A construction method for removing temporary support of a double-side-wall pilot tunnel method section of a water-rich large-section underground tunnel under weak geological conditions

Abstract

The present application belongs to the technical field of temporary support removal of tunneling, and particularly relates to a construction method for temporary support removal of double-side-wall pilot tunnel method of water-rich large-section tunneling under weak geological conditions; the method comprises the following steps: S1: removing the shotcrete and I-beam of the temporary mid-parting wall in the inverted arch range in sections; S2: constructing the inverted arch, so that the removed break of the temporary mid-parting wall is supported on the top surface of the reinforced concrete structure of the inverted arch to form a temporary support back-up state; S3: constructing the lower side wall below the temporary inverted arch; S4: removing the shotcrete of the remaining temporary support first, then erecting temporary I-beam cross braces between the top of the lower side walls on both sides, and finally removing the I-beam of the remaining temporary support; and S5: after the temporary support removal is completed, the upper side wall and arch construction are performed, and the inverted arch and secondary lining structure are closed to form a ring. The present application can permanently solve the problem of water seepage channel formed by the I-beam of the temporary support left between the primary support and the secondary lining structure, and ensure the integrity and safety of the structure.

Description

Technical Field

[0001] This invention belongs to the field of temporary support removal technology for mined tunnels, specifically relating to a construction method for temporary support removal of cross-sections of large-section mined tunnels with water abundance under weak geological conditions using the double-side wall pilot tunnel method. Background Technology

[0002] The mined tunnel, situated in a weak geological environment characterized by strongly weathered metamorphic sandstone and abundant water, faces inherently soft and unstable strata. The tunnel cross-section is large, with half of it located within the mountainside, and the support structure experiences complex surrounding conditions such as eccentric stress. The mined tunnel employs the double-sidewall pilot tunnel method for excavation and support construction. During construction, two vertical temporary central partition walls and a transverse temporary invert divide the entire cross-section into six pilot tunnels. Excavation and initial support construction are carried out according to the design requirements. After excavation, secondary lining construction begins, requiring the removal of temporary supports. Due to the instability and water-rich nature of the strata, the traditional technique of "removing one at a time" is often used during temporary support removal. That is, before constructing the invert, if... Figure 1 As shown, two vertical temporary partition walls are removed one at a time to ensure the stability of the overall structure during the construction of the invert arch. However, this technique results in a gap between the initial support and the invert arch structure due to the presence of a remaining temporary support I-beam. This creates a channel connecting the initial support and the invert arch structure, leading to discontinuous waterproofing construction. In addition, the water-rich environment can cause the I-beam to rust and leak under the track over a long period of time. Furthermore, the treatment is labor-intensive, difficult, costly, and time-consuming. Summary of the Invention

[0003] This invention aims to solve the problem of completely removing temporary supports for large-section, water-rich, underground tunnels under weak geological conditions.

[0004] This invention provides the following technical solution: a method for temporary support removal of a cross-section of a large-section, water-rich, cut-and-cover tunnel under weak geological conditions using the double-side-wall pilot tunnel method, comprising the following steps: S1: Under weak geological conditions, the cross-section of the water-rich, large-section tunnel is excavated using the double-side wall pilot tunnel method. After the initial support construction is completed, the shotcrete and I-beams of the temporary central partition wall within the invert arch area are removed section by section. S2: Construction of the invert arch, which allows the temporary central partition wall to be removed and re-supported on the top surface of the reinforced concrete structure of the invert arch, forming a temporary support and jacking state. S3: After the invert arch reaches the design strength, scaffolding is erected at the locations of the lower guide tunnels on both sides to construct the lower wall below the temporary invert arch; S4: After the lower wall reaches the design strength, first remove the remaining temporary support shotcrete in order from top to bottom, then install temporary I-beam cross bracing between the tops of the two lower walls, and finally remove the remaining temporary support I-beams in order from top to bottom. S5: After the temporary supports are removed, full-span scaffolding is erected to carry out the construction of the upper wall and arch, and the inverted arch and secondary lining structure are closed into a ring.

[0005] Furthermore, in step S1, the shotcrete of the temporary partition wall is first removed, and then the I-beams are cut. During the cutting process, the I-beams of the temporary partition walls on the left and right sides are cut in a staggered manner, and each I-beam is cut one by one.

[0006] Further, in step S1, the initial support is monitored during the removal of the temporary central diaphragm. A construction section is divided into several construction intervals. Before the H-beams of the temporary central diaphragm in each construction interval are cut off, initial monitoring data is collected. After the H-beams are cut off, a set of intermediate monitoring data is collected at intervals and compared with the initial monitoring data. At least three sets of intermediate monitoring data are collected for comparison and analysis. If there are no abnormalities in the intermediate monitoring data, the H-beams of the temporary central diaphragm in the next construction interval are cut off, and monitoring is carried out simultaneously until all the H-beams of the temporary central diaphragm in this construction section are cut off. Then, the final monitoring data is collected again and compared with the initial monitoring data. If there are no abnormalities in the final monitoring data, all the H-beams within the invert arch range are cut off.

[0007] Furthermore, in step S1, before the temporary partition wall's I-beam is cut off, a layout is carried out on the I-beam to mark the elevation position of the inner edge line of the invert arch design, and then it is cut off according to the marked position.

[0008] Further, in step S4, after the lower wall reaches the design strength, scaffolding is erected in the middle upper guide tunnel, the left lower guide tunnel, and the right lower guide tunnel. The shotcrete of the temporary supports is removed one by one in the following order: left upper middle partition wall, right upper middle partition wall, left temporary invert arch, right temporary invert arch, middle temporary invert arch, left lower middle partition wall, and right lower middle partition wall. After the shotcrete is removed, temporary I-beam cross braces are erected. After the temporary I-beam cross braces are welded, all temporary support I-beams are removed in the order of shotcrete removal. During the removal process, the invert arch, lower wall, and initial support of the adjacent construction sections are monitored.

[0009] Furthermore, in step S4, the temporary I-beam cross braces are erected at 1m intervals along the longitudinal direction of the tunnel, and the temporary I-beam cross braces are welded to the pre-embedded steel plates on the lower sidewall.

[0010] Furthermore, the construction of the invert arch includes the sequential processing of the base surface, waterproofing, and reinforced concrete structure construction. The waterproofing includes laying geotextile, PVC waterproofing board, and pouring a waterproof protective layer, with continuous waterproofing construction. During the construction of the reinforced concrete structure, the concrete pouring elevation is controlled so that the break position of the temporary partition wall is exactly located on the top surface of the reinforced concrete structure of the invert arch.

[0011] Compared with the prior art, the advantages of the present invention are: This invention provides a method for the temporary support removal of a large-section, water-rich, cut-and-cover tunnel under weak geological conditions using a pilot tunnel method with double-side walls. The method adjusts the length of the temporary central partition wall removal section based on changes in monitoring data during the removal process. If, after removing a certain length, the monitoring data shows an increasing trend, steel plates are used to re-weld the severed H-beams of the temporary central partition wall, forming a support structure to ensure structural safety and stability. Simultaneously, the severed H-beams are quickly cut away, and the base surface is rapidly cleaned, waterproofed, and the reinforced concrete structure of the invert arch is constructed, forming a support structure to ensure structural stability. After the invert arch concrete reaches its design strength, the process of cutting and removing the H-beams of the temporary central partition wall within the next section of the invert arch is continued. This method enables the complete removal of all temporary central partition wall H-beams in complex environments while ensuring safety, eliminating any remaining water inflow channels, reducing the risk of future structural leakage, and ensuring the overall quality of the structure. This construction method is simple and easy to implement, improving construction efficiency while maximizing structural quality.

[0012] This invention relates to a construction method for mine-excavated tunnels in complex environments with water-rich strata. The method involves constructing temporary intermediate diaphragms using the double-sidewall pilot tunnel method or the CRD method during excavation and initial support. After excavation and initial support construction, and before the secondary lining construction, the temporary supports can be safely and quickly dismantled, leaving no water seepage channels such as I-beams between the invert and initial support. This invention permanently solves the problem of water seepage channels formed by I-beams left from temporary supports between the initial and secondary lining structures, ensuring the integrity and safety of the structure. This invention not only accelerates the efficiency of temporary support dismantling in tunnels with a simple process but also ensures tunnel construction safety. Attached Figure Description

[0013] Figure 1 A schematic diagram illustrating the removal of temporary supports using traditional techniques; Figure 2 This is a cross-sectional view of a tunnel excavated using the double-side-wall pilot tunnel method. Figure 3 Construction drawings for the demolition of the temporary central diaphragm within the invert arch area; Figure 4 Construction drawing of the lower side wall below the temporary inverted arch; Figure 5 Construction drawings for the removal of remaining temporary supports; Figure 6 This is a construction drawing of the upper wall and arch.

[0014] In the diagram: 1-Initial support; 2-Left upper middle diaphragm wall; 3-Right upper middle diaphragm wall; 4-Left temporary invert arch; 5-Middle temporary invert arch; 6-Right temporary invert arch; 7-Left lower middle diaphragm wall; 8-Right lower middle diaphragm wall; 9-Invert arch; 10-Temporary middle diaphragm wall within the invert arch area; 11-Right lower side wall; 12-Left lower side wall; 13-Temporary I-beam cross brace; 14-Upper side wall and arch; Ⅰ-Left upper guide tunnel; Ⅱ-Left lower guide tunnel; Ⅲ-Right upper guide tunnel; Ⅳ-Right lower guide tunnel; Ⅴ-Middle upper guide tunnel; Ⅵ-Middle lower guide tunnel. Detailed Implementation

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] After the excavation and initial support construction of a cut-and-cover tunnel using the double-side-wall pilot tunnel method are completed, under conditions of geological instability, water abundance, uneven stress, and a large tunnel cross-sectional area, it is essential to remove the I-beams remaining from the traditional construction process and connected to the initial support, while ensuring safety. This permanently resolves the seepage channel problem and reduces the risk of water seepage under the tunnel track later on. For this situation, this embodiment provides a method for temporarily removing the cross-section support of a large-section cut-and-cover tunnel with water abundance under weak geological conditions using the double-side-wall pilot tunnel method. This method allows for the complete removal of temporary supports in such conditions, ensuring absolute safety during construction while permanently resolving the problem of water seepage channels formed by the remaining I-beams.

[0017] like Figure 2 As shown: The cut-and-cover tunnel adopts the double-side-wall pilot tunnel method for excavation and support construction. During the construction process, two vertical temporary central partition walls (left upper central partition wall 2 and left lower central partition wall 7 form one temporary central partition wall, right upper central partition wall 3 and right lower central partition wall 8 form one temporary central partition wall) and transverse temporary invert arches (left temporary invert arch 4, middle temporary invert arch 5 and right temporary invert arch 6) divide the entire cross-section into six pilot tunnels (left upper pilot tunnel I, left lower pilot tunnel II, right upper pilot tunnel III, right lower pilot tunnel IV, middle upper pilot tunnel V and middle lower pilot tunnel VI).

[0018] A method for temporary support removal of a cross-section in a large-section, water-rich, cut-and-cover tunnel under weak geological conditions using the double-side-wall pilot tunnel method includes the following steps: S1: Under weak geological conditions, the cross-section of a large-section water-rich tunnel is excavated using the double-side-wall pilot tunnel method, and initial support is provided. After construction is completed, if... Figure 3As shown, the shotcrete and I-beams of the temporary central diaphragm within the range of invert arch 9 are removed section by section, that is, the shotcrete and I-beams of the lower left central diaphragm 7 and the lower right central diaphragm 8 within the range of invert arch 9 are removed section by section. Figure 3 (The location indicated by the Chinese numeral "10" in the attached diagram).

[0019] When dismantling the temporary central partition wall 10 within the invert arch area, the shotcrete of the temporary central partition wall is first broken, and then the I-beams are cut. Before the I-beams of the temporary central partition wall are cut off, the layout is carried out on the I-beams to mark the elevation position of the inner edge line of the invert arch 9. Oxygen and acetylene are used to cut them off according to the marked position. During the cutting process, the I-beams of the temporary central partition walls on the left and right sides are cut off in a staggered manner, and each one is cut off one by one.

[0020] During the removal of the temporary central partition wall, the initial support 1 is monitored. A construction section is divided into several construction intervals, each with a length not exceeding 2 meters (along the tunnel longitudinal direction). Initial monitoring data is collected before the H-beams of the temporary central partition wall in each construction interval are cut off. After the H-beams are cut off, a set of intermediate monitoring data is collected every 4 hours and compared with the initial monitoring data for analysis. At least three sets of intermediate monitoring data are collected for comparison and analysis. If there are no abnormalities in the intermediate monitoring data, the H-beams of the temporary central partition wall in the next construction interval are cut off, and monitoring is carried out simultaneously using the same method. This continues until all the H-beams of the temporary central partition wall in this construction section are cut off. Then, the final monitoring data is collected again and compared with the initial monitoring data. If there are no abnormalities in the final monitoring data, all the H-beams within the invert arch area are cut off.

[0021] The method for removing the I-beams of the temporary central partition wall 10 within the invert arch range is to cut the I-beams in one construction section along the design inner edge elevation of the invert arch 9, and then conduct continuous monitoring. If the monitoring data is normal, the cutting of the I-beams in the next construction section will be carried out. After the cutting of the I-beams in the entire construction section is completed, the I-beams on the initial support 1 will be removed.

[0022] The length of the temporary partition wall construction section can be adjusted according to the changes in the corresponding monitoring data during the demolition process. When a certain length is demolished, if the changes in the monitoring data exceed the set value, steel plates are used to re-weld the I-beams of the temporary partition wall that are currently disconnected to form a support and ensure the structural safety and stability. At the same time, the I-beams of the previously disconnected temporary supports are quickly cut off, and the base surface cleaning, waterproofing, and inverted arch reinforced concrete structure construction are quickly organized.

[0023] S2: After the removal of the I-beams of the temporary central partition wall 10 within the construction section of the invert arch 9, the base surface within the invert arch 9 area is immediately treated, and waterproof materials such as geotextile and PVC waterproof board are laid. Waterproofing construction is ensured to be continuous. The waterproof protective layer is poured. The invert arch reinforcement and concrete pouring construction is organized according to the design requirements of the reinforcement type, spacing and concrete grade. During the pouring process, the pouring elevation is strictly controlled according to the design requirements so that the break position of the temporary central partition wall is exactly located on the top surface of the reinforced concrete structure of the invert arch 9 after the pouring is completed. After the concrete of the invert arch 9 reaches the design strength, it forms a support back-top state to ensure the stability of the overall initial support structure of the tunnel section.

[0024] S3: As Figure 4 As shown, after the invert arch 9 reaches its design strength, scaffolding is erected at the locations of the two lower guide tunnels (left lower guide tunnel II and right lower guide tunnel IV) to construct the lower walls below the temporary invert arch (left lower wall 12 below the left temporary invert arch 4 and right lower wall 11 below the right temporary invert arch 6). The left lower wall 12 and right lower wall 11 are first treated on the base surface, then the construction of waterproof structures such as geotextile and PVC waterproof board is carried out, followed by steel bar binding, formwork installation and reinforcement construction, and finally the lower wall concrete is poured.

[0025] S4: After the lower wall reaches the design strength, first remove the remaining temporary support shotcrete in order from top to bottom, then install temporary I-beam cross bracing 13 between the tops of the two lower walls, and finally remove the remaining temporary support I-beams in order from top to bottom.

[0026] like Figure 5 As shown: Specifically, after the lower wall reaches its design strength, scaffolding is erected in the upper guide tunnel V in the middle, and the lower guide tunnels II on the left and IV on the right. The shotcrete of the temporary supports is removed one by one in the following order: upper left middle partition wall 2, upper right middle partition wall 3, left temporary invert arch 4, right temporary invert arch 6, middle temporary invert arch 5, lower left middle partition wall 7, and lower right middle partition wall 8. After the shotcrete is removed, temporary I-beam cross braces 13 are erected. After the temporary I-beam cross braces 13 are welded, all temporary support I-beams are removed in the same order as the shotcrete removal. During the removal process, the invert arch, lower wall, and initial support 1 of the adjacent construction sections are monitored. The monitoring method is to collect a set of initial monitoring data of the invert arch, lower wall, and initial support 1 of the adjacent construction sections before removal. During the removal process, intermediate monitoring data of the invert arch, lower wall, and initial support 1 of the adjacent construction sections are collected. The intermediate monitoring data is compared with the initial monitoring data to determine whether the limits are exceeded.

[0027] Along the longitudinal direction of the tunnel, the temporary I-beam cross braces 13 are erected at intervals of 1m, and the temporary I-beam cross braces 13 are welded to the pre-embedded steel plates on the lower side wall.

[0028] S5: As Figure 6As shown: After the temporary supports are removed, full-span scaffolding is erected to carry out the construction of the upper wall and arch 14, and the inverted arch 9 and secondary lining structure are closed into a ring.

[0029] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for temporary support removal of the cross-section of a large-section, water-rich, cut-and-cover tunnel under weak geological conditions using the double-side-wall pilot tunnel method, characterized in that... Includes the following steps: S1: Under weak geological conditions, the cross-section of the water-rich large-section tunnel is excavated and initially supported by the double-side wall pilot tunnel method. (1) After the construction is completed, the shotcrete and I-beams of the temporary central partition wall within the invert arch (9) are removed section by section. S2: Construction of the inverted arch (9) allows the temporary middle partition wall to be removed and re-supported on the top surface of the reinforced concrete structure of the inverted arch (9) to form a temporary support back-top state; S3: After the invert arch (9) reaches the design strength, scaffolding is erected at the locations of the lower guide holes on both sides to construct the lower wall below the temporary invert arch; S4: After the lower wall reaches the design strength, first remove the remaining temporary support shotcrete in the order from top to bottom, then erect temporary I-beam cross bracing (13) between the top of the two lower walls, and finally remove the remaining temporary support I-beams in the order from top to bottom. S5: After the temporary support is removed, a full-span scaffold is erected to carry out the construction of the upper wall and arch (14), and the inverted arch (9) and secondary lining structure are closed into a ring.

2. The construction method for temporary support removal of a double-side wall pilot tunnel in a water-rich, large-section mined tunnel under weak geological conditions, as described in claim 1, is characterized in that: In step S1, the shotcrete of the temporary partition wall is first removed, and then the I-beams are cut. During the cutting process, the I-beams of the temporary partition walls on the left and right sides are cut in a staggered manner, and each one is cut in turn.

3. The construction method for temporary support removal of a double-side wall pilot tunnel in a water-rich, large-section mined tunnel under weak geological conditions, as described in claim 2, is characterized in that: In step S1, the initial support (1) is monitored during the removal of the temporary central partition wall. A construction section is divided into several construction sections. Before the H-beams of the temporary central partition wall in each construction section are cut off, initial monitoring data is collected. After the H-beams are cut off, a set of intermediate monitoring data is collected after a period of time and compared with the initial monitoring data. At least three sets of intermediate monitoring data are collected for comparison and analysis. If there are no abnormalities in the intermediate monitoring data, the H-beams of the temporary central partition wall in the next construction section are cut off and monitored simultaneously until all the H-beams of the temporary central partition wall in this construction section are cut off. Then, the final monitoring data is collected again and compared with the initial monitoring data. If there are no abnormalities in the final monitoring data, all the H-beams in the invert arch range are cut off.

4. The construction method for temporary support removal of a double-side wall pilot tunnel in a large-section, water-rich, mined tunnel under weak geological conditions, as described in claim 3, is characterized in that: In step S1, before the temporary partition wall is cut off, the I-beam is laid out on the I-beam, and the elevation position of the inner edge line of the inverted arch (9) is marked. The inverted arch is then cut off according to the marked position.

5. The construction method for temporary support removal of a double-side wall pilot tunnel in a large-section, water-rich, mined tunnel under weak geological conditions, as described in claim 4, is characterized in that: In step S4, after the lower wall reaches the design strength, scaffolding is erected in the middle upper guide tunnel (V), the left lower guide tunnel (II), and the right lower guide tunnel (IV). The shotcrete of the temporary supports is removed one by one in the order of the left upper middle partition wall (2), the right upper middle partition wall (3), the left temporary inverted arch (4), the right temporary inverted arch (6), the middle temporary inverted arch (5), the left lower middle partition wall (7), and the right lower middle partition wall (8). After the shotcrete is removed, temporary I-beam cross bracing (13) is erected. After the temporary I-beam cross bracing (13) is welded, all the temporary supports of the I-beams are removed in the order of the shotcrete removal. During the removal process, the inverted arch, lower wall, and initial support (1) of the adjacent construction section are monitored.

6. The construction method for temporary support removal of a double-side wall pilot tunnel in a large-section, water-rich, mined tunnel under weak geological conditions, as described in claim 5, is characterized in that: In step S4, the temporary I-beam cross braces (13) are erected at 1m intervals along the longitudinal direction of the tunnel, and the temporary I-beam cross braces (13) are welded to the pre-embedded steel plates on the lower side wall.

7. A method for temporary support removal of a cross-section in a large-section, water-rich, mined tunnel under weak geological conditions, as described in any one of claims 1 to 6, characterized in that: The construction of the invert arch includes the sequential treatment of the base surface, construction waterproofing, and construction of the reinforced concrete structure. The construction waterproofing includes laying geotextile, PVC waterproofing board, and pouring waterproof protective layer, and the waterproofing is carried out continuously. During the construction of the reinforced concrete structure, the concrete pouring elevation is controlled so that the break position of the temporary partition wall is exactly located on the top surface of the reinforced concrete structure of the invert arch.

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