Support system and construction method of large-section tunnel passing through giant cave hall

Abstract

The invention discloses a large-section tunnel support system and a construction method for passing through a giant karst cave hall. The support system comprises a plurality of steps and a tunnel base which are sequentially excavated downwards along the top of a backfill body of the karst cave hall, initial support is sequentially applied to each step, and the initial supports of all steps and the tunnel base are integrally closed into a ring; a karst cave top reinforcement body is arranged on the rock mass at the top of the first step, a plurality of grouting pipes are pre-buried in the rock wall at the top of the first step along the line direction, and an enlarged arch foot is arranged at the bottom of the initial support of the first step; advanced support, steel flower pipes and initial support are arranged in the excavated side walls of the remaining steps other than the first step, and the advanced support and the steel flower pipes are completely located in the backfill body, and the advanced support and the steel flower pipes are not connected to the corresponding initial support; grouting steel pipe piles and reserved grouting holes are arranged on the tunnel base.

Description

Technical Field

[0001] The invention relates to the field of tunnel construction, and in particular to a large-section tunnel support system and a construction method that passes through a giant karst cave hall. Background Art

[0002] my country is one of the countries with the largest karst distribution area in the world. With the large-scale construction of transportation infrastructure, a large number of tunnel projects passing through various types of caves will inevitably emerge.

[0003] At present, most roads and railways passing through karst caves adopt traditional construction methods such as mortar-laid rubble backfill, bridge structure crossing and tunnel structure crossing. The above construction schemes are all proposed based on small and medium-sized karst caves. However, when crossing giant karst caves with huge cavities, poor wall stability, large height and span, traditional construction methods are difficult to construct, require large engineering workload and cannot effectively control settlement. Summary of the invention

[0004] The purpose of the present invention is to provide a large-section tunnel support system and construction method for passing through a giant karst cave hall, which can effectively control the settlement of the structure base, reduce the construction difficulty, reduce the construction workload, and ensure the safety of construction and operation, in view of the fact that when a railway passes through a giant karst cave with a huge cavity, extremely poor cave wall stability, and a large height and span, the existing construction methods such as mortar-laid rubble backfilling, bridge structure spanning and tunnel structure crossing are difficult to construct, require a large amount of work, and cannot effectively control the settlement.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A large-section tunnel support system passing through a giant cave hall, comprising a plurality of steps and tunnel bases excavated downward in sequence along the top of the backfill body of the cave hall, each step is sequentially provided with initial support, and the initial support of all steps and tunnel bases is closed as a whole to form a ring;

[0007] A cave top reinforcement body is set at the top rock mass of the first step, a number of grouting pipes are pre-buried along the route direction on the top rock wall of the first step, an expanded arch foot is set at the bottom of the initial support of the first step, and the expanded arch foot is connected to the first step table;

[0008] The side walls of the excavation of the remaining steps other than the first step are provided with advance support, steel pipe and initial support, and the advance support and steel pipe are completely located in the backfill body, and the advance support and steel pipe are not connected to the corresponding initial support;

[0009] Grouting steel pipe piles and reserved grouting holes are set at the tunnel base.

[0010] Preferably, after initial support is applied to each step, lateral supports are provided according to force requirements.

[0011] Preferably, a locking foot anchor pipe is provided at the bottom of each step initial support.

[0012] Preferably, the cave top reinforcement body includes anchor rods and anchor cables embedded in the rock mass at the top of the cave, and a roof mesh spray protection connected to the rock wall at the top of the cave.

[0013] Preferably, the initial support includes primary shotcrete, steel frame and secondary shotcrete.

[0014] Preferably, a secondary lining is provided inside the closed-loop primary support.

[0015] Further preferably, the secondary lining includes a base plate structure, a side wall structure and an arch structure.

[0016] Further preferably, a buffer layer is provided between the primary support and the secondary lining.

[0017] Further preferably, the buffer layer comprises a plurality of polystyrene boards.

[0018] The present invention also provides a construction method for a large-section tunnel support system passing through a giant karst cave hall, comprising the following steps:

[0019] ① Backfill the cave hall to the first step below the top of the cave hall;

[0020] ② The cave roof reinforcement body is constructed on the top rock mass of the cave hall, and several grouting pipes are pre-buried along the route direction on the rock wall of the cave hall within the range of the vault;

[0021] ③ After the cave roof reinforcement meets the design requirements, initial support is applied on the first step, and the expanded arch feet are applied on the bottom of both sides of the initial support, and the filling body is applied on the first step outside the initial support;

[0022] ④ Excavate the second step under the protection of the initial support of the first step; when excavating the second step, first apply the side wall advance support and grouting, then excavate the backfill body, first apply the steel flower pipe on the second step wall and grouting, then apply the initial support, in which the advance support and steel flower pipe cannot be connected with the corresponding initial support, and their tail ends should all extend into the backfill body;

[0023] ⑤ Excavate the third step. The excavation process is the same as the second step. After the excavation and support of the third step is completed, the first transverse support is constructed. The first transverse support is supported on both side walls of the third step;

[0024] ⑥ Excavate the fourth step, the excavation process is the same as the second step;

[0025] ⑦ Excavate the fifth step. The excavation process is the same as the second step. After the excavation and support of the fifth step is completed, the second transverse support is constructed. The second transverse support is supported on both side walls of the fifth step.

[0026] ⑧ Excavate the sixth step, the excavation process is the same as the second step;

[0027] ⑨ Excavate to the tunnel base. The excavation process is the same as the second step excavation process. The initial support is applied in time to close the initial support into a ring. The tunnel base is reinforced by grouting steel pipe piles, and grouting holes are set at the tunnel base.

[0028] ⑩ After the base grouting meets the design requirements, cast the secondary lining bottom plate structure, set the first replacement support on the inner wall of the bottom plate structure, and remove the second horizontal support;

[0029] Cast the secondary lining side wall structure, set the second replacement support on the inner wall of the side wall structure, and remove the first transverse support;

[0030] Cast the secondary lining arch structure, and when the lining structure strength reaches 80% of the design strength, remove the first and second replacement supports.

[0031] Preferably, in step ①, tunnel waste is used to backfill the entire cave hall.

[0032] Preferably, in step ②, the cave top reinforcement body includes anchor rods, anchor cables and a roof mesh spray protection covering the top rock wall of the cave.

[0033] Preferably, in step ②, the grouting pipe is a PVC pipe.

[0034] Preferably, in step ②, a grouting pipe is provided every 5 m to facilitate grouting after the base settles in the later stage.

[0035] Preferably, in step ③, an initial support steel frame is erected on the first step, enlarged arch feet are arranged at the bottom of both sides of the initial support steel frame, and concrete is sprayed at the steel frame.

[0036] Further preferably, in step ③, a locking foot anchor pipe is constructed to enlarge the arch foot.

[0037] Further preferably, in step ③, the pumped concrete is filled in the first step area outside the initial support to form a filling body.

[0038] Preferably, in step ④, before excavating the second step, the side wall advance support and grouting are first performed, wherein the advance support is not connected to the steel frame.

[0039] Preferably, in step ④, after excavating the second step, a large externally inserted angle steel pipe is constructed and grouting is performed, and initial spraying of concrete is performed on the side wall of the second step, a steel frame is erected, and re-spraying of concrete is performed to the designed thickness.

[0040] Preferably, in step ⑤, the first lateral support is a steel pipe.

[0041] Preferably, in step ⑦, the second lateral support is a steel pipe.

[0042] Preferably, in step ⑩, after the base grouting meets the design requirements, polystyrene boards are laid on the side walls of the tunnel base, and then the secondary lining bottom plate structure is cast.

[0043] Preferably, the step In the process, polystyrene boards are laid on the side walls of the tunnel, and then the secondary lining side wall structure is cast.

[0044] Preferably, the step In the process, polystyrene boards are laid on the side walls of the tunnel arch, and then the secondary lining arch structure is cast.

[0045] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0046] 1. The large-section tunnel support system and construction method for passing through the giant cave hall of the present invention can smoothly pass through the giant cave, avoid the problems of construction delay, economic loss and adverse social impact caused by line rerouting, have good economic and social benefits, and have broad prospects for promotion and application;

[0047] 2. The large-section tunnel support system and construction method for passing through a giant karst cave hall of the present invention. When a railway line passes through a giant karst cave hall, if a roadbed backfill scheme or a bridge crossing scheme is simply adopted, the train faces the risk of falling blocks from the top wall of the karst cave during operation, and the safety factor is low. The large-section tunnel support system and construction method for passing through a giant karst cave hall of the present invention ensure that the train always operates under the protection of the secondary lining of the tunnel, which is safer and more reliable.

[0048] 3. The large-section tunnel support system and construction method for crossing the giant cave hall described in the present invention, if the tunnel is excavated in the backfill body after the cave is completely backfilled, the risk of collapse of the arch backfill body is extremely high during the excavation of the lower steps. Using the large-section tunnel support system and construction method for crossing the giant cave hall described in the present invention, first backfill the cave to the distance of the cave top, on the one hand, it can provide a construction platform for the protection of the cave top; on the other hand, after the initial support construction of the arch, the outer side of the initial support is backfilled with concrete, which can ensure the safety of the lower step excavation and support construction;

[0049] 4. The large-section tunnel support system and construction method of the present invention that passes through a giant cave hall, on the one hand, reserves grouting holes at the tunnel base for compensatory grouting during operation to effectively control the settlement of the structural base; on the other hand, reserves longitudinal grouting pipes at the vault range. Once the structural settlement causes the vault filling body and the cave top to be emptied, the emptied area can be filled densely by grouting to ensure that the vault backfill body effectively supports the cave top;

[0050] 5. The large-section tunnel support system and construction method for passing through a giant karst cave hall of the present invention adopts an open construction of the arch, a step-by-step dark excavation of the side walls and the tunnel bottom, partial support, multiple temporary cross braces, and pre-buried compensating grouting pipes. The construction method is safe, reliable, and highly operable. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a structural schematic diagram of a large-section tunnel support system for passing through a giant karst cave hall according to the present invention;

[0052] Figure 2 yes Figure 1 A is an enlarged schematic diagram;

[0053] Figure 3 is a schematic diagram of step ① in Example 2;

[0054] Figure 4 It is a schematic diagram of step ② in Example 2;

[0055] Figure 5 It is a schematic diagram of step ③ in Example 2;

[0056] Figure 6 It is a schematic diagram of step ④ in Example 2;

[0057] Figure 7 It is a schematic diagram of step ⑤ in Example 2;

[0058] Figure 8 It is a schematic diagram of step ⑥ in Example 2;

[0059] Fig. 9 It is a schematic diagram of step ⑦ in Example 2;

[0060] Fig.10 is a schematic diagram of step ⑧ and step ⑨ in Example 2;

[0061] Fig.11 is a schematic diagram of step ⑩ in Example 2;

[0062] Fig.12 It is the step in Example 2 Schematic diagram of

[0063] Fig.13 It is the step in Example 2 The hint Figure 1 ;

[0064] Fig.14 It is the step in Example 2 The hint Figure 2 .

[0065] Icons: 01-backfill body, 1-first step, 2-second step, 3-third step, 4-fourth step, 5-fifth step, 6-sixth step, 11-filling body, 12-initial support, 121-steel frame, 122-initial sprayed concrete, 123-re-sprayed concrete, 15-top plate mesh spraying protection, 16-expanded arch foot, 21-locking foot anchor pipe, 22-anchor rod, 23-anchor cable, 24-steel pipe pile, 25-grouting pipe, 26-steel flower pipe, 31-first horizontal support, 311-second replacement support, 32-second horizontal support, 321-first replacement support, 33-polystyrene board, 41-bottom plate structure, 42-side wall structure, 43-arch structure. DETAILED DESCRIPTION

[0066] The present invention will be described in detail below in conjunction with the accompanying drawings.

[0067] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0068] Example 1

[0069] like Figure 1-14 As shown, a large-section tunnel support system for passing through a giant cave hall described in the present invention includes a plurality of steps and tunnel bases excavated downward in sequence along the top of the cave hall backfill body 01, and each step is sequentially provided with an initial support 12, and the initial supports 12 of all steps and tunnel bases are integrally closed into a ring, and the initial support 12 includes primary sprayed concrete 122, a steel frame 121 and secondary sprayed concrete 123.

[0070] A cave top reinforcement body is provided at the top rock mass of the first step 1, and the cave top reinforcement body includes an anchor rod 22 and an anchor cable 23 embedded in the top rock mass of the cave, and a roof mesh spray protection 15 connected to the top rock wall of the cave. A plurality of grouting pipes 25 are pre-buried in the top rock wall of the first step 1 along the line direction, and an expanded arch foot 16 is provided at the bottom of the initial support 12 of the first step 1, and the expanded arch foot 16 is connected to the table top of the first step 1, and a locking foot anchor pipe 21 is provided at the bottom of the initial support 12 of each step.

[0071] Advance support, steel pipe 26 and initial support 12 are set in the excavation side walls of the remaining steps other than the first step 1, and the advance support and steel pipe 26 are completely located in the backfill body 01, and the advance support and steel pipe 26 are not connected to the corresponding initial support 12.

[0072] After the initial support is applied to each step, lateral supports are set according to the force requirements, and grouting steel pipe piles 24 and reserved grouting holes are set at the tunnel base.

[0073] A secondary lining is arranged inside the closed ring primary support 12 , and the secondary lining includes a bottom plate structure 41 , a side wall structure 42 and an arch structure 43 . A buffer layer is arranged between the primary support 12 and the secondary lining. Specifically, the buffer layer includes a plurality of polystyrene boards 33 .

[0074] The large-section tunnel support system for passing through the giant karst cave hall of the present invention is used to effectively support the full backfill dark excavation construction, and longitudinal grouting pipes 25 are reserved in the arch range and grouting holes are reserved in the tunnel base for compensatory grouting during operation to effectively control the settlement of the structure base; the construction methods of multi-step excavation, partial support + temporary cross bracing, permanent support + removal of cross bracing, and compensatory grouting can be adopted, with low construction difficulty, small engineering volume, and high operability; the giant karst cave can be smoothly passed, and the problems of construction delay, economic loss, and adverse social impact caused by line rerouting can be avoided, and the problems have good economic and social benefits and broad prospects for promotion and application.

[0075] Example 2

[0076] like Figure 1-14 As shown, the construction method of a large-section tunnel support system passing through a giant cave hall as described in Example 1 of the present invention comprises the following steps:

[0077] ① Such as Figure 3 As shown, the tunnel waste is used to backfill the cave hall to form a backfill body 01, which is backfilled to the first step 1 below the top of the cave hall;

[0078] ② If Figure 4 As shown in the figure, a cave top reinforcement body is applied to the rock mass at the top of the cave hall. The cave top reinforcement body includes anchor rods 22, anchor cables 23 and a roof mesh spray protection 15 covering the rock wall at the top of the cave. In the range of the arch, a plurality of φ10 PVC grouting pipes 25 are pre-buried in the rock wall of the cave hall along the line direction (in this embodiment, as shown in FIG. Figure 2 As shown, three grouting pipes 25 are pre-buried, with one section set every 5 m to facilitate grouting after the base settles in the later stage;

[0079] ③ Such as Figure 5 As shown, after the cave top reinforcement body meets the design requirements, an initial support 12 steel frame 121 is set up on the first step 1, and the expanded arch feet 16 are applied to the bottom of both sides of the initial support 12, and the locking foot anchor pipes 21 of the expanded arch feet 16 are applied, and C30 concrete is sprayed at the steel frame 121 to form the initial support 12 initial sprayed concrete 122. After the initial sprayed concrete 122 is completed, C30 concrete is sprayed immediately to form the initial support 12 re-sprayed concrete 123, and C25 concrete is pumped to fill the first step 1 area outside the initial support 12 to form the filling body 11;

[0080] ④ Such as Figure 6As shown, the second step 2 is excavated under the protection of the initial support 12 of the first step 1; when excavating the second step 2, first apply the side wall φ76 advance steel pipe support and grouting, then excavate the backfill body 01, then apply the large external insertion angle φ42 steel flower pipe 26 on the wall of the second step 2 and grouting, then apply 4cm thick initial sprayed concrete 122, set up the steel frame 121, and spray concrete 123 to the designed thickness, wherein the φ76 advance steel pipe and the φ42 steel flower pipe 26 cannot be connected to the corresponding initial support 12, and their tail ends should all extend into the backfill body 01;

[0081] ⑤ If Figure 7 As shown, the third step 3 is excavated, and the excavation process is the same as the excavation process of the second step 2. After the excavation and support of the third step 3 are completed, a φ609 first transverse support 31 steel pipe is constructed, and the first transverse support 31 is supported on both side walls of the third step 3;

[0082] ⑥ Such as Figure 8 As shown, the fourth step 4 is excavated, and the excavation process is the same as the excavation process of the second step 2;

[0083] ⑦ Such as Fig. 9 As shown, the fifth step 5 is excavated, and the excavation process is the same as the excavation process of the second step 2. After the excavation and support of the fifth step 5 are completed, a φ609 second transverse support 32 steel pipe is constructed, and the second transverse support 32 is supported on both side walls of the fifth step 5;

[0084] ⑧ Such as Fig.10 As shown, the sixth step 6 is excavated, and the excavation process is the same as the excavation process of the second step 2;

[0085] ⑨ Such as Fig.10 As shown, excavation is carried out to the tunnel base, and the excavation process is the same as the excavation process of the second step 2, and the initial support 12 is applied in time to close the initial support 12 into a ring, and the tunnel base is reinforced by grouting with φ108 steel pipe piles 24, and grouting holes are set at the tunnel base, and the grouting holes for later compensation grouting are protected. The comprehensive φ value of the base grouting body is not less than 45°;

[0086] ⑩ Such as Fig.11 As shown, after the base grouting reaches the design requirements, a 5 cm thick polystyrene board 33 is laid on the side wall of the tunnel base, and a secondary lining bottom plate structure 41 is cast. When the lining structure strength reaches 80% of the design strength, a first replacement support 321 is set on the inner wall of the bottom plate structure 41, and the second transverse support 32 is removed;

[0087] like Fig.12 As shown, a 5 cm thick polystyrene board 33 is laid on the side wall of the tunnel, and a secondary lining side wall structure 42 is cast. When the lining structure strength reaches 80% of the design strength, a second replacement support 311 is set on the inner wall of the side wall structure 42, and the first transverse support 31 is removed;

[0088] like Fig.13 and 14 As shown, a 5 cm thick polystyrene board 33 is laid on the side wall of the tunnel arch, and a secondary lining arch structure 43 is cast. When the lining structure strength reaches 80% of the design strength, the first replacement support 321 and the second replacement support 311 are removed;

[0089] Repeat the above steps ①~ Until the construction of the entire length of the tunnel line passing through the cave hall is completed.

[0090] By using the construction method of the large-section tunnel support system for passing through the giant karst cave hall of the present invention, full backfill dark excavation construction is effectively supported, longitudinal grouting pipes 25 are reserved in the arch range, and grouting holes are reserved in the tunnel base for compensatory grouting during operation to effectively control the settlement of the structure base; a construction method of multi-step excavation, partial support + temporary cross bracing, permanent support + removal of cross bracing, and compensatory grouting is adopted, with low construction difficulty, small engineering volume, and high operability; the giant karst cave can be smoothly passed, and problems such as construction delays, economic losses, and adverse social impacts caused by line rerouting can be avoided, and the problem has good economic and social benefits and has broad prospects for promotion and application.

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A large-section tunnel support system passing through a giant cave hall, characterized in that: It includes a plurality of steps and tunnel bases excavated downwards in sequence along the top of the cave hall backfill body (01), each step is sequentially provided with an initial support (12), and the initial supports (12) of all the steps and tunnel bases are integrally closed into a ring; A cave top reinforcement body is arranged on the top rock mass of the first step (1), a plurality of grouting pipes (25) are pre-buried in the top rock wall of the first step (1) along the line direction, an expanded arch foot (16) is arranged at the bottom of the initial support (12) of the first step (1), and the expanded arch foot (16) is connected to the table surface of the first step (1); An advance support, a steel pipe (26) and an initial support (12) are arranged in the excavation side walls of the remaining steps other than the first step (1), and the advance support and the steel pipe (26) are completely located in the backfill body (01), and the advance support and the steel pipe (26) are not connected to the corresponding initial support (12); Grouting steel pipe piles (24) and reserved grouting holes are arranged on the tunnel base.

2. The large-section tunnel support system for passing through a giant cave hall according to claim 1 is characterized in that: After initial support (12) is applied to each step, lateral support is provided according to the force requirements.

3. The large-section tunnel support system for passing through a giant cave hall according to claim 1 is characterized in that: A foot locking anchor pipe (21) is arranged at the bottom of each step initial support (12).

4. The large-section tunnel support system for passing through a giant cave hall according to claim 1 is characterized in that: The cave top reinforcement body comprises an anchor rod (22) and an anchor cable (23) embedded in the rock mass at the top of the cave, and a roof mesh spray protection (15) connected to the rock wall at the top of the cave.

5. The large-section tunnel support system for passing through a giant cave hall according to claim 1 is characterized in that: The initial support (12) includes primary sprayed concrete (122), a steel frame (121) and secondary sprayed concrete (123).

6. The large-section tunnel support system for passing through a giant cave hall according to any one of claims 1 to 5, characterized in that: A secondary lining is arranged inside the closed ring primary support (12).

7. The large-section tunnel support system for passing through a giant cave hall according to claim 6 is characterized in that: The secondary lining includes a bottom plate structure (41), a side wall structure (42) and an arch structure (43).

8. The large-section tunnel support system for passing through a giant cave hall according to claim 7 is characterized in that: A buffer layer is provided between the initial support (12) and the secondary lining.

9. The large-section tunnel support system for passing through a giant cave hall according to claim 8 is characterized in that: The buffer layer comprises a plurality of polystyrene boards (33).

10. A construction method for a large-section tunnel support system passing through a giant cave hall, characterized in that: The following steps are involved: ① Backfill the cave hall to the first step (1) below the top of the cave hall; ② constructing a cave roof reinforcement body on the top rock mass of the cave hall, and pre-burying a number of grouting pipes (25) on the rock wall of the cave hall along the route in the range of the vault; ③ After the cave roof reinforcement body meets the design requirements, an initial support (12) is applied on the first step (1), an expanded arch foot (16) is applied on the bottom of both sides of the initial support (12), and a filling body (11) is applied on the first step (1) outside the initial support (12); ④ Excavate the second step (2) under the protection of the initial support (12) of the first step (1); when excavating the second step (2), first apply the side wall advance support and grouting, then excavate the backfill body (01), first apply the steel flower pipe (26) on the wall of the second step (2) and grouting, then apply the initial support (12), wherein the advance support and the steel flower pipe (26) cannot be connected to the corresponding initial support (12), and their tail ends should all extend into the backfill body (01); ⑤ Excavating the third step (3), the excavation process is the same as the excavation process of the second step (2), after the excavation and support of the third step (3) is completed, the first transverse support (31) is constructed, and the first transverse support (31) is supported on both side walls of the third step (3); ⑥ Excavate the fourth step (4), the excavation process is the same as the excavation process of the second step (2); ⑦ Excavating the fifth step (5), the excavation process is the same as the excavation process of the second step (2), after the excavation and support of the fifth step (5) is completed, the second transverse support (32) is constructed, and the second transverse support (32) is supported on both side walls of the fifth step (5); ⑧ Excavating the sixth step (6), the excavation process is the same as the excavation process of the second step (2); ⑨ Excavate to the tunnel base, the excavation process is the same as the excavation process of the second step (2), and the initial support (12) is applied in time to close the initial support (12) into a ring, and the tunnel base is reinforced by grouting steel pipe piles (24), and grouting holes are set on the tunnel base; ⑩ After the base grouting reaches the design requirements, cast the secondary lining bottom plate structure (41), set the first replacement support (321) on the inner wall of the bottom plate structure (41), and remove the second transverse support (32); Casting a secondary lining side wall structure (42), setting a second replacement support (311) on the inner wall of the side wall structure (42), and removing the first transverse support (31); The secondary lining arch structure (43) is cast, and when the lining structure strength reaches 80% of the design strength, the first replacement support (321) and the second replacement support (311) are removed.

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