Pit-in-pit supporting structure and pit-in-pit supporting method
By adopting a pit support structure in the pit with mixing piles and backpressure plates under silt geological conditions, combined with the reinforcement method of steel plates and steel pipe support, the construction difficulties caused by the occupying space of the foundation pit support beam is solved, and construction without the need for pile driving equipment is achieved, and efficiency and safety are improved.
Patent Information
- Application Number
- CN202411785178.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-06
- Publication Date
- 2025-02-28
AI Technical Summary
Under silt geological conditions, when excavating and constructing a pit in the elevator shaft pit, the pile driving equipment cannot operate normally and cannot be vertically driven into metal piles or steel pipes, causing construction difficulties.
A pit support structure in pits is adopted, including mixing piles, backpressure plates, steel plates, inserts and steel pipe support. Through the cooperation of mixing piles and backpressure plates, a supporting base is formed, and reinforced by steel plates and steel pipe support to form a support structure that meets the strength requirements and avoid the use of pile driving equipment.
It realizes that pit support construction in pits can be carried out without the use of pile driving equipment under the condition of saving working space, improving construction efficiency and safety, and reducing material use and pre-construction steps.
Smart Images
Figure CN119531376A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of building construction methods, and in particular to a pit-in-pit support structure and a pit-in-pit support method. Background Art
[0002] During the construction of coastal cities, silt and silty soil are often encountered. This type of geology has the characteristics of high water content, large porosity, high compressibility, poor consolidation, high sensitivity, high disturbance, and low seismic performance. Under silty geological conditions, the excavation of the elevator pit needs to be supported to avoid mud flow and slope deformation.
[0003] When constructing pit-in-pit support, the presence of a foundation pit support beam at a height of 1m-3m above the pit-in-pit will occupy a certain space. This is because metal piles or steel pipes require a certain vertical space during the driving process, and the presence of the support beam limits this space. For example, if the support beam is close to the pit-in-pit, the working height and angle of the pile driving equipment (such as a static pile driver or a vibrating hammer) will be affected, and the metal piles or steel pipes cannot be driven vertically into the ground normally.
[0004] Therefore, a pit-in-pit support solution is needed that can save working space and can be constructed without the use of piling equipment. Summary of the invention
[0005] The purpose of this application is to provide a pit-in-pit support solution that can save working space and can be constructed without the use of piling equipment.
[0006] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a pit-in-pit support structure, which is applied to the periphery of a foundation pit, wherein the foundation pit has soft foundation soil, and the pit-in-pit support structure comprises: a plurality of mixing piles, which are arranged around the foundation pit, and the mixing piles are obtained by mixing and solidifying a curing agent and soft foundation soil; a back pressure plate, comprising a horizontally arranged concrete cover plate and a vertically arranged concrete perimeter purlin, wherein the concrete cover plate is laid on the top of the mixing piles, and the concrete perimeter purlin is against the side of the mixing piles close to the foundation pit; a steel plate, wherein the steel plate is fixed to the side of the concrete perimeter purlin close to the foundation pit; a dowel, wherein one end of the dowel is inserted into the mixing pile and the other end is anchored into the back pressure concrete cover plate, and is used to fix the back pressure concrete cover plate on the mixing pile; a steel pipe support, wherein one end of the steel pipe support is welded to the steel plate on one side of the foundation pit, and the other end of the steel pipe support is welded to the steel plate on the other side of the foundation pit.
[0007] In one embodiment, a plurality of reinforcing bars are provided in the concrete cover slab, and the plurality of reinforcing bars are horizontally spaced apart in the concrete perimeter purlin beam in the concrete cover slab.
[0008] In another embodiment, a plurality of longitudinal bars are provided in the concrete perimeter purlin beam, and the plurality of longitudinal bars are horizontally spaced apart in the concrete perimeter purlin beam.
[0009] On the basis of the above embodiments, in one embodiment, a plurality of longitudinal bars are arranged in two rows; a plurality of waist bars are also provided in the concrete purlin beam, the plurality of waist bars are placed horizontally, and the plurality of waist bars are arranged between the two rows of longitudinal bars.
[0010] In one embodiment, the steel plate is fixed to the concrete perimeter purlin beam by means of embedded reinforcement, one end of the embedded reinforcement is plug-welded to the steel plate through a hole, and the rest of the embedded reinforcement is embedded in the concrete perimeter purlin beam.
[0011] Based on the above embodiments, in one embodiment, the arrangement spacing of the embedded bars is equal to the diameter of the steel pipe support, and the arrangement center of the embedded bars and the welding position of the steel pipe support are both located at the center of the steel plate.
[0012] In another embodiment, the thickness of the concrete cover plate is 200 mm, the dowel rod is inserted into the mixing pile 850 mm and anchored into the concrete cover plate 150 mm, and the diameter of the dowel rod is 20 mm.
[0013] In another embodiment, the pit-in-pit support structure also includes metal piles and steel perimeter purlins. The metal piles are inserted into the soft foundation soil, and the steel perimeter purlins are fixed on the side of the metal piles close to the foundation pit. The steel perimeter purlins can be welded to the steel pipe supports to replace the welding of part of the steel plates and the steel pipe supports.
[0014] In a second aspect of the present application, a pit-in-pit support method is provided. The pit-in-pit support method is applied to a pit-in-pit support structure as provided in the first aspect of the present application. The pit-in-pit support structure is applied around a foundation pit. The foundation pit has soft foundation soil. The pit-in-pit support method includes: solidifying the soft foundation soil to obtain a plurality of mixing piles; fixing a concrete cover plate above the mixing piles using dowel bars; fixing a concrete perimeter purlin beam integrated with the concrete cover plate on a side of the mixing pile close to the foundation pit; fixing a steel plate on a side of the concrete perimeter purlin beam close to the foundation pit; welding one end of a steel pipe support to the steel plate on one side of the foundation pit, and welding the other end of the steel pipe support to the steel plate on the other side of the foundation pit.
[0015] In one embodiment, the pit-in-pit support method also includes: excavating the soft foundation soil in the foundation pit in layers and sections; constructing a pedestal, elevator shaft or water collection well in the foundation pit; and removing steel pipe supports, concrete purlins and concrete cover plates.
[0016] Compared with the prior art, the pit-in-pit support structure and the pit-in-pit support method in the embodiment of the present application have the following beneficial effects:
[0017] A pit-in-pit support structure and a pit-in-pit support method in the embodiments of the present application, through the cooperation of mixing piles and back pressure plates, only require steel reinforcement, and wait for the mixing piles and back pressure plates to solidify to form a support base, and then support reinforcement is carried out through steel plates and steel pipes to form a support structure that meets the strength requirements. Since the mixing piles and back pressure plates rely on solidification rather than hammering, there is no need to use piling equipment, which can save working space and can be constructed without the use of piling equipment. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 It is a cross-sectional schematic diagram of a pit-in-pit support structure shown in an example of an embodiment of the present application.
[0019] Figure 2 It is a plan view schematic diagram of a pit-in-pit support structure shown in an example row of an embodiment of the present application.
[0020] Figure 3 It is a cross-sectional schematic diagram of a pit-in-pit support structure with steel bars shown in an example of an embodiment of the present application.
[0021] Figure 4 It is a cross-sectional schematic diagram of a reinforcement structure of a steel plate shown in an example of an embodiment of the present application.
[0022] Figure 5 It is a plan view of another pit-in-pit support structure shown in an example row of an embodiment of the present application.
[0023] Figure 6 It is a flow chart of a pit-in-pit support method shown in an example of an embodiment of the present application.
[0024] Reference numerals:
[0025] 10. Pit-in-pit supporting structure, 101. Mixing piles, 102. Counter pressure plate, 1021. Concrete cover plate, 1022. Concrete perimeter purlin, 103. Steel plate, 104. Inserted reinforcement, 105. Steel pipe support, 10211. Reinforcement, 10221. Longitudinal reinforcement, 10222. Waist reinforcement, 10223. Embedded reinforcement, 106. Metal piles, 107. Steel perimeter purlin, 20. Foundation pit, 201. Soft foundation soil. DETAILED DESCRIPTION
[0026] The specific implementation methods of the present application are further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present application but are not intended to limit the scope of the present application.
[0027] There are many soft foundation soils in coastal cities. The soft foundation soil itself has low strength and is prone to deformation when subjected to vertical and lateral pressure. Therefore, when there is a pit-in-pit structure, the excavation of the pit-in-pit will form a local deep pit in the soft soil foundation.
[0028] For example, in construction projects, elevator pits are usually deeper than building foundation pits. This depth difference will cause the lateral pressure on the side walls of the pit to increase sharply. If there are no support measures, the soft soil on the side walls of the pit will easily collapse under the lateral pressure, thus affecting the stability of the entire foundation.
[0029] In order to maintain stability, pit-in-pit support is carried out, and the metal piles of pit-in-pit support need to be driven into the ground by vibration or static pressure. In this process, the movement range of the pile driving equipment is relatively large.
[0030] If there is already a support beam in the foundation pit, the support beam will occupy a certain space, resulting in limited construction space, and the piling equipment is likely to collide with the support beam during operation. This collision will not only damage the support beam and affect the overall stability of the foundation pit support, but may also cause damage to the piling equipment itself, resulting in equipment failure and inability to perform piling operations normally.
[0031] To solve this problem, Figure 1 and Figure 2 As shown ( Figure 1 is an exemplary cross-sectional view, Figure 2 is an exemplary top view), a pit-in-pit support structure 10 of a preferred embodiment of the present application is applied around a foundation pit 20, and the foundation pit 20 has a soft foundation soil 201. The pit-in-pit support structure 10 includes: a plurality of mixing piles 101, a back pressure plate 102, a steel plate 103, dowels 104, and a steel pipe support 105. The back pressure plate 102 includes a horizontally arranged concrete cover plate 1021 and a vertically arranged concrete surrounding purlin beam 1022.
[0032] A number of mixing piles 101 are arranged around the inner side of the foundation pit 20. The mixing piles 101 are obtained by mixing and solidifying a curing agent and soft foundation soil 201. A concrete cover plate 1021 is laid on top of the mixing piles 101. A concrete purlin 1022 is in contact with the side of the mixing piles 101 close to the foundation pit 20. A steel plate 103 is fixed to the side of the concrete purlin 1022 close to the foundation pit 20. One end of the dowel 104 is inserted into the mixing pile 101 and the other end is anchored into the counter-pressure concrete cover plate 1021, which is used to fix the counter-pressure concrete cover plate 1021 on the mixing pile 101. One end of the steel pipe support 105 is welded to the steel plate 103 on one side of the foundation pit 20, and the other end of the steel pipe support 105 is welded to the steel plate 103 on the other side of the foundation pit 20.
[0033] Through the above solution, the mixing piles 101 and the concrete structure are used to form the main support foundation, and the metal piles 106 are not needed for support, thereby avoiding the use of piling equipment such as vibration hammers, thereby reducing the demand for construction space.
[0034] At the same time, since the metal piles 106 are not required, materials are saved, the pre-construction steps are reduced, and the progress of the on-site construction is accelerated.
[0035] It can be understood that the number and depth of the mixing piles 101 in the present application are determined according to actual needs, and the drawings in the present application are only illustrative examples and are not used to limit the present application.
[0036] The curing agent used to mix with the soft foundation soil 201 to obtain the mixing pile 101 can be one or more of the following combinations: ordinary Portland cement, slag Portland cement, pozzolanic Portland cement, quicklime, slaked lime, cement-lime composite curing agent, cement-fly ash-lime composite curing agent. Those skilled in the art can also select other curing agents suitable for mixing with the foundation soil according to the actual geological conditions, which will not affect the implementation of the present application.
[0037] In one embodiment of the present application, Figure 3 As shown, a plurality of reinforcing bars 10211 may be provided in the concrete cover slab 1021 , and the plurality of reinforcing bars 10211 are horizontally placed and arranged at intervals in the concrete purlin beam 1022 in the concrete cover slab 1021 .
[0038] By providing the reinforcement 10211, the weight and earthquake resistance of the concrete cover 1021 can be increased, the durability of the concrete cover 1021 can be increased, and at the same time, the fixing effect of the mixing pile 101 below can be increased to achieve support stability.
[0039] It is understandable that the area of the back pressure plate 102 can be increased to increase the stability of the support according to the requirements such as the number, size, safety redundancy, etc. of the mixing piles 101. Since the back pressure plate 102 adopts the concrete cover plate 1021 and the concrete surrounding purlin beam 1022 made of concrete material, its size can be changed freely, and it can adapt to the size and shape of various foundation pits 20, and it is flexible and adaptable, and has strong versatility.
[0040] In another embodiment of the present application, also refer to Figure 3 A plurality of longitudinal bars 10221 may be provided in the concrete perimeter purlin beam 1022 , and the plurality of longitudinal bars 10221 are horizontally spaced apart in the concrete perimeter purlin beam 1022 .
[0041] Through the above solution, the structural strength of the concrete purlin beam 1022 is reinforced with the longitudinal reinforcement 10221, further improving the supporting effect. It can be understood that the length of the longitudinal reinforcement 10221 is determined according to the length of the concrete purlin beam 1022. When the concrete purlin beam 1022 is bent, multiple longitudinal reinforcements 10221 can be used to adapt to the concrete purlin beams 1022 in different directions.
[0042] For example, the concrete purlin beam 1022 in the present application may be a rectangle with a cross-sectional size of 400 mm×600 mm, which can meet most pit-in-pit support requirements. On this basis, the size of the steel plate 103 may be slightly smaller than 600 mm.
[0043] Based on the above embodiments, in one embodiment of the present application, reference is made to Figure 3 , a plurality of longitudinal reinforcements 10221 are arranged in two rows; a plurality of waist reinforcements 10222 are also provided in the concrete purlin beam 1022 , the plurality of waist reinforcements 10222 are placed horizontally, and the plurality of waist reinforcements 10222 are arranged between the two rows of the plurality of longitudinal reinforcements 10221 .
[0044] The strength of the concrete purlin beam 1022 is further strengthened by waist reinforcement 10222 to ensure the structural strength in the horizontal direction and provide relatively strong support for the foundation pit 20 around.
[0045] It is understandable that those skilled in the art can directly embed part of the steel plate 103 into the concrete surrounding purlin beam 1022 to fix the steel plate 103 .
[0046] In another embodiment of the present application, in order to further improve the fixing effect of the steel plate 103, refer to Figure 4 The steel plate 103 can be fixed to the concrete surrounding purlin beam 1022 through the embedded reinforcement 10223 , one end of the embedded reinforcement 10223 is plug-welded to the steel plate 103 , and the rest of the embedded reinforcement 10223 is embedded in the concrete surrounding purlin beam 1022 .
[0047] Figure 4 The embedded reinforcement 10223 can be exemplarily made of steel bars with a diameter of 18 mm. For foundation pits 20 of other sizes, the diameter of the embedded reinforcement 10223 can also be appropriately changed due to changes in the size of the concrete purlin beam 1022.
[0048] On the basis of this embodiment, in one embodiment of the present application, the arrangement spacing of the embedded ribs 10223 is equal to the diameter of the steel pipe support 105 , and the arrangement center of the embedded ribs 10223 and the welding position of the steel pipe support 105 are both located at the center of the steel plate 103 .
[0049] By making the arrangement spacing of the embedded bars 10223 equal to the diameter of the steel pipe support 105, it is possible to avoid the embedded bars 10223 from interfering with the hollow area of the steel pipe support 105, and to improve the bearing effect of the embedded bars 10223 on the steel pipe support 105. The use of the embedded bars 10223 not only improves the bearing capacity of the steel pipe support 105, but also improves the fixing effect of the steel plate 103 on the concrete purlin beam 1022, and it is not easy to fall out when the steel pipe support 105 is welded.
[0050] In another embodiment of the present application, illustratively, the thickness of the concrete cover 1021 may be 200 mm, the dowel 104 is inserted into the mixing pile 101850 mm and anchored into the concrete cover 1021150 mm, and the diameter of the dowel 104 is 20 mm.
[0051] In another embodiment, if Figure 5 As shown, the pit-in-pit support structure 10 can also include metal piles 106 and steel surrounding purlins 107. The metal piles 106 are inserted into the soft foundation soil 201. The steel surrounding purlins 107 are fixed on the side of the metal piles 106 close to the foundation pit 20. The steel surrounding purlins 107 can be welded to the steel pipe supports 105 to replace the welding of part of the steel plates 103 and the steel pipe supports 105.
[0052] Through the above solution, it can be explained that the solution of the present application can be combined with the existing solution of the metal pile 106. Figure 5 In the figure, Larsen IV steel plate 103 piles are used as exemplary metal piles 106 , and steel surrounding purlin beams 107 are used on the inner side of the metal piles 106 .
[0053] Therefore, there are three situations for the steel tube support 105 in the above scheme: Situation 1, the steel tube support 105 is located between two concrete perimeter purlin beams 1022, so both ends of the steel tube support 105 are welded to the steel plate 103; Situation 2, the steel tube support 105 is located between the concrete perimeter purlin beam 1022 and the steel perimeter purlin beam 107, so one end of the steel tube support 105 is welded to the steel plate 103, and the other end is directly welded to the steel perimeter purlin beam 107; Situation 3, the steel tube support 105 is located between two steel perimeter purlin beams 107, so both ends of the steel tube support 105 are welded to the steel perimeter purlin beam 107.
[0054] The above-mentioned combination scheme can adapt to more construction sites and meet the pit-in-pit support needs of multiple foundation pits 20. Since the conventional support structure and the pit-in-pit support structure 10 of the present application have different construction steps, the two combinations bring more construction freedom and can meet more construction deadline requirements.
[0055] Correspondingly, the present application also provides a pit-in-pit support method, referring to Figure 6 The pit-in-pit support method is applied to a pit-in-pit support structure 10 as in the present application. The pit-in-pit support structure 10 is applied around a foundation pit 20. The foundation pit 20 has a soft foundation soil 201. The pit-in-pit support method may include:
[0056] S101, solidifying the soft foundation soil 201 to obtain a plurality of mixing piles 101;
[0057] S102, using the dowel bars 104 to fix the concrete cover plate 1021 above the mixing pile 101;
[0058] S103, fixing the concrete purlin beam 1022 integrated with the concrete cover plate 1021 on the side of the mixing pile 101 close to the foundation pit 20;
[0059] S104, fixing the steel plate 103 on one side of the concrete purlin beam 1022 close to the foundation pit 20;
[0060] S105 , welding one end of the steel pipe support 105 to the steel plate 103 on one side of the foundation pit 20 , and welding the other end of the steel pipe support 105 to the steel plate 103 on the other side of the foundation pit 20 .
[0061] The pit-in-pit support structure 10 provided by the present application can be constructed by applying the above steps to complete the pit-in-pit support. The pit-in-pit support method in the present application has all the beneficial effects of the pit-in-pit support structure 10. Accordingly, the embodiments of the pit-in-pit support structure 10 in the present application can also be applied to the pit-in-pit support method in the present application, and the present application will not repeat them one by one.
[0062] In another embodiment, the pit-in-pit support method may also include: excavating the soft foundation soil 201 in the foundation pit 20 in layers and sections; constructing a pedestal, elevator shaft or water collection well in the foundation pit 20; and removing the steel pipe support 105, concrete purlin beams 1022 and concrete cover plates 1021.
[0063] It is understandable that the steps of the pit-in-pit support method in the present application are merely exemplary, and those skilled in the art may adjust the order and number of the steps appropriately according to actual needs.
[0064] In summary, the embodiments of the present application provide a pit-in-pit support structure 10 and a pit-in-pit support method. Through the cooperation of the mixing piles 101 and the back pressure plate 102, only steel reinforcement is required. After waiting for the mixing piles 101 and the back pressure plate 102 to solidify, a support matrix can be formed. The support is reinforced by the steel plates 103 and the steel pipe supports 105 to form a support structure that meets the strength requirements. Since the mixing piles 101 and the back pressure plate 102 rely on solidification rather than hammering, there is no need to use piling equipment, which can save working space and can be constructed without the use of piling equipment.
[0065] The above is only a preferred implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present application. These improvements and substitutions should also be regarded as the scope of protection of the present application.
Claims
1. A pit-in-pit support structure, characterized in that: Applied around a foundation pit (20), the foundation pit (20) has soft foundation soil (201), and the pit-in-pit support structure comprises: A plurality of mixing piles (101) are arranged around the inner side of the foundation pit (20), wherein the mixing piles (101) are obtained by mixing and solidifying a curing agent and the soft foundation soil (201); The back pressure plate (102) comprises a horizontally arranged concrete cover plate (1021) and a vertically arranged concrete purlin beam (1022), wherein the concrete cover plate (1021) is laid above the mixing pile (101), and the concrete purlin beam (1022) abuts against a side of the mixing pile (101) close to the foundation pit (20); A steel plate (103), wherein the steel plate (103) is fixed to a side of the concrete surrounding purlin beam (1022) close to the foundation pit (20); A dowel bar (104), one end of which is inserted into the mixing pile (101) and the other end of which is anchored into the counter-pressure concrete cover plate (1021), and is used to fix the counter-pressure concrete cover plate (1021) on the mixing pile (101); A steel pipe support (105), one end of the steel pipe support (105) is welded to the steel plate (103) on one side of the foundation pit (20), and the other end of the steel pipe support (105) is welded to the steel plate (103) on the other side of the foundation pit (20).
2. The pit-in-pit support structure according to claim 1, characterized in that: The concrete cover plate (1021) is provided with a plurality of reinforcing bars (10211), and the plurality of reinforcing bars (10211) are horizontally placed and arranged at intervals in the concrete surrounding purlin beam (1022) in the concrete cover plate (1021).
3. The pit-in-pit support structure according to claim 1, characterized in that: A plurality of longitudinal bars (10221) are arranged in the concrete purlin beam (1022), and the plurality of longitudinal bars (10221) are arranged horizontally and spaced apart in the concrete purlin beam (1022).
4. The pit-in-pit support structure according to claim 3, characterized in that: The plurality of longitudinal bars (10221) are arranged in two rows; the concrete purlin beam (1022) is also provided with a plurality of waist bars (10222), the plurality of waist bars (10222) are placed horizontally, and the plurality of waist bars (10222) are arranged between the plurality of longitudinal bars (10221) in two rows.
5. The pit-in-pit support structure according to claim 1, characterized in that: The steel plate (103) is fixed to the concrete surrounding purlin beam (1022) via embedded bars (10223), one end of the embedded bars (10223) is plug-welded to the steel plate (103) through a hole, and the rest of the embedded bars (10223) is embedded in the concrete surrounding purlin beam (1022).
6. The pit-in-pit support structure according to claim 5, characterized in that: The arrangement spacing of the embedded ribs (10223) is equal to the diameter of the steel pipe support (105), and the arrangement center of the embedded ribs (10223) and the welding position of the steel pipe support (105) are both located at the center of the steel plate (103).
7. The pit-in-pit support structure according to claim 1, characterized in that: The thickness of the concrete cover plate (1021) is 200 mm, the dowel bar (104) is inserted into the mixing pile (101) by 850 mm and anchored into the concrete cover plate (1021) by 150 mm, and the diameter of the dowel bar (104) is 20 mm.
8. The pit-in-pit support structure according to claim 1, characterized in that: The pit-in-pit support structure further comprises metal piles (106) and steel purlin beams (107), wherein the metal piles (106) are inserted into the soft foundation soil (201), and the steel purlin beams (107) are fixed on a side of the metal piles (106) close to the foundation pit (20), and the steel purlin beams (107) can be welded to the steel pipe support (105) to replace the welding of part of the steel plate (103) and the steel pipe support (105).
9. A method for supporting a pit in a pit, characterized in that: The pit-in-pit support method is applied to the pit-in-pit support structure according to any one of claims 1 to 8, the pit-in-pit support structure is applied around a foundation pit (20), the foundation pit (20) has soft foundation soil (201), and the pit-in-pit support method comprises: Solidifying the soft foundation soil (201) to obtain a plurality of mixing piles (101); Using dowel bars (104) to fix a concrete cover plate (1021) above the mixing pile (101); Fixing a concrete purlin beam (1022) integrally formed with the concrete cover plate (1021) on a side of the mixing pile (101) close to the foundation pit (20); Fixing a steel plate (103) on a side of the concrete purlin beam (1022) close to the foundation pit (20); One end of the steel pipe support (105) is welded to the steel plate (103) on one side of the foundation pit (20), and the other end of the steel pipe support (105) is welded to the steel plate (103) on the other side of the foundation pit (20).
10. The pit-in-pit support method according to claim 9, characterized in that , the pit-in-pit support method further comprises: Excavating the soft foundation soil (201) in the foundation pit (20) in layers and sections; constructing a cap, an elevator shaft or a water collection well in the foundation pit (20); The steel pipe support (105), the concrete purlin beam (1022) and the concrete cover plate (1021) are removed.