A kind of construction method and structure for backfilling of overhanging part bottom fat groove

Abstract

The application discloses a kind of for overhanging position bottom's fertilizer groove backfill structure and construction method, it is characterized by comprising the following steps: S1: according to the size of backfill soil compaction equipment, fertilizer groove is divided into bottom backfill area, middle soil retaining area and upper backfill area;S2: the bottom backfill area of fertilizer groove is carried out building outer wall waterproof structure and fertilizer groove backfill soil construction;S3: waterproof structure and soil retaining structure construction are carried out in middle soil retaining area, a height variable sealing area is constructed using soil retaining structure, and the middle soil retaining area is filled.S4: the upper backfill area of fertilizer groove is carried out overhanging part side outer wall waterproof structure and fertilizer groove backfill soil construction.Guarantees the compaction degree of fertilizer groove backfill under overhanging structure, eliminates weak point in fertilizer groove backfill, eliminates uneven settlement risk, and also reduces the settlement deformation amount of fertilizer groove backfill area later period.

Description

Technical Field

[0001] This invention relates to the field of trench backfilling for foundation pits, and specifically to a trench backfilling structure and construction method for the bottom of cantilevered sections. Background Technology

[0002] Currently, cantilever structures are highly regarded in building construction because they can reduce the scope of foundation treatment, decrease the size of the excavation pit, and lower project costs. However, during construction, the compaction equipment cannot reach a certain area under the cantilever section due to the cantilever, resulting in insufficient compaction of the backfill soil in that area. This can cause soil from other areas to slide into that area later, leading to large uneven settlement of the entire backfill soil. This can cause cracking or even damage to buildings and structures constructed later in the backfill area, resulting in significant maintenance costs.

[0003] Currently, there are two ways to improve the quality of backfill at the bottom of the cantilever section. One is to use lightweight aggregate concrete or low-grade plain concrete to fill the area at the bottom of the cantilever section that cannot be compacted. This method provides good backfill quality but is costly. The second method is to use the reverse construction method, which involves introducing a construction joint at the cantilever section to divide it in two. The main structure is constructed first, and the cantilever section is constructed only after the backfill reaches the bottom. This method delays the completion time of the entire structure, affecting the construction period. In addition, the introduction of the construction joint increases the risk of leakage in the structure. Summary of the Invention

[0004] To address the aforementioned deficiencies in existing technologies, a backfilling structure and construction method for the bottom of cantilevered sections are provided, aiming to improve the quality of backfilling and reduce the risk of uneven settlement in the cantilevered sections later.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0006] A method for backfilling trenches at the bottom of cantilevered sections, characterized by the following steps:

[0007] S1: Based on the size of the backfill compaction equipment, the backfill trench is divided into a bottom backfill area, a middle retaining area, and an upper backfill area;

[0008] S2: Construct waterproofing for the building's exterior walls and backfill soil for the fertilizer trench at the bottom of the backfill area;

[0009] S3: Construct waterproofing and retaining structures in the central retaining area, using the retaining structure to create a height-variable sealed area to fill the central retaining area.

[0010] S4: Construct waterproofing for the cantilevered side walls of the upper backfill area of ​​the fertilizer trench and construct the backfill soil for the fertilizer trench.

[0011] According to the above technical solution, the bottom backfill area refers to the area where the backfill compaction equipment can operate below the cantilevered part; the middle retaining area refers to the area between the cantilevered part and the bottom backfill area where the backfill compaction equipment cannot enter; and the upper backfill area refers to the area within the trench after removing the bottom backfill area and the middle retaining area.

[0012] According to the above technical solution, it also includes a lubrication part. In step S3, a lubrication part is provided between the retaining structure and the building exterior wall, and between the overlapping areas of the retaining structure and the side wall of the cantilevered part. The lubrication part is fixed on the building exterior wall and the side wall of the cantilevered part, and the lubrication part is in sliding contact with the retaining structure.

[0013] According to the above technical solution, the retaining structure includes retaining plates and a base. The base consists of a foundation, ground beams, and retaining plate foundations. The retaining plate foundations are horizontally arranged along the length of the cantilevered portion. The retaining plates are vertically arranged, with the bottom end of the retaining plate fixedly connected to the top of the retaining plate foundation, and the sides of the retaining plates adhering to the sidewalls of the cantilevered portion. Several ground beams are horizontally spaced below the cantilevered portion, with one end of the ground beam fixedly connected to the sidewall of the retaining plate foundation and the other end of the ground beam adhering to the exterior wall of the building below the cantilevered portion. The retaining plate foundations and ground beams are fixedly embedded in the foundation, and the sides of the foundation are adhering to the exterior wall of the building below the cantilevered portion.

[0014] According to the above technical solution, step S3 includes the following steps:

[0015] S31: Waterproofing construction shall be carried out on the exterior walls of the building, the bottom of the cantilevered section, and the overlapping area of ​​the retaining plate and the cantilevered section within the central retaining area, and lubrication parts shall be installed in the corresponding areas of the exterior walls and the cantilevered section.

[0016] S32: Construct the foundation at the bottom of the central retaining area, and select the foundation thickness according to requirements;

[0017] S33: Excavate a trench in reverse on the foundation, place the fixed and connected ground beams and retaining plates in the trench, and pour concrete in the trench;

[0018] S34: The retaining wall is formed by tying steel bars, erecting formwork, pouring concrete, and curing on the retaining foundation. There is a certain length of overlap between the retaining wall and the cantilever sidewall in the vertical direction.

[0019] According to the above technical solution, in step S32, the foundation is compacted in layers, with the thickness of a single layer not exceeding 20cm, and the foundation is made of lime-soil or cement-soil.

[0020] According to the above technical solution, step S2 includes the following steps:

[0021] S21: Construct a waterproof structure with a height of a cm on the exterior wall of the building;

[0022] S22: Perform backfilling of the area below b cm above the upper edge of the waterproof structure in step S21. The backfill soil shall be backfilled and compacted in layers, and the thickness of each layer of backfill soil shall not exceed 20 cm.

[0023] S23: Determine whether the backfilling of the bottom backfill area has been completed. If not, repeat steps S21 to S22 until the backfilling of the bottom backfill area is completed.

[0024] According to the above technical solution, step S4 includes the following steps:

[0025] S41: The upper backfill area on the side of the retaining structure shall be backfilled with soil in layers and compacted, and the thickness of each layer of backfill shall not exceed 20cm.

[0026] S42: Construct a waterproof structure with a height of c cm on the side exterior wall of the cantilever section;

[0027] S43: For the area below the upper edge of the waterproof structure in step S32, carry out backfilling of the trench. The backfill soil shall be backfilled and compacted in layers, and the thickness of each layer of backfill soil shall not exceed 20cm.

[0028] S44: Determine whether the backfilling of the bottom backfill area has been completed. If not, repeat steps S42 to S43 until the backfilling of the bottom backfill area is completed.

[0029] According to the above technical solution, it also includes a 3:7 lime-soil layer. The 3 lime-soil layer is located between the waterproof structure of the building exterior wall and the backfill soil in step S2, between the side of the retaining structure and the backfill soil in step S3, and between the waterproof structure of the side exterior wall of the cantilevered part and the backfill soil in step S4. The thickness of the 3 lime-soil layer ranges from 80cm to 100cm.

[0030] A backfilling structure for the bottom of a cantilever section, characterized in that it includes a retaining plate and a base;

[0031] The base consists of a foundation, ground beams, and retaining wall foundations. The retaining wall foundations are laid horizontally along the length of the cantilever section. Several ground beams are laid horizontally at intervals below the cantilever section. One end of the ground beams is fixedly connected to the inner wall of the retaining wall foundation, and the other end of the ground beams is attached to the exterior wall of the building below the cantilever section. The retaining wall foundations and ground beams are fixedly embedded in the foundation. The side of the foundation closest to the exterior wall of the building is flush with the other end of the ground beams, and the two are in contact with the exterior wall of the building below the cantilever section.

[0032] The retaining plates are installed vertically, with the bottom of the retaining plate fixedly connected to the top of the retaining plate foundation. The sides of the retaining plates are attached to the outer wall of the cantilever section and can be vertically slidable.

[0033] The present invention has the following beneficial effects:

[0034] 1. In the area below the cantilever, the backfill soil cannot be compacted due to the inaccessibility of compaction equipment, leading to irregular settlement. This embodiment sets up a retaining structure at the elevation where compaction equipment cannot effectively compact the soil. The retaining structure, the bottom surface of the cantilever, and the building's exterior wall below the cantilever form a rectangular sealed cavity, blocking the backfill soil in this area from the outside of the cantilever, eliminating the need for compaction. Furthermore, the retaining structure can move vertically downwards relative to the cantilever. When settlement occurs at the bottom of the retaining structure, it settles along with the soil in the trough using its own weight, compacting the settlement area and expanding the sealed area, thereby offsetting the voids caused by settlement at the bottom of the retaining structure. Considering the overall backfilling effect, this ensures the compaction of the trough backfill below the cantilever structure, eliminates weak points in the trough backfill, eliminates the risk of uneven settlement, and also reduces the amount of settlement deformation in the trough backfill area later.

[0035] 2. Lubrication points are installed between the vertical sidewalls of the vertical section and the cantilever section, and between the horizontal section and the building exterior wall. This prevents the retaining structure from applying vertical loads to the cantilever section due to friction when the retaining structure and the cantilever section move relative to each other, thus reducing safety hazards.

[0036] 3. In terms of economic benefits and construction efficiency, compared with backfilling processes such as lightweight aggregate concrete, the cost savings can reach 70%; compared with reverse construction, the construction speed is significantly improved, with a speed increase of up to 50%. At the same time, if the cantilevered part is a water-contaminated room, the risk of structural leakage caused by the introduction of construction joints in the cantilevered part can be reduced. Attached Figure Description

[0037] Figure 1 This is a diagram showing the division of the fertilizer trough area according to an embodiment of the present invention;

[0038] Figure 2 This is a cross-sectional view of the fertilizer trench after backfilling according to an embodiment of the present invention;

[0039] Figure 3 This is step S2 of the fertilizer tank backfilling in the embodiment of the present invention;

[0040] Figure 4 This is step S2 of the fertilizer trench backfilling in the embodiment of the present invention, which involves backfilling to the central retaining area;

[0041] Figure 5 This refers to step S3 of the backfilling of the trough provided in the embodiment of the present invention, which is the foundation construction of the retaining structure;

[0042] Figure 6This refers to step S3 of the backfilling of the trough provided in the embodiment of the present invention, which involves the construction of the retaining structure.

[0043] Figure 7 This is a cross-sectional view of the retaining structure provided in an embodiment of the present invention;

[0044] Figure 8 yes Figure 6 Sectional view of AA;

[0045] Figure 9 This is step S4 of the fertilizer tank backfilling in the embodiment of the present invention;

[0046] In the diagram, 1. Retaining structure; 1-1. Retaining plate; 1-2. Base; 1-21. Retaining plate foundation; 1-22. Ground beam; 1-23. Foundation; 2. Lubrication section; 3. Cantilever section; 4. Building exterior wall; 5. Fertilizer trench; 5-1. Bottom backfill area; 5-2. Middle retaining area; 5-3. Upper backfill area; 6. Pressurized equipment; 7. Waterproof structure; 8. Manhole; 9. 3:7 lime-soil layer; 10. Backfill soil. Detailed Implementation

[0047] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0048] Reference Figures 1-9 As shown, the present invention provides a method for backfilling a trench at the bottom of a cantilever section, comprising the following steps:

[0049] S1: Based on the dimensions of the backfill compaction equipment 6 (in the embodiment shown in the figure, when the top of the compaction equipment and the driver's head are at the same height as the bottom of the cantilever section), the backfill trough is divided into a bottom backfill area 5-1, a middle retaining area 5-2, and an upper backfill area 5-3.

[0050] S2: Construct the waterproof structure 7 of the building exterior wall 4 and the backfill soil 10 of the fertilizer trench at the bottom of the backfill area;

[0051] S3: Construct waterproofing and retaining structure 1 in the central retaining area, and use the retaining structure to build a height-variable sealed area to fill the central retaining area; the sealed area slides in contact with the building's exterior wall and the cantilevered part respectively, and the retaining structure moves up and down within a certain distance in the vertical direction.

[0052] S4: Construct waterproofing for the cantilevered three-sided exterior wall of the upper backfill area of ​​the fertilizer trench and construct the fertilizer trench backfill soil.

[0053] In the area below the cantilever, the backfill soil cannot be compacted because the compaction equipment cannot enter, which easily leads to irregular settlement. In this embodiment, a retaining structure is set up at the elevation where the compaction equipment cannot compact normally. The retaining structure, the bottom surface of the cantilever, and the building exterior wall below the cantilever form a sealed inner cavity with a rectangular cross-section, which blocks the backfill soil of the fertilizer trench located at this location from the outside of the cantilever, eliminating the need for backfill soil compaction in this area. The above measures ensure the overall backfill compaction degree of the fertilizer trench and improve the backfill quality.

[0054] Furthermore, the retaining structure can move vertically downwards relative to the cantilever section. When settlement occurs at the bottom of the retaining structure, it settles along with the soil in the trench using its own weight, compacting the settlement area and expanding the sealed area formed above, thereby offsetting the voids created by settlement at the bottom of the retaining structure. This ensures that even with slight settlement of the trench soil, the retaining structure settles uniformly with the soil without losing its lateral retaining capacity, ensuring the overall stability of the trench and the integrity of any subsequent structures built above.

[0055] Specifically, the bottom backfill area refers to the area where backfill compaction equipment can operate below the cantilever section; the middle retaining area refers to the area between the cantilever section and the bottom backfill area where backfill compaction equipment cannot enter; and the upper backfill area refers to the area within the trench after removing the bottom backfill area and the middle retaining area.

[0056] Furthermore, it also includes a lubrication part 2. In step S3, a lubrication part is provided between the retaining structure and the building exterior wall, and between the overlapping areas of the retaining structure and the side wall of the cantilevered portion. The lubrication part is fixed to the building exterior wall and the side wall of the cantilevered portion, and slides in contact with the retaining structure. Providing lubrication parts between the vertical section and the vertical side wall of the cantilevered portion, and between the horizontal section and the building exterior wall, prevents the retaining structure from applying a vertical load to the cantilevered portion due to friction when the retaining structure and the cantilevered portion move relative to each other, thus reducing safety hazards.

[0057] Furthermore, the lubrication system includes an intermediate plate and an adhesive. The intermediate plate is made of a flexible material. One side of the intermediate plate is adhered to the vertical sidewall of the cantilever section and the exterior wall of the building below the cantilever section via the adhesive, while the other side of the intermediate plate is attached to the retaining structure. The flexible material of the intermediate plate reduces the friction when the retaining structure slides down, allowing the retaining structure to slide vertically downwards along the exterior wall of the building with the backfill soil below it even with slight settlement, without losing its function of retaining the backfill soil on the sides.

[0058] Specifically, the retaining structure includes a retaining plate 1-1 and a base 1-2. The base consists of a foundation 1-23, a ground beam 1-22, and a retaining plate foundation 1-21. The retaining plate foundation is horizontally arranged along the length of the cantilever section. The retaining plate is vertically arranged, with its bottom end fixedly connected to the top of the retaining plate foundation, and its side surface fitting against the side wall of the cantilever section. Several ground beams are horizontally spaced below the cantilever section, with one end of the ground beam fixedly connected to the side wall of the retaining plate foundation and the other end fitting against the exterior wall of the building below the cantilever section. The retaining plate foundation and the ground beams are fixedly embedded in the foundation, and the side surface of the foundation fits against the exterior wall of the building below the cantilever section.

[0059] Specifically, step S3 includes the following steps:

[0060] S31: Waterproofing construction shall be carried out on the exterior walls of the building, the bottom of the cantilevered section, and the overlapping area of ​​the retaining plate and the cantilevered section within the central retaining area, and lubrication parts shall be installed in the corresponding areas of the exterior walls and the cantilevered section.

[0061] S32: Foundation construction is carried out at the bottom of the central retaining area, and the thickness of the foundation is selected according to the requirements; the thickness of the foundation is 80cm to 100cm. The main function of the foundation is waterproofing, while also restraining the horizontal displacement of the bottom of the retaining plate; in order to facilitate the foundation construction, backfill soil is carried out in the upper backfill area at the same height as the foundation.

[0062] S33: Excavate a trench on the foundation, place the fixed and connected ground beam and retaining plate in the trench, and pour concrete in the trench; the above operation rigidly connects the ground beam, retaining plate foundation and foundation into a whole, which is equivalent to the base of the retaining structure; since the retaining structure is in sliding contact with the cantilever part and the building exterior wall, it has a certain distance of downward sliding space in the vertical plane to overcome the settlement deformation of the backfill area in the later stage.

[0063] S34: Reinforcing steel is tied, formwork is erected, concrete is poured, and curing is carried out on the retaining foundation to form a retaining slab. There is a certain length of overlap between the retaining slab and the cantilevered sidewall in the vertical direction. The retaining slab, the base formed in step S33, the building's exterior wall, and the bottom surface of the cantilever section together constitute a sealed area. Because the retaining structure is in sliding contact with the cantilever section and the building's exterior wall, relative movement can occur between the retaining slab and the sidewall of the cantilever section, and between the base and the building's exterior wall, in the vertical direction. When the backfill soil directly below the central retaining area settles, the height of the sealed area can settle along with the backfill soil to overcome the later settlement deformation of the backfill area. The height of the overlapping area in the diagram is 50cm to fully consider the later settlement of the backfill area and ensure that the retaining slab still has its retaining function after settlement.

[0064] Preferably, in step S32, the foundation is compacted in layers, with each layer not exceeding 20cm in thickness, and the foundation is made of lime-soil or cement-soil; in the example shown in the figure, the foundation is made of 90cm thick lime-soil.

[0065] Specifically, step S2 includes the following steps:

[0066] S21: Construct a waterproof structure with a height of a cm on the exterior wall of the building; in the example shown in the figure, the height of the waterproof structure a is 200 cm, but other heights can also be selected, generally 150 cm to 200 cm. The waterproof structure must not exceed the backfill height by more than 200 cm to prevent the waterproof structure from being exposed to the air for a long time, which may cause damage.

[0067] S22: Perform backfilling of the area below b cm above the upper edge of the waterproof structure in step S21. The backfill soil is backfilled and compacted in layers, and the thickness of each layer of backfill soil does not exceed 20 cm. In the example shown in the figure, b is 50 cm, but other values ​​can also be selected. The height of b cm reserved in the waterproof structure is to ensure the quality of subsequent waterproof extension construction.

[0068] S23: Determine whether the backfilling of the bottom backfill area has been completed. If not, repeat steps S21-S22 until the backfilling of the bottom backfill area is completed. The backfilling of the trench and the construction of the waterproof structure are carried out in an interleaved manner. The waterproof structure is constructed first, followed by the backfilling of the trench, until the backfilling of the trench is completed.

[0069] Specifically, step S4 includes the following steps:

[0070] S41: The upper backfill area on the side of the retaining structure is backfilled with soil in the trench (in the example shown in the figure, after the concrete wall of the retaining plate reaches 100% strength, the soil trench backfilling work outside the retaining plate is carried out immediately). The soil trench backfill is backfilled and compacted in layers, and the thickness of each layer of backfill does not exceed 20cm.

[0071] S42: Construct a waterproof structure with a height of c cm on the side exterior wall of the cantilever section; the height of the waterproof structure c in the example shown in the figure is 200 cm, but other heights can also be selected; the waterproof structure must not exceed the backfill height by more than 2 meters to prevent the waterproof structure from being exposed to the air for a long time, which may cause damage.

[0072] S43: Perform backfilling of the area below the upper edge d cm of the waterproof structure in step S32. The backfill soil shall be backfilled and compacted in layers, and the thickness of each layer of backfill soil shall not exceed 20 cm. In the example shown in the figure, d is 50 cm, but other values ​​can also be selected.

[0073] S44: Determine whether the backfilling of the bottom backfill area has been completed. If not, repeat steps S42 to S43 until the backfilling of the bottom backfill area is completed.

[0074] Furthermore, the spacing of the ground beams is controlled according to the backfill height outside the retaining plate; the higher the retaining plate, the smaller the spacing of the ground beams.

[0075] Preferably, a manhole 8 is provided on the retaining plate, and steel bar joints are reserved at both ends of the manhole in advance to facilitate the entry and exit of formwork workers. After the concrete is poured, the manhole is sealed with blocks to ensure the retaining function.

[0076] Furthermore, it also includes a 3:7 lime-soil layer 9, which is located between the waterproof structure of the building exterior wall and the backfill soil in step S2, between the side of the retaining structure and the backfill soil in step S3, and between the waterproof structure of the side exterior wall of the cantilevered part and the backfill soil in step S4; the thickness of the 3:7 lime-soil layer ranges from 80cm to 100cm.

[0077] Furthermore, when constructing a waterproof structure for the building's exterior walls, grinding is required first. This mainly involves cutting, grinding, and applying anti-corrosion treatment to the wall bolts before proceeding with the waterproof structure construction.

[0078] The present invention also provides a backfill structure for the bottom of a cantilever section, characterized in that it includes a retaining plate and a base.

[0079] The base consists of a foundation, ground beams, and retaining wall foundations. The retaining wall foundations are laid horizontally along the length of the cantilever section. Several ground beams are laid horizontally at intervals below the cantilever section. One end of the ground beams is fixedly connected to the inner wall of the retaining wall foundation, and the other end of the ground beams is attached to the exterior wall of the building below the cantilever section. The retaining wall foundations and ground beams are fixedly embedded in the foundation. The side of the foundation closest to the exterior wall of the building is flush with the other end of the ground beams, and the two are in contact with the exterior wall of the building below the cantilever section. The thickness of the foundation is the same as the thickness of the 3:7 lime-soil layer.

[0080] The retaining plates are installed vertically, with the bottom of the retaining plate fixedly connected to the top of the retaining plate foundation. The sides of the retaining plates are attached to the outer wall of the cantilever section and can be vertically slidable.

[0081] The above are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, any equivalent changes made in accordance with the claims of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for backfilling trenches at the bottom of cantilevered sections, characterized in that: Includes the following steps: S1: Based on the size of the backfill compaction equipment, the backfill trench is divided into a bottom backfill area, a middle retaining area, and an upper backfill area; S2: Construct waterproofing for the building's exterior walls and backfill soil for the fertilizer trench at the bottom of the backfill area; S3: Construct waterproofing and retaining structures in the central retaining area, and use the retaining structure to create a height-variable sealed area to fill the central retaining area; It also includes a lubrication part. In step S3, a lubrication part is provided between the retaining structure and the building exterior wall, and between the overlapping areas of the retaining structure and the side wall of the cantilevered part. The lubrication part is fixed on the building exterior wall and the side wall of the cantilevered part, and the lubrication part slides in contact with the retaining structure. S4: Construct waterproofing for the cantilevered side walls of the upper backfill area of ​​the fertilizer trench and construct the backfill soil for the fertilizer trench.

2. The backfilling method for the bottom of the cantilever section according to claim 1, characterized in that: The bottom backfill area refers to the area where backfill compaction equipment can operate below the cantilever section; the middle retaining area refers to the area between the cantilever section and the bottom backfill area where backfill compaction equipment cannot enter; and the upper backfill area refers to the area within the trench after removing the bottom backfill area and the middle retaining area.

3. The backfilling method for the bottom of the cantilever section according to claim 1, characterized in that: The retaining structure includes retaining plates and a base. The base consists of a foundation, a ground beam, and a retaining plate foundation. The retaining plate foundation is laid horizontally along the length of the cantilevered portion. The retaining plates are laid vertically, with the bottom of the retaining plates fixedly connected to the top of the retaining plate foundation, and the sides of the retaining plates fitting against the sidewalls of the cantilevered portion. Several ground beams are horizontally spaced below the cantilever section. One end of the ground beam is fixedly connected to the side wall of the retaining slab foundation, and the other end of the ground beam is attached to the exterior wall of the building below the cantilever section. The retaining slab foundation and ground beam are fixedly embedded in the foundation, and the side of the foundation is attached to the exterior wall of the building below the cantilever.

4. The backfilling method for the bottom of the cantilever section according to claim 1, characterized in that: Step S3 includes the following steps: S31: Waterproofing construction shall be carried out on the exterior walls of the building, the bottom of the cantilevered section, and the overlapping area of ​​the retaining plate and the cantilevered section within the central retaining area, and lubrication parts shall be installed in the corresponding areas of the exterior walls and the cantilevered section. S32: Construct the foundation at the bottom of the central retaining area, and select the foundation thickness according to requirements; S33: Excavate a trench in reverse on the foundation, place the fixed and connected ground beams and retaining plates in the trench, and pour concrete in the trench; S34: Reinforcing bars are tied, formwork is erected, concrete is poured, and curing is carried out on the retaining foundation to form a retaining slab. There is a certain length of overlap between the retaining slab and the cantilevered sidewall in the vertical direction.

5. The backfilling method for the bottom of the cantilever section according to claim 4, characterized in that: In step S32, the foundation is compacted in layers, with each layer not exceeding 20cm in thickness. The foundation is made of lime-soil or cement-soil.

6. The backfilling method for the bottom of the cantilever section according to claim 1, characterized in that: Step S2 includes the following steps: S21: Construct a waterproof structure with a height of a cm on the exterior wall of the building; S22: Perform backfilling of the area below b cm above the upper edge of the waterproof structure in step S21. The backfill soil shall be backfilled and compacted in layers, and the thickness of each layer of backfill soil shall not exceed 20 cm. S23: Determine whether the backfilling of the bottom backfill area has been completed. If not, repeat steps S21~S22 until the backfilling of the bottom backfill area is completed.

7. The backfilling method for the bottom of the cantilever section according to claim 1, characterized in that: Step S4 includes the following steps: S41: The upper backfill area on the side of the retaining structure shall be backfilled with soil in layers and compacted, and the thickness of each layer of backfill shall not exceed 20cm. S42: Construct a waterproof structure with a height of c cm on the side exterior wall of the cantilever section; S43: For the area below the upper edge of the waterproof structure in step S32, carry out backfilling of the trench. The backfill soil shall be backfilled and compacted in layers, and the thickness of each layer of backfill soil shall not exceed 20cm. S44: Determine whether the backfilling of the bottom backfill area has been completed. If not, repeat steps S42~S43 until the backfilling of the bottom backfill area is completed.

8. The backfilling method for the bottom of the cantilever section according to claim 1, characterized in that: It also includes a 3:7 lime-soil layer, which is located between the waterproof structure of the building exterior wall and the backfill soil in step S2, between the side of the retaining structure and the backfill soil in step S3, and between the waterproof structure of the side exterior wall of the cantilevered part and the backfill soil in step S4; the thickness of the 3 lime-soil layer ranges from 80cm to 100cm.

9. A backfilling structure for the bottom of a cantilever section, characterized in that: Including retaining walls and base; The base consists of a foundation, a ground beam, and a retaining slab foundation, with the retaining slab foundation laid horizontally along the length of the cantilevered portion. Several ground beams are horizontally spaced below the cantilever section. One end of the ground beam is fixedly connected to the inner wall of the retaining slab foundation, and the other end of the ground beam is attached to the exterior wall of the building below the cantilever section. The retaining slab foundation and the ground beam are fixedly embedded in the foundation. The side of the foundation near the building's exterior wall is flush with the other end of the ground beam, and the two are in close contact with the building's exterior wall below the cantilevered part. The retaining plates are installed vertically, with the bottom of the retaining plate fixedly connected to the top of the retaining plate foundation. The sides of the retaining plates are attached to the outer wall of the cantilever section and can be vertically slidable.

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