CN113863706B

CN113863706B - Construction method and application device of existing building low-clearance lower rotary-jet static pressure composite pile

Info

Publication number: CN113863706B
Application number: CN202111077103.4A
Authority: CN
Inventors: 王曙光; 段启伟; 李湛; 李钦锐; 李鹏; 潘从建; 唐君; 夏长华; 王浩宇
Original assignee: Cabr Foundation Engineering Co ltd
Current assignee: Cabr Foundation Engineering Co ltd
Priority date: 2021-09-14
Filing date: 2021-09-14
Publication date: 2023-07-04
Anticipated expiration: 2041-09-14
Also published as: CN113863706A

Abstract

The invention discloses a construction method and an application device of a low-headroom down-rotation jet static pressure composite pile of an existing building, wherein the method comprises the following steps of determining the depth of the composite pile; step two, designing a lower composite pile; thirdly, constructing an application device by adopting a spinning integrated machine; controlling construction of a pile section of the composite pile; and fifthly, excavating the soil body at the lower part or gradually reinforcing the soil body. According to the invention, through the arrangement of the inner ribs of the reinforcing bearing platform and the reinforcing bearing platform, a connection and bearing foundation is provided; the pile foundation is designed for reinforcing foundation of different geology under the existing building through the arrangement of the composite pile, and the composite pile can be further utilized; by the application of the spinning integrated machine, construction can be performed in a narrow space, and construction is performed on the jet grouting pile and the core pile without displacement.

Description

Construction method and application device of existing building low-clearance lower rotary-jet static pressure composite pile

Technical Field

The invention belongs to the technical field of building construction, and particularly relates to a construction method and an application device of a low-headroom down-rotation jet static pressure composite pile of an existing building.

Background

The body volume of the existing buildings in China reaches 400 hundred million square meters (2018), wherein the existing buildings which need to be reinforced and reformed for various reasons are huge in quantity, and the body volume of the existing building reinforcing and reforming market is huge. The underground space development is carried out under the existing building, is an important mode for expanding the building area of the existing building or reinforcing the soil body at the lower part and improving the functions of the existing building, and adopts various underground space development modes to realize the underground capacity expansion market demand and huge market capacity for the existing building.

The existing building underground space is expanded and reinforced and transformed, a series of problems of deformation control, connection of new and old structures and the like of the existing building in the load transmission or transformation, reinforcement and transformation process of the existing building structure are required to be solved, and the structure is ensured to have good safety performance, usability and durability. And the corresponding design is lacking for convenient construction of poor geology or how to correspond to the stratum containing the groundwater in the small space of the basement.

Disclosure of Invention

The invention provides a construction method and an application device of a low-headroom down-rotation jet static pressure composite pile of an existing building, which are used for solving the design and construction problems of pile foundations in reinforcement transformation or underground layer addition of the existing building.

In order to achieve the above purpose, the invention adopts the following technical scheme:

the construction method of the existing building low-clearance down-rotation jet static pressure composite pile comprises the steps that the existing building comprises an original foundation, a floor slab or a basement roof which is positioned above the original foundation, and an excavation layer and/or a reinforced soil body of the building are/is planned to be built below the original foundation;

the method comprises the following specific steps:

step one, combining an in-situ investigation report and a supplementary investigation report, dividing a soil layer of a planned site or a reinforced soil body in an existing building in an investigation depth range into a large layer and a sub-layer according to the factors, and determining main physical and mechanical indexes, pile side friction resistance and pile end resistance of each soil layer in a pile body design range, thereby determining the design length of a composite pile; further ascertaining the groundwater level and groundwater type during the supplementary survey;

step two, carrying out three-way leveling on a planned construction site, grooving corresponding to a construction working surface, designing the position of a composite pile on the basis of the prior art, measuring and paying off, and adopting a static force for perforating; the bearing layer into which the pile end of the composite pile extends corresponds to the required embedding length of the composite pile, or the depth of the composite pile extending into the bottom of the designed reinforced soil body;

step three, before formal construction, in order to debug equipment and obtain on-site construction parameters, a test pile test is carried out; the pile hole of the composite pile is guided by adopting a rotary spraying component in the spinning integrated machine, the rotary spraying pile is selected to form a rotary spraying hole by adopting high-pressure rotary spraying according to engineering requirements and soil conditions, the rotary spraying pile is formed by spraying cement paste, gas and water, and then static pressure of the core pile is carried out by the spinning integrated machine; the construction of the jet grouting pile and the core pile can be divided into independent two-step construction or sectional alternation, the height of the spinning integrated machine is smaller than the height from the top of the original foundation to the floor slab or to the top plate of the basement, and the spinning integrated machine comprises a gate frame and a static pressure sub-assembly which are detachably connected to the gate frame;

fourthly, the core pile is in place and must be kept vertical, and the core pile and the jet grouting pile are concentric and coaxial; the same vertical line is kept, the bias voltage is not needed, and a steel pile cap is sleeved when the pile is pressed, and then the pile is pressed; meanwhile, the last section of core pile adopts a pile follower to control pile top elevation;

fifthly, pile sealing is carried out after the composite pile is installed, and then soil at the lower part of the original foundation is excavated until the soil is excavated to the bottom surface of the foundation to be built; or gradually constructing the composite piles on the soil body at the lower part from the middle to the periphery until the reinforced soil body meets the design requirement.

Further, in the third step, the spinning all-in-one machine is connected with the original foundation through the bottom connecting anchor rods, the number, the diameter and the anchoring length of the anchor rods are determined according to calculation, and hole forming burying is adopted; 3 pulling-resistant tests are carried out on the anchor rod before construction, and the single limiting pulling-resistant force meets the design requirement and is generally more than 80kN; the anchor rod hole is strictly positioned, the hole forming is vertical, the anchoring force is ensured, the hole forming is carried out by adopting a water drilling method, the bar planting glue is injected, then the reinforcing steel bar is placed, and after the strength of the bar planting glue reaches the design requirement, the gate frame of the spinning integrated machine is fixed on the anchor bolt and the nut is locked.

Further, when the spinning integrated machine is installed, pile machine alignment is carried out according to the pile position to be measured and released, wherein the verticality of a drill rod in the rotary spraying subassembly is controlled by a double-line hammer arranged on the drilling machine and a level bar on the drilling machine, and when necessary, correction is carried out by using a theodolite in a bidirectional 90-degree manner, and the verticality deviation is not more than 1%. And further, after the drilling machine is in place, starting the power head to rotate the drill rod, and drilling to the designed pile bottom elevation by spraying high-pressure water or not spraying high-pressure water in the horizontal direction or the bottom direction of the drill bit.

Further, after the pile bottom elevation is designed by drilling, the power head rotates the drill rod, starts the high-pressure grouting pump, supplies high-pressure air and slurry to the drill bit at the bottom of the drill rod, and simultaneously cuts and lifts soil body through high-pressure jet flow in the horizontal direction of the drill bit or the direction of the bottom of the drill bit and jets the slurry; and controlling the pressure of the high-pressure grouting pump, and spraying to the elevation of the top of the rotary spraying design pile.

Further, in the fourth step, the top of the composite pile is embedded into the original foundation, wherein the effective pile diameter of the jet grouting pile is 400-1000mm or is determined according to calculation, cement paste is adopted as slurry, the cement consumption meets the design requirement and is not less than 140kg/m, and the water-cement ratio is 0.6-1.2; the design parameters of the jet grouting pile are that the water spraying pressure is more than or equal to 20MPa; the guniting pressure is more than or equal to 10MPa; the pressure of the air flow is more than or equal to 0.7MPa; the lifting speed is less than or equal to 300mm/min; the core pile 31 is determined according to the net height according to the length of each section and is pressed in sections, and butt welding and segment welding are adopted for the core pile joint.

Further, in the fourth step, the elevation of the core pile top is not lower than the elevation of the designed pile top, and cement slurry in the core pile should be poured to be not less than 200mm above the elevation of the designed pile top; after the cement paste is hardened, pile head cutting construction is carried out, and the pile head of the core pile is cut to the designed pile top elevation; the core pile is internally provided with a reinforcement cage or a vertical reinforcement, and the tops of the reinforcement cage and the vertical reinforcement are anchored into a reinforcing bearing platform or respectively connected with inner ribs of the reinforcing bearing platform.

Further, the application device of the existing construction low-clearance lower rotary jet static pressure composite pile construction method comprises a grooving machine for original foundation perforation and a rotary jet integrated machine for composite piles;

the spinning all-in-one machine comprises a door type assembly, a bottom connecting assembly connected between the door type assembly and a bottom foundation, telescopic assemblies connected to two sides of the door type assembly, a power assembly connected to the upper middle part of the door type assembly, a spinning installation connecting part connected with the power assembly and positioned in the middle of the transverse direction of the door type assembly, and a positioning assembly connected with the lower middle part of the door type assembly;

the spinning installation assembly comprises a spinning installation top connected below the transverse part of the door assembly, a spinning installation connecting part connected right below the top, and a spinning sub-assembly or a static pressure sub-assembly connected to the spinning installation connecting part; the rotary spraying sub-assembly comprises a drill rod, a drill bit and a grouting pipe; the static pressure subassembly comprises a pressure connecting rod and a pressure piece;

the positioning assembly comprises positioning transverse plates detachably connected with two sides of the door-type assembly, positioning connecting plates connected between the positioning transverse plates and the door-type assembly, positioning connecting rods horizontally and vertically connected between the middle parts of the positioning transverse plates, and positioning cylinders connected to the outer end parts of the positioning connecting rods; the positioning cylinder is arranged corresponding to a drill rod in the jet grouting subassembly or a middle pressure connecting rod in the static pressure subassembly.

Further, the bottom connecting assembly comprises a bottom connecting plate and bottom connecting anchor rods connected with the bottom connecting plate and arranged in the original foundation, and the bottom connecting anchor rods are vertically arranged at intervals and/or obliquely arranged; the bottom connecting components are respectively connected to the bottoms of the door-type components; the door type assembly comprises two vertical parallel door uprights and a door cross beam connected to the tops of the two door uprights, a door upright sliding groove is vertically formed in the door uprights, and the door upright sliding groove corresponds to the telescopic assembly and is high in telescopic quantity corresponding to the telescopic assembly.

Further, the telescopic assembly comprises telescopic bases which are respectively connected to the bottom connecting plate, each telescopic base is provided with a vertical jack, the tops of the two jacks are connected with a horizontal telescopic beam, and the telescopic beams pass through a door upright post chute;

the power assembly comprises a motor, an electric gear, a transmission belt connected between the electric gear and the motor, and a motor mounting base connected between the motor and the telescopic beam; the electric gear is correspondingly connected to a rod piece corresponding to the rotary spraying subassembly or the static pressure subassembly between the rotary spraying installation top and the telescopic cross beam.

The core pile is a steel pipe pile, or a precast concrete pile such as a tubular pile and a square pile, or a section steel pile such as an H-shaped pile and an I-shaped pile; the diameter of the core pile is 108-400mm, and the strength of the steel is not lower than Q235;

the original foundation and the original column are reinforced concrete structures, or the original foundation is a concrete foundation, a brick foundation, a rubble concrete foundation, a gray soil foundation and other non-reinforced foundations, and the foundation is an extension foundation such as a column bottom strip foundation, a raft foundation or a box foundation.

The beneficial effects of the invention are as follows:

1) According to the invention, the composite pile is in a structure form of adding the core pile into the jet grouting pile, so that on one hand, pile foundation design is facilitated for the storey addition under different geological conditions of the existing building, and on the other hand, the composite pile can be further utilized by arranging the composite pile into the pile foundation at the lower part of the storey addition, so that one pile can be used for two purposes, and construction procedures and cost are saved;

2) The spinning integrated machine is beneficial to construction in a narrow space, and the comprehensive construction is carried out on the jet grouting pile and the core pile under the situation of no displacement, so that the spinning integrated machine not only can adapt to complex site construction conditions, but also is convenient to reduce construction procedures and save construction cost;

3) The construction method and the application device are easy to implement and convenient for underground storey addition and reinforcement under the special working condition of the existing building, and can be greatly adapted to the condition of an underground soil layer and different basic working conditions;

additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention; the primary object and other advantages of the invention may be realized and attained by means of the instrumentalities and particularly pointed out in the specification.

Drawings

FIG. 1 is a main construction flow chart of composite pile construction;

FIG. 2 is a schematic illustration of a spinning integrated machine and composite pile construction;

FIG. 3 is a partial schematic view of a spinning integrated machine and composite pile construction;

FIG. 4 is a schematic perspective view of a spinning integrated machine with a spin-on subassembly;

FIG. 5 is a schematic perspective view of a second spin-on integrated machine with a spin-on subassembly;

FIG. 6 is a schematic front view of a spin-on integrated machine with a spin-on subassembly;

FIG. 7 is a side schematic view of a spinning body;

FIG. 8 is a schematic side cross-sectional view of a spinning integrated machine;

FIG. 9 is a schematic side cross-sectional view of a spinning integrated machine with a static pressure subassembly;

FIG. 10 is a schematic view of the construction of a portion of a composite pile with the reinforcement foundation removed;

fig. 11 is a top view of a construction composite pile construction layout.

Reference numerals: 1-soil body, 2-rotary spraying hole, 3-composite pile, 31-core pile, 32-rotary spraying pile, 4-primary foundation, 5-primary cushion, 6-rotary spraying integrated machine, 61-bottom connecting component, 611-bottom connecting plate, 612-bottom connecting anchor rod, 62-door component, 621-door column, 622-door beam, 623-door column chute, 63-telescopic component, 631-telescopic base, 632-jack, 633-telescopic beam, 64-power component, 641-motor, 642-electric gear, 643-transmission belt, 644-motor mounting base, 65-rotary spraying mounting component, 651-rotary spraying mounting top, 652-rotary spraying mounting connecting part, 653-rotary spraying sub-component, 654-static pressure sub-component, 66-positioning component, 661-positioning transverse plate, 662-positioning connecting plate, 663-positioning cylinder, 664-positioning connecting rod, 7-reinforcing bearing platform, 8-primary column, 9-new foundation, 10-new column, 11-cushion, 12-new column reserved rib and 13-slope pile.

Detailed Description

Taking a certain atrium project as an example, the atrium project is positioned in a certain Chinese character 'hui' type building in Beijing city, and the periphery A, B, C, D, E, F business buildings are all provided with 1-3 floors of basements, and the atrium part is free of basement. The novel sinking square with 1 layer is added to the atrium position, the underground space is expanded, and the novel sinking square is communicated with the functions of surrounding buildings. The project to be built is business, 1 layer underground, frame structure, raft foundation, the plane size is 148m, the width is 36m, and the foundation burial depth is 6.0m. The long side direction of the north side is close to the A-seat commercial building, a newly-added atrium sinking square is communicated with a basement part, the foundation burial depth of the A-seat commercial building is 6.0m, the middle part of the A-seat commercial building is communicated with the door head of an atrium, and the foundation burial depth is 2m, so that the foundation burial depth needs to be subjected to underpinning, reinforcing design and construction.

As shown in fig. 11, the range of the current underpinning is four independent column foundations at the top, the original foundation 4 is buried at about 2m, the clearance is about 3.5m, the maximum load of a single column is about 170t, and a slope protection pile 13 is arranged at one side. The engineering reinforcement construction period is urgent, the control requirements on noise and environmental pollution are high, normal business of overground parts cannot be affected, and in addition, due to the limitation of construction ground plane space and construction clearance, the geological conditions are complex, and the targeted design is required.

The engineering needs to consider the following points at the same time in design and construction: firstly, the existing foundation plate is not large in size and the original main reinforcement is not damaged as much as possible, so that the diameter of an opening hole on the foundation plate is required to be as small as possible, but the diameter after piling is required to be as large as possible so as to obtain higher single pile bearing capacity; secondly, the lower part of the foundation is provided with a horizontal supporting structure such as soil nails or anchor rods which are unknown in the foundation pit and the original A-F seats, the pile position basically has no adjustment space, the drilling machine is required to have strong adaptability to stratum, and the pile can be formed once; thirdly, the space of the field is limited, and the equipment is required to be as small as possible, so that the requirements of low clearance and limited space operation are met; the requirements are comprehensively considered, and the rotary jet static pressure pile is adopted for underpinning for layer increasing and subsequent reinforcement.

The construction method of the existing building low-clearance down-rotation jet static pressure composite pile is applied, the existing building comprises an original foundation 4, an original cushion layer 5 positioned below the original foundation 4, a floor slab or a basement roof positioned above the original foundation 4, and a planned building excavation layer and/or a reinforced soil body are positioned below the original foundation 4. The composite pile 3 in fig. 1 is constructed mainly in a construction flow chart. Referring to fig. 1 to 11, a construction method of a low-headroom down-swing jet static pressure composite pile for an existing building is further described, and in this embodiment, the core pile 31 is a steel pipe pile. Or precast concrete piles such as pipe piles and square piles, or H-shaped and I-shaped steel piles; the diameter of the core pile 31 is 108-400mm, and the steel strength is not lower than Q235; these embodiments all ensure that the core pile 31 cooperates with the rotary spray soil pile; the core pile 31 adopts a steel pipe pile, the diameter of the steel pipe pile is 108-400mm, and the steel strength is not lower than Q235. The foundation is a reinforced concrete structure, and as a modification, a concrete foundation, a brick foundation, a rubble concrete foundation, a gray soil foundation and other non-reinforced foundations can be used, and the foundation is an extension foundation such as a column foundation, a raft foundation or a box foundation.

The method comprises the following specific steps:

step one, combining an in-situ investigation report and a supplementary investigation report, dividing a soil layer of a planned site in an existing building in an investigation depth range into a large layer and a sub-layer according to the factors, and determining main physical and mechanical indexes, pile side friction resistance and pile end resistance of each soil layer in a pile body design range, thereby determining the design length of a composite pile 3; the groundwater level and groundwater type are further ascertained during the supplementary survey.

In combination with in-situ investigation and supplementary investigation reports, the soil layer of the planned site within the depth range of 60.0m below the natural ground at the deepest investigation can be divided into 8 large layers and sublayers according to the factors, and the main physical and mechanical indexes and pile side friction resistance of each soil layer in the typical geological pile body design range are shown. The depth of the filling soil in the fertilizer groove is 11.10m. Through field excavation, peripheral deep foundation pit excavation and the like, the horizontal supporting structure such as soil nails or anchor rods and the like which are unknown in the existing foundation pit of the original A-F seats are arranged below the gate head foundation. 1 layer of stable groundwater was observed during the supplementary survey over the current depth of 25.0m below ground. The stable water level burial depth is 9.50-9.60 m, and the underground water type is interlayer water.

Step two, carrying out three-way leveling on a planned construction site, grooving corresponding to a construction operation surface, designing the position of a composite pile 3 on an original foundation 4, measuring and paying off, and adopting a static force perforating; the bearing layer into which the pile end of the composite pile 3 extends corresponds to the required embedding length of the composite pile 3, or the depth of the bottom of the soil body is reinforced for the extension of the composite pile 3.

Step three, before formal construction, in order to debug equipment and obtain on-site construction parameters, a test pile test is carried out; the pile hole of the composite pile 3 is guided by adopting a rotary spraying component in the spinning integrated machine 6, the rotary spraying pile 32 is formed into a rotary spraying hole 2 by adopting triple pipe high-pressure rotary spraying, then the rotary spraying pile 32 is formed by spraying cement paste, gas and water, and then the static pressure of the core pile 31 is carried out by the spinning integrated machine 6; the construction of the jet grouting pile 32 and the core pile 31 can be divided into independent two-step construction or segmented alternate construction, the height of the spinning integrated machine 6 is smaller than the height from the top of the original foundation 4 to the floor slab or to the top plate of the basement, and the spinning integrated machine 6 comprises a gate frame and a jet grouting sub-assembly 653 and a static pressure sub-assembly 654 which are detachably connected on the gate frame.

In this embodiment, 1 group of pile test is performed for debugging equipment and obtaining site construction parameters before the formal construction. The pile test termination pressing force is 2025kN. When the load reaches the design value, the pile body subsides by about 3mm, thereby meeting the design requirement of bearing capacity and the requirement of subsidence control after the support of the door head column. In this embodiment, the composite piles 3 are arranged in each independent foundation, and in order to support the upper structural load by the addition, the closer the pile foundation is to the original structural column from the viewpoint of load transmission, the better, but the construction space of the composite piles 3 and the distance from the original column 8 are also considered in pile placement. Meanwhile, the pile position centroid and the load gravity center are as close as possible; the smaller and better the opening of the foundation 4 is, in combination with consideration of the outer diameter of the lower core stake 31 being 245mm and the diameter of the static opening being 400mm.

In the embodiment, the applied device comprises a grooving machine for perforating the original foundation 4 and a spinning integrated machine 6 for the composite pile 3; the grooving machine is used for grooving the corresponding construction working surface; the spinning integrated machine 6 is used for not displacing the construction core pile 31. The core pile 31 comprises a temporary supporting pile body, temporary supporting pile ribs connected to the inner part of the temporary supporting pile body, and temporary supporting pile reserved ribs at the top part of the temporary supporting pile body. The temporary supporting pile body is composed of core piles 31 arranged in the jet grouting piles 32, temporary supporting pile ribs and temporary supporting pile reserved ribs are steel reinforcement cages, the temporary supporting pile ribs are located on the inner sides of the core piles 31, and the temporary supporting pile reserved ribs are anchored into the reinforcing bearing platform 7.

As shown in fig. 2 to 9, the spinning integrated machine 6 includes a door assembly 62, a bottom connecting assembly 61 connected between the door assembly 62 and a bottom foundation, telescopic assemblies 63 connected to both sides of the door assembly 62, a power assembly 64 connected to the upper middle portion of the door assembly 62, a spinning mounting connection 652 connected to the power assembly 64 and located at the middle and inner lateral portion of the door assembly 62, and a positioning assembly 66 connected to the lower middle portion of the door assembly 62.

In this embodiment, the spin-on mounting assembly 65 comprises a spin-on mounting top 651 connected under the lateral portion of the gate assembly 62, a spin-on mounting link 652 connected directly under the top, a spin-on subassembly 653 or a static pressure subassembly 654 connected to the spin-on mounting link 652; the jet grouting sub-assembly 653 comprises a drill stem, a drill bit and a grouting pipe; the static pressure subassembly 654 includes a pressure link and a pressure member. Installing a spinning integrated machine 6, and performing pile machine alignment according to the pile position to be measured, wherein the verticality of a drill rod in a rotary spraying sub-assembly 653 is controlled by a double-line hammer arranged on a drilling machine and a level bar on the drilling machine, and if necessary, correction is performed by a theodolite in a bidirectional 90 degree manner, wherein the verticality deviation is not more than 1%; after the pile bottom elevation is designed by drilling, starting a power head to rotate a drill rod, starting a high-pressure grouting pump, providing high-pressure air and slurry for a drill bit at the bottom of the drill rod, cutting soil body while sinking and drilling through double high-pressure jet flows in two directions of the drill bit level and the drill bit bottom, and simultaneously jetting the slurry; and controlling the pressure of the high-pressure grouting pump, and spraying to the elevation of the top of the rotary spraying design pile.

In the embodiment, the weight of water and cement is measured according to the designed water-cement ratio during construction of the jet grouting pile 32, and the cement is filtered through a 20-mesh sieve after being uniformly stirred in a slurry stirring barrel and is placed in a slurry storage barrel; the slurry storage barrel is used for continuously stirring the cement slurry to prevent the cement slurry from precipitating; the pump head of the grouting pump is covered by a fine mesh gauze cover, so that the nozzle of the drill bit is prevented from being blocked due to the suction of coarse particles. Drilling operation is performed once through water: after the drilling machine is in place, starting the power head to rotate the drill rod, providing high-pressure air for the drill bit at the bottom of the drill rod, and sinking while cutting soil to drill through double high-pressure jet flows in two directions of the drill bit level and the drill bit bottom, so as to drill and design pile bottom elevation; spraying high-pressure cement paste for one time: after the pile bottom elevation is designed in drilling, a power head is started to rotate a drill rod, a high-pressure grouting pump is started, high-pressure air and slurry are provided for a drill bit at the bottom of the drill rod, and the slurry is sprayed simultaneously while soil is cut and sunk into the pile through double high-pressure jet flows in the horizontal direction of the drill bit and the bottom direction of the drill bit. And controlling the pressure of the high-pressure grouting pump, and spraying to the elevation of the top of the rotary spraying design pile.

In this embodiment, the positioning assembly 66 comprises positioning cross plates 661 detachably connected to both sides of the door assembly 62, positioning cross plates 662 connected between the positioning cross plates 661 and the door assembly 62, positioning connecting rods 664 horizontally and vertically connected between the middle parts of the two positioning cross plates 661, and positioning cylinders 663 connected to the outer ends of the positioning connecting rods 664; the positioning cylinder 663 is arranged corresponding to the drill rod in the rotary spraying subassembly 653 or the medium-pressure connecting rod in the static pressure subassembly 654.

In this embodiment, the bottom connecting assembly 61 comprises a bottom connecting plate 611 and bottom connecting anchor rods 612 connected to the bottom connecting plate 611 and arranged in the original foundation 4, wherein the bottom connecting anchor rods 612 are vertically arranged at intervals and/or are obliquely arranged; the bottom connecting components 61 are respectively connected to the bottoms of the door-type components 62; the door assembly 62 comprises two vertically parallel door posts 621 and a door beam 622 connected to the tops of the two door posts 621, a door post chute 623 is vertically arranged on the door posts 621, and the door post chute 623 is arranged corresponding to the telescopic assembly 63 and corresponds in height to the telescopic assembly 63 in height.

In this embodiment, the telescopic assembly 63 includes telescopic bases 631 connected to the bottom connecting plate 611, each telescopic base 631 is provided with a vertical jack 632, the tops of the two jacks 632 are connected with a horizontal telescopic beam 633, and the telescopic beam 633 passes through the door upright chute 623.

In this embodiment, the power unit 64 includes a motor 641, a motor gear 642, a transmission belt 643 connected between the motor gear 642 and the motor 641, and a motor mounting base 644 connected between the motor 641 and the telescopic beam 633; the motor gear 642 is correspondingly connected to a rod corresponding to the rotary spraying subassembly 653 or the static pressure subassembly 654 between the rotary spraying mounting top 651 and the telescopic cross beam 633.

In the third step, the spinning integrated machine 6 is connected with the original ground through a bottom connecting anchor rod 612, the length of an anchor rod is not less than 350mm, the exposed section is not less than 200mm, and hole forming embedding is adopted; 3 pullout tests are carried out on the bottom connecting anchor rod 612 before construction, and the single limit pullout resistance is more than 80kN; the anchor rod hole is strictly positioned, the hole forming is vertical, the anchoring force is ensured, the hole forming is carried out by adopting a water drilling method, the bar planting glue is injected, then the steel bar is placed, and after the strength of the bar planting glue reaches the design requirement, the gate frame of the spinning integrated machine 6 is fixed on the anchor bolt and the nut is locked.

Step four, the composite pile 3 is in place and must be kept vertical, and the core pile 31 and the jet grouting pile 32 are concentric and coaxial; the same vertical line is kept, the bias voltage is not needed, and the pile top is sleeved with a steel pile cap and then pressed when the pile is pressed; meanwhile, the last section of the core pile 31 adopts a pile follower to control the pile top elevation.

In the fourth step, the top of the composite pile 3 is embedded into the original foundation 4, wherein the effective pile diameter of the jet grouting pile 32 is not less than 600mm, cement paste is adopted as slurry, the cement consumption is not less than 140kg/m, and the water-cement ratio is 0.7; the design parameters of the jet grouting pile 32 are that the water spraying pressure is less than or equal to 3MPa; the guniting pressure is more than or equal to 10MPa; the pressure of the air flow is more than or equal to 0.7MPa; the lifting speed is less than or equal to 300mm/min; the lifting rotating speed is 18-20 revolutions per minute; the core pile 31 is pressed in sections according to 2.5m of each section, and butt welding and segment welding are adopted for the joints of the core pile 31.

In the fourth step, the elevation of the top of the core pile 31 is not lower than the elevation of the top of the design pile, and cement slurry in the core pile 31 is poured to be not less than 200mm above the elevation of the top of the design pile; after the cement paste is hardened, pile head cutting construction is carried out, and the pile head of the core pile 31 is cut to the designed pile top elevation; the core pile 31 is also internally provided with a reinforcement cage or a vertical reinforcement, and the tops of the reinforcement cage and the vertical reinforcement are anchored into the reinforcement bearing platform 7 or respectively connected with the inner ribs of the reinforcement bearing platform 7.

In the embodiment, the rotary jet grouting pile 32 adopts a rotary-pressing integrated drill to drill holes, the rotary jet grouting pile 32 adopts triple pipe high-pressure rotary jet grouting, the effective pile diameter of the rotary jet grouting pile 32 is not less than 600mm, and the core pile 31 is implanted after rotary jet grouting. The outer diameter of the core pile 31 is 245mm, the wall thickness of the core pile 31 is 8mm, and the core pile 31 is made of Q345 material; the effective pile length is 21m, the fine sand of the layer (6) is used as a bearing layer, and the single pile bearing force characteristic value is 375kN, and the total number of the pile bearing force characteristic values is 24.

In the embodiment, before the primary setting of the grouting cement slurry for forming the holes of the core piles 31, a reinforcement cage is buried in the pile head, the lower part of the reinforcement cage is inserted into the core piles 311.5m, and the upper part of the reinforcement cage is anchored into a reinforcement carrier plate at least 1.1m.

Fifthly, sealing piles after the composite piles 3 are installed, connecting foundation bar planting around the original foundation 4 and vertically at intervals, connecting foundation column bar planting around the original columns 8 and vertically, and designing a reinforcing bearing platform 7 and inner bars of the reinforcing bearing platform 7 corresponding to the original foundation 4; pouring to finish the reinforcement bearing platform 7 and the internal ribs of the reinforcement bearing platform 7, and excavating the soil body 1 at the lower part of the original foundation 4 until the soil body is excavated to the bottom surface of the foundation to be built;

in the fifth step, when the reinforcement bearing platform 7 and the inner ribs of the reinforcement bearing platform 7 are constructed, the peripheries of the original foundation 4 and the original column 8 are firstly roughened, and foundation reinforcement ribs are symmetrically arranged; wherein the internal ribs of the reinforcing bearing platform 7 at least comprise double-layer horizontal ribs, and the height ranges of the horizontal ribs are all connected with the original columns 8. The design of the reinforcing bearing platform 7 needs to meet the requirements of bending resistance, punching resistance and shearing resistance; through calculation, the thickness of the reinforcing bearing platform 7 is 1100-1300mm, the concrete design strength is C30, the diameter of the double-layer bidirectional reinforcement bars is 12mm, the distance is 120mm, and the three-level steel can meet the design requirement.

As shown in fig. 10, a new cushion layer 11, a new foundation 9 and a new column 10 are constructed on the bottom surface of the constructed foundation, wherein the central axis of the new column 10 corresponds to the central axis of the original column 8, and the composite piles 3 are symmetrically arranged about the new column 10; the top of the new column 10 is connected to the bottom of the original foundation 4, the upper structural load is transferred into the new column 10 through the original foundation 4, after the new column 10 is connected stably, the load is transferred to the new column 10 from the composite pile 3, and then the reinforcing bearing platform 7 and the core pile 31 are cut off.

The connection of the original foundation 4 and the newly added reinforcing carrier plate is a key force transmission node for ensuring the function of the core pile 31. The engineering adopts a chemical reinforcement planting mode to realize the transmission of shearing force and bending moment of the original foundation 4 and the newly added reinforcing carrier plate. Firstly roughening an existing foundation surface layer, then drilling holes, cleaning holes, then chemically planting ribs, cleaning the foundation surface layer, coating an interfacial agent, and pouring the foundation surface layer and a steel bar cage on the top of a core pile 31 after binding the foundation steel bars, wherein after the project is used for 1 year, the maximum settlement of the foundation is about 4mm, and the maximum inclination rate of a building is 0.7 per mill, so that the design requirement is met.

In addition, the original column 8 comprises an original column body and an original column reinforcing steel bar, and the bottom of the original column body is a chiseled part so as to facilitate the connection of the new column 10; the new column 10 is also provided with new column retaining ribs 12 to facilitate the connection of the superstructure to form a unitary structure. The construction flow is developed step by step according to the partition of the construction operation, and the symmetry of the engineering structure and the load is considered, so that the construction operation surface of the composite pile 3 is symmetrical; only one pile can be constructed on the same foundation at a time, and the construction time interval between adjacent piles on the same foundation is not less than 1 day.

The foregoing is merely illustrative of preferred embodiments of the present invention, and the scope of the present invention is not limited thereto, but any changes or substitutions that would occur to those skilled in the art within the scope of the present invention are intended to be included in the scope of the present invention.

Claims

1. The construction method of the existing building low-clearance down-rotation jet static pressure composite pile is characterized in that the existing building comprises an original foundation (4), a floor slab or a basement roof which is positioned above the original foundation (4), and a planned building excavation layer and/or a reinforced soil body are positioned below the original foundation (4);

the method comprises the following specific steps:

step one, combining an in-situ investigation report and a supplementary investigation report, layering soil layers of a planned site or a reinforced soil body in the existing building within the investigation depth range, and determining physical and mechanical indexes of each soil layer, pile side friction resistance and pile end resistance of the pile body design range, thereby determining the design length of the composite pile (3); further ascertaining the groundwater level and groundwater type during the supplementary survey;

step two, carrying out three-way leveling on a planned construction site, grooving corresponding to a construction operation surface, designing the position of a composite pile (3) on an original foundation (4), measuring and paying off, and adopting a static force to carry out tapping; the bearing layer into which the pile end of the composite pile (3) extends corresponds to the needed embedding length of the composite pile (3), or the depth of the composite pile (3) extending into the bottom of the designed reinforced soil body;

step three, before formal construction, in order to debug equipment and obtain on-site construction parameters, a test pile test is carried out; the pile hole of the composite pile (3) is formed by adopting a rotary spraying component in a rotary pressing integrated machine (6), a rotary spraying pile (32) is formed into a rotary spraying hole (2) by adopting high-pressure rotary spraying according to engineering requirements and soil conditions, the rotary spraying pile (32) is formed by spraying cement paste, gas and water, and then static pressure of the core pile (31) is carried out by the rotary pressing integrated machine (6); the construction of the jet grouting pile (32) and the core pile (31) can be divided into independent two-step construction or segmented alternation, the height of the spinning integrated machine (6) is smaller than the height from the top of the original foundation (4) to a floor slab or to a basement roof, and the spinning integrated machine (6) comprises a gate frame and a static pressure sub-assembly (654) which are detachably connected with the gate frame;

the spinning all-in-one machine (6) comprises a door type assembly (62), a bottom connecting assembly (61) connected between the door type assembly (62) and a bottom foundation, telescopic assemblies (63) connected to two sides of the door type assembly (62), a power assembly (64) connected to the upper middle part of the door type assembly (62), a spinning installation connecting part (652) connected with the power assembly (64) and positioned at the middle part in the transverse direction of the door type assembly (62) and a positioning assembly (66) connected to the lower middle part of the door type assembly (62);

the spinning installation assembly (65) comprises a spinning installation top (651) connected below the transverse part of the door assembly (62), a spinning installation connecting part (652) connected right below the top, a spinning sub-assembly (653) or a static pressure sub-assembly (654) connected with the spinning installation connecting part (652); the rotary jetting sub-assembly (653) comprises a drill pipe, a drill bit, and a grouting pipe; the static pressure subassembly (654) includes a pressure link and a pressure element;

the positioning assembly (66) comprises positioning transverse plates (661) which are detachably connected with two sides of the door assembly (62), positioning connecting plates (662) which are connected between the positioning transverse plates (661) and the door assembly (62), positioning connecting rods (664) which are horizontally and vertically connected between the middle parts of the two positioning transverse plates (661), and positioning cylinders (663) which are connected with the outer end parts of the positioning connecting rods (664); the positioning cylinder (663) is arranged corresponding to a drill rod in the rotary spraying subassembly (653) or a medium-pressure connecting rod in the static pressure subassembly (654);

fourthly, the position of the core pile (31) must be kept vertical, and the core pile (31) and the jet grouting pile (32) are concentric and coaxial; the same vertical line is kept, the bias voltage is not needed, a steel pile cap is sleeved before pile pressing, and then pile pressing is carried out; simultaneously, the last section of core pile (31) adopts a pile driver to control the elevation of the pile top;

the core pile (31) is a steel pipe pile, or a precast concrete pile tubular pile, a precast concrete square pile, or an H-shaped steel pile or an I-shaped steel pile; the diameter of the core pile (31) is 108-400mm, and the steel strength is not lower than Q235;

the top of the composite pile (3) is embedded into the original foundation (4), wherein the effective pile diameter of the jet grouting pile (32) is 400-1000mm or is determined according to calculation, cement paste is adopted as slurry, the cement consumption meets the design requirement and is not less than 140kg/m, and the water-cement ratio is 0.7-1.2; design parameters of the jet grouting pile (32) are that the water spraying pressure is more than or equal to 20MPa; the guniting pressure is more than or equal to 10MPa; the pressure of the air flow is more than or equal to 0.7MPa; the lifting speed is less than or equal to 300mm/min; the core pile (31) is determined according to the net height according to the length of each section and is pressed in sections, and the joint of the core pile (31) adopts a butt welding and segment welding or sleeve wire connection or groove welding mode;

fifthly, sealing piles after the composite piles (3) are installed, and excavating soil bodies (1) at the lower parts of the original foundations (4) until the soil bodies are excavated to the bottom surface of the foundation to be built; or gradually constructing the composite piles (3) on the lower soil body (1) from the middle to the periphery until the reinforced soil body meets the design requirement.

2. The construction method of the existing building low-clearance lower rotary jet static pressure composite pile according to claim 1, wherein in the third step, the rotary jet integrated machine (6) is connected with the original foundation (4) through a bottom connecting anchor rod (612), the number, the diameter and the anchoring length of the anchor rods are determined according to calculation, and hole forming embedding is adopted; 3 pulling-resistant tests are carried out on the anchor rod before construction, and the single limiting pulling-resistant force meets the design requirement; the anchor rod hole is strictly positioned, the hole forming is vertical, the anchoring force is ensured, the hole forming is carried out by adopting a water drilling method, the bar planting glue is injected, then the steel bar is placed, and after the strength of the bar planting glue reaches the design requirement, the gate type frame of the spinning integrated machine (6) is fixed on the anchor bolt and is locked with the nut.

3. The construction method of the existing building low-clearance lower rotary-jet static-pressure composite pile according to claim 2, characterized in that when the spinning integrated machine (6) is installed, pile machine alignment is carried out according to the pile position to be measured and placed, wherein the verticality of a drill rod in the rotary-jet sub-assembly (653) is controlled by a double-line hammer equipped by a drilling machine and a horizontal rule on the drilling machine in a double manner, and if necessary, correction is carried out by using a theodolite in a bidirectional 90-degree manner, and the verticality deviation is not more than 1%.

4. The construction method of the existing building low-clearance lower rotary-jet static-pressure composite pile according to claim 3, wherein after the drilling machine is in place, the power head is started to rotate the drill rod, and the drilling is performed to the designed pile bottom elevation by jetting high-pressure water horizontally or in the direction of the bottom of the drilling bit or not jetting high-pressure water.

5. The construction method of the existing building low-clearance lower rotary-jet static-pressure composite pile according to claim 4, which is characterized in that after drilling the designed pile bottom elevation, a power head is started to rotate a drill rod, a high-pressure grouting pump is started, high-pressure air and slurry are provided for a drill bit at the bottom of the drill rod, and the slurry is jetted while cutting soil body and lifting through high-pressure jet flow in the horizontal direction or the bottom direction of the drill bit; and controlling the pressure of the high-pressure grouting pump, and spraying to the elevation of the top of the rotary spraying design pile.

6. The construction method of the existing building low headroom down-rotation spray static pressure composite pile according to claim 1, wherein in the fourth step,

the original foundation (4) and the original column (8) are of reinforced concrete structures, wherein the original foundation (4) is an expanded foundation, and the foundation is in the form of an under-column strip foundation, a raft foundation or a box foundation.

7. The construction method of the existing building low-clearance down-rotation jet static pressure composite pile according to claim 6, wherein in the fourth step, the top elevation of the core pile (31) is not lower than the designed pile top elevation, and cement slurry in the core pile (31) is poured to be not less than 200mm above the designed pile top elevation; after the cement paste is hardened, pile head cutting construction is carried out, and the pile head of the core pile (31) is cut to the designed pile top elevation; the inside of the core pile (31) is also provided with a reinforcement cage or a vertical reinforcement, and the tops of the reinforcement cage and the vertical reinforcement are anchored into the reinforcing bearing platform (7) or respectively connected with the inner ribs of the reinforcing bearing platform (7).

8. The application device of the existing construction low-clearance lower rotary-jet static pressure composite pile construction method is characterized by comprising a grooving machine for perforating an original foundation (4) and a rotary-pressing integrated machine (6) for a composite pile (3);

the positioning assembly (66) comprises positioning transverse plates (661) which are detachably connected with two sides of the door-type assembly (62), positioning connecting plates (662) which are connected between the positioning transverse plates (661) and the door-type assembly (62), positioning connecting rods (664) which are horizontally and vertically connected between the middle parts of the positioning transverse plates (661), and positioning cylinders (663) which are connected with the outer end parts of the positioning connecting rods (664); the positioning cylinder (663) is arranged corresponding to a drill rod in the rotary spraying subassembly (653) or a medium-pressure connecting rod in the static pressure subassembly (654).

9. The application device of the construction method of the existing building low-clearance down-rotation jet static pressure composite pile according to claim 8, wherein the bottom connecting assembly (61) comprises a bottom connecting plate (611) and bottom connecting anchor rods (612) connected with the bottom connecting plate (611) and arranged in the original foundation (4), and the bottom connecting anchor rods (612) are vertically arranged at intervals and/or obliquely arranged; the bottom connecting components (61) are respectively connected to the bottoms of the door-type components (62); the door assembly (62) comprises two vertical parallel door uprights (621) and a door cross beam (622) connected to the tops of the two door uprights (621), a door upright sliding groove (623) is vertically formed in the door uprights (621), and the door upright sliding groove (623) corresponds to the telescopic assembly (63) to be arranged and corresponds in height to the telescopic assembly (63) in height to be telescopic.

10. The application device of the construction method of the existing building low-clearance down-swing jet static pressure composite pile according to claim 9, wherein the telescopic assembly (63) comprises telescopic bases (631) connected to the bottom connecting plate (611) respectively, each telescopic base (631) is provided with a vertical jack (632), the tops of the two jacks (632) are connected with a horizontal telescopic beam (633), and the telescopic beam (633) penetrates through a door upright chute (623);

the power assembly (64) comprises a motor (641), a motor gear (642), a transmission belt (643) connected between the motor gear (642) and the motor (641), and a motor mounting base (644) connected between the motor (641) and a telescopic beam (633); the electric gear (642) is correspondingly connected to a rod corresponding to a rotary spraying subassembly (653) or a static pressure subassembly (654) between the rotary spraying installation top (651) and the telescopic cross beam (633).