Cable-beam suspension structure in surface hole of shallow-buried tunnel and construction method of cable-beam suspension structure

Abstract

The invention provides a cable beam suspension structure in a surface hole of a shallow-buried tunnel and a construction method of the cable beam suspension structure, and belongs to the technical field of municipal engineering subsurface tunnel design and construction. According to the technical scheme, the device comprises a double-spliced steel beam which is embedded into a ground surface groove and is perpendicular to the excavation direction, a double-spliced waist beam which is tightly attached to a primary support base plane in a hole and is parallel to the excavation direction, a pre-stressed anchor cable which is tightly buckled with the double-spliced waist beam to suspend a primary support on the double-spliced steel beam, and an anchorage device matched with the pre-stressed anchor cable, the load of the overlying strata is borne by the in-tunnel primary support and the cable beam suspension structure together, and the safety of tunnel support and the stability of surrounding rock can be guaranteed without arranging redundant span-reducing vertical supports and horizontal cross supports in the tunnel. The collapse risk caused by support removing and arch changing operation of a traditional underground excavation construction method and potential safety hazards of driving operation caused by water leakage of a lining of a support burying node can be completely avoided, the cable beam suspension structure can be suitable for various stratums and is basically not restricted by the engineering geological environment, and meanwhile the purpose of rapid support-free construction of large machinery in a hole can be achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of design and construction of underground tunnels in municipal engineering, and in particular relates to a cable-beam suspension structure in a surface hole of a shallow buried tunnel and a construction method thereof. Background Art

[0002] The underground tunnels of municipal engineering projects are shallow in depth and large in span. The tunnel bodies are mostly placed in the soft Quaternary soil layer. Improper selection of excavation methods and support measures during construction can easily induce collapse accidents. The design of construction methods generally follows the excavation concept of reducing large to small, breaking the whole into parts, and exchanging time for space. Most of them adopt pilot pit partial excavation methods such as double side wall pilot pit method, single side wall pilot pit method, CRD method, cross-intersection middle wall method, etc.

[0003] During the construction period, a large number of temporary span reduction supports need to be set up inside the tunnel, and there is no longer any operating space for large-scale mechanical operations. Construction units have long faced problems such as low construction efficiency, long operation cycle, and high construction period pressure. The engineering and economic benefits are not optimistic.

[0004] After the tunnel is completed, it is still necessary to rely on the spatial effect to remove the support and replace the arch. The original support system that handles the equilibrium state is instantly broken. Once the method and sequence of removing the support are not designed properly, the surrounding rock stress and the internal force of the support will be difficult to adjust to the equilibrium state again. The remaining initial support is not enough to withstand the load of the overlying strata, which will also induce landslides.

[0005] In addition, a small number of tunnels will choose to bury supports and cast secondary linings. Although this can avoid the risks of dismantling supports and replacing arches, the waterproof quality and water-stopping effect of buried support nodes are usually difficult to guarantee. After the tunnel is put into operation, the lining leakage is very serious, and the operation and maintenance rectification is difficult, ineffective, and frequent. In the long run, it will cause corrosion of the stressed steel bars and reduce the durability of the structure, which will seriously threaten the tunnel driving safety and operational stability.

[0006] In summary, the traditional tunnel excavation method and support method have the disadvantages of slow excavation, difficult support, multiple supports, complicated processes, large deformation, long construction period and high risk. The cable-beam suspension structure proposed in the present invention can effectively solve the above problems and has significant engineering, social and economic benefits. Summary of the invention

[0007] The present invention aims to solve the problems of slow excavation, difficult support, multiple supports, complicated processes, large deformation, long construction period and high risk in existing tunnel excavation methods, and proposes a cable-beam suspension structure in the surface hole of a shallow buried tunnel and a construction method thereof. The overlying stratum load of the method of the present invention is jointly borne by the initial support and the suspended cable-beam, and there is no need to set up redundant supports to reduce the span inside the tunnel, so as to ensure the support safety and the stability of the surrounding rock, avoid the risk of collapse in subsequent support removal and arch replacement operations or the safety hazard of water leakage in the lining of the buried support nodes, and at the same time meet the purpose of rapid construction of large-scale machinery without support in the tunnel.

[0008] In order to achieve the above-mentioned purpose, the present invention is implemented through the following technical scheme: a cable-beam suspension structure in the surface hole of a shallow buried tunnel, including initial support and secondary lining, a plurality of groups of double waist beams are arranged between the initial support and the secondary lining, the surface grooves above the tunnel are arranged perpendicular to the excavation direction and a plurality of groups of double steel beams are arranged inside the grooves, a plurality of groups of prestressed anchor cables are arranged between the double waist beams and the double steel beams, the prestressed anchor cables pass through the double waist beams, initial support, cave top surrounding rock, and double steel beams from bottom to top, and the two ends are anchored with matching anchors respectively, so that the initial support is suspended above the double steel beam on the ground.

[0009] Preferably, the arrangement spacing of the multiple groups of double-jointed steel beams is an integer multiple of the arrangement spacing of the internal grid steel frames for initial support in the tunnel, and the plane projections of the two overlap and cannot be misaligned.

[0010] Preferably, the multiple groups of double waist beams are evenly distributed in the range of more than 180° of the tunnel arch foot along the tunnel circumference, and locking anchor pipes are set on the arch foot grid steel frames on both sides. Each group of double waist beams is laid continuously in parallel to the tunnel excavation direction.

[0011] Preferably, each set of double waist beams needs to be installed closely to the initial support base surface and lag behind the palm face by a certain distance.

[0012] Preferably, the prestressed anchor cables are placed at the intersection of the grid steel frame and the double waist beam inside the initial support, in a rectangular arrangement.

[0013] Preferably, the double waist beam and the double steel beam are both provided with reserved holes for the prestressed anchor cables to pass through.

[0014] Another solution to be protected by the present invention is: a method for constructing a cable-beam suspension structure in a surface tunnel of a shallow buried tunnel, which is carried out according to the following steps:

[0015] S1: The soil of the tunnel arch is excavated in blocks, initial support and temporary span reduction support are implemented, and anchor pipes for arch foot locks are installed on both sides;

[0016] S2: Lag behind the tunnel face by a certain distance, and lay double waist beams parallel to the excavation direction, close to the initial support base surface;

[0017] S3: According to the designed hole position, the prestressed anchor cable is tightly attached to the double-jointed waist beam until it penetrates the ground surface;

[0018] S4: bury double steel beams perpendicular to the excavation direction in the surface groove;

[0019] S5: Pass the anchor cable to be prestressed through the reserved hole of the double steel beam, tension the matching anchor and lock it to the design value;

[0020] S6: Remove the temporary span reduction support and rely on the initial support and cable-beam suspension structure to jointly bear the overlying stratum load;

[0021] S7: excavate the remaining reserved core soil and the lower step soil, and apply corresponding initial support;

[0022] S8: Spray-mix and hang mesh to backfill the fertilizer trough within the height range of the double waist beam until the base surface is flat;

[0023] S9: Closely follow the fertilizer trough backfill base surface, lay the waterproof layer, tie the steel bars, erect the formwork, and mold the secondary lining;

[0024] S10: After curing to the designed strength, the formwork is removed and the construction of the entire tunnel lining is completed.

[0025] Preferably, in step S3, when the prestressed anchor cable passes through the initial support internal grid steel frame, care should be taken to avoid the main grid reinforcement to avoid damaging it.

[0026] Preferably, in step S5, the prestressed anchor cable passes through the double steel beam and is tensioned and locked to the designed value at the surface end, and then the surface groove is backfilled to the original ground.

[0027] Preferably, after the tunnel arch soil is excavated in blocks in step S1, reserved core soil and lower step soil will remain, and temporary span reduction supports are set on the reserved core soil. The top base surface of the reserved core soil also serves as an installation platform for the arch high-position prestressed anchor cables and the double waist beams in the tunnel.

[0028] Compared with the prior art, the invention has the following beneficial effects.

[0029] 1. The present invention overcomes the disadvantage of the traditional step-by-step excavation method of the pilot pit that it does not have the space for large-scale mechanical operation, and can significantly shorten the construction period, improve efficiency, and save investment.

[0030] 2. The cable-beam suspension structure in the surface hole of a shallow buried tunnel of the present invention does not need to face the safety hazard of water leakage in the lining of the buried support node during operation, thereby improving the service life and structural durability of the tunnel and reducing the later operation and maintenance costs and rectification frequency.

[0031] 3. The cable-beam suspension and initial support form a joint bearing system, which transfers the overlying stratum load to the double-jointed steel beams on the surface elastic foundation. There is no need to set up temporary span reduction supports inside the tunnel, avoiding the risk of collapse during the subsequent support removal and arch replacement operations.

[0032] 4. The tensioning and locking of prestressed anchor cables will produce a tensile force on the initial support, reducing the contact pressure transmitted from the initial support to the secondary lining and improving the safety reserve of the composite lining.

[0033] 5. The construction method of the present invention is completely unconstrained by geological conditions and is suitable for municipal dark-digging tunnels constructed in all types of geological environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a cross-sectional view of the suspended cable-beam structure in the ground hole of the present invention.

[0035] Figure 2 This is a plan view of the double-jointed steel beams on the ground according to the present invention.

[0036] Figure 3 It is a plan view of the double waist beam in the hole of the present invention.

[0037] Figure 4 It is a construction step diagram of the surface-in-tunnel suspended cable-beam structure of the present invention.

[0038] Figure 5 It is a large-scale drawing of the node of the surface-in-tunnel suspended cable-beam structure of the present invention.

[0039] In the figure, 1 is the initial support, 2 is the backfill of the fertilizer trough, 3 is the secondary lining, 4 is the prestressed anchor cable, 5 is the double-jointed steel beam, 6 is the matching anchor, 7 is the double-jointed waist beam, 8 is the locking foot anchor pipe, 9 is the grid steel frame, 10 is the arch soil, 11 is the reserved core soil, 12 is the temporary span reduction support, and 13 is the lower step soil. DETAILED DESCRIPTION

[0040] The following will describe the implementation methods of the present invention in detail with reference to the accompanying drawings and examples, so as to fully understand and implement the implementation process of how the present invention applies technical means to solve technical problems and achieve technical effects.

[0041] like Figure 1 As shown, a cable-beam suspension structure in the ground hole of a shallow buried tunnel includes an initial support 1, a secondary lining 3, a double-jointed waist beam 7, a double-jointed steel beam 5, a prestressed anchor cable 4 and a matching anchor 6. A plurality of groups of double-jointed steel beams 5 are embedded in surface grooves at intervals and each group of double-jointed steel beams 5 is placed perpendicular to the tunnel excavation direction. A plurality of groups of double-jointed waist beams 7 are arranged at intervals between the initial support 1 and the secondary lining 3. The prestressed anchor cable 4 passes through the double-jointed waist beam 7, the initial support 1, the surrounding rock of the cave top, and the double-jointed steel beam 5 from bottom to top, and the two ends are anchored with matching anchors 6 respectively, so that the initial support 1 is suspended above the double-jointed steel beam 5 on the ground.

[0042] The present invention forms a joint bearing system with cable-beam suspension and initial support 1. The initial support 1 and the suspended cable-beam jointly bear the overlying stratum load. There is no need to set up temporary span reduction support 12 inside the tunnel, avoiding the risk of collapse during the later support removal and arch replacement operations. At the same time, the purpose of rapid construction without support by large-scale machinery in the tunnel is met, which significantly shortens the construction period, improves efficiency and saves investment.

[0043] The above embodiment briefly introduces the cable-beam suspension structure in the surface hole of a shallow buried tunnel of the present invention, but does not provide a detailed description of the arrangement details of the double waist beam 7 and the double steel beam 5. In order to allow those skilled in the art to better understand the structure of the present invention, based on the above embodiment, the arrangement of each component is described in detail in this embodiment.

[0044] like Figure 2 As shown, the arrangement spacing of multiple groups of double steel beams 5 is an integral multiple of the arrangement spacing of the internal grid steel frame 9 of the initial support 1 in the tunnel. In this embodiment, the interval is 3.0m, and the arrangement spacing is 6 times the 0.5m setting spacing of the internal grid steel frame 9 of the initial support 1 in the tunnel. The two plane projections coincide and cannot be misaligned. The double steel beams 5 are embedded in the surface groove, and the embedding depth matching the height of the double steel beams 5 and the matching anchor 6 is 0.4m.

[0045] like Figure 3 As shown, multiple groups of double waist beams 7 are evenly distributed in the range of more than 180° of the tunnel arch foot along the tunnel circumference, with a circumferential interval of 1.8m. Two locking foot anchor pipes 8 are arranged at equal intervals with the grid steel frame 9 at the arch feet on both sides. Each group of double waist beams 7 is laid continuously parallel to the tunnel excavation direction. And each group of double waist beams 7 needs to be installed closely to the base surface of the initial support 1 and 2.5m behind the heading face.

[0046] In addition, both the double waist beam 7 and the double steel beam 5 are reserved with holes for the prestressed anchor cable 4 to pass through. The horizontal arrangement spacing of the former holes is 2.5m, and the longitudinal arrangement spacing of the latter holes is 3.0m.

[0047] like Figure 3 As shown, the prestressed anchor cable 4 is set at the intersection of the grid steel frame 9 and the double-jointed waist beam 7 in the initial support 1, in a rectangular arrangement, i.e. 1.8m in the circumferential direction and 3.0m in the longitudinal direction. The prestressed anchor cable 4 is also arranged in a rectangular manner on the ground double-jointed steel beam 5, i.e. 2.5m in the transverse direction and 3.0m in the longitudinal direction. The prestressed anchor cable 4 is set in a divergent manner from the inside of the cave to the surface, passing through the double-jointed waist beam 7, the initial support 1, the cave top surrounding rock, and the double-jointed steel beam 5 from bottom to top, and the two ends are anchored with matching anchors 6, respectively, to suspend the initial support 1 on the ground double-jointed steel beam 5.

[0048] The tensioning and locking of the prestressed anchor cable 4 in the cable-beam suspension structure of the present invention will produce a tensile force on the initial support 1, reducing the contact pressure transmitted from the initial support 1 to the secondary lining 3, improving the safety reserve of the composite lining, and there is no need to face the safety hazard of water leakage in the lining of the buried support node during operation, thereby increasing the service life and structural durability of the tunnel and reducing the later operation and maintenance costs and the frequency of rectification.

[0049] The above two embodiments have given a detailed introduction to the cable-beam suspension structure in the surface hole of a shallow tunnel of the present invention. Based on the above two embodiments, this embodiment specifically discloses a method for constructing a cable-beam suspension structure in the surface hole of a shallow tunnel.

[0050] like Figure 4 As shown, a method for constructing a cable-beam suspension structure in a shallow tunnel surface hole is carried out according to the following steps:

[0051] S1: The tunnel arch soil 10 is excavated in blocks, and the lower step soil 13 and the reserved core soil 11 are left. The initial support 1 is applied, and at the same time, a temporary span reduction support 12 is set up on the reserved core soil 11, and the arch foot locking anchor pipes 8 on both sides are driven. If the ground conditions are relatively good, the tunnel surrounding rock can achieve short-term self-stabilization during the period from the excavation of the arch soil to the driving of the anchor cable, then the setting of the temporary span reduction vertical support can be cancelled;

[0052] S2: 2.5m behind the heading face, close to the initial support 1 base surface, double waist beam 7 parallel to the excavation direction is laid;

[0053] S3: According to the designed hole position, the prestressed anchor cable 4 is driven tightly to the double waist beam 7 until it penetrates the ground surface. Care should be taken to avoid the main reinforcement of the grid to avoid damage to it;

[0054] S4: a double steel beam 5 perpendicular to the excavation direction is buried in the surface groove, and then the surface groove is backfilled to the original ground;

[0055] S5: Pass the prestressed anchor cable 4 through the reserved hole of the double steel beam 5, tension the matching anchor 6 and lock it to the design value;

[0056] S6: Remove the temporary span reduction support 12, and rely on the initial support 1 and the cable-beam suspension structure to jointly bear the overlying stratum load;

[0057] S7: excavate the remaining reserved core soil 11 and the lower step soil 13, and apply corresponding initial support 1;

[0058] S8: Spray-mix and hang mesh to backfill the fertilizer trough within the height range of the double waist beam 7 until the base surface is flat;

[0059] S9: Closely follow the fertilizer trough backfill 2 base surface to lay waterproof layer, tie steel bars, erect formwork, and mold secondary lining 3;

[0060] S10: After curing to the designed strength, the formwork is removed and the construction of the entire tunnel lining is completed.

[0061] The construction method of the present invention is completely unconstrained by geological conditions and is suitable for municipal dark-digging tunnels constructed in all types of geological environments, and can effectively improve construction efficiency and shorten construction period.

[0062] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A cable-beam suspension structure in a shallow tunnel surface, comprising an initial support (1) and a secondary lining (3), characterized in that: A plurality of groups of double-jointed waist beams (7) are arranged at intervals between the initial support (1) and the secondary lining (3); surface grooves above the tunnel are arranged at intervals perpendicular to the excavation direction and a plurality of groups of double-jointed steel beams (5) are arranged inside the grooves; a plurality of groups of prestressed anchor cables (4) are arranged at intervals between the double-jointed waist beams (7) and the double-jointed steel beams (5); the prestressed anchor cables (4) pass through the double-jointed waist beams (7), the initial support (1), the surrounding rock of the cave top, and the double-jointed steel beams (5) in sequence from bottom to top; both ends of the prestressed anchor cables (4) are anchored by matching anchors (6) respectively, so that the initial support (1) is suspended on the double-jointed steel beams (5) on the ground.

2. The cable-beam suspension structure in the surface of a shallow tunnel according to claim 1, characterized in that: The arrangement spacing of the plurality of groups of double-jointed steel beams (5) is an integer multiple of the arrangement spacing of the internal grid steel frame (9) of the initial support (1) in the tunnel, and the two planar projections overlap and cannot be misaligned.

3. A cable-beam suspension structure in a shallow tunnel surface according to claim 1 or 2, characterized in that: The multiple groups of double waist beams (7) are evenly distributed in the range of more than 180 degrees of the arch foot along the circumferential direction of the tunnel, and the arch foot grid steel frames (9) on both sides are provided with locking foot anchor pipes (8), and each group of double waist beams (7) is continuously laid in parallel with the tunnel excavation direction.

4. The cable-beam suspension structure in the surface of a shallow tunnel according to claim 3, characterized in that: Each set of double waist beams (7) needs to be closely attached to the base surface of the initial support (1) and installed after the face of the work.

5. The cable-beam suspension structure in the surface of a shallow tunnel according to claim 1, characterized in that: The prestressed anchor cable (4) is installed at the intersection of the grid steel frame (9) and the double waist beam (7) inside the initial support (1) in a rectangular arrangement.

6. The cable-beam suspension structure in the surface of a shallow tunnel according to claim 1, characterized in that: The double-jointed waist beam (7) and the double-jointed steel beam (5) both reserve holes for the prestressed anchor cable (4) to pass through.

7. A method for constructing a cable-beam suspension structure in a shallow tunnel surface, characterized in that: Follow these steps: S1: The soil of the tunnel arch (10) is excavated in blocks, initial support (1) and temporary span reduction support (12) are implemented, and arch foot locking anchor pipes (8) are installed on both sides; S2: Delayed face, close to the initial support (1) base surface with double waist beams (7) parallel to the excavation direction; S3: according to the designed hole position, the prestressed anchor cable (4) is tightly attached to the double-jointed waist beam (7) until it penetrates the ground surface; S4: burying a double steel beam (5) perpendicular to the excavation direction in the surface groove; S5: passing the prestressed anchor cable (4) through the reserved hole of the double steel beam (5), tensioning the matching anchor (6) and locking it to the design value; S6: Remove the temporary span reduction support (12), and rely on the initial support (1) and the cable-beam suspension structure to jointly bear the overlying stratum load; S7: excavating the remaining reserved core soil (11) and the lower step soil (13), and applying corresponding initial support (1); S8: backfilling (2) the fertilizer trough within the height range of the double waist beam (7) by spraying and mixing with mesh until the base surface is flat; S9: Closely backfill the fertilizer trough (2), lay a waterproof layer on the base surface, tie steel bars, erect formwork, and mold the secondary lining (3); S10: After curing to the designed strength, the formwork is removed and the construction of the entire tunnel lining is completed.

8. The method for constructing a cable-beam suspension structure in a shallow tunnel surface according to claim 7, characterized in that: In the step S3, when the prestressed anchor cable (4) passes through the internal grid steel frame (9) of the initial support (1), it needs to avoid the main grid reinforcement.

9. The method for constructing a cable-beam suspension structure in a shallow tunnel surface according to claim 1, characterized in that: In step S5, the prestressed anchor cable (4) passes through the double steel beam (5), is tensioned and locked to the designed value at the surface end, and then the surface groove is backfilled to the original ground.

10. The method for constructing a cable-beam suspension structure in a shallow tunnel surface according to claim 1, characterized in that: After the tunnel arch soil (10) is excavated in blocks in step S1, reserved core soil (11) and lower step soil (13) will remain. The temporary span reduction support (12) is set on the reserved core soil (11), and the top base surface of the reserved core soil (11) also serves as an installation platform for the arch high-position prestressed anchor cable (4) and the double waist beam (7) in the tunnel.

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