Raft foundation double-layer sinking-stopping structure and construction method

Abstract

The application discloses the technical field of building construction, and particularly relates to a double-layer settlement-stopping structure of an existing raft foundation and a construction method. An additional raft is arranged on the upper part of the existing raft foundation, the additional raft is connected with the existing vertical structure, the additional raft can share the load of the upper structure of the existing foundation, and a support column is connected between the existing raft foundation and the additional raft. The double-layer settlement-stopping structure formed by the existing raft foundation, the additional raft and the support column can increase the out-of-plane rigidity of the existing raft foundation and improve the anti-deformation capability of the existing raft foundation. The bearing capacity of the existing raft foundation is fully utilized, the out-of-plane rigidity of the double-layer settlement-stopping structure is effectively utilized, the settlement of the existing raft foundation is reduced, the settlement-stopping effect is achieved, and further, the excavation and reinforcement of the existing raft foundation with a certain embedding depth are reduced, large-area earth excavation is not needed, and the reinforcement cost is saved.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, and in particular to a double-layer anti-settlement structure for existing raft foundations and its construction method. Background Technology

[0002] With the acceleration of urban and rural construction, there is an increasing number of projects involving building performance modifications and construction on soft and filled foundations. Therefore, controlling foundation deformation and settlement is crucial. For building functional modifications, existing foundations often cannot meet the load-bearing and deformation resistance requirements after load adjustment, necessitating reinforcement. For soft foundations, under long-term superstructure loads, large and uneven settlement may occur due to soil compression deformation, leading to tilting or cracking of the superstructure and affecting foundation performance and project safety. For filled foundations, after undergoing consolidation under their own weight and softening due to changes in water content, the engineering properties of the soil change significantly, also resulting in large and uneven settlement, causing tilting or even cracking of the superstructure.

[0003] like Figure 1 As shown, the existing building uses piers 2 with a certain embedment depth, and an existing raft foundation 1 is set between the piers 2. An existing vertical structure 3 is set on the existing raft foundation 1. The existing raft foundation 1 is set below the ground level 8 and within the existing foundation 7. When the thickness of the existing raft foundation 1 is 400mm to 600mm, if the out-of-plane stiffness, bending resistance, or punching shear resistance of the existing raft foundation 1 cannot meet the requirements for direct reinforcement by composite foundation strengthening or pile foundation replacement to stop settlement and control uneven settlement, further reinforcement of the existing raft foundation 1 will not only significantly weaken its existing performance but also increase the cost of the reinforcement project. On the other hand, if the existing raft foundation 1 is demolished or reinforced in a superimposed manner, its performance will still be damaged, and the workload will also increase significantly.

[0004] If a transfer layer structure with a certain thickness and several short columns is set on the upper part of the existing raft foundation 1 to form a transfer layer structure with greater planar stiffness, and at the same time, some reinforcing piles are added under the existing raft foundation 1 at the location where the short columns are set, the additional load caused by the settlement of the existing raft foundation 1 due to the existing foundation 7, including the additional load caused by excessive deformation due to insufficient out-of-plane bending and shear resistance of the existing raft foundation 1, can be transferred to the new transfer layer structure to bear the load, thereby achieving the effect of stopping settlement. That is, the bearing capacity of the existing raft foundation 1 can be fully utilized, and the excavation and re-reinforcement of the existing raft foundation 1 with a certain embedment depth can be greatly reduced, saving reinforcement costs. Summary of the Invention

[0005] The present application aims at solving the problems in the background art, and provides a raft foundation double-layer settlement-stopping structure and a construction method, which can make full use of the bearing capacity of the existing raft foundation and greatly reduce the excavation and reinforcement of the existing raft foundation with a certain burial depth.

[0006] To achieve the above-mentioned purposes, the present application provides the following technical solutions.

[0007] The raft foundation double-layer settlement-stopping structure comprises an existing raft foundation, an existing vertical structure arranged at the end of the existing raft foundation, a new raft plate arranged at the upper part of the existing raft foundation, and a support column arranged between the new raft plate and the existing raft foundation.

[0008] The raft foundation double-layer settlement-stopping structure can make the new raft plate share the upper load of the existing foundation, and the support column arranged between the existing raft foundation and the new raft plate can increase the out-of-plane stiffness of the existing raft foundation and improve the anti-deformation capacity of the existing raft foundation, so that the bearing capacity of the existing raft foundation can be fully utilized, the out-of-plane stiffness of the double-layer settlement-stopping structure can be effectively utilized to reduce the settlement of the existing raft foundation, and the settlement-stopping effect can be achieved.

[0009] The raft foundation double-layer settlement-stopping structure can be constructed in intervals under the premise of slightly disturbing the engineering performance of the existing foundation and the existing raft foundation, and can provide good protection for the existing foundation and the existing raft foundation.

[0010] Preferably, at least two support columns are arranged between adjacent existing vertical structures.

[0011] Preferably, a reinforcing device is arranged at the bottom of the existing raft foundation, which can further strengthen the settlement-stopping effect of the double-layer settlement-stopping structure and effectively support the existing raft foundation.

[0012] Preferably, at least one reinforcing device is arranged between adjacent existing vertical structures.

[0013] Preferably, the number of the support columns and the number of the reinforcing devices can be different, and the support columns and the reinforcing devices can be arranged in a staggered manner.

[0014] The application further discloses a construction method of the double-layer settlement-stopping structure of the existing raft foundation.

[0015] Step S1: according to the upper structure load added according to the existing building, the settlement or uneven settlement of the existing foundation, and the actual state of the existing foundation embedding depth and the existing foundation, the distance between the new raft and the existing raft foundation, the number of the support columns and the distance between adjacent support columns and the number of the reinforcing devices and the distance between adjacent reinforcing devices are determined.

[0016] Step S2: according to the distance between the new raft and the existing raft foundation and the setting state of the support columns, the connection mode of the new raft and the existing vertical structure is determined.

[0017] Step S3: the ground is excavated to the bottom surface elevation position of the new raft, then a mounting hole is excavated to the top surface of the existing raft foundation (1) at the bottom surface elevation position of the new raft, and the support column is arranged in the mounting hole, the bottom of the support column is connected with the existing raft foundation, and the top of the top of the support column extends to the bottom surface elevation position of the new raft.

[0018] Step S4: the new raft is constructed, wherein the new raft is connected with the top of the support column.

[0019] The construction method of the double-layer settlement-stopping structure of the existing raft foundation has the advantages that the new raft is arranged on the upper portion of the existing raft foundation, the support column is arranged between the existing raft foundation and the new raft, the double-layer settlement-stopping structure is formed, the bearing capacity of the existing raft foundation is fully utilized, the overall out-of-plane rigidity of the double-layer settlement-stopping structure is effectively utilized to reduce the settlement of the existing raft foundation, the settlement-stopping effect is achieved, the excavation and reinforcement of the existing raft foundation with a certain embedding depth are reduced, and the engineering cost is saved.

[0020] Preferably, the step S3 further comprises the following steps: the reinforcing steel bars of the top surface of the existing raft foundation are excavated at the bottom of the mounting hole, and the reinforcing steel bars are implanted, and the bottom of the support column is connected with the reinforcing steel bars. The bottom of the support column is connected with the reinforcing steel bars of the top surface of the existing raft foundation, so that the connection between the support column and the existing raft foundation is more stable.

[0021] Preferably, the step S4 further comprises the following step: the reinforcing steel bars are arranged on the top of the support column, and the reinforcing steel bars are connected with the reinforcing cage of the new raft. The reinforcing steel bars arranged on the top of the support column are connected with the reinforcing cage of the new raft, so that the support column and the new raft are connected into an integrated whole.

[0022] Preferably, in the step S3: when the reinforcing device needs to be set, the installation hole is drilled through the existing raft foundation and excavated to the bottom elevation of the reinforcing device, and then the reinforcing device is set, the top of the reinforcing device extends to the existing raft foundation and is connected with the existing raft foundation. The reinforcing device is connected with the existing raft foundation, so that the reinforcing device can effectively support the existing raft foundation, thereby reinforcing the existing raft foundation.

[0023] Preferably, the reinforcing device is connected with the support column, so that the new raft can transmit the load to the existing raft foundation through the support column, and at the same time, part of the load is transmitted to the existing foundation through the support column, thereby better playing the supporting effect of the double-layer settlement stopping structure of the existing raft foundation.

[0024] Preferably, the reinforcing device and the support column are arranged integrally, which is convenient for actual construction operation, thereby simplifying the construction process and improving the construction efficiency.

[0025] Preferably, the number of the reinforcing bars is the same as the number of the main reinforcement of the support column and is at least 4, thereby ensuring that the support column is firmly connected with the existing raft foundation and ensuring the stability of the double-layer settlement stopping structure of the existing raft foundation.

[0026] Preferably, the diameter of the reinforcing bar is greater than or equal to the diameter of the main reinforcement.

[0027] Compared with the prior art, the present application has the following beneficial effects:

[0028] 1. The double-layer settlement stopping structure of the existing raft foundation according to the present application, the new raft is arranged on the upper part of the existing raft foundation, and the new raft is connected with the existing vertical structure, so that the new raft can share the upper load of the existing foundation, and the support column is connected between the existing raft foundation and the new raft, and the double-layer settlement stopping structure is formed by the existing raft foundation, the new raft and the support column, so as to increase the out-of-plane stiffness of the existing raft foundation and improve the anti-deformation ability, that is, the bearing capacity of the existing raft foundation is fully utilized, and the overall out-of-plane stiffness of the double-layer settlement stopping structure is effectively utilized to reduce the settlement of the existing raft foundation, so as to achieve the effect of stopping settlement. Further, by arranging the double-layer settlement stopping structure of the existing raft foundation, the excavation and reinforcement of the existing raft foundation with a certain embedding depth are greatly reduced, and large-area earth excavation is not needed, thereby saving the reinforcement cost.

[0029] 2. The double-layer settlement stopping structure of the existing raft foundation according to the present application, when the new raft is connected with the existing vertical structure, the new raft is arranged in an integral manner, so that a larger range of double-layer settlement stopping structure can be formed, the overall out-of-plane stiffness of the existing raft foundation in a certain range is enhanced, and the overall settlement of the existing building is reduced to a greater extent.

[0030] 3. The construction method of the double-layer anti-settlement structure for existing raft foundations described in this invention involves setting up a new raft foundation on top of the existing raft foundation and setting up supporting columns between the existing raft foundation and the new raft foundation to form a double-layer anti-settlement structure. This fully utilizes the bearing capacity of the existing raft foundation and effectively leverages the overall out-of-plane stiffness of the double-layer anti-settlement structure to reduce the settlement of the existing raft foundation and achieve the anti-settlement effect. At the same time, it greatly reduces the excavation and reinforcement of existing raft foundations with a certain burial depth, saving project costs. Attached image description:

[0031] Figure 1 This is a schematic diagram of an existing raft foundation before compensation in the background art of this application.

[0032] Figure 2 This is a schematic diagram of an existing double-layer anti-settlement structure for raft foundations according to the present invention.

[0033] Figure 3 yes Figure 2 Sectional view at point AA (existing foundation omitted).

[0034] Figure 4 This is a schematic diagram of the reinforcing device of the present invention. Figure 1 .

[0035] Figure 5 This is a schematic diagram of the reinforcing device of the present invention. Figure 2 (Reinforcing devices and support columns are arranged alternately)

[0036] Figure 6 This is a schematic diagram of the reinforcing device of the present invention. Figure 2 (The reinforcement device and the support column are integrated into one unit).

[0037] Figure 7 This is a schematic diagram of the box-shaped raft plate unit of the present invention.

[0038] The markings in the diagram are: 1-existing raft foundation, 2-column pier, 3-existing vertical structure, 4-supporting column, 5-reinforcement device, 6-newly added raft foundation, 7-existing foundation, 8-ground level. Detailed Implementation

[0039] The present invention will be further described in detail below with reference to experimental examples and specific embodiments. However, this should not be construed as limiting the scope of the above-mentioned 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.

[0040] Example 1

[0041] like Figures 2-3As shown, a double-layer anti-settlement structure for an existing raft foundation includes an existing raft foundation 1, an existing vertical structure 3 at the end of the existing raft foundation 1, a new raft foundation 6 on the upper part of the existing raft foundation 1, the new raft foundation 6 being connected to the existing vertical structure 3, and a support column 4 connecting the new raft foundation 6 and the existing raft foundation 1.

[0042] The present invention discloses a double-layer anti-settlement structure for existing raft foundations. A new raft slab 6 is installed on top of the existing raft foundation 1, and the new raft slab 6 is connected to the existing vertical structure 3. This allows the new raft slab 6 to share the upper load of the existing raft foundation 1. Simultaneously, a support column 4 connects the existing raft foundation 1 and the new raft slab 6. The double-layer anti-settlement structure formed by the existing raft foundation 1, the new raft slab 6, and the support column 4 increases the out-of-plane stiffness of the existing raft foundation 1 and improves its deformation resistance. This fully utilizes the bearing capacity of the existing raft foundation 1 and effectively leverages the overall out-of-plane stiffness of the double-layer anti-settlement structure to reduce the settlement of the existing raft foundation 1, achieving an anti-settlement effect. Furthermore, by setting up the double-layer anti-settlement structure for existing raft foundations, the excavation and reinforcement of existing raft foundations 1 with a certain burial depth are significantly reduced, and large-area earthwork excavation is not required, saving reinforcement costs. Furthermore, intermittent construction can be carried out with only minor local disturbance to the existing foundation 7 and the engineering performance of the existing raft foundation 1.

[0043] In a preferred manner, the new raft foundation 6 is laid as a whole when connected to the existing vertical structure 3, which can form a larger-scale double-layer anti-settlement structure to enhance the overall out-of-plane stiffness of the existing raft foundation 1 within a certain range and reduce the overall settlement of the existing building to a greater extent.

[0044] In a preferred manner, at least two support columns 4 are provided between adjacent existing vertical structures 3.

[0045] A preferred method, such as Figure 4 As shown, a reinforcing device 5 is provided at the bottom of the existing raft foundation 1. By providing a reinforcing device 5 at the bottom of the existing raft foundation 1, the anti-settlement effect of the double-layer anti-settlement structure is further enhanced, and the existing raft foundation is also effectively supported.

[0046] In a preferred manner, at least two reinforcing devices 5 are provided between adjacent existing vertical structures 3.

[0047] A preferred way is to adjust the number of support columns and the spacing between adjacent support columns according to the spacing between the existing raft foundation and the newly added raft foundation, so that the double-layer settlement-stopping structure of the existing raft foundation can adapt to the existing raft foundation in different states, and has various structural forms. For example, when the spacing between the existing raft foundation and the newly added raft foundation is large, the connection between the existing raft foundation and the newly added raft foundation is more stable by increasing the number of support columns and reducing the spacing between the support columns.

[0048] A preferred way is to adjust the number of support columns and the spacing between adjacent support columns according to the spacing between the existing raft foundation and the newly added raft foundation, so that the double-layer settlement-stopping structure of the existing raft foundation can adapt to the existing raft foundation in different states, and has various structural forms. For example, when the spacing between the existing raft foundation and the newly added raft foundation is large, the connection between the existing raft foundation and the newly added raft foundation is more stable by increasing the number of support columns and reducing the spacing between the support columns.

[0049] A preferred way is that, in actual construction, the reinforcing device 5 is a reinforcing pile or a composite foundation reinforcement, and further, the reinforcing pile can be a precast pile (including a steel pipe pile) or a cast-in-place pile, and the composite foundation reinforcement can be a plain concrete pile or a reinforced concrete pile.

[0050] A preferred way is that the existing vertical structure 3 is a column or a wall between the existing raft foundation 1 and the upper structure.

[0051] A preferred way is that the support column 4 is a short-leg column.

[0052] A preferred way is that the newly added raft 6 can be a reinforced concrete slab or a hybrid reinforced slab (ordinary reinforcement + composite material reinforcement FRP-CFRP, GFRP, BFRP arranged at intervals with steel reinforcement).

[0053] A preferred way is that, as shown in Figure 5 , the number of support columns 4 and the number of reinforcing devices 5 can be different, and the support columns 4 and the reinforcing devices 5 can be arranged in a staggered manner.

[0054] Embodiment 2

[0055] As shown in Figures 2-3 , based on Embodiment 1, the present embodiment also discloses a construction method of a double-layer settlement-stopping structure of an existing raft foundation, which is used to construct the double-layer settlement-stopping structure of an existing raft foundation according to Embodiment 1, and the construction method comprises the following steps:

[0056] Step S1: According to the settlement increase of the existing building, the upper structure load, the uneven settlement condition of the existing foundation, and the actual condition of the existing foundation, the thickness of the existing raft foundation 1, the height and number of the support column 4 of the existing raft foundation 1, and the box-shaped raft unit base pressure and deformation are calculated according to the design calculation method of the current raft foundation technical specification and standard and the bearing capacity and deformation capacity index of the existing foundation 7. When the base pressure is less than the bearing capacity of the existing foundation 7 and less than the deformation requirement of the existing vertical structure 3 interval 5 / 10000, the height and number of the support column 4 of the existing raft foundation 1 and the newly added raft 6 are the design results. If the above requirements are not met, the thickness of the newly added raft 6 and the height and number of the support column 4 of the existing raft foundation 1 are adjusted until the bearing capacity and deformation requirements of the existing foundation 7 are met, as shown in FIG. 1. Figure 7 As shown in FIG. 1, B is the area of the box-shaped raft unit, and the boundary lines of the two sides of the box-shaped raft unit are the boundary lines of the adjacent existing vertical structure 3.

[0057] Step S2: According to the interval between the newly added raft 6 and the existing raft foundation 1 and the setting condition of the support column 4, the connection mode of the newly added raft 6 and the existing vertical structure 3 is determined.

[0058] Step S3: Excavate to the bottom surface elevation position of the newly added raft 6 from the ground, then excavate and install a hole to the top surface of the existing raft foundation 1, and set a support column 4 in the installation hole. The bottom of the support column 4 is connected with the existing raft foundation 1, and the top of the support column 4 extends to the bottom surface elevation position of the newly added raft 6.

[0059] Step S4: Construct the newly added raft 6, wherein the newly added raft 6 is connected with the top of the support column 4.

[0060] In a preferred manner, step S3 further comprises: digging the top surface reinforcement of the existing raft foundation 1 at the bottom of the installation hole and implanting a planted reinforcement. One end of the planted reinforcement is welded firmly with the top surface reinforcement of the existing raft foundation 1, and the other end of the planted reinforcement is connected with the bottom of the support column 4. By connecting the bottom of the support column 4 with the planted reinforcement of the existing raft foundation 1, the connection between the support column 4 and the existing raft foundation 1 is more stable.

[0061] In a preferred manner, the number of the planted reinforcement of the existing raft foundation 1 is the same as the number of the main reinforcement of the support column 4 and is at least 4, so as to ensure that the support column 4 is connected firmly with the existing raft foundation 1 and ensure the stability of the double-layer settlement stopping structure of the existing raft foundation.

[0062] In a preferred manner, the diameter of the planted reinforcement of the existing raft foundation 1 is greater than or equal to the diameter of the main reinforcement of the support column 4. Further, the planted reinforcement of the existing raft foundation 1 further has a reserved section, the length of the reserved section is not less than 20 times the diameter of the main reinforcement of the support column 4 and is not less than 500 mm, and the reserved section is used for connecting the main reinforcement of the support column 4.

[0063] In a preferred mode, step S4 further comprises: a steel anchor is arranged on the top of the support column 4, and the steel anchor is connected with the steel cage of the new raft 6. By connecting the steel anchor arranged on the top of the support column 4 with the steel cage of the new raft 6, the support column 4 and the new raft 6 are connected into one body.

[0064] In a preferred mode, when the support column 4 is a prefabricated component, a steel anchor for connecting the new raft 6 is reserved on the top of the support column 4, the length of the steel anchor is not less than 500 mm, a cavity for inserting the steel bar of the existing raft foundation 1 is reserved on the bottom of the support column 4, and the cavity is filled with a bonding material such as sulfur mortar; when the support column 4 is cast in situ, the steel cage of the support column 4 is placed in the installation hole after being bound, the end of the main steel bar of the steel cage of the support column 4 is reserved for an anchoring length for connecting the new raft 6, the anchoring length is not less than 500 mm, the main steel bar of the steel cage of the support column 4 is firmly bound with the reserved section of the steel bar of the existing raft foundation 1, then the concrete required by the design is poured to the bottom elevation of the new raft 6, and a floating mortar removal height is reserved.

[0065] In a preferred mode, in step S4, the bottom cushion layer of the new raft 6 is first made, the cushion layer C10 is a plain concrete cushion layer, the thickness of the cushion layer is not less than 50 mm, then the double-layer steel mesh of the new raft 6 is bound according to the design requirements, the steel anchor is anchored into the double-layer steel mesh, and then the concrete is poured to the top surface elevation of the new raft 6 to complete the making of the new raft 6.

[0066] In a preferred mode, as shown in FIG. 5, in step S3: when the reinforcing device 5 needs to be arranged, the installation hole is drilled through the existing raft foundation 1 and excavated to the bottom elevation of the reinforcing device 5, then the reinforcing device 5 is arranged in the installation hole, and the top of the reinforcing device 5 extends to the existing raft foundation 1 and is connected with the existing raft foundation 1. By connecting the reinforcing device 5 with the existing raft foundation 1, the reinforcing device 5 can effectively support the existing raft foundation 1, thereby reinforcing the existing raft foundation 1. Figure 4 In a preferred mode, when the reinforcing device 5 is a prefabricated component, the reinforcing device 5 is sunk by pressing or hitting through the installation hole, so that the top of the reinforcing device 5 is raised to the top surface elevation of the existing raft foundation 1, the main steel bar on the top of the reinforcing device 5 is manually chiseled out, the main steel bar is bound with the top surface steel bar of the existing raft foundation 1, then the steel cage of the support column 4 is placed in the installation hole, the main steel bar of the steel cage of the support column 4 is firmly bound with the top main steel bar of the reinforcing device 5, the concrete required by the design is poured to the bottom elevation of the new raft 6, and a floating mortar removal height is reserved.

[0067] In a preferred mode, as shown in FIG. 5, in step S3: when the reinforcing device 5 needs to be arranged, the installation hole is drilled through the existing raft foundation 1 and excavated to the bottom elevation of the reinforcing device 5, then the reinforcing device 5 is arranged in the installation hole, and the top of the reinforcing device 5 extends to the existing raft foundation 1 and is connected with the existing raft foundation 1. By connecting the reinforcing device 5 with the existing raft foundation 1, the reinforcing device 5 can effectively support the existing raft foundation 1, thereby reinforcing the existing raft foundation 1.

[0068] Figure 6 ​As shown, when the reinforcing device 5 uses cast-in-place piles, the reinforcing device 5 and the support column 4 are set as one unit. During construction, after the reinforcing cage of the reinforcing device 5 is tied, it is lowered into the installation hole. The end of the main reinforcement of the reinforcing cage of the reinforcing device 5 is reserved with an anchorage length of not less than 500mm to connect with the new raft foundation 6. Then, concrete is poured to the top surface elevation of the existing raft foundation 1. The top surface reinforcement of the existing raft foundation 1 is tied firmly to the main reinforcement of the reinforcing device 5. Then, the concrete is poured to the bottom surface elevation of the new raft foundation 6 and the height for removing laitance is reserved.

[0069] In a preferred manner, when the reinforcement device 5 uses plain concrete cast-in-place piles, plain concrete is poured into the installation hole up to the bottom elevation of the existing raft foundation 1. Then, the steel cage of the support column 4 is tied into the installation hole. A section of anchorage length is reserved at the end of the main reinforcement of the support column 4 to connect with the new raft 6. After the bottom of the main reinforcement of the support column 4 is firmly tied to the reserved section of the existing raft foundation 1, the concrete required by the design is poured up to the bottom elevation of the new raft 6, and a height for removing laitance is reserved.

[0070] Example 3

[0071] like Figures 2-6 As shown in the figure, the construction method of a double-layer anti-settlement structure for an existing raft foundation described in this embodiment is a preferred combination in actual construction, specifically as follows:

[0072] S1: Based on the settlement or uneven settlement of the existing building and the actual characteristics of the existing foundation, calculate the out-of-plane stiffness (slab thickness) of the existing raft foundation 1 that meets the requirements of the current specifications and standards, or calculate and determine the required foundation engineering performance (foundation bearing capacity, deformation capacity) based on the engineering indicators of the existing foundation 7. Subtract the existing stiffness of the existing raft foundation 1 or the bearing capacity of the existing foundation 7 to obtain the required thickness of the new raft slab 6 and the number and spacing of the support columns 4, or the length and number of the reinforcement devices 5 that need to be added.

[0073] S2: Determine the connection method of the double-layer anti-settlement structure of the existing raft foundation based on the determined required additional support columns 4, the thickness of the new raft foundation 6, the distance between the new raft foundation 6 and the existing raft foundation 1, and the spacing of the reinforcement devices 5.

[0074] S3: The reinforcement device 5 includes reinforcement piles and composite foundation reinforcement. The reinforcement piles can be precast piles (including steel pipe piles) or cast-in-place piles, and the composite foundation reinforcement can be plain concrete piles or reinforced concrete piles. The new raft slab 6 can be a reinforced concrete slab or a mixed reinforcement slab (ordinary steel bars + composite material bars FRP-CFRP, GFRP, BFRP spaced apart from the steel bars).

[0075] S4: the new raft 6 is connected to the existing vertical structure 3 (column, wall) by anchoring on it; the new raft 6 can be continuously laid with reinforcement in the area connected to the existing vertical structure 3;

[0076] S5: the monitoring system of the implementation process is arranged on the existing building columns and walls; the wall and column components can be monitored by displacement meters, strain gauges or pasted lateral reflection sheets, and static level systems, and have the function of testing at any time;

[0077] S6: the indoor ground of the existing building is excavated to the bottom elevation of the new raft 6 according to the design scheme and a thickness required for ground restoration is left;

[0078] S6: manual hole digging is adopted to the top surface of the existing raft foundation 1; when the embedding depth of the existing raft foundation 1 is large, measures should be taken to stabilize the hole digging; the hole size should be 1.1-1.2 times larger than the side length or diameter of the support column 4 or the reinforcing pile, composite foundation reinforcement, or reinforcing pile;

[0079] S7: when a double-layer foundation structure system is adopted (no reinforcing pile or composite foundation reinforcement is added under the existing raft foundation 1), (1) the reinforcement on the top surface of the existing raft foundation 1 is removed and anchoring is performed; the number of diameters should be the same as the number of main reinforcement of the support column 4 and should not be less than 4; the diameter of the anchoring should not be less than the diameter of the main reinforcement of the support column 4 and a length (not less than 20 times the diameter of the main reinforcement of the short column and not less than 500 mm) reserved for the binding connection with the main reinforcement of the support column 4; (2) when the support column 4 is a prefabricated component, a steel reinforcement anchor reserved at the top of the new raft 6 should be reserved; the length is not less than 500 mm; the bottom should be reserved with a hole for the insertion of the anchoring and filled with a bonding material such as sulfur cement; (3) when the support column 4 is cast in situ, the steel reinforcement cage of the support column 4 can be placed in the installation hole after the binding is completed; the length of the steel reinforcement cage of the support column 4 should be reserved for the anchoring length of the new raft 6, not less than 500 mm; (4) after the main reinforcement of the steel reinforcement cage of the support column 4 is firmly bound with the reserved reinforcement, the concrete required by the design is poured to the bottom of the new raft 6 and the floating slurry removal height is reserved;

[0080] S8: When the reinforcing pile or composite foundation and double-layer foundation structure combination system is adopted (both the reinforcing pile and the composite foundation reinforcement are added under the existing raft foundation 1), (1) the reinforcing steel bars on the top surface of the existing raft foundation 1 are removed and the upper bending is blocked, a small drill is used to drill an installation hole, the diameter of which is larger than the diameter or the side length of the reinforcing pile or the composite foundation reinforcement; (2) when the reinforcing pile or the composite foundation reinforcement is a prefabricated component, the pile can be driven by pressing or hitting, and the top elevation of the pile is up to the top elevation of the existing raft foundation 1; the main reinforcement of the prefabricated component is manually removed, and the exposed reinforcing steel bars of the existing raft foundation 1 are bound; after the reinforcing steel cage of the support column 4 is bound, it is placed in the installation hole, the length of the reinforcing steel cage of the support column 4 should be reserved for the anchoring length for connecting the new raft 6, and the anchoring length is not less than 500 mm; after the main reinforcement of the reinforcing steel cage of the support column 4 is firmly bound with the main reinforcement of the prefabricated component, the concrete is poured to the bottom of the new raft 6 according to the design requirements, and the height of the floating layer is reserved for removal; (3) when the reinforcing pile is a cast-in-place pile, the installation hole can be drilled by a drill; the reinforcing steel cage of the reinforcing pile is bound and lowered, and the main reinforcement of the reinforcing steel cage of the reinforcing pile should be reserved for the anchoring length for connecting the new raft 6; the concrete is poured to the bottom surface elevation of the existing raft foundation 1; the main reinforcement of the reinforcing pile is firmly bound with the main reinforcement of the existing raft foundation 1; the concrete is poured to the bottom elevation of the new raft 6 and the height of the floating layer is reserved for removal; (4) when the plain concrete cast-in-place pile is used as the composite foundation reinforcement, the installation hole can be drilled by a drill and the concrete is poured to the bottom surface elevation of the existing raft foundation 1; the reinforcing steel cage of the support column 4 is bound and lowered into the installation hole, and the main reinforcement of the reinforcing steel cage of the support column 4 should be reserved for the anchoring length for connecting the new raft 6; the concrete is poured to the bottom surface elevation of the existing raft foundation 1 and the height of the floating layer is reserved for removal; after the main reinforcement of the reinforcing steel cage of the support column 4 is firmly bound with the main reinforcement of the prefabricated component, the concrete is poured to the bottom of the new raft 6 according to the design requirements, and the height of the floating layer is reserved for removal;

[0081] S9: The concrete floating layer on the top of the reinforcing device 5 or the support column 4 is removed; the C10 plain concrete cushion layer with a thickness of not less than 50 mm is constructed on the bottom of the new raft 6, the double-layer reinforcing mesh is bound according to the design requirements, the main reinforcement of the reinforcing device 5 or the support column 4 is anchored into the double-layer reinforcing mesh, and then the concrete is poured to the top surface elevation of the new raft 6;

[0082] S10: According to the unevenness of the existing settlement, the area with larger settlement is constructed first, then the area with smaller settlement is constructed, and the construction is interval, and the construction speed and the batch quantity are adjusted according to the deformation monitoring during the construction process.

[0083] S10: The ground is recovered;

[0084] The above only describes the preferred embodiments of the present application, and is not used to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A construction method for an existing raft foundation double-layer anti-settlement structure, used for constructing an existing raft foundation double-layer anti-settlement structure, wherein the existing raft foundation double-layer anti-settlement structure includes an existing raft foundation (1), and an existing vertical structure (3) is provided on the existing raft foundation (1), characterized in that, A new raft foundation (6) is provided above the existing raft foundation (1). The new raft foundation (6) is connected to the existing vertical structure (3). A support column (4) is connected between the new raft foundation (6) and the existing raft foundation (1). The existing raft foundation (1) is equipped with a reinforcement device (5) at its bottom; At least two of the support columns (4) shall be provided between adjacent existing vertical structures (3); This construction method includes the following steps: Step S1: Based on the existing building's increased superstructure load, existing foundation settlement or uneven settlement, existing foundation embedment depth, and the actual characteristics of the existing foundation, determine the spacing between the newly added raft slab (6) and the existing raft foundation (1), the number of the support columns (4), and the spacing between adjacent support columns (4). Step S2: Determine the connection method between the new raft slab (6) and the existing raft foundation (1) based on the distance between the new raft slab (6) and the existing raft foundation (1) and the setting of the support column (4); Step S3: Excavate from the ground to the bottom elevation of the newly added raft foundation (6), then excavate an installation hole from the bottom elevation of the newly added raft foundation (6) to the top surface of the existing raft foundation (1), and install the support column (4) in the installation hole. The bottom of the support column (4) is connected to the existing raft foundation (1), and the top of the support column (4) extends to the bottom elevation of the newly added raft foundation (6). Step S3 further includes: chiseling out the top surface steel bars of the existing raft foundation (1) at the bottom of the mounting hole and inserting the reinforcing bars, with the bottom of the support column (4) connected to the reinforcing bars; In step S3: the mounting hole passes through the existing raft foundation (1) and is excavated to the bottom elevation of the reinforcing device (5), and then the reinforcing device (5) is installed. The top of the reinforcing device (5) extends to the existing raft foundation (1) and is connected to the existing raft foundation (1). Step S4: Construct the new raft slab (6), wherein the new raft slab (6) is connected to the top of the support column (4).

2. The construction method of a double-layer anti-settlement structure for an existing raft foundation according to claim 1, characterized in that, At least one of the reinforcing devices (5) shall be provided between adjacent existing vertical structures (3).

3. The construction method of a double-layer anti-settlement structure for an existing raft foundation according to claim 1, characterized in that, Step S4 further includes: a steel anchor bolt is provided on the top of the support column (4), and the steel anchor bolt is connected to the steel cage of the newly added raft slab (6).

4. The construction method of a double-layer anti-settlement structure for an existing raft foundation according to claim 1, characterized in that, The reinforcing device (5) is connected to the support column (4).

5. The construction method of a double-layer anti-settlement structure for an existing raft foundation according to claim 4, characterized in that, The reinforcing device (5) and the support column (4) are integrated.

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