Large-section tunnel in-situ reconstruction and extension subsection construction method based on existing tunnel state

Abstract

The invention relates to the technical field of tunnel engineering, in particular to a large-section tunnel in-situ reconstruction and extension subsection construction method based on an existing tunnel state. A preceding pilot tunnel and a following pilot tunnel are excavated in sequence, a middle partition wall temporary support of the preceding pilot tunnel is dismantled after excavation is completed, and the dismantling length of each time is 3-5 m; then, an inverted arch is excavated; secondary lining construction is conducted, specifically, inverted arch secondary lining construction is conducted firstly, and then arch wall secondary lining construction is conducted; and the steps are repeated to complete construction of single-side in-situ reconstruction and extension of the large-section tunnel. According to the construction method, direct construction can be achieved without backfilling the existing tunnel, and the work amount and the construction cost are remarkably reduced. Meanwhile, a segmented excavation mode with few procedures is adopted, the first pilot tunnel is excavated and formed at a time, and the number of steps of the later pilot tunnel can be adjusted according to the stability of surrounding rock, so that the construction process is simplified, the flexibility of setting the number of the steps of the later pilot tunnel is enhanced, and the construction efficiency is effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tunnel engineering, in particular to a large-section tunnel in-situ reconstruction and expansion construction method based on the state of an existing tunnel. BACKGROUND

[0002] With the continuous advancement of urbanization, the demand for highway transportation is showing an explosive growth trend. However, the early built highway tunnels have been difficult to adapt to the development needs of modern transportation systems due to problems such as traffic capacity lag. Tunnel reconstruction and expansion, with the advantages of efficient resource utilization, small environmental impact, and outstanding economy, has become an effective way to improve the adaptability and service capacity of the road network. In recent years, the progress of construction technology and the upgrading of equipment have promoted the development of highway tunnel reconstruction and expansion projects towards large section and large span, and the scientific selection of construction methods is crucial to ensure construction safety and improve construction efficiency.

[0003] To reduce safety risks, the existing in-situ reconstruction and expansion technology is still relatively single and traditional, and the current unilateral in-situ reconstruction and expansion tunnel construction method is still mainly based on the traditional CD method and CRD method. Among them, the CD method is to excavate one side first and set a middle partition wall, and then excavate the other side; the CRD method divides the section into small blocks in the upper and lower, left and right, and excavates and supports in cross steps. However, these methods require backfilling the existing tunnel to the hance position before expanding in-situ, and then excavating according to the corresponding method. The existing tunnel needs to be backfilled before construction, the construction process is complex, and the construction efficiency is low, but the advantage is that it can effectively control the deformation of surrounding rock, and is suitable for highway tunnels with large excavation section, small tunnel net distance, and poor stability of surrounding rock. The bench method is also used in unilateral in-situ reconstruction and expansion projects. The bench method has the advantages of simple construction process and high construction efficiency, and is suitable for tunnels with good surrounding rock conditions and small excavation section. Its applicability in the in-situ reconstruction and expansion construction process of large-section tunnels still needs further research.

[0004] Chinese patent application CN118208243A discloses a method for in-situ expansion of a section tunnel, which is aimed at the problem of poor stability of rock mass in some local sections of the tunnel body, and does not set a middle partition wall. Chinese patent application CN108131143A discloses a construction method of super-large span tunnel step method, which is aimed at tunnels with poor surrounding rock conditions, and does not aim at reconstruction and expansion tunnels.

[0005] Therefore, in the unilateral in-situ reconstruction and expansion construction of the large-section tunnel, the arch waist part of the existing tunnel needs to be backfilled before expansion, and then the expansion is carried out in sections. In the actual construction process, the backfilling and excavation processes of the existing tunnel are time-consuming and labor-intensive, the excessive sections affect the construction efficiency and the operation space is narrow, the construction processes interfere with each other, the construction process is long and the work efficiency is low, and a new construction method needs to be developed according to the actual situation of the existing tunnel to improve the unilateral in-situ construction efficiency of the large-section tunnel. SUMMARY

[0006] The purpose of the present application is to provide a large-section tunnel in-situ reconstruction and expansion construction method based on the state of an existing tunnel to solve the problem of long construction process and low work efficiency of unilateral in-situ reconstruction and expansion construction of a large-section tunnel when the surrounding rock has a certain self-stability (one-time excavation of the pilot heading, and the excavation surface can be self-stable).

[0007] In order to achieve the above purpose, the present application provides a large-section tunnel in-situ reconstruction and expansion construction method based on the state of an existing tunnel, comprising the following steps:

[0008] S1. Dividing the large-section tunnel into a pilot heading and a trailing heading, and the area where the existing tunnel is located is the pilot heading;

[0009] S2. Excavating the pilot heading, specifically comprising steps S201-S202:

[0010] S201. The length of the pilot heading is excavated to 5-10 m;

[0011] S202. Then, the initial support of the pilot heading is constructed, and the temporary support of the mid-parting wall of the pilot heading is constructed;

[0012] S3. Excavating the trailing heading, specifically comprising steps S301-S304:

[0013] S301. Excavating the upper step of the trailing heading: when the length of the pilot heading reaches 5-10 m, excavate the upper step of the trailing heading, and the length of the step is 5-10 m;

[0014] S302. Constructing the initial support of the upper step of the trailing heading;

[0015] S303. Excavating the lower step of the trailing heading, and the height of the lower step of the trailing heading is 3-5 m and the length is 5-10 m;

[0016] S304. Constructing the initial support of the lower step of the trailing heading;

[0017] S4. Removing the temporary support of the mid-parting wall of the pilot heading, and the length of each removal is 3-5 m;

[0018] S5. Excavating the inverted arch;

[0019] S6. Secondary lining is applied: secondary lining of inverted arch is applied first, and then secondary lining of arch wall is applied;

[0020] S7. Steps S2-S6 are repeated to complete the construction of the large-section tunnel in-situ unilateral reconstruction and extension.

[0021] Preferably, the surrounding rock in the large-section tunnel construction area has self-stability, and the pilot heading is excavated in one time, and the excavation surface can be self-stable.

[0022] Preferably, the surrounding rock in the large-section tunnel construction area is of grade IV or above.

[0023] Preferably, the excavation of the trailing heading (4) in step S3 is excavated in one time, and the following three conditions are met simultaneously:

[0024] a. The advanced geological prediction confirms that the surrounding rock in front is of grade IV or above, and there is no adverse geological body, including faults, fracture zones, and water-rich areas;

[0025] b. The deformation of the tunnel primary support in the constructed area is basically stable, and the cumulative displacement value is less than U0 / 6, U0 being the design limit displacement value, wherein the tunnel primary support in the constructed area includes the primary support of the pilot heading, the primary support of the upper step of the trailing heading, and the lower step of the trailing heading;

[0026] c. The monitoring excavation section self-measuring point is reduced to ≤0.2mm / d within 7 days from the date of laying, and the level is maintained for 2 consecutive days, and the overall deformation-time curve shows a rapid convergence trend.

[0027] Preferably, the area above the excavation area of the pilot heading to the large-section tunnel excavation contour, and the area below the existing tunnel pavement, the existing tunnel pavement is not excavated during the excavation of the pilot heading and the trailing heading.

[0028] Preferably, the large-section tunnel is a single-hole four-lane highway tunnel or a tunnel with an excavation span of not less than 18m.

[0029] The above scheme of the present application has the following advantages:

[0030] The present application proposes a tunnel construction method suitable for in-situ unilateral reconstruction and extension of surrounding rock with certain self-stability for large-section tunnel in-situ reconstruction and extension construction process, and develops a method of directly constructing without backfilling the existing tunnel for the case of surrounding rock with certain self-stability (the pilot heading is excavated in one time, and the excavation surface can be self-stable), which abandons the conventional method of large-scale backfilling of the existing tunnel, thereby significantly reducing the workload and construction cost.

[0031] Meanwhile, the method of the present application adopts the sub-construction method with less sub-parts, each part is constructed independently, there is no mutual interference problem of process, and the construction space is large, which is beneficial to the mechanized construction; when the reconstruction and expansion construction is carried out, the existing tunnel pavement can be fully utilized, and there is no need to harden the pavement again;

[0032] The first pilot pit is excavated in advance, and the flexibility of setting the number of steps of the subsequent pilot pit is enhanced. In the excavation process of the subsequent pilot pit, the number of steps of the subsequent pilot pit can be adjusted from two-step excavation to one-step excavation according to the site surrounding rock conditions, structure and surrounding rock displacement stress, the process is simplified, and the construction efficiency and quality stability of the large-span tunnel reconstruction and expansion are significantly improved.

[0033] Other beneficial effects of the present application will be described in detail in the subsequent specific embodiment part. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The figure is a construction structure schematic diagram of the embodiment of the present application.

[0035]

Explanation of reference signs

[0036] 1-first pilot pit; 2-first pilot pit initial support; 3-intermediate wall temporary support; 4-subsequent pilot pit; 41-upper step of subsequent pilot pit; 42-initial support of upper step of subsequent pilot pit; 43-lower step of subsequent pilot pit; 44-initial support of lower step of subsequent pilot pit; 5-inverted arch; 6-inverted arch secondary lining arch wall; 7-secondary lining; 8-existing tunnel. DETAILED DESCRIPTION

[0037] In order to make the technical problems, technical solutions and advantages of the present application clearer, specific embodiments will be described in detail below with reference to the drawings and specific embodiments. Obviously, the described embodiments are part of the embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application. In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0038] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", "third" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance.

[0039] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "linking" should be understood in a broad sense, for example, it can be a locking connection, or a detachable connection, or an integral connection; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or a communication within two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0040] As shown in Figure 1 The embodiment of the present application provides a large-section tunnel in-situ reconstruction and expansion construction method based on existing tunnel state, which comprises the following steps:

[0041] S1. The large-section tunnel is divided into a leading pilot pit 1 and a trailing pilot pit 4, and the region where the existing tunnel 8 is located is the leading pilot pit 1. Correspondingly, the other region without the existing tunnel 8 is the trailing pilot pit 4. It should be noted that the surrounding rock of the large-section tunnel construction region has self-stability, and the specific surrounding rock self-stability refers to that when the leading pilot pit 1 is excavated once, the excavation surface can be self-stable. In the embodiment, the surrounding rock grade of the large-section tunnel construction region is greater than or equal to grade IV, and in other embodiments, V-grade surrounding rock can also be used after reinforcement to reach the condition of grade IV surrounding rock. For the single-side in-situ reconstruction and expansion construction of the large-section tunnel with good surrounding rock, the significance of backfilling this step is mainly to provide a working platform, and the counterpressure effect on the tunnel can basically be ignored, which instead increases the construction steps and reduces the construction efficiency. Therefore, the present application innovatively develops a construction method which does not need to backfill the existing tunnel before in-situ reconstruction and expansion construction.

[0042] S2. Excavating the leading pilot pit 1, specifically comprising steps S201-S202:

[0043] S201. The length of the leading pilot pit 1 is 5-10 m; in the embodiment, the preferred specific length of the construction length of the leading pilot pit 1 is 10 m, and the longer leading pilot pit 1 can reduce the alternating frequency of support and excavation, facilitate the operation and circulation of mechanical equipment, and be beneficial to continuous construction.

[0044] S202. Then, the initial support 2 of the leading pilot pit 1 is constructed, and the temporary support 3 of the mid-parting wall of the leading pilot pit 1 is constructed.

[0045] Preferably, the upper part of the excavation region of the leading pilot pit 1 to the large-section tunnel excavation contour and the lower part to the road surface of the existing tunnel 8 are not excavated when the leading pilot pit 1 and the trailing pilot pit 4 are excavated, and the road surface of the existing tunnel 8 can be fully utilized as a temporary channel for transportation and personnel access during construction, which can further simplify the construction process.

[0046] S3. Excavate the subsequent pilot tunnel, and the specific steps include:

[0047] S301. Excavate the subsequent pilot tunnel upper step 41: when the excavation length of the first pilot tunnel 1 reaches 5-10 m (10 m in this embodiment), start excavating the subsequent pilot tunnel upper step 41, the length of the subsequent pilot tunnel upper step 41 is 5-10 m, and the length of the subsequent pilot tunnel upper step 41 can be consistent with the excavation length of the first pilot tunnel 1 or be adjusted flexibly according to the actual situation of the site construction;

[0048] S302. Construct the subsequent pilot tunnel upper step initial support 42;

[0049] S303. Excavate the subsequent pilot tunnel lower step 43, and specifically, the height of the subsequent pilot tunnel lower step 43 is 3-5 m, and the length is 5-10 m;

[0050] S304. Construct the subsequent pilot tunnel lower step initial support 44.

[0051] In step S3, during the excavation of the subsequent pilot tunnel 4, according to the conditions of the surrounding rock, the structure and the displacement stress of the surrounding rock, the number of steps of the subsequent pilot tunnel 4 can be adjusted from two-step excavation to one-step excavation, thereby simplifying the process and speeding up the construction efficiency. Specifically, the following conditions need to be met for one-step excavation of the subsequent pilot tunnel 4:

[0052] (1) The advanced geological prediction confirms that the surrounding rock in front is consistent with the current construction section or is better (greater than or equal to IV level), and there is no unfavorable geological body such as fault, fracture zone, and water-rich area;

[0053] (2) The deformation of the tunnel initial support construction area is basically stable, and the cumulative displacement value is less than U0 / 6, U0 is the design limit displacement value, and the tunnel initial support construction area includes the first pilot tunnel initial support 2, the subsequent pilot tunnel upper step initial support 42, and the subsequent pilot tunnel lower step 43;

[0054] (3) The monitoring section is reduced to ≤0.2 mm / d within 7 days from the date of monitoring point layout, and this level is maintained for 2 consecutive days, and the overall deformation-time curve shows a rapid convergence trend.

[0055] S4. Remove the temporary support of the middle partition wall of the first pilot tunnel, and the length removed at a time is 3-5 m;

[0056] S5. Excavate the inverted arch 5;

[0057] S6. Construct the secondary lining: first construct the inverted arch secondary lining 6, and then construct the arch wall secondary lining 7;

[0058] S7. Repeat steps S2-S6 to complete the construction of the in-situ expansion of the large cross-section tunnel on one side.

[0059] In the embodiment, the large-section tunnel is a single-hole four-lane highway tunnel or a tunnel with an excavation span of no less than 18 m.

[0060] The in-situ reconstruction and expansion construction method for the existing tunnel provided by the embodiment solves the problems of slow construction progress, high construction cost and the like caused by backfilling first and then construction, too many parts, and complicated processes in the in-situ reconstruction and expansion construction of a large-section tunnel on one side when the surrounding rock has a certain self-stability (a first pilot heading is excavated once, and the excavation surface can be self-stable). The conventional method of large-scale backfilling of the existing tunnel is abandoned, thereby significantly reducing the workload and construction cost; a sub-division construction method with fewer sub-divisions is adopted, each part is independently constructed, there is no problem of mutual interference of processes, and the construction space is large, which is beneficial to mechanized construction; the existing tunnel pavement can be fully utilized during reconstruction and expansion construction, and there is no need to harden the construction pavement again. The first pilot heading is excavated once, thereby enhancing the flexibility of the number of steps of the subsequent pilot heading, the subsequent pilot heading can be excavated once, thereby greatly simplifying the construction process and improving the construction efficiency.

[0061] The technical features of the above embodiments can be combined arbitrarily, and to make the description concise, all possible combinations of the technical features in the above embodiments are not described, however, as long as the combinations of the technical features do not exist contradictory, it should be considered that the combinations are within the scope of the present disclosure.

[0062] The above embodiments only express several implementation manners of the present application, the description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the application. It should be noted that, for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A large-section tunnel in-situ reconstruction and expansion construction method based on existing tunnel state, characterized in that, It comprises the following steps: S1. The large-section tunnel is divided into a leading pilot tunnel (1) and a trailing pilot tunnel (4), and the area where the existing tunnel (8) is located is the leading pilot tunnel (1); S2. The leading pilot tunnel (1) is excavated, specifically comprising steps S201-S202: S201. The length of the leading pilot tunnel (1) is excavated to 5-10 m; S202. Then the leading pilot tunnel initial support (2) is constructed, and the temporary support (3) of the middle partition wall of the leading pilot tunnel (1) is constructed; S3. The trailing pilot tunnel (4) is excavated, which can be excavated in one step or two steps, and the two steps specifically comprise steps S301-S304: S301. Excavate the upper step (41) of the trailing pilot tunnel: when the length of the leading pilot tunnel (1) reaches 5-10 m, excavate the upper step (41) of the trailing pilot tunnel, and the length of the upper step of the trailing pilot tunnel is 5-10 m; S302. Construct the upper step initial support (42) of the trailing pilot tunnel; S303. Excavate the lower step (43) of the trailing pilot tunnel, and the height of the lower step (43) of the trailing pilot tunnel is 3-5 m and the length is 5-10 m; S304. Construct the lower step initial support (44) of the trailing pilot tunnel; S4. Remove the temporary support (3) of the middle partition wall of the leading pilot tunnel (1), and the length removed each time is 3-5 m; S5. Excavate the inverted arch (5); S6. Construct the secondary lining: first construct the inverted arch secondary lining (6), and then construct the arch wall secondary lining (7); S7. Repeat steps S2-S6 to complete the construction of the large-section tunnel single-side in-situ reconstruction.

2. The in-situ reconstruction and extension method of large cross-section tunnel based on existing tunnel state according to claim 1, characterized in that, The surrounding rock in the construction area of the large-section tunnel has self-stability, and the leading pilot tunnel (1) can be self-stable after one excavation.

3. The in-situ reconstruction and extension method of large cross-section tunnel based on existing tunnel state according to claim 2, characterized in that, The surrounding rock grade in the construction area of the large-section tunnel is greater than or equal to grade IV.

4. The in-situ reconstruction and extension method of large cross-section tunnel based on existing tunnel state according to claim 1, characterized in that, In step S3, the excavation of the trailing pilot tunnel (4) in one step needs to meet the following three conditions: a. The advanced geological prediction confirms that the surrounding rock grade in front is greater than or equal to grade IV, and there is no adverse geological body, including faults, fracture zones, and water-rich areas; b. The deformation of the tunnel initial support constructed area is basically stable, and the cumulative displacement value is less than U0 / 6, U0 being the design ultimate displacement value, wherein the tunnel initial support constructed area includes the leading pilot tunnel initial support (2), the trailing pilot tunnel upper step initial support (42), and the trailing pilot tunnel lower step (43); c. The monitoring excavation section self-measuring point is reduced to ≤0.2 mm / d within 7 days from the date of laying, and this level is maintained for 2 consecutive days, and the overall deformation-time curve shows a rapid convergence trend.

5. The in-situ reconstruction and extension method of large cross-section tunnel based on existing tunnel state according to claim 1, characterized in that, The upper part of the excavation area of the leading pilot tunnel (1) to the excavation contour of the large-section tunnel, and the lower part to the road surface of the existing tunnel (8), the road surface of the existing tunnel (8) is not excavated during the excavation of the leading pilot tunnel (1) and the trailing pilot tunnel (4).

6. The in-situ reconstruction and extension method of large cross-section tunnel based on existing tunnel state according to claim 1, characterized in that, The large-section tunnel is a single-hole four-lane highway tunnel or a tunnel with an excavation span of not less than 18 m.

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