CN113863706A - Construction method and application device of low-clearance lower jet grouting static pressure composite pile of existing building - Google Patents

Abstract

The invention discloses a construction method and an application device of a low-clearance lower jet grouting static pressure composite pile of an existing building, wherein the method comprises the following steps of firstly, determining the depth of the composite pile; designing a lower composite pile; thirdly, constructing the application device by adopting a spinning all-in-one machine; fourthly, controlling construction of a composite pile section; and fifthly, excavating the soil body at the lower part or gradually reinforcing the soil body. The invention provides a connection and bearing foundation by arranging the reinforcing bearing platform inner rib and the reinforcing bearing platform; through the arrangement of the composite piles, pile foundation design is carried out on foundation reinforcement of different geological foundations under the existing building, and the composite piles can be further utilized; through the application of spinning all-in-one, can construct in narrow and small space, and spout stake and core pile construction to the spinning under not shifting.

Description

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

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-clearance lower jet grouting static pressure composite pile of an existing building.

Background

The quantity of the existing buildings in China reaches 400 hundred million square meters (2018), the existing buildings needing to be reinforced and modified for various reasons are large in quantity, and the market quantity of the existing building reinforcement and modification is huge. The underground space development is carried out under the existing building, which is an important mode for expanding the area of the existing building or reinforcing the soil body at the lower part of the existing building and improving the functions of the existing building, and various underground space development forms are adopted to realize huge underground expansion market demands and huge market capacity for the existing building.

The existing building underground space expansion and reinforcement transformation needs to solve a series of problems of load transmission or conversion of the existing building structure, deformation control of the existing building in the reinforcement transformation process, connection of new and old structures and the like, and ensures that the structure has good safety performance, service performance and durability. And the corresponding design is lacked for how to correspond the convenient construction in this narrow and small space of basement to unfavorable geology or stratum that contains groundwater.

Disclosure of Invention

The invention provides a construction method and an application device of a low-clearance lower jet grouting static pressure composite pile of an existing building, which are used for solving the design and construction problems of pile foundations in existing building reinforcement and reconstruction or underground storey addition.

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

the construction method of the low-clearance lower rotary-spraying static-pressure composite pile of the existing building comprises the steps that the existing building comprises an original foundation and a floor slab or a basement top plate which is positioned above the original foundation, and a building excavation layer and/or a reinforced soil body are/is constructed and positioned below the original foundation;

the method comprises the following specific steps:

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

step two, carrying out tee joint leveling on the proposed site, grooving corresponding to a construction working surface, designing the position of the composite pile on the original foundation, measuring and setting out, and opening holes by static force; the pile end of the composite pile extends into the bearing layer corresponding to the required embedded length of the composite pile or the depth of the composite pile extending into the bottom of the reinforced soil body;

step three, before formal construction, in order to debug equipment and obtain site construction parameters, a pile test is carried out; the pile hole of the composite pile adopts a rotary spraying component in a rotary spraying all-in-one machine to guide the hole, the rotary spraying pile adopts high-pressure rotary spraying to form a rotary spraying hole according to engineering requirements and soil conditions, the rotary spraying pile is formed by spraying cement paste, air and water, and then the static pressure of the core pile is carried out by a rotary pressing all-in-one machine; the construction of the jet grouting pile and the core pile can be divided into two independent steps of construction or alternatively performed in sections, the height of the spinning all-in-one machine is smaller than the height from the top of an original foundation to a floor slab or to a top plate of the basement, and the spinning all-in-one machine comprises a portal frame and a jet grouting subassembly and a static pressure subassembly which are detachably connected to the portal frame;

fourthly, the core pile is required to be kept vertical in position, and the core pile and the rotary jet grouting pile are concentric and coaxial; keeping the same vertical line without bias voltage, sleeving a steel pile cap during pile pressing and then pressing the pile; meanwhile, the elevation of the pile top of the last section of core pile is controlled by a pile feeder;

step five, after the composite pile is installed, sealing the pile, and excavating the soil body at the lower part of the original foundation until the soil body is excavated to the bottom surface of the proposed foundation; or gradually constructing the composite piles on the lower soil body from the middle to the periphery until the reinforced soil body meets the design requirements.

Further, in the third step, the spinning all-in-one machine is connected with the original foundation through bottom connection anchor rods, the number, the diameter and the anchoring length of the anchor rods are determined according to calculation, and the anchor rods are embedded by adopting formed holes; 3 pullout tests are carried out on the anchor rod before construction, and the ultimate pullout resistance of a single anchor rod meets the design requirement and is generally greater than 80 kN; 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, 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 portal frame of the spinning all-in-one machine is fixed on the anchor bolt and the nut is locked.

Further, when the spinning all-in-one machine is installed, pile machine alignment is carried out according to the measured pile position, the perpendicularity of a drill rod in the spinning and spraying sub-assembly is controlled by a double-line hammer arranged on the drilling machine and a horizontal ruler on the drilling machine, the perpendicularity is corrected by a theodolite at 90 degrees in two directions when necessary, and the perpendicularity deviation is not more than 1%. Furthermore, after the drilling machine is in place, the power head is started to rotate the drill rod, and the drill rod is drilled to the designed pile bottom elevation through the horizontal direction of the drill bit or the direction of the bottom of the drill bit by spraying high-pressure water or not spraying high-pressure water.

Further, after the pile bottom elevation is designed by drilling, the power head rotates the drill rod, the high-pressure grouting pump is started, high-pressure air and slurry are provided for the drill bit at the bottom of the drill rod, the soil body is cut and lifted at the same time through a high-pressure jet flow in the horizontal direction of the drill bit or the bottom direction of the drill bit, and the slurry is sprayed at the same time; and controlling the pressure of the high-pressure grouting pump, and spraying to the elevation of the designed pile top of the rotary spraying.

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, the slurry adopts cement paste, the cement consumption meets the design requirement and is not less than 140kg/m, and the water cement ratio is 0.6-1.2; designing parameters of the jet grouting pile, wherein the water spraying pressure is more than or equal to 20 MPa; the guniting pressure is more than or equal to 10 MPa; the airflow pressure is more than or equal to 0.7 MPa; the lifting speed is less than or equal to 300 mm/min; the core pile 31 is determined according to the net height and pressed in sections according to the length of each section, and the joint of the core pile adopts butt welding and segment welding.

Further, in the fourth step, the elevation of the top of the core pile is not lower than the elevation of the designed pile top, and cement slurry in the core pile is 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 elevation of the designed pile top; 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 the reinforcing bearing platform or are respectively connected with the inner ribs of the reinforcing bearing platform.

Further, the application device of the construction method of the low-clearance lower rotary spraying static pressure composite pile of the existing building comprises a grooving machine for holing the original foundation and a rotary spraying all-in-one machine for the composite pile;

the spinning all-in-one machine comprises a door type component, a bottom connecting component connected between the door type component and a bottom foundation, telescopic components connected to two sides of the door type component, a power component connected to the middle upper part of the door type component, a spinning mounting connecting part connected with the power component and located in the transverse inner middle part of the door type component, and a positioning component connected with the middle lower part of the door type component;

the spinning mounting assembly comprises a spinning mounting top connected below the transverse part of the door type assembly, a spinning mounting connecting part connected right below the top, and a spinning spraying sub assembly or a static pressure sub assembly connected to the spinning mounting connecting part; the rotary jetting subassembly 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 two 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 rotary spraying subassembly or a medium-pressure connecting rod in the static pressure subassembly.

Further, the bottom connecting assembly comprises a bottom connecting plate and bottom connecting anchor rods connected to 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 assemblies are respectively connected to the bottoms of the door type assemblies; the door type assembly comprises two vertical parallel door stand columns and a door beam connected to the tops of the two door stand columns, wherein door stand column sliding grooves are arranged in the vertical direction of the door stand columns, and the door stand column sliding grooves correspond to the telescopic assemblies and are highly corresponding to the telescopic assemblies in height.

Furthermore, 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 top parts of the two jacks are connected with a horizontal telescopic cross beam, and the telescopic cross beam penetrates through the door upright post sliding groove;

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 cross 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 mounting top and the telescopic cross beam.

The core pile is a steel pipe pile, or a precast concrete pile such as a pipe pile and a square pile, or an H-shaped or I-shaped steel 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 of reinforced concrete structures, or the original foundation is a reinforcement-free expansion foundation, an expansion foundation, a strip foundation under the column, a raft foundation or a box foundation such as a concrete foundation, a brick foundation, a rubble concrete foundation, a lime-soil foundation and the like.

The invention has the beneficial effects that:

1) according to the invention, the composite pile is a structural form of adding the core pile into the jet grouting pile, so that the pile foundation design of the storey-adding under different geological conditions under the existing building is facilitated on one hand, and the composite pile can be further utilized by designing the composite pile as the pile foundation at the lower part of the storey-adding, so that one pile has two purposes, and the construction process and cost are saved;

2) by applying the spinning all-in-one machine, the construction in a narrow space is facilitated, and the comprehensive construction is carried out on the spinning jet piles and the core piles under the condition of no displacement, so that the complex site construction conditions can be adapted, the construction procedures can be reduced, and the construction cost can be saved;

3) the construction method and the application device are easy to implement, convenient for underground layer increasing and reinforcing under the special working condition of the existing building and capable of greatly adapting to the underground soil layer condition 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 objects and other advantages of the invention may be realized and attained by the instrumentalities particularly pointed out in the specification.

Drawings

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

FIG. 2 is a schematic view 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 first schematic perspective view of a spinning integrated machine with a spinning and spraying subassembly;

FIG. 5 is a schematic perspective view II of a spinning integrated machine with a spinning and spraying subassembly;

FIG. 6 is a schematic front view of a spinning all-in-one machine with a spinning jet subassembly;

FIG. 7 is a schematic side view of a spinning all-in-one machine;

FIG. 8 is a schematic side cross-sectional view of a spinning all-in-one machine;

FIG. 9 is a schematic side cross-sectional view of a spinning manifold with a hydrostatic subassembly;

FIG. 10 is a schematic view of the construction of a demolished reinforced foundation and a partial composite pile;

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

Reference numerals: 1-soil body, 2-rotary spraying holes, 3-composite piles, 31-core piles, 32-rotary spraying piles, 4-original foundation, 5-original cushion layer, 6-rotary pressing integrated machine, 61-bottom connecting component, 611-bottom connecting plate, 612-bottom connecting anchor rod, 62-door component, 621-door upright post, 622-door beam, 623-door upright post sliding groove, 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 pressing mounting component, 651-rotary pressing mounting top, 652-rotary pressing mounting connecting part, 653-rotary spraying sub component, 654-static pressing sub component, 66-positioning components, 661-positioning transverse plates, 662-positioning connecting plates, 663-positioning cylinders, 664-positioning connecting rods, 7-reinforcing bearing platforms, 8-original columns, 9-new foundations, 10-new columns, 11-cushion layers, 12-new column reserved ribs and 13-slope protection piles.

Detailed Description

Taking a proposed atrium project as an example, the proposed atrium project is located in a Hui-shaped building in Beijing City, A, B, C, D, E, F commercial buildings at the periphery all have 1-3 floors of basements, and the atrium part originally has no basements. And (3) newly adding 1 layer of sinking plazas in the middle court position, expanding the underground space and communicating with the peripheral building functions. The proposed project is commercial, the underground is 1 layer, the frame structure is a raft foundation, the plane dimension is 148m in length, 36m in width and 6.0m in foundation burial depth. The long side direction of the north side is close to the commercial buildings A, a newly-added atrium sinking square is communicated with an underground chamber part, the burial depth of the foundation of the commercial buildings A is 6.0m, the middle part of the foundation is communicated with the door head of the atrium, the burial depth of the foundation is 2m, and the design and construction of underpinning and reinforcement are needed.

As shown in fig. 11, the range of the present underpinning is four independent column foundations at the door head, the burial depth of the original foundation 4 is 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 on one side. The project reinforcement construction period is urgent, the control requirements on noise and environmental pollution are high, normal business of the overground part cannot be influenced, and in addition, due to the limitation of the plane space and the construction net height of a construction site, the geological conditions are complex and the targeted design needs to be made.

When the engineering is designed and constructed, the following points need to be considered simultaneously: firstly, the existing foundation plate is not large in size and should not damage the original main reinforcement as much as possible, so that the diameter of the hole formed in the foundation plate is required to be as small as possible, but the diameter after pile forming needs to be as large as possible so as to obtain higher single pile bearing capacity; secondly, the lower part of the foundation is filled with miscellaneous filling soil and the original A-F seats have horizontal supporting structures such as unknown soil nails or anchor rods of the foundation pit, the pile position basically has no space for adjustment, and a drilling machine is required to have strong adaptability to the stratum, so that the pile can be formed at one time; thirdly, the space of the site is limited, and the equipment is required to be as small as possible, so that the requirements of low headroom and limited space operation are met; comprehensively considering the requirements, the jet grouting static pressure pile is adopted for underpinning for layer adding and subsequent reinforcement.

The construction method of the low-clearance lower jet grouting static pressure composite pile of the existing building 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 top slab positioned above the original foundation 4, and a building excavation layer and/or a reinforced soil body to be built are/is positioned below the original foundation 4. The main construction flow chart of the composite pile 3 in fig. 1 is shown. Referring to fig. 1 to 11, a method for constructing a low-clearance lower jet grouting static pressure composite pile of an existing building will be further described, in which the core pile 31 is a steel pipe pile in the present embodiment. Or precast concrete piles such as tubular piles and square piles, or H-shaped and I-shaped steel piles; the diameter of the core pile 31 is 108-400mm, and the strength of steel is not lower than Q235; these embodiments all ensure that the core pile 31 and the jet grouting cement pile work together; the core pile 31 is a steel pipe pile, the diameter of the steel pipe pile is generally 108-400mm, and the strength of steel is not lower than Q235. The foundation is a reinforced concrete structure, and as a variation, the foundation can be a concrete foundation, a brick foundation, a rubble concrete foundation, a cement-soil foundation and other reinforcement-free expansion foundations, a bar foundation under a column, a raft foundation or a box foundation. The method comprises the following specific steps:

combining an in-situ survey report and a supplementary survey report, dividing a soil layer of a proposed site in an existing building within a survey depth range into a large layer and a sub-layer according to the cause, and determining main physical and mechanical indexes, pile side friction resistance and pile end resistance of each soil layer within 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 replenishment survey.

Combining the original geological exploration and supplementary exploration reports, the soil layer of the planned site in the depth range of 60.0m below the natural ground at the deepest exploration can be divided into 8 large layers and sub-layers according to the cause, and the main physical mechanical index and the pile side friction resistance of each soil layer in the typical geological pile body design range. The depth of the filling soil in the fertilizer groove is 11.10 m. Through on-site excavation, excavation of peripheral deep foundation pits and the like, the lower part of the door head foundation is provided with miscellaneous filling soil and the original A-F seats are provided with horizontal supporting structures such as unknown soil nails or anchor rods of the foundation pits. And 1 layer of stable underground water is detected in the depth range of 25.0m under the current ground during the supplementary exploration. The stable water level burial depth is 9.50-9.60 m, and the underground water type is interlayer water.

Step two, carrying out tee joint leveling on the proposed site, grooving corresponding to the construction working face, designing the position of the composite pile 3 on the original foundation 4, measuring and setting out, and opening holes by static force; the pile end of the composite pile 3 extends into a bearing layer corresponding to the required 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 site construction parameters, a pile test is carried out; the pile hole of the composite pile 3 is guided by a rotary spraying component in a rotary spraying all-in-one machine 6, the rotary spraying pile 32 is formed into a rotary spraying hole 2 by triple-pipe high-pressure rotary spraying, then the rotary spraying pile 32 is formed by spraying cement paste, air and water, and then the static pressure of the core pile 31 is carried out by the rotary pressing all-in-one machine 6; the construction of the jet grouting pile 32 and the core pile 31 can be divided into two independent steps or alternatively performed in sections, the height of the spinning all-in-one machine 6 is smaller than the height from the top of the original foundation 4 to a floor or a top plate of a basement, and the spinning all-in-one machine 6 comprises a portal frame and a jet grouting subassembly 653 and a static pressure subassembly 654 detachably connected to the portal frame.

In this embodiment, before formal construction, 1 set of test pile tests is performed in order to debug equipment and obtain site construction parameters. The pile-test ending pile-pressing force is 2025 kN. When the load reaches the design value, the pile body settlement is about 3mm, and the bearing capacity design requirement and the settlement control requirement after the underpinning of the door head column are met. In this embodiment, the composite piles 3 are arranged in each individual foundation, and in order to support the superstructure load by newly adding, from the perspective of load transfer, the closer the newly added pile foundation is to the original structural column, the better, but the construction space of the composite piles 3 and the distance from the original structural column 8 are also considered in the pile position arrangement. Meanwhile, the position centroid of the pile is close to the position of the load gravity center as much as possible; in addition, the hole of the original foundation 4 needs to be as small as possible, and the outer diameter of the core pile 31 below is 245mm, and the diameter of the static hole is 400 mm.

In the embodiment, the applied device comprises a grooving machine for opening the hole of the original foundation 4 and a spinning all-in-one machine 6 for the composite pile 3; the grooving machine is used for grooving corresponding to the construction working face; the spinning integrated machine 6 is used for not displacing the construction core pile 31. The core pile 31 comprises a pile body, pile ribs connected to the inner part of the pile body, and pile pre-reserved ribs at the top of the pile body. Wherein, face to prop the pile body and set up core pile 31 by the jet grouting pile 32 and constitute, face to prop a muscle and face to prop a reservation muscle and be the steel reinforcement cage, face to prop a muscle and be located core pile 31 inboard, face to prop a reservation muscle anchor of stake and go into and consolidate cushion cap 7.

As shown in fig. 2 to 9, the spinning all-in-one machine 6 includes a door assembly 62, a bottom connecting assembly 61 connected between the door assembly 62 and the bottom base, a telescopic assembly 63 connected to both sides of the door assembly 62, a power assembly 64 connected to the middle upper portion of the door assembly 62, a spinning mounting connecting portion 652 connected to the power assembly 64 and located at the middle portion of the door assembly 62 in the transverse direction, and a positioning assembly 66 connected to the middle lower portion of the door assembly 62.

In this embodiment, the spin mount assembly 65 includes a spin mount top 651 attached below the lateral portion of the gate assembly 62, a spin mount link 652 attached directly below the top, a spin jet subassembly 653 attached to the spin mount link 652, or a static pressure subassembly 654; the jet subassembly 653 comprises a drill pipe, a drill bit, and a slip pipe; the hydrostatic subassembly 654 includes a compression link and a compression element. Installing a spinning integrated machine 6, aligning the pile machine according to the measured pile position, wherein the verticality of a drill rod in the spinning sub-assembly 653 is controlled by a double-line hammer arranged on a drilling machine and a horizontal ruler on the drilling machine, and if necessary, correcting by using a theodolite for 90 degrees in two directions, wherein the verticality deviation is not more than 1 percent; after the designed pile bottom elevation is drilled, 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 a soil body while sinking and drilling through double high-pressure jet flows in the horizontal direction of the drill bit and the bottom direction of the drill bit, and simultaneously spraying the slurry; and controlling the pressure of the high-pressure grouting pump, and spraying to the elevation of the designed pile top of the rotary spraying.

In the embodiment, when the jet grouting pile 32 is constructed, the weight of water and cement is measured according to the designed water cement ratio, and after the water and cement are uniformly stirred in a slurry stirring barrel, the mixture is filtered by a 20-mesh sieve 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 screen to prevent coarse particles from being sucked to block a drill nozzle. Drilling operation and water treatment: after the drilling machine is in place, the power head is started to rotate the drill rod, high-pressure air is provided for a drill bit at the bottom of the drill rod, soil is cut while sinking and drilling are carried out through double high-pressure jet flows in the horizontal direction of the drill bit and the bottom direction of the drill bit, and the designed pile bottom elevation is drilled; spraying high-pressure cement slurry for one time: after the designed pile bottom elevation is drilled, the power head is started to rotate the drill rod, the high-pressure grouting pump is started, high-pressure air and slurry are provided for the drill bit at the bottom of the drill rod, and the slurry is sprayed while soil is cut and the drill bit sinks through the double high-pressure jet flows in the horizontal direction 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 designed pile top of the rotary spraying.

In this embodiment, the positioning transverse plates 661 of the positioning assembly 66 include positioning transverse plates 662 detachably connected to two sides of the door assembly 62, positioning connecting rods 664 horizontally and vertically connected between the middle portions of the two positioning transverse plates 662, and positioning cylinders 663 connected to the outer ends 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.

In this embodiment, the bottom connecting assembly 61 includes a bottom connecting plate 611, bottom connecting anchor rods 612 connected to the bottom connecting plate 611 and disposed in the original foundation 4, and the bottom connecting anchor rods 612 are vertically arranged at intervals and/or obliquely arranged; the bottom connecting assemblies 61 are respectively connected to the bottoms of the door assemblies 62; the door type assembly 62 comprises two vertical parallel door uprights 621 and a door beam 622 connected to the tops of the two door uprights 621, a door upright chute 623 is vertically arranged on the door upright 621, and the door upright chute 623 corresponds to the arrangement of the telescopic assembly 63 and highly corresponds to the telescopic amount of the telescopic assembly 63 in height.

In this embodiment, the telescopic assembly 63 includes telescopic bases 631 respectively 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 to a horizontal telescopic beam 633, and the telescopic beam 633 passes through the door upright chute 623.

In this embodiment, the power assembly 64 includes an electric motor 641, an electric gear 642, a transmission belt 643 connected between the electric gear 642 and the electric motor 641, and a motor mounting base 644 connected between the electric motor 641 and the telescopic beam 633; the motorized gears 642 are correspondingly attached to corresponding rods of the spin jet subassembly 653 or the hydrostatic subassembly 654 between the spin mount top 651 and the telescoping beam 633.

In the third step, the spinning all-in-one machine 6 is connected with the original ground through a bottom connecting anchor rod 612, an anchoring section with the length of 550mm of the anchor rod is not less than 350mm, an exposed section is not less than 200mm, and the spinning all-in-one machine is embedded by adopting hole forming; the bottom-connected anchor rod 612 is subjected to 3 anti-pulling tests before construction, and the ultimate anti-pulling force of a single anchor rod is greater than 80 kN; 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, 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 portal frame of the spinning all-in-one machine 6 is fixed on the anchor bolt and the nut is locked.

Fourthly, 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; keeping the same vertical line without bias voltage, and sleeving a steel pile cap on the pile top during pile pressing and then pressing the pile; meanwhile, the last core pile 31 adopts a pile feeder 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, the slurry adopts cement paste, 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 3 MPa; the guniting pressure is more than or equal to 10 MPa; the airflow pressure is more than or equal to 0.7 MPa; the lifting speed is less than or equal to 300 mm/min; the lifting rotating speed is 18-20 r/min; the core pile 31 is pressed into the pile according to 2.5m sections, and the joint of the core pile 31 adopts butt welding and segment welding.

In the fourth step, the elevation of the top of the core pile 31 is not lower than the elevation of the designed pile top, and cement slurry in the core pile 31 is 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 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 reinforcing bearing platform 7 or are respectively connected with the inner ribs of the reinforcing bearing platform 7.

In this embodiment, the jet grouting pile 32 adopts a hole leading of a spinning integrated drilling machine, the jet grouting pile 32 adopts triple-pipe high-pressure jet grouting, the effective pile diameter of the jet grouting pile 32 is not less than 600mm, and the core pile 31 is implanted after the jet grouting. The outer diameter of the core pile 31 is 245mm, the wall thickness of the core pile 31 is 8mm, and the material of the core pile is Q345; the effective pile length is 21m, the support layer is formed by the fine sand of the sixth layer, and the characteristic value of the bearing capacity of a single pile is 375kN, and the total number of the piles is 24.

In this embodiment, before the core pile 31 is initially set, a reinforcement cage is embedded in the pile head, the lower portion of the reinforcement cage is inserted into the core pile 311.5m, and the upper portion is anchored into the reinforcement bearing plate not less than 1.1 m.

Fifthly, sealing the pile after the composite pile 3 is installed, then connecting foundation embedded bars at intervals around the original foundation 4 and in the vertical direction, connecting foundation embedded bars around the original column 8 and in the vertical direction, and designing a reinforcing bearing platform 7 and reinforcing ribs in the reinforcing bearing platform 7 corresponding to the original foundation 4; pouring to finish the reinforcement bearing platform 7 and the inner ribs of the reinforcement bearing platform 7, and excavating the soil body 1 at the lower part of the original foundation 4 until the bottom surface of the proposed foundation is excavated;

in the fifth step, when the reinforcing bearing platform 7 and the reinforcing ribs in the reinforcing bearing platform 7 are constructed, the peripheries of the original foundation 4 and the original column 8 are chiseled, and foundation planting ribs are symmetrically arranged; wherein the reinforcing bearing platform 7 inner rib at least comprises a double-layer horizontal rib, and the height range of the horizontal rib is connected with the original column 8. The design of the reinforced bearing platform 7 needs to meet the requirements of bending resistance, impact cutting resistance and shearing resistance; through calculation, the thickness of the reinforcing bearing platform 7 is 1100-1300mm, the design strength of concrete is C30, the diameter of the double-layer bidirectional reinforcing steel bar is 12mm, the distance between the double-layer bidirectional reinforcing steel bar and the double-layer bidirectional reinforcing steel bar 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 proposed 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 structure load is transmitted into the new column 10 through the original foundation 4, after the new column 10 is stably connected, the load is transferred from the composite pile 3 to the new column 10, 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 bearing plate is a key force transmission node for ensuring the core pile 31 to play a role. The mode of chemical bar planting is adopted in this engineering, realizes the transmission of shear force and the moment of flexure of former basis 4 and newly-increased reinforcement carrier plate. The method comprises the steps of roughening the surface layer of the existing foundation, drilling, cleaning holes, carrying out chemical bar planting, removing the surface layer of the foundation and coating an interface agent, and pouring together with a core pile 31 top reinforcement cage after binding of the foundation reinforcement, wherein after the project is used for 1 year, the maximum settlement of the foundation is about 4mm, and the maximum inclination rate of the building is 0.7 per mill, and all the design requirements are 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 pre-cut ribs 12 to facilitate the joining of the superstructure to form a unitary structure. The construction process is gradually developed according to the subareas of the construction operation, the symmetry of the engineering structure and the load is considered, and 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 above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that may be made by those skilled in the art within the technical scope of the present invention will be covered by the scope of the present invention.

Claims (10)

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

the method comprises the following specific steps:

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

step two, carrying out tee joint leveling on the proposed site, grooving corresponding to a construction working surface, designing the position of the composite pile (3) on the original foundation (4), measuring and setting out, and opening holes by static force; the pile end of the composite pile (3) extends into a bearing layer corresponding to the required embedded length of the composite pile (3), or the depth of the composite pile (3) extending into the bottom of a designed reinforced soil body;

step three, before formal construction, in order to debug equipment and obtain site construction parameters, a pile test is carried out; the pile hole of the composite pile (3) is guided by a rotary spraying component in a rotary pressing integrated machine (6), the rotary spraying pile (32) is formed by high-pressure rotary spraying according to engineering requirements and soil conditions, the rotary spraying pile (32) is formed by spraying cement paste, air and water, and then the 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 two independent steps of construction or alternatively performed in sections, the height of the spinning all-in-one machine (6) is smaller than the height from the top of the original foundation (4) to a floor or a top plate of a basement, and the spinning all-in-one machine (6) comprises a portal frame and a jet grouting subassembly (653) and a static pressure subassembly (654) which are detachably connected to the portal frame;

fourthly, the core pile (31) is positioned vertically, and the core pile (31) and the jet grouting pile (32) are concentric and coaxial; keeping the same vertical line without bias voltage, sleeving a steel pile cap before pile pressing, and then pressing the pile; meanwhile, the last section of core pile (31) adopts a pile feeder to control the elevation of the pile top;

fifthly, after the composite pile (3) is installed, pile sealing is carried out, and then the soil body (1) at the lower part of the original foundation (4) is excavated until the bottom surface of the proposed foundation is excavated; 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 rotary spraying static pressure composite pile under the existing building low clearance, according to the claim 1, is characterized in that, in the third step, the rotary spraying 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 rod are determined according to calculation, and the anchor rod is embedded by adopting a hole; 3 pullout tests are carried out on the anchor rod before construction, and the ultimate pullout resistance of a single anchor rod 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, 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 portal frame of the spinning all-in-one machine (6) is fixed on the anchor bolt and the nut is locked.

3. The construction method of the low-clearance lower rotary spraying static pressure composite pile of the existing building as claimed in claim 2, characterized in that when the rotary spraying all-in-one machine (6) is installed, the pile machine alignment is carried out according to the measured pile position, wherein the verticality of a drill rod in the rotary spraying sub-assembly (653) is dually controlled by a double-line hammer equipped on a drilling machine and a horizontal ruler on the drilling machine, if necessary, the verticality is corrected by 90 degrees in two directions by a theodolite, and the verticality deviation is not more than 1 percent.

4. The method for constructing the low-clearance rotary-jetting static-pressure composite pile in the existing building as claimed in claim 3, wherein after the drilling machine is in place, the drilling head is started to rotate the drill stem, and the high-pressure water is jetted or not jetted through the horizontal direction or the bottom direction of the drill bit to drill to the designed pile bottom elevation.

5. The method for constructing the low-clearance downward rotary-grouting static-pressure composite pile of the existing building as claimed in claim 4, wherein after the designed pile bottom elevation is drilled, the power head is started to rotate the drill stem, the high-pressure grouting pump is started, high-pressure air and slurry are supplied to the drill bit at the bottom of the drill stem, and the slurry is sprayed while cutting the soil body by the high-pressure jet flow in the horizontal direction of the drill bit or the direction of the bottom of the drill bit; and controlling the pressure of the high-pressure grouting pump, and spraying to the elevation of the designed pile top of the rotary spraying.

6. The construction method of the rotary spraying static pressure composite pile under the existing building low clearance according to claim 1 is characterized in that for the fourth step, the top of the composite pile (3) is embedded into the original foundation (4), wherein the effective pile diameter of the rotary spraying pile (32) is 400-1000mm or determined according to calculation, the slurry adopts cement paste, the cement amount meets the design requirement and is not less than 140kg/m, and the water cement ratio is 0.7-1.2; the design parameters of the jet grouting pile (32) are that the water spraying pressure is more than or equal to 20 MPa; the guniting pressure is more than or equal to 10 MPa; the airflow pressure is more than or equal to 0.7 MPa; the lifting speed is less than or equal to 300 mm/min; the core pile (31) is determined according to the net height according to the length of each section and pressed in sections, and the joint of the core pile (31) adopts a butt welding and segment welding mode or a mantle fiber connection mode or a groove welding mode;

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

the original foundation (4) and the original columns (8) are of a reinforced concrete structure, and the original foundation (4) is a reinforcement-free expansion foundation, an expansion foundation, a strip foundation under columns, a raft foundation or a box foundation such as a concrete foundation, a brick foundation, a rubble concrete foundation, a lime-soil foundation and the like.

7. The construction method of the low-clearance lower rotary jet static pressure composite pile of the existing building as claimed in claim 6, characterized in that for the fourth step, the height of the top of the core pile (31) is not lower than the designed pile top elevation, and the cement grout in the core pile (31) should be 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 core pile (31) 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 the reinforcing bearing platform (7) or are respectively connected with the inner ribs of the reinforcing bearing platform (7).

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

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 middle upper part of the door type assembly (62), a spinning mounting connecting part (652) connected with the power assembly (64) and located in the transverse inner middle part of the door type assembly (62), and a positioning assembly (66) connected with the middle lower part of the door type assembly (62);

the spinning mounting assembly (65) comprises a spinning mounting top part (651) connected below the transverse part of the door type assembly (62), a spinning mounting connecting part (652) connected right below the top part, a spinning spraying sub assembly (653) connected to the spinning mounting connecting part (652) or a static pressure sub assembly (654); the jet subassembly (653) comprises a drill pipe, a drill bit and a grouting pipe; the hydrostatic subassembly (654) includes a compression link and a compression element;

the positioning assembly (66) comprises positioning transverse plates (661) detachably connected with two sides of the door type assembly (62), positioning transverse plates (662) connected between the positioning transverse plates (661) and the door type assembly (62), positioning connecting rods (664) horizontally and vertically connected between the middle parts of the two positioning transverse plates (661), and positioning cylinders (663) 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 low-clearance rotary-jetting static-pressure composite pile construction method for the existing building is characterized in that the bottom connecting component (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), and the bottom connecting anchor rods (612) are arranged at intervals vertically and/or obliquely; the bottom connecting assemblies (61) are respectively connected to the bottoms of the door type assemblies (62); door-type subassembly (62) contain two vertical parallel door stand (621) and connect in door crossbeam (622) at two door stand (621) tops, be provided with door stand spout (623) on door stand (621) is vertical, and door stand spout (623) correspond flexible subassembly (63) setting and highly correspond flexible volume on the flexible subassembly (63) height.

10. The application device of the existing building low-clearance downward rotary spraying static pressure composite pile construction method is characterized in that the telescopic assembly (63) comprises telescopic bases (631) respectively 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 cross beam (633), and the telescopic cross beam (633) penetrates through a door upright chute (623);

the power assembly (64) comprises an electric motor (641), an electric gear (642), a transmission belt (643) connected between the electric gear (642) and the electric motor (641), and a motor mounting base (644) connected between the electric motor (641) and a telescopic cross beam (633); the electric 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).

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