Temporary inverted arch and inferior surrounding rock tunnel construction method

Abstract

The invention provides a temporary inverted arch and an inferior surrounding rock tunnel construction method.The temporary inverted arch comprises an arch frame body, and the arch frame body comprises a plurality of steel frameworks linearly arranged in the tunnel excavation direction and connecting ribs connected among the steel frameworks; the two ends of each steel framework are detachably connected with a primary supporting steel arch on the inner wall of the tunnel, and a concrete layer is poured on an arch body. The inferior surrounding rock tunnel construction method comprises the steps that after a core soil section is excavated, the temporary inverted arch is constructed above a step section; the step section is excavated, and the primary support is constructed, so that the temporary inverted arch and the primary support after the annular arch section is excavated can be quickly closed to form a group of complete temporary stress rings, and the stress rings can effectively bear surrounding rock pressure from the periphery, uniformly transfer loads and remarkably inhibit arch crown sinking and side wall convergence; therefore, surrounding rock deformation is controlled to the maximum extent, and construction safety is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of tunnel construction, and more specifically, to a method for constructing tunnels with temporary inverts and poor surrounding rock. Background Technology

[0002] The ring excavation method with reserved core soil is the preferred construction method for tunnels with poor geological conditions and weak surrounding rock that is prone to collapse. It is mostly used for the construction of tunnels with Class V or Class VI surrounding rock.

[0003] In existing technologies, the excavation and initial support of the annular arch section, the excavation of the core soil section, and the excavation and initial support of the stepped section are carried out sequentially. During construction, a certain length of core soil is reserved at the tunnel excavation section as support for the tunnel excavation section, which can prevent the collapse or instability of the excavation section. The core soil provides a stable working platform for the excavation and support of the annular arch, which facilitates mechanical operation and personnel construction and reduces the risk of high-altitude operations. At the same time, the soil of the stepped section provides support for the lower side of the surrounding rock, ensuring the safety of construction. However, when the above method is applied to the construction of tunnels in some more severe surrounding rock conditions, the excavation process of the stepped section will to some extent damage the original support system of the surrounding rock, making the surrounding rock susceptible to deformation and collapse. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings mentioned in the background art and to provide a method for constructing temporary inverted arches and tunnels in poor surrounding rock.

[0005] The objective of this invention is achieved through the following solutions: On one hand, the present invention provides a temporary inverted arch, including an arch frame body, the arch frame body including a plurality of steel frames extending along the tunnel width direction and connecting bars connecting the plurality of steel frames, the plurality of steel frames being arranged at intervals along the tunnel excavation direction; both ends of each group of steel frames are detachably connected to the initial support steel arch frame on the inner wall of the tunnel, and a concrete layer is poured on the arch frame body.

[0006] The temporary inverted arch of the present invention has at least the following beneficial effects: The temporary inverted arch is constructed by building a metal arch frame body with several steel frames and connecting bars. Then, a layer of concrete is sprayed and poured on the arch frame body to form a load-bearing whole. It can be used for temporary support during the excavation of tunnels in poor surrounding rock to ensure construction safety. After construction is completed, the concrete layer on the arch frame body can be removed and the arch frame body can be recycled and reused to reduce construction costs.

[0007] Furthermore, the steel frame includes several frame segments, and each pair of adjacent frame segments are connected by flange assemblies; this ensures the overall connection strength and reliability of the steel frame while also making the steel frame easy to disassemble, assemble, and transport.

[0008] Furthermore, each set of skeleton segments has wing plates welded to its outer wall, and the wing plates have multiple through holes, with connecting bars passing through each set of through holes; by passing the connecting bars through the wing plates, spot welding can be used to ensure the stability of the overall structure of the arch frame.

[0009] On the other hand, the present invention also provides a method for constructing tunnels in poor surrounding rock, comprising the following steps: S1. Divide the tunnel excavation section into a stepped section on the lower side, a core soil section on the upper side, and an annular arch section on the periphery of the core soil section. S2. Excavate the cross-section of the annular arch and construct the initial support, which includes the initial support steel frame. S3. Excavate the core soil section and construct the aforementioned temporary inverted arch above the stepped section; S4. Excavate the bench section and construct initial support; S5. Construct the permanent invert arch and secondary lining, and dismantle the temporary invert arch; S6. Repeat steps S1 to S5 until the tunnel construction is completed.

[0010] The method for constructing tunnels in substandard surrounding rock according to the present invention has at least the following beneficial effects: Before excavating the bench section, a temporary inverted arch is constructed on the side bench section. This allows the temporary inverted arch to quickly close with the initial support after the excavation of the annular arch section, forming a complete temporary stress ring. This stress ring can effectively withstand the pressure from the surrounding rock, evenly transfer the load, significantly suppress the settlement of the arch crown and the convergence of the sidewalls, thereby controlling the deformation of the surrounding rock to the greatest extent and ensuring construction safety.

[0011] Meanwhile, during the subsequent excavation of the stepped section, the temporary inverted arch ensured the stability of the completed upper support structure, preventing it from becoming unstable due to the lower part being suspended, and providing a safe working environment for the construction workers.

[0012] Further, step S2 includes the following sub-steps: S20. Along the outer contour of the annular arch section, advanced small guide pipes are installed on the tunnel excavation section and grouting is performed to reinforce and improve the surrounding rock outside the excavation contour line, thereby enhancing the overall strength of the surrounding rock structure. S21. Gradually excavate the annular arch section from the top of the arch to both sides, and promptly implement initial support.

[0013] Furthermore, step S3 includes the following sub-steps: S30, Excavation of the core soil section; S31. The arch frame body is constructed one step at a time along the excavation direction of the core soil section, and concrete is sprayed inside the steel arch frame; in particular, by constructing the arch frame body one step at a time, it can be ensured that the excavated part can be supported by the temporary inverted arch in a timely manner.

[0014] Furthermore, in step S4, the step section is divided into a horizontally adjacent first step section and a second step section, and the first step section and the second step section are excavated in sections by skipping trenches. The skipping trench excavation method is used to control the excavation sequence and spatial interval of the first step section and the second step section, so as to avoid excessive concentrated load and disturbance to the surrounding rock caused by large-scale and continuous operations, thereby ensuring construction safety.

[0015] Furthermore, step S5 includes the following sub-steps: S50. Construct permanent invert arches and invert arch backfill structures and level them to serve as access routes for construction personnel and machinery. S51. Construct a secondary lining to build a more stable permanent surrounding rock support system; S52. Remove the temporary inverted arch and break the concrete layer on the temporary inverted arch so that the arch frame body can be recycled and reused.

[0016] Furthermore, the single excavation advance of the annular arch section is between 0.5m and 1m, and the single excavation advance of the first and second step sections is between 1m and 3m; the distance between the annular arch section and the core soil section after a single excavation is 3m to 5m. Attached Figure Description

[0017] Figure 1 A cross-sectional schematic diagram of the tunnel construction method for substandard surrounding rock provided in an embodiment of the present invention; Figure 2 A longitudinal cross-sectional schematic diagram of the tunnel construction method for substandard surrounding rock provided in an embodiment of the present invention; Figure 3 A schematic diagram of the construction process of the tunnel construction method for substandard surrounding rock provided in an embodiment of the present invention; Figure 4 A schematic diagram of a temporary inverted arch structure provided in an embodiment of the present invention; The attached diagram lists the components represented by each number as follows: 1. Temporary invert arch; 10. Steel frame; 100. Frame segment; 11. Connecting reinforcement; 12. Wing plate; 120. Through-reinforcement hole; 2. Excavation section; 20. Annular arch section; 21. Core soil section; 22. Stepped section; 220. First stepped section; 221. Second stepped section; 3. Initial support; 30. Pre-installed small guide pipe; 4. Permanent invert arch; 5. Secondary lining; 6. Invert arch backfill structure. Detailed Implementation

[0018] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0019] Example 1: Reference Figure 4 This embodiment provides a temporary inverted arch 1, which includes an arch frame body and a layer of concrete (not shown) sprayed onto the arch frame body.

[0020] The arch frame body includes several steel frames 10 extending along the tunnel width direction and connecting bars 11 connecting the several steel frames 10. The several steel frames 10 are arranged at intervals along the tunnel excavation direction. Both ends of each group of steel frames 10 are detachably connected to the initial support steel arch frame on the inner wall of the tunnel by bolts.

[0021] Therefore, the temporary inverted arch 1 is constructed into a metal arch frame body by several steel frames 10 and connecting bars 11, and then a concrete layer is sprayed and poured on the arch frame body to form a load-bearing whole. It can be used for temporary support during the excavation of tunnels in poor surrounding rock to ensure the safety of construction.

[0022] After construction is completed, the concrete layer on the arch frame can be removed by using pneumatic jackhammers, electric picks, etc., and the arch frame can be recycled and reused, reducing construction costs.

[0023] Reference Figure 4 Each steel frame 10 includes several frame segments 100. Each pair of adjacent frame segments 100 are connected by a flange assembly, which can ensure the overall connection strength and reliability of the steel frame 10, and also make the steel frame 10 easy to disassemble and transport.

[0024] When installing the temporary invert arch 1, several skeleton segments 100 of each group of steel skeleton 10 are assembled one by one at the construction site. The two ends of the steel skeleton 10 are then fastened to the initial support steel arch frame on the inner wall of the tunnel by bolts. Then, several steel skeletons 10 are connected together by several connecting bars 11, and concrete is sprayed on the arch frame body to form the aforementioned concrete layer.

[0025] Reference Figure 4 Optionally, wing plates 12 can be welded to the outer wall of each set of skeleton segments 100. The wing plates 12 are provided with multiple through holes 120, and the aforementioned connecting ribs 11 are inserted into each set of through holes 120. By inserting the connecting ribs 11 into the wing plates 12, spot welding can be used to ensure the stability of the overall structure of the arch frame. At the same time, the diameter of the through holes 120 can be much larger than the diameter of the connecting ribs 11. During disassembly, the spot welded part between the connecting ribs 11 and the through holes 120 can be directly struck to detach the connecting ribs 11 from the steel skeleton 10.

[0026] Example 2: Reference Figures 1 to 3 This embodiment provides a method for constructing tunnels in substandard surrounding rock, including the following steps: S1. First, refer to Figure 1The excavation section 2 of the tunnel (i.e. the tunnel face) is divided into a step section 22 located on the lower side, a core soil section 21 located on the upper side, and an annular arch section 20 located around the core soil section 21. S2, then, refer to Figure 2 and Figure 3 Excavate the annular arch section 20 and construct the initial support 3 on the inner wall of the tunnel on the outer periphery of the annular arch section 20; wherein, the initial support 3 includes the erected initial support steel frame and drilled anchor rods and other structures, and then spray concrete to form a temporary support system. S3. Reference Figure 2 Excavate the core soil section 21 and construct the temporary inverted arch 1 designed in Example 1 above the step section 22, wherein the steel frame 10 of the temporary inverted arch 1 is supported on the upper surface of the step section 22.

[0027] S4. Refer to the excavation bench section 22 and construct the initial support 3 on the inner walls of the tunnel on both sides of the bench section 22; S5. Then, a permanent invert arch 4 is constructed at the bottom of the tunnel, and a secondary lining 5 is constructed on the surface of the initial support 3 on the inner wall of the tunnel perimeter. The temporary invert arch 1 is then removed. S6. Repeat steps S1 to S5 until the construction of the entire tunnel is completed segment by segment.

[0028] In this embodiment, the single excavation advance of the annular arch section 20 is controlled between 0.5m and 1m; in addition, the distance between the annular arch section 20 and the core soil section 21 after a single excavation is controlled between 3m and 5m.

[0029] Based on the existing ring excavation method with reserved core soil, in this embodiment, a temporary inverted arch 1 is constructed above the lower step section 22 before the excavation of the step section 22. This allows the temporary inverted arch 1 to quickly close with the initial support 3 after the excavation of the ring arch section 20, forming a complete temporary stress ring. This stress ring can effectively withstand the pressure from the surrounding rock, evenly distribute the load, significantly suppress the settlement of the arch crown and the convergence of the sidewalls, thereby controlling the deformation of the surrounding rock to the greatest extent and ensuring construction safety. In addition, during the subsequent excavation of the step section 22, the temporary inverted arch 1 ensures the stability of the completed upper support structure, preventing the risk of instability caused by suspension during the excavation of the lower step section 22, and providing a safe working environment for the construction personnel.

[0030] In some embodiments, step S2 may include the following sub-steps: S20. First, along the outer contour of the annular arch section 20, advance small guide pipes 30 are installed on the tunnel excavation section 2 and grout is injected to reinforce and improve the surrounding rock outside the excavation contour line and enhance the overall strength of the surrounding rock structure. S21. Then, the annular arch section 20 is excavated gradually from the top of the arch to both sides, and the initial support 3 is applied in a timely manner.

[0031] In some embodiments, step S3 includes the following sub-steps: S30, Excavation of core soil section 21; S31. Along the excavation direction of the core soil section 21, the arch frame body is built one step at a time, and concrete is sprayed inside the steel arch frame; in particular, by building the arch frame body one step at a time, it can be ensured that the excavated part can be supported in time by the temporary inverted arch 1.

[0032] Reference Figure 1 and Figure 3 In some embodiments, in step S4, the step section 22 can be divided into a first step section 220 and a second step section 221 that are horizontally adjacent to each other, and the first step section 220 and the second step section 221 can be excavated by a segmented trenching method.

[0033] Among them, the method of skip-slot excavation is adopted to control the excavation sequence and spatial interval of the first bench section 220 and the second bench section 221, so as to avoid excessive concentrated load and disturbance to the surrounding rock caused by large-scale and continuous operations, thereby ensuring construction safety; for example, the single excavation advance of the first bench section 220 and the second bench section 221 is controlled between 1m and 3m.

[0034] In some embodiments, step S5 includes the following sub-steps: S50. Construct permanent invert arch 4 and invert arch backfill structure 6 and level them. The upper surface of invert arch backfill structure 6 can serve as an operating passage for construction personnel and machinery. S51. Then, construct the secondary lining 5 to build a more stable permanent surrounding rock support system. S52. Then, the temporary invert arch 1 is dismantled, and the concrete layer on the temporary invert arch 1 is broken, so that the arch frame body can be recycled and reused.

[0035] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used 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 limitations on this invention.

[0036] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0037] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0038] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0039] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0040] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A temporary inverted arch, characterized in that, The system includes an arch frame body, which comprises a plurality of steel frames extending along the tunnel width direction and connecting bars connecting the plurality of steel frames, and the plurality of steel frames are arranged at intervals along the excavation direction of the tunnel; both ends of each group of steel frames are detachably connected to the initial support steel arch frame on the inner wall of the tunnel, and a concrete layer is poured on the arch frame body.

2. The temporary inverted arch of claim 1, wherein, The steel frame includes several frame segments, and each pair of adjacent sets of frame segments are connected by a flange assembly.

3. The temporary inverted arch of claim 2, wherein, Each set of the skeleton segments has a wing plate welded to its outer wall. The wing plate has multiple through holes, and each set of through holes has a connecting rib inserted through it.

4. A method of constructing a tunnel in poor surrounding rock, characterized by, Includes the following steps: S1. Divide the tunnel excavation section into a stepped section on the lower side, a core soil section on the upper side, and an annular arch section on the periphery of the core soil section. S2. Excavate the cross-section of the annular arch and construct initial support; wherein, the initial support includes an initial steel frame. S3. Excavate the core soil section and construct the temporary inverted arch as described in claim 1, 2 or 3 above the stepped section; S4. Excavate the aforementioned step cross-section and construct initial support; S5. Construct the permanent invert arch and secondary lining, and dismantle the temporary invert arch; S6. Repeat steps S1 to S5 until the tunnel construction is completed.

5. The method for constructing tunnels in substandard surrounding rock according to claim 4, characterized in that, Step S2 includes the following sub-steps: S20. Install advanced small guide pipes along the outer contour of the annular arch section on the tunnel excavation section and inject grout; S21. The annular arch section is excavated gradually from the top of the arch to both sides, and initial support is provided.

6. The method for constructing tunnels in substandard surrounding rock according to claim 4, characterized in that, Step S3 includes the following sub-steps: S30. Excavate the core soil section; S31. The arch frame body is constructed one by one along the excavation direction of the core soil section, and concrete is sprayed inside the steel arch frame.

7. The method for constructing tunnels in substandard surrounding rock according to claim 4, characterized in that, In step S4, the step cross-section is divided into a first step cross-section and a second step cross-section that are horizontally adjacent, and the first step cross-section and the second step cross-section are excavated in sections with skip trenches.

8. The method for constructing tunnels in substandard surrounding rock according to claim 4, characterized in that, Step S5 includes the following sub-steps: S50. Construct the permanent invert arch and invert arch backfill structure and level the surface. S51. Perform the secondary lining as described above; S52. Remove the temporary inverted arch.

9. The method for constructing tunnels in substandard surrounding rock according to claim 7, characterized in that, The single excavation advance of the annular arch section is between 0.5m and 1m, and the single excavation advance of the first step section and the second step section is between 1m and 3m.

10. The method for constructing tunnels in substandard surrounding rock according to claim 9, characterized in that, The distance between the annular arch section and the core soil section after a single excavation is 3m to 5m.

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