Construction method of large-diameter double-layer steel casing

Abstract

The present application relates to the construction method of large diameter double-layer steel casing, specifically includes the following steps: step one, construction preparation; step two, outer casing installation and adjustment; step three, inner casing pressure sinking system installation; step four, inner casing pressure sinking construction; step five, grouting consolidation construction. The present application realizes the accurate control of casing position and perpendicularity, stability enhancement, efficient construction, resistance reduction and reliable quality through the adjustable arc-shaped casing, reasonable pressure sinking system, grouting consolidation design, blade foot cutting tool and lubricating grouting pipe cooperation.

Description

Technical Field

[0001] The present invention belongs to the field of civil engineering construction technology, and specifically relates to a large-diameter double-layer steel casing structure suitable for complex geological conditions such as quicksand strata and its high-precision construction method. It is particularly suitable for controlling the verticality and coaxiality of permanent steel casings in pile foundation projects of cross-river and cross-sea bridges. Background Art

[0002] Quicksand strata, due to their unique geological characteristics, have always been a major construction challenge in large-scale infrastructure projects. Quicksand strata are characterized by high fluidity, low bearing capacity, and easy deformation. Traditional single-layer steel casings struggle to maintain stability and verticality in this stratum, prone to tilting, shifting, and even collapse. This makes it difficult to achieve the required construction precision, severely impacting project quality and progress.

[0003] At the same time, conventional pressure sinking and consolidation construction techniques are ineffective in quicksand formations. During the pile foundation casing construction process, due to the unevenness of the strata, the casing is not evenly stressed, which can easily lead to localized stress concentrations, making it difficult to sink the casing or even causing damage. During the consolidation phase, conventional grouting methods struggle to form an effective solid mass, unable to provide sufficient support for the casing, and unable to meet the project's requirements for casing stability and load-bearing capacity.

[0004] Furthermore, existing construction technology also suffers from shortcomings in efficiency and cost control. The complex construction process often requires significant manpower, material resources, and time, increasing construction costs. Furthermore, the lack of recyclable structural designs further increases the overall project cost. Therefore, a large-diameter, double-layer steel casing structure specifically designed for quicksand formations, along with an efficient and reliable construction method, is urgently needed to overcome the shortcomings of existing technology and meet the demands of modern engineering construction. Summary of the Invention

[0005] The purpose of the present invention is to solve the above problems in the prior art and provide a construction method for a large-diameter double-layer steel casing.

[0006] The construction method of large-diameter double-layer steel casing includes the following specific steps:

[0007] Step 1: Construction preparation;

[0008] Step 2: Install and adjust the outer casing;

[0009] S21. Outer casing sinking: sink the outer casing into the quicksand stratum to the designed elevation;

[0010] S22. Installing and adjusting the gap of the curved tube: Install the curved tube vertically along the gap between the outer casing and the inner casing. Install a hollow rod on the curved tube. The hollow rod passes through the curved tube. The upper end of the curved tube is fixed to the inner wall of the outer casing through a bracket. Lift the inner casing into the outer casing.

[0011] S23, Rotation adjustment: by rotating the hollow rod to drive the arc tube to rotate, adjust the local distance between the outer casing and the inner casing;

[0012] S24, gap locking: The arc tube is locked by the bracket so that it cannot rotate, thereby forming a uniform annular gap between the outer casing and the inner casing;

[0013] Step 3: Installation of inner casing pressure sinking system:

[0014] S31. Assembling the pressure-bearing structure: Install several pressure-bearing beams on the top of the inner casing. The pressure-bearing beams are arranged radially relative to the top center of the inner casing. Ring beams are installed above the pressure-bearing beams, and a bearing plate is installed in the center above the pressure-bearing beams.

[0015] S32. Layout of the center pressure sinking system: Install a center jack on the bearing plate, connect the top of the center jack to the center pressure rod, and set a pressure sinking guide frame on the top of the center pressure rod;

[0016] S33. Layout of the side pressure sinking system: Install the combined pressure bearing members symmetrically along the periphery of the inner casing. Insert the column feet at the bottom of the combined pressure bearing members into the ground. The side ring plates, side ring reinforcements, and bottom ring plates on the combined pressure bearing members enclose a cylindrical space, which is filled with concrete blocks.

[0017] S34. Install the pressure sinking guide frame: Install the ring side jack on the ring beam, install the ring side pressure rod on the upper end of the ring side jack, install a parallel connecting rod on the ring side pressure rod, connect one end of the parallel connecting rod to the ring side pressure rod, install a column on the other end of the parallel connecting rod, and connect the column to the combined pressure bearing member;

[0018] Step 4: Inner casing pressure sinking construction;

[0019] Step 5: Grouting consolidation construction.

[0020] Preferably, the specific method of step one is as follows:

[0021] S11. Measurement and positioning: Locate the axis of the outer casing and the inner casing according to the design coordinates, and mark the range of the quicksand formation;

[0022] S12, prefabricated outer casing, inner casing, curved casing, hollow rod, pressure beam, ring beam, bearing plate, center jack, center pressure rod, pressure sinking guide frame, combined pressure-bearing parts, cutting tool, grouting pipe, and grouting material.

[0023] As a preference, the specific method of step 4 is as follows:

[0024] S41. Installation of the cutting tool: Weld an annular base plate to the bottom of the inner casing. A plurality of cutting blades are disposed on the annular base plate in a circular array. A lubricating grouting pipe is installed on the outer side of the inner casing. The bottom of the lubricating grouting pipe passes through the annular base plate and extends to the gap between adjacent cutting blades.

[0025] S42, staged sinking operation:

[0026] First, perform center sinking; start the center jack and apply downward pressure to the inner casing through the center pressure rod and the bearing plate;

[0027] Then the ring side is pressed down; the ring side jack is started and downward pressure is applied to the inner casing;

[0028] S43. Lubrication grouting assistance: During the sinking process of the inner casing, friction-reducing slurry is injected into the cutting blade area through the lubrication grouting pipe.

[0029] As a preference, the specific method of step five is as follows:

[0030] S51. Grouting of the consolidation block at the bottom of the outer casing: Connect the upper end of the hollow rod to the grouting equipment, and inject grout downward through the hollow rod on the arc tube to form a consolidation block at the lower end of the hollow rod;

[0031] S52. Grouting at the bottom consolidation end of the inner casing: The inner wall of the inner casing is arranged with an inner wall grouting pipe and an annular grouting pipe. The lower end of the inner wall grouting pipe is connected to the annular grouting pipe. The upper end of the inner wall grouting pipe is connected to the grouting equipment. High-strength slurry is injected into the annular grouting pipe through the grouting equipment to form a consolidation end at the bottom of the inner casing.

[0032] Preferably, after step 5 is completed, the combined pressure-bearing parts are recovered and inspected. The specific method for recovering and inspecting the combined pressure-bearing parts is as follows:

[0033] S61. Removal of combined pressure-bearing parts: Clear the concrete blocks in the cylindrical space and remove the side ring plate and bottom ring plate;

[0034] S62. Quality acceptance: Check the verticality, gap uniformity, consolidation strength and overall structural stability of the outer and inner casings.

[0035] Preferably, the cross section of the arc-shaped cylinder is elliptical.

[0036] Preferably, the column is connected to the center of the bottom ring disk of the combined pressure-bearing member, and a diagonal brace is installed between the parallel connecting rod and the column to reinforce the pressure sinking guide frame.

[0037] Preferably, in step S23, the verticality error between the outer casing and the inner casing is ≤1%.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1) Precise control of the position and perpendicularity of the casing: The local spacing between the outer and inner casings can be flexibly adjusted by the rotatable arc-shaped cylinder, ensuring that the axes of the double casings are parallel and the perpendicularity error is less than or equal to 1%, improving the precision of casing installation and facilitating the smooth progress of subsequent construction.

[0040] 2) Enhanced stability of the casing: The bottom end of the outer casing is grouted through the hollow rod to form a consolidated block, and the bottom of the inner casing is grouted through the inner wall grouting pipe and the annular grouting pipe to form a consolidated end, enhancing the stability of the casing in the quicksand formation and improving the bearing capacity of the overall structure.

[0041] 3) Efficient and flexible sinking system: The combination of the center sinking system and the ring-side sinking system can uniformly apply pressure to the inner casing, allowing it to sink smoothly and improving construction efficiency. At the same time, the combined pressure-bearing components in the ring-side sinking system provide stable support by filling concrete blocks, which can be recycled, reducing construction costs.

[0042] 4) Reduce construction resistance: The blade foot cutter is combined with the lubricating grouting pipe to inject friction-reducing grout into the cutting blade area during the sinking process, reducing the resistance of the inner casing during sinking, reducing construction difficulty, and improving the smoothness of construction. BRIEF DESCRIPTION OF DRAWINGS

[0043] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0044] Figure 1 It is a large-diameter double-layer steel casing construction schematic diagram.

[0045] Figure 2 It is another view of a large-diameter double-layer steel casing construction schematic diagram.

[0046] Figure 3 It is a sinking guide frame and combined pressure-bearing component structure schematic diagram.

[0047] Figure 4 It is Figure 2 Detail schematic diagram of node A.

[0048] In the drawings, the component list represented by each number is as follows:

[0049] In the figure: 1. Inner casing; 2. Outer casing; 3. Arc-shaped tube; 4. Hollow rod; 5. Consolidation block; 6. Pressure beam; 7. Connecting bolts; 8. Ring beam; 9. Bearing plate; 10. Center pressure rod; 11. Center jack; 12. Ring side pressure rod; 13. Ring side jack; 14. Sinking guide frame; 15. Combined pressure-bearing parts; 16. Blade cutting tool; 17. Bottom ring plate; 18. Side ring plate; 19. Bottom ring reinforcement; 20. Side ring reinforcement; 21. Column foot; 22. Concrete block; 23. Column; 24. Flat connecting rod; 25. Diagonal brace; 26. Annular base plate; 27. Cutting blade; 28. Lubrication grouting pipe; 29. ​​Inner wall grouting pipe; 30. Annular grouting pipe. DETAILED DESCRIPTION

[0050] The following will be combined with the accompanying drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of this application.

[0051] Those skilled in the art should understand that, in the disclosure of this application, the terms "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the above terms cannot be understood as limiting this application.

[0052] Example:

[0053] See also Figure 1-4As shown, in the present embodiment, a large-diameter double-layer steel casing is provided, including an outer casing 2 and an inner casing 1, the outer casing 2 is arranged in a quicksand formation, and the inner casing 1 is installed under the protection of the outer casing 2; an arc-shaped casing 3 is arranged between the outer casing 2 and the inner casing 1 in a spaced manner, the arc-shaped casing 3 is arranged along the vertical direction, and a gap between the outer casing 2 and the inner casing 1 is formed by the arc-shaped casing 3, the upper end of the arc-shaped casing 3 is fixed by a support and is in rotating cooperation with the support, so that the arc-shaped casing 3 can rotate relative to the support. The center of the arc-shaped casing 3 has a hollow rod 4, which can drive the arc-shaped casing 3 to rotate by rotating the hollow rod 4, the hollow rod 4 penetrates the arc-shaped casing 3, and the distance between the outer casing 2 and the inner casing 1 is adjusted by rotating the arc-shaped casing 3, so as to ensure that the relative position and perpendicularity of the two are controllable. In the present application, the cross section of the arc-shaped casing 3 is elliptical. After the outer casing 2 and the inner casing 1 are sunk into position, a consolidation block 5 is formed by grouting through the hollow rod 4, and the consolidation block 5 is located at the bottom end of the outer casing 2; the inner wall of the inner casing 1 is arranged with an inner wall grouting pipe 29 and an annular grouting pipe 30, the lower end of the inner wall grouting pipe 29 is connected with the annular grouting pipe 30, the annular grouting pipe 30 is located at the bottom of the inner casing 1, a plurality of grouting holes are arranged on the annular grouting pipe 30, and the grouting holes are used to form a consolidated end at the bottom of the inner casing 1.

[0054] The present application also includes a sinking system, which includes a center sinking system and a ring side sinking system.

[0055] Wherein, the top of the inner casing 1 is provided with a plurality of pressure bearing beams 6, the pressure bearing beams 6 are fixedly connected with the top of the inner casing 1 through connecting bolts 7, the plurality of pressure bearing beams 6 are arranged in a central radiation manner with the inner casing 1, and a ring beam 8 and a bearing disc 9 are arranged on the upper part of the pressure bearing beams 6; the center sinking system includes a center jack 11 arranged on the bearing disc 9 and a center pressing rod 10, the center jack 11 is directly installed on the bearing disc 9, and the center pressing rod 10 is arranged on the upper part of the center pressing rod 10.

[0056] The ring side pressure sinking system includes a pressure sinking guide frame 14 and a combined pressure bearing member 15 arranged at intervals on the periphery of the inner casing 1. The pressure sinking guide frame 14 includes a column 23, a flat connecting rod 24, a diagonal brace 25, a ring side pressure rod 12 and a ring side jack 13. One end of the flat connecting rod 24 is connected to the top of the column 23, and the other end of the flat connecting rod 24 is connected to the ring side pressure rod 12. The diagonal brace 25 is arranged between the column 23 and the flat connecting rod 24; the ring side pressure rod 12 is connected to the ring side jack 13, and the ring side jack 13 is connected to the ring beam 8. The ring side jack 13 directly acts on the ring beam 8, and the ring beam 8 transmits pressure to the inner casing 1 through the pressure beam 6; The column 23 is connected to the combined pressure-bearing member 15, and the combined pressure-bearing member 15 includes a bottom ring plate 17, a bottom ring rib 19, a side ring plate 18, and a side ring rib 20. The bottom ring plate 17 is provided with a bottom ring rib 19. The column 23 is located at the center of the combined pressure-bearing member 15. The bottom of the column 23 is connected to the bottom ring plate 17 and the bottom ring rib 19. The bottom of the bottom ring plate 17 has a column foot 21. The side ring plate 18 is provided on the side of the combined pressure-bearing member 15. Side ring ribs 20 are provided between adjacent side ring plates 18. The side ring plates 18, the side ring ribs 20 and the bottom ring plate 17 enclose a cylindrical space centered on the column 23, and concrete blocks 22 can be installed in the cylindrical space.

[0057] The present invention also includes a blade cutting tool 16, which is fixed to the bottom of the inner casing 1. The blade cutting tool 16 includes an annular base plate 26, on which a plurality of cutting blades 27 are provided. The cutting blades 27 are arranged in a circular array on the annular base plate 26. A lubricating grouting pipe 28 is arranged on the outside of the inner casing 1. The bottom of the lubricating grouting pipe 28 passes through the annular base plate 26 and extends to the gap between adjacent cutting blades 27.

[0058] The construction methods of large diameter double-layer steel casing include:

[0059] Step 1: Construction preparation:

[0060] S11. Measurement and positioning: Locate the axis of the outer casing 2 and the inner casing 1 according to the design coordinates, and mark the range of the quicksand formation;

[0061] S12. Materials entering the site: prefabricated outer casing 2, inner casing 1, curved casing 3, hollow rod 4, pressure beam 6, ring beam 8, bearing plate 9, center jack 11, center pressure rod 10, pressure sinking guide frame 14, combined pressure-bearing parts 15, blade cutting tool 16, grouting pipes 29, 30 and grouting materials.

[0062] Step 2: Installation and adjustment of outer casing:

[0063] S21, sinking the outer casing 2: Use a vibratory hammer or static pressure equipment to sink the outer casing 2 into the quicksand stratum to the designed elevation;

[0064] S22. Install the curved tube 3 and adjust the gap: Install the curved tube 3 vertically along the gap between the outer casing 2 and the inner casing 1. Install the hollow rod 4 on the curved tube 3. The hollow rod 4 passes through the curved tube 3. The upper end of the curved tube 3 is fixed to the inner wall of the outer casing 2 through a bracket. Lift the inner casing 1 into the outer casing 2.

[0065] S23, Rotation adjustment: by rotating the hollow rod 4 to drive the arc tube 3 to rotate, adjust the local distance between the outer casing 2 and the inner casing 1, ensure that the axis of the outer casing 2 and the inner casing 1 are parallel, and the verticality error of the outer casing 2 and the inner casing 1 is ≤1%;

[0066] S24. Gap locking: After the adjustment is completed, the arc tube 3 is locked by the bracket so that it cannot rotate, thereby forming a uniform annular gap between the outer casing 2 and the inner casing 1; wherein, when the arc tube 3 is locked by the bracket, the arc tube 3 and the bracket can be directly welded, thereby locking the rotation angle of the arc tube 3 and preventing it from rotating.

[0067] Step 3: Installation of inner casing pressure sinking system:

[0068] S31. Assembling the pressure-bearing structure: Install several pressure-bearing beams 6 on the top of the inner casing 1 using connecting bolts 7. The pressure-bearing beams 6 are arranged radially relative to the top center of the inner casing 1. Ring beams 8 are installed above the pressure-bearing beams 6. A bearing plate 9 is installed in the center above the pressure-bearing beams 6.

[0069] S32. Arrangement of the central pressure sinking system: Install the central jack 11 on the bearing plate 9 , and connect the top of the central jack 11 to the central pressure rod 10 .

[0070] S33. Layout of the side pressure sinking system: Install the combined pressure-bearing members 15 symmetrically along the periphery of the inner casing 1. Insert the column foot 21 at the bottom of the combined pressure-bearing members 15 into the ground. The side ring plates 18, side ring ribs 20, and bottom ring plate 17 on the combined pressure-bearing members 15 enclose a cylindrical space, which is filled with concrete blocks 22.

[0071] S34. Install the pressure sinking guide frame 14: The installation method of the pressure sinking guide frame 14 is as follows: install the ring side jack 13 on the ring beam 8, install the ring side pressure rod 12 on the upper end of the ring side jack 13, install the flat connecting rod 24 on the ring side pressure rod 12, one end of the flat connecting rod 24 is connected to the ring side pressure rod 12, and the other end of the flat connecting rod 24 is installed with the column 23, connect the column 23 to the combined pressure bearing member 15, and the column 23 is connected to the center of the bottom ring plate 17 of the combined pressure bearing member 15. Install a diagonal brace 25 between the flat connecting rod 24 and the column 23 to reinforce the pressure sinking guide frame 14.

[0072] Step 4: Inner casing sinking construction:

[0073] S41. Installation of the cutting tool 16: An annular base plate 26 is welded to the bottom of the inner casing 1. A plurality of cutting blades 27 are provided on the annular base plate 26. The cutting blades 27 are arranged in a circular array on the annular base plate 26. A lubricating grouting pipe 28 is installed on the outer side of the inner casing 1. The bottom of the lubricating grouting pipe 28 passes through the annular base plate 26 and extends to the gap between adjacent cutting blades 27.

[0074] S42, staged sinking operation:

[0075] First, perform center sinking; start the center jack 11, and apply downward pressure to the inner casing 1 through the center pressure rod 10 and the bearing plate 9;

[0076] Then the ring side is pressed down; the ring side jack 13 is started to transmit pressure through the ring beam 8 and the pressure beam 6, and exert downward pressure on the inner casing 1;

[0077] S43, lubrication grouting assistance: During the sinking process of the inner casing 1, friction-reducing slurry is injected into the cutting blade 27 area through the lubrication grouting pipe 28.

[0078] Step 5: Grouting consolidation construction:

[0079] S51, grouting the consolidation block 5 at the bottom of the outer casing 2: connect the upper end of the hollow rod 4 to the grouting equipment, and inject grout downward through the hollow rod 4 on the arc tube 3 to form a consolidation block 5 at the lower end of the hollow rod 4;

[0080] S52. Grouting at the bottom consolidation end of the inner casing 1: The inner wall of the inner casing 1 is arranged with an inner wall grouting pipe 29 and an annular grouting pipe 30. The lower end of the inner wall grouting pipe 29 is connected to the annular grouting pipe 30. The upper end of the inner wall grouting pipe 29 is connected to the grouting equipment. High-strength slurry is injected into the annular grouting pipe 30 through the grouting equipment, thereby forming a consolidation end at the bottom of the inner casing 1.

[0081] Step 6. Recovery and acceptance of combined pressure-bearing parts:

[0082] S61, dismantling the combined pressure-bearing member 15: clearing the concrete block 22 in the cylindrical space, and removing the side ring plate 18 and the bottom ring plate 17;

[0083] S62. Quality acceptance: Check the verticality, gap uniformity, solid body strength and overall structural stability of the outer casing 2 and the inner casing 1.

Claims

1. The construction method of large diameter double-layer steel casing is characterized by: The specific steps include: Step 1: Construction preparation; Step 2: Install and adjust the outer casing; S21, sinking the outer casing (2): sinking the outer casing (2) into the quicksand stratum to the designed elevation; S22. Installation of the arc tube (3) and gap adjustment: Install the arc tube (3) vertically along the gap between the outer casing (2) and the inner casing (1), install the hollow rod (4) on the arc tube (3), the hollow rod (4) passes through the arc tube (3), and the upper end of the arc tube (3) is fixed to the inner wall of the outer casing (2) through a bracket; hoist the inner casing (1) into the outer casing (2); S23, rotation adjustment: by rotating the hollow rod (4) to drive the arc tube (3) to rotate, the local distance between the outer casing (2) and the inner casing (1) is adjusted; S24, gap locking: locking the arc tube (3) by the bracket so that it cannot rotate, thereby forming a uniform annular gap between the outer casing (2) and the inner casing (1); Step 3: Installation of inner casing pressure sinking system: S31, assembling the pressure-bearing structure: installing a plurality of pressure-bearing beams (6) on the top of the inner casing (1), the pressure-bearing beams (6) being arranged radially relative to the top center of the inner casing (1), installing a ring beam (8) above the pressure-bearing beams (6), and erecting a bearing plate (9) at the center above the pressure-bearing beams (6); S32, center pressure sinking system layout: install the center jack (11) on the bearing plate (9), and the top of the center jack (11) is connected to the center pressure rod (10); S33, layout of the ring side pressure sinking system: symmetrically install the combined pressure bearing member (15) along the outer periphery of the inner casing (1), insert the column foot (21) at the bottom of the combined pressure bearing member (15) into the ground soil, and the side ring plate (18), side ring reinforcement (20) and bottom ring plate (17) on the combined pressure bearing member (15) enclose a cylindrical space, and fill the cylindrical space with concrete blocks (22); S34, installing the pressure sinking guide frame (14): installing the ring side jack (13) on the ring beam (8), installing the ring side pressure rod (12) on the upper end of the ring side jack (13), installing the flat connecting rod (24) on the ring side pressure rod (12), one end of the flat connecting rod (24) is connected to the ring side pressure rod (12), and the other end of the flat connecting rod (24) is installed with the column (23), and the column (23) is connected to the combined pressure bearing member (15); Step 4: Inner casing pressure sinking construction; Step 5: Grouting consolidation construction.

2. The construction method of large-diameter double-layer steel casing according to claim 1 is characterized in that: The specific method of step one is as follows: S11. Measurement and positioning: locate the axis of the outer casing (2) and the inner casing (1) according to the design coordinates, and mark the range of the quicksand formation; S12, prefabricated outer casing (2), inner casing (1), arc tube (3), hollow rod (4), pressure beam (6), ring beam (8), bearing plate (9), center jack (11), center pressure rod (10), pressure sinking guide frame (14), combined pressure bearing member (15), cutting tool (16), inner wall grouting pipe (29), annular grouting pipe (30) and grouting material.

3. The construction method of large-diameter double-layer steel casing according to claim 1 is characterized in that: The specific method of step four is as follows: S41. Installation of the cutting tool (16): an annular base plate (26) is welded to the bottom of the inner casing (1), a plurality of cutting blades (27) are provided on the annular base plate (26), and the cutting blades (27) are arranged on the annular base plate (26) in a circular array. A lubricating grouting pipe (28) is installed on the outer side of the inner casing (1), and the bottom of the lubricating grouting pipe (28) passes through the annular base plate (26) and extends to the gap between adjacent cutting blades (27); S42, staged sinking operation: First, perform center sinking; start the center jack (11) to apply downward pressure to the inner casing (1) through the center pressure rod (10) and the bearing plate (9); Then, the ring side is sunk; the ring side jack (13) is started and downward pressure is applied to the inner casing (1); S43, lubrication grouting assistance: During the sinking process of the inner casing (1), friction-reducing slurry is injected into the cutting blade (27) area through the lubrication grouting pipe (28).

4. The construction method of large-diameter double-layer steel casing according to claim 1 is characterized in that: The specific method of step five is as follows: S51, grouting the consolidation block (5) at the bottom of the outer casing (2): connecting the upper end of the hollow rod (4) to the grouting equipment, and grouting downward through the hollow rod (4) on the arc tube (3) to form a consolidation block (5) at the lower end of the hollow rod (4); S52. Grouting of the bottom consolidation end of the inner casing (1): An inner wall grouting pipe (29) and an annular grouting pipe (30) are arranged on the inner wall of the inner casing (1). The lower end of the inner wall grouting pipe (29) is connected to the annular grouting pipe (30). The upper end of the inner wall grouting pipe (29) is connected to a grouting device. High-strength slurry is injected into the annular grouting pipe (30) through the grouting device, thereby forming a consolidation end at the bottom of the inner casing (1).

5. The construction method of large-diameter double-layer steel casing according to claim 1 is characterized in that: After step 5 is completed, the combined pressure-bearing parts are recovered and inspected. The specific methods for recovering and inspecting the combined pressure-bearing parts are as follows: S61, removal of the combined pressure-bearing member (15): clearing the concrete block (22) in the cylindrical space, and removing the side ring plate (18) and the bottom ring plate (17); S62. Quality acceptance: Check the verticality, gap uniformity, consolidation strength and overall structural stability of the outer casing (2) and the inner casing (1).

6. The construction method of large-diameter double-layer steel casing according to claim 1, characterized in that: The cross section of the arc-shaped cylinder (3) is elliptical.

7. The construction method of large-diameter double-layer steel casing according to claim 1 is characterized in that: The column (23) is connected to the center of the bottom ring plate (17) of the combined pressure bearing member (15), and a diagonal brace (25) is installed between the flat connecting rod (24) and the column (23) to reinforce the pressure sinking guide frame (14).

8. The construction method of large-diameter double-layer steel casing according to claim 1 is characterized in that: In step S23, the verticality error between the outer casing (2) and the inner casing (1) is ≤1%.

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