An integral support structure for a multi-arch tunnel and its rapid construction method

Abstract

The present invention discloses an integral support structure for a multi-arch tunnel and a rapid construction method thereof, which directly conducts sectional excavation on the main tunnel and sets up combined support, reducing the number of disturbances and improving the stability of the tunnel and surrounding rock. The primary support and waterproofing can be constructed independently. The primary support of adjacent chambers is integrally supported, with good deformation control effect and good waterproofing effect. Compared with the previous construction methods, this technology has less temporary support and simple processes; the support construction is simple and of good quality; the excavation and support construction of the left and right chambers can be carried out by means of the stagger distance between the left and right chambers and separated by the middle partition wall, effectively avoiding cross-operation and ensuring the engineering quality. The technology of the present invention can effectively solve the problems existing in the traditional construction methods, meet the construction requirements of double-arch or even multi-arch tunnels in China, and has broad application prospects.

Description

Technical Field

[0001] The present invention is applied to the field of tunnel engineering, and specifically relates to an integral support structure for a connected-arch tunnel and a rapid construction method thereof. Background Art

[0002] Connected-arch tunnels have become an important structural form in tunnel engineering. Based on the structural characteristics of connected-arch tunnels, their construction methods, support technologies, etc. are quite different from those of conventional separated tunnels, and in most cases, their construction difficulty is greater and the cost is higher. At present, most connected-arch tunnels are constructed by using the middle-drift method in combination with the CD method, the CRD method or the double-side drift method. This method constructs a large cross-section into small cross-sections, excavates and supports simultaneously, and has a good effect on controlling the deformation of the surrounding rock. However, it has the disadvantages of many construction processes, many temporary supports, narrow working space, low construction efficiency, etc. Moreover, the support and waterproof construction at the junction of the connected-arch structure are difficult, the level of mechanized construction is low, and problems such as water seepage and middle-wall settlement are likely to occur, resulting in quality disease problems in the later stage of the tunnel. Therefore, this method has poor adaptability and is not an ideal construction method for connected-arch tunnels.

[0003] China is one of the countries with the largest scale, the most complex situation and the fastest development of tunnel and underground engineering in the world. Based on the mountainous characteristics of China and the current situation of continuous development of urban underground space in China, restricted by conditions such as terrain, geology and alignment, the tunnel clear distance is getting smaller and smaller, resulting in a large number of engineering examples of connected-arch tunnels in actual projects. Connected-arch tunnels have become an important structural form in tunnel engineering. Compared with separated tunnels, connected-arch tunnels have the advantages of less land occupation, less environmental damage, shorter line length and lower project cost. However, the tunnel has a connected-arch structure form, with a large span, complex construction technology, numerous processes and great interference between processes. The quality and cost of the entire project are directly affected by the advantages and disadvantages of its construction technology. The traditional excavation method and tunnel cross-section support form of connected-arch tunnels have the above-mentioned numerous disadvantages, and there is an urgent need for a new support structure and construction method. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an integral support structure for a connected-arch tunnel and a rapid construction method thereof in view of the deficiencies of the prior art.

[0005] To solve the above technical problem, an integral support structure for a connected-arch tunnel of the present invention is used for the support operation of a connected-arch tunnel project. The support structure includes multiple groups of circumferential steel arch frames that are mirror-symmetrically and fixedly connected in a longitudinal arrangement. The adjacent circumferential steel arch frames in the mirror image are fixed through Y-shaped nodes. Multiple groups of longitudinal steel beams are arranged between the multiple groups of circumferential steel arch frames that are mirror-symmetrically and fixedly connected in a longitudinal arrangement. The longitudinal steel beams and the circumferential steel arch frames are fixed through circumferential-longitudinal nodes. And a transverse steel beam perpendicular to the longitudinal steel beam is provided between the adjacent circumferential steel arch frames in the mirror image.

[0006] As a possible implementation manner, further, the Y-shaped node includes a first fixed arm and a second fixed arm corresponding to the circumferential steel arch adjacent to the mirror image. One end of the second fixed arm is bolted to the middle section of the first fixed arm to form a Y-shaped structure.

[0007] As a possible implementation manner, further, the first fixed arm is bent outward from the connection point connected to the second fixed arm.

[0008] As a possible implementation manner, further, one end of the first fixed arm close to the second fixed arm is bent in an arc shape, and the end far from the second fixed arm is bent vertically.

[0009] As a possible implementation manner, further, multiple groups of fixing steel plates are provided inside both the first fixed arm and the second fixed arm.

[0010] A rapid construction method for an integral support structure of a multi-arch tunnel, which includes the following steps:

[0011] Complete the preliminary work in construction preparation;

[0012] Carry out the excavation of the four pilot tunnels with staggered distances and the reserved core soil in the upper and lower benches;

[0013] Alternately excavate each chamber in the cyclic process;

[0014] Carry out the erection operation of the steel rigid frame;

[0015] Waterproof and reinforce the primary support structure and carry out the construction of the secondary lining.

[0016] As a possible implementation, further, the steps of staggering the excavation of the four pilot tunnels and leaving a core soil in the upper and lower benches specifically include: constructing advanced small ducts and pipe roofs at the designed positions outside the excavation contour. Under the protection of the advanced support, the first pilot tunnel is excavated using the method of leaving a core soil, and the excavation footage is controlled within the distance of 2 - 3 sets of steel frames; applying the initial support: initially spraying 2 - 4 cm of concrete, then erecting steel arch frames, installing bolts and hanging steel meshes; after the excavation and support of the first pilot tunnel for 3 - 5 m, the second pilot tunnel is excavated, and the excavation footage is controlled within the distance of 2 - 3 sets of steel frames; applying the initial support: initially spraying 2 - 4 cm of concrete, erecting steel arch frames, installing bolts and hanging steel meshes, and re-spraying the concrete on the part where the steel arch frames have been installed to the designed thickness; after the excavation and support of the second pilot tunnel for 10 m, the third pilot tunnel is excavated, and the excavation footage is controlled within the distance of 2 - 3 sets of steel frames, applying the initial support: initially spraying 2 - 4 cm of concrete, installing steel arch frames, installing bolts and hanging steel meshes; after the excavation and support of the third pilot tunnel for 3 - 5 m, the fourth pilot tunnel is excavated, and the excavation footage is controlled within the distance of 2 - 3 sets of steel frames, applying the initial support: initially spraying 2 - 4 cm of concrete, erecting steel arch frames, installing bolts and hanging steel meshes, and re-spraying the concrete on the part where the steel arch frames have been installed to the designed thickness.

[0017] As a possible implementation, further, the specific operation steps for the alternate excavation of each chamber in the cyclic process specifically include: completing one cycle of the excavation of the first to the fourth pilot tunnels. For the upper soil of the first and third pilot tunnels, the core soil is reserved manually and the soil is transported out through the passage reserved by the temporary inverted arch, turned over to the lower bench, and transported out of the tunnel by a small excavator; for the lower soil of the second and fourth pilot tunnels, the excavation is carried out manually in cooperation with a small excavator, and the soil is transported out of the tunnel by a small wheel loader. The left and right chambers are excavated with a staggering distance of 2 - 3 times the tunnel span.

[0018] As a possible implementation, further, the specific operation steps for the erection of the steel section arch frames specifically include: using I25a type I-beams for the middle wall part of the initial support structure, and I20a type I-beams for the remaining parts of the initial support structure. Layout and cut the materials, and weld them in sections; manually install the steel sections in the upper pilot tunnel and transport them using a small flatbed truck. The steel sections in the lower pilot tunnel are installed manually in cooperation with a small excavator and mechanically connected to the steel frames in the upper pilot tunnel; the circumferential and longitudinal steel frames are also mechanically connected to form a combined support structure.

[0019] As a possible implementation, further, the steps for waterproof reinforcement of the initial support structure and the construction of the secondary lining specifically include: the left and right chambers are excavated with a staggering distance and independently constructed under the isolation of the middle partition wall to form a combined initial support structure; reinforce the area above the Y-shaped node, backfill it with rubble concrete, re-spray it to a full state, then hang the waterproof board, construct the secondary lining concrete, and after completion, remove the transverse steel beam for the traffic test.

[0020] The present invention adopts the above technical solutions and has the following beneficial effects: The present invention directly conducts sectional excavation on the main tunnel and sets up combined support, reducing the number of disturbances and improving the stability of the tunnel and surrounding rock. The primary support and waterproofing can be constructed independently. The primary support of adjacent chambers is connected integrally for support, with good deformation control effect and good waterproofing effect. Compared with the previous construction methods, this technology has less temporary support and simple processes; the support construction is simple and of good quality; the excavation and support construction of the left and right chambers can be carried out by using the stagger distance of the left and right chambers and separated by the middle partition wall, effectively avoiding the mutual influence of cross operations and ensuring the engineering quality. The technology of the present invention can effectively solve the problems existing in the traditional construction methods, meet the construction requirements of double-arch or even multi-arch tunnels in China, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments:

[0022] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0023] Figure 2 It is a schematic diagram of the Y-shaped node structure of the present invention;

[0024] Figure 3 It is a schematic diagram of the construction sequence of the partial cross-section of the method of the present invention;

[0025] Figure 4 It is a schematic diagram of the construction sequence of the partial longitudinal section of the method of the present invention. SPECIFIC EMBODIMENTS

[0026] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention.

[0027] As Figure 1-2 shown, the present invention provides an integral support structure for a multi-arch tunnel, which is used for the support operation of a multi-arch tunnel project. The support structure includes a plurality of groups of circumferential steel arch frames 1 that are longitudinally arranged and fixedly connected in mirror symmetry. The adjacent circumferential steel arch frames 1 in mirror symmetry are fixed by Y-shaped nodes 2. A plurality of groups of longitudinal steel beams 3 are arranged between the plurality of groups of circumferential steel arch frames 1 that are longitudinally arranged and fixedly connected in mirror symmetry. The longitudinal steel beams 3 and the circumferential steel arch frames 1 are fixed by circumferential-longitudinal nodes. And a transverse steel beam 4 perpendicular to the longitudinal steel beam 3 is provided between the adjacent circumferential steel arch frames 1 in mirror symmetry.

[0028] As a possible implementation, further, the Y-shaped node 2 includes a first fixed arm 21 and a second fixed arm 22 corresponding to the circumferential steel arch frame 1 adjacent to the mirror image. One end of the second fixed arm 22 is bolted to the middle section of the first fixed arm 21 to form a Y-shaped structure. The first fixed arm 21 is bent outward from the connection point where it is connected to the second fixed arm 22. One end of the first fixed arm 21 close to the second fixed arm 22 is bent in an arc shape, and the end far from the second fixed arm 22 is bent vertically. Multiple groups of fixed steel plates 23 are provided inside both the first fixed arm 21 and the second fixed arm 22.

[0029] As Figure 3-4 shown, a rapid construction method for an integral support structure of a connected-arch tunnel includes the following steps:

[0030] (1) Construction preparation. On the basis of familiarizing with and checking the design drawings, the on-site geology, hydrology and surrounding environment are verified; according to the on-site topography, "three connections and one leveling" is done on-site, sufficient construction materials, machinery and tools, etc. are equipped, and preliminary surveying and lofting and other work are done.

[0031] (2) Excavation of the four pilot tunnels with staggered distances and the upper and lower benches with reserved core soil. Advance small pipes + pipe roofs are constructed at the designed positions outside the excavation contour. Under the protection of the advance support, the reserved core soil method is used to excavate the ① pilot tunnel, and the excavation footage is controlled to be the distance of 2-3 sets of steel frames; the initial support is constructed: initially spray concrete 2-4 cm, then erect steel arch frames, construct anchor bolts and hang steel wire meshes; after the excavation and support of the ① pilot tunnel for 3-5 m, the ② pilot tunnel is excavated, and the excavation footage is controlled to be the distance of 2-3 sets of steel frames; the initial support is constructed: initially spray concrete 2-4 cm, erect steel arch frames, construct anchor bolts and hang steel wire meshes, and re-spray the concrete of the part where the steel arch frames have been constructed to the designed thickness; after the excavation and support of the ② pilot tunnel for 10 m, the ③ pilot tunnel is excavated, and the excavation footage is controlled to be the distance of 2-3 sets of steel frames, and the initial support is constructed: initially spray concrete 2-4 cm, set steel arch frames, construct anchor bolts and hang steel wire meshes; after the excavation and support of the ③ pilot tunnel for 3-5 m, the ④ pilot tunnel is excavated, and the excavation footage is controlled to be the distance of 2-3 sets of steel frames, and the initial support is constructed: initially spray concrete 2-4 cm, erect steel arch frames, construct anchor bolts and hang steel wire meshes, and re-spray the concrete of the part where the steel arch frames have been constructed to the designed thickness. As Figure 3 shown.

[0032] (3) Process cycle, alternate excavation of each chamber. According to the above construction method, the excavation of the ①-④ pilot tunnels is completed in one cycle. The upper soil of the ①③ is excavated by manually reserving the core soil, and the soil is transported out through the passage reserved by the temporary inverted arch, turned into the lower bench, and transported out of the tunnel by a small excavator; the lower soil of the ②④ is excavated by manual cooperation with a small excavator, and the soil is transported out of the tunnel by a small loader. The left and right chambers are excavated with a staggered distance of (2-3)D (D is the tunnel span), and the specific distance can be reasonably set according to the actual stratum conditions and the monitoring and measurement results.

[0033] (4) Erection of steel section frames. As Figure 4 shown. ① In the middle wall part of the primary support structure, I25a type I-beams are used, and I20a type I-beams are used in the remaining parts. They are accurately lofted and cut, and fabricated by sectional welding; ② The steel sections in the upper pilot tunnel are installed manually and transported by small flatbed trucks. The steel sections in the lower pilot tunnel are installed manually in cooperation with small excavators. During installation, pay attention to the verticality of the steel frame to prevent the phenomena of left-front and right-rear or forward-tilt and backward-tilt, and make mechanical connections with the steel frame in the upper pilot tunnel, that is, connect them with ordinary bolts M20. Similarly, the circumferential and longitudinal steel frames are also mechanically connected to form a combined support structure. The combined support form formed after the tunnel excavation is as Figure 1 shown, and the position and construction method of the joint nodes of the initial combined support are also the key technologies of the present invention. The detail drawing of the joints is as Figure 2 .

[0034] (5) Waterproof reinforcement of the primary support structure and construction of the secondary lining. The left and right chambers are excavated with a staggered distance and independently constructed under the isolation of the middle partition wall to form a combined primary support structure. For reinforcement above the Y-shaped node, rubble concrete can be used for backfilling and then sprayed again until it is in a full state. Then, waterproof sheets are hung, the secondary lining concrete is constructed, and the transverse steel beam is removed after completion for a traffic test.

[0035] The above are the embodiments of the present invention. For those of ordinary skill in the art, according to the teachings of the present invention, all equal changes, modifications, substitutions, and variations made within the scope of the patent application of the present invention without departing from the principle and spirit of the present invention shall fall within the scope covered by the present invention.

Claims

1. An integral support structure for a multi-arch tunnel, which is used for the support operation of a multi-arch tunnel project, and is characterized in that: The support structure includes multiple groups of circumferential steel arch frames that are longitudinally arranged and fixedly connected in mirror symmetry. The adjacent circumferential steel arch frames in mirror symmetry are fixed through Y-shaped nodes. Multiple groups of longitudinal steel beams are arranged between the multiple groups of circumferential steel arch frames that are longitudinally arranged and fixedly connected in mirror symmetry. The longitudinal steel beams and the circumferential steel arch frames are fixed through circumferential-longitudinal nodes. A transverse steel beam perpendicular to the longitudinal steel beam is provided between the adjacent circumferential steel arch frames in mirror symmetry. The Y-shaped node includes a first fixed arm and a second fixed arm corresponding to the adjacent circumferential steel arch frames in mirror symmetry. One end of the second fixed arm is bolted to the middle section of the first fixed arm to form a Y-shaped structure.

2. The integral support structure of a multi-arch tunnel according to claim 1, characterized in that: The first fixed arm is bent outward from the connection point connected to the second fixed arm.

3. The integral support structure of a multi-arch tunnel according to claim 2, wherein: One end of the first fixed arm close to the second fixed arm is bent in an arc, and the end far from the second fixed arm is bent vertically.

4. The integral support structure of a multi-arch tunnel according to claim 3, wherein: Multiple groups of fixing steel plates are provided in both the first fixed arm and the second fixed arm.

5. A rapid construction method for an integral support structure of a multi-arch tunnel, characterized in that, The method needs to provide an integral support structure for a double-arch tunnel as described in Claim 1, which includes the following steps: Complete the preliminary work of construction preparation. Carry out the excavation of the four pilot tunnels with staggered distances and the reserved core soil for the upper and lower benches. Specifically, it includes: Constructing advanced small ducts and pipe roofs at the designed positions outside the excavation contour. Under the protection of the advanced support, the first pilot tunnel is excavated using the reserved core soil method, and the excavation footage is controlled within the distance of 2-3 sets of steel arch frames. Applying the initial support: Initially spraying concrete with a thickness of 2-4 cm, then erecting the steel arch frames, installing the anchor bolts and hanging the steel mesh. After the excavation and support of the first pilot tunnel for 3-5 m, the second pilot tunnel is excavated, and the excavation footage is controlled within the distance of 2-3 sets of steel arch frames. Applying the initial support: Initially spraying concrete with a thickness of 2-4 cm, erecting the steel arch frames, installing the anchor bolts and hanging the steel mesh, and re-spraying the concrete on the part where the steel arch frames have been installed to the designed thickness. After the excavation and support of the second pilot tunnel for 10 m, the third pilot tunnel is excavated, and the excavation footage is controlled within the distance of 2-3 sets of steel arch frames. Applying the initial support: Initially spraying concrete with a thickness of 2-4 cm, installing the steel arch frames, installing the anchor bolts and hanging the steel mesh. After the excavation and support of the third pilot tunnel for 3-5 m, the fourth pilot tunnel is excavated, and the excavation footage is controlled within the distance of 2-3 sets of steel arch frames. Applying the initial support: Initially spraying concrete with a thickness of 2-4 cm, erecting the steel arch frames, installing the anchor bolts and hanging the steel mesh, and re-spraying the concrete on the part where the steel arch frames have been installed to the designed thickness. Perform the alternating excavation operations for each chamber in the cyclic process. Specifically, it includes: Completing one cycle of the excavation of the first to the fourth pilot tunnels. The upper soil of the first and the third pilot tunnels is excavated by manually reserving the core soil, and the soil is transported out through the passage reserved by the temporary inverted arch. The tunnel slag enters the lower bench and is transported outside the tunnel by a small excavator. The lower soil of the second and the fourth pilot tunnels is excavated manually in cooperation with a small excavator, and the soil is transported outside the tunnel by a small loader. The left and right chambers are excavated with a staggered distance of 2-3 times the tunnel span. Carry out the operation of erecting the steel arch frames. Perform the waterproof reinforcement construction of the initial support structure and carry out the construction of the secondary lining.

6. A rapid construction method for an integral support structure of a multi-arch tunnel according to claim 5, characterized in that: The operation steps for erecting the steel arch frame specifically include: using I25a type I-beams for the middle wall part of the primary support structure, and I20a type I-beams for the remaining parts of the primary support structure, carrying out lofting and cutting, and welding in sections; manually installing the steel arch frames of the first and third pilot tunnels, and transporting them using small flatbed trucks. The steel arch frames of the second and fourth pilot tunnels are installed manually in cooperation with small excavators and mechanically connected to the steel arch frames of the first and third pilot tunnels; the circumferential steel arch frames and the longitudinal steel beams are also mechanically connected to form a combined support structure.

7. A rapid construction method for an integral support structure of a multi-arch tunnel according to claim 5, characterized in that: The steps for waterproof reinforcement of the primary support structure and construction of the secondary lining specifically include: excavating the left and right chambers with staggered distances and independently constructing under the isolation of the middle partition wall to form a combined primary support structure; reinforcing the area above the Y-shaped node, backfilling with rubble concrete, re-spraying to a full state, then hanging the waterproof board, constructing the secondary lining concrete, and removing the transverse steel beam after completion for a traffic test.

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