Combined cofferdam suitable for deeply-buried bridge bearing platform foundation

Abstract

The utility model 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. 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 bottom of each fore shaft steel pipe pile of the fore shaft steel pipe pile cofferdam is inserted into the U-shaped groove, and a high-strength support grouting material is poured between the U-shaped groove and the fore shaft steel pipe pile cofferdam; a plurality of annular cofferdams are arranged on the inner side of the fore shaft steel pipe pile cofferdam; the combined cofferdam structure is more reasonable in stress, safe and reliable; according to the combined cofferdam, sinking assisting measures such as a built-in air curtain and water injection ballasting in the upper locking opening steel pipe piles are adopted, it can be effectively guaranteed that the combined cofferdam can sink to the designed elevation, and the defects that a concrete cofferdam and a steel sheet pile cofferdam are combined to sink difficultly, and the suitable foundation embedding depth is not large are overcome.

Description

Technical Field

[0001] The utility model belongs to the technical field of bridge construction foundation construction, and particularly relates to a combined cofferdam applicable to a deep-buried bridge pier cap foundation. Background Art

[0002] In the construction of the main pier cap of a deep-buried bridge located on a floodplain across a large river or a large river, in order to ensure the slope stability and effective water stop during the pier cap construction, a cofferdam is an indispensable temporary structure. For rivers with dredging and strong scouring in the later stage of the river course (such as the Yellow River), it is necessary to demolish the part of the cofferdam above the pier cap to ensure the flood discharge section of the river. In the construction of deep foundation pits of pier caps located on floodplains across large rivers or large rivers, at present, domestic general technologies such as concrete caisson cofferdams, double-wall steel cofferdams, steel sheet pile cofferdams, locked steel pipe pile cofferdams, and bored pile cofferdams are used to construct deep foundation pits of pier caps. However, the above technologies all have a certain scope of applicability and limitations. Among them, the construction period of concrete caisson cofferdams, double-wall steel cofferdams, and bored pile cofferdams is long, the cost is high, and they cannot be demolished when the surrounding overburden is deeply buried after construction, which has a great impact on the later dredging of the river course and it is difficult to pass the approval of the river course management department; steel sheet pile cofferdams and locked steel pipe pile cofferdams have the characteristics of being light, easy to demolish, reusable, short construction period, and low cost, but the integrity is poor, the horizontal load they can bear is small, and they are not applicable to deep foundation pits greater than 18 meters.

[0003] Therefore, it is necessary to provide an improved technical solution to overcome the deficiencies of the above-mentioned existing technologies, which is suitable for deep foundation pits, has a relatively fast construction speed, and is easy to demolish in the later stage. Content of the Utility Model

[0004] The purpose of the utility model is to overcome the deficiencies of the existing technologies and provide a combined cofferdam applicable to a deep-buried bridge pier cap foundation.

[0005] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0006] A combined cofferdam applicable to a deep-buried bridge pier cap foundation includes a lower concrete cofferdam and an upper locked steel pipe pile cofferdam, and an air curtain structure for assisting the cofferdam to sink is arranged inside the combined cofferdam;

[0007] A U-shaped groove is arranged at the top of the concrete cofferdam, the bottoms of the locked steel pipe piles of the locked steel pipe pile cofferdam are inserted into the U-shaped groove, and high-strength support grout is poured between the U-shaped groove and the locked steel pipe pile cofferdam; several annular cofferdams and internal supports are arranged inside the locked steel pipe pile cofferdam;

[0008] The air curtain structure includes several air niches embedded in the concrete cofferdam, ventilation steel pipes connected to the air niches, joint pipes connected to the ventilation steel pipes, and a ventilation main pipe detachably connected to the joint pipes; the upper end of the joint pipe extends beyond the top surface of the concrete cofferdam; the ventilation main pipe passes upward through the lock steel pipe piles of the lock steel pipe pile cofferdam.

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

[0010] Further, the height of the concrete cofferdam is the sum of the bottom seal thickness and the cap thickness, and the thickness of the concrete cofferdam is 160 - 200 cm.

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

[0012] Further, a circular purlin is arranged every 3 - 6 m in the height direction of the lock steel pipe pile cofferdam. The circular purlin is fabricated by welding H-shaped steel, and the internal support adopts steel pipe members; the gap between the circular purlin and the lock steel pipe pile cofferdam is filled with fine aggregate concrete.

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

[0014] Further, embedded parts are arranged at the top of the concrete cofferdam, and a positioning frame for assisting in positioning the lock steel pipe pile is installed on the embedded parts.

[0015] The present utility model also proposes a construction method using the aforementioned combined cofferdam applicable to deep-buried bridge cap foundations, which is characterized by including the following steps:

[0016] S1. Level the site at the pier position, erect formwork, bind steel bars and pour cofferdam concrete, and set a reserved U-shaped groove at the center of the top surface of the lower concrete cofferdam. During construction, reserve the ventilation steel pipe and joint pipe of the air curtain structure.

[0017] S2. Use a long-arm excavator to stand outside the concrete cofferdam to remove the soil inside the concrete cofferdam, so that the concrete cofferdam sinks until the top surface is about 50 - 100 cm above the ground; use the ventilation main pipe to extend the reserved joint pipe, and use a crane to hoist the lock steel pipe pile into the reserved U-shaped groove at the top of the top layer of the concrete cofferdam. After the installation of the lock steel pipe pile cofferdam is completed, pour high-strength bearing grouting material into the notch of the U-shaped groove by the gravity method to ensure the dense connection between the lock steel pipe pile cofferdam and the concrete cofferdam.

[0018] After all the lock-pile steel pipe cofferdams are installed, brackets are welded on the lock-pile steel pipe cofferdams, and the bottom ring-shaped purlins and internal supports are installed. The gaps between the ring-shaped purlins and the lock-pile steel pipe cofferdams are filled with fine aggregate concrete.

[0019] S4. Use equipment such as excavators, grab buckets or dredgers to remove the soil inside the combined cofferdam. Adopt air curtains and water ballasting by injecting water into the lock-pile steel pipe cofferdams to assist in sinking, so that the combined cofferdam continues to sink to the design installation position of the second layer of ring-shaped purlins and internal supports, where the design elevation is about 50 - 100 cm higher than the ground. Brackets are welded on the lock-pile steel pipe cofferdams, and the second layer of ring-shaped purlins and internal supports are installed. The gaps between the purlins and the lock-pile steel pipe cofferdams are filled with fine aggregate concrete.

[0020] S5. And so on, repeat step S4 to continue taking soil to sink the combined cofferdam to the design elevation position, and install the remaining ring-shaped purlins and internal supports at the same time. Finally, the combined cofferdam is sealed at the bottom, and the construction of the bearing platform is carried out.

[0021] S6. After the construction of the bridge bearing platform, pier body, etc. is completed and the combined cofferdam can be demolished, backfill the soil layer by layer to demolish the ring-shaped purlins and internal supports, and finally use a vibrating pile driver to pull out the lock-pile steel pipe cofferdams one by one.

[0022] Further, in step S2, when installing the lock-pile steel pipe cofferdams in the U-shaped groove, 1 - 5 lock-pile steel pipe cofferdams are installed by the crane each time. Preferably, 2 lock-pile steel pipe cofferdams are installed by the crane each time.

[0023] Further, when installing the lock-pile steel pipe cofferdams, a positioning frame is installed on the concrete cofferdam to assist in positioning each lock-pile steel pipe cofferdam. The positioning frame is removed after the lock-pile steel pipe cofferdam is installed.

[0024] The beneficial effects of the present utility model are as follows:

[0025] 1) The combined cofferdam composed of the concrete cofferdam and the lock-pile steel pipe cofferdam of the present utility model has a large structural stiffness for the concrete cofferdam, which is placed at the lower part with large water and soil pressure, and the lock-pile steel pipe cofferdam is placed at the upper part with small water pressure, making the whole structure more reasonable in force and the structure safe and reliable.

[0026] 2) The combined cofferdam of the present utility model adopts sinking assistance measures such as built-in air curtains and water ballasting by injecting water into the upper lock-pile steel pipe cofferdams, which can effectively ensure that the combined cofferdam can sink to the design elevation, overcoming the disadvantages of difficult combined sinking of concrete cofferdams and steel sheet pile cofferdams and limited applicable foundation embedment depth.

[0027] 3) The combined cofferdam of the present utility model overcomes the drawbacks of the long construction period of traditional concrete cofferdams, and overcomes the drawbacks of the overly long single-pile length of traditional steel sheet piles and locked-joint steel pipe pile cofferdams in ultra-deep geology (considering that the general total length of the calculated embedded depth of traditional steel sheet piles or locked-joint steel pipe piles is more than 30 meters), the difficulty in driving and the long construction period; the combined cofferdam provided by the present utility model reduces the pouring height of the concrete cofferdam. At the same time, the locked-joint steel pipe pile cofferdam does not need to be driven, the installation speed is high, the installation accuracy is easy to control, and the operation is simple, effectively reducing the construction difficulty and improving the construction efficiency.

[0028] 4) In the installation stage of the combined cofferdam of the present utility model, in addition to the traditional method of installing locked-joint steel pipe piles one by one, 2 or more locked-joint steel pipe piles can be installed at one time by a crane, improving the efficiency; at the same time, using a crane for installation instead of a pile driver in the installation stage can save equipment costs.

[0029] 5) The upper part of the combined cofferdam of the present utility model uses locked-joint steel pipe piles to replace the upper concrete cofferdam, which can be pulled out by a vibrating pile driver after the main structure of the bridge emerges from the ground, overcoming the drawback that conventional concrete cofferdams and double-wall steel cofferdams cannot be demolished in deep-buried geology; the demolished locked-joint steel pipe pile cofferdam can be recycled, saving resources and thus saving funds; the top of the lower concrete cofferdam is at the same elevation as the top of the bearing platform, which does not affect river channel dredging and can also be used as a scour prevention structure for the bearing platform. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The schematic drawings forming a part of this application are used to provide a further understanding of the present utility model. The illustrative embodiments and descriptions thereof of the present utility model are used to explain the present utility model and do not constitute an improper limitation of the present utility model. Among them:

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

[0032] Figure 2 is Figure 1 a sectional view of the concrete cofferdam of

[0033] Figure 3 is Figure 1 a sectional view of the locked-joint steel pipe pile cofferdam of

[0034] Figure 4 is a construction schematic diagram of pouring the concrete cofferdam of an embodiment of the present utility model.

[0035] Figure 5 is a hoisting construction schematic diagram of the locked-joint steel pipe pile of an embodiment of the present utility model.

[0036] Figure 6 is a construction schematic diagram of the locked-joint steel pipe pile cofferdam of an embodiment of the present utility model.

[0037] Figure 7 Schematic diagram of the sinking construction of the combined cofferdam according to an embodiment of the present utility model.

[0038] Figure 8 Schematic diagram of the construction of the combined cofferdam cap according to an embodiment of the present utility model.

[0039] Figure 9 Schematic diagram of the filling between the U-shaped notches of the combined cofferdam according to an embodiment of the present utility model.

[0040] Figure 10 Schematic diagram of the usage state of the positioning frame according to an embodiment of the present utility model.

[0041] Figure 11 Front view structural schematic diagram of the internal expansion type pile gripper according to an embodiment of the present utility model.

[0042] Figure 12 It is Figure 11 Top view structural schematic diagram of

[0043] Figure 13 Structural schematic diagram of the internal expansion type pile gripper according to another embodiment of the present utility model.

[0044] In the figure: 1. Concrete cofferdam; 2. Locked steel pipe pile; 3. U-shaped groove; 4. Ring-shaped purlin; 5. Bottom sealing concrete; 6. Cap; 7. Mud suction equipment; 8. Excavator; 9. Air curtain structure; 10. High-strength support grout; 11. Fine aggregate concrete; 12. Bored pile; 13. Corbels; 14. Formwork; 15. Sand cushion; 16. Embedded parts; 17. Positioning frame; 18. Guide rod; 19. Vertical plate; 20. Support bars; 21. Internal expansion type pile gripper; 22. Claw; 23. Lifting lug; 24. Claw; 25. Suspension beam. Detailed implementation manners

[0045] The technical solutions in the embodiments of the present utility model will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model belong to the scope of protection of the present utility model.

[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 directions or positional relationships based on the directions 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 direction. Therefore, they cannot be understood as limitations on the present invention. The terms "connected" and "connection" 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 the 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-mentioned 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-sealing concrete 5 and the thickness of the bearing platform 6. The specific wall thickness and steel bar configuration are determined according to calculations, and the available thickness is 160 - 200 cm. The lock-pile steel pipe cofferdam is determined according to calculations. Steel pipes with a diameter of 82 - 100 cm and a wall thickness of 12 - 20 mm can be used for processing. The lock can adopt the "CT" lock of welded open small steel pipes and I-beams, or the "CO" lock of large and small steel pipes, or the lock of welded steel sheet piles. A circular collar 4 and internal supports are arranged at intervals of 3 - 6 m in the height direction of the lock-pile steel pipe cofferdam according to the calculation conditions. The circular collar 4 and internal supports can be fabricated by welding H-shaped steel. Fine aggregate concrete 11 is filled between the circular collar 4 and internal supports and the lock-pile steel pipe cofferdam to ensure effective force transfer of the structure.

[0053] Further, as Figure 4 、 Figure 5 shown, the joint pipe is connected to the ventilation main pipe by thread or through a quick connector; the joint pipe extends a certain distance beyond the concrete top surface; the ventilation main pipe is mainly made of steel pipe, and a high-pressure hose is connected to the top according to needs. Before installing the lock-pile steel pipe cofferdam, first connect the ventilation main pipe and the joint pipe. At this time, the ventilation main pipe stands on the top surface of the concrete cofferdam 1, and then the lock-pile steel pipe 2 is lifted by a crane and lowered with the lock-pile steel pipe 2 aligned with the ventilation main pipe.

[0054] Further, as Figure 5 shown, a buried part 16 is provided at the top of the concrete cofferdam 1, and a positioning frame 17 for assisting in positioning the lock-pile steel pipe 2 is installed on the buried part 16; the structure of the positioning frame 17 is not limited as long as it can satisfy guiding the bottom of the lock-pile steel pipe 2 into the U-shaped groove 3. After the lock-pile steel pipe cofferdam is installed and before the concrete cofferdam 1 sinks underground, the positioning frame 17 is removed. For example, a section steel type positioning frame 17 can be directly adopted, the positioning frame 17 is welded to the buried part 16, and the positioning frame 17 is removed by cutting off the buried part 16 during removal.

[0055] The present utility model also proposes a construction method for a combined cofferdam applicable to a deep-buried bridge bearing platform foundation, including the following steps:

[0056] S1. Level the site at the pier position, set up the formwork 14 (using the rammed sand cushion 15 as the inclined soil mold for the cutting edge), bind the steel bars and pour the cofferdam concrete. A reserved U-shaped groove 3 is provided at the center of the top surface of the lower concrete cofferdam 1, and the ventilation steel pipe and joint pipe of the air curtain structure 9 are reserved during construction; note that the concrete cofferdam 1 is cast in layers along the height direction to form a ring; Figure 4 is the formwork 14 of the concrete cofferdam 1 that has been set up;

[0057] Among them, the construction method of the U-shaped groove 3 is as follows: When building the formwork 14 of the concrete cofferdam 1, use bamboo plywood or steel formwork 14 to reserve the U-shaped groove 3, fix the position of the formwork 14 of the U-shaped groove 3 to ensure that its position does not shift and there is no leakage of slurry during concrete pouring; after the concrete cofferdam 1 solidifies, remove the formwork 14 at the groove opening, clean the garbage in the groove, and it is also possible to grind the uneven parts at the bottom of the groove;

[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 - 100 cm higher than the ground; Connect the ventilation main pipe to the extended joint pipe, and use a crane to hoist the lock-pile steel pipe pile 2 into the U-shaped groove 3 reserved at the top of the concrete cofferdam 1. After the installation of the lock-pile steel pipe pile cofferdam is completed, pour high-strength bearing grout 10 into the groove opening of the U-shaped groove 3 by the gravity method to ensure the dense connection between the lock-pile steel pipe pile cofferdam and the concrete cofferdam 1; The lock-pile steel pipe pile cofferdam can be hoisted by a crawler crane, tower crane or floating crane; Figure 5 is the lock-pile steel pipe pile 2 being hoisted; Figure 10 schematically shows the high-strength bearing grout 10;

[0059] S3. After all the lock-pile steel pipe pile cofferdams are installed, weld brackets 13 on the lock-pile steel pipe pile cofferdams, install the bottom ring-shaped purlin 4 and internal supports, and fill the gap between the ring-shaped purlin 4 and the lock-pile steel pipe pile cofferdam with fine aggregate concrete 11; Figure 9 schematically shows the filled fine aggregate concrete 11;

[0060] S4. As shown in Figure 6 , use equipment such as an excavator 8, grab or dredger to remove the soil inside the combined cofferdam, and use an air curtain and water ballast injection into the lock-pile steel pipe pile 2 to assist in sinking, so that the combined cofferdam continues to sink to the design and installation position of the second layer of ring-shaped purlin 4 and internal supports, where the design elevation is about 50 - 100 cm higher than the ground; Weld brackets 13 on the lock-pile steel pipe pile cofferdam, install the second layer of ring-shaped purlin 4 and internal supports, and fill the gap between the purlin and the lock-pile steel pipe pile cofferdam with fine aggregate concrete 11; In this step, it is necessary to pay attention to symmetrically and evenly removing the soil inside the cofferdam;

[0061] In addition, when the geology is mainly cohesive soil and the seepage volume is not large, mainly use an excavator 8 to drain and excavate the soil; when the geology is mainly sandy soil and the seepage volume is relatively large, mainly use a dredging equipment 7 to excavate the soil without drainage by suction; Figure 7 is the dredging equipment 7 in operation;

[0062] The water ballast injection into the lock-pile steel pipe pile 2 can also be replaced with materials such as sand or crushed stone filling; These auxiliary sinking measures are to avoid the difficulty of sinking caused by insufficient self-weight of the cofferdam to overcome the frictional resistance;

[0063] S5. And so on. Repeat step S4 to continue taking soil until the combined cofferdam sinks to the designed elevation. Meanwhile, install the remaining circular purlins 4 and internal supports; pour the concrete 5 for the cofferdam bottom seal, and construct the bored piles 12 and the cap 6 of the pile cap. Figure 8 The outer contour (dotted line) of the pile cap 6 is schematically drawn.

[0064] S6. When the construction of the bridge pile cap 6, pier body, etc. is completed and the condition for demolishing the combined cofferdam is met, backfill the soil layer by layer to demolish the circular purlins 4 and the internal supports, and finally use a vibrating pile driver to pull out the lock-pile steel pipe pile cofferdam one by one.

[0065] Furthermore, in step S2, when installing the lock-pile steel pipe piles 2 in the U-shaped groove 3, 1 - 5 lock-pile steel pipe piles 2 are installed by the crane each time. Specifically, when the crane installs one lock-pile steel pipe pile 2 at a time, a clamp-type pile gripper or an internal expanding pile gripper 21 is used under the lifting rope of the crane; when the crane installs multiple lock-pile steel pipe piles 2 at a time, multiple clamping mechanisms are required, and a special lifting tool with the corresponding number of lock-pile steel pipe piles 2 is made according to the number of piles to be clamped. As Figure 11 、 12 shown, it is a structural schematic diagram of a lifting tool for lifting two lock-pile steel pipe piles 2 at one time. The lifting tool includes a lifting beam 25 and two internal expanding pile grippers 21 installed on the lifting beam 25, which have the same position layout as the two lock-pile steel pipe piles 2 during installation. These two internal expanding pile grippers 21 are aligned in a row, and the center distance between these two internal expanding pile grippers 21 is equal to the center distance between two adjacent lock-pile steel pipe piles 2 in the lock-pile steel pipe pile cofferdam. As Figure 13 shown, it is a lifting tool for lifting three lock-pile steel pipe piles 2 at one time. The lifting tool includes a lifting beam 25 and three internal expanding pile grippers 21 installed on the lifting beam 25. The adjacent distance between these three internal expanding pile grippers 21 is also equal to the distance between two adjacent lock-pile steel pipe piles 2 in the lock-pile steel pipe pile cofferdam. At the same time, according to the orientation description in Figure 13 , the two internal expanding pile grippers 21 on both sides are aligned on a straight line, and the internal expanding pile gripper 21 in the middle is set to be inclined downward, so that the arrangement or included angle of these three internal expanding pile grippers 21 matches the arrangement of each lock-pile steel pipe pile 2 in the lock-pile steel pipe pile cofferdam. Similarly, by reasonably distributing the clamp-type pile grippers on the lifting beam 25, the purpose of clamping and installing more lock-pile steel pipe piles 2 at the same time can also be achieved. Considering the construction difficulty and construction efficiency comprehensively, preferably, the crane is used to lift and install two lock-pile steel pipe piles 2 at one time.

[0066] Refer to Figures 11 to 13Schematic diagram of the internal expansion type pile gripper 21. The internal expansion type pile gripper 21 generally includes a main body, several upper jaws arranged on the main body, and a hydraulic cylinder and a transmission structure for driving the jaws to expand and contract; the number of jaws is 4 to 12. After the jaws extend, they abut against the inner wall of the steel pipe pile, and the lock seam steel pipe pile 2 is lifted by using friction. Lifting lugs 23 are also arranged on the top and side of the main body of the internal expansion type pile gripper 21. The lifting lug 23 on the top is used to connect with the lifting beam 25 or the lifting rope of the crane, and the lifting lug 23 on the side of the main body is used for personnel to assist in adjusting the attitude or fine-tuning the position of the internal expansion type pile gripper 21. The internal expansion type pile gripper 21 can also adopt the internal expansion type pile lifter in Patent CN218843094U or the internal expansion type pile gripper and pile turner in CN115679958A. For multiple lock seam steel pipe piles 2, when in use, taking the simultaneous turning over and installation of two lock seam steel pipe piles 2 as an example, the locks of these two lock seam steel pipe piles 2 on the barge need to be in a connected state (the lock seam steel pipe piles 2 can be directly connected in pairs when loaded onto the barge or before the transportation of the lock seam steel pipe piles 2). At the same time, several pile turners are installed on the barge. One end of each lock seam steel pipe pile 2 is placed and temporarily fixed on the pile turner, and the other end of each lock seam steel pipe pile 2 is open, providing a prerequisite for the entry of the internal expansion type pile gripper 21. When turning over, the crane lowers the internal expansion type pile gripper 21, and manually assists in sending the internal expansion type pile gripper 21 with the jaws in the contracted state into the open end of the lock seam steel pipe pile 2. Then, the jaws of the internal expansion type pile gripper 21 extend and abut against the inner wall of the steel pipe of the lock seam steel pipe pile 2. The surface of the jaws is rough or fixed with a rubber pad, etc., and the lock seam steel pipe pile 2 can be fixed by using friction. After that, while the pile turner rotates upward, the crane lifts the internal expansion type pile gripper 21, so that the lower and upper ends of the two lock seam steel pipe piles 2 are simultaneously stressed and turned over and erected. Then, the temporary fixation of the lock seam steel pipe pile 2 is released, and the crane hoists the two lock seam steel pipe piles 2 to the installation position of the U-shaped groove 3 through the internal expansion type pile gripper 21.

[0067] Furthermore, in order to facilitate the smooth and accurate entry of a single or multiple lock seam steel pipe piles 2 into the U-shaped groove 3, before installing the lock seam steel pipe piles 2, a positioning frame 17 is installed on the concrete cofferdam 1 to assist in positioning each lock seam steel pipe pile 2; the positioning frame 17 is removed after the installation of the lock seam steel pipe pile cofferdam is completed. As Figure 5 、 Figure 10As shown, the embedded part 16 uses embedded steel bars. The positioning frame 17 includes a main I-shaped steel frame, several guiding rods 18 spaced on the main I-shaped steel frame, a vertical plate 19 welded to the bottom surface of the main I-shaped steel frame, and a reinforcing triangular plate welded between the vertical plate 19 and the bottom surface of the main I-shaped steel frame. The vertical plate 19 preferably has a curved surface that fits the outer periphery of the concrete cofferdam 1. The larger contact surface between the vertical plate 19 and the concrete cofferdam 1 can prevent damage to the concrete cofferdam 1 when the locked steel pipe pile 2 impacts the positioning frame 17. The fixing of the embedded steel bars and the auxiliary positioning of the vertical plate 19 provide stable support for the main I-shaped steel frame. The guiding rods 18 are obliquely fixed on the top surface of the main I-shaped steel frame through support ribs 20. The guiding rods 18 can be made of round steel or plain round bars, etc., and the support ribs 20 are made of steel bars, etc. to ensure firm and durable. Two groups of guiding rods 18 correspond to one locked steel pipe pile 2, symmetrically supporting both sides of the steel pipe of the locked steel pipe pile 2. The horizontal projection of the lower end of the guiding rod 18 falls within the bottom of the U-shaped groove 3. Preferably, the distance from the horizontal projection of the lower end of the guiding rod 18 to the radius midline of the U-shaped groove 3 is the outer diameter of the locked steel pipe pile 2, which can ensure that the locked steel pipe pile 2 accurately falls to the center of the U-shaped groove 3, facilitating the uniform pouring of the subsequent high-strength bearing grout 10 inside and outside. Each group of guiding rods 18 can have one or more. Fixed holes corresponding to the embedded steel bars are provided on the main I-shaped steel frame. During installation, after passing the main I-shaped steel frame through the embedded steel bars, it is fixed by welding or 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 stable installation and convenience, multiple locked steel pipe piles 2 can be guided into the groove on one positioning frame 17, such as Figure 10 As shown, six groups of guiding rods 18 are installed on one main I-shaped steel frame. Four of the groups of guiding rods 18 are in pairs, and the other two groups of guiding rods 18 are paired with the groups of guiding rods 18 on the adjacent positioning frames 17 respectively. When the crane installs the locked steel pipe pile 2, the bottom end of the offset locked steel pipe pile 2 can slide along the surface of the guiding rod 18 into the U-shaped groove 3.

[0068] The utility model is mainly applicable to the construction of the deep - buried bridge main pier cap located on the beach across large rivers. Especially for rivers with dredging in the later stage and strong scouring due to wandering (such as the Yellow River), it is necessary to remove the cofferdam above the cap to ensure the river flood - discharge section.

[0069] When the main body is designed and the bearing platform is buried deep below the ground surface considering the influence of later river dredging or highly scouring rivers with strong wandering characteristics, especially when the buried depth and water depth exceed 18m, conventional steel sheet piles and lock-joint steel pipe pile cofferdams are no longer applicable due to insufficient structural strength and stiffness. Strong support such as double-wall steel cofferdams, caissons, and bored piles is required to ensure the safety of foundation construction. However, the above three types of cofferdams are difficult to demolish in the case of deep overburden layers and cannot meet the requirements of river management to ensure the flood discharge cross-section. The combined cofferdam of the present utility model overcomes the drawbacks existing in the above-mentioned traditional cofferdams. Considering that the concrete cofferdam has a large structural stiffness and is placed in the lower part with greater water and soil pressure, and the lock-joint steel pipe pile cofferdam is placed in the upper part with smaller water pressure, the entire structure is more reasonable in force and the structure is safe and reliable. The upper lock-joint steel pipe piles of the combined cofferdam can be pulled out by a vibrating pile driver after the main structure is constructed above the ground surface. The top of the lower concrete cofferdam is at the same elevation as the top of the bearing platform, which does not affect river dredging and can also be used as an anti-scouring structure for the bearing platform. Auxiliary sinking measures such as air curtains are set in the lower concrete cofferdam and water ballasting is injected into the upper lock-joint steel pipe piles, which can effectively ensure that the combined cofferdam can sink to the design elevation. The lock-joint steel pipe piles can be directly installed without driving, and the waling can also be installed when it sinks to the ground surface, greatly accelerating the construction speed of the cofferdam and enabling the ability to construct the bearing platform relatively quickly.

[0070] The present utility model ensures that the structural strength and stiffness of the cofferdam for the construction of the deep-buried bridge bearing platform with high and low water levels in the beach meet the requirements of use safety, and it is convenient to demolish the part of the cofferdam above the top surface of the bearing platform without affecting the management requirements of later river dredging. The demolished cofferdam is a general-purpose and reusable material, effectively saving resources. The structure of the present utility model is safe and reliable, convenient for construction, the cofferdam above the bearing platform can be demolished and reused, saving resources and funds. At the same time, by installing multiple steel pipe piles at one time, the construction progress can be significantly accelerated. It is especially suitable for the construction of deep foundation pit bearing platforms with rich groundwater, highly scouring rivers with strong wandering characteristics in shallow beaches, deep buried soil layers, rivers that need to be dredged later, and depths greater than 18 meters.

[0071] The above are only the preferred embodiments of the present utility model and are not intended to limit the present utility model. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present utility model are within the scope of protection of the pending claims of the present utility model.

Claims

1. A combined cofferdam suitable for a deep-buried bridge cap foundation, characterized in that: The combined cofferdam for the 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; 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 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 cofferdam; a plurality of annular cofferdams and internal supports are arranged on the inner side of the locking steel pipe pile 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 cofferdam.

2. The combined cofferdam suitable for deep-buried bridge cap foundation according to claim 1 is characterized in that: 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 deep-buried bridge cap foundation according to claim 1 is characterized in that: 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 is characterized in that: 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 deep-buried bridge cap foundation according to claim 1 is characterized in that: An annular purlin (4) is arranged every 3 to 6 meters in the height direction of the locking steel pipe pile cofferdam. 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 locking steel pipe pile cofferdam is filled with fine stone concrete (11).

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

7. The combined cofferdam suitable for deep-buried bridge cap foundation according to claim 1 is characterized in that: 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).

Images