Anti-floating structure suitable for ultra-shallow covering soil shield tunnel and applicable judgment method thereof

Abstract

The application provides an anti-floating structure suitable for an ultra-shallow soil-covered shield tunnel and a suitable judgment method thereof, comprising a tunnel main body, a base is arranged at the lower side of the inside of the tunnel main body, a plurality of anti-floating assemblies are mounted on the two sides of the inside of the base, the other end of the anti-floating pile extends obliquely downward to the lower side outside the tunnel main body, a plurality of first barbs are hingedly arranged on the outer wall of the anti-floating pile, a plurality of pairs of clamping columns are arranged on the two sides of each first barb, a plurality of second barbs are arranged on the outer wall of each first barb, the plurality of first barbs are circumferentially arranged on the outer wall of the anti-floating pile as a group, and the plurality of groups of first barbs are axially spaced on the outer wall of the anti-floating pile. The beneficial effect of the application is that the connection port and the annular cavity converge with the plasma to form a three-dimensional reinforcement system from the inside to the outside. The construction cost of unnecessary anti-floating measures is greatly reduced through quantitative determination; at the same time, the precise deployment of the anti-floating device can reduce the later maintenance investment caused by the buoyancy disease, and the life cycle cost is optimized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of shield tunneling, in particular to an anti-floating structure suitable for an ultra-shallow overburden shield tunnel and a method for determining the applicability thereof. BACKGROUND

[0002] Traditional shield tunnels have a relatively deep burial depth. In the case of meeting the minimum overburden condition, the tunnel structure can achieve the anti-floating requirement by the overburden pressure of the upper deep overburden. When the tunnel needs to be excavated in the ultra-shallow overburden that does not meet the minimum overburden condition due to various conditions on the line or when the upper overburden does not meet the minimum overburden requirement due to the unloading excavation on the top of the existing tunnel, the shield tunnel cannot meet the anti-floating requirement relying on the overburden and the self-weight of the segment. Anti-floating measures need to be taken to prevent the deformation of the tunnel. The existing anti-floating structure of the tunnel is difficult to meet the anti-floating requirement of the ultra-shallow overburden shield tunnel, and has the following defects:

[0003] 1. In the prior art, the anti-floating structure of the shield tunnel has a simple barb structure, which leads to a small contact area between the structure and the foundation, reduces the anti-floating effect, and thus reduces the stability and bearing capacity of the structure.

[0004] 2. A Chinese patent with the application number CN202121647518.6 discloses an anti-floating structure for a shallow-buried shield tunnel. The patent technology includes a tunnel segment, a groove, a water pumping hole, a sealing cover, an anti-floating pile, and an anti-floating hole. The groove can pump out the air and water in the groove through the water pumping hole to ensure that the tunnel segment can be adsorbed in the soil body and reduce the overall floating force of the tunnel. The anti-floating pile can firmly fix the tunnel segment in the soil body to improve the overall anti-floating performance of the tunnel. The pouring hole is arranged to deliver the mortar to the barb groove through the pouring port to push the barb open, so as to ensure that the mortar can fill around the barb. After the mortar solidifies around the barb, the anti-floating pile is firmly fixed in the soil body to further improve the overall anti-floating performance of the tunnel. The above-mentioned patent has problems in use. The mortar is used to push the barb open, which leads to different degrees of opening of the barbs, limited anti-floating performance, and difficulty in unfolding the barbs, which reduces the contact area between the barbs and the foundation, reduces the anti-pulling force, and weakens the anti-floating effect.

[0005] 3、There is a Chinese patent with the application number CN202322492465.0, which discloses an ultra-shallow buried shield tunnel anti-floating combined structure, relates to the technical field of shield tunnel, and comprises a tunnel main body, a segment, a bottom plate and an anti-floating combined structure. The anti-floating combined structure comprises an anti-floating pile body (containing a pile tip, a mounting block, a connecting rod, a fixing rod, a pressing rod, an extrusion column, a mounting groove, a pulley assembly, a conical groove, a limiting disc, a limiting hole, a through hole, a wedge block, an inclined surface fixing block, a booster wheel, a first grouting hole, a second grouting hole, a pressing block, an extrusion cone head), a stand, a reinforcing block and a positioning rod. The above patent realizes anti-floating effect by the contact of the wedge block and the soil body. However, the contact firmness of the wedge block and the soil body is poor, thereby reducing the stability and bearing capacity of the structure.

[0006] Therefore, the existing structure and defects are improved, and an anti-floating structure suitable for an ultra-shallow soil shield tunnel and a suitable judgment method thereof are needed to achieve a more practical and valuable purpose. SUMMARY

[0007] To solve the problem that the current technology realizes anti-floating effect by the contact of the wedge block and the soil body, but reduces the stability and bearing capacity of the structure.

[0008] The anti-floating structure suitable for the ultra-shallow soil shield tunnel comprises a tunnel main body, a base arranged at the lower side of the inside of the tunnel main body, and a plurality of anti-floating assemblies arranged at the two sides of the inside of the base.

[0009] The anti-floating assembly comprises an anti-floating pile, a flange plate connected to the base is fixedly arranged on the outer wall of one end of the anti-floating pile, the other end of the anti-floating pile extends downward and downward to the outside below the tunnel main body, a plurality of first barbs are hingedly arranged on the outer wall of the anti-floating pile, a plurality of pairs of clamping columns are arranged on the two sides of each first barb, a plurality of second barbs are arranged on the outer wall of each first barb, a plurality of first barbs are circumferentially arranged on the outer wall of the anti-floating pile as a group, a plurality of groups of first barbs are axially spaced on the outer wall of the anti-floating pile, a pressing plate is slidably arranged in the inside of the anti-floating pile, a movable rod is fixedly arranged on one side of the pressing plate, a plurality of first movable rings are fixedly arranged on the outer wall of the movable rod, a connecting rod is arranged on the inner wall of each first barb, and a connecting block is arranged between the outer wall of the first movable ring and the other end of each connecting rod.

[0010] Further, a plurality of groups of avoiding grooves are vertically and spacedly arranged on the outer wall of the anti-floating pile, and the other end of the connecting rod axially slides in the avoiding groove.

[0011] Further, the upper inner wall of the anti-floating pile is provided with a first annular cavity, the lower inner wall of the anti-floating pile is provided with a second annular cavity, the outer wall of the first annular cavity is provided with a plurality of first grouting openings, the outer wall of the second annular cavity is provided with a plurality of second grouting openings, the first annular cavity and the second annular cavity are communicated and provided with a first connecting channel, the upper side of the first annular cavity is provided with a first grouting hole, the inner part of the anti-floating pile is provided with a limiting assembly, the inner part of the anti-floating pile is divided into a first pouring cavity and a second pouring cavity by the limiting assembly, the pressing plate is provided with a second grouting hole, and the second annular cavity and the second pouring cavity are communicated and provided with a connecting port.

[0012] Further, the outer wall of the movable rod is axially and fixedly provided with a plurality of third movable rings, the limiting assembly comprises a fixed ring and a second movable ring, the fixed ring is fixed to the inner wall of the anti-floating pile, the second movable ring slides axially in the anti-floating pile, the outer wall of the movable rod is in sliding contact with the inner wall of the fixed ring, the outer wall of the movable rod is in sliding contact with the inner wall of the second movable ring, and the movable rod extrudes the second movable ring downward through the third movable ring, a plurality of first V-shaped elastic members are connected between one side of the fixed ring and one side of the second movable ring, the middle part of each first V-shaped elastic member is provided with a limiting block, and the outer wall of the movable rod is axially and fixedly provided with a plurality of groups of limiting grooves.

[0013] Further, the plurality of first V-shaped elastic members are circumferentially arranged between the fixed ring and the second movable ring, each group of limiting grooves is circumferentially arranged on the outer wall of the movable rod, a second V-shaped elastic member is connected between the inner walls of the two ends of each first V-shaped elastic member, the middle part of each second V-shaped elastic member is provided with a wedge block, and one end of the wedge block slides in the second grouting opening.

[0014] Further, the lower side of the first annular cavity is provided with a plurality of second connecting channels, the second connecting channels and the interiors of the wedge blocks are communicated and provided with telescopic connecting pipes, and the two sides of the wedge blocks are provided with a plurality of pairs of discharge holes.

[0015] As a preferred scheme, the inner part of the base is symmetrically and fixedly provided with two vertical plates.

[0016] As a preferred scheme, the outer part of the tunnel body is provided with a reinforcing assembly, the reinforcing assembly comprises two longitudinal connecting beams, a plurality of reinforced concrete plates are connected between the two longitudinal connecting beams, and the lower side of each longitudinal connecting beam is spaced apart and provided with a plurality of pouring piles.

[0017] The application also provides a method for judging the applicability of an anti-floating structure for an ultra-shallow soil-covered shield tunnel, comprising the following steps:

[0018] S1, determining the minimum overburden thickness of the construction stratum:

[0019] The minimum overburden thickness H of the construction stratum can be calculated by the following formula:

[0020]

[0021] wherein, D is the diameter of the tunnel structure; gamma w is the specific weight of water; gamma c is the specific weight of the shield tunnel lining segment; delta c is the ratio of the shield tunnel segment thickness; gamma s ’ is the effective specific weight of the soil.

[0022] S2, judging whether the tunnel burial depth meets the minimum overburden thickness

[0023] The minimum overburden thickness H obtained by S1 is obtained. The minimum overburden thickness H' is obtained by correcting the minimum overburden thickness H. It is judged whether the tunnel burial depth h meets the minimum overburden thickness H'. When h >= H', the burial depth of the tunnel meets the minimum overburden requirement under the current stratum condition, and the anti-floating device is not set. When h < H', the burial depth of the tunnel does not meet the minimum overburden requirement, and the anti-floating device is set.

[0024] The present application has the beneficial effects of:

[0025] 1. The anti-floating pile of the present application is inclined and deeply embedded in the stable stratum, and a plurality of circumferential array type first barbs arranged on the outer wall of the pile are embedded in the soil layer to generate a strong mechanical engagement force. When the tunnel is subjected to the action of buoyancy, the inclined surface of the barb provides anchoring resistance downward, and the clamping column prevents the barb from retracting, forming a multi-stage anti-pulling mechanism, which significantly improves the bearing capacity of a single pile. Through the partition design of the first annular cavity and the second annular cavity, the grout is layered and exuded from the first grouting port and the second grouting port, fills the gap between the pile and the soil, and penetrates and reinforces the soil at different depths. The grouting pressure is transmitted to the V-shaped elastic member in the wedge through the connecting channel, pushing the wedge to move outward and open the side wall of the second grouting port, and the grout is immediately injected from the two side discharge holes of the wedge at high pressure, expanding the reinforced radius. The grout is injected into the first pouring cavity and the second pouring cavity through the second grouting hole of the pressing plate, enhancing the integrity of the pile body, and the grout from the connecting port and the annular cavity converges to form a three-dimensional reinforcement system from the inside to the outside. After the grout hardens, it wraps the barb and clamping column, and the mechanical anchoring point and the improved soil are integrated as a whole, greatly improving the stiffness and anti-pulling force of the pile-soil composite.

[0026] 2. The present application quantifies the minimum overburden requirement for anti-floating stability from the mechanical essence by comprehensively considering the balance relationship of the tunnel self-weight, water and soil buoyancy and the effective stress of the soil, avoids the blindness of traditional empirical determination, significantly improves the engineering applicability and reliability of the determination result, and realizes the precise control of the anti-floating measure

[0027] By comparing the actual burial depth of the tunnel, a clear decision branch is formed, and the construction cost of unnecessary anti-floating measures is greatly reduced through quantitative determination. At the same time, precise deployment of anti-floating devices can reduce the maintenance investment due to floating force damage, and realize the optimal whole life cycle cost. BRIEF DESCRIPTION OF DRAWINGS

[0028] For the purpose of making the content of the present application more easily understood, the present application is further described in detail below according to specific embodiments and in conjunction with the accompanying drawings, in which

[0029] Figure 1 is a flow chart of the judging method of the present application;

[0030] Figure 2 is a schematic diagram of the first isometric structure of the present application;

[0031] Figure 3 is a schematic diagram of the second isometric structure of the present application;

[0032] Figure 4 is a schematic diagram of the first isometric structure of the anti-floating assembly in the present application;

[0033] Figure 5 is a schematic diagram of the second isometric structure of the anti-floating assembly in the present application;

[0034] Figure 6 is a schematic diagram of the top view structure of the present application;

[0035] Figure 7 is a schematic diagram of the top view structure of the present application; Figure 6 is a schematic diagram of the section structure at A-A in the present application;

[0036] Figure 8 is a schematic diagram of the first top view structure of the anti-floating assembly in the present application;

[0037] Figure 9 is a schematic diagram of the section structure at B-B in the present application; Figure 8

[0038] is a schematic diagram of the second top view structure of the anti-floating assembly in the present application; Figure 10

[0039] is a schematic diagram of the section structure at C-C in the present application; Figure 11 Figure 10 is a schematic diagram of the section structure at D in the present application;

[0040] Figure 12 Figure 11 is a schematic diagram of the enlarged structure at D in the present application.

[0041] Reference signs in the drawings are as follows:

[0042] ​​10. tunnel body, 11. base, 12. anti-floating pile, 13. first barb, 14. first connecting block, 15. clamping column, 16. second barb, 17. flange, 18. pressing plate, 19. movable rod, 20. first movable ring, 21. second connecting block, 22. avoiding groove, 23. first annular cavity, 24. first grouting hole, 25. first grouting port, 26. second annular cavity, 27. first connecting channel, 28. second grouting port, 29. fixed ring, 30. second movable ring, 31. first V-shaped elastic piece, 32. limiting block, 33. limiting groove, 34. second V-shaped elastic piece, 35. wedge block, 36. second connecting channel, 37. discharge hole, 38. third movable ring, 39. connecting port, 40. second grouting hole, 41. vertical plate, 42. first pouring cavity, 43. second pouring cavity, 44. longitudinal connecting beam, 45. reinforced concrete slab, 46. pouring pile, 47. telescopic connecting pipe. DETAILED DESCRIPTION

[0043] To illustrate the features of the present application, the present application will be further described below in conjunction with the drawings and examples.

[0044] Example 1:

[0045] Please refer to Figures 2 to 10 The present embodiment provides an anti-floating structure suitable for super-shallow soil-covered shield tunnel, and the specific structure is described as follows:

[0046] The core of the structure is a tunnel body 10. A base 11 is fixedly arranged inside the lower side of the tunnel body 10. Two vertical plates 41 are symmetrically and fixedly installed on both sides inside the base 11. In the two side regions inside the base 11, an anti-floating assembly is installed.

[0047] Each anti-floating assembly includes an anti-floating pile 12. A flange 17 is fixedly arranged on the outer wall of the upper end of the anti-floating pile 12, and the anti-floating pile 12 is fixedly connected with the base 11 through the flange 17. The lower end of the anti-floating pile 12 extends obliquely downward and penetrates the tunnel body 10, and is located below the outside of the tunnel body 10. On the outer wall of the anti-floating pile 12, four first barbs 13 are arranged in a circumferential direction to form a group of barb structures; two groups of such barb structures are arranged in an axial direction. Five pairs of clamping columns 15 are fixedly arranged on both sides of each first barb 13, and six second barbs 16 are fixedly arranged on the outer wall thereof.

[0048] The inner slide of the anti-floating pile 12 is provided with a pressing plate 18. One side of the pressing plate 18 is fixedly connected with a movable rod 19. The outer wall of the movable rod 19 is fixedly provided with a plurality of first movable rings 20. The inner wall of each first barb 13 is hingedly connected with a connecting rod 14. The upper end of each connecting rod 14 is hingedly connected with the outer wall of a corresponding one of the first movable rings 20 through a connecting block 21. The outer wall of the anti-floating pile 12 is vertically spaced apart to be provided with a plurality of groups of avoiding grooves 22, and the lower end of the connecting rod 14 is located in a corresponding avoiding groove 22 and can axially slide along the avoiding groove 22.

[0049] The internal structure of the anti-floating pile 12 comprises: a first annular cavity 23 is arranged in the upper inner wall thereof, a first grouting hole 24 is arranged on the upper side of the first annular cavity 23, and 42 (6 rows x 7) first grouting openings 25 are uniformly arranged on the outer wall of the first annular cavity 23. A second annular cavity 26 is arranged in the lower inner wall of the anti-floating pile 12, and 12 (6 rows x 2) second grouting openings 28 are arranged on the outer wall of the second annular cavity 26. The first annular cavity 23 and the second annular cavity 26 are in communication with each other through a first connecting channel 27.

[0050] On the outside of the tunnel body 10, a reinforcing assembly is arranged. The reinforcing assembly comprises two longitudinally arranged longitudinal connecting beams 44. The two longitudinal connecting beams 44 are fixedly connected with a plurality of reinforced concrete slabs 45. The lower side of each longitudinal connecting beam 44 is fixedly provided with a plurality of cast-in-place piles 46 along the length direction thereof.

[0051] In this embodiment, the anti-floating pile arranged obliquely penetrates into the stable stratum, and a plurality of groups of circumferential array type first barbs arranged on the outer wall thereof are embedded into the soil layer to generate strong mechanical clamping force. When the tunnel is subjected to the action of the buoyancy, the inclined surface of the barb faces downward to provide anchoring resistance, and the clamping column prevents the barb from retracting, thereby forming a multi-stage anti-pulling mechanism and significantly improving the bearing capacity of a single pile. Through the partition design of the first annular cavity and the second annular cavity, the grout seeps out from the first grouting openings and the second grouting openings in layers, fills the gap between the pile and the soil, and penetrates and reinforces the soil layer at different depths. The grout is injected into the first pouring cavity and the second pouring cavity through the second grouting hole of the pressing plate, thereby enhancing the integrity of the pile body, and the grout in the connecting openings and the annular cavities is combined, thereby forming a three-dimensional reinforcing system from the inside to the outside. After the grout hardens, the barb and the clamping column are wrapped, the mechanical anchoring point and the improved soil body are integrated into a whole, and the stiffness and the anti-pulling force of the pile-soil composite body are greatly improved.

[0052] Embodiment 2:

[0053] Please refer to Figures 11 to 12 On the basis of the embodiment 1, a limiting assembly is additionally arranged at the middle position in the interior of the anti-floating pile 12, which divides the interior space of the anti-floating pile 12 into the first pouring cavity 42 and the second pouring cavity 43. The pressing plate 18 is provided with a second grouting hole 40. The second annular cavity 26 in the lower inner wall of the anti-floating pile 12 and the second pouring cavity 43 are in communication with each other through a connecting opening 39.

[0054] The outer wall of the movable rod 19 is axially spaced apart and fixedly provided with a plurality of third movable rings 38. The limiting assembly includes a fixed ring 29 and a second movable ring 30. The fixed ring 29 is fixedly installed on the inner wall of the anti-floating pile 12. The second movable ring 30 can slide axially along the inner wall of the anti-floating pile 12. The outer wall of the movable rod 19 is in sliding contact with the inner wall of the fixed ring 29, and also in sliding contact with the inner wall of the second movable ring 30. When the movable rod 19 moves downward, the third movable ring 38 on the outer wall thereof will press the second movable ring 30 downward.

[0055] Between one side of the fixed ring 29 and one side of the second movable ring 30, eight (2x4) first V-shaped elastic members 31 are connected in a circumferential array. The middle part of each first V-shaped elastic member 31 is provided with a limiting block 32. The outer wall of the movable rod 19 is axially spaced apart and provided with two groups of limiting grooves 33, each group of limiting grooves 33 being distributed in a circumferential array on the outer wall of the movable rod 19. The limiting block 32 can be embedded in the corresponding limiting groove 33, for locking the position of the movable rod 19.

[0056] Between the inner walls at both ends of each first V-shaped elastic member 31, a second V-shaped elastic member 34 is connected and provided. The middle part of each second V-shaped elastic member 34 is fixedly provided with a wedge block 35. One end of the wedge block 35 slides in the second grouting opening 28 on the outer wall of the anti-floating pile 12. When the second V-shaped elastic member 34 is deformed, the wedge block 35 can be driven to extend and retract in the second grouting opening 28, thereby controlling the opening or closing of the grouting opening.

[0057] The lower side of the first annular cavity 23 is provided with a plurality of second connecting channels 36. Each second connecting channel 36 is in communication with the inside of the corresponding wedge block 35 through an extension connecting pipe 47. Four pairs of discharge holes 37 are provided on the two side walls of the wedge block 35. When the grout enters the inside of the wedge block 35 from the first annular cavity 23 through the second connecting channel 36 and the extension connecting pipe 47, it can be discharged to the outside soil from these discharge holes 37.

[0058] This embodiment increases a set of limiting assemblies on the basis of Embodiment 1, so that the grouting pressure is transmitted to the V-shaped elastic member in the wedge block through the connecting channel, the wedge block is pushed out to open the side wall of the second grouting opening, the grout is then high-pressure injected from the discharge holes on both sides of the wedge block, the reinforcement radius is expanded, and the reinforcement system is more three-dimensional.

[0059] Embodiment 3:

[0060] Please refer to Figure 1 , the present embodiment provides a method for judging the applicability of an anti-floating structure suitable for an ultra-shallow soil-covered shield tunnel. The project is a certain shield interval project of the Suzhou section of the Tongyong high-speed rail, and the tunnel structure has a diameter of 14.3 m. The specific gravity of water is 10.0 kN / m 3 ; the specific gravity of the shield tunnel lining section is 26.0 kN / m 3; the ratio of the shield tunnel segment thickness to the tunnel outer diameter is 0.084; the effective gravity of the soil body is 20.0 kN / m 3 :

[0061] S1, determining the minimum overburden thickness of the construction stratum:

[0062] The minimum overburden thickness H of the construction stratum can be calculated by the following formula:

[0063] = 8.88 m;

[0064] D is the diameter of the tunnel structure; γ w is the gravity of water; γ c is the gravity of the shield tunnel lining segment; δ c is the ratio of the shield tunnel segment thickness to the tunnel outer diameter; γ s ’ is the effective gravity of the soil body.

[0065] S2, judging whether the tunnel burial depth meets the minimum overburden thickness;

[0066] The minimum overburden thickness H obtained by S1 is corrected to obtain the minimum overburden thickness H ’ = αH = 1.25 x 8.88 = 11.10 m; judging whether the tunnel burial depth h meets the minimum overburden thickness H ’ ; in this embodiment, the minimum burial depth h of the tunnel in the ultra-shallow overburden segment is 1.39 m < 11.10 m, and the burial depth of the tunnel does not meet the minimum overburden requirement, and the anti-floating device described in embodiment 1 or embodiment 2 needs to be set.

[0067] This embodiment quantifies the minimum overburden requirement for meeting the anti-floating stability from the mechanical essence by comprehensively considering the balance relationship of the tunnel self-weight, water and soil buoyancy and the effective stress of the soil body, avoids the blindness of traditional empirical determination, significantly improves the engineering applicability and reliability of the determination result, realizes the precise control of the anti-floating measure, forms a clear decision branch by comparing the actual burial depth of the tunnel, greatly reduces the construction cost of unnecessary anti-floating measures through quantitative determination; at the same time, the precise deployment of the anti-floating device can reduce the post-maintenance investment caused by the buoyancy disease, and realize the optimal life cycle cost.

[0068] The above embodiments and drawings are only used to illustrate the technical solutions of the present application, and are not a limitation of the present application. The present application is described in detail with reference to the preferred embodiments, and those skilled in the art should understand that the changes, modifications, additions or substitutions made by those skilled in the art within the essential scope of the present application do not deviate from the purpose of the present application, and should also belong to the protection scope of the claims of the present application. Other related technical structures not fully disclosed in the present application are the existing technologies in the art.

Claims

1. An anti-buoyancy structure suitable for ultra-shallow overburden shield tunnels, comprising a tunnel body (10), a base (11) provided on the lower side of the interior of the tunnel body (10), and several anti-buoyancy components installed on both sides of the interior of the base (11). Its features are: The anti-buoyancy component includes an anti-buoyancy pile (12). One end of the anti-buoyancy pile (12) is fixedly provided with a flange (17) connecting to a base (11). The other end of the anti-buoyancy pile (12) extends downward at an angle to the outside of the tunnel body (10). The outer wall of the anti-buoyancy pile (12) is hinged with a number of first barbs (13). Each first barb (13) has a number of pairs of locking posts (15) on both sides. The outer wall of each first barb (13) is provided with a number of second barbs (16). The number of first barbs (13) are arranged in a circumferential array to resist... The outer wall of the floating pile (12) is a group, and several groups of first barbs (13) are axially spaced on the outer wall of the anti-buoyancy pile (12). The anti-buoyancy pile (12) is slidably provided with a pressure plate (18). A movable rod (19) is fixedly provided on one side of the pressure plate (18). Several first movable rings (20) are fixedly provided on the outer wall of the movable rod (19). A connecting rod (14) is provided on the inner wall of each first barb (13). A connecting block (21) is connected between one end of each connecting rod (14) and the outer wall of the first movable ring (20). The upper inner wall of the anti-buoyancy pile (12) is provided with a first annular cavity (23), the lower inner wall of the anti-buoyancy pile (12) is provided with a second annular cavity (26), the outer wall of the first annular cavity (23) is provided with a number of first grouting ports (25), the outer wall of the second annular cavity (26) is provided with a number of second grouting ports (28), the first annular cavity (23) and the second annular cavity (26) are connected by a first connecting channel (27), the upper side of the first annular cavity (23) is provided with a first grouting hole (24), the middle of the interior of the anti-buoyancy pile (12) is provided with a limiting component, the interior of the anti-buoyancy pile (12) is separated by the limiting component into a first pouring cavity (42) and a second pouring cavity (43), the pressure plate (18) is provided with a second grouting hole (40), and the second annular cavity (26) and the second pouring cavity (43) are connected by a connecting port (39).

2. The anti-buoyancy structure for ultra-shallow overburden shield tunnels according to claim 1, characterized in that: The outer wall of the anti-buoyancy pile (12) is provided with several sets of clearance grooves (22) at vertical intervals, and the other end of the connecting rod (14) slides axially in the clearance groove (22).

3. The anti-buoyancy structure for ultra-shallow overburden shield tunnels according to claim 1, characterized in that: The outer wall of the movable rod (19) is axially spaced and fixed with several third movable rings (38). The limiting component includes a fixed ring (29) and a second movable ring (30). The fixed ring (29) is fixed to the inner wall of the anti-buoyancy pile (12). The second movable ring (30) slides axially within the anti-buoyancy pile (12). The outer wall of the movable rod (19) slides in contact with the inner wall of the fixed ring (29). The outer wall of the movable rod (19) slides in contact with the inner wall of the second movable ring (30). The second movable ring (30) is pressed downward by the third movable ring (38). Several first V-shaped elastic elements (31) are connected between one side of the fixed ring (29) and one side of the second movable ring (30). Each first V-shaped elastic element (31) has a limiting block (32) in the middle. Several sets of limiting grooves (33) are axially spaced on the outer wall of the movable rod (19).

4. The anti-buoyancy structure for ultra-shallow overburden shield tunnels according to claim 3, characterized in that: A number of first V-shaped elastic elements (31) are arranged in a circular array between the fixed ring (29) and the second movable ring (30). A number of limiting grooves (33) are arranged in a circular array on the outer wall of the movable rod (19). A second V-shaped elastic element (34) is connected between the inner walls of the two ends of each first V-shaped elastic element (31). A wedge (35) is provided in the middle of each second V-shaped elastic element (34). One end of the wedge (35) slides in the second grouting port (28).

5. The anti-buoyancy structure for ultra-shallow overburden shield tunnels according to claim 4, characterized in that: The lower side of the first annular cavity (23) is provided with several second connecting channels (36), and the second connecting channels (36) are connected to the interior of the wedge (35) by telescopic connecting pipes (47). Several pairs of discharge holes (37) are provided on both sides of the wedge (35).

6. The anti-buoyancy structure for ultra-shallow overburden shield tunnels according to claim 1, characterized in that: The base (11) has two upright plates (41) fixedly and symmetrically inside.

7. The anti-buoyancy structure applicable to ultra-shallow overburden shield tunnels according to claim 1, characterized in that: The tunnel body (10) is provided with a reinforcement component on the outside. The reinforcement component includes two longitudinal connecting beams (44), and a number of reinforced concrete slabs (45) are connected between the two longitudinal connecting beams (44). A number of cast-in-place piles (46) are provided at intervals on the lower side of each longitudinal connecting beam (44).

8. A method for determining the applicability of an anti-buoyancy structure for a shallow-overburden shield tunnel as described in claim 1, characterized in that, Includes the following steps: S1. Determine the minimum overburden thickness of the stratum under construction: The minimum overburden thickness H of the construction stratum can be calculated using the following formula: Where D is the diameter of the tunnel structure; γ w The specific weight of water; γ c The density of the shield tunnel lining section; δ c γ is the ratio of the thickness of the shield tunnel segments; s ’ The effective unit weight of the soil; S2. Determine whether the tunnel burial depth meets the minimum overburden thickness: The minimum overburden thickness H calculated in S1 is used to obtain the corrected minimum overburden thickness H' = αH; it is then determined whether the tunnel burial depth h meets the minimum overburden thickness H'; when h ≥ H', under this geological condition, the tunnel burial depth meets the minimum overburden requirement, and the above-mentioned anti-buoyancy structure is not required; when h < H', the tunnel burial depth does not meet the minimum overburden requirement, and the above-mentioned anti-buoyancy structure is required.

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