A method for constructing a precast pile
By laying an aggregate layer and grouting it at the pile driving location of the precast pile, the problems of insufficient pile end resistance and dispersion in the existing technology are solved, and the stability and consistency of the pile foundation bearing capacity are improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HUNAN QIYAN ZHUCHUANG ENGINEERING TECHNOLOGY CO LTD
- Filing Date
- 2026-04-30
- Publication Date
- 2026-06-19
AI Technical Summary
In existing precast pile construction methods, the pile end resistance is difficult to reach the ideal value and has a large dispersion. This is mainly because the soft soil layer on the surface is brought into the hard rock and soil layer, resulting in insufficient bearing capacity.
An aggregate layer is laid at the location where the precast pile is driven. The precast pile and the aggregate are pressed into the ground together using a pile driving device. The aggregate forms a cone-shaped pile tip. Grout is injected during the pile driving process to reinforce the pile bottom and the surrounding soil and enhance the pile end resistance.
It increases the end resistance of the pile, reduces the influence of weak soil layers, ensures the stability and consistency of the pile foundation bearing capacity, and enhances the friction around the pile.
Smart Images
Figure CN122236098A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for constructing precast piles, belonging to the field of precast pile construction technology. Background Technology
[0002] Most existing precast piles (including concrete pipe piles, solid concrete piles, and steel pipe piles) have a closed end plate at the bottom (during construction, the end plate is roughly horizontal, with vertical ribs below it). Precast pile construction uses static pressure or hammer driving methods to press the precast pile down and squeeze the soil, driving it to the bearing layer (a relatively strong, hard soil or rock layer) to achieve the desired end resistance. However, precast piles constructed using this method sometimes fail to achieve the desired bearing capacity during bearing capacity testing, and different precast piles exhibit varying end resistances, resulting in significant dispersion in pile foundation bearing capacity. Summary of the Invention
[0003] In order to overcome the problems existing in the prior art, the present invention provides a precast pile construction method that can stably improve the pile end resistance of precast piles. The specific technical solution is as follows.
[0004] A method for constructing precast piles, wherein the lower end of the precast pile has an end plate, characterized by comprising the following steps:
[0005] 1) Lay an aggregate layer at the location where the precast piles are driven;
[0006] 2) The lower end of the precast pile is placed against the aggregate layer, and the precast pile and the aggregate layer are driven into the ground to a predetermined depth using a pile driving device.
[0007] A thorough study of existing precast pile construction methods revealed that when the lower end of a precast pile is driven into the ground, it first contacts the surface soil layer. This soil layer typically has relatively low strength. Constrained by the structural characteristics of the horizontal end plate, during pile driving, the initially soft surface soil beneath the end plate sinks along with the precast pile under the pressure and constraint of the surrounding soil. This soft surface soil is retained at the pile bottom until the pile tip sinks into the hard rock and soil layer at the design depth. At this point, a certain amount of soft surface soil is trapped between the pile bottom and the hard rock and soil layer, resulting in a pile tip resistance lower than the theoretically calculated design value. This is because the compression modulus (deformation modulus) of the soft soil layer is small, leading to greater deformation under load (while the allowable settlement deformation of the pile foundation is very small), thus reducing the pile foundation's bearing capacity. Although the rib plate has high structural strength and is not easily deformed, its thinness makes it prone to damaging the hard rock and soil layer; that is, the rib plate alone cannot provide sufficient pile tip resistance. Furthermore, the varying degrees of softness of the surface soil at different pile locations can lead to differences in the degree of reduction in resistance at the end of each pile, resulting in significant dispersion in the bearing capacity of the pile foundation.
[0008] The above technical solution involves first laying an aggregate layer at the precast pile driving location, then pressing the precast pile and aggregate together into the ground. During the driving process, some of the aggregate at the edges will slide down to the vicinity of the precast pile due to friction, while the remaining aggregate will form a cone-shaped pile tip at the lower end of the precast pile. This continues until the precast pile sinks into the hard soil layer. Under pressure, the aggregate at the lower end of the precast pile will tend to flatten and stabilize, thus overcoming the technical problem in existing technologies where soft soil is brought into the hard soil layer and the pile tip causes a decrease in pile end resistance.
[0009] Furthermore, in step 1), a groove is excavated at the location where the precast pile is driven, and an aggregate layer is laid in the groove.
[0010] Furthermore, in step 1), a groove is first formed by pressing down the precast pile at the pile driving position, then the precast pile is pulled out upwards, and then an aggregate layer is laid in the groove.
[0011] Preferably, the aggregate layer is made of at least one of dry-hard concrete, cement-stabilized crushed stone, or sand, crushed stone, and pebbles. Preferably, the upper part of the aggregate layer is crushed stone, and the lower part is sand. Sand facilitates the formation of a relatively smooth soil-sliding surface at the pile bottom during pile driving, improving pile driving efficiency. Dry-hard concrete is a mixture of crushed stone, sand, and cement with low water content, while cement-stabilized crushed stone is a mixture of crushed stone and cement without water. Dry-hard concrete or cement-stabilized crushed stone can also better enhance the pile bottom strength without grouting.
[0012] Furthermore, a hydraulic dry powder material is laid beneath the aggregate layer. This hydraulic dry powder material can be cement powder, quicklime powder, or a curing agent, etc. During pile driving, the hydraulic dry powder material is pushed down by the pile tip aggregate assembly, rubbing against the dissipated soil sliding surface and dispersing on it, ultimately forming a pile-soil contact surface containing dry powder. After absorbing pore water from the soil, this dry powder undergoes a hydration and hardening reaction, consolidating around the pile and forming a high-strength soil reinforcement layer, thereby significantly increasing the frictional force around the pile.
[0013] Furthermore, vertical ribs are fixedly installed below the end plate, and the ribs are radially distributed on the end plate. The ribs not only improve the strength of the end plate, but also divide the area below the end plate into several spaces for accommodating aggregates, which helps to improve the stability of the aggregates during pile driving.
[0014] Furthermore, the edge of the end plate is fixedly provided with vertically downward extending anti-slip plates, and several of the anti-slip plates are spaced apart or all of the anti-slip plates are together to form a cylindrical shape. By setting anti-slip plates, it is beneficial to ensure that a large amount of aggregate can be stably held below the end plate during the pile driving process, and to ensure that enough aggregate will form a cone-shaped pile tip at the lower end of the precast pile.
[0015] Furthermore, the precast pile includes a precast pile body and the end plate. The precast pile body has a hollow cavity. A grout diffusion box is fixedly installed on the end plate. The grout diffusion box is located in the hollow cavity. The end plate is provided with several through holes. The through holes communicate with the inner cavity of the grout diffusion box. The grout diffusion box is provided with a grouting pipe joint communicating with the inner cavity. The particle size of the sand, gravel, or pebbles in the aggregate layer is larger than the diameter of the through holes.
[0016] The precast pile construction method also includes a grouting step: during or after pile driving, grout is injected into the underside of the end plate through grouting pipes and grout diffusion boxes. The particle size of the crushed stone is larger than the diameter of the through-hole, which effectively prevents blockage. Grouting is then performed at the pile bottom through grouting pipes located inside the precast pile body, thereby reinforcing the pile bottom aggregate and the soil and rock mass, which helps to improve the pile end resistance (pile end bearing capacity).
[0017] Furthermore, the edge of the end plate is fixedly provided with vertically downward extending anti-slip plates, all of which together form a cylindrical shape. Viewed along the axial direction of the precast pile body, at least a portion of the end plate extends to the outside of the precast pile body. The end plate is also provided with a return flow hole, located inside the anti-slip plates and outside the precast pile body. When grout is injected under the end plate using a grouting pipe, the grout can flow back from the return flow hole into the gap between the precast pile body and the pile hole, thereby reinforcing the soil around the pile and improving the pile's frictional force (pile bearing capacity).
[0018] Furthermore, before the grouting step, a plugging operation is performed: air or water is injected into the grout diffusion box using the grouting pipe. High-pressure air or clean water can be used to open the through holes on the end plate and the gaps around the precast pile body. Successful plugging is indicated when air or water emerges from the ground, creating favorable conditions for the next step of grouting.
[0019] Compared with the prior art, the present invention can fill the space between the precast pile tip and the hard soil layer (pile tip bearing layer) with high-strength aggregate, overcoming the technical problem in the prior art that the introduction of soft soil into the space between the hard soil layer and the precast pile tip causes a decrease in pile tip resistance. Attached Figure Description
[0020] Figure 1 This is a schematic diagram of a precast pile according to Embodiment 1 of the present invention;
[0021] Figure 2 yes Figure 1 A bottom view;
[0022] Figure 3 This is a schematic diagram of the first construction process of the precast pile in Embodiment 1 of the present invention;
[0023] Figure 4 This is a schematic diagram of the second construction process of the precast pile in Embodiment 1 of the present invention;
[0024] Figure 5 This is a schematic diagram of a modified embodiment 1 of the present invention;
[0025] Figure 6 This is a schematic diagram of a precast pile according to Embodiment 2 of the present invention;
[0026] Figure 7 This is a schematic diagram of a precast pile according to Embodiment 3 of the present invention;
[0027] Figure 8 yes Figure 7 A bottom view;
[0028] Figure 9 This is a schematic diagram of the precast pile construction process in Embodiment 3 of the present invention;
[0029] Figure 10 This is a schematic diagram of a precast pile according to Embodiment 4 of the present invention;
[0030] Figure 11 yes Figure 10 A bottom view;
[0031] Figure 12 This is a schematic diagram of the construction process of some precast piles in Embodiment 5 of the present invention.
[0032] In the figure: 1. Precast pile body, 1.1 Hollow cavity, 2. End plate, 2.1 Through hole, 2.2 Return flow hole, 3. Rib plate, 4. Aggregate layer, 5. Groove, 6. Hydraulic dry powder material, 7. Anti-slip plate, 8. Grout diffusion box, 9. Grouting pipe joint, 10. Air compressor, 11. Pile driving equipment, 12. Grouting equipment. Detailed Implementation
[0033] The present invention will now be described in further detail with reference to the accompanying drawings.
[0034] Example 1
[0035] See Figure 1-3 The precast pile includes a precast pile body 1 and an end plate 2 located at the lower end of the precast pile body 1. A vertical rib plate 3 is fixedly installed below the end plate 2, and the rib plate 3 is radially distributed on the end plate 2.
[0036] The precast pile construction method includes the following steps:
[0037] 1) Lay an aggregate layer 4 at the location where the precast piles are driven;
[0038] 2) The lower end of the precast pile is placed against the aggregate layer 4, and the precast pile and the aggregate layer 4 are pressed into the ground to a predetermined depth using the pile driving equipment 12.
[0039] like Figure 3 As shown, in step 1), a groove 5 is first excavated at the location where the precast pile is driven, and an aggregate layer 4 is laid in the groove 5. Of course, those skilled in the art will understand that: Figure 4 As shown in step 1), a groove 5 is first formed by pressing down the precast pile at the pile driving position, and then the precast pile is pulled out upward. Then, an aggregate layer 4 is laid in the groove 5.
[0040] The aggregate layer 4 is made of at least one of dry-hard concrete, cement-stabilized crushed stone, or sand, crushed stone, and pebbles. The aggregate layer 4 must have a certain degree of mobility and structural strength. Preferably, the upper part of the aggregate layer 4 is crushed stone, and the lower part is sand. Sand facilitates the formation of a relatively smooth soil-sliding surface at the bottom of the pile during pile driving, thus improving pile driving efficiency.
[0041] More preferably, such as Figure 5 As shown, a hydraulic dry powder material 6 is also laid below the aggregate layer 4. The hydraulic dry powder material 6 can be cement dry powder, quicklime powder, or a curing agent, etc. During the pile driving process, the hydraulic dry powder material 6 is pushed down by the pile tip aggregate assembly, rubs against the displaced soil sliding surface, and disperses on the sliding surface, eventually forming a pile-soil contact surface with dry powder. After absorbing the pore water in the soil, these dry powders undergo a hydration and hardening reaction, consolidating around the pile and forming a thin soil reinforcement layer with high strength, thereby significantly improving the friction around the pile.
[0042] It should be noted that: although Figure 1 The precast pile body shown in the diagram is a hollow structure, but solid concrete piles can also be used. Rib plate 3 can be omitted in some cases. The pile driving device 12 uses a static pressure device or a hammer driving device.
[0043] In this embodiment, firstly, an aggregate layer 4 is laid at the location where the precast pile is driven. Then, the precast pile and the aggregate are pressed into the ground together. During the driving process, some of the aggregate at the edge will slide down to the vicinity of the precast pile under the action of friction. The remaining aggregate will form a cone-shaped pile tip at the lower end of the precast pile until the precast pile sinks into the hard rock and soil layer. Under the action of pressure, the aggregate at the lower end of the precast pile will tend to be flat and stable, reducing or avoiding the retention of too much soft soil between the aggregate and the hard rock and soil layer. This overcomes the technical problem in the prior art of bringing soft soil into the hard rock and soil layer and causing a decrease in pile end resistance.
[0044] Example 2
[0045] See Figure 6Based on Embodiment 1, Embodiment 2 features vertically downward-extending anti-slip plates 7 fixedly installed along the edge of the end plate 2, with all anti-slip plates 7 forming a cylindrical shape. The anti-slip plates 7 help ensure that a large amount of aggregate remains stably below the end plate 2 during pile driving, ensuring sufficient aggregate forms a cone-shaped pile tip at the lower end of the precast pile. It should be noted that, as an alternative to having all anti-slip plates 7 form a cylindrical shape, several anti-slip plates 7 can be spaced apart (not shown), allowing for a certain distance between adjacent anti-slip plates.
[0046] Example 3
[0047] See Figures 7-9 Based on Embodiment 1 or Embodiment 2, the precast pile of Embodiment 3 includes a precast pile body 1 and an end plate 2 located at the lower end of the precast pile body 1. The precast pile body 1 has a hollow cavity 1.1. A grout diffusion box 8 is fixedly installed on the end plate 2. The grout diffusion box 8 is located inside the hollow cavity 1.1. The end plate 2 is provided with several through holes 2.1. The through holes 2.1 communicate with the inner cavity of the grout diffusion box 8. A grouting pipe joint 9 is provided on the grout diffusion box 8 and communicates with the inner cavity. The grouting pipe joint 9 is used to connect the grouting pipe 10. The particle size of the sand, gravel or pebble is larger than the diameter of the through hole 2.1.
[0048] The precast pile construction method also includes a grouting step: during or after pile driving, grout is injected into the underside of the end plate 2 through the grouting equipment 13, the grouting pipe 10 (the grouting pipe 10 is connected to the grouting pipe joint 9), and the grout diffusion box 8. The particle size of the sand, gravel, or pebbles is larger than the diameter of the through hole 2.1, which can effectively prevent the through hole 2.1 from becoming blocked. Grout is injected into the pile bottom through the grouting pipe 10 located inside the precast pile body 1, thereby reinforcing the pile bottom aggregate and the soil and rock mass at the pile bottom, which is beneficial to improving the pile end resistance (pile end bearing capacity).
[0049] Among them, anti-backflow measures (such as one-way valves) can be set in the grouting pipe 10 or the grout diffusion box 8 to prevent underground mud and water from entering the grouting pipe, polluting and blocking the grouting pipe passage during the piling process, and to prevent the injected grout from flowing back out of the grouting pipe and grout loss.
[0050] Example 4
[0051] See Figures 10-11Based on Example 3, Example 4 has a vertically downward extending anti-slip plate 7 fixedly installed on the edge of the end plate 2, with all anti-slip plates 7 forming a cylindrical shape. Viewed along the axial direction of the precast pile body 1, at least a portion of the end plate 2 extends to the outside of the precast pile body 1. A return flow hole 2.2 is also provided on the end plate 2, located inside the anti-slip plate 7 and outside the precast pile body 1. When grout is injected into the underside of the end plate 2 using the grouting pipe 10, the grout can flow upwards from the return flow hole 2.2 into the gap between the precast pile body 1 and the pile hole, as well as into the surrounding soil and rock. This strengthens the soil around the pile, forming a cement-soil composite reinforcement. After solidification, it forms a composite pile with a larger diameter together with the precast pile, thereby significantly improving the pile side friction and pile foundation bearing capacity.
[0052] Example 5
[0053] See Figure 12 Based on Example 3 or Example 4, Example 5 performs a plugging operation before the grouting step: air or water is injected into the grout diffusion box 8 using the grouting pipe 10 of the air compressor 11 (or grouting machine). High-pressure air or clean water can be used to open the through hole 2.1 on the end plate 2 and the gap around the precast pile body 1. The plugging is successful when air or water is seen emerging from the ground, creating favorable conditions for the next step of grouting.
[0054] The embodiments of the present invention have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention is not limited to the specific embodiments described above; these embodiments are merely illustrative and not limiting. Those skilled in the art, under the guidance of the present invention, can make many modifications without departing from the spirit and scope of the claims, and all such modifications fall within the scope of protection of the present invention.
Claims
1. A method for constructing precast piles, wherein the lower end of the precast pile has an end plate (2), characterized in that, Includes the following steps: 1) Lay an aggregate layer at the location where the precast piles are driven (4); 2) The lower end of the precast pile is placed against the aggregate layer (4), and the precast pile and the aggregate layer (4) are pressed into the ground to a predetermined depth using the pile driving equipment (12).
2. The precast pile construction method according to claim 1, characterized in that, In step 1), a groove (5) is excavated at the location of the precast pile driving, and an aggregate layer (4) is laid in the groove (5).
3. The precast pile construction method according to claim 1, characterized in that, In step 1), a groove (5) is first formed by pressing down the precast pile at the pile driving position, and then the precast pile is pulled out upward. Then, an aggregate layer (4) is laid in the groove (5).
4. The precast pile construction method according to claim 1, characterized in that, The aggregate layer (4) is made of at least one of dry hard concrete, cement-stabilized crushed stone, sand, crushed stone, and pebbles; or the upper part of the aggregate layer (4) is crushed stone and the lower part is sand.
5. A precast pile construction method according to claim 1 or 4, characterized in that, A hydraulic dry powder material (6) is also laid below the aggregate layer (4).
6. The precast pile construction method according to claim 1, characterized in that, A vertical rib (3) is fixedly installed below the end plate (2), and the rib (3) is radially distributed on the end plate (2).
7. The precast pile construction method according to claim 1, characterized in that, The edge of the end plate (2) is fixedly provided with a vertically downward extending anti-slip plate (7), and a plurality of the anti-slip plates (7) are spaced apart or all the anti-slip plates (7) are together to form a cylindrical shape.
8. A precast pile construction method according to claim 1, characterized in that, The precast pile includes a precast pile body (1) and an end plate (2). The precast pile body (1) has a hollow cavity (1.1). A grout diffusion box is fixedly installed on the end plate (2). The grout diffusion box is located inside the hollow cavity (1.1). The end plate (2) is provided with several through holes (2.1). The through holes (2.1) are connected to the inner cavity of the grout diffusion box. A grouting pipe joint (9) connected to the inner cavity is provided on the grout diffusion box. The particle size of the sand, gravel, or pebbles in the aggregate layer (4) is larger than the aperture of the through holes (2.1). The precast pile construction method also includes a grouting step: during or after pile driving, grout is injected into the underside of the end plate (2) through the grouting pipe (10) and grout diffusion box.
9. A precast pile construction method according to claim 8, characterized in that, The edge of the end plate (2) is fixedly provided with a vertically downward extending anti-slip plate (7), and a plurality of the anti-slip plates (7) are spaced apart or all the anti-slip plates (7) are together to form a cylindrical shape; when viewed along the axial direction of the precast pile body (1), at least a portion of the end plate (2) extends to the outside of the precast pile body (1); the end plate (2) is also provided with a return flow hole (2.2), which is located on the inner side of the anti-slip plate (7) and the outer side of the precast pile body (1).
10. A method for constructing precast piles according to claim 8 or 9, characterized in that, Before the grouting step, the plugging operation is performed: air or water is injected into the grout diffusion box using the grouting pipe (10).