Combined cofferdam suitable for deeply-buried bridge bearing platform foundation and construction method

Abstract

The invention belongs to the field of bridge construction foundation construction, and particularly relates to a combined cofferdam suitable for a deep-buried bridge bearing platform foundation and a construction method. The combined cofferdam comprises a lower concrete cofferdam and an upper locking steel pipe pile cofferdam, and an air curtain structure for assisting the cofferdam in sinking is arranged in the combined cofferdam; a U-shaped groove is formed in the top of the concrete cofferdam, the bottoms of all the fore shaft steel pipe piles of the fore shaft steel pipe pile cofferdam are inserted into the U-shaped groove, and the whole combined cofferdam structure is more reasonable in stress and safe and reliable in structure. The construction method comprises the steps that a lock catch steel pipe pile cofferdam is installed on a concrete cofferdam through a crane, water is injected into an air curtain and lock opening steel pipe piles for ballasting to assist sinking, and finally after construction of a bridge bearing platform, a pier body and the like is completed, the lock opening steel pipe pile cofferdam is pulled out one by one through a vibration pile driver. According to the construction method, the installation speed is high, the installation precision is easy to control, operation is easy, the construction difficulty is effectively reduced, and the construction efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge construction foundation construction, and in particular relates to a combined cofferdam suitable for a deep-buried bridge cap foundation and a construction method. Background Art

[0002] In the construction of deep-buried bridge main pier caps located on the beach across large rivers, the use of cofferdams is an indispensable temporary structure to ensure the stability of the slope and effective water stopping during the construction of the cap. For rivers with dredging in the later stage and rivers with strong wandering erosion (such as the Yellow River), it is necessary to remove the cofferdam above the cap to ensure the river flood section. In the construction of deep foundation pit caps located on the beach across large rivers, the country currently generally uses concrete caisson cofferdams, double-walled steel cofferdams, steel sheet pile cofferdams, lock-mouth steel pipe pile cofferdams, bored pile cofferdams and other technologies to construct deep foundation pit caps, but the above technologies all have a certain range of applicability and limitations. Among them, concrete caisson cofferdam, double-wall steel cofferdam and bored pile cofferdam have a long construction period and high cost. After the construction is completed, the surrounding covering layer is deeply buried and cannot be removed. It has a great impact on the later dredging of the river channel and is difficult to pass the approval of the river management department. Steel sheet pile cofferdam and locked steel pipe pile cofferdam are light, easy to dismantle, reusable, short construction period and low cost, but have poor integrity and withstand small horizontal loads. They are not suitable for deep foundation pits greater than 18 meters.

[0003] Therefore, it is necessary to provide an improved technical solution for the above-mentioned deficiencies of the prior art, so as to adapt to deep foundation pits, have a faster construction speed, and be easy to dismantle in the later stage. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a combined cofferdam and a construction method suitable for deep-buried bridge pedestal foundations.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A combined cofferdam suitable for a deep-buried bridge cap foundation, comprising a lower concrete cofferdam and an upper locking steel pipe pile cofferdam, wherein an air curtain structure for assisting the cofferdam to sink is arranged in the combined cofferdam;

[0007] A U-shaped groove is arranged on the top of the concrete cofferdam, and the bottom of each locking steel pipe pile of the locking steel pipe pile cofferdam is inserted into the U-shaped groove, and high-strength support grouting material is poured between the U-shaped groove and the locking steel pipe pile cofferdam; a plurality of annular cofferdams and internal supports are arranged on the inner side of the locking steel pipe pile cofferdam;

[0008] The air curtain structure includes a plurality of air niches pre-buried in the concrete cofferdam, ventilation steel pipes connected to the air niches, joint pipes connected to the ventilation steel pipes, and ventilation main pipes detachably connected to the joint pipes; the upper end of the joint pipe exceeds the top surface of the concrete cofferdam; the ventilation main pipe passes upward through the locking steel pipe piles of the locking steel pipe pile cofferdam.

[0009] Furthermore, the width of the notch of the U-shaped groove is 18 to 24 cm larger than the outer diameter of the locking steel pipe pile, and the depth of the U-shaped groove is 80 to 100 cm.

[0010] Furthermore, the height of the concrete cofferdam is the sum of the bottom thickness and the foundation thickness, and the thickness of the concrete cofferdam is 160 to 200 cm.

[0011] Furthermore, the diameter of the locking steel pipe pile is 82-100 cm and the wall thickness is 12-20 mm; the locking of the locking steel pipe pile can adopt the "CT" locking of welded open small steel pipes and industrial steel, or the "CO" locking of large and small steel pipes, or the locking of welded steel sheet piles.

[0012] Furthermore, the annular purlin is arranged every 3 to 6 meters in the height direction, the annular purlin is welded by H-shaped steel, and the inner support is a steel pipe component; the gap between the annular purlin and the locking steel pipe pile cofferdam is filled with fine stone concrete.

[0013] Furthermore, the joint pipe is connected to the ventilation main pipe by thread or by a quick connector.

[0014] Furthermore, an embedded part is provided on the top of the concrete cofferdam, and a positioning frame for assisting the positioning of the locking steel pipe piles is installed on the embedded part.

[0015] The present invention also proposes a construction method using the aforementioned combined cofferdam suitable for deep-buried bridge cap foundation, which is characterized by comprising the following steps:

[0016] S1. Level the site at the pier, erect formwork, tie steel bars and pour cofferdam concrete. Set a reserved U-shaped groove at the center of the top surface of the lower concrete cofferdam, and reserve ventilation steel pipes and joint pipes for the air curtain structure during construction;

[0017] S2. Use a long-arm excavator to remove the soil inside the concrete cofferdam, and let the concrete cofferdam sink until the top surface is about 50 to 100 cm above the ground; use the ventilation main pipe to extend the reserved joint pipe, and use a crane to hoist the locking steel pipe piles into the U-shaped groove reserved on the top of the top layer of the concrete cofferdam. After the locking steel pipe pile cofferdam is installed, use the gravity method to pour high-strength bearing grouting material into the groove of the U-shaped groove to ensure that the locking steel pipe pile cofferdam and the concrete cofferdam are tightly connected;

[0018] S3. After all the interlocking steel pipe pile cofferdams are installed, the brackets are welded on the interlocking steel pipe pile cofferdams, the bottom ring purlins and inner supports are installed, and the gap between the ring purlins and the interlocking steel pipe pile cofferdams is filled with fine stone concrete;

[0019] S4. Use excavators, grabs or mud suction machines to remove the soil in the combined cofferdam, use air curtains and water injection weight in the interlocking steel pipe piles to assist the cofferdam to sink to the designed installation position of the second-layer annular purlin and internal support, where the designed elevation is about 50 to 100 cm above the ground; weld corbels on the interlocking steel pipe pile cofferdam, install the second-layer annular purlin and internal support, and fill the gap between the purlin and the interlocking steel pipe pile cofferdam with fine stone concrete;

[0020] S5, and so on, repeat step S4 to continue taking soil to make the combined cofferdam sink to the designed elevation, and install the remaining annular purlins and internal supports at the same time; finally, the combined cofferdam is sealed at the bottom, and the foundation is constructed;

[0021] S6. When the construction of bridge abutments, piers, etc. is completed and the conditions for dismantling the combined cofferdam are met, backfill the soil layer by layer to remove the annular purlins and internal supports. Finally, a vibrating pile driver is used to remove the locked steel pipe cofferdam piles one by one.

[0022] Furthermore, in step S2, when installing the locking steel pipe piles in the U-shaped groove, a crane is used to install 1 to 5 locking steel pipe piles each time. Preferably, a crane is used to install 2 locking steel pipe piles each time.

[0023] Furthermore, when installing the locking steel pipe piles, a positioning frame is installed on the concrete cofferdam to assist in positioning each locking steel pipe pile; after the locking steel pipe pile cofferdam is installed, the positioning frame is removed.

[0024] The beneficial effects of the present invention are:

[0025] 1) The combined cofferdam composed of the concrete cofferdam and the interlocking steel pipe pile cofferdam of the present invention has a large structural rigidity of the concrete cofferdam and is placed in the lower part where the water and soil pressure is large, and the interlocking steel pipe pile cofferdam is placed in the upper part where the water pressure is small, so that the whole structure is more reasonably stressed and the structure is safe and reliable.

[0026] 2) The combined cofferdam of the present invention adopts sinking-aiding measures such as built-in air curtain and water injection and weighting in the upper lock-mouth steel pipe piles, which can effectively ensure that the combined cofferdam can sink to the designed elevation, overcoming the disadvantages of the combination of concrete cofferdam and steel sheet pile cofferdam being difficult to sink and the limited depth of applicable foundation burial.

[0027] 3) The combined cofferdam of the present invention overcomes the drawbacks of the long construction period of the traditional concrete cofferdam, and overcomes the drawbacks of the traditional steel sheet pile and locking steel pipe pile cofferdams in ultra-deep geology that the single pile length is too long (considering the calculation of the depth of the embedded traditional steel sheet pile or locking steel pipe pile, the total length is generally more than 30 meters), the difficulty of driving and the long construction period; the combined cofferdam provided by the present invention reduces the pouring height of the concrete cofferdam, and the locking steel pipe pile cofferdam does not need to be driven, the installation speed is efficient, the installation accuracy is easy to control, and the operation is simple, the construction difficulty is effectively reduced, and the construction efficiency is improved.

[0028] 4) In addition to the traditional method of installing the steel pipe piles one by one during the installation phase, the combined cofferdam of the present invention can also install two or more steel pipe piles at a time by a crane, thereby improving work efficiency; at the same time, the use of a crane instead of a pile driver during the installation phase can save equipment costs.

[0029] 5) The upper part of the combined cofferdam of the present invention adopts locking steel pipe piles to replace the upper concrete cofferdam, which can be removed by a vibrating pile driver after the main structure of the bridge is constructed out of the ground, thus overcoming the disadvantage that conventional concrete cofferdams and double-walled steel cofferdams cannot be removed under deep geological conditions; the removed locking steel pipe pile cofferdam can be recycled, saving resources and thus money; the top of the lower concrete cofferdam is at the same elevation as the top of the pedestal, which does not affect the dredging of the river channel, and can also serve as an anti-scouring structure for the pedestal. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. Among them:

[0031] Figure 1 It is a schematic structural diagram of an embodiment of the present invention.

[0032] Figure 2 for Figure 1 Cross-section of a concrete cofferdam.

[0033] Figure 3 for Figure 1 Cross-section of the locked steel pipe pile cofferdam.

[0034] Figure 4 It is a schematic diagram of the construction of pouring concrete cofferdam according to an embodiment of the present invention.

[0035] Figure 5 It is a schematic diagram of the hoisting construction of the locking steel pipe pile according to an embodiment of the present invention.

[0036] Figure 6 It is a schematic diagram of the construction of the locking steel pipe pile cofferdam according to an embodiment of the present invention.

[0037] Figure 7It is a schematic diagram of the sinking construction of the combined cofferdam according to an embodiment of the present invention.

[0038] Figure 8 It is a schematic diagram of the construction of the combined cofferdam cap according to an embodiment of the present invention.

[0039] Fig. 9 It is a schematic diagram of filling between U-shaped notches of a combined cofferdam according to an embodiment of the present invention.

[0040] Fig.10 Schematic diagram of the use status of the positioning frame according to the embodiment of the present invention.

[0041] Fig.11 It is a schematic diagram of the front structure of an internal expansion type pile clamp according to one embodiment of the present invention.

[0042] Fig.12 for Fig.11 Schematic diagram of the top view structure.

[0043] Fig.13 It is a schematic structural diagram of an internal expansion type pile clamp according to another embodiment of the present invention.

[0044] In the figure: 1. Concrete cofferdam; 2. Locking steel pipe piles; 3. U-shaped groove; 4. Annular purlin; 5. Bottom sealing concrete; 6. Capping platform; 7. Mud suction equipment; 8. Excavator; 9. Air curtain structure; 10. High-strength bearing grouting material; 11. Fine stone concrete; 12. Bored piles; 13. Corbel; 14. Formwork; 15. Sand cushion; 16. Embedded parts; 17. Positioning frame; 18. Guide rod; 19. Vertical plate; 20. Support rib; 21. Internal expansion pile clamp; 22. Claw; 23. Lifting ear; 24. Claw; 25. Lifting beam. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0046] In the description of the present invention, the terms "longitudinal", "lateral", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and do not require that the present invention must be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the present invention. The terms "connected" and "connected" used in the present invention should be understood in a broad sense. For example, they can be fixed connections or detachable connections; they can be directly connected or indirectly connected through intermediate components. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0047] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0048] like Figures 1 to 10 As shown, a combined cofferdam suitable for a deep-buried bridge cap foundation comprises a lower concrete cofferdam 1 and an upper locking steel pipe pile cofferdam, and an air curtain structure 9 is arranged inside the combined cofferdam to assist the cofferdam in sinking;

[0049] A U-shaped groove 3 is arranged on the top of the concrete cofferdam 1, and the bottom of each locking steel pipe pile 2 of the locking steel pipe pile cofferdam is inserted into the U-shaped groove 3. A high-strength support grouting material 10 is poured between the U-shaped groove 3 and the locking steel pipe pile cofferdam to ensure that the locking steel pipe pile cofferdam and the concrete cofferdam 1 have sufficient embedding strength when subjected to water and soil pressure; a plurality of annular cofferdams and internal supports are arranged on the inner side of the locking steel pipe pile cofferdam; the gap between the annular purlin 4 and the locking steel pipe pile cofferdam is filled with fine stone concrete 11;

[0050] The air curtain structure 9 includes a plurality of air niches pre-buried in the concrete cofferdam 1, ventilation steel pipes connected to the air niches, joint pipes connected to the ventilation steel pipes, and ventilation main pipes detachably connected to the joint pipes; the upper end of the joint pipe exceeds the top surface of the concrete cofferdam 1; the ventilation main pipe passes upward through the locking steel pipe piles 2 of the locking steel pipe pile cofferdam.

[0051] The width of the U-shaped groove 3 is 18 to 24 cm larger than the outer diameter of the locking steel pipe pile 2, and the depth of the U-shaped groove 3 is 80 to 100 cm. The size of the U-shaped groove 3 is appropriate so that the high-strength bearing grouting material 10 has sufficient depth and width to ensure that the locking steel pipe pile cofferdam is firmly connected to the concrete cofferdam 1.

[0052] The above concrete cofferdam 1 is a cast-in-place reinforced concrete structure. The height of the concrete cofferdam 1 is the sum of the thickness of the bottom concrete 5 and the thickness of the pedestal 6. The specific wall thickness and steel bar configuration are determined according to calculation, and the available thickness is 160-200cm. The interlocking steel pipe pile cofferdam 2 is determined according to calculation, and can be processed by steel pipes with a diameter of 82-100cm and a wall thickness of 12-20mm. The interlocking can be welded open small steel pipes and "CT" interlocking of industrial steel, or "CO" interlocking of large and small steel pipes, or welded steel sheet pile interlocking. In the height direction of the interlocking steel pipe pile cofferdam 2, according to calculation, an annular purlin 4 and an inner support are set every 3-6m. The annular purlin 4 and the inner support can be welded by H-shaped steel. Fine stone concrete 11 is used to fill the space between the annular purlin 4 and the inner support and the interlocking steel pipe pile cofferdam 2 to ensure effective force transmission of the structure.

[0053] Further, such as Figure 4 , Figure 5 As shown, the joint pipe is connected to the ventilation main pipe by thread or by a quick joint; the joint pipe is beyond the concrete top surface by a certain distance; the ventilation main pipe is mainly a steel pipe, and a high-pressure hose is connected to the top as needed. Before installing the locking steel pipe pile cofferdam, the ventilation main pipe is first connected to the joint pipe, and the ventilation main pipe is erected on the top surface of the concrete cofferdam 1, and then the locking steel pipe pile 2 is hoisted by a crane, and the locking steel pipe pile 2 is aligned with the ventilation main pipe and lowered.

[0054] Further, such as Figure 5 As shown, the top of the concrete cofferdam 1 is provided with an embedded part 16, and a positioning frame 17 for assisting the positioning of the locking steel pipe pile 2 is installed on the embedded part 16; the structure of the positioning frame 17 is not limited, as long as it can guide the bottom of the locking steel pipe pile 2 into the U-shaped groove 3. After the locking steel pipe pile cofferdam is installed, the positioning frame 17 is removed before the concrete cofferdam 1 is sunk into the ground. For example, a steel positioning frame 17 can be directly used, the positioning frame 17 can be welded to the embedded part 16, and the positioning frame 17 can be removed by cutting off the embedded part 16 when removing it.

[0055] The present invention also proposes a construction method for a combined cofferdam suitable for a deep-buried bridge cap foundation, comprising the following steps:

[0056] S1. Level the site at the pier, erect the formwork 14 (use the compacted sand cushion 15 as the blade foot inclined soil formwork), tie the steel bars and pour the cofferdam concrete. Set a reserved U-shaped groove 3 at the center of the top surface of the lower concrete cofferdam 1. Reserve the ventilation steel pipe and joint pipe of the air curtain structure 9 during construction. Note that the concrete cofferdam 1 is poured in layers along the height direction to form a ring. Figure 4 The template 14 of the concrete cofferdam 1 has been built;

[0057] The construction method of the U-shaped groove 3 is as follows: when constructing the concrete cofferdam 1 template 14, a bamboo plywood or steel template 14 is used to reserve the U-shaped groove 3, and the position of the U-shaped groove 3 template 14 is fixed to ensure that the position is not offset and the slurry does not leak during the concrete pouring; after the concrete cofferdam 1 solidifies, the groove template 14 is removed, the garbage in the groove is cleaned, and the uneven groove bottom can also be polished;

[0058] S2. Use a long-arm excavator 8 to stand outside the concrete cofferdam 1 to remove the soil inside the concrete cofferdam 1, so that the concrete cofferdam 1 sinks until the top surface is about 50 to 100 cm above the ground; use the ventilation main pipe to extend the reserved joint pipe, and use a crane to hoist the locking steel pipe pile 2 into the U-shaped groove 3 reserved at the top of the top layer of the concrete cofferdam 1. After the locking steel pipe pile cofferdam is installed, use the gravity method to pour high-strength bearing grouting material 10 into the groove of the U-shaped groove 3 to ensure that the locking steel pipe pile cofferdam is tightly connected to the concrete cofferdam 1; the locking steel pipe pile cofferdam can be hoisted by a crawler crane, a tower crane or a floating ship crane; Figure 5 The interlocking steel pipe pile 2 is being hoisted; Fig.10 The high-strength bearing grouting material 10 is schematically shown in FIG.

[0059] S3. After all the interlocking steel pipe pile cofferdams are installed, the brackets 13 are welded on the interlocking steel pipe pile cofferdams, the bottom annular purlins 4 and the inner supports are installed, and the gap between the annular purlins 4 and the interlocking steel pipe pile cofferdams is filled with fine stone concrete 11; Fig. 9 The filled fine stone concrete 11 is schematically shown in FIG.

[0060] S4, such as Figure 6 As shown, the soil in the combined cofferdam is removed by using an excavator 8, a grab bucket or a mud suction machine, and the combined cofferdam is further sunk to the second-layer annular purlin 4 and the designed installation position of the inner support by using an air curtain and water injection weight in the locking steel pipe pile 2, where the designed elevation is about 50 to 100 cm above the ground; a corbel 13 is welded on the locking steel pipe pile cofferdam, and the second-layer annular purlin 4 and the inner support are installed, and the gap between the purlin and the locking steel pipe pile cofferdam is filled with fine stone concrete 11; in this step, it is necessary to pay attention to symmetrically and evenly removing the soil in the cofferdam;

[0061] In addition, when the geology is mainly clay soil and the amount of water seepage is not large, the excavator 8 is mainly used to drain and excavate the soil; when the geology is mainly sandy soil and the amount of water seepage is large, the mud suction equipment 7 is mainly used to suck the mud out of the soil without drainage; Figure 7 The middle one is the mud suction equipment 7 in operation;

[0062] The water injection weight inside the locking steel pipe pile 2 can also be replaced by filling with sand or gravel; these auxiliary sinking measures are to avoid the cofferdam's insufficient deadweight to overcome the frictional resistance and cause sinking difficulties;

[0063] S5, and so on, repeat step S4 to continue taking soil to make the combined cofferdam sink to the designed elevation, and at the same time install the remaining annular purlins 4 and internal supports; pour the cofferdam bottom sealing concrete 5, and construct the cap 6 bored piles 12 and the cap 6; Figure 8 The outer contour of the platform 6 is schematically drawn (dashed line);

[0064] S6. When the construction of the bridge abutment 6 and the pier body is completed and the conditions for dismantling the combined cofferdam are met, the annular purlin 4 and the inner support are removed by backfilling the soil layer by layer, and finally the locking steel pipe piles of the cofferdam are removed one by one using a vibrating pile driver.

[0065] Furthermore, in step S2, when installing the locking steel pipe piles 2 in the U-shaped groove 3, a crane is used to install 1 to 5 locking steel pipe piles 2 each time. Specifically, when the crane installs one locking steel pipe pile 2 at a time, a clamp-type pile clamp or an internal expansion pile clamp 21 is used under the crane's lifting rope; when the crane installs multiple locking steel pipe piles 2 at a time, multiple clamping mechanisms are required, and special hoists with corresponding number of locking steel pipe piles 2 are manufactured according to the number of pile clamps required. Fig.11 , 12 As shown in the figure, it is a schematic diagram of the structure of a lifting device for lifting two interlocking steel pipe piles 2 at one time. The lifting device includes a lifting beam 25 and two internal expansion type pile clamps 21 installed on the lifting beam 25. The position layout is the same as that of the two interlocking steel pipe piles 2 during installation. The two internal expansion type pile clamps 21 are aligned in a row, and the center distance between the two internal expansion type pile clamps 21 is equal to the center distance between two adjacent interlocking steel pipe piles 2 in the interlocking steel pipe pile cofferdam. Fig.13 As shown in the figure, it is a lifting device for lifting three interlocking steel pipe piles 2 at one time. The lifting device includes a lifting beam 25 and three internal expansion type pile clamps 21 installed on the lifting beam 25. The adjacent spacing of the three internal expansion type pile clamps 21 is also equal to the spacing between two adjacent interlocking steel pipe piles 2 in the interlocking steel pipe pile cofferdam. Fig.13 In the azimuth description, the two inner expansion type pile clamps 21 located on both sides are aligned in a straight line, and the inner expansion type pile clamp 21 located in the middle is arranged downward, so that the arrangement or angle of the three inner expansion type pile clamps 21 matches the arrangement of each locking steel pipe pile 2 of the locking steel pipe pile cofferdam. Similarly, by reasonably distributing the clamp type pile clamps on the hanging beam 25, the purpose of simultaneously clamping and installing more locking steel pipe piles 2 can also be achieved. Considering the construction difficulty and construction efficiency, it is preferred to use a crane to lift and install two locking steel pipe piles 2 at a time.

[0066] Reference Figures 11 to 13The schematic diagram of the structure of the internal expansion type pile clamp 21 in the figure shows that the internal expansion type pile clamp 21 generally includes a main body, a plurality of upper clamping claws arranged on the main body, and a hydraulic cylinder and a transmission structure for driving the clamping claws to extend and retract; the number of the clamping claws is 4 to 12, and the clamping claws are extended to abut against the inner wall of the steel pipe pile, and the locked steel pipe pile 2 is lifted by friction. Lifting ears 23 are also arranged on the top and side of the main body of the internal expansion type pile clamp 21. The lifting ears 23 on the top are used to connect with the lifting beam 25 or the lifting rope of the crane, and the lifting ears 23 on the side of the main body are used for personnel to assist in adjusting the posture or fine-tuning the position of the internal expansion type pile clamp 21. The internal expansion type pile clamp 21 can also adopt the internal expansion type pile lifter in patent CN218843094U, or the internal expansion type pile clamp pile turner in CN115679958A. For multiple interlocking steel pipe piles 2, when in use, taking the simultaneous turning over and installation of two interlocking steel pipe piles 2 as an example, the lock buckles of the two interlocking steel pipe piles 2 on the barge need to be in a connected state (the interlocking steel pipe piles 2 can be directly connected in groups of two when loaded on the barge or before the interlocking steel pipe piles 2 are transported), and at the same time, a number of pile turners are installed on the barge, one end of each interlocking steel pipe pile 2 is placed and temporarily fixed on the pile turner, and the other end of each interlocking steel pipe pile 2 is open, providing a prerequisite for the entry of the inner expansion type pile clamp 21; when turning over, the crane lowers the inner expansion type pile clamp 21, and the manual assistance The inner expansion type pile clamp 21 with its claws in the retracted state is sent into the open end of the locking steel pipe pile 2, and then the claws of the inner expansion type pile clamp 21 are extended to press against the inner wall of the steel pipe of the locking steel pipe pile 2. The surface of the claws is rough or fixed with rubber pads, etc., and the locking steel pipe pile 2 can be fixed by friction; then, while the pile turner rotates upward, the crane lifts the inner expansion type pile clamp 21, so that the lower and upper ends of the two locking steel pipe piles 2 are simultaneously turned over and erected by force, and then the temporary fixation of the locking steel pipe piles 2 is released, and the crane simultaneously lifts the two locking steel pipe piles 2 to the installation position of the U-shaped groove 3 through the inner expansion type pile clamp 21.

[0067] Furthermore, in order to facilitate the smooth and accurate entry of a single or multiple interlocking steel pipe piles 2 into the U-shaped groove 3, before installing the interlocking steel pipe piles 2, a positioning frame 17 is installed on the concrete cofferdam 1 to assist in positioning each interlocking steel pipe pile 2; the positioning frame 17 is removed after the interlocking steel pipe pile cofferdam is installed. Figure 5 , Fig.10As shown, the embedded parts 16 use embedded steel bars, and the positioning frame 17 includes an I-shaped steel main frame, a plurality of guide rods 18 spaced apart on the I-shaped steel main frame, a vertical plate 19 welded on the bottom surface of the I-shaped steel main frame, and a reinforcing triangular plate welded between the vertical plate 19 and the bottom surface of the I-shaped steel main frame; the vertical plate 19 preferably has a curved surface that fits the outer periphery of the concrete cofferdam 1, and the larger contact surface between the vertical plate 19 and the concrete cofferdam 1 can prevent the locking steel pipe piles 2 from colliding with the positioning frame 17 and causing damage to the concrete cofferdam 1; the embedded steel bar fixation and the vertical plate 19 auxiliary positioning provide stable support for the I-shaped steel main frame; the guide rod 18 is tilted and fixed on the top surface of the I-shaped steel main frame through the support rib 20, and the guide rod 18 can be made of round steel or smooth steel bars, and the support rib 20 can be made of steel bars, etc. to ensure Ensure durability; two groups of guide rods 18 correspond to one locking steel pipe pile 2, symmetrically supporting both sides of the steel pipe of the locking steel pipe pile 2; the horizontal projection of the lower end of the guide rod 18 falls within the bottom of the U-shaped groove 3. Preferably, the distance between the horizontal projection of the lower end of the guide rod 18 and the center line of the radius of the U-shaped groove 3 is the outer diameter of the locking steel pipe pile 2, so as to ensure that the locking steel pipe pile 2 accurately falls into the center of the U-shaped groove 3, so as to facilitate the subsequent high-strength bearing grouting material 10 to be poured evenly inside and outside; each group of guide rods 18 can have one or more; the I-shaped steel main frame is provided with fixing holes corresponding to the embedded steel bars. During installation, the I-shaped steel main frame is passed through the embedded steel bars and then welded or fixed with nuts; after the steel pipe pile cofferdam is installed, the positioning frame 17 is removed and the exposed part of the embedded steel bars can be cut off. Preferably, considering the aspects of stable installation and convenience, a positioning frame 17 can be used to guide multiple locking steel pipe piles 2 into the groove, such as Fig.10 As shown, six groups of guide rods 18 are installed on one I-shaped steel main frame, of which four groups of guide rods 18 are grouped in pairs, and the remaining two groups of guide rods 18 are respectively paired with the guide rods 18 on the adjacent positioning frame 17. When the locking steel pipe pile 2 is installed by the crane, the bottom end of the offset locking steel pipe pile 2 can slide along the surface of the guide rod 18 into the U-shaped groove 3.

[0068] The present invention is mainly suitable for the construction of main pier caps of deeply buried bridges across large rivers and located on beach land, especially when the river channel is dredged in the later stage and the river has strong wandering erosion (such as the Yellow River), it is necessary to remove part of the cofferdam above the cap to ensure the flood discharge section of the river.

[0069] When the main body is designed to consider the influence of the later dredging of the river or the wandering and strong scouring river, the cap is buried deep below the ground, especially when the burial depth and water depth exceed 18m. Conventional steel sheet piles and locking steel pipe pile cofferdam supports are no longer applicable due to insufficient structural strength and rigidity. Strong supports such as double-walled steel cofferdams, caissons, and bored piles are required to ensure the safety of foundation construction. However, the above three types of cofferdams are difficult to dismantle under the condition of deep covering layers, and cannot meet the requirements of river management to ensure the flood discharge section. The combined cofferdam of the present invention overcomes the drawbacks of the traditional cofferdam in the above situation. Considering that the concrete cofferdam has a large structural rigidity and is placed in the lower part where the water and soil pressure is large, the locking steel pipe pile cofferdam is placed in the upper part where the water pressure is small, so that the whole structure is more reasonably stressed and the structure is safe and reliable. The locking steel pipe piles on the upper part of the combined cofferdam can be removed by a vibrating pile driver after the main structure is constructed out of the ground. The top of the lower concrete cofferdam is at the same elevation as the cap top, which does not affect the dredging of the river and can also be used as a cap anti-scouring structure. The lower concrete cofferdam is equipped with an air curtain and the upper locking steel pipe piles are filled with water to help sink, which can effectively ensure that the combined cofferdam can sink to the designed elevation. The locking steel pipe piles can be installed directly without being driven in, and the surrounding purlins can also be installed when they sink to the ground. The cofferdam construction speed is greatly accelerated, and the ability to construct the foundation can be achieved more quickly.

[0070] The present invention ensures that the strength and rigidity of the cofferdam support structure for the construction of deep-buried bridge caps at high and low water levels in the beach meet the safety of use, and is convenient for dismantling the cofferdam above the top surface of the cap without affecting the management requirements of the later river dredging. The dismantled cofferdam is a versatile and recyclable material, which effectively saves resources. The structure of the present invention is safe and reliable, convenient for construction, and the cofferdam above the cap can be dismantled and used for turnover, saving resources and funds. At the same time, by installing multiple steel pipe piles at one time, the construction can be significantly accelerated. It is particularly suitable for the construction of deep foundation pit caps in shallow rivers with abundant groundwater, strong wandering scouring, deep buried soil layers, and rivers that need to be dredged in the later stage, with a depth greater than 18 meters.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are within the scope of protection of the pending claims of the present invention.

Claims

1. A combined cofferdam suitable for deep-buried bridge cap foundations. Features: The combined cofferdam for the deep-buried bridge cap foundation comprises a lower concrete cofferdam (1) and an upper locking steel pipe pile (2) cofferdam, and an air curtain structure (9) for assisting the cofferdam to sink is arranged in the combined cofferdam; A U-shaped groove (3) is arranged on the top of the concrete cofferdam (1), the bottom of each locking steel pipe pile (2) of the locking steel pipe pile (2) cofferdam is inserted into the U-shaped groove (3), and high-strength support grouting material (10) is poured between the U-shaped groove (3) and the locking steel pipe pile (2) cofferdam; a plurality of annular cofferdams and internal supports are arranged on the inner side of the locking steel pipe pile (2) cofferdam; The air curtain structure (9) comprises a plurality of air niches pre-buried in the concrete cofferdam (1), ventilation steel pipes connected to the air niches, joint pipes connected to the ventilation steel pipes, and ventilation main pipes detachably connected to the joint pipes; the upper end of the joint pipe exceeds the top surface of the concrete cofferdam (1); the ventilation main pipe passes upward through the locking steel pipe piles (2) of the locking steel pipe pile (2) cofferdam.

2. The combined cofferdam suitable for the deep-buried bridge cap foundation according to claim 1, Features: The width of the notch of the U-shaped groove (3) is 18 to 24 cm larger than the outer diameter of the locking steel pipe pile (2), and the depth of the U-shaped groove (3) is 80 to 100 cm.

3. The combined cofferdam suitable for the deep-buried bridge cap foundation according to claim 1, Features: The height of the concrete cofferdam (1) is the sum of the thickness of the bottom cover and the thickness of the foundation (6), and the thickness of the concrete cofferdam (1) is 160 to 200 cm.

4. The combined cofferdam suitable for deep-buried bridge cap foundation according to claim 1, Features: The diameter of the locking steel pipe pile (2) is 82-100 cm, and the wall thickness is 12-20 mm; the locking of the locking steel pipe pile (2) can adopt the "CT" locking of welded open small steel pipes and industrial steel, or the "CO" locking of large and small steel pipes, or the locking of welded steel sheet piles.

5. The combined cofferdam suitable for the deep-buried bridge cap foundation according to claim 1, Features: The annular purlin (4) is arranged every 3 to 6 meters in the height direction. The annular purlin is welded by H-shaped steel, and the inner support is a steel pipe component. The gap between the annular purlin (4) and the cofferdam of the locking steel pipe pile (2) is filled with fine stone concrete (11).

6. The combined cofferdam suitable for the deep-buried bridge cap foundation according to claim 1, Features: The joint pipe is connected to the ventilation main pipe by thread or by a quick joint.

7. The combined cofferdam suitable for the deep-buried bridge cap foundation according to claim 1, Features: An embedded part (16) is arranged on the top of the concrete cofferdam (1), and a positioning frame (17) for assisting the positioning of the locking steel pipe pile (2) is installed on the embedded part (16).

8. A construction method for a combined cofferdam suitable for a deep-buried bridge cap foundation as claimed in any one of claims 1 to 7, It is characterized in that The following steps are involved: S1, leveling the site at the pier position, erecting a formwork (14), tying steel bars and pouring cofferdam concrete, setting a reserved U-shaped groove (3) at the center of the top surface of the lower concrete cofferdam (1), and reserving ventilation steel pipes and joint pipes of the air curtain structure (9) during construction; S2. Using a long-arm excavator (8) to stand outside the concrete cofferdam (1) to remove the soil inside the concrete cofferdam (1), the concrete cofferdam (1) is sunk until the top surface is about 50 to 100 cm above the ground; using a ventilation main pipe to extend the reserved joint pipe, using a crane to hoist the locking steel pipe pile (2) into the U-shaped groove (3) reserved at the top of the top layer of the concrete cofferdam (1). After the locking steel pipe pile (2) cofferdam is installed, high-strength bearing grouting material (10) is poured into the groove of the U-shaped groove (3) by gravity to ensure that the locking steel pipe pile (2) cofferdam and the concrete cofferdam (1) are tightly connected; S3. After all the locking steel pipe pile (2) cofferdams are installed, the brackets are welded on the locking steel pipe pile (2) cofferdams, the bottom annular purlins and the inner supports are installed, and the gap between the annular purlins and the locking steel pipe pile (2) cofferdams is filled with fine stone concrete (11); S4, using an excavator (8), grab or mud suction machine and other equipment to remove the soil in the combined cofferdam, using air curtain and water injection weight in the interlocking steel pipe pile (2) to assist the sinking, and allowing the combined cofferdam to continue to sink to the design installation position of the second layer of annular purlin and internal support, where the design elevation is about 50 to 100 cm above the ground; welding a corbel on the interlocking steel pipe pile (2) cofferdam, installing the second layer of annular purlin and internal support, and filling the gap between the purlin and the interlocking steel pipe pile (2) cofferdam with fine stone concrete (11); S5, and so on, repeat step S4 to continue taking soil so that the combined cofferdam sinks to the designed elevation, and at the same time install the remaining annular purlins and internal supports; finally, the combined cofferdam is sealed at the bottom, and the foundation (6) is constructed; S6. When the construction of the bridge pedestal (6) and pier is completed and the conditions for removing the combined cofferdam are met, the annular purlin and the inner support are removed layer by layer by backfilling, and finally the locking steel pipe piles (2) of the cofferdam are removed one by one using a vibrating pile driver.

9. The construction method of the combined cofferdam applicable to the deep-buried bridge cap foundation according to claim 8, Features: In step S2, when installing the locking steel pipe piles (2) in the U-shaped groove (3), a crane is used to install 1 to 5 locking steel pipe piles (2) each time.

10. The construction method of the combined cofferdam applicable to the deep-buried bridge cap foundation according to claim 8, Features: When installing the locking steel pipe piles (2), a positioning frame (17) is installed on the concrete cofferdam (1) to assist in positioning each locking steel pipe pile (2); after the locking steel pipe pile (2) cofferdam is installed, the positioning frame (17) is removed.

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