A rectangular large-section shallow-buried tunnel excavation method
By dividing the tunnel into multiple frames and forming closed loops in a rectangular large-section shallow buried tunneling method, combined with grid steel frame and anchor pipe support, the problem of large soil disturbance during tunnel construction was solved, and the stability and applicability of the tunnel were improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-06-30
- Publication Date
- 2026-04-07
AI Technical Summary
Existing tunnel construction methods cause significant disturbance to the surrounding soil and have poor stability, making them unsuitable for tunnels in complex environments, those passing through cultural heritage sites, those surrounded by dense buildings, or those with poor engineering geological conditions.
The tunnel face was divided into three rows and four columns, totaling twelve frames. Each frame was excavated and promptly sealed into a ring. Initial support was provided using a grid steel frame and anchor pipes. The surrounding rock was reinforced by advanced large pipe roof grouting, and secondary lining was carried out gradually.
It reduces soil disturbance during tunnel excavation, improves construction stability, is suitable for complex environments and geological conditions, and protects the surrounding environment.
Smart Images
Figure CN115126491B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of building construction, and in particular to a method for excavating a rectangular large-section shallow buried tunnel. Background Technology
[0002] Currently, the most common cross-section of urban tunnels is the arch structure. This structure has a clear stress distribution and is easy to stabilize, but its net width is limited to a certain extent. As the requirements for urban road traffic continue to increase, in order to meet the driving conditions, the use of a large rectangular cross-section can increase the traffic volume and better adapt to the traffic requirements.
[0003] Existing tunnel construction methods, such as the CRD method or CD method, all have the problems of large disturbance to the surrounding soil and poor stability. They are not suitable for tunnels with complex surrounding environments, those passing through cultural heritage protection areas, those with dense surrounding buildings, or those with poor engineering geological conditions. Summary of the Invention
[0004] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a method for excavating shallow buried tunnels with rectangular large cross-sections, which can reduce disturbance to the soil around the tunnel and improve the stability during tunnel construction.
[0005] According to an embodiment of the present invention, a method for excavating a rectangular large-section shallow buried tunnel includes the following steps: Step S1, dividing the tunnel end face into a first row, a second row, and a third row, and further dividing each row into a left part, a left middle part, a right middle part, and a right part, thus dividing the tunnel end face into a total of twelve frames; Step S2, excavating the twelve frames one by one in sequence, and providing initial support for each frame after excavation, and promptly sealing the frames in the same section of the tunnel after excavation; Step S3, after all frames have been excavated, performing secondary lining on the basis of the initial support in the order of bottom plate, side plate, and top plate.
[0006] The invention offers at least the following advantages: In the tunnel excavation method of this invention, the tunnel face is divided into three rows and four columns, totaling twelve frames, for excavation. Increasing the number of frames reduces the excavation span and height, thereby minimizing disturbance to the surrounding soil and effectively preventing damage to the surrounding environment. The tunnel excavation method of this invention is particularly suitable for tunnels in complex environments, those traversing protected cultural sites, those surrounded by dense buildings, or those with poor geological conditions. Furthermore, this invention adopts the principle of segmented ring formation and timely closure, ensuring that the excavated cross-sections are interlocked, forming a full-section initial support and closure structure.
[0007] According to some embodiments of the present invention, the following steps are included before step S1: constructing an advanced large pipe roof and performing pipe roof grouting at the tunnel initiation excavation site, injecting a mixture of MC type ultrafine cement and PO silicate cement into the surrounding rock area, and injecting a two-liquid grout of cement and water glass into the core soil area within the excavation outline inside the surrounding rock.
[0008] According to some embodiments of the present invention, the excavation sequence in step S2 is as follows: Step S2.1, excavate the left area of the first row, and construct grouting pipes, install the grid steel frame, spray concrete, and erect temporary vertical supports. Locking anchor pipes are installed on both the left and right sides of the left area of the first row; Step S2.2, excavate the left area of the second row, install the grid steel frame, spray concrete, and erect temporary vertical supports. Locking anchor pipes are installed on both the left and right sides of the left area of the second row; Step S2.3, excavate the left area of the third row, install the grid steel frame, spray concrete, and erect temporary vertical supports. Locking anchor pipes are installed on both the left and right sides of the left area of the third row; Step S2.4, excavate the right area of the first row... In step S2.1, the area is excavated, and grouting pipes are installed, a steel grid frame is installed, shotcrete is applied, and temporary vertical supports are erected. Anchor pipes are installed on both sides of the right side of the first row. In step S2.5, the right side of the second row is excavated, a steel grid frame is installed, shotcrete is applied, and temporary vertical supports are erected. Anchor pipes are installed on both sides of the right side of the second row. In step S2.6, the anchor pipes on the right side of the left side of the first row are removed. Simultaneously, the right side of the third row and the left-middle area of the first row are excavated, and grouting pipes are installed in the left-middle area of the first row. Steel grid frames are installed, shotcrete is applied, and temporary vertical supports are erected in both the right side of the third row and the left-middle area of the first row. In step S2.6, the anchor pipes on the right side of the left-middle region of the first row are installed, and anchor pipes on both sides of the right region of the third row are installed. In step S2.7, the anchor pipes on the right side of the left-middle region of the first row in step S2.6, the anchor pipes on the left side of the right region of the first row in step S2.4, and the anchor pipes on the right side of the left region of the second row in step S2.2 are removed. At the same time, the right-middle region of the first row and the left-middle region of the second row are excavated. In the right-middle region of the first row, grouting pipes are installed and grid steel frames are installed. In both the right-middle region of the first row and the left-middle region of the second row, shotcrete is applied and temporary vertical supports are erected. Anchor pipes are installed on the right side of the left-middle region of the second row. Step S2.8: Remove the anchor pipes on the right side of the left area of the third row in Step S2.3, the anchor pipes on the left side of the right area of the second row in Step S2.5, and the anchor pipes on the right side of the left-middle area of the second row in Step S2.7. Simultaneously excavate the right-middle area of the second row and the left-middle area of the third row, and install a grid steel frame in the left-middle area of the third row. Spray concrete is applied to both the right-middle area of the second row and the left-middle area of the third row, and temporary vertical supports are erected. Anchor pipes are installed on the right side of the left-middle area of the third row. Step S2.9: Remove the anchor pipes on the right side of the left-middle area of the third row in Step S2.8, excavate the right-middle area of the third row, and install a grid steel frame.
[0009] According to some embodiments of the present invention, in step S2, during the forward excavation of each frame, the excavation depth of each subsequent step lags behind that of the previous step by a certain distance.
[0010] According to some embodiments of the present invention, the hysteresis distance is between 2 meters and 3 meters.
[0011] According to some embodiments of the present invention, the initial support in step S2 is provided by a grating steel frame. Before the grating steel frame is used, the welded grating steel frame needs to be trial-assembled.
[0012] According to some embodiments of the present invention, the grating steel frame adopts a width of 250mm, and the initial support process also includes temporary support, which adopts I22b type I-beams.
[0013] According to some embodiments of the present invention, the allowable deviation of the perimeter assembly of the grating steel frame needs to be controlled within the range of ±30mm, and the planar warping needs to be less than 20mm.
[0014] According to some embodiments of the present invention, during the tunnel excavation process, it is necessary to monitor and measure the displacement of the tunnel perimeter, the subsidence of the arch, the surface settlement, and the displacement and pressure of the surrounding rock.
[0015] According to some embodiments of the present invention, in the secondary lining process of step S3, a secondary lining support is first erected on the basis of the initial support, and a template is laid on the outer ring of the secondary lining support. Finally, concrete is injected into the area between the template and the initial support structure.
[0016] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description
[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:
[0018] Figures 1 to 9 This is a schematic diagram of steps S2.1 to S2.9 in an embodiment of the present invention;
[0019] Figure 10 This is a structural schematic diagram of the secondary lining step in an embodiment of the present invention;
[0020] Figure 11 This is a top view diagram illustrating the relative excavation depth of each frame in an embodiment of the present invention.
[0021] Icon labels:
[0022] Tunnel end face 100, first row left area 110, first row left middle area 120, first row right middle area 130, first row right area 140, second row left area 150, second row left middle area 160, second row right middle area 170, second row right area 180, third row left area 190, third row left middle area 1000, third row right middle area 1100, third row right area 1200;
[0023] Surrounding rock 200, excavation outline 210;
[0024] 300mm anchor pipe for locking feet;
[0025] 400mm grating steel frame;
[0026] Temporary support level: 500;
[0027] Secondary lining area 600, formwork 610, secondary lining support 620. Detailed Implementation
[0028] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.
[0029] In the description of this invention, it should be understood that the orientation descriptions, such as front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.
[0030] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.
[0031] Reference Figures 1 to 11 This invention discloses a method for excavating a rectangular large-section shallow buried tunnel, specifically including the following steps:
[0032] Step S1: Divide the tunnel end face 100 into the first row, the second row and the third row, and further divide each row into the left part, the left middle, the right middle and the right part, so that the tunnel end face 100 is divided into a total of twelve frames.
[0033] Step S2: Excavate the twelve frames one by one in sequence. Each frame needs to be initially supported after excavation. After all frames on the same cross section of the tunnel are excavated, they should be sealed into a ring in time.
[0034] Step S3: After all the frames have been excavated, secondary lining is carried out on the basis of the initial support, following the order of bottom plate, side plate and top plate.
[0035] In the tunnel excavation method of this invention, the tunnel end face 100 is divided into three rows and four columns, totaling twelve frames for excavation. Increasing the number of frames reduces the excavation span and height, thereby minimizing disturbance to the surrounding soil and effectively preventing damage to the nearby environment from tunnel excavation. This tunnel excavation method is particularly suitable for tunnels in complex environments, those traversing protected cultural heritage areas, those with dense surrounding buildings, or those with poor geological conditions. Furthermore, this invention adopts the principle of segmented ring formation and timely closure, ensuring that the excavated cross-sections are interlocked, forming a full-section initial support and closure structure.
[0036] It is understood that the embodiments of the present invention further include the following steps before step S1: constructing an advanced large pipe roof and performing pipe roof grouting at the tunnel's initial excavation point; injecting a mixture of MC-type ultrafine cement and PO silicate cement into the surrounding rock area; and injecting a two-component grout of cement and water glass into the core soil area within the excavation outline 210 of the surrounding rock 200. The mixture of MC-type ultrafine cement and PO silicate cement has fine particles, allowing for large-scale injection into fine sand layers, achieving good sand-fixing and water-blocking effects, and resulting in high strength of the consolidated body. PO silicate cement is a hydraulic cementitious material made by grinding silicate cement clinker, 5%-20% of mixed materials, and an appropriate amount of gypsum. It possesses characteristics such as high strength, high heat of hydration, good frost resistance, low shrinkage, good wear resistance, good carbonation resistance, poor corrosion resistance, and poor high-temperature resistance. Pre-grouting reinforcement and water-stopping of the surrounding rock 200 and core soil provides safe construction conditions for excavation.
[0037] Specifically, φ108mm advanced large pipe roofs can be used as advanced pre-support. In the tunnel excavation section, the advanced large pipe roofs are installed within the open-cut foundation pit. A φ108mm advanced large pipe roof combined with φ42mm grouting small pipes is installed in a 40m long area at the tunnel entrance to ensure construction safety. The grouting small pipes are installed throughout the entire tunnel length. The grouting small pipes are 3.5m long steel pipes, driven into the soil using a jacking drill. The front end of the steel pipe is pointed, and the borehole openings are arranged in two rows within a 180-degree range along the excavation profile arch, with an external insertion angle of 10 to 15 degrees and a longitudinal spacing of 200cm. The horizontal overlap length between adjacent rows of grouting small pipes is no less than 1m.
[0038] like Figures 1 to 9 As shown, the specific mining sequence in step S2 of this embodiment of the invention is as follows:
[0039] Step S2.1: Excavate the left area 110 of the first row, and install grouting pipes, install grid steel frame 400, spray concrete and erect vertical temporary support 500, and install anchor pipes 300 on both the left and right sides of the left area 110 of the first row.
[0040] Step S2.2: Excavate the left area 150 of the second row, install the grid steel frame 400, spray concrete and erect the vertical temporary support 500, and install the locking anchor pipe 300 on both the left and right sides of the left area 150 of the second row.
[0041] Step S2.3: Excavate the left area 190 of the third row, install the grid steel frame 400, spray concrete and erect the vertical temporary support 500, and install the locking anchor pipe 300 on both the left and right sides of the left area 190 of the third row.
[0042] Step S2.4: Excavate the right side area 140 of the first row, and install grouting pipes, install grid steel frame 400, spray concrete and erect vertical temporary support 500, and install anchor pipes 300 on both the left and right sides of the right side area 140 of the first row.
[0043] Step S2.5: Excavate the right side area 180 of the second row, install the grid steel frame 400, spray concrete and erect the vertical temporary support 500, and install the locking anchor pipe 300 on both the left and right sides of the right side area 180 of the second row.
[0044] Step S2.6: Remove the anchor pipe 300 on the right side of the left area 110 of the first row in step S2.1. At the same time, excavate the right area 1200 of the third row and the left middle area 120 of the first row. Install grouting pipes in the left middle area 120 of the first row. Install grid steel frame 400 and sprayed concrete in both the right area 1200 of the third row and the left middle area 120 of the first row, and erect vertical temporary supports 500. Install anchor pipe 300 on the right side of the left middle area 120 of the first row, and install anchor pipe 300 on both the left and right sides of the right area 1200 of the third row.
[0045] Step S2.7: Remove the anchor pipe 300 on the right side of the left middle area 120 of the first row in step S2.6, the anchor pipe 300 on the left side of the right area 140 of the first row in step S2.4, and the anchor pipe 300 on the right side of the left area 150 of the second row in step S2.2. At the same time, excavate the right middle area 130 of the first row and the left middle area 160 of the second row. In the right middle area 130 of the first row, install the grouting pipe and the grid steel frame 400. Spray concrete in the right middle area 130 of the first row and the left middle area 160 of the second row and erect the vertical temporary support 500. Install the anchor pipe 300 on the right side of the left middle area 160 of the second row.
[0046] Step S2.8: Remove the anchor pipe 300 on the right side of the left area 190 of the third row in step S2.3, the anchor pipe 300 on the left side of the right area 180 of the second row in step S2.5, and the anchor pipe 300 on the right side of the left middle area 160 of the second row in step S2.7. At the same time, excavate the right middle area 170 of the second row and the left middle area 1000 of the third row, and install the grid steel frame 400 in the left middle area 1000 of the third row. Spray concrete and erect vertical temporary supports 500 in the right middle area 170 of the second row and the left middle area 1000 of the third row. Install the anchor pipe 300 on the right side of the left middle area 1000 of the third row.
[0047] Step S2.9: Remove the anchor pipe 300 on the right side of the left middle area 1000 in the third row in step S2.8, excavate the right middle area 1100 in the third row, and install the grid steel frame 400.
[0048] Using the above excavation sequence minimizes disturbance to the surrounding soil. Furthermore, it should be noted that in the above shotcrete process, early-strength concrete can be used, and the concrete mix proportion should be determined based on testing. Concrete with alkali-reactive aggregates is strictly prohibited. Additionally, admixtures can be added according to project requirements.
[0049] like Figure 11 As shown, during the excavation of each frame in step S2, the excavation depth of each subsequent step lags behind that of the previous step by a certain distance. That is, each frame is staggered from the others to reduce disturbance to the surrounding rock. Specifically, the aforementioned lag distance can be controlled between 2 and 3 meters.
[0050] Reference Figure 10 In step S2 of this embodiment of the invention, initial support is provided using the grating steel frame 400. Before using the grating steel frame 400, the welded grating steel frame 400 needs to be trial-assembled to check whether the connection parts of each grating steel frame 400 fit together, so as to avoid misalignment during actual installation and improve construction efficiency. The allowable deviation of the grating steel frame 400 perimeter assembly needs to be controlled within ±30mm, and the planar warping needs to be less than 20mm.
[0051] Specifically, the grating steel frame 400 can be made of 250mm wide steel bars, structural steel, or steel rails. The grating steel frame 400 includes main reinforcement, figure-eight reinforcement, and connecting plates. The figure-eight reinforcement within the grating steel frame 400 must be uniform, symmetrical, and staggered in direction, with a spacing of no more than 50mm. The figure-eight reinforcement and the main reinforcement and connecting plates should be double-sided welded, with smooth, full, and continuous welds. A reinforcing mesh can be installed between the grating steel frames 400. The reinforcing mesh can be made of Q235 steel with a diameter between 6mm and 12mm, and a mesh size between 150mm and 300mm. The reinforcing mesh must be securely connected to the anchor pipe 300 or other fixing devices. The initial support process also includes temporary support, which can use I22b type I-beams.
[0052] During the tunnel excavation process in this embodiment of the invention, it is necessary to monitor and measure the displacement of the tunnel perimeter, the subsidence of the arch, the surface settlement, and the displacement and pressure of the surrounding rock.
[0053] In the secondary lining process of step S3 of this embodiment, a secondary lining support 620 can be erected first on the basis of the initial support, and a template 610 can be laid on the outer ring of the secondary lining support 620. Finally, concrete is poured into the secondary lining area 600 between the template 610 and the initial support structure. The thickness of the secondary lining can be 1.2m. The above secondary lining method does not require the use of a trolley, which is especially suitable for tunnels with short excavation lengths, because the construction space in such tunnels is limited, and the trolley is often large and inconvenient to enter and exit. Furthermore, secondary lining on the basis of the initial support does not require the removal of the temporary support 500 structure of the initial support, which can ensure a more stable secondary lining process.
[0054] It should be noted that the template 610 is made of several steel bars lapped together in a mesh. When installing the steel bars, the joints of the main reinforcing bars should be welded. The lap length of single-sided lap welding should not be less than 10 times the outer diameter of the steel bar, and the lap length of double-sided lap welding should not be less than 5 times the outer diameter of the steel bar. When cutting the steel bars, the joints of the steel bars should be staggered by 50%, and the staggered distance should not be less than 100cm. When installing the steel bars, the positioning of the layer spacing is generally determined by welding positioning steel bars. The positioning steel bars should be laid out using a total station to determine the position of the positioning steel bars and the corresponding inner ring steel bars. Before the steel bars are installed, there should be no less than 7 positioning points in each cross section. Then, a skeleton for fixing the steel bars should be erected at the positioning points. The ends of the positioning steel bars should be covered with plastic protective sleeves to protect the waterproof layer.
[0055] The rectangular large-section shallow buried tunnel excavation method in this embodiment of the invention specifically includes the following steps:
[0056] Step S1: Divide the tunnel end face 100 into the first row, the second row and the third row, and further divide each row into the left part, the left middle, the right middle and the right part, so that the tunnel end face 100 is divided into a total of twelve frames.
[0057] Step S2.1: Excavate the left area 110 of the first row, and install grouting pipes, install grid steel frame 400, spray concrete and erect vertical temporary support 500, and install anchor pipes 300 on both the left and right sides of the left area 110 of the first row.
[0058] Step S2.2: Excavate the left area 150 of the second row, install the grid steel frame 400, spray concrete and erect the vertical temporary support 500, and install the locking anchor pipe 300 on both the left and right sides of the left area 150 of the second row.
[0059] Step S2.3: Excavate the left area 190 of the third row, install the grid steel frame 400, spray concrete and erect the vertical temporary support 500, and install the locking anchor pipe 300 on both the left and right sides of the left area 190 of the third row.
[0060] Step S2.4: Excavate the right side area 140 of the first row, and install grouting pipes, install grid steel frame 400, spray concrete and erect vertical temporary support 500, and install anchor pipes 300 on both the left and right sides of the right side area 140 of the first row.
[0061] Step S2.5: Excavate the right side area 180 of the second row, install the grid steel frame 400, spray concrete and erect the vertical temporary support 500, and install the locking anchor pipe 300 on both the left and right sides of the right side area 180 of the second row.
[0062] Step S2.6: Remove the anchor pipe 300 on the right side of the left area of the first row in step S2.1. At the same time, excavate the right area 1200 of the third row and the left middle area 120 of the first row. Install grouting pipes in the left middle area 120 of the first row. Install grid steel frame 400 and sprayed concrete in both the right area 1200 of the third row and the left middle area 120 of the first row, and erect vertical temporary supports 500. Install anchor pipe 300 on the right side of the left middle area 120 of the first row, and install anchor pipe 300 on both the left and right sides of the right area 1200 of the third row.
[0063] Step S2.7: Remove the anchor pipe 300 on the right side of the left middle area 120 of the first row in step S2.6, the anchor pipe 300 on the left side of the right area 140 of the first row in step S2.4, and the anchor pipe 300 on the right side of the left area 150 of the second row in step S2.2. At the same time, excavate the right middle area 130 of the first row and the left middle area 160 of the second row. In the right middle area 130 of the first row, install the grouting pipe and the grid steel frame 400. Spray concrete in the right middle area 130 of the first row and the left middle area 160 of the second row and erect the vertical temporary support 500. Install the anchor pipe 300 on the right side of the left middle area 160 of the second row.
[0064] Step S2.8: Remove the anchor pipe 300 on the right side of the left area 190 of the third row in step S2.3, the anchor pipe 300 on the left side of the right area 180 of the second row in step S2.5, and the anchor pipe 300 on the right side of the left middle area 160 of the second row in step S2.7. At the same time, excavate the right middle area 170 of the second row and the left middle area 1000 of the third row, and install the grid steel frame 400 in the left middle area 1000 of the third row. Spray concrete and erect vertical temporary supports 500 in the right middle area 170 of the second row and the left middle area 1000 of the third row. Install the anchor pipe 300 on the right side of the left middle area 1000 of the third row.
[0065] Step S2.9: Remove the anchor pipe 300 on the right side of the left middle area 1000 in the third row in step S2.8, excavate the right middle area 1100 in the third row, and install the grid steel frame 400.
[0066] Step S3: After all the frames have been excavated, a secondary lining support 620 is erected on the basis of the initial support, and a template 610 is laid on the outer ring of the secondary lining support 620. Finally, concrete is injected into the secondary lining area 600 between the template 610 and the initial support structure, and the secondary lining is carried out in the order of bottom plate, side plate and top plate.
[0067] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0068] Of course, the present invention is not limited to the above-described embodiments. Those skilled in the art can make equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.
Claims
1. A method for excavating a rectangular large-section shallow buried tunnel, characterized in that, Includes the following steps: At the tunnel's initial excavation point, an advanced large pipe roof is constructed and grouting is performed. A mixture of MC-type ultrafine cement and PO silicate cement is injected into the surrounding rock area. A two-component grout of cement and water glass is injected into the core soil area within the excavation outline inside the surrounding rock. Step S1: Divide the tunnel end face into the first row, the second row and the third row, and further divide each row into the left part, the left middle, the right middle and the right part, so that the tunnel end face is divided into a total of twelve frames; Step S2: Excavate the twelve frames one by one in sequence. Each frame needs to be initially supported after excavation. After the excavation of each frame on the same cross section of the tunnel is completed, the frame is closed into a ring in a timely manner. The excavation sequence in step S2 is as follows: Step S2.1: Excavate the left area of the first row, install grouting pipes, install the grid steel frame, spray concrete and erect temporary vertical supports, and install anchor pipes on both the left and right sides of the left area of the first row. Step S2.2: Excavate the left area of the second row, install the grid steel frame, spray concrete and erect temporary vertical supports, and install anchor pipes on both the left and right sides of the left area of the second row. Step S2.3: Excavate the left area of the third row, install the grid steel frame, spray concrete and erect temporary vertical supports, and install anchor pipes on both the left and right sides of the left area of the third row. Step S2.4: Excavate the right side of the first row, install grouting pipes, install the grid steel frame, spray concrete and erect temporary vertical supports, and install anchor pipes on both the left and right sides of the right side of the first row. Step S2.5: Excavate the right side of the second row, install the grid steel frame, spray concrete and erect temporary vertical supports, and install anchor pipes on both the left and right sides of the right side of the second row. Step S2.6: Remove the anchor pipe on the right side of the left area of the first row in step S2.1, and excavate the right area of the third row and the left middle area of the first row. Install grouting pipes in the left middle area of the first row. Install grid steel frame and sprayed concrete in both the right area of the third row and the left middle area of the first row and erect temporary vertical supports. Install anchor pipe on the right side of the left middle area of the first row and install anchor pipe on both the left and right sides of the right area of the third row. Step S2.7: Remove the anchor pipe on the right side of the left middle area of the first row in step S2.6, the anchor pipe on the left side of the right area of the first row in step S2.4, and the anchor pipe on the right side of the left area of the second row in step S2.
2. At the same time, excavate the right middle area of the first row and the left middle area of the second row, and install grouting pipes and grid steel frames in the right middle area of the first row. Spray concrete is applied to both the right middle area of the first row and the left middle area of the second row, and temporary vertical supports are erected. An anchor pipe is installed on the right side of the left middle area of the second row. Step S2.8: Remove the anchor pipes on the right side of the left area of the third row in step S2.3, the anchor pipes on the left side of the right area of the second row in step S2.5, and the anchor pipes on the right side of the left middle area of the second row in step S2.
7. At the same time, excavate the right middle area of the second row and the left middle area of the third row, install a grid steel frame in the left middle area of the third row, spray concrete and erect temporary vertical supports in the right middle area of the second row and the left middle area of the third row, and install anchor pipes on the right side of the left middle area of the third row. Step S2.9: Remove the anchor pipe on the right side of the left middle area of the third row in step S2.8, excavate the right middle area of the third row, and install the grid steel frame; Step S3: After all the frames have been excavated, a secondary lining support is erected on the basis of the initial support, and a template is laid on the outer ring of the secondary lining support. Finally, concrete is injected into the area between the template and the initial support, and the secondary lining is carried out in the order of bottom plate, side plate and top plate.
2. The method for excavating a rectangular large-section shallow buried tunnel according to claim 1, characterized in that, In step S2, during the process of each frame digging forward, the digging depth of each subsequent step lags behind that of the previous step by a certain distance.
3. The method for excavating a rectangular large-section shallow buried tunnel according to claim 2, characterized in that, The lag distance is between 2 and 3 meters.
4. The method for excavating a rectangular large-section shallow buried tunnel according to claim 1, characterized in that, In step S2, initial support is provided by a grating steel frame. Before the grating steel frame is used, the welded grating steel frame needs to be trial-assembled.
5. The method for excavating a rectangular large-section shallow buried tunnel according to claim 4, characterized in that, The grating steel frame is 250mm wide. The initial support process also includes temporary support, which uses I22b type I-beams.
6. The method for excavating a rectangular large-section shallow buried tunnel according to claim 5, characterized in that, The allowable deviation of the perimeter assembly of the grating steel frame must be controlled within ±30mm, and the planar warping must be less than 20mm.
7. The method for excavating a rectangular large-section shallow buried tunnel according to claim 1, characterized in that, During tunnel excavation, it is necessary to monitor and measure the displacement of the tunnel's perimeter, the subsidence of the arch, the surface settlement, and the displacement and pressure within the surrounding rock.
Citation Information
Patent Citations
Small-angle bottom-penetrating construction method of highway grid tunnel
CN106401591A