CN113373972A

CN113373972A - Old pile lower connecting pile structure and construction method thereof

Info

Publication number: CN113373972A
Application number: CN202110602865.5A
Authority: CN
Inventors: 邹正盛; 刘健; 范利丹; 邹友峰; 王树仁; 王新宇; 顿志林; 任连伟; 秦莞臻
Original assignee: Henan University of Technology
Current assignee: Henan University of Technology
Priority date: 2021-05-31
Filing date: 2021-05-31
Publication date: 2021-09-10

Abstract

The invention relates to an old pile lower pile connecting structure, which comprises a bearing platform and an old pile, wherein the old pile is arranged below the bearing platform, a lower pile hole is formed in the pile bottom of the old pile, the section of the lower pile hole is circular, symmetrical fan-shaped or elliptical, and the section outline of the lower pile hole is larger than the minimum enveloping outline of the outer edge of the old pile; lower piles are distributed in the lower pile holes, the lower piles correspond to 2-4 old piles below the same bearing platform, and the lower piles are overlapped with the old piles; an upper pile hole is formed in one side of the old pile in parallel, the section outline of the upper pile hole is smaller than that of the lower pile hole, an upper pile is arranged in the upper pile hole, the upper pile and the lower pile are overlapped, and the bearing platform, the lower pile, the upper pile and the old pile are poured into a whole. The invention also relates to a pile splicing construction method for the old pile. According to the invention, the upper pile is implanted beside the old pile, and the lower pile is implanted below the old pile, so that the upper pile, the old pile and the lower pile are poured into a whole, the cooperative bearing capacity of a new structure and an old structure can be increased, and the construction of old city reconstruction and building reconstruction and extension can be well served.

Description

Old pile lower connecting pile structure and construction method thereof

Technical Field

The invention relates to the technical field of construction of old building piles, in particular to an old pile connecting structure and a construction method thereof.

Background

The vigorous development of the urbanization construction of China promotes the transformation of old cities and the transformation and expansion of buildings. The reconstruction of old cities and the reconstruction and expansion of buildings usually involve the demolition of old buildings to reconstruct high-rise buildings. To soft soil area or bad soil property district, the pile foundation is adopted to old-fashioned building more, and when this regional new construction adopted the pile foundation, the construction of new pile foundation can receive the influence of old building pile foundation.

At present, the common method for eliminating the influence of the old pile foundation is to remove a bearing platform and pull out the old foundation pile. And a new pile is constructed after the old pile foundation is pulled out, but if the quality of the old pile is good, the old pile foundation is pulled out as a waste pile, so that some disadvantages are caused, and the sustainable development concept is not met.

Once the old pile foundation is pulled out, not only the pulling out expense is high, the pulling out period is long, especially pile foundation interval is little in the pile group, the pulling out degree of difficulty is big one by one, also easily induce geological disasters simultaneously like the earth's surface sinks or even ground collapses, foundation soil destroys etc. seriously influence the bearing capacity of new foundation pile, be unfavorable for the construction of newly-built building.

The utility model discloses a pile foundation reinforced structure who adopts composite pile construction that authorization notice number CN204282388U discloses, its week side at former pile foundation constructs composite pile, connects composite pile and former pile foundation into a whole through the cushion cap, and the region that adds the stake is properly enlarged, solves the problem of the settlement and the bearing capacity insufficiency of former pile foundation. The method is a technology for compensating the performance insufficiency of the original pile foundation by adding the composite pile aiming at the condition that the bearing capacity of the pile foundation is insufficient and/or the settlement requirement can not be met, and is not suitable for the condition that the bearing capacity of the new pile foundation is greatly different from that of the old pile foundation and the bearing layer of the pile foundation is greatly changed.

Disclosure of Invention

The invention aims to solve the problems that the construction difficulty of removing an old pile is high and the bearing capacity of a foundation is easily influenced, and provides a pile splicing structure under the old pile and a construction method thereof.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a pile splicing structure under an old pile comprises a bearing platform and the old pile, wherein the cross section of the bearing platform is square, rectangular or polygonal, the old pile is arranged under the bearing platform, a pile inserting hole is formed in the pile bottom of the old pile, the cross section of the pile inserting hole is symmetrical fan-shaped, oval or circular, and the cross section contour of the pile inserting hole is larger than the minimum enveloping contour of the outer edge of the old pile;

lower piles are distributed in the lower pile holes and correspond to 2-4 old piles below the same bearing platform, the lower piles are of a pile structure formed by pouring concrete into a reinforcement cage, the reinforcement cage comprises main reinforcements and stirrups, the stirrups are of a rope structure made of flexible steel wire rods, an overlap height H1 exists between the lower piles and the old piles, and the range of H1 is 0.5-1.0 m;

an upper pile hole is formed in one side of the old pile in parallel, the section of the upper pile hole is circular, the section outline of the upper pile hole is smaller than that of the lower pile hole, an upper pile is arranged in the upper pile hole and is a cast-in-place pile, a precast pile or a plain pile, an overlap height H2 exists between the upper pile and the lower pile, the range of H2 is 0.5 m-1.0 m, and the bearing platform, the lower pile, the upper pile and the old pile are poured into a whole.

Furthermore, the lower pile corresponds to the two old piles, the lower pile is arranged between the two old piles, the upper pile is located at the center of the lower pile, and the section of the lower pile is in a symmetrical fan shape, an oval shape or a circular shape.

Furthermore, the lower pile corresponds to the three old piles, the upper pile is located at the center of the lower pile, and the cross section of the lower pile is circular.

Furthermore, the lower pile corresponds to the four old piles, the four old piles are grouped in pairs, the lower pile is arranged between the two old piles in the same group, the upper pile is positioned at the center of the lower pile, and the section of the lower pile is in an oval shape or a symmetrical fan shape; and the lower piles are arranged among the four old piles, and the cross sections of the lower piles are circular.

A construction method for connecting piles under old piles adopts the structure for connecting piles under old piles, and the method comprises the following steps:

step 1: pile information and engineering geological information are collected;

step 2: determining the type, rotary spraying mode and construction parameters of rotary spraying equipment;

and step 3: manufacturing an upper pile reinforcement cage and a lower pile reinforcement cage, removing a vertical bar when the lower pile reinforcement cage is manufactured, and replacing a thin steel bar with a thin steel wire rope by using a stirrup;

connecting the air bags in the cage and the side air bags with respective vent pipes, then compacting the lower pile reinforcement cage along the radial direction, and binding the lower pile reinforcement cage by adopting a nylon hasp;

and 4, step 4: and (3) bearing platform opening and reinforcing: if the bearing platform exists, a hole needs to be formed in the bearing platform, and the bearing platform is reinforced when necessary; if no bearing platform exists or the bearing platform is removed, necessary reinforcement is carried out on the range according to the safety requirement;

and 5: making leading holes of an upper pile hole and a lower pile hole: manufacturing guide holes of an upper pile hole and a lower pile hole with the diameters of 300-600 mm by adopting a conventional drilling technology;

step 6: pile hole making: adopting a high-pressure rotary jet cutting hole-forming technology, starting from the height of 0.5-1.0 m above the old pile bottom, using a rotary jet pipe to make a lower pile hole, enabling the rotary jet pipe to slowly descend along a guide hole of the lower pile hole, simultaneously jetting high-pressure hydraulic jet or high-pressure hydraulic jet and air jet to cut and destroy a soil body, enabling the soil impacted by high-pressure steam to become water-based thin slurry, enabling the water-based thin slurry to overflow the ground surface along the upper pile hole and enter a slurry pond, slowly descending the rotary jet pipe while carrying out rotary jet cutting on the soil body until the lower pile hole bottom is designed, and then removing sediment at the hole bottom;

and 7: hoisting the lower pile reinforcement cage: hoisting the lower pile reinforcement cage in a binding and tight state into a lower pile hole through an upper pile hole by a hoisting steel wire rope;

and 8: and (3) unfolding and positioning the lower pile reinforcement cage: inflating the air bags in the multi-layer cages to gradually increase, unbinding the nylon buckles, expanding the lower pile reinforcement cage radially outwards, and inflating the side air bags to be full and molded when the lower pile reinforcement cage is expanded sufficiently; when the air bag in the cage, the reinforcement cage, the side air bag and the lower pile hole wall are mutually restricted to reach balance, the horizontal positioning of the reinforcement cage is successful;

and step 9: pouring lower pile concrete: pouring concrete into the pile descending hole through the concrete guide pipe, when the concrete surface is close to the air bag in the lowermost cage, detaching the hoisting steel wire rope, releasing the air in the air bag in the lowermost cage, enabling the air bag to shrink and become shrunken and fall down, and lifting the air bag in the lowermost cage to the ground surface through slowly pulling the vent pipe;

continuously pouring concrete to be close to the air bag in the next layer of cage, deflating the air bag and lifting the air bag to the ground surface, repeating the steps until all the air bags in the lower pile reinforcement cage are lifted to the ground surface, releasing the air in the side air bag, filling cement paste into the side air bag, continuously pouring concrete to the bottom of the upper pile hole and vibrating the concrete to be compact;

step 10: hoisting the pile reinforcement cage: hoisting the upper pile reinforcement cage into the upper pile hole, then pouring upper pile body concrete, and vibrating to compact;

step 11: repairing a bearing platform: and when the upper pile concrete reaches the required strength, chiseling out a laitance solidified body at the top of the upper pile, cleaning the exposed section of the upper pile reinforcement cage, connecting the upper pile reinforcement cage with the pile cap reinforcement, and pouring concrete for forming to finish the pile cap restoration.

Further, the pile information includes pile types, pile numbers, pile positions, pile diameters, pile lengths, pile splicing positions, steel reinforcement cage parameters of old piles, old pile quality, pile cap parameters and the like of the old piles, upper piles and lower piles;

the engineering geological information comprises lithology and engineering geological property indexes thereof and underground water conditions.

Further, the rotary spraying type is single-pipe, double-pipe, triple-pipe or multi-pipe rotary spraying, the rotary spraying mode is swinging spraying and rotary spraying, and the construction parameters are water and air jet pressure, rotating speed and the like.

Furthermore, a plurality of movable barbs are annularly bound on the inner side of the lower pile reinforcement cage, one ends of the movable barbs are bent downwards, and the air bag in the cage is arranged below the movable barbs and limited by the movable barbs;

and limiting short ribs are also bound on the lower pile reinforcement cage and are positioned above the movable barbs.

Furthermore, the air bag in the cage is gradually enlarged, and the movable barb continuously deflects until the movable barb is limited by the limit short rib and does not deflect; and the side air bag is bound with the lower pile reinforcement cage.

Further, the lower end of the upper pile cage is required to be inserted into the lower pile opening to a depth that will form an elevation overlap with the lower pile cage, typically 0.5m to 1.0 m.

Through the technical scheme, the invention has the beneficial effects that:

the design idea of the invention is that a new hole is drilled/led to the bottom of a lower pile beside an old pile or among a plurality of old piles, then the technology of cutting soil into aqueous slurry by high-pressure rotary spraying is adopted to slowly and simultaneously carry out rotary spraying and overflow the aqueous slurry to the surface of the earth along an upper pile hole to a slurry pool from the old pile bottom to the upper height of 0.5-1.0 m, and the lower pile bottom is designed to be a lower pile hole; then, a lower pile reinforcement cage bound by nylon buckles is put into a lower pile hole, wherein an inner cage air bag and a side air bag are arranged on the reinforcement cage, the inner cage air bag is inflated to expand the reinforcement cage, and the side air bag is expanded with the reinforcement cage air bag to control the thickness of a pile reinforcement cage protection layer and assist the reinforcement cage to be centered; after the position of the steel reinforcement cage is controlled, concrete is poured into the hole through the guide pipe, meanwhile, concrete is also poured into the drilled hole of the old pile section to form an upper pile, and when the aperture of the upper pile hole is large, steel bars can be prepared, so that pile splicing is completed.

The invention has reasonable structural design, fully utilizes the original old pile structure, does not need to pull out the old pile, shortens the construction period, pours the upper pile beside the old pile and the lower pile below the old pile into a whole to bear the load together, reasonably utilizes the old pile, prolongs the service life of the old pile, improves the bearing capacity of the old pile foundation, and can well serve the construction of old city reconstruction and building reconstruction and extension.

The construction method of the lower pile extension of the old pile is a novel pile or pile group formed by reforming and connecting the old pile or the old pile group, has the advantages of cost saving, small foundation disturbance and avoidance of insufficient pile pulling conditions, can combine the pulling operation of the old pile, and can be well applied to the construction operation of reforming old cities and reforming and expanding buildings.

Drawings

Fig. 1 is a schematic diagram of a lower pile structure of an old pile in the embodiment of the invention.

Fig. 2 is a schematic diagram of a pile driving-down process for an old pile according to an embodiment of the present invention, wherein fig. (a) shows the making of a pile hole and the guiding of a pile hole, fig. (b) shows the making of a pile hole, fig. (c) shows the making of a pile hole, fig. (d) shows the hoisting of a pile cage, and fig. (e) shows the unfolding of a pile cage.

Fig. 3 is a second schematic diagram illustrating the old pile-underpinning construction process according to the embodiment of the present invention, wherein fig. (f) illustrates the placement of the underpinning concrete, (g) illustrates the suspension of the upper pile cage, (h) illustrates the placement of the upper pile concrete, and (i) illustrates the repair pile cap.

FIG. 4 is a schematic representation of the uninflated state of the air bags and side air bags within the cage in an embodiment of the present invention.

FIG. 5 is a schematic representation of the inflated condition of the air bag and side air bag in the cage of an embodiment of the present invention.

Fig. 6 is a construction forming diagram of a first pile foundation structure under an old pile under a rectangular bearing platform in the embodiment of the invention.

Fig. 7 is a construction forming diagram of a second original structure of the pile under the old pile under the polygonal bearing platform in the embodiment of the invention.

Fig. 8 is a construction forming diagram of a third pile foundation structure under an old pile under a square bearing platform in the embodiment of the invention.

The reference numbers in the drawings are as follows: the pile comprises a bearing platform 1, an old pile 2, a lower pile hole 3, a lower pile 4, a main rib 5, an upper pile hole 6, an upper pile 7, an inner cage air bag 8, a side air bag 9, a vent pipe 10, a nylon hasp 11, a rotary jet pipe 12, a hoisting steel wire rope 13, a movable barb 14, a limiting short rib 15, a binding wire 16 and a guide hole 17.

Detailed Description

The following detailed description of embodiments of the invention refers to the accompanying drawings in which:

as shown in fig. 1-5, a pile structure under old stake, including cushion cap 1 and

old stake

2, 1 cross-section of cushion cap is rectangle, square or polygonal one, lays under 1 cushion cap old stake 2, pile hole 3 has been seted up down at 2 pile bottoms of old stake, 3 cross-sections in pile hole are circular, the fan-shaped or oval-shaped one of symmetry, and 3 cross-sectional profile in pile hole is greater than the minimum envelope profile in 2 outer fringe of old stake.

Lower stake 4 has been laid in lower stake hole 3, and is corresponding, and lower stake 4 cross-section is the same with lower stake hole 3 cross-section, also is circular, symmetrical fan-shaped or oval one, every lower stake 4 is corresponding with 2~4 old stakes 2 under the same cushion cap 1, and a lower stake 4 can support two, three or four old stakes 2 promptly.

In this embodiment, lower 4 pile structures for steel reinforcement cage concreting makes, the steel reinforcement cage includes main muscle 5 and stirrup, the stirrup is the rope structure that flexible steel wire rod made, and is concrete, and the stirrup can be thin wire rope, adopts thin wire rope to replace traditional thin steel bar, and then steel reinforcement cage can follow its radial shrink or extension.

The lower pile 4 and the old pile 2 are overlapped, the overlapping height of the lower pile 4 and the old pile 2 is H1, and the range of H1 is 0.5 m-1.0 m.

An upper pile hole 6 is formed in one side of the old pile 2 in parallel, the section outline of the upper pile hole 6 is smaller than that of the lower pile hole 3, an upper pile 7 is arranged in the upper pile hole 6, the upper pile 7 is a cast-in-place pile, a precast pile or a plain pile, the upper pile 7 is overlapped with the lower pile 4, the overlapping height between the upper pile 7 and the lower pile 4 is H2, and the range of H2 is 0.5 m-1.0 m.

Go up stake 7 and extend cushion cap 1, and with cushion cap 1 overlap joint, cushion cap 1, lower stake 4, go up stake 7 and old stake 2 pour as an organic wholely.

The old pile-connecting pile structure takes the following three structures as basic structures:

the basic structure is as follows: the lower piles 4 correspond to the two old piles 2, the lower piles 4 are arranged between the two old piles 2, the upper piles 7 are located at the center of the lower piles 4, and the sections of the lower piles 4 are symmetrical fan-shaped, oval-shaped or circular.

The basic structure II: the lower pile 4 corresponds to the three old piles 2, the upper pile 7 is located at the center of the lower pile 4, and the section of the lower pile 4 is circular.

The basic structure is three: the lower pile 4 corresponds to the four old piles 2, the four old piles 2 are grouped in pairs, the lower pile 4 is arranged between the two old piles 2 in the same group, the upper pile 7 is positioned at the center of the lower pile 4, and the section of the lower pile 4 is oval or symmetrical fan-shaped;

or the lower piles 4 are arranged among the four old piles 2, the upper piles 7 are positioned at the center positions of the lower piles 4, and the sections of the lower piles 4 are circular.

A construction method for connecting old piles at the lower part adopts the structure for connecting old piles, takes the situation that one lower pile 4 is connected with two old piles 2 under the same bearing platform 1 as an example, and comprises the following steps:

step 1: pile information is collected, wherein the pile information comprises pile types, pile numbers, pile positions, pile diameters, pile lengths, pile splicing positions, steel reinforcement cage parameters, the quality of an old pile 2, parameters of a bearing platform 1 and the like of the old pile 2, an upper pile 7 and a lower pile 4;

and collecting engineering geological information, wherein the engineering geological information comprises lithology and engineering geological property indexes thereof, underground water conditions and the like.

Step 2: and determining the type of the rotary spraying equipment, the rotary spraying mode and the construction parameters.

The rotary spraying equipment is in a single-pipe, double-pipe, triple-pipe or multi-pipe rotary spraying type;

the rotary spraying mode is swinging spraying and rotary spraying, the cross section of the lower pile hole 3 is determined by the functions of rotary spraying equipment and the rotary spraying mode, the lower pile hole 3 with a symmetrical fan shape can be formed by swinging spraying, and the lower pile hole 3 with an oval or round shape can be formed by rotary spraying;

the construction parameters comprise water and air jet pressure, rotating speed and the like.

And step 3: and manufacturing the upper pile 7 and the lower pile 4 reinforcement cages, wherein the manufacturing method of the upper pile 7 reinforcement cage is a conventional method and is not described again.

The erection reinforcement is required to be removed when the lower pile 4 steel reinforcement cage is manufactured, the stirrup is replaced by a thin steel wire rope instead of the traditional thin steel bar, other methods are similar to the conventional method, after the lower pile 4 steel reinforcement cage is manufactured, the thin steel wire rope is adopted, so that the steel reinforcement cage is not limited in the radial direction, the steel reinforcement cage can be contracted or expanded in the radial direction, and the diameter and the shape of the steel reinforcement cage can be changed.

At 4 steel reinforcement cage inboard vertical intervals down set up at least two-layer uninflated annular cage inside bag 8, and the quantity of bag 8 is one in every layer of cage, and 8 quantity of bag are decided according to 4 steel reinforcement cage length down in the cage, and bag 8 can dismantle with 4 steel reinforcement cage of lower stake in the cage and be connected.

Specifically, a plurality of movable barbs 14 are annularly bound on the inner side of the reinforcement cage of the lower pile 4, one ends of the movable barbs 14 are bent downwards, and the air bag 8 in the cage is arranged below the movable barbs 14 and limited by the movable barbs 14; still the ligature has many spacing short muscle 15 on 4 steel reinforcement cages down, every spacing short muscle 15 corresponds with activity barb 14, just is located activity barb 14 top.

The position department that 4 steel reinforcement cage outside of lower stake, corresponding with gasbag 8 in the cage sets up annular limit gasbag 9 that does not aerify, and gasbag 8 is annular circle form in limit gasbag 9 and the cage, and gasbag 9 cross-section is less than 8 cross-sections of gasbag in the cage, limit

gasbag

9 and 4 steel reinforcement cage ligatures of lower stake, and concrete adoption ligature wire 16 is ligatured, and 16 ligature wires are coiled into the annular and are enclosed and establish in limit gasbag 9 outer fringe and leave certain surplus during the ligature to it is required that 9 inflation of limit gasbags expand.

After the cage inner air bags 8 and the side air bags 9 are arranged at the appointed positions of the steel reinforcement cage of the lower pile 4, the cage inner air bags 8 and the side air bags 9 are connected with respective vent pipes 10, the multi-layer cage inner air bags 8 can be respectively and independently communicated by the vent pipes 10, or the cage inner air bags 8 positioned at the uppermost layer of the steel reinforcement cage of the lower pile 4 are independently connected with one vent pipe 10, and the rest cage inner air bags 8 share one vent pipe 10; the side air bags 9 share one vent pipe 10 to be communicated;

and then the lower pile 4 reinforcement cage is compacted along the radial direction, namely the reinforcement cage is shrunk inwards, and then the lower pile 4 reinforcement cage is bound by adopting the nylon fastener 11.

And 4, step 4: 1, hole opening and reinforcing of the bearing platform: if the bearing platform 1 exists, a hole needs to be formed in the bearing platform 1, and the bearing platform 1 is reinforced if necessary so as to prevent the bearing platform 1 from sinking when the pile hole 3 is constructed; if the bearing platform 1 is not available or the bearing platform 1 is removed, necessary reinforcement is carried out on the range according to the safety requirement, people are far away from heavy objects, and a safety warning line is arranged.

And 5: and (3) making a leading hole 17 of the upper pile hole 6 and the lower pile hole 3: the guide holes 17 of the upper pile hole 6 and the lower pile hole 3 are manufactured by adopting the conventional drilling technology, and the diameter of the guide hole 17 of the lower pile hole 3 can be different from that of the upper pile hole 6 but is not larger than that of the upper pile hole 6.

The cross section of the upper pile hole 6 is circular, the diameter range of the upper pile hole is 300-600 mm, and if the upper pile 7 is a precast pile, the size of the designed cross section of the upper pile hole 6 is smaller than that of the upper pile 7.

Step 6: pile hole making 3: a high-pressure rotary jet cutting hole forming technology is adopted, a rotary jet pipe 12 is used for making a lower pile hole 3 from the height of 0.5-1.0 m above the bottom of an old pile 2, the rotary jet pipe 12 slowly descends along a guide hole 17 of the lower pile hole 3, high-pressure hydraulic jet flow or high-pressure hydraulic and air jet flow is jetted at the same time, soil bodies are cut and damaged, soil impacted by high-pressure steam becomes water-based thin slurry, the water-based thin slurry overflows from the ground surface along an upper pile hole 6 and enters a slurry pond, and sediment at the bottom of the hole is removed after hole forming.

And 7: hoisting the pile 4 steel reinforcement cage: hoisting the steel reinforcement cage of the lower pile 4 in a binding and tightening state into the lower pile hole 3 through the upper pile hole 6 by using a hoisting steel wire rope 13;

because the upper pile hole 6 is small and the lower pile hole 3 is large, the reinforcement cage of the lower pile 4 needs to be contracted into a small bundle shape so as to be convenient to enter the lower pile hole 3 from the upper pile hole 6.

And 8: unfolding and positioning of a lower pile 4 reinforcement cage: the air bags 8 in the multi-layer cage are inflated and gradually increased, the movable barbs 14 are continuously deflected along with the gradual increase of the air bags 8 in the cage until the air bags are limited by the short limiting ribs 15 and then do not deflect, and the air bags 8 in the cage are limited by the movable barbs 14 to be fixed in position.

Along with the gradual increase of the air bag 8 in the cage, the nylon hasp 11 is unbundled, the lower pile 4 steel reinforcement cage is expanded outwards in the radial direction, and when the lower pile 4 steel reinforcement cage is expanded fully, the lower pile 4 steel reinforcement cage is inflated into the side air bag 9 until the side air bag is fully formed; when the air bag 8, the reinforcement cage, the side air bag 9 and the lower pile hole 3 are mutually restricted to achieve balance in the cage, the reinforcement cage is successfully horizontally positioned, meanwhile, the side air bag 9 also assists the lower pile 4 reinforcement cage to enable the lower pile 4 reinforcement cage to be in a centered state in the lower pile hole 3, and the cross section outline of the lower pile 4 reinforcement cage is matched with the cross section outline of the lower pile hole 3.

And step 9: pouring concrete of the lower pile 4: pouring concrete into the pile drop hole 3 through a concrete guide pipe 17, when the concrete surface approaches to the air bag 8 in the lowermost cage, detaching the hoisting steel wire rope 13, releasing the gas in the air bag 8 in the lowermost cage, removing all the gas by a vacuum pump if necessary, shrinking the air bag, falling down, separating from the control of the movable barb 14, lifting the air bag 8 in the lowermost cage to the ground surface by slowly pulling the vent pipe 10, and simultaneously keeping the gas in the air bags 8 in the rest cages not to be released;

and continuously pouring concrete to be close to the air bags 8 in the next layer of cage, deflating the air bags and lifting the air bags to the ground surface, repeating the steps until all the air bags 8 in the multiple layers of cages are lifted to the ground surface, releasing the air in the side air bags 9, filling cement paste into the side air bags 9, and continuously pouring the concrete to the bottom of the upper pile hole 6 and vibrating the concrete to be compact.

Step 10: hoisting an upper pile 7 steel reinforcement cage: hoisting an upper pile 7 steel reinforcement cage into an upper pile hole 6, wherein the lower end of the upper pile 7 steel reinforcement cage is required to be inserted into a port 3 of a lower pile hole by a certain depth to form a certain overlap with a lower pile 4 steel reinforcement cage in elevation, and the overlap is usually 0.5-1.0 m; and then pouring concrete of the pile body of the upper pile 7, namely pouring the concrete according to the conventional method and requirements, and vibrating and compacting.

Compared with the lower pile 4, the upper pile 7 is in a small-size shape, can be a poured reinforced concrete pile, and can also be a reinforced concrete precast pile or other precast piles; the construction of the precast pile should meet the corresponding standard requirements;

if the diameter of the upper pile hole 6 is smaller, the upper pile 7 can be a cast-in-place concrete plain pile without steel bars, and the steel bar cages of the lower pile 4 and the upper pile 7 have two sizes but should be overlapped by a certain amount which meets the specification.

Step 11: repairing the bearing platform 1: and when the concrete of the upper pile 7 reaches the required strength, chiseling off a laitance solidified body at the top of the upper pile 7, cleaning an exposed section of a reinforcement cage of the upper pile 7, connecting the reinforcement cage with the bearing platform 1, pouring concrete for forming, and finishing the repair of the bearing platform 1.

And if the original bearing platform 1 is removed, constructing the bearing platform 1 according to the requirement of the newly designed bearing platform 1.

As shown in fig. 6 to 8, the three basic structures of the old pile extension pile are as follows:

construction for the basic structure one: taking the example of laying two old piles 2 below a rectangular bearing platform 1, adopting a single lower pile 4 to support two old piles 2 for construction, namely, one lower pile 4 is corresponding to one lower pile 2, one lower pile 4 is corresponding to one upper pile 7, the cross section outline of the lower pile 4 wraps the two old piles 2, adopting swing jet cutting hole-forming technology for construction, and making the cross section of the lower pile 4 into a symmetrical fan shape, as shown in fig. 6 (a); or constructing by adopting a periodic variable-pressure rotary jet cutting hole-forming technology, and manufacturing a lower pile 4 with an oval section as shown in fig. 6 (b); the construction can also be carried out by the isostatic spinning jet cutting hole-forming technology, and the cross section of the produced lower pile 4 is circular, as shown in fig. 6 (c).

And (3) construction aiming at the second basic structure: taking three old piles 2 arranged below a polygonal bearing platform 1 as an example, a single lower pile 4 is adopted to support three old piles 2 for construction, namely, one lower pile 4 is corresponding to one lower pile 4 below the three old piles 2, one lower pile 4 is corresponding to one upper pile 7, the cross section profile of the lower pile 4 wraps the three old piles 2, an isobaric rotary jet cutting hole forming technology is adopted for construction, and the cross section of the manufactured lower pile 4 is circular, as shown in fig. 7 (a).

And (3) construction aiming at the third basic structure: taking the example of laying four old piles 2 under a square bearing platform 1, a single lower pile 4 can be adopted to support the four old piles 2 for construction, namely the four old piles 2 are grouped in pairs, a single lower pile 4 is adopted to support two old piles 2, two lower piles 4 are laid, each lower pile 4 corresponds to one upper pile 7, swing jet cutting hole forming technology is adopted for construction, and the section of the produced lower pile 4 is in a symmetrical fan shape, as shown in fig. 8 (a); or constructing by adopting a periodic variable-pressure rotary jet cutting hole-forming technology, and manufacturing a lower pile 4 with an oval section as shown in fig. 8 (b);

or the four old piles 2 can be seen as a whole, only a single lower pile 4 is adopted to support the four old piles 2, the single lower pile 4 corresponds to an upper pile 7, the construction is carried out by adopting the isobaric rotary jet cutting hole forming technology, and the section of the manufactured lower pile 4 is circular, as shown in fig. 8 (c).

If five old piles 2 are arranged under the same bearing platform 1, combined construction can be carried out according to the three basic forms: five old piles 2 can be divided into two groups and three groups, wherein the two groups can refer to the construction of the first basic structure, and the three groups can refer to the construction of the second basic structure.

If six old piles 2 are arranged under the same bearing platform 1, combined construction can be carried out according to the three basic forms: the six old piles 2 may be divided into two groups and three groups in total, or three groups and two groups in total, the two groups may refer to the construction of the first basic structure, and the three groups may refer to the construction of the second basic structure.

If seven, eight, nine or even more old piles 2 are arranged under the same bearing platform 1, the combined construction can be carried out according to the three basic forms.

It should be noted that: 1. the isobaric in the isobaric rotary jet cutting pore-forming means that the pressure of water and air jet flow is fixed, so that a circular section can be generated; the hole is formed by periodical pressure change and rotary spray cutting, namely the pressure of water and air jet flow is periodically changed along the circumference, so that an oval section can be generated.

2. If one lower pile 4 corresponds to five or more old piles 2, the diameter of the lower pile 4 needs to be large, the instability possibility of a pile hole is high due to the large diameter of the lower pile 2, and therefore it is preferable to control one lower pile 4 to correspond to no more than four old piles 2.

3. The size of the cross section of the lower pile 4 depends on the number of old piles 2 supported by the lower pile, the design requirement of bearing capacity of the old pile and the supporting safety requirement of the old pile 2, and the cross section of the lower pile at least covers the minimum enveloping contour of the outer edge of the old pile 2.

4. The 4 steel reinforcement cages of lower stake are in the expansion back, and its cross-sectional profile not only is circular, and it expands into rather than the corresponding shape that matches according to 3 cross-sectional profiles in lower stake hole, and for example lower stake hole 3 is symmetrical fan-shaped, and its profile encloses and establishes symmetrical fan-shaped after 4 steel reinforcement cages of lower stake expand, and if 3 cross-sections in lower stake hole are oval again, its profile encloses and establishes oval after 4 steel reinforcement cages of lower stake expand.

5. If the cage air bag 8 can not be lifted to the ground surface, the construction method like the side air bag 9 is adopted, and cement paste is filled into the cage air bag 8 through the vent pipe 10 so as to be cast with the lower pile 4 into a whole.

6. The upper pile hole 6 can be a drilled pile hole; if the pile groups under the same bearing platform 1 are more and the pile spacing is small, the upper pile hole 6 arranged among the pile groups can be the pile hole left by pulling out the old pile 2, namely the construction method can be combined with the pulling out of the old pile 2 for use, the combination mode not only can save the cost, but also can avoid the inconvenience caused by the fact that the proper new hole cannot be arranged due to the small pile spacing, and also can avoid the engineering and environmental problems caused by the fact that the pile groups under the same bearing platform 1 are pulled out one by one.

The construction method of the pile extension under the old pile is a novel pile or pile group method formed by reforming and connecting the old pile 2 or the old pile 2 group, the formed pile is called as the pile extension under the old pile, and the method has the following advantages:

1. the cost is saved: the pile pulling cost is high, the pile needs to be rebuilt in situ after pile pulling, and the cost is only once for connecting the old pile 2, so that the construction cost can be saved.

2. Undisturbed foundation soil: the space section formed by pulling out the old pile 2 is larger than the original pile, the damage to foundation soil is large, especially pile groups are large, the foundation piles under one bearing platform 1 are multiple, the distance is small, the old pile 2 is completely pulled out and can generate strong disturbance to the foundation soil, the bearing capacity of a new pile in the area is greatly influenced, and the problem is avoided by connecting the old pile 2 downwards.

3. The problem of pile pulling condition insufficiency is avoided: the pile pulling by trepanning requires a larger soil area around the pile, particularly for pile group, the distance between the pile pulling condition and the old pile 2 under the bearing platform 1 is small, the pile pulling condition is difficult to meet, the condition of relaxation can cause geological disasters or increase the cost caused by auxiliary means, sometimes only individual pile has the condition, but the condition is difficult to ensure that all foundation piles under the same bearing platform 1 can meet the condition.

The method for connecting the old pile 2 downwards only drills holes in the foundation pile group, the hole spacing can be larger, the aperture adaptability is good, the problem that the drilling condition does not exist, and the problem that the pile pulling condition is insufficient is avoided.

4. Can be combined with pile pulling: the upper pile hole 6 can be designed on the position of an old pile 2, and the upper pile hole 6 is formed after the old pile 2 is pulled out, so that the section size of the upper pile hole 6 is widened, the upper pile 7 with larger diameter is designed, and the application condition of the lower connection method of the old pile 2 is widened.

5. Can be combined with a new pile: in some projects, under the condition that the old pile 2 is completely utilized to be reformed into the old pile-under-pile, the project requirements cannot be completely met, or only part of the old pile 2 has the reforming value or the reforming necessity, at this time, the old piles 2 in some proper positions can be reformed into the old pile-under-pile, some new piles are constructed, and the new piles and the old pile-under-pile are combined to form the optimal pile foundation combination form of the project, so that the project value is maximized.

The above-described embodiments are merely preferred embodiments of the present invention, and not intended to limit the scope of the invention, so that equivalent changes or modifications in the structure, features and principles described in the present invention should be included in the claims of the present invention.

Claims

1. The pile connecting structure under the old pile comprises a bearing platform (1) and the old pile (2), and is characterized in that the cross section of the bearing platform (1) is square, rectangular or polygonal, the old pile (2) is arranged under the bearing platform (1), a lower pile hole (3) is formed in the pile bottom of the old pile (2), the cross section of the lower pile hole (3) is symmetrical fan-shaped, oval or circular, and the cross section outline of the lower pile hole (3) is larger than the minimum enveloping outline of the outer edge of the old pile (2);

lower piles (4) are distributed in the lower pile holes (3), the lower piles (4) correspond to 2-4 old piles (2) below the same bearing platform (1), the lower piles (4) are of a pile structure made of concrete poured in a reinforcement cage, the reinforcement cage comprises main reinforcements (5) and stirrups, the stirrups are of a rope structure made of flexible steel wire rods, an overlap height H1 exists between the lower piles (4) and the old piles (2), and the range of H1 is 0.5-1.0 m;

old stake (2) one side parallel has been seted up and has been gone up stake hole (6), it is circular to go up stake hole (6) cross-section, goes up stake hole (6) cross-section profile and is less than down stake hole (3) cross-section profile, goes up to lay in stake hole (6) and is equipped with last stake (7), go up stake (7) for bored concrete pile, precast pile or plain stake, go up stake (7) with there is overlap height H2 down between stake (4), the H2 scope is 0.5m ~1.0m, cushion cap (1), lower stake (4), go up stake (7) and old stake (2) pour as an organic wholely.

2. An old pile lower pile structure according to claim 1, wherein said lower pile (4) corresponds to two of said old piles (2), said lower pile (4) is arranged between said two of said old piles (2), said upper pile (7) is located at the center of said lower pile (4), and the cross section of said lower pile (4) is one of a symmetrical fan shape, an oval shape or a circular shape.

3. An old pile lower pile structure according to claim 1, wherein said lower pile (4) corresponds to three of said old piles (2), said upper pile (7) is located at the center of said lower pile (4), and said lower pile (4) is circular in cross section.

4. An old pile lower pile structure according to claim 1, wherein the lower pile (4) corresponds to four old piles (2), the four old piles (2) are grouped in pairs, the lower pile (4) is arranged between two old piles (2) in the same group, the upper pile (7) is positioned at the center of the lower pile (4), and the cross section of the lower pile (4) is elliptical or symmetrical fan-shaped;

the lower piles (4) are arranged among the four old piles (2), and the sections (4) of the lower piles are circular.

5. A construction method of an old pile lower pile, characterized in that the old pile lower pile structure of any one of claims 1 to 4 is adopted, the method comprising the steps of:

step 1: pile information and engineering geological information are collected;

and step 3: manufacturing an upper pile (7) and a lower pile (4) reinforcement cage, removing a vertical bar when the lower pile (4) reinforcement cage is manufactured, replacing a thin steel bar with a thin steel wire rope by a stirrup, and other methods are the same as the conventional methods, after the lower pile (4) reinforcement cage is manufactured, vertically arranging at least two layers of uninflated cage inner air bags (8) at intervals on the inner side of the lower pile (4) reinforcement cage, detachably connecting the cage inner air bags (8) with the lower pile (4) reinforcement cage, and arranging uninflated side air bags (9) on the outer side of the lower pile (4) reinforcement cage and at positions corresponding to the cage inner air bags (8);

the air bag (8) and the side air bag (9) in the cage are connected with respective vent pipes (10), then the reinforcement cage of the lower pile (4) is compacted along the radial direction, and the reinforcement cage of the lower pile (4) is bound by adopting a nylon hasp (11);

and 4, step 4: the bearing platform (1) is perforated and reinforced: if the bearing platform (1) exists, holes need to be formed in the bearing platform (1), and the bearing platform (1) is reinforced when necessary; if the bearing platform (1) is not available or the bearing platform (1) is removed, necessary reinforcement is carried out on the range according to the safety requirement;

and 5: a hole (17) for making the upper pile hole (6) and the lower pile hole (3): manufacturing a guide hole (17) of the upper pile hole (6) and the lower pile hole (3) by adopting a conventional drilling technology;

step 6: making a pile hole (3): adopting a high-pressure rotary jet cutting hole forming technology, constructing a lower pile hole (3) by using a rotary jet pipe (12) from the height of 0.5-1.0 m from the bottom of an old pile (2) upwards, slowly descending the rotary jet pipe (12) while carrying out rotary jet cutting on a soil body until the bottom of the lower pile hole (3) is designed, and then removing sediments at the bottom of the hole;

and 7: hoisting a pile (4) and placing a steel reinforcement cage: hoisting the lower pile (4) reinforcement cage in a binding and tightening state into the lower pile hole (3) through the upper pile hole (6) by a hoisting steel wire rope (13);

and 8: the lower pile (4) is unfolded and positioned by a steel reinforcement cage: inflating the air bags (8) in the multi-layer cage to gradually increase, unbinding the nylon hasp (11), expanding the reinforcement cage of the lower pile (4) outwards in the radial direction, and inflating the side air bags (9) to be full and molded when the reinforcement cage of the lower pile (4) is expanded fully; when the air bag (8), the reinforcement cage, the side air bag (9) and the lower pile hole (3) are mutually restricted to reach balance, the reinforcement cage is successfully horizontally positioned;

and step 9: pouring concrete of the lower pile (4): concrete is poured into the pile descending hole (3) through a concrete guide pipe (17), when the concrete surface is close to the cage inner air bag (8) positioned at the lowest layer, a hoisting steel wire rope (13) is dismounted, the air in the cage inner air bag (8) at the lowest layer is released, the air bag is contracted to become flat and fall down, and the air bag (8) in the cage at the lowest layer is lifted to the ground surface through slowly pulling a vent pipe (10);

continuously pouring concrete to be close to the air bag (8) in the next layer of cage, deflating the air bag and lifting the air bag to the ground surface, repeating the steps until all the air bags (8) in the reinforcement cage of the lower pile (4) are lifted to the ground surface, releasing the air in the side air bag (9), filling cement paste into the side air bag (9), continuously pouring concrete to the bottom of the upper pile hole (6) and vibrating the concrete to be compact;

step 10: hoisting an upper pile (7) and a reinforcement cage: hoisting the reinforcement cage of the upper pile (7) into the upper pile hole (6), then pouring the pile body concrete of the upper pile (7), and vibrating to compact;

step 11: repair bearing platform (1): and when the concrete of the upper pile (7) reaches the required strength, chiseling off a laitance solidification body at the top of the upper pile (7), cleaning the exposed section of the reinforcement cage of the upper pile (7), connecting the reinforcement cage with the bearing platform (1) through steel bars, pouring concrete for forming, and finishing the restoration of the bearing platform (1).

6. The construction method of the old pile lower pile according to the claim 5, characterized in that the pile information includes the pile type, the pile number, the pile position, the pile diameter, the pile length, the pile splicing position, the steel reinforcement cage parameters of the old pile (2), the upper pile (7) and the lower pile (4), the quality of the old pile (2), the parameters of the bearing platform (1), etc.;

7. The construction method for an old pile extension pile under the old pile as claimed in claim 5, wherein the rotary spraying type is single pipe, double pipe, triple pipe or multiple pipe rotary spraying, the rotary spraying mode is swing spraying and rotary spraying, and the construction parameters are water and air jet pressure, rotating speed and the like.

8. The construction method for connecting the old pile downwards is characterized in that a plurality of movable barbs (14) are annularly bound on the inner side of a reinforcement cage of the lower pile (4), one end of each movable barb (14) is bent downwards, and a bag (8) in the cage is placed below the movable barbs (14) and limited by the movable barbs (14);

and a limiting short rib (15) is bound on the lower pile (4) reinforcement cage, and the limiting short rib (15) is positioned above the movable barb (14).

9. The construction method for connecting the lower pile of the old pile is characterized in that the air bag (8) in the cage is gradually enlarged, the movable barb (14) is continuously deflected until the movable barb is limited by the limit short rib (15) and then does not deflect;

and the side air bag (9) is bound with a reinforcement cage of the lower pile (4).

10. A method for piling according to claim 5, wherein the lower end of the reinforcement cage of the upper pile (7) is inserted into the opening of the lower pile hole (3) to a certain depth, and is overlapped with the reinforcement cage of the lower pile (4) in elevation by a certain amount, usually 0.5m to 1.0 m.