Small counter-force device for pre-pressing newly-added reinforcing pile foundation and reinforcing method

Abstract

The invention relates to the technical field of bridge old pile foundation reinforcement, in particular to a small counter-force device for pre-pressing a newly-added reinforcement pile foundation and a reinforcement method. The bearing mechanism is arranged on the connecting part and stretches across the containing space, and the pre-pressing mechanism is arranged at the top of the new pile foundation and used for pre-pressing the bearing mechanism so as to share part of dead load borne by the old pile foundation to the new pile foundation. The small counter-force device further comprises a temporary steel supporting piece which is cushioned between the new pile foundation and the bearing mechanism and used for replacing the pre-pressing mechanism or jointly stressed with the pre-pressing mechanism so as to share part of dead load borne by the old pile foundation to the new pile foundation. Anchor piles need to be additionally constructed, and the construction process is tedious and long in period.

Description

Technical Field

[0001] The present invention relates to the technical field of reinforcement of old bridge pile foundations, and particularly relates to a small reaction device for preloading newly added reinforced pile foundations and a reinforcement method.

Background Art

[0002] In the prior art, reaction devices for applying pre-pressure to pile foundations include a gravity platform reaction device, an anchor pile reaction device, and a ground anchor reaction device. The gravity platform reaction device is composed of piers, main beams, secondary beams, and stacked heavy objects, and has the characteristics of simple construction and relatively fast construction speed. It is the most common reaction device in current pile foundation preloading tests, but it occupies a large space and has a low loading efficiency. The anchor pile reaction device provides reaction force by connecting a reaction frame with anchor piles. The reaction frame is lifted by a jack at the pile top, and the connected anchor piles provide the reaction force. This device is not restricted by site conditions and loading tonnage, but usually still requires the construction of 1-2 anchor piles in addition to using engineering piles. The construction process is cumbersome and the cycle is long, and the economy is poor. The ground anchor reaction device is suitable for small-tonnage pile foundations and is relatively convenient for loading, but it has high requirements for the geological conditions of the foundation soil layer and cannot provide effective anchoring on soft soil foundations.

[0003] In view of the above technical problems, the present invention is specifically studied and proposed.

Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a small reaction device for preloading newly added reinforced pile foundations and a reinforcement method. By setting a bearing mechanism, a preloading mechanism, and a temporary steel support member, the reinforced structure can be fully utilized as an anchor, eliminating the need for additional construction of anchor piles, facilitating on-site construction, and effectively reducing the construction difficulty. It solves the problems of large on-site construction difficulty, the need for additional construction of anchor piles, cumbersome construction process, high cost, and long cycle.

[0005] To solve the above technical problems, the present invention provides a small reaction device for preloading newly added reinforced pile foundations. A reinforced bearing platform is horizontally provided on the old pile foundation and fixedly connected thereto. Both sides of the reinforced bearing platform extend out of the old pile foundation to form connecting parts, and accommodation spaces for accommodating part of the structure of the small reaction device are formed in the connecting parts. New pile foundations embedded in the ground are preset on both sides of the old pile foundation. The small reaction device includes a bearing mechanism provided on the connecting part and spanning the accommodation space, and a preloading mechanism provided on the top of the new pile foundation for preloading the bearing mechanism to distribute part of the permanent load borne by the old pile foundation to the new pile foundation. The small reaction device further includes a temporary steel support member pad-supported between the new pile foundation and the bearing mechanism for replacing the preloading mechanism or jointly bearing force with the preloading mechanism to distribute part of the permanent load borne by the old pile foundation to the new pile foundation.

[0006] A small reaction device for preloading the newly added and fixed pile foundation as described above, the bearing mechanism includes a crossbeam assembly cooperating with the preloading mechanism and a fixing member for detachably fixing the crossbeam assembly to the connecting part.

[0007] A small reaction device for preloading the newly added and fixed pile foundation as described above, the preloading mechanism includes a jack disposed on the new pile foundation.

[0008] A small reaction device for preloading the newly added and fixed pile foundation as described above, the preloading mechanism further includes an upper stress diffusion steel plate, a force - transmitting steel section, and a lower stress diffusion steel plate sequentially arranged at the bottom of the jack.

[0009] A small reaction device for preloading the newly added and fixed pile foundation as described above, the crossbeam assembly includes a pair of connecting crossbeams connected to the connecting part and a bearing crossbeam erected between the two connecting crossbeams. The bearing crossbeam is located above the accommodation space and abuts against the preloading mechanism. Both ends of the bearing crossbeam are fixedly connected to the corresponding connecting crossbeams, and the connecting crossbeams are detachably connected to the connecting part through fixing members.

[0010] A small reaction device for preloading the newly added and fixed pile foundation as described above, the fixing member is a vertical anchor rod and there are multiple of them. The lower part of the vertical anchor rod is embedded in the connecting part and forms an integral body with the connecting part, and the upper part of the vertical anchor rod is connected to the connecting crossbeam.

[0011] A small reaction device for preloading the newly added and fixed pile foundation as described above, there is an interval between the connecting part and the crossbeam assembly to facilitate the removal of the preloading mechanism.

[0012] The present invention also provides a reinforcement method for preloading and reinforcing old pile foundations, using a small reaction device for preloading the newly added and fixed pile foundation as described above, including the following steps;

[0013] S1, preset the new pile foundation and the reinforcement cap. Build new pile foundations on both sides of the old pile foundation; add a reinforcement cap to the old pile foundation to form an integral body with the old pile foundation. The two sides of the reinforcement cap extend outward to form a connecting part, and the connecting part reserves an accommodation space for the preloading mechanism, and fixing members are preset on the connecting part. The newly built new pile foundations are located below the corresponding connecting parts;

[0014] S2, deploy the small reaction device. When deploying the small reaction device, first deploy the preloading mechanism, and deploy the preloading mechanism at the central position on the top of the new pile foundation. Subsequently, deploy the bearing mechanism, connect the crossbeam assembly in the bearing mechanism to the fixing member in S1, so that the entire bearing mechanism forms an integral body with the connecting part, and the crossbeam assembly spans the accommodation space and is located above the preloading mechanism;

[0015] S3, start the small reaction device to distribute part of the dead load borne by the old pile foundation to the new pile foundation. When starting the small reaction device, first start the preloading mechanism, and lift it upward to the crossbeam assembly through the preloading mechanism, so as to preload the new pile foundation. After preloading to a preset value, a temporary steel support is used to replace the preloading mechanism or to bear force together with the preloading mechanism to distribute part of the dead load borne by the old pile foundation to the new pile foundation.

[0016] S4, pour concrete on the pile head of the new pile foundation to connect the bearing structure, the new pile foundation and the reinforced cap into a whole.

[0017] In the reinforcement method for reinforcing an old pile foundation by pre-stressing as described above, in S4, after the poured concrete is formed, the beam assembly is disassembled.

[0018] In the reinforcement method for reinforcing an old pile foundation by prestressing as described above, in S4, when the reinforcement pedestal is preset, a steel bar reserved opening that passes through the accommodating space is reserved in the connection part, and in S3, after the prestressing mechanism completes the prestressing, steel bars that pass through the accommodating space are implanted at the steel bar reserved opening, and the steel bars are arranged along the length direction of the reinforcement pedestal.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] 1. The small reaction device applied for has small overall size and is easy to load, making it very suitable for preloading reinforced pile foundations in narrow spaces.

[0021] 2. The small reaction force device of the present application has a simple structure and makes full use of the reinforced structure as an anchor. There is no need to construct additional anchor piles, which is convenient for on-site construction, effectively reduces the construction difficulty, and has good overall economic efficiency.

[0022] 3. The small reaction force device of the present application can be prefabricated in the factory and installed on site, which requires a short construction period and has the advantage of rapid construction.

[0023] 4. The pre-compression mechanism and the crossbeam assembly in the small reaction force device of the present application can be disassembled and recycled, which can reduce the production cost.

[0024] 5. The reinforcement method of the present application adopts pre-compression reinforcement of old pile foundation, relying on the small reaction force device in the present application, does not need to construct anchor piles separately, can facilitate on-site construction, effectively reduce the construction difficulty, and can effectively improve the construction efficiency. Moreover, the small reaction force device in the present application can be prefabricated in the factory and installed on site, the required construction period is short, and it has the advantage of fast construction.

Brief Description of the Drawings

[0025] The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings, wherein:

[0026] Figure 1 It is a schematic structural diagram of the present invention.

[0027] Figure 2 It is another schematic structural diagram of the bearing mechanism in the present invention.

[0028] Figure 3 It is a schematic structural diagram of the preloading mechanism in the present invention.

[0029] In the figure: 1, old pile foundation; 2, reinforced bearing platform; 20, connecting part; 3, new pile foundation; 4, bearing mechanism; 40, crossbeam assembly; 400, connecting crossbeam; 401, bearing crossbeam; 41, fixing part; 5, preloading mechanism; 50, jack; 51, upper stress diffusion steel plate; 52, force transmission steel section; 53, lower stress diffusion steel plate; 6, temporary steel support.

Specific Embodiment

[0030] The following will describe in detail the embodiments of the present invention with reference to the accompanying drawings.

[0031] As Figures 1-3 shown, a small reaction force device for preloading newly added reinforced pile foundations. A reinforced bearing platform 2 fixedly connected thereto is horizontally provided on the old pile foundation 1. Both sides of the reinforced bearing platform 2 extend out of the old pile foundation 1 to form a connecting part 20. A receiving space for accommodating part of the structure of the small reaction force device is formed in the connecting part 20, and the receiving space is not marked in the figure. New pile foundations 3 embedded in the ground are preset on both sides of the old pile foundation 1. The small reaction force device includes a bearing mechanism 4 provided on the connecting part 20 and spanning the receiving space, and a preloading mechanism 5 provided on the top of the new pile foundation 3 to preload the bearing mechanism 4 so as to distribute part of the permanent load borne by the old pile foundation 1 to the new pile foundation 3. The small reaction force device further includes a temporary steel support 6 pad inserted between the new pile foundation 3 and the bearing mechanism 4 for replacing the preloading mechanism 5 or jointly bearing force with the preloading mechanism 5 to distribute part of the permanent load borne by the old pile foundation 1 to the new pile foundation 3. The temporary steel support 6 is a solid cube made of Q235b material, and thin steel plates (not shown in the figure) can be pad inserted up and down to fill the gaps, playing the role of replacing the preloading mechanism 5.

[0032] In this embodiment, when constructing the new pile foundation 3 and the reinforced bearing platform 2, the construction is carried out through the following steps:

[0033] (1) According to the under-bridge construction clearance condition, whether pile foundation construction requires excavation and the excavation depth, the excavation depth should be controlled to be the minimum during construction.

[0034] (2) Build the new pile foundation 3, and follow-up construction is carried out through a steel casing. The steel casing should penetrate the silt layer. The construction uses a rotary drill and avoids using impact drilling for construction to avoid disturbing the original structure during the construction of the new pile foundation 3.

[0035] (3) Pour the new pile foundation 3. After the drilling is completed, the steel bars should be placed and the pile foundation concrete should be poured as soon as possible. To ensure the safety of the old pile foundation 1, one pile of the new pile foundation 3 should be poured after drilling one pile.

[0036] (4) After all the pile foundation construction is completed, excavate or fill the soil to the design elevation at the bottom of the newly built and reinforced bearing platform 2, level and compact it, and pour C20 plain concrete with a thickness of 10 cm to 20 cm below the design elevation at the bottom of the newly built and reinforced bearing platform 2 to ensure the reliability of the connection between the newly built and reinforced bearing platform 2 and the original structural concrete. In addition, the relative settlement during the concrete setting process needs to be strictly controlled, and the requirements are as follows: A. The soil at the bottom of the reinforced bearing platform 2 must be tamped to a compactness of not less than 95% before pouring the concrete; B. The concrete at the bottom of the reinforced bearing platform 2 must not be disturbed during the setting process.

[0037] (5) Carry out rebar planting and surface treatment on the connecting part 20 of the old pile foundation 1 and the reinforced bearing platform 2. The layout of the steel bars of the reinforced bearing platform 2 should not affect the rebar planting operation.

[0038] (6) Pour the concrete of the reinforced bearing platform 2. After the concrete strength reaches 90% of the design value and the age is not less than seven days, remove the formwork and backfill the foundation pit.

[0039] It should be noted that in the above steps, when adding and building the reinforced bearing platform 2, a accommodation space for accommodating the preloading mechanism 5 will be reserved.

[0040] After the new pile foundation 3 and the reinforced bearing platform 2 are built, the preloading mechanism 5 is installed on the top of the new pile foundation 3. Subsequently, the bearing mechanism 4 is installed on the connecting part 20 and cooperates with the preloading mechanism 5. The bottom of the bearing mechanism 4 is preloaded upward by the preloading mechanism 5. After reaching the set value, the temporary steel support 6 is padded. The temporary steel support 6 can replace the preloading mechanism 5 to bear the force or bear the force together with the preloading mechanism 5 to transfer part of the dead load on the old pile foundation 1 to the new pile foundation 3. Subsequently, concrete can be poured at the pile head part of the new pile foundation 3 to fill the accommodation space, so that the new pile foundation 3, the reinforced bearing platform 2 and the temporary steel support 6 form a whole, and the old pile foundation 1 can be strengthened. It should be noted that in this embodiment, when pouring concrete, the preloading mechanism 5 can be disassembled and used again next time. And because the cost of the preloading mechanism 5 is relatively low, the preloading mechanism 5 can also be left on the new pile foundation 3.

[0041] The overall size of the small reaction device in this embodiment is small, the loading is convenient, and it is very suitable for the preloading of pile foundation reinforcement in a narrow space. Moreover, the small reaction device of this application has a simple structure, makes full use of the reinforcement structure as an anchor, and does not require additional construction of anchor piles, which is convenient for on-site construction, effectively reduces the construction difficulty, and has good overall economy. In addition, the small reaction device of this application can be prefabricated in the factory and installed on-site, and the required construction period is short, with the advantage of fast construction.

[0042] As Figures 1 to 3 shown, as a further solution of this embodiment, the bearing mechanism 4 includes a crossbeam assembly 40 cooperating with the preloading mechanism 5 and a fixing member 41 for detachably fixing the crossbeam assembly 40 to the connecting portion 20.

[0043] The crossbeam assembly 40 includes a pair of connecting crossbeams 400 connected to the connecting portion 20 and a bearing crossbeam 401 disposed between the two connecting crossbeams 400. The bearing crossbeam 401 is located above the accommodation space and abuts against the preloading mechanism 5. Both ends of the bearing crossbeam 401 are fixedly connected to the corresponding connecting crossbeams 400. The connecting crossbeams 400 are detachably connected to the connecting portion 20 through the fixing member 41. The bearing crossbeam 401 and the connecting crossbeams 400 are fixedly connected by welding.

[0044] The fixing member 41 is a vertical anchor rod and there are multiple of them. The lower part of the vertical anchor rod is embedded in the connecting portion 20 and forms an integral body with the connecting portion 20. The upper part of the vertical anchor rod is connected to the connecting crossbeam 400. The vertical anchor rod is made of a rolled threaded steel with a diameter of 32 mm. One end is embedded into the reinforced bearing platform 2, and the other end is poured with concrete at the pile head part of the pile foundation. After the concrete solidifies, the crossbeam assembly 40 can be disassembled and used repeatedly.

[0045] As Figures 1 to 3 shown, as a further solution of this embodiment, the preloading mechanism 5 includes a jack 50 disposed on the new pile foundation 3. In this embodiment, the cost of using the jack 50 is low and the stability is high, and it can adapt to a small space.

[0046] As Figures 1 to 3 shown, as a further solution of this embodiment, the preloading mechanism 5 further includes an upper stress diffusion steel plate 51, a force transmission steel section 52, and a lower stress diffusion steel plate 53 sequentially disposed at the bottom of the jack 50. The jack 50, the upper stress diffusion steel plate 51, the force transmission steel section 52, the lower stress diffusion steel plate 53, and the center of the new pile foundation 3 are coaxially arranged. By providing the upper stress diffusion steel plate 51, the force transmission steel section 52, and the lower stress diffusion steel plate 53, the jack 50 can be effectively supported, solving the problem of insufficient height of the jack 50. After jacking up, the jack 50, the upper stress diffusion steel plate 51, the force transmission steel section 52, and the lower stress diffusion steel plate 53 can be taken out without affecting the pouring of the concrete.

[0047] As Figure 1 shown, as a further solution of this embodiment, there is a gap between the connecting portion 20 and the crossbeam assembly 40 to facilitate the removal of the preloading mechanism 5. By providing a gap between the crossbeam assembly 40 and the connecting portion 20 of the reinforced bearing platform 2, the jack 50, the upper stress diffusion steel plate 51, the force transmission steel section 52, and the lower stress diffusion steel plate 53 in the preloading mechanism 5 can be easily taken out, effectively improving the construction efficiency.

[0048] As shown Figures 1 to 3 in the figure, the present invention also provides a reinforcement method for preloading and reinforcing old pile foundations, using the above-mentioned small reaction device for preloading newly added reinforced pile foundations, including the following steps;

[0049] S1. Preset new pile foundations 3 and a reinforcement cap 2. New pile foundations 3 are constructed on both sides of the old pile foundation 1, and a reinforcement cap 2 is added to the old pile foundation 1 to integrate the reinforcement cap 2 with the old pile foundation 1. Both sides of the reinforcement cap 2 extend outward to form a connecting portion 20, and a receiving space for accommodating the preloading mechanism 5 is reserved in the connecting portion 20. And a fixing member 41 is preset on the connecting portion 20. The newly constructed new pile foundations 3 are located below the corresponding connecting portions 20. The construction process of presetting the new pile foundations 3 and the reinforcement cap 2 is carried out according to the above steps, and will not be elaborated here.

[0050] S2. Install the small reaction device. When installing the small reaction device, first install the preloading mechanism 5. The preloading mechanism 5 is installed at the central position on the top of the new pile foundation 3. Subsequently, install the bearing mechanism 4. Connect the crossbeam assembly 40 in the bearing mechanism 4 with the fixing member 41 in S1, so that the entire bearing mechanism 4 and the connecting portion 20 form a whole, and the crossbeam assembly 40 spans across the receiving space and is located above the preloading mechanism 5.

[0051] S3. Start the small reaction device to distribute part of the dead load borne by the old pile foundation 1 to the new pile foundations 3. When starting the small reaction device, first start the preloading mechanism 5. The preloading mechanism 5 jacks upward to the crossbeam assembly 40, thereby preloading the new pile foundations 3. After preloading to the preset value, pad and insert a temporary steel support member 6 to replace the preloading mechanism 5 or jointly bear the force with the preloading mechanism 5 to distribute part of the dead load borne by the old pile foundation 1 to the new pile foundations 3.

[0052] S4. Pour concrete on the pile heads of the new pile foundations 3 to connect the bearing mechanism 4, the new pile foundations 3 and the reinforcement cap 2 into a whole. In this step, after padding and inserting the temporary steel support member 6, the preloading mechanism 5 can be disassembled and used continuously next time. And due to the low cost of the preloading mechanism 5, the preloading mechanism 5 can also be left on the new pile foundations 3.

[0053] As a further solution of this embodiment, after the poured concrete is formed, disassemble the crossbeam assembly 40. After disassembling the crossbeam assembly 40, it can be used continuously next time, saving costs.

[0054] As a further solution of this embodiment, when presetting and reinforcing the bearing platform 2 in S4, a steel bar reserved opening penetrating the accommodation space is reserved in the connecting portion 20, and in S3, after the preloading mechanism 5 finishes preloading, the preloading mechanism 5 is removed, and a steel bar penetrating the accommodation space is implanted at the steel bar reserved opening, and the steel bar is arranged along the length direction of the reinforced bearing platform 2. After the preloading device is disassembled, the steel bar is implanted. By arranging the steel bar, the connection strength between the new pile foundation 3 and the reinforced bearing platform 2 can be enhanced. It should be noted that the steel bar reserved opening and the steel bar are not shown in this application.

[0055] A reinforcement method for preloading and reinforcing an old pile foundation in this application relies on the small reaction force device in this application and reinforces the old pile foundation 1 of the bridge through the above steps. There is no need to construct anchor piles additionally, which is convenient for on-site construction, effectively reduces the construction difficulty, and can effectively improve the construction efficiency. Moreover, the small reaction force device of this application can be prefabricated in the factory and installed on-site, with a short construction period required, and has the advantage of fast construction.

Claims

1. A small reaction force device for pre-stressing a newly added reinforced pile foundation, wherein a reinforcement cap (2) fixedly connected to the old pile foundation (1) is transversely provided on the old pile foundation (1), and both sides of the reinforcement cap (2) extend out of the old pile foundation (1) to form a connecting portion (20), and a receiving space for accommodating a part of the structure of the small reaction force device is formed in the connecting portion (20), and both sides of the old pile foundation (1) are pre-set with new pile foundations (3) embedded in the ground, characterized in that The small reaction force device comprises a bearing mechanism (4) arranged on the connection part (20) and spanning the accommodation space, and a pre-stressing mechanism (5) arranged on the top of the new pile foundation (3) for pre-stressing the bearing mechanism (4) and distributing part of the constant load borne by the old pile foundation (1) to the new pile foundation (3). The small reaction force device also comprises a temporary steel support (6) which is inserted between the new pile foundation (3) and the bearing mechanism (4) and is used to replace the pre-stressing mechanism (5) or to bear force together with the pre-stressing mechanism (5) and distribute part of the constant load borne by the old pile foundation (1) to the new pile foundation (3).

2. A small reaction force device for preloading a newly added pile foundation according to claim 1, characterized in that The bearing mechanism (4) comprises a crossbeam assembly (40) cooperating with the pre-pressing mechanism (5) and a fixing member (41) used for detachably fixing the crossbeam assembly (40) on the connecting portion (20).

3. A small reaction force device for preloading a newly added pile foundation according to claim 1, characterized in that The pre-pressing mechanism (5) comprises a jack (50) arranged on the new pile foundation (3).

4. A small reaction force device for preloading a newly added pile foundation according to claim 3, characterized in that The pre-pressing mechanism (5) also includes an upper stress diffusion steel plate (51), a force transmission steel (52) and a lower stress diffusion steel plate (53) which are sequentially arranged at the bottom of the jack (50).

5. A small reaction force device for preloading a newly added pile foundation according to claim 2, characterized in that The crossbeam assembly (40) comprises a pair of connecting crossbeams (400) connected to the connecting portion (20) and a bearing crossbeam (401) arranged between the two connecting crossbeams (400). The bearing crossbeam (401) is located above the accommodating space and abuts against the pre-pressing mechanism (5). Both ends of the bearing crossbeam (401) are fixedly connected to the corresponding connecting crossbeams (400). The connecting crossbeam (400) is detachably connected to the connecting portion (20) via a connecting piece.

6. A small reaction force device for preloading a newly added pile foundation according to claim 5, characterized in that The fixing member (41) is a plurality of vertical anchor rods, the lower portion of which is pre-buried in the connecting portion (20) and forms an integral body with the connecting portion (20), and the upper portion of which is connected to the connecting crossbeam (400).

7. A small reaction force device for preloading a newly added pile foundation according to claim 5, characterized in that There is a gap between the connecting portion (20) and the crossbeam assembly (40) for facilitating the removal of the pre-pressing mechanism (5).

8. A reinforcement method for preloading an old pile foundation, using a small reaction force device for preloading a newly added reinforced pile foundation as claimed in any one of claims 1 to 7, characterized in that The steps include: S1, pre-setting a new pile foundation (3) and a reinforcement cap (2), and building a new pile foundation (3) on both sides of the old pile foundation (1); adding a reinforcement cap (2) on the old pile foundation (1), so that the reinforcement cap (2) and the old pile foundation (1) form an integral body, and the two sides of the reinforcement cap (2) extend outward to form a connecting portion (20), and the connecting portion (20) reserves a space for accommodating a pre-pressing mechanism (5), and a fixing member (41) is pre-set on the connecting portion (20), and the newly built new pile foundation (3) is located below the corresponding connecting portion (20); S2, arranging a small reaction device. When arranging the small reaction device, first arrange the pre-stressing mechanism (5), arrange the pre-stressing mechanism (5) at the center of the top of the new pile foundation (3), then arrange the bearing mechanism (4), connect the crossbeam assembly (40) in the bearing mechanism (4) with the fixing member (41) in S1, so that the entire bearing mechanism (4) and the connecting part (20) of the crossbeam form a whole, and the crossbeam assembly (40) spans the accommodation space and is located above the pre-stressing mechanism (5); S3, start the small reaction device to distribute part of the constant load borne by the old pile foundation (1) to the new pile foundation (3). When starting the small reaction device, first start the preloading mechanism (5), and lift it upward to the crossbeam assembly (40) through the preloading mechanism (5), so as to preload the new pile foundation (3). After preloading to a preset value, a temporary steel support member (6) is used to replace the preloading mechanism (5) or to bear force together with the preloading mechanism (5) to distribute part of the constant load borne by the old pile foundation (1) to the new pile foundation (3); S4, pouring concrete on the pile head of the new pile foundation (3) so that the bearing structure (4), the new pile foundation (3) and the reinforced cap (2) are connected into a whole.

9. The reinforcement method of old pile foundation by pre-pressing according to claim 8, characterized in that In S4, after the poured concrete is formed, the crossbeam assembly (40) is disassembled.

10. The reinforcement method of old pile foundation by pre-pressing according to claim 8, characterized in that When the reinforcement cap (2) is preset, a steel bar reserved opening that passes through the accommodation space is reserved in the connection portion (20), and in S3, after the pre-stressing mechanism (5) completes the pre-stressing, steel bars that pass through the accommodation space are implanted at the steel bar reserved opening, and the steel bars are arranged along the length direction of the reinforcement cap (2).

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