A construction method of PC work method pile suitable for special-shaped foundation pit under rapid flow condition

Abstract

The application relates to a construction method of a special-shaped foundation pit PC method pile suitable for a rapid flow situation, wherein the pipe pile in the same direction as the water flow direction is preferentially driven according to the water flow direction; after the pipe piles on both sides are constructed, the Larsen steel sheet pile is driven in the gap between the existing pipe piles; after the water flow in the same direction is constructed, the transverse pile construction is carried out, the downstream pipe pile is preferentially driven, and then the upstream pipe piles are sequentially driven; after all the pipe piles are constructed, the Larsen steel sheet pile is sequentially constructed from the downstream to the upstream. The application has the beneficial effects that the construction sequence of the PC method pile is changed, the influence of the water flow on the pile body verticality is weakened, the construction precision can be effectively improved, and the same type of piles are continuously inserted and driven, so that the equipment rental cost is saved.

Description

Technical Field

[0001] This invention relates to the field of pile construction technology, and more specifically, to a PC pile construction method suitable for irregularly shaped foundation pits under rapid flow conditions. Background Technology

[0002] With the development of urban space and the continuous improvement of construction technology, the development and utilization of multi-level underground spaces are increasing, leading to the emergence of various retaining pile technologies. Among them, PC method piles (a combination of steel pipe piles and Larssen sheet piles) are being used more and more widely in foundation pit engineering in various complex environments. PC method piles bear the load of buildings or other structures through the friction and end resistance between the pile body and the soil. They have attracted widespread attention due to their high pile stiffness, wide applicability to various strata, deep construction depth, significant water-stopping effect, low environmental pollution, high wall quality, and recyclability.

[0003] Existing PC (precast concrete) pile methods generally employ a sequential driving approach, inserting steel pipe piles and adjacent Larssen sheet piles in turn. Some projects experience incomplete closure, leading to problems such as water and mud leakage in the foundation pit. This is often due to poor verticality control of individual piles, resulting in accumulated verticality errors and ultimately causing issues like "narrower at the top and wider at the bottom" or "wider at the top and narrower at the bottom" at the closure. Furthermore, the verticality of some piles is susceptible to deviations in insertion angle due to water flow impact. After the retaining piles are completed, gaps exist between the Larssen sheet piles and the steel walers during construction. The conventional approach is to seal these gaps with reinforced concrete, which is time-consuming, makes it difficult to achieve optimal concrete curing conditions on-site, and results in poor bearing capacity. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a PC pile construction method suitable for irregular foundation pits under rapid flow conditions.

[0005] Firstly, a method for constructing PC piles in irregularly shaped foundation pits under rapid flow conditions is provided, including:

[0006] Step 1: Transport and store the pipe piles and Larssen sheet piles;

[0007] Step 2: Install PC steel pipe pile retaining structure in water. When constructing pipe piles, use pipe pile verticality control clamps to control the verticality of the pile body.

[0008] The driving sequence is as follows: drive pipe piles in the same direction as the water flow first; after the pipe piles on both sides are completed, drive Larssen steel sheet piles in the gaps between the existing pipe piles; after the construction of the pipe piles in the same direction of water flow is completed, carry out the construction of the transverse piles, drive the downstream pipe piles first, and then drive the upstream pipe piles in sequence; after all the pipe piles are completed, then drive the Larssen steel sheet piles in sequence from downstream to upstream.

[0009] Step 3: The PC steel pipe pile retaining structure is closed;

[0010] Step 4: Carry out foundation pit construction and install jack support structure;

[0011] Step 5: After backfilling the earthwork and refilling the water, remove the support piles and backfill the pile holes.

[0012] Preferably, when driving the first pipe pile, two theodolites are used to control its verticality in two directions; and when the pile is driven to half the designed depth, the driving is paused to check whether the verticality of the pile is within the preset threshold. If it meets the requirements, the vibratory hammer driving continues; otherwise, the pile is pulled out and driven again.

[0013] In a second aspect, a verticality control clamp for pipe piles as described in the first aspect is provided, comprising: an upper cover plate, a cover plate connecting column, and a lower cover plate;

[0014] The upper cover plate is connected to the lower cover plate via the cover plate connecting column; the upper cover plate is provided with several lifting points; both the upper and lower cover plates are provided with two circular holes, wherein the first circular hole is used for the passage of completed pipe piles, and the second circular hole is used for the passage of pipe piles to be constructed; the first circular hole is provided with a locking device along the long side of the upper or lower cover plate, and a hinge is provided on the opposite side of the locking device; the lower part of the lower cover plate is provided with a load-bearing block located at the four corners of the first circular hole; the load-bearing block is connected to an arc-shaped load-bearing block via a connecting rod; the arc-shaped load-bearing block is made of strong magnet and has a vacuum adsorption device in the middle.

[0015] Preferably, the connecting rod has a built-in thread and its length can be adjusted by rotation; the arc of the arc-shaped load-bearing block matches the pipe pile.

[0016] Thirdly, a method for installing the verticality control clamp for pipe piles as described in the second aspect is provided, including:

[0017] Step 1: Use the hoisting point to hoist the verticality control clamp of the pipe pile, attach the four arc-shaped load-bearing blocks to the completed pipe pile, and make the completed pipe pile pass through the first circular hole;

[0018] Step 2: After the fixture reaches the predetermined position, the vacuum adsorption device is evacuated.

[0019] Step 3: Rotate the connecting rod to adjust the length and level the clamp;

[0020] Step 4: Lock using the locking device;

[0021] Step 5: Allow the pipe pile to be constructed to pass through the clamp via the second circular hole.

[0022] Fourthly, a jack support structure as described in the first aspect is provided, comprising: a steel waler and a jack support;

[0023] The steel waler is fixed to the Larssen sheet pile; the jack support includes a jack support shell and a jack support hook; the jack support shell is a semi-circular steel plate used to support the jack; the jack support hook is located at the end of the jack support shell away from the load-bearing steel plate, used to fix the jack support to the steel waler; the load-bearing steel plate is placed at the connection between the jack and the Larssen sheet pile.

[0024] Preferably, the pressure data of the jacks can be monitored in real time, and the pressure of a single jack can be adjusted.

[0025] Preferably, the load-bearing steel plate has the same width as the Larssen sheet pile and is square in shape.

[0026] The beneficial effects of this invention are:

[0027] 1. This invention reduces the impact of water flow on the verticality of the pile by changing the construction sequence of PC piles, which can effectively improve construction accuracy; and the continuous driving of similar piles saves equipment rental costs.

[0028] 2. The pipe pile verticality control clamp provided by the present invention can be fixed on the completed pipe pile body to control the verticality of the pipe pile to be constructed, thereby improving the stability and safety of the support structure; at the same time, the device can be reused, and has a simple structure and low cost.

[0029] 3. This invention addresses the gap between the steel waler and the Larssen steel sheet pile during construction by using hydraulic jacks to resist the deformation of the Larssen steel sheet pile. It is convenient to use, easy to install and disassemble, and can be reused repeatedly, providing reliable temporary support. At the same time, the hydraulic jack pressure is adjustable, which can be adjusted according to the actual situation to ensure the overall stability of the retaining structure and increase the overall mobility. Attached Figure Description

[0030] Figure 1 The PC method pile construction flowchart provided in this application;

[0031] Figure 2 A schematic diagram of the pile insertion sequence for the rapid flow irregular PC method piles provided in this application;

[0032] Figure 3 This is a detailed drawing of the pipe pile verticality control fixture provided in this application;

[0033] Figure 4 Front view of the pipe pile verticality control clamp provided in this application;

[0034] Figure 5 Rear view of the pipe pile verticality control fixture provided in this application;

[0035] Figure 6 This is a top view of the pipe pile verticality control clamp provided in this application;

[0036] Figure 7 A bottom view of the pipe pile verticality control clamp provided in this application;

[0037] Figure 8 The jack support location diagram provided in this application;

[0038] Figure 9 The layout diagram of the retaining piles, steel walers, and jack supports provided in this application;

[0039] Figure 10 The jack support detail drawing provided in this application;

[0040] Explanation of reference numerals in the attached drawings: 1. Completed pipe pile; 2. Pipe pile to be constructed; 3. Pipe pile verticality control clamp body; 4. Upper cover plate; 5. Cover plate connecting column; 6. Lower cover plate; 7. Lifting point; 8. Locking device; 9. Hinge; 10. Bearing block; 11. Connecting rod; 12. Arc-shaped bearing block; 13. Pipe pile; 14. Larssen sheet pile; 15. Steel waler; 16. Jack support; 17. Jack support shell; 18. Jack support hook; 19. Jack; 20. Load-bearing steel plate. Detailed Implementation

[0041] The present invention will be further described below with reference to embodiments. The description of the embodiments below is only for the purpose of helping to understand the present invention. It should be noted that those skilled in the art can make several modifications to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0042] Example 1:

[0043] Embodiment 1 of this application provides a method for constructing PC piles in irregularly shaped foundation pits under rapid flow conditions, including:

[0044] Step 1: Transport and store pipe piles and Larssen sheet piles.

[0045] Step 2: Install PC steel pipe pile retaining structure in water. When constructing the pipe piles, use pipe pile verticality control clamps to control the verticality of the pile body.

[0046] like Figure 2 As shown, the driving sequence is as follows: drive pipe piles in the same direction as the water flow first; after the pipe piles on both sides are completed, drive Larssen steel sheet piles in the gaps between the existing pipe piles; after the construction of the pipe piles in the same direction as the water flow is completed, carry out the construction of the transverse piles, drive the downstream pipe piles first, and then drive the upstream pipe piles in sequence; after all the pipe piles are completed, then drive the Larssen steel sheet piles in sequence from downstream to upstream.

[0047] Specifically, the steel sheet piles are first hoisted to the insertion point using a crane, and the interlocks must be aligned during insertion. After each sheet pile is inserted, a pile cap is placed on and the pile is gently hammered. During the pile driving process, two theodolites are used to control verticality in two directions to ensure verticality. To prevent displacement of the center plane of the interlocks, a verticality control clamp for the pipe pile is used during pile driving. The initial driving position and direction should be strictly controlled with precision. It is advisable to measure one side every 1m into the soil. After reaching the predetermined depth, the pipe pile should be temporarily welded and fixed to the waler support with steel bars or steel plates. Then, the verticality control clamp for the pipe pile is hoisted to the predetermined position and fixed to the initial pipe pile. The next pipe pile is driven through the pre-drilled hole in the clamp.

[0048] Step 3: The PC steel pipe pile retaining structure is closed.

[0049] Step 4: Carry out foundation pit construction and install jack support structure.

[0050] Step 5: After backfilling the earthwork and refilling the water, remove the support piles and backfill the pile holes.

[0051] Example 2:

[0052] Based on Example 1, Example 2 of this application provides a more specific construction scheme for PC piles in irregularly shaped foundation pits under rapid flow conditions, such as... Figure 1 As shown, it includes:

[0053] Step 1: Fabricate steel pipe piles.

[0054] On a flat site, a jig for processing interlocking steel pipe piles is made. First, the steel pipes are joined together to the designed length. Then, the interlocking is positioned and welded to the steel pipe. Finally, stiffening ribs and limiting ribs are welded.

[0055] The locking buckles on each interlocking steel pipe pile must be symmetrically located on the same diameter line of the steel pipe. The direction of the locking buckles can be either unidirectional or reversed depending on the combination. The steel pipe joints should be located 1m below the excavation surface, and the joints of two adjacent steel pipes should be staggered by more than 1m. All welds should be continuous and fully welded, with a weld height of 8mm. After the pipes are fully welded, they should be cooled for more than 30 minutes before being lifted. The butt welds of the interlocking steel pipe piles should be inspected and accepted according to the Class I weld quality standard; the remaining welds should be visually inspected according to the Class M weld quality standard, requiring fullness, no cracks, and no leakage; the interlocking steel pipe piles should be straight, without bends or kinks.

[0056] Step 2: Piling.

[0057] For underwater installation of PC steel pipe pile retaining structures, firstly, a limiting frame is erected based on the pile foundation platform to accurately position the steel pipes. Then, control survey points are set at certain intervals along the foundation pit, and the inner contour line of the support structure is marked out using a total station. The positions of the pipe piles and sheet piles are then located according to the designed combination. During the alternating driving of interlocking steel pipe piles and sheet piles, the verticality of the piles is controlled using the forward intersection method with two theodolites. Specifically, this step includes:

[0058] Step 2.1: The main hook of the crane lifts the upper part of the locked steel pipe pile (or steel sheet pile) and the auxiliary hook lifts the lower part, lifting the pile simultaneously to suspend it in the air. Then the main hook continues to lift until the pile is vertical, and finally the auxiliary hook is released.

[0059] Step 2.2: The crane lifts the locking steel pipe pile (or steel sheet pile) to the pile driving position, so that its locking is engaged with the locking of the already driven steel sheet pile (or locking steel pipe pile), and slowly lowers it until it enters the soil layer without sinking and becomes self-stabilized.

[0060] Step 2.3: Remove the pile head jack rope, use the crane's main hook to lift the vibratory hammer to the pile head, and clamp the pile wall with the hammer clamp; start the vibratory hammer to drive the pile, and the sinking speed must be well controlled, generally 1m / min, until the designed depth is reached. During the sinking process, the crane's lifting rope should be loosened simultaneously to control the hammer body to remain perpendicular to the pile body.

[0061] It should be noted that if the interlocking steel pipe piles cannot be driven to the designed depth, water jetting or mud suction methods can be used to assist in sinking.

[0062] In step 2, the verticality of the first interlocking steel pipe pile after it is driven in affects the verticality of the other piles in the entire retaining structure. Therefore, it should be driven slowly, pausing when it reaches half the designed depth to check if the verticality of the pile is within 1%L. If it meets the requirement, continue driving with the vibratory hammer; otherwise, pull it out and drive it again. The other piles, under the combined action of the interlocking, generally do not have significant deviations. It is sufficient to check every 5 to 10 piles to ensure that the verticality of the pile is within 1%L.

[0063] Step 3: Close them together.

[0064] Before the retaining structure is closed, when the last 4 to 5 piles are driven, the width of the gap is measured, the outer diameter of the closing pile is accurately calculated, and appropriately sized interlocking steel pipe piles are fabricated and transported to the construction site for driving. To ensure that the interlocking piles on both sides are parallel when the retaining structure is closed, to avoid using irregularly shaped piles for closure, and to reduce the difficulty of closure, when the distance between the two ends of the retaining structure is 10 to 15 piles, the verticality of each pile must be controlled with a theodolite. If there is any deviation in the pile body, it should be corrected one by one to disperse the deviation and adjust for closure.

[0065] Step 4: Remove the pile.

[0066] After backfilling and water injection, first use a pile driver to clamp the pile head and vibrate for 1-2 minutes to loosen the soil around the pile and induce liquefaction, reducing the frictional resistance between the soil and the pile. Then, slowly pull the pile upwards. During pile extraction, pay attention to the load on the pile driver. If it becomes difficult to pull the pile out or it cannot be pulled out at all, stop extraction, shake the pile for 1-2 minutes, then hammer it down 0.5-1 meter before pulling it upwards again. Repeat this process until the pile is extracted. During pile extraction, strengthen monitoring and promptly fill the voids within the retaining pile with coarse sand or grout to reduce soil settlement and deformation caused by pile extraction.

[0067] Step 5: Install waler supports.

[0068] The walers and internal supports were hoisted using a truck crane. The first internal support was installed, with steel brackets supporting the structural steel sections. Due to the presence of steel casings in deep underwater foundation pits, installing the walers support layer by layer from top to bottom is difficult. Therefore, each waler support should be pre-assembled and installed inside the pit after the bottom is sealed. As the pit is dewatered, each support is then installed in place. After the walers are constructed, the jack supports are arranged, and the jacks are pressurized until they are tightly fitted against the walers and Larssen sheet piles.

[0069] The steel supports are constructed from steel pipes, consisting of three parts: movable ends, fixed ends, and intermediate standard sections. The pipe sections are connected using flanges and high-strength bolts. The supports are erected on-site using a crane for hoisting and assembly. Installation requires first installing the brackets, then hoisting the steel supports into position, and finally applying pre-axial force. The steel supports are assembled on the ground. When the excavation reaches 50cm below the supports, a truck crane is used for hoisting, with manual installation carried out inside the pit.

[0070] It should be noted that the parts in this embodiment that are the same as or similar to those in Embodiment 1 can be referred to each other, and will not be repeated in this application.

[0071] Example 3:

[0072] Based on Embodiment 1, Embodiment 3 of this application provides a pipe pile verticality control clamp, such as... Figures 3 to 7 As shown, it includes: an upper cover plate 4, a cover plate connecting post 5, and a lower cover plate 6;

[0073] The upper cover plate 4 is connected to the lower cover plate 6 via the cover plate connecting column 5. The upper cover plate 4 is provided with several lifting points 7. Both the upper cover plate 4 and the lower cover plate 6 have two circular holes. The first circular hole is for the passage of the completed pipe pile 1, and the second circular hole is for the passage of the pipe pile 2 to be constructed, effectively controlling the verticality of the piles. The completed pipe pile 1 is the first steel pipe pile to be constructed in the retaining structure. The verticality deviation of this steel pipe pile is mainly determined by a level and the experience of the construction personnel. Controlling the verticality of this steel pipe pile is crucial, as it affects the verticality of subsequent steel pipe piles. Furthermore, the two circular holes are provided with clip passage positions to facilitate the passage of clips on the pipe pile.

[0074] A locking device 8 is provided along the long side of the upper cover plate 4 or the lower cover plate 6 at the first circular hole. The locking device 8 is welded to the cover plate by a fixing block, and its tightness is controlled by two bolts. Both the upper cover plate 4 and the lower cover plate 5 are provided with a set of locking devices. A hinge 9 is provided on the opposite side of the locking device 8 to ensure the normal use of the opening and closing function of the cover plate. A load-bearing block 10 is provided at the lower part of the lower cover plate 6, located at the four corners of the first circular hole. The load-bearing block 10 is connected to the arc-shaped load-bearing block 12 through the connecting rod 11. The arc-shaped load-bearing block 12 is made of strong magnet and has a vacuum adsorption device in the middle to increase the overall firmness.

[0075] The connecting rod 11 has a built-in thread and its length can be adjusted by rotation, thereby fine-tuning the entire clamp and compensating for clamp deviations caused by insufficient component precision; the arc-shaped load-bearing block 12 has an arc that matches the pipe pile and can fit tightly against the outside of the pipe pile.

[0076] The installation method of the above-mentioned pipe pile verticality control clamp includes:

[0077] Step 1: Use the hoisting point 7 to hoist the verticality control clamp of the pipe pile, attach the four arc-shaped load-bearing blocks 12 to the completed pipe pile, and make the completed pipe pile 1 pass through the first circular hole;

[0078] Step 2: After the fixture reaches the predetermined position, the vacuum adsorption device is evacuated.

[0079] Step 3: Rotate connecting rod 11 to adjust the length and level the clamp;

[0080] Step 4: Lock using locking device 8;

[0081] Step 5: Allow the pipe pile 2 to be constructed to pass through the clamp via the second circular hole.

[0082] Considering extreme cases, even if both clamping devices 8 fail simultaneously, the clamps will not fall directly due to the action of the arc-shaped load-bearing block 12 and the connecting rod 11.

[0083] Specifically, the device provided in this embodiment is the same as the device corresponding to the method provided in embodiment 1. Therefore, the parts in this embodiment that are the same as or similar to those in embodiment 1 can be referred to each other, and will not be described again in this application.

[0084] Example 4:

[0085] Based on Embodiment 1, Embodiment 4 of this application provides a jack support structure, such as... Figures 8 to 10 As shown, it includes: steel waler 15 and jack support 16;

[0086] The steel waler 15 is fixed to the Larssen sheet pile 14; the jack support 16 includes a jack support shell 17 and a jack support hook 18; the jack support shell 17 is a semi-circular steel plate used to support the jack 19 and prevent the jack 19 from falling; the jack support hook 18 is located at the end of the jack support shell 17 away from the load-bearing steel plate 20, used to fix the jack support 16 to the steel waler 15, and there are two jack support hooks 18 in total, which increases the stability of the jack support; the load-bearing steel plate 20 is placed at the connection between the jack 19 and the Larssen sheet pile 14.

[0087] In addition, the jack 19 is an ultra-thin split hydraulic jack, and the pressure data of each jack can be monitored in real time. At the same time, the pressure of a single jack can be adjusted to improve the overall stress condition of the retaining pile.

[0088] The load-bearing steel plate 20 has the same width as the Larssen sheet pile 14 and is square in shape to optimize pressure transmission and improve overall stability.

[0089] Specifically, the device provided in this embodiment is the same as the device corresponding to the method provided in embodiment 1. Therefore, the parts in this embodiment that are the same as or similar to those in embodiment 1 can be referred to each other, and will not be described again in this application.

Claims

1. A method for constructing PC piles in irregularly shaped foundation pits under rapid flow conditions, characterized in that, include: Step 1: Transport and store the pipe piles and Larssen sheet piles; Step 2: Install PC steel pipe pile retaining structure in water. When constructing pipe piles, use pipe pile verticality control clamps to control the verticality of the pile body. The driving sequence is as follows: drive pipe piles in the same direction as the water flow first; after the pipe piles on both sides are completed, drive Larssen steel sheet piles in the gaps between the existing pipe piles; after the construction of the pipe piles in the same direction of water flow is completed, carry out the construction of the transverse piles, drive the downstream pipe piles first, and then drive the upstream pipe piles in sequence; after all the pipe piles are completed, then drive the Larssen steel sheet piles in sequence from downstream to upstream. Step 3: The PC steel pipe pile retaining structure is closed; Step 4: Carry out foundation pit construction and install jack support structure; Step 5: After backfilling the earthwork and refilling the water, remove the support piles and backfill the pile holes.

2. The PC pile construction method for irregularly shaped foundation pits under rapid flow conditions according to claim 1, characterized in that, In step 2, when driving the first pipe pile, two theodolites are used to control its verticality in two directions; and when the pile is driven to half the designed depth, the pile driving is paused to check whether the verticality of the pile body is within the preset threshold. If the requirements are met, the vibratory hammer is turned on to drive the pile; otherwise, it is pulled out and driven again.

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