A stepped pile and its construction method

Abstract

The present application relates to the technical field of foundation treatment, and particularly to a stepped pile and its construction method, which includes a pile body. The pile body includes a plurality of pile segments that are coaxially connected and whose outer diameters gradually increase or decrease along the axis direction of the pile body. An installation skeleton is arranged inside the pile body. The installation skeleton includes a top ring and a bottom ring. The outer diameter of the top ring is larger than that of the bottom ring. A plurality of installation rods are arranged between the top ring and the bottom ring. The plurality of installation rods are evenly spaced along the circumferential direction of the top ring. A strain gauge and a protective shell for protecting the strain gauge are arranged on the installation rods. The protective shell is detachably connected to the installation rod, achieving the effects of facilitating the installation of the strain gauge inside the stepped pile and facilitating the analysis of the force on the pile body.

Description

Technical Field

[0001] The present application relates to the technical field of foundation treatment, and particularly relates to a stepped pile and a construction method thereof. Background Art

[0002] According to relevant information, the annual pile usage in China in 2012 was nearly 8 million. Among them, the cast-in-place pile foundation is widely used due to its advantages such as high single-pile bearing capacity, easy control of construction depth, low cost, and low noise.

[0003] Chinese Patent with Publication No. CN204738290U discloses a stepped variable cross-section cast-in-place rotary-expanded pile, which includes a cast-in-place upper pile body, a cast-in-place lower pile body, and a bearing plate. The diameter of the cast-in-place upper pile body is larger than that of the cast-in-place lower pile body. The cast-in-place upper pile body and the cast-in-place lower pile are fixedly connected. The bearing plate is arranged on the cast-in-place lower pile body. An N-shaped groove is arranged on a stepped variable cross-section cast-in-place rotary-expanded pile.

[0004] The above-mentioned existing technical solutions have the following defects: When applying the above cast-in-place pile to actual working conditions, people still need to study the distribution characteristics of the axial force of the pile body and the side resistance of the pile under the action of the upper load. In this research process, strain gauges are required to monitor the stress situation of the cast-in-place pile. Affected by the concrete inside the pile body, it is difficult to install the strain gauges inside the pile body. Summary of the Invention

[0005] In order to facilitate the installation of strain gauges inside the stepped pile and facilitate the analysis of the stress of the pile body, the present application provides a stepped pile and a construction method thereof.

[0006] The above technical objectives of the present application are achieved through the following technical solutions:

[0007] A stepped pile includes a pile body. The pile body includes a plurality of pile sections that are coaxially connected and whose outer diameters gradually increase or decrease along the axis direction of the pile body. An installation skeleton is arranged inside the pile body. The installation skeleton includes a top ring and a bottom ring. The outer diameter of the top ring is larger than that of the bottom ring. A plurality of installation rods are arranged between the top ring and the bottom ring. The plurality of installation rods are evenly spaced along the circumferential direction of the top ring. Strain gauges and protective shells for protecting the strain gauges are arranged on the installation rods. The protective shells are detachably connected to the installation rods.

[0008] By adopting the above scheme, when casting and fabricating the stepped pile, first drill a casting hole on the ground that matches the stepped pile, and then assemble the installation skeleton. During the assembly of the installation skeleton, install multiple strain gauges on the side of the installation rod in sequence along the length direction of the installation rod, and then install the protective shell on the installation rod. After that, lower the installation skeleton into the casting hole. When pouring concrete into the casting hole, the protective shell will protect the strain gauges on the installation rod. After the concrete is poured, people can remove the protective shell from the installation rod so that the strain gauges can directly contact the concrete. After the concrete solidifies, people can use the strain gauges to detect the distribution characteristics of the axial force of the pile body and the lateral resistance of the pile under the action of the upper load, thus achieving the effect of facilitating the installation of strain gauges inside the stepped pile and facilitating the analysis of the stress of the pile body.

[0009] Preferably, the protective shell covers the outer surface of the installation rod. The side surface of the protective shell is embedded inside the outer surface of the installation rod and is slidably connected to the installation rod. The two end surfaces of the protective shell are rotatably connected to the side surface of the protective shell away from the installation rod. A driving member for driving the end surface of the protective shell to rotate on the protective shell is provided on the protective shell.

[0010] Preferably, a rotating shaft is provided between the two end surfaces of the protective shell and the side surface of the protective shell away from the installation rod. A torsion spring for driving the end surface of the protective shell to rotate towards the installation rod is sleeved on the rotating shaft.

[0011] Preferably, the driving member includes a transmission rope penetrating inside the side surface of the protective shell away from the installation rod. Both ends of the transmission rope extend inside the two end surfaces of the protective shell on the side away from the installation rod of the rotating shaft and are fixedly connected to the two end surfaces of the protective shell.

[0012] Preferably, the two end surfaces of the protective shell are inclined towards the center of the protective shell along the direction from near to far from the installation rod.

[0013] Preferably, T-shaped sliding strips are provided on the end surfaces of the two side surfaces of the protective shell close to the installation rod, and sliding grooves adapted to the T-shaped sliding strips are provided on the side surface of the installation rod.

[0014] Preferably, a calibration rod is erected on the top ring. The calibration rod is detachably connected to the top ring. A sliding rod is inserted at one end of the calibration rod away from the top ring. A limit bolt is provided between the sliding rod and the calibration rod.

[0015] Preferably, load-bearing protrusions are provided on the outer surface of the pile section. The load-bearing protrusions are distributed in a spiral shape on the outer surface of the pile section.

[0016] A construction method for a stepped pile includes the following steps:

[0017] Drilling: Use drilling equipment with different drilling diameters to drill the casting hole for the stepped pile;

[0018] Assembly: The installation skeleton is assembled by welding the top ring and the bottom ring to the positions near both ends of the installation rod respectively. The strain gauges are sequentially installed on the installation rod, and the protective shell is slidably installed on the installation rod.

[0019] Lower cage: The assembled installation skeleton;

[0020] Pouring: Pour the mixed concrete into the pouring hole.

[0021] Removing the shell: Pull the transmission rope outward at the position of the rotating shaft between the end face near the upper part of the protective shell and the protective shell, and at the same time pull the protective shell in the direction outside the pouring hole until the protective shell is pulled out of the pouring hole.

[0022] Forming: The concrete in the pouring hole is left standing until it cools, and the stepped pile is formed.

[0023] Preferably, before removing the protective shell from the inside of the pouring hole, use the calibration rod and the sliding rod to check and adjust the coaxiality between the installation skeleton and the pouring hole; after removing the protective shell from the inside of the pouring hole, use the calibration rod and the sliding rod again to check and adjust the coaxiality between the installation skeleton and the pouring hole.

[0024] In summary, the present application has the following technical effects:

[0025] 1. By setting an installation skeleton with an installation rod and a protective shell, the installation of the strain gauges can be completed while installing the installation skeleton. During the pouring of concrete, the protective shell can protect the strain gauges, thus achieving the effects of facilitating the installation of the strain gauges and facilitating the study of the stress conditions of the pile body.

[0026] 2. By setting a protective shell with inclined end faces at both ends, on the one hand, it is convenient to lower the installation skeleton into the pouring hole, reducing the possible resistance on the protective shell; on the other hand, it can reduce the rotation angle of the end face of the protective shell to a certain extent when pulling the protective shell out of the concrete, thereby facilitating the pulling of the protective shell out of the poured concrete.

[0027] 3. By setting a calibration rod and a sliding rod, after the installation skeleton is lowered into the pouring hole and the concrete is poured, the position of the installation skeleton may shift. The calibration rod and the sliding rod cooperate with each other to keep the installation skeleton and the pouring hole coaxial, thereby ensuring the strength of the pile body. Description of the Drawings

[0028] Figure 1 It is a cross-sectional view after the stepped pile is formed in the embodiment of the present application (the outermost shaded part in the figure is the ground structure);

[0029] Figure 2It is a sectional view when the installation skeleton is just lowered into the casting hole before the stepped pile is cast in the embodiment of the present application;

[0030] Figure 3 It is Figure 2 a partial enlarged view of part A in

[0031] Figure 4 It is a state diagram when the protective shell is being removed from the inside of the casting hole after the stepped pile is cast with concrete in the embodiment of the present application (the lower end surface of the protective shell in the figure has been opened).

[0032] In the figure, 1 is the pile body; 11 is the pile section; 2 is the installation skeleton; 21 is the top ring; 22 is the bottom ring; 23 is the middle ring; 24 is the installation rod; 25 is the fixing rod; 26 is the detection component; 261 is the strain gauge; 262 is the protective shell; 263 is the driving part; 264 is the T-shaped slide bar; 265 is the rotating shaft; 266 is the torsion spring; 267 is the transmission rope; 3 is the casting hole; 4 is the calibration rod; 41 is the sliding rod; 42 is the limit bolt; 43 is the spirit level; 5 is the bearing projection. Detailed implementation manners

[0033] The present application will be further described in detail below with reference to the accompanying drawings.

[0034] Referring to Figure 1 , the present application provides a stepped pile, including a pile body 1 and an installation skeleton 2. The installation skeleton 2 is arranged inside the pile body 1. The pile body 1 includes a plurality of pile sections 11 coaxially connected together, and the outer diameters of the plurality of pile sections 11 gradually increase or decrease along the axial direction of the pile body 1. During molding, a casting hole 3 with a specific diameter is drilled at a designated position on the ground. The inner diameter of the casting hole 3 gradually increases from top to bottom. Then, the installation skeleton 2 is placed in the casting hole 3, and then concrete is poured into the casting hole 3. The position of the installation skeleton 2 is adjusted to make the installation skeleton 2 coaxial with the casting hole 3. After the concrete is completely cooled, the manufacturing process of the stepped pile is completed.

[0035] Referring to Figure 2, the installation framework 2 includes a top ring 21, a bottom ring 22, intermediate rings 23, installation rods 24, fixing rods 25, and a detection assembly 26. There are multiple intermediate rings 23, one top ring 21 and one bottom ring 22. After lowering the installation framework 2 into the casting hole 3, the top ring 21, multiple intermediate rings 23, and one bottom ring 22 are distributed in sequence from top to bottom. The outer diameter of the top ring 21 is greater than that of the intermediate rings 23 which is greater than that of the bottom ring 22. There are multiple fixing rods 25, and multiple fixing rods 25 are evenly spaced along the circumferential direction of the top ring 21; there are also multiple installation rods 24, and multiple installation rods 24 are also evenly spaced along the circumferential direction of the top ring 21, and the installation rods 24 and the fixing rods 25 are spaced apart. In this embodiment, in order to improve the overall stability of the installation framework 2, the fixing rods 25 are fixedly connected to the top ring 21, the bottom ring 22, and the multiple intermediate rings 23 on the inner sides of the top ring 21, the bottom ring 22, and the intermediate rings 23, and the installation rods 24 are fixedly connected to the top ring 21, the bottom ring 22, and the intermediate rings 23 on the outer sides of the top ring 21, the bottom ring 22, and the intermediate rings 23. The number of groups of the detection assembly 26 is the same as the number of installation rods 24 and the two correspond one by one. The detection assembly 26 is arranged on the installation rods 24 to detect the stress condition of the pile body 1 after the pile body 1 is formed.

[0036] Referring to Figure 3 and Figure 4 , the detection assembly 26 includes strain gauges 261, a protective shell 262, and a driving member 263. There are multiple strain gauges 261, and multiple strain gauges 261 are installed along the length direction of each installation rod 24. It should be noted here that when installing the strain gauges 261, try to ensure that there are strain gauges 261 in horizontal planes at different heights; the length of the protective shell 262 is slightly less than the length of the installation rod 24. The protective shell 262 covers the side of the installation rod 24 away from the fixing rod 25. The side of the protective shell 262 close to the installation rod 24 is completely open. On one side of two opposite sides of the protective shell 262 close to the installation rod 24, there are T-shaped sliding strips 264. On the side of the installation rod 24, there are chutes adapted to the T-shaped sliding strips 264. The T-shaped sliding strips 264 enter the chutes and can slide inside the chutes. The chutes penetrate the upper end of the installation rod 24, enabling the protective shell 262 to be detachably connected to the installation rod 24; the two end faces of the protective shell 262 are inclined towards the center of the protective shell 262 in the direction from close to far from the installation rod 24, and there is a rotating shaft 265 between the two end faces of the protective shell 262 and the side of the protective shell 262 away from the installation rod 24. The two end faces of the protective shell 262 are rotatably connected to the side of the protective shell 262 through the rotating shaft 265. The driving member 263 is arranged on the protective shell 262 and can control the opening or closing of the two end faces of the protective shell 262.

[0037] Before lowering the installation framework 2 into the pouring hole 3, install the protective shell 262 on the installation rod 24. When lowering the installation framework 2 into the pouring hole 3, the installation of the strain gauge 261 is also completed; when pouring concrete, the protective shell 262 can protect the strain gauge 261, reducing the possibility that the concrete flushes away the strain gauge 261 or damages the strain gauge 261 itself; after the concrete pouring is completed, drive the end face of the protective shell 262 located inside the pouring hole 3 to open through the driving member 263, separate the protective shell 262 from the installation rod 24, then take out the protective shell 262 from the pouring hole 3, and wait for the concrete to completely solidify, thus completing the process of installing the strain gauge 261 inside the stepped pile.

[0038] Refer to Figure 3 , the driving member 263 includes a torsion spring 266 and a transmission rope 267. The torsion spring 266 is sleeved on the rotating shaft 265 and can drive the end face of the protective shell 262 to rotate towards the direction close to the installation rod 24. The transmission rope 267 is threaded inside the side of the protective shell 262 away from the installation rod 24. A through hole for the transmission rope 267 to pass through is opened inside the side of the protective shell 262 away from the installation rod 24. Both ends of the transmission rope 267 pass through from the side of the rotating shaft 265 away from the installation rod 24 and finally extend into the two end faces of the protective shell 262 and are fixedly connected to the two end faces of the protective shell 262. When pouring concrete in the pouring hole 3, the two end faces of the protective shell 262 are always in a closed state under the action of the torsion spring 266. When it is necessary to take out the protective shell 262 from the pouring hole 3, people can pull the transmission rope 267 at the position of the end face of the protective shell 262 located outside the pouring hole 3. The transmission rope 267 will drive the end face of the protective shell 262 located inside the pouring hole 3 to rotate, and then slide the protective shell 262 on the installation rod 24, so that the protective shell 262 can be taken out from the inside of the pouring hole 3 without affecting the normal use of the strain gauge 261.

[0039] Refer to Figure 3 , after lowering the installation framework 2 into the pouring hole 3 and completing the concrete pouring, the position of the installation framework 2 may shift, resulting in the installation framework 2 being unable to be coaxial with the pouring hole 3. In order to facilitate people to calibrate and adjust the coaxiality of the installation framework 2 and the pouring hole 3, a calibration rod 4 is provided on the top ring 21. An embedding groove for the top ring 21 to enter is opened at the position of the calibration rod 4 close to the top ring 21. A sliding rod 41 is inserted at one end of the calibration rod 4 away from the top ring 21. A limit bolt 42 is provided on the calibration rod 4. The limit bolt 42 is arranged above the calibration rod 4. One end of the limit bolt 42 extends downward through the side wall of the calibration rod 4 and then abuts against the side of the sliding rod 41. A spirit level 43 is embedded inside the upper surface of the calibration rod 4.

[0040] When it is necessary to calibrate the coaxiality between the installation skeleton 2 and the pouring hole 3, the calibration rod 4 is placed on the top ring 21, and then by observing the spirit level 43, the calibration rod 4 is kept horizontal; the sliding rod 41 is moved on the calibration rod 4 so that the end of the sliding rod 41 away from the calibration rod 4 is flush with the inner wall of the pouring hole 3, and the limit bolt 42 is tightened to keep the calibration rod 4 and the sliding rod 41 relatively fixed; then the calibration rod 4 is removed and placed at other positions on the top ring 21. According to the size of the gap between the end of the sliding rod 41 away from the calibration rod 4 and the inner wall of the pouring hole 3, the coaxiality relationship between the installation skeleton 2 and the pouring hole 3 can be determined, and then the coaxiality between the pouring hole 3 and the installation skeleton 2 can be adjusted.

[0041] In this embodiment, in order to further improve the anti-settlement ability of the pile body 1 after molding, threaded grooves are provided on the inner wall of the pouring hole 3, that is: after the stepped pile is molded, bearing protrusions 5 are formed on the outer surface of each pile section 11, and the bearing protrusions 5 are distributed in a threaded shape on the pile section 11.

[0042] This application also provides a construction method for a stepped pile, including the following steps:

[0043] Drilling: Use drilling equipment with different drilling diameters to drill the pouring holes 3 of the stepped pile;

[0044] Assembly: The installation skeleton 2 is assembled by welding the top ring 21 and the bottom ring 22 to the positions close to both ends of the installation rod 24 respectively. The strain gauges 261 are sequentially installed on the installation rod 24, and the protective shell 262 is slidably installed on the installation rod 24;

[0045] Cage lowering: For the assembled installation skeleton 2, use the calibration rod 4 and the sliding rod 41 to calibrate and adjust the coaxiality between the installation skeleton 2 and the pouring hole 3;

[0046] Pouring: Pour the mixed concrete into the pouring hole 3, and use the calibration rod 4 and the sliding rod 41 again to calibrate and adjust the coaxiality between the installation skeleton 2 and the pouring hole 3;

[0047] Shell removal: Pull the transmission rope 267 outward at the position of the rotating shaft 265 between the end face close to the upper part of the protective shell 262 and the protective shell 262, and at the same time pull the protective shell 262 in the direction outside the pouring hole 3 until the protective shell 262 is pulled out of the pouring hole 3;

[0048] Molding: The concrete in the pouring hole 3 is left standing until the concrete cools and the stepped pile is formed.

[0049] This specific embodiment is only an interpretation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A stepped pile, comprising a pile body (1), the pile body (1) including a plurality of pile sections (11) that are coaxially connected and whose outer diameters gradually increase or decrease along the axial direction of the pile body (1), and an installation framework (2) is arranged inside the pile body (1), characterized in that: The mounting frame (2) comprises a top ring (21) and a bottom ring (22), the outer diameter of the top ring (21) being larger than the outer diameter of the bottom ring (22), a plurality of mounting rods (24) being arranged between the top ring (21) and the bottom ring (22), the plurality of mounting rods (24) being evenly spaced and distributed along the circumference of the top ring (21), a strain gauge (261) and a protective shell (262) for protecting the strain gauge (261) being arranged on the mounting rod (24), the protective shell (262) being detachably connected to the mounting rod (24); the protective shell (262) being arranged on the outer surface of the mounting rod (24), the side surface of the protective shell (262) being embedded in the inner part of the outer surface of the mounting rod (24) and being slidably connected to the mounting rod (24), the two end surfaces of the protective shell (262) being rotatably connected to the side surface of the protective shell (262) away from the mounting rod (24), the protective shell (262) being provided with a drive for driving the end surface of the protective shell (262) to move in the protective shell (262) A driving member (263) is rotated on the protective shell (262); a rotating shaft (265) is arranged between the two end surfaces of the protective shell (262) and the side surface of the protective shell (262) away from the mounting rod (24), and a torsion spring (266) is sleeved on the rotating shaft (265) for driving the end surface of the protective shell (262) to rotate in a direction close to the mounting rod (24); the driving member (263) includes a transmission rope (267) passing through the inside of the side surface of the protective shell (262) away from the mounting rod (24), and the two ends of the transmission rope (267) extend to the inside of the two end surfaces of the protective shell (262) on the side of the rotating shaft (265) away from the mounting rod (24) and are fixedly connected to the two end surfaces of the protective shell (262); T-shaped slide bars (264) are arranged on the end surfaces of the two side surfaces of the protective shell (262) close to the mounting rod (24), and slide grooves matching the T-shaped slide bars (264) are opened on the side surfaces of the mounting rod (24).

2. The stepped pile according to claim 1, wherein: The two end surfaces of the protective shell (262) are inclined in a direction from approaching to moving away from the mounting rod (24) toward a direction approaching the center of the protective shell (262).

3. The stepped pile according to claim 1, wherein: A calibration rod (4) is mounted on the top ring (21), the calibration rod (4) and the top ring (21) are detachably connected, a sliding rod (41) is inserted into one end of the calibration rod (4) away from the top ring (21), and a limiting bolt (42) is arranged between the sliding rod (41) and the calibration rod (4).

4. The stepped pile according to claim 1, characterized in that: The outer surface of the pile section (11) is provided with a load-bearing protrusion (5), and the load-bearing protrusion (5) is distributed in a threaded shape on the outer surface of the pile section (11).

5. A construction method for stepped piles, characterized in that: The following steps are involved: Drilling: Drilling holes for step pile casting using drilling equipment with different drilling diameters (3); Assembly: The top ring (21) and the bottom ring (22) are respectively welded to positions close to both ends of the mounting rod (24) to complete the assembly of the mounting frame (2), the strain gauge (261) is sequentially mounted on the mounting rod (24), and the protective shell (262) is slidably mounted on the mounting rod (24); Lower cage: Assemble the mounting frame (2); Pouring: pouring the mixed concrete into the pouring hole (3); Demoulding: Pull the transmission rope (267) outward at the position of the rotating shaft (265) between the end face near the upper part of the protective shell (262) and the protective shell (262), and at the same time pull the protective shell (262) in the direction outside the pouring hole (3) until the protective shell (262) is pulled out of the pouring hole (3). Forming: Let the concrete in the pouring hole (3) stand until the concrete cools and the stepped pile is formed.

6. The construction method of a stepped pile according to claim 5, characterized in that: Before removing the protective shell (262) from the inside of the pouring hole (3), use the calibration rod (4) and the sliding rod (41) to check and adjust the coaxiality between the installation skeleton (2) and the pouring hole (3); after removing the protective shell (262) from the inside of the pouring hole (3), use the calibration rod (4) and the sliding rod (41) again to check and adjust the coaxiality between the installation skeleton (2) and the pouring hole (3).

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