Middle wall of multi-arch tunnel, initial support steel frame closed multi-arch tunnel and construction method

Abstract

The invention discloses a closed type multi-arch tunnel with a middle wall and an initial support steel frame of a multi-arch tunnel and a construction method, which belongs to the field of tunnel engineering and aims to enhance the integrity of the connection between the middle wall and the initial support of the tunnel. The steel frame of the middle wall includes a left hole steel arch frame segment 2, a right hole steel arch frame segment 2 and a transverse connecting steel bar, one end of which is connected to the left hole steel arch frame segment 2, and the other end is connected to the right hole steel arch frame segment 2. In the invention, the left hole steel arch frame segment 2 and the left hole steel support segment 2 constituting the middle wall steel frame are simultaneously used as a part of the left hole initial support steel frame, so that the left hole initial support steel frame is closed into a ring; the right hole steel arch frame segment 2 and the left hole steel support segment 2 constituting the middle wall steel frame are simultaneously used as a part of the right hole initial support steel frame, so that the right hole initial support steel frame is closed into a ring, thereby ensuring the integrity of the initial support, improving the reliability of the initial support, and significantly improving the stress performance of the connection between the initial support and the middle wall.

Description

Technical Field

[0001] The invention belongs to the field of tunnel engineering, and specifically relates to a middle wall of a multi-arch tunnel, an initial support steel frame closed multi-arch tunnel and a construction method. Background Art

[0002] Arch tunnels are often used for medium and short tunnels because of their advantages such as easy wiring and wiring at the tunnel opening and less occupied area at the tunnel opening. As the name implies, arch tunnels refer to tunnels in which the lining structures of the left and right arch parts are connected by a middle wall. The middle wall is usually a reinforced concrete structure. The steel frame of the middle wall of the arch tunnel is currently a steel cage formed by steel bar binding. The connecting steel plates are fixed at the top and bottom of the steel frame respectively. During pouring, the connecting steel plates are poured inside so as to be connected with the initial support steel frame of the arch tunnel later. Due to the setting of the middle wall steel frame, the initial support steel frame of the arch tunnel is cut off, so that the initial support steel frame of the arch tunnel extends along the tunnel circumference to the middle wall steel frame. The connection between the middle wall structure and the initial support steel frame becomes the weak point of the entire structure, which is prone to cracking, water leakage and other problems, thereby affecting the safety and durability of the entire structure of the arch tunnel. Summary of the invention

[0003] The purpose of the present invention is to solve the problem of cracking and water leakage at the connection between the middle wall and the initial support, and to provide a closed multi-arch tunnel with a middle wall of a multi-arch tunnel and an initial support steel frame and a construction method to enhance the integrity of the connection between the middle wall and the initial support of the tunnel.

[0004] The technical solution adopted by the present invention is: a middle wall of a multi-arch tunnel, wherein the initial support steel frame of the multi-arch tunnel comprises a left hole steel arch frame and a right hole steel arch frame;

[0005] The left hole steel arch frame extends from the outer side wall of the left hole along the left hole circumferential direction to the inner side wall of the left hole, and is formed by connecting the left hole steel arch frame segment 1 and the left hole steel arch frame segment 2 in series along the left hole circumferential direction;

[0006] The right hole steel arch frame extends from the outer side wall of the right hole along the right hole circumferential direction to the inner side wall of the right hole, and is formed by connecting the right hole steel arch frame segment 1 and the right hole steel arch frame segment 2 in series along the right hole circumferential direction;

[0007] The steel frame of the middle wall includes a left hole steel arch frame segment 2, a right hole steel arch frame segment 2 and a transverse connecting steel bar, one end of the transverse connecting steel bar is connected to the left hole steel arch frame segment 2, and the other end is connected to the right hole steel arch frame segment 2.

[0008] Further, an embedded steel plate is fixedly connected to the top of the left hole steel arch frame segment 2, and embedded bolts are installed on the embedded steel plate; a connecting steel plate 1 is fixedly connected to the end of the left hole steel arch frame segment 1 adjacent to the left hole steel arch frame segment 2, and the embedded steel plate and the connecting steel plate 1 are connected via embedded bolts and nuts;

[0009] An embedded steel plate is fixedly connected to the top of the right hole steel arch frame segment two, and embedded bolts are installed on the embedded steel plate; a connecting steel plate one is fixedly connected to the end of the right hole steel arch frame segment one adjacent to the right hole steel arch frame segment two, and the embedded steel plate and the connecting steel plate one are connected via embedded bolts and nuts.

[0010] Furthermore, the bottom end of the left hole steel arch frame segment 2 is connected to the wall foot support; the bottom end of the right hole steel arch frame segment 2 is connected to the wall foot support.

[0011] Furthermore, the wall foot support is a channel steel with an opening facing upward;

[0012] A second connecting steel plate is fixedly connected to the bottom end of the second left hole steel arch frame segment; the second connecting steel plate is arranged in the groove of the channel steel and connected to the waist of the channel steel through connecting bolts;

[0013] A second connecting steel plate is fixedly connected to the bottom end of the second right hole steel arch frame segment; the second connecting steel plate is arranged in the groove of the channel steel and is connected to the waist of the channel steel through connecting bolts.

[0014] Furthermore, the initial support steel frame of the multi-arch tunnel also includes a left tunnel inverted arch steel support and a right tunnel inverted arch steel support;

[0015] The left hole inverted arch steel support is formed by connecting the left hole steel support segment 1 and the left hole steel support segment 2 in series;

[0016] The right hole inverted arch steel support is formed by connecting the right hole steel support segment 1 and the right hole steel support segment 2 in series;

[0017] The steel frame of the middle wall also includes a left hole steel support segment 2 and a right hole steel support segment 2; the left hole steel support segment 2 is connected to the left hole steel arch frame segment 2; the right hole steel support segment 2 is connected to the right hole steel arch frame segment 2.

[0018] Furthermore, grooves are arranged on both sides of the middle wall.

[0019] An initial support steel frame closed multi-arch tunnel, comprising a left tunnel, a right tunnel and a middle wall; the left tunnel comprises an outer layer of a left tunnel initial support steel frame and an inner layer of a left tunnel secondary lining along its radial direction, and the left tunnel initial support steel frame comprises a left tunnel steel arch frame adapted to the left tunnel at the top and a left tunnel inverted arch steel support at the bottom; the right tunnel comprises an outer layer of a right tunnel initial support steel frame and an inner layer of a right tunnel secondary lining along its radial direction, and the right tunnel initial support steel frame comprises a right tunnel steel arch frame adapted to the right tunnel at the top and a right tunnel inverted arch steel support at the bottom;

[0020] The two ends of the left hole steel arch frame are respectively connected to the left hole inverted arch steel support, and the left hole steel arch frame and the left hole inverted arch steel support are surrounded to form a closed loop adapted to the left hole; the left hole steel arch frame is formed by connecting the left hole steel arch frame segment 1 and the left hole steel arch frame segment 2 in series; the left hole inverted arch steel support is formed by connecting the left hole steel support segment 1 and the left hole steel support segment 2 in series;

[0021] The two ends of the right hole steel arch frame are respectively connected to the right hole inverted arch steel bracket, and the right hole steel arch frame and the right hole inverted arch steel bracket are surrounded to form a closed ring adapted to the right hole; the right hole steel arch frame is formed by connecting the right hole steel arch frame segment 1 and the right hole steel arch frame segment 2 in series; the right hole inverted arch steel bracket is formed by connecting the right hole steel bracket segment 1 and the right hole steel bracket segment 2 in series;

[0022] The middle wall is arranged between the outer wall of the secondary lining of the left hole and the outer wall of the secondary lining of the right hole, and is formed by an internal steel frame and cast-in-place concrete; the middle wall steel frame includes a left hole steel arch frame segment two, a right hole steel arch frame segment two, a left hole steel support segment two and a right hole steel support segment two; the left hole steel support segment two is connected to the left hole steel arch frame segment two; the right hole steel support segment two is connected to the right hole steel arch frame segment two; the left hole steel arch frame segment two is connected to the right hole steel arch frame segment two via transverse connecting steel bars.

[0023] The construction method of the initial support steel frame closed double-arch tunnel includes the following steps:

[0024] Step 1: Excavation of pilot hole in the middle wall;

[0025] Step 2: Construct the middle wall in the middle wall guide hole:

[0026] First, the left hole steel arch frame segment 2 and the right hole steel arch frame segment 2 are installed in the middle wall guide hole, and the adjacent left hole steel arch frame segments 2 are connected by longitudinal connecting steel bars along the longitudinal direction of the middle wall guide hole, and the adjacent right hole steel arch frame segments 2 are connected by longitudinal connecting steel bars;

[0027] Next, the left hole steel support segment 2 is connected to the left hole steel arch frame segment 2, and the right hole steel support segment 2 is connected to the right hole steel arch frame segment 2;

[0028] Then, the left tunnel steel arch frame segment 2 and the right tunnel steel arch frame segment 2 are connected by using transverse connecting steel bars;

[0029] Finally, pour the concrete;

[0030] Step 3: excavate the left tunnel, install the left tunnel steel arch frame segment 1, and splice the left tunnel steel arch frame segment 1 with the left tunnel steel arch frame segment 2;

[0031] The right tunnel is excavated, the right tunnel steel arch frame segment 1 is installed, and the right tunnel steel arch frame segment 1 is spliced ​​with the right tunnel steel arch frame segment 2;

[0032] Step 4: Construction of secondary lining of left tunnel. The secondary lining of left tunnel surrounds the initial support steel frame of left tunnel in a circle. Construction of secondary lining of right tunnel. The secondary lining of right tunnel surrounds the initial support steel frame of right tunnel in a circle.

[0033] The beneficial effects of the present invention are as follows: the middle wall of the multi-arch tunnel disclosed by the present invention utilizes the left-hole steel arch frame segment 2 and the right-hole steel arch frame segment 2 as components of the middle wall steel frame, so that the left-hole steel arch frame and the right-hole steel arch frame take into account the dual functions of initial support and the middle wall steel frame, and the left-hole steel arch frame and the right-hole steel arch frame do not need to be cut off when encountering the middle wall, thereby ensuring the integrity of the left-hole initial support and the right-hole initial support, eliminating the weak stress points at the connection between the left-hole steel arch frame and the right-hole steel arch frame and the middle wall, so that the force from the surrounding rock is directly transmitted to the base through the left-hole steel arch frame and the right-hole steel arch frame, thereby avoiding the problem of cracking and water leakage at the connection between the left-hole steel arch frame and the right-hole steel arch frame and the middle wall.

[0034] The initial support steel frame closed multi-arch tunnel disclosed by the present invention has a left tunnel steel arch frame segment 2 and a left tunnel steel bracket segment 2 constituting the middle wall steel frame, which also serve as a part of the left tunnel initial support steel frame, so that the left tunnel initial support steel frame is closed into a ring; the right tunnel steel arch frame segment 2 and the left tunnel steel bracket segment 2 constituting the middle wall steel frame also serve as a part of the right tunnel initial support steel frame, so that the right tunnel initial support steel frame is closed into a ring; the integrity of the initial support of the multi-arch tunnel is ensured, thereby improving the reliability of the initial support, significantly improving the stress performance of the connection between the initial support and the middle wall, ensuring safety, and reducing the probability of disease occurrence. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is the cross-section of the double-arch tunnel;

[0036] Figure 2 This is a schematic diagram of the middle wall of a multi-arch tunnel;

[0037] Figure 3 This is the node diagram of the connection between the middle wall and the initial support steel arch frame of the multi-arch tunnel;

[0038] Figure 4 This is the node diagram of the middle wall foot.

[0039] In the figure, the left tunnel initial support steel frame 1, the left tunnel steel arch frame 11, the left tunnel steel arch frame segment one 111, the left tunnel steel arch frame segment two 112, the left tunnel inverted arch steel bracket 12, the left tunnel steel bracket segment one 121, the left tunnel steel bracket segment two 122, the right tunnel initial support steel frame 2, the right tunnel steel arch frame 21, the right tunnel steel arch frame segment one 211, the right tunnel steel arch frame segment two 212, the right tunnel inverted arch steel bracket 22, the right tunnel steel bracket segment one 221, the right tunnel steel bracket segment two 222, the middle wall 3, the transverse connecting steel bars 31, the groove 32, the left tunnel secondary lining 4, the right tunnel secondary lining 5, the embedded bolts 61, the embedded steel plate 62, the connecting steel plate one 63, the wall foot support 71, and the connecting steel plate two 72. DETAILED DESCRIPTION

[0040] The present invention will be further described below in conjunction with the accompanying drawings:

[0041] The middle wall of the multi-arch tunnel, such as Figure 2 As shown, the initial support steel frame of the multi-arch tunnel includes a left tunnel steel arch frame 11 and a right tunnel steel arch frame 21; the left tunnel steel arch frame 11 extends from the outer side wall of the left tunnel along the left tunnel circumferential direction to the inner side wall of the left tunnel, and is formed by connecting the left tunnel steel arch frame segment 1 111 and the left tunnel steel arch frame segment 2 112 in series along the left tunnel circumferential direction; the right tunnel steel arch frame 21 extends from the outer side wall of the right tunnel along the right tunnel circumferential direction to the inner side wall of the right tunnel, and is formed by connecting the right tunnel steel arch frame segment 1 211 and the right tunnel steel arch frame segment 2 212 in series along the right tunnel circumferential direction;

[0042] The steel frame inside the middle wall includes a left hole steel arch frame segment 112, a right hole steel arch frame segment 212 and a transverse connecting steel bar 31, one end of the transverse connecting steel bar 31 is connected to the left hole steel arch frame segment 112, and the other end is connected to the right hole steel arch frame segment 212.

[0043] The middle wall of the multi-arch tunnel disclosed in the present invention utilizes the left-hole steel arch frame segment 112 and the right-hole steel arch frame segment 212 as components of the middle wall steel frame, that is, the left-hole steel arch frame 11 and the right-hole steel arch frame 21 take into account the dual functions of initial support and the middle wall steel frame, so that the left-hole steel arch frame 11 and the right-hole steel arch frame 21 do not need to be cut off when encountering the middle wall, which is beneficial to ensuring the integrity of the left-hole initial support and the right-hole initial support, eliminating the weak stress points where the left-hole steel arch frame 11 and the right-hole steel arch frame 21 are connected to the middle wall, so that the force from the surrounding rock is directly transmitted to the base through the left-hole steel arch frame 11 and the right-hole steel arch frame 21, thereby avoiding the problem of cracking and water leakage at the connection between the left-hole steel arch frame 11 and the right-hole steel arch frame 21 and the middle wall.

[0044] In order to facilitate the construction of the middle wall, the left tunnel steel arch frame segment 2 112 is connected with the left tunnel steel arch frame segment 1 111 to form an integral left tunnel initial support steel frame. Figure 3As shown, an embedded steel plate 62 is fixedly connected to the top of the left hole steel arch frame segment 2 112, and an embedded bolt 61 is installed on the embedded steel plate 62; a connecting steel plate 1 63 is fixedly connected to one end of the left hole steel arch frame segment 1 111 adjacent to the left hole steel arch frame segment 2 112, and the embedded steel plate 62 and the connecting steel plate 1 63 are connected via the embedded bolt 61 and the nut;

[0045] Similarly, an embedded steel plate 62 is fixedly connected to the top of the right hole steel arch frame segment 212, and an embedded bolt 61 is installed on the embedded steel plate 62; a connecting steel plate 1 63 is fixedly connected to the end of the right hole steel arch frame segment 1 112 adjacent to the right hole steel arch frame segment 212, and the embedded steel plate 62 and the connecting steel plate 1 63 are connected via embedded bolts 61 and nuts.

[0046] In order to fix the left tunnel steel arch frame segment 2 112, Figure 4 As shown, the bottom end of the left hole steel arch frame segment 212 is connected to the wall foot support 71; in order to fix the right hole steel arch frame segment 212, the bottom end of the right hole steel arch frame segment 212 is connected to the wall foot support 71.

[0047] In order to reduce the stress level at the arch foot, preferably, the wall foot support 71 is a channel steel with an opening facing upward; a second connecting steel plate 72 is fixedly connected to the bottom end of the second left hole steel arch frame segment 112; the second connecting steel plate 72 is arranged in the groove of the channel steel and connected to the waist of the channel steel through connecting bolts;

[0048] A second connecting steel plate 72 is fixedly connected to the bottom end of the second right hole steel arch frame segment 212; the second connecting steel plate 72 is arranged in the groove of the channel steel and is connected to the waist of the channel steel through connecting bolts.

[0049] The setting of channel steel increases the contact area between the arch foot of the left tunnel steel arch frame segment 112 and the foundation, thereby reducing the stress level at the arch foot and further reducing the settlement of the structure.

[0050] For the inverted arch tunnel, preferably, the initial support steel frame of the multi-arch tunnel also includes a left hole inverted arch steel support 12 and a right hole inverted arch steel support 22; the left hole inverted arch steel support 12 is formed by connecting the left hole steel support segment 1 121 and the left hole steel support segment 2 122 in series; the right hole inverted arch steel support 22 is formed by connecting the right hole steel support segment 1 221 and the right hole steel support segment 2 222 in series; the steel frame of the middle wall also includes the left hole steel support segment 2 122 and the right hole steel support segment 2 222; the left hole steel support segment 2 122 is connected to the left hole steel arch frame segment 2 112; the right hole steel support segment 2 222 is connected to the right hole steel arch frame segment 2 212.

[0051] This structure can ensure that the initial support steel frames of the left and right tunnels of the tunnel form a closed ring, greatly improving the overall stress performance and reducing the safety performance of the connection between the initial support of the left tunnel, the initial support of the right tunnel and the middle wall.

[0052] Preferably, grooves 32 are provided on both sides of the middle wall 3. The grooves 32 are used to arrange the longitudinal drain pipes.

[0053] Initial support steel frame closed double arch tunnel, such as Figure 1 As shown, it includes a left hole, a right hole and a middle wall 3; the left hole includes an outer left hole initial support steel frame 1 and an inner left hole secondary lining 4 along its radial direction, and the left hole initial support steel frame 1 includes a left hole steel arch frame 11 adapted to the left hole at the top and a left hole inverted arch steel support 12 at the bottom; the right hole includes an outer right hole initial support steel frame 2 and an inner right hole secondary lining 5 along its radial direction, and the right hole initial support steel frame 2 includes a right hole steel arch frame 21 adapted to the right hole at the top and a right hole inverted arch steel support 22 at the bottom;

[0054] The two ends of the left hole steel arch frame 11 are respectively connected to the left hole inverted arch steel support 12, and the left hole steel arch frame 11 and the left hole inverted arch steel support 12 are surrounded to form a closed loop adapted to the left hole; the left hole steel arch frame 11 is formed by connecting the left hole steel arch frame segment 1 111 and the left hole steel arch frame segment 2 112 in series; the left hole inverted arch steel support 12 is formed by connecting the left hole steel support segment 1 121 and the left hole steel support segment 2 122 in series;

[0055] The two ends of the right hole steel arch frame 21 are respectively connected to the right hole inverted arch steel support 22, and the right hole steel arch frame 21 and the right hole inverted arch steel support 22 are surrounded to form a closed loop adapted to the right hole; the right hole steel arch frame 21 is formed by connecting the right hole steel arch frame segment 1 211 and the right hole steel arch frame segment 212 in series; the right hole inverted arch steel support 22 is formed by connecting the right hole steel support segment 1 221 and the right hole steel support segment 2 222 in series;

[0056] The middle wall 3 is arranged between the outer wall of the left hole secondary lining 4 and the outer wall of the right hole secondary lining 5, and is formed by an internal steel frame and cast-in-place concrete; the middle wall 3 steel frame includes a left hole steel arch frame segment 112, a right hole steel arch frame segment 212, a left hole steel support segment 122 and a right hole steel support segment 222; the left hole steel support segment 122 is connected to the left hole steel arch frame segment 112; the right hole steel support segment 222 is connected to the right hole steel arch frame segment 212; the left hole steel arch frame segment 112 is connected to the right hole steel arch frame segment 212 via a transverse connecting steel bar 31.

[0057] The initial support steel frame closed multi-arch tunnel disclosed by the present invention has a left tunnel steel arch frame segment 2 112 and a left tunnel steel support segment 2 122 constituting the middle wall 3 steel frame and also serving as a part of the left tunnel initial support steel frame 1, so that the left tunnel initial support steel frame 1 is closed into a ring; the right tunnel steel arch frame segment 212 and the left tunnel steel support segment 222 constituting the middle wall 3 steel frame and also serving as a part of the right tunnel initial support steel frame 2, so that the right tunnel initial support steel frame 2 is closed into a ring; the integrity of the initial support of the multi-arch tunnel is ensured, thereby improving the reliability of the initial support, significantly improving the stress performance of the connection between the initial support and the middle wall, ensuring safety, and reducing the probability of disease occurrence.

[0058] The construction method of the above-mentioned initial support steel frame closed multi-arch tunnel comprises the following steps:

[0059] Step 1: Excavation of pilot hole in the middle wall;

[0060] Step 2: Construct the middle wall 3 in the middle wall guide hole:

[0061] First, the left hole steel arch frame segment 2 112 and the right hole steel arch frame segment 212 are installed in the middle wall guide hole, and the adjacent left hole steel arch frame segments 2 112 are connected by longitudinal connecting steel bars along the longitudinal direction of the middle wall guide hole, and the adjacent right hole steel arch frame segments 2 212 are connected by longitudinal connecting steel bars;

[0062] Next, the left hole steel support segment 2 122 is connected to the left hole steel arch frame segment 2 112, and the right hole steel support segment 222 is connected to the right hole steel arch frame segment 212;

[0063] Then, the left hole steel arch frame segment 2 112 and the right hole steel arch frame segment 2 212 are connected by using the transverse connecting steel bar 31;

[0064] Finally, pour the concrete;

[0065] Step 3: excavate the left tunnel, install the left tunnel steel arch frame segment 1 111, and splice the left tunnel steel arch frame segment 1 111 with the left tunnel steel arch frame segment 2 112;

[0066] The right hole is excavated, and the right hole steel arch frame segment 1 211 is installed, and the right hole steel arch frame segment 1 211 and the right hole steel arch frame segment 2 212 are spliced ​​together;

[0067] Step 4: Construction of secondary lining 4 of the left tunnel; construction of secondary lining 5 of the right tunnel.

Claims

1. An initial support steel frame closed multi-arch tunnel, comprising a left tunnel, a right tunnel and a middle wall (3); the left tunnel comprises an outer layer of a left tunnel initial support steel frame (1) and an inner layer of a left tunnel secondary lining (4) along its radial direction, the left tunnel initial support steel frame (1) comprising a left tunnel steel arch frame (11) adapted to the left tunnel at the top and a left tunnel inverted arch steel support (12) at the bottom; the right tunnel comprises an outer layer of a right tunnel initial support steel frame (2) and an inner layer of a right tunnel secondary lining (5) along its radial direction, the right tunnel initial support steel frame (2) comprising a right tunnel steel arch frame (21) adapted to the right tunnel at the top and a right tunnel inverted arch steel support (22) at the bottom; Features: The two ends of the left hole steel arch frame (11) are respectively connected to the left hole inverted arch steel support (12), and the left hole steel arch frame (11) and the left hole inverted arch steel support (12) are surrounded to form a closed loop adapted to the left hole; the left hole steel arch frame (11) is formed by connecting the left hole steel arch frame segment 1 (111) and the left hole steel arch frame segment 2 (112) in series; the left hole inverted arch steel support (12) is formed by connecting the left hole steel support segment 1 (121) and the left hole steel support segment 2 (122) in series; The two ends of the right hole steel arch frame (21) are respectively connected to the right hole inverted arch steel support (22), and the right hole steel arch frame (21) and the right hole inverted arch steel support (22) are surrounded to form a closed loop adapted to the right hole; the right hole steel arch frame (21) is formed by connecting the right hole steel arch frame segment 1 (211) and the right hole steel arch frame segment 2 (212) in series; the right hole inverted arch steel support (22) is formed by connecting the right hole steel support segment 1 (221) and the right hole steel support segment 2 (222) in series; The middle wall (3) is arranged between the outer wall of the left hole secondary lining (4) and the outer wall of the right hole secondary lining (5), and is formed by an internal steel frame and cast-in-place concrete; the steel frame of the middle wall (3) includes a left hole steel arch frame segment 2 (112), a right hole steel arch frame segment 2 (212), a left hole steel support segment 2 (122) and a right hole steel support segment 2 (222); the left hole steel support segment 2 (122) is connected to the left hole steel arch frame segment 2 (112); the right hole steel support segment 2 (222) is connected to the right hole steel arch frame segment 2 (212); the left hole steel arch frame segment 2 (112) is connected to the right hole steel arch frame segment 2 (212) via a transverse connecting steel bar (31).

2. The initial support steel frame closed multi-arch tunnel according to claim 1, characterized in that: A pre-buried steel plate (62) is fixedly connected to the top of the left hole steel arch frame segment 2 (112), and a pre-buried bolt (61) is installed on the pre-buried steel plate (62); a connecting steel plate 1 (63) is fixedly connected to the end of the left hole steel arch frame segment 1 (111) adjacent to the left hole steel arch frame segment 2 (112), and the pre-buried steel plate (62) and the connecting steel plate 1 (63) are connected via the pre-buried bolt (61) and the nut; An embedded steel plate (62) is fixedly connected to the top of the right hole steel arch frame segment 2 (212), and an embedded bolt (61) is installed on the embedded steel plate (62); a connecting steel plate 1 (63) is fixedly connected to the end of the right hole steel arch frame segment 1 (112) adjacent to the right hole steel arch frame segment 2 (212), and the embedded steel plate (62) and the connecting steel plate 1 (63) are connected via embedded bolts (61) and nuts.

3. The initial support steel frame closed multi-arch tunnel according to claim 1 or 2, characterized in that: The bottom end of the left hole steel arch frame segment 2 (112) is connected to the wall foot support (71); the bottom end of the right hole steel arch frame segment 2 (212) is connected to the wall foot support (71).

4. The initial support steel frame closed multi-arch tunnel as claimed in claim 3, characterized in that: The wall foot support (71) is a channel steel with an opening facing upward; A second connecting steel plate (72) is fixedly connected to the bottom end of the second left hole steel arch frame segment (112); the second connecting steel plate (72) is arranged in the groove of the channel steel and connected to the waist of the channel steel through connecting bolts; A second connecting steel plate (72) is fixedly connected to the bottom end of the second right hole steel arch frame segment (212); the second connecting steel plate (72) is arranged in the groove of the channel steel and is connected to the waist of the channel steel through connecting bolts.

5. The initial support steel frame closed multi-arch tunnel according to claim 1 or 2, characterized in that: Grooves (32) are provided on both sides of the middle wall (3).

6. The construction method of the initial support steel frame closed multi-arch tunnel as claimed in claim 1, characterized in that: The following steps are involved: Step 1: Excavation of pilot hole in the middle wall; Step 2: Construct the middle wall in the middle wall guide hole (3): First, a left hole steel arch frame segment 2 (112) and a right hole steel arch frame segment 2 (212) are installed in the middle wall guide hole, and along the longitudinal direction of the middle wall guide hole, the adjacent left hole steel arch frame segments 2 (112) are connected by longitudinal connecting steel bars, and the adjacent right hole steel arch frame segments 2 (212) are connected by longitudinal connecting steel bars; Next, the left hole steel support segment 2 (122) is connected to the left hole steel arch frame segment 2 (112), and the right hole steel support segment 2 (222) is connected to the right hole steel arch frame segment 2 (212); Then, the left hole steel arch frame segment 2 (112) and the right hole steel arch frame segment 2 (212) are connected by using transverse connecting steel bars (31); Finally, pour the concrete; Step 3: excavate the left tunnel, install the left tunnel steel arch frame segment 1 (111), and splice the left tunnel steel arch frame segment 1 (111) and the left tunnel steel arch frame segment 2 (112) together; The right tunnel is excavated, the right tunnel steel arch frame segment 1 (211) is installed, and the right tunnel steel arch frame segment 1 (211) is spliced ​​with the right tunnel steel arch frame segment 2 (212); Step 4: Construction of the secondary lining of the left tunnel (4); construction of the secondary lining of the right tunnel (5).

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