Sectional steel casing with self-locking slot connection device

Abstract

This invention relates to the field of civil engineering technology and discloses a segmented steel casing with a self-locking slot connection device, comprising: a permanent steel casing section; a fixed and recyclable steel casing section above the permanent steel casing section; a fixed and recyclable section retaining ring fitted on the surface of the fixed and recyclable steel casing section; and a conventional steel casing section above the fixed and recyclable steel casing section. A self-locking device is provided at one end of the conventional steel casing section. The self-locking device includes a latch on the surface of the conventional steel casing section, with a compression spring at one end of the latch. This invention achieves functional differentiation by designing the steel casing as a combination of a permanent steel casing section, a fixed and recyclable steel casing section, and a conventional steel casing section. After the pile foundation construction is completed, the permanent steel casing section covering the unfavorable geological layer is left underground, while the upper fixed and recyclable steel casing section and all conventional steel casing sections can be recycled and reused as a whole.

Description

Technical Field

[0001] This invention relates to the field of civil engineering technology, specifically to a segmented steel casing with a self-locking slot connection device. Background Technology

[0002] In karst development sites, areas with large karst caves, soil caves, soft soil sites (peat soil, organic soil, silt, liquefiable sand, etc.), and where the soil around the pile is prone to collapse (hereinafter referred to as soft soil sites), and where the confined water head is higher than the pile bottom, pile foundation construction often encounters problems such as borehole wall collapse, concrete loss, and necking. In these soil layers, permanent steel casings are usually required for pile foundation construction. The casing in these soil layers serves not only as "temporary support" but also as a "permanent barrier." If the casing is removed, the pile concrete will directly face the flowing silt or quicksand, leading to concrete slurry loss, pile necking, mud inclusion, or even pile breakage, causing the pile foundation to completely lose its bearing capacity. Therefore, the casing must be permanently retained and integrated with the concrete to become part of the pile body. Traditionally, it is an integral steel structure cylinder whose core function is to provide a stable casing for the drilling process, preventing borehole wall collapse under complex geological conditions, while effectively isolating surface water and confined water, creating a stable working environment for subsequent reinforcement cage placement and concrete pouring. The existing integral steel casing is installed in the early stage of pile foundation construction. The construction machinery will sink this complete steel casing to the predetermined geological layer through vibration, hammering or static pressure. After it is installed in place, the drilling rig will carry out soil extraction and hole drilling under the protection of the casing. After the hole is formed, the steel cage is lowered and the concrete is poured, it can be left underground to be consolidated together with the pile body concrete.

[0003] However, existing conventional steel casings are laid down either as a single piece or in sections. For sectioned casings, the main connection methods between the sections are currently welding or threaded connections. 1. Welded connection Welding is a technique used to join two steel casing sections together. This method typically involves welding the contact surfaces of the two casing sections to create a strong connection.

[0004] 2. Threaded connection A threaded connection is achieved by machining threads at the connection point of the steel casing and then rotating it to join two sections of the casing together. This method typically involves machining external threads at one end of the steel casing and internal threads at the other end, then connecting them by rotation.

[0005] The above connections are similar to integral steel casings, all of which are "whole-piece placement and removal". That is, once the placement is completed, either the whole casing is removed or it is permanently placed in the soil. Currently, there are also some connection methods that can use slots, but they also have the above-mentioned problems.

[0006] When the poor soil that requires permanent steel casing is located deep in the stratum, only the lower part of the casing is necessary after the concrete is poured. It plays a role in covering the poor geological layer and forming a permanent bond with the pile body. The upper part of the casing becomes redundant after the pile foundation is formed. Leaving the upper part of the casing permanently will result in a large amount of steel being wasted in vain, increasing the material cost of the project. Therefore, this invention proposes a segmented steel casing with a self-locking slot connection device to overcome the shortcomings of the prior art. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a segmented steel casing with a self-locking slot connection device, which solves the problem that the upper casing becomes a redundant part after the pile foundation is formed, and permanently leaving the upper casing would lead to the ineffective consumption of a large amount of steel, increasing the material cost of the project.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a segmented steel casing with a self-locking slot connection device, comprising: a permanent steel casing section; a fixed recycling section above the permanent steel casing section; a fixed recycling section retaining ring fitted on the surface of the fixed recycling section; a conventional steel casing recycling section above the fixed recycling section; and a self-locking device at one end of the conventional recycling section. The self-locking device includes a latch on the surface of the conventional recycling section, a compression spring at the center of the latch, a fixing hook on the surface of the conventional recycling section, and a pin inside the conventional recycling section, with the latch rotatably connected to the pin surface.

[0009] Preferably, a steel casing cap is provided above the conventional recycling section of the steel casing, and a liner is provided at the lower end of the steel casing cap. First comb-shaped slot connectors are provided at both the upper and lower ends of the conventional recycling section of the steel casing, and the liner is inserted into the conventional recycling section of the steel casing.

[0010] Preferably, a second comb-shaped slot connector is provided at the end of the permanent section of the steel casing near the fixed recycling section of the steel casing, and a wedge is provided at the end of the permanent section of the steel casing away from the fixed recycling section of the steel casing.

[0011] Preferably, the surface of the fixed recovery section of the steel casing is provided with a retaining ring bolt positioning groove, and the retaining ring of the fixed recovery section is provided with a retaining ring screw hole. The retaining ring bolt positioning groove corresponds to the retaining ring screw hole, and the retaining ring of the fixed recovery section is fixed to the surface of the fixed recovery section of the steel casing by bolts.

[0012] Preferably, the fixed recycling section retaining ring is provided with retaining teeth at one end near the permanent section of the steel casing, and the retaining teeth engage with the second comb-shaped retaining groove connector.

[0013] Preferably, the conventional recycling section and the fixed recycling section of the steel casing can be freely combined. The length and quantity of the conventional recycling section are determined according to the pile length and the depth of the unfavorable soil, and the length and quantity of the permanent recycling section are determined according to the thickness of the unfavorable soil.

[0014] Preferably, the diameter of the permanent section of the steel casing is larger than the diameter of the fixed recycling section of the steel casing.

[0015] Preferably, the fixing hook and the locking buckle are engaged with each other, the end of the compression spring away from the locking buckle is fixedly connected to the side wall of the conventional recycling section of the steel casing, and the end of the locking buckle away from the pin is located inside the first comb-shaped slot connector.

[0016] Preferably, the steel casing cap, the conventional steel casing recycling section, the fixed steel casing recycling section, the permanent steel casing section, and the retaining ring of the fixed recycling section are all coated with a special release coating.

[0017] Preferably, the conventional recycling section of the steel casing includes at least two sections, and the at least two conventional recycling sections of the steel casing are disassembled and connected by the self-locking device.

[0018] This invention provides a segmented steel casing with a self-locking slot connection device, which has the following advantages: 1. This invention achieves functional differentiation by designing the steel casing as a combination of a permanent steel casing section, a fixed recyclable steel casing section, and a conventional recyclable steel casing section. After the pile foundation construction is completed, the permanent steel casing section covering the unfavorable geological layer is left underground, while the upper fixed recyclable steel casing section and all conventional recyclable steel casing sections can be recycled and reused as a whole. This separation and recycling function is achieved by setting a retaining ring for the fixed recyclable section and by using the design that the outer diameter of the fixed recyclable steel casing section is smaller than the inner diameter of the permanent steel casing section. This ensures that the recyclable section can smoothly slide off and separate from the permanent section. Compared with the traditional practice of discarding the entire steel casing underground, the recyclable design reduces the ineffective consumption of steel and brings direct cost savings to the project.

[0019] 2. This invention employs a self-locking device in the connection between conventional and fixed recyclable sections of the steel casing. During the lowering and installation process, after each section of the casing is connected, the latches on the surface of the conventional recyclable section automatically spring back and engage with the slots of the lower casing under the action of a compression spring, achieving locking. This eliminates the need for time-consuming and laborious bolt tightening. During recycling, the axial locking formed by the self-locking device can be used to pull out the conventional and fixed recyclable sections of the steel casing as a whole. Alternatively, during disassembly, the locking can be released by the fixing hook to remove individual casing sections. This quick connection and quick unlocking design improves the operational efficiency of both the installation and recycling stages, reduces on-site auxiliary work, and shortens the overall cycle of pile foundation construction.

[0020] 3. This invention employs different connection schemes to ensure the safety and reliability of the overall structure under stress. At the connection between the fixed recovery section and the permanent section of the steel casing, the teeth at the lower end of the fixed recovery section's retaining ring engage with the second comb-shaped groove connector at the upper end of the permanent section, ensuring that the axial force during downward pressing can be stably transmitted to the permanent section. During recovery and upward pulling, the self-locking device between each recovery section provides a stable axial tensile force lock, ensuring that all recovery sections can be lifted as a rigid whole, avoiding the disengagement accident that occurs under the action of huge upward pulling force in traditional sleeve structures. This differentiated, high-strength connection design for different stress conditions provides a safety guarantee for the entire construction and recovery process. Attached Figure Description

[0021] Figure 1 This is a perspective view of the present invention; Figure 2 This is a schematic diagram of the lining wall of the present invention; Figure 3 This is a schematic diagram of the conventional recycling section of the steel casing of the present invention; Figure 4 This is a schematic diagram of the steel casing fixed recovery section of the present invention; Figure 5 This is a schematic diagram of the permanent section of the steel casing of the present invention; Figure 6 This is a schematic diagram of the self-locking device of the present invention; Figure 7 This is a schematic diagram of the self-locking device during the insertion process of the present invention; Figure 8 This is a schematic diagram of the self-locking device in operation of the present invention; Figure 9 This is a schematic diagram of the self-locking device for enhancing the locked state according to the present invention; Figure 10 This is a schematic diagram of the self-locking device in the unlocked state of the present invention; Figure 11 This is a schematic diagram of the self-locking device in the non-working state of the present invention.

[0022] 1. Steel casing cap; 11. Liner; 2. Conventional recovery section of steel casing; 21. First comb-shaped slot connector; 3. Fixed recovery section of steel casing; 31. Clamping bolt positioning groove; 4. Permanent section of steel casing; 41. Wedge; 42. Second comb-shaped slot connector; 5. Self-locking device; 51. Locking buckle; 52. Compression spring; 53. Fixing hook; 54. Pin; 6. Fixed recovery section clamping ring; 61. Clamping ring screw hole; 62. Clamping tooth. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] (Comparative Example 1) High-speed railway bridge project: The pile foundation needed to traverse a heavily karstified area (with numerous sinkholes and soil caves) at a depth of 20-25 meters, beneath which lay stable bedrock. According to the design, a permanent steel casing was required to penetrate this unfavorable geological layer. The 30 meters above this layer consisted of intact soil. The pile foundation construction employed an integral steel casing, exceeding 50 meters in length. After construction, the entire 50-meter-long steel casing remained inside the borehole. Calculations show that the bridge has 120 piles, resulting in a steel waste of 480 tons (calculated at 0.8 tons per meter of casing, with 30 meters wasted: 120 piles × 30 meters / pile × 0.8 tons / meter). This not only caused a direct material loss of several million yuan but also placed enormous pressure on environmental resources. The project attempted to use a segmented casing with flange connections, but after the concrete was poured, the flange connections were solidified by mud and cement slurry, and the bolts rusted. Large jacks and vibratory hammers could not loosen them, and the recycling ultimately failed, resulting in the abandonment of the planned recycling section.

[0025] (Comparative Example 2) Karst landform region: The pile foundations of high-rise buildings or important facilities must be supported on stable bedrock. However, the overlying soil layers through which the piles pass contain numerous karst caves, soil cavities, and fissures of varying sizes. To prevent the overlying soil from collapsing into the karst caves during the drilling process, and to prevent the large-scale loss of concrete through fissures and karst caves during concrete pouring, which could lead to incomplete piles and economic losses, as well as to prevent groundwater from flowing along the fissures and eroding the uncured concrete of the piles, permanent steel casings are required. These casings need to penetrate the entire karst development zone down to the intact bedrock surface. Since the depth of karst development can reach tens of meters, this means that tens of meters of casing will have to be completely discarded.

[0026] (Comparative Example 3) Densely networked waterways: Bridge foundations often need to penetrate extremely soft silt or quicksand layers exceeding 15 meters in thickness. These soil layers have extremely poor self-supporting capacity; without casing support, the borehole walls will collapse within a very short time after drilling is completed. The casing in these soil layers serves not only as "temporary support" but also as a "permanent barrier." If the casing is removed, the pile concrete will directly face the flowing silt or quicksand, leading to concrete slurry loss, pile necking, mud inclusion, or even pile breakage, causing the foundation to completely lose its bearing capacity. Therefore, the casing must be permanently retained, integrated with the concrete and becoming part of the pile body. A medium-sized river-crossing bridge may require hundreds of piles; an integral casing results in hundreds of tons of steel being permanently buried underground, serving only a short support distance "through quicksand layers," while the longer section of casing penetrating the better soil layers above is discarded.

[0027] These engineering comparison examples fully expose the inherent defects of existing steel casing technology in terms of economy and recyclability.

[0028] Embodiments of the present invention: Please see Figures 1-11This invention provides a segmented steel casing with a self-locking slot connection device, including a permanent steel casing section 4, which is the foundation part that is ultimately solidified with the pile concrete and permanently left underground. A fixed recovery section 3 is provided above the permanent steel casing section 4, serving as a transitional connector between the recovery section and the permanent section and a key link in achieving the separation and recovery function. A fixed recovery section retaining ring 6 is fitted on the surface of the fixed recovery section 3, which is the main load-bearing component transmitting the enormous downward pressure. The fixed recovery section retaining ring 6 and the permanent steel casing section 4 are designed to be separable. A conventional steel casing recovery section 2 is provided above the fixed recovery section 3, which is a standardized unit constituting the main length of the recovery section. Multiple sections can be connected in series to adjust the overall length as needed. A self-locking device 5 is provided at one end of the conventional steel casing recovery section 2; the self-locking device 5 enables the fixed recovery section 3 and the conventional steel casing recovery section 2 to automatically lock together, thus securing the steel casing. The fixed recovery section 3 and the conventional recovery section 2 of the steel casing can be automatically locked after installation. The self-locking device 5 includes a latch 51 set on the surface of the conventional recovery section 2 of the steel casing. The latch 51, as the locking actuator of the self-locking device 5, can wedge into the slot of the fixed recovery section 3 of the steel casing to form an axial limit and realize the locking operation. One end of the compression spring 52 is set in the middle of the latch 51. The compression spring 52 provides the driving force for the latch 51 to automatically reset through its own elastic force, so that the latch 51 can achieve automatic locking without manual operation. The surface of the conventional recovery section 2 of the steel casing is provided with a fixing hook 53. The fixing hook 53 is used for manual intervention during disassembly. The fixing hook and 53 hook the latch 51 to force the latch 51 to remain in the unlocked state, which is convenient for manual disassembly and separation. The conventional recovery section 2 of the steel casing is provided with a pin 54. The latch 51 is rotatably connected to the surface of the pin 54, so that the latch 51 can swing around the pin 54 as the center, realizing the lifting under the action of external force and the locking action of falling back under the action of spring force.

[0029] Please see Figures 1-2 A steel casing cap 1 is installed above the conventional recovery section 2 of the steel casing. The steel casing cap 1 is used to connect construction driving equipment such as vibratory hammers and to protect the port of the uppermost steel casing from damage under hammering. A liner 11 is installed at the lower end of the steel casing cap 1, and the liner 11 forms an annular flange at the lower end of the steel casing cap 1. The upper and lower ends of the conventional recovery section 2 of the steel casing are provided with first comb-shaped slot connectors 21. The first comb-shaped slot connectors 21 increase the contact area between the first comb-shaped slot connectors 21 and the connecting segments of the conventional recovery section 2 of the steel casing through a dense toothed groove structure, so as to enhance the transmission of axial force. The liner 11 is inserted into the conventional recovery section 2 of the steel casing. The liner 11 can be inserted into the lower steel casing. Through the tight fit between the liner 11 and the inner wall of the lower steel casing, it plays a role in precise centering and positioning, preventing misalignment between the upper casing and the driving equipment due to uneven force during the pressing process.

[0030] Please see Figure 1 , Figure 4 , Figure 5 The permanent section 4 of the steel casing is provided with a second comb-shaped slot connector 42 at one end near the fixed recovery section 3. The slot structure of the second comb-shaped slot connector 42 matches the teeth 62 at the lower end of the fixed recovery section ring 6, which is intended to form a stable meshing structure to bear and transmit the huge downward pressure load of the entire superstructure and construction equipment. The permanent section 4 of the steel casing is provided with a wedge 41 at one end away from the fixed recovery section 3. The wedge 41 forms a cutting edge, which can cut into the soil in the initial stage of pressing, reduce the soil resistance of the permanent section 4 of the steel casing, and guide the entire steel casing to sink vertically.

[0031] Please see Figure 4 The surface of the fixed recovery section 3 of the steel casing is provided with a retaining ring bolt positioning groove 31. The retaining ring bolt positioning groove 31 provides axial and circumferential positioning reference for the installation of the retaining ring, preventing the retaining ring 6 of the fixed recovery section from rotating or sliding under huge torque or impact force. The retaining ring 6 of the fixed recovery section is provided with a retaining ring screw hole 61. The retaining ring bolt positioning groove 31 corresponds to the retaining ring screw hole 61. The retaining ring 6 of the fixed recovery section is fixed to the surface of the fixed recovery section 3 of the steel casing by bolts. The high-strength bolt connection ensures that the retaining ring 6 of the fixed recovery section and the fixed recovery section 3 of the steel casing form a rigid whole, ensuring that there will be no relative displacement between the two during the downward pressing construction process, thereby ensuring reliable force transmission.

[0032] Please see Figure 1 , Figure 4 The fixed recovery section retaining ring 6 is provided with a retaining tooth 62 at one end near the permanent section 4 of the steel casing. The retaining tooth 62 is designed as a convex tooth that perfectly matches the groove shape of the second comb-shaped retaining groove connector 42 below. The retaining tooth 62 and the second comb-shaped retaining groove connector 42 engage with each other. The engagement between the retaining tooth 62 and the second comb-shaped retaining groove connector 42 increases the contact surface area between the fixed recovery section retaining ring 6 and the permanent section 4 of the steel casing and enhances the shear resistance of the fixed recovery section retaining ring 6 and the permanent section 4 of the steel casing. It can evenly distribute and transfer the downward pressure load transmitted from the upper part to the permanent section 4 of the steel casing, avoiding the risk of connection failure caused by stress concentration.

[0033] Please see Figures 3-5The conventional recovery section 2 and the fixed recovery section 3 of the steel casing can be freely combined because the present invention uses a standardized self-locking device 5 as a connection interface, which allows the conventional recovery sections 2 of different lengths to be arbitrarily spliced. The length and quantity of the conventional recovery sections 2 are determined according to the pile length and the depth of the unfavorable soil, which enhances the flexibility of the present invention. It can accurately match the total length of the required recovery sections according to the specific geological report and designed pile length for each construction, avoiding material waste. The length and quantity of the permanent section 4 of the steel casing are determined according to the thickness of the unfavorable soil, ensuring that the permanent section 4 of the steel casing can completely cover the weak or permeable geological layer that needs to be isolated, thus guaranteeing the quality of the project.

[0034] Please see Figure 1 , Figure 4 The diameter of the permanent section 4 of the steel casing is larger than that of the fixed recovery section 3 of the steel casing. This difference in size is the key to achieving smooth recovery. An annular gap is reserved between the permanent section 4 and the fixed recovery section 3 of the steel casing. When the fixed recovery section 3 of the steel casing is pulled out upwards, the gap can reduce the friction between the two and avoid jamming caused by mud or concrete residue. This ensures that the fixed recovery section 3 of the steel casing, together with the conventional recovery section 2 of the steel casing, can be cleanly and neatly slid off from the permanent section 4 of the steel casing.

[0035] Please see Figures 6-11 The fixing hook 53 and the locking buckle 51 are engaged with each other. The engagement action of the fixing hook 53 and the locking buckle 51 is completed manually when the steel casing fixed recovery section 3 needs to be disassembled in sections. By rotating the fixing hook 53 to a specific position to hook the locking buckle 51, the locking buckle 51 can overcome the elastic force of the compression spring 52 and keep the locking buckle 51 in the unlocked state. The end of the compression spring 52 away from the locking buckle 51 is fixedly connected to the side wall of the conventional recovery section 2 of the steel casing. The conventional recovery section 2 of the steel casing provides a stable support point for the spring, so that it can continuously apply a tendency force to the locking buckle 51 to make it pop out and lock. The end of the locking buckle 51 away from the pin 54 is located inside the first comb-shaped slot connector 21. Through this wedge-type locking, the locking buckle 51 forms an axial limit on the steel casing fixed recovery section 3, so that the steel casing fixed recovery section 3 and the steel casing conventional recovery section 2 will not separate when subjected to upward pulling force.

[0036] Please see Figures 1-11The steel casing cap 1, the conventional steel casing recovery section 2, the fixed steel casing recovery section 3, the permanent steel casing section 4, and the fixed recovery section retaining ring 6 are all coated with a special release coating. The main function of the special release coating is to reduce the bond strength between the steel surface and the pile concrete. For the conventional steel casing recovery section 2, the fixed steel casing recovery section 3, and the fixed recovery section retaining ring 6, the special release coating reduces the concrete gripping force that needs to be overcome during extraction, reduces the tonnage requirements of the lifting equipment, and makes the recovery process easier and safer. At the same time, the special release coating can also reduce the side wall friction resistance during downward pressure to a certain extent.

[0037] Please see Figures 1-5 The conventional recycling section 2 of the steel casing consists of at least two sections. The at least two conventional recycling sections 2 of the steel casing are disassembled and connected by a self-locking device 5. Since the self-locking device 5 is standardized, the top and bottom ends of any conventional recycling section 2 of the steel casing have the same connection interface, which ensures their interchangeability and quick connection capability and improves the convenience of on-site construction.

[0038] Working principle: The construction method mainly includes the following steps: Step 1: Steel Casing Fabrication: Determine the diameter of the steel casing based on the designed pile diameter. Determine the length of the permanent section of the steel casing based on the thickness of the adverse soil. Then, determine the length and number of conventional recovery sections of the steel casing based on the pile length and the depth of the adverse soil. The conventional and fixed recovery sections of the steel casing can be freely combined to adapt to different depths of adverse soil. Determine the placement order of the conventional, fixed, and permanent sections of the steel casing according to different pile foundations, and mark them for easy on-site construction. The inner diameter of the permanent section is 2mm larger than that of the fixed recovery section to ensure smooth separation of the fixed recovery section from the permanent section during the extraction process.

[0039] Step Two: Steel Casing Installation: During construction, the steel casing can be lowered using conventional machinery such as a pipe rolling machine or static pressure machine. The machinery should first connect to the steel casing cap. Based on the specific geological cross-section and the location of unfavorable soil, the permanent section, the fixed recovery section, and the conventional recovery section of the steel casing should be lowered sequentially. When lowering the conventional recovery section, the speed should be carefully controlled to ensure the self-locking device is locked and will not detach during lifting. When there are multiple conventional recovery sections, they should be lowered one section at a time.

[0040] Step 3: Steel Casing Retrieval: After the pile foundation is poured as usual, the steel casing is pulled out immediately. During the pulling process, each section of the casing is automatically locked and will not fall off. The steel casing is retrieved in two stages: a regular retrieval section and a fixed retrieval section. The retrieval can be done all at once or in sections. When retrieving in sections, the fixing holes need to be exposed. This is done by passing the support through the hole, releasing the self-locking device, and then removing the previous section. This process is repeated until the retrieval is complete.

[0041] Based on geological survey data, the length of the permanent section 4 of the steel casing is determined to cover the unfavorable geological layer. The combination and lowering sequence of the conventional recovery section 2 and the fixed recovery section 3 of the steel casing are planned. During construction, the fixing hook 53 is opened, releasing the limitation of the locking buckle 51. Conventional machinery, through the steel casing cap 1 inserted into the uppermost steel casing via the lining wall 11, positions the casing and drives it downwards. The permanent section 4, the fixed recovery section 3, and the conventional recovery section 2 are lowered sequentially. During the descent, the locking buckle 51 rises upwards, overcoming the elasticity of the compression spring 52. After the first comb-shaped slot connector 21 fully enters the top toothed groove of the lower section, the locking buckle 51 automatically springs back to a horizontal state under the action of the compression spring 52, completing the locking and engaging with the toothed groove of the lower steel casing, forming a stable axial lock. The permanent section 4, the fixed recovery section 3, the conventional recovery section 2, and the steel casing cap 1 become a single unit. The fixed recovery section 3... The connection to the permanent section 4 of the steel casing is achieved through a fixed recovery section retaining ring 6. The retaining teeth 62 at the lower end of the fixed recovery section retaining ring 6 engage with the second comb-shaped retaining groove connector 42 at the upper end of the permanent section 4 of the steel casing, ensuring the force transmission when the permanent section 4 of the steel casing descends. After the pile foundation concrete is poured, when the conventional recovery section 2 of the steel casing is lifted upward, due to the locking of the self-locking device 5, all conventional recovery sections 2 and fixed recovery sections 3 of the steel casing are pulled upward as a whole. When subjected to lifting force, the fixed recovery section 3 of the steel casing, together with the fixed recovery section retaining ring 6 on the surface of the fixed recovery section 3, will smoothly slide and separate from the permanent section 4 of the steel casing. The recovery process can be completed in one go. The lifting can also be carried out by disassembling in sections, that is, lifting section by section until the connection is exposed. After manually releasing the locking state of the lock 51 by the fixing hook 53, the section of steel casing is removed. This step is repeated until all recovery sections are removed, leaving only the permanent section 4 of the steel casing and the pile concrete to be fixed underground together.

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A segmented steel casing with a self-locking slot connection device, characterized in that, include: A permanent section (4) of steel casing is provided above the permanent section (4) of steel casing, a fixed recycling section (3) of steel casing is provided above the fixed recycling section (3), a fixed recycling section retaining ring (6) is provided on the surface of the fixed recycling section (3), a conventional recycling section (2) of steel casing is provided above the fixed recycling section (3), a self-locking device (5) is provided at one end of the conventional recycling section (2), and a first comb-shaped slot connector (21) is provided at both the upper and lower ends of the conventional recycling section (2). The self-locking device (5) includes a latch (51), a compression spring (52), a fixing hook (53), and a pin (54) disposed on the surface of the conventional recycling section (2) of the steel casing. One end of the compression spring (52) acts on the latch (51) and the other end is connected to the side wall of the conventional recycling section (2) of the steel casing, so that the latch (51) has a tendency to pop out to the outside of the conventional recycling section (2) of the steel casing and can be locked into the groove of the first comb-shaped slot connector (21) of the adjacent steel casing section to form an axial lock. The fixing hook (53) is disposed on the surface of the conventional recycling section (2) of the steel casing and is used to hook the latch (51). The conventional recycling section (2) of the steel casing is provided with a pin (54) inside, and the latch (51) is rotatably connected to the surface of the pin (54).

2. A segmented steel casing with a self-locking slot connection device according to claim 1, characterized in that, A steel casing cap (1) is provided above the conventional recycling section (2) of the steel casing, and a liner (11) is provided at the lower end of the steel casing cap (1). The liner (11) is inserted into the conventional recycling section (2) of the steel casing.

3. A segmented steel casing with a self-locking slot connection device according to claim 1, characterized in that, The permanent section (4) of the steel casing is provided with a second comb-shaped slot connector (42) at one end near the fixed recycling section (3) of the steel casing, and a wedge (41) is provided at the other end of the permanent section (4) away from the fixed recycling section (3).

4. A segmented steel casing with a self-locking slot connection device according to claim 1, characterized in that, The surface of the fixed recycling section (3) of the steel casing is provided with a clasp bolt positioning groove (31), and the clasp (6) of the fixed recycling section is provided with a clasp screw hole (61). The clasp bolt positioning groove (31) corresponds to the clasp screw hole (61), and the clasp (6) of the fixed recycling section is fixed to the surface of the fixed recycling section (3) of the steel casing by bolts.

5. A segmented steel casing with a self-locking slot connection device according to claim 3, characterized in that, The fixed recycling section retaining ring (6) is provided with a retaining tooth (62) at one end near the permanent section (4) of the steel casing, and the retaining tooth (62) is engaged with the second comb-shaped groove connector (42).

6. A segmented steel casing with a self-locking slot connection device according to claim 1, characterized in that, The conventional recycling section (2) and the fixed recycling section (3) of the steel casing can be freely combined. The length and quantity of the conventional recycling section (2) of the steel casing are determined according to the pile length and the depth of the unfavorable soil. The length and quantity of the permanent section (4) of the steel casing are determined according to the thickness of the unfavorable soil.

7. A segmented steel casing with a self-locking slot connection device according to claim 1, characterized in that, The diameter of the permanent section (4) of the steel casing is larger than the diameter of the fixed recycling section (3) of the steel casing.

8. A segmented steel casing with a self-locking slot connection device according to claim 2, characterized in that, The inner surfaces of the steel casing cap (1), the conventional steel casing recycling section (2), the fixed steel casing recycling section (3), the permanent steel casing section (4), and the retaining ring (6) of the fixed recycling section are all coated with a special release coating.

9. A segmented steel casing with a self-locking slot connection device according to claim 1, characterized in that, The conventional recycling section (2) of the steel casing includes at least two sections, which are detachably connected by the self-locking device (5).

Images