A pile connection structure under old pile and construction method thereof

Abstract

The present invention relates to a structure for connecting piles under old piles, comprising a cap and an old pile, wherein the old pile is arranged under the cap, a lower pile hole is provided at the bottom of the old pile, the cross section of the lower pile hole is a circular, symmetrical fan-shaped or elliptical shape, and the cross section profile of the lower pile hole is larger than the minimum envelope profile of the outer edge of the old pile; a lower pile is arranged in the lower pile hole, and the lower pile corresponds to 2 to 4 old piles under the same cap, and there is overlap between the lower pile and the old pile; an upper pile hole is provided in parallel on one side of the old pile, and the cross section profile of the upper pile hole is smaller than the cross section profile of the lower pile hole, an upper pile is arranged in the upper pile hole, and there is overlap between the upper pile and the lower pile, and the cap, the lower pile, the upper pile and the old pile are cast as one. The present invention also relates to a construction method for connecting piles under old piles. The present invention implants an upper pile beside the old pile and a lower pile below the old pile, so that the three are cast as one, and the coordinated bearing capacity of the new and old structures can be increased, and the construction of old city reconstruction and building expansion can be well served.

Description

Technical Field

[0001] The invention relates to the technical field of construction utilizing old building piles, and in particular to a pile connection structure under an old pile and a construction method thereof. Background Art

[0002] The vigorous development of urbanization in my country has given rise to the reconstruction of old cities and the expansion of buildings. The reconstruction of old cities and the expansion of buildings usually involve the demolition of old buildings and the reconstruction of high-rise buildings. In soft soil areas or areas with poor soil quality, old buildings mostly use pile foundations. When new buildings in this area use pile foundations, the construction of new pile foundations will be affected by the pile foundations of old buildings.

[0003] At present, the common method to eliminate the impact of old pile foundation is to remove the foundation and pull out the old piles. After the old pile foundation is pulled out, the new piles are constructed. However, if the old piles themselves are of good quality, it is a pity to pull them out as waste piles, which is not in line with the concept of sustainable development.

[0004] Once the old pile foundation is removed, not only is the removal cost high and the removal period long, especially when the distance between pile foundations in a pile group is small, it is difficult to remove them one by one. At the same time, it is also easy to induce geological disasters such as surface subsidence or even ground collapse, foundation soil damage, etc., which seriously affect the bearing capacity of the new piles and are not conducive to the construction of new buildings.

[0005] Authorization announcement number CN204282388U discloses a pile foundation reinforcement structure using composite piles. Composite piles are constructed around the original pile foundation, and the composite piles and the original pile foundation are connected as a whole through the cap. The pile-added area is appropriately expanded to solve the settlement and insufficient bearing capacity problems of the original pile foundation. It is a technology that uses composite piles to compensate for the insufficient performance of the original pile foundation in the case of insufficient bearing capacity of the pile foundation and / or failure to meet settlement requirements. It is not suitable for the case where the bearing capacity of the new and old pile foundations is very different and the bearing layer of the pile foundation has undergone a major change. Summary of the invention

[0006] In order to solve the problem that it is difficult to remove old piles and it is easy to affect the bearing capacity of the foundation, the present invention provides a pile connection structure under the old piles and a construction method thereof. By splicing and combining the old piles with the new piles, the service life of the old pile foundation is extended and the old pile foundation is suitable for new buildings.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A pile connection structure under an old pile, comprising a cap and an old pile, wherein the cap has a square, rectangular or polygonal cross section, the old pile is arranged under the cap, a pile hole is opened at the bottom of the old pile, the cross section of the pile hole is a symmetrical fan-shaped, elliptical or circular, and the cross-sectional profile of the pile hole is larger than the minimum envelope profile of the outer edge of the old pile;

[0009] The lower piles are arranged in the lower pile holes, and the lower piles correspond to 2 to 4 old piles under the same cap, and the lower piles are pile structures made of a steel cage poured with concrete, and the steel cage includes main bars and stirrups, and the stirrups are rope structures made of flexible steel wires, and there is an overlapping height H1 between the lower piles and the old piles, and the range of H1 is 0.5m to 1.0m;

[0010] An upper pile hole is opened parallel to one side of the old pile, the cross-section of the upper pile hole is circular, the cross-sectional profile of the upper pile hole is smaller than the cross-sectional profile of the lower pile hole, an upper pile is arranged in the upper pile hole, the upper pile is a cast-in-place pile, a prefabricated pile or a plain pile, there is an overlapping height H2 between the upper pile and the lower pile, and the range of H2 is 0.5m~1.0m, and the cap, lower pile, upper pile and old pile are cast as one.

[0011] 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 cross-section of the lower pile is a symmetrical sector, an ellipse or a circle.

[0012] 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.

[0013] Furthermore, the lower pile corresponds to the four old piles, the four old piles are grouped in pairs, the lower pile is arranged between two old piles in the same group, the upper pile is located at the center of the lower pile, and the cross-section of the lower pile is elliptical or symmetrical fan-shaped; the lower pile is arranged between the four old piles, and the cross-section of the lower pile is circular.

[0014] A construction method for connecting piles under old piles, using the above-mentioned connecting pile structure under old piles, the method comprises the following steps:

[0015] Step 1: Collect pile information and engineering geological information;

[0016] Step 2: Determine the type of jet grouting equipment, jet grouting method and construction parameters;

[0017] Step 3: Make the upper pile and lower pile steel cages. When making the lower pile steel cage, remove the frame reinforcement, and use thin steel wire ropes instead of thin steel bars for the stirrups. Other methods are the same as the conventional method. After the lower pile steel cage is made, at least two layers of uninflated cage air bags are arranged vertically at intervals inside the lower pile steel cage. The cage air bags are detachably connected to the lower pile steel cage. Uninflated side air bags are arranged on the outer side of the lower pile steel cage and at positions corresponding to the cage air bags.

[0018] The airbag inside the cage and the side airbag are connected to their respective ventilation pipes, and then the pile reinforcement cage is tightened radially and the pile reinforcement cage is tied with Velcro;

[0019] Step 4: Drill holes and reinforce the foundation: If there is a foundation, drill holes on it and reinforce it if necessary. If there is no foundation or it has been removed, reinforce the area as required according to safety requirements.

[0020] Step 5: Make the guide holes for the upper pile hole and the lower pile hole: Use conventional drilling technology to make the guide holes for the upper pile hole and the lower pile hole with a diameter of 300~600mm;

[0021] Step 6: Make the pile hole: Use high-pressure rotary jet cutting and hole-making technology, starting from a height of 0.5m~1.0m above the bottom of the old pile, use a rotary jet pipe to make the pile hole, the rotary jet pipe slowly descends along the lead hole of the pile hole, and at the same time sprays out high-pressure hydraulic jets or high-pressure hydraulic and air jets to cut and destroy the soil. The soil impacted by high-pressure water and gas becomes water-based thin mud, and overflows from the surface along the upper pile hole into the mud pool. The rotary jet pipe slowly descends while rotary jetting and cutting the soil until the designed bottom of the pile hole, and then removes the sediment at the bottom of the hole;

[0022] Step 7: Lifting the lower pile reinforcement cage: Lift the lower pile reinforcement cage in a tightly bound state through the upper pile hole into the lower pile hole by lifting the steel wire rope;

[0023] Step 8: Expand and position the pile reinforcement cage: Inflate the airbags in the multi-layer cage to gradually expand it, untie the Velcro, and expand the pile reinforcement cage radially outward. When the pile reinforcement cage is fully expanded, inflate the side airbags to full shape; when the airbags in the cage, the reinforcement cage, the side airbags and the pile hole wall restrain each other and reach a balance, the horizontal positioning of the reinforcement cage is successful;

[0024] Step 9: Pour concrete for the lower pile: Pour concrete into the lower pile hole through the concrete guide tube. When the concrete surface is close to the airbag in the cage at the bottom, remove the lifting wire rope to release the gas in the airbag in the cage at the bottom. The airbag shrinks and falls down. The airbag in the cage at the bottom is lifted to the surface by slowly pulling the ventilation pipe.

[0025] Continue pouring concrete until it is close to the airbags in the next layer of cages, deflate them and lift them to the surface, repeat this process until all the airbags in the lower pile steel cage are lifted to the surface, then release the gas in the side airbags, fill the side airbags with cement slurry, and continue pouring concrete to the bottom of the upper pile hole and vibrate to compact it;

[0026] Step 10: Lifting the upper pile reinforcement cage: Lift the upper pile reinforcement cage into the upper pile hole, then pour the upper pile body concrete and vibrate it to make it dense;

[0027] Step 11: Repair the cap: Wait until the concrete of the pile reaches the required strength, chisel off the solidified slurry on the top of the pile, clean the exposed section of the pile steel cage, connect it with the cap steel, pour concrete to form it, and complete the cap repair.

[0028] Furthermore, the pile information includes the pile type, pile number, pile position, pile diameter, pile length, pile connection position, reinforcement cage parameters, as well as the quality of the old pile, the upper pile, and the lower pile, and the like;

[0029] The engineering geological information includes rock properties and their engineering geological property indicators, and groundwater conditions.

[0030] Furthermore, the rotary spraying type is single-tube, double-tube, triple-tube or multi-tube rotary spraying, the rotary spraying mode is swing spraying and rotary spraying, and the construction parameters are water and air jet pressure, rotation speed, etc.

[0031] Furthermore, a plurality of movable barbs are circumferentially tied to the inner side of the pile reinforcement cage, one end of the movable barb is bent downward, and the airbag in the cage is placed under the plurality of movable barbs and is restricted by the movable barbs;

[0032] The pile reinforcement cage is also tied with limited short bars, and the limited short bars are located above the movable barbs.

[0033] Furthermore, the airbags in the cage gradually increase in size, and the movable barbs continuously deflect until they are restricted by the limiting short reinforcement and no longer deflect; the side airbags are tied to the pile reinforcement cage.

[0034] Furthermore, the lower end of the upper pile reinforcement cage is required to be inserted into the lower pile hole to a certain depth and to overlap with the lower pile reinforcement cage in elevation, usually by 0.5m~1.0m.

[0035] Through the above technical solution, the beneficial effects of the present invention are:

[0036] The design concept of the present invention is to drill a new hole / lead hole to the bottom of the lower pile beside the old pile or between multiple old piles, and then start from the height of 0.5m~1.0m above the bottom of the old pile, use the technology of high-pressure rotary spraying to cut the soil into water-based thin mud and slowly spray it downwards, and the water-based thin mud overflows the surface along the upper pile hole to the mud pool, so as to form the designed lower pile bottom elevation into the lower pile hole; then lower the lower pile steel bar cage tied with nylon buckle into the lower pile hole, wherein the cage air bag and the side air bag are placed on the steel bar cage, the cage air bag is inflated to expand the steel bar cage, and the side air bag is expanded accordingly to control the thickness of the pile steel bar cage protective layer and assist the steel bar cage to be centered; after the position of the steel bar cage is controlled, concrete is poured into the hole through a catheter, and at the same time, concrete is poured into the drilled hole of the old pile section to form an upper pile. When the diameter of the upper pile hole is large, steel bars can be prepared, and the pile connection is completed.

[0037] The present invention has a reasonable structural design and makes full use of the original old pile structure. It does not need to pull out the old piles, shortens the construction period, and by implanting an upper pile next to the old pile and a lower pile below the old pile, the three are cast as one and bear the load together. The old piles are reasonably utilized, the service life of the old piles is extended, and the bearing capacity of the old pile foundation is improved, which can well serve the construction of old city reconstruction and building renovation and expansion.

[0038] The construction method of connecting old piles to piles of the present invention is a method of using old piles or old pile groups to transform and connect to form a new type of pile or pile group. It has the advantages of saving costs, small foundation disturbance, and avoiding the problem of insufficient conditions for pulling out piles. At the same time, it can also be combined with the removal of old piles, and can be well applied to the construction operations of old city reconstruction and building renovation and expansion. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic diagram of the pile connection structure under the old pile in an embodiment of the present invention.

[0040] Figure 2 It is one of the schematic diagrams of the construction process of connecting piles under old piles in an embodiment of the present invention, wherein Figure (a) shows the construction of the upper pile hole and the lower pile hole, Figure (b) shows the construction of the lower pile hole, Figure (c) shows the forming of the lower pile hole, Figure (d) shows the hanging of the lower pile steel cage, and Figure (e) shows the unfolding of the lower pile steel cage.

[0041] Figure 3 This is the second schematic diagram of the construction process of connecting the old piles under the embodiment of the present invention, wherein Figure (f) is pouring the lower pile concrete, Figure (g) is hanging the upper pile steel cage, Figure (h) is pouring the upper pile concrete, and Figure (i) is repairing the foundation.

[0042] Figure 4 It is a schematic diagram of the uninflated state of the airbags in the cage and the side airbags in an embodiment of the present invention.

[0043] Figure 5 It is a schematic diagram of the inflated state of the airbags in the cage and the side airbags in an embodiment of the present invention.

[0044] Figure 6 It is a construction forming diagram of a basic structure 1 of connecting piles under an old pile under a rectangular cap in an embodiment of the present invention.

[0045] Figure 7 It is a construction forming diagram of the basic structure 2 of connecting piles under the polygonal cap in the embodiment of the present invention.

[0046] Figure 8 It is a construction forming diagram of the basic structure three of the connection pile under the old pile under the square cap in the embodiment of the present invention.

[0047] The numbers in the attached figure are: 1 is the base, 2 is the old pile, 3 is the pile hole, 4 is the lower pile, 5 is the main reinforcement, 6 is the upper pile hole, 7 is the upper pile, 8 is the air bag in the cage, 9 is the side air bag, 10 is the ventilation pipe, 11 is the nylon buckle, 12 is the rotary spray pipe, 13 is the lifting wire rope, 14 is the movable barb, 15 is the limiting short reinforcement, 16 is the binding wire, and 17 is the lead hole. DETAILED DESCRIPTION

[0048] The specific implementation of the present invention is described in detail below with reference to the accompanying drawings:

[0049] like Figure 1~Figure 5 As shown, a pile-connected structure under an old pile comprises a cap 1 and an old pile 2, wherein the cap 1 has a rectangular, square or polygonal cross section, the old pile 2 is arranged under the cap 1, a pile hole 3 is opened at the bottom of the old pile 2, and the pile hole 3 has a circular, symmetrical fan-shaped or elliptical cross section, and the cross-sectional contour of the pile hole 3 is larger than the minimum envelope contour of the outer edge of the old pile 2.

[0050] A lower pile 4 is arranged in the pile hole 3. Correspondingly, the cross-section of the lower pile 4 is the same as that of the lower pile hole 3, and is also circular, symmetrical fan-shaped or elliptical. Each of the lower piles 4 corresponds to 2 to 4 old piles 2 under the same cap 1, that is, one lower pile 4 can support two, three or four old piles 2.

[0051] In this embodiment, the lower pile 4 is a pile structure made of a steel cage cast in concrete. The steel cage includes main bars 5 and stirrups. The stirrups are rope structures made of flexible steel wires. Specifically, the stirrups can be thin steel wire ropes. Thin steel wire ropes are used to replace traditional thin steel bars, so that the steel cage can shrink or expand along its radial direction.

[0052] There is an overlap between the lower pile 4 and the old pile 2 , and the overlapping height between the lower pile 4 and the old pile 2 is H1 , and the range of H1 is 0.5m~1.0m.

[0053] An upper pile hole 6 is opened parallel to one side of the old pile 2, and the cross-sectional profile of the upper pile hole 6 is smaller than the cross-sectional profile of the lower pile hole 3. An upper pile 7 is arranged in the upper pile hole 6, and the upper pile 7 is a cast-in-place pile, a prefabricated pile or a plain pile. There is an overlap between the upper pile 7 and the lower pile 4, and the overlapping height between the upper pile 7 and the lower pile 4 is H2, and the range of H2 is 0.5m~1.0m.

[0054] The upper pile 7 extends to the cap 1 and overlaps with the cap 1. The cap 1, the lower pile 4, the upper pile 7 and the old pile 2 are cast as a whole.

[0055] The basic structures of the pile connection under the old pile are as follows:

[0056] Basic structure 1: The lower pile 4 corresponds to the two old piles 2, the lower pile 4 is arranged between the two old piles 2, the upper pile 7 is located at the center of the lower pile 4, and the cross-section of the lower pile 4 is a symmetrical sector, ellipse or circle.

[0057] Basic structure 2: 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 cross section of the lower pile 4 is circular.

[0058] Basic structure three: the lower pile 4 corresponds to the four old piles 2, the four old piles 2 are arranged in groups of two, the lower pile 4 is arranged between two old piles 2 in the same group, the upper pile 7 is located at the center of the lower pile 4, and the cross-section of the lower pile 4 is an ellipse or a symmetrical sector;

[0059] Or the lower pile 4 is arranged between the four old piles 2, the upper pile 7 is located at the center of the lower pile 4, and the cross section of the lower pile 4 is circular.

[0060] A construction method for connecting piles under old piles, using the above-mentioned connecting pile structure under old piles, taking the case where a lower pile 4 is connected to two old piles 2 under the same cap 1 as an example, the method comprises the following steps:

[0061] Step 1: Collect pile information, including pile type, number of piles, pile position, pile diameter, pile length, pile connection position, reinforcement cage parameters, quality of old pile 2, parameters of cap 1, etc. of old pile 2, upper pile 7 and lower pile 4;

[0062] Collect engineering geological information, including rock properties and their engineering geological property indicators, groundwater conditions, etc.

[0063] Step 2: Determine the type of jet grouting equipment, jet grouting method and construction parameters.

[0064] The type of the rotary spraying equipment is single-tube, double-tube, triple-tube or multi-tube rotary spraying;

[0065] The rotary spraying method includes swing spraying and rotary spraying. The function of the rotary spraying equipment and the rotary spraying method determine the cross section of the pile hole 3. The swing spraying can make a symmetrical fan-shaped pile hole 3, and the rotary spraying can make an elliptical or circular pile hole 3.

[0066] The construction parameters include water and air jet pressure, rotation speed, etc.

[0067] Step 3: Make the upper pile 7 and the lower pile 4 reinforcement cages. The method for making the upper pile 7 reinforcement cage is a conventional method and will not be repeated here.

[0068] When making the 4 pile reinforcement cage, the frame reinforcement needs to be removed, and the stirrups are replaced by thin steel wire ropes instead of traditional thin steel bars. Other methods are the same as conventional methods. After the 4 pile reinforcement cage is made, the thin steel wire rope is used, and the radial direction of the reinforcement cage is not restricted. The reinforcement cage can shrink or expand radially, and its diameter and shape are variable.

[0069] At least two layers of uninflated annular cage airbags 8 are vertically spaced inside the steel cage of the lower pile 4. The number of cage airbags 8 is one in each layer. The number of cage airbags 8 depends on the length of the steel cage of the lower pile 4. The cage airbags 8 are detachably connected to the steel cage of the lower pile 4.

[0070] Specifically, a plurality of movable barbs 14 are circumferentially tied to the inner side of the steel cage of the lower pile 4, one end of the movable barbs 14 is bent downward, and the airbag 8 in the cage is placed below the plurality of movable barbs 14 and restricted by the movable barbs 14; a plurality of limiting short bars 15 are also tied to the steel cage of the lower pile 4, each of the limiting short bars 15 corresponds to the movable barbs 14 and is located above the movable barbs 14.

[0071] An uninflated annular side airbag 9 is arranged on the outside of the steel cage of the lower pile 4 and at a position corresponding to the airbag 8 in the cage. The side airbag 9 and the airbag 8 in the cage are both annular. The cross-section of the side airbag 9 is smaller than that of the airbag 8 in the cage. The side airbag 9 is tied to the steel cage of the lower pile 4, specifically by using binding wire 16. When binding, the binding wire 16 is wound into a ring and arranged around the outer edge of the side airbag 9, leaving a certain margin to prepare for the expansion of the side airbag 9.

[0072] After the airbags 8 and the side airbags 9 are placed at the designated positions of the steel cage of the lower pile 4, the airbags 8 and the side airbags 9 are connected to their respective ventilation pipes 10. The airbags 8 in the multiple layers of the cage can be connected separately by the ventilation pipes 10, or the airbags 8 in the cage located at the top layer of the steel cage of the lower pile 4 can be connected to a ventilation pipe 10 separately, and the remaining airbags 8 in the cage share a ventilation pipe 10; multiple side airbags 9 share a ventilation pipe 10 for communication;

[0073] Then the reinforcement cages of the pile 4 are tightened radially, that is, the reinforcement cages are shrunk inwards, and then the reinforcement cages of the pile 4 are bound with nylon buckles 11.

[0074] Step 4: Drill holes and reinforce cap 1: If there is cap 1, it is necessary to drill holes on cap 1 and reinforce cap 1 if necessary to prevent it from sinking during the construction of pile hole 3. If there is no cap 1 or cap 1 has been removed, it is also necessary to reinforce the area according to safety needs, keep people and heavy objects away, and set up safety warning lines.

[0075] Step 5: Make the guide hole 17 for the upper pile hole 6 and the lower pile hole 3: Use conventional drilling technology to make the guide hole 17 for the upper pile hole 6 and the lower pile hole 3. The diameter of the guide hole 17 of the lower pile hole 3 may be inconsistent with the diameter of the upper pile hole 6, but not larger than the diameter of the upper pile hole 6.

[0076] The cross section of the upper pile hole 6 is circular, and its diameter ranges from 300 to 600 mm. If the upper pile 7 adopts a prefabricated pile, the upper pile hole 6 should be smaller than the designed cross section size of the upper pile 7.

[0077] Step 6: Make the pile hole 3: Use high-pressure rotary jet cutting and hole-making technology, start from the height of 0.5m~1.0m upward from the bottom of the old pile 2, and use the rotary jet pipe 12 to make the pile hole 3. The rotary jet pipe 12 slowly descends along the lead hole 17 of the pile hole 3, and at the same time sprays out high-pressure hydraulic jets or high-pressure hydraulic and air jets to cut and destroy the soil. The soil impacted by the high-pressure water and gas becomes water-based thin mud, and overflows from the surface along the upper pile hole 6 into the mud pool. After the hole is formed, the sediment at the bottom of the hole is removed.

[0078] Step 7: Lifting the lower pile 4 reinforcement cage: Lift the lower pile 4 reinforcement cage in a tightly bound state through the upper pile hole 6 into the lower pile hole 3 by lifting the wire rope 13;

[0079] Since the upper pile hole 6 is small and the lower pile hole 3 is large, the steel cage of the lower pile 4 needs to be compressed into a small bundle to facilitate entering the lower pile hole 3 from the upper pile hole 6.

[0080] Step 8: Deployment and positioning of the pile 4 reinforcement cage: Inflate the airbags 8 in the multi-layer cage and gradually enlarge them. As the airbags 8 in the cage gradually enlarge, the movable barbs 14 continue to deflect until they are restricted by the limiting short bars 15 and no longer deflect. At this time, the airbags 8 in the cage are restricted by the movable barbs 14 to fix their position.

[0081] As the airbag 8 in the cage gradually increases in size, the nylon fastener 11 is untied, and the reinforcement cage of the pile 4 expands radially outward. When the reinforcement cage of the pile 4 is fully expanded, it is inflated into the side airbag 9 until it is full and formed; when the airbag 8 in the cage, the reinforcement cage, the side airbag 9 and the wall of the pile hole 3 restrain each other and reach a balance, the horizontal positioning of the reinforcement cage is successful, and at the same time, the side airbag 9 also assists the reinforcement cage of the pile 4 to make it centered in the pile hole 3. At this time, the cross-sectional contour of the reinforcement cage of the pile 4 is adapted to the cross-sectional contour of the pile hole 3.

[0082] Step 9: pouring concrete for the lower pile 4: pouring concrete into the lower pile hole 3 through the concrete conduit 17. When the concrete surface is close to the airbag 8 in the cage at the lowest layer, remove the lifting wire rope 13 to release the gas in the airbag 8 in the cage at the lowest layer. If necessary, connect a vacuum pump to exhaust all the gas therein. The airbag shrinks and falls down, breaking away from the control of the movable barb 14. The airbag 8 in the cage at the lowest layer is lifted to the surface by slowly pulling the vent pipe 10, while the gas in the airbags 8 in the cages of the remaining layers is kept from being released.

[0083] Continue pouring concrete until it approaches the next layer of cage airbags 8, deflate it and lift it to the ground surface, and repeat this process until all the multiple layers of cage airbags 8 are lifted to the ground surface, then release the gas in the side airbags 9, fill the side airbags 9 with cement slurry, and continue pouring concrete to the bottom of the upper pile hole 6 and vibrate it to make it dense.

[0084] Step 10: Lifting the reinforcement cage of the upper pile 7: Lift the reinforcement cage of the upper pile 7 into the upper pile hole 6. The lower end of the reinforcement cage of the upper pile 7 is required to be inserted into the lower pile hole 3 to a certain depth and overlap with the reinforcement cage of the lower pile 4 in elevation, usually 0.5m~1.0m; then pour the concrete of the upper pile 7, that is, pour the concrete according to conventional methods and requirements, and vibrate it to make it dense.

[0085] Compared with the lower pile 4, the upper pile 7 is a small-sized pile, which can be a cast-in-place reinforced concrete pile, or a reinforced concrete precast pile or other precast pile; the construction of the precast pile should meet the corresponding specification requirements;

[0086] If the diameter of the upper pile hole 6 is smaller, the upper pile 7 can be a cast-in-place concrete pile without reinforcement. Although the reinforcement cages of the lower pile 4 and the upper pile 7 are of two sizes, there should be a certain amount of overlap that meets the specifications.

[0087] Step 11: Repairing the cap 1: Wait until the concrete of the upper pile 7 reaches the required strength, chisel off the solidified slurry on the top of the upper pile 7, clean the exposed section of the steel cage of the upper pile 7, connect it with the steel bars of the cap 1, pour concrete to form it, and complete the repair of the cap 1.

[0088] If the original cap 1 is removed, the cap 1 is constructed according to the requirements of the new design cap 1.

[0089] like Figure 6~Figure 8 As shown in the figure, the three basic structures of connecting piles under the old piles mentioned above have the following construction forms:

[0090] For the construction of basic structure 1: take the arrangement of two old piles 2 under the rectangular cap 1 as an example, a single lower pile 4 is used to support the two old piles 2, that is, one lower pile 4 corresponds to one upper pile 7 under the two old piles 2, and one lower pile 4 corresponds to one upper pile 7. The cross-sectional contour of the lower pile 4 wraps the two old piles 2, and the swing jet cutting hole-forming technology is used to construct the cross-sectional shape of the lower pile 4 to be symmetrical fan-shaped, such as Figure 6 (a); or use periodic variable pressure jet cutting hole forming technology to construct the pile 4 with an elliptical cross section, such as Figure 6 (b); isobaric jet jet cutting and hole-forming technology can also be used to construct the pile 4 with a circular cross section, such as Figure 6 (c) shown.

[0091] For the construction of basic structure 2: take the arrangement of three old piles 2 under the polygonal cap 1 as an example, a single lower pile 4 is used to support the construction of the three old piles 2, that is, one lower pile 4 corresponds to the bottom of the three old piles 2, and one lower pile 4 corresponds to an upper pile 7. The cross-sectional contour of the lower pile 4 wraps the three old piles 2, and the isobaric rotary jet cutting and hole-forming technology is used to construct the cross-sectional shape of the lower pile 4 to be circular, such as Figure 7 (a) shown.

[0092] For the construction of basic structure three: taking the arrangement of four old piles 2 under the square cap 1 as an example, a single lower pile 4 can be used to support the four old piles 2 for construction, that is, the four old piles 2 can be grouped in pairs, and a single lower pile 4 can be used to support two old piles 2, and two lower piles 4 are arranged, each lower pile 4 corresponds to an upper pile 7, and the swing spray cutting hole forming technology is used for construction, so that the cross section of the lower pile 4 is symmetrical fan-shaped, such as Figure 8 (a); or use periodic variable pressure jet cutting hole forming technology to construct the pile 4 with an elliptical cross section, such as Figure 8 (b) as shown;

[0093] The four old piles 2 can also be regarded as a whole, and only a single lower pile 4 is used to support the four old piles 2. The single lower pile 4 corresponds to an upper pile 7. The isobaric jet cutting and hole-forming technology is used to construct the lower pile 4 with a circular cross-section. Figure 8 (c) shown.

[0094] If five old piles 2 are arranged under the same foundation 1, they can be constructed in combination according to the three basic forms mentioned above: the five old piles 2 can be divided into groups of two or three. Groups of two can refer to the construction of basic structure one, and groups of three can refer to the construction of basic structure two.

[0095] If six old piles 2 are arranged under the same foundation 1, they can be constructed in combination according to the three basic forms mentioned above: the six old piles 2 can be divided into two groups, a total of three groups, or divided into three groups, a total of two groups. The construction of two groups can refer to the construction of basic structure one, and the construction of three groups can refer to the construction of basic structure two.

[0096] If seven, eight, nine or even more old piles 2 are arranged under the same cap 1, they can be constructed in combination according to the three basic forms mentioned above.

[0097] It should be noted that: 1. The isobaric method in isobaric jet milling refers to that the pressure of the water and air jets is fixed, so that a circular cross-section can be generated; the periodic variable pressure jet milling refers to that the pressure of the water and air jets changes periodically along the circumference, so that an elliptical cross-section can be generated.

[0098] 2. If one pile 4 corresponds to five or more old piles 2, the diameter of the pile 4 needs to be large. A large diameter of the pile 2 is likely to cause a high possibility of instability in the pile hole, so it is advisable to control one pile 4 to correspond to no more than four old piles 2.

[0099] 3. The cross-sectional dimensions of the lower pile 4 depend on the number of old piles 2 it supports, the bearing capacity design requirements of the connecting piles under the old piles, and the support safety requirements for the old piles 2. Its cross-sectional dimensions should at least cover the minimum envelope contour of the outer edge of the old pile 2.

[0100] 4. After the lower pile 4 reinforcement cage is unfolded, its cross-sectional profile is not only circular, but it is unfolded into a corresponding shape matching the cross-sectional profile of the lower pile hole 3. For example, if the lower pile hole 3 is a symmetrical sector, the outline of the lower pile 4 reinforcement cage is set to a symmetrical sector after it is unfolded. If the cross-sectional profile of the lower pile hole 3 is an ellipse, the outline of the lower pile 4 reinforcement cage is set to an ellipse after it is unfolded.

[0101] 5. If the airbag 8 in the cage cannot be lifted to the ground surface, the construction method of the side airbag 9 is adopted, and cement slurry is filled into the airbag 8 in the cage through the ventilation pipe 10 so that it is cast as one with the lower pile 4.

[0102] 6. The upper pile hole 6 can be a drilled pile hole; if there are many pile groups under the same cap 1 and the pile spacing is small, the upper pile hole 6 arranged between the pile groups can also be the pile hole left by pulling out the old piles 2, that is, this construction method can be used in combination with the pulling out of the old piles 2. This combination method can not only save costs, but also avoid the inconvenience caused by the inability to arrange suitable new holes due to the small pile spacing, and also avoid the engineering and environmental problems caused by pulling out the pile groups under the same cap 1 one by one.

[0103] The construction method of connecting old piles is to transform and connect old piles 2 or old pile groups to form a new type of pile or pile group. The piles formed are called old piles connecting piles, which have the following advantages:

[0104] 1. Cost saving: The cost of pulling out piles is high, and after pulling out the piles, piles must be rebuilt in the original position, which also incurs a cost. However, the cost of connecting the old piles is only one time, which can save construction costs.

[0105] 2. No disturbance to the foundation soil: The space section formed by the removal of the old pile 2 is larger than the original pile, which causes great damage to the foundation soil, especially for pile groups. There are many piles under a cap 1 with small spacing. The removal of all the old piles 2 will undoubtedly cause strong disturbance to the foundation soil, which will have a great impact on the bearing capacity of the new piles in the area. The connection of the old pile 2 avoids this problem.

[0106] 3. Avoid the problem of insufficient conditions for pulling out piles: Drilling and pulling out piles requires a large soil area around the piles, especially for pile groups. The old piles 2 under the same cap 1 are close to each other, and the conditions for pulling out piles are difficult to meet. Relaxing the conditions will cause geological disasters or increase the cost of auxiliary means. Sometimes only individual piles meet the conditions, but it is difficult to ensure that all foundation piles under the same cap 1 can meet the conditions.

[0107] The method of connecting the old pile 2 is only to drill holes in the foundation pile group. The hole spacing can be larger and the hole diameter has good adaptability. There is no problem of insufficient drilling conditions, and the problem of insufficient conditions for pulling out piles is also avoided.

[0108] 4. It can be combined with pile extraction: the pile hole 6 can be designed on an old pile 2. After the old pile 2 is extracted, the pile hole 6 is formed. In this way, the cross-sectional size of the pile hole 6 is widened, and a pile 7 with a larger diameter can be designed, thereby widening the application conditions of the old pile 2 connection method.

[0109] 5. Can be combined with new piles: For some projects, even if the old piles 2 are fully utilized and transformed into connecting piles under the old piles, the project requirements cannot be fully met, or only some of the old piles 2 have transformation value or need to be transformed. At this time, some old piles 2 at suitable locations can be transformed into connecting piles under the old piles, and some new piles can be constructed at the same time. The new piles and the connecting piles under the old piles are combined to form the optimal pile foundation combination form of the project, thereby maximizing its engineering value.

[0110] The embodiments described above are only preferred embodiments of the present invention and are not intended to limit the scope of implementation of the present invention. Therefore, any equivalent changes or modifications made according to the structures, features and principles described in the patent scope of the present invention should be included in the scope of the patent application of the present invention.

Claims

1. A construction method for connecting piles under old piles, comprising a cap (1) and old piles (2), characterized in that: The old pile (2) is arranged under the cap (1), a pile hole (3) is opened at the bottom of the old pile (2), and the cross-sectional profile of the pile hole (3) is larger than the minimum envelope profile of the outer edge of the old pile (2); A lower pile (4) is arranged in the pile hole (3), and the lower pile (4) corresponds to 2 to 4 old piles (2) under the same cap (1), and there is an overlapping height H1 between the lower pile (4) and the old pile (2); An upper pile hole (6) is opened parallel to one side of the old pile (2), the cross-sectional profile of the upper pile hole (6) is smaller than the cross-sectional profile of the lower pile hole (3), an upper pile (7) is arranged in the upper pile hole (6), and there is an overlap height H2 between the upper pile (7) and the lower pile (4); The method comprises the following steps: Step 1: Collect pile information and engineering geological information; Step 2: Determine the type of jet grouting equipment, jet grouting method and construction parameters; Step 3: making the upper pile (7) and the lower pile (4) steel cages, removing the frame reinforcement when making the lower pile (4) steel cage, replacing the thin steel bars with thin steel wire ropes as stirrups, after the lower pile (4) steel cage is made, at least two layers of uninflated cage air bags (8) are arranged vertically at intervals inside the lower pile (4) steel cage, the cage air bags (8) are detachably connected to the lower pile (4) steel cage, uninflated side air bags (9) are arranged at the outer side of the lower pile (4) steel cage and at positions corresponding to the cage air bags (8), and the side air bags (9) are tied to the lower pile (4) steel cage; the cage air bags (8) and the side air bags (9) are connected to their respective ventilation pipes (10), and then the lower pile (4) steel cage is tightened in the radial direction, and the lower pile (4) steel cage is tied with Velcro (11); A plurality of movable barbs (14) are circumferentially tied to the inner side of the steel cage of the lower pile (4), one end of the movable barbs (14) is bent downward, and the air bag (8) in the cage is placed below the plurality of movable barbs (14) and is restricted by the movable barbs (14); a limited short reinforcement (15) is also tied to the steel cage of the lower pile (4), and the limited short reinforcement (15) is located above the movable barbs (14); Step 4: Drilling and reinforcing the foundation (1); Step 5: Make the lead holes (17) of the upper pile hole (6) and the lower pile hole (3); Step 6: Make the pile hole (3); Step 7: Lifting and lowering the pile (4) reinforcement cage: lifting and lowering the lower pile (4) reinforcement cage in a tightly bound state through the upper pile hole (6) into the lower pile hole (3) by means of a lifting wire rope (13); Step 8: Expanding and positioning the steel cage for pile lowering (4): Inflate the airbags (8) in the multi-layer cage to gradually increase their size, and the airbags (8) in the cage gradually increase in size, and the movable barbs (14) continue to deflect until they are restricted by the limiting short bars (15) and no longer deflect; untie the Velcro (11), and expand the steel cage for pile lowering (4) radially outward; when the steel cage for pile lowering (4) is fully expanded, inflate the side airbags (9) to full shape; when the airbags (8) in the cage, the steel cage, the side airbags (9) and the wall of the pile lowering hole (3) mutually restrict each other to reach a balance, the horizontal positioning of the steel cage is successful; Step 9: pouring concrete for the lower pile (4): pouring concrete into the lower pile hole (3) through the concrete guide tube (17). When the concrete surface approaches the airbag (8) in the cage at the lowest level, remove the lifting wire rope (13) to release the gas in the airbag (8) in the cage at the lowest level. The airbag shrinks and falls down, and the airbag (8) in the cage at the lowest level is lifted to the ground surface by slowly pulling the ventilation pipe (10). Continue pouring concrete until it approaches the airbag (8) in the cage at the next level, deflate it and lift it to the ground surface, and repeat this process until all the airbags (8) in the steel cage of the lower pile (4) are lifted to the ground surface, and then release the gas in the side airbag (9), fill the side airbag (9) with cement slurry, and continue pouring concrete to the bottom of the upper pile hole (6) and vibrate it to compact it. Step 10: Lift and place the steel cage on the pile (7); Step 11: Repair the abutment (1).

2. The construction method of a pile connection structure under an old pile according to claim 1, characterized in that: The cross section of the cap (1) is one of square, rectangular or polygonal; the cross section of the pile hole (3) is one of symmetrical fan-shaped, elliptical or circular; the pile (4) is a pile structure made of a steel cage cast in concrete, the steel cage includes main bars (5) and stirrups, and the stirrups are rope structures made of flexible steel wire; the range of H1 is 0.5m~1.0m; The cross section of the upper pile hole (6) is circular; the upper pile (7) is a cast-in-place pile, a prefabricated pile or a plain pile; the range of H2 is 0.5m to 1.0m, and the cap (1), the lower pile (4), the upper pile (7) and the old pile (2) are cast as a whole.

3. The construction method of a pile connection structure under an old pile according to claim 2, characterized in that: The lower pile (4) corresponds to the two old piles (2), the lower pile (4) is arranged between the two old piles (2), the upper pile (7) is located at the center of the lower pile (4), and the cross section of the lower pile (4) is a symmetrical sector, an ellipse or a circle.

4. The construction method of a pile connection structure under an old pile according to claim 2, characterized in that: 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 cross section of the lower pile (4) is circular.

5. The construction method of a pile connection structure under an old pile according to claim 2, characterized in that: The lower pile (4) corresponds to the four old piles (2), the four old piles (2) are arranged in groups of two, the lower pile (4) is arranged between two old piles (2) in the same group, the upper pile (7) is located 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 pile (4) is arranged between the four old piles (2), and the cross-section of the lower pile (4) is circular.

6. The construction method of a pile connection structure under an old pile according to claim 1, characterized in that: The pile information includes the pile type, number of piles, pile position, pile diameter, pile length, pile connection position, reinforcement cage parameters, and the quality of the old pile (2) and the parameters of the foundation (1) of the old pile (2), the upper pile (7) and the lower pile (4); the engineering geological information includes the lithology and its engineering geological property indicators, and the groundwater conditions.

7. The construction method for connecting piles under old piles according to claim 1, characterized in that: The jet grouting type is single-tube, double-tube, triple-tube or multi-tube jet grouting, and the construction parameters are water and air jet pressure and rotation speed; the pile hole (3) is made by high-pressure jet grouting cutting and hole-making technology, starting from a height of 0.5m to 1.0m upward from the bottom of the old pile (2), and using a jet grouting pipe (12) to make the pile hole (3), the jet grouting pipe (12) slowly descends while jet grouting and cutting the soil until it reaches the bottom of the designed pile hole (3), and then the sediment at the bottom of the hole is removed.

8. The construction method for connecting piles under old piles according to claim 1, characterized in that: The lower end of the upper pile (7) steel cage is required to be inserted into the lower pile hole (3) to a certain depth and to overlap with the lower pile (4) steel cage in elevation to a certain extent, with the overlap being 0.5m to 1.0m. In step 10, the upper pile (7) steel cage is hoisted into the upper pile hole (6), and then the upper pile (7) pile body concrete is poured and vibrated to compact it. In step 11, when the upper pile (7) concrete reaches the required strength, the floating slurry solidified body on the top of the upper pile (7) is chiseled off, the exposed section of the upper pile (7) steel cage is cleaned, and connected with the steel bars of the cap (1), and concrete is poured to form, thereby completing the repair of the cap (1).

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