Pile-forming construction method and pile-forming device for cast-in-situ bored pile in karst area

Abstract

The invention discloses a pile forming construction method and a pile forming device for a cast-in-situ bored pile in a karst area. The method comprises the following steps: wrapping the periphery of a reinforcement cage with rectangular flexible cloth to form a flexible pile casing; at least part of the first geotechnical cloth layer of each connecting part located at the first end is bent to form a first bent part, all the first bent parts are pressed to the first geotechnical cloth layer of the connecting part of the second end and sewn, and the waterproof membrane layers of the two connecting parts of the first end are fixedly connected with the waterproof membrane layers of the two connecting parts of the second end. At least part of the second geotechnical cloth layer of each connecting part of the first end is bent to form a second bent part, and each second bent part is pressed to the second geotechnical cloth layer of the connecting part of the second end and sewn; the flexible pile casing and the reinforcement cage are fixed, and one end of the reinforcement cage is sleeved with a steel pile casing; the steel reinforcement cage wrapped with the flexible pile casing and the steel pile casing are put into the pile hole; injecting concrete grout to form a pile; the cost is reduced, the pile forming quality is guaranteed, and concrete loss at the karst cave is prevented.

Description

Technical Field

[0001] The present invention relates to the technical field of pile foundation engineering in geotechnical engineering, and in particular to a bored cast-in-place pile construction method and a pile forming device in karst areas. Background Art

[0002] Karst landforms are widespread in southwest my country, and their complex geological conditions pose a significant challenge to infrastructure construction. Traditional pile foundation construction techniques, characterized by high energy consumption, high disturbance, and low efficiency, struggle to meet the demands of today's green development.

[0003] At present, the main contradictions faced by pile foundation construction in karst landform areas are reflected in three aspects: first, the traditional steel casing follow-up method is costly and non-recyclable, which is contrary to the requirement of resource conservation; second, the grouting method and backfill method are prone to cause groundwater pollution and ecological disturbance, and it is impossible to strictly control the negative impact of construction on sensitive geological environments; third, the quality of piles produced by existing technologies is unstable, and it is difficult to meet the high standards for pile foundation bearing capacity and durability in karst areas in the "Code for Design of Building Foundations". Summary of the Invention

[0004] The main purpose of the present invention is to provide a bored cast-in-place pile construction method and a pile construction device in karst areas, aiming to solve the above problems.

[0005] To achieve the above object, the present invention proposes a method for constructing bored cast-in-place piles in karst areas, comprising the following steps: Step S200: Wrapping a rectangular flexible fabric around the periphery of a steel cage to form a flexible casing, wherein the flexible fabric has a first end and a second end in its length direction, and includes a first geotextile layer, a waterproof membrane layer, and a second geotextile layer stacked sequentially along its thickness direction. The flexible fabric includes a main body located in the middle and four connecting portions located at four corners. The first geotextile layer, the waterproof membrane layer, and the second geotextile layer at the four connecting portions are in an unconnected state, and the first geotextile layer is in contact with the steel cage. Step S300: bending at least a portion of the first geotextile layer of each of the connecting portions at the first end in a direction close to the steel cage to form a first bent portion, pressing each of the first bent portions onto the corresponding first geotextile layer of the connecting portion at the second end and sewing the first bent portions to each other, fixedly connecting the two waterproof membrane layers of the connecting portions at the first end to the two waterproof membrane layers of the connecting portions at the second end in a one-to-one correspondence, bending at least a portion of the second geotextile layer of each of the connecting portions at the first end in a direction close to the waterproof membrane layer to form a second bent portion, pressing each of the second bent portions onto the corresponding second geotextile layer of the connecting portion at the second end and sewing the second bent portions to each other; Step S400: The flexible casing is fixedly connected to both ends of the steel cage, and a steel casing is sheathed around one end of the steel cage wrapped with the flexible casing; Step S500: lowering the steel cage wrapped with the flexible casing and the steel casing into the pile hole, with the steel casing located at the bottom of the hole; Step S600: injecting concrete slurry into the steel cage to form piles.

[0006] Furthermore, the step S300 further includes: Each of the first bent portions is bonded to its corresponding first geotextile layer located at the first end, and each of the second bent portions is bonded to its corresponding second geotextile layer located at the first end.

[0007] Furthermore, the step S400 specifically includes: Step S410: using a plurality of first U-shaped bolts and a plurality of first nuts to securely connect the stirrups at one end of the reinforcement cage to the flexible casing and the steel casing; Step S420: Use a plurality of second U-shaped bolts and a plurality of second nuts to securely connect the stirrups at the other end of the reinforcement cage to the flexible casing.

[0008] Furthermore, before step S200, the following steps are further included: Step S100: Calculate the length and width of the flexible casing according to the location of the cave.

[0009] The present invention also provides a bored pile construction device for karst areas, which is applicable to a bored pile construction method for karst areas. The bored pile construction device for karst areas comprises: a steel cage into which concrete slurry is injected; A flexible casing is formed by wrapping a rectangular flexible fabric around the outer periphery of the steel cage, the flexible fabric having a first end and a second end in its length direction, and including a first geotextile layer, a waterproof membrane layer, and a second geotextile layer stacked in sequence along its thickness direction, the flexible fabric including a main body located in the middle and four connecting parts located at four corners, the first geotextile layer contacts the steel cage, at least a portion of the first geotextile layer of each connecting part located at the first end is bent in a direction close to the steel cage to form a first bend, each first bend is pressed onto the first geotextile layer of the corresponding connecting part located at the second end and sewn together, the waterproof membrane layers of the two connecting parts located at the first end are fixedly connected to the waterproof membrane layers of the two connecting parts located at the second end in a one-to-one correspondence, at least a portion of the second geotextile layer of each connecting part located at the first end is bent in a direction close to the waterproof membrane layer to form a second bend, the second bend is pressed onto the second geotextile layer of the corresponding connecting part located at the second end and sewn together, the flexible casing is fixedly connected to both ends of the steel cage; and, The steel casing is sleeved outside the flexible casing and is located at one end of the steel cage and is used to be arranged at the bottom of the pile hole.

[0010] Furthermore, each of the first bent portions is bonded to its corresponding first geotextile layer located at the first end; Each of the second bent portions is bonded to its corresponding second geotextile layer located at the first end.

[0011] Furthermore, the waterproof membrane layers of the two connecting parts located at the first end are thermally connected to the waterproof membrane layers of the two connecting parts located at the second end in a one-to-one correspondence.

[0012] Furthermore, one end of the steel cage is fixedly connected to the flexible casing and the steel casing by a plurality of first U-shaped bolts and a plurality of first nuts; The other end of the steel cage is fixedly connected to the flexible casing through a plurality of second U-shaped bolts and a plurality of second nuts.

[0013] Furthermore, the opening of the first U-shaped bolt and the opening of the second U-shaped bolt are respectively arranged toward the outside of the steel cage.

[0014] Furthermore, two second nuts are respectively threadedly connected to the two threaded rods of each second U-bolt, and each threaded rod is inserted into the steel cage and the flexible protective tube in sequence. The two first nuts on each threaded rod are respectively arranged on the inner and outer sides of the flexible protective tube, and the distance between the two first nuts is greater than or equal to 40 mm.

[0015] In the technical solution of the present invention, a pile-forming method combining flexible casing and rigid casing is adopted, which can greatly reduce the cost of pile-forming and ensure the quality of pile-forming. It can also prevent the loss of concrete in the cave and reduce the damage to the karst hydrogeological environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0017] Figure 1 A flow chart of the bored cast-in-place pile construction method for karst areas provided by the present invention; Figure 2 A schematic diagram of the structure of the bored pile forming device for karst areas provided by the present invention; Figure 3 for Figure 1 Schematic diagram of part of the structure of bored pile device in middle karst area; Figure 4 for Figure 3 Top view of the middle part A; Figure 5 for Figure 1 Schematic diagram of the structure of Sinosteel casing; Figure 6 for Figure 1 Schematic diagram of the structure of the first U-bolt and the first nut.

[0018] Description of Figure Numbers:

[0019] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0021] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), such directional indications are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0022] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the meaning of "and / or" appearing throughout the text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme in which A and B are satisfied at the same time. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0023] Karst landforms are widespread in southwest my country, and their complex geological conditions pose a significant challenge to infrastructure construction. Traditional pile foundation construction techniques, characterized by high energy consumption, high disturbance, and low efficiency, struggle to meet the demands of today's green development.

[0024] At present, the main contradictions faced by pile foundation construction in karst landform areas are reflected in three aspects: first, the traditional steel casing follow-up method is costly and non-recyclable, which is contrary to the requirement of resource conservation; second, the grouting method and backfill method are prone to cause groundwater pollution and ecological disturbance, and it is impossible to strictly control the negative impact of construction on sensitive geological environments; third, the quality of piles produced by existing technologies is unstable, and it is difficult to meet the high standards for pile foundation bearing capacity and durability in karst areas in the "Code for Design of Building Foundations".

[0025] In view of this, the present invention provides a method for constructing bored piles in karst areas. Figure 1 The method for constructing bored piles in karst areas comprises the following steps: Step S200: Wrap a flexible fabric in a rectangular shape around the outer periphery of the steel cage 1 to form a flexible casing 2, wherein the flexible fabric has a first end and a second end in its length direction, and includes a first geotextile layer 21, a waterproof membrane layer 22, and a second geotextile layer 23 stacked in sequence along its thickness direction. The flexible fabric includes a main body located in the middle and four connecting parts located at the four corners. The first geotextile layer 21, the waterproof membrane layer 22, and the second geotextile layer 23 of the four connecting parts are in an unconnected state, and the first geotextile layer 21 is in contact with the steel cage 1.

[0026] In this step, the flexible fabric and the reinforcement cage 1 are assembled on-site, eliminating the need for lifting and saving costs. Specifically, before assembly, the flexible fabric is laid flat on the ground, and the reinforcement cage 1 is placed parallel to the flexible fabric. The first and second ends of the flexible fabric are brought together above the reinforcement cage 1 to wrap the reinforcement cage 1 in a cylindrical shape, forming the flexible casing 2. However, the first geotextile layer 21, waterproof membrane layer 22, and second geotextile layer 23 at each connection portion are unconnected, and the flexible fabric only contacts the reinforcement cage 1.

[0027] Step S300, bend at least a portion of the first geotextile layer 21 of each of the connecting parts located at the first end in a direction close to the steel cage 1 to form a first bent portion, and press each of the first bent portions onto the corresponding first geotextile layer 21 of the connecting part located at the second end and sew them together, fix the waterproof membrane layers 22 of the two connecting parts located at the first end to the waterproof membrane layers 22 of the two connecting parts located at the second end in a one-to-one correspondence, bend at least a portion of the second geotextile layer 23 of each of the connecting parts located at the first end in a direction close to the waterproof membrane layer 22 to form a second bent portion, and press each of the second bent portions onto the corresponding second geotextile layer 23 of the connecting part located at the second end and sew them together.

[0028] In this step, the second geotextile layer 23 is connected by bending and sewing to achieve a fixed connection between the first end and the second end of the flexible casing 2, thereby ensuring the sealing and waterproof properties of the flexible casing 2. Specifically, the connection of the flexible casing 2 should achieve a completely waterproof effect, so the waterproof membrane layer 22 at the first end and the waterproof membrane layer 22 at the second end must be directly fixedly connected without any interlayer in between.

[0029] More specifically, in one embodiment of the present invention, the two waterproof membrane layers 22 at the first end and the two waterproof membrane layers 22 at the second end are thermally bonded in a one-to-one correspondence. Furthermore, a climbing welding machine is used for thermal bonding.

[0030] Step S400: The flexible casing 2 is fixedly connected to both ends of the steel cage 1, and a steel casing 3 is sheathed around one end of the steel cage 1 wrapped with the flexible casing 2.

[0031] In this step, the steel casing 3 is sleeved outside the steel cage 1 and the flexible casing 2, and serves as a supporting member to support the flexible casing 2, thereby preventing the concrete leakage at the bottom of the pile caused by insufficient expansion of the flexible casing 2 at the bottom of the pile when concrete slurry is subsequently injected into the pile hole 200, and is beneficial to improving the bearing capacity and durability of the pile foundation.

[0032] It should be noted that, in the present invention, the rigid casing is provided through the axial direction thereof or one end of the rigid casing abutting against the steel cage 1 is hollowed out to facilitate hole cleaning and ensure pile quality.

[0033] Step S500: lower the steel cage 1 wrapped with the flexible casing 2 and the steel casing 3 into the pile hole 200, with the steel casing 3 located at the bottom of the hole.

[0034] Step S600: inject concrete slurry into the steel cage 1 to form piles.

[0035] During the grouting process, the flexible casing 2 is deformed and expanded outwards due to the force. When the concrete slurry rises to the cavities 300 in the pile hole 200, it is blocked by the flexible casing 2, thereby preventing the loss of concrete. After the concrete slurry solidifies, the pile is formed.

[0036] In the technical solution of the present invention, the pile-forming method of combining the flexible casing 2 and the rigid casing can greatly reduce the pile-forming cost and ensure the pile-forming quality, and can prevent the loss of concrete in the cave 300 and reduce the damage to the karst hydrogeological environment.

[0037] Further, see Figure 1 , the step S300 further includes: Each of the first bent portions is bonded to its corresponding first geotextile layer 21 located at the first end, and each of the second bent portions is bonded to its corresponding second geotextile layer 23 located at the first end.

[0038] In this step, the first and second ends of the flexible casing 2 are connected by bending and sewing, and then bonded together to further improve the sealing, waterproofness, and tensile strength of the flexible casing 2. Specifically, the seam strength of the flexible casing 2 must be higher than the parent material strength. Therefore, when the first geotextile layer 21 at the first end and the first geotextile layer 21 at the second end are connected, and when the second geotextile layer 23 at the first end and the second geotextile layer 23 at the second end are connected, they should be bent, sewn, and bonded to avoid direct pulling of the sutures after direct sewing. In this way, the tensile strength of the seam of the flexible casing 2 can be improved by combining the strength of the sutures and the bonding strength of the adhesive.

[0039] For details, please refer to Figure 1 , the step S400 specifically includes: Step S410: Use multiple first U-shaped bolts 4 and multiple first nuts 5 to fix the stirrups at one end of the steel cage 1 with the flexible casing 2 and the steel casing 3.

[0040] Step S420: Use multiple second U-shaped bolts 6 and multiple second nuts 7 to fix the stirrups at the other end of the steel cage 1 to the flexible casing 2.

[0041] In this way, the steel cage 1, the flexible casing 2 and the steel cage 1 are fixedly connected by bolts and nuts, which is simple and convenient to operate and has low cost.

[0042] It should be noted that in steps S410 and S420, the openings of the first U-shaped bolts 4 and the openings of the second U-shaped bolts 6 are respectively arranged to face the outside of the steel cage 1. In this way, during the grouting process, the first U-shaped bolts 4 and the second U-shaped bolts 6 are forced to move outward, providing space for the flexible casing 2 to expand outward under force. However, when they move to a certain distance, the bent parts of the U-shaped bolts interfere with the stirrups of the steel cage 1, preventing the first U-shaped bolts 4 and the second U-shaped bolts 6 from further outward movement, that is, preventing the flexible casing 2 from expanding outward, thereby preventing concrete loss.

[0043] For details, please refer to Figure 1 , before step S200, the method further includes: Step S100 : Calculate the length and width of the flexible casing 2 according to the position of the cave 300 .

[0044] In a specific embodiment of the present invention, the length of the flexible casing 2 is set to L, the width is set to W, the height of the cave is set to H, and the radius of the bored pile is set to R, then L=H+6 (m), W=9R.

[0045] The present invention also provides a bored pile construction device 100 for karst areas, which is applicable to the bored pile construction method for karst areas described above. Figures 2 to 5 The bored pile forming device 100 in karst areas includes a steel cage 1, a flexible casing 2 and a steel casing 3. The steel cage 1 is used to inject concrete slurry; the flexible casing 2 is formed by a flexible fabric arranged in a rectangular shape wrapped around the outer periphery of the steel cage 1, and the flexible fabric has a first end and a second end in its length direction, and includes a first geotextile layer 21, a waterproof membrane layer 22 and a second geotextile layer 23 stacked in sequence along its thickness direction. The flexible fabric includes a main body located in the middle and four connecting parts located at the four corners. The first geotextile layer 21 contacts the steel cage 1, and at least a portion of the first geotextile layer 21 of each of the connecting parts located at the first end is bent in a direction close to the steel cage 1 to form a first bending part, and each of the first bending parts The bent portion is pressed onto the first geotextile layer 21 of the connecting portion corresponding to it at the second end and sewn together, the waterproof membrane layers 22 of the two connecting portions at the first end are fixedly connected one by one with the waterproof membrane layers 22 of the two connecting portions at the second end, at least part of the second geotextile layer 23 of each connecting portion at the first end is bent in a direction close to the waterproof membrane layer 22 to form a second bent portion, the second bent portion is pressed onto the second geotextile layer 23 of the connecting portion corresponding to it at the second end and sewn together, the flexible casing 2 is fixedly connected to both ends of the steel cage 1; the steel casing 3 is sleeved outside the flexible casing 2, and is located at one end of the steel cage 1, and is used to be located at the bottom of the pile hole 200.

[0046] In this way, the bored pile construction device 100 in the karst area has low cost and high pile construction quality, can prevent concrete loss in the cave 300, and reduce damage to the karst hydrogeological environment.

[0047] Furthermore, each first bent portion is bonded to its corresponding first geotextile layer 21 at the first end, and each second bent portion is bonded to its corresponding second geotextile layer 23 at the first end, thereby further improving the sealing and waterproof properties of the flexible casing 2.

[0048] Specifically, the waterproof membrane layers 22 of the two connecting portions at the first end are thermally connected to the waterproof membrane layers 22 of the two connecting portions at the second end in a one-to-one correspondence.

[0049] For details, please refer to Figure 2 and Figure 6One end of the steel cage 1 is fixedly connected to the flexible casing 2 and the steel casing 3 via a plurality of first U-shaped bolts 4 and a plurality of first nuts 5; the other end of the steel cage 1 is fixedly connected to the flexible casing 2 via a plurality of second U-shaped bolts 6 and a plurality of second nuts 7. In this way, the use of bolts and nuts to securely connect the steel cage 1, the flexible casing 2, and the steel cage 1 is simple, convenient, and low-cost.

[0050] Furthermore, the openings of the first U-shaped bolt 4 and the openings of the second U-shaped bolt 6 are respectively arranged toward the outside of the steel cage 1 .

[0051] Furthermore, two second nuts 7 are threadedly connected to the two threaded rods of each second U-bolt 6. Each of the threaded rods is sequentially inserted into the steel cage 1 and the flexible casing 2. The two first nuts 5 on each threaded rod are respectively disposed on the inner and outer sides of the flexible casing 2, and the distance between the two first nuts 5 is greater than or equal to 40 mm. In this way, the outward expansion space of the flexible casing 2 is limited by limiting the distance between the two first nuts 5.

[0052] More specifically, in one embodiment of the present invention, the distance between the two first nuts 5 is 40 mm.

[0053] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made by using the contents of the present invention description and drawings under the inventive concept of the present invention, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for constructing bored piles in karst areas, characterized in that: The karst area bored cast-in-place pile construction method comprises the following steps: Step S200: Wrapping a rectangular flexible fabric around the periphery of a steel cage to form a flexible casing, wherein the flexible fabric has a first end and a second end in its length direction, and includes a first geotextile layer, a waterproof membrane layer, and a second geotextile layer stacked sequentially along its thickness direction. The flexible fabric includes a main body located in the middle and four connecting portions located at four corners. The first geotextile layer, the waterproof membrane layer, and the second geotextile layer at the four connecting portions are in an unconnected state, and the first geotextile layer is in contact with the steel cage. Step S300: bending at least a portion of the first geotextile layer of each of the connecting portions at the first end in a direction close to the steel cage to form a first bent portion, pressing each of the first bent portions onto the corresponding first geotextile layer of the connecting portion at the second end and sewing the first bent portions to each other, fixedly connecting the two waterproof membrane layers of the connecting portions at the first end to the two waterproof membrane layers of the connecting portions at the second end in a one-to-one correspondence, bending at least a portion of the second geotextile layer of each of the connecting portions at the first end in a direction close to the waterproof membrane layer to form a second bent portion, pressing each of the second bent portions onto the corresponding second geotextile layer of the connecting portion at the second end and sewing the second bent portions to each other; Step S400: The flexible casing is fixedly connected to both ends of the steel cage, and a steel casing is sheathed around one end of the steel cage wrapped with the flexible casing; Step S500: lowering the steel cage wrapped with the flexible casing and the steel casing into the pile hole, with the steel casing located at the bottom of the hole; Step S600: injecting concrete slurry into the steel cage to form piles.

2. The method for constructing bored piles in karst areas according to claim 1, wherein: The step S300 further includes: Each of the first bent portions is bonded to its corresponding first geotextile layer located at the first end, and each of the second bent portions is bonded to its corresponding second geotextile layer located at the first end.

3. The method for constructing bored piles in karst areas according to claim 1, wherein: The step S400 specifically includes: Step S410: using a plurality of first U-shaped bolts and a plurality of first nuts to securely connect the stirrups at one end of the reinforcement cage to the flexible casing and the steel casing; Step S420: Use a plurality of second U-shaped bolts and a plurality of second nuts to securely connect the stirrups at the other end of the reinforcement cage to the flexible casing.

4. The method for constructing bored piles in karst areas according to claim 1, wherein: Before step S200, the following steps are also included: Step S100: Calculate the length and width of the flexible casing according to the location of the cave.

5. A bored pile construction device in karst areas, suitable for the bored pile construction method in karst areas according to any one of claims 1 to 4, characterized in that: The karst area bored pile forming device comprises: a steel cage into which concrete slurry is injected; A flexible casing is formed by wrapping a rectangular flexible fabric around the outer periphery of the steel cage, the flexible fabric having a first end and a second end in its length direction, and including a first geotextile layer, a waterproof membrane layer, and a second geotextile layer stacked in sequence along its thickness direction, the flexible fabric including a main body located in the middle and four connecting parts located at four corners, the first geotextile layer contacts the steel cage, at least a portion of the first geotextile layer of each connecting part located at the first end is bent in a direction close to the steel cage to form a first bend, each first bend is pressed onto the first geotextile layer of the corresponding connecting part located at the second end and sewn together, the waterproof membrane layers of the two connecting parts located at the first end are fixedly connected to the waterproof membrane layers of the two connecting parts located at the second end in a one-to-one correspondence, at least a portion of the second geotextile layer of each connecting part located at the first end is bent in a direction close to the waterproof membrane layer to form a second bend, the second bend is pressed onto the second geotextile layer of the corresponding connecting part located at the second end and sewn together, the flexible casing is fixedly connected to both ends of the steel cage; and, The steel casing is sleeved outside the flexible casing and is located at one end of the steel cage and is used to be arranged at the bottom of the pile hole.

6. The bored pile forming device for karst areas according to claim 5, characterized in that: Each of the first bent portions is bonded to its corresponding first geotextile layer located at the first end; Each of the second bent portions is bonded to its corresponding second geotextile layer located at the first end.

7. The bored pile forming device for karst areas according to claim 5, characterized in that: The waterproof membrane layers of the two connecting parts at the first end are thermally connected to the waterproof membrane layers of the two connecting parts at the second end in a one-to-one correspondence.

8. The bored pile forming device for karst areas according to claim 5, characterized in that: One end of the steel cage is fixedly connected to the flexible casing and the steel casing by a plurality of first U-shaped bolts and a plurality of first nuts; The other end of the steel cage is fixedly connected to the flexible casing through a plurality of second U-shaped bolts and a plurality of second nuts.

9. The bored pile forming device for karst areas according to claim 8, characterized in that: The opening of the first U-shaped bolt and the opening of the second U-shaped bolt are respectively arranged toward the outside of the steel cage.

10. The bored pile forming device for karst areas according to claim 9, characterized in that: Two second nuts are threadedly connected to the two threaded rods of each second U-bolt, and each threaded rod is inserted into the steel cage and the flexible casing in sequence. The two first nuts on each threaded rod are respectively arranged on the inner and outer sides of the flexible casing, and the distance between the two first nuts is greater than or equal to 40 mm.

Images