Precast pile structure for sea silt soil site and pile body grouting reinforcement method

Abstract

The invention relates to the technical field of foundation piles, in particular to a precast pile structure for a sea silt soil site and a pile body grouting reinforcement method. The precast pile structure comprises a plurality of pile columns which can be spliced with one another and a pile tip connected to the lowest pile column; the pile column comprises a pile body, an upper connecting flange and a lower connecting flange, wherein the upper connecting flange and the lower connecting flange are connected to the two ends of the pile body. By injecting a curing agent into a soil layer with a preset depth to cure the soil layer around the pile body and grouting and curing the soil body around the pile, the strength of the soil layer is improved, the side frictional resistance of a pile-soil interface is improved, meanwhile, pile end grouting forms an expanded head effect, the end bearing force is increased, and the method is particularly suitable for a site with a shallow bearing layer missing; due to the fact that the soil body is solidified, the compactness and the impermeability of the soil layer are improved, the risk of soil body liquefaction under the dynamic load is remarkably reduced, the impermeability of the solidified soil body around the pile is improved, and strength degradation caused by underground water erosion is relieved.

Description

Technical Field

[0001] The present invention relates to the technical field of foundation piles, and particularly to a precast pile structure for a marine silt soil site and a method for grouting and strengthening the pile body. Background Art

[0002] In the field of civil engineering, precast pile technology is widely used in the foundation treatment of infrastructure such as buildings, bridges, and ports due to its advantages of fast construction speed and controllable quality. Especially in projects in coastal areas, river deltas, and reclamation areas, the pile foundation needs to penetrate marine sedimentary layers or silt soil layers with high water content and low bearing capacity. These soil layers generally exhibit characteristics such as high compressibility, low permeability, and easy thixotropy, resulting in multiple challenges in traditional precast pile construction.

[0003] Existing precast pile construction mostly relies on the direct interaction between the pile body and natural soil, and its bearing capacity mainly depends on the inherent strength of the soil around the pile. However, in soft soil layers, the soil structure is loose and the shear strength is low, which easily leads to problems such as insufficient side friction resistance of the pile and difficulty in exerting end bearing capacity. Although increasing the pile length or expanding the pile diameter can partially make up for the bearing capacity defect, such methods greatly increase the material cost and are prone to construction risks such as pile body inclination and pile breakage in complex strata.

[0004] During the construction of precast piles in a marine silt soil site, due to factors such as the large size, heavy self-weight of the pile driver equipment, poor site bearing capacity, and high water content, it is easy to cause construction machine sinking, posing safety hazards and quality problems such as pile body inclination and pile position deviation after precast pile construction. Therefore, people have tried to improve the performance of the pile foundation by introducing soil solidifying agents, and through the dual actions of high-pressure jet grouting solidifying agent stirring and forced stirring for forced consolidation. Although the properties of the marine silt soil are changed after the site is solidified, it can ensure construction safety and the quality of the pile body for a certain period of time, but it is difficult to adjust the bearing capacity according to the actual load change or geological condition evolution after construction, resulting in an increase in later maintenance requirements and a decline in comprehensive economic benefits. Summary of the Invention

[0005] In view of the technical problems existing in precast piles in the prior art, the first aspect of the present invention provides a precast pile structure for a marine silt soil site, including a plurality of mutually spliceable pile columns and a pile tip connected to the lowermost pile column;

[0006] The pile column includes a pile body and an upper connecting flange and a lower connecting flange connected to both ends of the pile body;

[0007] The pile body includes a concrete structure and steel bars and grouting pipes embedded in the concrete structure, and the upper connecting flange and the lower connecting flange are provided with first openings corresponding to the positions of the steel bars and second openings corresponding to the positions of the grouting pipes;

[0008] Wherein, a grouting cavity is provided inside the upper connecting flange. The grouting cavity is configured to have a first jack connected to the upper end face of the upper connecting flange and a second jack connected to the lower end face of the upper connecting flange. The grouting cavity also has a grouting hole facing the outside of the pile body;

[0009] The grouting pipe is configured such that its upper end extends into the second jack of the grouting cavity, and its lower end extends below the lower connecting flange. When two adjacent pile columns are butt - jointed, the lower end of the grouting pipe extends into the first jack;

[0010] A plug is detachably connected inside the grouting cavity. The plug is configured to control the on - off state between the grouting pipe and the grouting cavity, enabling the grouting pipe inlet of the uppermost pile column to communicate with the grouting hole of any one of the lower pile columns, so as to inject a reinforcing agent into the soil layer at a predetermined depth.

[0011] Preferably, the grouting cavity is configured as an annular structure. Along the axial direction of the pile column, the width at the middle position of the grouting cavity is greater than the widths at the upper and lower ends. The maximum outer diameter of the plug is less than the maximum width of the grouting cavity, and the grouting holes are arranged at the middle position of the grouting cavity.

[0012] Preferably, a plurality of grouting holes are provided on the outer side of the grouting cavity and are distributed in a circumferential array.

[0013] Preferably, the plug is configured as a columnar shape, and the cross - sectional dimension of the middle part is greater than that of the two ends. The plug is an elastic structure, and the plug includes a first plug, a second plug, and a third plug;

[0014] The first plug is a solid columnar structure, and the height of the first plug is greater than the height of the grouting cavity. When the first plug is filled into the grouting cavity, the grouting pipes at adjacent upper and lower positions are not connected;

[0015] The second plug is a hollow columnar structure, and the height of the second plug is greater than the height of the grouting cavity. When the second plug is filled into the grouting cavity, the grouting pipes at adjacent upper and lower positions are connected;

[0016] The third plug is a solid columnar structure, and the height of the third plug is less than the height of the grouting cavity. When the third plug is filled into the grouting cavity, it is used to block the lower grouting pipe.

[0017] Preferably, the end of the plug is configured such that its diameter is less than the inner diameter of the grouting cavity, enabling the plug to extend into the inner wall of the grouting cavity, and the outer wall of the plug is configured to have a bevel with a gradually changing diameter.

[0018] Preferably, a plurality of the grouting pipes are provided in each of the pile bodies, and the plugs in each grouting cavity are configured to include at least one third plug and a plurality of first plugs and / or a plurality of second plugs, so that the grouting pipe in the uppermost pile body is communicated with any one of the grouting pipes in the lower layer of pile bodies.

[0019] Preferably, the upper connecting flange includes a first plate body, an outer connecting ring, an inner connecting ring and a second plate body. The outer connecting ring and the inner connecting ring are located between the first plate body and the second plate body. A grouting cavity is formed between the outer connecting ring and the inner connecting ring. The grouting holes are provided in the outer connecting ring, and a first reinforcing plate extending downward is provided on the periphery of the first plate body.

[0020] Preferably, the lower connecting flange includes a third plate body and a second reinforcing plate. The second reinforcing plate is located on the periphery of the third plate body and extends upward.

[0021] Preferably, a plurality of the steel bars are distributed around the grouting pipes, or a plurality of the steel bars include a first part distributed around the grouting pipes and a second part distributed on the same circumference as the grouting pipes.

[0022] In a second aspect of the present invention, a technical solution is proposed. A method for grouting and reinforcing the pile body of the precast pile structure for a marine silt soil site as described above includes the following steps:

[0023] Step 1: Number all the pile columns in sequence according to the order of pile column pressing, where the one connected to the pile tip is No. 1. At the same time, in the axial direction of the pile column, number all the grouting pipes in sequence in the clockwise direction;

[0024] Step 2: Before connecting each next pile column according to the number of the pile columns, press plugs into the grouting cavity in a predetermined order;

[0025] Step 3: During the process of pressing the pile columns, connect all the pile columns in sequence, and press plugs in the manner of this step;

[0026] Step 4: After all the pile columns are connected and pressed, grout around the grouting holes of each pile column in sequence through the grouting pipe at the upper end of the uppermost pile column. After curing, a strengthening area is formed in the soil layer around the connection of two adjacent pile columns.

[0027] Compared with the prior art, the advantages of the present invention are as follows:

[0028] The precast pile structure proposed in this solution is configured with a grouting system, which can achieve the comprehensive goals of bearing capacity improvement, construction controllability, maintenance convenience and cost optimization for complex geological scenarios such as marine silt soil.

[0029] The soil layer around the pile is solidified by injecting a solidifying agent into the soil layer at a predetermined depth. After the soil around the pile is grouted and solidified, the strength of the soil layer is improved, the side friction resistance at the pile-soil interface is increased. At the same time, the end grouting forms an enlarged head effect, increasing the end bearing capacity, which is especially suitable for sites lacking shallow bearing layers. Further, since the solidified soil improves the density and impermeability of the soil layer, the risk of soil liquefaction under dynamic loads is significantly reduced. The impermeability of the soil around the pile after solidification is improved, slowing down the strength degradation caused by groundwater erosion.

[0030] Through the grouting channel arranged inside the pile body, the strength of the soil can be improved by grouting, and the pile length can be reduced by 10% - 20%, saving the consumption of concrete and steel bars; inclined piles can be continued to be used after in-situ rectification through grouting reinforcement, reducing the waste pile rate. During the above grouting reinforcement process, only the local soil around the pile is reinforced, avoiding large-area excavation and replacement, and protecting the site ecology.

[0031] In addition, even if it is found during construction that the actual geological conditions do not match the exploration report, for example, there are local soft interlayers, the soil can still be reinforced by supplementary grouting to avoid pile foundation failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in each figure may be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Now, embodiments of various aspects of the present invention will be described by way of example and with reference to the drawings, wherein:

[0033] Figure 1 is a schematic structural view of a precast pile structure shown in the present invention being pressed into a soil layer for a marine mucky soil site;

[0034] Figure 2 is a schematic structural view of a precast pile structure shown in the present invention for a marine mucky soil site;

[0035] Figure 3 is a schematic structural view of an upper connecting flange shown in the present invention;

[0036] Figure 4 is a top view of an upper connecting flange shown in the present invention;

[0037] Figure 5 is a schematic numbering view of a grouting pipe connected to an upper connecting flange shown in the present invention;

[0038] Figure 6 is a schematic structural view of a first plug and a second plug in a grouting cavity shown in the present invention;

[0039] Figure 7 is a schematic structural view of a third plug and a second plug in a grouting cavity shown in the present invention;

[0040] Figure 8 It is a schematic diagram of the plug distribution in the pile bodies with different depths shown in the present invention. Specific Embodiments

[0041] For a better understanding of the technical content of the present invention, specific embodiments are hereby given and described in conjunction with the accompanying drawings as follows.

[0042]

Prefabricated Pile Structure for Marine Silt Soil Site

[0043] Combined with Figures 1 to 4 As shown, a first aspect of the present invention provides a prefabricated pile structure for a marine silt soil site, which includes a plurality of mutually spliceable pile columns 100 and a pile tip 200 connected to the lowermost pile column 100. After a plurality of mutually spliced pile columns 100 are pressed into the soil layer, the upper layer of the soil layer is a strengthened area T1, and the lower layer of the soil layer is an unstrengthened area T2. The strengthened area T1 is solidified by a curing agent before the pile columns 100 are pressed in, and its strength is greater than that of the unstrengthened area T2.

[0044] It should be understood that since the unstrengthened area T2 has creep property and low strength, there is a risk of pile body deflection in the subsequent process. To improve the strength of the unstrengthened area T2, the present application aims to spray a curing agent around the pile columns 100 through the pile columns 100 to form a strengthened area T1 in part of the unstrengthened area T2.

[0045] Combined with Figure 2 As shown, the pile column 100 includes a pile body 110 and an upper connection flange 120 and a lower connection flange 130 connected to both ends of the pile body 110.

[0046] Combined with Figure 4 As shown, the pile body 110 includes a concrete structure 111 and steel bars 112 and grouting pipes 113 embedded in the concrete structure 111. The upper connection flange 120 and the lower connection flange 130 are provided with first openings 124a corresponding to the positions of the steel bars 112 and second openings 124b corresponding to the positions of the grouting pipes 113.

[0047] Through the setting of the first opening 124a, the steel bar 112 can pass through the first opening 124a, and through the setting of the second opening 124b, the grouting pipe 113 can pass through the second opening 124b.

[0048] Furthermore, a grouting cavity 125 is provided inside the upper connection flange 120. The grouting cavity 125 is provided with a first jack connected to the upper end face of the upper connection flange 120 and a second jack connected to the lower end face of the upper connection flange 120. The grouting cavity 125 also has a grouting hole 126 facing the outside of the pile body 110.

[0049] Among them, the grouting pipe 113 is arranged such that its upper end extends to the second jack of the grouting cavity 125, and the lower end of the grouting pipe 113 extends below the lower connecting flange 130. When two adjacent upper and lower pile columns 100 are butted, the lower end of the grouting pipe 113 extends into the first jack.

[0050] In this way, the curing agent can be injected into the grouting cavity 125 through the grouting pipe 113, and then shot into the surrounding soil layer through the grouting holes 126 on the outer side of the pile body 110. The principle of the curing agent curing is that by adding curing materials, the free water saturated in the silt becomes crystal water or water ions combined with soil particles.

[0051] In an alternative embodiment, a silt curing agent is used. This type of curing agent reacts with water to produce Ca(OH) 2 products. These products undergo an ion exchange reaction with clay particles and adsorb between the particles to form a solidified substance. Eventually, the free water in the silt decreases and the strength increases. The permeability coefficient of the solidified silt is very small, making it difficult for harmful substances to leach and dissolve again to form secondary pollution.

[0052] Furthermore, in order to control the curing agent to reach different depths, a plug 140 is detachably connected in the grouting cavity 125. The plug 140 is arranged to control the conduction and blocking states of the grouting pipe 113 and the grouting cavity 125, so that the inlet of the grouting pipe 113 of the uppermost pile column 100 can communicate with the grouting hole 126 of any one of the lower pile columns 100, and the reinforcing agent is injected into the soil layer at a predetermined depth.

[0053] In this way, for the soil layer characteristics at different depths, such as shallow soft soil, middle - layer flowing mud, and deep - layer dense sand layer, different types of curing agents and dosages can be differentially injected according to the above - mentioned soil layer characteristics to achieve a better curing effect.

[0054] Combined Figure 3 As shown, the grouting cavity 125 is arranged in an annular structure. Along the axial direction of the pile column 100, the width at the middle position of the grouting cavity 125 is greater than the widths at the upper and lower ends. The maximum outer diameter of the plug 140 is less than the maximum width of the grouting cavity 125, and the grouting holes 126 are arranged at the middle position of the grouting cavity 125.

[0055] Preferably, a plurality of grouting holes 126 are arranged on the outer side of the grouting cavity 125 in a circumferential array.

[0056] In this way, after the curing agent enters the grouting cavity 125, the plug 140 cannot prevent the curing agent from flowing circumferentially along the grouting cavity 125. The curing agent can enter all the grouting holes 126 communicating with the annular cavity of the grouting cavity 125, and spray the curing agent around the pile column 100 to cure the soil layer around the pile column 100.

[0057] In an alternative embodiment, in combination with Figure 3 As shown, the plug 140 is provided in a columnar shape, and the cross-sectional dimension of the middle part is larger than that of both ends. The plug 140 is an elastic structure and includes a first plug 141, a second plug 142, and a third plug 143.

[0058] In this way, the plug 140 can be inserted into the grouting cavity 125, and the communication state between the grouting pipe 113 and the grouting cavity 125 can be controlled by its both ends.

[0059] In order to meet the requirement of grouting and solidifying at different depths through the second opening 124b of the uppermost pile column 100, the plug 140 has three structures. The first one is arranged in the grouting cavity 125 and makes the upper and lower grouting pipes 113 not communicate with each other, that is, the curing agent in the grouting pipe 113 in the upper pile column 100 cannot be transmitted downward anymore. The second one is arranged in the grouting cavity 125 and makes the upper and lower grouting pipes 113 communicate, that is, the curing agent in the grouting pipe 113 in the upper pile column 100 can continue to be transmitted downward into the grouting pipe 113 of the lower pile column 100. The third one is arranged in the grouting cavity 125, keeps the grouting pipe 113 in the upper pile column 100 communicating with the grouting cavity 125, but blocks the lower grouting pipe 113, so that the curing agent can enter the grouting cavity 125.

[0060] Specifically, in combination with Figures 5 to 7 As shown, the first plug 141 is a solid columnar structure, and the height of the first plug 141 is greater than the height of the grouting cavity 125.

[0061] In this way, after the first plug 141 is filled into the grouting cavity 125, the two grouting pipes 113 at adjacent upper and lower positions do not communicate.

[0062] Specifically, the second plug 142 is a hollow columnar structure, and the height of the second plug 142 is greater than the height of the grouting cavity 125.

[0063] In this way, after the second plug 142 is filled into the grouting cavity 125, the two grouting pipes 113 at adjacent upper and lower positions communicate.

[0064] Specifically, the third plug 143 is a solid columnar structure, and the height of the third plug 143 is less than the height of the grouting cavity 125.

[0065] In this way, after the third plug 143 is filled into the grouting cavity 125, it is used to block the lower grouting pipe 113, while the upper grouting pipe 113 communicates with the grouting cavity 125.

[0066] In a preferred embodiment, the end of the plug 140 is set to have a diameter smaller than the inner diameter of the grouting cavity 125.

[0067] In this way, the plug 140 can extend into the inner wall of the grouting cavity 125.

[0068] Furthermore, the outer wall of the plug 140 is provided with an inclined surface with a gradually changing diameter. In this way, a part of the plug 140 can extend into the grouting pipe 113, playing a better sealing role.

[0069] Specifically, multiple grouting pipes 113 are provided in each pile body 110, and the plugs 140 in each grouting cavity 125 are configured to include at least one third plug 143 and multiple first plugs 141 and / or multiple second plugs 141, so that the grouting pipe 113 in the uppermost pile body 110 is communicated with the grouting pipe 113 in any lower pile body 110.

[0070] Combined with Figure 8 As shown in the figure, the figure shows the pile body structure formed by splicing 4 pile bodies 110 together. Each pile body 110 has six grouting pipes 113, numbered A, B, C, D, E, and F respectively; from the bottom to the top, they are the pile body numbered 1, the pile body numbered 2, the pile body numbered 3, and the pile body numbered 4.

[0071] Combined with Figure 8 As shown in the figure, the plug at the A position of the pile body numbered 1 is the third plug 143, and the rest are the first plugs 141; the plug at the A position of the pile body numbered 2 is the second plug 142, the plug at the B position is the third plug 143, and the rest are the first plugs 141; the plugs at the A and B positions of the pile body numbered 3 are the second plugs 142, the plug at the C position is the third plug 143, and the rest are the first plugs 141; the plugs at the A, B, and C positions of the pile body numbered 4 are the second plugs 142, the plug at the D position is the third plug 143, and the rest are the first plugs 141.

[0072] Specifically, the curing agent is provided from the A grouting pipe 113 in the pile body numbered 4 into the grouting cavity 125 in the pile body numbered 1, and its flow path is shown by the red line. The curing agent is provided from the B grouting pipe 113 in the pile body numbered 4 into the grouting cavity 125 in the pile body numbered 2, and its flow path is shown by the blue line. The curing agent is provided from the C grouting pipe 113 in the pile body numbered 4 into the grouting cavity 125 in the pile body numbered 3, and its flow path is shown by the green line. The curing agent is provided from the D grouting pipe 113 in the pile body numbered 4 into the grouting cavity 125 in the pile body numbered 4, and its flow path is shown by the purple line.

[0073] In an alternative embodiment, as Figure 3As shown, the upper connecting flange 120 includes a first plate body 121, an outer connecting ring 122, an inner connecting ring 123, and a second plate body 124. The outer connecting ring 122 and the inner connecting ring 123 are located between the first plate body 121 and the second plate body 124. A grouting cavity 125 is formed between the outer connecting ring 122 and the inner connecting ring 123. A grouting hole 126 is provided on the outer connecting ring 122. A first reinforcing plate 127 extending downward is provided on the periphery of the first plate body 121.

[0074] Among them, a space exposed on the outside is formed between the first plate body 121 and the second plate body 124, and the grouting hole 126 can spray the curing agent outward from this notch.

[0075] As Figure 3 As shown, the lower connecting flange 130 includes a third plate body 131 and a second reinforcing plate 132. The second reinforcing plate 132 is located on the periphery of the third plate body 131 and extends upward.

[0076] In this way, through the design of the first reinforcing plate 127 and the second reinforcing plate 132, the strength at both ends of the pile body can be enhanced.

[0077] In an alternative embodiment, multiple steel bars 112 are distributed around the grouting pipe 113, or the multiple steel bars 112 include a first part distributed around the grouting pipe 113 and a second part distributed on the same circumference as the grouting pipe 113.

[0078]

Pile Body Grouting Reinforcement Method for Prefabricated Pile Structure in Marine Silt Soil Site

[0079] The second aspect of the present invention proposes a technical solution. The above-mentioned pile body grouting reinforcement method for the prefabricated pile structure in the marine silt soil site includes the following steps:

[0080] Step 1: Sequentially number all the pile columns 100 according to the order in which the pile columns 100 are pressed in. Among them, the one connected to the pile tip 200 is No. 1. At the same time, in the axial direction of the pile column 100, sequentially number all the grouting pipes 113 in the clockwise direction;

[0081] Step 2: According to the number of the pile column 100, before connecting the next pile column 100, press the plug 140 into the grouting cavity 125 in a predetermined order;

[0082] Step 3: During the process of pressing in the pile column 100, connect all the pile columns 100 in sequence, and press the plug 140 in the manner of Step 2;

[0083] Step 4: After all the pile columns 100 are connected and pressed in, grout is injected successively through the grouting pipes 113 at the upper ends of the uppermost pile columns 100 around the grouting holes 126 of each pile column 100. After curing, a strengthened area is formed in the soil layer around the joints of adjacent two pile columns 100.

[0084] In a specific embodiment, in combination with Figure 8 As shown, the figure shows a pile body structure formed by splicing 4 pile bodies 110 together. Each pile body 110 has six grouting pipes 113, numbered A, B, C, D, E, and F respectively; from the bottom to the top, there are the pile body numbered 1, the pile body numbered 2, the pile body numbered 3, and the pile body numbered 4.

[0085] In combination with Figure 8 As shown, the plug at the A position of the pile body numbered 1 is the third plug 143, and the rest are the first plugs 141; the plug at the A position of the pile body numbered 2 is the second plug 142, the plug at the B position is the third plug 143, and the rest are the first plugs 141; the plugs at the A and B positions of the pile body numbered 3 are the second plugs 142, the plug at the C position is the third plug 143, and the rest are the first plugs 141; the plugs at the A, B, and C positions of the pile body numbered 4 are the second plugs 142, the plug at the D position is the third plug 143, and the rest are the first plugs 141.

[0086] Specifically, the curing agent is provided from the A grouting pipe 113 in the pile body numbered 4 into the grouting cavity 125 in the pile body numbered 1, and its flow path is as shown by the red line. The curing agent is provided from the B grouting pipe 113 in the pile body numbered 4 into the grouting cavity 125 in the pile body numbered 2, and its flow path is as shown by the blue line. The curing agent is provided from the C grouting pipe 113 in the pile body numbered 4 into the grouting cavity 125 in the pile body numbered 3, and its flow path is as shown by the green line. The curing agent is provided from the D grouting pipe 113 in the pile body numbered 4 into the grouting cavity 125 in the pile body numbered 4, and its flow path is as shown by the purple line.

[0087] Combined with the above embodiments,

[0088] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Those with ordinary knowledge in the technical field to which the present invention pertains can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to what is defined by the claims.

Claims

1. A prefabricated pile structure for sea silt sites, characterized in that: It comprises a plurality of piles (100) that can be connected to each other and a pile tip (200) connected to the lowest pile (100); The pile column (100) comprises a pile body (110) and an upper connecting flange (120) and a lower connecting flange (130) connected to two ends of the pile body (110); The pile body (110) comprises a concrete structure (111) and a steel bar (112) and a grouting pipe (113) embedded in the concrete structure (111); the upper connecting flange (120) and the lower connecting flange (130) are provided with a first opening (124a) corresponding to the position of the steel bar (112) and a second opening (124b) corresponding to the position of the grouting pipe (113); The upper connection flange (120) is provided with a grouting cavity (125), the grouting cavity (125) is configured to have a first plug hole connected to the upper end surface of the upper connection flange (120), and a second plug hole connected to the lower end surface of the upper connection flange (120), and the grouting cavity (125) also has a grouting hole (126) facing the outside of the pile body (110); The grouting pipe (113) is configured such that the upper end thereof extends to the second insertion hole of the grouting cavity (125), the lower end of the grouting pipe (113) extends to below the lower connecting flange (130), and when two upper and lower adjacent piles (100) are butt-jointed, the lower end of the grouting pipe (113) extends into the first insertion hole; A plug (140) is detachably connected in the grouting cavity (125), and the plug (140) is configured to control the connection and blocking state between the grouting pipe (113) and the grouting cavity (125), so that the entrance of the grouting pipe (113) of the uppermost pile column (100) can be connected to the grouting hole (126) of any pile column (100) below, so as to inject a reinforcing agent into a soil layer of a predetermined depth.

2. The prefabricated pile structure for sea silt sites according to claim 1, characterized in that: The grouting cavity (125) is arranged to be an annular structure. Along the axial direction of the pile column (100), the width of the middle position of the grouting cavity (125) is greater than the widths of the upper end and the lower end. The maximum outer diameter of the plug (140) is smaller than the maximum width of the grouting cavity (125). The grouting hole (126) is arranged in the middle position of the grouting cavity (125).

3. The prefabricated pile structure for sea silt sites according to claim 2, characterized in that: The outer side of the grouting cavity (125) is provided with a plurality of grouting holes (126) distributed in a circular array.

4. The prefabricated pile structure for sea silt sites according to claim 1, characterized in that: The plug (140) is configured to be columnar, and the cross-sectional size of the middle portion is larger than the cross-sectional size of the two ends. The plug (140) is an elastic structure. The plug (140) comprises a first plug (141), a second plug (142) and a third plug (143); The first plug (141) is a solid columnar structure, the height of the first plug (141) is greater than the height of the grouting cavity (125), and when the first plug (141) is filled into the grouting cavity (125), two grouting pipes (113) located at upper and lower adjacent positions are not connected; The second plug (142) is a hollow columnar structure. The height of the second plug (142) is greater than the height of the grouting cavity (125). When the second plug (142) is filled into the grouting cavity (125), two grouting pipes (113) located at upper and lower adjacent positions are connected. The third plug (143) is a solid columnar structure. The height of the third plug (143) is less than the height of the grouting cavity (125). When the third plug (143) is filled into the grouting cavity (125), it is used to block the grouting pipe (113) below.

5. The prefabricated pile structure for sea silt sites according to claim 4, characterized in that: The end of the plug (140) is configured to have a diameter smaller than the inner diameter of the grouting cavity (125), so that the plug (140) can extend into the inner wall of the grouting cavity (125), and the outer wall of the plug (140) is configured to have an inclined surface with a gradually changing diameter.

6. The prefabricated pile structure for sea silt sites according to claim 4, characterized in that: A plurality of grouting pipes (113) are arranged in each pile body (110), and the plug (140) in each layer of grouting cavity (125) is configured to include at least one third plug (143) and a plurality of first plugs (141) and / or a plurality of second plugs (141), so that the grouting pipe (113) in the uppermost pile body (110) is connected to the grouting pipe (113) in any pile body (110) in the lower layer.

7. The prefabricated pile structure for sea silt sites according to claim 1, characterized in that: The upper connecting flange (120) comprises a first plate body (121), an outer connecting ring (122), an inner connecting ring (123) and a second plate body (124); the outer connecting ring (122) and the inner connecting ring (123) are located between the first plate body (121) and the second plate body (124); a grouting cavity (125) is formed between the outer connecting ring (122) and the inner connecting ring (123); the grouting hole (126) is arranged on the outer connecting ring (122); and a first reinforcing plate (127) extending downward is provided on the periphery of the first plate body (121).

8. The prefabricated pile structure for sea silt sites according to claim 1, characterized in that: The lower connecting flange (130) comprises a third plate body (131) and a second reinforcing plate (132), wherein the second reinforcing plate (132) is located at the periphery of the third plate body (131) and extends upward.

9. The prefabricated pile structure for sea silt sites according to claim 1, characterized in that: The plurality of steel bars (112) are distributed around the periphery of the grouting pipe (113), or the plurality of steel bars (112) include a first portion distributed around the periphery of the grouting pipe (113) and a second portion distributed around the same circumference as the grouting pipe (113).

10. The pile grouting reinforcement method for a prefabricated pile structure used in a sea silt site according to any one of claims 1 to 9, characterized in that: The following steps are involved: Step 1: number all the piles (100) in sequence according to the order in which the piles (100) are pressed in, wherein the pile connected to the pile tip (200) is numbered one, and at the same time, number all the grouting pipes (113) in sequence along the axial direction of the pile (100) in the clockwise direction; Step 2: According to the numbering of the piles (100), before connecting the next pile (100), the plug (140) is pressed into the grouting cavity (125) in a predetermined order; Step 3, in the process of pressing the piles (100), all the piles (100) are connected in sequence, and the plugs (140) are pressed in according to the method of step 2; Step 4: After all the piles (100) are connected and pressed in, grouting is sequentially performed to the periphery of the grouting hole (126) of each pile (100) through the grouting pipe (113) at the upper end of the uppermost pile (100). After solidification, a reinforced area is formed in the soil layer around the connection between two adjacent piles (100).

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