CN111827275A - Karst area pile foundation construction system and construction method - Google Patents

Abstract

The invention provides a karst region pile foundation construction system and a construction method, wherein an upper casing of a joint-by-joint necking follow-up double casing is positioned and installed on a lower casing; the outer side wall of the section-by-section necking follow-up double protection barrel is provided with a bag arranged corresponding to the position of the karst area; the gradual necking follow-up double protecting cylinders are sleeved on the inner steel protecting cylinder; a reinforcement cage for pouring a pile foundation is arranged in the inner steel casing; the steel reinforcement cage limiting support frame is positioned at the top of the steel reinforcement cage to realize the upper limiting of the steel reinforcement cage; the floating closed bag is arranged in the pile hole. The positioning protection of the inner steel casing is realized by arranging the gradual necking follow-up double casings, and meanwhile, the effective limiting of the gradual necking follow-up double casings in a karst area is realized by arranging the bag; the floating closed bag is placed in the pile hole, when concrete is poured, the closed bag floats upwards along with the concrete to serve as a concrete pouring monitoring device, and pile forming efficiency and pile forming quality of the pile foundation during pile foundation construction in a karst area are greatly improved.

Description

Karst area pile foundation construction system and construction method

Technical Field

The invention relates to the technical field of pile foundation construction, in particular to a karst region pile foundation construction system and a construction method.

Background

In recent years, along with the encryption and the perfection of a road network, the geological conditions encountered in the construction process of a bridge pile foundation are more complex and diversified, the pile foundation construction of multilayer beaded large karst cave piles in a karst region is always the key and difficult point of the pile foundation construction in the karst region, the pile foundation construction of the karst cave has unpredictability and dangerousness, particularly, the pile foundation construction of string-shaped multilayer karst caves is compared with the traditional pile foundation construction, the bearing capacity of the pile foundation and the like are needed to be paid more attention to so as to ensure the integral bearing capacity of a road or a bridge, and the problems of settlement and the like in the later.

The conventional construction of the pile foundation in the karst area is usually carried out by lowering a steel casing, excavating a guide hole by using a drilling machine and finally pouring concrete to form a pile. If the pressure-bearing water is met in the pile foundation construction process, no measures are taken at the construction process position, water gushing is easily caused, and other common problems such as slurry leakage, deflection, drill sticking, pile breaking and the like are caused. Therefore, it is necessary to develop an improved karst region pile foundation construction system and method to solve the above construction problems and improve the pile-forming efficiency and quality of the pile foundation.

Disclosure of Invention

The invention aims to provide a karst region pile foundation construction system and a construction method, and aims to solve the technical problems of improving pile forming efficiency and pile forming quality of a pile foundation during karst region pile foundation construction at the present stage.

In order to achieve the purpose, the invention is realized by the following technical scheme:

a karst area pile foundation construction system comprises a joint-by-joint necking follow-up double casing and an inner steel casing which are arranged in a pile hole;

the section-by-section necking follow-up double protection cylinders comprise an upper protection cylinder and a lower protection cylinder; the upper pile casing is positioned and arranged on the lower pile casing;

the outer side wall of the section-by-section necking follow-up double protection barrel is provided with a bag arranged corresponding to the position of the karst area; the section-by-section necking follow-up double protecting cylinders are sleeved on the inner steel protecting cylinder;

a reinforcement cage for pouring a pile foundation is arranged in the inner steel casing;

a steel reinforcement cage limiting support frame and a floating closed bag are also arranged; the steel reinforcement cage limiting support frame is positioned at the top of the steel reinforcement cage to realize upper limiting of the steel reinforcement cage; the floating closed bag is arranged in the pile hole.

As a further improvement of the invention, the axial lower end of the upper protecting cylinder is in threaded connection with the axial upper end of the upper protecting cylinder, so as to realize the axial detachable fixed connection of the upper protecting cylinder and the lower protecting cylinder.

As a further improvement of the invention, the lower casing is also provided with a pin bolt; the pin bolt is arranged corresponding to the limiting groove hole in the upper protective cylinder, and the pin bolt is connected with the limiting groove hole in a penetrating manner, so that the upper protective cylinder and the lower protective cylinder are quickly positioned in the axial direction.

As a further improvement of the invention, the limiting slotted hole is a through hole; the through hole is a long waist-shaped hole arranged along the circumferential direction of the upper protective cylinder; the pin bolt penetrates through the through hole, so that the upper protective barrel and the lower protective barrel are axially and quickly positioned.

As a further improvement of the invention, a bag and a gas injection pipe are positioned and arranged on the outer side of the upper protective cylinder; the gas injection tube is in communication with the bladder.

As a further improvement of the invention, the steel reinforcement cage limiting strut comprises a stay bar, a cross bar and a connecting frame; the stay bar is matched with the inner side of the reinforcement cage in size; the cross rod is arranged in the stay bar, and two ends of the cross rod are respectively connected with the inner side of the stay bar; one end of the connecting frame is connected with the cross rod, and the other end of the connecting frame extends outwards; and the outer end of the connecting frame is provided with a downward pointed top for realizing the inserting positioning of the peripheral ground of the pile hole.

As a further improvement of the invention, the circumferential outer side edge of the stay bar is also provided with a rubber buckle which can be clamped and limited with a transverse stirrup of the reinforcement cage.

As a further improvement of the invention, the pile foundation pore-forming top plate is also provided with a small-diameter hole guiding device; the hole guiding device comprises a conical top, a fan-shaped steel sheet, a steel wire, a pressing plate, a fixed rod and a pull rope;

a fixed penetrating ring is arranged in the conical top; the lower end of the fan-shaped steel sheet is arranged on the conical top; one end of the steel wire is connected with the inner side of the fan-shaped steel sheet in a positioning mode, and the other end of the steel wire is connected with the pressing plate in a positioning mode; the fixed rod is positioned on the pressing plate; one end of the pull rope sequentially penetrates through the pressing plate and the penetrating ring and then is connected with the pressing plate in a positioning mode;

the fan-shaped steel sheets are axially and uniformly distributed on the cone top, and the pressing plate is arranged on the inner side of the top of each fan-shaped steel sheet, so that an inverted cone framework structure is formed.

As a further improvement of the invention, the fan-shaped steel sheets are connected with the pressure plate through an umbrella framework structure, so that the fan-shaped steel sheets can be unfolded and contracted in an umbrella shape.

A karst area pile foundation construction method comprises the following steps:

s1, construction preparation: leveling a field, removing impurities, replacing soft soil on the surface layer of the field, and compacting by ramming; the position of a mud pit, a steel bar processing field, a construction access and the like are reasonably arranged, special measures are adopted when necessary, and preparation work is done before entering the field for construction; carefully researching geological survey data, determining the thickness of a soft soil layer on the earth surface of the pile foundation to be implemented, the position and range of the karst cave to be penetrated and the possible karst cave filling condition, and preliminarily judging the stratum which is likely to collapse;

s2, measurement and positioning: determining a hole site center pile by using a total station and a steel ruler, arranging guard piles around the pile site, reinforcing the guard piles by using cement mortar, and establishing an obvious mark; a slurry making tank and a sedimentation tank are arranged between every two adjacent pier positions so as to meet the requirement of slurry for drilling;

s3, embedding an inner steel casing: after the hitting position of the inner steel casing is determined, the inner steel casing is placed down by using a crane, the plane position deviation of the inner steel casing is controlled within 5cm, and the inclination deviation is controlled within 1%;

s4, necking down one by one and following the arrangement of double protective sleeves: after the inner steel casing is positioned, firstly, the lower casing is hung in the inner steel casing, a through hole on an inner ring plate at the lower end of the upper casing is connected with a pin bolt on an outer ring plate at the upper end of the lower casing in a penetrating manner, and then the upper casing is rotated to be fastened with the lower casing;

s5, excavating: in the excavation operation of the karst top plate, in order to prevent the collapse hole condition, firstly, a hole guiding device is used for adjusting the hole guiding taper to excavate local small holes, and then, hammering holes are formed around the small holes;

s6, positioning a drilling machine: firstly, performing stone ballast replacement treatment on an operation foundation of a drilling machine, and mounting the drilling machine in place after tamping; after the percussion drill rig is installed, the center of a drill bit is accurately aligned to the cross center of the pile casing, the drill bit is lifted and slowly placed into the inner steel pile casing, a slurry pump is started, and the percussion is started after a certain amount of slurry is conveyed into the hole;

s7, preparing slurry: excavating a mud pit and a sedimentation tank outside the orifice 5m, and connecting a casing gap and the mud pit by using a mud ditch;

s8, drilling: according to the geological histogram, frequently observing and frequently checking when approaching a karst cave, and judging whether approaching a karst stratum or not according to the extracted rock sample, the length measured by the measuring rope and the sound of an impact rock stratum; when the karst stratum is approached, the prepared mud is confirmed to be sufficient before breakdown, and the phenomenon that the mud is suddenly lost after the karst cave is broken down to cause insufficient pressure in the hole to form hole collapse is avoided; penetrating through a multilayer karst cave, controlling the impact amplitude when drilling in a harder rock stratum, backfilling the mixture to a position above a collapse position if collapse occurs, and impacting the hole again until the designed elevation is drilled;

s9, final hole and hole cleaning: after finishing hole forming, checking the hole forming quality, performing first hole cleaning after the hole forming quality is qualified, and cleaning the hole by adopting a slurry changing and hole cleaning method; when cleaning the hole, the height of a water head in the hole must be kept to prevent hole collapse; before the steel bar cage is hoisted, cleaning holes for the first time;

s10, hoisting a reinforcement cage and installing a detection pipe: immediately organizing a reinforcement cage to be put down after the first hole cleaning is finished, slowly putting the reinforcement cage into the hole, accurately centering the reinforcement cage after the hole is put into the hole, welding a mouth-shaped hoisting reinforcement at the inner side of each hoisting position of a stiffening reinforcement, and performing limiting and fixing by using a reinforcement cage limiting support frame of an inner support outer hoop so as to prevent displacement or floating in the pouring process;

s11, secondary hole cleaning: timely lowering the guide pipe after the steel reinforcement cage is lowered, and performing secondary hole cleaning, and pouring concrete after the slurry index and sediment thickness in the hole meet the requirements;

s12, balloon inflation: before pouring, the test is carried out, and the air injection pipe is used for injecting air to the bag to expand the bag; placing a floating closed bag in the foundation pit;

s13, pouring concrete: the concrete guide pipe is always buried more than 2m deep during pouring, so that pile breakage is prevented; when the concrete passes through the karst cave, the speed of pouring the concrete is properly slowed down; the pile top pouring elevation is 0.5-0.8 m higher than the designed elevation, after the concrete pouring is finished, the guide pipe is slowly pulled out after the concrete surface is observed for about 30 minutes and is unchanged;

s14, pile head chiseling: after the pouring of the concrete foundation pile is completed and the final setting is carried out for 3 hours, the excess concrete and the floating closed bag are manually excavated, and other parts and equipment are removed, so that the construction of the pile foundation is completed.

Compared with the prior art, the invention has the beneficial effects that:

the positioning protection of the inner steel casing is realized by arranging the gradual necking follow-up double casings, and meanwhile, the effective limiting of the gradual necking follow-up double casings in a karst area is realized by arranging the bag; the floating closed bag is placed in the pile hole, when concrete is poured, the closed bag floats upwards along with the concrete to serve as a concrete pouring monitoring device, and pile forming efficiency and pile forming quality of the pile foundation during pile foundation construction in a karst area are greatly improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is an overall schematic view of a karst region pile foundation hole forming;

FIG. 2 is a schematic view of a progressive necking follow-up dual casing configuration of the present invention;

FIG. 3 is a sectional view of the present invention in the installed state of FIG. 3;

FIG. 4 is a schematic structural diagram of an upper casing of the present invention;

FIG. 5 is a schematic view of a hole guiding device according to the present invention;

FIG. 6 is a top view of the hole guiding apparatus of the present invention;

FIG. 7 is a schematic view of a reinforcement cage position-limiting bracket of the present invention;

FIG. 8 is a top view of the present invention of FIG. 7;

FIG. 9 is a process flow diagram of pile foundation hole forming and steel casing construction processes of the present invention;

the reference numbers in the figures illustrate:

1. necking one by one to follow the double protective cylinders; 11. an upper protective cylinder; 111. perforating; 12. a lower protective cylinder; 121. a pin; 2. an inner steel casing; 3. a karst zone; 4. a pouch; 5. a reinforcement cage; 6. a steel reinforcement cage limiting support frame; 61. a stay bar; 62. a cross bar; 63. a connecting frame; 631. a sharp top; 64. a rubber buckle; 7. floating up and sealing the sac; 8. pile holes; 9. a gas injection pipe; 10. a hole guiding device; 101. a cone top; 1011. fixing a through ring; 102. a fan-shaped steel sheet; 103. a steel wire; 104. pressing a plate; 105. fixing the rod; 106. and pulling a rope.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention provides a karst region pile foundation construction system and a construction method by combining with attached drawings 1 to 9, and aims to solve the technical problems of improving pile forming efficiency and pile forming quality of a pile foundation during karst region pile foundation construction at the present stage.

Specifically, the karst area pile foundation construction system comprises a gradual necking follow-up double casing 1 and an inner steel casing 2 which are arranged in a pile hole 8;

the section-by-section necking follow-up double-protection barrel 1 comprises an upper protection barrel 11 and a lower protection barrel 12; the upper protective sleeve 11 is positioned and installed on the lower protective sleeve 12;

the outer side wall of the section-by-section necking follow-up double-protection barrel 1 is provided with a bag 4 which corresponds to the position of the karst area 3; the section-by-section necking follow-up double protection cylinders 1 are sleeved on the inner steel protection cylinder 2;

a reinforcement cage 5 for pouring a pile foundation is arranged in the inner steel casing 2;

a steel reinforcement cage limiting support frame 6 and a floating closed bag 7 are also arranged; the steel reinforcement cage limiting support frame 6 is positioned at the top of the steel reinforcement cage 5 to realize upper limiting of the steel reinforcement cage 5; the floating closed bag 7 is arranged in the pile hole 8.

According to the method, the inner steel casing 2 is positioned and protected by arranging the section-by-section necking follow-up double casings 1, and meanwhile, the effective limiting of the section-by-section necking follow-up double casings 1 in a karst area 3 is realized by arranging the bag 4; the floating closed bag 7 is placed in the pile hole 8, when concrete is poured, the closed bag 4 floats upwards along with the concrete to serve as a concrete pouring monitoring device, and pile forming efficiency and pile forming quality of a pile foundation during pile foundation construction in a karst area are greatly improved.

Further, the axial lower end of the upper casing 11 is in threaded connection with the axial upper end of the upper casing 11, so as to realize the axial detachable fixed connection of the upper casing 11 and the lower casing 12.

Further, a pin bolt 121 is further arranged on the lower casing 12; the pin bolt 121 is arranged corresponding to the limiting groove hole on the upper casing 11, and the axial quick positioning of the upper casing 11 and the lower casing 12 is realized through the penetration of the pin bolt 121 and the limiting groove hole.

Specifically, an inner ring plate is arranged at the lower end of the upper protection cylinder 11; the inner ring plate is provided with a through hole 111 corresponding to the pin bolt 121; an internal thread structure is arranged on the circumferential inner side wall of the inner ring plate;

the upper end of the lower protective cylinder 12 is provided with an outer ring plate, and a plurality of pins 121 are circumferentially positioned on the outer ring plate; the outer ring plate is provided with an outer thread structure on the circumferential outer side wall; thereby realizing the threaded connection of the outer ring plate and the inner ring plate.

It should be noted that the limiting slot hole is a through hole 111; the through hole 111 is a long waist-shaped hole arranged along the circumferential direction of the upper protective sleeve 11; will pass through cotter 121 and perforation 111 cross-under to this realizes protecting a section of thick bamboo 11 and protecting a section of thick bamboo 12 under with the axial quick location, and the rethread rotates and protects a section of thick bamboo 11 and realize protecting a threaded fastening connection of section of thick bamboo 12 under with, and the structure sets up rationally, and convenient operation is swift.

Further, a bag 4 and an air injection pipe 9 are positioned on the outer side of the upper casing 11; the gas injection pipe 9 is communicated with the bag 4, and gas in the bag 4 is conveyed by injecting gas into the gas injection pipe 9, so that the bag 4 is abutted against the karst area 3 in an expansion manner, and the slurry leakage condition during concrete pouring is avoided.

Further, the steel reinforcement cage position-limiting support frame 6 comprises support rods 61, cross rods 62 and connecting frames 63; the stay bar 61 is matched with the inner side of the reinforcement cage 5 in size; the cross bar 62 is arranged in the stay bar 61, and two ends of the cross bar are respectively connected with the inner side of the stay bar 61; one end of the connecting frame 63 is connected with the cross bar 62, and the other end extends outwards; the outer end of the connecting frame 63 is provided with a downward tip 631 for realizing the insertion positioning of the peripheral ground of the pile hole 8.

It should be noted that, the stay bars 61 are embedded in the inner side of the steel reinforcement cage 5, the connecting frame 63 on the outer side is used for positioning the whole steel reinforcement cage limiting strut 6, and the connecting frame 63 is connected with the steel bars of the steel reinforcement cage 5 in a clamping manner from top to bottom to limit the clamping of the steel reinforcement cage 5.

Preferably, the circumferential outer side edge of the stay bar 61 is further provided with a rubber buckle 64, and the rubber buckle 64 can be limited by clamping with a transverse stirrup of the reinforcement cage 5.

Preferably, the connecting frame 63 has a U-shaped steel bar structure.

In another embodiment, a guiding hole device 10 for a small hole on the periphery of the pile foundation hole forming top plate is further arranged; the hole guiding device 10 comprises a conical top 101, a fan-shaped steel sheet 102, a steel wire 103, a pressing plate 104, a fixing rod 105 and a pull rope 106;

a fixing penetrating ring 1011 is arranged in the conical top 101; the lower end of the fan-shaped steel sheet 102 is arranged on the conical top 101; one end of the steel wire 103 is connected with the inner side of the fan-shaped steel sheet 102 in a positioning way, and the other end of the steel wire is connected with the pressing plate 104 in a positioning way; the fixing rod 105 is positioned on the pressing plate 104; one end of the pull rope 106 sequentially penetrates through the pressing plate 104 and the penetrating ring and then is connected with the pressing plate 104 in a positioning manner;

the plurality of fan-shaped steel sheets 102 are axially and uniformly distributed on the conical top 101, and the pressing plate 104 is arranged on the inner side of the top of the fan-shaped steel sheet 102, so that an inverted conical framework structure is formed.

It should be noted that, when the hole-forming radius of the hole-guiding device 10 needs to be adjusted, taking enlarging the hole-forming radius as an example, the pull rope 106 is pulled upwards, and the pressing plate 104 is positioned by the fixing rod 105, so that the conical top 101 moves upwards to drive the fan-shaped steel sheet 102 to move upwards; the inner side of the fan-shaped steel sheet 102 is abutted and limited with the pressure plate 104, so that the annular steel sheet expands radially outwards, and the whole conical framework plate is opened; similarly, the shrinkage of the whole conical framework plate can be realized by downwards loosening the pull rope 106, so that the adjustment of the taper is realized, the adjustment is convenient and fast, and the design is ingenious.

In another embodiment, the sides of the fan-shaped steel sheets 102 are connected by soft steel sheets.

Preferably, a plurality of the fan-shaped steel sheets 102 are connected with the pressure plate 104 through an umbrella frame structure, so that the fan-shaped steel sheets 102 can be unfolded and folded in an umbrella shape.

A karst area pile foundation construction method comprises the following steps:

s1, construction preparation: leveling the field, removing impurities, replacing soft soil on the surface layer of the field, and compacting by ramming. The position of a mud pit, a steel bar processing field, a construction access and the like are reasonably arranged, special measures are adopted when necessary, and preparation work is done before entering the field for construction; carefully researching geological survey data, determining the thickness of a soft soil layer on the earth surface of the pile foundation to be implemented, the position and range of the karst cave to be penetrated and the possible karst cave filling condition, and preliminarily judging the stratum which is likely to collapse;

s2, measurement and positioning: determining a hole site center pile by using a total station and a steel ruler, arranging guard piles around the pile site, reinforcing the guard piles by using cement mortar, and establishing an obvious mark; a slurry making tank and a sedimentation tank are arranged between every two adjacent pier positions so as to meet the requirement of slurry for drilling;

s3, embedding an inner steel casing: after the hitting position of the inner steel casing 2 is determined, the inner steel casing 2 is placed by a crane, the plane position deviation of the inner steel casing 2 is controlled within 5cm, and the inclination deviation is controlled within 1%;

s4, necking down one by one and following the arrangement of double protective sleeves: after the inner steel casing 2 is positioned, firstly, the lower casing 12 is hung in the inner steel casing 2, after a through hole 111 on an inner ring plate at the lower end of the upper casing 11 is connected with a pin bolt 121 on an outer ring plate at the upper end of the lower casing 12 in a penetrating manner, the upper casing 11 is rotated to be fastened with the lower casing 12;

s5, excavating: in the excavation operation of the karst top plate, in order to prevent the collapse hole condition, firstly, the hole guiding device 10 is used for adjusting the hole guiding taper to excavate local small holes, and then, hammering hole forming is carried out on the periphery of the small holes;

s6, positioning a drilling machine: firstly, performing stone ballast replacement treatment on an operation foundation of a drilling machine, and mounting the drilling machine in place after tamping; after the percussion drill rig is installed, the center of a drill bit is accurately aligned to the cross center of the pile casing, the drill bit is lifted and slowly placed into the inner steel pile casing 2, a slurry pump is started, and the percussion is started after a certain amount of slurry is conveyed into the hole;

s7, preparing slurry: excavating a mud pit and a sedimentation tank outside the orifice 5m, and connecting a casing gap and the mud pit by using a mud ditch;

s8, drilling: according to the geological histogram, frequently observing and frequently checking when approaching a karst cave, and judging whether approaching a karst stratum or not according to the extracted rock sample, the length measured by the measuring rope and the sound of an impact rock stratum; when the karst stratum is approached, the prepared mud is confirmed to be sufficient before breakdown, and the phenomenon that the mud is suddenly lost after the karst cave is broken down to cause insufficient pressure in the hole to form hole collapse is avoided; penetrating through a multilayer karst cave, controlling the impact amplitude when drilling in a harder rock stratum, backfilling the mixture to a position above a collapse position if collapse occurs, and impacting the hole again until the designed elevation is drilled;

s9, final hole and hole cleaning: after finishing hole forming, checking the hole forming quality, performing first hole cleaning after the hole forming quality is qualified, and cleaning the hole by adopting a slurry changing and hole cleaning method; when cleaning the hole, the height of a water head in the hole must be kept to prevent hole collapse; before the steel bar cage 5 is hoisted, hole cleaning is carried out for the first time;

s10, hoisting a reinforcement cage and installing a detection pipe: immediately descending the reinforcement cage 5 after the first hole cleaning is finished, slowly descending the reinforcement cage 5 into the hole, accurately centering the reinforcement cage 5 after the hole is entered, welding a mouth-shaped hoisting reinforcement at the inner side of each hoisting position, and performing limiting and fixing by using a reinforcement cage limiting support frame 6 of an inner support outer hoop so as to prevent displacement or floating in the casting process;

s11, secondary hole cleaning: after the steel reinforcement cage 5 is placed, timely placing the guide pipe to perform secondary hole cleaning, and pouring concrete after the slurry index and sediment thickness in the hole meet the requirements;

s12, balloon inflation: before pouring, the test is carried out, and the air injection pipe 9 is used for injecting air to the bag 4 to expand the bag; a floating closed bag 7 is placed in the foundation pit;

s13, pouring concrete: the concrete guide pipe is always buried more than 2m deep during pouring, so that pile breakage is prevented; when the concrete passes through the karst cave, the speed of pouring the concrete is properly slowed down; the pile top pouring elevation is 0.5-0.8 m higher than the designed elevation, after the concrete pouring is finished, the guide pipe is slowly pulled out after the concrete surface is observed for about 30 minutes and is unchanged;

s14, pile head chiseling: after the pouring of the concrete foundation pile is completed and the final setting is carried out for 3 hours, the excess concrete and the floating closed bag 7 are manually excavated, and other parts and equipment are removed, so that the construction of the pile foundation is completed.

It should be noted that the detailed description of the invention is not included in the prior art, or can be directly obtained from the market, and the detailed connection mode can be widely applied in the field or daily life without creative efforts, and the detailed description is not repeated here.

In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

Claims (10)

1. The utility model provides a karst district pile foundation construction system which characterized in that: comprises a gradual necking follow-up double casing and an inner steel casing which are arranged in a pile hole;

the section-by-section necking follow-up double protection cylinders comprise an upper protection cylinder and a lower protection cylinder; the upper pile casing is positioned and arranged on the lower pile casing;

the outer side wall of the section-by-section necking follow-up double protection barrel is provided with a bag arranged corresponding to the position of the karst area; the section-by-section necking follow-up double protecting cylinders are sleeved on the inner steel protecting cylinder;

a reinforcement cage for pouring a pile foundation is arranged in the inner steel casing;

a steel reinforcement cage limiting support frame and a floating closed bag are also arranged; the steel reinforcement cage limiting support frame is positioned at the top of the steel reinforcement cage to realize upper limiting of the steel reinforcement cage; the floating closed bag is arranged in the pile hole.

2. The karst region pile foundation construction system of claim 1, wherein: the axial lower end of the upper protective cylinder is in threaded connection with the axial upper end of the upper protective cylinder, and the upper protective cylinder and the lower protective cylinder are axially detachably and fixedly connected.

3. The karst region pile foundation construction system of claim 1, wherein: the lower protective cylinder is also provided with a pin bolt; the pin bolt is arranged corresponding to the limiting groove hole in the upper protective cylinder, and the pin bolt is connected with the limiting groove hole in a penetrating manner, so that the upper protective cylinder and the lower protective cylinder are quickly positioned in the axial direction.

4. The karst region pile foundation construction system of claim 3, wherein: the limiting slotted hole is a through hole; the through hole is a long waist-shaped hole arranged along the circumferential direction of the upper protective cylinder; the pin bolt penetrates through the through hole, so that the upper protective barrel and the lower protective barrel are axially and quickly positioned.

5. The karst region pile foundation construction system of claim 1, wherein: the outer side of the upper protective cylinder is also provided with a bag and a gas injection pipe in a positioning way; the gas injection tube is in communication with the bladder.

6. The karst region pile foundation construction system of claim 1, wherein: the steel reinforcement cage limiting support frame comprises a support rod, a cross rod and a connecting frame; the stay bar is matched with the inner side of the reinforcement cage in size; the cross rod is arranged in the stay bar, and two ends of the cross rod are respectively connected with the inner side of the stay bar; one end of the connecting frame is connected with the cross rod, and the other end of the connecting frame extends outwards; and the outer end of the connecting frame is provided with a downward pointed top for realizing the inserting positioning of the peripheral ground of the pile hole.

7. The karst region pile foundation construction system of claim 6, wherein: the circumference outside limit of vaulting pole still is equipped with the rubber buckle, the rubber buckle can with the joint of the horizontal stirrup of steel reinforcement cage is spacing.

8. The karst region pile foundation construction system of claim 1, wherein: the pile foundation pore-forming top plate is also provided with a small-diameter hole guiding device; the hole guiding device comprises a conical top, a fan-shaped steel sheet, a steel wire, a pressing plate, a fixed rod and a pull rope;

a fixed penetrating ring is arranged in the conical top; the lower end of the fan-shaped steel sheet is arranged on the conical top; one end of the steel wire is connected with the inner side of the fan-shaped steel sheet in a positioning mode, and the other end of the steel wire is connected with the pressing plate in a positioning mode; the fixed rod is positioned on the pressing plate; one end of the pull rope sequentially penetrates through the pressing plate and the penetrating ring and then is connected with the pressing plate in a positioning mode;

the fan-shaped steel sheets are axially and uniformly distributed on the cone top, and the pressing plate is arranged on the inner side of the top of each fan-shaped steel sheet, so that an inverted cone framework structure is formed.

9. The karst region pile foundation construction system of claim 8, wherein: the fan-shaped steel sheets are connected with the pressing plate through an umbrella framework structure, so that the fan-shaped steel sheets can be unfolded and contracted in an umbrella shape.

10. A karst region pile foundation construction method based on the karst region pile foundation construction system of any one of claims 1 to 9, characterized by comprising the steps of:

s1, construction preparation: leveling a field, removing impurities, replacing soft soil on the surface layer of the field, and compacting by ramming; the position of a mud pit, a steel bar processing field, a construction access and the like are reasonably arranged, special measures are adopted when necessary, and preparation work is done before entering the field for construction; carefully researching geological survey data, determining the thickness of a soft soil layer on the earth surface of the pile foundation to be implemented, the position and range of the karst cave to be penetrated and the possible karst cave filling condition, and preliminarily judging the stratum which is likely to collapse;

s2, measurement and positioning: determining a hole site center pile by using a total station and a steel ruler, arranging guard piles around the pile site, reinforcing the guard piles by using cement mortar, and establishing an obvious mark; a slurry making tank and a sedimentation tank are arranged between every two adjacent pier positions so as to meet the requirement of slurry for drilling;

s3, embedding an inner steel casing: after the hitting position of the inner steel casing is determined, the inner steel casing is placed down by using a crane, the plane position deviation of the inner steel casing is controlled within 5cm, and the inclination deviation is controlled within 1%;

s4, necking down one by one and following the arrangement of double protective sleeves: after the inner steel casing is positioned, firstly, the lower casing is hung in the inner steel casing, a through hole on an inner ring plate at the lower end of the upper casing is connected with a pin bolt on an outer ring plate at the upper end of the lower casing in a penetrating manner, and then the upper casing is rotated to be fastened with the lower casing;

s5, excavating: in the excavation operation of the karst top plate, in order to prevent the collapse hole condition, firstly, a hole guiding device is used for adjusting the hole guiding taper to excavate local small holes, and then, hammering holes are formed around the small holes;

s6, positioning a drilling machine: firstly, performing stone ballast replacement treatment on an operation foundation of a drilling machine, and mounting the drilling machine in place after tamping; after the percussion drill rig is installed, the center of a drill bit is accurately aligned to the cross center of the pile casing, the drill bit is lifted and slowly placed into the inner steel pile casing, a slurry pump is started, and the percussion is started after a certain amount of slurry is conveyed into the hole;

s7, preparing slurry: excavating a mud pit and a sedimentation tank outside the orifice 5m, and connecting a casing gap and the mud pit by using a mud ditch;

s8, drilling: according to the geological histogram, frequently observing and frequently checking when approaching a karst cave, and judging whether approaching a karst stratum or not according to the extracted rock sample, the length measured by the measuring rope and the sound of an impact rock stratum; when the karst stratum is approached, the prepared mud is confirmed to be sufficient before breakdown, and the phenomenon that the mud is suddenly lost after the karst cave is broken down to cause insufficient pressure in the hole to form hole collapse is avoided; penetrating through a multilayer karst cave, controlling the impact amplitude when drilling in a harder rock stratum, backfilling the mixture to a position above a collapse position if collapse occurs, and impacting the hole again until the designed elevation is drilled;

s9, final hole and hole cleaning: after finishing hole forming, checking the hole forming quality, performing first hole cleaning after the hole forming quality is qualified, and cleaning the hole by adopting a slurry changing and hole cleaning method; when cleaning the hole, the height of a water head in the hole must be kept to prevent hole collapse; before the steel bar cage is hoisted, cleaning holes for the first time;

s10, hoisting a reinforcement cage and installing a detection pipe: immediately organizing a reinforcement cage to be put down after the first hole cleaning is finished, slowly putting the reinforcement cage into the hole, accurately centering the reinforcement cage after the hole is put into the hole, welding a mouth-shaped hoisting reinforcement at the inner side of each hoisting position of a stiffening reinforcement, and performing limiting and fixing by using a reinforcement cage limiting support frame of an inner support outer hoop so as to prevent displacement or floating in the pouring process;

s11, secondary hole cleaning: timely lowering the guide pipe after the steel reinforcement cage is lowered, and performing secondary hole cleaning, and pouring concrete after the slurry index and sediment thickness in the hole meet the requirements;

s12, balloon inflation: before pouring, the test is carried out, and the air injection pipe is used for injecting air to the bag to expand the bag; placing a floating closed bag in the foundation pit;

s13, pouring concrete: the concrete guide pipe is always buried more than 2m deep during pouring, so that pile breakage is prevented; when the concrete passes through the karst cave, the speed of pouring the concrete is properly slowed down; the pile top pouring elevation is 0.5-0.8 m higher than the designed elevation, after the concrete pouring is finished, the guide pipe is slowly pulled out after the concrete surface is observed for about 30 minutes and is unchanged;

s14, pile head chiseling: after the pouring of the concrete foundation pile is completed and the final setting is carried out for 3 hours, the excess concrete and the floating closed bag are manually excavated, and other parts and equipment are removed, so that the construction of the pile foundation is completed.

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