A double-pipe drill pipe structure suitable for tri-axial mixing piles

Abstract

The utility model discloses a two -layer pipe drill rod structure suitable for three -axis mixing stake, including at least one two -layer pipe drill rod subassembly, two -layer pipe drill rod subassembly includes outer drill rod and sets up the inner drill rod in the inside of outer drill rod, and, the cavity is formed between the inner drill rod with outer drill rod, the confluence part is connected in the lower part of two -layer pipe drill rod subassembly, the inside of confluence part is provided with the confluence chamber, and the cavity in two -layer pipe drill rod subassembly intercommunication with confluence chamber, the confluence part is provided with the discharge gate, forms at least two independent slurry flow path, first slurry flow path is along the inside of inner drill rod and flows to the soil body, and second slurry flow path flows into the confluence chamber from the cavity and flows to the soil body from the discharge gate. The utility model cooperates through the inner drill rod and outer drill rod and formed two independent paths can respectively transport different materials, and this greatly expands the flexibility and functionality of construction.

Description

Technical Field

[0001] This utility model relates to the technical field of triaxial mixing piles, and in particular to a double-tube drill rod structure suitable for triaxial mixing piles. Background Technology

[0002] Tri-axis mixing piles originated from deep mixing pile technology and emerged with the increasing demands on foundations in modern construction. Relying on three mixing shafts operating simultaneously, they can efficiently and uniformly mix the curing agent with the soil to form high-quality piles. They offer significant advantages in improving efficiency, ensuring quality, enhancing reinforcement, and providing waterproofing, and are widely used in various engineering projects.

[0003] Disadvantages of existing technology: Although triaxial mixing piles have many advantages, they also have certain disadvantages. They use a single concrete material, which makes them often inadequate when facing micro-disturbance conditions. Due to the limitations of material properties, it is difficult to flexibly adapt to and effectively resist the impact of such micro-disturbances, which may affect the overall construction effect and the stability of surrounding existing buildings, underground facilities, etc., thus limiting their application scope in such special working conditions. Utility Model Content

[0004] (a) Technical problems to be solved

[0005] The technical problem to be solved by this utility model is to provide a double-tube drill rod structure suitable for triaxial mixing piles, in which the inner drill rod and the outer drill rod cooperate to form two independent paths that can transport different materials separately, which greatly expands the flexibility and functionality of construction.

[0006] (II) Technical Solution

[0007] The solution adopted by this utility model to solve the above-mentioned technical problems is a double-tube drill rod structure suitable for triaxial mixing piles, including...

[0008] At least one double-tube drill pipe assembly, the double-tube drill pipe assembly including an outer drill pipe and an inner drill pipe disposed inside the outer drill pipe, and a cavity is formed between the inner drill pipe and the outer drill pipe;

[0009] A manifold component is connected to the lower part of the double-tube drill pipe assembly. The manifold component has a manifold cavity inside, which is in communication with the cavity inside the double-tube drill pipe assembly.

[0010] The confluence component is provided with a discharge port;

[0011] At least two independent slurry flow paths are formed: the first slurry flow path flows along the interior of the inner drill rod to the soil, and the second slurry flow path flows from the cavity into the confluence cavity and from the outlet to the soil.

[0012] Specifically, the cavity is a ring-shaped cavity arranged circumferentially outside the inner drill rod.

[0013] In some embodiments, the first slurry flow path is used to transport curing agents such as cement slurry and cement-water glass slurry, and the second slurry flow path is used to transport functional additives such as bentonite slurry and polymer solution.

[0014] Using the above scheme, the inner and outer drill pipes work together to form two independent paths that can separately deliver different materials, achieving material function separation. This avoids material mixing within the pipes and ensures that each material fully performs its intended purpose. For example, the first slurry flow path can precisely deliver cement slurry, cement-water glass slurry, and other curing agents to predetermined locations, ensuring thorough and uniform mixing with the soil and improving pile strength. The second slurry flow path can precisely deliver bentonite slurry, polymer solutions, and other functional additives to predetermined locations, enabling the modification of soil properties as needed, such as enhancing soil fluidity and plasticity, facilitating smoother construction, and also synergistically strengthening the water-stopping effect of the pile, making material application more efficient. This design is specifically tailored to better adapt to different geological and engineering requirements. Furthermore, while traditional single-pipe systems render an entire pile unusable if blocked, this invention provides redundant pipelines. Even if one path is temporarily blocked, the other can still function, improving the reliability and continuity of construction. It also separates the delivery of slurries of different properties, preventing unnecessary chemical reactions within the pipes that could lead to blockages. In addition, the double-pipe structure is physically more stable than a single-pipe structure, better resisting lateral forces and other external forces from the strata during drilling and mixing, reducing the probability of bending or deformation of the drill rod under complex geological conditions, and enhancing overall structural stability.

[0015] In some embodiments, the system includes multiple drill rod assemblies, at least one of which is the double-tube drill rod assembly; and the multiple drill rod assemblies are connected by the manifold, which enhances the overall rigidity and stability of the multiple drill rod assemblies during drilling and lifting, reduces the swaying of a single drill rod, and helps to ensure the verticality and overlap quality of the pile.

[0016] In some embodiments, the manifold is assembled at the lower part of a multi-drill rod assembly. In use, the manifold is inserted deep into the soil to fix the triaxial mixing pile in the soil.

[0017] In some embodiments, the system includes three drill pipe assemblies arranged in parallel, wherein the two drill pipe assemblies located on both sides are the double-tube drill pipe assemblies, and the drill pipe assembly located in the middle is the single-tube drill pipe assembly.

[0018] The above scheme adopts a double-pipe design for the drill rods on both sides, which can deliver composite slurry in two directions at the same time, expand the coverage area, and improve the uniformity of the surrounding soil properties; the middle drill rod uses a single pipe to deliver the main curing agent, which simplifies the structure of the middle drill rod and reduces manufacturing and maintenance costs while ensuring the core function.

[0019] In some embodiments, a third slurry flow path is formed inside the single-tube drill pipe assembly, the third slurry flow path flowing along the interior of the single-tube drill pipe assembly toward the soil.

[0020] Specifically, the slurry transported by the third slurry flow path may be the same as the slurry transported by the first or second slurry flow path, or it may be different from the slurry transported by both paths.

[0021] In some embodiments, the third slurry flow path is used to transport curing agents such as cement slurry and cement-water glass slurry, and is consistent with the slurry transported by the first slurry flow path, thereby improving the curing effect in the central area of ​​the pile. Furthermore, the first slurry flow path inside the inner drill rods on both sides and the third slurry flow path inside the single-pipe drill rod assembly in the middle simultaneously transport curing agents such as cement slurry and cement-water glass slurry to the soil, making the curing agent more evenly distributed in the soil, thereby improving the uniformity of the overall strength of the pile.

[0022] In some embodiments, the confluence component includes two double-tube mating portions covering the double-tube drill rod assemblies located on both sides and a single-tube mating portion covering the single-tube drill rod assembly located in the middle; and the two double-tube mating portions and the single-tube mating component form a connecting portion; wherein, the interior of the two double-tube mating portions and the adjacent connecting portion forms a confluence cavity with an annular structure, and the two connecting portions have the discharge port on the side near the soil, so that the slurry is directly sprayed into the soil, reducing the flow distance.

[0023] In some embodiments, the outer wall of the outer drill rod is provided with a grouting port, which is used to connect the cavity and the manifold.

[0024] In some embodiments, the grout nozzle is located at the lower part of the outer drill rod.

[0025] With the above scheme, the grouting nozzle is directly opened on the wall of the outer drill rod, so that the grouting nozzle is always in communication with the confluence cavity as the outer drill rod rotates. No matter how the outer drill rod rotates, the grout can flow into the confluence cavity stably.

[0026] In some embodiments, the number of the double-tube drill rod assembly is two, and the outer drill rod of each double-tube drill rod assembly is provided with two of the grouting ports, for a total of four grouting ports.

[0027] Specifically, the two grout nozzles are arranged at intervals along the outer periphery of the outer drill rod, and the grout flows into the confluence cavity from different directions, resulting in a more uniform flow.

[0028] By adopting the above scheme, the setting of multiple grouting nozzles allows the grout in the second grout flow path to enter the confluence cavity and soil from multiple points, avoiding the possibility of local grout being too thick or too thin due to single-point injection, and further improving the uniformity of grout mixing with soil; at the same time, the multi-nozzle design also reduces the risk of the path completely failing due to blockage of a single grouting nozzle.

[0029] In some embodiments, a sealing device is provided on the outer periphery of the spray nozzle.

[0030] In some embodiments, the sealing device is a rubber waterstop ring, used to seal the gap between the grout nozzle and the manifold, providing good sealing performance. Furthermore, the rubber material is elastic and can adapt to the relative movement of the drill rod assembly during rotation, maintaining the sealing effect.

[0031] By adopting the above solution, the sealing device can effectively prevent slurry from overflowing from the gap between the slurry nozzle and the manifold, ensuring that all the slurry enters the manifold.

[0032] In some embodiments, the discharge port is provided on the side of the confluence component near the soil; and the discharge port is connected to a grouting pipe, and the end of the grouting pipe is provided with an anti-clogging device, which can prevent soil from flowing back into the grouting pipe when grouting stops or pressure fluctuates, avoid clogging of the grouting pipe, and ensure smooth flow of grout during the next construction.

[0033] In some embodiments, the anti-clogging device is one or more combinations of a filter screen, a one-way valve, or a protective cover; wherein the filter screen can block large particles of debris from entering the pipeline; the one-way valve can prevent backflow of soil or groundwater when the pump is stopped; and the protective cover can prevent drilled soil from directly impacting and clogging the outlet.

[0034] In some embodiments, the inner drill rod includes a first portion and a second portion arranged sequentially along the flow direction of the first slurry flow path, wherein the shaft diameter of the first portion is smaller than the shaft diameter of the second portion; and the outer drill rod is coaxially disposed on the outside of the first portion.

[0035] In some embodiments, the manifold is assembled on the outer drill rod, and the second part is arranged opposite to the manifold below it. The second part extends below the manifold and penetrates directly into the soil, so that the grout is sprayed directly from the end of the second part into the depth of the soil, thereby improving the solidification effect of the bottom and core area of ​​the pile.

[0036] (III) Beneficial Effects

[0037] Compared with the existing technology, this utility model designs a double-tube drill rod structure suitable for triaxial mixing piles.

[0038] (1) This utility model forms two independent paths through the cooperation of the inner and outer drill rods, which can transport different materials separately, realizing the separation of material functions. This can avoid the mixing of materials in the pipeline and ensure that the performance of each material is fully utilized. For example, the first slurry flow path can accurately transport cement slurry, cement-water glass slurry and other curing agents to the predetermined position, ensuring that they are fully and evenly mixed with the soil and improving the strength of the pile. The second slurry flow path can accurately transport bentonite slurry, polymer solution and other functional additives to the predetermined position, which can improve the soil properties as needed, such as enhancing the plasticity of the soil, helping the construction to be smoother, and can also synergistically enhance the water-stopping effect of the pile, so as to improve the application of materials. More targeted and better adapted to different geological and engineering requirements; while traditional single-pipe systems are rendered unusable if blocked, this utility model provides redundant pipelines, so even if one path is temporarily blocked, the other can still work, improving the reliability and continuity of construction. In addition, it separates the delivery of slurries of different properties, avoiding unnecessary chemical reactions that could lead to blockages within the pipes; furthermore, the double-pipe structure is more physically stable than the single-pipe structure, better able to resist the lateral forces and other external forces from the strata during drilling and mixing, reducing the probability of the drill rod bending or deforming under complex geological conditions, and enhancing the overall structural stability.

[0039] (2) The two sides of the drill rod of this utility model adopt a double pipe design, which can deliver composite slurry in two directions at the same time, expand the coverage area, and improve the surrounding soil properties to be more uniform; the middle drill rod adopts a single pipe to deliver the main curing agent, which simplifies the structure of the middle drill rod and reduces manufacturing and maintenance costs while ensuring the core function.

[0040] (3) The grouting nozzle of this utility model is directly opened on the wall of the outer drill rod, so that the grouting nozzle rotates with the outer drill rod and is always in communication with the confluence cavity. No matter how the outer drill rod rotates, the grout can flow into the confluence cavity stably. Moreover, the setting of multiple grouting nozzles allows the grout in the second grout flow path to enter the confluence cavity and the soil from multiple points, avoiding the possibility of local grout being too thick or too thin due to single-point injection, and further improving the uniformity of grout mixing with the soil. At the same time, the multi-port design also reduces the risk of the path completely failing due to blockage of a single grouting nozzle.

[0041] (4) The sealing device designed in this utility model can effectively prevent the slurry from overflowing from the gap between the slurry nozzle and the confluence chamber, ensuring that all the slurry enters the confluence chamber;

[0042] (5) The present invention is equipped with an anti-blocking device at the end of the grouting pipe, which can prevent soil from backflowing into the grouting pipe when grouting stops or pressure fluctuates, avoid clogging of the grouting pipe, and ensure smooth flow of grout during the next construction. Attached Figure Description

[0043] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a schematic diagram of a double-tube drill rod structure applicable to a triaxial mixing pile according to the present invention;

[0045] Figure 2 This is a schematic diagram of the external drill rod of this utility model;

[0046] Figure 3 This is a schematic diagram of the structure of the busbar component of this utility model;

[0047] Figure 4 This is a diagram showing the flow path of drill rod slurry for a double-tube drill rod structure suitable for triaxial mixing piles according to this utility model.

[0048] The component names corresponding to the various reference numerals in the figure are as follows: 1. Outer drill pipe; 2. Inner drill pipe; 21. First part; 22. Second part; 3. Confluence component; 31. Double pipe mating part; 32. Single pipe mating part; 33. Connecting part; 4. Grouting nozzle; 5. Confluence cavity; 6. Discharge port; 7. Grouting pipe; 8. First slurry flow path; 9. Second slurry flow path; 10. Third slurry flow path; 11. Cavity. Detailed Implementation

[0049] The specific embodiments of this utility model will be further described in detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate this utility model, but should not be used to limit the scope of this utility model.

[0050] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0051] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0052] It should be noted that the following description covers various aspects of embodiments within the scope of the appended claims. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0053] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The drawings only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0054] Additionally, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that practice can be carried out without these specific details.

[0055] The technical solutions provided by the various embodiments of this application are described below with reference to the accompanying drawings.

[0056] like Figures 1-4As shown, this utility model provides a double-tube drill rod structure suitable for triaxial mixing piles, including two double-tube drill rod assemblies. Each double-tube drill rod assembly includes an outer drill rod 1 and an inner drill rod 2 disposed inside the outer drill rod 1, with a cavity 11 formed between the inner drill rod 2 and the outer drill rod 1. A confluence component 3 is connected to the lower part of the double-tube drill rod assembly, and a confluence cavity 5 is provided inside the confluence component 3, which communicates with the cavity 11 within the double-tube drill rod assembly. The confluence component 3 is provided with a discharge port 6. The double-tube drill rod assembly forms two independent slurry flow paths: a first slurry flow path 8 flows along the interior of the inner drill rod 2 towards the soil, and a second slurry flow path 9 flows from the cavity 11 into the confluence cavity 5 and then from the discharge port 6 towards the soil. Specifically, the cavity 11 is a ring-shaped cavity 11 arranged circumferentially outside the inner drill rod 2. In some embodiments, the first slurry flow path 8 is used to transport curing agents such as cement slurry and cement-water glass slurry, while the second slurry flow path 9 is used to transport functional additives such as bentonite slurry and polymer solution. Using the above scheme, the inner drill rod 2 and the outer drill rod 1 cooperate to form two independent paths that can transport different materials separately, achieving material function separation. This avoids material mixing within the pipes and ensures that each material's performance is fully utilized. For example, the first slurry flow path 8 can precisely deliver curing agents such as cement slurry and cement-water glass slurry to predetermined locations, ensuring thorough and uniform mixing with the soil and improving pile strength. The second slurry flow path 9 can precisely deliver functional additives such as bentonite slurry and polymer solution to predetermined locations, improving soil properties as needed, such as enhancing soil fluidity and facilitating smoother construction. It can also synergistically strengthen the water-stopping effect of the pile, allowing for better material application. More targeted and better adapted to different geological and engineering requirements; while traditional single-pipe systems render the entire pile unusable once blocked, this utility model provides redundant pipelines, so even if one path is temporarily blocked, the other can still work, improving the reliability and continuity of construction. In addition, it separates the delivery of slurries of different properties, avoiding unnecessary chemical reactions that could lead to blockages within the pipes; furthermore, the double-pipe structure is more physically stable than a single-pipe structure, better able to resist external forces such as lateral forces from the strata during drilling and mixing, reducing the probability of the drill rod bending or deforming under complex geological conditions, and enhancing the overall structural stability.

[0057] In some embodiments, the system includes three drill rod assemblies, two of which are double-tube drill rod assemblies. These three drill rod assemblies are connected by the manifold 3, enhancing the overall rigidity and stability of the multiple drill rod assemblies during drilling and lifting, reducing the swaying of individual drill rods, and helping to ensure the verticality and overlap quality of the pile. In some embodiments, the manifold 3 is assembled at the lower part of the multiple drill rod assemblies. During use, the manifold 3 is inserted deep into the soil to fix the triaxial mixing pile in the soil. In some embodiments, the system includes three parallel drill rod assemblies, wherein the two drill rod assemblies on both sides are double-tube drill rod assemblies, and the drill rod assembly in the middle is a single-tube drill rod assembly. Using the above scheme, the double-tube design of the drill rods on both sides allows for simultaneous delivery of composite grout in two directions, expanding the coverage area and improving the uniformity of the surrounding soil properties; the single-tube delivery of the main curing agent in the middle drill rod simplifies the structure of the middle drill rod while ensuring its core function, reducing manufacturing and maintenance costs. In some embodiments, a third slurry flow path 10 is formed inside the single-tube drill rod assembly, and the third slurry flow path 10 flows into the soil along the interior of the single-tube drill rod assembly. In some embodiments, the third slurry flow path 10 is used to transport curing agents such as cement slurry and cement-water glass slurry, and the slurry transported by the first slurry flow path 8 is consistent with that transported by the first slurry flow path 8, thereby improving the curing effect in the central area of ​​the pile; moreover, the first slurry flow path 8 inside the inner drill rods 2 on both sides and the third slurry flow path 10 inside the single-tube drill rod assembly in the middle simultaneously transport curing agents such as cement slurry and cement-water glass slurry into the soil, making the curing agent more evenly distributed in the soil, thereby improving the uniformity of the overall strength of the pile.

[0058] In some embodiments, the confluence component 3 includes two double-tube mating portions 31 covering the double-tube drill rod assemblies located on both sides and a single-tube mating portion 32 covering the single-tube drill rod assembly located in the middle; and the two double-tube mating portions 31 and the single-tube mating portion 32 form a connecting portion 33; wherein, the interior of the two double-tube mating portions 31 and the adjacent connecting portion 33 forms a confluence cavity 5 with an annular structure, and the two connecting portions 33 have a discharge port 6 on the side near the soil, so that the slurry is directly sprayed into the soil, reducing the flow distance.

[0059] In some embodiments, the outer wall of the outer drill rod 1 is provided with a grouting port 4, which connects the cavity 11 and the manifold 5. In some embodiments, the grouting port 4 is located at the lower part of the outer drill rod 1. With the above arrangement, the grouting port 4 is directly formed on the wall of the outer drill rod 1, ensuring that the grouting port 4 remains in communication with the manifold 5 as the outer drill rod 1 rotates, allowing the grout to flow steadily into the manifold 5 regardless of the rotation of the outer drill rod 1. In some embodiments, the number of the double-tube drill rod assembly is two, and each outer drill rod 1 of the double-tube drill rod assembly is provided with two grouting ports 4, for a total of four grouting ports 4. Specifically, the two grouting ports 4 are arranged at intervals along the outer periphery of the outer drill rod 1, allowing the grout to flow into the manifold 5 from different directions, resulting in a more uniform flow. By employing the above-described scheme, the arrangement of multiple grouting nozzles 4 allows the grout in the second grout flow path 9 to enter the confluence cavity 5 and the soil from multiple points, avoiding the possibility of excessively thick or thin grout in certain areas due to single-point injection, and further improving the uniformity of grout mixing with the soil. Simultaneously, the multi-nozzle design reduces the risk of the path completely failing due to blockage of a single grouting nozzle 4. In some embodiments, a sealing device (not shown in the figure) is provided on the outer periphery of the grouting nozzle 4. In some embodiments, the sealing device is a rubber waterstop ring, used to seal the gap between the grouting nozzle 4 and the confluence cavity 5, providing good sealing performance. Furthermore, the rubber material is elastic and can adapt to the relative movement of the drill rod assembly during rotation, maintaining the sealing effect. By employing the above-described scheme, this sealing device can effectively prevent grout from overflowing from the gap between the grouting nozzle 4 and the confluence cavity 5, ensuring that all grout enters the confluence cavity 5.

[0060] In some embodiments, the outlet 6 is provided on the side of the confluence component 3 near the soil; and the outlet 6 is connected to a shotcrete pipe 7, and the end of the shotcrete pipe 7 is provided with an anti-clogging device (not shown in the figure), which can prevent soil from flowing back into the shotcrete pipe 7 when shotcreting stops or when pressure fluctuates, avoid blockage of the shotcrete pipe 7, and ensure smooth flow of grout during the next construction. In some embodiments, the anti-clogging device is a filter screen; the filter screen can block large particles of debris from entering the shotcrete pipe 7.

[0061] In some embodiments, the inner drill rod 2 includes a first portion 21 and a second portion 22 arranged sequentially along the flow direction of the first slurry flow path 8, wherein the shaft diameter of the first portion 21 is smaller than the shaft diameter of the second portion 22; and the outer drill rod 1 is coaxially disposed outside the first portion 21. In some embodiments, the confluence component 3 is assembled on the outer drill rod 1, and the second portion 22 is arranged opposite to the lower part of the confluence component 3, extending below the confluence component 3 and penetrating directly into the soil, so that the slurry is directly sprayed from the end of the second portion 22 into the depth of the soil, thereby improving the solidification effect of the pile bottom and core area.

[0062] The same or similar parts between the various embodiments in this specification can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments.

[0063] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A double-tube drill rod structure suitable for triaxial mixing piles, characterized in that: include At least one double-tube drill pipe assembly, the double-tube drill pipe assembly including an outer drill pipe (1) and an inner drill pipe (2) disposed inside the outer drill pipe (1), and a cavity (11) is formed between the inner drill pipe (2) and the outer drill pipe (1). A manifold component (3) is connected to the lower part of the double-tube drill rod assembly. A manifold cavity (5) is provided inside the manifold component (3). The manifold cavity (5) is interconnected with the cavity (11) inside the double-tube drill rod assembly. The confluence component (3) is provided with a discharge port (6); At least two independent slurry flow paths are formed: the first slurry flow path (8) flows along the interior of the inner drill rod (2) to the soil, and the second slurry flow path (9) flows from the cavity (11) into the confluence cavity (5) and from the outlet (6) to the soil.

2. The double-tube drill rod structure for triaxial mixing piles according to claim 1, characterized in that: It includes multiple drill pipe assemblies, at least one of which is the double-tube drill pipe assembly; and the multiple drill pipe assemblies are connected through the manifold (3).

3. The double-tube drill rod structure suitable for triaxial mixing piles according to claim 2, characterized in that: It includes three drill pipe assemblies arranged in parallel, wherein the two drill pipe assemblies on both sides are the double-tube drill pipe assemblies, and the drill pipe assembly in the middle is the single-tube drill pipe assembly.

4. The double-tube drill rod structure for triaxial mixing piles according to claim 3, characterized in that: A third slurry flow path (10) is formed inside the single-tube drill rod assembly, and the third slurry flow path (10) flows into the soil along the inside of the single-tube drill rod assembly.

5. The double-tube drill rod structure for triaxial mixing piles according to claim 3, characterized in that: The confluence component (3) includes two double-tube mating parts (31) covering the double-tube drill rod assembly located on both sides and a single-tube mating part (32) covering the single-tube drill rod assembly located in the middle; and the two double-tube mating parts (31) and the single-tube mating part (32) form a connecting part (33); wherein, the two double-tube mating parts (31) and the adjacent connecting part (33) form a confluence cavity (5) with an annular structure, and the two connecting parts (33) have the discharge port (6) on the side closer to the soil.

6. The double-tube drill rod structure for triaxial mixing piles according to any one of claims 1-5, characterized in that: The outer wall of the outer drill rod (1) is provided with a grouting port (4), which is used to connect the cavity (11) and the confluence cavity (5).

7. The double-tube drill rod structure for triaxial mixing piles according to claim 6, characterized in that: The number of the double-tube drill rod assembly is two, and each double-tube drill rod assembly has two grouting ports (4) on the outer drill rod (1).

8. The double-tube drill rod structure for triaxial mixing piles according to claim 6, characterized in that: A sealing device is provided on the outer periphery of the spray nozzle (4).

9. The double-tube drill rod structure for triaxial mixing piles according to claim 1, characterized in that: The discharge port (6) is provided on the side of the confluence component (3) near the soil; and the discharge port (6) is connected to the grouting pipe (7), and the end of the grouting pipe (7) is provided with an anti-clogging device.

10. The double-tube drill rod structure for triaxial mixing piles according to claim 1, characterized in that: The inner drill rod (2) includes a first part (21) and a second part (22) arranged sequentially along the flow direction of the first slurry flow path (8). The shaft diameter of the first part (21) is smaller than that of the second part (22). The outer drill rod (1) is coaxially arranged on the outside of the first part (21).

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