Stand column pile structure and construction method thereof

Abstract

The invention provides a stand column pile structure and a construction method thereof, and belongs to the technical field of foundation pit supporting. Comprising cast-in-place concrete piles, latticed columns and a plurality of bottom plates, and the cast-in-place concrete piles are fixedly embedded in pile holes; the lower part of the latticed column is embedded and fixed in the cast-in-place concrete pile; the bottom plates are in one-to-one correspondence with the angle steel of the latticed column and arranged at the bottom ends of the angle steel, and the plate faces of the bottom plates are parallel to the cross section of the latticed column and used for increasing the pressure-bearing contact area of the bottom end of the latticed column and the cast-in-place concrete pile. Due to the fact that a load transmission mechanism is changed, the bottom plate is welded to the bottom end of each angle steel of the latticed column, the load transmission mode is converted into the mode of depending on local pressure bearing between the bottom plate and concrete, and under the same load condition, the depth of the latticed column embedded into a cast-in-place concrete pile can be greatly reduced; accordingly, the drilling work amount of the pile hole in the rock stratum can be greatly reduced, and the construction period is remarkably shortened. And secondly, the using amount of reinforcing steel bars and concrete is directly reduced by shortening the pile length of the cast-in-place concrete pile, and the cost is reduced.

Description

Technical Field

[0001] This invention relates to the technical field of foundation pit support, and more specifically, to a column pile structure and its construction method. Background Technology

[0002] The internal support system for an excavation pit is a temporary framework built for the pit. Its fundamental task is to resist the soil and water pressure from the outside of the pit, prevent the pit from collapsing, control deformation, and protect the safety of the surrounding environment. The support system consists of a retaining structure, internal supports, and piles. The retaining structure, acting as a wall, is directly installed on the sidewalls of the pit to withstand the soil and water pressure from all around. The internal supports are placed between the retaining structures to balance the enormous lateral pressure transmitted from them, preventing the pit from collapsing inward. The piles are vertical members erected from the bottom of the pit to bear the internal supports and additional vertical loads; they consist of upper steel lattice columns and lower concrete cast-in-place piles.

[0003] To ensure the effective transfer of the load from the upper steel lattice column to the lower concrete pile, relevant technical standards (such as SJG05-2020 "Shenzhen Municipal Standard for Foundation Pit Support Design") clearly stipulate that the length of the lattice column inserted into the pile should not be less than four times the side length of its angle steel, and the depth of embedment in the pile should not be less than 4 meters. Therefore, the actual pile length must also meet this minimum insertion depth. However, when the bottom of the foundation pit is located in moderately or slightly weathered rock strata, a large amount of time-consuming and costly rock drilling is required to meet the approximately 4-meter embedment depth. This not only leads to a sharp decline in the efficiency of construction machinery and severe equipment wear, but also significantly increases project costs and greatly extends the construction period. In other words, under these geological conditions, the excessive rock excavation required to ensure the connection between the lattice column and the pile is a huge waste from both a technical and economic perspective. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a column pile structure and its construction method. By altering the structural form of the lattice column, the length of the lattice column embedded in the concrete of the cast-in-place pile is reduced, thereby simultaneously reducing the pile length of the cast-in-place pile, thus shortening the construction time and reducing the project cost.

[0005] See Figure 1 To address the aforementioned problems, this invention provides a column pile structure, comprising: A cast-in-place pile, wherein the cast-in-place pile is embedded in a pile hole; A lattice column, the lower part of which is embedded in the cast-in-place pile; and Multiple base plates are provided, with each base plate corresponding to and set with an angle steel of the lattice column. Each base plate is connected to the bottom end of the corresponding angle steel. The surface of the base plate is parallel to the cross-section of the lattice column to increase the bearing contact area between the bottom end of the lattice column and the cast-in-place pile.

[0006] Preferably, the lattice column includes four angle steels, all of which extend vertically and their bottom ends are connected to the corresponding base plate. The four angle steels are spaced apart and together form a column structure with a square cross-section. The 90° apex angles of the four angle steels respectively form the four edges of the column structure.

[0007] Preferably, the lattice column further includes connecting plates, and any two adjacent angle steels are connected by a plurality of connecting plates, and the plurality of connecting plates are spaced apart along the height direction of the lattice column.

[0008] Preferably, each of the base plates is a horizontally arranged L-shaped steel plate.

[0009] Preferably, each L-shaped steel plate includes an outwardly extending portion that extends horizontally outward from the outer side of its corresponding angle steel, and an inner extension that extends horizontally inward to the right angle of the angle steel; the extension dimensions of the outwardly extending portion and the extension dimensions of the inner extension are both functions of the thickness t1 of the L-shaped steel plate.

[0010] Preferably, the extension dimension of the outer extension is 3t1, and the extension dimension of the inner extension is t1.

[0011] Preferably, each L-shaped steel plate is welded to the bottom end of the corresponding angle steel by a single-sided fillet weld, the single-sided fillet weld being located on the outside of the angle steel, and its weld angle dimension being 6mm.

[0012] Preferably, the lower part of the lattice column is embedded in the cast-in-place pile for a length of less than 2m.

[0013] On the other hand, the present invention also provides a construction method for a column pile structure, based on the column pile structure described above, comprising the following steps: Piling holes are formed by rotary drilling at the pile location, and the pile holes are cleaned for the first time. The steel reinforcement cage of the cast-in-place pile is hoisted and temporarily fixed to the opening of the pile hole; then the lattice column with a base plate at the bottom is hoisted to the opening of the pile hole and connected and fixed to the steel reinforcement cage to form an integral structure; The overall structure is lowered to the design elevation inside the pile hole, and the lattice column is corrected and then fixed to the opening of the pile hole; The guide pipe is lowered from inside the lattice column to a predetermined distance from the bottom of the pile hole; a second cleaning of the hole is performed through the guide pipe until the sediment and mud indicators at the bottom of the pile hole meet the requirements; The concrete is continuously poured through the duct, ensuring that the initial embedment depth of the duct is not less than a predetermined value, and the embedment depth of the duct in the concrete is controlled during the pouring process to complete the pouring of the cast-in-place pile 1.

[0014] Preferably, the initial burial depth of the conduit is not less than 0.8m, and the depth of the conduit embedded in the concrete during the continuous pouring of concrete is 2~6m.

[0015] The intended technical effects of this invention are as follows: This invention provides a column-pile structure that, by welding a base plate to the bottom end of each angle steel of the lattice column, transforms the load transfer method into relying on local bearing pressure between the base plate and the concrete. Under the same load conditions, the embedment depth of the lattice column into the concrete pile can be reduced, and the embedment depth of the concrete pile into the rock strata below the bottom of the foundation pit is also greatly reduced. Therefore, the amount of drilling work for pile holes in moderately and slightly weathered rock strata is greatly reduced, thereby significantly shortening the construction cycle, reducing mechanical equipment wear and energy consumption, and improving construction efficiency. Secondly, the reduction in the length of the concrete pile directly reduces the amount of steel reinforcement and concrete used, lowering material costs. This invention, through the simple and easy-to-implement structural modification of local reinforcement of the base plate, achieves the dual goals of improving construction efficiency and reducing project costs, especially providing a safe and economical solution for foundation pit engineering in areas with high rock embedment.

[0016] The construction method of the column pile structure of the present invention has the same beneficial effects as the above-mentioned column pile structure compared with the prior art, and will not be repeated here. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a column pile structure in one embodiment of the present invention.

[0018] Figure 2 This is a top view of a lattice column in one embodiment of the present invention.

[0019] Figure 3 This is a top view schematic diagram of the construction of a column pile structure in one embodiment of the present invention.

[0020] Figure 4 This is a top view of the angle steel of the lattice column in one embodiment of the present invention.

[0021] Figure 5 This is a schematic diagram of the base plate and angle steel in one embodiment of the present invention.

[0022] Explanation of reference numerals in the attached figures: 1-Cast-in pile; 11-Reinforcing cage; 2-Foundation pit; 21-Foundation pit bottom; 3-Lattice column; 31-Angle steel; 32-Draped plate; 4-Bottom plate; 41-Single-sided fillet weld; 5-Pile hole; 6-Conduit pipe. Detailed Implementation

[0023] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Although some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the accompanying drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0024] The term "comprising" and its variations as used herein are open-ended, meaning "including but not limited to"; the term "based on" means "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; and the term "optionally" means "optional embodiments". Definitions of other terms will be given in the following description. It should be noted that the concepts of "first," "second," etc., mentioned in this invention are used only to distinguish different devices, modules, or units, and are not intended to limit the order of functions performed by these devices, modules, or units or their interdependencies.

[0025] It should be noted that the terms "a" and "a plurality of" used in this invention are illustrative rather than restrictive. Those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0026] In related technologies, the formula for calculating the length of the traditional lattice steel column (lattice column 3) inserted into the reinforced concrete cast-in-place pile 1 is as follows: Formula (1), where: The length (m) of the concrete pile 1 inserted into the reinforced concrete. The design value of the vertical axial force (KN) for the lattice steel column; For safety, a factor of 2.0 to 2.5 is used; This is the design value of the axial compressive strength of concrete (kPa). The cross-sectional area (m²) of the lattice steel column 2 ); The cross-sectional perimeter (m) of the lattice steel column; The bond design strength (kPa) can be approximated by the tensile design strength of concrete if no experimental data is available. Under the mud wall protection process, the bonding design strength is considered with a reduction factor of 0.5.

[0027] Taking the common calculation of the insertion length of the column pile structure as an example, the concrete cast-in-place pile 1 is often formed by underwater C30 concrete casting. According to the drawing set 11SG814 "Construction of Support Structure for Building Foundation Pit", for the common specifications of steel lattice column (lattice column 3), the steel lattice column is composed of Q235 angle steel, of which the Q235 angle steel uses 4L160×14, and the cross-sectional dimensions of the steel lattice column are 460×460mm. When the calculated length of lattice column 3 is 4m, its bearing capacity design value is 2720kN, that is, N is taken as 2720kN. Secondly, Take 2.5; The design value for the axial compressive strength of C30 concrete is taken as 14300 kPa. The cross-sectional area of ​​the four Q235 angle steels is taken as 0.0173m². 2 ; The perimeter of the four Q235 angle steels is taken as 2.519m; the tensile design strength value of C30 concrete. Under the mud-wall protection process, the bond design strength considers a reduction factor of 0.5, and the final bond design strength is... Take 715 kPa. Using the above formula (1), calculate the length of the lattice column 3 inserted into the lower reinforced concrete cast-in-place pile 1. The insertion depth is 3.43m. In areas with high rock embedment, this 3.43m insertion depth needs to ensure that the rock embedment depth of pile hole 5 is about 4m, which significantly increases the construction cost.

[0028] See Figure 1 To address the problems existing in the aforementioned related technologies, the present invention provides a column pile structure, including a concrete cast-in-place pile 1, a lattice column 3, and multiple base plates 4. The concrete cast-in-place pile 1 is embedded in a pile hole 5; the lower part of the lattice column 3 is embedded in the concrete cast-in-place pile 1; the angle steels 31 of the base plates 4 and the lattice column 3 are correspondingly arranged and set one-to-one, and each base plate 4 is connected to the bottom end of the corresponding angle steel 31. The surface of the base plate 4 is parallel to the cross-section of the lattice column 3 to increase the bearing contact area between the bottom end of the lattice column 3 and the concrete cast-in-place pile 1.

[0029] It should be noted that the pile hole 5 is drilled in the rock stratum below the bottom surface 21 of the foundation pit. When the column pile structure bears load, the force is transferred from the lattice column 3 to the concrete pile 1 and then to the rock stratum where the concrete pile 1 is located. In related technologies, the lattice column 3 relies on the bond force between its surface and the concrete of the concrete pile 1 to transfer the load. According to the formula, the insertion depth needs to reach 3.43 meters, which means that the excavation depth of the pile hole 5 in the rock stratum also needs to reach about 4 meters, making construction in hard rock strata extremely difficult and expensive. Because this invention changes the load transfer mechanism, by welding a base plate 4 to the bottom end of each angle steel 31 of the lattice column 3, the load transfer method is changed to rely on the local bearing pressure between the base plate 4 and the concrete. Under the same load conditions, this invention can greatly reduce the insertion depth. Therefore, as the rock embedment depth of the concrete pile 1 decreases, the amount of drilling work in moderately and slightly weathered rock strata is greatly reduced, thereby significantly shortening the construction cycle, reducing mechanical equipment wear and energy consumption, and improving construction efficiency. Secondly, the shortening of the concrete pile length directly reduces the amount of steel reinforcement and concrete used, thus lowering material costs. This invention, through the simple and easy-to-implement structural modification of locally reinforcing the base plate 4, achieves the dual goals of improved construction efficiency and reduced project costs, providing a safe and economical solution, especially for foundation pit engineering in areas with high rock embedment.

[0030] See Figure 2 In one embodiment of the present invention, the lattice column 3 includes four angle steels 31, all of which extend vertically and their bottom ends are connected to the corresponding base plate 4. The four angle steels 31 are spaced apart and together form a column structure with a square cross-section. The 90° apex angles of the four angle steels 31 respectively form the four edges of the column structure.

[0031] It should be noted that the square cross-section column structure provides symmetry and stability to the lattice column 3, giving it uniform and excellent bending stiffness and load-bearing capacity in all directions. This ensures that the lattice column 3 maintains reliable load-bearing performance when subjected to complex loads transmitted from the support beams within the foundation pit 2. Furthermore, the square cross-section column structure has optimal compatibility with commonly used standard components and connection methods in engineering, facilitating connection construction with horizontal components such as support beams.

[0032] In one embodiment of the present invention, the lattice column 3 further includes a connecting plate 32, and any two adjacent angle steels 31 are connected by a plurality of connecting plates 32, and the plurality of connecting plates 32 are spaced apart along the height direction of the lattice column 3.

[0033] It should be noted that the connecting plate 32 firmly connects the originally independent four angle steels 31 into a highly integrated hollow space truss structure, enhancing the overall stability and deformation resistance of the lattice column 3. Specifically, the connecting plate 32 effectively restricts the local buckling of the angle steels 31, ensuring that the lattice column 3 maintains its cross-sectional shape and structural integrity under compression, especially when subjected to vertical pressure from the supporting beam. This stable overall structure ensures that the load can be effectively transferred through the lattice column 3 to the base plate 4 at its bottom. If the lattice column 3 itself is unstable, the base plate 4 at its bottom cannot reliably distribute the load into the concrete.

[0034] In one embodiment of the present invention, each base plate 4 is a horizontally arranged L-shaped steel plate.

[0035] It should be noted that the L-shaped plate structure of the base plate 4 achieves optimal shape matching and force transfer with the angle steel 31 of the lattice column 3. The two limbs of the L-shaped steel plate can closely fit the two vertical outer surfaces of the angle steel 31, which allows the load to be directly and smoothly transferred from the angle steel 31 to the base plate 4. The force flow path is clear and direct, avoiding stress concentration caused by shape mismatch.

[0036] More importantly, the bottom ends of the four angle steels 31 are regularly distributed at the four corners of the square cross-section, and the L-shaped base plate 4 welded to the bottom end of each angle steel 31 forms a uniform and reasonable stress distribution, ensuring that the extended bearing surface of the base plate 4 can work together to optimally transfer the upper load to the lower concrete. Furthermore, the two L-shaped limbs of the base plate 4 constitute a maximized horizontal bearing surface. Compared with the cross-sectional area of ​​the angle steel 31 itself, the base plate 4 significantly expands the contact area with the lower concrete. By extending the bearing surface from the angle steel 31 to the base plate 4, the stress state of the concrete is greatly improved, and the local compressive stress is reduced to a safe range. At the same time, this design increases the bearing area while minimizing the occupation of the internal space of the lattice column 3, ensuring that the concrete pouring duct can be lowered unimpeded from the center of the lattice column 3, thus ensuring the quality of underwater concrete pouring.

[0037] In one embodiment of the present invention, each L-shaped steel plate includes an outwardly extending portion that extends horizontally outward from the outer side of its corresponding angle steel 31, and an inner extension portion that extends horizontally inward to the right angle of the angle steel 31; the extension dimensions of the outwardly extending portion and the extension dimensions of the inner extension portion are both functions of the thickness t1 of the L-shaped steel plate.

[0038] It should be noted that the thickness of the L-shaped steel plate is t1 (t1 is determined by calculation and is generally taken as 15mm~20mm). To avoid shear failure of the base plate 4, according to the "Design Manual for Steel Structure Connection Nodes", the extended dimension of the base plate 4 should generally not exceed 18 times its thickness, i.e., 18t1.

[0039] See Figure 4 and Figure 5 In one embodiment of the present invention, the extension dimension of the outer extension is 3t1, and the extension dimension of the inner extension is t1.

[0040] It should be noted that the specifications of the angle steel 31 of the lattice column 3 are L×t, that is, the length of both sides of the angle steel 31 is L, and the width of both sides is t. Then the length of both sides of the horizontally placed L-shaped steel plate is L+6t1, and the width of both sides is t+4t1.

[0041] In one embodiment of the present invention, taking the angle steel 31 with specifications of L160x14 (i.e., L=160mm, t=14mm) and the L-shaped steel plate thickness t1 of 15mm as an example, the derivation is performed. The maximum allowable overhang dimension on one side of the L-shaped steel plate = 18×t1 = 18 × 15mm = 270mm, L+6t1 = 160mm + (6×15mm) = 160mm + 90mm = 250mm, t+4t1 = 14mm + (4×15mm) = 14mm + 60mm = 74mm. It can be seen that the above dimensions are set under the premise of absolute safety (far less than 18t1), and the bearing area is maximized (from the cross-sectional area of ​​the angle steel 31 to the projected area of ​​the L-shaped base plate), thereby significantly reducing the local compressive stress of the concrete by increasing the bearing area.

[0042] It should be noted that the dimensions of the aforementioned L-shaped steel plate's outward and inward extensions strictly adhere to the specification requirement in the "Steel Structure Connection Node Design Manual" that "the outward extension should not exceed 18 times the thickness of the base plate," completely avoiding the risk of shear failure or plastic deformation of the base plate 4 due to excessive cantilever length. Simultaneously, the smaller t1 dimension of the inward extension provides the necessary inner bearing surface while minimizing encroachment on the internal space of the lattice column.

[0043] In one embodiment of the present invention, each L-shaped steel plate is welded to the bottom end of the corresponding angle steel 31 by a single-sided fillet weld 41, the single-sided fillet weld 41 being located on the outside of the angle steel 31 and having a weld angle size of 6mm.

[0044] It should be noted that placing the single-sided fillet weld 41 on the outside of the angle steel 31 is the optimal force transfer path. The load is transferred vertically downwards from the lattice column 3 through the angle steel 31. The single-sided fillet weld 41, located on its outside, allows for the most direct and smooth transfer of force to the horizontally positioned base plate 4, avoiding complex stress transformations and ensuring the rigidity and strength of the joint area. The weld fillet size is 6mm. This size provides sufficient effective thickness of the single-sided fillet weld 41 to withstand the enormous vertical axial force transmitted from the lattice column 3, ensuring absolute safety of the connection, while avoiding risks such as excessive welding heat input, increased residual stress, and material embrittlement caused by an excessively thick single-sided fillet weld 41. From a construction feasibility perspective, using a single-sided outer weld allows all welding operations to be completed in advance on the ground or at the orifice, providing ample operating space for the welder and ensuring weld quality and ease of inspection.

[0045] In one embodiment of the present invention, the lower part of the lattice column 3 is embedded in the concrete cast-in-place pile 1 for a length of less than 2m.

[0046] It should be noted that, according to the calculation formula (1) in the above-mentioned related technologies, The steel lattice columns in formula (1) are composed of Q235 angle steel, of which the Q235 angle steel is 4L160×14. The cross-sectional dimensions of lattice column 3 are 460×460mm. When the calculated length of lattice column 3 is 4m, its design bearing capacity is 2720kN, that is, N is taken as 2720kN. Secondly, Take 2.5, Take 14300 kPa, Take 2.519m, Take 715 kPa. Wherein, The cross-sectional area of ​​the four base plates is taken as 0.1261m². 2 Each base plate is 15mm thick, with each L-shaped side measuring 250mm in length and 74mm in width. Substituting these values ​​into the above formula and taking the equality sign, we obtain the result. It is 1.27m. Comparison with relevant technologies shows that... The insertion depth of the concrete-filled pile 1 can be reduced from 4m to less than 2m, from 3.43m to 1.27m. This greatly reduces the pile construction time and concrete usage of the lattice column 3.

[0047] See Figure 3 On the other hand, the present invention also provides a construction method for a column pile structure, based on the column pile structure described above, comprising the following steps: Piling hole 5 is formed by rotary drilling at the pile location, and the pile hole 5 is cleaned for the first time; The steel cage 11 of the concrete-filled pile 1 is hoisted and temporarily fixed to the opening of the pile hole 5; then the lattice column 3 with a bottom plate 4 at the bottom end is hoisted to the opening of the pile hole 5 and connected and fixed to the steel cage 11 to form an integral structure. The overall structure is lowered to the design elevation inside the pile hole 5, and the lattice column 3 is corrected and then fixed to the opening of the pile hole 5. The guide pipe 6 is lowered from inside the lattice column 3 to a predetermined distance from the bottom of the pile hole 5; the hole is cleaned a second time through the guide pipe 6 until the sediment and mud indicators at the bottom of the pile hole 5 meet the requirements; Concrete is continuously poured through the guide pipe 6 to ensure that the initial embedment depth of the guide pipe 6 is not less than the predetermined value, and the embedment depth of the guide pipe 6 in the concrete is controlled during the pouring process.

[0048] It should be noted that pile hole 5 refers to the hole drilled from the bottom surface 21 of the foundation pit down into the rock strata. This pile hole 5 is the section from the bottom surface 21 of the foundation pit to the designed pile bottom, which is the solid pile section of the concrete cast-in-place pile 1. After pouring concrete, the concrete cast-in-place pile 1 is formed. The bottom end of the solid pile section is the solid pile bottom elevation, and the top end is the solid pile top elevation. Under normal circumstances, the solid pile top elevation and the bottom surface 21 of the foundation pit are located on the same plane.

[0049] In one embodiment of the present invention, the initial burial depth of the conduit 6 is not less than 0.8m, and the burial depth of the conduit 6 in the concrete during the continuous concrete pouring process is 2~6m.

[0050] It should be noted that during the initial pouring, the initial embedment depth must be no less than 0.8m to instantly establish a huge concrete pressure at the bottom of the guide pipe 6, sufficient to displace the mud slurry throughout the entire pile hole 5. This forms the initial driving force, ensuring that the concrete can quickly spread outwards, completely pushing the mud slurry upwards and discharging it. This effectively prevents serious defects such as mud slurry entrapment and mud-filled pile breakage caused by insufficient initial concrete volume, laying a solid foundation for the integrity of the entire pile.

[0051] During continuous concrete pouring, the embedment depth of the guide pipe 6 in the concrete is 2-6m, which is a guarantee for achieving high-quality grouting. Maintaining the guide pipe 6 at a certain depth embedded in the poured concrete is fundamentally aimed at ensuring that the newly poured concrete always flows and rises within the previous concrete with the same properties. This isolates the concrete from contact with mud and slurry, effectively preventing potential quality problems such as looseness and interlayering caused by concrete segregation, slurry loss, or mud mixing. This ensures that the resulting cast-in-place pile is uniform, dense, and has high strength.

[0052] In one embodiment of the present invention, a construction method for a column pile structure specifically includes the following steps: S1. Construction and primary cleaning of pile hole 5: A rotary drilling rig was used to drill downwards at the pile location to form pile hole 5. After the borehole reached the designed depth (actual pile bottom elevation), the first cleaning was carried out to remove most of the sediment inside the hole and ensure the stability of the hole wall.

[0053] S2. Ground connections form an integral structure: A crawler crane was used to lift the steel cage 11 of the concrete-filled pile 1 into the pile hole 5, and two No. 14 channel steels were used to temporarily fix its top to the steel casing at the hole opening.

[0054] Using a crawler crane, the lattice column 3, whose bottom end has been pre-welded with a base plate 4, is lifted to the opening.

[0055] The lower part of the lattice column 3 is welded and fixed to the steel cage 11 with auxiliary steel bars, so that the two are connected to form a solid whole structure.

[0056] S3. Overall lowering and calibration fixation: Remove the channel steel that secures the reinforcing cage 11, and slowly lower the connected overall structure into the pile hole 5 using a crawler crane.

[0057] During the lowering process, measuring instruments were used throughout to check and control the verticality and planar position of the lattice column 3.

[0058] After lowering it to the design elevation (the bottom of the lattice column 3 is at the predetermined depth from the bottom of the hole), its position and deflection are checked again. After confirming that there are no errors, the lattice column 3 is firmly fixed to the steel casing at the hole opening using channel steel.

[0059] S4. Conduit installation and secondary cleaning: S41. Install concrete pouring guide pipe 6: Guide pipe 6 is made of steel pipe with a wall thickness of 6mm and a diameter of 300mm. The length of the bottom section is not less than 4 meters. The joint is a double-threaded square quick connector with an O-ring. Lower guide pipe 6 through the hollow interior of lattice column 3 so that the bottom of guide pipe 6 is 300-500mm from the bottom of the hole.

[0060] S42. Perform a second cleaning: Lower the duct from inside guide 6 to the predetermined depth, connecting an air volume of 6-9. For air compressors with a capacity of 0.5 min, a reverse circulation air-lift process is used for hole cleaning.

[0061] S43. The standards for borehole cleaning are as follows: mud specific gravity <1.25, viscosity <28s, sand content <8% at 500mm from the bottom of the borehole, and sediment thickness at the bottom of the borehole ≤50mm. Once the standards are met, stop the borehole cleaning and immediately remove the air duct.

[0062] S5. Underwater concrete pouring: Immediately begin continuous underwater concrete pouring through conduit 6. The hopper must be securely connected to the top of the conduit to prevent displacement.

[0063] During the initial pouring (initial grouting), it must be ensured that the initial amount of concrete poured is sufficient to embed the bottom end of the guide pipe 6 into the concrete to a depth of not less than 800mm.

[0064] The pouring process must be continuous and uninterrupted. During the pouring process, the rise of the concrete surface is measured by a measuring hammer to control the embedment depth of the guide pipe 6 in the concrete to always be between 2 and 6 meters, and the guide pipe 6 is disassembled in a timely manner.

[0065] The actual top surface of the concrete pouring should be 0.8~1.0m higher than the designed actual pile top elevation of the concrete pile 1 under the lattice column 3, in order to ensure the quality of the pile head of the concrete pile 1.

[0066] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A column pile structure, characterized in that, include: A cast-in-place pile (1) is embedded in a pile hole (5); A lattice column (3) is embedded in the lower part of the cast-in-place pile (1); as well as Multiple base plates (4) are provided, and the angle steel (31) of the base plate (4) and the lattice column (3) are provided in a one-to-one correspondence. Each base plate (4) is connected to the bottom end of its corresponding angle steel (31). The plate surface of the base plate (4) is parallel to the cross-section of the lattice column (3) to increase the bearing contact area between the bottom end of the lattice column (3) and the cast-in-place pile (1).

2. The column pile structure according to claim 1, characterized in that, The lattice column (3) includes four angle steels (31), all of which extend vertically and their bottom ends are connected to the corresponding base plate (4). The four angle steels (31) are spaced apart and together form a column structure with a square cross-section. The 90° apex angles of the four angle steels (31) respectively form the four edges of the column structure.

3. The column pile structure according to claim 2, characterized in that, The lattice column (3) also includes a connecting plate (32), and any two adjacent angle steels (31) are connected by a plurality of connecting plates (32), and the plurality of connecting plates (32) are spaced apart along the height direction of the lattice column (3).

4. The column pile structure according to claim 3, characterized in that, Each of the base plates (4) is a horizontally arranged L-shaped steel plate.

5. The column pile structure according to claim 4, characterized in that, Each L-shaped steel plate includes an outwardly extending portion that extends horizontally outward from the outer side of its corresponding angle steel (31), and an inner extension that extends horizontally inward to the right angle of the angle steel (31); the extension dimensions of the outwardly extending portion and the extension dimensions of the inner extension are both functions of the thickness t1 of the L-shaped steel plate.

6. The column pile structure according to claim 5, characterized in that, The extension dimension of the outer extension is 3t1, and the extension dimension of the inner extension is t1.

7. The column pile structure according to claim 6, characterized in that, Each L-shaped steel plate is welded to the bottom end of the corresponding angle steel (31) by a single-sided fillet weld (41), the single-sided fillet weld (41) being located on the outside of the angle steel (31) and having a weld angle size of 6mm.

8. The column pile structure according to claim 7, characterized in that, The lower part of the lattice column (3) is embedded in the cast-in-place pile (1) for a length of less than 2m.

9. A construction method for a column-pile structure, based on the column-pile structure as described in any one of claims 1 to 8, characterized in that, Includes the following steps: Piling holes (5) are formed by rotary drilling at the pile location, and the pile holes (5) are cleaned for the first time; The steel cage (11) of the cast-in-place pile (1) is hoisted and temporarily fixed at the opening of the pile hole (5); then the lattice column (3) with a bottom plate (4) at the bottom end is hoisted to the opening of the pile hole (5) and connected and fixed with the steel cage (11) to form an integral structure. The overall structure is lowered to the design elevation inside the pile hole (5), and the lattice column (3) is corrected and then fixed to the opening of the pile hole (5); The guide pipe (6) is lowered from inside the lattice column (3) to a predetermined distance from the bottom of the pile hole (5); the hole is cleaned a second time through the guide pipe (6) until the sediment and mud at the bottom of the pile hole (5) meet the requirements; The concrete is continuously poured through the conduit (6) to ensure that the initial burial depth of the conduit (6) is not less than the predetermined value, and the burial depth of the conduit (6) in the concrete is controlled during the pouring process to complete the pouring of the concrete pile (1).

10. The construction method according to claim 9, characterized in that: The initial burial depth of the conduit (6) is not less than 0.8m, and the depth of the conduit (6) buried in the concrete during the continuous pouring of the concrete is 2~6m.

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