An initial support structure for a multi-arch tunnel without a central guide and its construction method

Abstract

The present invention provides a primary support structure for a tunnel without a central guide arch and its construction method. The structure comprises a leading tunnel support structure and a trailing tunnel support structure equipped with steel arch frame units. The steel arch frame units comprise cross-arranged steel arch frames, with the leading and trailing tunnel steel arch frames being staggered and connected. A conduit device and a shock-absorbing device are installed between the webs of the steel arch frames within the same tunnel. The conduit device comprises transverse and longitudinal conduits. This invention enhances the stability and deformation resistance of the tunnel's primary support arch frames, prevents the formation of cavities within the primary support, and improves the seismic resistance of the structural system.

Description

Technical Field

[0001] The present invention belongs to the technical field of tunnel initial support, and in particular relates to an initial support structure for a tunnel without a central guide arch and a construction method thereof. Background Art

[0002] Traditional multi-arch tunnel construction typically begins with the excavation of a central pilot tunnel, followed by the construction of a shared central wall. The two sides are then gradually expanded, and the arch sections of the two chambers are then joined together on the central wall. This type of multi-arch tunnel construction involves numerous steps and is costly. A non-central pilot multi-arch tunnel is a relatively new type of multi-arch tunnel structure. This structure utilizes separate tunnels without a central pilot tunnel. Unlike traditional multi-arch tunnel designs, this construction method does not incorporate a shared central wall. Instead, the steel arch frame of the trailing tunnel is directly joined to the primary steel arch frame of the leading tunnel for spraying. This reduces the number of construction steps, reduces costs, and holds broad application prospects.

[0003] However, due to the lack of a central pilot tunnel and the fact that the steel arch frame of the subsequent tunnel is directly attached to the steel arch frame of the leading tunnel, existing technologies for tunnels without a central pilot tunnel suffer from relatively poor initial support structure stability. Due to the stress changes in the surrounding rock caused by the subsequent tunnel excavation, resulting in a biasing effect, and the vibration effects of the subsequent tunnel blasting, the initial support structure is prone to significant deformation, causing cracks in the secondary lining of the leading tunnel. Furthermore, this initial support structure has poor seismic resistance, and the shotcrete process used in the initial tunnel support process has the problem of internal voids in the initial support. Summary of the Invention

[0004] The purpose of the present invention is to provide an initial support structure for a tunnel without a central guide arch and a construction method thereof, so as to solve the problems of poor integrity and deformation resistance, poor seismic effect and internal voids of the initial support structure in the prior art.

[0005] In order to achieve the above-mentioned purpose, the present invention provides an initial support structure for a non-central guide continuous arch tunnel and a construction method thereof, wherein the initial support structure for a non-central guide continuous arch tunnel comprises: a leading hole support structure 1 and a trailing hole support structure 2, wherein the leading hole support structure 1 is sequentially provided with a plurality of first steel arch frame units 11 along the axial direction of the tunnel, wherein the first steel arch frame unit 11 comprises two cross-arranged first steel arch frames, wherein the first steel arch frame comprises a first segment 111, a second segment 112, a vault segment 113, a third segment 114, a first segment 115, a second segment 116, a first segment 117, a second segment 118, a first segment 119, a first segment 1111, a second segment 112, a vault segment 113, a third segment 114, a first segment 115, a first segment 116, a first segment 117, a first segment 118, a first segment 119, a first segment 1111, a second segment 112, a vault segment 114, a first segment 115, a first segment 116, a first segment 117, a first segment 118, a first segment 119, a first segment 119, a first segment 119, a first segment 119, a first segment 111 The fourth segment 115 and the fifth segment 117 are further provided with an inverted arch segment 116 at the bottom of the first steel arch frame. The two cross-arranged first steel arch frames are provided with cross nodes at the highest point of the arch crown segment 113 and the lowest point of the inverted arch segment 116. The arch frames are gradually opened downward and upward from the cross nodes, respectively, and reach the maximum opening distance at the arch foot. The arch crown segment 113 and the inverted arch segment 116 are common segments of the two cross-arranged first steel arch frames in the same first steel arch frame unit 11. The two ends of the inverted arch segment 116 are respectively connected to the first segment 111 and the fifth segment 117;

[0006] The back tunnel support structure 2 is sequentially provided with a plurality of second steel arch frame units 12 along the axial direction of the tunnel. The second steel arch frame unit 12 includes two cross-arranged second steel arch frames. The second steel arch frame includes a first segment 111, a second segment 112, a crown segment 113, a third segment 114 and a fourth segment 115 sequentially connected along the circumferential direction of the tunnel from the outside to the inside of the back tunnel. An inverted arch segment 116 is further provided at the bottom of the second steel arch frame. The two cross-arranged second steel arch frames are at the highest point of the crown segment 113 and the A cross node is provided at the lowest point of the inverted arch segment 116, and the arch frame gradually opens downward and upward from the cross node, reaching the maximum opening distance at the arch foot; the arch crown segment 113 and the inverted arch segment 116 are common segments of two steel arch frames in the same second steel arch frame unit 12, and the two ends of the inverted arch segment 116 are respectively connected to the first segment 111 and the fifth segment 117; the fifth segment 117 is provided with two steel sections, and the fifth segment 117 is a common segment of the steel arch frames of the first steel arch frame unit 11 and the second steel arch frame unit 12.

[0007] The first steel arch frame unit 11 in the leading tunnel support structure 1 and the second steel arch frame unit 12 in the trailing tunnel support structure 2 are respectively connected in an interlaced manner, and the two steel arch frames of the first steel arch frame unit 11 are respectively connected to the nearest one of the two adjacent second steel arch frame units 12;

[0008] A conduit device 3 is respectively provided between adjacent steel arch frames of the first steel arch frame unit 11 and between adjacent steel arch frames of the second steel arch frame unit 12, and the conduit device 3 includes a plurality of transverse conduits 31 and a plurality of longitudinal conduits 32. The transverse conduits 31 are arranged on both sides of the steel web along the axial direction of the tunnel, and the transverse conduits 31 pass through the steel arch frame web and are fixedly connected to the steel web; the longitudinal conduits 32 are radially arranged along the radial direction of the tunnel, one end of the longitudinal conduit 32 is fixedly connected to the transverse conduit 31, and the other end is conical and inserted into the surrounding rock; a plurality of grouting holes 34 are provided on the transverse conduits 31 and the longitudinal conduits 32.

[0009] In a specific embodiment, a limiting plate 36 is provided at the connection between the transverse duct 31 and the steel web, and a fixed support 35 is provided at the connection between the longitudinal duct 32 and the transverse duct 31. The transverse duct 31 passes through one end of the fixed support 35 and is fixedly connected to the fixed support 35, and the longitudinal duct 32 passes through the other end of the fixed support 35 and is fixed on the fixed support 35.

[0010] In a specific embodiment, the conduit device 3 further includes a threaded sleeve 33 , and threads matching the threaded sleeve 33 are provided at both ends of the transverse conduit 31 , and the transverse conduits 31 are connected together through the threaded sleeve 33 .

[0011] In a specific embodiment, the outer diameter of the transverse conduit 31 is 32-45 mm, and the wall thickness is 6-12 mm; the outer diameter of the longitudinal conduit 32 is 25-35 mm, and the wall thickness is 2-5 mm.

[0012] In a specific embodiment, the first joint 6 is used at the connection between the inverted arch segment 116 and the first segment 111 and the fifth segment 117 respectively, and the second joint 5 is used at the connection between the remaining segments; half of the steel section of the inverted arch segment 116 in the first joint 6 extends forward, and a corresponding shape connecting plate is set along the edge of the web, the corresponding positions of the steel flanges of the first segment 111 and the fifth segment 117 are recessed inward, and the shape and size of the recess match the extended part of the steel of the inverted arch segment 116, a connecting plate is set along the edge of the web, and the connecting plate at the first joint 6 is connected by a joint bolt 118; all the second joints 5 include a Z-shaped joint section, the two inner angles of the Z-shaped joint section are both right angles, a connecting plate is set along the edge of the cross-section steel web, and the connecting plate at the second joint 5 is connected by a joint bolt 118.

[0013] In a specific embodiment, the crown segment 113 and the inverted arch segment 116 are integrally cast structures.

[0014] In a specific embodiment, a shock-absorbing device 4 is further provided along the axial direction of the tunnel between the steel webs of the first steel arch frame unit 11 and the second steel arch frame unit 12, and the shock-absorbing device 4 and the transverse duct 31 are alternately provided. The shock-absorbing device 4 includes a shell 42 and support rods 47 provided on both sides of the shell 42. One end of the support rod 47 is connected to the shell 42, and the other end is connected to the steel web. A sealed cavity is formed between the shell 42 and the support rods 47 on both sides. A partition 43 is also provided in the sealed cavity, which is in close contact with the shell 42 and can slide horizontally. A plurality of flow holes 46 are provided on the partition 43, and a spring 44 is also provided between the two ends of the partition 43 and the support rods 47. The sealed cavity is filled with a viscous liquid 41.

[0015] In a specific embodiment, the support rod 47 is provided with a connecting plate 45 at one end connected to the steel web. The connecting plate 45 is connected to the steel web via bolts. The support rod 47 is a round tube.

[0016] The construction method of the initial support structure of the non-central guide multi-arch tunnel includes:

[0017] The first step is to excavate the upper steps of the pilot hole. After the excavation of the upper steps of the pilot hole is completed, the arch segment 113 and the third segment 114 are installed first. Then, the transverse guide tube 31 is installed between adjacent steel arch frames. According to the position of the transverse guide tube 31 where the longitudinal guide tube 32 is required to be installed, holes are drilled in the surrounding rock. The longitudinal guide tube 32 is inserted into the surrounding rock and fixed. Grouting is injected into the surrounding rock through the longitudinal guide tube 31, and concrete is sprayed on the installed part.

[0018] The second step is to excavate the steps in the pilot hole, and install the second segment 112 and the fourth segment 115 on both sides of the pilot hole respectively. The upper end of the second segment 112 is connected to the lower end of the arch segment 113, and the upper end of the fourth segment 115 is connected to the lower end of the third segment 114; install the transverse guide tube 31 between adjacent steel arch frames, drill holes in the surrounding rock according to the positions of the transverse guide tube 31 where the longitudinal guide tube 32 needs to be set, insert the longitudinal guide tube 32 into the surrounding rock and fix it, grouting is injected into the surrounding rock through the longitudinal guide tube 31, and concrete is sprayed on the installed part;

[0019] The third step is to excavate the lower steps of the advance tunnel, and install the first segment 111 and the fifth segment 117 on both sides respectively. The upper end of the first segment 111 is connected to the lower end of the second segment 112, and the upper end of the fifth segment 117 is connected to the lower end of the fourth segment 115; install transverse conduits 31 between adjacent steel arch frames, wherein two rows of transverse conduits 31 are installed in the fifth segment 117, and holes are drilled in the surrounding rock according to the positions of the transverse conduits 31 where the longitudinal conduits 32 need to be installed, and the longitudinal conduits 32 are inserted into the surrounding rock and fixed, and grouting is injected into the surrounding rock through the longitudinal conduits 31, and concrete is sprayed on the installed part;

[0020] The fourth step is to excavate the inverted arch section 116 after excavating the advance tunnel. The two sides of the inverted arch section 116 are connected to the lower ends of the first section 111 and the fifth section 117 respectively, and concrete is sprayed on the installed part.

[0021] Step 5: After excavation, the tunnel is stepped up. After the excavation of the upper steps is completed, the arch segment 113 and the third segment 114 are installed. Then, the transverse guide tube 31 is installed between adjacent steel arch frames. Holes are drilled in the surrounding rock at the positions where the longitudinal guide tubes 32 are required to be installed on the transverse guide tube 31. The longitudinal guide tubes 32 are inserted into the surrounding rock and fixed. Grouting is injected into the surrounding rock through the longitudinal guide tube 31, and concrete is sprayed on the installed part.

[0022] Step 6: Excavate the steps in the rear tunnel, install the second segment 112 and the fourth segment 115 on both sides of the rear tunnel, connect the upper end of the second segment 112 to the lower end of the arch segment 113, connect the upper end of the fourth segment 115 to the lower end of the third segment 114, and connect the lower end of the fourth segment 115 to the upper end of the fifth segment 117 of the leading tunnel; install the transverse guide tube 31 between adjacent steel arch frames, drill holes in the surrounding rock at the positions where the longitudinal guide tube 32 needs to be set on the transverse guide tube 31, insert the longitudinal guide tube 32 into the surrounding rock and fix it, inject grout into the surrounding rock through the longitudinal guide tube 31, and spray concrete on the installed part;

[0023] Step 7: Excavate the lower steps of the rear tunnel and install the first segment 111 on the outer side of the rear tunnel. The upper end of the first segment 111 is connected to the lower end of the second segment 112. Install the transverse guide tube 31 between adjacent steel arches. Drill holes in the surrounding rock at the locations where the longitudinal guide tubes 32 are to be installed on the transverse guide tube 31. Insert the longitudinal guide tube 32 into the surrounding rock and fix it. Grouting is injected into the surrounding rock through the longitudinal guide tube 31. Concrete is sprayed on the installed part.

[0024] In the eighth step, after excavating the back tunnel, the inverted arch segment 116 is installed. The two sides of the inverted arch segment 116 are respectively connected to the lower ends of the first segment 111 and the fifth segment 117, and concrete is sprayed on the installed part.

[0025] In the ninth step, after the initial support structure of the tunnel is completed, grouting is injected into the interior of the initial support through the transverse guide tube 31 to fill the internal cavities and cracks.

[0026] In a specific embodiment, during the construction process of the first, second, third, fifth, sixth and seventh steps, after the installation of the transverse duct 31 and the longitudinal duct 32 is completed and the longitudinal duct 32 is grouted, the shock absorbing device 4 is installed, and finally concrete is sprayed on the installed part, and after the initial support structure is installed, grouting is finally performed through the transverse duct 31.

[0027] The beneficial effects of the present invention include at least:

[0028] In the embodiment disclosed herein, two adjacent steel arch frames are cross-arranged, and the steel arch frames of the leading tunnel and the rear tunnel are staggered and connected, so that the stability and deformation resistance of the arch frames are enhanced; the transverse connection area of the first joint and the second joint mainly bears pressure, and the longitudinal connection area mainly bears shear force. The use of this joint structure can increase the connection area of the two steel sections and improve the shear and bending resistance of the connection area; the fifth segment steel section is composed of two steel sections, and the upper ends thereof are respectively connected to the fourth segment of the leading tunnel steel arch frame and the fourth segment of the rear tunnel steel arch frame, so that the arch frame of the rear tunnel can form a ring alone, reducing the deformation of the leading tunnel arch frame and improving the stability of the structure.

[0029] In the embodiment disclosed herein, the conduit device is composed of a transverse conduit and a longitudinal conduit, which are connected by a fixed support to form a coordinated force system, thereby enhancing the stability and deformation resistance of the initial support structure system; the transverse conduit is distributed between the steel sections of the steel arch frame to play a role of transverse fixation, and the longitudinal conduit can reinforce the surrounding rock after grouting, and through the connection with the transverse conduit, it plays a role of fixing the support structure and reducing settlement deformation; after the initial support of the tunnel is completed, grouting is injected into the interior of the initial support through the transverse conduit to fill the internal cavities and cracks to prevent the occurrence of cavities inside the initial support.

[0030] In the disclosed embodiment, the shock absorbing device absorbs the energy of vibration by driving the spring to expand and contract through the reciprocating motion of the partition in the sealed cavity. At the same time, the reciprocating motion of the partition forces the viscous liquid to flow back and forth in the cavities on both sides of the partition through the flow holes provided on the partition to consume the energy of vibration and improve the seismic resistance of the structural system. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic structural perspective diagram of a specific embodiment of the present invention;

[0032] Figure 2 A top view of a specific embodiment of the present invention;

[0033] Figure 3 A front view of the first steel arch frame of the pilot tunnel according to a specific embodiment of the present invention;

[0034] Figure 4 A front view of the second steel arch frame of the rear tunnel according to a specific embodiment of the present invention;

[0035] Figure 5 A front view of the first steel arch frame of the leading tunnel and a front view of the second steel arch frame of the trailing tunnel after installation according to a specific embodiment of the present invention;

[0036] Figure 6 A structural diagram of a dome segment according to a specific embodiment of the present invention;

[0037] Figure 7A structural diagram of an inverted arch segment according to a specific embodiment of the present invention;

[0038] Figure 8 A diagram of the second joint structure of a specific embodiment of the invention;

[0039] Figure 9 A structural diagram of a first joint according to a specific embodiment of the invention;

[0040] Figure 10 A schematic diagram of the installation of a catheter device according to a specific embodiment of the invention;

[0041] Figure 11 A schematic diagram of the installation of a transverse conduit according to a specific embodiment of the invention;

[0042] Figure 12 A schematic diagram of the installation of a shock absorbing device according to a specific embodiment of the invention;

[0043] Figure 13 A schematic cross-sectional view of a shock absorbing device according to a specific embodiment of the invention;

[0044] Figure 14 A schematic diagram of a partition structure of a specific embodiment of the invention;

[0045] Figure 15 A displacement cloud diagram of the surrounding rock of a structure numerically calculated in the prior art;

[0046] Figure 16 A numerically calculated displacement cloud diagram of the surrounding rock of a structure according to a specific embodiment of the present invention;

[0047] Figure 17 A numerical calculation displacement cloud diagram of a structural steel arch frame of a structure in the prior art;

[0048] Figure 18 This is a numerically calculated displacement cloud diagram of a steel arch frame according to a specific embodiment of the present invention.

[0049] Description of reference numerals:

[0050]

[0051] DETAILED DESCRIPTION

[0052] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure and are not used to limit the present invention.

[0053] Please refer to Figures 1 to 14The present invention provides an initial support structure for a non-central guide continuous arch tunnel and a construction method thereof, comprising a leading tunnel support structure 1 and a trailing tunnel support structure 2, wherein the leading tunnel support structure 1 is sequentially provided with a plurality of first steel arch frame units 11 along the axial direction of the tunnel, wherein the first steel arch frame unit 11 comprises two cross-arranged first steel arch frames, wherein the first steel arch frame comprises a first segment 111, a second segment 112, a crown segment 113, a third segment 114, a fourth segment 115 and a fifth segment 117 connected in sequence along the circumferential direction of the tunnel and from the outside to the inside of the leading tunnel, and an inverted arch segment 116 is further provided at the bottom of the first steel arch frame. The two cross-arranged first steel arch frames are provided with cross nodes at the highest point of the arch crown segment 113 and the lowest point of the inverted arch segment 116. The arch frames are gradually opened downward and upward from the cross nodes, reaching the maximum opening distance at the arch foot. The maximum opening distance of the cross-arranged steel arch frames or the distance between the two closest arch feet of two adjacent cross-arranged steel arch frames is set according to the surrounding rock conditions. The arch crown segment 113 and the inverted arch segment 116 are common segments of the two cross-arranged first steel arch frames in the same first steel arch frame unit 11. The two ends of the inverted arch segment 116 are respectively connected to the first segment 111 and the fifth segment 117.

[0054] The back tunnel support structure 2 is sequentially provided with a plurality of second steel arch frame units 12 along the axial direction of the tunnel, and the second steel arch frame unit 12 includes two cross-arranged second steel arch frames, and the second steel arch frame includes a first segment 111, a second segment 112, a crown segment 113, a third segment 114 and a fourth segment 115 sequentially connected along the circumferential direction of the tunnel from the outside to the inside of the back tunnel, and an inverted arch segment 116 is further provided at the bottom of the second steel arch frame. The two cross-arranged second steel arch frames are provided with cross nodes at the highest point of the crown segment 113 and the lowest point of the inverted arch segment 116, and the arch frames are gradually opened downward and upward from the cross nodes respectively. , reaching the maximum opening distance at the arch foot; the arch crown segment 113 and the inverted arch segment 116 are common segments of two steel arch frames in the same second steel arch frame unit 12, and the two ends of the inverted arch segment 116 are respectively connected to the first segment 111 and the fifth segment 117 of the leading tunnel, which can make the steel arch frame of the rear tunnel form a ring independently, reduce the deformation of the steel arch frame of the leading tunnel, and improve the stability of the structure; the fifth segment 117 is a steel frame with two wings connected, which can be connected by welding, riveting and other processes. The two connected steel frames can withstand greater pressure. The fifth segment 117 is a common segment of the steel arch frames of the first steel arch frame unit 11 and the second steel arch frame unit 12.

[0055] The first steel arch frame unit 11 in the advance tunnel support structure 1 and the second steel arch frame unit 12 in the rear tunnel support structure 2 are respectively connected in an interlaced manner, and the two steel arch frames of the first steel arch frame unit 11 are respectively connected to the nearest steel arch frames of the two adjacent second steel arch frame units 12; through the cross placement and interlaced connection of the steel arch frames, the stability and deformation resistance of the arch frames are enhanced.

[0056] A conduit device 3 is respectively provided between adjacent steel arches of the first steel arch unit 11 and between adjacent steel arches of the second steel arch unit 12. The conduit device 3 includes a plurality of transverse conduits 31 and a plurality of longitudinal conduits 32. The transverse conduits 31 are arranged on both sides of the steel web along the axial direction of the tunnel. The transverse conduits 31 pass through the steel arch web and are fixedly connected to the steel web. The transverse conduits 31 play the role of transversely fixing the steel arch and later transporting cement slurry to fill the internal cavity of the primary support; the longitudinal conduits 32 are arranged radially along the radial direction of the tunnel. One end of the longitudinal conduit 32 is fixedly connected to the transverse conduit 31, and the other end is conical and inserted into the tunnel. Inside the surrounding rock, it plays a role in reinforcing the surrounding rock and fixing the support structure; in order to facilitate the injection of cement slurry, a plurality of grouting holes 34 are provided on the transverse conduit 31 and the longitudinal conduit 32. After grouting, the longitudinal conduit 32 can reinforce the surrounding rock and, through the connection with the transverse conduit 31, play a role in fixing the support structure and reducing settlement deformation; the transverse conduit 31 preferably adopts a thick-walled high-strength round tube that can withstand a large force. The transverse conduit 31 is distributed between the steel webs and plays a role in transverse fixing. The outer diameter of the transverse conduit 31 is 32 to 45 mm, and the wall thickness is 6 to 12 mm. The outer diameter of the longitudinal conduit 32 is 25 to 35 mm, and the wall thickness is 2 to 5 mm. The transverse conduits 31 can be connected in a variety of ways, such as threaded connection, flange connection, etc.; preferably, a threaded connection is adopted, that is, the conduit device 3 further includes a threaded sleeve 33, and both ends of the transverse conduit 31 are provided with threads matching the threaded sleeve 33. The transverse conduits 31 are rotatably connected together through the threaded sleeve 33. The use of the threaded sleeve 33 connection can facilitate the adjustment of the distance between the two transverse conduits 31 to be connected during installation.

[0057] A limit plate 36 is provided at the connection between the transverse conduit 31 and the steel web. The limit plate 36 positions the transverse conduit 31 and strengthens the perforation of the steel web at the same time; a fixed support 35 is provided at the connection between the longitudinal conduit 32 and the transverse conduit 31, the transverse conduit 31 passes through one end of the fixed support 35 and is fixedly connected to the fixed support 35, and the longitudinal conduit 32 passes through the other end of the fixed support 35 and is fixed on the fixed support 35; the fixed support 35 and the transverse conduit 31 can be connected outside the cave by welding, riveting, bolting, etc. The angle for installing the longitudinal conduit 32 should be determined according to the insertion angle of the longitudinal conduit 32 in the design. After the hole is formed in the cave wall, the longitudinal conduit 32 is inserted into the surrounding rock at a set angle and connected by bolts.

[0058] The inverted arch segment 116 is connected to the first segment 111 and the fifth segment 117 respectively by a first joint 6, and the other segments are connected to each other by a second joint 5; half of the steel section of the inverted arch segment 116 in the first joint 6 extends forward, and a corresponding shape connecting plate is set along the edge of the web, the corresponding positions of the steel flanges of the first segment 111 and the fifth segment 117 are concave inward, and the shape and size of the concave are matched with the extended part of the steel of the inverted arch segment 116, and a connecting plate is set along the edge of the web. The connecting plates at the first joint 6 are connected by joint bolts 118. This structure can not only transmit the pressure between the steel of each segment of the arch ring and the inverted arch segment 116, but also better withstand the shear of the arch ring steel on the inverted arch segment 116. force; all second joints 5 include a Z-shaped joint section, the two inner angles of the Z-shaped joint section are both right angles, a connecting plate is arranged along the edge of the cross-section steel web, the connecting plate at the second joint 5 is connected by a joint bolt 118, the transverse connection area at the joint mainly bears pressure, and the longitudinal connection area mainly bears shear force. This structure can increase the connection area of the two steel sections; the joint bolts 118 are preferably high-strength bolts, the connecting plates in the two transverse connection areas of the second joint 5 are each provided with no less than two joint bolts 118 for fixing, the connecting plates in the longitudinal connection area are provided with no less than two joint bolts 118 for fixing, and the connecting plates in each direction of the first joint 6 are each provided with no less than two joint bolts 118 for fixing.

[0059] Because the arch crown segment 113 and the inverted arch segment 116 include two cross-nodes of steel arch frames, they need to withstand large forces and have high strength requirements and structural precision. They cannot be assembled in the cave and generally need to be processed and assembled in a processing plant. After the steel is processed into a suitable shape, it is advisable to use welding, riveting and other processes for connection.

[0060] As a more preferred embodiment of the present invention, the crown segment 113 and the inverted arch segment 116 are integrally cast structures.

[0061] As a better embodiment of the present invention, in order to improve the seismic resistance of the initial support structure, a shock-absorbing device 4 is further arranged along the tunnel axis between the steel webs of the first steel arch frame unit 11 and the second steel arch frame unit 12. The shock-absorbing device 4 and the transverse duct 31 are arranged alternately. The arrangement density of the transverse duct 31, the longitudinal duct 32 and the shock-absorbing device 4 is determined according to factors such as the surrounding rock grade, the tunnel size, and the blasting construction. The shock-absorbing device 4 includes a shell 42 and support rods 47 arranged on both sides of the shell 42. One end of the support rod 47 is connected to the shell 42 and the other end is connected to the steel web. A sealed cavity is formed between the shell 42 and the support rods 47 on both sides. A partition 43 is also arranged in the sealed cavity, which is in close contact with the shell 42 and can slide horizontally. A plurality of flow holes 46 are provided on the partition 43. A spring 44 is also provided between the two ends of the partition 43 and the support rod 47. The sealed cavity is filled with a viscous liquid 41. When an earthquake occurs, the arch steel drives the support rod 47 to move. The support rod 47 drives the shock absorber 4 to operate, causing the partition 43 to reciprocate within the sealed cavity, thereby driving the spring 44 to expand and contract, absorbing the vibration energy. Simultaneously, the reciprocating motion of the partition 43 forces the viscous fluid to flow back and forth through the flow holes 46 provided in the partition 43 within the cavities on both sides of the partition, dissipating the vibration energy and improving the seismic resistance of the structural system. A connecting plate 45 is provided at the end of the support rod 47 connected to the steel web. The connecting plate 45 is connected to the steel web by bolts. The support rod 47 is a circular tube.

[0062] The construction method of the initial support structure of the non-central guide multi-arch tunnel includes:

[0063] The first step is to excavate the upper steps of the pilot hole. After the excavation of the upper steps of the pilot hole is completed, the arch segment 113 and the third segment 114 are installed first. Then, the transverse guide tube 31 is installed between adjacent steel arch frames. According to the position of the transverse guide tube 31 where the longitudinal guide tube 32 is required to be installed, holes are drilled in the surrounding rock. The longitudinal guide tube 32 is inserted into the surrounding rock and fixed. Grouting is injected into the surrounding rock through the longitudinal guide tube 31, and concrete is sprayed on the installed part.

[0064] The second step is to excavate the steps in the pilot hole, and install the second segment 112 and the fourth segment 115 on both sides of the pilot hole respectively. The upper end of the second segment 112 is connected to the lower end of the arch segment 113, and the upper end of the fourth segment 115 is connected to the lower end of the third segment 114; install the transverse guide tube 31 between adjacent steel arch frames, drill holes in the surrounding rock according to the positions of the transverse guide tube 31 where the longitudinal guide tube 32 needs to be set, insert the longitudinal guide tube 32 into the surrounding rock and fix it, grouting is injected into the surrounding rock through the longitudinal guide tube 31, and concrete is sprayed on the installed part;

[0065] The third step is to excavate the lower steps of the advance tunnel, and install the first segment 111 and the fifth segment 117 on both sides respectively. The upper end of the first segment 111 is connected to the lower end of the second segment 112, and the upper end of the fifth segment 117 is connected to the lower end of the fourth segment 115; install transverse conduits 31 between adjacent steel arch frames, wherein two rows of transverse conduits 31 are installed in the fifth segment 117, and holes are drilled in the surrounding rock according to the positions of the transverse conduits 31 where the longitudinal conduits 32 need to be installed, and the longitudinal conduits 32 are inserted into the surrounding rock and fixed, and grouting is injected into the surrounding rock through the longitudinal conduits 31, and concrete is sprayed on the installed part;

[0066] The fourth step is to excavate the inverted arch section 116 after excavating the advance tunnel. The two sides of the inverted arch section 116 are connected to the lower ends of the first section 111 and the fifth section 117 respectively, and concrete is sprayed on the installed part.

[0067] Step 5: After excavation, the tunnel is stepped up. After the excavation of the upper steps is completed, the arch segment 113 and the third segment 114 are installed. Then, the transverse guide tube 31 is installed between adjacent steel arch frames. Holes are drilled in the surrounding rock at the positions where the longitudinal guide tubes 32 are required to be installed on the transverse guide tube 31. The longitudinal guide tubes 32 are inserted into the surrounding rock and fixed. Grouting is injected into the surrounding rock through the longitudinal guide tube 31, and concrete is sprayed on the installed part.

[0068] Step 6: Excavate the steps in the rear tunnel, install the second segment 112 and the fourth segment 115 on both sides of the rear tunnel, connect the upper end of the second segment 112 to the lower end of the arch segment 113, connect the upper end of the fourth segment 115 to the lower end of the third segment 114, and connect the lower end of the fourth segment 115 to the upper end of the fifth segment 117 of the leading tunnel; install the transverse guide tube 31 between adjacent steel arch frames, drill holes in the surrounding rock at the positions where the longitudinal guide tube 32 needs to be set on the transverse guide tube 31, insert the longitudinal guide tube 32 into the surrounding rock and fix it, inject grout into the surrounding rock through the longitudinal guide tube 31, and spray concrete on the installed part;

[0069] Step 7: Excavate the lower steps of the rear tunnel and install the first segment 111 on the outer side of the rear tunnel. The upper end of the first segment 111 is connected to the lower end of the second segment 112. Install the transverse guide tube 31 between adjacent steel arches. Drill holes in the surrounding rock at the locations where the longitudinal guide tubes 32 are to be installed on the transverse guide tube 31. Insert the longitudinal guide tube 32 into the surrounding rock and fix it. Grouting is injected into the surrounding rock through the longitudinal guide tube 31. Concrete is sprayed on the installed part.

[0070] In the eighth step, after excavating the back tunnel, the inverted arch segment 116 is installed. The two sides of the inverted arch segment 116 are respectively connected to the lower ends of the first segment 111 and the fifth segment 117, and concrete is sprayed on the installed part.

[0071] In the ninth step, after the initial support structure of the tunnel is completed, grouting is injected into the interior of the initial support through the transverse guide tube 31 to fill the internal cavities and cracks.

[0072] In a specific embodiment, during the construction process of the first, second, third, fifth, sixth and seventh steps, after the installation of the transverse duct 31 and the longitudinal duct 32 is completed and the longitudinal duct 32 is grouted, the shock absorbing device 4 is installed, and finally concrete is sprayed on the installed part, and after the initial support structure is installed, grouting is finally performed through the transverse duct 31.

[0073] Finite element numerical simulation software is used to numerically analyze the existing non-central guide arch tunnel structure and the structure of the present invention under set working conditions. The displacement calculation results of the surrounding rock and steel arch frame of the two structures are as follows: Figures 14-17 As shown:

[0074] from Figure 15 and Figure 16 It can be seen that the maximum displacement of the surrounding rock of the conventional non-central guide continuous arch tunnel structure is 11.46 mm, while the maximum displacement of the surrounding rock of the structure of the present invention is 1.98 mm. From the results of numerical calculations, the maximum displacement of the surrounding rock of the structure of the present invention is 82.7% smaller than the maximum displacement of the conventional non-central guide continuous arch tunnel structure, which shows that the structure of the present invention can more effectively control the deformation of the surrounding rock.

[0075] from Figure 17 and Figure 18 It can be seen that the maximum displacement of the steel arch frame of the existing technology without a central guide multi-arch tunnel is 11.36mm, while the maximum displacement of the steel arch frame of the structure of the present invention is 1.96mm. From the results of numerical calculation, the maximum displacement of the steel arch frame of the structure of the present invention is 82.7% smaller than that of the steel arch frame of the structure without a central guide multi-arch tunnel. Figure 16 It can be seen from the above that the traditional structural steel arch frame overlap area has a large deformation, while the structure of the present invention avoids this problem.

[0076] The above content is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, several simple deductions and substitutions can be made without departing from the concept of the present invention, and all of these should be considered to fall within the scope of protection of the present invention.

Claims

1. An initial support structure for a non-central guide multi-arch tunnel, comprising a leading tunnel support structure (1) and a trailing tunnel support structure (2), characterized in that: The pilot tunnel support structure (1) is provided with a plurality of first steel arch frame units (11) in sequence along the tunnel axial direction, wherein the first steel arch frame unit (11) comprises two cross-arranged first steel arch frames, the first steel arch frame comprising a first segment (111), a second segment (112), a crown segment (113), a third segment (114), a fourth segment (115) and a fifth segment (117) connected in sequence along the tunnel circumference and from the outside to the inside of the pilot tunnel, and an inverted arch segment (116) is further provided at the bottom of the first steel arch frame. The two cross-arranged first steel arch frames are provided with cross nodes at the highest point of the arch crown segment (113) and the lowest point of the inverted arch segment (116), and the arch frames are gradually opened downward and upward from the cross nodes, and reach the maximum opening distance at the arch foot. The arch crown segment (113) and the inverted arch segment (116) are common segments of the two cross-arranged first steel arch frames in the same first steel arch frame unit (11), and the two ends of the inverted arch segment (116) are respectively connected to the first segment (111) and the fifth segment (117); The rear tunnel support structure (2) is provided with a plurality of second steel arch frame units (12) in sequence along the axial direction of the tunnel. The second steel arch frame unit (12) includes two cross-arranged second steel arch frames. The second steel arch frame includes a first segment (111), a second segment (112), a crown segment (113), a third segment (114) and a fourth segment (115) which are sequentially connected from the outside to the inside of the rear tunnel along the circumferential direction of the tunnel. An inverted arch segment (116) is further provided at the bottom of the second steel arch frame. The two cross-arranged second steel arch frames are connected at the highest point of the crown segment (113) and the inverted arch segment (116). The lowest point of the arch segment (116) is provided with a cross node, and the arch frame is gradually opened downward and upward from the cross node, and reaches the maximum opening distance at the arch foot; the arch crown segment (113) and the inverted arch segment (116) are common segments of two shaped steel arch frames in the same second shaped steel arch frame unit (12), and the two ends of the inverted arch segment (116) are respectively connected to the first segment (111) and the fifth segment (117); the fifth segment (117) is provided with two shaped steels, and the fifth segment (117) is a common segment of the shaped steel arch frames of the first shaped steel arch frame unit (11) and the second shaped steel arch frame unit (12); The first steel arch frame unit (11) in the leading tunnel support structure (1) and the second steel arch frame unit (12) in the trailing tunnel support structure (2) are respectively connected in an interlaced manner, and the two steel arch frames of the first steel arch frame unit (11) are respectively connected to the nearest one of the two adjacent second steel arch frame units (12); A conduit device (3) is provided between adjacent steel arches of the first steel arch unit (11) and between adjacent steel arches of the second steel arch unit (12), respectively. The conduit device (3) comprises a plurality of transverse conduits (31) and a plurality of longitudinal conduits (32). The transverse conduits (31) are provided on both sides of the steel web along the tunnel axis, and the transverse conduits (31) pass through the steel arch web and are fixedly connected to the steel web; the longitudinal conduits (32) are provided radially along the tunnel radial direction, one end of the longitudinal conduit (32) is fixedly connected to the transverse conduit (31), and the other end is conical and inserted into the surrounding rock; and a plurality of grouting holes (34) are provided on the transverse conduits (31) and the longitudinal conduits (32).

2. The primary support structure for a tunnel without a central guide arch according to claim 1, characterized in that: A limit plate (36) is provided at the connection between the transverse conduit (31) and the steel web, and a fixed support (35) is provided at the connection between the longitudinal conduit (32) and the transverse conduit (31). The transverse conduit (31) passes through one end of the fixed support (35) and is fixedly connected to the fixed support (35), and the longitudinal conduit (32) passes through the other end of the fixed support (35) and is fixed on the fixed support (35).

3. The primary support structure for a tunnel without a central guide arch according to claim 1 is characterized in that: The conduit device (3) further comprises a threaded sleeve (33), both ends of the transverse conduit (31) are provided with threads matching the threaded sleeve (33), and the transverse conduits (31) are connected together via the threaded sleeve (33).

4. The primary support structure for a tunnel without a central guide arch according to claim 1, characterized in that: The outer diameter of the transverse conduit (31) is 32-45 mm, and the wall thickness is 6-12 mm; the outer diameter of the longitudinal conduit (32) is 25-35 mm, and the wall thickness is 2-5 mm.

5. The primary support structure for a tunnel without a central guide arch according to claim 1 is characterized in that: The inverted arch segment (116) is connected to the first segment (111) and the fifth segment (117) respectively by a first joint (6), and the other segments are connected to each other by a second joint (5); half of the steel section of the inverted arch segment (116) in the first joint (6) extends forward, and a connecting plate of corresponding shape is arranged along the edge of the web; the corresponding positions of the steel flanges of the first segment (111) and the fifth segment (117) are recessed inward, and the shape and size of the recess match the extended portion of the steel section of the inverted arch segment (116); a connecting plate is arranged along the edge of the web at the recessed portion, and the connecting plates at the first joint (6) are connected by joint bolts (118); all second joints (5) include Z-shaped joint sections, the two inner angles of the Z-shaped joint sections are both right angles, a connecting plate is arranged along the edge of the section steel web, and the connecting plates at the second joints (5) are connected by joint bolts (118).

6. The primary support structure for a tunnel without a central guide arch according to claim 1, characterized in that: The dome segment (113) and the inverted arch segment (116) are integrally cast structures.

7. The primary support structure for a tunnel without a central guide arch according to claim 1, characterized in that: A shock absorbing device (4) is provided along the tunnel axis between the steel webs of the first steel arch frame unit (11) and the second steel arch frame unit (12). The shock absorbing device (4) and the transverse duct (31) are alternately provided. The shock absorbing device (4) comprises a shell (42) and support rods (47) provided on both sides of the shell (42). One end of the support rod (47) is connected to the shell (42) and the other end is connected to the steel web. A sealed cavity is formed between the shell (42) and the support rods (47) on both sides. A partition (43) in close contact with the shell (42) and capable of horizontal sliding is provided in the sealed cavity. A plurality of flow holes (46) are provided on the partition (43). A spring (44) is provided between the two ends of the partition (43) and the support rods (47). The sealed cavity is filled with a viscous liquid (41).

8. The primary support structure for a tunnel without a central guide arch according to claim 7, characterized in that: The support rod (47) is provided with a connecting plate (45) at one end connected to the steel web. The connecting plate (45) is connected to the steel web via bolts. The support rod (47) is a round tube.

9. The construction method of the primary support structure of a tunnel without a central guide arch according to any one of claims 1 to 6, characterized in that: include: The first step is to first excavate the upper step of the advance hole. After the excavation of the upper step of the advance hole is completed, the arch segment (113) and the third segment (114) are installed first, and then the transverse guide tube (31) is installed between adjacent steel arch frames. According to the position of the longitudinal guide tube (32) on the transverse guide tube (31), holes are drilled on the surrounding rock, and the longitudinal guide tube (32) is inserted into the surrounding rock and fixed. Grouting is performed on the surrounding rock through the longitudinal guide tube (31), and concrete is sprayed on the installed part. The second step is to excavate the steps in the pilot hole, install the second segment (112) and the fourth segment (115) on both sides of the pilot hole respectively, connect the upper end of the second segment (112) to the lower end of the arch segment (113), and connect the upper end of the fourth segment (115) to the lower end of the third segment (114); install the transverse guide tube (31) between adjacent steel arch frames, drill holes on the surrounding rock where the longitudinal guide tube (32) needs to be set on the transverse guide tube (31), insert the longitudinal guide tube (32) into the surrounding rock and fix it, grout the surrounding rock through the longitudinal guide tube (31), and spray concrete on the installed part; The third step is to excavate the lower steps of the advance hole, install the first segment (111) and the fifth segment (117) on both sides respectively, connect the upper end of the first segment (111) to the lower end of the second segment (112), and connect the upper end of the fifth segment (117) to the lower end of the fourth segment (115); install transverse conduits (31) between adjacent steel arch frames, wherein two rows of transverse conduits (31) are installed in the fifth segment (117), and holes are drilled on the surrounding rock according to the positions of the longitudinal conduits (32) on the transverse conduits (31), insert the longitudinal conduits (32) into the surrounding rock and fix them, grouting is performed into the surrounding rock through the longitudinal conduits (31), and concrete is sprayed on the installed part; The fourth step is to install the inverted arch segment (116) after excavating the inverted supply part of the advance hole, wherein both sides of the inverted arch segment (116) are respectively connected to the lower ends of the first segment (111) and the fifth segment (117), and concrete is sprayed on the installed part; The fifth step is to excavate the hole and go up the steps. After the excavation of the steps is completed, the vault segment (113) and the third segment (114) are installed. Then, the transverse guide tube (31) is installed between the adjacent steel arch frames. Holes are drilled on the surrounding rock according to the positions of the longitudinal guide tube (32) required to be set on the transverse guide tube (31). The longitudinal guide tube (32) is inserted into the surrounding rock and fixed. Grouting is performed on the surrounding rock through the longitudinal guide tube (31). Concrete is sprayed on the installed part. The sixth step is to excavate the steps in the rear tunnel, and respectively install the second segment (112) and the fourth segment (115) on both sides of the rear tunnel, the upper end of the second segment (112) is connected to the lower end of the arch segment (113), the upper end of the fourth segment (115) is connected to the lower end of the third segment (114), and the lower end of the fourth segment (115) is connected to the upper end of the fifth segment (117) of the leading tunnel; install the transverse guide tube (31) between adjacent steel arch frames, drill holes on the surrounding rock where the longitudinal guide tube (32) needs to be set on the transverse guide tube (31), insert the longitudinal guide tube (32) into the surrounding rock and fix it, grout the surrounding rock through the longitudinal guide tube (31), and spray concrete on the installed part; The seventh step is to excavate the lower step of the rear tunnel, install the first segment (111) on the outer side of the rear tunnel, and connect the upper end of the first segment (111) to the lower end of the second segment (112); install the transverse guide tube (31) between adjacent steel arch frames, drill holes in the surrounding rock according to the position of the longitudinal guide tube (32) required to be set on the transverse guide tube (31), insert the longitudinal guide tube (32) into the surrounding rock and fix it, grout the surrounding rock through the longitudinal guide tube (31), and spray concrete on the installed part; In the eighth step, after excavating the inverted portion of the tunnel, an inverted arch segment (116) is installed, both sides of the inverted arch segment (116) are connected to the lower ends of the first segment (111) and the fifth segment (117), and concrete is sprayed on the installed portion; The ninth step is to wait for the initial support structure of the tunnel to be completed, and then inject grout into the initial support through the transverse guide tube (31) to fill the internal cavities and cracks.

10. The construction method of the primary support structure of a tunnel without a central guide arch according to claim 9, characterized in that: During the construction process of the first, second, third, fifth, sixth and seventh steps, after the transverse duct (31) and the longitudinal duct (32) are installed, the longitudinal duct (32) is grouted, the shock absorbing device (4) is installed, and finally concrete is sprayed on the installed portion. After the initial support structure is installed, grouting is finally performed through the transverse duct (31).

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