Reinforced concrete combined cofferdam suitable for vibration sensitive area under unbalanced soil pressure effect

Abstract

The utility model provides a steel-concrete combined cofferdam suitable for a vibration sensitive area under the action of unbalanced soil pressure, which comprises a plurality of lock catch steel pipe-cast-in-situ bored combined support piles, high-pressure jet grouting piles, a back pressure platform, bottom sealing concrete and an inner support, and the lock catch steel pipe-cast-in-situ bored combined support piles are sequentially connected end to end around a bearing platform operation area; the high-pressure jet grouting piles are arranged along the inner side and the outer side of the lock catch steel pipe-cast-in-situ bored combined supporting pile and in a crack between every two supporting piles, the back pressure platform is arranged on the lower side of the ground, and the periphery of the bottom sealing concrete is connected with the pile foundation steel casing and the lock catch steel pipe-cast-in-situ bored combined supporting pile. The inner support is fixedly installed on the inner wall of an area defined by the lock catch steel pipe-cast-in-situ bored combined supporting pile through fasteners, the inner support comprises multiple sets of supporting rods, the multiple sets of supporting rods are sequentially and evenly distributed along the lock catch steel pipe-cast-in-situ bored combined supporting pile from top to bottom, and auxiliary supporting pieces are further arranged on the multiple sets of supporting rods; and the anti-floating stability of the cofferdam can be improved.

Description

Technical Field

[0001] The utility model relates to the technical field of bridge engineering, and particularly relates to a steel-concrete composite cofferdam applicable to unbalanced earth pressure in a vibration-sensitive area. Background Technique

[0002] When constructing a bridge in water, through a water retaining structure such as a cofferdam, a dry working environment is provided for the construction of the bearing platform, which is crucial for ensuring quality and construction safety. Common types of cofferdams include earth cofferdams, steel sheet pile cofferdams, locked steel pipe pile cofferdams, double-wall steel cofferdams, etc. The earth cofferdam is applicable to river shoals with relatively small flow velocities (≤0.5 m / s) and shallow water depths (≤1.5 m). At the same time, the earth cofferdam will compress the river cross-section and pollute the water source, so its use is limited. The steel sheet pile cofferdam uses steel sheet piles to be inserted one by one (group), and the steel sheet piles are mutually locked to form a construction space, which can be applicable to situations with a water depth within 10 m. As the water depth further increases, the locked steel pipe pile cofferdam or double-wall steel cofferdam with stronger bearing capacity becomes a better choice. The double-wall steel cofferdam is complex in processing and manufacturing, has a low reuse rate, and is costly. The locked steel pipe pile has a large flexural rigidity, and the steel pipe model can be selected according to the force requirements. It is simple and fast in processing and manufacturing, and has a high material recycling rate, and is widely used in actual projects. The piling method of the locked steel pipe pile is divided into the hammering method and the vibration method. When the bridge pier is set on the river embankment, the shock wave formed by hammering or vibration will threaten the stability of the embankment. Especially when there is a liquefiable soil layer under the embankment, the harm is greater, and the shock wave increases sharply with the increase of the steel pipe cross-section and the penetration depth. The cofferdam is generally located in water, resisting the water pressure around and the lateral earth pressure below the riverbed surface. The top elevation of the cofferdam is consistent, generally 0.5 - 0.7 m higher than the highest water surface (including waves). When constructing the underground part of a building on the shore, the space formed by excavation from the ground downwards is a foundation pit, and retaining soil members such as cast-in-place concrete support piles are often used to bear the lateral earth pressure. The top elevation of the pile is generally the original ground elevation. The elevation difference between the river embankment slope and the ground is large, and the water level drop is large in different seasons. The temporary area enclosed for the dry working construction of the bearing platform has the characteristics of both a cofferdam and a foundation pit. By comprehensively utilizing the advantages of the locked steel pipe pile of the cofferdam and the cast-in-place bored pile of the foundation pit, developing a locked steel pipe - cast-in-place bored combined support pile has important engineering value for projects with large elevation differences between the original ground of the river embankment slope and being vibration-sensitive.

[0003] The purpose of the utility model is to provide a steel-concrete composite cofferdam applicable to unbalanced earth pressure in a vibration-sensitive area and a calculation and revision method to solve the problems mentioned in the above background technique. Content of the Utility Model

[0004] To achieve the above object, the utility model provides a steel-concrete composite cofferdam applicable to the unbalanced earth pressure in the vibration-sensitive area, which includes a number of locked steel pipe - drilled cast-in-place composite support piles, high-pressure jet grouting piles, a counterweight platform, internal supports, and a bottom-sealing concrete. A plurality of pile foundation casings are arranged in the construction area. A number of the locked steel pipe - drilled cast-in-place composite support piles are connected end to end in sequence along the outside of the construction area of the pile cap. The high-pressure jet grouting piles are arranged along the inner and outer sides of the locked steel pipe - drilled cast-in-place composite support piles and in the gaps between every two support piles. The counterweight platform is arranged on the side with a lower ground elevation and is close to the locked steel pipe - drilled cast-in-place composite support piles. The internal supports are fixedly installed on the inner wall of the area enclosed by the locked steel pipe - drilled cast-in-place composite support piles through fasteners. The internal supports include multiple groups of struts. Multiple groups of the struts are evenly distributed from top to bottom along the locked steel pipe - drilled cast-in-place composite support piles. Auxiliary supports are also provided on multiple groups of the struts. A circle of anchoring steel bars is welded on the outer wall of the pile foundation casing, and the distance between each two of the anchoring steel bars is set at 50 cm. The periphery of the bottom-sealing concrete is connected to the pile foundation steel casing and the locked steel pipe - drilled cast-in-place composite support piles. The anchoring steel bars are arranged 20 cm upward from the bottom of the bottom-sealing concrete. The auxiliary supports are arranged between the struts and the bottom-sealing concrete and are fixedly connected to both of them. The locked steel pipe - drilled cast-in-place composite support piles are divided into three parts: the hollow section of the locked steel pipe pile, the locked steel pipe - concrete composite section, and the concrete pile section.

[0005] As a further improvement of the utility model, the struts include multiple transverse supports, longitudinal supports, and support pads. Support pads 1 are provided at both ends of the transverse supports and the longitudinal supports. A number of fasteners are provided on the inner wall of the area enclosed by the inner side of the locked steel pipe - drilled cast-in-place composite support piles. The ends of the transverse supports and the longitudinal supports close to the inner side of the locked steel pipe - drilled cast-in-place composite support piles are fixedly connected to the fasteners through the support pads 1. The longitudinal supports are arranged between each two of the transverse supports. The auxiliary supports are fixedly installed on the longer longitudinal supports.

[0006] As a further improvement of the utility model, the fasteners include waling beams, corbels, and steel suspension rods. The corbels are evenly distributed on the inner side of the locked steel pipe - drilled cast-in-place composite support piles. The waling beams are all installed on the tops of the corbels. The vertical surfaces of the corbels connected to the locked steel pipe piles are fixed by welding. Steel suspension rods are welded on the vertical surfaces of the corbels connected to the reinforced concrete piles and are fixedly connected to the locked steel pipe piles through the steel suspension rods.

[0007] As a further improvement of the utility model, fine aggregate concrete is also filled between the waling beams and the locked steel pipe - drilled cast-in-place composite support piles.

[0008] As a further improvement of the present utility model, the auxiliary support member includes a steel lattice column and a pre-embedded plate. The steel lattice columns are evenly distributed along the horizontal direction of the longitudinal support, and are fixedly connected to each longitudinal support in sequence from top to bottom, and the bottom is fixedly connected to the pre-embedded plate. Anchor bars welded to the bottom of the pre-embedded plate are inserted into the internal part of the bottom-sealing concrete for fixation.

[0009] As a further improvement of the present utility model, high-pressure jet grouting piles are arranged between the locked steel pipe - drilled cast-in-place combined retaining piles. The top of the high-pressure jet grouting piles outside the locked steel pipe - drilled cast-in-place combined retaining piles is flush with the ground line. The top of the high-pressure jet grouting piles inside the locked steel pipe - drilled cast-in-place combined retaining piles is slightly higher than the top surface of the bottom-sealing concrete, and the bottom end of the high-pressure jet grouting piles is lower than the bottom of the bottom-sealing concrete.

[0010] As a further improvement of the present utility model, a plurality of diagonal braces are also welded at the four corners of the inner wall of the area surrounded by the locked steel pipe - drilled cast-in-place combined retaining piles. Support pads II are provided at both ends of the plurality of diagonal braces, and are fixedly connected to the collar beam arranged on the inner wall of the locked steel pipe - drilled cast-in-place combined retaining piles through the support pads II.

[0011] As a further improvement of the present utility model, a sloping drainage ditch is provided around the top of the bottom-sealing concrete, and sump pits are provided at the four corners of the drainage ditch where the elevation is relatively low.

[0012] As a further improvement of the present utility model, earth and stone fillers with relatively small water permeability are filled on the side of the counterweight platform close to the locked steel pipe - drilled cast-in-place combined retaining piles, and block stones are filled on the far side to prevent scouring.

[0013] As a further improvement of the present utility model, the anti-leakage dam provided at the place where the original ground is relatively low is composed of filled soil and anti-seepage geotextile.

[0014] Compared with the prior art, the beneficial effects of the present utility model are as follows:

[0015] 1. The present utility model is provided with a locked steel pipe - drilled cast-in-place combined retaining pile. The insertion of the locked steel pipe pile only needs to penetrate the surface of poor geology and meet the requirements of the construction casing of the drilled pile. Compared with the traditional locked steel pipe pile, the insertion depth is shallower, greatly reducing the impact of vibration on the vibration-sensitive dike.

[0016] 2. The present utility model is provided with a counterweight platform. The part of the counterweight platform adjacent to the locked steel pipe - drilled cast-in-place combined retaining pile uses fillers with a large internal friction angle and a small permeability coefficient. Sufficient anti-pushing stiffness can ensure that the overall deformation of the combined cofferdam is controllable under the action of unbalanced earth pressure and keep the inside of the cofferdam in a dry operation environment. The part of the counterweight platform farther from the locked steel pipe - drilled cast-in-place combined retaining pile is filled with block stones to improve the anti-scouring ability.

[0017] 3. The utility model is provided with a leak-proof dam, which is composed of filler and anti-seepage geotextile, and can collect waste water and waste residues generated during the construction process to protect the ecological environment.

[0018] 4. The lockable hollow section of the lockable steel pipe - drilled cast-in-place combined retaining pile can meet the requirement of the same top elevation when there is a large ground elevation difference, and meet the demand for the rising water level of the river-side bank slope during the flood season.

[0019] 5. The utility model welds a plurality of anchoring steel bars around the pile foundation casing. By the bond strength between the anchoring steel bars and the concrete, on the premise of ensuring the anti-floating stability of the cofferdam, the thickness of the bottom-sealing concrete is reduced, the input of personnel, materials and equipment is reduced, the work efficiency is improved, and the project progress is accelerated.

[0020] 6. Multiple corbels are arranged on the lockable steel pipe - drilled cast-in-place combined retaining pile according to the force requirements. The corbels are fixed by welding or steel suspenders. A purlin is placed on the corbels. Fine aggregate concrete is filled in the gap between the purlin and the lockable steel pipe - drilled cast-in-place combined retaining pile. The internal support of the cofferdam is connected to the purlin, and a steel lattice column is used as an auxiliary support for the internal support, thereby improving the stability of the internal support. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is the plan view of the cofferdam of the utility model;

[0022] Figure 2 is the sectional view of the cofferdam of the utility model;

[0023] Figure 3 is the structural schematic diagram of the lockable steel pipe - drilled cast-in-place combined retaining pile of the utility model;

[0024] Figure 4 is the detailed schematic diagram of the purlin corbel suspender of the utility model;

[0025] Figure 5 is the schematic diagram of filling fine aggregate concrete between the purlin and the lockable steel pipe - drilled cast-in-place combined retaining pile of the utility model;

[0026] Figure 6 is the partial pile position layout diagram of the high-pressure jet grouting pile of the utility model;

[0027] Figure 7 is the structural schematic diagram of the steel lattice column of the utility model;

[0028] Figure 8 is the plan view of the anchoring steel bars of the bottom-sealing concrete of the utility model;

[0029] Figure 9 is the elevation view of the anchoring steel bars of the bottom-sealing concrete of the utility model.

[0030] In the figure: 1. Locked steel pipe - drilled cast - in - place combined retaining pile; 2. Hollow section of the locked steel pipe pile; 3. Locked steel pipe - reinforced concrete combined section; 4. Reinforced concrete pile section; 5. High - pressure jet grouting pile; 6. Internal support; 601. Inclined support; 602. Transverse support; 603. Longitudinal support; 604. Support pad 1; 605. Support pad 2; 7. Back - pressure platform; 8. Block stone; 9. Steel lattice column; 901. Embedded plate; 10. Leak - proof dike; 11. Anti - seepage geotextile; 12. Bottom - sealing concrete; 13. Anchor reinforcement; 14. Sump; 15. Pile foundation casing; 16. Waling; 17. Fine aggregate concrete; 18. Corbels; 19. Steel suspender. Detailed implementation mode

[0031] To facilitate the understanding of the present utility model, the present utility model will be described more comprehensively below with reference to the relevant attached drawings. Several embodiments of the present utility model are given in the attached drawings. However, the present utility model can be implemented in different forms and is not limited to the embodiments described in the text. On the contrary, these embodiments are provided to make the disclosure of the present utility model more thorough and comprehensive.

[0032] It should be noted that when an element is referred to as "fixedly installed on" another element, it can be directly on the other element or there can be an intermediate element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used in this article are only for the purpose of illustration.

[0033] Unless otherwise defined, all technical and scientific terms used in this article have the same meaning as commonly understood by those skilled in the technical field to which the present utility model belongs. The terms used in the description of the present utility model in this article are only for the purpose of describing specific embodiments and are not intended to limit the present utility model. The term "and / or" used in this article includes any and all combinations of one or more of the related listed items.

[0034] The following further elaborates on the present utility model in conjunction with the attached drawings.

[0035] Embodiment 1:

[0036] Please refer to Figures 1-9, the present utility model provides a steel-concrete composite cofferdam applicable to unbalanced earth pressure in vibration-sensitive areas, which includes several lock-up steel pipe - drilled cast-in-place composite support piles 1, high-pressure jet grouting piles 5, counter-pressure platforms 7, internal supports 6, and bottom-sealing concrete 12. There are multiple pile foundation casings 15 in the construction area. Several of the lock-up steel pipe - drilled cast-in-place composite support piles 1 are connected end to end in sequence along the outside of the pile cap construction area. The high-pressure jet grouting piles 5 are arranged on both the inside and outside of the lock-up steel pipe - drilled cast-in-place composite support piles 1 and in the gaps between every two support piles. The counter-pressure platform 7 is arranged on the side with a lower ground elevation and is close to the lock-up steel pipe - drilled cast-in-place composite support piles 1. The internal support 6 is fixedly installed on the inner wall of the area enclosed by the lock-up steel pipe - drilled cast-in-place composite support piles 1 through fasteners. The internal support 6 includes multiple groups of struts, and the multiple groups of struts are evenly distributed from top to bottom along the lock-up steel pipe - drilled cast-in-place composite support piles 1. Auxiliary support members are also provided on the multiple groups of struts. Several anchoring steel bars 13 are welded to the outer wall of the pile foundation casing 15, and the distance between each of the anchoring steel bars 13 is set at 50 cm. The periphery of the bottom-sealing concrete 12 is connected to the pile foundation steel casing and the lock-up steel pipe - drilled cast-in-place composite support piles 1. The anchoring steel bars 13 are arranged 20 cm above the bottom of the bottom-sealing concrete 12. The auxiliary support members are arranged between the struts and the bottom-sealing concrete 12 and are fixedly connected to both of them. The lock-up steel pipe - drilled cast-in-place composite support pile 1 includes three parts: a hollow section 2 of the lock-up steel pipe pile, a lock-up steel pipe - reinforced concrete composite section 3, and a reinforced concrete pile section 4.

[0037] High-pressure jet grouting piles 5 are provided between the lock-up steel pipe - drilled cast-in-place composite support piles 1. The top of the high-pressure jet grouting piles 5 on the outside of the lock-up steel pipe - drilled cast-in-place composite support piles 1 is flush with the ground line. The top of the high-pressure jet grouting piles 5 on the inside of the lock-up steel pipe - drilled cast-in-place composite support piles 1 is slightly higher than the top surface of the bottom-sealing concrete 12. The bottom end of the high-pressure jet grouting piles 5 is lower than the bottom of the bottom-sealing concrete 12.

[0038] During use, first install the locked steel pipe - drilled cast - in - place combined retaining pile 1. Insert the locked steel pipe pile into the ground. The locked steel pipe pile also serves as the casing for pile foundation construction. The penetration depth of the locked steel pipe pile only needs to meet the requirements of cast - in - place pile construction to minimize the vibration caused by the driving of the steel pipe pile. The top elevation of the locked steel pipe piles should be unified to meet the construction requirements for resisting the highest water level during construction. The driving of the locked steel pipe pile only needs to pass through the surface poor geology and meet the requirements of the casing for bored pile construction. Compared with the traditional locked steel pipe pile, its penetration depth is shallower, greatly reducing the impact of vibration on the vibration - sensitive dike. The hollow section 2 of the locked steel pipe pile can meet the requirement of the same top elevation when there is a large ground elevation difference, and meet the requirement of the rising water level on the river - side slope during the flood season. The concrete is poured to the original ground elevation to facilitate the subsequent cutting of the hollow section 2 of the locked steel pipe pile along the ground. Before concrete pouring, lower the steel cage of the cast - in - place pile. For the locked steel pipe piles in the cofferdam closure section, C - T - shaped locks or L - T - shaped locks with certain adjustment capabilities should be selected, and C - C - shaped locks should not be used. Subsequently, construct high - pressure jet grouting piles 5 on both the inner and outer sides of the locked steel pipe - drilled cast - in - place combined retaining pile 1 and in the gap between every two retaining piles. The high - pressure jet grouting piles 5 form a water - stop curtain to ensure no water seepage, providing a dry - operation construction environment inside the cofferdam. Immediately afterwards, excavate inside the cofferdam and install the internal support 6 on the inner wall of the area enclosed by the locked steel pipe - drilled cast - in - place combined retaining pile 1 in a timely manner. An auxiliary support member is arranged between the internal support 6 and the bottom - sealed concrete 12 to improve the stability of the internal support 6. In this embodiment, by welding anchor bars 13 around the casing, through the bond force between the anchor bars 13 and the concrete, on the premise of ensuring the anti - floating stability of the cofferdam, reduce the thickness of the bottom - sealed concrete 12, reduce the input of personnel, materials and equipment, improve work efficiency and speed up the project progress.

[0039] Embodiment Two:

[0040] On the basis of Embodiment One, in this embodiment, as Figures 1-4 shown, the strut includes a plurality of transverse supports 602, longitudinal supports 603, and support pads 604. Both ends of the transverse supports 602 and the longitudinal supports 603 are provided with support pads 605. The inner wall of the area enclosed by the locked steel pipe - drilled cast - in - place combined retaining pile 1 is provided with a plurality of fasteners. The ends of the transverse supports 602 and the longitudinal supports 603 close to the inner side of the locked steel pipe - drilled cast - in - place combined retaining pile 1 are connected and fixed to the fasteners through the support pads 605. The longitudinal supports 603 are arranged between each of the transverse supports 602. The auxiliary support member is fixedly installed on the longitudinal supports 603.

[0041] The fasteners include a collar 16, a bracket 18, and a steel hanger rod 19. The brackets 18 are evenly distributed inside the locked steel pipe - cast - in - place pile composite retaining wall 1. The collar 16 is installed on top of each bracket 18. The vertical surface of the bracket 18 connected to the locked steel pipe pile is fixed by welding. The vertical surface of the bracket 18 connected to the reinforced concrete pile is welded with a steel hanger rod 19, and is connected and fixed to the locked steel pipe pile through the steel hanger rod 19.

[0042] Fine aggregate concrete 17 is also filled between the collar 16 and the locked steel pipe - cast - in - place pile composite retaining wall 1.

[0043] At the four corners of the inner wall of the area enclosed by the locked steel pipe - cast - in - place pile composite retaining wall 1, a plurality of diagonal braces 601 are welded. Both ends of the plurality of diagonal braces 601 are provided with support pads two 605, and are connected and fixed to the collar 16 arranged on the inner wall of the locked steel pipe - cast - in - place pile composite retaining wall 1 through the support pads two 605.

[0044] The steel hanger rod 19 is made of H - shaped steel or I - shaped steel.

[0045] During use, a plurality of brackets 18 are distributed from top to bottom on the inner wall of the locked steel pipe - cast - in - place pile composite retaining wall 1. The brackets 18 on the locked steel pipe pile are fixed by welding. At the reinforced concrete pile, a steel hanger rod 19 is pre - welded and installed at the upper - end locked steel pipe column section. The bracket 18 is connected and fixed to the locked steel pipe pile section through the steel hanger rod 19. Then, the collar 16 is installed on top of the bracket 18, and the transverse support 602 and the longitudinal support 603 are installed in sequence. Further, in order to improve the overall stability of the cofferdam, fine aggregate concrete 17 is filled in the gap between the collar 16 and the locked steel pipe - cast - in - place pile composite retaining wall 1, which can effectively disperse the stress transfer between the collar 16 and the locked steel pipe - cast - in - place pile composite retaining wall 1 and improve the bearing capacity. Subsequently, the auxiliary support member, the longitudinal support 603, is installed and fixed. In this embodiment, the steel hanger rod 19 is made of H - shaped steel, I - shaped steel and other steel sections with a planar structure, which is convenient for welding and fixing with the collar 16.

[0046] Embodiment Three:

[0047] Based on Embodiment One, in this embodiment, as Figure 1 、 Figure 2 、 Figure 7 shown, the auxiliary support member includes a steel lattice column 9 and a embedded plate 901. The steel lattice column 9 is sequentially connected to each longitudinal support 603 and is fixedly connected to the embedded plate 901 at the bottom. Anchor bars are arranged at the bottom of the embedded plate 901 and inserted into the internal seal concrete 12 for fixation.

[0048] During use, multiple steel lattice columns 9 are installed at equal intervals along the longitudinal support 603. The embedded plate 901 fixedly connected to the bottom of the steel lattice column 9 is pre-inserted into the bottom-sealing concrete 12 for fixation. The steel lattice column 9 is provided to provide vertical support for the internal support 6, thereby enhancing the overall stability of the internal support 6 system and preventing the longitudinal support 603 from buckling due to a relatively large out-of-plane free length.

[0049] Embodiment 4:

[0050] Based on Embodiment 1, in this embodiment, as Figure 2 shown, a sloped drainage ditch is provided around the top of the bottom-sealing concrete 12, and sump pits 14 are provided at the four corners of the drainage ditch where the elevation is relatively low.

[0051] During use, the drainage ditch can effectively collect rainwater, seepage water, etc. within the cofferdam and converge them into the sump pits 14, ensuring the dryness inside the cofferdam and providing favorable conditions for construction.

[0052] Embodiment 5:

[0053] Based on Embodiment 1, in this embodiment, as Figure 1 、 Figure 2 shown, the surcharge platform 7 is filled with two types of materials on the inner and outer sides. The inner material requires a large internal friction angle and a small permeability coefficient, and the outer material requires a strong erosion resistance. The leakage-proof dike 10 is composed of filler and anti-seepage geotextile 11.

[0054] During use, the part of the surcharge platform 7 adjacent to the locked steel pipe - cast-in-place bored pile 1 uses a filler with a large internal friction angle and a small permeability coefficient. Sufficient anti-pushing stiffness can ensure that the overall deformation of the combined cofferdam is controllable under the action of unbalanced earth pressure and maintain a dry working environment inside the cofferdam. The part of the surcharge platform 7 farther from the locked steel pipe - cast-in-place bored pile 1 is filled with rubble 8 to improve the erosion resistance.

[0055] The leakage-proof dike 10 is composed of filler and anti-seepage geotextile 11, which can collect waste water and waste residues generated during construction for centralized disposal and protect the ecological environment.

[0056] The above has made an exemplary description of the present invention in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited by the above methods. As long as such non-substantial improvements are made using the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A steel-concrete composite cofferdam suitable for use under unbalanced earth pressure in vibration-sensitive areas, characterized in that: The invention comprises a plurality of locking steel pipe-bored cast-in-place combined support piles (1), high-pressure rotary jet piles (5), a back pressure platform (7), an inner support (6), and bottom sealing concrete (12). A plurality of pile foundation casings (15) are provided in the construction area. A plurality of the locking steel pipe-bored cast-in-place combined support piles (1) are connected end to end in sequence along the outer side of the foundation construction area. The high-pressure rotary jet piles (5) are arranged along the inner and outer sides of the locking steel pipe-bored cast-in-place combined support piles (1) and in the gap between every two support piles. The back pressure platform (7) is arranged on the side with lower ground elevation and is close to the locking steel pipe-bored cast-in-place combined support piles (1). The inner support (6) is fixedly installed on the inner wall of the area surrounded by the locking steel pipe-bored cast-in-place combined support piles (1) by fasteners. The inner support (6) comprises a plurality of groups of support rods. The rods are evenly distributed from top to bottom along the locking steel pipe-drilling and grouting combined support pile (1), and auxiliary support members are also provided on multiple groups of the support rods. A plurality of anchoring steel bars (13) are welded to the outer wall of the pile foundation casing (15), and each of the anchoring steel bars (13) is arranged at intervals of 50 cm. The periphery of the bottom seal concrete (12) is connected to the pile foundation steel casing and the locking steel pipe-drilling and grouting combined support pile (1), and the anchoring steel bars (13) are arranged 20 cm above the bottom of the bottom seal concrete (12). The auxiliary support members are arranged between the support rods and the bottom seal concrete (12), and are connected and fixed to the two. The locking steel pipe-drilling and grouting combined support pile (1) comprises three parts: a locking steel pipe pile hollow section (2), a locking steel pipe-reinforced concrete combination section (3), and a reinforced concrete pile section (4).

2. The steel-concrete composite cofferdam suitable for use under unbalanced earth pressure in vibration-sensitive areas according to claim 1, characterized in that: The support rod comprises a plurality of transverse supports (602), a longitudinal support (603), and a support seat (604). Both ends of the transverse supports (602) and the longitudinal supports (603) are provided with a support seat (604). The inner wall of the area enclosed by the locking steel pipe-drilled cast-in-place composite support pile (1) is provided with fasteners. The transverse supports (602) and the longitudinal supports (603) are connected and fixed to the fasteners via the support seat (604). The auxiliary support is fixedly mounted on the longitudinal supports (603).

3. The steel-concrete composite cofferdam suitable for use under unbalanced earth pressure in vibration-sensitive areas according to claim 2, characterized in that: The fasteners include a purlin (16), a corbel (18), and a steel hanger (19); the corbels (18) are evenly distributed on the inner side of the locking steel pipe-bored cast-in-place combined support pile (1); the purlins (16) are all installed on the top of the corbels (18); the vertical surface of the corbels (18) connected to the locking steel pipe pile is fixed by welding; the vertical surface of the corbels (18) connected to the reinforced concrete pile is welded with a steel hanger (19), and is connected and fixed to the locking steel pipe pile by the steel hanger (19).

4. The steel-concrete composite cofferdam suitable for use under unbalanced earth pressure in vibration-sensitive areas according to claim 3, characterized in that: Fine stone concrete (17) is filled between the surrounding purlin (16) and the locking steel pipe-drilled cast-in-place combined support pile (1).

5. The steel-concrete composite cofferdam suitable for use under unbalanced earth pressure in vibration-sensitive areas according to claim 2, characterized in that: The auxiliary support members include steel lattice columns (9) and embedded plates (901); the steel lattice columns (9) are evenly distributed along the horizontal direction of the longitudinal supports (603), and are connected and fixed to each of the longitudinal supports (603) in sequence from top to bottom, and are fixedly connected to the embedded plates (901) at the bottom; and the bottom welded anchor bars of the embedded plates (901) are inserted into the bottom sealing concrete (12) for fixation.

6. The steel-concrete composite cofferdam suitable for use under unbalanced earth pressure in vibration-sensitive areas according to claim 1, characterized in that: High-pressure rotary jet piles (5) are arranged between the locking steel pipe-drilling and grouting combined support piles (1), the top of the high-pressure rotary jet pile (5) outside the locking steel pipe-drilling and grouting combined support pile (1) is flush with the ground line, the top of the high-pressure rotary jet pile (5) inside the locking steel pipe-drilling and grouting combined support pile (1) is slightly higher than the top surface of the bottom sealing concrete (12), and the bottom of the high-pressure rotary jet pile (5) is lower than the bottom of the bottom sealing concrete (12).

7. The steel-concrete composite cofferdam suitable for use under unbalanced earth pressure in vibration-sensitive areas according to claim 4, characterized in that: A plurality of diagonal braces (601) are welded to the four corners of the inner wall of the area enclosed by the locking steel pipe-drilled cast-in-place combined supporting pile (1), and a second supporting cushion seat (605) is provided at both ends of the plurality of diagonal braces (601), and the second supporting cushion seat (605) is connected and fixed to the surrounding purlin (16) provided on the inner wall of the locking steel pipe-drilled cast-in-place combined supporting pile (1).

8. The steel-concrete composite cofferdam suitable for use under unbalanced earth pressure in vibration-sensitive areas according to claim 1, characterized in that: A sloped drainage ditch is arranged around the top of the bottom sealing concrete (12), and water collection pits (14) are arranged at the four corners of the drainage ditch at lower elevations.

9. The steel-concrete composite cofferdam suitable for use under unbalanced earth pressure in vibration-sensitive areas according to claim 1, characterized in that: The back pressure platform (7) is filled with soil and stone filling material with low water permeability on the side close to the locking steel pipe-bored cast-in-place combined support pile (1), and is filled with block stones (8) on the side away from the back pressure platform to prevent scouring.

10. The steel-concrete composite cofferdam suitable for use under unbalanced earth pressure in vibration-sensitive areas according to claim 3, characterized in that: The anti-leakage dam (10) arranged at the lower part of the original ground is composed of fill soil and anti-seepage geotextile (11).

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