A reverse construction method for deep foundation pit basement

Abstract

The present application relates to the technical field of deep foundation pit construction, and provides a reverse construction method for a deep foundation pit basement, including: constructing supporting piles around a deep foundation pit to be excavated; excavating earthwork in the enclosed area of ​​the supporting piles to the design elevation of a reserved earth platform; continuing to excavate earthwork outside the area of ​​the reserved earth platform to the design elevation of the basement, and constructing pile foundations within the area of ​​the reserved earth platform; constructing structural columns of the basement on the pile foundation; excavating the earthwork between the structural columns of the reserved earth platform and the main structure of the basement, and constructing the main structure, and connecting the main structure to the structural columns. The reserved earth platform is adopted to realize the counter-pressure effect on the supporting piles, replacing the existing anchor cable support structure, without drilling holes on the walls around the foundation pit and threading anchor cables, effectively meeting the application of deep foundation pit excavation construction scenarios such as those near subways, developed groundwater systems, many surrounding buildings, complex surrounding underground pipe networks, or small construction land areas.

Description

Technical Field

[0001] The present application relates to the technical field of deep foundation pit construction, and in particular to a reverse construction method for a deep foundation pit basement. Background Art

[0002] Deep foundation pit refers to a project with an excavation depth of more than 5 meters (including 5 meters), or a project with a depth of less than 5 meters but with particularly complex geological conditions, surrounding environment and underground pipelines. When constructing a basement of a high-rise building, it is necessary to excavate a deep foundation pit; in traditional construction methods, the earthwork is usually excavated to the preset elevation of the basement floor before the basement structure is constructed; during the excavation of the foundation pit, in order to protect the safety of the underground main structure construction and the surrounding environment of the foundation pit, a foundation pit support structure will be set up. After the foundation pit support structure is set up, the basement structure will be constructed; the most commonly used foundation pit support structure is the anchor cable support structure; the anchor cable support structure uses metal parts, wood parts, polymer parts or other materials to make poles and columns, which are driven into pre-drilled holes in the surface rock mass or the rock mass around the chamber, and use the special structure of the head and rod body and the tail support plate (optional), or rely on bonding to combine the surrounding rock with the stable rock mass to achieve the purpose of support.

[0003] However, for deep foundation pit excavation construction scenarios such as those near subways, well-developed groundwater systems (near lakes, rivers, and seas), many surrounding buildings (for example, there are deep basements under buildings), complex surrounding underground pipelines, or small construction land areas, it is not suitable to drill holes on the walls around the foundation pit, and the anchor cable support structure is not applicable. In addition, when constructing the anchor cable support structure, the waist beam must be constructed first, and then holes are drilled and anchor cables are installed after the strength is reached. The overall construction period is relatively long.

[0004] Therefore, the existing deep foundation pit construction technology has defects and needs to be improved and developed. Summary of the invention

[0005] The technical problem to be solved by this application is that the anchor cable support method used in the existing deep foundation pit construction method is not suitable for deep foundation pit excavation construction scenarios such as those near subways, well-developed groundwater systems, complex surrounding underground pipelines, or small construction land areas. In view of the above-mentioned defects of the prior art, a reverse construction method for a deep foundation pit basement is provided.

[0006] The technical solution adopted by the present application to solve the technical problem is as follows: A reverse construction method for a deep foundation pit basement, comprising:

[0007] Carry out support pile construction around the deep foundation pit to be excavated;

[0008] Excavating earth in the enclosed area of ​​the supporting piles to the design elevation of the reserved earth platform;

[0009] Continue to excavate earth outside the area of ​​the reserved soil platform to the design elevation of the basement, and carry out pile foundation construction within the area of ​​the reserved soil platform;

[0010] Carrying out structural column construction of the basement on the pile foundation;

[0011] Excavating the earth between the structural columns and the main structure of the basement on the reserved soil platform, and constructing the main structure, while connecting the main structure to the structural columns;

[0012] Excavating the remaining reserved soil platform layer by layer downward to the design elevation of the basement, and installing support rods layer by layer downward between the main structure and the support piles;

[0013] The remaining structural construction of the basement is completed layer by layer, and the support rods are removed layer by layer.

[0014] Optionally, the construction of structural columns of the basement on the pile foundation specifically includes:

[0015] prefabricating a steel cage for the structural column;

[0016] Opening a mounting hole at the top of the pile foundation, and inserting the steel cage into the mounting hole;

[0017] Concrete is poured on the steel cage, and first connecting bars are reserved on the steel cage, where the first connecting bars are used to connect the main structure.

[0018] Optionally, the prefabricated steel cage of the structural column specifically includes:

[0019] Pre-binding the steel cage of the structural column and assembling the formwork outside the steel cage, wherein both ends of the steel cage protrude from the formwork;

[0020] The step of opening a mounting hole at the top of the pile foundation and inserting the steel cage into the mounting hole specifically includes:

[0021] According to the preset construction position of the structural column, measuring, locating and marking the location of the pile foundation;

[0022] A mounting hole is opened at the top of the pile foundation, and a positioning rib is vertically installed in the mounting hole according to the marked position;

[0023] Insert one end of the steel cage protruding from the template into the mounting hole, wherein the positioning ribs are inserted into the steel cage and abut against the corners of the steel cage.

[0024] Optionally, the step of inserting the end of the steel cage protruding from the template into the mounting hole further comprises:

[0025] According to the marked position, cross fixing bars are installed at the openings of the construction holes of the pile foundation, and the cross fixing bars are connected and fixed to the steel cage, wherein the cross positions of the cross fixing bars correspond to the corners of the steel cage;

[0026] Backfill earth between the template and the construction hole in sections.

[0027] Optionally, the constructing of the main structure and connecting the main structure to the structural columns specifically includes:

[0028] The main structure is constructed from the design elevation of the basement to the lowest floor slab, and a second connecting rib of the lowest floor slab is reserved;

[0029] connecting the second connecting rib to the first connecting rib;

[0030] The remaining structural construction of the main structure is completed layer by layer upwards.

[0031] Optionally, excavating the remaining reserved soil platform layer by layer downward to the design elevation of the basement, and installing support rods layer by layer downward between the main structure and the support piles, before that, it also includes:

[0032] Before excavating the remaining reserved soil platform, the support rods between the main structure and the support piles are pre-installed above the reserved soil platform.

[0033] Optionally, the step of pre-installing the support rods between the main structure and the support piles above the reserved soil platform specifically includes:

[0034] constructing a cap beam on the support piles, and then installing the support rods between the cap beam and the main structure; or,

[0035] Constructing a crown beam on the supporting piles, and constructing at least one first waist beam on the portion of the supporting piles exposed outside the reserved soil platform;

[0036] The support rods are installed between the crown beam and the main structure, and the support rods are installed one by one between the first waist beam and the main structure.

[0037] Optionally, excavating the remaining reserved soil platform layer by layer downward to the design elevation of the basement, and installing support rods layer by layer downward between the main structure and the support piles, specifically includes:

[0038] Excavating downwards the reserved soil platform between the structural column and the supporting pile;

[0039] If the excavation depth of the reserved soil platform reaches the floor slab of the main structure, support rods are installed between the floor slab and the support piles until the excavation depth reaches the lowest floor slab of the main structure;

[0040] Stop installing the support rods, and excavate the reserved soil platform to the design elevation of the basement.

[0041] Optionally, piers are provided on the floor slab of the main structure, and the support rods are connected to the main structure via the piers.

[0042] Optionally, completing the remaining structural construction of the basement layer by layer and removing the support rods layer by layer at the same time specifically includes:

[0043] Carrying out the remaining structure construction of the basement upwards, and when the construction height of the remaining structure reaches the support rod at the lowest end, removing the support rod at the lowest end;

[0044] The remaining structure construction is continued, and each time the remaining structure construction height reaches the support rod, the support rod is removed until the remaining structure construction is completed.

[0045] The present application provides a structural reverse construction method for a deep foundation pit with a reserved earth platform. The reserved earth platform is used to achieve the counter-pressure effect on the supporting piles, replacing the existing anchor cable supporting structure. There is no need to drill holes in the walls around the foundation pit and insert anchor cables. It can effectively meet the application of deep foundation pit excavation construction scenarios such as those near subways, developed groundwater systems, many surrounding buildings, complex surrounding underground pipelines, or small construction land areas. When constructing the anchor cable supporting structure, the waist beam must be constructed first, and then holes are drilled after the strength is reached, which will extend the overall construction period. The present application can continuously carry out earth excavation after the supporting piles are constructed, which can effectively shorten the construction period. It is suitable for projects with tight construction periods and need to be rushed. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a process flow chart of the reverse construction method provided in this application;

[0047] Figure 2 It is a top view schematic diagram of a deep foundation pit in the top-down construction method provided in this application;

[0048] Figure 3 It is a cross-sectional schematic diagram of a deep foundation pit in the top-down construction method provided in this application;

[0049] Figure 4It is a partial schematic diagram of the basement structure changes in steps S510 and S600 in the reverse construction method provided in this application;

[0050] Figure 5 It is a partial schematic diagram of the basement structure change in step S700 of the reverse construction method provided in this application;

[0051] Figure 6 It is a top view schematic diagram of the connection structure between the pile foundation and the steel cage in the top-down construction method provided in the present application;

[0052] Figure 7 It is a cross-sectional schematic diagram of the connection structure between the pile foundation and the steel cage in the top-down construction method provided in the present application;

[0053] Figure 8 It is a structural schematic diagram of the support rod installation in the reverse construction method provided in this application;

[0054] Description of reference numerals:

[0055] 10. Deep foundation pit; 11. Support piles; 12. Reserved soil platform; 13. Basement; 14. Support rods; 15. Crown beam; 16. First waist beam; 17. Second waist beam; 18. Pier; 19. Z-shaped connector; 121. Upper soil platform; 122. Lower soil platform; 131. Pile foundation; 132. Structural column; 133. Main structure; 134. Remaining structure; 135. Positioning ribs; 136. Cross fixing ribs; 137. Support plate; 1311. Installation hole; 1312. Construction hole; 1321. Steel cage; 1322. Formwork; 1331. The bottom floor slab. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solution and advantages of the present application clearer and more specific, the present application is further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific examples described here are only used to explain the present application and are not used to limit the present application.

[0057] Deep foundation pit refers to a project with an excavation depth of more than 5 meters (including 5 meters), or a project with a depth of less than 5 meters but with particularly complex geological conditions, surrounding environment and underground pipelines. When constructing a basement of a high-rise building, it is necessary to excavate a deep foundation pit; in traditional construction methods, the earthwork is usually excavated to the preset elevation of the basement floor before the basement structure is constructed; during the excavation of the foundation pit, in order to protect the safety of the underground main structure construction and the surrounding environment of the foundation pit, a foundation pit support structure will be set up. After the foundation pit support structure is set up, the basement structure will be constructed; the most commonly used foundation pit support structure is the anchor cable support structure; the anchor cable support structure uses metal parts, wood parts, polymer parts or other materials to make poles and columns, which are driven into pre-drilled holes in the surface rock mass or the rock mass around the chamber, and use the special structure of the head and rod body and the tail support plate (optional), or rely on bonding to combine the surrounding rock with the stable rock mass to achieve the purpose of support. However, for deep foundation pit excavation construction scenarios such as those near subways, well-developed groundwater systems (near lakes, rivers, and seas), many surrounding buildings (for example, there are deep basements under buildings), complex surrounding underground pipelines, or small construction land areas, it is not suitable to drill holes on the walls around the foundation pit, and the anchor cable support structure is not applicable. In addition, when constructing the anchor cable support structure, the waist beam must be constructed first, and then holes are drilled and anchor cables are installed after the strength is reached. The overall construction period is relatively long.

[0058] The present application is based on the anchor cable support method adopted in the existing deep foundation pit construction method, which is not suitable for deep foundation pit excavation construction scenarios such as those near subways, developed groundwater systems, complex surrounding underground pipelines or small construction land areas. It provides a reverse construction method for deep foundation pit basements, which adopts the method of reserving earth platforms to achieve the counter-pressure effect on the support piles, replacing the existing anchor cable support structure, and does not require drilling holes on the walls around the foundation pit and threading anchor cables, which can effectively meet the application of deep foundation pit excavation construction scenarios such as those near subways, developed groundwater systems, many surrounding buildings, complex surrounding underground pipelines or small construction land areas; when constructing the anchor cable support structure, the waist beam must be constructed first, and drilling is performed after the strength is reached, which will extend the overall construction period. The present application can continuously carry out earth excavation after the support piles are constructed, which can effectively shorten the construction period and is suitable for projects with tight construction periods and need to be rushed; please refer to the following embodiments for details.

[0059] Please refer to Figures 1 to 5 In the first embodiment of the present application, a reverse construction method of a deep foundation pit 10 and a basement 13 is provided, comprising:

[0060] S100, constructing support piles 11 around the deep foundation pit 10 to be excavated;

[0061] like Figure 2As shown, before the deep foundation pit 10 is excavated, it is usually surveyed and laid out first. After the predetermined excavation area of ​​the deep foundation pit 10 is determined, the support piles 11 are constructed around the entire deep foundation pit 10. After the construction, the earthwork is excavated in the enclosed area of ​​the rows of support piles 11; the support piles 11 can play a role in retaining soil, improve the stability of the foundation pit slope, avoid deformation and collapse of the soil on the foundation pit slope during the excavation process, and ensure the safety of adjacent buildings (structures), roads, and underground pipelines to avoid being affected by the foundation pit excavation; the support piles 11 can be in the form of concrete cast-in-place piles, and the arrangement methods include interval type, double row type and continuous type, which are specifically determined according to the construction conditions and design requirements;

[0062] S200, excavating earth in the enclosed area of ​​the supporting piles 11 to the design elevation of the reserved earth platform 12;

[0063] like Figure 2 and Figure 3 As shown, when excavating downward, the soil around the foundation pit will form pressure on the supporting piles 11, which will cause the supporting piles 11 to break and the foundation pit to collapse; the reserved soil platform 12 can play a counter-pressure role on the supporting piles 11, and the design elevation of the reserved soil platform 12 refers to the elevation determined by the construction drawings to ensure that the reserved soil platform 12 can play an effective counter-pressure role on the supporting piles 11; the reserved soil platform 12 replaces the anchor cable structure to achieve the reinforcement of the foundation pit slope, and there is no need to drill holes on the wall around the foundation pit to set anchor cables. It is suitable for areas near subways, developed groundwater systems, and surrounding buildings. The deep foundation pit excavation construction scene is suitable for deep foundation pit excavation with many surrounding underground pipe networks or small construction land area; during construction, the earth is excavated from the ground elevation downward to the design elevation of the reserved soil platform 12. During the excavation process, the crown beam 15 will be constructed on the support pile 11, and safety guardrails and drainage ditches will also be set up; according to actual design needs, during the excavation process, the waist beam will be constructed on the part of the support pile 11 exposed outside the reserved soil platform 12, and the waist beam plays a role in reinforcing the support pile 11, so as to enhance the protection effect of the support pile 11 on the foundation pit slope;

[0064] S300, continue to excavate earth outside the area of ​​the reserved earth platform 12 to the design elevation of the basement 13, and construct the pile foundation 131 within the area of ​​the reserved earth platform 12;

[0065] like Figure 3As shown, continue to excavate the earth downwards. According to the design requirements, leave the reserved earth platform 12 without excavation first, so as to play a counter-pressure role on the supporting piles 11, and keep excavating the earth downwards to the designed elevation of the basement 13; the pile foundation 131 is the supporting foundation of the structural column 132 in the basement 13; the construction of the pile foundation 131 is carried out in advance within the area of ​​the reserved earth platform 12, and the earth excavation is carried out outside the area of ​​the reserved earth platform 12, so that the construction process of the pile foundation 131 does not conflict with the earth excavation process, and can be carried out simultaneously; considering that in a large-area basement building, the number of structural columns 132 of the basement 13 is relatively large, and the number of pile foundations 131 corresponding to the structural columns 132 is also relatively large, during the earth excavation process, the construction of the pile foundation 131 is carried out simultaneously, which is conducive to shortening the construction period; the construction of the pile foundation 131 can be carried out in the form of punched cast-in-place piles;

[0066] S400, constructing the structural columns 132 of the basement 13 on the pile foundation 131;

[0067] like Figure 3 As shown, in this step, the construction of the structural columns 132 of the basement 13 can also be carried out synchronously with the earth excavation process. After the pile foundation 131 is solidified, the construction of the structural columns 132 can be carried out on the pile foundation 131, and there is no need to wait for the earth to be completely excavated before carrying out the construction, which is conducive to shortening the construction period; the construction of the pile foundations 131 in rows and the construction of the structural columns 132 in rows are not carried out in order, but can be carried out synchronously. For example, when the number of pile foundations 131 is large, the pile foundations 131 that have been completed first have been solidified and meet the strength conditions. At this time, the structural columns 132 can be constructed on the solidified pile foundations 131, and the construction of other pile foundations 131 can also be continued, which is conducive to shortening the construction period; the structural columns 132 are constructed in the reserved soil platform 12, and the rows of structural columns 132 can enhance the structural stability of the reserved soil platform 12, which is conducive to enhancing the back pressure effect of the reserved soil platform 12 on the supporting piles 11;

[0068] S500, excavating the earth between the structural column 132 and the main structure 133 of the basement 13 of the reserved soil platform 12, and constructing the main structure 133, and connecting the main structure 133 to the structural column 132;

[0069] like Figure 3 and Figure 4As shown, after excavating earth outside the area of ​​the reserved earth platform 12 to the design elevation of the basement 13, the main structure 133 of the basement 13 can be constructed; during the construction of the main structure 133 of the basement 13, the steel bars of the floor slab in the main structure 133 are overlapped with the structural columns 132 and cast together; the structural columns 132 are located at the edge of the main structure 133, and as a whole with the main structure 133, they play a major supporting role for the floor slabs of each layer in the main structure 133; before the construction of the main structure 133, it is necessary to clean the earth between the structural columns 132 and the main structure 133, that is, to excavate part of the reserved earth platform 12, so as to facilitate the construction of the bottom slab in the main structure 133; the construction of the main structure 133 is from the bottom slab to the first floor slab;

[0070] S600, excavating the remaining reserved soil platform 12 layer by layer downward to the design elevation of the basement 13, and installing support rods 14 between the main structure 133 and the support piles 11 layer by layer downward;

[0071] like Figure 4 As shown, after the construction of the main structure 133 of the basement 13 is completed, the main structure 133 has a remaining reserved soil platform 12 near the supporting pile 11; the remaining reserved soil platform 12 is excavated from top to bottom, and during the excavation process, support rods 14 are installed between the main structure 133 and the supporting piles 11, so that the support rods 14 and the reserved soil platform 12 are exchanged to achieve the reinforcement of the supporting piles 11 and avoid deformation and collapse of the foundation pit slope; a long-arm excavator can be used to excavate or a conveyor belt can be selected to excavate the earth of the reserved soil platform 12; during the downward excavation of the soil, each time the excavation reaches the predetermined installation position of the support rod 14, a support rod 14 is installed, and the operation is repeated until the installation of all support rods 14 is completed and the remaining reserved soil platform 12 is completely excavated; the support rod 14 can adopt a steel pipe support structure; the support rod 14 is installed in a horizontal or nearly horizontal direction;

[0072] S700, completing the construction of the remaining structure 134 of the basement 13 layer by layer, and removing the support rods 14 layer by layer. Figure 5 As shown, after the reserved soil platform 12 between the main structure 133 and the supporting piles 11 is excavated, it is still necessary to complete the construction of the structure between the main structure 133 and the supporting piles 11, that is, the remaining structure 134 of the basement 13; the remaining structure 134 of the basement 13 is constructed from bottom to top, and each time the construction position is close to the predetermined installation position of the support rod 14, the support rod 14 is first removed, and then the construction upward is continued until all the support rods 14 are removed, and at the same time, the floor slab of the first floor of the basement 13 is also constructed, that is, the construction of the overall structure of the basement 13 is completed.

[0073] It can be understood that in the reverse construction method of the deep foundation pit 10 and the basement 13 provided in the present application, a reserved earth platform 12 is adopted to realize the counter-pressure effect on the support piles 11, replacing the existing anchor cable support structure. There is no need to drill holes in the walls around the foundation pit and pass anchor cables. It can effectively meet the application of deep foundation pit excavation construction scenarios such as those near subways, developed groundwater systems, many surrounding buildings, complex surrounding underground pipelines, or small construction land areas. When constructing the anchor cable support structure, the waist beam must be constructed first, and then holes must be drilled after the strength is reached, which will extend the overall construction period. The present application can carry out uninterrupted earth excavation after the construction of the support piles 11, which can effectively shorten the construction period. It is suitable for projects with tight construction periods and need to be rushed, and avoids the expenses of drilling holes and setting anchor cables, which is beneficial to reducing construction costs.

[0074] Please continue reading Figure 3 In some embodiments, the reserved soil platform 12 includes an upper soil platform 121 and a lower soil platform 122 , the upper soil platform 121 is located on the top of the lower soil platform 122 , and the pile foundation 131 is constructed on the top of the lower soil platform 122 .

[0075] It can be understood that the reserved earth platform 12 is stepped, divided into an upper earth platform 121 and a lower earth platform 122. The upper earth platform 121 is located on the top of the lower earth platform 122. The lower earth platform 122 is closer to the design elevation of the basement 13 than the upper earth platform 121. The construction workers directly construct the pile foundation 131 on the lower earth platform 122, which effectively reduces the drilling depth during the construction process and reduces the construction difficulty.

[0076] Please continue reading Figure 3 In some implementations, before step S400, the step further includes:

[0077] The upper soil platform 121 and the lower soil platform 122 are sloped away from the supporting piles 11, and reinforced with steel mesh sprayed concrete.

[0078] It can be understood that the upper earth platform 121 and the lower earth platform 122 are both provided with a slope on one side close to the main structure 133, which can effectively prevent the collapse of the soil on the upper earth platform 121 and the lower earth platform 122, thereby ensuring the counter-pressure effect of the reserved earth platform 12 on the supporting piles 11; by setting a steel mesh sprayed concrete reinforcement on the slope to enhance the structural stability of the reserved earth platform 12, and avoid the reserved earth platform 12 from being affected by precipitation and soil loss, thereby effectively ensuring the counter-pressure effect of the reserved earth platform 12 on the supporting piles 11.

[0079] Please continue reading Figure 3 In some implementations, step S400 specifically includes:

[0080] S40, prefabricate the steel cage 1321 of the structural column 132; pre-tie the steel cage 1321 of the structural column 132 to avoid affecting the construction period;

[0081] S41, opening a mounting hole at the top of the pile foundation 131, and inserting the steel cage 1321 into the mounting hole; after the pile foundation 131 is constructed and the pile foundation 131 is solidified to meet the strength requirements, a mounting hole is drilled on the top surface of the pile foundation 131 to facilitate the installation of the steel cage 1321 of the structural column 132; the depth of the mounting hole is determined according to specific design requirements to meet the reliability of the connection between the structural column 132 and the pile foundation 131;

[0082] S42, pouring concrete on the steel cage 1321, and reserving a first connecting bar on the steel cage 1321, the first connecting bar is used to connect to the main structure 133. When pouring concrete on the steel cage 1321, usually a formwork is set up first, and then concrete is poured; when pouring concrete on the steel cage 1321, concrete is only poured to the bottom floor 1331 of the main structure 133, and a first connecting bar is reserved on the steel cage 1321 to facilitate connection with the main structure 133; the bottom layer of the main structure 133 has a bottom plate and a floor plate, and the bottom floor 1331 is on the bottom plate.

[0083] It can be understood that the structural column 132 is located at the edge of the main structure 133, and as a whole with the main structure 133, it plays a major supporting role for the floors of each floor in the main structure 133; when pouring concrete on the steel cage 1321, the first connecting reinforcement is reserved to reserve a lap position for the subsequent construction of the main structure 133, so that the main structure 133 and the structural column 132 can be constructed together to make full use of the construction period; the structural column 132 has a reinforcement effect on the reserved soil platform 12 to ensure that during the construction of the main structure 133, the reserved soil platform 12 plays an effective counter-pressure role on the support piles 11; at the same time, the structural column 132 is used as It is a part of the main structure 133 and is not an additional structure. Before constructing the main structure 133 of the basement 13, the construction of the structural column 132 is completed first to avoid waste. An installation hole is drilled on the top of the pile foundation 131, and one end of the steel cage 1321 is inserted into the installation hole. The steel cage 1321 is poured with concrete to form the structural column 132. The part of the structural column 132 located in the installation hole is fixedly linked to the pile foundation 131, which can enhance the reliability of the connection between the structural column 132 and the pile foundation 131, and ensure the supporting effect of the structural column 132 on the main structure 133 and the reinforcement effect on the reserved soil platform 12.

[0084] Please refer to Figure 6 and Figure 7 In some implementations, step S40 specifically includes:

[0085] S401, pre-binding the steel cage 1321 of the structural column 132, and assembling the template 1322 outside the steel cage 1321, wherein both ends of the steel cage 1321 are protruding from the template 1322.

[0086] It can be understood that before pouring concrete on the steel cage 1321, it is necessary to assemble the template 1322 outside the steel cage 1321; after placing the steel cage 1321 into the construction hole 1312 where the pile foundation 131 is located, the template 1322 is assembled, which increases the difficulty of assembly; pre-tying the steel cage 1321 and assembling the template 1322 outside the steel cage 1321 is conducive to reducing the difficulty of construction and improving construction efficiency, that is, shortening the construction period; both ends of the steel cage 1321 protrude from the template 1322 to facilitate connection with the pile foundation 131 and the main structure 133 during subsequent construction.

[0087] Please continue to refer to Figure 6 and Figure 7 In some implementations, step S41 specifically includes:

[0088] S411, measuring and positioning the location of the pile foundation 131 according to the preset construction position of the structural column 132 and marking it;

[0089] Before installing the steel cage 1321 of the structural column 132, the preset construction position of the structural column 132 can be determined according to the construction design drawings of the structural column 132. It is also necessary to measure and locate at the actual construction site and make marks (for example, punctuation and marking) to facilitate the construction of the structural column 132 according to the marked position; total station and steel ruler and other tools can be used for measurement and positioning; there are four points corresponding to the four corners of the structural column 132, and a "well" line or a "cross" line can be drawn at the opening of the construction hole 1312 of the pile foundation 131 (that is, on the surface of the reserved soil platform 12), and the marks are made; a casing is installed in the construction hole 1312 of the pile foundation 131, and the end face and wall of the casing can be marked; when the steel cage 1321 is installed later, it can be adjusted according to the marked position to ensure that the steel cage 1321 is installed in place;

[0090] S412, opening a mounting hole 1311 at the top of the pile foundation 131, and vertically installing a positioning rib 135 in the mounting hole 1311 according to the marked position; the positioning rib 135 plays a role in positioning the steel cage 1321, and specifically, 2, 3, or 4 positioning ribs 135 can be installed, corresponding to each corner of the steel cage 1321 respectively; after measuring and positioning the opening of the construction hole 1312 of the pile foundation 131 and marking it, a "well"-shaped or "cross"-shaped bracket can be installed corresponding to the marked position, and a wire cone can be connected at the intersection of the bracket. The position of each corner of the steel cage 1321 is determined in the mounting hole 1311 by the wire cone, and then the positioning rib 135 can be installed at the corresponding position of each corner;

[0091] S413, inserting one end of the steel cage 1321 protruding from the template 1322 into the installation hole 1311, wherein the positioning ribs 135 are inserted into the steel cage 1321 and abut against the corners of the steel cage 1321. The positioning ribs 135 correspond to the four corners of the steel cage 1321. The steel cage 1321 is inserted into the installation hole 1311, and the positioning ribs 135 are inserted into the four corners of the steel cage 1321 to form a connection, which can ensure that the steel cage 1321 is installed in place and can effectively ensure the verticality of the steel cage 1321; after the steel cage 1321 is inserted into the installation hole 1311, the template 1322 is connected to the top surface of the pile foundation 131 or is slightly higher than the top surface of the pile foundation 131.

[0092] It can be understood that through the above steps, it can be ensured that the steel cage 1321 of the structural column 132 is accurately installed on the pile foundation 131, and the verticality of the steel cage 1321 can be ensured, thereby improving the construction quality of the structural column 132.

[0093] Please continue reading Figure 7 In some implementations, the step S413 further includes:

[0094] S414, according to the marked position, cross fixing ribs 136 are installed at the openings of the construction holes 1312 of the pile foundation 131, and the cross fixing ribs 136 are connected and fixed to the steel cage 1321, and the cross positions of the cross fixing ribs 136 correspond to the corners of the steel cage 1321; specifically, the cross fixing ribs 136 can be set in a "well" shape or a "cross" shape, and the cross fixing ribs 136 are installed according to the measured and marked positions, so that the cross positions of the cross fixing ribs 136 correspond to the corners of the steel bars; the cross fixing ribs 136 are connected and fixed to the steel cage 1321, and the cross positions of the cross fixing ribs 136 are connected to the corners of the steel cage 1321, which can effectively ensure that the installation position of the steel cage 1321 is not skewed, ensure the verticality of the structural column 132, and provide support for the steel cage 1321, thereby avoiding deformation and position deviation during concrete pouring;

[0095] S415, backfill earth between the template 1322 and the construction hole 1312 in sections. After fixing the steel cage 1321, backfill earth between the template 1322 and the inner wall of the construction hole 1312. The earth can provide support for the template 1322 to avoid deformation of the template 1322 during the subsequent concrete pouring process. When backfilling earth, a segmented backfilling method is adopted, that is, the entire depth of the construction hole 1312 is divided into multiple sections for backfilling, so as to avoid excessive earth on one side of the template 1322 during the backfilling process, forming a unidirectional pressure on the side of the template 1322, causing the template 1322 to tilt, affecting Affects the pouring quality; adopts the segmented backfilling method with limited depth of a single section, which can effectively avoid excessive pressure when there is too much earth on one side, ensure uniform backfilling of the earth, and avoid unidirectional pressure on the side of the template 1322; when backfilling in sections, specifically adopts a symmetrical segmented backfilling method, that is, backfilling the earth on both sides in the symmetrical direction of the outer periphery of the entire template 1322, or backfilling one side first and then the other side, and the height difference of the backfilled earth on both sides is required to be no more than 30cm, so as to effectively avoid excessive pressure when there is too much earth on one side.

[0096] Please continue to refer to Figure 6 and Figure 7 In some implementations, the step S414 further includes:

[0097] A support plate 137 is installed between the template 1322 and the construction hole 1312 .

[0098] It can be understood that a support plate 137 is installed between the template 1322 and the construction hole 1312. The two ends of the support plate 137 support the template 1322 and the inner wall of the construction hole 1312, which has a supporting effect on the template 1322, can avoid deformation of the template 1322 during the subsequent concrete pouring process, and ensure the construction quality of the structural column 132.

[0099] Please continue to refer to Figure 3 and Figure 4 In some embodiments, the construction of the main structure 133 and connecting the main structure 133 to the structural column 132 specifically include:

[0100] S50, constructing the main structure 133 from the design elevation of the basement 13 upward to the lowest floor slab 1331, and reserving the second connecting ribs of the lowest floor slab 1331; the second connecting ribs are used to overlap the first connecting ribs reserved on the structural column 132;

[0101] S51, connecting the second connecting rib to the first connecting rib;

[0102] S52, completing the construction of the remaining structure 134 of the main structure 133 layer by layer. After completing the construction of the bottom layer of the main structure 133, continue to construct layer by layer upward until the construction of the first layer structure is completed.

[0103] It can be understood that during the upward construction of the main structure 133, a second connecting rib is reserved for the lowest floor slab to facilitate connection with the first connecting rib on the structural column 132, thereby ensuring that the main structure 133 and the structural column 132 are connected as a whole, thereby ensuring the supporting effect of the structural column 132 on the floor slab on the main structure 133.

[0104] Please continue reading Figure 4 In some implementations, before step S600, the step further includes:

[0105] S510, before excavating the remaining reserved soil platform 12, pre-install the support rods 14 between the main structure 133 and the support piles 11 above the reserved soil platform 12.

[0106] It can be understood that after the construction of the main structure 133 is completed, completing the installation of the support rods 14 above the reserved earth platform 12 in advance will help shorten the construction period and reduce the time for the subsequent installation of the support rods 14. At the same time, it can also avoid the generation of counter pressure on the support piles 11 around the foundation pit when the reserved earth platform 12 is excavated, causing the support piles 11 to break and the foundation pit to collapse.

[0107] Please continue reading Figure 4 In some embodiments, the support rod 14 is installed between the main structure 133 and the support pile 11 above the reserved soil platform 12 in advance, specifically including:

[0108] The crown beam 15 is constructed on the support pile 11, and then the support rod 14 is installed between the crown beam 15 and the main structure 133; specifically, the crown beam 15 is arranged on the top surface of the support pile 11, and the crown beam 15 has a reinforcement effect on the support pile 11, and can also effectively ensure the support effect of the support rod 14 on the support pile 11;

[0109] Or, a crown beam 15 is constructed on the support pile 11, and at least one first waist beam 16 is constructed on the portion of the support pile 11 exposed outside the reserved soil platform 12; specifically, the waist beam is arranged on the support pile 11, and the waist beam outside the area of ​​the reserved soil platform 12 is used as the first waist beam 16, and the waist beam within the area of ​​the reserved soil platform 12 is used as the second waist beam 17, and both the first waist beam 16 and the second waist beam 17 can be used to connect the support rod 14; according to actual design requirements, the design elevation of the reserved soil platform 12 is not consistent, and there may be a construction space without the first waist beam 16, and there may be a situation where one or more first waist beams 16 can be constructed, which can be adjusted according to the actual construction design;

[0110] The support rods 14 are installed between the crown beam 15 and the main structure 133, and the support rods 14 are installed one by one between the first waist beams 16 and the main structure 133. Specifically, the crown beam 15 is arranged on the top surface of the support pile 11, and the first waist beam 16 is arranged on the periphery of the support pile 11 outside the area of ​​the reserved soil platform 12. The crown beam 15 and the first waist beam 16 have a reinforcement effect on the support pile 11, and can also effectively ensure the support effect of the support rod 14 on the support pile 11.

[0111] It can be understood that the construction of the crown beam 15 can be carried out after the construction of the supporting piles 11 is completed, and the construction of the first waist beam 16 is determined according to the actual construction design. By setting the crown beam 15 and the first waist beam 16, the supporting piles 11 are reinforced and the supporting effect of the support rods 14 on the supporting piles 11 is effectively guaranteed.

[0112] Please continue reading Figure 4 In some embodiments, when the remaining reserved soil platform 12 is excavated downward layer by layer to the design elevation of the basement 13, the second waist beam 17 is constructed, and the support rod 14 is installed between the second waist beam 17 and the main structure 133.

[0113] It can be understood that the second waist beam 17 has a reinforcement effect on the supporting piles 11 and can also effectively ensure the supporting effect of the supporting rods 14 on the supporting piles 11 .

[0114] Please continue to refer to Figure 3 and Figure 4 In some implementations, step S600 specifically includes:

[0115] S60, digging downwards the reserved soil platform 12 between the structural column 132 and the supporting pile 11;

[0116] S61. If the excavation depth of the reserved soil platform 12 reaches the floor of the main structure 133, a support rod 14 is installed between the floor and the support pile 11 until the excavation depth reaches the lowest floor of the main structure 133; specifically, when the excavation depth reaches the lowest floor of the main structure 133, the support rod 14 is no longer installed; for example, when the basement 13 is designed as a negative four-story structure, the main structure 133 has a first floor, a negative first floor, a negative second floor, a negative third floor and a bottom plate, wherein the negative third floor is the lowest floor 1331, and the support rod 14 is only installed to the negative second floor;

[0117] S62, stop installing the support rods 14, and excavate the reserved soil platform 12 to the design elevation of the basement 13.

[0118] It can be understood that when excavating the reserved earth platform 12 downward, each time the predetermined installation position of the support rod 14 is exposed, the installation of the support rod 14 between the main structure 133 and the supporting pile 11 at that position is completed first; wherein, the support rod 14 is installed between the floor slab of the main structure 133 and the supporting pile 11. At the lowest floor slab of the main structure 133, you can choose not to install the support rod 14. The supporting function of the supporting pile 11 can be met by several support rods 14 on the upper floors. At the same time, because the construction of the basement 13 structure between the main structure 133 and the supporting pile 11 is about to be carried out later, the support rods 14 on the corresponding floors need to be removed. Of course, you can also choose to install the support rod 14 on the lowest floor slab 1331 to enhance the supporting function. The specific details can be adjusted according to the actual construction design.

[0119] Please continue reading Figure 4 In some embodiments, a pier 18 is provided on the floor of the main structure 133 , and the support rod 14 is connected to the main structure 133 through the pier 18 .

[0120] It can be understood that the pier 18 is arranged on the floor of the main structure 133, corresponding to the support rod 14, so that the support rod 14 is connected to the main structure 133 through the pier 18; the pier 18 plays a supporting role for the support rod 14, enhances the connection reliability between the support rod 14 and the main structure 133, and can effectively ensure the supporting role of the support rod 14 on the support pile 11; the cross-section of the pier 18 is trapezoidal, and the side of the pier 18 away from the support rod 14 is set as an inclined surface, and the pier 18 is specifically a concrete structure with stirrups arranged therein; specifically, the two ends of the support rod 14 are respectively connected to the pier 18 and the first waist beam 16 or the pier 18 and the second waist beam 17.

[0121] Please refer to Figure 4 and Figure 8 In some embodiments, both ends of the support rod 14 are respectively connected to the pier 18 and the first waist beam 16 or the second waist beam 17 through a Z-shaped connector 19, one end of the Z-shaped connector 19 abuts against the top surface of the pier 18, the first waist beam 16 or the second waist beam 17, and the other end of the Z-shaped connector 19 abuts against the bottom end of the support rod 14.

[0122] It can be understood that by setting up the Z-shaped connector 19, the difficulty of installing the support rod 14 between the supporting pile 11 and the main structure 133 can be effectively reduced. During installation, the Z-shaped connector 19 can be placed on the pier 18, the first waist beam 16 or the second waist beam 17 according to the predetermined installation position, and then the support rod 14 can be moved between the two Z-shaped connectors 19. The supporting effect of the Z-shaped connector 19 on the bottom end of the support rod 14 makes it convenient for the operator to adjust the prestress between the support rod 14 and the supporting pile 11 and the main structure 133, thereby ensuring that the support rod 14 can effectively support the supporting pile 11; the Z-shaped connector 19 can be fixedly connected to the top surface of the pier 18, the first waist beam 16 or the second waist beam 17 through a bolt connector.

[0123] Please continue reading Figure 5 In some implementations, step S700 specifically includes:

[0124] S70, construct the remaining structure 134 of the basement 13 upwards, and when the construction height of the remaining structure 134 reaches the support rod 14 at the lowest end, remove the support rod 14 at the lowest end; Figure 5 In the figure, "×" is used to indicate the support rod 14 to be removed;

[0125] S71, continue to construct the remaining structure 134, and each time the construction height of the remaining structure 134 reaches the support rod 14, remove the support rod 14 until the construction of the remaining structure 134 is completed. Specifically, there is a certain gap between the outer wall of the remaining structure 134 and the support pile 11. During the construction process, a concrete force transmission belt is set between the outer wall and the support pile 11, and cement stone powder slag is backfilled between the concrete force transmission belt to ensure that the remaining structure 134 forms a stable support for the support pile 11, thereby avoiding deformation and collapse of the foundation pit slope.

[0126] It can be understood that during the upward construction of the remaining structure 134 of the basement 13, the construction is carried out layer by layer, and the remaining structure 134 of the basement 13 replaces the support rods 14 to form a supporting effect on the supporting piles 11; during the upward construction process, the support rods 14 are removed one by one, and it is not chosen to remove all the support rods 14 at once, so as to ensure the supporting effect of the support rods 14 on the supporting piles 11 and avoid deformation and collapse of the foundation pit slope.

[0127] In summary, the present application provides a reverse construction method for a deep foundation pit basement, including: constructing supporting piles around a predetermined deep foundation pit; excavating earth in the enclosed area of ​​the supporting piles to the design elevation of a reserved earth platform; continuing to excavate earth outside the area of ​​the reserved earth platform to the design elevation of the basement, and constructing pile foundations within the area of ​​the reserved earth platform; constructing structural columns of the basement on the pile foundation; excavating the earth between the structural columns of the reserved earth platform and the main structure of the basement, and constructing the main structure, while connecting the main structure to the structural columns; excavating the remaining reserved earth platform layer by layer downwards to the design elevation of the basement, while installing support rods between the main structure and the supporting piles layer by layer downwards; completing the remaining structural construction of the basement layer by layer upwards, while removing the support rods layer by layer upwards. By adopting the method of reserving earth platforms, the counter-pressure effect on the supporting piles is realized, replacing the existing anchor cable supporting structure. There is no need to drill holes in the walls around the foundation pit and insert anchor cables. It can effectively meet the application of deep foundation pit excavation construction scenarios such as those near subways, developed groundwater systems, many surrounding buildings, complex surrounding underground pipelines, or small construction land areas. When constructing the anchor cable supporting structure, the waist beam must be constructed first, and then holes are drilled after the strength is reached, which will extend the overall construction period. This application can carry out earth excavation uninterruptedly after the supporting piles are constructed, which can effectively shorten the construction period. It is suitable for projects with tight construction periods and need to be rushed.

[0128] It should be understood that the application of the present application is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to this application.

Claims

1. A reverse construction method for a deep foundation pit basement, characterized in that: include: Carry out support pile construction around the deep foundation pit to be excavated; Excavating earth in the enclosed area of ​​the supporting piles to the designed elevation of the reserved soil platform, so as to realize the counter pressure of the reserved soil platform on the supporting piles, replacing the existing anchor cable supporting structure; Continue to excavate earth outside the area of ​​the reserved soil platform to the design elevation of the basement, and carry out pile foundation construction within the area of ​​the reserved soil platform; Carrying out structural column construction of the basement on the pile foundation; Excavating the earth between the structural columns and the main structure of the basement on the reserved soil platform, and constructing the main structure, while connecting the main structure to the structural columns; Excavating the remaining reserved soil platform layer by layer downward to the design elevation of the basement, and installing support rods layer by layer downward between the main structure and the support piles; The remaining structural construction of the basement is completed layer by layer, and the support rods are removed layer by layer; The reserved soil platform is stepped, and is divided into an upper soil platform and a lower soil platform, wherein the upper soil platform is located on the top of the lower soil platform, so that the lower soil platform is closer to the design elevation of the basement than the upper soil platform, so as to construct the pile foundation on the lower soil platform; The upper soil platform and the lower soil platform are both sloped away from the support piles, and reinforced with steel mesh sprayed concrete; The construction of the structural columns of the basement is carried out on the pile foundation, specifically including: prefabricating a steel cage for the structural column; Opening a mounting hole at the top of the pile foundation, and inserting the steel cage into the mounting hole; pouring concrete on the steel cage, and reserving first connecting bars on the steel cage, wherein the first connecting bars are used to connect the main structure; Excavating the remaining reserved soil platform layer by layer downward to the design elevation of the basement, and installing support rods layer by layer between the main structure and the support piles, before that, it also includes: Before excavating the remaining reserved soil platform, pre-install the support rods between the main structure and the support piles above the reserved soil platform; Installing the support rod between the main structure and the support piles in advance above the reserved soil platform specifically includes: constructing a cap beam on the support piles, and then installing the support rods between the cap beam and the main structure; or, Constructing a crown beam on the supporting piles, and constructing at least one first waist beam on the portion of the supporting piles exposed outside the reserved soil platform; Install the support rods between the crown beam and the main structure, and install the support rods one by one between the first waist beam and the main structure; Excavating the remaining reserved soil platform layer by layer downward to the design elevation of the basement, and installing support rods layer by layer between the main structure and the support piles, specifically including: Excavating downwards the reserved soil platform between the structural column and the supporting pile; If the excavation depth of the reserved soil platform reaches the floor slab of the main structure, support rods are installed between the floor slab and the support piles until the excavation depth reaches the lowest floor slab of the main structure; Stop installing the support rods, and excavate the reserved soil platform to the design elevation of the basement.

2. The reverse construction method according to claim 1, characterized in that: The prefabricated steel cage of the structural column specifically comprises: Pre-binding the steel cage of the structural column and assembling the formwork outside the steel cage, wherein both ends of the steel cage protrude from the formwork; The step of opening a mounting hole at the top of the pile foundation and inserting the steel cage into the mounting hole specifically includes: According to the preset construction position of the structural column, measuring, locating and marking the location of the pile foundation; A mounting hole is opened at the top of the pile foundation, and a positioning rib is vertically installed in the mounting hole according to the marked position; Insert one end of the steel cage protruding from the template into the mounting hole, wherein the positioning ribs are inserted into the steel cage and abut against the corners of the steel cage.

3. The reverse construction method according to claim 2, characterized in that: Inserting one end of the steel cage protruding from the template into the mounting hole, and then further comprising: According to the marked position, cross fixing bars are installed at the openings of the construction holes of the pile foundation, and the cross fixing bars are connected and fixed to the steel cage, wherein the cross positions of the cross fixing bars correspond to the corners of the steel cage; Backfill earth between the template and the construction hole in sections.

4. The reverse construction method according to claim 1, characterized in that: Carrying out the main structure construction and connecting the main structure to the structural columns specifically includes: The main structure is constructed from the design elevation of the basement to the lowest floor slab, and a second connecting rib of the lowest floor slab is reserved; connecting the second connecting rib to the first connecting rib; The remaining structural construction of the main structure is completed layer by layer upwards.

5. The reverse construction method according to claim 1, characterized in that: The floor slab of the main structure is provided with buttresses, and the support rods are connected to the main structure via the buttresses.

6. The reverse construction method according to claim 1, characterized in that: The remaining structural construction of the basement is completed layer by layer, and the support rods are removed layer by layer, specifically including: Carrying out the remaining structure construction of the basement upwards, and when the construction height of the remaining structure reaches the support rod at the lowest end, removing the support rod at the lowest end; The remaining structure construction is continued, and each time the remaining structure construction height reaches the support rod, the support rod is removed until the remaining structure construction is completed.

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