Closed prefabricated framework and method for karst geological pile foundation and closed hoisting process

Abstract

The invention discloses a closed prefabricated framework and method for a karst geological pile foundation and a closed hoisting process. The closed prefabricated framework comprises an inner mold round steel pipe body; the bottom bracing steel plate platform is assembled on the inner mold circular steel pipe body in a sleeving manner in a directional sliding manner; the iron sheet outer ring formwork is correspondingly arranged on the side portion of the periphery of the inner mold round steel pipe body, one end of the iron sheet outer ring formwork abuts against the interior of the outer side edge of the bottom bracing steel plate platform, and the other end of the iron sheet outer ring formwork is flush with the end, away from the bottom bracing steel plate platform, of the inner mold round steel pipe body; the embedded steel bars penetrate through the bottom bracing steel plate platform; the U-shaped limiting buckles are clamped to the end, away from the bottom bracing steel plate platform, of the inner mold circular steel pipe body and the other end of the iron sheet outer ring template in a limiting mode. The technical problem that in the prior art, when pile foundation construction is conducted on the geology that the karst cave is deep and multiple karst caves are distributed in a bead-string-type layered mode, follow-up filling is conducted through a permanent steel protection cylinder is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge pile foundation engineering. Specifically, it relates to a closed prefabricated structure, method and closed hoisting process for piles in karst geology. Background Art

[0002] With the continuous high-speed development of the transportation industry, bridges, as a key component of transportation lines, have become increasingly important. The construction technology of bridge pile foundations has gradually improved and is widely used.

[0003] Currently, when constructing near existing operating railway lines, it is usually necessary to minimize the disturbance to the normal operation of the existing railway. Due to its strong impact and vibration characteristics, the traditional impact drill hole-forming method is extremely likely to cause adverse effects on the existing railway subgrade and track structure, so it is generally strictly prohibited. The rotary drilling rig hole-forming method, with its efficient and low-disturbance operation characteristics, has become the preferred construction technology in this working condition.

[0004] At the same time, due to complex geological conditions, different geological conditions will be encountered in different regions. Among them, the impact of karst caves on pile foundation construction is particularly prominent. When facing relatively shallow karst caves, the treatment method of mixing crushed stones and loess for backfilling and then drilling is usually adopted during construction. This method can fill the cave space to a certain extent and create relatively stable geological conditions for hole-forming operations. When the karst cave is relatively deep below the ground line or multiple caves are distributed in a beaded stratified manner, backfilling can no longer meet the filling requirements.

[0005] In response to this, the conventional process generally fills by following up with permanent steel casing. However, many problems have emerged in the actual operation of this process. For example, the processes of lowering and welding the steel casing are time-consuming, seriously restricting the construction efficiency; the welding operation has low efficiency and difficult quality assurance, not only affecting the connection firmness of the steel casing, but also extremely likely to pose a potential threat to the overall stability of the pile foundation; at the same time, it is difficult to accurately control the verticality during the process of lengthening the steel casing, further affecting the bearing performance of the pile foundation; in addition, in the conventional geological section between caves, the use of steel casing also causes unnecessary material waste, significantly increasing the construction cost and having a greater negative impact on construction efficiency and economic benefits. Summary of the Invention

[0006] Therefore, the present invention provides a closed prefabricated structure, method and closed hoisting process for piles in karst geology to solve the above technical problems existing in the permanent steel casing follow-up filling during pile foundation construction for relatively deep karst caves and multi-cave beaded stratified distribution geology in the prior art.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A closed prefabricated structure for karst geology pile foundation, comprising:

[0009] An inner mold circular steel pipe body, serving as the forming inner mold of the prefabricated closed ring;

[0010] A bottom support steel plate platform, which is sleeved and assembled on the outer periphery of the inner mold circular steel pipe body in a directionally slidable manner, and the outer edge of the bottom support steel plate platform is higher than its inner edge relative to the outer edge of the inner mold circular steel pipe body;

[0011] An iron sheet outer ring template, which is correspondingly arranged on the outer side of the inner mold circular steel pipe body, and one end of the iron sheet outer ring template is detachably and correspondingly limited and abutted against the inner part of the outer edge of the bottom support steel plate platform, and the other end of the iron sheet outer ring template is flush with the position of the end of the inner mold circular steel pipe body away from the bottom support steel plate platform, so as to serve as the forming outer mold of the prefabricated closed ring;

[0012] Embedded steel bars, provided in several groups, and several groups of the embedded steel bars penetrate through the bottom support steel plate platform, and both ends of several groups of the embedded steel bars respectively extend to the outer side of the end of the inner mold circular steel pipe body away from the bottom support steel plate platform and the outer side of the bottom support steel plate platform;

[0013] U-shaped limit buckles, and both ends are respectively and correspondingly limited and clamped on the end of the inner mold circular steel pipe body away from the bottom support steel plate platform and the other end of the iron sheet outer ring template.

[0014] On the basis of the above technical solutions, the following further description is made for the present invention:

[0015] As a further solution of the present invention,

[0016] The inner mold circular steel pipe body is set as a circular steel pipe with an inner diameter not less than the outer diameter of the karst geology pile foundation steel cage;

[0017] The bottom support steel plate platform is set as an annular platform sleeved on the outer periphery of the inner mold circular steel pipe body;

[0018] The longitudinal section of any position of the annular bottom support steel plate platform is L-shaped.

[0019] As a further solution of the present invention,

[0020] At least four groups of reinforcing bar passing reserved holes extending longitudinally are uniformly arranged on the circumferential position of the bottom support steel plate platform; at least four groups of the embedded steel bars are provided, and one ends of at least four groups of the embedded steel bars respectively extend through at least four groups of the reinforcing bar passing reserved holes correspondingly, and the other ends of at least four groups of the embedded steel bars all extend beyond the end of the inner mold circular steel pipe body away from the bottom support steel plate platform.

[0021] As a further solution of the present invention, it further includes:

[0022] A flexible steel bar mesh, which is wound around the outer peripheral side of at least four groups of the embedded steel bars, and the flexible steel bar mesh is fixedly arranged by binding wires with at least four groups of the embedded steel bars.

[0023] A prefabrication method for a closed prefabricated structure for karst geological pile foundations, specifically including the following steps:

[0024] Based on the inner mold circular steel pipe body, slide and adjust the position of the bottom support steel plate platform to determine the inner mold length of the inner mold circular steel pipe body according to the length requirement of the prefabricated closed ring;

[0025] Based on the bottom support steel plate platform on the outer peripheral side of the inner mold circular steel pipe body, pass the embedded steel bars through the reinforcing bar penetration reserved holes respectively, and use the embedded steel bars as the subsequent connecting components of the prefabricated closed ring;

[0026] After the embedded steel bars are inserted, use foaming glue to seal the side gaps of the reinforcing bar penetration reserved holes;

[0027] Wind the flexible steel bar mesh around the outer peripheral side of the inserted embedded steel bars, and further use binding wires to bind and fix the embedded steel bars and the flexible steel bar mesh;

[0028] Install a specific length of iron sheet outer ring formwork corresponding to the outer peripheral side of the flexible steel bar mesh, make the other end of the iron sheet outer ring formwork flush with the end position of the inner mold circular steel pipe body, and place support pads for improving the position stability between the iron sheet outer ring formwork and the flexible steel bar mesh;

[0029] Continue to configure a number of groups of U-shaped limit buckles with a specific spacing between the iron sheet outer ring formwork and the inner mold circular steel pipe body, and fix the position between the iron sheet outer ring formwork and the inner mold circular steel pipe body;

[0030] Pour concrete between the iron sheet outer ring formwork and the inner mold circular steel pipe body, and after the strength reaches 70%, remove the U-shaped limit buckles and the iron sheet outer ring formwork to form a prefabricated closed ring with embedded steel bars, stack the prefabricated closed rings for curing, and wait for use in pile foundation construction.

[0031] A closed hoisting process including the prefabrication method of the closed prefabricated structure for karst geological pile foundations described above, including the following steps:

[0032] Accurately loft according to the designed pile foundation position to determine the designed construction pile position;

[0033] Drill detection hole positions corresponding to the designed construction pile positions;

[0034] Based on the detection hole positions, obtain the specific positions of the karst caves and their development depth parameters;

[0035] The specific process is as follows: Use an in-hole imaging detector to extend into each hole for detection respectively. According to the displayed images and depth information, determine the specific location of the karst cave and its development depth parameters;

[0036] Install a tool steel casing;

[0037] Based on the designed construction pile position, perform rotary drilling to form a construction pile hole;

[0038] According to the determined specific location of the karst cave and its development depth parameters, based on the construction pile hole and the tool steel casing, connect the karst caves in series from bottom to top and lower a precast closed ring;

[0039] Continue to lower the steel reinforcement cage corresponding to the tool steel casing and the connected precast closed ring;

[0040] After the steel reinforcement cage is lowered in place, install a conduit extending to the bottom of the pile hole for pumping and cleaning the hole. After the cleaning operation is completed, pour concrete corresponding to the steel reinforcement cage to complete the entire pile foundation construction process.

[0041] As a further solution of the present invention,

[0042] The drilling of the detection hole positions corresponding to the designed construction pile positions specifically includes:

[0043] Preset a tool steel casing position coaxially with the pile center position of the designed construction pile position, and vertically drill holes respectively at the outer side and the pile center position of the designed construction pile position to form at least four groups of outer detection hole positions and one group of center detection hole positions;

[0044] The diameter of the circle formed by connecting the at least four groups of outer detection hole positions is greater than the diameter of the preset tool steel casing position.

[0045] As a further solution of the present invention,

[0046] The obtaining of the specific location of the karst cave and its development depth parameters based on the detection hole positions specifically includes:

[0047] Use an in-hole imaging detector to extend into each hole for detection respectively. According to the displayed images and depth information, determine the specific location of the karst cave and its development depth parameters;

[0048] The installation of the tool steel casing specifically includes:

[0049] Install the tool steel casing according to the preset position. The height of the tool steel casing exposed above the ground is not less than 50 cm, and use the tool steel casing as the protection and guiding foundation for subsequent drilling and construction.

[0050] As a further solution of the present invention,

[0051] According to the determined specific position of the karst cave and its development depth parameters, the precast closed rings are connected in series to the karst cave in sequence from bottom to top based on the construction pile hole and the tool steel casing, specifically including:

[0052] Lower the first precast closed ring corresponding to the construction pile hole, and weld the four groups of embedded steel bars of the first precast closed ring to the tool steel casing respectively to establish a temporary fixation.

[0053] After that, lift the next precast closed ring, bend the four groups of embedded steel bars of the next precast closed ring and the four groups of embedded steel bars of the first precast closed ring respectively according to the determined specific position of the karst cave and its development depth parameters to obtain steel bar hooks for the length and connect the above two precast closed rings correspondingly, and then cut off the temporary fixation between the first precast closed ring and the tool steel casing.

[0054] Continue to lower the next precast closed ring and the first precast closed ring, and weld the four groups of embedded steel bars of the next precast closed ring to the tool steel casing respectively. After that, continue to lift the next precast closed ring and connect the steel bars between the next precast closed ring and the previous precast closed ring. Use this process until all the precast closed rings are lowered in place, and retain the temporary fixation between the last precast closed ring and the tool steel casing, so that all the precast closed rings are firmly connected to the tool steel casing, and the targeted plugging of the distributed karst caves is completed.

[0055] As a further solution of the present invention,

[0056] According to the determined specific position of the karst cave and its development depth parameters, the precast closed rings are connected in series to the karst cave in sequence from bottom to top based on the construction pile hole and the tool steel casing, and specifically further includes:

[0057] According to the determined specific position of the karst cave and its development depth parameters, pre-select precast closed rings with a specific length that can completely plug the karst cave, and when connecting through steel bar hooks, determine the bending positions of the steel bar hooks based on the standard that the pre-selected precast closed rings can be accurately aligned with the corresponding karst caves, and / or install extension steel bars with at least a preset length between the steel bar hooks corresponding to adjacent two precast closed rings, and finally accurately plug all the distributed karst caves with determined specific positions and development depths.

[0058] The present invention has the following beneficial effects:

[0059] The architecture and method can accurately determine the specific development parameters of karst caves around the pile shaft before the formal construction of the pile foundation, and by constructing a precast closed ring to replace the permanent steel casing, it can effectively combine the specific development parameters of the karst caves to conduct targeted butt-joint lengthening and plugging of the karst caves, effectively reducing the material waste in non-karst cave sections. At the same time, this precast architecture does not occupy the construction period and can flexibly precast the closed ring independently according to the specific conditions of different pile foundations, significantly improving the functional adaptability of the architecture. In addition, compared with the lowering and connection of the permanent steel casing, it can further reduce the welding time, thereby further improving the operation efficiency and functional practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. The structures, ratios, sizes, etc. shown in this specification are only used to cooperate with the content disclosed in the specification for those who are familiar with this technology to understand and read. Any modification of the structure, change in the ratio relationship, or adjustment of the size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope that can be covered by the technical content disclosed in the present invention.

[0061] Figure 1 FIG. is a schematic side sectional view of a closed precast architecture for karst geological pile foundations provided by an embodiment of the present invention.

[0062] Figure 2 For the closed precast architecture for karst geological pile foundations provided by an embodiment of the present invention corresponding to Figure 1 the isometric structural schematic diagram of the state.

[0063] Figure 3 FIG. is one of the schematic side sectional views of the closed precast architecture and method for karst geological pile foundations provided by an embodiment of the present invention corresponding to its assembly process state.

[0064] Figure 4 For the closed precast architecture and method for karst geological pile foundations provided by an embodiment of the present invention corresponding to Figure 3 the isometric structural schematic diagram of the state.

[0065] Figure 5 FIG. is the second of the schematic side sectional views of the closed precast architecture and method for karst geological pile foundations provided by an embodiment of the present invention corresponding to its assembly process state.

[0066] Figure 6 For the closed precast architecture and method for karst geological pile foundations provided by an embodiment of the present invention corresponding to Figure 5 the isometric structural schematic diagram of the state.

[0067] Figure 7This is the third schematic side-sectional view of the closed prefabricated structure and method for karst geological pile foundations provided by the embodiments of the present invention corresponding to their assembly process states.

[0068] Figure 8 This is for the closed prefabricated structure and method for karst geological pile foundations provided by the embodiments of the present invention corresponding to Figure 7 the isometric structure schematic diagram of the state.

[0069] Figure 9 This is the fourth schematic overall side-sectional view of the closed prefabricated structure and method for karst geological pile foundations provided by the embodiments of the present invention corresponding to their assembly process states.

[0070] Figure 10 This is for the closed prefabricated structure and method for karst geological pile foundations provided by the embodiments of the present invention corresponding to Figure 9 the overall isometric structure schematic diagram of the state.

[0071] Figure 11 This is the first schematic diagram of the process state structure of the closed hoisting process for karst geological pile foundations provided by the embodiments of the present invention;

[0072] Figure 12 This is the second schematic diagram of the process state structure of the closed hoisting process for karst geological pile foundations provided by the embodiments of the present invention;

[0073] Figure 13 This is the third schematic diagram of the process state structure of the closed hoisting process for karst geological pile foundations provided by the embodiments of the present invention;

[0074] Figure 14 This is the fourth schematic diagram of the process state structure of the closed hoisting process for karst geological pile foundations provided by the embodiments of the present invention;

[0075] Figure 15 This is the fifth schematic diagram of the process state structure of the closed hoisting process for karst geological pile foundations provided by the embodiments of the present invention;

[0076] Figure 16 This is the sixth schematic diagram of the process state structure of the closed hoisting process for karst geological pile foundations provided by the embodiments of the present invention;

[0077] Figure 17 This is the seventh schematic diagram of the process state structure of the closed hoisting process for karst geological pile foundations provided by the embodiments of the present invention;

[0078] Figure 18 This is the assembly structure schematic diagram of the prefabricated closed ring and its steel bar lifting hook in the closed hoisting process for karst geological pile foundations provided by the embodiments of the present invention.

[0079] Figure 19Schematic diagram of the assembly structure of the precast closed ring, its steel bar hook and the extended steel bar in the closed hoisting process for karst geology pile foundations provided by the embodiments of the present invention.

[0080] In the attached drawings, the list of components represented by each reference numeral is as follows:

[0081] Inner mold circular steel pipe body 1; bottom support steel plate platform 2, steel bar passing reserved hole 21; embedded steel bar 3; flexible steel bar mesh 4; binding wire 5; iron sheet outer ring formwork 6; U-shaped limit buckle 7;

[0082] Designed construction pile position a; peripheral detection hole position b; central detection hole position c; tool steel casing d; construction pile hole e; precast closed ring f; steel bar hook g; extended steel bar h; steel reinforcement cage j; conduit k; karst cave p. Specific implementation manners

[0083] The following specific embodiments illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope protected by the present invention.

[0084] Terms such as "upper", "lower", "left", "right", "middle", etc. cited in this specification are only for the convenience of clear description and are not used to limit the scope of implementation of the present invention. The change or adjustment of their relative relationships, without substantial change in the technical content, should also be regarded as the scope of implementation of the present invention.

[0085] As Figures 1 to 10 shown, the embodiments of the present invention provide a closed precast structure for karst geology pile foundations, including an inner mold circular steel pipe body 1, a bottom support steel plate platform 2, an embedded steel bar 3, a flexible steel bar mesh 4, a binding wire 5, an iron sheet outer ring formwork 6 and a U-shaped limit buckle 7, which are used to accurately determine the specific development parameters of karst caves around the pile body before the formal construction of the pile foundation, and replace the permanent steel casing with a precast closed ring f, which can effectively combine the specific development parameters of karst caves to perform targeted butt joint and plugging of karst caves, effectively reducing the material waste in non-karst cave sections. At the same time, this precast structure does not occupy the construction period and can be independently and flexibly precast the closed ring according to the specific conditions of different pile foundations, significantly improving the functional adaptability of the structure. In addition, compared with the lowering and connecting process of the permanent steel casing, the welding time can be further reduced, thereby further improving the operation efficiency and functional practicality of the overall structure. The following is a specific description.

[0086] Please refer to Figures 1 to 4 (where Figure 2 and Figure 4As a three-dimensional schematic diagram, some details are omitted), the inner mold circular steel pipe body 1 is set as a circular steel pipe with an inner diameter not less than the outer diameter of the karst pile foundation steel reinforcement cage, and is used to form the inner mold of the precast closed ring through the inner mold circular steel pipe body 1.

[0087] The bottom support steel plate platform 2 is sleeved around the inner mold circular steel pipe body 1, and the bottom support steel plate platform 2 has an annular bottom and a side wall extending upward along the outer circumference of the ring.

[0088] At least four groups of longitudinal extension rebar reserved holes 21 are evenly arranged circumferentially along the bottom of the bottom support steel plate platform 2; there are at least four groups of the embedded rebars 3, and the first end of each group of the embedded rebars 3 passes through one of the rebar reserved holes 21, and the second ends all extend beyond the top of the side wall of the inner mold circular steel pipe body 1.

[0089] Please refer to Figures 5 to 10 , the flexible steel mesh 4 is wound around the periphery of each of the embedded rebars 3, and the flexible steel mesh 4 is fixedly arranged by tying with the embedded rebars 3 through the tying wires 5, so as to improve the anchoring performance of the subsequent cast-in-place concrete.

[0090] The iron sheet outer ring formwork 6 is set as an annular cylindrical structure, and the first end of the iron sheet outer ring formwork 6 is detachably and limitably abutted against the inner side of the outer edge of the annular bottom support steel plate platform 2, and the second end of the iron sheet outer ring formwork 6 is flush with the end position of the inner mold circular steel pipe body 1 away from the bottom support steel plate platform 2; there are at least four groups of the U-shaped limit buckles 7, and at least four groups of the U-shaped limit buckles 7 are evenly limit buckled between the end position of the inner mold circular steel pipe body 1 away from the bottom support steel plate platform 2 and the second end of the iron sheet outer ring formwork 6, so as to form an end transverse limiting effect through the U-shaped limit buckles 7 and effectively prevent the iron sheet outer ring formwork 6 from expanding and running off the form due to the subsequent cast-in-place concrete.

[0091] As a preferred solution of this embodiment, a demoulding agent layer and / or an oil layer are coated on the outer side part of the inner mold circular steel pipe body 1, the inner end face of the bottom support steel plate platform 2, the inner side part of the iron sheet outer ring formwork 6 and the inner end face of the U-shaped limit buckle 7, so as to make it more convenient to demould the precast closed ring f.

[0092] As another preferred solution of this embodiment, several groups of cushion blocks are arranged between the inner side part of the iron sheet outer ring formwork 6 and the flexible steel mesh 4, so as to further improve the position stability of the iron sheet outer ring formwork 6.

[0093] As still another preferred solution of this embodiment, the inner mold circular steel pipe body 1 and the bottom support steel plate platform 2 are slidably assembled, and the other end of the iron sheet outer ring template 6 is always flush with the end of the inner mold circular steel pipe body 1 to adapt to the preparation of precast closed rings of different lengths.

[0094] Please continue to refer to Figures 3 to 10 , the embodiment of the present invention also provides a prefabrication method for the closed prefabricated structure for karst geological pile foundations as described above, specifically including the following steps:

[0095] S101: Based on the inner mold circular steel pipe body 1, slide and adjust the position of the bottom support steel plate platform 2 to determine the inner mold length of the inner mold circular steel pipe body 1 according to the length requirement of the precast closed ring f;

[0096] Based on the bottom support steel plate platform 2 on the outer side of the inner mold circular steel pipe body 1, pre-embedded steel bars 3 are respectively passed through the steel bar passing and reserved holes 21, and the pre-embedded steel bars 3 are used as subsequent connecting components for the precast closed ring f;

[0097] After the pre-embedded steel bars 3 are inserted, the side gaps of the steel bar passing and reserved holes 21 are sealed with foaming glue;

[0098] S102: Wind the flexible steel bar mesh 4 around the outer side of the pre-embedded steel bars 3, and further use binding wires 5 to bind and fix the pre-embedded steel bars 3 and the flexible steel bar mesh 4;

[0099] S103: Install a specific length of iron sheet outer ring template 6 corresponding to the outer side of the flexible steel bar mesh 4, make the other end of the iron sheet outer ring template 6 flush with the end of the inner mold circular steel pipe body 1, and place support pads for improving the position stability between the iron sheet outer ring template 6 and the flexible steel bar mesh 4;

[0100] S104: Continue to configure several groups of U-shaped limit buckles 7 with a specific spacing between the iron sheet outer ring template 6 and the inner mold circular steel pipe body 1, and fix the position between the iron sheet outer ring template 6 and the inner mold circular steel pipe body 1;

[0101] S105: Pour concrete between the iron sheet outer ring template 6 and the inner mold circular steel pipe body 1, and after the strength reaches 70%, remove the U-shaped limit buckles 7 and the iron sheet outer ring template 6 to form a precast closed ring f with pre-embedded steel bars 3, stack the precast closed rings f for curing, and wait for use in pile foundation construction.

[0102] Please refer to Figures 11 to 19 , the embodiment of the present invention also provides a closed hoisting process including the prefabrication method of the closed prefabricated structure for karst geological pile foundations as described above, specifically including the following steps:

[0103] S201: Accurately loft according to the designed pile foundation position to determine the designed construction pile position a;

[0104] S202: Drill detection hole positions corresponding to the designed construction pile position a;

[0105] The specific process is as follows: Based on the pile center position of the designed construction pile position a, preset the position of a tool steel casing d coaxially, and vertically drill holes respectively at the outer side and the pile center position corresponding to the designed construction pile position a to form at least four groups of outer detection hole positions b and one group of center detection hole positions c. The diameter of the circle formed by connecting the at least four groups of outer detection hole positions b is greater than the diameter of the preset tool steel casing position d;

[0106] S203: Obtain the specific position of the karst cave p and its development depth parameters based on the detection hole positions;

[0107] The specific process is as follows: Use a downhole imaging detector to extend into the detection corresponding to each hole position, and determine the specific position of the karst cave p and its development depth parameters according to the displayed image and depth information;

[0108] S204: Bury the tool steel casing d;

[0109] The specific process is as follows: Bury the tool steel casing d according to the preset position. The height of the tool steel casing d exposed above the ground is not less than 50 cm, and use the tool steel casing d as the protection and guiding foundation for subsequent drilling and construction;

[0110] S205: Carry out rotary drilling and hole forming operation based on the designed construction pile position a to form a construction pile hole e;

[0111] S206: According to the determined specific position of the karst cave p and its development depth parameters, sequentially align and connect the karst cave p from bottom to top based on the construction pile hole e and the tool steel casing d and lower the precast closed ring f;

[0112] The specific process is as follows: Lower the first section of the precast closed ring f corresponding to the construction pile hole e, and weld the four groups of embedded steel bars 3 of the first section of the precast closed ring f to the tool steel casing d respectively to establish a temporary fixation;

[0113] After that, lift and lower the next section of the precast closed ring. Bend the four groups of embedded steel bars 3 of the next section of the precast closed ring and the four groups of embedded steel bars 3 of the first section of the precast closed ring respectively according to the determined specific position of the karst cave p and its development depth parameters to obtain steel bar hooks g for the corresponding length and connect the above two sections of the precast closed rings correspondingly, and then cut off the temporary fixation between the first section of the precast closed ring and the tool steel casing d;

[0114] Continue to lower the next precast closed ring and the first precast closed ring, and weld the four groups of embedded steel bars 3 of the next precast closed ring to the tool steel casing d respectively. Then continue to lift the subsequent precast closed ring and connect the steel bars between the subsequent precast closed ring and the next precast closed ring. By this process until all the precast closed rings are lowered in place, retain the temporary fixation between the last precast closed ring and the tool steel casing d, so that all the precast closed rings f are stably connected to the tool steel casing d, and complete the targeted plugging of the distributed karst caves;

[0115] More specifically, according to the specific position of the karst cave p and its development depth parameters determined, pre-select precast closed rings with a specific length that can completely plug the karst cave. When connecting through the steel bar lifting hook g, determine the bending position of the steel bar lifting hook according to the standard that the pre-selected precast closed ring can be accurately aligned with the corresponding karst cave, and / or install an extension steel bar h with at least a preset length between the steel bar lifting hooks corresponding to two adjacent precast closed rings, and finally accurately plug all the distributed karst caves p with determined specific positions and development depths;

[0116] S207: Continue to lower the steel reinforcement cage j corresponding to the tool steel casing d and the serially connected precast closed rings f;

[0117] S208: After the steel reinforcement cage is lowered in place, install a conduit k extending to the bottom of the pile hole for pumping and cleaning the hole. After the cleaning operation is completed, pour concrete corresponding to the steel reinforcement cage to complete the entire pile foundation construction process.

[0118] Although the present invention has been described in detail above with general descriptions and specific embodiments, on the basis of the present invention, some modifications or improvements can be made, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope claimed by the present invention.

Claims

1. A closed prefabricated framework for karst geological pile foundation, characterized in that: include: The inner mold round steel tube body is used as the inner mold for forming the prefabricated closed ring; The bottom support steel plate platform has an annular bottom and a side wall extending upward along the outer circumference of the annular ring, and the bottom support steel plate platform is assembled on the inner mold circular steel tube body in a directionally slidable manner through the annular bottom; The iron sheet outer ring template is correspondingly arranged at the outer side of the inner mold circular steel tube body, and the first end of the iron sheet outer ring template is detachably correspondingly limited and abutted against the inner side edge of the bottom support steel plate platform, and the second end of the iron sheet outer ring template is kept flush with the end position of the inner mold circular steel tube body away from the bottom support steel plate platform, so as to serve as the outer mold for forming the prefabricated closed ring; Embedded steel bars are provided in several groups, and the embedded steel bars in several groups are passed through the bottom support steel plate platform, and the two ends of the embedded steel bars in several groups extend to the outer side of the end position of the inner mold circular steel tube body away from the bottom support steel plate platform and the outer side of the bottom support steel plate platform respectively and one by one; The U-shaped limit buckle has two ends which are respectively and one by one correspondingly set at the end position of the inner mold circular steel tube body away from the bottom support steel plate platform and the second end of the iron sheet outer ring template.

2. The closed prefabricated framework for karst geological pile foundation according to claim 1, characterized in that: The inner mold circular steel tube body is set as a circular steel tube with an inner diameter not less than the outer diameter of the karst pile foundation steel cage; The bottom support steel plate platform is configured as an annular platform sleeved on the outer side of the inner mold circular steel tube body; The longitudinal section of the annular bottom support steel plate platform at any position is L-shaped.

3. The closed prefabricated framework for karst geological pile foundation according to claim 1, characterized in that: At least four groups of longitudinally extending reserved holes for reinforcing bars are evenly opened along the bottom circumferential position of the bottom support steel plate platform; at least four groups of embedded steel bars are provided, and the first end of each group of embedded steel bars passes through one of the reserved holes for reinforcing bars, and the second ends all extend beyond the top of the side wall of the inner mold circular steel tube body.

4. The closed prefabricated framework for karst geological pile foundation according to claim 3, characterized in that: Also includes: The flexible steel mesh is wound around the periphery of each of the embedded steel bars, and the flexible steel mesh is fixedly arranged by binding with the embedded steel bars through binding steel wires.

5. A method for prefabricating a closed prefabricated framework for karst geological pile foundation according to any one of claims 1 to 4, characterized in that: The specific steps include: The position of the bottom support steel plate platform is adjusted based on the sliding of the inner mold round steel tube body to determine the inner mold length of the inner mold round steel tube body to adapt to the length requirement of the prefabricated closed ring; Based on the bottom support steel plate platform on the outer side of the inner mold circular steel tube body, embedded steel bars are respectively inserted into the reserved holes for reinforcing bars, and the embedded steel bars are used as subsequent serial connection components of the prefabricated closed loop; After the embedded steel bars are inserted, the side gaps of the reserved holes for reinforcing bars are sealed with foam glue; The flexible steel mesh is wound around the outer side of the embedded steel bars, and the embedded steel bars and the flexible steel mesh are further tied and fixed by tying steel wires; An iron sheet outer ring template of a specific length is installed corresponding to the outer side of the flexible steel mesh, so that the other end of the iron sheet outer ring template is flush with the end position of the inner mold circular steel tube body, and a support pad is placed between the iron sheet outer ring template and the flexible steel mesh to improve the position stability; Continue to configure a number of sets of U-shaped limit buckles with specific spacing between the iron sheet outer ring template and the inner mold round steel tube body to fix the iron sheet outer ring template and the inner mold round steel tube body; Concrete is poured between the iron outer ring formwork and the inner mold circular steel tube body, and after the strength reaches 70%, the U-shaped limit buckle and the iron outer ring formwork are removed to form a prefabricated closed ring with embedded steel bars. The prefabricated closed rings are centrally stacked for curing and are ready for use in pile foundation construction.

6. A closed hoisting process comprising the method for prefabricating a closed prefabricated framework for karst geological pile foundations as claimed in claim 5, characterized in that: The steps include: Accurately stake out the designed pile foundation position and determine the designed construction pile position; Drill detection holes corresponding to the designed construction pile positions; Obtain the specific location of the cave and its development depth parameters based on the detection holes; The specific process is as follows: using an in-hole imaging detector to probe into each hole, and determining the specific location of the cave and its development depth parameters based on the displayed image and depth information; burying tool steel casing; Carry out rotary drilling and hole-forming operations based on the designed construction pile position to form the construction pile hole; According to the determined specific location of the karst cave and its development depth parameters, the prefabricated closed ring is placed in series with the karst cave from bottom to top based on the construction pile holes and tool steel casings; Continue to lower the steel cage corresponding to the tool steel casing and the prefabricated closed ring connected in series; After the steel cage is lowered into place, a conduit extending to the bottom of the pile hole is installed to carry out pumping and hole cleaning operations. After the hole cleaning operation is completed, concrete is poured into the corresponding steel cage to complete the entire pile foundation construction process.

7. The closed hoisting process according to claim 6, characterized in that: The drilling of detection holes corresponding to the designed construction pile positions specifically includes: A tool steel casing position is preset based on the coaxial center position of the designed construction pile position, and vertical holes are drilled corresponding to the outer side and the pile center position of the designed construction pile position to form at least four groups of outer detection holes and one group of center detection holes; The diameter of a circle formed by connecting lines of at least four groups of peripheral detection hole positions is larger than the diameter of the preset tool steel casing position.

8. The closed hoisting process according to claim 7, characterized in that: The method of obtaining the specific location of the cave and its development depth parameters based on the detection hole position specifically includes: Use the in-hole imaging detector to extend into each hole for detection, and determine the specific location of the cave and its development depth parameters based on the displayed image and depth information; The buried tool steel casing specifically comprises: Tool steel casing is buried according to the preset position. The height of the tool steel casing exposed above the ground is not less than 50cm. The tool steel casing is used as a protective and guiding foundation for subsequent drilling and construction.

9. The closed hoisting process according to claim 8, characterized in that: The method of connecting the karst caves in series and placing prefabricated closed loops in sequence from bottom to top based on the determined specific location of the karst caves and their development depth parameters is specifically as follows: Lower the first section of prefabricated closed ring to the construction pile hole, and weld the four sets of embedded steel bars of the first section of prefabricated closed ring to the tool steel casing to establish temporary fixation; Then, the next prefabricated closed ring is hoisted, and the four sets of embedded steel bars of the next prefabricated closed ring and the four sets of embedded steel bars of the first prefabricated closed ring are bent according to the determined specific location of the karst cave and its development depth parameters, so as to obtain steel bar hooks of the appropriate length and connect the above two prefabricated closed rings accordingly, and then the temporary fixation between the first prefabricated closed ring and the tool steel casing is cut off; Continue to lower the next section of prefabricated closed ring and the first section of prefabricated closed ring, and weld the four groups of embedded steel bars of the next section of prefabricated closed ring to the tool steel casing respectively. Then continue to lift the next section of prefabricated closed ring, and connect the steel bars between the next section of prefabricated closed ring and the next section of prefabricated closed ring. Repeat this process until all prefabricated closed rings are lowered into place, retaining the temporary fixation between the last section of prefabricated closed ring and the tool steel casing, so that all prefabricated closed rings are firmly connected to the tool steel casing, completing the targeted blocking of distributed caves.

10. The closed hoisting process according to claim 9, characterized in that: The method further comprises: connecting the karst caves in series and placing prefabricated closed loops in sequence from bottom to top based on the construction pile holes and tool steel casings according to the determined specific locations of the karst caves and their development depth parameters; According to the determined specific location of the karst cave and its development depth parameters, a prefabricated closed ring of a specific length that can completely block the karst cave is pre-selected, and when connected through the steel bar hook, the bending position of the steel bar hook is determined based on the standard that the pre-selected prefabricated closed ring can accurately align with the corresponding karst cave, and / or, at least one extended steel bar of a preset length is installed and connected between the steel bar hooks corresponding to two adjacent sections of the prefabricated closed ring, ultimately accurately blocking all distributed karst caves with determined specific locations and development depths.

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