A root type concrete press grouting pile combined foundation and construction method

Abstract

The application discloses a root type concrete pressure grouting pile combined foundation and a construction method, and relates to the technical field of building engineering. The root type concrete pressure grouting pile combined foundation comprises a vertical main root pile body and multi-stage fibrous root expansion units distributed in a forked manner. An extrusion head is fixed on the top of the main reinforcement cage through a grouting guide rod. A plurality of auxiliary reinforcement cages are uniformly distributed on the periphery of the main reinforcement cage. The auxiliary reinforcement cages are obliquely distributed on the periphery of the main reinforcement cage. A mesh cover is fixedly installed on the top of the main reinforcement cage. The mesh cover and the auxiliary reinforcement cages are symmetrically distributed along the horizontal direction and are associated with each other. A closure member is installed in the main reinforcement cage to provide a closed structure. The closure member is extruded and attached to the top of the mesh cover and is in extrusion contact with the extrusion head. The root type concrete pressure grouting pile combined foundation and the construction method have the effects of high structural strength, high stability and high bearing capacity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building engineering, and particularly relates to a root type concrete pressure grouting pile combined foundation and a construction method. BACKGROUND

[0002] Traditional concrete cast-in-place piles or pressure grouting piles are usually single cylindrical or slightly expanded pile body structures; such foundations rely on the side friction and end resistance of the pile body to bear the vertical pressure load transmitted by the upper structure; however, in the face of special geological conditions or complex load conditions, such as collapsible loess areas, newly filled areas, etc., or the uplift force, horizontal force or huge overturning moment of structures such as power transmission towers, wind turbine towers, offshore platforms, etc., the traditional pile foundation has the disadvantage of low efficiency.

[0003] The uplift force of the traditional concrete pressure grouting pile foundation mainly relies on the side friction of the pile body to resist, and the gravity bearing also mainly relies on the friction and end resistance to resist, in order to improve the efficiency, the pile length or diameter needs to be increased, which is poor in economy, and the pile body is like a cantilever beam, which produces a large bending moment in the deep part, which easily leads to cracking of the pile body, and in the prior art, although expansion piles, anchor rods and other reinforcement measures are used, the construction is complex, the reliability is greatly affected by the geological conditions, and the synergistic reinforcement effect on multi-directional loads is limited. SUMMARY

[0004] The present application discloses a root type concrete pressure grouting pile combined foundation and a construction method, which aims to solve the technical problem that the bearing capacity of the traditional concrete pressure grouting pile foundation mainly relies on the vertical pile body side friction and the pile bottom end resistance, resulting in the need to improve the operation efficiency and structural strength.

[0005] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0006] A root type concrete pressure grouting pile combined foundation and a construction method, comprising a vertical main root pile body and a multi-stage rootlet expansion unit distributed in a branched manner, a longitudinal foundation pit, an inclined pile hole and a longitudinal pile hole are formed on the ground in sequence by a drilling machine;

[0007] The main root pile body comprises a main reinforcement cage, a grouting guide rod for concrete slurry grouting is vertically distributed in the inside of the main reinforcement cage, an extrusion head is fixedly sleeved on the outside of the grouting guide rod and covers the top of the main reinforcement cage, a mesh cover is fixedly installed on the top of the main reinforcement cage, a sealing element providing sealing is sleeved and installed in the inside of the main reinforcement cage, the sealing element is extruded and fitted on the top of the mesh cover and is in extruded contact with the extrusion head, a plurality of uniformly distributed outer expansion ribs are prefabricated and welded on the outside of the mesh cover below, a reverse hook-shaped tail hook is arranged on the bottom of the outer expansion rib, and the tail hook is hooked on the outside of the hoop element;

[0008] The multi-stage root extension unit includes several secondary reinforcing cages evenly distributed around the main reinforcing cage. The secondary reinforcing cages are inclinedly distributed around the main reinforcing cage and located inside the inclined pile hole.

[0009] Based on traditional concrete pressure-grouted pile foundation and construction techniques, this method incorporates multiple individual secondary reinforcement cages that work in conjunction with the main reinforcement cage. First, positioning plates facilitate the quick installation of the secondary reinforcement cages. Then, connecting structures such as mesh covers and closure components complete the combined use of the secondary and main reinforcement cages. On one hand, the main and secondary reinforcement cages form a root-like distribution structure along the foundation's interior. On the other hand, pressure grouting causes the formed foundation to develop tree-like splits along the pile holes, providing an "anchor bar" effect through inclined branches. This significantly increases the bearing capacity compared to traditional piles of the same volume. Simultaneously, the secondary reinforcement cages greatly increase the effective width and moment of inertia of the foundation, effectively enhancing its resistance to bending moments and horizontal forces. Furthermore, the multi-directional branches work together with the main piles to efficiently distribute complex spatial loads to deeper and wider areas of soil, resulting in a more rational stress pattern and high stability, thus enabling this foundation to have a wider range of applications and value.

[0010] In a preferred embodiment, the positioning plate has several inclined positioning openings through its interior. Inclined pile holes are drilled along the foundation sidewall through the positioning openings, and then the secondary reinforcing cage is inserted into the inclined pile holes through the positioning openings.

[0011] By setting up inclined positioning ports inside the positioning plate, the positioning ports assist workers in processing inclined pile holes and installing and fixing secondary steel reinforcement cages, thereby improving the convenience of this combined foundation construction.

[0012] In a preferred embodiment, the main body of the secondary reinforcing cage is composed of several longitudinal reinforcing bars evenly distributed around an axis. At the same time, several evenly distributed stirrups are welded and fixed to the outside of the longitudinal reinforcing bars. The main reinforcing cage and the secondary reinforcing cage have the same structure but different dimensions. Several evenly distributed outward-expanding bars are prefabricated and welded to the lower outer side of the mesh cover. The outward-expanding bars and the longitudinal reinforcing bars are in contact by compression. The bottom of the outward-expanding bars is provided with a barb-shaped tail hook, which is hooked to the outside of the stirrup.

[0013] By adding an externally expanding bar structure with a built-in tail hook to the mesh cover, the external expansion and compression of the bar firstly causes the secondary steel cage to contact the mesh cover, improving the structural strength and stability of the concrete composite foundation after grouting and solidification. At the same time, the tail hook at the bottom of the bar can engage with the stirrups of the secondary steel cage, improving the resistance to upward pull of the main and secondary steel cages when workers perform pressurized grouting on the foundation, thereby significantly improving the operational reliability of the equipment.

[0014] In a preferred scheme, the inside of the closure is provided with a plurality of evenly distributed grouting openings, and each grouting opening is in close proximity to a secondary reinforcement cage.

[0015] By additionally providing grouting openings in the inside of the closure, after the workers complete the preliminary grouting of the combined foundation, the grouting pipe at the position of the grouting opening is used to perform secondary grouting at the position of each secondary reinforcement cage, thereby improving the compactness between the foundation and the ground.

[0016] A construction method of a root type concrete pressure grouting pile combined foundation comprises the following steps.

[0017] S1: Workers first control the drilling machine to perform preliminary longitudinal foundation pit preparation along the set point, and the longitudinal foundation pit has the same peripheral size as the positioning plate, and then the workers splice and fit two positioning plates to the inner wall of the hole along the hole wall to prevent the hole wall from collapsing;

[0018] S2: Workers control the drilling machine to tilt, replace the drill bit, and drill a slanting pile hole along the inner side of the positioning plate towards the side wall of the longitudinal foundation pit;

[0019] S3: Workers disassemble the positioning plate, reset the drilling machine, and perform deep hole drilling along the longitudinal foundation pit to form a longitudinal pile hole, and simultaneously, a plurality of secondary reinforcement cages are sequentially inserted into the slanting pile hole, and then the main reinforcement cage is hoisted into the longitudinal pile hole by using a crane;

[0020] S4: Workers control the external press machine connected to the grouting guide rod to drive the extrusion head to press the main reinforcement cage into the longitudinal pile hole to a specified depth, so that the mesh cover and the plurality of secondary reinforcement cages are connected, and the closure is covered above the secondary reinforcement cage;

[0021] S5: Then, workers control the external press machine to vertically lift the grouting guide rod and the extrusion head upward to disengage, and in this process, the grouting guide rod slowly injects concrete slurry into the inside of the main reinforcement cage;

[0022] S6: The grouting pressure in the pile hole is maintained by using the closure, secondary sealing and grouting are performed, the closure is removed from the top of the main reinforcement cage, and the work flow is completed.

[0023] The root type concrete pressure grouting pile combined foundation and the construction method provided by the application have the following technical effects.

[0024] By setting up the vice steel reinforcement cage in the form of multiple individuals to cooperate with the main steel reinforcement cage on the basis of traditional concrete pressure grouting pile foundation and construction technology, first, the positioning plate is used to complete the quick installation of the vice steel reinforcement cage, then the net cover and the closure and other connection structures are used to complete the combined use of the vice steel reinforcement cage and the main steel reinforcement cage, and the following effects are achieved.

[0025] Firstly, the main and vice steel reinforcement cages form a root-like distribution structure along the inside of the foundation, on the basis of which, the pressure grouting mode is used to cause the foundation after forming to produce a root-like splitting along the inside of the foundation, so that the inclined branches provide an effect similar to "anchor reinforcement", and the bearing capacity can be greatly improved compared with the traditional pile of the same volume.

[0026] Secondly, the vice steel reinforcement cage can greatly increase the effective width and moment of inertia of the foundation, and the ability to resist bending moment and horizontal force is multiplied, and the multi-directional branches work together with the main pile to efficiently disperse and transmit the complex spatial load to deeper and wider soil, and the stress mode is more reasonable, so that the foundation has higher stability and wider application environment and use value. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The overall structure schematic diagram of the present application is shown.

[0028] Figure 2 The front view structure schematic diagram of the present application is shown.

[0029] Figure 3 The vice steel reinforcement cage structure schematic diagram of the present application is shown.

[0030] Figure 4 The overall structure explosion diagram of the present application is shown.

[0031] Figure 5 The closure structure schematic diagram of the present application is shown.

[0032] Figure 6 The net cover structure schematic diagram of the present application is shown.

[0033] Figure 7 The main steel reinforcement cage installation structure schematic diagram of the present application is shown.

[0034] Figure 8 The Figure 7 The structure enlarged view of A in the present application is shown.

[0035] Figure 9 The vice steel reinforcement cage structure plan view of the present application is shown.

[0036] Figure 10 The longitudinal foundation pit structure schematic diagram of the present application is shown.

[0037] Figure 11A schematic diagram of the oblique pile hole structure proposed by the present application.

[0038] Figure 12 A schematic diagram of the longitudinal pile hole structure proposed by the present application.

[0039] Figure 13 A schematic diagram of the state when the tail hook contacts the stirrup member proposed by the present application, and the arrow is the deformation direction of the tail hook.

[0040] Figure 14 A schematic diagram of the state after the tail hook contacts the stirrup member proposed by the present application, and the arrow is the deformation direction of the tail hook.

[0041] In the figure: 1, main reinforcement cage; 2, grouting guide rod; 3, extrusion head; 4, positioning plate; 401, positioning port; 402, handle; 5, auxiliary reinforcement cage; 501, longitudinal reinforcement member; 502, stirrup member; 6, mesh cover; 601, outward expanding rib; 602, tail hook; 603, through port; 7, closure member; 701, bolt sleeve; 702, grouting port; 8, longitudinal foundation pit; 9, oblique pile hole; 10, longitudinal pile hole. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all.

[0043] The root type concrete pressure grouting pile combined foundation and construction method disclosed by the present application is mainly applied to the scene of installing and constructing a combined concrete pressure grouting pile foundation.

[0044] Reference Figures 1 to 14 A root type concrete pressure grouting pile combined foundation, comprising a vertical main root pile body and a multi-stage branch root expansion unit distributed in a branched manner, and a longitudinal foundation pit 8, an oblique pile hole 9 and a longitudinal pile hole 10 are formed in sequence on the ground by a drilling machine.

[0045] The main root pile body comprises a main reinforcement cage 1, a grouting guide rod 2 for concrete slurry grouting is vertically distributed inside the main reinforcement cage 1, an extrusion head 3 is fixedly sleeved on the outside of the grouting guide rod 2 and covers the top of the main reinforcement cage 1, a mesh cover 6 is fixedly installed on the top of the main reinforcement cage 1, a closure member 7 is sleeved and installed inside the main reinforcement cage 1 to provide closure, the closure member 7 is extruded and attached to the top of the mesh cover 6 and is in extruded contact with the extrusion head 3, a plurality of uniformly distributed outward expanding ribs 601 are prefabricated and welded on the lower side of the outside of the mesh cover 6, a tail hook 602 in the shape of a barb is arranged at the bottom of the outward expanding rib 601, and the tail hook 602 is barbed on the outside of the stirrup member 502.

[0046] The multi-stage fibrous root extension unit comprises a plurality of auxiliary reinforcement cages 5 evenly distributed on the periphery of the main reinforcement cage 1, and the auxiliary reinforcement cages 5 are inclinedly distributed on the periphery of the main reinforcement cage 1 and located inside the inclined pile hole 9.

[0047] In the embodiment, the worker first controls the drilling machine to perform preliminary longitudinal foundation pit 8 preparation along the set point, the longitudinal foundation pit 8 and the peripheral size of the positioning plate 4 are the same, then the worker splices and fits two positioning plates 4 along the hole wall to the hole inner wall to prevent the hole wall from collapsing and provide guidance for subsequent drilling and pre-buried auxiliary reinforcement cage 5, then the worker controls the drilling machine to tilt, replaces the drilling machine and tilts along the inner side of the positioning plate 4 to the side wall of the longitudinal foundation pit 8 to drill the inclined pile hole 9, then the positioning plate 4 is removed, the drilling machine is reset, then the hole is drilled along the longitudinal foundation pit 8 to form the longitudinal pile hole 10, then a plurality of auxiliary reinforcement cages 5 are sequentially inserted into the inclined pile hole 9, then the main reinforcement cage 1 is hoisted into the longitudinal pile hole 10 by using the crane, then the external stamping machine connected to the grouting guide rod 2 is controlled to drive the extrusion head 3 to press the main reinforcement cage 1 into the longitudinal pile hole 10 to the specified depth, so that the mesh cover 6 and the plurality of auxiliary reinforcement cages 5 are connected and the closure 7 is covered above the auxiliary reinforcement cage 5, then the worker controls the external stamping machine to vertically lift the grouting guide rod 2 and the extrusion head 3 upward to separate, in the process, the grouting guide rod 2 slowly injects the concrete slurry into the main reinforcement cage 1, and the closure 7 maintains the grouting pressure inside the pile hole, then secondary closed grouting is performed, finally the closure 7 is removed from the top of the main reinforcement cage 1 to complete the work flow.

[0048] It is worth noting that the drilling machine of the present application can be selected according to the construction requirements, and the "rotary drilling head" or "screw drilling head" can be used in combination, the "rotary drilling head" can be used for rotary drilling when the longitudinal foundation pit 8 is constructed, the "screw drilling head" can be replaced for rotary drilling when the inclined pile hole 9 is constructed, and the "rotary drilling head" can be continued to be used for rotary drilling when the longitudinal pile hole 10 is constructed, which is the existing construction technical means and will not be described here;

[0049] It is further worth noting that, as shown in Figure 10 and Figure 12 , the inner opening size of the longitudinal foundation pit 8 is greater than the inner opening size of the longitudinal pile hole 10, which is to provide more working space for the construction of the inclined pile hole 9 and the installation of the auxiliary reinforcement cage 5, and the main reinforcement cage 1 will not be affected during installation, and since the "rotary drilling head" may enter some residual soil into the longitudinal foundation pit 8 and the inclined pile hole 9 when it is lifted upward during the construction of the longitudinal pile hole 10, a baffle can be used to block the inclined pile hole 9 in advance to prevent residual soil from entering, and a soil suction machine can be used to clean the residual soil in the longitudinal foundation pit 8.

[0050] Specifically, the size of the "rotary drill bit" during the construction of the longitudinal foundation pit 8 is larger than that during the construction of the longitudinal pile hole 10, so as to ensure that the inner opening size of the longitudinal foundation pit 8 is larger than that of the longitudinal pile hole 10.

[0051] In addition, the application provides two or more sets of the fibrous root extension unit, and the drawings of the application take four sets as an example.

[0052] The inside of the positioning plate 4 is provided with a plurality of inclined positioning openings 401, the inclined pile hole 9 is drilled along the side wall of the foundation through the positioning openings 401, and the auxiliary reinforcement cage 5 is inserted into the inclined pile hole 9 through the positioning openings 401. The top of each positioning plate 4 is fixedly provided with a handle 402, so as to facilitate the workers to hold and operate, and the positioning plate 4 is made of elastic metal material, such as stainless steel sheet.

[0053] Referring to Figure 4 , Figures 6 to 8 In a preferred embodiment, the main body of the auxiliary reinforcement cage 5 is composed of a plurality of longitudinal reinforcement members 501 uniformly distributed around the axis point, and the outer side of the longitudinal reinforcement member 501 is welded and fixed with a plurality of uniformly distributed stirrup members 502. The main reinforcement cage 1 and the auxiliary reinforcement cage 5 are the same in structure but different in size, and a plurality of uniformly distributed outer expansion bars 601 are prefabricated and welded on the outer side of the mesh cover 6. The outer expansion bars 601 are in extrusion contact with the longitudinal reinforcement members 501, and the bottom of the outer expansion bars 601 is provided with a hook-shaped tail hook 602, which is hooked on the outer side of the stirrup member 502.

[0054] When the extrusion head 3 is pressed and covered to the specified depth of the longitudinal pile hole 10, the outer expansion bars 601 on the outer side of the mesh cover 6 and the longitudinal reinforcement members 501 of the plurality of auxiliary reinforcement cages 5 will be in contact, and the tail hook 602 at the bottom of the outer expansion bars 601 will be hooked on the outer side of the stirrup member 502 of the auxiliary reinforcement cage 5. At this time, the closure member 7 is attached to the inner wall of the longitudinal foundation pit 8 and covers the auxiliary reinforcement cage 5 above. Then, the worker controls the external stamping machine to vertically lift and separate upward together with the traction grouting guide rod 2 and the extrusion head 3. In this process, the grouting guide rod 2 slowly injects the concrete slurry into the inside of the main reinforcement cage 1, and the closure member 7 is used to maintain the grouting pressure inside the pile hole. In this process, the main reinforcement cage 1 and the auxiliary reinforcement cage 5 are fixed together by the tail hook 602, thereby improving the resistance to upward displacement during the whole foundation closed grouting.

[0055] It is worth noting that, as shown in Figure 7 and Figure 8 , after the auxiliary reinforcement cage 5 is inserted into the inclined pile hole 9, the upper end of the auxiliary reinforcement cage 5 will be partially exposed. The exposed part will not affect the installation of the main reinforcement cage 1, but it is necessary to ensure that the tail hook 602 can contact the stirrup member 502 of the auxiliary reinforcement cage 5. During the contact process, the tail hook 602 and the outer expansion bars 601 will be deformed by the inward extrusion force (as shown inFigure 13 As shown, the arrow is the deformation direction of the tail hook 602), and after the main reinforcement cage 1 is installed to the specified depth, at this time the tail hook 602 is located below the stirrup member 502, and is deformed back by the outer expansion rib 601 (as shown Figure 14 As shown, the arrow is the deformation direction of the tail hook 602), so that the tail hook 602 is hooked on the outside of the stirrup member 502, so as to improve the anti-pulling ability during the closed grouting, wherein the tail hook 602 presents an outwardly expanding arc shape, so as to ensure that the tail hook 602 can be in contact with the stirrup member 502 and deformed during the process of the main reinforcement cage 1 descending, and after being located below the stirrup member 502, a reverse hook locking structure is formed.

[0056] Wherein, the inside of the mesh cover 6 is provided with a plurality of uniformly distributed through openings 603 for the flow of concrete slurry.

[0057] Referring to Figure 5 In a preferred embodiment, the top of the closure member 7 is provided with symmetrically distributed bolt sleeves 701, the outer surface of the bolt sleeve 701 is provided with a slot, and the bolt sleeve 701 is slidingly sleeved on the outside of the main reinforcement cage 1 and tightened by a nut, during the tightening process, the bolt sleeve 701 is tightened through the slot, so as to fix the closure member 7 on the outside of the main reinforcement cage 1.

[0058] Under normal circumstances, the closure member 7 is fixed on the outside of the main reinforcement cage 1 by the bolt sleeve 701, when the worker completes the pressure grouting of the entire combined foundation, at this time the worker rotates the nut installed on the outside of the bolt sleeve 701, and the closure member 7 is removed.

[0059] Specifically, the inside of the closure member 7 is provided with a plurality of uniformly distributed grouting openings 702, each grouting opening 702 is close to one of the auxiliary reinforcement cages 5, after the worker completes the preliminary grouting of the combined foundation, since the grouting opening 702 is additionally provided with a grouting pipe structure, and then the grouting pipe is used to perform secondary grouting at each inclined pile hole 9, by means of pressure grouting and secondary grouting, a radial or bifurcated "branching expansion body" can be formed at the bottom and inner wall of the inclined pile hole 9 and the longitudinal pile hole 10, which is similar to the expansion of tree roots, thereby improving the bearing capacity of the pile foundation.

[0060] Working principle: in use, the worker first controls the drilling machine to preliminarily prepare the longitudinal foundation pit 8 along the set point (as shown Figure 10 As shown, the peripheral size of the longitudinal foundation pit 8 is the same as that of the positioning plate 4, thereafter the worker splices and abuts the two positioning plates 4 along the hole wall, for preventing the hole wall from collapsing, then the worker controls the drilling machine to tilt, changes the drill bit, and drills the inclined pile hole 9 along the inside of the positioning plate 4 towards the side wall of the longitudinal foundation pit 8 (as shown Figure 11As shown), then the workers will remove the positioning plate 4, and then control the drill to reset and make deep drilling along the longitudinal foundation pit 8 and form the longitudinal pile hole 10 (as shown) Figure 12 As shown), and then the workers control the external stamping machine connected to the grouting guide rod 2 to drive the extrusion head 3 to press the main reinforcement cage 1 into the longitudinal pile hole 10 to a specified depth, in the process, the tail hook 602 outside the mesh cover 6 will contact the longitudinal reinforcing members 501 of the plurality of auxiliary reinforcement cages 5, after the main reinforcement cage 1 is installed to the specified position, at this time, the tail hook 602 is located below the stirrup member 502, and is reset by the external expansion rib 601, so that the tail hook 602 is hooked outside the stirrup member 502, at this time, the closure member 7 is attached to the inner wall of the longitudinal foundation pit 8 and covers the auxiliary reinforcement cage 5 above, then the workers control the external stamping machine to vertically lift and separate the grouting guide rod 2 and the extrusion head 3 upward, in the process, the grouting guide rod 2 slowly injects concrete slurry into the inside of the main reinforcement cage 1, and the closure member 7 is used to maintain the grouting pressure inside the pile hole, as the grouting height continuously increases, the grouting finally fills the longitudinal pile hole 10 and the inclined pile hole 9, in the process, the main reinforcement cage 1 and the auxiliary reinforcement cage 5 are connected to form a whole under the cooperation of the tail hook 602, thereby improving the upward resistance of the closure member 7, thereby improving the anti-uplift ability of the entire pile foundation during closed grouting, after grouting, secondary grouting is continued into the inclined pile hole 9 to improve the grouting effect of the inner wall of the inclined pile hole 9, finally the closure member 7 is removed, and the work flow is completed.

[0061] The above is only a preferred embodiment of the present application, but the protection scope of the present application is not limited thereto, any skilled person in the art can make equivalent replacement or change according to the technical solution and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A root-type concrete pressure-grouted pile composite foundation, comprising a vertical main root pile body and a multi-level root extension unit distributed in a branched manner, characterized in that, The drilling rig sequentially forms a longitudinal foundation pit (8), an inclined pile hole (9), and a longitudinal pile hole (10) on the ground. The main root pile body includes a main steel cage (1), and grouting guide rods (2) for concrete grouting are vertically distributed inside the main steel cage (1). An extrusion head (3) is fixedly sleeved on the outside of the grouting guide rod (2) and pressed against the top of the main steel cage (1). A mesh cover (6) is fixedly installed on the top of the main steel cage (1). A sealing member (7) for providing sealing is sleeved inside the main steel cage (1). The sealing member (7) is pressed against the top of the mesh cover (6) and presses against the extrusion head (3). Several evenly distributed outward expansion bars (601) are prefabricated and welded on the lower outside of the mesh cover (6). The bottom of the outward expansion bars (601) is provided with a barb-shaped tail hook (602). The multi-level root extension unit includes several secondary reinforcing cages (5) evenly distributed around the main reinforcing cage (1). The secondary reinforcing cages (5) are inclinedly distributed around the main reinforcing cage (1) and located inside the inclined pile hole (9). The main body of the secondary steel cage (5) is composed of several longitudinal reinforcement members (501) evenly distributed around the axis. At the same time, several evenly distributed stirrup members (502) are welded and fixed on the outside of the longitudinal reinforcement members (501). The tail hook (602) is hooked on the outside of the stirrup members (502). The longitudinal foundation pit (8) is provided with a positioning plate (4) on its inner wall. The positioning plate (4) has several inclined positioning ports (401) through which a drilling machine drills an inclined pile hole (9) along the side wall of the foundation through the positioning ports (401). Then the secondary steel cage (5) is inserted into the inclined pile hole (9) through the positioning ports (401). The mesh cover (6) has several evenly distributed openings (603) running through its interior. The top of the closure (7) is provided with symmetrically distributed bolt sleeves (701). The bolt sleeves (701) are slidably sleeved on the outside of the main steel cage (1) and tightened by nuts to fix the closure (7) to the outside of the main steel cage (1). The interior of the closure (7) is provided with several evenly distributed grouting ports (702), each of which is close to a secondary steel cage (5).

2. The root-type concrete pressure-grouted pile combined foundation according to claim 1, characterized in that, Each of the positioning plates (4) is fixedly fitted with a handle (402) on its top.

3. The root-type concrete pressure-grouted pile combined foundation according to claim 1, characterized in that, The main steel cage (1) and the secondary steel cage (5) have the same structure but different dimensions.

4. The root-type concrete pressure-grouted pile combined foundation according to claim 3, characterized in that, The outer expansion rib (601) and the longitudinal rib (501) are in extrusion contact.

5. The construction method of a root-type concrete pressure-grouted pile composite foundation according to claim 1, characterized in that, Includes the following steps; S1: The worker first controls the drilling machine to prepare the initial longitudinal foundation pit (8) along the set point. The longitudinal foundation pit (8) and the positioning plate (4) have the same outer dimensions. After that, the worker splices the two positioning plates (4) along the hole wall and attaches them to the inner wall of the hole to prevent the hole wall from collapsing. S2: The worker controls the drilling rig to tilt, changes the drill bit and drills the inclined pile hole (9) along the inner side of the positioning plate (4) towards the side wall of the longitudinal foundation pit (8). S3: The worker removes the positioning plate (4), resets the drilling machine, drills deep holes along the longitudinal foundation pit (8) and forms a longitudinal pile hole (10), and inserts several of the auxiliary steel cages (5) into the inclined pile hole (9) in sequence. Then, the main steel cage (1) is hoisted into the longitudinal pile hole (10) using a crane. S4: The worker controls the external punching machine connected to the grouting guide rod (2), drives the extrusion head (3) to press the main steel cage (1) to a specified depth in the longitudinal pile hole (10), so that the mesh cover (6) and several secondary steel cages (5) are connected, and the sealing member (7) covers the secondary steel cage (5). S5: After that, the worker controls the external punching machine to pull the grouting guide rod (2) and the extrusion head (3) to be lifted vertically upward and separated. During this process, the grouting guide rod (2) slowly injects concrete grout into the interior of the main steel cage (1). S6: Use the sealing element (7) to maintain the grouting pressure inside the pile hole, then perform a second sealing and grouting, and remove the sealing element (7) from the top of the main steel cage (1) to complete the workflow.

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