Precast tubular pile sinking assisting negative pressure pile cap

Abstract

A sinking-assisting negative pressure pile cap for a prefabricated pipe pile comprises a pile cap body, a vacuum pump, a storage battery, an automatic control unit, a pressure release valve, a starting switch and a flexible sealing gasket. By integrating the negative pressure pile cap of the air exhaust system, two core resistance sources of pile sinking, namely the uprush resistance of a compressed air cushion in the pile pipe and the upward friction resistance of a soil plug, are synchronously and directly solved. The hammering energy transmission efficiency is maximized, the pile sinking speed is remarkably increased, energy consumption and equipment loss are reduced, soil plug compaction is actively delayed through the lifting effect of negative pressure, and the construction difficulty and the sinking rejection risk of a complex stratum are reduced. Meanwhile, the pressure of the inner cavity of the pipe pile can be managed on the premise that the complexity of the piling process is not increased, the pile sinking efficiency is improved, pile body trepanning is omitted, the structural integrity is guaranteed, meanwhile, the complexity of field operation is not increased, and the problems of section weakening and stress concentration caused by trepanning to a pile body concrete structure or a steel pipe wall are solved.

Description

Technical Field

[0001] This invention belongs to the technical field of auxiliary equipment for precast pile foundation construction in civil engineering, and specifically relates to a negative pressure pile cap for precast pipe pile driving method construction, which improves pile driving efficiency and reduces soil jamming effect by actively forming negative pressure inside the precast pipe pile. Background Technology

[0002] When using hammering or vibration methods to drive precast concrete pipe piles or steel pipe piles, a soil plug forms inside the pile pipe, trapping some air. As the pile penetrates, the air inside the pipe is violently compressed, generating enormous upward pressure. This severely counteracts the downward energy of the pile hammer, leading to a significant decrease in pile driving efficiency, a surge in the number of hammer blows, and even pile driving safety accidents. The traditional solution is to create vent holes in the pile to release pressure, but this method not only increases the pile manufacturing process and weakens the pile structure cross-section, but also fails to solve the problem of frictional resistance between the soil plug and the pipe wall. The occlusion effect of the soil plug significantly increases the total resistance of pile driving, especially in dense cohesive soil layers, potentially causing premature pile "rejection." Currently, the industry lacks an integrated device that can simultaneously solve the two major problems of "compressed air backlash" and "soil plug frictional occlusion," thus restricting construction efficiency and cost control. Summary of the Invention

[0003] To address the aforementioned problems, the present invention aims to provide a negative pressure pile cap for aiding the settlement of precast pipe piles.

[0004] To achieve the above objectives, the precast pipe pile sinking-assisted negative pressure pile cap provided by the present invention includes a pile cap body, a vacuum pump, a storage battery, an automatic control unit, a pressure relief valve, a start switch, and a flexible sealing gasket. The pile cap body is a hollow cylindrical structure, with its lower end edge extending downwards to form a cap wall for covering the top of the precast pipe pile. One side of the circumferential wall has an exhaust hole, and the other side has a pressure relief hole for installing the pressure relief valve. A connecting hole is formed in the center of the bottom surface. The vacuum pump, storage battery, and automatic control unit are located inside the pile cap body, and the exhaust port of the vacuum pump is connected to the exhaust hole through a sealed pipeline. The start switch is installed outside the pile cap body and has a built-in charging interface for charging the storage battery. The automatic control unit is electrically connected to the vacuum pump, storage battery, and start switch. The storage battery supplies power to the vacuum pump and automatic control unit. The flexible sealing gasket is located in the upper part of the inner wall of the cap and has an opening in its center corresponding to the connecting hole on the pile cap body.

[0005] The automatic control unit uses an STM32 series microcontroller as the main control chip and is equipped with an MPXV5004 series vacuum pressure sensor.

[0006] The pile cap body is made of steel and has sufficient strength and rigidity to withstand hammer loads.

[0007] The flexible sealing gasket is made of high-strength rubber material to ensure that the pile cap body can form an airtight seal when it is placed on the top of the precast pipe pile.

[0008] The precast pipe pile sinking negative pressure pile cap provided by this invention has the following beneficial effects:

[0009] By integrating a vacuum system into the negative pressure pile cap, the two core resistance sources for pile driving are simultaneously and directly addressed: the upward resistance of the compressed air cushion inside the pile tube and the upward friction of the soil plug. This not only maximizes the efficiency of hammer energy transfer, significantly increasing pile driving speed and reducing energy consumption and equipment wear, but also actively delays soil plug compaction through the "lifting" effect of negative pressure, reducing the construction difficulty and "rejection" risk in complex strata. Simultaneously, as a replacement for traditional pile caps, the negative pressure pile cap can manage the internal pressure of the pipe pile without increasing the complexity of the pile driving process. While improving pile driving efficiency, eliminating the need for drilling holes in the pile body, and ensuring structural integrity, it does not increase the complexity of on-site operations. It avoids the cross-sectional weakening and stress concentration problems caused by drilling into the pile body's concrete structure or steel pipe wall, ensuring the structural integrity and design bearing capacity of the pile body, while also making the pile manufacturing process more standardized and simplified. Attached Figure Description

[0010] Figure 1 This is a front view of the precast pipe pile sinking negative pressure pile cap provided by the present invention.

[0011] Figure 2 A schematic diagram of the usage status of the precast pipe pile sinking negative pressure pile cap provided by the present invention. Detailed Implementation

[0012] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0013] like Figures 1-2 As shown, the precast pipe pile sinking negative pressure pile cap provided by the present invention includes a pile cap body 1, a vacuum pump 2, a storage battery 3, an automatic control unit 4, a pressure relief valve 5, a start switch 7, and a flexible sealing gasket 10; wherein, the pile cap body 1 is a hollow cylindrical structure, with the lower end edge extending downward to form a cap wall 11 for covering the top of the precast pipe pile 9, an exhaust hole 6 is formed on one side of the circumferential wall, a pressure relief hole for installing the pressure relief valve 5 is formed on the other side, and a connecting hole 8 is formed in the middle of the bottom surface; the vacuum pump 2, the storage battery 3, and the automatic control unit 4, pressure relief valve 5, start switch 7, and flexible sealing gasket 10 are also included. The control unit 4 is located inside the pile cap body 1, and the outlet of the vacuum pump 2 is connected to the exhaust port 6 through a sealed pipeline; the start switch 7 is installed on the outside of the pile cap body 1 and has a built-in charging interface for charging the battery 3; the automatic control unit 4 is electrically connected to the vacuum pump 2, the battery 3 and the start switch 7 respectively; the battery 3 supplies power to the vacuum pump 2 and the automatic control unit 4; the flexible sealing gasket 10 is located in the upper part of the cap wall 11, and has an opening in the middle that corresponds to the connecting hole 8 on the pile cap body 1.

[0014] The automatic control unit 4 uses an STM32 series microcontroller as the main control chip and is equipped with an MPXV5004 series vacuum pressure sensor.

[0015] The pile cap body 1 is made of steel and has sufficient strength and rigidity to withstand hammer loads.

[0016] The flexible sealing gasket 10 is made of high-strength rubber material to ensure that the pile cap body 1 can form an airtight seal when it is placed on the top of the precast pipe pile 9.

[0017] The installation and use method of the precast pipe pile sinking negative pressure pile cap provided by the present invention is described below:

[0018] Lifting and sealing: After the precast pipe pile 9 is driven to the predetermined starting elevation, a crane is used to lift the negative pressure pile cap and accurately cover the top of the precast pipe pile 9 with the cap wall 11 and the flexible sealing gasket 10 inside it. The initial sealing is automatically completed by the self-weight of the negative pressure pile cap and the deformation of the flexible sealing gasket 10.

[0019] System Start-up: The operator presses the start switch 7. Under the control of the automatic control unit 4, the vacuum pump 2 is started. The vacuum pump 5 quickly draws most of the air inside the precast pipe pile 9 through the opening on the flexible sealing gasket 10 and the connecting hole 8 on the pile cap body 1, and discharges it to the outside through the exhaust hole 6.

[0020] Negative pressure maintenance: During operation, the built-in vacuum pressure sensor in the automatic control unit 4 automatically detects the vacuum level inside the precast pipe pile 9 and controls the start and stop of the vacuum pump 2. When the vacuum level is 2 kPa lower than the preset target value (-0.7 atmospheres), the vacuum pump 2 is started. During subsequent hammering and penetration, when the vacuum level is 2 kPa higher than the preset target value, the vacuum pump 2 stops working and enters intermittent operation mode, ensuring that the precast pipe pile 9 is always maintained at a negative pressure of no less than 0.7 atmospheres. This dynamically compensates for possible gas leakage and automatically maintains a stable negative pressure environment throughout the entire pile driving process. This fundamentally eliminates the upward recoil force of the pile hammer caused by the "air cushion" formed by compressed air inside the precast pipe pile 9, allowing the hammering kinetic energy to be converted into the penetration energy of the pile body more efficiently, significantly improving the effective work done per blow. In addition, the negative pressure of the precast pipe pile 9 generates a "lifting" effect, actively reducing soil plug resistance. A stable negative pressure is established within the precast pipe pile 9 using a high-efficiency air extraction device integrated with the negative pressure pile cap. This creates a continuous pressure difference between the upper surface of the soil plug inside the precast pipe pile 9 (i.e., the lower interface of the closed air cavity inside the precast pipe pile 9) and the external atmosphere. This pressure difference is equivalent to applying an upward "lifting" force to the soil plug. This force can partially offset the weight of the soil plug itself and the static friction between it and the inner wall of the precast pipe pile 9, thereby effectively delaying the compaction and sealing process of the soil plug, reducing the lateral frictional resistance between the soil plug and the pipe wall, and making it easier for the pile to penetrate downwards.

[0021] Construction Completion and Recovery: Once the pile driving reaches the design elevation, turn off the start switch 7 and manually open the pressure relief valve 5 to restore normal pressure inside the precast pipe pile 9. The negative pressure pile cap 1 can then be easily lifted off, ready for the construction of the next precast pipe pile 9. Simultaneously, the battery 3 can be charged via the charging interface built into the start switch 7 as needed.

Claims

1. A precast pipe pile sinking-aiding negative pressure pile cap, characterized in that: The precast pipe pile sinking negative pressure pile cap includes a pile cap body (1), a vacuum pump (2), a storage battery (3), an automatic control unit (4), a pressure relief valve (5), a start switch (7), and a flexible sealing gasket (10); wherein, the pile cap body (1) is a hollow cylindrical structure, with the lower end edge extending downward to form a ring of cap wall (11) for covering the top of the precast pipe pile (9), an exhaust hole (6) is formed on one side of the circumferential wall, a pressure relief hole for installing the pressure relief valve (5) is formed on the other side, and a connecting hole (8) is formed in the middle of the bottom surface; the vacuum pump (2), the storage battery (3), and the automatic control unit (4) The vacuum pump (2) is installed inside the pile cap body (1), and the outlet of the vacuum pump (2) is connected to the exhaust port (6) through a sealed pipeline; the start switch (7) is installed outside the pile cap body (1) and has a built-in charging interface for charging the storage battery (3); the automatic control unit (4) is electrically connected to the vacuum pump (2), the storage battery (3) and the start switch (7) respectively; the storage battery (3) supplies power to the vacuum pump (2) and the automatic control unit (4); the flexible sealing gasket (10) is installed in the upper part of the cap wall (11) and has an opening in the middle that corresponds to the connecting hole (8) on the pile cap body (1).

2. The precast pipe pile sinking-aiding negative pressure pile cap according to claim 1, characterized in that: The automatic control unit (4) uses an STM32 series microcontroller as the main control chip and is equipped with an MPXV5004 series vacuum pressure sensor.

3. The precast pipe pile sinking negative pressure pile cap according to claim 1, characterized in that: The main body of the pile cap (1) is made of steel.

4. The precast pipe pile sinking-aiding negative pressure pile cap according to claim 1, characterized in that: The flexible sealing gasket (10) is made of high-strength rubber material.

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