A synchronous installation process for multiple arches

Abstract

The application relates to a multi-arch synchronous installation process, which comprises the following steps: S1. Dividing arches into at least one middle section and multiple side sections according to the arch span required by a tunnel, and hingedly connecting the middle section and the side section at the inner arc sides of the two or hingedly connecting the middle section and another middle section at the inner arc sides of the two; S2. Welding cross ribs and meshes on the middle section and the side section; S3. Hoisting the middle section and the side section hingedly connected thereto into the tunnel together, lifting the middle section to make the middle section fit the tunnel dome, lifting the side section to make the side section fit the upper part of the tunnel side, locking the middle section and the side section or the middle section and another middle section, and supporting the connecting part of the two along the arc surface contour; and S4. Installing another side section on the ground of the tunnel side to support the side section connected with the middle section, and locking the two adjacent side sections. The application has the effect of significantly improving the shearing resistance of the joint part of the multi-arch, thereby improving the bearing capacity and the structural stability of the multi-arch.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of multi-arch arch construction of large-section tunnels, in particular to a multi-arch arch synchronous installation process. BACKGROUND

[0002] At present, the installation process of the multi-arch arch used is mainly a multi-unit assembly method, which requires manual assembly of the arch outside the tunnel and then hoisting into the tunnel for installation. On the one hand, the construction efficiency is difficult to be effectively improved, and on the other hand, the construction personnel are not fully protected during the installation of the arch, which has a great safety hazard.

[0003] In the related art, a Chinese patent with the publication number CN109488345A proposes a tunnel arch rapid installation construction method, which includes: dividing the arch into at least two sections according to the required arch span of the tunnel, wherein one section is a main arch section, and the remaining sections are auxiliary arch sections, wherein the main arch section is a multi-section arch section assembled outside the tunnel; assembling the multi-arch main arch section on the bench outside the tunnel, and welding the cross ribs and the mesh on the multi-arch main arch section to form an integrated structure; using a hoisting mechanism to hoist the multi-arch main arch section to the multi-arch clamping tray of the main arm; the arch machine with the multi-arch main arch section enters the tunnel and reaches the tunnel face; the main arm of the arch machine lifts the multi-arch main arch section to the installation position at one time, and the operator stands on the ground or uses the left and right auxiliary arms to assemble the remaining arch sections with the multi-arch main arch section into an integrated structure. The construction process provided by the present application can significantly improve the construction efficiency and save labor.

[0004] The related art in the above has the following defects: the spliced multi-arch arch bears the downward pressure from the tunnel dome and the inward extrusion force from the tunnel side wall when it is in the tunnel; and the assembled multi-arch arch is basically divided into a middle section abutting against the tunnel dome and side sections abutting against both sides of the tunnel, and the middle section and the side sections can be divided into multiple sections; thus, when actually stressed, the middle section and the middle section connection part and the middle section and the side section connection part receive a large downward pressure from the tunnel dome, and even if high-strength bolts are used between the above connection parts, the pressure from the tunnel dome will be converted into shear force on the high-strength bolts at the above connection parts, which easily causes the bearing instability of the assembled multi-arch arch, especially in the installation of the multi-arch arch of the large-section tunnel, this hidden danger will become more obvious. SUMMARY

[0005] In order to improve the problem that the shear force borne by the middle section connection part of the assembled multi-arch arch during installation is large and easily causes the instability of the overall structure of the multi-arch arch, the present application provides a multi-arch arch synchronous installation process.

[0006] The application provides a multi-arch synchronous installation process which adopts the following technical scheme:

[0007] A multi-arch synchronous installation process comprises the following steps:

[0008] S1. According to the arch span required by the tunnel, the arch is divided into at least one middle section and multiple side sections, the middle section and the side section are hingedly connected on the inner arc side, or the middle section and another middle section are hingedly connected on the inner arc side;

[0009] S2. Welding transverse ribs and mesh on the middle section and the side section;

[0010] S3. Hoisting the middle section and the side section hingedly connected thereto into the tunnel, lifting the middle section to fit the tunnel dome, lifting the side section to fit the upper part of the tunnel side, locking the middle section and the side section or the middle section and another middle section, and supporting the connecting part of the two sections along the arc surface contour;

[0011] S4. Installing another side section on the ground of the tunnel side to support the side section connected with the middle section, and locking the adjacent two side sections.

[0012] Further, the middle section and the side section each comprise a plurality of arc-shaped I-beams arranged in parallel and a whole connecting plate fixedly connected to the end of the arc-shaped I-beams, a plurality of mounting holes are formed in the whole connecting plate, and the inner arc sides of the adjacent two whole connecting plates are hingedly connected and fixed by bolts and nuts.

[0013] Further, a long hole with a hole wall matched with the web of the arc-shaped I-beam is formed in each of the two hingedly connected whole connecting plates, one of the whole connecting plates is fixedly connected to the web of the arc-shaped I-beam connected thereto in the long hole, and a support arc plate with one end fixedly connected to the web of the arc-shaped I-beam and the other end protruding from the side of the whole connecting plate away from the arc-shaped I-beam is fixedly connected to the other whole connecting plate, and the free end of the support arc plate is inserted into the long hole.

[0014] When the two hingedly connected whole connecting plates are turned to be matched, the free end of the support arc plate passes through the long hole aligned therewith and abuts against the lower end surface of the upper flange plate of the other whole connecting plate.

[0015] The arc surface contour support is realized by the abutment between the support arc plate of the two whole connecting plates after locking and the flange plate of the arc-shaped I-beam.

[0016] Further, the whole connecting plate not fixed with the support arc plate is fixed with a guide slope which is attached to the flange of the arc-shaped I-beam, the guide slope is arranged on the side of the flange close to the web of the arc-shaped I-beam, and the slope surface of the guide slope is arranged as an arc surface extending towards the hinge part of the two whole connecting plates.

[0017] Further, the web of the arc-shaped I-beam is further fixed with a support slope arranged opposite to the guide slope, the slope surface of the support slope is also arranged as an arc surface, and a gap is reserved between the slope surfaces of the support slope and the guide slope for the sliding of the support arc plate.

[0018] Further, the opposite sides of the two whole connecting plates are respectively provided with a protrusion and a groove, when the two whole connecting plates are turned to be attached, the protrusion is embedded in the groove.

[0019] Further, before the intermediate section and the side section are hoisted to the tunnel in the step S3, the two whole connecting plates are turned to be attached to the two arc-shaped I-beams fixed therewith.

[0020] Further, after the intermediate section and the side section are hoisted to the tunnel in the step S3, the remaining side sections are installed under the side sections, and the side sections above are aligned with the intermediate section or two adjacent intermediate sections by pushing the side sections below to the tunnel side wall.

[0021] In summary, the beneficial technical effects of the present application are:

[0022] 1. The large-span arch frame is divided into multiple intermediate sections and side sections, and the intermediate sections and part of the side sections are hinged, so that the intermediate sections and the side sections can be folded when being installed, and unfolded when being installed in the tunnel, which can significantly reduce the hoisting difficulty of the arch frame during hoisting to the tunnel and the installation difficulty in the tunnel, thereby improving the construction efficiency and greatly ensuring the safety of the construction personnel.

[0023] 2. After the adjacent two intermediate sections and the intermediate section and the side section are locked, the locking part is supported by an arc profile, so that the intermediate section and the side section are pre-stressed by the component with arc profile support when bearing external force, which can significantly reduce the shear force of the bolts used to lock the components of the arch frame, thereby improving the bearing capacity and structural stability of the multiple arch frames to a certain extent. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a schematic diagram of the whole structure of a single multiple arch frame of the embodiment of the present application.

[0025] Figure 2is a schematic view of a connecting structure of two intermediate sections in the embodiment of the present application.

[0026] Figure 3 is Figure 2 is a schematic view of a partial enlargement of part A.

[0027] Figure 4 is a schematic view of a butt joint structure of the support arc plates on the integral connecting plates in the embodiment of the present application.

[0028] Reference signs: 1, intermediate section; 2, side section; 3, arc-shaped I-beam; 4, integral connecting plate; 41, mounting hole; 42, long hole; 43, support arc plate; 51, guide slope; 52, support slope; 53, embedding groove; 61, protrusion; 62, recess. DETAILED DESCRIPTION

[0029] The technical solutions of the present application will be described clearly and completely below with reference to the drawings. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0030] The embodiment of the present application discloses a multi-arch synchronous installation process. Referring to Figure 1 , the multi-arch synchronous installation process comprises the following steps:

[0031] S1. According to the arch span required by the tunnel, the arch is divided into at least one intermediate section 1 and multiple side sections 2, and the intermediate section 1 and the side section 2 are hingedly connected on the inner arc side of the two, or the intermediate section 1 and another intermediate section 1 are hingedly connected on the inner arc side of the two;

[0032] S2. Welding transverse ribs and mesh on the intermediate section 1 and the side section 2;

[0033] S3. Hoisting the intermediate section 1 and the side section 2 hingedly connected thereto into the tunnel together, and lifting so that the intermediate section 1 fits the tunnel dome and the side section 2 fits the upper part of the tunnel side, and locking and supporting the intermediate section 1 and the side section 2 or the intermediate section 1 and another intermediate section 1 along the arc surface profile of the connecting part of the two;

[0034] S4. Installing another side section 2 on the ground of the tunnel side to support the side section 2 connected with the intermediate section 1, and locking the two adjacent side sections 2.

[0035] Wherein, referring to Figure 1 , Figure 2 and Figure 3The intermediate section 1 and the side section 2 each include a plurality of arc-shaped I-beams 3 arranged in parallel and a plurality of integral connecting plates 4 integrally connected to the ends of the plurality of arc-shaped I-beams 3, and a plurality of mounting holes 41 are formed through the integral connecting plates 4, and the adjacent two integral connecting plates 4 are hingedly connected to the inner arc side and are fixed by bolts and nuts.

[0036] The plurality of arch frames of the single unit include at least one intermediate section 1 and at least two side sections 2, and the at least two side sections 2 are arranged at the two ends of the intermediate section 1. In the actual construction, the plurality of arch frames can be selected according to the span of the tunnel section, and one intermediate section 1 or two intermediate sections 1 or three or more intermediate sections 1 can be selected, and one side section 2 or two side sections 2 or three or more side sections 2 can be selected according to the height of the tunnel section. The selection can be made according to the actual situation. In the embodiment of the present application, in order to show the technical principle of the present application, the intermediate section 1 is provided as two, and the side section 2 is provided as two on one side.

[0037] Therefore, in step S1, the construction personnel first processes a plurality of intermediate sections 1 and a plurality of side sections 2 outside the tunnel, hingedly connects the two integral connecting plates 4 of the abutting portions of the two intermediate sections 1 for abutting the tunnel dome, such as using a pin or a hinge to hinge the side of the integral connecting plate 4 close to the inner arc side of the intermediate section 1; at the same time, the intermediate section 1 is hingedly connected to the side section 2 for abutting the upper part of the tunnel side in the same way; so that the above-mentioned components form the main part of the plurality of arch frames, and the remaining two independent side sections 2 serve as the support part. After the two intermediate sections 1 and the two side sections 2 are hingedly connected in sequence, the two side sections 2 and the two intermediate sections 1 are turned to be as close as possible, such as the arc-shaped I-beams 3 in the side section 2 abutting the arc-shaped I-beams 3 in the intermediate section 1, and if necessary, the main part after being folded can be bound by a steel wire to prevent loosening.

[0038] In this way, when hoisting the main part of the plurality of arch frames, the overall land occupation of the main part is small, which is convenient for hoisting by the hoisting equipment, and the folded main part can freely move in the tunnel. In the conventional technology, the integral plurality of arch frames are curved to adapt to the inner wall of the tunnel, and it is difficult to move and install to the specified position in the tunnel, and it is also difficult to install from the outside to the inside, which has a great safety hazard. Therefore, the split plurality of arch frames provided by the present application have great advantages in hoisting efficiency, installation efficiency, and safety protection of construction personnel.

[0039] Meanwhile, in order to further improve the installation efficiency of the main body part of the multiple-arch frame in the tunnel, especially when the main body part is unfolded to fit and support the upper part of the tunnel dome and the tunnel side, even if the main body part is supported by construction equipment, when a tunnel with a large span is encountered, the support surface is wide, and the requirements for the construction equipment are high, the construction efficiency and cost are still high.

[0040] Therefore, further, after the intermediate section 1 and the side section 2 in the main body part are hoisted into position in step S3, the remaining side sections 2 are installed at the lower part of the main body part, and the lower part of the side section 2 is pushed to fit the tunnel side wall to align the upper part of the side section 2 with the intermediate section 1 or two adjacent intermediate sections 1. Specifically, after the hoisting equipment hoists the main body part, the main body part is stretched to nearly fit the upper part of the tunnel, and then the integral connecting plate 4 on the lower part of the side section 2 is movably connected to the integral connecting plate 4 on the upper part of the side section 2 by bolts to prevent the two integral connecting plates 4 from being misaligned. At this time, the lower part of the side section 2 is inclined to the tunnel, and the lower part of the connecting plate is pushed by a jack or a hydraulic cylinder to gradually slide towards the tunnel side wall, thereby achieving step-by-step support of the main body part.

[0041] Until the lower part of the side section 2 fits the tunnel side wall, the upper part of the side section 2 and the intermediate section 1, and the intermediate section 1 and the intermediate section 1 are fitted under the push of the lower part of the side section 2, thereby making it more convenient and fast to pass the bolt through the mounting hole 41 of the adjacent two integral connecting plates 4 of the main body part at this time, which can greatly improve the construction speed of the multiple-arch frame in the tunnel, especially for the construction of the multiple-arch frame in a large-span tunnel, and the improvement of construction efficiency is more obvious.

[0042] In this way, when assembling the multiple-arch frame, the main body part can be conveniently aligned by pushing the lower part of the side section 2, and then the bolt is passed through the mounting hole 41 of the adjacent two integral connecting plates 4 of the main body part and locked with a nut, and then the arc contour of the connecting part is supported, so that the intermediate section 1 and the side section 2 are pre-stressed by the components supported by the arc contour when subjected to external force, which can significantly reduce the shear force of the bolt used to lock the components of the arch frame, thereby improving the load-bearing performance and structural stability of the multiple-arch frame to some extent.

[0043] More specifically, in order to realize the arc contour support of the connecting part of the adjacent two integral connecting plates 4, refer to Figure 3 and Figure 4, two integral connecting plates 4 are provided with a long hole 42 penetrating through the hole wall and adhering to the web of the arc-shaped I-steel 3, one of the integral connecting plates 4 is fixed with a support arc plate 43 in the long hole 42, one end of the support arc plate 43 is fixed on the web of the arc-shaped I-steel 3 connected therewith, the other end of the support arc plate 43 protrudes from the side of the integral connecting plate 4 away from the arc-shaped I-steel 3, and the free end of the support arc plate 43 is inserted and fitted with the long hole 42.

[0044] When the two integral connecting plates 4 are turned to adhere to each other, the free end of the support arc plate 43 penetrates through the long hole 42 aligned therewith and abuts against the lower end surface of the upper flange of the other integral connecting plate 4; the abutment of the support arc plate 43 in the two integral connecting plates 4 after locking and the flange of the arc-shaped I-steel 3 realizes the arc contour support in the above step S2.

[0045] Meanwhile, referring to Figure 3 and Figure 4 , the integral connecting plate 4 not fixed with the support arc plate 43 is fixed with a guide slope 51 adhering to the flange of the arc-shaped I-steel 3 connected therewith, the guide slope 51 is arranged on the side of the flange of the arc-shaped I-steel 3 close to the web, and the slope surface of the guide slope 51 is arranged as an arc surface extending towards the hinge part between the two integral connecting plates 4.

[0046] In this way, when the two integral connecting plates 4 are aligned, the free end of the support arc plate 43 penetrates through the long hole 42 on the opposite integral connecting plate 4, and with the locking of the bolt and nut between the two integral connecting plates 4, on the one hand, the upper arc surfaces at both ends of the support arc plate 43 abut against the lower arc surfaces of the upper flanges of the corresponding arc-shaped I-steel 3, which can realize the shear resistance support effect on the two butt-jointed arc-shaped I-steel 3; on the other hand, in the process of sliding of the support arc plate 43 on the web of the corresponding arc-shaped I-steel 3, the guide slope 51 guides the upper arc surface of the support arc plate 43, so that the support arc plate 43 has a downward bending trend, that is, the support arc plate 43 stores a prestress for restoring the support arc plate 43 upward, so that when the external downward pressure from the tunnel dome is applied on the two adjacent intermediate sections 1 or the intermediate section 1 and the side section, the downward pressure is transmitted and first applied on the support arc plate 43, the prestress on the support arc plate 43 offsets part of the downward pressure, so that the ability of the multiple sets of arch frame main bodies to resist vertical shear force can be further significantly improved, thereby reducing the bearing capacity of the bolt between the two hinge-connected integral connecting plates 4, so that the bearing performance and structural stability of the multiple sets of arch frames are significantly improved, and the safety performance of the multiple sets of arch frames after construction is improved.

[0047] Furthermore, in another possible embodiment, referring to Figure 3 and Figure 4The web of the arc-shaped I-beam 3 is further fixedly connected with a support slope 52 which is oppositely arranged with the guide slope 51. The slope surface of the support slope 52 is also arranged as an arc surface. A gap is reserved between the slope surface of the support slope 52 and the slope surface of the guide slope 51 for the sliding of the support arc plate 43. The gap is adapted to the width of the support arc plate 43.

[0048] In this way, the support arc plate 43 can store sufficient prestress through the combined limiting effect of the support slope 52 and the guide slope 51, so as to provide effective shear resistance for the two hingedly connected plates 4.

[0049] Meanwhile, correspondingly, referring to Figure 4 A slot 53 is provided on the side of the guide slope 51 and the support slope 52 which is close to the web of the arc-shaped I-beam 3, for the free end of the support arc plate 43 to be embedded in the width direction, so as to ensure that the support arc plate 43 does not fold laterally during the storage of internal stress. As an optimization, the side of the slot 53 close to the support arc plate 43 can be flared, so that the support arc plate 43 can be smoothly inserted into the slot 53.

[0050] Similarly, as an alternative, in order to facilitate the accurate sliding of the support arc plate 43 into the slot 53 during the prestress storage process, referring to Figure 4 The opposite sides of the two hingedly connected plates 4 can also be respectively provided with a protrusion 61 and a groove 62. When the two hingedly connected plates 4 are flipped to be attached, the protrusion 61 is embedded in the groove 62. Specifically, the protrusion 61 is a strip-shaped protrusion which is integrally formed with the plate 4 and perpendicular to the plate 4.

[0051] In this way, when the two hingedly connected plates 4 are being locked by the bolt and nut, the protrusion 61 is embedded in the groove 62 to position and guide the two hingedly connected plates 4, so that the support arc plate 43 can accurately align with the slot 53 on the guide slope 51 and the support slope 52 after passing through the long hole 42 on the other plate 4, thereby improving the construction efficiency and quality.

[0052] The implementation principle of the embodiment of the application is that after the main body of the multiple-arch frame is manufactured outside the tunnel, the main body is folded and hoisted into the tunnel by a hoisting device for unfolding and installation. The main body can freely move in the tunnel, and the installation of the multiple-arch frame can be performed from the outside to the inside, which significantly improves the safety of the construction personnel and greatly improves the hoisting efficiency and installation efficiency of the multiple-arch frame.

[0053] In actual installation, by unfolding the two intermediate sections 1 and the intermediate section 1 and the side section 2 which are hingedly connected, and then locking by bolts and nuts, the fitting degree of the multiple-arch frames to the inner wall of the tunnel after assembly can be effectively ensured, and the supporting effect is guaranteed. In the process of locking the two hingedly connected integral connecting plates 4, the supporting arc plate 43 on one of the integral connecting plates 4 is embedded between the guide slope 51 and the supporting slope 52 of the corresponding arc-shaped I-beam 3 of the other integral connecting plate 4. On the one hand, the upper arc surface at both ends of the supporting arc plate 43 is tightly abutted against the lower arc surface of the upper flange of the corresponding arc-shaped I-beam 3, which can play a shearing supporting effect on the two abutted arc-shaped I-beams 3.

[0054] On the other hand, in the process of sliding of the supporting arc plate 43 on the web of the corresponding arc-shaped I-beam 3, the guide slope 51 guides the upper arc surface of the supporting arc plate 43, so that the supporting arc plate 43 has a downward bending trend and stores a prestress for restoring the supporting arc plate 43 upward. When the external downward pressure from the tunnel dome is applied on the two adjacent intermediate sections 1 or the intermediate section 1 and the side section, the prestress on the supporting arc plate 43 offsets part of the downward pressure, so that the ability of the multiple-arch frame main body to resist vertical shear force can be further significantly improved, and the carrying capacity of the bolts between the two hingedly connected integral connecting plates 4 is reduced, thereby significantly improving the carrying performance and structural stability of the multiple-arch frame, and improving the safety performance of the multiple-arch frame after construction.

[0055] The above are preferred embodiments of the present application, and do not limit the protection scope of the present application. Therefore, any equivalent changes made on the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A process for simultaneous installation of multiple arch frames, characterized in that, Includes the following steps: S1. The arch frame is divided into at least one intermediate section (1) and multiple side sections (2) according to the required arch frame span of the tunnel. The intermediate section (1) and the side sections (2) are hinged to each other on their inner arc sides or the intermediate section (1) and another intermediate section (1) are hinged to each other on their inner arc sides. S2. Weld horizontal ribs and wire mesh onto the middle section (1) and the side section (2); S3. Hoist the middle section (1) and the side section (2) hinged thereto into the tunnel, and lift it so that the middle section (1) fits against the tunnel dome and the side section (2) fits against the upper side of the tunnel. Lock the middle section (1) and the side section (2) or the middle section (1) and another middle section (1) and support them along the arc contour of the connection between them. S4. Install another side section (2) on the ground side of the tunnel to support the side section (2) connected to the middle section (1) and lock the two adjacent side sections (2). Both the middle section (1) and the side section (2) include multiple parallel arc-shaped I-beams (3) and integral connecting plates (4) fixedly connected to the ends of the multiple arc-shaped I-beams (3); each of the two hinged integral connecting plates (4) has a long hole (42) through which the hole wall fits against the web of the arc-shaped I-beam (3), and one of the integral connecting plates (4) is fixed in the long hole (42) with one end fixed to the web of the arc-shaped I-beam (3) connected thereto, and the other end protruding from the integral connecting plate (4) away from the arc-shaped I-beam. The supporting arc plate (43) on one side of the I-beam (3) is adapted to be inserted into the elongated hole (42); when the two hinged integral connecting plates (4) are flipped to fit together, the free end of the supporting arc plate (43) passes through the elongated hole (42) aligned with it and abuts against the lower end face of the upper wing plate of the other integral connecting plate (4); in step S2, the arc contour support is achieved by the abutment of the supporting arc plate (43) in the two locked integral connecting plates (4) with the wing plate of the arc-shaped I-beam (3); A guide slope (51) is fixed to the integral connecting plate (4) that is not fixed to the supporting arc plate (43) and is attached to the flange of the arc-shaped I-beam (3) connected thereto. The guide slope (51) is located on the side of the flange of the arc-shaped I-beam (3) near the web plate, and the slope surface of the guide slope (51) is set as an arc surface extending toward the hinge part of the two integral connecting plates (4). The web of the arc-shaped I-beam (3) is also fixed with a support slope (52) that is opposite to the guide slope (51). The slope surface of the support slope (52) is also set as an arc surface, and a gap is reserved between the slope surface of the support slope (52) and the slope surface of the guide slope (51) for the support arc plate (43) to slide into. The two integral connecting plates (4) that are hinged together are provided with protrusions (61) and grooves (62) on their opposite sides. When the two integral connecting plates (4) are flipped to fit together, the protrusions (61) are embedded in the grooves (62).

2. The synchronous installation process for multiple arch frames according to claim 1, characterized in that, Multiple mounting holes (41) are provided through the integral connecting plate (4). The inner arc sides of two adjacent integral connecting plates (4) are hinged and fixed by bolts and nuts.

3. The synchronous installation process for multiple arch frames according to claim 2, characterized in that, In step S3, the middle section (1) and the side section (2) are hoisted to the front of the tunnel, and the two hinged integral connecting plates (4) are flipped so that the two arc-shaped I-beams (3) fixed thereto fit together.

4. The synchronous installation process for multiple arch frames according to claim 3, characterized in that, In step S3, after the middle section (1) and the side section (2) are hoisted into place, the remaining side sections (2) are installed at the bottom of the two side sections (2), and the lower side sections (2) are pushed against the tunnel sidewall to align the upper side sections (2) with the middle section (1) or the two adjacent middle sections (1).

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