Double-wall steel cofferdam with pre-biased sinking and construction method thereof

Abstract

The present application relates to steep terrain combination counterpressure reinforcement pre-biased sinking double-wall steel cofferdam and its construction method, aiming at the problems of steel cofferdam deflection caused by embankment slope pressure and channel scouring and side pressure of bottom sealing concrete, a comprehensive solution is proposed. The method comprises: reinforcing the embankment slope through front and rear protection piles and integral steel frame, combining with grouting and rotary jet pile to enhance the stability of soil; laying dense shear keys on the inner wall of the steel cofferdam to improve the shear strength of the bottom sealing concrete; using pre-biased guide frame and guide groove, ensuring the vertical sinking of the steel cofferdam through pulley sliding guide; balancing the pressure on both sides by using channel side throwing filling pebbles and precast concrete frame counterpressure, embankment side bagged pebbles; pouring bottom sealing concrete in a partitioned and symmetrical manner to reduce the risk of cofferdam deviation. The supporting devices include adjustable pre-biased guide frame, guide pipe support and pentagonal precast concrete frame. Through structure optimization and construction collaborative control, the present application effectively improves the sinking precision, anti-scouring ability and overall stability of the steel cofferdam.

Description

TECHNICAL FIELD

[0001] The present application relates to bridge enclosure engineering, in particular to a steep terrain combined counterpressure reinforcement pre-deviation sinking double-wall steel cofferdam and a construction method thereof. BACKGROUND

[0002] When carrying out construction work in the water area, it often needs to face the challenge of constructing a stable construction structure under complex geological conditions and water flow environment. When it involves engineering construction around the embankment, the original balance state of the soil body is broken when the embankment slope is excavated. If the pressure cannot be effectively resisted, the slope is prone to collapse and other instability phenomena. The traditional setting method of the protection pile is not good at preventing the slope from being unstable when facing complex geology and large excavation scale. When carrying out foundation construction in the deep water area, the steel cofferdam plays a crucial role as a common enclosure structure. However, the water flow speed on the channel side is usually fast, and uneven scouring frequently occurs, which makes the cofferdam bottom prone to be suspended, greatly weakening the stability of the cofferdam. Moreover, 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 has an adverse effect on the position and stability of the steel cofferdam. In addition, the steel cofferdam is prone to deviation during the sinking process due to the interference of water flow, geology and other factors.

[0003] In view of the many technical problems faced in the above engineering construction, it is necessary to develop an innovative construction method to effectively resist the unbalanced soil pressure of the slope, ensure the stability and sinking accuracy of the steel cofferdam, and optimize the construction process of the bottom sealing concrete, which has become a key problem to be solved in the current engineering field. SUMMARY

[0004] The purpose of the present application is to solve the above problems in the prior art, and to provide a steep terrain combined counterpressure reinforcement pre-deviation sinking double-wall steel cofferdam and a construction method thereof.

[0005] In order to achieve the above-mentioned purpose of the application, the following technical solutions are adopted: the steep terrain combined counterpressure reinforcement pre-deviation sinking double-wall steel cofferdam construction method comprises the following steps:

[0006] Step 1, embankment protection: setting front and rear protection piles at the boundary of the steel cofferdam on the embankment side slope, grooves are opened at the top of the piles and are bolted to the front and rear crown beams of the integral steel frame through the hoops, and the crown beams are fixed through the connecting beams; grouting reinforcement is carried out between the two rows of protection piles and the outward extension area, and a rotary jet pile is arranged on the side of the front protection pile;

[0007] Step 2, shear key installation: arranging shear keys in the bottom sealing concrete pouring range near the channel side of the steel cofferdam;

[0008] Step three, pre-biased guide frame installation: install multiple layers of pre-biased guide frames on the inner wall of the steel cofferdam, and set guide grooves on the surface of the steel casing; the pulley of the guide frame is in sliding cooperation with the guide groove;

[0009] Step four, steel cofferdam sinking: install a support frame at the bottom of the steel cofferdam on the channel side, and then lower the other side after balancing the inner cabin; the pre-biased guide frame is vertically guided along the guide groove;

[0010] Step five, throwing and filling pebbles for counterpressure: after the steel cofferdam is bedded, bagged pebbles are piled on the embankment side, and pebbles are thrown and filled on the channel side to place the prefabricated concrete frame for counterpressure;

[0011] Step six, bottom sealing concrete pouring: set a steel support frame on the steel casing, erect a bottom sealing platform with a hole, and pour the bottom sealing concrete in a symmetrical partition.

[0012] Further, in step one, the front and rear protection piles are bored piles, a hoop is installed below the groove at the top of the pile, and the hoop is provided with a connecting plate at four corners which is bolted with the L-shaped connecting plate of the crown beam.

[0013] Further, in step one, the grouting reinforced area extends in a "M-shaped" manner towards the embankment, and the rotary jet pile is located between the front and rear crown beams and close to the front crown beam.

[0014] Further, in step three, the pre-biased guide frame includes a fixed plate, an extension support movable along a sliding rail, and a pulley, and the extension support is fixed in position by a latch.

[0015] Further, in step four, two guide grooves are symmetrically installed on each steel casing, and the corresponding two pre-biased guide frames form a deviation prevention guide device.

[0016] Further, in step five, the pebbles on the channel side are piled in a triangular shape, and the prefabricated concrete frame is an irregular pentagon, which is inverted with the longest diagonal edge adhering to the pebble pile and the shortest edge tightly adhering to the outer wall of the steel cofferdam.

[0017] Further, in step six, the guide pipe support includes a rectangular steel support, a support plate, and a fixing plate, the guide pipe port of the support plate is aligned with the hole of the steel plate, and is fixed by a fastening bolt.

[0018] The steep terrain combined counterpressure reinforcement pre-biased sinking double-wall steel cofferdam is constructed by the above construction method.

[0019] Compared with the prior art, the beneficial effects of the present application are as follows:

[0020] 1. The present application adopts the combination of double-row protection piles and integral steel frames, effectively resisting the unbalanced soil pressure after the embankment slope excavation, and at the same time, the soil is reinforced by rotary jet piles and grouting reinforcement, ensuring the stability of the slope.

[0021] 2. The application further sets up a support frame on the steel cofferdam to solve the problem of uneven scour on the channel side causing the cofferdam bottom to be suspended, and sets up a plurality of shear keys on the inner wall of the cofferdam to increase the shear strength of the contact surface with the bottom sealing concrete, thereby ensuring the anti-floating property of the cofferdam; after the cofferdam is bedded, gravel is thrown and filled on the embankment side and the channel side of the cofferdam, wherein the channel side uses a prefabricated concrete support for counterpressure, thereby ensuring the pressure balance on both sides of the steel cofferdam and offsetting the lateral pressure of the bottom sealing concrete on the steel cofferdam.

[0022] 3. The application plays a role in preventing the deviation of the steel cofferdam by setting up a pre-deviation guide frame, and effectively ensures the sinking accuracy of the steel cofferdam by setting up a guide groove on the steel casing and two pre-deviation guide frames on the steel cofferdam.

[0023] 4. The application reduces the influence of the lateral pressure of the bottom sealing concrete on the deviation of the steel cofferdam by partitioning the bottom sealing concrete platform, setting up a plurality of discharge points, and using a guide pipe support as a support device for the guide pipe to pour from the embankment side and the channel side and then converge in the middle. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a construction schematic diagram of embankment protection and steel cofferdam gravel counterpressure of the application;

[0025] Figure 2 is a schematic diagram of a groove opened on the top of a pile of the application;

[0026] Figure 3 is an enlarged view of A of the application;

[0027] Figure 4 is a plan view of embankment protection of the application;

[0028] Figure 5 is an enlarged view of B of the application;

[0029] Figure 6 is a layout plan of shear keys of the application;

[0030] Figure 7 is an A-A sectional view of the application;

[0031] Figure 8 is a layout plan of pre-deviation guide frames of the application;

[0032] Figure 9 is a layout elevation schematic diagram of pre-deviation guide frames of the application;

[0033] Figure 10 is an enlarged view of C of the application;

[0034] Figure 11 is a plan view of a bottom sealing concrete platform of the application;

[0035] Figure 12 Figure is a structure diagram of the conduit support of the present application.

[0036] In the figure, 1 is a front protective stake, 2 is a rear protective stake, 3 is a front crown beam, 4 is a rear crown beam, 5 is a connecting beam, 6 is a rotary jetting stake, 7 is grouting reinforcement, 8 is a bagged pebble, 9 is a pebble, 10 is a support frame, 11 is a prefabricated concrete frame, 12 is a groove, 13 is a stake top, 14 is a hoop, 15 is an L-shaped connecting plate, 16 is a connecting plate, 17 is an integral steel frame, 18 is a high-strength bolt, 19 is a shear key, 20 is an inner wall of a steel cofferdam, 21 is a bottom sealing concrete pouring range, 22 is a pre-biased guide frame, 23 is a guide groove, 24 is a steel casing, 25 is a bolt, 26 is an extension support, 27 is a sliding rail, 28 is a pulley, 29 is a fixed plate, 30 is a conduit support, 31 is a conduit opening, 32 is a bottom sealing concrete platform, 33 is a steel plate, 34 is a profile steel support, 35 is a support plate, 36 is a fixing piece, and 37 is a fastening bolt. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application belong to the scope of protection of the present application.

[0038] Those skilled in the art should understand that in the disclosure of the present application, the orientations or positional relationships indicated by the terms "longitudinal", "transverse", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientations or positional relationships shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore the above terms cannot be understood as a limitation of the present application.

[0039] Embodiment 1

[0040] As shown in Figures 1-12 The steep terrain combined counterpressure reinforcement pre-biased sinking double-wall steel cofferdam construction method includes the following steps:

[0041] Step one, dike protection

[0042] The steel cofferdam has one side on the embankment slope, the slope is excavated first to reduce the pressure of the side soil on the steel cofferdam, before the embankment slope is excavated, front protection piles 1 are installed at the boundary of the slope excavation, and rear protection piles 2 are installed on the side of the embankment, the two rows of protection piles are bored piles, when the concrete is poured, a groove 12 is arranged on the top 13 of the pile, after the front and rear rows of protection piles are constructed, a clamp 14 is installed below the groove 12 on the top 13 of the pile, and an integral steel frame 17 is installed, that is, a front crown beam 3 and a rear crown beam 4 made of profile steel are respectively installed at the groove 12 on the top 13 of the front protection pile 1 and the rear protection pile 2, then the connecting plate 16 on the clamp 14 is bolted with the L-shaped connecting plate 15 on the crown beam, the front and rear crown beams 4 are fixed on the top 13 of the pile, a plurality of connecting beams 5 are installed at equal intervals between the front and rear crown beams 4 and are fixed by high-strength bolts 18. After the construction of the protection piles is completed, grouting reinforcement 7 is carried out in the middle of the two rows of protection piles and extends outward to reinforce the soil in the embankment range, and a row of rotary jet piles 6 is arranged near the front protection pile 1.

[0043] Specifically, the front protection pile 1 and the rear protection pile 2 are both bored piles with a diameter of 2 m and a length of 50 m, the distance between the front protection pile and the rear protection pile is 8 m, and the distance between each bored pile is 2 m, and the top 13 of the pile is provided with a groove 12 for placing the crown beam.

[0044] In this embodiment, a clamp 14 with a connecting plate 16 is installed directly below the groove 12 on the top 13 of the pile, and the connecting plate 16 is fixed to the four corners of the clamp 14.

[0045] Preferably, the integral steel frame 17 includes the front crown beam 3, the rear crown beam 4 and the connecting beam 5, the integral steel frame 17 is made of Q345B profile steel, the front crown beam 3 and the rear crown beam 4 have the same size and a cross section of 600*800 mm, the connecting beam 5 has a smaller size than the crown beam and a cross section of 400*600 mm, and a connecting beam 5 is arranged every 2 m between the two rows of crown beams and is connected by high-strength bolts 18.

[0046] In this embodiment, a clamp 14 with a connecting plate 16 is installed directly below the groove 12 on the top 13 of the pile, and the connecting plate 16 is fixed to the four corners of the clamp 14.

[0047] In this embodiment, rotary jet pile 6 construction is carried out between the front crown beam 3 and the rear crown beam 4 and near the side of the front crown beam 3.

[0048] In this embodiment, the rotary jet pile 6 construction is carried out between the front crown beam 3 and the rear crown beam 4 and near the side of the front crown beam 3.

[0049] In this embodiment, the grouting reinforcement 7 is carried out between the front and rear crown beams 3 and 4, and extends to the embankment direction on both sides of the grouting reinforcement 7, that is, in the shape of "eight characters", so as to reinforce the soil at the embankment.

[0050] In the formula, different grouting pressures are set according to the types of the soil. When the loose sandy soil is grouted, the grouting pressure is set to 0.2-0.3 MPa; when the relatively dense sandy soil is grouted, the grouting pressure is set to 0.4-0.5 MPa; and when the loose clay soil is grouted, the grouting pressure is set to 0.1-0.3 MPa. The grout uses the silicate cement with a strength grade of 42.5 MPa, and the water-cement ratio is set to 0.7.

[0051] Step two, shear key installation of the steel cofferdam

[0052] The shear key 19 is installed on the inner wall 20 of the steel cofferdam near the waterway side, and the installation range of the shear key 19 is the pouring range 21 of the bottom sealing concrete, and the interval is 600 mm.

[0053] Specifically, the size of the shear key 20 is 100 mm x 100 mm x 15 mm (length x width x thickness), and the ordinary carbon structural steel Q235B is used, and the shear key 19 is installed on the inner wall of the steel cofferdam on the waterway side, that is, 1 / 2 of the inner wall of the steel cofferdam, and the interval of the shear key is 600 mm in the up, down, left and right directions.

[0054] It is worth noting that due to the scouring of the waterway, the bottom of the steel cofferdam on the waterway side is suspended, and a plurality of shear keys 19 are arranged on the 1 / 2 range of the inner wall 20 of the steel cofferdam (on the waterway side), specifically on the contact area with the bottom sealing concrete, so as to increase the shear strength of the contact surface between the inner wall and the bottom sealing concrete.

[0055] Step three, pre-bias guide frame installation

[0056] The pre-bias guide frame 22 is installed on the inner wall of the steel cofferdam in four directions, and the pre-bias guide frame 22 is installed in two layers with an interval of 10 m. Meanwhile, the guide groove 23 is installed on the steel casing 24, and two guide grooves 23 are installed on the steel casing 24, and two pre-bias guide frames 22 are installed on the inner wall 20 of the corresponding steel cofferdam.

[0057] Specifically, the pre-bias guide frame 22 mainly includes a fixed plate 29, an extension support 26 and a pulley 28, wherein the fixed plate 29 is provided with a sliding rail 27, the extension support 26 moves on the sliding rail 27, moves to the specified position, and is fixed by a bolt 25 to prevent the extension support 26 from moving.

[0058] Among them, the extension support 26 is driven by hydraulic pressure, the stroke adjustment range is ±200 mm, and the positioning accuracy is ±5 mm.

[0059] In this embodiment, the laser range finder at the end of the telescopic support 26 is linked with the hydraulic adjustment system to realize real-time deviation feedback and the deviation correction response time is less than 30 seconds.

[0060] In this embodiment, the guide groove has a U-shaped cross section and the total length is 15 m, and the welding angle deviation with the steel casing 24 is less than or equal to 0.5°.

[0061] In this embodiment, the pulley 28 is installed at the front end of the telescopic support 26 and closely contacts the guide groove 23 to move up and down on the guide groove 23.

[0062] Step four, sinking of the steel cofferdam

[0063] Before sinking of the steel cofferdam, the support frame 10 is installed at the bottom of the steel cofferdam near the channel side, and the inner cabin is filled with water on the other side of the steel cofferdam to maintain the balance of the two sides of the steel cofferdam, and the steel cofferdam is slowly lowered, the pulley 28 on the pre-deviation guide frame 22 is attached to the guide groove 23 on the steel casing 24, each steel casing 24 with a guide groove 23 has two pre-deviation guide frames 22 to form a deviation prevention guide device, and as the steel cofferdam sinks, the pulley 28 on the pre-deviation guide frame 22 moves downward along the guide groove 23.

[0064] Specifically, the support frame 10 adopts a truss structure and is welded by H-shaped steel (HM500x300), and 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 channel side, and the support frame is installed at the blade foot of the steel cofferdam near the channel side to make the steel cofferdam on the channel side smoothly contact the riverbed.

[0065] The amount of water filled in the inner cabin is calculated according to the formula Q=K·ΔH·S, wherein K is the balance coefficient (1.2), ΔH is the water level difference, and S is the cabin cross-sectional area. The sinking rate is controlled at 0.5m / h, and the inclination is monitored and adjusted to be less than or equal to 0.5%.

[0066] It is worth noting that two pre-deviation guide frames 22 are symmetrically arranged on the inner wall 20 of the steel cofferdam corresponding to the steel casing 24 with a guide groove 23, and the two guide frames are used to prevent the steel cofferdam from deviating from the riverbed.

[0067] Step five, throwing and filling of the gravel counterpressure

[0068] After the steel cofferdam is placed on the riverbed, the excavator is used to pile up the bagged gravel 8 on the embankment side, and after the gravel 9 is thrown and filled on the channel side, the prefabricated concrete frame 11 is lifted and slowly placed in the water to press on the gravel 9, at this time, the pressure on both sides of the steel cofferdam is equivalent, and the side pressure of the steel cofferdam against the bottom sealing concrete is resisted.

[0069] 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.

[0070] 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.

[0071] 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%.

[0072] 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.

[0073] Step Six: Sealing the Bottom

[0074] 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.

[0075] 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.

[0076] Wherein, the support plate 35 opening roundness tolerance is ≤0.1mm, the conduit port 31 nominal diameter D = conduit outer diameter + (0.2-0.5) mm.

[0077] Wherein, the conduit support 30 adopts Q235B type steel, the section is 200x200mm, and the fastening bolt 37 torque value is set as 350N·m.

[0078] In the embodiment, the conduit support 30 is installed 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 by the fastening bolt 37.

[0079] It is worth noting that the sealing concrete platform 32 is divided into several unloading points, and the pouring is started on both sides of the dike and the channel, and finally converges in the middle, which reduces the influence of the side pressure of the sealing concrete on the cofferdam deviation.

[0080] Embodiment 2

[0081] The application further discloses a steep terrain combined counter-pressure reinforced pre-biased sinking double-wall steel cofferdam, which is obtained by the construction method of the steep terrain combined counter-pressure reinforced pre-biased sinking double-wall steel cofferdam.

[0082] The part of the application not described in detail is the prior art, so the application does not perform detailed description on it.

[0083] The application is not limited to the above best embodiment, and anyone can derive other various forms of products under the inspiration of the application, but regardless of any change in shape or structure, any technical solution with the same or similar to the application falls within the protection scope of the application.

Claims

1. A construction method of steep terrain combined counterpressure reinforced pre-biased sinking double-wall steel cofferdam, characterized in that, The method comprises the following steps: Step one, dike protection: front protection pile (1) and rear protection pile (2) are arranged on the side slope of the steel cofferdam near the dike, a groove (12) is formed on the top (13) of the pile, and the groove (12) is connected with the front crown beam (3) and the rear crown beam (4) of the integral steel frame (17) through a hoop (14) and a bolt, and the crown beams are fixed through a connecting beam (5); grouting reinforcement (7) is carried out between the two rows of protection piles and the outward extension area, and rotary jet piles (6) are arranged on the side of the front protection pile; Step two, shear key installation: shear keys (19) are arranged in the bottom sealing concrete pouring range (21) of the inner wall (20) of the steel cofferdam near the waterway side; Step three, pre-bias guide frame installation: a plurality of pre-bias guide frames (22) are installed on the inner wall of the steel cofferdam, a guide groove (23) is arranged on the surface of the steel casing (24), and the pulley (28) of the guide frame is in sliding fit with the guide groove; Step four, steel cofferdam sinking: a support frame (10) is installed at the bottom of the steel cofferdam on the waterway side, and the other side is lowered after the water balance is injected into the inner cabin, the pre-bias guide frame is vertically guided along the guide groove; Step five, throwing and filling of gravel counterpressure: after the steel cofferdam is bedded, bagged gravel (8) is piled on the dike side, gravel (9) is thrown and filled on the waterway side, and a prefabricated concrete frame (11) is placed for counterpressure; Step six, bottom sealing concrete pouring: a profiled steel support frame (10) is arranged on the steel casing (24), a bottom sealing platform (32) with holes is erected, and the bottom sealing concrete is poured in a partitioned and symmetrical manner.

2. The construction method according to claim 1, characterized in that, The front protection pile (1) and the rear protection pile (2) in step one are bored piles, a hoop (14) is installed below the groove (12) on the top (13) of the pile, and the hoop is fixed with the L-shaped connecting plate (15) of the crown beam through the connecting plate (16) at the four corners.

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

4. The construction method according to claim 1, characterized in that, In step three, the pre-bias guide frame (22) comprises a fixed plate (29), a telescopic support (26) movable along a sliding rail (27), and a pulley (28), and the telescopic support is fixed in position through a bolt (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-bias guide frames (22) form a bias prevention guide device.

6. The construction method according to claim 1, characterized in that, In step five, the gravel (9) thrown and filled on the waterway is triangularly piled, the prefabricated concrete frame (11) is irregular pentagonal, and after being inverted, the longest inclined edge of the prefabricated concrete frame (11) is attached to the gravel pile, and the shortest edge is tightly attached to the outer wall of the steel cofferdam.

7. The construction method according to any one of claims 1 to 6, characterized in that, In step six, it further comprises: When assembling the last section of the guide pipe, a guide pipe support (30) is installed on each steel plate (33), a guide pipe opening (31) of the guide pipe support (30) is aligned with a hole on the steel plate (33), the last section of the guide pipe is then inserted through the guide pipe opening (31) and connected with the previous section of the guide pipe at the hole, and then the last section of the guide pipe is lowered to the designated position, and finally the guide pipe is fixed on the guide pipe support (30), the guide pipe support (30) comprises a rectangular profiled steel support (34), a support plate (35), and a fixing plate (36), the guide pipe opening (31) of the support plate is aligned with the hole on the steel plate (33), and the guide pipe support (30) is fixed through a fastening bolt (37).

8. A steep terrain combination counter pressure reinforced pre-deflected sinking double-wall steel cofferdam, characterized in that, by the construction method according to any one of claims 1 to 7.

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