Prestressed mechanical joint with spring snap, precast concrete pile and connecting method

Abstract

The pre-tightening mechanical joint, precast concrete pile and connecting method of the application, wherein the joint comprises a plug rod with a plug provided with external thread teeth on the outer wall; a large nut provided with a receiving cavity; the plug-in cavity of the pre-tightening nut is provided with internal thread teeth, the pre-tightening nut comprises a pre-tightening nut threaded connection part and a pre-tightening nut driving part; the pre-tightening nut threaded connection part is threadedly connected with the receiving cavity; the clamping spring is placed in the internal thread teeth; when the plug is inserted into the clamping spring, the clamping spring is contracted and clamped on the plug, the driving part drives the pre-tightening nut driving part, so that the pre-tightening nut rotates and moves axially along the large nut, and the plug and the pre-tightening nut are axially locked. The pre-tightening mechanical joint effectively eliminates the gap between the plug and the pre-tightening nut, so that when the precast concrete pile is connected by using the mechanical joint and is subjected to pulling force, shearing force or bending force, the precast concrete pile connection part will not crack and generate cracks.

Description

Technical Field

[0001] This invention relates to the field of precast component technology, and in particular to a pre-tightening mechanical joint with snap-fit ​​spring snap-fit, a precast concrete pile, and a connection method. Background Technology

[0002] Most engineering piles (precast piles) are multi-section piles, and the ends of existing precast concrete piles are generally connected quickly between piles using mechanical joints.

[0003] Article 5.1.7 of the "Technical Standard for Prestressed Concrete Pipe Piles" (JGJ / T406-2017) stipulates that for prestressed pipe piles that are strictly required to be free of cracks, the crack control level should be Level I. Article 5.1.8 stipulates that when the pipe pile is under axial tension, the crack control level is Level I; when the pipe pile is under bending, the crack control level is Level II for pipe piles in weakly corrosive environments and above, and Level I for pipe piles in moderately and strongly corrosive environments and above.

[0004] Article 3.4.4 of the "Code for Design of Concrete Structures" (GB50010-2015) stipulates that the stress crack control level of the cross-section of structural members is divided into three levels, and the classification and requirements shall comply with the following provisions:

[0005] Level 1 – For components that are strictly required to be free of cracks, when calculated according to the standard load combination, the concrete at the tension edge of the component should not generate tensile stress.

[0006] Level 2 – For components that are generally required to be free of cracks, when calculated according to the standard load combination, the tensile stress in the concrete at the tension edge of the component should not exceed the standard value of the tensile strength of the concrete.

[0007] Level 3 – Components Allowed to Crack: For reinforced concrete components, when calculating based on the quasi-permanent load combination and considering the long-term effects, the maximum crack width of the component should not exceed the maximum crack width limit specified in Table 3.4.5 of this code. For prestressed concrete components, when calculating based on the standard load combination and considering the long-term effects, the maximum crack width of the component should not exceed the maximum crack width limit specified in Clause 3.4.5 of this code; for prestressed concrete components in Class 2a environments, calculations should also be performed based on the quasi-permanent load combination, and the tensile stress in the concrete at the tension edge of the component should not exceed the standard value of the tensile strength of the concrete. Clause 3.4.5 of this code specifies that the crack control level for prestressed concrete structures is Level 1 in Class 3a and 3b environments, and Level 2 in Class 2b environments. Cracks are not allowed in either Level 1 or Level 2 crack control levels. In Class 2a environments, the crack control level is Level 3, with a maximum crack width limit of 0.1 mm. In Class 1 environments, the crack control level is Level 3, with a maximum crack width limit of 0.2 mm.

[0008] like Figure 21 The diagram shows the first structural form of an existing mechanical joint, including a large nut 2, a small nut 21, a plug rod 1, and a connector 90. One end of the plug rod is threaded to the small nut, and the other end has a plug. The connector is threaded to the large nut, and the end of the connector inside the large nut has multiple elastic clips. The plug is inserted from one end of the connector and can abut against the elastic clips to achieve a snap-fit ​​between the plug rod and the connector. This mechanical joint allows for the rapid connection of two precast concrete piles. However, this type of mechanical joint for connecting precast concrete piles has the following shortcomings: 1. When using this mechanical joint for connecting precast concrete piles, due to factors such as the inclination of the pile end face, the plug rod may be over-inserted into the connector. When this occurs, the precast concrete pile, under the action of tensile force, shear force, or bending force, will cause axial clearance in all or part of the mechanical joint at the pile connection end face, resulting in axial clearance at the precast concrete pile connection, causing cracks to form at the mechanical joint connection. Specifically, for example... Figure 21 The diagram shows the insertion of the plug rod into the connector. After the plug rod is inserted into the connector, an axial gap Δh will be formed between the end of the elastic clip and the stop surface of the plug. As a result, when an external force is applied, a corresponding axial gap will also be generated between the connecting end faces of the precast concrete pile. This makes it impossible to meet the requirements of Article 5.1.7 of the "Technical Standard for Prestressed Concrete Pipe Piles" JGJ / T406-2017, which stipulates that for prestressed pipe piles that are strictly required to be free of cracks, the crack control level should be Level 1; Article 5.1.8 stipulates that when the pipe pile body is under axial tension, the crack control level should be Level 1; when the pipe pile body is under bending... 1. The crack control level for pipe piles in weakly corrosive environments and above is Level II, while the crack control level for pipe piles in moderately and strongly corrosive environments and above is Level I; 2. Since the large nut and the connector, and the small nut and the insert rod are both connected by threads, there will be a certain axial clearance in the threaded connection. Therefore, when the mechanical joint is subjected to pull-out force, the axial clearance of the threaded connection will also cause a corresponding axial clearance between the connecting end faces of the precast concrete pile, further increasing the size of the cracks at the connection of the precast concrete pile, making it impossible to meet the crack control requirements in the "Technical Standard for Prestressed Concrete Pipe Piles" when used for precast concrete pile connections; 3. If Figure 22 As shown, when using this mechanical connector to connect precast concrete piles, there is a problem that the plug of the insert rod is not properly inserted into the connector. That is, when the insert rod is inserted into the connector, the end of the elastic clip does not enter the annular groove of the insert rod. Therefore, the insert rod and the connector cannot be engaged, resulting in the failure of the pile connection.

[0009] like Figure 23The diagram shows a second structural form of an existing mechanical joint, including a large nut 2, a small nut 21, a plug rod 1, an intermediate nut 91, an elastic element 92, and a clip 93. One end of the plug rod is threaded to the small nut, and the other end has a plug. The intermediate nut is threaded to the large nut, and the intermediate nut has a tapered snap-fit ​​surface at one end of the large nut. An elastic element and multiple clips are located within the receiving cavity of the large nut. The elastic element abuts the multiple clips against the tapered snap-fit ​​surface of the intermediate nut. The plug is inserted from one end of the intermediate nut and can compress the elastic element, allowing the plug to pass through the space formed by the multiple clips and snap-fit ​​between the intermediate nut and the plug, thus achieving a rapid connection of two precast concrete piles. However, using this type of mechanical joint for connecting precast concrete piles has the following drawbacks: 1. During the insertion of the plug rod into the intermediate nut, there is a situation where the central axis xx of the plug rod and the central axis yy of the intermediate nut are not aligned. Therefore, if... Figure 23 , Figure 24 and Figure 25 As shown, during the insertion of the plug into the middle nut, the card closer to the plug axis contacts the plug first, while the card further away from the plug axis contacts the plug later. The lower card contacts the plug first and compresses the spring under the action of the plug, while the upper card contacts the plug later. Therefore, the following may occur: Figure 24 The card on one side of the diagram enters between the plug and the center nut, while the card on the other side cannot enter between the plug and the center nut; or, as shown... Figure 25 The different engagement positions of the multiple clips, plugs, and intermediate nuts shown lead to pile connection failure or low connection strength of the mechanical joint. Consequently, when the precast concrete pile is subjected to tensile, shear, or bending forces, axial slippage occurs between the insert rod and the clip of the mechanical joint. This results in axial clearance in all or part of the mechanical joint at the pile connection end face, causing cracks to form at the connection point of the precast concrete pile mechanical joint. 2. When the plug is inserted into the intermediate nut and engages with the clip, a complete wedge-shaped fit is not formed between the plug, clip, and intermediate nut (at the plug and clip...). The interaction force between the plates is very small. Therefore, when the insert is subjected to tensile, shear, or bending forces, the plug of the insert will squeeze the card, causing the card to slide axially relative to the plug. As a result, when using this mechanical joint to connect precast concrete piles, the precast concrete pile will experience tensile, shear, or bending forces, causing all or part of the mechanical joint at the pile connection end face to have axial clearance. This will lead to a corresponding axial clearance at the precast concrete pile connection, causing cracks to form at the mechanical joint connection of the precast concrete pile. 3. If Figure 24 As shown, since both the card and the plug have conical or cylindrical contact surfaces, and because the contact position between the card and the plug is uncertain, the contact surfaces of the card and the plug will not completely fit together when they are engaged. Figure 26As shown in the figure, curves Q1 to Q5 represent the cross-sectional radius curves at different positions of the plug's contact surface, and curve J represents the cross-sectional radius curve at a certain position of the card. As shown in the figure, when curve J is at position Q1, curve J is completely in contact with Q1. When curve J is at positions Q2 to Q5, the gap between curve J and curve Q gradually increases. In other words, when the card is at different positions of the plug, the contact state between the card and the plug is different, meaning that it cannot be guaranteed that the contact surface of the card and the contact surface of the plug are completely in contact. In other words, the contact between the card and the plug is line contact. When the mechanical joint is subjected to tensile, shear, or bending forces, axial slippage will occur between the card and the plug, or the card may partially embed into the plug (or the card may deform under force), resulting in axial clearance in the mechanical joint. That is, when using this type of mechanical joint to connect precast concrete piles, when subjected to tensile, shear, or bending forces, a corresponding axial clearance will also occur between the connecting end faces of the precast concrete piles, causing cracks to form at the mechanical joint connection of the precast concrete piles. 4. Since the large nut and the middle nut, and the small nut and the plug rod are all connected by threads, the threaded connection will also have a certain axial clearance. Therefore, when the mechanical joint is subjected to tensile, shear, or bending forces, the axial clearance of the threaded connection will also cause a corresponding axial clearance between the connecting end faces of the precast concrete piles, resulting in cracks to form at the mechanical joint connection of the precast concrete piles. This mechanical structure has several shortcomings, therefore, when using this mechanical joint for connecting precast concrete piles, the connection may fail to meet the requirements of Article 5.1.7 of the "Technical Standard for Prestressed Concrete Pipe Piles" (JGJ / T406-2017), which stipulates that for prestressed pipe piles with strict requirements to be free of cracks, the crack control level should be Level 1; Article 5.1.8 stipulates that when the pipe pile is under axial tension, the crack control level should be Level 1; and when the pipe pile is under bending, the crack control level should be Level 2 for pipe piles in weakly corrosive environments and above, and Level 1 for pipe piles in moderately and strongly corrosive environments and above.

[0010] Existing mechanical joints have axial clearance issues, which cause gaps to form at the joints of precast concrete piles when subjected to tensile, shear, and / or bending forces. Since precast pile foundations are underground concealed works, the precast piles themselves cannot be repaired.

[0011] Safety hazards of cracks in precast concrete pile joints in building pile foundations:

[0012] When precast concrete piles are subjected to bending and shear forces, the axial clearance of the mechanical joints at the precast concrete pile joints will cause cracks at the connection of the precast concrete piles, which will lead to the piles not being on the same axis, resulting in local eccentric stress on the connection end face of the piles; causing damage or cracking of the concrete at the pile end face, resulting in safety hazards in the building pile foundation.

[0013] When precast concrete piles are subjected to tensile forces, it is impossible to ensure that the axial gaps generated by the aforementioned mechanical joints are completely consistent. Furthermore, the design value of the axial tensile bearing capacity of the precast pile body is based on the total number of main reinforcement bars (number of mechanical joints). As a result, the aforementioned mechanical joints will be broken one by one when subjected to tensile forces, leading to potential safety hazards in the building pile foundation.

[0014] When precast concrete piles are subjected to bending, shear, and tensile forces, axial gaps at the pile joints can lead to cracks. This can cause groundwater intrusion and corrosion of mechanical connections and / or the main reinforcement of the precast pile, making it difficult to guarantee the pile's durability. Specifically, according to Table 4.1.18 of the "Technical Specification for Building Pile Foundations" (JGJ94-2008), the annual corrosion rate of steel piles is 0.05–0.1 mm when the steel pile is above ground and in an environment without corrosive gases or corrosive volatile media. / y; When the steel pile is located below the ground and above the water level, the single-sided corrosion rate is 0.05 mm / y; when the steel pile is located below the ground and below the water level, the single-sided corrosion rate is 0.03 mm / y; when the steel pile is located below the ground and in a water level fluctuation zone, the single-sided corrosion rate is 0.1 to 0.3 mm / y. Therefore, it can be seen that when precast concrete piles develop cracks due to the axial gap of the mechanical joint, the mechanical joint and / or main reinforcement will be rapidly corroded, making it difficult to guarantee the durability of the precast pile. The severity of the damage is self-evident. Summary of the Invention

[0015] This invention addresses the problems caused by axial clearance in existing mechanical joint connection mechanisms, which leads to cracks at the connection of precast concrete piles, resulting in corrosion of the main reinforcement and / or mechanical joint, and local pressure on the pile end face. It proposes a pre-tightened mechanical joint with snap-fit ​​spring snap-fit ​​to solve the safety hazards caused by the axial clearance after the connection of existing mechanical joints.

[0016] The technical means employed in this invention are as follows:

[0017] A pre-tightening mechanical connector with snap-fit ​​spring engagement includes a plug, one end of which is a plug, and the outer wall of the plug is provided with external thread teeth;

[0018] A large nut, wherein the large nut has a receiving cavity;

[0019] A preload nut has an insertion cavity inside, and the inner wall of the insertion cavity has internal thread teeth. The outer wall of the preload nut includes a preload nut threaded connection part and a preload nut driving part. The preload nut threaded connection part is placed in the receiving cavity and threadedly connected to the receiving cavity, and at least part of the preload nut driving part is located outside the receiving cavity.

[0020] A snap-fit ​​spring, wherein the snap-fit ​​spring is placed in the tooth groove of the internal thread;

[0021] During the insertion of the plug into the insertion cavity, the plug can drive the snap-fit ​​spring to open in the tooth groove along the radial direction of the large nut. After the plug is inserted into the snap-fit ​​spring, the snap-fit ​​spring can radially retract and clamp onto the external thread teeth of the plug.

[0022] After the snap-fit ​​spring clamps onto the external thread teeth, the drive component can drive the preload nut drive unit from the side of the preload nut, causing the preload nut to rotate radially and move axially along the large nut, thereby locking the plug and the preload nut in the axial direction of the large nut.

[0023] Furthermore, the preload nut drive unit is provided with drive teeth, the drive component is a lead screw, and the lead screw is provided with engagement teeth that can mesh with the drive teeth.

[0024] Furthermore, the driving teeth are straight teeth parallel to the axis of the preload nut or helical teeth at a certain angle to the axis of the preload nut.

[0025] Furthermore, the cross-section of the snap-fit ​​spring is triangular, and the external thread teeth and the internal thread teeth are sawtooth-shaped teeth;

[0026] When the plug and the preload nut are locked together in the axial direction of the large nut, the side with the larger tooth angle of the internal thread teeth and the two sides of the external thread teeth respectively abut against the different sides of the snap-fit ​​spring.

[0027] Furthermore, the direction of rotation of the internal thread teeth is opposite to the direction of rotation of the thread at the threaded connection of the preload nut.

[0028] Furthermore, the pitch of the internal thread teeth is twice the pitch of the external thread teeth, and the pitch of the internal thread teeth is different from the pitch at the threaded connection of the preload nut.

[0029] Furthermore, the insertion end of the insertion cavity is provided with a guide cone surface. When the plug of the insertion rod is inserted into the insertion cavity, the side of the plug first fits against the guide cone surface and moves downward along the guide cone surface.

[0030] Furthermore, before the plug and the pre-tightening nut are locked in the axial direction of the large nut, the threaded connection between the pre-tightening nut and the large nut is a loose-fit threaded connection.

[0031] Furthermore, after the plug and the pre-tightening nut are locked together in the axial direction of the large nut, the tensile strength of the connection between the plug and the snap-fit ​​spring is greater than or equal to the tensile strength of any one of the main rib, the large nut, and the small nut.

[0032] Furthermore, it also includes a small nut for connecting to the base of the insert rod.

[0033] A precast concrete pile includes a precast concrete pile body, main reinforcement bars, and a pre-tightening mechanical joint with snap-fit ​​springs as described in any one of claims 1 to 10.

[0034] The main reinforcement is set in the body of the precast concrete pile. One end of the precast concrete pile body is provided with the large nut. The large nut is internally threaded with the pre-tightening nut. The insertion cavity of the pre-tightening nut is provided with the snap-fit ​​spring.

[0035] The insertion rod is installed at the other end of the precast concrete pile body;

[0036] The end of the precast concrete pile body is provided with a drive component receiving groove;

[0037] When two adjacent precast concrete piles are connected, one end of the drive component receiving groove is connected to the outer wall of the precast concrete pile body, and the other end extends to the end of the locking nut. After the drive component is inserted into the drive component receiving groove from the outer wall of the precast concrete pile body, the drive component can interact with the pre-tightening nut drive part, causing the pre-tightening nut to rotate and move along the axial direction of the large nut, thereby locking the plug and the pre-tightening nut in the axial direction of the large nut.

[0038] Furthermore, the precast concrete pile body has a small nut at one end of the insertion rod, and one end of the large nut and the small nut are respectively connected to the two ends of the main reinforcement. The insertion rod is threadedly connected to the other end of the small nut.

[0039] Furthermore, after the drive component drives the preload nut to rotate radially and locks the plug and the preload nut in the axial direction of the large nut, the drive component remains in or is removed from the drive component receiving groove.

[0040] Furthermore, structural adhesive is injected into the connecting end face of the precast concrete pile body and the pre-tightening mechanical joint that is snapped by the snap-fit ​​spring.

[0041] A method for connecting precast concrete piles disclosed in this invention includes the following steps:

[0042] The end of the precast concrete pile with the insertion rod and the end of the adjacent precast concrete pile with the pre-tightening nut are moved relative to each other, and the plug is inserted into the insertion cavity of the pre-tightening nut to achieve the engagement of the plug with the snap-fit ​​spring.

[0043] The drive component is inserted into the outer wall of the precast concrete pile, and the drive component drives the pre-tightening nut drive part, thereby causing the pre-tightening nut to rotate radially and move axially along the large nut, thereby locking the plug and the pre-tightening nut in the axial direction of the large nut.

[0044] Compared with the prior art, the snap-fit ​​spring snap-fit ​​pre-tightening mechanical connector disclosed in this invention has the following beneficial effects: The snap-fit ​​spring snap-fit ​​pre-tightening mechanical connector disclosed in this application, due to the presence of a pre-tightening nut driving part, can be driven laterally by a driving component after the plug is inserted into the cavity and the snap-fit ​​spring is clamped onto the external thread teeth. This causes the pre-tightening nut to move axially along the large nut, thereby locking the plug, snap-fit ​​spring, and pre-tightening nut in the axial direction of the large nut. This effectively eliminates the axial gap between the plug, snap-fit ​​spring, and pre-tightening nut. Furthermore, because the pre-tightening nut, insert rod, and snap-fit ​​spring are locked in the axial direction, the pre-tightening nut... The tightening nut, insert rod, and snap-fit ​​spring generate a certain axial force (tightening force) in the axial direction. Under the action of this axial force, the axial gaps between the pre-tightening nut, insert rod, large nut, snap-fit ​​spring, and small nut can be effectively eliminated. Therefore, when using the mechanical joint disclosed in this invention for precast concrete pile connection, the precast concrete pile connection will not crack under tensile, shear, or bending forces. This ensures that the mechanical joint disclosed in this invention meets the relevant requirements for crack level control in the "Technical Standard for Prestressed Concrete Pipe Piles" JGJ / T406-2017. Furthermore, it eliminates the problem of gaps generated in existing mechanical joint connections, which cause cracks at the precast concrete pile joint and pose safety hazards to the building pile foundation. Attached Figure Description

[0045] Figure 1 This is an axial view of the snap-fit ​​spring-loaded pre-tightened mechanical joint disclosed in this invention;

[0046] Figure 2 This is a front view of the snap-fit ​​spring snap-fit ​​pre-tightening mechanical joint disclosed in this invention;

[0047] Figure 3 This is a cross-sectional view of the snap-fit ​​spring-loaded pre-tightened mechanical joint disclosed in this invention;

[0048] Figure 4 This is a schematic diagram of the state of the pre-tightened mechanical joint with snap-fit ​​spring disclosed in this invention when the plug and snap-fit ​​spring are not axially locked after the plug is inserted into the pre-tightening nut.

[0049] Figure 5 for Figure 4 A magnified view of a section at point A in the middle;

[0050] Figure 6 This is a schematic diagram of the state of the pre-tightened mechanical connector with snap-fit ​​spring disclosed in this invention after the plug is inserted into the pre-tightening nut and the plug and snap-fit ​​spring are axially locked.

[0051] Figure 7 for Figure 6 A magnified view of a section at point B in the middle;

[0052] Figure 8 This is a schematic diagram of the preload nut of the preload mechanical joint with snap-fit ​​spring according to the present invention;

[0053] Figure 9 This is a cross-sectional view of the preload nut of the preload mechanical joint with snap-fit ​​spring snap-fit ​​disclosed in this invention;

[0054] Figure 10 This is a top view of the preload nut of the snap-fit ​​spring snap-fit ​​preload mechanical joint disclosed in this invention;

[0055] Figure 11 This is a front view of the drive component of the snap-fit ​​spring-loaded pre-tightened mechanical joint disclosed in this invention;

[0056] Figure 12 This is a right view of the drive component of the snap-fit ​​spring-locked pre-tightened mechanical joint disclosed in this invention;

[0057] Figure 13 This is a front view of the large nut of the pre-tightened mechanical joint with snap-fit ​​spring disclosed in this invention;

[0058] Figure 14 This is a cross-sectional view of the large nut of the pre-tightened mechanical joint with snap-fit ​​spring according to the present invention;

[0059] Figure 15 This is a structural diagram of the insertion rod of the pre-tightening mechanical joint with snap-fit ​​spring according to the present invention;

[0060] Figure 16 This is a schematic diagram of a precast concrete pile connection with a pre-tightened mechanical joint using a snap-fit ​​spring snap-fit ​​mechanism as disclosed in this invention. The number of piles in the diagram is two sections.

[0061] Figure 17A cross-sectional view of a precast concrete pile connection having a pre-tightened mechanical joint with a snap-fit ​​spring snap-fit ​​as disclosed in this invention.

[0062] Figure 18 for Figure 17 A magnified view of a section at point D;

[0063] Figure 19 An end view of a precast concrete pile connection having a pre-tightened mechanical joint with a snap-fit ​​spring snap-fit ​​as disclosed in this invention.

[0064] Figure 20 for Figure 19 A magnified view of a section at point F in the middle;

[0065] Figure 21 This is a structural diagram of the first type of existing mechanical connector, with the plug in an over-insertion state.

[0066] Figure 22 This is a structural diagram of the first type of existing mechanical connector, with the plug in a partially inserted state.

[0067] Figure 23 This is a structural diagram of the existing second type of mechanical connector, showing the insertion process when the axis of the insertion rod and the axis of the intermediate nut are not collinear.

[0068] Figure 24 The diagram shows the structure of the second type of mechanical connector. In the diagram, the plug of the insertion rod contacts the lower card first, preventing the lower card from entering between the plug and the middle nut.

[0069] Figure 25 This is a structural diagram of the existing second type of mechanical connector, in which multiple clips are held at different positions between the plug and the intermediate nut;

[0070] Figure 26 This is a schematic diagram showing the contact state between the card and the plug contact surface of the existing second type of mechanical connector.

[0071] In the diagram: 1. Insert rod; 10. Plug; 11. First tooth; 12. Insert rod base; 13. Insertion cone surface; 14. Insert rod connecting part; 2. Large nut; 20. Receiving cavity; 21. Small nut; 4. Preload nut; 40. Insertion cavity; 41. Preload nut threaded connection part; 42. Preload nut drive part; 43. Internal thread tooth; 44. Drive tooth; 45. Guide cone surface; 5. Snap-fit ​​spring; 6. Drive component; 60. Screw; 8. Precast concrete pile; 80. Precast concrete pile body; 81. Main reinforcement; 82. Drive component receiving groove. Detailed Implementation

[0072] Example 1

[0073] like Figure 1 , Figure 2and Figure 3 The image shows a pre-tightening mechanical connector with snap-fit ​​spring engagement disclosed in this invention, comprising a plug 1, one end of which is a plug 10, the outer wall of which is provided with external thread teeth 11; as shown Figure 13-14 As shown, the large nut 2 has a receiving cavity 20 inside;

[0074] The preload nut 4 has an insertion cavity 40 inside, and the inner wall of the insertion cavity has internal thread teeth 43. The outer wall of the preload nut includes a preload nut threaded connection part 41 and a preload nut driving part 42. The preload nut threaded connection part 41 is placed in the receiving cavity 20 and threadedly connected to the receiving cavity 20, and at least part of the preload nut driving part 42 is located outside the receiving cavity.

[0075] A snap-fit ​​spring 5 is placed in the tooth groove of the internal thread 43;

[0076] During the process of inserting the plug 10 into the insertion cavity 40, the plug 10 can drive the snap-fit ​​spring 5 to open in the tooth groove along the radial direction of the large nut 2. After the plug 10 is inserted into the snap-fit ​​spring 5, the snap-fit ​​spring 5 can radially retract and clamp onto the external thread teeth 11 of the plug 10.

[0077] After the snap-fit ​​spring 5 clamps onto the external thread teeth 11, the drive component 6 can drive the pre-tightening nut drive part 42 from the side of the pre-tightening nut 4, so that the pre-tightening nut 4 rotates radially and moves axially along the large nut 2, thereby locking the plug 10 and the pre-tightening nut in the axial direction of the large nut 2.

[0078] The pre-tightening mechanical joint disclosed in this application, due to the presence of a pre-tightening nut drive part, such as Figure 4 and Figure 6 As shown, the preload nut drive unit is capable of being driven from the side of the preload nut after the plug of the insert rod is inserted into the insertion cavity of the preload nut and the snap-fit ​​spring placed in the receiving cavity clamps onto the external thread teeth of the plug, as shown. Figure 4 The diagram illustrates the movement process. Specifically, after the plug is inserted into the preload nut, there is a certain axial gap L between the snap-fit ​​spring and the snap-fit ​​surface of the preload nut, such as... Figure 5 , Figure 6 As shown, the drive component 6 rotates under the action of an external force (the direction of movement of the drive component 6 is as follows). Figure 4 (As indicated by arrow B), causing the preload nut 4 to rotate ( Figure 4 (As indicated by the middle arrow C) and moves axially along the large nut 2. Figure 4(As indicated by the arrow E), thereby locking the plug 10 and the snap-fit ​​spring 5 in the axial direction of the large nut 2. That is, after the snap-fit ​​spring clamps onto the external thread teeth of the plug, the preload nut 4 can rotate and move in the axial direction of the large nut 2 under the drive of the drive component 6. Thus, the axial movement of the preload nut 4 eliminates the axial gap L between the plug 10, the snap-fit ​​spring, and the preload nut 4. Figure 6 , Figure 7 As shown; furthermore, since the preload nut, insert rod, and snap-fit ​​spring are locked in the axial direction, a torque (tightening force) is generated between the locking nut and the large nut during the locking process. This tightening force causes the preload nut, insert rod, and snap-fit ​​spring to generate a certain axial force in the axial direction. Under the action of this axial force, the axial gaps between the preload nut, insert rod, large nut, snap-fit ​​spring, and small nut can be effectively eliminated, for example, the gap in the threaded connection between the preload nut and the large nut ( Figure 6 The axial clearance of the threaded connection in the area shown in E2), and the clearance of the threaded connection between the insert base and the small nut ( Figure 6 The mechanical joint disclosed in this invention, which addresses issues such as the axial clearance of the threaded connection in area E1, and the clearance between the plug and the snap-fit ​​spring, ensures that when using this mechanical joint for precast concrete pile connections, the connection will not crack under tensile, shear, or bending forces. This means the mechanical joint provides high tensile, bending, and shear resistance at the pile connection, meeting the crack level control requirements of the "Technical Standard for Prestressed Concrete Pipe Piles" JGJ / T406-2017. Furthermore, it eliminates the safety hazards associated with existing mechanical joints that cause gaps and cracks at the precast concrete pile joints.

[0079] Meanwhile, in this invention, since the insertion rod and the pre-tightening nut are engaged by a snap-fit ​​spring, a large contact distance is achieved between them in the axial direction, thereby improving the bending and shear resistance of the pile connected using this mechanical joint. Furthermore, the pre-tightening mechanical joint disclosed in this invention, by employing a snap-fit ​​spring to engage the insertion rod and the pre-tightening nut, generates a radially inward gripping force on the insertion rod during and after insertion, thus guiding and positioning it. Simultaneously, after the insertion rod is engaged with the snap-fit ​​spring, the radial contact between the insertion rod and the pre-tightening nut is reduced, facilitating the rotation of the pre-tightening nut under the drive of the driving component. This enables the axial movement of the pre-tightening nut and locks the pre-tightening nut and insertion rod along the axial direction of the large nut.

[0080] Furthermore, such as Figure 8 , Figure 10 As shown, the preload nut drive unit 42 is provided with drive teeth 44, such as... Figure 11 , Figure 12 As shown, the driving component 6 is a lead screw 60, which has engagement teeth 61 that can mesh with the driving teeth 44. The lead screw 60 can engage with the engagement teeth 61 from the side of the preload nut 4 and drive the preload nut 4 to rotate.

[0081] Specifically, in this embodiment, the driving tooth 44 is a straight tooth parallel to the axis of the preload nut 4 or an oblique tooth at a certain angle to the axis of the preload nut. The figure shows a straight tooth. The driving component is a lead screw. The preload nut has an insertion cavity 40 for the insertion of the plug 10 of the insertion rod 1. The outer wall of the preload nut includes a preload nut threaded connection part 41 with external threads for threaded connection with the large nut 2 and a preload nut threaded driving part 42 with driving teeth 44 for engaging with the meshing teeth on the lead screw to drive the preload nut 4 to rotate. A driving component receiving groove 82 communicating with the outer wall of the pile is provided at one end of the precast concrete pile. The other end of the driving component receiving groove 82 extends to the end of the large nut 2. The driving component... The receiving groove 52 allows the lead screw 60 to be inserted between two sections of precast concrete piles, and enables the lead screw 60 to engage with the drive teeth 44 on the pre-tightening nut 4 located inside the large nut 2. This drives the lead screw to rotate at the outer wall of the precast concrete pile. In this embodiment, the end of the lead screw 60 is provided with an internal hexagonal hole, a slotted groove, or a cross-shaped groove, etc., to facilitate rotation via a tool. The rotation of the lead screw drives the pre-tightening nut to rotate via the pre-tightening nut driving part 42 (the drive teeth 44 structure on the pre-tightening nut), thereby achieving axial movement of the pre-tightening nut to lock the plug and the pre-tightening nut in the axial direction, and eliminating axial clearance between the plug, the snap-fit ​​spring, and the pre-tightening nut. Driving the pre-tightening nut to rotate via the tooth structure of the lead screw not only has a simple structure but also a large stroke, allowing the pre-tightening nut to move a large distance within a small space, ensuring locking performance. The spur gear structure offers the advantage of easy machining, while the helical gear structure allows the lead screw to apply a larger circumferential driving force to the preload nut, thus facilitating the rotation of the preload nut to achieve axial movement. The driving teeth can be machined directly onto the preload nut drive unit, or they can be a separate structure, where the preload nut drive unit is fitted with an intermediate sleeve, and the intermediate sleeve has driving teeth (forming a gear-like structure). The intermediate sleeve and the preload nut drive unit are connected by a key or other structure.

[0082] The cross-sectional shape of the snap-fit ​​spring 5 can be circular, quadrilateral, elliptical, polygonal or irregular, etc. Preferably, the cross-section of the snap-fit ​​spring 5 is triangular, and the external thread teeth 11 and the internal thread teeth 43 are sawtooth teeth.

[0083] When the plug 10 and the pre-tightening nut are locked in the axial direction of the large nut 2, the side with the larger tooth angle of the internal thread tooth 43 and the two sides of the external thread tooth 11 respectively abut against different sides of the snap-fit ​​spring 5. While eliminating the gap between the snap-fit ​​spring, the pre-tightening nut and the plug rod, the sides of the internal thread tooth and the sides and bottom of the external thread tooth 11 form three abutment surfaces in different directions against the snap-fit ​​spring, and generate a stabilizing force on the snap-fit ​​spring to ensure the firmness and stability of the connection between the pre-tightening nut, the snap-fit ​​spring and the plug rod. This ensures that when the mechanical joint disclosed in this invention is used to connect precast concrete piles, the connection of the precast concrete pile will not crack or generate cracks when subjected to tensile force, shear force or bending force, thus reducing the safety hazards of the building pile foundation.

[0084] Furthermore, the pitch of the internal thread 43 is twice the pitch of the external thread 11. The pitch of the internal thread is different from the pitch at the threaded connection of the preload nut. The snap-fit ​​spring is fixed on the internal thread 43 before the insert rod is inserted into the preload nut insertion cavity 40. After the insert rod is inserted into the preload nut insertion cavity 40, the snap-fit ​​spring can radially contract and clamp onto the external thread 11 of the plug 10. The pitch of the internal thread 43 is twice the pitch of the external thread 11, so that when the insert rod is inserted into the preload nut and the two are not axially locked, the insert rod... The axial clearance between the plug and the preload nut is less than or equal to the distance of one tooth. Simultaneously, because the pitch of the inner nut teeth differs from the pitch of the threaded connection of the preload nut, a travel difference exists between the movement of the threaded connection and the inner thread teeth during the rotation of the preload nut. This allows the inner thread teeth to engage with the snap-fit ​​spring and the insert rod during rotation. In other words, the axial clearance between the plug and the preload nut is relatively small. Therefore, when driving the preload nut axially, it only needs to move a small distance axially to quickly achieve axial locking between the plug and the preload nut. When the driving component 6 drives the preload nut to rotate radially and move axially along the large nut 2, the clearance between the snap-fit ​​spring, the insert rod, and the preload nut is eliminated, locking the plug 10 and the preload nut in the axial direction of the large nut 2. Preferably, the direction of rotation of the inner thread teeth is opposite to the direction of rotation of the thread at the threaded connection of the preload nut, making axial locking between the preload nut, snap-fit ​​spring, and insert rod easier and resulting in a better locking effect.

[0085] Furthermore, such as Figure 9 As shown, the insertion end of the insertion cavity 40 is provided with a guide cone surface 45, which facilitates the insertion of the rod during the insertion of the pre-tightening nut, making the insertion convenient and accurate.

[0086] Furthermore, before the plug 10 and the pre-tightening nut are locked in the axial direction of the large nut 2, the threaded connection between the pre-tightening nut 4 and the large nut 2 is a loose-fit threaded connection.

[0087] Specifically, the tolerances of the internal threads on the inner wall of the large nut's receiving cavity and the external threads on the outer wall of the preload nut can be reasonably selected as needed, so that the threaded connection between the preload nut and the large nut is a loose-fit threaded connection. Since the preload nut and the large nut are loose-fit threaded connections, the force between the preload nut and the large nut is relatively small before the plug and the preload nut are locked, which makes it easier for the drive component to drive the preload nut to rotate from the side, so that the preload nut moves along the axial direction of the large nut, thereby locking the plug and the preload nut in the axial direction of the large nut.

[0088] Furthermore, after the plug 10 and the pre-tightening nut are locked in the axial direction of the large nut 2, the tensile strength of the plug connected to the snap-fit ​​spring is greater than or equal to the tensile strength of any one of the main rib, the large nut, and the small nut. Preferably, after the plug 10 and the pre-tightening nut are locked in the axial direction of the large nut 2, the plug connected to the snap-fit ​​spring exhibits no ductile deformation when subjected to a pull-out force of 11.7 MPa. In this application, after the plug 10 and the pre-tightening nut are locked in the axial direction of the large nut 2, the tensile strength of the plug connected to the snap-fit ​​spring is greater than or equal to the tensile strength of any one of the main reinforcement, the large nut, and the small nut. Furthermore, after the plug is connected to the snap-fit ​​spring, it exhibits no ductile deformation when subjected to a pull-out force of 11.7 MPa. This ensures that before the precast concrete pile with the pre-tightening mechanical joint disclosed in this invention is subjected to a pull-out force that causes ductile deformation of the main reinforcement, the large nut, small nut, insert rod, snap-fit ​​spring, and pre-tightening nut will not undergo ductile deformation. Consequently, no cracks or gaps will occur between the connection ends of the two precast piles. Before the main reinforcement becomes ductile and breaks, the pre-tightening mechanical joint disclosed in this invention can reliably connect without being damaged, further guaranteeing the connection performance of precast concrete piles connected using the pre-tightening mechanical joint disclosed in this invention. Specifically, the National Building Standard Design Atlas "Precast Concrete Square Piles" (Atlas No.: 20G361) details the relationship between the pile type and the prestressed main reinforcement in its table of reinforcement and mechanical properties for prestressed concrete square piles. For example, it specifies that the main prestressed reinforcement for a pile with a cross-section of 600x600 is 24Φ D12.6; The table details the pile section type and the design value Nt (kN) of the axial tensile bearing capacity of the pile body in terms of the axial compressive strength and flexural bearing capacity of the prestressed concrete square pile. The table specifies that for a B-shaped pile with a pile section of 600x600, the design value of the axial tensile bearing capacity is 2544kN. From the above data, the design value of the tensile bearing capacity of the prestressed main reinforcement of the precast pile can be calculated as 2544 / 24=10.6kN; 10.6x1.1=11.66≈11.7kN. That is, when the pull-out force of the pre-tightened mechanical joint disclosed in this application is within 11.7kN, neither the main reinforcement of the precast concrete pile nor the pre-tightened mechanical joint undergoes ductile deformation, and there is no slippage between the components of the mechanical joint. Therefore, no gap will be generated between the connection end faces of the precast concrete pile, thus ensuring the connection performance of the precast concrete pile.

[0089] Furthermore, it also includes a small nut 21 for connecting to the plug base 12 of the plug 1.

[0090] Specifically, in this embodiment, the insertion rod 1 is fixed to one end of the precast concrete pile by the small nut 21, and the large nut 2 is fixed to the other end of the precast concrete pile. The large nut 2 and the small nut 21 are respectively fixedly connected to the two ends of the main reinforcement in the precast concrete pile. The large nut is equipped with a positioning sleeve and a pre-tightening nut, etc., and two adjacent precast concrete piles can be quickly connected by the pre-tightening mechanical joint disclosed in this application.

[0091] Example 2

[0092] like Figure 16 and Figure 17 The image shows a precast concrete pile 8 disclosed in this invention, comprising a precast concrete pile body 80, main reinforcement bars 81, and the pre-tightening mechanical joint described in this invention.

[0093] like Figure 18 , Figure 19 and Figure 20 As shown, the main reinforcement 81 is set inside the precast concrete pile body 80, and the precast concrete pile body 80 is provided with the large nut 2 at one end, and the large nut 2 is internally threaded with the pre-tightening nut 4; the insertion cavity 40 of the pre-tightening nut is provided with the snap-fit ​​spring 5.

[0094] The insertion rod 1 is installed at the other end of the precast concrete pile body 80;

[0095] The end of the precast concrete pile body 80 is provided with a drive component receiving groove 82;

[0096] When two adjacent precast concrete piles are connected, one end of the drive component receiving groove 82 is connected to the outer wall of the precast concrete pile body 80, and the other end extends to the end of the locking nut 4. After the drive component 6 is inserted into the drive component receiving groove 82 from the outer wall of the precast concrete pile body 80, the drive component 6 can interact with the pre-tightening nut drive part, causing the pre-tightening nut 4 to rotate and move along the axial direction of the large nut 2, thereby locking the plug 10 and the pre-tightening nut in the axial direction of the large nut 2.

[0097] One end of the drive component receiving groove 82 is connected to the outer side wall of the precast concrete pile, and the other end extends to the end of the large nut 2. After the drive component 6 is inserted into the drive component receiving groove 82 from the outer side wall of the precast concrete pile, the drive component 6 can interact with the pre-tightening nut drive part 42 on the pre-tightening nut 4, causing the pre-tightening nut 4 to rotate radially and move axially along the large nut 2, thereby locking the plug 10 and the pre-tightening nut 4 in the axial direction of the large nut 2.

[0098] The pre-tightening mechanical connector disclosed in this application features a pre-tightening nut drive unit. This drive unit allows the plug to be inserted into the insertion cavity of the pre-tightening nut, with the retaining spring within the cavity clamping onto the external thread teeth of the plug. Then, a drive component drives the pre-tightening nut laterally, causing it to select and move axially along the larger nut. This locks the plug and the pre-tightening nut together in the axial direction of the larger nut. In other words, after the plug and the pre-tightening nut are engaged, the pre-tightening nut moves axially along the larger nut under the drive of the pre-tightening nut drive unit and the drive component. This axial movement of the pre-tightening nut eliminates the axial gap between the plug, the retaining spring, and the pre-tightening nut. Furthermore, because the pre-tightening nut, plug, and retaining spring are locked axially, a certain axial force is generated during the locking process. Under the action of this axial force, the axial gaps between components such as the preload nut, insert rod, large nut, snap-fit ​​spring, and small nut can be effectively eliminated. For example, the gap between the threaded connection of the preload nut and the large nut, the gap between the threaded connection of the insert rod base and the small nut, and the gap between the insert rod plug and the snap-fit ​​spring. Therefore, when using the mechanical joint disclosed in this invention for precast concrete pile connection, the precast concrete pile connection will not crack under tensile, shear, or bending forces. In other words, using the mechanical joint disclosed in this invention for precast concrete pile connection can ensure that the pile connection has high tensile, bending, and shear resistance, thus meeting the relevant requirements for crack level control in the "Technical Standard for Prestressed Concrete Pipe Piles" JGJ / T406-2017. Furthermore, it eliminates the problem of gaps generated in existing mechanical joint connections, which can cause cracks at the precast concrete pile joint and lead to safety hazards in the building pile foundation.

[0099] According to claim 11, the precast concrete pile is characterized in that: one end of the precast concrete pile body 80 with the insert rod 1 is also provided with a small nut 21, one end of the large nut 2 and the small nut 21 are respectively connected to both ends of the main reinforcement 81, and the insert rod 1 is threadedly connected to the other end of the small nut 21. That is, the mechanical joint is set at both ends of the main reinforcement, so that the main reinforcement and the mechanical joint are coaxial, which means that the main reinforcement and the mechanical joint are on the same axis when under force, thus improving the pull-out resistance of the pile. The drive component receiving groove 82 can also be set at the end of the precast concrete pile with the small nut. When the drive component receiving groove 82 is set at the end of the precast concrete pile with the small nut, the end of the precast concrete pile with the small nut is provided with a locking nut receiving hole, so that when the upper and lower precast piles are connected, the upper part of the locking nut is placed in the hole. One end of the drive component receiving groove 82 is connected to the precast concrete pile, and the other end is connected to the drive component receiving groove 82, so that the drive component can drive the locking nut to rotate.

[0100] Furthermore, after the driving component 6 drives the preload nut 4 to rotate radially and locks the plug 10 and the preload nut in the axial direction of the large nut 2, the driving component 6 remains in or is removed from the driving component receiving groove 82. Specifically, in the connection of precast concrete piles, multiple preload nuts on the precast concrete piles can be driven to rotate radially by a single lead screw to achieve axial locking of all mechanical joints, eliminate axial clearance, improve the pull-out resistance of the pile, and the lead screw can be reused, saving usage costs. Alternatively, in the connection of precast concrete piles, each mechanical joint can be driven by a lead screw. After the lead screw drives the preload nut to rotate and achieves axial locking, the lead screw remains in the driving component receiving groove, that is, the lead screw is not removed from the driving component receiving groove. Since multiple lead screw structures are provided between the two sections of precast concrete piles, the compressive strength of the precast pile ends is further improved.

[0101] Furthermore, structural adhesive is injected into the connecting end face of the precast concrete pile body 80 and the pre-tightening mechanical joint connected by the snap-fit ​​spring. The structural adhesive can fill, bond and seal the connecting end face, mechanical joint and various grooves on the end face, further improving the connection performance and corrosion resistance between piles.

[0102] Example 3

[0103] A method for connecting precast concrete piles disclosed in this invention includes the following steps:

[0104] Move the end of the precast concrete pile with the insert rod toward the end of the adjacent precast concrete pile with the pre-tightening nut, and insert the plug of the insert rod into the insertion cavity of the pre-tightening nut to achieve the engagement of the plug with the snap-fit ​​spring;

[0105] The drive component is inserted into the outer wall of the precast concrete pile, and the drive component drives the pre-tightening nut drive part, thereby causing the pre-tightening nut to rotate radially and move axially along the large nut, thereby locking the plug and the pre-tightening nut in the axial direction of the large nut.

[0106] When the preload nut is driven to rotate via the drive component (lead screw) and the preload nut drive unit, the following two situations may occur: 1. When the force generated by the threaded connection between the preload nut and the large nut is small, i.e., the connection between the preload nut and the large nut is relatively loose, during the process of the lead screw entering the receiving groove of the drive component, the lead screw meshes with the teeth and drives the preload nut to start rotating and move axially along the large nut. When the preload nut achieves axial locking between the snap spring and the plug, the preload nut stops rotating. At this time, the lead screw moves into the receiving groove of the drive component under the action of the tooth structure until the end of the lead screw abuts against the end of the receiving groove. When the lead screw is continued to be driven, the interaction between the lead screw and the teeth will cause the preload nut to generate a pretension force on the plug rod, thereby causing the precast concrete pile connection to generate a pretension force. 1. Pre-stressing prevents buckling deformation under certain forces after pile connection, thus improving the strength of precast concrete pile connection; 2. When the force generated by the threaded connection between the pre-tightening nut and the large nut is large, that is, the connection between the pre-tightening nut and the large nut is tight, the screw enters the receiving groove of the drive component. During this process, the screw engages with the teeth. At this time, the teeth structure cannot drive the pre-tightening nut to rotate. Under the action of the teeth structure, the screw moves into the receiving groove of the drive component until the end of the screw abuts against the end of the receiving groove. Then, the screw starts to drive the pre-tightening nut to rotate through the teeth structure to achieve axial locking between the snap spring and the plug. Thus, the axial movement of the pre-tightening nut eliminates the axial gap between the plug, snap spring and pre-tightening nut of the plug rod, ensuring the strength of the precast pile connection. Furthermore, since the preload nut, insert rod, and snap-fit ​​spring are locked in the axial direction, a tightening force is generated between the locking nut and the large nut during the locking process. This causes the preload nut, insert rod, and snap-fit ​​spring to generate a certain axial force in the axial direction. Under the action of this axial force, the axial gaps between the preload nut, insert rod, large nut, snap-fit ​​spring, and small nut can be effectively eliminated. For example, the gap between the threaded connection of the preload nut and the large nut, the gap between the threaded connection of the insert rod base and the small nut, and the gap between the insert rod plug and the snap-fit ​​spring, etc., further improve the connection performance of the mechanical joint and improve the pull-out resistance of the precast concrete pile after being connected by the preload mechanical joint.

[0107] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A pre-tightening mechanical joint with snap-fit ​​spring engagement, used for end connection between precast concrete piles, characterized in that: include, Insert rod (1), one end of the insert rod (1) is a plug (10), and the outer wall of the plug is provided with external thread teeth (11); Large nut (2), the large nut (2) is provided with a receiving cavity (20); A preload nut (4) is provided with an insertion cavity (40) and an internal thread tooth (43) on the inner wall of the insertion cavity. The outer wall of the preload nut includes a preload nut threaded connection part (41) and a preload nut driving part (42). The preload nut threaded connection part (41) is placed in the receiving cavity (20) and threadedly connected to the receiving cavity (20), and at least part of the preload nut driving part (42) is located outside the receiving cavity. A snap-fit ​​spring (5) is placed in the tooth groove of the internal thread tooth (43); During the process of inserting the plug (10) into the insertion cavity (40), the plug (10) can drive the snap-fit ​​spring (5) to open in the tooth groove along the radial direction of the large nut (2). After the plug (10) is inserted into the snap-fit ​​spring (5), the snap-fit ​​spring (5) can radially retract and clamp onto the external thread teeth (11) of the plug (10). After the snap-fit ​​spring (5) clamps onto the external thread teeth (11), the drive component (6) can drive the preload nut drive part (42) from the side of the preload nut (4), causing the preload nut (4) to rotate radially and move axially along the large nut (2), thereby eliminating the gap between the plug (10) and the preload nut (4) in the axial direction of the large nut (2), and locking the plug (10) and the preload nut in the axial direction of the large nut (2).

2. The pre-tightening mechanical joint with snap-fit ​​spring according to claim 1, characterized in that: The preload nut drive part (42) is provided with drive teeth (44), and the drive component (6) is a lead screw (60). The lead screw (60) is provided with engagement teeth (61) that can engage with the drive teeth (44).

3. The pre-tightening mechanical joint with snap-fit ​​spring according to claim 2, characterized in that: The drive tooth (44) is a straight tooth parallel to the axis of the preload nut (4) or a helical tooth at a certain angle to the axis of the preload nut.

4. The pre-tightening mechanical joint with snap-fit ​​spring according to any one of claims 1 to 3, characterized in that: The cross-section of the snap-fit ​​spring (5) is triangular, and the external thread teeth (11) and the internal thread teeth (43) are sawtooth-shaped teeth; When the plug (10) and the pre-tightening nut are locked in the axial direction of the large nut (2), the side with the larger tooth angle of the internal thread tooth (43) and the two sides of the external thread tooth (11) respectively abut against the different sides of the snap-fit ​​spring (5).

5. The pre-tightening mechanical joint with snap-fit ​​spring according to claim 4, characterized in that: The direction of rotation of the internal thread teeth is opposite to the direction of rotation of the thread at the threaded connection of the preload nut.

6. The pre-tightening mechanical joint with snap-fit ​​spring according to claim 5, characterized in that: The pitch of the internal thread teeth (43) is twice the pitch of the external thread teeth (11), and the pitch of the internal thread teeth is different from the pitch at the threaded connection of the preload nut.

7. The pre-tightening mechanical joint with snap-fit ​​spring according to claim 6, characterized in that: The insertion end of the insertion cavity (40) is provided with a guide cone surface (45).

8. The pre-tightening mechanical joint with snap-fit ​​spring according to claim 1, characterized in that: Before the plug (10) and the pre-tightening nut are locked in the axial direction of the large nut (2), the threaded connection between the pre-tightening nut (4) and the large nut (2) is a loose-fit threaded connection.

9. The pre-tightening mechanical joint with snap-fit ​​spring according to claim 1, characterized in that: After the plug (10) and the pre-tightening nut are locked in the axial direction of the large nut (2), the tensile strength of the plug connected to the snap-fit ​​spring is greater than or equal to the tensile strength of any one of the main rib, the large nut and the small nut.

10. The pre-tightening mechanical joint with snap-fit ​​spring according to claim 1, characterized in that: It also includes a small nut (21) for connecting to the insert base (12) of the insert (1).

11. A precast concrete pile, characterized in that: Includes a precast concrete pile body (80), main reinforcement (81), and a pre-tightening mechanical joint with snap-fit ​​spring according to any one of claims 1 to 10; The main reinforcement (81) is set inside the precast concrete pile body (80). One end of the precast concrete pile body (80) is provided with the large nut (2). The large nut (2) is internally threaded with the pre-tightening nut (4). The insertion cavity (40) of the pre-tightening nut is provided with the snap-fit ​​spring (5). The other end of the precast concrete pile body (80) is equipped with the insertion rod (1). The end of the precast concrete pile body (80) is provided with a drive component receiving groove (82). When two adjacent precast concrete piles are connected, one end of the drive component receiving groove (82) is connected to the outer wall of the precast concrete pile body (80), and the other end extends to the end of the pre-tightening nut (4). After the drive component (6) is inserted into the drive component receiving groove (82) from the outer wall of the precast concrete pile body (80), the drive component (6) can interact with the pre-tightening nut drive part, so that the pre-tightening nut (4) rotates and moves along the axial direction of the large nut (2), thereby locking the plug (10) and the pre-tightening nut in the axial direction of the large nut (2).

12. The precast concrete pile according to claim 11, characterized in that: The precast concrete pile body (80) is provided with a small nut (21) at one end of the insert rod (1). One end of the large nut (2) and the small nut (21) are respectively connected to the two ends of the main reinforcement (81). The insert rod (1) is threadedly connected to the other end of the small nut (21).

13. The precast concrete pile according to claim 11, characterized in that: After the drive component (6) drives the preload nut (4) to rotate radially and locks the plug (10) and the preload nut in the axial direction of the large nut (2), the drive component (6) remains in or is removed from the drive component receiving groove (82).

14. The precast concrete pile according to claim 13, characterized in that: Structural adhesive is also injected into the connecting end face of the precast concrete pile body (80) and the pre-tightening mechanical joint of the snap-fit ​​spring.

15. A method for connecting precast concrete piles according to any one of claims 11 to 14, characterized in that: Includes the following steps: The end of the precast concrete pile with the insertion rod and the end of the adjacent precast concrete pile with the pre-tightening nut are moved relative to each other, and the plug is inserted into the insertion cavity of the pre-tightening nut to achieve the engagement of the plug with the snap-fit ​​spring. The drive component is inserted into the outer wall of the precast concrete pile, and the drive component drives the pre-tightening nut drive part, thereby causing the pre-tightening nut to rotate radially and move axially along the large nut, thereby locking the plug and the pre-tightening nut in the axial direction of the large nut.

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