Device and method for completely transmitting newly-added load of existing building to anchor rod pile

Abstract

The invention discloses a device and a method for completely transmitting a newly-added load of an existing building to an anchor rod pile, and the breakthrough technical effect that the newly-added load of the existing building is completely transmitted to a newly-added pile foundation bearing platform is achieved through accurate calculation, flexible isolation, accurate load underpinning and original foundation base stress recovery. It is ensured that the newly-added load is completely borne by the newly-added anchor rod piles, and distribution characteristics of the newly-added load are accurately calculated by establishing a building structure-foundation-foundation collaborative stress model; the flexible isolation layer is innovatively designed, and the transmission path of the newly-added load to the original foundation is effectively cut off; and a vertical deformation barostat is researched and developed, plastic deformation of the vertical deformation barostat is utilized, then the newly-added anchor rod pile is always in a preset stress state after being loaded, and the stability of the stress state of an original foundation in the load transfer process is ensured. The method is suitable for the working condition that the bearing capacity of the base is insufficient due to storey adding, functional transformation and the like of the existing building, the reinforcement cost can be reduced by about 35%, the construction period can be shortened by about 40%, remarkable economic and social benefits are achieved, and a brand new technical path is provided for foundation reinforcement of the existing building.

Description

Technical Field

[0001] The present invention belongs to the field of civil engineering foundation reinforcement, and in particular relates to a device and method for completely transferring the newly added load of an existing building to an anchor pile. Background Art

[0002] With the development of urbanization and the improvement of people's living standards, some old houses can no longer meet people's requirements for living quality. At the same time, the planning and functions of the areas where some old houses are located have changed. Therefore, the demand for large-scale engineering construction and renovation of old houses is becoming increasingly prominent.

[0003] During the renovation of existing buildings, it is common for the load on the superstructure to increase as the functional requirements and space requirements change. As an essential component of the building structure, the foundation plays a crucial role in evenly transferring the load of the superstructure to the foundation. Insufficient foundation bearing capacity can lead to serious safety hazards such as foundation settlement, wall cracking, and even overall building tilt, directly threatening the lives and property of users. Therefore, when the additional load exceeds the original foundation design bearing capacity, appropriate reinforcement measures must be taken to increase the bearing capacity of the existing foundation to ensure the safety of the structure during subsequent use.

[0004] Reinforcement measures for the original foundation refer to scientific and reasonable foundation reinforcement measures, such as expanding the bottom area of ​​the foundation, adding pile foundation pedestals or strengthening the foundation, so as to effectively improve the bearing capacity of the foundation so that it can adapt to the requirements of the new load. The existing foundation reinforcement methods (such as expanding the foundation, adding pile foundations, etc.) are to excavate the original pile foundation of the existing building column piles, cast the new pile foundations, and reliably connect the new pile foundations with the original pile foundations and building column piles so that the load of the building column piles can be transferred to the new pile foundations. However, in actual applications, the existing foundation reinforcement methods are difficult to ensure that the new and old structures are subjected to coordinated forces, and the new foundation structure has obvious stress lag disadvantages, which can easily lead to the original foundation still bearing a large amount of the new load, making it impossible for the new foundation to fully play its role, resulting in differential settlement of the new and old structures, which can easily lead to cracking of the connection nodes, posing a potential threat to structural safety. Furthermore, due to the lack of precise load distribution control, the added load may be diverted through the rigid connection between the existing foundation and the anchor piles. According to field data, approximately 30% to 50% of the added load in traditional pile foundation replacements is still transmitted through the existing foundation. Furthermore, traditional foundation expansion construction requires excavation of the existing foundation, which further reduces the bearing capacity of the existing foundation by 20% to 40%.

[0005] Therefore, how to ensure that the original foundation load of the renovated building remains unchanged while allowing the newly added pile foundation to fully play its bearing role is an urgent problem that needs to be solved to ensure the safety of the renovated building. Summary of the Invention

[0006] To address the problem of stress lag in the newly added foundation structure caused by traditional foundation reinforcement methods, resulting in the original foundation bearing a large additional load, posing a potential threat to structural safety, the present invention provides a device and method for completely transferring the newly added load of an existing building to anchor piles. Through "precise calculation + flexible isolation + precise load replacement + stress restoration of the original foundation base," this breakthrough technical approach achieves the complete transfer of the newly added load of an existing building to the newly added anchor piles, ensuring that 100% of the newly added load is borne by the newly added anchor piles. The specific technical solution is as follows:

[0007] First, the present invention provides a device for completely transferring the newly added load of an existing building to an anchor pile, comprising a frame column, an original foundation located at the bottom of the frame column, and a newly added pile foundation pedestal arranged around the bottom of the frame column and reliably connected to the frame column; an anchor pile is provided at the bottom of the newly added pile foundation pedestal, and the anchor pile passes through a pile-pressing hole in the original foundation; the top of the anchor pile is located in the pile position hole of the newly added pile foundation pedestal, and a vertical deformation constant pressure device and a pile-sealing steel pipe are provided on the top of the anchor pile in sequence; the upper end of the pile-sealing steel pipe is flush with the upper surface of the newly added pile foundation pedestal, and a jack is provided thereon; a load beam is horizontally provided on the jack, and the load beam is fixed to the newly added pile foundation pedestal by threaded anchor rods symmetrically embedded on both sides of the jack; when sealing the pile, the load beam provides stable and reliable reaction force support for the jack, thereby applying preload pressure to the anchor pile; and through the plastic deformation of the vertical deformation constant pressure device, the anchor pile is always in a predetermined stress state after loading, thereby achieving complete transfer of the newly added load on the frame column to the anchor pile.

[0008] The aforementioned device completely transfers the newly added load of the existing building to the anchor pile. The vertical deformation constant pressure device is preferably a metal yield damper with a yield strength set to 1.01F and a deformation ≥ 30mm, where F is the newly added load on the frame column; when the pressure borne by the vertical deformation constant pressure device is ≥ 1.01F, buckling deformation occurs to disperse the newly added load, thereby ensuring that the anchor pile is always in a predetermined stress state after loading, ensuring that 100% of the newly added load is borne by the anchor pile.

[0009] The aforementioned device completely transfers the newly added load of the existing building to the anchor piles. The anchor piles are preferably made of steel and their axial stiffness is much greater than the original foundation stiffness to ensure that the load is preferentially transferred to the anchor piles. Specifically:

[0010]

[0011] K 桩 ≥10·K 基础

[0012] Where:

[0013] K 桩is the axial stiffness of the anchor pile;

[0014] K 基础 is the original foundation stiffness;

[0015] E 桩 is the elastic modulus of the anchor pile, and the steel pile is 200GPa;

[0016] A 桩 is the cross-sectional area of ​​the anchor pile, m2;

[0017] L 桩 is the length of the anchor pile, m.

[0018] The aforementioned device completely transfers the newly added load of the existing building to the anchor piles, and an isolation material is provided between the anchor piles and the original foundation. The isolation material is an elastic polymer material (such as polyurethane elastomer), which is used to effectively isolate the anchor piles and the original foundation to avoid the newly added load from being diverted through the rigid connection between the anchor piles and the original foundation.

[0019] The aforementioned device completely transfers the newly added load of the existing building to the anchor pile. The jack is a self-locking jack, and its axis coincides with the axis of the pile sealing steel pipe and the vertical deformation constant pressure device, ensuring that the pre-load pressure of the jack can be effectively transferred to the anchor pile when sealing the pile.

[0020] The aforementioned device completely transfers the additional load of the existing building to the anchor pile. The jack applies pre-load pressure to the anchor pile under the control of the pressure controller, which is a hydraulic device. When sealing the pile, the pre-load pressure meets the following requirements:

[0021]

[0022] Where:

[0023] P pre is the preload pressure applied to the anchor pile, kN;

[0024] F 新增 is the total additional load, kN;

[0025] n is the number of anchor piles;

[0026] k 安全 is the safety factor, which is 1.02;

[0027] ΔP 损失 It is the prestress loss during prestressing construction, which is 5% of the design value.

[0028] The aforementioned device completely transfers the newly added load of the existing building to the anchor pile, the load beam is made of steel, and the threaded anchor rod is a precision-rolled threaded rod; the end of the threaded anchor rod is pre-buried in the newly added pile foundation pedestal, and the reserved length at the upper end meets the requirement that the threaded anchor rod passes through the load beam and is locked with a nut when sealing the pile.

[0029] The aforementioned device completely transfers the newly added load of the existing building to the anchor piles. The newly added pile foundation pedestal is a reinforced concrete component, which is reliably connected to the original foundation and frame columns through steel bar binding and newly poured concrete; a plurality of pile holes are reserved on the newly added pile foundation pedestal for anchor pile construction and pile sealing.

[0030] Secondly, the present invention provides a construction method for completely transferring the newly added load of an existing building to the anchor piles. The method adopts the above-mentioned device for construction and specifically comprises the following steps:

[0031] 1) Calculate the original load G and the new load F on the frame column, and satisfy G ≥ 1.2F;

[0032] 2) Select the vertical deformation constant pressure device according to the additional load F on the frame column;

[0033] 3) Use isolation materials to densely fill the pile holes outside the anchor piles to ensure effective isolation between the anchor piles and the original foundation, and avoid a rigid connection between the anchor piles and the original foundation when the piles are sealed;

[0034] 4) Based on the calculated additional load F, use the pressure controller to control the jack to apply preload pressure. Through the reaction force support of the load beam, the preload pressure applied by the jack is transmitted downward through the pile sealing steel pipe and the vertical deformation constant pressure device to the anchor pile; observe the vertical displacement of the frame column, and when its settlement rate reaches the predetermined requirement, lock the pile;

[0035] 6) Use concrete pouring to seal the pile holes and maintain them, so that the anchor piles are always in the predetermined stress state after loading, ensuring that the new load F is fully borne by the anchor piles, and the construction is completed.

[0036] As a preferred technical solution, the aforementioned construction method of completely transferring the newly added load of the existing building to the anchor piles, in step 4), the preload pressure is applied once, and the specific process is: use a jack to load a pressure of 1.0F at one time, then let it stand and monitor the vertical displacement of the frame column, and when its settlement rate is ≤0.04mm / d, lock the pile.

[0037] The beneficial effects of the present invention are as follows:

[0038] Compared with traditional reinforcement technology, this invention has the following significant advantages:

[0039] 1) This invention addresses the problem of insufficient bearing capacity of the original foundation due to the added load on existing buildings. It proposes a solution of "precise calculation + flexible isolation + precise load replacement + stress restoration of the original foundation base". This solution achieves a breakthrough technical effect of fully transferring the added load of the existing building to the newly added anchor piles.

[0040] 2) The present invention establishes a coordinated stress model of "building structure-foundation-subgrade" by adopting a precise load calculation and transmission system, and accurately calculates the distribution characteristics of the new load; innovatively designs a flexible isolation layer to effectively cut off the transmission path of the new load to the original foundation; develops a vertical deformation constant pressure device, and utilizes the plastic deformation of the vertical deformation constant pressure device to ensure that the new anchor piles are always in a predetermined stress state after loading, ensuring the stability of the stress state of the original foundation during the load transfer process, so as to achieve the purpose of the new load being completely borne by the anchor piles.

[0041] 3) The device of the present invention can achieve a 100% efficiency in transferring the newly added load to the newly added pile foundation cap, completely solving the technical bottleneck of the traditional method where 30% to 50% of the load is still borne by the original foundation; through stress recovery technology, the original foundation is completely restored to its initial stress state after reinforcement, avoiding the risk of secondary foundation settlement; and the vertical deformation constant pressure device used has an automatic compensation function, which can adapt to long-term load changes and ensure the long-term stability of the stress system; and the construction process has minimal impact on the normal use of the building, significantly reducing the safety risks of the reinforcement project.

[0042] 4) The device and method of the present invention are applicable to working conditions where the base bearing capacity is insufficient due to the addition of floors or functional transformation of existing buildings. Engineering verification shows that the present invention can reduce the reinforcement cost by about 35% and shorten the construction period by 40%. It has significant economic and social benefits and provides a new technical path for the reinforcement of the foundation of existing buildings. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of the device structure for completely transferring the new load of an existing building to the anchor piles.

[0044] In the figure: 1. Frame column; 2. Original foundation; 21. Pile hole; 3. New pile foundation cap; 31. Pile position hole; 4. Anchor pile; 5. Vertical deformation constant pressure device; 6. Pile sealing steel pipe; 7. Jack; 8. Load beam; 9. Threaded anchor rod; 10. Isolation material; 11. Pressure controller. DETAILED DESCRIPTION

[0045] The following will be combined with the embodiments and drawings to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only preferred embodiments of the present invention, not all embodiments, and are not intended to limit the present invention in any other form. Any person skilled in the art may use the disclosed technical content to make changes or modifications. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

[0046] Example 1

[0047] This embodiment addresses the problems of traditional foundation reinforcement methods, such as the lag in stress of the newly added foundation structure, which causes the original foundation to bear a large new load, posing a potential threat to structural safety; and the lack of precise load distribution control in the case of new loads, which may cause diversion of the new load through the rigid connection between the original foundation and the anchor piles. It proposes a device and method for completely transferring the new load of an existing building to the anchor piles. The method proposes a breakthrough technical effect of completely transferring the new load of an existing building to the new anchor piles through "precise calculation + flexible isolation + precise load replacement + original foundation base stress recovery", ensuring that 100% of the new load is borne by the new anchor piles. The details are as follows:

[0048] First, to address the problem that the stress lag of the newly added foundation structure causes the original foundation to bear a large new load, posing a potential threat to the structural safety, this embodiment provides a device that completely transfers the new load of the existing building to the anchor piles, such as Figure 1 As shown, the device includes a frame column 1, an existing foundation 2 located at the bottom of the frame column 1, and a newly added pile foundation cap 3 arranged around the bottom of the frame column 1 and reliably connected to the frame column 1. The newly added pile foundation cap 3 is a reinforced concrete member, which can be reliably connected to the existing foundation 2 and the frame column 1 through steel bar binding and newly poured concrete. That is, the newly added pile foundation cap 3 tightly embraces the frame column 1, providing support for it and sharing the added load.

[0049] In order to enable the newly added pile foundation pedestal 3 to truly and effectively bear the newly added load on the frame column 1, the device described in this embodiment is designed as follows: a plurality of pile holes 31 are reserved on the newly added pile foundation pedestal 3, each pile hole 31 corresponds to an anchor pile, and the pile hole 31 is used for the construction and sealing of the anchor piles 4. That is, an anchor pile 4 is provided at the bottom of the newly added pile foundation pedestal 3, and the anchor pile 4 passes through the pile hole 21 on the original foundation 2; the top of the anchor pile 4 is located in the pile position hole 31 of the newly added pile foundation pedestal 3, and a vertical deformation constant pressure device 5 and a pile sealing steel pipe 6 are provided on the top of the anchor pile 4 in sequence; the upper end of the pile sealing steel pipe 6 is flush with the upper surface of the newly added pile foundation pedestal 3, and a jack 7 is provided thereon; a load beam 8 is horizontally arranged on the jack 7, and the load beam 8 is fixed to the newly added pile foundation pedestal 3 by threaded anchor rods 9 symmetrically embedded on both sides of the jack 7; when sealing the pile, the load beam 8 provides a stable and reliable reaction force support for the jack 7, thereby applying preload pressure to the anchor pile 4; and through the plastic deformation of the vertical deformation constant pressure device 5, the anchor pile 4 is always in a predetermined stress state after loading, so that the newly added load on the frame column 1 is completely transferred to the anchor pile 4.

[0050] In this embodiment, the vertical barostat 5 is a metal yield-type damper with a yield strength set at 1.01F and a deformation ≥ 30mm, where F represents the additional load on the frame column 1. When the pressure on the vertical barostat 5 exceeds 1.01F, it buckles to distribute the additional load, thereby ensuring that the anchor pile 4 remains in a predetermined stress state after loading, ensuring that 100% of the additional load is borne by the anchor pile 4. In other words, the anchor pile 4 only bears the additional load on the frame column 1. The load exceeding the additional load is still borne by the existing foundation 2 under the action of the vertical barostat 5. This not only ensures that the existing foundation does not bear the additional load, but also addresses the stress lag problem of the newly added foundation structure, ensuring the safety of the existing building.

[0051] In this embodiment, the anchor pile 4 is made of pile-type steel, and its axial stiffness is much greater than the original foundation stiffness to ensure that the load is preferentially transferred to the anchor pile 4, specifically:

[0052]

[0053] K 桩 ≥10·K 基础

[0054] Where:

[0055] K 桩 is the axial stiffness of the anchor pile 4;

[0056] K 基础 is the stiffness of the original foundation 2;

[0057] E 桩is the elastic modulus of the anchor pile 4, which is 30 GPa for concrete piles and 200 GPa for steel piles. In this embodiment, 200 GPa is used for steel piles;

[0058] A 桩 is the cross-sectional area of ​​anchor pile 4, m2;

[0059] L 桩 The anchor piles are 4 m long.

[0060] In this embodiment, in order to solve the problem that the added load may be diverted through the rigid connection between the original foundation and the anchor pile, an isolation material 10 is provided between the anchor pile 4 and the original foundation 2. The isolation material 10 is an elastic polymer material, and in this embodiment, a polyurethane elastomer is used to effectively isolate the anchor pile 4 from the original foundation 2, thereby preventing the added load from being diverted through the rigid connection between the anchor pile 4 and the original foundation 2.

[0061] In this embodiment, the jack 7 is a self-locking jack. When sealing the pile, the jack 7 is a key device for applying pre-pressure to the anchor pile 4. The axes of the jack 7, the pile sealing steel pipe 6, and the vertical deformation constant pressure device 5 coincide with each other, ensuring that the pre-pressure of the jack 7 can be effectively transmitted to the anchor pile 4 when sealing the pile.

[0062] In this embodiment, the jack 7 applies pre-load pressure to the anchor pile 4 under the control of the pressure controller 11, which is a hydraulic device. When packaged, the pre-load pressure meets the following requirements:

[0063]

[0064] Where:

[0065] P pre is the preload pressure applied to the anchor pile 4, kN;

[0066] F 新增 is the total additional load, kN;

[0067] n is the number of anchor piles 4;

[0068] k 安全 is the safety factor, which is 1.02;

[0069] ΔP 损失 It is the prestress loss during prestressing construction, which is 5% of the design value.

[0070] In this embodiment, the load beam 8 is made of steel, and the threaded anchor rod 9 is made of precision-rolled screw steel; the end of the threaded anchor rod 9 is pre-buried in the newly added pile foundation pedestal 3, and the reserved length at the upper end meets the requirement that the threaded anchor rod 9 passes through the load beam 8 and is locked with a nut when sealing the pile.

[0071] This embodiment provides a construction method for completely transferring the additional load of an existing building to the anchor piles, employing multiple sets of the aforementioned devices. Specifically, the newly added pile foundation cap 3 has multiple pile holes 31 reserved, each corresponding to an anchor pile, and each anchor pile corresponding to one set of the aforementioned devices. The specific construction steps are as follows:

[0072] 1) Calculate the original load G and the new load F on frame column 1, and satisfy G ≥ 1.2F.

[0073] 2) Select the vertical barostat 5 based on the additional load F on the frame column 1, specifically a metal yield damper with a yield strength set to 1.01F and a deformation ≥ 30mm. Specifically, when the pressure on the vertical barostat 5 is ≥ 1.01F, it buckles to distribute the additional load, ensuring that the anchor pile 4 remains in the predetermined stress state after loading, ensuring that 100% of the additional load is borne by the anchor pile 4. In other words, the anchor pile 4 only bears the additional load on the frame column 1. Any load exceeding the additional load is still borne by the existing foundation 2 under the action of the vertical barostat 5. This precise load distribution control not only protects the existing foundation from bearing the large additional load, but also addresses the stress lag problem of the newly added foundation structure, thereby ensuring the safety of the existing building.

[0074] 3) Use the isolation material 10 to densely fill the pile hole 21 outside the anchor pile 4 to ensure that the anchor pile 4 and the original foundation 2 are effectively isolated and avoid a rigid connection between the anchor pile 4 and the original foundation 2 when the pile is sealed.

[0075] 4) According to the calculated additional load F, the pressure controller 11 is used to control the jack 7 to apply preload pressure, and the preload pressure applied by the jack 7 is supported downward by the reaction force of the load beam 8, and is transmitted to the anchor pile 4 through the pile sealing steel pipe 6 and the vertical deformation constant pressure device 5; the vertical displacement of the frame column 1 is observed, and when its settlement rate reaches the predetermined requirement, the pile is locked; the preload pressure is applied once, and the specific process is: use the jack 7 to load a pressure of 1.0F at one time, then let it stand and monitor the vertical displacement of the frame column 1, and when its settlement rate is ≤0.04mm / d, the pile is locked.

[0076] 5) The pile holes 21 are sealed and maintained by pouring concrete, so that the anchor piles 4 are always in a predetermined stress state after loading, ensuring that the newly added load F is fully borne by the anchor piles 4, and the construction is completed.

[0077] Example 2

[0078] This embodiment is to use the device and method described in Example 1 to completely transfer the newly added load of the existing building to the anchor piles to renovate and reinforce the factory building of a certain enterprise in Anhui. The construction area of ​​the project is about 20,000 square meters, with 2 floors above ground and a building height of 16.15m. It is a reinforced concrete frame structure with an independent foundation under the column. Due to the functional adjustment of the owner, the newly added load on the upper part exceeds the design bearing capacity of the original foundation. After research and demonstration, the present invention is used to reinforce the original foundation, taking a frame column of the original structure as an example. The upper load of the original frame column G = 2000kN, and the newly added load F = 1200kN. The specific implementation process is as follows:

[0079] 1) G = 2000kN, F = 1200kN, satisfying G ≥ 1.2F, and establishing the original foundation-anchor pile collaborative model;

[0080] 2) Determine the size of the new foundation and the type of anchor piles (4 Φ273 anchor piles, with a single pile bearing capacity characteristic value of Ra = 300kN) based on the additional upper load F and the original foundation. The anchor piles are arranged symmetrically around the frame column.

[0081] 3) Select a vertical barostat based on the additional load F of the superstructure. The damper yield force of this device is 300 kN (model: DN-MYD-300). The vertical barostat should ensure that the plastic deformation curve under the action of ΔF conforms to the Ramberg-Osgood model.

[0082] 4) Use isolation materials to densely fill the pile holes outside the anchor piles to ensure effective isolation between the anchor piles and the original foundation, and avoid a rigid connection between the anchor piles and the original foundation when the piles are sealed;

[0083] 5) Construct the anchor piles to the design elevation as required and verify the characteristic value of the single pile bearing capacity Ra = 300kN;

[0084] 6) Calculate the preload pressure of the pile according to the newly added load as follows:

[0085] (1) Single pile design load:

[0086] P 单桩 =300kN

[0087] Preload pressure (including loss)

[0088]

[0089] 7) Using the present invention, the anchor piles are loaded to 321 kN at one time (preloading is applied to four anchor piles simultaneously) → the piles are left to stand and the vertical displacement of the superstructure is monitored. When the settlement rate is ≤ 0.04 mm / d → the piles are locked;

[0090] 8) Use concrete to seal the pile holes and maintain them, and the construction is completed.

[0091] Example 3

[0092] This embodiment also utilizes the device and method described in Example 1 for completely transferring the newly added load of an existing building to the anchor piles to renovate and reinforce the existing building. The building was built in 2002, with a frame structure, four floors above ground, and a reinforced concrete raft structure as the foundation. Due to the upgrade of the owner's building function, two floors were added to the top of the building, resulting in the newly added load on the upper part exceeding the original foundation design bearing capacity. Therefore, by adding anchor piles, the newly added load on the upper structure is fully replaced. It has been demonstrated that the present invention is used to reinforce the original foundation. Taking the first-floor concrete column as an example: the upper load of the original concrete column is G = 2850kN, and the newly added load is F = 1600kN. The specific implementation process is as follows:

[0093] 1) G = 2850kN, F = 1600kN, satisfying G ≥ 1.2F, and using finite element software to establish the original foundation-anchor pile collaborative model;

[0094] 2) Determine the anchor pile type based on the additional load F of the superstructure and the foundation type (4 Φ325 single piles with a characteristic bearing capacity of Ra = 400kN). The four anchor piles are arranged symmetrically around the frame column;

[0095] 3) Select a vertical barostat based on the additional load F of the superstructure. The damper yield force of this device is 400 kN (model: DN-MYD-400). The vertical barostat should ensure that the plastic deformation curve under the action of ΔF conforms to the Ramberg-Osgood model.

[0096] 4) Construct the anchor piles to the design elevation as required and verify the characteristic value of the single pile bearing capacity Ra = 400kN;

[0097] 5) Use isolation materials to densely fill the pile holes outside the anchor piles to ensure effective isolation between the anchor piles and the original foundation, and avoid a rigid connection between the anchor piles and the original foundation when the piles are sealed;

[0098] 6) Calculate the preload pressure of the pile according to the newly added load as follows:

[0099] (1) Single pile design load:

[0100] P 单桩 =400kN

[0101] (2) Preload pressure (including loss)

[0102]

[0103] 7) Using the present invention, the anchor piles are loaded to 428 kN at one time (preloading is applied to four anchor piles simultaneously) → the piles are left to stand and the vertical displacement of the superstructure is monitored. When the settlement rate is ≤ 0.04 mm / d → the piles are locked;

[0104] 8) Use concrete to pour into the pile holes to seal the piles and maintain them, and the construction is completed.

[0105] In general, the solution of "precise calculation + flexible isolation + precise load replacement + stress restoration of the original foundation base" proposed in this invention achieves the breakthrough technical effect of completely transferring the new load of the existing building to the newly added anchor piles. By adopting a precise load calculation and transfer system, a "building structure-foundation-subgrade" collaborative force model is established to accurately calculate the distribution characteristics of the new load; an innovative flexible isolation layer is designed to effectively cut off the transmission path of the new load to the original foundation; and a vertical deformation constant pressure device is developed. The plastic deformation of the vertical deformation constant pressure device is used to ensure that the new anchor piles are always in a predetermined stress state after loading, ensuring the stability of the stress state of the original foundation during the load transfer process, so that the new load is completely borne by the anchor piles.

[0106] Engineering verification has shown that the device of the present invention can achieve a 100% efficiency in transferring the newly added load to the newly added pile foundation pedestal, completely solving the technical bottleneck of the traditional method in which 30% to 50% of the load is still borne by the original foundation; through stress recovery technology, the original foundation is completely restored to its initial stress state after reinforcement, avoiding the risk of secondary settlement of the foundation; and the vertical deformation constant pressure device used has an automatic compensation function, which can adapt to long-term load changes and ensure the long-term stability of the force system; and the construction process has minimal impact on the normal use of the building, significantly reducing the safety risks of the reinforcement project.

[0107] In addition, the device and method of the present invention are applicable to working conditions where the base bearing capacity is insufficient due to adding floors or functional transformation of existing buildings. The present invention can reduce the reinforcement cost by about 35% and shorten the construction period by 40%, with significant economic and social benefits. It provides a new technical path for the reinforcement of the foundation of existing buildings and has good practical value.

[0108] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be viewed as exemplary and non-restrictive in all respects. Furthermore, it should be understood that although this specification is described in terms of implementation methods, it does not encompass only one technical solution. This narrative is provided for clarity only, and those skilled in the art should consider the specification as a whole. The technical solutions in the embodiments may also be appropriately combined to form other implementation methods that are understandable to those skilled in the art.

Claims

1. A device for completely transferring the newly added load of an existing building to an anchor pile, comprising a frame column (1), an existing foundation (2) located at the bottom of the frame column (1), and a newly added pile foundation cap (3) arranged around the bottom of the frame column (1) and reliably connected to the frame column (1); characterized in that: An anchor pile (4) is provided at the bottom of the newly added pile foundation pedestal (3), and the anchor pile (4) passes through the pile hole (21) on the original foundation (2); The top of the anchor pile (4) is located in the pile hole (31) of the newly added pile foundation pedestal (3), and a vertical deformation constant pressure device (5) and a pile sealing steel pipe (6) are sequentially provided on the top of the anchor pile (4); The upper end of the pile sealing steel pipe (6) is flush with the upper surface of the newly added pile foundation pedestal (3), and a jack (7) is provided on it; A load beam (8) is horizontally arranged on the jack (7), and the load beam (8) is fixed to the newly added pile foundation pedestal (3) through threaded anchor rods (9) symmetrically embedded on both sides of the jack (7); When sealing the pile, the load beam (8) provides a stable and reliable reaction force support for the jack (7), thereby applying preload pressure to the anchor pile (4); and through the plastic deformation of the vertical deformation constant pressure device (5), the anchor pile (4) is always in a predetermined stress state after loading, so that the newly added load on the frame column (1) is completely transferred to the anchor pile (4).

2. The device for completely transferring the newly added load of an existing building to the anchor piles according to claim 1, characterized in that: The vertical deformation constant pressure device (5) is a metal yield type damper, the yield strength of which is set to 1.01F, and the deformation amount is ≥30mm, and the F is the additional load on the frame column (1); When the pressure borne by the vertical deformation constant pressure device (5) is ≥1.01F, buckling deformation occurs to disperse the newly added load, thereby ensuring that the anchor pile (4) is always in a predetermined stress state after loading, ensuring that 100% of the newly added load is borne by the anchor pile (4).

3. The device for completely transferring the newly added load of an existing building to the anchor piles according to claim 1, characterized in that: The anchor pile (4) is made of steel and its axial stiffness is much greater than the original foundation stiffness to ensure that the load is preferentially transferred to the anchor pile (4), specifically: K 桩 ≥10·K 基础 Where: K 桩 is the axial stiffness of the anchor pile (4); K 基础 is the original foundation (2) stiffness; E 桩 is the elastic modulus of the anchor pile (4), which is 30 GPa for concrete piles and 200 GPa for steel piles; A 桩 is the cross-sectional area of ​​the anchor pile (4), m 2 ; L 桩 is the length of anchor pile (4), m.

4. The device for completely transferring the newly added load of an existing building to the anchor piles according to claim 3, characterized in that: An isolation material (10) is provided between the anchor pile (4) and the original foundation (2). The isolation material (10) is an elastic polymer material and is used to effectively isolate the anchor pile (4) and the original foundation (2), thereby preventing the newly added load from being diverted through the rigid connection between the anchor pile (4) and the original foundation (2).

5. The device for completely transferring the newly added load of an existing building to the anchor piles according to claim 1, characterized in that: The jack (7) is a self-locking jack (7), and its axis coincides with the axis of the pile sealing steel pipe (6) and the vertical deformation constant pressure device (5), ensuring that the preload pressure of the jack (7) can be effectively transmitted to the anchor pile (4) when sealing the pile.

6. The device for completely transferring the newly added load of an existing building to the anchor piles according to claim 5, characterized in that: The jack (7) applies pre-load pressure to the anchor pile (4) under the control of a pressure controller (11), which is a hydraulic device. When sealing the pile, the pre-load pressure meets the following requirements: Where: P pre is the preload pressure applied to the anchor pile (4), kN; F 新增 is the total additional load, kN; n is the number of anchor piles (4); k 安全 is the safety factor, which is 1.02; ΔP 损失 It is the prestress loss during prestressing construction, which is 5% of the design value.

7. The device for completely transferring the newly added load of an existing building to the anchor piles according to claim 1, characterized in that: The load beam (8) is made of section steel, and the threaded anchor rod (9) is finely rolled threaded steel; The end of the threaded anchor rod (9) is pre-buried in the newly added pile foundation pedestal (3), and the reserved length of the upper end meets the requirement that the threaded anchor rod (9) passes through the load beam (8) and is locked with a nut when sealing the pile.

8. The device for completely transferring the newly added load of an existing building to the anchor piles according to claim 1, characterized in that: The newly added pile foundation pedestal (3) is a reinforced concrete component, which is reliably connected to the original foundation (2) and the frame column (1) by steel bar binding and newly poured concrete; a plurality of pile position holes (31) are reserved on the newly added pile foundation pedestal (3) for the construction and sealing of anchor piles (4).

9. A construction method for completely transferring the newly added load of an existing building to anchor piles, characterized by: The construction is carried out using the device according to any one of claims 1 to 8; specifically comprising the following steps: 1) Calculate the original load G and the new load F on the frame column (1), and satisfy G ≥ 1.2F; 2) Select the vertical deformation constant pressure device (5) according to the additional load F on the frame column (1); 3) Using the isolation material (10) to densely fill the pile hole (21) outside the anchor pile (4), ensuring that the anchor pile (4) and the original foundation (2) are effectively isolated, and avoiding the generation of a rigid connection between the anchor pile (4) and the original foundation (2) when the pile is sealed; 4) Based on the calculated additional load F, the pressure controller (11) is used to control the jack (7) to apply preload pressure. The preload pressure applied by the jack (7) is supported downward by the reaction force of the load beam (8) and is transmitted to the anchor pile (4) through the pile sealing steel pipe (6) and the vertical deformation constant pressure device (5); the vertical displacement of the frame column (1) is observed, and when its settlement rate reaches the predetermined requirement, the pile is locked; 5) The pile holes (21) are sealed and maintained by pouring concrete, so that the anchor piles (4) are always in a predetermined stress state after loading, ensuring that the newly added load F is completely borne by the anchor piles (4), and the construction is completed.

10. The construction method for completely transferring the newly added load of an existing building to the anchor piles according to claim 9, characterized in that: In step 4), the preload pressure is applied once, and the specific process is: use the jack (7) to load a pressure of 1.0F once, then let it stand and monitor the vertical displacement of the frame column (1). When its settlement rate is ≤0.04mm / d, lock the pile.

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