A local stiffness-reinforced tunnel primary support structure and construction method

Abstract

The present invention discloses a local stiffness-reinforced tunnel primary support structure, which is arranged in a load-concentrated area in a tunnel and includes a steel arch frame, an L-shaped perforated channel steel, a high-strength pin rod, and a perforated steel bar. The steel arch frame is a plurality of annular I-beams arranged at equal intervals, and the plurality of annular I-beams are connected by L-shaped perforated channel steel, a high-strength pin rod, and a perforated steel bar to form an integral steel arch frame. The connection is located at the inner edge of the annular I-beam and is located in the load-concentrated area of ​​the steel arch frame. The outer edge of the annular I-beam fits tightly against the inner wall of the tunnel. When obvious load concentration is found in the surrounding rock of the tunnel after tunnel excavation, the local stiffness-reinforced tunnel primary support structure can be installed to quickly increase the stiffness of the steel arch frame at the stress concentration location, so that the stiffness of the steel arch frame matches the surrounding rock load, and the stress of the steel arch frame is secondary distributed to make its force more reasonable, thereby carrying a larger concentrated load.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel construction, and in particular to a local stiffness reinforced tunnel primary support structure and a construction method. Background Art

[0002] The primary support structure of a tunnel is generally composed of anchor rods, steel mesh, shotcrete, and steel arch frames. It is increasingly valued for its ability to quickly seal the rock face after tunnel excavation and form a common force-bearing system with the surrounding rock. To facilitate construction, the thickness of the primary support and the type of steel frame are generally the same in the same tunnel section. However, due to factors such as topography, geological structure, and groundwater, the surrounding rock pressure after tunnel excavation is significantly uneven, resulting in local stress concentration in the primary support structure and bearing a large concentrated load. There are two traditional solutions to this problem. One is to allow the primary support to deform locally to unload, which can easily cause primary support intrusion and affect the overall stiffness of the primary support. The other is to increase the entire steel arch frame model, thereby increasing the primary support stiffness of the section to resist the eccentric load. This method is expensive and wasteful. Summary of the Invention

[0003] Based on the current problems, the present invention provides a local stiffness reinforced tunnel primary support structure and construction method, which aims to quickly increase the stiffness of the steel arch frame at the stress concentration position after tunnel excavation, match the steel frame stiffness with the surrounding rock load, and perform secondary distribution of the steel frame stress to make its force more reasonable.

[0004] The technical solution adopted in the present invention is:

[0005] A local stiffness-reinforced tunnel primary support structure is provided in a load-concentrated area in a tunnel, and comprises a steel arch frame, an L-shaped perforated channel steel 1, a high-strength pin rod 2 and a perforated steel bar 3; the steel arch frame is a plurality of annular I-beams arranged at equal intervals, and the plurality of annular I-beams are connected by the L-shaped perforated channel steel, the high-strength pin rod and the perforated steel bar to form an integral steel arch frame, the connection being located at the inner edge of the annular I-beam and in the load-concentrated area of ​​the steel arch frame, and the outer edge of the annular I-beam is in close contact with the inner wall of the tunnel.

[0006] Furthermore, the perforated steel bars form a group of three, and a group of perforated steel bars constitutes an isosceles triangle reinforcement structure and is installed on a ring-shaped I-beam, and the three perforated steel bars are respectively located at the center line position and two isosceles side positions of the isosceles triangle; several groups of isosceles triangle reinforcement structures are connected by pins at the three corner points and the intersection of the center line position and the bottom edge to form an overall reinforcement structure.

[0007] Furthermore, the L-shaped perforated channel steel is an L-shaped steel plate, one of whose right-angled end faces is welded to the annular I-steel, and the other right-angled end face is provided with a through hole for the high-strength pin rod to pass through. The high-strength pin rod passes through the through hole at one end of the perforated steel bar and the through hole on the L-shaped perforated channel steel in sequence, and then threaded bolts are connected at both ends; the other end of the perforated steel bar is provided with a through hole for the high-strength pin rod to pass through, and the through holes at the other end of the three perforated steel bars of each group of isosceles triangle reinforcement structures are located at the same point, and the high-strength pin rod passes through this point and then threaded bolts are connected at both ends.

[0008] A construction method for a locally stiffened tunnel primary support structure is provided. The construction method is based on the aforementioned locally stiffened tunnel primary support structure and comprises the following steps:

[0009] Step 1: L-shaped perforated channel steel, high-strength pins and perforated steel bars are pre-fabricated in the factory;

[0010] Step 2: After tunnel excavation reveals significant load concentration in the surrounding rock, take several L-shaped perforated channels and high-strength pins, weld the L-shaped perforated channels to the annular I-beams at the load concentration point, and pass the high-strength pins through the through holes in the L-shaped perforated channels to form a steel arch.

[0011] Step 3: Install perforated steel bars on the basis of the steel arch frame. The perforated steel bars form a group of three, and a group of perforated steel bars forms an isosceles triangle reinforcement structure and is installed on a ring-shaped I-beam;

[0012] Step 4: When the through-holes at the other ends of the three perforated steel bars of each set of isosceles triangle reinforcement structures are rotated to the same point through the high-strength pin rods, all the perforated steel bars are passed through this point, and bolts are installed at both ends of the high-strength pin rods, so that multiple sets of isosceles triangle reinforcement structures form an articulated steel bar system. At the same time, the perforated steel bars, high-strength pin rods and arch frames form a force-bearing system.

[0013] Furthermore, among the steel bars arranged in an isosceles triangle reinforcement structure, the length of the steel bar N1 located at the waist of the isosceles triangle is determined by the thickness of the initial support and re-spraying of the tunnel, and the length of the steel bar N2 is determined by the range of the load concentration area of ​​the tunnel cross section; the length of the steel bar N2 is determined by the range of the load concentration area of ​​the tunnel cross section.

[0014] Furthermore, assuming that the load concentration area is l, the length of the steel bar N2 located at the center line of the steel bars arranged in an isosceles triangle reinforcement structure is 0.5l; due to the randomness of the bias area range, when the factory prefabricates the steel bar N2, it is necessary to prefabricate multiple lengths to meet on-site requirements.

[0015] Furthermore, the hinged steel bar system can provide a supporting reaction force to the steel arch frame in the load concentration area, so that the stress of the steel arch frame is redistributed.

[0016] The beneficial effects of the present invention are:

[0017] After localized bias pressure occurs during tunnel excavation, this locally stiffened primary support structure rapidly connects L-shaped perforated channels, high-strength pins, and perforated steel bars. This allows several circular I-beams to form a monolithic, stressed steel arch. Furthermore, the L-shaped perforated channels, high-strength pins, and perforated steel bars also form a monolithic reinforcement structure comprised of several groups of isosceles triangles. This rapidly increases the local stiffness of the steel arch, aligning the stiffness of the arch with the unloading of the surrounding rock and improving the primary support's load-bearing performance. This locally stiffened primary support structure boasts convenient material sourcing and simple construction, quickly and effectively resolving the problem of localized bias pressure in the surrounding rock after tunnel excavation, facilitating widespread application. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the overall structure of the primary support structure of the locally stiffened tunnel;

[0019] Figure 2 This is a schematic diagram of the installation position of the primary support structure of the locally stiffened tunnel;

[0020] Figure 3 This is a schematic diagram of the connection between the L-shaped perforated channel steel, high-strength pin rod and perforated steel bar;

[0021] Figure 4 Schematic diagram of the primary support structure of the locally stiffened tunnel under local eccentric load;

[0022] Figure 5 is the bending moment diagram of the primary support structure of the locally stiffened tunnel;

[0023] Figure 1 —5, 1—L-shaped perforated channel steel, 2—high-strength pin rod, 3—perforated steel bar, 4—annular I-beam, 5—load concentration area. DETAILED DESCRIPTION

[0024] The following will be combined with the accompanying drawings of the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all 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.

[0025] For ease of description, spatially relative terms such as "upper," "lower," "left," and "right" may be used herein to describe the relationship of one element or feature shown in a figure to another element or feature. It should be understood that, in addition to the orientation shown in the processing figures, the spatial terms are intended to include different orientations of the device in use or operation. For example, if the device in the figure is inverted, an element described as being "below" another element or feature would be defined as being "above" the other element or feature. Thus, the exemplary term "below" can encompass both upper and lower orientations. The device can be positioned in other ways, and the spatially relative descriptions used herein should be interpreted accordingly.

[0026] In view of the obvious unevenness of surrounding rock pressure after tunnel excavation, which leads to stress concentration in the primary support structure and the problem of bearing large concentrated loads, this embodiment provides a tunnel primary support structure with local stiffness reinforcement. Through this local stiffness reinforcement tunnel primary support structure, the stiffness of the steel arch frame at the stress concentration location can be quickly improved after tunnel excavation, so that the steel frame stiffness matches the surrounding rock load, and the stress of the steel frame is secondary distributed, so that the force is more reasonable. Figure 1 As shown in FIG, the primary support structure of the locally stiffened tunnel includes a steel arch frame, an L-shaped perforated channel steel 1, a high-strength pin rod 2, and a perforated steel bar 3; Figure 2 As shown, the local stiffness reinforced tunnel primary support structure is arranged in the load concentration area 5 in the tunnel.

[0027] Among them, the steel arch frame is composed of six annular I-beams 4 arranged at equal intervals. The six annular I-beams 4 are connected by L-shaped perforated channel steels 1, high-strength pins 2 and perforated steel bars 3 to form an integral steel arch frame. The connection is located at the inner edge of the annular I-beams 4 and is in the load concentration area of ​​the steel arch frame. The outer edge of the annular I-beams 4 fits tightly against the inner wall of the tunnel.

[0028] Each group of three perforated steel bars 3 forms an isosceles triangle reinforcement structure and is installed on a ring-shaped I-beam 4. The three perforated steel bars 3 are respectively located at the center line and two isosceles sides of the isosceles triangle; the six groups of isosceles triangle reinforcement structures are connected by high-strength pins 2 at the three corner points and the intersection of the center line and the bottom edge to form an overall articulated steel bar system to improve the stiffness of the primary support of the tunnel in the load concentration area.

[0029] like Figure 3As shown, the L-shaped perforated channel steel 1 is an L-shaped steel plate, one of whose right-angled end faces is welded to the annular I-beam 4, and the other right-angled end face is provided with a through hole for the high-strength pin rod 2 to pass through. The high-strength pin rod 2 passes through the through hole at one end of the perforated steel bar 3 and the through hole on the L-shaped perforated channel steel 1 in sequence, and then threaded bolts are connected at both ends; the other end of the perforated steel bar 3 is provided with a through hole for the high-strength pin rod 2 to pass through, and the through holes at the other ends of the three perforated steel bars 3 of each group of isosceles triangle reinforcement structures are located at the same point, and the high-strength pin rod 2 passes through this point and then threaded bolts are connected at both ends.

[0030] The implementation process of the local stiffness-enhanced tunnel primary support structure is as follows:

[0031] (1) The L-shaped perforated channel steel 1, high-strength pin rod 2 and perforated steel bar 3 are prefabricated in the factory. The length of the perforated steel bar N1 is determined by the thickness of the initial support and spraying of the tunnel, which is generally 5 cm. The length of the perforated steel bar N2 is determined by the range of the load concentration area in the tunnel cross section. Assuming that the range of the load concentration area is l, the length of the perforated steel bar N2 can be taken as 0.5l. Since the range of the bias area is random, when the perforated steel bar N2 is prefabricated in the factory, various lengths can be prefabricated to meet the site requirements. The length of the high-strength pin rod 2 is determined according to the number of four ring-shaped I-beams with enhanced stiffness and the range of the load concentration area in the longitudinal direction of the tunnel.

[0032] (2) After tunnel excavation, it is found that there is obvious load concentration in the tunnel surrounding rock. Take a number of L-shaped hole channel steels 1 and high-strength pins 2, weld the L-shaped hole channel steels 1 to the annular I-beam 4 at the load concentration point, and pass the high-strength pins 2 through the through holes on the L-shaped hole channel steels 1 to form a steel arch.

[0033] (3) Install perforated steel bars N1 and N2 on the basis of the steel arch frame. The perforated steel bars 3 are grouped into three pieces. A group of perforated steel bars 3 forms an isosceles triangle reinforcement structure and is installed on a ring-shaped I-beam 4.

[0034] (4) When the through-holes at the other end of the three perforated steel bars 3 of each set of isosceles triangle reinforcement structures are rotated to the same point through the high-strength pin rod 2, all the perforated steel bars 3 are passed through this point, and bolts are installed at both ends of the high-strength pin rod 2, so that multiple sets of isosceles triangle reinforcement structures form a hinged steel bar system, and at the same time, the perforated steel bars 3, the high-strength pin rod 2 and the arch frame form a force-bearing system.

[0035] like Figure 4 As shown, when a large local load acts on the annular I-beam 4, the annular I-beam 4 in this area will further deform, transferring the load to the hinged steel bar system behind it. The perforated steel bars 3 are hinged together by high-strength pins 2, forming a load-bearing whole with the steel arch. This increases the local stiffness of the individual annular I-beams 4 and prevents further deformation.

[0036] like Figure 5 As shown, a bending moment analysis is performed on a single annular I-beam 4 after forming the primary support structure of the locally stiffened tunnel. The load mechanics diagram of the single annular I-beam 4 can be simplified to a two-span continuous beam structure with a length l and a uniformly distributed load q. Based on mechanical knowledge, it is known that after forming the primary support structure of the locally stiffened tunnel, the perforated steel bars 3 can provide a supporting reaction force to the steel frame in the load-concentrated area, causing stress redistribution in the annular I-beam 4. The maximum bending moment of a single annular I-beam 4 can reach ,like Figure 5 As shown in b. Under the same load, the maximum bending moment of the ordinary annular I-beam 4 is only ,like Figure 5 As shown in (a), the bending moment diagrams of the two show that the stress of the primary support structure of the locally stiffened tunnel is more reasonable and the material utilization is higher.

[0037] Because the perforated steel bars 3 are hinged together via high-strength pins 2, they only bear axial forces and no bending moments, significantly improving the bars' load-bearing properties. Furthermore, since all components of the hinged steel bar system are prefabricated in the factory, the L-shaped perforated channel steel 1 is tightly connected to the annular I-beam 4 by welding during construction, making construction simple and efficient, and quickly resolving the problem of uneven initial support.

[0038] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A tunnel primary support structure with local stiffness reinforcement, characterized by: The locally stiffened tunnel primary support structure is located in the load-concentrated area of ​​the tunnel and comprises a steel arch frame, L-shaped perforated channel steel, high-strength pins and perforated steel bars. The steel arch frame is a plurality of annular I-beams arranged at equal intervals. The plurality of annular I-beams are connected by L-shaped perforated channel steel, high-strength pins and perforated steel bars to form an integral steel arch frame. The connection is located at the inner edge of the annular I-beam and in the load-concentrated area of ​​the steel arch frame. The outer edge of the annular I-beam fits tightly against the inner wall of the tunnel. The perforated steel bars are grouped into three pieces, each of which forms an isosceles triangle reinforcement structure and is mounted on a ring-shaped I-beam. The three perforated steel bars are located at the center line and two isosceles sides of the isosceles triangle, respectively. Several groups of isosceles triangle reinforcement structures are connected by pins at the three corner points and the intersection of the center line and the base to form an overall reinforcement structure. The L-shaped perforated channel steel is an L-shaped steel plate, one of whose right-angled end faces is welded to the annular I-steel, and a through hole is provided on the other right-angled end face for high-strength pin rods to pass through. The high-strength pin rods pass through the through hole at one end of the perforated steel bar and the through hole on the L-shaped perforated channel steel in sequence, and then threaded bolts are connected at both ends; the other end of the perforated steel bar is provided with a through hole for high-strength pin rods to pass through, and the through holes at the other ends of the three perforated steel bars of each group of isosceles triangle reinforcement structures are located at the same point, and the high-strength pin rods pass through this point and then threaded bolts are connected at both ends.

2. A construction method for a locally stiffened tunnel primary support structure, the construction method being based on the locally stiffened tunnel primary support structure according to claim 1, characterized in that: The following steps are involved: Step 1: L-shaped perforated channel steel, high-strength pins and perforated steel bars are pre-fabricated in the factory; Step 2: After tunnel excavation reveals significant load concentration in the surrounding rock, take several L-shaped perforated channels and high-strength pins, weld the L-shaped perforated channels to the annular I-beams at the load concentration point, and pass the high-strength pins through the through holes in the L-shaped perforated channels to form a steel arch. Step 3: Install perforated steel bars on the basis of the steel arch frame. The perforated steel bars form a group of three, and a group of perforated steel bars forms an isosceles triangle reinforcement structure and is installed on a ring-shaped I-beam; Step 4: When the through-holes at the other ends of the three perforated steel bars of each set of isosceles triangle reinforcement structures are rotated to the same point through the high-strength pin rods, all the perforated steel bars are passed through this point, and bolts are installed at both ends of the high-strength pin rods, so that multiple sets of isosceles triangle reinforcement structures form an articulated steel bar system. At the same time, the perforated steel bars, high-strength pin rods and arch frames form a force-bearing system.

3. The construction method of the local stiffness reinforced tunnel primary support structure according to claim 2 is characterized by: Among the steel bars arranged in an isosceles triangle reinforcement structure, the length of the steel bar N1 located at the waist of the isosceles triangle is determined by the thickness of the initial support and re-spraying of the tunnel, and the length of the steel bar N2 is determined by the range of the load concentration area of ​​the tunnel cross section; the length of the steel bar N2 is determined by the range of the load concentration area of ​​the tunnel cross section.

4. The construction method of the local stiffness reinforced tunnel primary support structure according to claim 2, characterized in that: The hinged steel bar system can provide a supporting reaction force to the steel arch frame in the load concentration area, so that the stress of the steel arch frame is redistributed.

Images