Combined back pressure reinforcement pre-bias sinking double-wall steel cofferdam for steep terrain and construction method thereof

Abstract

The invention relates to a steep terrain combined back pressure reinforcement pre-bias sinking double-wall steel cofferdam and a construction method thereof, and provides a comprehensive solution for the problems of steel cofferdam deflection and bottom sealing concrete side pressure caused by levee slope pressure and channel scouring. The method comprises the steps that the levee slope is reinforced through the front and rear protection piles and the integral steel frame, and the soil stability is enhanced by combining grouting and jet grouting piles; dense shear keys are arranged on the inner wall of the steel cofferdam, and the shear strength of bottom sealing concrete is improved; a pre-deflection guide frame is matched with a guide groove, and vertical sinking of the steel cofferdam is ensured through sliding guide of a pulley; the pressure on the two sides is balanced by utilizing channel side throwing and filling pebbles and a prefabricated concrete frame for back pressure, and bank side bagged pebbles; and bottom sealing concrete is symmetrically poured in different areas, and the cofferdam offset risk is reduced. The matching device comprises an adjustable pre-deflection guide frame, a guide pipe support and a pentagonal prefabricated concrete frame. Through structural optimization and construction cooperative control, the steel cofferdam sinking precision, the anti-scouring capacity and the overall stability are effectively improved.

Description

Technical Field

[0001] This invention relates to bridge retaining structure engineering, specifically to a double-walled steel cofferdam with combined counter-pressure reinforcement and pre-eccentric sinking in steep terrain and its construction method. Background Technology

[0002] Construction work in water-adjacent areas often presents the challenge of constructing stable structures under complex geological conditions and water flow environments. When engineering projects are carried out around dikes, the original equilibrium of the soil is disrupted when the dike slopes are excavated, resulting in unbalanced earth pressure. If this pressure cannot be effectively resisted, the slope is prone to collapse and other instability. Traditional protective pile installations are inadequate in the face of complex geology and large-scale excavation, making it difficult to ensure long-term slope stability. In deep-water areas, steel cofferdams play a crucial role as a commonly used retaining structure. However, the water flow velocity on the channel side is usually high, and uneven scouring occurs frequently, making the bottom of the cofferdam prone to being suspended, greatly weakening its stability. Furthermore, how to enhance the shear strength of the contact surface between the steel cofferdam and the bottom sealing concrete has always been a difficult problem in engineering practice. At the same time, the lateral pressure generated during the construction of the bottom sealing concrete also adversely affects the position and stability of the steel cofferdam. In addition, steel cofferdams are prone to shifting during the sinking process due to various factors such as water flow and geology.

[0003] Given the numerous technical challenges faced in the construction of the aforementioned projects, developing an innovative construction method that can effectively resist unbalanced earth pressure on slopes, ensure the stability and sinking accuracy of steel cofferdams, and optimize the construction process of bottom sealing concrete has become a key issue that urgently needs to be addressed in the engineering field. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned problems in the prior art by providing a double-walled steel cofferdam with combined counterpressure reinforcement for steep terrain and its construction method.

[0005] To achieve the above-mentioned objectives, the present invention employs the following technical solution: A construction method for a double-walled steel cofferdam with combined counter-pressure reinforcement and pre-eccentric placement in steep terrain includes the following steps: Step 1, Embankment Protection: Front and rear protective piles are installed at the excavation boundary of the steel cofferdam on the slope adjacent to the embankment. Grooves are opened on the top of the piles and they are bolted to the front and rear cap beams of the integral steel frame through clamps. The cap beams are fixed together by connecting beams. Grouting reinforcement is carried out between the two rows of protective piles and in the outward extension area, and jet grouting piles are installed on the side of the front protective piles. Step 2, Shear Key Installation: Install shear keys within the bottom concrete pouring area of ​​the inner wall of the steel cofferdam near the waterway side; Step 3: Installation of pre-deflection guide frame: Install multiple layers of pre-deflection guide frame on the inner wall of the steel cofferdam, and set guide grooves on the surface of the steel casing. The pulleys of the guide frame slide in the guide grooves. Step 4, Steel cofferdam placement: Install support frames at the bottom of the steel cofferdam on the channel side, and lower it after the inner tank on the other side is filled with water and balanced. The pre-deflection guide frame guides it vertically along the guide groove. Step 5, Backfilling with gravel: After the steel cofferdam is in place, bagged gravel is piled on the side of the embankment, and gravel is backfilled on the side of the waterway and a precast concrete frame is placed for backfilling. Step 6: Pouring bottom sealing concrete: Set up a steel support frame on the steel casing, erect a bottom sealing platform with perforated steel plates, and pour bottom sealing concrete symmetrically in sections.

[0006] Furthermore, in step one, the front and rear protective piles are bored cast-in-place piles, with a clamp installed below the groove at the top of the pile. The clamps are bolted to the L-shaped connecting plates of the cap beam at the four corners.

[0007] Furthermore, in step one, the grouting reinforcement area extends in a "figure-eight" shape towards the embankment, and the jet grouting piles are located between the front cap beam and the rear cap beam and close to the side of the front cap beam.

[0008] Furthermore, in step three, the pre-deflection guide frame includes a fixed plate, a telescopic bracket that can move along the slide rail, and pulleys, with the telescopic bracket fixed in position by a pin.

[0009] Furthermore, in step four, two guide grooves are symmetrically installed on each steel casing, and the corresponding two pre-deflection guide frames form an anti-deflection guide device.

[0010] Furthermore, in step five, the pebbles on the channel side are piled up in a triangular shape, and the precast concrete frame is an irregular pentagon. After being inverted, the longest inclined side is attached to the pebble pile, and the shortest side is attached to the outer wall of the steel cofferdam.

[0011] Furthermore, in step six, the conduit support includes a rectangular steel support, a support plate, and a fixing plate. The conduit opening of the support plate is aligned with the hole in the steel plate and fixed by fastening bolts.

[0012] The double-walled steel cofferdam, reinforced by counterpressure and pre-deflected sinking, was constructed using the methods described above.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention combines double-row protective piles with an integral steel frame, which effectively resists the unbalanced earth pressure after the embankment slope is excavated. At the same time, the soil is reinforced by jet grouting and grouting to ensure the stability of the slope.

[0014] 2. The present invention further includes a support frame on the steel cofferdam to solve the problem of the bottom of the cofferdam being suspended due to uneven scouring on the channel side. At the same time, several shear keys are set on the inner wall of the cofferdam to increase the shear strength of the contact surface with the bottom sealing concrete and ensure the buoyancy resistance of the cofferdam. After the cofferdam is in place, pebbles are filled on both the cofferdam embankment side and the channel side. The channel side is supported by a precast concrete support for counterpressure, which ensures the pressure balance on both sides of the steel cofferdam and at the same time offsets the lateral pressure of the bottom sealing concrete on the steel cofferdam.

[0015] 3. This invention prevents the steel cofferdam from deviating by setting up pre-deflection guide frames. By setting guide grooves on the steel casing and two pre-deflection guide frames on the corresponding steel cofferdam, the sinking accuracy of the steel cofferdam is effectively guaranteed.

[0016] 4. In the construction of the bottom sealing concrete, the present invention divides the sealing concrete platform into sections and sets up several material feeding points. At the same time, it uses the guide pipe support as the support device for the guide pipe, and pours the concrete from one side of the dike and the other side of the waterway, and then merges them in the middle, thereby reducing the influence of the side pressure of the bottom sealing concrete on the displacement of the steel cofferdam. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the construction of the dike protection and steel cofferdam with gravel backfilling for counterpressure in this invention; Figure 2 This is a schematic diagram of the groove opening on the pile top according to the present invention; Figure 3 This is an enlarged view of A of the present invention; Figure 4 This is a plan view of the dike protection structure of the present invention; Figure 5 This is an enlarged view of B in this invention; Figure 6 This is a plan view of the shear key arrangement of the present invention; Figure 7 This is a cross-sectional view (AA) of the present invention; Figure 8 This is a plan view of the pre-deflection guide frame arrangement of the present invention; Figure 9 This is a schematic elevation view of the pre-deflection guide frame arrangement of the present invention; Figure 10 This is an enlarged view of C in this invention; Figure 11 This is a plan view of the bottom sealing concrete platform of the present invention; Figure 12 This is a structural diagram of the catheter stent of the present invention.

[0018] In the diagram, 1. Front protective pile; 2. Rear protective pile; 3. Front cap beam; 4. Rear cap beam; 5. Connecting beam; 6. Jet grouting pile; 7. Grouting reinforcement; 8. Bagged pebbles; 9. Pebbles; 10. Support frame; 11. Precast concrete frame; 12. Groove; 13. Pile top; 14. Hoop; 15. L-shaped connecting plate; 16. Connecting plate; 17. Integral steel frame; 18. High-strength bolt; 19. Shear key; 20. Inner wall of steel cofferdam; 21. Bottom sealing concrete pouring range; 22. Pre-deflection guide frame; 23. Guide groove; 24. Steel casing; 25. Pin; 26. Telescopic support; 27. Slide rail; 28. Pulley; 29. ​​Fixing plate; 30. Guide support; 31. Guide port; 32. Bottom sealing concrete platform; 33. Steel plate; 34. Steel frame; 35. Support plate; 36. Fixing plate; 37. Fastening bolt. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0020] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention.

[0021] Example 1 like Figure 1-12 As shown, the construction method of a double-walled steel cofferdam with pre-eccentric sinking and reinforcement in steep terrain includes the following steps: Step 1: Dike Protection On one side of the steel cofferdam, on the slope of the embankment, the slope is first excavated to reduce the pressure of the side soil on the steel cofferdam. Before excavating the slope of the embankment, front protective piles 1 are installed at the excavation boundary of the slope, and rear protective piles 2 are installed on the side adjacent to the embankment. Both rows of protective piles are bored cast-in-place piles. When pouring concrete, grooves 12 are set on the pile tops 13. After the construction of the front and rear rows of protective piles is completed, clamps 14 are installed below the grooves 12 on the pile tops 13. Then, an integral steel frame 17 is installed, that is, the front crown beams 3 and rear crown beams 4 made of steel sections are installed at the grooves 12 on the pile tops 13 of the front protective piles 1 and the rear protective piles 2, respectively. Then, the connecting plates 16 on the clamps 14 are bolted to the L-shaped connecting plates 15 on the crown beams. After the front and rear crown beams 4 are fixed on the pile tops 13, several connecting beams 5 are installed equidistantly between the front and rear crown beams 4 and fixed with high-strength bolts 18. After the protective piles are completed, grouting reinforcement is carried out between the two rows of protective piles 7, and it extends outward to reinforce the soil within the embankment area. A row of jet grouting piles 6 is set near the front protective pile 1.

[0022] Specifically, both the front protective pile 1 and the rear protective pile 2 are bored cast-in-place piles with a diameter of 2m and a length of 50m. The distance between the front and rear protective piles is 8m, and each bored cast-in-place pile is spaced 2m apart. The top 13 of the pile is provided with a groove 12 to accommodate the cap beam.

[0023] In this embodiment, a clamp 14 with a connecting plate 16 is installed directly below the groove 12 on the pile top 13, and the connecting plate 16 is fixed to the four corners of the clamp 14.

[0024] Preferably, the integral steel frame 17 includes a front crown beam 3, a rear crown beam 4, and a connecting beam 5. The integral steel frame 17 is made of Q345B steel. The front crown beam 3 and the rear crown beam 4 have the same size, with a cross section of 600×800mm. The connecting beam 5 is smaller than the crown beam, with a cross section of 400×600mm. A connecting beam 5 is arranged every 2m between the two rows of crown beams and is connected by high-strength bolts 18.

[0025] Among them, several L-shaped connecting plates 15 are welded on both sides of the front crown beam 3 and the rear crown beam 4. The welding position of the L-shaped connecting plates 15 corresponds exactly to the connecting plate 16 of the clamp 14 so as to make bolt connection. M24 high-strength bolts are used, and the preload reaches 70% of the design value.

[0026] In this embodiment, jet grouting piles 6 are constructed between the front crown beam 3 and the rear crown beam 4, and closer to the side of the front crown beam 3.

[0027] The rotational speed of the jet grouting pile is set to 15 rpm, the lifting speed is controlled at 20 cm / min, the jetting pressure is set to 20~30 MPa, and the slurry flow rate is controlled at 100 L / min.

[0028] In this embodiment, grouting reinforcement 7 is performed between the front crown beam 3 and the rear crown beam 4. The grouting reinforcement 7 extends towards the embankment on both sides in a "figure-eight" shape to reinforce the soil at the embankment.

[0029] The grouting pressure is set differently depending on the soil type. For grouting reinforcement of loose sandy soil, a grouting pressure of 0.2~0.3 MPa is set; for grouting reinforcement of relatively dense sandy soil, a grouting pressure of 0.4~0.5 MPa is set; and for grouting reinforcement of loose cohesive soil, the grouting pressure is set to 0.1-0.3 MPa. The grout uses silicate cement with a strength grade of 42.5 MPa and a water-cement ratio of 0.7.

[0030] Step 2: Installation of shear keys for steel cofferdam Shear keys 19 are installed on the inner wall 20 of the steel cofferdam on the side closest to the waterway. The installation range of shear keys 19 is the bottom sealing concrete pouring range 21, and the spacing between them is 600mm.

[0031] Specifically, the shear key 20 has dimensions of 100mm×100mm×15mm (length×width×thickness) and is made of ordinary carbon structural steel of Q235B. The shear key 19 is installed on the inner wall of the steel cofferdam on one side of the waterway, that is, 1 / 2 of the inner wall of the steel cofferdam. The spacing between the shear keys in the top, bottom, left and right is 600mm.

[0032] It is worth noting that, due to the scouring of the waterway, the bottom of the steel cofferdam on one side of the waterway is suspended. Within 1 / 2 of the inner wall 20 of the steel cofferdam (on the waterway side), specifically in the area in contact with the bottom sealing concrete, several shear keys 19 are arranged to increase the shear strength of the contact surface between the inner wall and the bottom sealing concrete.

[0033] Step 3: Installation of the pre-deflection guide frame Pre-deflection guide frames 22 are installed on the inner walls of the four sides of the steel cofferdam. Two layers of pre-deflection guide frames 22 are installed with a spacing of 10m. At the same time, guide grooves 23 are installed on the steel casing 24. Two guide grooves 23 are installed on each steel casing 24. Two pre-deflection guide frames 22 are installed on the corresponding inner wall 20 of the steel cofferdam.

[0034] Specifically, the pre-deflection guide frame 22 mainly consists of a fixed plate 29, a telescopic bracket 26, and a pulley 28. The fixed plate 29 is provided with a slide rail 27, and the telescopic bracket 26 moves on the slide rail 27. When it moves to the designated position, it is fixed with a pin 25 to prevent the telescopic bracket 26 from moving.

[0035] The telescopic bracket 26 is hydraulically driven, with a stroke adjustment range of ±200mm and a positioning accuracy of ±5mm.

[0036] In this embodiment, a laser rangefinder is installed at the end of the telescopic bracket 26 and linked with the hydraulic adjustment system to achieve real-time feedback of the deviation amount and a correction response time of <30s.

[0037] In this embodiment, the guide groove adopts a U-shaped cross-section, with a total length of 15m, and the welding angle deviation with the steel casing 24 is ≤0.5°. In this embodiment, a pulley 28 is installed at the front end of the telescopic bracket 26. The pulley 28 is in close contact with the guide groove 23 and moves up and down on the guide groove 23.

[0038] Step 4: Sinking of the steel cofferdam Before the steel cofferdam is lowered, a support frame 10 is installed at the bottom of the steel cofferdam near the waterway side. At the same time, water is injected into the inner tank of the corresponding steel cofferdam on the other side to maintain the balance of the two sides of the steel cofferdam. The steel cofferdam is slowly lowered. The pulleys 28 on the pre-deflection guide frame 22 are attached to the guide grooves 23 on the steel casing 24. Each steel casing 24 with a guide groove 23 has two pre-deflection guide frames 22 to form an anti-deflection guide device. As the steel cofferdam sinks, the pulleys 28 on the pre-deflection guide frame 22 move downward along the guide grooves 23.

[0039] Specifically, the support frame 10 adopts a truss structure and is welded from H-beams (HM500×300). Due to the scouring of the riverbed, there is a 5m height difference between the riverbed on one side of the embankment and the riverbed on the navigation channel side. The support frame is installed at the cutting edge of the steel cofferdam near the navigation channel side so that the steel cofferdam on the navigation channel side can smoothly contact the riverbed.

[0040] The water injection volume into the inner compartment is calculated using the formula Q=K·ΔH·S, where K is the balance coefficient (taken as 1.2), ΔH is the water level difference, and S is the cross-sectional area of ​​the compartment. The sinking rate is controlled at 0.5 m / h, and the tilt angle is monitored in real time and adjusted to ≤0.5%.

[0041] It is worth noting that two symmetrical pre-deflection guide frames 22 are set on the inner wall 20 of the steel cofferdam corresponding to the steel casing 24 with guide groove 23. With the assistance of the two guide frames, the steel cofferdam is prevented from tilting and landing.

[0042] Step 5: Fill with pebbles for counter-pressure After the steel cofferdam is in place, bagged pebbles 8 are piled up on the side of the dike by an excavator, and pebbles 9 are dumped on the side of the waterway. Then, a precast concrete frame 11 is lifted and slowly lowered into the water and placed on the pebbles 9 for counter-pressure. At this time, the pressure on both sides of the steel cofferdam is equal and it resists the lateral pressure of the bottom sealing concrete on the steel cofferdam.

[0043] Specifically, pebbles 9 are dumped on the channel side, and the pebbles 9 are piled in a triangular shape. The longest inclined side is pressed tightly against the pebbles, the shortest contact side is pressed tightly against the outer wall of the steel cofferdam and the support frame 10, the base connection side is pressed tightly against the riverbed, the horizontal transition side is parallel to the base connection side, and the inclined support side connects the horizontal transition side and the base connection side. Bagged pebbles 8 are piled on the embankment side, and are piled tightly between the outer wall of the steel cofferdam and the front protective pile 1.

[0044] Among them, the gravel 9 on the channel side has a slope of 1:1.5, a particle size of 50-150mm, and a compaction degree of ≥90%. The precast concrete frame 11 uses C40 concrete and has the following dimensions: the longest inclined side is 2000mm, the horizontal transition side is 1500mm, the inclined support side is 1200mm, the shortest contact side is 800mm, and the base connection side is 1000mm. The longest inclined side and the base connection side, as well as the longest inclined side and the shortest contact side, are both at 120° to form a gravel pile contact surface. The horizontal transition side and the shortest contact side are at 90° to ensure vertical contact with the steel cofferdam. The inclined support side and the horizontal transition side are at 105°, and the side connecting to the base side is at 75° to enhance the anti-sliding performance.

[0045] It is worth noting that when the slope of the pebble pile is 1:1.5, the counterpressure efficiency reaches 92%, which is 37% higher than that of the conventional rectangular structure, and effectively suppresses the horizontal displacement of the cofferdam by 89%.

[0046] Preferably, the precast concrete frame 11 is an irregular pentagon, placed upside down on the triangularly stacked pebbles 9. The longest inclined side of the precast concrete frame 11 is close to the pebbles 9, and the shortest side is close to the outer wall of the steel cofferdam. The weight of the precast concrete frame 11 is used to counteract the pile of pebbles 9.

[0047] Step Six: Sealing the Bottom The bottom sealing concrete pouring is carried out in a sectional manner. Several support frames 10 made of spliced ​​steel sections are set on the steel casing 24. Steel plates 33 of the same size are spliced ​​to form a bottom sealing concrete platform 32, which is placed on the support frame 10. Each steel plate 33 has a hole with a diameter slightly larger than the guide pipe opening 31. The guide pipe is first lowered along the hole. When assembling the last section of the guide pipe, the guide pipe support 30 is installed on each steel plate 33, with its guide pipe opening 31 aligned with the hole on the steel plate 33. Then, the last section of the guide pipe is passed through the guide pipe opening 31 and connected to the previous section of the guide pipe at the hole. It is then lowered to the designated position, and finally the guide pipe is fixed on the guide pipe support 30. During the pouring, pouring starts from the dike side and the channel side separately until they meet in the middle.

[0048] Specifically, the conduit support 30 is mainly made of a steel bracket 34, a support plate 35, and a fixing plate 36. The steel bracket 34 is made of four steel sections spliced ​​together to form a rectangle. Fixing plates 36 are welded to both sides of the long side steel section. Bolt holes are provided on the fixing plates 36. The support plate 35 is welded to the middle of the steel bracket 34. The support plate 35 is provided with a conduit port 31.

[0049] Among them, the roundness tolerance of the opening of the support plate 35 is ≤0.1mm, and the nominal diameter D of the guide tube opening 31 is D=outer diameter of the guide tube + (0.2-0.5)mm.

[0050] The catheter support 30 is made of Q235B steel with a cross section of 200×200mm, and the torque value of the fastening bolt 37 is set to 350N·m.

[0051] In this embodiment, the conduit support 30 is mounted on the steel plate 33, the conduit port 31 is aligned with the hole on the steel plate 33, and the conduit support 30 is fixed on the steel plate 33 with fastening bolts 37.

[0052] It is worth noting that the bottom sealing concrete platform was divided into 32 sections with several material feeding points. The concrete was poured starting from both sides of the dike and the waterway and finally converged in the middle, which reduced the impact of the lateral pressure of the bottom sealing concrete on the cofferdam offset.

[0053] Example 2 The present invention also discloses a double-walled steel cofferdam with combined counterpressure reinforcement for steep terrain, which is constructed by the construction method of the double-walled steel cofferdam with combined counterpressure reinforcement for steep terrain in Example 1.

[0054] The parts of this invention not described in detail are prior art, therefore they are not described in detail here.

[0055] This invention is not limited to the preferred embodiments described above. Anyone can derive other products in various forms under the guidance of this invention. However, regardless of any changes made to their shape or structure, any technical solution that is the same as or similar to that of this application falls within the protection scope of this invention.

Claims

1. A construction method for a double-walled steel cofferdam with counterpressure reinforcement and pre-eccentric sinking in steep terrain, characterized in that... Includes the following steps: Step 1, Embankment Protection: Front protective piles (1) and rear protective piles (2) are installed at the excavation boundary of the steel cofferdam on the side slope adjacent to the embankment. Grooves (12) are opened on the top (13) of the piles and bolted to the front cap beam (3) and rear cap beam (4) of the integral steel frame (17) through clamps (14). The cap beams are fixed by connecting beams (5). Grouting reinforcement (7) is carried out between the two rows of protective piles and in the outward extension area, and jet grouting piles (6) are installed on the side of the front protective piles. Step 2, Shear key installation: Shear keys (19) are installed in the bottom sealing concrete pouring range (21) of the inner wall (20) of the steel cofferdam near the waterway side. Step 3, Installation of pre-deflection guide frame: Install multi-layer pre-deflection guide frame (22) on the inner wall of the steel cofferdam, and set guide groove (23) on the surface of the corresponding steel casing (24). The pulley (28) of the guide frame slides in conjunction with the guide groove. Step 4, Steel cofferdam placement: Install support frame (10) at the bottom of the steel cofferdam on the channel side, and lower it after the inner tank on the other side is filled with water and balanced. The pre-deflection guide frame guides vertically along the guide groove. Step 5, Filling with gravel for counter-pressure: After the steel cofferdam is in place, bagged gravel (8) is piled on the side of the dike, gravel (9) is filled on the side of the waterway and a precast concrete frame (11) is placed for counter-pressure; Step 6, bottom sealing concrete pouring: Set up a steel support frame (10) on the steel casing (24), erect a bottom sealing platform (32) with perforated steel plate (33), and pour bottom sealing concrete symmetrically in sections.

2. The construction method according to claim 1, characterized in that, The front protective pile (1) and rear protective pile (2) mentioned in step one are bored piles. A clamp (14) is installed below the groove (12) on the top (13) of the pile. Connecting plates (16) are provided at the four corners of the clamp and bolted to the L-shaped connecting plate (15) of the crown beam.

3. The construction method according to claim 1, characterized in that, In step one, the grouting reinforcement (7) area extends in a "figure-eight" shape towards the embankment, and the jet grouting pile (6) is located between the front cap beam (3) and the rear cap beam (4) and close to the side of the front cap beam (3).

4. The construction method according to claim 1, characterized in that, In step three, the pre-deflection guide frame (22) includes a fixed plate (29), a telescopic bracket (26) that can move along the slide rail (27), and a pulley (28). The telescopic bracket is fixed in position by a pin (25).

5. The construction method according to claim 1, characterized in that, In step four, two guide grooves (23) are symmetrically installed on each steel casing (24), and the corresponding two pre-deflection guide frames (22) form an anti-deflection guide device.

6. The construction method according to claim 1, characterized in that, In step five, the pebbles (9) on the channel side are stacked in a triangular shape, and the precast concrete frame (11) is an irregular pentagon. After being inverted, the longest inclined side is attached to the pebble pile, and the shortest side is attached to the outer wall of the steel cofferdam.

7. The construction method according to any one of claims 1-6, characterized in that, In step six, the catheter support (30) includes a rectangular steel support (34), a support plate (35) and a fixing plate (36). The catheter opening (31) of the support plate is aligned with the hole of the steel plate (33) and fixed by fastening bolts (37).

8. A double-walled steel cofferdam with counterpressure reinforcement and pre-sinking design for steep terrain, characterized in that... It is obtained by the construction method described in any one of claims 1-7.

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