A beam-type underpinning structure for existing foundations and its construction method

Abstract

This invention discloses a beam-type support structure for existing foundations and its construction method in the field of building construction technology. The structure includes an existing foundation, an existing vertical structure on top of the existing foundation, and a support beam located at the connection between the existing foundation and the existing vertical structure. Adjacent existing foundations are connected by the support beam, and reinforcing piles are connected to the underside of the support beam. The support beam transfers part or all of the load from the existing structure to the existing foundation via the existing vertical structure to the reinforcing piles. Simultaneously, because the support beam connects adjacent existing foundations, it enhances the overall rigidity and resistance to differential deformation between the existing foundations. Furthermore, by setting up the support beam and reinforcing piles, the settlement of the existing foundation is reduced, the amount of earthwork excavation is reduced, and the disturbance to the existing foundation is minimized. The reinforcing piles, by compressing the foundation soil, effectively reinforce the existing foundation.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, and in particular to an existing foundation beam-type support structure and its construction method. Background Technology

[0002] With the acceleration of urban and rural construction, the upgrading and renovation of existing buildings, as well as the increasing use of soft foundations and reclaimed land for engineering construction, have made the control of foundation deformation and settlement crucial. When the renovation of existing buildings increases the load transferred from the superstructure to the vertical structure, thereby raising the requirements for the bearing capacity and deformation resistance of the existing foundation, insufficient bearing capacity of the existing foundation can lead to excessive or irregular foundation deformation, resulting in cracking or tilting of the superstructure. For soft foundations or under-consolidated reclaimed land, under the long-term action of the load generated by the superstructure, excessive foundation settlement or uneven settlement due to excessive foundation compression deformation may cause tilting or cracking of the superstructure, affecting the foundation performance, building functionality, and engineering safety. For soft foundations that are filled or have not yet completed self-weight consolidation, the soil properties will change significantly after undergoing self-weight consolidation and softening deformation due to changes in water content at different stages. This can lead to excessive or uneven foundation settlement and tilting or cracking of the superstructure. When the superstructure transfers loads to the existing vertical structure due to the renovation of existing buildings, thereby increasing the requirements for the bearing capacity and deformation resistance of the existing foundation, the insufficient bearing capacity of the existing foundation can also cause excessive or irregular deformation of the foundation, leading to cracking or tilting of the superstructure.

[0003] like Figures 1-3 As shown, the existing foundation 3 is located below the ground level 8 and within the existing foundation 7. An existing vertical structure 1 is installed on the upper part of the existing foundation 3 to transfer the load of the superstructure. The existing foundation 3 includes an independent foundation 5 and a pile cap 6. When the existing building uses an independent foundation 5 with a certain embedment depth or a pile cap 6 with a certain embedment depth, due to insufficient overall rigidity, limited area, or limitations in the performance and construction space of the existing foundation 3, it cannot meet the technical requirements for direct pile underpinning to reinforce uneven settlement. If the existing foundation 3 is forcibly reinforced, it will not only disturb the existing foundation state, weaken the existing engineering performance, reduce the safety of the project, but also increase the cost of the reinforcement project.

[0004] Therefore, there is an urgent need for an existing foundation support structure. This structure can share the load transferred from the superstructure of the existing foundation 3, thereby reducing the load-bearing ratio of the existing foundation 3 and achieving the purpose of settling prevention and reinforcement. This fully utilizes the bearing capacity of the existing foundation 3 and also leverages the load-sharing function of the newly added support structure to reduce the settlement of the existing foundation 3 or control differential settlement. At the same time, it can reduce the excavation disturbance to the existing foundation 3 with a certain burial depth, effectively control building deformation, and save on reinforcement project costs. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the background technology by providing an existing foundation beam-type underpinning structure and its construction method. This solution aims to address how to share the load transferred from the superstructure to the existing foundation through the existing vertical structure, thereby reducing the load-bearing ratio of the existing foundation and achieving the purpose of settling prevention and reinforcement. At the same time, it reduces the excavation disturbance to existing foundations with a certain burial depth and lowers the reinforcement cost.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] An existing foundation beam-type underpinning structure includes an existing foundation, an existing vertical structure on the upper part of the existing foundation, and an underpinning beam. The underpinning beam is located at the connection between the existing foundation and the existing vertical structure. Adjacent existing foundations are connected by the underpinning beam, and reinforcing piles are provided on the underpinning beam.

[0008] The present invention discloses an existing foundation beam-type underpinning structure, in which an underpinning beam is set at the connection between the existing foundation and the existing vertical structure. Through the underpinning beam, all or part of the load transferred from the upper structure of the existing foundation to the existing foundation through the existing vertical structure is transferred to the reinforcing piles. At the same time, since the underpinning beam connects adjacent existing foundations together, it enhances the overall rigidity of the existing foundation and its ability to resist differential deformation. Furthermore, by setting up the underpinning beam and reinforcing piles to reinforce the existing foundation, it not only avoids the adverse effects of large-scale earthwork excavation and its disturbance, shortens the construction period, but also the concrete of the foundation soil by the driving of the reinforcing piles can effectively reinforce the existing foundation and limit the lateral deformation of the foundation soil, thereby controlling the vertical deformation of the existing foundation to a certain extent.

[0009] The existing foundation beam-type underpinning structure described in this invention can be used to underpin the existing foundation entirely or partially, depending on the needs of load-bearing capacity reinforcement, settlement prevention, or differential settlement control. Overall underpinning is suitable for underpinning and reinforcing the entire existing foundation, while partial underpinning is suitable for underpinning and reinforcing and controlling a portion of the existing foundation in areas with significant settlement or differential deformation. This allows the existing foundation beam-type underpinning structure described in this invention to adapt to various usage environments and has a wider range of applications.

[0010] The existing foundation beam-type underpinning structure described in this invention utilizes the existing foundation as a component of the newly added beam-type underpinning structure, effectively reducing the number or length of reinforcing piles, reducing the scope of earthwork excavation and disturbance to the performance of the existing foundation, significantly shortening the reinforcement cycle, and making the cost of the existing foundation beam-type underpinning structure described in this invention more scientific and reasonable.

[0011] Preferably, multiple existing foundations are connected in a linear or grid-like manner by the supporting beam. By connecting multiple existing foundations in a linear or grid-like manner, the overall rigidity and resistance to differential deformation among the existing foundations are further enhanced.

[0012] Preferably, at least two reinforcing piles are provided under the supporting beam to reduce the span of the supporting beam and enhance its load-bearing capacity, while also enabling the existing foundation beam-type supporting structure of the present invention to evenly and effectively distribute the load on the existing foundation.

[0013] Preferably, the reinforcing piles are arranged in a single row or double row under the supporting beam.

[0014] Preferably, the reinforcing pile is a precast pile or a cast-in-place pile.

[0015] This invention also discloses a construction method for an existing foundation beam-type underpinning structure, used for constructing the existing foundation beam-type underpinning structure described in this invention. The construction method includes the following steps:

[0016] Step S1: Based on the existing foundation settlement or uneven settlement and the existing characteristics of the foundation, calculate the load N that the existing foundation needs to bear. 1i Required foundation area F 1i And verify the foundation deformation S that meets the current standard limits. 1i Subtract the load N that the existing foundation can bear. 2i Existing foundation area F 2i and measured deformation S 2i The required load ΔN = N is obtained. 1i -N 2i and control deformation amount ΔS=S 1i -S 2i ;

[0017] Step S2: Based on the load △N and the controlled deformation △S, calculate and select the spacing between adjacent reinforcing piles, the diameter of the reinforcing piles, and the length and number of the reinforcing piles according to the current specifications, and verify that the settlement deformation of the reinforcing piles is not greater than the limit value of △S.

[0018] Step S3: Calculate the shear force, bending moment, and reinforcement at the root of the supporting beam according to the number and arrangement of the reinforcing piles and the continuous beam mode that is fixedly connected to the existing vertical structure;

[0019] Step S4: Based on the connection method between the replacement beam and the existing foundation and the existing vertical structure, remove the side reinforcement or four-sided reinforcement of the existing vertical structure at the connection point, and remove the top reinforcement of the existing foundation. Determine the number of rebars to be implanted on the existing foundation and the existing vertical structure according to the current standard method based on the shear and tensile capacity of the joint surface. The number of rebars shall not be less than the number of main reinforcement bars of the replacement beam. Determine the position and direction of the rebars according to the arrangement of the main reinforcement bars of the replacement beam.

[0020] Step S5: Tie the steel cage of the replacement beam according to the reinforcement amount of the replacement beam, and connect it firmly with the rebar. Reserve the installation hole at the position of the reinforcing pile, and then pour the concrete of the replacement beam.

[0021] Step S6: After the concrete strength of the supporting beam reaches the design strength, the pile driving operation of the reinforcing pile is carried out.

[0022] The present invention discloses a construction method for an existing foundation beam-type underpinning structure, which involves setting up underpinning beams and reinforcing piles. The underpinning beams transfer the load from the existing foundation superstructure to the existing foundation via the existing vertical structure to the reinforcing piles. At the same time, since the underpinning beams connect multiple existing foundations together, they enhance the overall rigidity and resistance to differential deformation among the existing foundations. Furthermore, by setting up underpinning beams and reinforcing piles to reinforce the existing foundation, not only is the volume of earthwork excavation reduced, but the reinforcing piles can also effectively reinforce the existing foundation, control the vertical deformation of the existing foundation soil to a certain extent, save on project costs, and are applicable to various types of existing foundations with insufficient bearing capacity or large settlement deformation and differential deformation.

[0023] Preferably, in step S2: the connection method of the connection part is determined based on the shear force and bending moment transmitted by the support beam to the connection part with the existing foundation and / or the existing vertical structure.

[0024] Preferably, in step S2: the main reinforcement of the supporting beam is replaced with composite FRP according to the principle of equal strength. The reinforcement method of using composite FRP as the main reinforcement and ordinary steel bars as stirrups gives full play to the lightweight and high strength characteristics of composite FRP to replace a large number of ordinary steel bars, effectively reducing resource waste, reducing project costs, and improving resource and environmental protection.

[0025] Preferably, in step S3: the diameter of the anchor bar is greater than or equal to 1.2 times the diameter of the main bar, the exposed length of the anchor bar is greater than or equal to 15 times the diameter of the main bar of the supporting beam, and the anchor bar is connected to the main bar of the supporting beam by binding.

[0026] Preferably, step S4 further includes: on the supporting beam, within a length L from the center of the mounting hole, the cross-sectional area and reinforcement of the supporting beam are greater than or equal to the cross-sectional area and reinforcement of the supporting beam without the mounting hole, wherein the length L is 3 to 3.5 times the diameter of the mounting hole, so that the load-bearing capacity of the area of ​​the supporting beam with the mounting hole is not lower than that of the area without the mounting hole, thereby ensuring the overall load-bearing capacity of the supporting beam and avoiding damage to the area with the mounting hole under stress due to uneven overall load-bearing capacity.

[0027] Preferably, step S4 further includes: setting reaction anchors for pile driving on the supporting beam. The reaction anchors are symmetrically arranged on both sides of the mounting hole along the length direction of the supporting beam. Setting the reaction anchors on the supporting beam first makes it easier to provide the required reaction force for the reinforcement pile during subsequent installation.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. The existing foundation beam-type underpinning structure described in this invention involves setting an underpinning beam at the connection between the existing foundation and the existing vertical structure. Through the underpinning beam, all or part of the load transferred from the upper structure of the existing foundation to the existing foundation via the existing vertical structure is transferred to the reinforcing piles. At the same time, since the underpinning beam connects adjacent existing foundations, it enhances the overall rigidity of the existing foundation and its ability to resist differential deformation. Furthermore, by setting the underpinning beam and reinforcing piles to reinforce the existing foundation, it not only avoids the adverse effects of large-scale earthwork excavation and its disturbance, shortening the construction period, but also the concrete compaction of the foundation soil by the reinforcing piles can effectively reinforce the existing foundation and limit the lateral deformation of the foundation soil, thereby controlling the vertical deformation of the existing foundation to a certain extent.

[0030] 2. The existing foundation beam-type underpinning structure described in this invention can be used to underpin the existing foundation entirely or partially, depending on the needs of load-bearing capacity reinforcement, settlement prevention, or differential settlement control. Entire underpinning is suitable for reinforcing the entire existing foundation, while partial underpinning is suitable for reinforcing and controlling a portion of the existing foundation in areas with significant settlement or differential deformation. This allows the existing foundation beam-type underpinning structure described in this invention to adapt to various usage environments and has a wider range of applications.

[0031] 3. The existing foundation beam-type underpinning structure described in this invention utilizes the existing foundation as a component of the newly added beam-type underpinning structure, effectively reducing the number of reinforcing piles or shortening the length of reinforcing piles, and reducing the earthwork excavation range and disturbance to the performance of the existing foundation, significantly shortening the reinforcement cycle, and making the cost of the existing foundation beam-type underpinning structure described in this invention more scientific and reasonable.

[0032] 4. The construction method of the existing foundation beam-type underpinning structure described in this invention involves setting up underpinning beams and reinforcing piles. The underpinning beams transfer the load from the existing foundation superstructure to the existing foundation via the existing vertical structure to the reinforcing piles. At the same time, since the underpinning beams connect multiple existing foundations together, they enhance the overall rigidity and resistance to differential deformation among the existing foundations. Furthermore, by setting up underpinning beams and reinforcing piles to reinforce the existing foundation, not only is the volume of earthwork excavation reduced, but the reinforcing piles can also effectively reinforce the existing foundation, control the vertical deformation of the existing foundation soil to a certain extent, save on project costs, and are applicable to various types of existing foundations with insufficient bearing capacity or large settlement deformation and differential deformation. Attached image description:

[0033] Figure 1 This is a schematic diagram of an existing foundation in the background art without a replacement structure.

[0034] Figure 2 This is a schematic diagram of an independent foundation without a supporting structure in the background art.

[0035] Figure 3 This is a schematic diagram of a pile cap without a supporting structure in the background art.

[0036] Figure 4 This is a structural schematic diagram of an existing foundation beam-type support structure as described in this invention.

[0037] Figure 5 yes Figure 4 Sectional view at point AA.

[0038] Figure 6 This is a schematic diagram of an independent foundation beam-type support structure according to the present invention.

[0039] Figure 7 This is a schematic diagram of a pile foundation cap beam-type support structure according to the present invention.

[0040] Figure 8 This invention describes a construction method for an existing foundation beam-type underpinning structure (beams first, then piles).

[0041] Figure 9 This invention describes a construction method for an existing foundation beam-type underpinning structure (pile first, then beam).

[0042] The markings in the diagram are: 1-existing vertical structure, 2-support beam, 3-existing foundation, 4-reinforcing pile, 41-installation hole, 5-independent foundation, 6-pile cap, 7-existing foundation, 8-ground level. Detailed Implementation

[0043] The present invention will be further described in detail below with reference to embodiments and specific implementation methods. However, this should not be construed as limiting the scope of the above-described subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0044] Example 1

[0045] like Figures 4-5 As shown, an existing foundation beam-type support structure includes an existing foundation 3, an existing vertical structure 1 at the end of the existing foundation 3, and a support beam 2. The support beam 2 is located at the connection between the existing foundation 3 and the existing vertical structure 1. Adjacent existing foundations 3 are connected by the support beam 2, and a reinforcing pile 4 is connected to the support beam 2.

[0046] The existing foundation beam-type underpinning structure described in this embodiment involves setting an underpinning beam 2 at the connection between the existing foundation 3 and the existing vertical structure 1. The underpinning beam 2 transfers the load from the superstructure of the existing foundation 3 to the reinforcing piles 4 through the existing vertical structure 1. At the same time, since the underpinning beam 2 connects adjacent existing foundations 3 together, it enhances the overall rigidity of the existing foundation 3 and its ability to resist differential deformation. Furthermore, by setting the underpinning beam 2 and the reinforcing piles 4 to reinforce the existing foundation, not only is large-scale earthwork excavation reduced, saving project costs, but the reinforcing piles 4 can also effectively reinforce the existing foundation by squeezing the foundation soil and laterally restricting the deformation of the foundation soil, thereby controlling the vertical deformation of the existing foundation to a certain extent.

[0047] In a preferred embodiment, multiple existing foundations 3 are connected in a linear fashion by a support beam 2. By connecting multiple existing foundations 3 in a linear fashion, the overall rigidity of the existing foundations 3 and their ability to resist differential deformation are enhanced.

[0048] In a preferred manner, multiple existing foundations 3 are connected into a grid by a support beam 2. By connecting multiple existing foundations 3 into a grid, the overall rigidity of the existing foundations 3 and their ability to resist differential deformation are further enhanced.

[0049] In a preferred embodiment, at least two reinforcing piles 4 are provided on the supporting beam 2 to enhance the load-bearing capacity of the supporting beam 2, and at the same time enable the existing foundation beam supporting structure of the present invention to effectively share the load of the existing structure.

[0050] In a preferred manner, the reinforcing piles 4 are arranged in a single row or double row under the supporting beam 2 to enhance the bearing capacity of the supporting beam 2.

[0051] In a preferred embodiment, the reinforcing pile 4 includes anchored static pressure steel pipe piles, precast reinforced concrete piles, and cast-in-place piles, wherein the diameter or cross-sectional dimensions, shape, spacing, and length of the reinforcing pile 4 are determined according to the degree of reinforcement or underpinning and the current foundation conditions.

[0052] In a preferred embodiment, when the mounting hole is circular and the reinforcing pile 4 is circular, the diameter of the mounting hole 41 is not less than the diameter of the reinforcing pile 4. In actual construction, the diameter of the mounting hole 41 exceeds the diameter of the reinforcing pile 4 by 40 mm. When the mounting hole 41 is rectangular and the reinforcing pile 4 is rectangular, the side length of the mounting hole 41 is not less than the corresponding side length of the reinforcing pile 4. In actual construction, the side length of the mounting hole 41 exceeds the corresponding side length of the reinforcing pile 4 by 20 mm.

[0053] In a preferred manner, during actual construction, the existing vertical structure 1 is either a column or a short-limb wall, both of which are suitable for transferring the load of the superstructure to the existing foundation 3.

[0054] In a preferred embodiment, the replacement beam 2 described in this application is a shallow-buried replacement beam.

[0055] The following is a brief introduction using the existing foundation 3 as an independent foundation 5 as an example:

[0056] The existing foundation beam-type underpinning structure described in this embodiment is also applicable to independent foundation 5, such as... Figure 6 As shown, the independent foundation 5 is equivalent to the existing foundation 3 described in this embodiment.

[0057] The following is a brief introduction using existing foundation 3 as an example of pile foundation cap 6:

[0058] The existing foundation beam-type underpinning structure described in this embodiment is also applicable to pile foundation cap 6, such as... Figure 7 As shown, the pile cap 6 is equivalent to the existing foundation 3 described in this embodiment.

[0059] Example 2

[0060] Based on Example 1, such as Figures 4-8 As shown, a construction method for an existing foundation beam-type underpinning structure is used to construct the existing foundation beam-type underpinning structure described in Example 1. The construction method includes the following steps:

[0061] Step S1: Based on the increased load, settlement, or uneven settlement of the existing foundation 3, and the existing characteristics of the foundation, calculate the load N that each existing foundation 3 needs to bear to meet the requirements of the current specifications and standards, according to the existing foundation property index. 1i Required foundation area F 1iAnd verify the foundation deformation S that meets the current standard limits. 1i Subtract the load N that the existing foundation 7 can bear under the existing foundation 3. 2i Existing foundation 3 Existing area F 2i and measured deformation S 2i The required load to be replaced is ΔN = N. 1i -N 2i and control deformation amount ΔS=S 1i -S 2i ;

[0062] Step S2: Based on the load change ΔN and the control deformation ΔS, calculate the single pile bearing capacity R of the reinforcing pile 4 according to the current standard for pile bearing capacity and settlement calculation methods, the existing foundation bearing capacity and deformation index, and the initially selected diameter and length. Then, determine the number of reinforcing piles 4 and the arrangement (spacing) between adjacent existing foundations 3 according to (ΔN / R). Verify that the deformation and differential deformation after the reinforcing piles 4 have settled and are not greater than the limit value of ΔS. If not, readjust the diameter or length of the reinforcing piles 4. Then, based on the determined spacing of the reinforcing piles 4 and the distance between the reinforcing piles 4 and the existing foundation 3, determine the cross-sectional area and reinforcement of the supporting beam 2 according to the continuous beam structure internal force calculation method.

[0063] Step S3: Based on the number and arrangement of the reinforcing piles 4, calculate the shear force, bending moment and reinforcement amount of the supporting beam 2 as a continuous beam fixedly connected to the existing vertical structure 1, and determine the reinforcement and arrangement.

[0064] Step S4: Based on the connection method between the replacement beam 2 and the existing foundation 3 and the existing vertical structure 1, remove the side reinforcement or four-sided reinforcement of the existing vertical structure 1 at the connection point, and remove the top reinforcement of the existing foundation 3. Determine the number of rebars to be installed on the existing foundation 3 and the existing vertical structure 1 according to the current standard method based on the shear and tensile capacity verification of the joint surface, and determine the position and direction of the rebars to be installed according to the arrangement of the main reinforcement of the replacement beam 2.

[0065] Step S5: Tie the steel cage of the replacement beam 2 according to the amount of reinforcement of the replacement beam 2, and connect it firmly with the rebar. Reserve the installation hole 41 at the location of the reinforcing pile 4, and then pour the concrete.

[0066] Step S6: After the concrete reaches the design strength, the reinforcement piles are driven in batches according to the uneven settlement of the existing building. The areas with larger settlement are constructed first, followed by the areas with smaller settlement, and construction is carried out at intervals. The construction speed and the number of batches are adjusted according to the deformation monitoring during the construction process.

[0067] The construction method of the existing foundation beam-type underpinning structure described in this embodiment adopts the beam-first, pile-later construction method. That is, the underpinning beam 2 with pre-reserved installation holes 41 is constructed first, and then the underpinning beam 2 is used as a reaction structure to press the reinforcing pile 4. The load transferred from the superstructure of the existing foundation 3 to the existing foundation 3 through the existing vertical structure 1 is transferred to the reinforcing pile 4 through the underpinning beam 2. At the same time, since the underpinning beam 2 connects the adjacent existing foundations 3 together, it enhances the overall rigidity between the existing foundations 3 and the ability to resist differential deformation. Furthermore, by setting the underpinning beam 2 and the reinforcing pile 4 to reinforce the existing foundation 3, not only is large-scale earthwork excavation reduced and the project cost saved, but the reinforcing pile can also effectively reinforce the existing foundation and control the deformation of the existing foundation to a certain extent. It is suitable for various types of existing foundations with insufficient bearing capacity or large settlement deformation and differential deformation.

[0068] In a preferred manner, in step S2: the connection method and structure of the connection part are determined based on the internal force at the connection part between the supporting beam 2 and the existing foundation 3 and / or the existing vertical structure 1, including rebar connection or circumferential connection.

[0069] In a preferred manner, in step S2: the main reinforcement of the support beam 2 is replaced with composite FRP according to the principle of equal strength. The reinforcement method of using composite FRP as the main reinforcement and ordinary steel bars as the stirrups takes advantage of the lightweight and high strength characteristics of composite FRP. By replacing a large amount of ordinary steel bars with composite FRP, resource waste is effectively reduced, project costs are reduced, and resource utilization is improved. The composite FRP is formed by gluing multiple strands of continuous fibers (such as glass fiber, carbon fiber, etc.) with a base material (such as polyamide resin, polyethylene resin, epoxy resin, etc.) and then extruding and drawing them through a special mold. It includes carbon fiber composite FRP, basalt composite FRP, etc.

[0070] In a preferred manner, in step S3: the diameter of the rebar is greater than or equal to 1.2 times the diameter of the main reinforcement bar of the supporting beam, the exposed length of the rebar is greater than or equal to 15 times the diameter of the main reinforcement bar of the supporting beam, and the rebar is connected by binding.

[0071] In a preferred embodiment, step S4 further includes: on the supporting beam 2, within a range L from the center of the mounting hole 41, the cross-sectional area and reinforcement of the supporting beam 2 are greater than or equal to the cross-sectional area and reinforcement of the supporting beam 2 without the mounting hole 41, and the length L is 3 to 3.5 times the diameter of the mounting hole 41. In other words, on the supporting beam 2, within a range L from the center of the mounting hole 41, the cross-sectional area and reinforcement of the supporting beam 2 should not be less than the cross-sectional area and reinforcement calculated in the design, so that the bearing capacity of the area of ​​the supporting beam 2 with the mounting hole 41 is not lower than the bearing capacity of the area without the mounting hole 41, thereby ensuring the overall bearing capacity of the supporting beam 2 and avoiding the situation where some areas of the supporting beam 2 are damaged after being stressed due to uneven overall bearing capacity. Wherein, when the mounting hole 41 is a rectangular hole and the reinforcing pile 4 is a rectangular pile, the length L is 3 to 3.5 times the maximum side length of the mounting hole 41.

[0072] In a preferred embodiment, step S4 further includes: installing reaction anchor bolts for pile driving on the supporting beam. The reaction anchor bolts are symmetrically arranged on both sides of the installation hole along the length direction of the supporting beam. By first installing the reaction anchor bolts on the supporting beam, it is convenient to provide the reaction force required for the installation of the reinforcing pile 4 through the reaction anchor bolts during subsequent installation.

[0073] In a preferred embodiment, step S5 further includes: adjusting the unevenness of the existing foundation by using prestressed pile sealing based on the settlement observation results during construction.

[0074] In a preferred manner, before constructing the reinforcing pile 4, a monitoring system for the implementation process is installed on the existing building columns and walls. The wall and column components can be monitored using displacement gauges, strain gauges, or attached tilt reflectors, as well as a static leveling system with real-time testing capabilities. The monitoring system is used to monitor the stress on the existing building throughout the entire construction process.

[0075] A preferred method, such as Figure 9 As shown, it also includes a construction method of pile first and beam later. After step S3, piles are driven or pressed in sections on the original ground. Then, the foundation trench is excavated under the original ground according to the cross-sectional dimensions of the replacement beam 2. The main reinforcement of the reinforcing pile 4 is removed. Then, the reinforcement cage of the replacement beam 2 is tied according to the design requirements. During the tying process, it is tied firmly with the main reinforcement of the reinforcing pile 4 and firmly tied with the anchor bars on the existing foundation 3 and / or the existing vertical structure 1 or short limb wall. The foundation trench is poured with concrete that meets the design strength grade. After the construction is completed, the ground is restored.

[0076] Example 3

[0077] like Figures 4-9 As shown in the figure, the construction method of the existing foundation beam-type underpinning structure described in this embodiment is a preferred combination in actual construction, specifically as follows:

[0078] S1: Based on the settlement or uneven settlement of the existing building and the existing characteristics of the existing foundation, calculate the existing foundation that meets the requirements of the current specifications and standards according to the existing foundation characteristics index (3) bearing capacity required to bear the load N 1i Required foundation area F 1i And verify the foundation deformation S that meets the current standard limits. 1i Subtract the load N that the existing foundation (7) can bear. 2i Existing foundation (3) area F 2i and measured deformation S 2i The required load to be replaced is ΔN = N. 1i -N 2i and control deformation amount ΔS=S 1i -S 2i ;

[0079] S2: Based on the load △N and the controlled deformation △S, the spacing, diameter or side length and length of the reinforcing piles 4 are selected by trial calculation according to the current specifications, and the settlement of the reinforcing piles is verified to meet the limit of not exceeding △S. Based on the spacing of the reinforcing piles 4 and the distance between the reinforcing piles 4 and the existing foundation 3, the amount of reinforcement of the replacement beam 2 is determined. Based on the principle of equal strength, composite FRP is used to replace ordinary steel bars. Based on the internal force of the connection between the replacement beam 2 and the existing foundation 3 and / or the existing vertical structure 2, the connection method and structure (rebar connection or circumferential connection) are determined.

[0080] S3: The reinforcing pile 4 can be an anchored static pressure steel pipe pile or a precast reinforced concrete pile, or a cast-in-place pile. The diameter or cross-sectional dimensions, shape, spacing and length of the reinforcing pile 4 are determined according to the degree of reinforcement or underpinning and the current foundation indicators.

[0081] S4: Install a monitoring system for the implementation process on existing building columns and walls: wall and column component monitoring can use displacement gauges, strain gauges or attached tilt reflectors, as well as a static leveling system, and have real-time testing capabilities;

[0082] S5: The following construction methods can be adopted: first construct the reinforcing piles and then implement the replacement beam (pile first, beam later), or first construct the replacement beam 2 with the reserved installation holes 41 and then use the replacement beam 2 as a reaction force to press the reinforcing pile 4 (beam first, pile later).

[0083] S6: Based on the connection method between the replacement beam 2 and the existing foundation 3 and / or the existing vertical structure 1, remove the side reinforcement of the existing foundation 3 and / or the side and top reinforcement of the existing vertical structure 1 and the existing foundation 3 at the connection location. Determine the number of rebars to be installed on the existing foundation 3 and / or the existing vertical structure 1 according to the current standard method based on the shear capacity calculation of the interface. Determine the location of the rebars based on the arrangement of the main reinforcement of the replacement beam 2. The number of rebars to be installed should not be less than 1.2 times the number of main reinforcements installed in the replacement beam, and the exposed length should not be less than 15 times the diameter of the main reinforcement of the replacement beam. The rebars should be connected by binding.

[0084] S6: When using the beam-beam-then-pile construction method, excavate a foundation trench below the original ground according to the cross-sectional dimensions of the replacement beam 2. Reinforce the beam cage according to design requirements and secure it firmly with the anchor bars. Reserve installation holes 41 at the location of the reinforcing pile 4, 20 mm larger than the diameter of the reinforcing pile 4 or its side length. Pre-embed anchor bolts on both sides of the installation holes 41 of the replacement beam 2 to provide subsequent pile driving reaction force. Pour concrete of the design strength grade into the original trench. After the concrete reaches the design strength, drive the piles in batches according to the uneven settlement of the existing building, first constructing areas with larger settlement and then areas with smaller settlement, with intervals between construction. Adjust the construction speed and batch quantity based on deformation monitoring during construction. Based on the settlement observation results during construction, use prestressed sealing piles to appropriately adjust the unevenness of the existing foundation.

[0085] S7: When using the construction method of first pile and then beam, piles can be driven in sections or batches on the original ground. The foundation trench is excavated below the original ground according to the cross-sectional dimensions of the supporting beam. The main reinforcement of the pile body is removed, and the beam reinforcement cage is tied according to the design requirements and firmly tied with the anchoring reinforcement. The original trench is then filled with concrete of the design strength grade.

[0086] S8: Restore the ground.

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A construction method of an existing foundation beam underpinning structure, characterized by, The application relates to a construction method for a foundation beam underpinning structure, which comprises existing foundations (3) provided with existing vertical structures (1) in the upper part, and underpinning beams (2) arranged at the connecting part of the existing foundations (3) and the existing vertical structures (1), and adjacent existing foundations (3) are connected through the underpinning beams (2), and reinforcing piles (4) are arranged on the underpinning beams (2), and a plurality of existing foundations (3) are connected into a linear or grid shape through the underpinning beams (2). The construction method comprises the following steps: Step S1: According to the settlement or uneven settlement condition of the existing foundation (3) and the existing characteristics of the existing foundation, the load that the existing foundation (3) needs to bear is calculated , the required foundation area , and the foundation deformation amount that satisfies the limit value of the current specification is checked , the load that the existing foundation (3) under the existing foundation (7) can bear is deducted , the area of the existing foundation (3) , and the measured deformation amount , the load that needs to be underpinned and the control deformation amount are obtained; Step S2: according to the load and the control deformation , the spacing between adjacent reinforcing piles (4), the diameter of the reinforcing pile (4) and the length and number of the reinforcing pile (4) are selected by trial, and it is checked that the settlement deformation of the reinforcing pile (4) satisfies not more than the limit value; Step S3: according to the number and arrangement mode of the reinforcing piles (4), the shear force and bending moment of the root part of the underpinning beam (2) are calculated in the continuous beam mode fixedly connected with the existing vertical structure (1); According to the shear force and bending moment of the connecting part of the underpinning beam (2) transmitted to the connecting part of the existing foundation (3) and the existing vertical structure (1), the connecting mode of the connecting part is determined; Step S4: according to the connecting mode of the underpinning beam (2) and the existing foundation (3) and the existing vertical structure (1) at the connecting part, the side steel bars of the existing vertical structure (1) or the four-side steel bars of the existing vertical structure (1) and the top steel bars of the existing foundation (3) are removed, the number of embedded steel bars on the existing foundation (3) and the existing vertical structure (1) is determined according to the current standard method based on the shear and tensile capacity of the joint surface, the number of the embedded steel bars is not less than the number of the main steel bars of the underpinning beam (2), and the position and direction of the embedded steel bars are determined according to the arrangement mode and cross-sectional size of the main steel bars of the underpinning beam (2); Step S5: the steel cage of the underpinning beam (2) is bound according to the reinforcement amount of the underpinning beam (2), is firmly connected with the embedded steel bars, and installation holes (41) are reserved at the positions of the reinforcing piles (4), and then the concrete pouring of the underpinning beam (2) is carried out; Step S6: after the concrete strength of the underpinning beam (2) reaches the design strength, the reinforcing pile (4) sinking operation is carried out.

2. The construction method of an existing foundation beam underpinning structure according to claim 1, characterized in that, At least two reinforcing piles (4) are arranged on the underpinning beam (2).

3. The construction method of an existing foundation beam underpinning structure according to claim 1, characterized in that, The reinforcing piles (4) are arranged in a single row or a double row under the underpinning beam (2).

4. The construction method of an existing foundation beam underpinning structure according to claim 1, characterized by, In the step S3: the main steel bars of the underpinning beam (2) are replaced by composite steel bars FRP according to the equal strength principle.

5. The construction method of an existing foundation beam underpinning structure according to claim 1, characterized in that, In the step S4: the diameter of the embedded steel bars is greater than or equal to 1.2 times the diameter of the main steel bars of the underpinning beam (2), and the exposed length of the embedded steel bars is greater than or equal to 15 times the diameter of the main steel bars of the underpinning beam (2).

6. The construction method of an existing foundation beam underpinning structure according to claim 1, characterized by, The step S5 further comprises: setting counterforce anchors for pile pressing on the underpinning beam (2), and the counterforce anchors are symmetrically arranged on both sides of the installation holes (41) along the length direction of the underpinning beam (2).

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