Open caisson structure and construction method thereof

Abstract

A well wall of the open caisson structure comprises a first-section well wall body and a heightening well wall body which are sequentially connected together in the vertical direction, and the first-section well wall body comprises a well shaft, a counter-force beam on the lower side of the well shaft and a blade foot on the lower side of the counter-force beam; an operation hole for containing the sinking mechanism is formed in the lower end of the shaft, an axial hole is formed in the counter-force beam in the axial direction, an anchor rod body of the anti-pulling anchor rod can freely penetrate through the axial hole upwards and then is connected to the sinking mechanism, and the sinking mechanism can provide counter force through the anchor rod body to push the first section of well wall to move downwards relative to the anchor rod body. And the first section of well wall is pushed to sink in the underground soil body. A part of the first section of well wall is used as the counter-force beam, the sinking mechanism is arranged in the operation hole, the defect caused by the fact that the counter-force beam needs to be frequently installed and dismantled when loads are applied to the tops of all the well walls is overcome, and when the well wall located on the uppermost side sinks to the designed heightening position, sinking of the well wall only needs to be stopped, and the well wall can be lifted. Therefore, the construction efficiency is effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of underground structure construction, specifically relating to a caisson structure and its construction method. Background Technology

[0002] Caisson construction is a common method for deep underground foundation construction, widely used in projects such as pump stations, bridge piers, and tunnel boring machine shafts. There are two methods of caisson sinking: relying solely on the caisson's own weight and applying external reaction forces. When relying solely on the caisson's own weight, the soil at the bottom of the caisson needs to be excavated before the caisson can sink, overcoming the side friction resistance of the caisson wall and the resistance at the lower end of the cutting edge. During the sinking process, controlling the caisson's attitude is difficult, and it is prone to sudden sinking or tilting, and it is also quite sensitive to geological conditions.

[0003] The external reaction force caisson construction method involves first causing the caisson to sink under the influence of external force. After the excavation of the soil within the caisson is completed, it is sunk again. The sinking of the caisson and the excavation of the soil are alternated until the caisson is fully sunk. The external reaction force method can directly place weights on top of the caisson, utilizing the weight of the weights and the caisson's own weight to sink it. This method requires a large number of weights and involves a huge amount of construction work. Therefore, anti-uplift structures are constructed around the foundation pit, and a reaction force is erected on top of the caisson to increase the sinking reaction force. In the external reaction force caisson construction method, a reaction beam needs to be erected on top of the uppermost caisson wall for each sinking. After sinking to the designated height, the reaction beam is removed before the next section of the caisson wall can be installed. After the next section of the caisson wall is installed, a reaction beam needs to be erected on top of the newly installed caisson wall again, making the construction process cumbersome and affecting construction efficiency.

[0004] Therefore, improving the construction methods for caisson sinking to increase the efficiency of caisson construction remains a problem faced in caisson construction. Summary of the Invention

[0005] To improve the efficiency of caisson construction, this application first proposes a caisson structure, which includes at least two sections of caisson wall connected vertically in sequence. The caisson wall located at the bottom is called the first section of caisson wall, and the remaining caisson walls are called the connecting caisson walls. The first section of caisson wall includes a caisson cylinder, a ring-shaped reaction beam formed on the lower side of the caisson cylinder, and a cutting edge formed on the lower side of the reaction beam. When viewed axially along the first section of caisson wall, the outer wall of the reaction beam extends radially outward beyond the outer wall of the caisson cylinder, and the outer wall of the reaction beam also extends radially outward beyond the outer wall of any connecting caisson wall. A working hole is provided at the lower end of the caisson cylinder, and a sinking mechanism is located in the working hole. An axial hole is provided in the reaction beam, and the anchor body of the pull-out anchor rod can freely pass upward through the axial hole and connect to the sinking mechanism. The sinking mechanism can provide reaction force through the anchor body, pushing the first section of caisson wall to move downward relative to the anchor body, thereby pushing the first section of caisson wall to sink in the underground soil. In the radial direction, the outer wall of the reaction beam extends outward by 0.25-0.5m compared to the outer wall of the well casing.

[0006] In this application, a working hole is provided inside the first section of the well wall, allowing the anchor body of the anchor bolt to be connected to a sinking mechanism installed in the working hole. The sinking mechanism and the anchor bolt drive the first section of the well wall to sink. Because the outer wall of the reaction beam extends radially outward beyond the outer wall of the well cylinder, an upward-facing step surface is formed between the reaction beam and the outer wall of the well cylinder, thereby reducing the friction between the underground soil and the remaining well walls. This allows the well walls to sink synchronously with the first section of the well wall under their own weight. Since a portion of the first section of the well wall itself is used as the reaction beam, and the sinking mechanism is arranged inside the working hole, the drawbacks of frequently installing and removing reaction beams when applying loads to the tops of each well wall are avoided. When the uppermost section of the well wall sinks to the designed height, the sinking of the well wall can be paused before installing the next section of the well wall, effectively improving construction efficiency.

[0007] Furthermore, to facilitate the prefabrication of the first section of the well wall, an inner sleeve is installed inside the axial hole, and the anchor rod body freely passes through the inner sleeve and is connected to the sinking mechanism.

[0008] To further reduce the sinking resistance of each well wall, a grouting pipe is installed on the well shaft of the first well wall section. This grouting pipe penetrates the well shaft radially, allowing thixotropic mud to be injected through this pipe into the gap between the first well wall section and the external soil. After all well walls have sunk, cement mortar is injected through the same pipe into the gap between the first well wall section and the outer soil to replace the thixotropic mud. This application does not specify requirements for the cement mortar; any cement mortar used for grouting can be used. Preferably, 6-8% of an expanding agent is added to the cement mortar to improve the density of the cement-soil mixture formed by the cement mortar and the underground soil, thereby enhancing the bond between the cement-soil mixture and the caisson structure.

[0009] While thixotropic mud can effectively reduce the friction between the well wall and the soil, it needs to be stably maintained within the set elevation when the caisson structure sinks to that elevation. However, the presence of thixotropic mud is detrimental to both pull-out resistance and buoyancy resistance of the caisson structure. Replacing the thixotropic mud with cement mortar can remove more than 85-90% of it. Although a small amount of thixotropic mud remains underground, it is mixed with the cement mortar and combines with the underground soil to form a cement-soil structure. This improves the bonding force between the well wall and the underground soil, thereby enhancing the stability of the caisson structure underground.

[0010] Furthermore, to prevent external soil from entering the first section of the well wall through the working hole during the sinking process, an outer baffle is installed on the outer wall of the well shaft to seal the outer end of the working hole. This outer baffle also serves as an external formwork for pouring concrete inside the working hole. The outer baffle is preferably made of steel plate.

[0011] Specifically, the anchor body of the pull-out anchor is made of steel strand or precision-rolled threaded steel. When the anchor body is made of steel strand, the sinking mechanism is a hollow hydraulic jack; when the anchor body is made of precision-rolled threaded steel, the sinking mechanism is a hollow hydraulic jack or a precision-rolled nut. The selection of the anchor body and the sinking mechanism can be based on the specific construction conditions, but a hollow hydraulic jack is preferred as the sinking mechanism. The models and operating methods of hollow hydraulic jacks are well-established, and existing mature technology can be used. The hollow hydraulic jack is installed on the bottom surface of the working hole.

[0012] Furthermore, in order to make full use of the pull-out resistance of the anchor bolt, when the first section of the well wall sinks to the set depth, the anchor bolt body is locked in the working hole by a locking device, and then concrete or grout is poured into the working hole.

[0013] Secondly, this application also discloses a construction method for the caisson structure described in any of the above claims, which includes the following steps:

[0014] (1) Construct anti-pull anchor bolts at the designated location on the ground, then install the first section of the well wall on the ground, and make the upper end of the anchor bolt body of the anti-pull anchor bolt pass through the axial hole and extend into the working hole, and install the sinking mechanism on the anchor bolt body;

[0015] (2) Excavate the earthwork of the foundation pit inside the well, and simultaneously start the sinking mechanism to move the sinking mechanism downward along the anchor body, driving the first section of the well wall to sink until the first section of the well wall sinks to the designed height position, then stop the sinking mechanism to stop the sinking of the first section of the well wall; during the sinking process of the first section of the well wall, simultaneously cut off the excess anchor body that extends upward from the sinking mechanism.

[0016] (3) Install the second section of the well wall on the first section of the well wall, continue the excavation of the foundation pit inside the well, and start the sinking mechanism to make the first section of the well wall continue to sink, and simultaneously drive the second section of the well wall to sink until it reaches the designed height position again. Then stop the sinking mechanism so that the first section of the well wall and the second section of the well wall stop sinking. During the sinking process of the first section of the well wall, simultaneously cut off the excess anchor rods that extend upwards from the sinking mechanism.

[0017] (4) Repeat step (3) until the entire caisson structure is completely sunk.

[0018] In this construction method, because a portion of the first section of the well wall is used as a reaction beam and the sinking mechanism is arranged inside the working hole, the drawbacks of frequently installing and removing the reaction beam when applying loads to the top of each well wall are avoided. When the uppermost well wall sinks to the designed height position, the sinking of the well wall can be paused before installing the next section of the well wall, thus effectively improving construction efficiency.

[0019] To prevent thixotropic mud from overflowing onto the ground during injection, a ring-shaped anti-overflow ring is installed on the ground. The anti-overflow ring is fitted onto the well wall, and the inner end of the anti-overflow ring elastically presses against the outer circumferential surface of the well wall.

[0020] Furthermore, to improve sinking efficiency, during the sinking of the first section of the well wall, thixotropic mud is injected through a grouting pipe into the gap between the first section of the well wall and the external underground soil. After the entire caisson structure has sunk, cement mortar is injected through a grouting pipe onto the outside of the caisson structure to replace the thixotropic mud. This application does not have specific requirements for the cement mortar; any cement mortar used for grouting can be used in this application. Preferably, an expansion agent with a cement content of 6-8% is added to the cement mortar to improve the density of the cement-soil mixture formed by the cement mortar and the underground soil, thereby enhancing the bond strength between the cement-soil mixture and the caisson structure.

[0021] Furthermore, the height of the cutting edge is 2.5-4 meters. During the sinking of the first section of the well wall, the bottom surface of the pit inside the well is higher than the lower end face of the cutting edge, and the distance from the bottom surface of the pit to the lower end face of the cutting edge is 20-50% of the height of the cutting edge. This continues until the first section of the well wall sinks to the set elevation, at which point the pit inside the well is excavated to the set depth. This design ensures that the lower end of the cutting edge of the first section of the well wall remains inserted into the underground soil before the sinking is complete, forming a pre-support to reduce tilting and sudden sinking of the caisson structure during sinking, thus improving the stability of the caisson structure during sinking. Simultaneously, the lower end of the cutting edge inserted into the soil also serves as a guide and water stopper.

[0022] Furthermore, a hydraulic station is installed on the inner wall of the well shaft or reaction beam. The first hydraulic inlet pipe of this hydraulic station is connected to the second hydraulic outlet pipe of the sinking mechanism, and vice versa. After the entire caisson structure has been sinked, the anchor bolts are locked in the working hole using locking devices, and the sinking mechanism and hydraulic station are removed. This design avoids frequent connection of hydraulic pipes during the sinking process of the caisson structure, thereby preventing damage to the hydraulic pipes due to errors and preventing hydraulic oil leakage. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the first section of the well wall.

[0024] Figure 2 for Figure 1 Cross-sectional view along the AA direction.

[0025] Figure 3 for Figure 1 Enlarged view of section B.

[0026] Figure 4 This is a schematic diagram showing the first section of the well wall positioned on the ground.

[0027] Figure 5 This is a schematic diagram showing the first section of the well wall sinking to the designed height position.

[0028] Figure 6 for Figure 5 Enlarged view of section C.

[0029] Figure 7 This is a schematic diagram showing the second section of the well wall installed on top of the first section.

[0030] Figure 8 This is a schematic diagram showing the second section of the well wall sinking to the designed height position.

[0031] Figure 9 This is a schematic diagram showing the third section of the well wall installed on top of the second section.

[0032] Figure 10 This is a schematic diagram showing the complete sinking of all well walls.

[0033] Figure 11 This is a schematic diagram showing the completion of sealing the bottom of the foundation pit inside the well.

[0034] Figure 12 This is a schematic diagram of the caisson structure after construction is completed. Detailed Implementation

[0035] The following section first describes the caisson structure; please refer to [link / reference]. Figures 1-3 as well as Figure 12The caisson structure comprises three sections of caisson wall connected vertically in sequence. From bottom to top, these sections are the first section 100, the second section 200, and the third section 300. The second and third sections are both raised sections. The radially outer side of the base plate 92 is cast into the bottom groove 112 on the inner side of the first section. A top plate 93 is cast on top of the caisson structure, and a sealing layer 91 made of plain concrete is formed at the bottom of the pit. In this embodiment, the caisson structure is circular. It is understood that in other embodiments, the caisson structure may also be elliptical or rectangular.

[0036] The first section of the well wall 100 includes a well cylinder 11, a ring-shaped reaction beam 12 formed on the lower side of the well cylinder 11, and a cutting edge 121 formed on the lower side of the reaction beam. Viewed axially along the first section of the well wall, the outer wall of the reaction beam extends radially outward beyond the outer wall of the well cylinder, forming an upward-facing stepped surface 122 between the reaction beam and the outer wall of the well cylinder. Furthermore, the outer wall of the reaction beam extends radially outward beyond the outer wall of any connecting well wall. In this embodiment, the first outer diameter D1 of the reaction beam is 12.4 meters, the second outer diameter D2 of the well cylinder is 11.6 meters, and the outer diameter of all connecting well walls is 11.6 meters, meaning the outer wall of the reaction beam extends radially outward beyond the outer wall of the well cylinder by 0.4 meters. In this embodiment, the well cylinder, reaction beam, and cutting edge are integrally cast, and the outer diameter of the cutting edge is the same as the outer diameter of the reaction beam.

[0037] Eight working holes 13 are provided at the lower end of the well shaft, and the eight working holes are evenly spaced along the circumference of the well shaft. An outer baffle 131 is installed on the outer wall of the well shaft, which closes the outer ends of the working holes. In this embodiment, the outer baffle is made of steel plate to prevent external soil from entering the pit inside the well through the working holes during the sinking of the first section of the well wall. The outer baffle also serves as an outer formwork when pouring concrete into the working holes. To reinforce the edges of the working holes, a steel top plate 132 is pre-embedded at the top of the working holes, steel side plates 134 are pre-embedded on the inner walls of both sides of the working holes, and a steel bottom plate 133 is pre-embedded at the bottom of the working holes to disperse the downward pressure generated by the sinking mechanism during operation.

[0038] The working hole is used to install the sinking mechanism 16. Eight axial holes 14 are opened along the axial direction inside the reaction beam, each corresponding to one working hole. An inner sleeve is installed in the circumferential hole. The inner sleeve is specifically made of rigid PVC pipe. It can be understood that the inner sleeve can also be made of other rigid plastic pipes or steel pipes. The anchor body 151 of the pull-out anchor 15 can freely pass upward through the inner cavity of the inner sleeve and connect to the sinking mechanism. The sinking mechanism can provide reaction force through the anchor body, pushing the first section of the well wall to move downward relative to the anchor body, thereby pushing the first section of the well wall to sink in the underground soil. The lower end of the anchor body 151 is anchored underground through a concrete enlarged head 152.

[0039] In this embodiment, the anchor body 151 of the pull-out anchor 15 is specifically made of fine-rolled threaded steel. The sinking mechanism uses a hollow hydraulic jack, which is movably installed on a steel base plate 133 at the bottom of the working hole and is freely positioned by the anchor body 151. The upper end of the fine-rolled threaded steel extends into the inner cavity of the hollow piston rod of the hollow hydraulic jack. To avoid frequent connection of hydraulic pipes and to avoid damage to the hydraulic pipes due to errors, resulting in hydraulic oil leakage, in this embodiment, a hydraulic station installation position is provided on the inner side of the reaction ring beam. A bracket steel plate 123 is pre-embedded in the hydraulic station installation position, and a bracket 124 is welded to the bracket steel plate. The hydraulic station 105 is bolted to the bracket 124. After the sinking of the caisson structure is completed, the hydraulic station 105 is disassembled, and then the bracket 124 is cut off. Of course, bolts can also be pre-embedded in the hydraulic station installation position, and the bracket can be installed on the pre-embedded bolts, or expansion bolts or other methods can be used to install the bracket in the hydraulic station installation position. Alternatively, the installation can be eliminated by installing a corresponding mounting part on the hydraulic station, which then mounts the hydraulic station to its mounting position. This application does not restrict the installation method of the hydraulic station, as long as it can be easily disassembled after use.

[0040] It is understood that, in another embodiment, steel strand can also be used to make the anchor rod body, with the upper end of the steel strand extending into the inner cavity of the hollow piston rod of the hollow hydraulic jack. Of course, when using precision-rolled threaded steel as the anchor rod body, a precision-rolled nut can also be used as the sinking mechanism. This precision-rolled nut is screwed onto the precision-rolled threaded steel serving as the anchor rod body. However, when using a precision-rolled nut as the sinking mechanism, the operating efficiency is low, and it is generally not recommended; it is only used in environments where hollow hydraulic jacks cannot be used.

[0041] A grouting pipe 111 is pre-embedded in the well barrel of the first section of the well wall, and the grouting pipe penetrates the well barrel radially. The grouting pipe is used to inject thixotropic mud into the gap between the caisson structure and the external soil, as well as cement mortar to replace the thixotropic mud.

[0042] When the first section of the well wall sinks to the set depth, the anchor bolt body is locked in the working hole by a locking device, and then concrete 110 is poured into the working hole. In this embodiment, the locking device is a precision-rolled nut. It can be understood that in another embodiment, grouting material can also be used to pour the working hole. When the anchor bolt body is made of steel strand, the locking device is a clamp-type anchor.

[0043] The construction method of the caisson structure in this embodiment is described below, and the construction method specifically includes the following steps:

[0044] (1) Please refer to Figure 4An anti-pull-out anchor bolt 15 is installed at a designated location on the ground. Then, a ring-shaped guide beam 81 is constructed, and the first section of the well wall 100 is installed on the ground, positioned within the area enclosed by the guide beam 81. The upper end of the anchor bolt body 151 of the anti-pull-out anchor bolt 15 extends upward through the axial hole into the working hole, and a hollow hydraulic jack is installed on the anchor bolt body. A hydraulic station is installed at the hydraulic station mounting position, with the first hydraulic inlet pipe of the hydraulic station connected to the second hydraulic outlet pipe of the hollow hydraulic jack, and vice versa. In the attached drawings, hydraulic pipes including the first hydraulic inlet pipe, first hydraulic outlet pipe, second hydraulic inlet pipe, and second hydraulic outlet pipe are not shown; the connections of each hydraulic pipe can be made according to existing technology. Mark 800 in the attached drawings indicates the ground.

[0045] (2) Please refer to Figure 5 During the excavation of the foundation pit inside the well, the hollow hydraulic jacks are simultaneously activated to move downward along the anchor rods, driving the first section of the well wall to sink until it reaches the designed height. The hollow hydraulic jacks are then stopped to halt the sinking of the first section of the well wall. During the sinking of the first section of the well wall, the excess anchor rods extending upward from the sinking mechanism are simultaneously cut off.

[0046] When the height of the grouting pipe is lower than the ground, thixotropic mud 89 is injected through the grouting pipe into the gap between the first section of the well wall and the external underground soil to reduce the friction between the first section of the well wall and the external soil. During the subsequent sinking of each well wall, thixotropic mud is continued to be injected through the grouting pipe into the gap between the first section of the well wall and the external underground soil.

[0047] Please see Figure 6 To prevent thixotropic mud from overflowing to the surface, a ring-shaped anti-overflow ring 82 is fixedly installed on the guide beam 81 using bolts 84. The anti-overflow ring is fitted onto the first section of the well wall. The anti-overflow ring is made of rubber, and its inner edge is bent downward to form an elastic anti-overflow part 821. The elastic anti-overflow part 821 is ring-shaped, and its inner wall elastically presses against the outer circumference of the first section of the well wall. During the subsequent sinking of the second and third sections of the well wall, the anti-overflow part successively presses against the outer walls of the second and third sections of the well wall. To facilitate the holding of the anti-overflow ring, a pressure plate 83 is placed on the anti-overflow ring, and bolts are used to fix the anti-overflow ring to the guide beam via the pressure plate 83.

[0048] (3) Please refer to Figure 7 and Figure 8The second section of the well wall 200 is installed on top of the first section of the well wall 100. The earthwork excavation of the foundation pit inside the well continues, and the hollow hydraulic jacks are started to make the first section of the well wall continue to sink, which simultaneously drives the second section of the well wall to sink until it reaches the designed height position again. Then the hollow hydraulic jacks are stopped, so that the sinking of the first and second sections of the well wall stops. During the sinking of the first section of the well wall, the excess anchor rods extending upward from the hollow hydraulic jacks are cut off simultaneously.

[0049] (4) Please refer to Figure 9 and Figure 10 Repeat step (3) to complete the sinking of the third section of the well wall, so that the entire caisson structure is sinking. Use precision-rolled nuts to lock the upper end of the anchor rod body into the working hole, and use hollow hydraulic jacks and hydraulic stations. Pour 110 concrete into the working hole to seal the working hole, and the precision-rolled nuts and the top of the anchor rod body are poured into the concrete.

[0050] During the sinking of the first section of the well wall, the bottom surface 88 of the pit inside the well is higher than the lower end face of the cutting edge, and the distance between the bottom surface of the pit inside the well and the lower end face of the cutting edge is 30-40% of the height of the cutting edge. This continues until the first section of the well wall sinks to the set elevation, and then the pit inside the well is excavated to the set depth. In this embodiment, the height H of the cutting edge is 3 meters. During the sinking of the first section of the well wall, the distance S between the bottom surface of the pit inside the well and the lower end face of the cutting edge is controlled between 0.9 and 1.2 meters, so that the lower end of the cutting edge forms advanced support.

[0051] Please see Figure 11 Plain concrete is poured at the bottom of the foundation pit inside the well to form the sealing layer 91, followed by the pouring of the bottom slab 92 and the top slab 93. The overflow ring 82 is removed, and cement mortar is injected through the grouting pipe onto the outside of the caisson structure to replace the thixotropic mud. Most of the thixotropic mud overflows to the ground under the impetus of the cement mortar, while a small amount of thixotropic mud and cement mortar infiltrate into the soil outside the caisson structure, forming a cement-soil structure to improve the bond between the caisson structure and the underground soil. In this embodiment, the weight ratio of cement, water, quartz sand, and expanding agent in the cement mortar is 1:0.50:0.8:0.06, and the expanding agent is specifically calcium oxide.

Claims

1. A caisson structure, characterized in that, The well wall comprises at least two sections connected vertically in sequence. The lowermost section is called the first section, and the remaining sections are called the connecting sections. The first section includes a well cylinder, a ring-shaped reaction beam formed on the lower side of the well cylinder, and a cutting edge formed on the lower side of the reaction beam. Viewed axially along the first section, the outer wall of the reaction beam extends radially outward beyond the outer wall of the well cylinder, and the outer wall of the reaction beam also extends radially outward beyond the outer wall of any connecting section. A working hole is provided at the lower end of the well cylinder, and a sinking mechanism is located in the working hole. An axial hole is provided in the reaction beam, and the anchor body of the pull-out anchor rod can freely pass upward through the axial hole and connect to the sinking mechanism. The sinking mechanism can provide reaction force through the anchor body, pushing the first section of the well wall to move downward relative to the anchor body, thereby pushing the first section of the well wall to sink in the underground soil.

2. The caisson structure according to claim 1, characterized in that, An inner sleeve is installed inside the axial hole, and the anchor rod body freely passes through the inner sleeve and is connected to the sinking mechanism.

3. The caisson structure according to claim 1, characterized in that, A grouting pipe is installed on the well casing of the first section of the well wall. The grouting pipe runs radially through the well casing. Thixotropic mud can be injected into the gap between the first section of the well wall and the external soil through the grouting pipe. After all the well walls have settled, cement mortar can be injected into the gap between the first section of the well wall and the external soil through the grouting pipe to replace the thixotropic mud.

4. The caisson structure according to claim 1, characterized in that, An outer baffle is installed on the outer wall of the wellbore to seal the outer end of the working hole.

5. The caisson structure according to claim 1, characterized in that, The anchor body of the pull-out anchor is made of steel strand or precision-rolled threaded steel. When the anchor body is made of steel strand, the sinking mechanism is a hollow hydraulic jack; when the anchor body is made of precision-rolled threaded steel, the sinking mechanism is a hollow hydraulic jack or a precision-rolled nut.

6. The caisson structure according to claim 1, characterized in that, When the first section of the well wall sinks to the set depth, the anchor bolt body is locked in the working hole by the locking device, and then concrete or grout is poured into the working hole.

7. The construction method of the caisson structure according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Construct anti-pull anchor bolts at the designated location on the ground, then install the first section of the well wall on the ground, and make the upper end of the anchor bolt body of the anti-pull anchor bolt pass through the axial hole and extend into the working hole, and install the sinking mechanism on the anchor bolt body; (2) Excavate the earthwork of the foundation pit inside the well, and simultaneously start the sinking mechanism to move the sinking mechanism downward along the anchor body, driving the first section of the well wall to sink until the first section of the well wall sinks to the designed height position, then stop the sinking mechanism to stop the sinking of the first section of the well wall; during the sinking process of the first section of the well wall, simultaneously cut off the excess anchor body that extends upward from the sinking mechanism. (3) Install the second section of the well wall on the first section of the well wall, continue the excavation of the foundation pit inside the well, and start the sinking mechanism to make the first section of the well wall continue to sink, and simultaneously drive the second section of the well wall to sink until it reaches the designed height position again. Then stop the sinking mechanism so that the first section of the well wall and the second section of the well wall stop sinking. During the sinking process of the first section of the well wall, simultaneously cut off the excess anchor rods that extend upwards from the sinking mechanism. (4) Repeat step (3) until the entire caisson structure is completely sunk.

8. The construction method according to claim 7, characterized in that, During the sinking of the first section of the well wall, thixotropic mud is injected into the gap between the first section of the well wall and the external underground soil through the grouting pipe. After the entire caisson structure has been sunk, cement mortar is injected into the outside of the caisson structure through the grouting pipe to replace the thixotropic mud.

9. The construction method according to claim 7, characterized in that, The height of the cutting edge is 2.5-4 meters. During the sinking of the first section of the well wall, the bottom surface of the pit inside the well is higher than the lower end surface of the cutting edge, and the distance from the bottom surface of the pit inside the well to the lower end surface of the cutting edge is 20-50% of the height of the cutting edge. This continues until the first section of the well wall sinks to the set elevation, and then the pit inside the well is excavated to the set depth.

10. The construction method according to claim 7, characterized in that, A hydraulic station is installed on the inner wall of the shaft or reaction beam. The first hydraulic inlet pipe of the hydraulic station is connected to the second hydraulic outlet pipe of the sinking mechanism, and the first hydraulic outlet pipe of the hydraulic station is connected to the second hydraulic inlet pipe of the sinking mechanism. After the caisson structure is completely sinked, the anchor bolt is locked in the working hole by a locking device, and the sinking mechanism and the hydraulic station are removed.

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