Precast pile and foundation reinforcing method

Abstract

The invention relates to a precast pile and a foundation reinforcing method, and the precast pile comprises a bottom pile and a connecting pile; the bottom pile comprises a first pile body, a pile tip and a first pile splicing connector, and the pile tip and the first pile splicing connector are located at the two ends of the first pile body in the axial direction correspondingly. The connecting pile comprises a second pile body and second pile splicing connectors, the second pile splicing connectors are located at the two ends of the second pile body in the axial direction, and the second pile splicing connector at one end of the connecting pile is connected with the first pile splicing connector of the bottom pile; the first pile body and the second pile body comprise a plurality of pile bodies, each pile body is provided with a first pile section and a second pile section, the direction from the connecting pile to the bottom pile is defined as the first direction, the diameter of the first pile section is linearly increased in the first direction, the diameter of the second pile section is linearly decreased in the first direction, and the maximum diameter of the first pile section is equal to the maximum diameter of the second pile section. The precast pile can effectively improve the friction force between the pile wall and soil around the pile, and the single-pile bearing capacity of a friction pile is improved.

Description

Technical Field

[0001] The present application relates to the technical field of foundation treatment engineering, and in particular to a prefabricated pile and a foundation reinforcement method. Background Art

[0002] Using prefabricated piles for foundation reinforcement is a common foundation treatment method. According to the force characteristics of the piles, they are mainly divided into friction piles and end-bearing piles. Among them, friction piles mainly rely on the friction between the pile wall and the soil around the pile to provide bearing capacity. Therefore, the length of friction piles is generally long, which brings difficulty to construction and also increases the investment in foundation treatment. Summary of the invention

[0003] A first aspect of an embodiment of the present application provides a prefabricated pile, which can effectively increase the friction between the pile wall and the soil around the pile, and improve the single pile bearing capacity of the friction pile, thereby achieving the goal of reducing the pile length or pile diameter of the single pile at the same reinforcement density, or reducing the pile quantity at the same single pile size.

[0004] The prefabricated pile provided in a first aspect of the embodiment of the present application comprises: a bottom pile, the bottom pile comprising a first pile body, a pile tip and a first pile connection joint, the pile tip and the first pile connection joint are respectively located at two ends of the first pile body along the axial direction;

[0005] A connecting pile, the connecting pile comprises a second pile body and a second pile connection joint, the second pile connection joints are located at both ends of the second pile body along the axial direction, the second pile connection joint at one end of the connecting pile is connected to the first pile connection joint of the bottom pile; the first pile body and the second pile body comprise a plurality of pile bodies, the pile bodies have a first pile segment and a second pile segment, the direction from the connecting pile to the bottom pile is defined as a first direction, then the diameter of the first pile segment increases linearly along the first direction, the diameter of the second pile segment decreases linearly along the first direction, and the maximum diameter of the first pile segment is equal to the maximum diameter of the second pile segment.

[0006] In addition, the prefabricated piles provided in the embodiments of the present application may also have the following additional technical features:

[0007] In an optional solution, the bottom pile and the connecting pile have a hollow cavity, the length direction of the cavity extends along the first direction, at least one hole is provided between two adjacent pile bodies of the first pile body and the second pile body, the hole passes through the side wall of the pile body and is connected to the cavity; stones and cement slurry are provided in the cavity.

[0008] In an optional solution, an end wall is provided at the bottom of the pile tip, a through hole is provided on the end wall, the diameter of the through hole is 3 to 5 cm, and the through hole passes through the end wall; or, the cavity extends along the first direction and passes through the end of the pile tip.

[0009] In an optional solution, the through hole is located in the middle of the end wall; the number of the holes is 3 to 4, and the diameter of the holes is 3 to 5 cm.

[0010] In an optional solution, the prefabricated pile has an installation state. In the installation state, the bottom pile and the connecting pile are connected and located below the foundation, the second pile connection joint on one side of the top of the connecting pile is connected to the pile top cap, a pile bottom slurry diffusion area is formed at the bottom of the pile tip, and a pile wall cement slurry is formed on the outside of the pile body.

[0011] A second aspect of the embodiments of the present application provides a foundation reinforcement method, wherein the foundation reinforcement method uses the prefabricated piles in the embodiment of the first aspect to perform foundation reinforcement, and the foundation reinforcement method comprises the following steps:

[0012] 1) According to the properties of the reinforced foundation soil, the precast piles are sunk to the designed pile depth by means of vibration and / or static pressure;

[0013] 2) Filling the cavity of the prefabricated pile with stones whose maximum diameter is slightly smaller than the inner diameter of the cavity until the cavity is flush with the top of the pile;

[0014] 3) injecting cement slurry into the cavity in batches to perform segmented grouting;

[0015] 4) Construct the pile top cap. When constructing the pile top cap, the construction sequence should be determined taking into account the soil squeezing effect and construction efficiency.

[0016] In an optional scheme, when performing segmented grouting, the first grouting is pile bottom reinforcement grouting to increase the end bearing capacity of the precast pile. When there is groundwater within the pile body, a water pump is used to drain the groundwater entering the cavity before grouting. The grouting height is higher than the groundwater level and is not less than 3m. The grouting after the first grouting is pile body side wall grouting, which is performed in segments. The grouting height does not exceed 3m each time to fill the gap between the concave outer wall of the pile body and the soil around the pile, thereby increasing the friction between the pile body and the soil around the pile.

[0017] In an optional scheme, when performing segmented grouting, the water-cement ratio of the cement slurry is 1:1 to 1:0.5. When the voids in the underlying soil are large and the particles are coarse, a thick slurry is used, and when the voids in the underlying soil are small and the particles are fine, a thin slurry is used.

[0018] The beneficial effects of the embodiments of the present application are:

[0019] The pile body of the precast pile in the embodiment of the present application includes a first pile segment and a second pile segment, and the first pile segment and the second pile segment form a concave-convex surface structure, so that a reliable wave-shaped contact is formed between the pile and the soil around the pile, and the soil at the bottom of the pile is reinforced, thereby increasing the friction between the pile body and the soil around the pile and the bearing capacity of the pile bottom, and improving the overall bearing capacity of the single pile. In addition, after filling the cavity of the precast pile with stones and injecting slurry to solidify, the bearing capacity of the pile body itself can be improved, compensating for the damage to the pile body during the pile sinking process. The further diffusion of the slurry around the pile is also conducive to the reinforcement of the soil around the pile, and the bearing capacity of the surrounding soil around the pile is improved, which is particularly suitable for coarse-grained soil foundations with a certain degree of permeability.

[0020] It should be understood that the foregoing general description and the following detailed description are exemplary only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of the structure of a bottom pile provided in the present application in a specific embodiment;

[0022] Figure 2 A schematic diagram of the structure of a connecting pile provided in the present application in a specific embodiment;

[0023] Figure 3 Installation diagram of the bottom piles and connecting piles provided for this application after installation and reinforcement.

[0024] Figure numerals: bottom pile 1, first pile body 11, pile tip 12, first pile joint 13, connecting pile 2, second pile body 21, second pile joint 22, pile body 3, first pile section 31, second pile section 32, cavity 4, hole 41, stone 5, cement slurry in pile 6, pile top cap 7, pile bottom slurry diffusion area 8, pile wall cement slurry 9.

[0025] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application. DETAILED DESCRIPTION

[0026] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0027] It should be clear that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0028] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0029] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0030] It should be noted that the directional words such as "upper", "lower", "left", and "right" described in the embodiments of the present application are described at the angles shown in the accompanying drawings and should not be understood as limiting the embodiments of the present application. In addition, in the context, it is also necessary to understand that when it is mentioned that an element is connected to another element "upper" or "lower", it can not only be directly connected to another element "upper" or "lower", but also indirectly connected to another element "upper" or "lower" through an intermediate element.

[0031] like Figure 1-3 As shown, the first aspect of the embodiment of the present application provides a prefabricated pile, which mainly includes a bottom pile 1 and a connecting pile 2. The bottom pile 1 includes a first pile body 11, a pile tip 12 and a first pile joint 13, and the pile tip 12 and the first pile joint 13 are respectively located at two ends of the first pile body 11 along the axial direction; the connecting pile 2 includes a second pile body 21 and a second pile joint 22, and the second pile joint 22 is located at two ends of the second pile body 21 along the axial direction, and the second pile joint 22 at one end of the connecting pile 2 is connected to the first pile joint 13 of the bottom pile 1; the first pile body 11 and the second pile body 21 include a plurality of pile bodies 3, and the pile body 3 has a first pile segment 31 and a second pile segment 32, and the direction from the connecting pile 2 to the bottom pile 1 is defined as the first direction, then the diameter of the first pile segment 31 increases linearly along the first direction, and the diameter of the second pile segment 32 decreases linearly along the first direction, and the maximum diameter of the first pile segment 31 is equal to the maximum diameter of the second pile segment 32.

[0032] In this embodiment, the pile body 3 of the prefabricated pile includes a first pile segment 31 and a second pile segment 32. The first pile segment 31 and the second pile segment 32 form a concave-convex surface structure, so that the pile forms a reliable wave-shaped contact with the soil around the pile, and the pile bottom soil is reinforced, thereby increasing the friction between the pile body 3 and the soil around the pile and the pile bottom bearing capacity, and improving the overall bearing capacity of the single pile. Specifically, under the same pile diameter condition, the prefabricated pile can effectively increase the friction between the pile wall and the soil around the pile during the operation period without increasing the difficulty of pile sinking, and improve the single pile bearing capacity of the friction pile, thereby achieving the reduction of the size of the single pile (pile length or pile diameter) under the same reinforcement density, or reducing the number of piles under the same single pile size.

[0033] like Figure 1-3 As shown, in a specific embodiment, the bottom pile 1 and the connecting pile 2 have a hollow cavity 4, the length direction of the cavity 4 extends along the first direction, and at least one hole 41 is provided between two adjacent pile bodies 3 of the first pile body 11 and the second pile body 21, and the hole 41 penetrates the side wall of the pile body 3 and is connected to the cavity 4; stones 5 and cement slurry 6 are provided in the cavity 4, and the amount of slurry injection can be reduced by adding stones 5 into the cavity 4, and the maximum diameter of the stones 5 is slightly smaller than the inner diameter of the cavity 4, so the flow of slurry will not be hindered due to the presence of the stones 5.

[0034] In addition, in a specific embodiment, the bottom of the pile tip 12 is provided with an end wall, the end wall is provided with a through hole, the diameter of the through hole is 3 to 5 cm, and the through hole passes through the end wall; or, the cavity 4 extends along the first direction and passes through the end of the pile tip 12. The through hole is located in the middle of the end wall; the number of holes 41 is 3 to 4, and the diameter of the hole 41 is 3 to 5 cm.

[0035] like Figure 3 As shown, in a specific embodiment, the prefabricated pile has an installation state. In the installation state, the bottom pile 1 and the connecting pile 2 are connected and located below the foundation, the second pile connection joint 22 on one side of the top of the connecting pile 2 is connected to the pile top cap 7, a pile bottom slurry diffusion area 8 is formed at the bottom of the pile tip 12, and a pile wall cement slurry 9 is formed on the outside of the pile body 3.

[0036] After filling the cavity 4 of the precast pile with stones 5 and injecting slurry to solidify, the bearing capacity of the pile body 3 itself can be improved, compensating for the damage to the pile body during the pile sinking process. Further diffusion of the slurry around the pile is also beneficial to the reinforcement of the soil around the pile, improving the bearing capacity of the surrounding soil around the pile, and is particularly suitable for coarse-grained soil foundations with a certain degree of permeability.

[0037] In the embodiment of the first aspect, the pile body (the first pile segment 31 and the second pile segment 32) adopts a concave-convex structure, and the wavy contact between the pile and the soil around the pile is theoretically conducive to increasing the friction between the pile body 3 and the soil around the pile. This effect of increasing friction is related to the resilience of the soil. In actual engineering, after the soil between the piles is squeezed by the convex part, gaps may be formed in the concave part. The existence of the gap affects the friction enhancement effect brought by the wavy contact. At the same time, the pile bottom and the pile wall are reinforced by grouting in the pile body. Grouting at the bottom of the pile improves the end bearing capacity of the pile, and the reinforcement of the pile wall closes the gap that may exist between the concave part of the pile body and the soil around the pile, further increasing the friction enhancement brought by the wavy contact. The improvement of the end bearing capacity and the friction of the pile body can greatly improve the bearing capacity of the single pile, thereby reducing the amount of engineering work for foundation treatment.

[0038] A second aspect of the embodiments of the present application provides a foundation reinforcement method, which uses the prefabricated piles in the embodiment of the first aspect to reinforce the foundation, and the foundation reinforcement method includes the following steps:

[0039] 1) According to the properties of the reinforced foundation soil, the precast piles are sunk to the designed pile depth by means of vibration and / or static pressure;

[0040] 2) Fill the cavity 4 of the prefabricated pile with stones 5 whose maximum diameter is slightly smaller than the inner diameter of the cavity 4 until the stones are flush with the top of the pile;

[0041] 3) Injecting cement slurry into the cavity 4 in batches to perform segmented grouting;

[0042] 4) Construct the pile top cap 7. When constructing the pile top cap 7, the construction sequence should be determined by considering the soil squeezing effect and construction efficiency.

[0043] In a specific embodiment, when performing segmented grouting, the first grouting is pile bottom reinforcement grouting to increase the end bearing capacity of the prefabricated pile. When there is groundwater within the pile body, a water pump is used to drain the groundwater entering the cavity 4 before grouting, and the grouting height is higher than the groundwater level and is not less than 3m; the grouting after the first grouting is completed is the pile body side wall grouting, which is carried out in segments, and the grouting height does not exceed 3m each time to fill the gap between the concave outer wall of the pile body and the soil around the pile, thereby increasing the friction between the pile body and the soil around the pile.

[0044] In addition, it should be noted that when performing segmented grouting, the water-cement ratio of the cement slurry is 1:1 to 1:0.5. The specific water-cement ratio can be selected according to the properties of the underlying soil. For example, a thick slurry is used when the voids in the underlying soil are large and the particles are coarse, and a thin slurry is used when the voids in the underlying soil are small and the particles are fine.

[0045] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A prefabricated pile, characterized in that: include: A bottom pile, the bottom pile comprising a first pile body, a pile tip and a first pile connection joint, wherein the pile tip and the first pile connection joint are respectively located at two ends of the first pile body along the axial direction; A connecting pile, the connecting pile comprises a second pile body and a second pile connection joint, the second pile connection joints are located at both ends of the second pile body along the axial direction, the second pile connection joint at one end of the connecting pile is connected to the first pile connection joint of the bottom pile; the first pile body and the second pile body comprise a plurality of pile bodies, the pile bodies have a first pile segment and a second pile segment, the direction from the connecting pile to the bottom pile is defined as a first direction, then the diameter of the first pile segment increases linearly along the first direction, the diameter of the second pile segment decreases linearly along the first direction, and the maximum diameter of the first pile segment is equal to the maximum diameter of the second pile segment.

2. The prefabricated pile according to claim 1, characterized in that: The bottom pile and the connecting pile have a hollow cavity, the length direction of the cavity extends along the first direction, at least one hole is provided between two adjacent pile bodies of the first pile body and the second pile body, the hole penetrates the side wall of the pile body and is connected to the cavity; stones and cement slurry are provided in the cavity.

3. The prefabricated pile according to claim 2, characterized in that: The bottom of the pile tip is provided with an end wall, the end wall is provided with a through hole, the diameter of the through hole is 3-5 cm, and the through hole passes through the end wall; or the cavity extends along the first direction and passes through the end of the pile tip.

4. The prefabricated pile according to claim 3, characterized in that: The through hole is located in the middle of the end wall; the number of the holes is 3 to 4, and the diameter of the holes is 3 to 5 cm.

5. The precast pile according to any one of claims 2 to 4, characterized in that: The prefabricated pile has an installation state. In the installation state, the bottom pile and the connecting pile are connected and located below the foundation, the second pile connection joint on one side of the top of the connecting pile is connected to the pile top cap, a pile bottom slurry diffusion area is formed at the bottom of the pile tip, and a pile wall cement slurry is formed on the outside of the pile body.

6. A foundation reinforcement method, characterized in that: The foundation reinforcement method uses the prefabricated piles described in any one of claims 1 to 5 to reinforce the foundation, and the foundation reinforcement method comprises the following steps: 1) According to the properties of the reinforced foundation soil, the precast piles are sunk to the designed pile depth by means of vibration and / or static pressure; 2) Filling the cavity of the prefabricated pile with stones whose maximum diameter is slightly smaller than the inner diameter of the cavity until the cavity is flush with the top of the pile; 3) injecting cement slurry into the cavity in batches to perform segmented grouting; 4) Construct the pile top cap. When constructing the pile top cap, the construction sequence should be determined taking into account the soil squeezing effect and construction efficiency.

7. The foundation reinforcement method according to claim 6, characterized in that: When performing segmented grouting, the first grouting is the pile bottom reinforcement grouting to increase the end bearing capacity of the precast pile. When there is groundwater within the pile body, a water pump is used to drain the groundwater entering the cavity before grouting. The grouting height is higher than the groundwater level and is not less than 3m. The grouting after the first grouting is the pile body side wall grouting, which is carried out in segments. The grouting height does not exceed 3m each time to fill the gap between the concave outer wall of the pile body and the soil around the pile, thereby increasing the friction between the pile body and the soil around the pile.

8. The foundation reinforcement method according to claim 6 or 7, characterized in that: When performing segmented grouting, the water-cement ratio of the cement slurry is 1:1 to 1:0.

5. When the voids in the underlying soil are large and the particles are coarse, a thick slurry is used, and when the voids in the underlying soil are small and the particles are fine, a thin slurry is used.

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