A method for constructing internal supports in ultra-large and deep foundation pits without dismantling

Abstract

This invention provides a method for constructing ultra-deep foundation pits with internal supports without dismantling, comprising: excavating the foundation pit to the depth of the bottom slab corresponding to a predetermined underground level, and constructing the main structure of the excavation and cut-and-cover structure and a temporary support system; dividing the area where the temporary internal supports of the temporary support system are located into multiple areas to be constructed, nested from the outside in, and constructing permanent columns in the corresponding areas in order from the outside in; dividing the area where the temporary internal supports and the top of the excavation and cut-and-cover structure to be poured are located from one side of the foundation pit to the other into multiple adjacent areas to be poured, and pouring each area in a predetermined order; dismantling the temporary columns in the areas to be poured after completion; and constructing the main structure of the station within the foundation pit in sections and layers. The solution provided by this invention improves the overall strength of the foundation pit and its internal structure, avoids secondary impacts on the existing structure within the foundation pit due to the removal of the support structure, and improves construction efficiency.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, and more specifically, to a method for constructing ultra-large deep foundation pits with internal supports that do not require dismantling. Background Technology

[0002] Currently, for open-cut railway station foundation pits, there is a diaphragm wall-internal support system for the main structure of the station inside the pit. After the support is completed, the process of dismantling the temporary internal support system (concrete internal support, vertical lattice columns) may have a potential impact on the deformation of the main structure inside the pit.

[0003] Currently, the size of typical open-cut railway station foundation pits is relatively small, and the main structure inside the pit is mostly not in direct contact with the internal supports. However, for foundation pit support projects where the main side walls of the station are closely attached to the diaphragm walls, the foundation pit area is large, and the internal supports are connected to the main structure, the deformation control requirements of the main structure are much higher than those for conventional open-cut railway station foundation pit projects. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a construction method for internal support without dismantling in ultra-large and deep foundation pits, so as to avoid the deformation of the main structure inside the pit when the temporary internal support system is dismantled.

[0005] To address the aforementioned technical problems, embodiments of the present invention provide a method for constructing ultra-large, deep foundation pits with internal supports that do not require dismantling, comprising:

[0006] The foundation pit is excavated to the depth of the bottom slab corresponding to the underground preset level, and the cut-and-cover main structure and temporary support system corresponding to the underground preset level, the preset level above the underground preset level, and the preset level below the underground preset level are constructed respectively.

[0007] The area where the temporary inner support of the temporary support system is located is divided into multiple areas to be constructed from the outside to the inside, and permanent columns are constructed at the preset positions of the corresponding areas to be constructed in the order from the outside to the inside.

[0008] The area where the temporary internal support to be poured in the temporary support system and the area where the top of the cut-and-cover main structure is located are divided into multiple adjacent areas to be poured from one side of the foundation pit to the other, and each area to be poured is poured in blocks according to a preset order.

[0009] Remove the temporary columns in the temporary support system after the concrete pouring is completed;

[0010] The main structure of the station inside the foundation pit is divided into sections, and the main structure of the station is constructed layer by layer according to the preset construction sequence of the sections.

[0011] In one embodiment, the underground preset level is the third underground level; the construction of the cut-and-cover main structure and temporary support system corresponding to the underground preset level, the preset levels above the underground preset level, and the preset levels below the underground preset level includes:

[0012] The top slab of the first underground level is constructed upwards, and the bottom slab and side wall structure of the first underground level, the second underground level, and the third underground level are constructed downwards in reverse order.

[0013] Temporary columns are constructed downwards, and temporary internal supports are constructed upwards for the first, second, and third underground levels, with each level's temporary internal support fixedly connected to the temporary columns.

[0014] Excavate downwards to the bottom slab of the fourth underground level, and after constructing temporary internal supports for the fifth underground level in reverse, construct the bottom slab of the fourth underground level.

[0015] Excavation proceeds downwards to the location of the bottom slab of the fifth underground level, and the side wall structure of the fourth underground level, the bottom slab of the fifth underground level, and the side wall structure of the fifth underground level are constructed sequentially.

[0016] In one embodiment, the temporary column comprises multiple temporary lattice columns sequentially connected between two adjacent underground levels, and the downward installation of the temporary column includes:

[0017] Multiple temporary lattice columns are arranged vertically between two adjacent underground levels, and adjacent temporary lattice columns are welded together and connected by steel gusset plates and ribs.

[0018] Temporary column brackets are installed at the positions where the end temporary lattice columns between two adjacent underground levels are connected to the corresponding temporary internal supports in the underground level, and are connected to the corresponding temporary internal supports in the underground level by steel beams.

[0019] In one embodiment, the plurality of areas to be constructed include area a, area b, and area c, with area c nested within area b and area b nested within area a; areas a and b are both cubically distributed, and the permanent pillars constructed in areas a and b are evenly distributed along the four sides of the cube in the horizontal direction; area c is rectangular and distributed along the vertical direction of the cube within area b, and the permanent pillars constructed in area c are evenly distributed along the sides of the rectangle in the horizontal direction.

[0020] In one embodiment, permanent pillars are constructed at predetermined locations corresponding to the area to be constructed, in an order from the outside in, including:

[0021] The steel pipe columns in each underground level of Zone A are hoisted layer by layer from bottom to top, and the two ends of the steel pipe columns in each underground level are fixed to the reserved holes on the temporary internal support of Zone A. After all the steel pipe columns in the underground levels are hoisted, concrete is poured into the steel pipe columns through the reserved grouting holes on the temporary internal support of Zone A to form permanent columns in Zone A.

[0022] The steel pipe columns in each underground level of Zone B are hoisted layer by layer from bottom to top, and the two ends of the steel pipe columns in each underground level are fixed to the reserved holes on the temporary internal support of Zone B. After all the steel pipe columns in the underground levels are hoisted, concrete is poured into the steel pipe columns through the reserved grouting holes on the temporary internal support of Zone B to form permanent columns in Zone B.

[0023] The steel pipe columns in each underground level of Zone C are hoisted layer by layer from bottom to top, and the two ends of the steel pipe columns in each underground level are fixed to the reserved holes on the temporary internal support of Zone C. After all the steel pipe columns in the underground levels are hoisted, concrete is poured into the steel pipe columns through the reserved grouting holes on the temporary internal support of Zone C to form permanent columns in Zone C.

[0024] In one embodiment, the construction of permanent pillars at predetermined locations corresponding to the area to be constructed, in a sequence from the outside in, further includes:

[0025] Vertical stiffening plates and horizontal stiffening plates are installed at the connection nodes between temporary internal supports and steel pipe columns at any underground level. The vertical stiffening plates are installed on the outside of the steel pipe column, and the horizontal stiffening plates are installed inside the steel pipe column.

[0026] A sleeve is provided below the connection node, and the sleeve is fitted over the outside of the steel pipe column;

[0027] An additional flange reinforcement is welded at the connection node, the additional flange reinforcement bypassing the steel pipe column and connecting to the sleeve.

[0028] In one embodiment, the plurality of areas to be poured include area d, area e, and area f; wherein area e is located between area d and area f.

[0029] In one embodiment, pouring each area to be poured in blocks according to a preset sequence includes:

[0030] According to the first preset block jump sequence, the other layers of temporary internal supports below the first layer of temporary internal supports in the temporary support system of the d area are cast into the d area plate support, and the first layer of temporary internal supports in the temporary support system of the d area and the top of the cut-and-cover main structure are cast into the d area cover plate.

[0031] According to the second preset block jump sequence, the other layers of temporary internal supports below the first layer of temporary internal supports in the temporary support system of the f area are cast into the f area plate support, and the first layer of temporary internal supports in the temporary support system of the f area and the top of the cut-and-cover main structure are cast into the f area cover plate.

[0032] According to the third preset block jump sequence, the other layers of temporary internal supports below the first layer of temporary internal supports in the temporary support system of zone e are cast into the slab support of zone e, and the first layer of temporary internal supports in the temporary support system of zone e and the top of the cut-and-cover main structure are cast into the cover plate of zone e.

[0033] In one embodiment, removing the temporary columns in the temporary support system after the concrete pouring is completed includes:

[0034] The temporary pillars outside area a, the temporary pillars in area a, the temporary pillars in area b, the temporary pillars between area a and area b, and the temporary pillars in area c are dismantled in sequence.

[0035] In one embodiment, the temporary pillars outside area a, the temporary pillars in area a, the temporary pillars in area b, the temporary pillars between area a and area b, and the temporary pillars in area c are dismantled sequentially, each including:

[0036] Cut off the connection between the cover plate formed after the pouring is completed and the temporary column, or cut off the connection between the plate support formed after the pouring is completed and the temporary column;

[0037] Cut off the ribs welded between the multiple sections of the temporary lattice columns of the temporary columns between two adjacent underground levels;

[0038] Cut off the steel gusset plates welded between the multiple sections of the temporary lattice columns of the temporary columns between two adjacent underground levels.

[0039] The above-described solution of the present invention has at least the following beneficial effects:

[0040] (1) By reducing the dismantling work in the diaphragm wall-internal support system in the foundation pit, the temporary internal support in the temporary support system is poured as a permanent plate support after construction. On the one hand, it has a good suppression effect on the overall displacement of the structure in the pit; on the other hand, for the soil in the foundation pit, the load of the surrounding main structure is directly transferred to the foundation by the permanent column. After the plate support is poured, it forms a rigid whole with the permanent column, which can not only greatly reduce the uneven settlement in the pit, but also effectively reduce the bottom rebound effect of the ultra-deep foundation pit. In addition, it can also reduce the deformation of the main structure and the retaining structure caused by the dismantling of the support, and greatly reduce the impact of secondary construction on the existing structure.

[0041] (2) After the temporary support system of the foundation pit is completed, steel pipe columns are constructed in the temporary support system as vertical supports to replace the temporary columns. After the steel pipe columns are cast into permanent columns, the temporary internal supports are cast in layers after they reach the support strength and are connected with the main structure of the skirt to form an integral whole. This greatly saves the time of dismantling the temporary structure and ensures the overall stability of the foundation pit. At the same time, the permanent columns are cast before the plate supports are cast, which can enhance the overall strength of the support structure.

[0042] (3) The solution provided by this invention adopts an alternating construction method of gradually dismantling temporary columns in sections and simultaneously pouring permanent columns in blocks, which provides a new solution to the problem of the troublesome dismantling of the support structure of ultra-large and deep foundation pits. During the replacement of temporary columns, the internal support is poured and the temporary columns are dismantled, which not only ensures the overall stability of the foundation pit support system, but also plays a good role in controlling the deformation of the surrounding main structure, and also greatly saves the construction period and improves the construction efficiency. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of construction steps 1 for excavation, cut-and-cover main structure and support system of foundation pit provided in an optional embodiment of the present invention;

[0044] Figure 2 This is a schematic diagram of construction steps 2 of the foundation pit excavation, cut-and-cover main structure and support system provided in an optional embodiment of the present invention;

[0045] Figure 3 This is a schematic diagram of construction steps 3 of the foundation pit excavation, cut-and-cover main structure and support system provided in an optional embodiment of the present invention;

[0046] Figure 4 This is a schematic diagram of step 4 of the construction of the foundation pit excavation, cut-and-cover main structure and support system provided in an optional embodiment of the present invention;

[0047] Figure 5 This is a schematic diagram of step 5 of the construction of the foundation pit excavation, cut-and-cover main structure and support system provided in an optional embodiment of the present invention;

[0048] Figure 6 This is a schematic diagram of construction steps 6 of the foundation pit excavation, cut-and-cover main structure and support system provided in an optional embodiment of the present invention;

[0049] Figure 7 This is a schematic diagram of the overlap between the side wall structure and the diaphragm wall provided in an optional embodiment of the present invention;

[0050] Figure 8 This is a cross-sectional view of the connection between the temporary column and the internal support provided in an optional embodiment of the present invention;

[0051] Figure 9 This is a top view of the connection between the temporary column and the internal support provided in an optional embodiment of the present invention;

[0052] Figure 10 This is a structural diagram of a temporary column provided in an optional embodiment of the present invention;

[0053] Figure 11 This is a cross-sectional view of the connection between the steel pipe column and the internal support provided in an optional embodiment of the present invention;

[0054] Figure 12 This is a top view of the connection between the steel pipe column and the internal support provided in an optional embodiment of the present invention;

[0055] Figure 13 This is a schematic diagram showing the distribution of temporary and permanent columns according to an optional embodiment of the present invention;

[0056] Figure 14 This is a schematic diagram of the internal support permanent column replacement zone casting provided in an optional embodiment of the present invention;

[0057] Figure 15 This is a schematic diagram of the main structure of the excavation and cover of the foundation pit and the support base inside the pit provided in an optional embodiment of the present invention;

[0058] Figure 16 This is a schematic diagram of the temporary column removal provided in an optional embodiment of the present invention;

[0059] Figure 17 This is a schematic diagram of step 1 of the construction of the main structure of the station in the foundation pit, provided in an optional embodiment of the present invention;

[0060] Figure 18 This is a schematic diagram of step 2 of the construction of the main structure of the station in the foundation pit, provided in an optional embodiment of the present invention;

[0061] Figure 19 This is a schematic diagram of step 3 of the zoning construction of the main structure of the station within the foundation pit, provided in an optional embodiment of the present invention;

[0062] Figure 20 This is a schematic diagram of step 4 of the construction of the main structure of the station in the foundation pit, provided in an optional embodiment of the present invention.

[0063] Explanation of icon numbers:

[0064] 1. Slope protection; 2. Diaphragm wall; 3. Column pile; 4. Tension pile; 5. Side wall structure; 6. Temporary column; 7. Cap beam; 8. Plain concrete; 9. Internal bracing; 10. Temporary lattice column; 11. Steel gusset plate; 12. Rib plate; 13. Bolt; 14. Angle steel; 15. Temporary column steel bracket; 16. Steel beam; 17. Base plate; 18. Subbase; 19. Temporary support system; 20. Steel pipe column; 21. 21. Grouting hole; 22. Vertical stiffening plate; 23. Horizontal stiffening plate; 24. Sleeve; 25. Additional flange reinforcement; 26. Top weld; 27. Pit support seat; 28. Main structure of the north station; 29. ​​Main structure of the south station; 30. Existing station; 31. Pit corner brace; 32. Pit retaining pile; 33. Main structure of the east station; 34. Pit steel support; 35. Bridge pile; 36. Cast-in-place pile. Detailed Implementation

[0065] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0066] In the description of this invention, it should be understood that the terms "comprising / including," "consisting of," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a product, apparatus, process, or method that comprises a list of elements includes not only those elements but may also include, where necessary, other elements not expressly listed, or elements inherent to such a product, apparatus, process, or method. Without further limitation, an element defined by the phrases "comprising / including," "consisting of," does not exclude the presence of additional identical elements in the product, apparatus, process, or method that includes said element.

[0067] It should also be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device, component or structure referred to must have a specific orientation, be constructed or operated in a specific orientation, and should not be construed as a limitation of the present invention.

[0068] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0069] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0070] Because conventional open-cut railway station foundation pits are relatively small in size, and considering the complexity of supporting ultra-deep foundation pits and the high requirements for deformation control, embodiments of this invention provide a method for constructing ultra-deep foundation pits with internal supports that do not require dismantling. By using the internal supports as a cover plate structure for casting, the dismantling process is reduced, the construction schedule is significantly shortened, and the support structure is fully utilized, resulting in substantial cost savings. This includes:

[0071] Step 11: Excavate the foundation pit to the depth of the bottom slab corresponding to the underground preset level, and construct the cut-and-cover main structure and temporary support system corresponding to the underground preset level, the preset level above the underground preset level, and the preset level below the underground preset level respectively.

[0072] Step 12: Divide the area where the temporary inner support 9 of the temporary support system is located into multiple areas to be constructed from the outside to the inside, and construct permanent columns at the preset positions of the corresponding areas to be constructed in the order from the outside to the inside.

[0073] Step 13: Divide the area where the temporary internal support 9 to be poured in the temporary support system and the area where the top of the cut-and-cover main structure is located into multiple adjacent areas to be poured from one side of the foundation pit to the other side, and pour each area to be poured in blocks according to the preset order.

[0074] Step 14: Remove the temporary columns in the temporary support system after the concrete pouring is completed;

[0075] Step 15: Divide the main station structure inside the foundation pit into sections, and construct the main station structure in layers according to the preset construction sequence of the sections.

[0076] In this embodiment, before the excavation of the foundation pit, the opposite sides of the foundation pit are first sloped (one side of the opposite sides is a large adjacent foundation pit to be constructed, and the other side has an adjacent underground integrated structure and an existing station 30 structure to be constructed later; here, the opposite sides can be the north and south sides of the foundation pit) to avoid collapse; preferably, the slope support 1 after the slope treatment can be supported by wire mesh anchor spraying plus soil nailing wall support.

[0077] like Figure 1 As shown, after the foundation pit is excavated to a certain depth, a diaphragm wall 2 can be constructed as a retaining structure for the excavated area; as... Figure 2 As shown, after the diaphragm wall 2 is completed, the excavation continues downward to the bottom slab of the preset underground level. The columns of the main structure and their column piles 3 can be constructed first, and at the same time, the tensile piles 4 for installing temporary columns are constructed at the bottom of the foundation pit. Here, the tensile piles 4 are arranged in a matrix at the preset depth at the bottom of the foundation pit.

[0078] Furthermore, the cut-and-cover main structures and temporary support systems for each of the following levels can be constructed separately: the underground pre-set level, the pre-set level above the underground pre-set level, and the pre-set level below the underground pre-set level. In one feasible example, the cut-and-cover main structures and temporary support systems for the pre-set levels above the underground pre-set level can be constructed sequentially, and then the cut-and-cover main structures and temporary support systems for the pre-set levels below the underground pre-set level can be constructed in reverse. Here, due to the large area of ​​the foundation pit, such as... Figure 14 As shown, two temporary support systems 19 can be constructed within the foundation pit. Preferably, each temporary support system is symmetrical about the north and south sides of the foundation pit to further ensure the stability of the overall structure of the foundation pit.

[0079] Since the temporary columns 6 in the temporary support system 19 do not have a strong support effect as a temporary support structure, but the deformation control of the temporary internal supports in the temporary support system 19 is more stringent after they are cast into permanent slab supports, after the foundation pit is constructed to the last level of the bottom slab and the surrounding cut-and-cover main structure is completed and forms a closed structure, the permanent columns can be constructed in the temporary support system first, and then the temporary internal supports can be cast. At the same time, the temporary columns in the slab support structure formed after casting can be removed in sections and layers to form a slab support-permanent column support system in the foundation pit. On the one hand, this meets the deformation standards required by the specifications and ensures the stability of the overall structure in the foundation pit. On the other hand, it avoids the secondary impact of removing the temporary internal supports on the existing structure in the foundation pit.

[0080] Here, each layer of temporary internal support 9 has reserved installation positions for permanent columns, and these installation positions are vertically distributed from top to bottom; the distribution positions of permanent and temporary columns in the temporary internal support are as follows: Figure 13 and Figure 14 As shown, Figure 13The small blue circle indicates the location of temporary pillar 6, while the large gray shaded circle indicates the location of permanent pillars. Figure 14 The large circle in the diagram represents the location of the permanent support column, and the small circle represents the location of the temporary support column. By alternating the arrangement of the permanent and temporary support columns 6, the overall stability of the temporary support system 19 before and after the removal of the temporary support columns 6 can be guaranteed.

[0081] Here, the area where the temporary internal support in the temporary support system 19 is located can be divided into multiple areas to be constructed from the outside to the inside. Permanent columns can be constructed in the preset positions (that is, the permanent column installation positions reserved on the temporary internal support 9) of each area to be constructed in the order from the outside to the inside, so as to meet the deformation standards required by the specifications and ensure the structural stability.

[0082] like Figure 14 As shown in the schematic diagram of the foundation pit from above, in one feasible example of the present invention, multiple areas to be constructed may include area a (area with red lines), area b (area with orange lines), and area c (area with yellow lines) from the outside to the inside. Area c is nested within area b, and area b is nested within area a. Areas a and b are both cubically distributed, and the permanent columns constructed on areas a and b are evenly distributed along the four sides of the cube in the horizontal direction. Area c is rectangular and distributed along the vertical direction of the cube within area b, and the permanent columns constructed on area c are evenly distributed along the sides of the rectangle in the horizontal direction. By constructing permanent columns on areas a, b, and c in the order from the outside to the inside on the two temporary support systems 19 within the foundation pit, the deformation standards required by the specifications can be met, thereby ensuring the overall structural stability of the temporary support system 19 and further guaranteeing the stability of the foundation pit structure.

[0083] Here, the area containing the temporary internal supports that need to be poured in the temporary support system within the foundation pit, as well as the area at the top of the cut-and-cover main structure, are divided into multiple areas to be poured. These multiple areas are distributed from one side of the foundation pit to the other. During pouring, the top of the cut-and-cover main structure and the area containing the first layer of temporary internal supports in the temporary support system are poured into a cover plate, while the areas containing the temporary internal supports of other layers in the temporary support system are poured into slab supports. Figure 14 As shown in the schematic diagram of the foundation pit from above, in one feasible example of the present invention, multiple areas to be poured may include area d, area e, and area f; where area e is located between area d and area f, that is, the foundation pit is divided into three sections from north to south: area d, area e, and area f (wherein, the top of the cut-and-cover main structure and the first layer of temporary internal support in the temporary support system correspond to three adjacent long strip-shaped structural areas d, f, and e (to be poured as a cover plate); the areas d and f corresponding to other temporary internal supports in the temporary support system are divided into...). Figure 14The trapezoidal areas at both ends of the temporary support system (to be poured as plate bracing), and the e-area corresponding to other temporary internal supports in the temporary support system is the rectangular area between two trapezoidal structures (to be poured as plate bracing).

[0084] During the actual pouring process, each area to be poured can be poured in a segmented, skip-pour manner according to a preset sequence, while the temporary internal supports in the temporary support system are poured from bottom to top. The plate supports or cover plates formed after pouring can better control their own deformation and cracks, and the plate supports and permanent columns formed after pouring form a rigid whole, which can not only significantly reduce uneven settlement in the pit, but also effectively reduce the bottom rebound effect of ultra-large deep foundation pits, thus enhancing the overall stability of the soil in the foundation pit. At the same time, segmented and skip-pour pouring can also reduce concrete cracking caused by the heat of hydration during the pouring of large-volume concrete, as well as the shrinkage and expansion effects between adjacent concrete. Since the two temporary support systems 19 in the foundation pit are far apart and have little impact, the construction of different areas to be poured can be arranged and organized simultaneously.

[0085] Furthermore, after the permanent columns are constructed and the area to be poured is poured, and after the strength of the current temporary support system meets certain requirements, the temporary columns in the poured temporary support system can be removed in sequence. Here, the temporary columns can also be removed in the order from the outside to the inside (the order from the outside to the inside can be along the outer perimeter of the currently poured slab support structure in the direction of indentation towards the center of the currently poured slab support structure).

[0086] It should be understood that after the temporary support system is erected, the construction sequence within the temporary support system is not limited to the order of permanent column installation, temporary internal bracing pouring, and temporary column removal. Any other construction sequence that meets the overall deformation standards of the support system and does not affect the stability of the existing structure within the foundation pit is acceptable. For example, construction can be carried out in the order of the different areas (the area to be constructed and the area to be poured) after the area has been divided, as long as the overall deformation standards of the support system are met and the stability of the existing structure within the foundation pit is not affected. The existing structure within the foundation pit must be stable. Specifically, construction can proceed in the following order: construction of permanent columns in area a, pouring of concrete in areas d and f, construction of permanent columns in area b, removal of temporary columns outside area a and between area a and b, construction of permanent columns in area c, pouring of concrete in area e, and removal of temporary columns within area c; or construction can proceed in the following order: construction of permanent columns in area a, construction of permanent columns in area b, construction of permanent columns in area c, pouring of concrete in area d, removal of temporary columns within area d, pouring of concrete in area f, removal of temporary columns within area f, pouring of concrete in area e, and removal of temporary columns within area e.

[0087] After all temporary pillars 6 have been completely removed, as Figure 15As shown, a plate-braced permanent column support system is formed in the foundation pit. The plate-braced permanent column support system includes two pit support seats 27 that are evenly and symmetrically distributed in the foundation pit. At this time, the main station structure inside the foundation pit and outside the two pit support seats 27 is constructed. Specifically, it can be constructed in layers according to the bottom-up and pre-set zoning construction sequence to ensure the stability of the two pit support seats 27 and the overall structure of the cut-and-cover structure, which has a good effect on the deformation control of the cut-and-cover structure.

[0088] See 1 to Figure 7 In an optional embodiment of the present invention, the underground preset level is the third underground level; in step 11 above, the cut-and-cover main structure and temporary support system corresponding to the underground preset level, the preset level above the underground preset level, and the preset level below the underground preset level are respectively constructed, which may specifically include:

[0089] Step 111: Construct the top slab of the first underground level upwards, and then construct the bottom slab 17 and side wall structure 5 of the first, second, and third underground levels downwards in reverse order; as follows... Figure 3 and Figure 7 As shown, the side wall structure 5 is closely adjacent to the diaphragm wall 2. The top of the side wall structure 5 and the diaphragm wall 2 are overlapped, and the top of the side wall structure 5 and the diaphragm wall 2 are fixedly connected by the cap beam 7. Preferably, the gap between the side wall structure 5 and the diaphragm wall 2 can be backfilled with plain concrete 8.

[0090] Step 112: Construct temporary columns 6 downwards, and construct temporary internal supports 9 upwards for the first, second, and third underground levels, fixing each level's temporary internal support 9 to the temporary column 6; preferably, one end of the tension pile 4 facing into the pit is provided with a cast-in-place pile 36, one end of the temporary column 6 is inserted into the cast-in-place pile 36, and the other end of the temporary column 6 passes through the internal supports 9 of the preset underground levels in sequence, connecting with each level's internal temporary support 9 to improve the overall rigidity between the temporary internal support 9 and the temporary column 6; preferably, as Figure 10 As shown, a cushion layer 18 is provided between the cast-in-place pile 36 and the bottom slab of the layer. The cushion layer 18 is generally plain concrete, which has the effect of waterproofing and protecting the bottom slab.

[0091] Step 113: Excavate downwards to the location of the fourth underground level's bottom slab, and after constructing the temporary internal support 9 for the fifth underground level, construct the bottom slab of the fourth underground level; (e.g.) Figure 15 As shown, simultaneously, corner bracing 31 is constructed in the northwest corner of the pit to increase the stability of the local soil. Meanwhile, steel supports 34 are constructed in a portion of the main station structure 33 on the east side of the pit to create a closed system between the main excavated and covered structure and the external retaining structure (diaphragm wall). Figure 5As shown, the fourth underground level base slab and the fifth underground level internal support form a closed whole, which will greatly increase the overall rigidity of the structure before proceeding to the next step of construction.

[0092] Step 114, as follows Figure 6 As shown, the excavation proceeds downwards to the bottom slab of the fifth underground level. The side wall structure of the fourth underground level, the bottom slab of the fifth underground level, and the side wall structure of the fifth underground level are then constructed in sequence. At this point, the main structure around the station and its temporary support system are completed.

[0093] See Figures 8 to 10 In an optional embodiment of the present invention, the temporary column 6 includes multiple temporary lattice columns 10 connected sequentially between two adjacent underground levels. The downward installation of the temporary column 6 in step 112 may specifically include:

[0094] Step 1121: Multiple temporary lattice columns 10 are arranged vertically between two adjacent underground levels, and adjacent temporary lattice columns 10 are welded together and connected by steel connecting plates 11 and ribs 12; For example... Figure 8 and Figure 9 As shown, preferably, the ribs 12 can be connected by M20 strength bolts 13 to ensure the stability and rigidity of the temporary column 6; preferably, as shown... Figure 9 As shown, angle steel 14 is provided at the four top corners of one side of the steel gusset plate 11;

[0095] Step 1122: Temporary steel brackets 15 are installed at the connection points between the end temporary lattice columns between two adjacent underground levels and the corresponding temporary internal supports within the underground level, and connected to the corresponding temporary internal supports within the underground level by steel beams 16, so as to improve the overall rigidity between the temporary internal supports and the temporary lattice columns 10.

[0096] In an optional embodiment of the present invention, step 12 above, in which permanent pillars are constructed at preset positions corresponding to the area to be constructed in an order from the outside in, may specifically include:

[0097] Step 121: Install the steel pipe columns 20 in each underground level of area A from bottom to top, and fix both ends of the steel pipe columns 20 in each underground level to the reserved holes on the temporary internal support of area A; after all the steel pipe columns 20 in all levels are installed, pour concrete into the steel pipe columns 20 through the reserved grouting holes 21 on the temporary internal support of area A to form permanent columns in area A;

[0098] Step 122: The steel pipe columns 20 in each underground level of area b are hoisted from bottom to top, and the two ends of the steel pipe columns 20 in each underground level are fixed to the reserved holes on the temporary internal support of area b; after all the steel pipe columns 20 in the underground levels are hoisted, concrete is poured into the steel pipe columns 20 through the reserved grouting holes 21 on the temporary internal support of area b to form permanent columns in area b;

[0099] Step 123: The steel pipe columns 20 in each underground level of area C are hoisted from bottom to top, and the two ends of the steel pipe columns 20 in each underground level are fixed to the reserved holes on the temporary internal support of area C. After all the steel pipe columns 20 in the underground levels are hoisted, concrete is poured into the steel pipe columns 20 through the reserved grouting holes 21 on the temporary internal support of area C to form permanent columns in area C.

[0100] In this embodiment, the permanent columns constructed in areas a, b, and c are all concrete-filled steel tubular columns (steel tubular columns 20 are cast in concrete). Before constructing the permanent columns, the pre-drilled holes on the temporary internal supports 9 in the different areas to be constructed are pre-treated, and then the steel tubular columns 20 are hoisted and fixed. Here, the specific process of constructing permanent columns in areas a, b, and c is the same, the only difference being the order in which the permanent columns are constructed in the different areas; here, the permanent columns are constructed in the order of area a first, then area b, and finally area c, to meet the deformation standards required by the specifications.

[0101] like Figure 11 and Figure 12 As shown, in an optional embodiment of the present invention, the construction of permanent columns at predetermined positions corresponding to the area to be constructed, in an order from the outside in, may further include:

[0102] Step 12-a1: At the connection node between the temporary internal support and the steel pipe column 20 at any underground level, a vertical stiffening plate 22 and a horizontal stiffening plate 23 are installed. The vertical stiffening plate 22 is installed on the outside of the steel pipe column 20, and the horizontal stiffening plate 23 is installed inside the steel pipe column 20. The vertical stiffening plate 22 is installed in the vertical direction to increase the overall stiffness of the permanent column after pouring.

[0103] Step 12-a2: A sleeve 24 is installed below the connection node. The sleeve 24 is fitted onto the outside of the steel pipe column 20 to enhance the reliable connection between the internal support and the steel pipe column 20 at the connection node, ensuring equal strength, alignment, inspection, and replaceability. It also plays a role in fixing the steel pipe column 20 during construction. Preferably, the sleeve 24 can be a steel sleeve.

[0104] Step 12-a3: Weld additional flange reinforcing ribs 25 at the connection node. The additional flange reinforcing ribs 25 bypass the steel pipe column 20 and connect to the sleeve 24. By setting additional flange reinforcing ribs 25, the longitudinal crack resistance and shear resistance of the inner support flange area can be improved, thereby meeting the stress requirements when the inner support is subsequently cast into a permanent structure with plate bracing function.

[0105] It should be understood that when constructing permanent columns in areas a, b, and c, the process described in steps 12-a1 to 12-a3 above can be followed. After the steel pipe column 20 in the current area to be constructed is hoisted and fixed, concrete is poured into the steel pipe column 20 through the grouting holes 21 reserved on the temporary internal support of that area, and a permanent column is formed after the concrete is poured. At this time, the permanent column and the temporary internal support form an integral frame to ensure the continuous and reliable transmission of internal forces. After the strength of the poured concrete reaches 75% of the design strength, the construction of permanent columns in the next area can be carried out.

[0106] After the permanent columns are installed and their strength meets the requirements, the area to be poured can be constructed. For example... Figure 14 As shown, in an optional embodiment of the present invention, each area to be poured is poured in sections according to a preset order, which may specifically include:

[0107] Step 131: According to the first preset block jump order, cast the other layers of temporary internal supports below the first layer of temporary internal supports in the temporary support system of zone d into zone d plate supports, and cast the first layer of temporary internal supports in the temporary support system of zone d and the top of the cut-and-cover main structure into zone d cover plate.

[0108] Step 132: According to the second preset block jump sequence, cast the other layers of temporary internal supports below the first layer of temporary internal supports in the temporary support system of zone f into zone f plate supports, and cast the first layer of temporary internal supports in the temporary support system of zone f and the top of the cut-and-cover main structure into zone f cover plates.

[0109] Step 133: According to the third preset block jump sequence, the other layers of temporary internal supports below the first layer of temporary internal supports in the temporary support system of zone e are poured into zone e plate supports, and the first layer of temporary internal supports in the temporary support system of zone e and the top of the cut-and-cover main structure are poured into zone e cover plates.

[0110] Here, the first, second, and third pre-set block pouring sequences can all be set according to the specific requirements during construction, and no specific limitations are made here. Each area to be poured is poured in a block pouring manner and in a pre-set sequence to reduce the impact of large-volume concrete pouring. At the same time, the temporary internal supports are used as permanent slab supports after the permanent columns are constructed, and are poured in a bottom-up order during construction. This reduces the deformation of the main structure and retaining structure caused by the removal of supports, reduces the impact of secondary construction on the existing structure, saves time due to the removal of temporary structures, and ensures the overall stability of the foundation pit.

[0111] In an optional embodiment of this invention, the process of pouring each area to be poured in blocks according to a preset sequence may further include:

[0112] Step 13-a1: Erect a first temporary steel reinforcement support near each layer of temporary internal support in zone d, and fix the main beam and secondary beam of the temporary internal support in zone d to the first temporary steel reinforcement support respectively. At the same time, evenly lay multiple templates on the first frame formed after fixing. After laying multiple templates, according to the first preset block jump order, first pour the temporary internal supports of other layers below the first layer of temporary internal support in the temporary support system of zone d and their corresponding first temporary steel reinforcement supports and templates in order from bottom to top to form the slab support of zone d. Then pour the top of the cut-and-cover main structure of zone d, the first layer of temporary internal support and its corresponding first temporary steel reinforcement supports and templates to form the cover plate of zone d.

[0113] Step 13-a2: Erect a second temporary steel reinforcement support near each layer of temporary internal support in zone f, and fix the main beam and secondary beam of the temporary internal support in zone f to the second temporary steel reinforcement support respectively. At the same time, evenly lay multiple templates on the second frame formed after fixing. After laying multiple templates, according to the second preset block jump sequence, first pour the temporary internal supports of other layers below the first layer of temporary internal support in the temporary support system of zone f and their corresponding second temporary steel reinforcement supports and templates in order from top to bottom to form the slab support of zone f. Then pour the top of the cut-and-cover main structure of zone f, the first layer of temporary internal support and its corresponding first temporary steel reinforcement support and templates to form the cover plate of zone f.

[0114] Step 13-a3: Erect a third temporary steel reinforcement support near each layer of temporary internal support in zone e, and fix the main beam and secondary beam of the temporary internal support in zone e to the third temporary steel reinforcement support respectively. At the same time, lay multiple templates evenly on the third frame formed after fixing. After laying multiple templates, according to the third preset block jump sequence, first pour the temporary internal supports of other layers below the first layer of temporary internal support in the temporary support system of zone e, as well as their corresponding third temporary steel reinforcement supports and templates, in order from bottom to top to form the zone e slab support. Then pour the top of the cut-and-cover main structure of zone e, the first layer of temporary internal support, and its corresponding first temporary steel reinforcement support and templates to form the zone e cover plate.

[0115] In this embodiment, an expansion joint is reserved between each pair of adjacent templates in the multiple templates laid to avoid cracks caused by thermal expansion and contraction due to temperature changes or cracks caused by uneven settlement of the support. Preferably, the expansion joint can be filled with foam board. After all adjacent templates are poured, the expansion joint is preferably filled with micro-expansion concrete to ensure the overall stress of the subsequently poured support structure during the use stage.

[0116] Here, after erecting the temporary steel reinforcement frame and laying the formwork in the area to be poured, the large-area slab structure corresponding to the area to be poured is further divided into multiple small blocks (cells), and concrete is poured intermittently using a skip-pour method. This segmented skip-pour method reduces the impact of large-area concrete pouring, thereby controlling temperature shrinkage, reducing cracks, and improving construction efficiency. It should be noted that during concrete pouring, the construction joints between the formwork and the side wall structure must not be misaligned.

[0117] In an optional embodiment of the present invention, step 14 above may specifically include:

[0118] Step 141: The temporary pillars 6 outside area a, the temporary pillars 6 in area a, the temporary pillars 6 in area b, the temporary pillars 6 between area a and area b, and the temporary pillars 6 in area c are dismantled in sequence.

[0119] Here, the specific process for dismantling temporary pillar 6 in areas a, b, and c is the same; for example... Figure 16 As shown, in an optional embodiment of this invention, step 141 above, which involves dismantling temporary pillars at different locations, may include:

[0120] Step 1411: Cut off the connection between the cover plate formed after the completion of the pouring and the temporary column, or cut off the connection between the plate support formed after the completion of the pouring and the temporary column; the connection here can be the top weld 26 between the temporary lattice column 10 and the top cover plate, or the top weld 26 between the temporary lattice column 10 and other layer plate supports.

[0121] Step 1412: Cut the rib plate 12 welded between the multiple sections of temporary lattice columns 10 of the temporary columns 6 between two adjacent underground levels;

[0122] Step 1413: Cut the steel gusset plate 11 welded between the multiple sections of temporary lattice columns 10 of the temporary columns 6 between two adjacent underground levels.

[0123] Before dismantling the temporary columns 6 outside area a, the temporary columns 6 in area a, the temporary columns 6 in area b, the temporary columns 6 between area a and area b, and the temporary columns 6 in area c, a temporary construction platform should be erected and guardrails installed to ensure the safety of the dismantling work. It should be noted that the temporary columns 6 should be dismantled section by section from top to bottom (each section of the temporary lattice column 10), and one section of the temporary lattice column 10 should be dismantled at a time. During the dismantling process, the overall deformation and stress of the current support system should be closely monitored. After dismantling, allow one day for stress release and observe that the monitoring data is normal before proceeding with subsequent procedures.

[0124] For the pouring of floor slabs in the main structure of large-volume stations, it is essential to first rationally divide the pouring areas and pour the areas with higher stress concentration at the corners first to avoid deformation of the main structure and the two in-pit supports within the foundation pit. Figures 17 to 20 As shown, the main station structure to be constructed inside the foundation pit, excluding the two pit supports 27, can be divided into seven areas: M1, M2, M3, M4, M5, M6, and M7. Areas M1 and M7 are located on the east and west sides of the foundation pit, respectively. Areas M2 and M3 are located on either side of one of the pit supports, with M2 located west of the support and adjacent to M1, and M3 located east of the support. Areas M5 and M6 are located on either side of the other pit support, with M5 located west of the support and M6 located east of the support and adjacent to M7. Area M4 is located between areas M3 and M5.

[0125] In an optional embodiment of the present invention, step 15 above may specifically include:

[0126] Step 151, as follows Figure 17 and Figure 18As shown, the fifth underground level of the main station structure in sections M1, M4, and M7 is constructed sequentially. When pouring the floor slabs of the main station structure in sections M1, M4, and M7, appropriate expansion joints must be reserved at the connection points. Furthermore, temperature monitoring of the poured concrete must be strengthened, and heat dissipation measures must be implemented between adjacent levels of the main station structure to prevent large cracks caused by hydration heat. In addition, monitoring of deformation of the surrounding cut-and-cover main structure must be strengthened during construction.

[0127] Step 152, as follows Figure 19 and Figure 20 As shown, the main structure of the station in areas M2 and M6 will continue to be constructed, and expansion joints will be reserved at the connection points. After the main structure of the station has reached the strength requirements, the main structure in areas M3 and M5 will be constructed. After the concrete has reached the strength requirements, the fifth underground level of the main structure of the station will be closed, and the construction of this area will be completed.

[0128] Step 153: Following the process of steps 151 and 152, continue to construct the fourth and third underground levels of the station's main structure within the foundation pit. Once all parts are fully constructed, the main structure of the station will be completed and closed.

[0129] The foundation pit construction method provided in the above embodiments of the present invention involves pouring temporary internal supports in a bottom-up sequence after the main structure (cut-and-cover main structure) around the foundation pit is completed. For the main structure around the foundation pit, the supports have good rigidity and stability, and have a good suppression effect on the overall displacement of the structure within the pit. At the same time, for the soil in the foundation pit, the load of the main structure around the foundation pit can be directly transferred to the foundation through permanent columns. The supports formed after pouring and the vertical permanent columns form a rigid whole, which can not only significantly reduce uneven settlement in the pit, but also effectively reduce the bottom rebound effect of ultra-large and deep foundation pits. In addition, it can also enhance the overall stability of the soil in the foundation pit.

[0130] For construction, the main structure of the station within the ultra-large foundation pit, due to the similarity between the slab bracing and floor slab construction, can be designed according to the reinforcement standards for floor slabs. Based on numerical simulation results, local reinforcement can be applied to areas under high stress to ensure deformation complies with specifications. Furthermore, this construction method not only allows for better scheduling adjustments but also enables the slab bracing to be constructed as a semi-permanent structure during alternating forward and reverse construction, allowing for permanent adjustments after reasonable safety calculations.

[0131] Before pouring the temporary internal support slabs, the temporary columns have relatively weak support strength, but deformation control is more stringent for permanent structures. Therefore, the vertical permanent supports must be constructed first to enhance the overall strength of the support structure. The construction of permanent columns is carried out in sections, and after the permanent columns are completed, the slab supports to be poured in the foundation pit are poured in a segmented, skip-pour manner. Temporary columns are then removed alternately. Finally, after the permanent columns and slab supports in a given area are completed, all temporary columns in that area are removed. This process of replacing temporary columns with slab supports, followed by pouring the slab supports and removing the temporary columns, significantly saves on construction time, ensures the overall stability of the foundation pit support system, and effectively controls the deformation of the surrounding main structure.

[0132] The above are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principles described in the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for constructing ultra-large deep foundation pits with internal supports that do not require dismantling, characterized in that, include: The foundation pit is excavated to the depth of the bottom slab corresponding to the predetermined underground level, which is the third underground level. The main cut-and-cover structure and temporary support system for the predetermined underground level, the levels above the predetermined underground level, and the levels below the predetermined underground level are constructed. Specifically, this includes: constructing the top slab of the first underground level upwards, and constructing the bottom slab and sidewall structure of the first, second, and third underground levels downwards in reverse order; constructing temporary columns downwards, and constructing temporary internal supports for the first, second, and third underground levels upwards, fixing the temporary internal supports of each level to the temporary columns; excavating downwards to the bottom slab position of the fourth underground level, and constructing the temporary internal supports for the fifth underground level in reverse order. After support is provided, the base slab of the fourth underground level is constructed; excavation continues downward to the base slab of the fifth underground level, and the side wall structure of the fourth underground level, the base slab of the fifth underground level, and the side wall structure of the fifth underground level are constructed sequentially; wherein, the temporary columns include multiple sections of temporary lattice columns connected sequentially between adjacent underground levels, and the construction of temporary columns downward includes: arranging multiple sections of the temporary lattice columns sequentially in a vertical direction between adjacent underground levels, and welding adjacent sections of the temporary lattice columns together and connecting them with steel gusset plates and ribs; temporary column steel brackets are installed at the positions where the end temporary lattice columns between adjacent underground levels are connected to the corresponding temporary internal supports within the underground level, and are connected to the corresponding temporary internal supports within the underground level by steel beams; The temporary internal support area of ​​the temporary support system is divided into multiple areas to be constructed, nested from the outside in. Permanent columns are then constructed at predetermined positions in the corresponding areas, in an order from the outside in. The multiple areas to be constructed include area a, area b, and area c. Area c is nested within area b, and area b is nested within area a. Areas a and b are both cubic in shape, and the permanent columns constructed in areas a and b are evenly distributed along the four horizontal sides of the cube. Area c is rectangular and is located within area b along the vertical direction of the cube, with the permanent columns constructed in area c evenly distributed along the horizontal sides of the rectangle. The area where the temporary internal support to be poured in the temporary support system and the area where the top of the cut-and-cover main structure is located are divided into multiple adjacent areas to be poured from one side of the foundation pit to the other, and each area to be poured is poured in blocks according to a preset order. Remove the temporary columns in the temporary support system after the concrete pouring is completed; The main structure of the station inside the foundation pit is divided into sections, and the main structure of the station is constructed layer by layer according to the preset construction sequence of the sections.

2. The method for constructing ultra-large deep foundation pits with internal supports that do not require dismantling, as described in claim 1, is characterized in that... Permanent pillars are constructed at predetermined locations within the corresponding areas to be constructed, proceeding from the outside in, including: The steel pipe columns in each underground level of Zone A are hoisted layer by layer from bottom to top, and the two ends of the steel pipe columns in each underground level are fixed to the reserved holes on the temporary internal support of Zone A. After all the steel pipe columns in the underground levels are hoisted, concrete is poured into the steel pipe columns through the reserved grouting holes on the temporary internal support of Zone A to form permanent columns in Zone A. The steel pipe columns in each underground level of Zone B are hoisted layer by layer from bottom to top, and the two ends of the steel pipe columns in each underground level are fixed to the reserved holes on the temporary internal support of Zone B. After all the steel pipe columns in the underground levels are hoisted, concrete is poured into the steel pipe columns through the reserved grouting holes on the temporary internal support of Zone B to form permanent columns in Zone B. The steel pipe columns in each underground level of Zone C are hoisted layer by layer from bottom to top, and the two ends of the steel pipe columns in each underground level are fixed to the reserved holes on the temporary internal support of Zone C. After all the steel pipe columns in the underground levels are hoisted, concrete is poured into the steel pipe columns through the reserved grouting holes on the temporary internal support of Zone C to form permanent columns in Zone C.

3. The method for constructing ultra-large deep foundation pits with internal supports that do not require dismantling, as described in claim 2, is characterized in that... Permanent pillars are installed at predetermined locations within the corresponding areas to be constructed, proceeding from the outside in. This also includes: Vertical stiffening plates and horizontal stiffening plates are installed at the connection nodes between temporary internal supports and steel pipe columns at any underground level. The vertical stiffening plates are installed on the outside of the steel pipe column, and the horizontal stiffening plates are installed inside the steel pipe column. A sleeve is provided below the connection node, and the sleeve is fitted over the outside of the steel pipe column; Additional flange reinforcing ribs are welded at the connection node, and the additional flange reinforcing ribs bypass the steel pipe column and are connected to the sleeve.

4. The method for constructing ultra-large deep foundation pits with internal supports that do not require dismantling, as described in claim 1, is characterized in that... The multiple areas to be poured include area d, area e, and area f; wherein area e is located between area d and area f.

5. The method for constructing ultra-large deep foundation pits with internal supports that do not require dismantling, as described in claim 4, is characterized in that... Each area to be poured will be poured in sections according to a preset sequence, including: According to the first preset block jump sequence, the other layers of temporary internal supports below the first layer of temporary internal supports in the temporary support system of the d area are cast into the d area plate support, and the first layer of temporary internal supports in the temporary support system of the d area and the top of the cut-and-cover main structure are cast into the d area cover plate. According to the second preset block jump sequence, the other layers of temporary internal supports below the first layer of temporary internal supports in the temporary support system of the f area are cast into the f area plate support, and the first layer of temporary internal supports in the temporary support system of the f area and the top of the cut-and-cover main structure are cast into the f area cover plate. According to the third preset block jump sequence, the other layers of temporary internal supports below the first layer of temporary internal supports in the temporary support system of zone e are cast into the slab support of zone e, and the first layer of temporary internal supports in the temporary support system of zone e and the top of the cut-and-cover main structure are cast into the cover plate of zone e.

6. The method for constructing ultra-large deep foundation pits with internal supports that do not require dismantling, as described in claim 1, is characterized in that... The temporary columns in the temporary support system after the concrete pouring is completed are removed, including: The temporary pillars outside area a, the temporary pillars in area a, the temporary pillars in area b, the temporary pillars between area a and area b, and the temporary pillars in area c are dismantled in sequence.

7. The method for constructing ultra-large deep foundation pits with internal supports that do not require dismantling, as described in claim 6, is characterized in that... The temporary pillars outside area a, the temporary pillars in area a, the temporary pillars in area b, the temporary pillars between area a and area b, and the temporary pillars in area c are dismantled sequentially, including: Cut off the connection between the cover plate formed after the pouring is completed and the temporary column, or cut off the connection between the plate support formed after the pouring is completed and the temporary column; Cut off the ribs welded between the multiple sections of the temporary lattice columns of the temporary columns between two adjacent underground levels; Cut off the steel gusset plates welded between the multiple sections of the temporary lattice columns of the temporary columns between two adjacent underground levels.

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