the I-beam frame form a local bending stiffness enhancement zone, reducing the peak stress in the welding area by 30%, suppressing buckling deformation at the base of the steel frame, and adapting to the uneven surrounding rock pressure in the fault fracture zone.
[0045] I-beam frame: I20b type I-beams (section height 200mm, flange width 100mm, web thickness 9mm), each section is 3m long, and the bottom 30cm section is covered with 0.5mm thick polyethylene film (overlap width ≥20mm).
[0046] Channel steel support beam: 28a channel steel (height 280mm, web thickness 7.5mm), length 2.5m, with Φ12×50mm shear studs welded to the bottom in a quincunx pattern (longitudinal spacing 300mm, transverse spacing 150mm); Φ50mm drainage holes are reserved in the web, spaced 1m apart, with permeable hoses (HDPE material, outer diameter 50mm, permeability coefficient ≥1×10⁻³cm / s) pre-embedded in the holes.
[0047] Connecting sleeve: Forged from No. 45 steel (inner diameter 42mm, wall thickness 8mm), with M40×3 trapezoidal threads machined on the inner wall. The allowable error of the angle between the sleeve axis and the steel frame web is ≤5°. The inner wall is coated with a graphite-based lubricating coating (thickness 0.1-0.2mm).
[0048] Early-strength concrete foundation: C30 concrete with 3% quick-setting agent (sodium silicate-based), water-cement ratio 0.4, 100mm thickness, with φ8@150mm steel mesh inside; after pouring, cover with curing film, 3-day compressive strength ≥25MPa.
[0049] Installation of channel steel support beams: Hoist the support beams onto the subgrade, and use hydraulic jacks to adjust the levelness (error ≤ 3mm / m). Shear studs should be embedded in the concrete to a depth ≥ 30mm. Adjacent support beams are fixed with bolts using longitudinal connecting plates (20mm thick, length × width = 400mm × 200mm), employing M24 high-strength bolts (preload 350kN). Bolt holes are arranged in two staggered rows (hole spacing 80mm longitudinally and 60mm laterally).
[0050] I-beam frame assembly: Vertically weld the I-beam frame to the top surface of the channel steel support beam (weld height ≥ 8mm, Class II weld standard), and symmetrically weld stiffening ribs (size 150mm×120mm×12mm) to the bottom of the steel frame, with a rib spacing of 500mm.
[0051] Horizontal anchor pipe: Φ89×6mm seamless steel pipe, 3.5m long, driven into the surrounding rock at a 20° elevation angle (drilling diameter Φ108mm, hole depth 3.8m). Grouting uses PO 42.5 cement grout (water-cement ratio 0.45, grouting pressure 1.2MPa), with a grouting fullness ≥95%. The exposed end of the anchor pipe is fixed to the steel frame bolts (M20 bolts, torque 200N·m) via a double-hole connecting plate (16mm thickness, Φ22mm hole diameter).
[0052] Vertical anchor pipe reinforcement: Φ42×4mm anchor pipes (2.5m long, 1m spacing) are driven into the arch foot of the steel frame, forming a 45°-60° intersection angle with the horizontal anchor pipes. The ends of the anchor pipes are connected via sleeve threads (tapered bolts with an inclination angle of 3°), and after tightening, the exposed thread length is ≤20mm.
[0053] Directional drainage: The permeable hose of the web of the channel steel support beam is connected to the tunnel side ditch, and the pipe opening is wrapped with 200g / m² geotextile to filter mud and sand, with a drainage slope ≥5‰.
[0054] Steel frame base isolation: Before secondary lining construction, the polyethylene film at the bottom of the I-beam steel frame is manually peeled off. When cutting the steel frame with an oxy-acetylene flame, care is taken to avoid damaging the concrete lining. The cut surfaces are then coated with epoxy zinc-rich primer for corrosion protection.
[0055] Accuracy testing: The total station verifies that the deviation of the steel frame installation axis is ≤10mm, the deviation of the anchor pipe angle is ≤2°, and the coaxiality of the connecting sleeve is ≤1mm.
[0056] Strength verification: Three groups of concrete test blocks for the foundation layer were randomly selected. The average compressive strength after 3 days was ≥28MPa. Anchor pull-out force was randomly tested (10% of the samples). The pull-out force of a single anchor pipe was ≥150kN.
[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.
Claims
1. A composite anchoring connection structure of a tunnel primary support steel frame and a channel steel joist, characterized in that, The utility model relates to a tunnel support structure, which comprises: Parallelly arranged I-beam frames (11), crosswise through the I-beam frames, channel steel joists (1), and early strength concrete cushion layers (8) filled in the bottom of the channel steel joists; The bottom end of the I-beam frame (11) is vertically welded to the top surface center of the channel steel joist (1), two vertical anchor pipe perforations are symmetrically formed in the two side flanges of the channel steel joist (1), vertical locking leg anchor pipes (5) are arranged in the vertical anchor pipe perforations and are obliquely inserted into the surrounding rock; The two ends of the channel steel joist (1) extend to the position of 1 / 2 of the distance between adjacent I-beam frames, and are bolted to the adjacent channel steel joists through longitudinal joist connecting plates (3); The I-beam frame (11) is wrapped with a peelable plastic film (9) in the range of 30 cm in height from the bottom, anchor pipe connecting plates with double holes are welded to the two sides of the web, and transverse locking leg anchor pipes (4) are arranged in the double holes.
2. The tunnel primary support steel frame and channel section joist composite anchoring connection structure according to claim 1, characterized in that, A connecting sleeve (2) with internal threads is welded to the channel steel joist (1), and the included angle between the axis of the connecting sleeve (2) and the axis of the steel frame is less than or equal to 5°.
3. The composite anchoring connection structure of the tunnel primary support steel frame and the channel section joist according to claim 1, characterized in that, The longitudinal joist connecting plate (3) is a trapezoidal steel plate, the bottom of which is welded to the flange of the channel steel joist (1), two rows of bolt holes are formed in the bottom in a staggered arrangement, and the adjacent joist connecting plates (3) are connected through connecting bolts (10).
4. The tunnel primary support steel frame and channel section joist composite anchoring connection structure according to claim 1, characterized in that, The transverse locking leg anchor pipe (4) comprises two groups of Φ42×4 mm seamless steel pipes, which are obliquely punched into the surrounding rock at an angle of 20° and 3.5 m deep, and the end of the transverse locking leg anchor pipe (4) is welded and fixed to the web of the I-beam frame (11) through an anchor pipe connecting plate.
5. The composite anchoring connection structure of the initial support steel frame and the channel section joist according to claim 1, characterized in that, The early strength concrete cushion layer (8) is 25 cm thick, has a steel mesh embedded therein, and the compressive strength of the concrete is greater than or equal to 25 MPa after 3 days.
6. The composite anchoring connection structure of the initial support steel frame and the channel section joist according to claim 1, characterized in that, The plastic film (9) is 0.5 mm thick and made of polyethylene, and is wrapped in the range of 30 cm from the bottom of the I-beam frame (11) upwards and is fixed at the top by a binding belt.
7. The composite anchoring connection structure of the initial support steel frame and the channel section joist according to claim 1, characterized in that, A Φ50 mm drainage hole is formed in the web of the channel steel joist (1), a water permeable hose is embedded in the hole, and the outlet of the hose is connected to a tunnel drainage ditch.
8. The composite anchoring connection structure of the initial support steel frame and the channel section joist according to claim 2, characterized in that, The inner wall of the connecting sleeve (2) is coated with a graphite lubricating layer, and the matching bolt shaft is processed with a guide taper with an angle of 3-5°.
9. The composite anchoring connection structure of the initial support steel frame and the channel section joist according to claim 1, characterized in that, Shear nails (12) are arranged in an array on the bottom surface of the channel steel joist (1), the shear nails are 12 mm in diameter and 50 mm in height, are arranged in a quincunx shape with a spacing of 30 cm, and are embedded in the early strength concrete cushion layer (8) to form a shear engagement structure.
10. The composite anchoring connection structure of the initial support steel frame and the channel section joist according to claim 1, characterized in that, Stiffening rib plates are arranged circumferentially in the welding area of the I-beam frame (11) and the channel steel joist (1), the stiffening rib plates are rectangular steel plates, are symmetrically welded along the front and back sides of the I-beam frame, and form a local bending stiffness reinforcement area.