An initial support structure and construction method for a tunnel with a steel arch frame

Abstract

The present invention belongs to the technical field of tunnel construction, and specifically relates to an initial support structure and construction method for a steel arch in a tunnel, including an inner chord bracing structure connected to the steel arch, and a connecting bracing structure connected to the inner chord bracing and the steel arch, which anchors the cable in two stages. The outer anchor of the inner chord bracing in the present invention can effectively utilize the stability of the tunnel surrounding rock, make full use of the stability of the surrounding rock, re-compact and stabilize the loosened surrounding rock through prestressed cables, and effectively combine with the rock mass behind the steel arch through the cables and the steel arch to form a stressed whole, improving the stability of the surrounding rock, and retaining the integrity of the tunnel construction space to the greatest extent, which is beneficial to the mechanized operation of large equipment in the tunnel excavation space.

Description

Technical Field

[0001] The present invention belongs to the technical field of tunnel construction, and particularly relates to an initial support structure and construction method of a steel arch in a tunnel. Background Art

[0002] During the construction of tunnels and underground space projects, initial support construction is required after the excavation of the heading face. According to the size of the excavation section, common excavation methods are as follows: (1) For general small sections, according to the surrounding rock conditions, the full-face method and the bench method can be adopted; (2) For large sections, according to the surrounding rock conditions, the middle diaphragm method, the double-side drift method, the double-arch connection method, etc. can be adopted. At present, for the excavation sections of tunnels and underground spaces, in order to meet the requirements of various usage functions, the section sizes are getting larger and larger, which has caused difficulties in excavation. The increase in the section has brought about the progress and changes in excavation methods and support technologies. The middle diaphragm method, the double-side drift method, and the double-arch connection method all have a common problem, that is, the construction of temporary supports will occupy the middle space of the tunnel excavation section. For excavation safety, the tunnel excavation section is artificially divided, making the large section smaller to effectively reduce the excavation safety risk, but this increases the construction difficulty. Because after the erection of temporary supports, such as the CD method, the excavation section is reduced by half after the erection of the temporary support, and the CRD method reduces the excavation section to 1 / 4 of the original excavation section after the erection of the temporary support, and the double-side drift method reduces the excavation section to 1 / 3 of the original excavation section. Due to the reduction of the excavation section by these methods, large-scale machinery such as high-power excavators, three-boom rock drilling jumbo, shotcrete machines and other large equipment cannot effectively construct in the tunnel, which will affect the tunnel construction efficiency and increase the construction cost. On the premise of safety, being able to quickly and efficiently solve the above-mentioned support problems can ensure smooth construction and shorten the project construction period. This is the problem existing in the current construction and is also the topic that has been continuously studied and improved during the construction process. Summary of the Invention

[0003] The present invention aims to solve the deficiencies of the prior art and provides an initial support structure and construction method of a steel arch in a tunnel.

[0004] The present invention is achieved through the following technical solutions:

[0005] An initial support structure for a tunnel with a steel arch frame, including a steel arch frame. Cable bolts are driven into the steel arch frame. Along the tunnel excavation direction, several groups of inner chord bracing structures are arranged. Each group of inner chord bracing structures includes two inner chord braces. The upper ends of the two inner chord braces are fixed on the steel arch frame at the tunnel crown position, and the lower ends are respectively fixed on the steel arch frame at two arch springing angle positions above the tunnel springing line; several connecting braces are arranged between the steel arch frame and the inner chord braces. One end of the connecting brace is fixed on the steel arch frame, and the other end is fixed on the inner chord brace. Several triangular closed structures are formed between the connecting brace and the inner chord brace; on the surface of the initial support of the tunnel, a collar beam A is fixed at the intersection of the cable bolt and the steel arch frame. Drilling holes are evenly arranged on the collar beam A, and the first anchoring is carried out through the anchor fittings; at the intersection of the cable bolt and the inner chord brace, a collar beam B is set. The collar beam B is perpendicular to the inner chord brace. Drilling holes are evenly arranged on the collar beam B, and the second anchoring is carried out through the anchor fittings.

[0006] The steel arch frame is prefabricated in advance.

[0007] The inner chord braces and the steel arch frame adopt the same type of I-beam.

[0008] The inner chord braces are connected to the steel arch frame through steel plates and bolts.

[0009] Both the collar beam A and the collar beam B are selected as I16 I-beams.

[0010] The spacing of the drilling holes is 1 - 2 meters.

[0011] The construction method of the above initial support structure of the tunnel with a steel arch frame includes the following steps:

[0012] (1) Prefabricate and process the steel arch frame;

[0013] (2) After the upper bench of the tunnel is excavated, install the steel arch frame, spray concrete, promptly seal the face, and drive the cable bolts;

[0014] (3) Connect the inner chord braces to the steel arch frame and fix the connecting braces;

[0015] (4) On the shotcrete and bolt surface of the initial support of the tunnel, fix the collar beam A at the intersection of the cable bolt and the steel arch frame. Arrange the drilling holes for the prestressed cable bolts on the collar beam A, apply prestress, and fix the anchor fittings after reaching the locking value to complete the first anchoring; set the collar beam B at the intersection of the cable bolt and the inner chord brace. Arrange the drilling holes for the prestressed cable bolts on the collar beam B, apply prestress, and fix the anchor fittings after reaching the locking value to complete the second anchoring;

[0016] (5) After the upper bench excavates and advances a certain distance, carry out the construction of the lower bench. After the lower bench advances a certain distance, construct the inverted arch of the secondary lining of the tunnel. After the construction of the inverted arch of the secondary lining of the tunnel is completed, according to the length of the secondary lining side top arch formwork trolley of the secondary lining, remove the inner chord braces and the connecting braces of the upper bench in sections.

[0017] The present invention adopts a tunnel initial support technology with internal chord braces and external double anchoring in a conventional initial support steel arch, which can effectively avoid the problem that in the conventional middle diaphragm excavation method, the operation space is reduced due to the division of the tunnel excavation face after the erection of the middle diaphragm, thus reducing the construction efficiency of personnel and equipment. The internal chord braces and external anchoring of the present invention can effectively utilize the stability of the tunnel surrounding rock, better reflect the construction principle of the new Austrian tunneling method for tunnel excavation, make full use of the stability of the surrounding rock, re-compact and stabilize the loosened surrounding rock through prestressed anchor cables, and effectively combine with the rock mass behind the steel arch through the anchor cables and the steel arch to form a stress-bearing whole, improving the stability of the surrounding rock. Through the external double-anchoring setting, the stress conversion during the removal of the internal chord braces is solved, realizing the possibility of quickly and efficiently excavating the tunnel under the condition of ensuring the stability of the surrounding rock.

[0018] On the basis of ensuring the stability of the surrounding rock of the initial support, the present invention maximally retains the integrity of the tunnel construction space, which is conducive to the mechanized operation of large equipment in the tunnel excavation space. The steps of the present invention are simple, highly operable, save construction space, and have remarkable economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a structural schematic diagram of the present invention.

[0020] Figure 2 is an enlarged structural schematic diagram at the waist beam B of the present invention.

[0021] In the figure, 1 is the steel arch, 2 is the anchor cable, 3 is the internal chord brace, 4 is the connecting brace, 5 is the waist beam A, 6 is the waist beam B, 7 is the drilling hole, 8 is the anchor fitting, and 9 is the triangular closed structure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent transformations made on the basis of the technical solution of the present application fall within the protection scope of the present invention.

[0023] The tunnel initial support structure of the steel arch of the present invention includes the existing steel arch 1, and anchor cables 2 are provided on the steel arch 1. Compared with the prior art, the improvement lies in:

[0024] The steel arch 1 is prefabricated in the factory in advance.

[0025] A number of groups of internal chord brace structures are arranged on the steel arch 1 along the tunnel excavation direction. Each group of internal chord brace structures includes two internal chord braces 3. The upper ends of the two internal chord braces 3 are fixed at the tunnel crown position and are connected to the steel arch 1 through steel plate bolts. The lower ends are respectively fixed at two arch springing angle positions above the tunnel springing line and are also connected to the steel arch 1 through steel plate bolts.

[0026] Preferably, the inner chord bracing structure form is the same as that of the steel arch frame 1. Here, the same structure form means that both the inner chord bracing structure and the steel arch frame 1 use the same type of steel components for processing materials, such as the same type of I-beams, etc., and the connection form uses steel plate bolt connection.

[0027] A number of connecting braces 4 are arranged between the steel arch frame 1 and the inner chord bracing 3. One end of the connecting brace 4 is fixed on the steel arch frame 1, and the other end is fixed on the inner chord bracing 3. A small triangular closed structure 9 is formed between the connecting brace 4 and the inner chord bracing 3, and the triangular closed structure 9 improves the supporting force of the original steel arch frame 1. The anchor cable of the present invention adopts an external double-anchoring design: on the surface of the initial support of the tunnel, at the intersection of the anchor cable 2 and the steel arch frame 1, a waist beam A5 is provided, and holes 7 are evenly arranged and drilled on the waist beam A5, and the first anchoring is carried out through the anchor 8; at the intersection of the anchor cable 2 and the inner chord bracing 3, a waist beam B6 is provided, the waist beam B6 is perpendicular to the inner chord bracing 3, and holes 7 are evenly arranged and drilled on the waist beam B6, and the second anchoring is carried out through the anchor 8.

[0028] Preferably, both the waist beam A5 and the waist beam B6 are made of I16 I-beams, and the spacing of the drilled holes 7 is 1-2 meters.

[0029] The construction method of the tunnel initial support structure using the above-mentioned steel arch frame of the present invention includes the following steps:

[0030] Step 1: Prefabricate and process the upper bench steel arch frame 1 in the factory.

[0031] Step 2: After the upper bench of the tunnel is excavated, install the initial support steel arch frame 1 prefabricated in Step 1, then carry out shotcrete construction to timely seal the face, and then carry out the construction of driving the anchor cable 2.

[0032] When spraying concrete, pay attention to pre-covering the positions connected to the steel arch frame 1 in the subsequent steps to prevent being covered by concrete during spraying.

[0033] Step 3: According to the design unit of the upper bench steel arch frame 1, set a number of groups of inner chord bracing structures along the tunnel excavation direction, and the inner chord bracing structures are connected to the steel arch frame 1. Each group of inner chord bracing structures includes two inner chord bracings 3. The upper ends of the two inner chord bracings 3 are fixed at the tunnel crown position and are connected to the steel arch frame 1 through steel plate bolts, and the lower ends are respectively fixed at two arch springing angle positions above the tunnel springing line and are also connected to the steel arch frame 1 through steel plate bolts.

[0034] A number of connecting braces 4 are arranged between the steel arch frame 1 and the inner chord bracing 3. One end of the connecting brace 4 is fixed on the steel arch frame 1, and one end is fixed on the inner chord bracing 3. A small triangular closed structure 9 is formed between the connecting brace 4 and the inner chord bracing 3, and the triangular closed structure 9 improves the supporting force of the original steel arch frame 1. Step 4: To ensure the reasonable force of the external anchor system and the inner chord bracing 3 and the safety of the upper bench initial support when the inner chord bracing 3 is removed later, the present invention adopts an external double-anchoring design, which is introduced in detail as follows:

[0035] The first anchoring is set on the surface of the initial support of the tunnel. By setting the waist beam A5 on the shotcrete and bolt surface of the initial support of the tunnel, the waist beam A5 is made of I16 steel I-beam. Prestressed anchor cables 2 are evenly arranged on the waist beam A5 at intervals of 1-2 m, and the holes 7 are drilled. Prestress is applied, and after reaching the locking value, the anchor 8 is fixed to complete the first anchoring.

[0036] The second anchoring uses the I16 steel I-beam longitudinally connected to the inner chord brace 3 as the waist beam B6, that is, the I16 steel I-beam is vertically connected and fixed to the inner chord brace 3. Similarly, prestressed anchor cables 2 are evenly arranged on the waist beam B6 at intervals of 1-2 m, and the holes 7 are drilled. Prestress is applied, and after reaching the locking value, the anchor 8 is fixed to complete the second anchoring.

[0037] In the external double-anchoring design of the present invention, the first anchoring is the main one and the second anchoring is for reserve, which is convenient for the force conversion safety during the construction of the tunnel structure waterproofing and the secondary lining.

[0038] Step Five: After the upper bench excavation advances a certain distance, the lower bench construction is carried out. After the lower bench advances a certain distance, the inverted arch of the tunnel secondary lining is constructed. After the construction of the inverted arch of the tunnel secondary lining is completed, because there is still the first anchoring support for the steel arch frame 1 and the initial support of the tunnel has been closed, after the tunnel settlement and force are stable, according to the length of the secondary lining side-top arch formwork trolley of the secondary lining, generally 9-12 m, the inner chord brace 3 and the connecting brace 4 on the upper bench are removed in sections, and the structure waterproofing, steel bar binding and concrete pouring construction are carried out.

[0039] Due to the adoption of the inner chord brace 3 and the external double-anchoring support system in the present invention, the erection position of the inner chord brace 3 is just at the positions of two arch axils above the tunnel spring line, which will not divide the cross-section of the overall excavation section of the tunnel, and retains the integrity of the tunnel excavation cross-section to the greatest extent, ensures the effective construction space, and is convenient for the mechanized construction of large-scale excavation and support equipment.

[0040] The above-described embodiments are only one of the more preferred specific embodiments of the present invention. The general changes and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A construction method for the initial support structure of a tunnel with a steel arch frame, characterized in that: It includes a steel arch frame (1) with cable bolts (2) driven into it. It is characterized in that: several groups of inner chord bracing structures are arranged along the tunnel excavation direction. Each group of inner chord bracing structures includes two inner chord braces (3). The upper ends of the two inner chord braces (3) are fixed on the steel arch frame (1) at the tunnel crown position, and the lower ends are respectively fixed on the steel arch frame (1) at two arch springing angle positions above the tunnel springing line; several connecting braces (4) are arranged between the steel arch frame (1) and the inner chord brace (3). One end of the connecting brace (4) is fixed on the steel arch frame (1), and the other end is fixed on the inner chord brace (3). Several triangular closed structures (9) are formed between the connecting brace (4) and the inner chord brace (3); on the surface of the initial tunnel support, a collar beam A (5) is fixed at the intersection of the cable bolt (2) and the steel arch frame (1). Boring holes (7) are evenly arranged on the collar beam A (5), and the first anchoring is carried out through the anchor fitting (8); at the intersection of the cable bolt (2) and the inner chord brace (3), a collar beam B (6) is set. The collar beam B (6) is perpendicular to the inner chord brace (3). Boring holes (7) are evenly arranged on the collar beam B (6), and the second anchoring is carried out through the anchor fitting (8); The construction method of the initial tunnel support structure of the steel arch frame includes the following steps: (1) Prefabricate and process the steel arch frame (1); (2) After the upper bench of the tunnel is excavated, install the steel arch frame (1), spray concrete, promptly seal the tunnel face, and drive the cable bolts (2); (3) Connect the inner chord brace (3) with the steel arch frame (1) and fix the connecting brace (4); (4) On the shotcrete surface of the initial tunnel support, at the intersection of the cable bolt (2) and the steel arch frame (1), fix the collar beam A (5). Boring holes (7) for prestressed cable bolts (2) are arranged on the collar beam A (5). Apply prestress. After reaching the locking value, fix the anchor fitting (8) to complete the first anchoring; at the intersection of the cable bolt (2) and the inner chord brace (3), set the collar beam B (6). Boring holes (7) for prestressed cable bolts (2) are arranged on the collar beam B (6). Apply prestress. After reaching the locking value, fix the anchor fitting (8) to complete the second anchoring; (5) After the upper bench excavates and advances a certain distance, carry out the construction of the lower bench. After the lower bench advances a certain distance, construct the inverted arch of the secondary lining of the tunnel. After the construction of the inverted arch of the secondary lining of the tunnel is completed, according to the length of the secondary lining side top arch formwork trolley of the secondary lining, segmentally remove the inner chord brace (3) and the connecting brace (4) of the upper bench.

2. The construction method of the initial tunnel support structure of the steel arch as claimed in claim 1, characterized in that: The steel arch frame (1) is prefabricated in advance.

3. The construction method of the initial tunnel support structure of the steel arch as claimed in claim 1, characterized in that: The inner chord brace (3) and the steel arch frame (1) adopt the same type of I-beam.

4. The construction method of the initial tunnel support structure of the steel arch as claimed in claim 1, characterized in that: The inner chord brace (3) is connected to the steel arch frame (1) through steel plates and bolts.

5. The construction method of the initial tunnel support structure of the steel arch frame according to claim 1, characterized in that: Both the collar beam A (5) and the collar beam B (6) are selected as I16 I-beams.

6. The construction method of the initial tunnel support structure of the steel arch frame according to claim 1, characterized in that: The spacing of the boring holes (7) is 1 - 2 meters.

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