An assembled steel lattice column for foundation pit support and a construction method thereof

Abstract

The present application relates to a kind of assembled steel lattice column for foundation pit support and its construction method, and the assembled steel lattice column for foundation pit support includes top fixed node, standard node, floor conversion node, support beam conversion node, permanent buried node, each layer of basement is equipped with standard node, floor conversion node is equipped with on the floor of each layer of basement, support beam conversion node is correspondingly equipped with on the support beam between adjacent two layers of basement, top fixed node is correspondingly buried on the support beam of the top of basement, permanent buried node is buried on the column pile of basement, and support platform is equipped on top fixed node and support beam conversion node, and support beam is supported on corresponding support platform.The beneficial effects of the present application are that after the completion of basement structure construction, the remaining segments of steel lattice column can be removed without damage except for permanent buried node, the removal method is simple, the removal efficiency is high, the reusability of steel lattice column can be greatly improved, and the material cost can be effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of building engineering technology, specifically to a prefabricated steel lattice column for foundation pit support and its construction method. Background Technology

[0002] Steel lattice columns are the most commonly used column structure for horizontal support in deep foundation pits. Traditionally, steel lattice columns are welded as a single unit from top to bottom. After the basement structure is completed, they are dismantled section by section by cutting them apart. This process is not only difficult and inefficient, but also results in low reuse rates and increased material costs. Furthermore, traditional steel lattice columns penetrate floor slabs by leaving openings before pouring concrete. As supports and beams are removed, the bending length of the steel lattice columns gradually increases. With large basement heights, excessive bending length can lead to overall instability of the steel lattice columns, posing a safety hazard to the foundation pit. Alternatively, using higher-grade steel lattice columns may be necessary, significantly increasing costs. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a prefabricated steel lattice column for foundation pit support and its construction method, which can solve the problems of difficult dismantling, low efficiency, low reusability and high material cost caused by the overall welding of traditional steel lattice columns.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] A prefabricated steel lattice column for foundation pit support includes a top fixed section, standard sections, floor slab transition sections, support beam transition sections, and permanently embedded sections. Each basement level has a standard section, and each basement floor slab has a floor slab transition section running through it. Corresponding support beam transition sections run through the support beams between adjacent basement levels. The standard sections, support beam transition sections, and floor slab transition sections between adjacent basement levels are detachably connected from top to bottom via connecting steel plates and fastening components. A top fixed section is embedded in the support beam at the top of the basement. The top fixed section, the floor slab transition section at the top of the basement, and the standard section at the top of the basement are connected... The components are detachably connected from top to bottom via connecting steel plates and fastening components. Permanently embedded sections are installed on the basement column piles. The permanently embedded sections and the standard sections of the basement floor are detachably connected via connecting steel plates and fastening components. Support platforms are provided on the top fixed section and the support beam transition section. The support beams are supported on the corresponding support platforms. The support platform includes a first fixed plate, a second fixed plate, stiffening ribs, and a support plate. One end of the first fixed plate is vertically welded to one end of the bottom surface of the second fixed plate. The stiffening ribs are vertically welded to the bottom surface of the second fixed plate and perpendicularly welded to the surface of the first fixed plate. The support plate is anchored to the top surface of the second fixed plate, and the support beams are supported on the support plates.

[0006] Furthermore, the permanently embedded section, standard section, support beam transfer section, floor slab transfer section, and top fixed section all include four L-shaped angle steels arranged symmetrically in pairs. The two adjacent L-shaped angle steels in the permanently embedded section and standard section are detachably connected by a gusset plate.

[0007] Furthermore, the L-shaped angle steel is provided with a first connecting hole at its end, and a second connecting hole is provided on the connecting steel plate. The L-shaped angle steel is detachably connected to the connecting steel plate through the fastening components, the first connecting hole, and the second connecting hole.

[0008] Furthermore, the first fixing plate is detachably connected to the L-shaped angle steel.

[0009] Furthermore, based on the above-mentioned prefabricated steel lattice columns for foundation pit support, the present invention also provides a construction method for prefabricated steel lattice columns for foundation pit support, comprising the following steps:

[0010] The number and length of each segment of the steel lattice column structure are determined based on the basement structure. The segment of the steel lattice column structure is selected through finite element simulation. Then, the segments of the steel lattice column structure are spliced ​​together to form the steel lattice column structure.

[0011] After the basement column piles are poured, the steel lattice column structure is sunk so that the lower end of the permanent embedded section is embedded in the column pile. The sinking depth of the steel lattice column structure is controlled by the long-distance laser positioning control method.

[0012] The construction positions of the support beams for each floor of the basement are excavated from top to bottom in the basement foundation pit. At the bottom of the construction position of each support beam, a pit is excavated to accommodate the support platform. The support platform is installed on the top fixed section and the support beam transition section. Foam paper is wrapped around the top fixed section and the support beam transition section. The support beams for each floor are constructed from top to bottom. The top of the top fixed section is buried in the corresponding support beam, the support beam transition section passes through the corresponding support beam, and the support platform supports the corresponding support beam.

[0013] The construction location of the basement floor slab is excavated in the basement foundation pit, and then the floor slab is constructed. A reserved post-pouring hole is set at the permanent embedded section to expose the connection joint between the permanent embedded section and the standard section, so that the standard section above the permanent embedded section can be removed without damage later.

[0014] Foam paper is wrapped around the floor slab transfer joint. The floor slabs of each basement level are constructed from bottom to top at the floor slab construction positions below the support beams of each level, and the floor slab transfer joints are made to penetrate the corresponding floor slabs. After the construction of each basement floor slab is completed and the floor slab concrete reaches the required strength, the basement support beams are removed layer by layer, and the load of the support beams is transferred to the floor slabs.

[0015] Remove the connecting steel plate and fastening components between the top floor slab transfer section and the top fixed section of the basement, then remove the top fixed section. Next, remove the floor slab transfer sections, standard sections and support beam transfer sections of each basement floor in sequence from top to bottom, and repair the reserved post-pouring holes formed on the bottom slab and the post-pouring holes formed on the floor slab after removal.

[0016] Furthermore, the long-distance laser positioning control method is used to control the sinking depth of the steel lattice column structure, including the following steps:

[0017] A laser instrument and a fixed ruler are set up on opposite sides of the foundation pit area. The laser instrument is set up on a base with a known elevation. During the sinking of the steel lattice column structure, a horizontal laser is emitted by the laser instrument. The horizontal laser is calibrated and its elevation is determined by the fixed ruler. Based on the elevation of the horizontal laser, the sinking depth of the steel lattice column structure is controlled by moving the ruler.

[0018] Furthermore, the removal of the floor slab transfer sections, standard sections, and supporting beam transfer sections on each basement level includes the following steps:

[0019] Remove the connecting steel plate and fastening components between the floor slab transition section and the standard section, without pulling out the L-shaped angle steel of the floor slab transition section. Anchor the suspension rod on the lacing plate at the top of the standard section. Then remove the connecting steel plate and fastening components at the lower end of the support beam transition section. Next, pull out the L-shaped angle steel of the floor slab transition section. Use a forklift to support the suspension rod and invert the standard section and the support beam transition section together in the preset direction.

[0020] Furthermore, when repairing the pre-cast holes formed on the foundation slab and the post-cast holes formed on the floor slab, the following steps are included:

[0021] The bottom surface of the reserved post-pouring hole on the flat base plate is cut off, the protruding steel lattice column structure is removed, the surface of the reserved post-pouring hole on the base plate is roughened and cleaned, and then repair concrete is poured into the reserved post-pouring hole on the base plate to fill the reserved post-pouring hole on the base plate.

[0022] A baffle is installed at the bottom of the post-cast hole in the floor slab, and then repair cement mortar is poured into the post-cast hole in the floor slab to fill the post-cast hole in the floor slab.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The prefabricated steel lattice column for foundation pit support of the present invention has segments that are detachably connected by connecting steel plates and fastening components. After the basement structure is completed, except for the permanently embedded segments, the remaining segments of the steel lattice column can be dismantled without damage. The dismantling method is simple and efficient, which can greatly improve the reuse rate of the steel lattice column and effectively reduce material costs. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of an overall structure of the steel lattice support structure in this invention;

[0026] Figure 2 This is a schematic diagram of another overall structure of the steel lattice support structure in this invention;

[0027] Figure 3 for Figure 2 Enlarged schematic diagram of the structure at point A in the diagram;

[0028] Figure 4 for Figure 2 Enlarged schematic diagram of the structure at point B in the diagram;

[0029] Figure 5 This is a schematic diagram of the structure of the permanently embedded joint in this invention;

[0030] Figure 6 This is a schematic diagram of the standard section in this invention;

[0031] Figure 7 This is a schematic diagram of the floor slab transfer joint in this invention;

[0032] Figure 8 This is a schematic diagram of the support beam transfer joint in this invention;

[0033] Figure 9 This is a schematic diagram of the top fixing section in this invention;

[0034] Figure 10 for Figure 9 A schematic diagram of the cross-sectional structure in the CC direction;

[0035] Figure 11 for Figure 9 A schematic diagram of the cross-sectional structure in the DD direction;

[0036] Figure 12 This is a schematic diagram of the connecting steel plate structure in this invention;

[0037] Figure 13 for Figure 12 Enlarged schematic diagram of the structure at point E in the diagram;

[0038] Figure 14 This is a schematic diagram of the construction process of the steel lattice support structure in this invention;

[0039] Figure 15 This is a schematic diagram of the earthwork excavation for the first supporting beam in this invention;

[0040] Figure 16 This is a construction schematic diagram of the basement support beam in this invention;

[0041] Figure 17This is a construction diagram of the basement floor slab in this invention;

[0042] Figure 18 This is a schematic diagram of the settlement control of the steel lattice support structure in this invention;

[0043] Figure 19 This is a schematic diagram of the dismantling of the steel lattice support structure in this invention;

[0044] Figure 20 This is a schematic diagram illustrating the repair of the basement floor slab and basement bottom slab in this invention;

[0045] Figure 21 This is a front view schematic diagram of the support platform structure in this invention;

[0046] Figure 22 This is a bottom view of the support platform structure in this invention;

[0047] Figure 23 for Figure 21 A schematic diagram of the cross-sectional structure in the FF direction.

[0048] 101. Support beam; 101a. First depth ground; 101b. Pit; 102. Floor slab; 102a. Repair cement mortar; 103. Base slab; 103a. Reserved post-cast hole; 103b. Repair concrete; 104. Column pile; 105. Pit bottom; 2. Steel lattice column structure; 201. Permanently embedded section; 202. Standard section; 202a. Suspension rod; 203. Floor slab transition section; 204. Support beam transition section; 205. Top fixed section; 206. Support platform; 206a. First fixed plate; 206b. Second... Fixed plate; 206c, stiffening rib; 206d, support plate; 206e, third bolt hole; 206f, third bolt hole reinforcing protrusion; 206g, fourth bolt hole; 207, foam paper; 3, connecting steel plate; 4, high-strength bolt; 401, first bolt hole; 401a, first bolt hole reinforcing protrusion; 402, second bolt hole; 402a, second bolt hole reinforcing protrusion; 5, L-shaped angle steel; 6, lacing plate; 701, laser instrument; 702, base; 703, fixed ruler; 704, horizontal laser line; 705, movable ruler. Detailed Implementation

[0049] The present invention will be further described below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following description.

[0050] like Figures 1-13 , Figures 16-17As shown, a prefabricated steel lattice column for foundation pit support is used for foundation pit support, including a top fixed section 205, a standard section 202, a floor slab transition section 203, a support beam transition section 204, and a permanently embedded section 201. Each basement level is equipped with a standard section 202, and each basement floor slab 102 is equipped with a floor slab transition section 203. A support beam transition section 204 is correspondingly installed on the support beam 101 between two adjacent basement levels. The standard section 202, support beam transition section 204, and floor slab transition section 203 between two adjacent basement levels are detachably connected from top to bottom via connecting steel plates 3 and fastening components. A top fixing section 205 is correspondingly embedded on the support beam 101 at the top of the basement. The top fixing section 205, the floor slab transition section 203 at the top of the basement, and the standard section 202 at the top of the basement are detachably connected from top to bottom via connecting steel plates 3 and fastening components. A permanent embedded section 201 is embedded in the column pile 104 of the basement. The permanent embedded section 201 and the standard section 202 at the bottom of the basement are detachably connected via connecting steel plates 3 and fastening components. A support platform 206 is provided on the top fixing section 205 and the support beam transition section 204, and the support beam 101 is supported on the corresponding support platform 206.

[0051] Both the permanently embedded section 201 and the standard section 202 include four L-shaped angle steels 5 and a detachable connecting plate 6 between two adjacent L-shaped angle steels 5. Both the floor transition section 203 and the top fixed section 205 include four L-shaped angle steels 5.

[0052] The permanent embedded section 201, standard section 202, floor slab transition section 203, and top fixed section 205 are sequentially spliced ​​together by connecting steel plates and 3 fastening components.

[0053] Among them, the four L-shaped angle steels 5 are symmetrically arranged in pairs, and there is a certain interval between the two adjacent L-shaped angle steels 5.

[0054] In this embodiment, the permanently embedded section 201 and the standard section 202 are detachably connected by a connecting steel plate and a fastening assembly. The standard section 202 and the floor transition section 203 are detachably connected by a connecting steel plate 3 and a fastening assembly. The floor transition section 203 and the top fixed section 205 are detachably connected by a connecting steel plate 3 and a fastening assembly. The fastening assembly is a high-strength bolt 4.

[0055] The four L-shaped angle steels 5 of the permanently embedded section 201 are connected by the gusset plate 6 to form the permanently embedded section 201. Figure 5 As shown, the length of the permanently embedded section 201 Including the depth of the inserted column pile and the length embedded in the basement floor slab Based on the required depth of the inserted pile and the thickness of the basement, one of the following lengths of the permanently embedded section 201 can be selected: 4m, 6m, and 8m. The insertion depth of the pile can be... , For safety, a value of 2.0 to 2.5 is used. This refers to the vertical bearing capacity of the steel lattice column structure, expressed in N (newtons). This is the design value of the axial compressive strength of concrete, in N / mm². 2 , The cross-sectional area of ​​the steel lattice column structure is expressed in mm². 2 , This refers to the perimeter of the cross-section of the steel lattice column structure, in mm. This is the design value for the tensile strength of concrete, in N / mm². 2 .

[0056] The four L-shaped angle steels 5 of standard section 202 are connected by the lacing plate 6 to form standard section 202. For example... Figure 6 As shown, the length of the first standard section 202 is... Includes 2 connection segments and standard segments Depending on the floor height, one of the following options can be selected: 1200mm, 1500mm, 1800mm, 2100mm, and 2400mm.

[0057] like Figure 7 As shown, the floor slab transfer joint 203 is formed by four L-shaped angle steels 5. The length of the floor slab transfer joint 203 is... Includes 2 connection segments and floor transition section It can be set to a fixed length of 600mm.

[0058] like Figure 9 As shown, the top fixing section 205 is formed by four L-shaped angle steels 5. The length of the top fixing section 205 is... Including connection segments Support platform section and fixed section It can be set to a fixed length of 900mm.

[0059] The L-shaped angle steel used to manufacture the permanent embedded section 201, standard section 202, floor slab transition section 203 and top fixed section 205 can be selected from one of the following sizes: L120mm×12mm, L140mm×14mm, L160mm×16mm and L180mm×18mm. The steel strength grade can be Q235B or Q345B.

[0060] The cross-sectional dimensions of the permanently embedded section 201, standard section 202, floor transition section 203, and top fixed section 205 can be one of 420mm, 440mm, and 460mm. Correspondingly, the connecting steel plates and lacing plates 6 of the permanently embedded section 201 and standard section 202 can be selected from one of the following sizes: 400mm×300mm×12mm, 420mm×300mm×12mm, and 440mm×300mm×12mm.

[0061] For basements with a single floor, the prefabricated steel lattice columns for foundation pit support are assembled sequentially from a permanently embedded section 201, a standard section 202, a floor slab transition section 203, and a top fixed section 205.

[0062] In the embodiments of this application, the segments of the prefabricated steel lattice column for foundation pit support are detachably connected by connecting steel plates 3 and fastening components. After the basement structure is completed, except for the permanently embedded segments, the remaining segments of the prefabricated steel lattice column for foundation pit support can be dismantled without damage. The dismantling method is simple and efficient, which can greatly improve the reusability of the steel lattice column structure and effectively reduce material costs.

[0063] For basement floors with multiple floors, the number of standard sections 202 is greater than or equal to 2. The prefabricated steel lattice column for foundation pit support also includes at least one support beam transfer section 204. The number of support beam transfer sections 204 is one less than the number of standard sections 202. The support beam transfer section 204 includes four L-shaped angle steels 5.

[0064] A floor slab transition section and a support beam transition section 204 are sequentially spliced ​​together between two adjacent standard sections via connecting steel plates 3 and fastening components.

[0065] In this embodiment of the application, when the number of standard sections 202 is equal to 2, such as Figure 2 As shown, the prefabricated steel lattice column for foundation pit support is assembled sequentially from a permanently embedded section 201, a standard section 202, a floor slab transfer section 203, a support beam transfer section 204, and a top fixed section 205. This type of column is suitable for basements with two floors. The sum of the lengths of the standard section 202, floor slab transfer section 203, and support beam transfer section 204 equals the height of the second basement level. The sum of the lengths of the standard section 202, floor slab transfer section 203, and top fixed section 205 equals the height of the first basement level.

[0066] The permanently embedded section 201 is detachably connected to the standard section 202 via connecting steel plate 3 and fastening components. The standard section 202 is detachably connected to the floor slab transition section 203 via connecting steel plate 3 and fastening components. The floor slab transition section 203 is detachably connected to the support beam transition section 204 via connecting steel plate 3 and fastening components. Figure 3 As shown, the support beam transition section 204 and the standard section 205 are detachably connected via connecting steel plate 3 and fastening components, as follows: Figure 4 As shown, the floor transition section 203 and the top fixed section 205 are detachably connected by a connecting steel plate 3 and a fastening assembly.

[0067] When the number of standard sections 202 is equal to 3, the prefabricated steel lattice column for foundation pit support is assembled sequentially from one permanently embedded section 201, one standard section 202, one floor slab transfer section 203, one support beam transfer section 204, another standard section 202, another floor slab transfer section 203, another support beam transfer section 204, another standard section 202, another floor slab transfer section 203, and one top fixed section 205. This is suitable for basements with 3 floors. The sum of the lengths of the standard section 202, floor slab transfer section 203, and support beam transfer section 204 is the height of the third basement level. The sum of the lengths of the standard section 202, floor slab transfer section 203, and support beam transfer section 204 is the height of the second basement level. The sum of the lengths of the standard section 202, floor slab transfer section 203, and top fixed section 205 is the height of the first basement level.

[0068] When the number of standard sections 202 is greater than 3, the above-mentioned cases where the number of standard sections 202 is 2 or 3 can be referred to, and will not be repeated here.

[0069] like Figure 8 As shown, the support beam transfer section 204 is formed by four L-shaped angle steels 5. The length of the support beam transfer section 204 is... Includes 2 connection segments Support platform section and support beam transition section It can be set to a fixed length of 1500mm.

[0070] The L-shaped angle steel used to fabricate the support beam transfer section 204 can be one of the following sizes: L120mm×12mm, L140mm×14mm, L160mm×16mm, and L180mm×18mm. The steel strength grade can be Q235B or Q345B. The cross-sectional dimensions of the support beam transfer section 204 can be one of 420mm, 440mm, and 460mm.

[0071] In one embodiment, the top of the L-shaped angle steel 5 of the permanently embedded section 201, the top and bottom of the L-shaped angle steel 5 of the standard section 202, the top and bottom of the L-shaped angle steel 5 of the floor slab transition section 203, and the bottom of the L-shaped angle steel 5 of the top fixing section 205 are all provided with a first connecting hole, and a second connecting hole corresponding to the first connecting hole is provided on the connecting steel plate.

[0072] The fastening assembly passes through the second connection hole and the first connection hole, and the permanently embedded section 201, standard section 202, floor slab transition section 203 and top fixed section 205 are spliced ​​together in sequence.

[0073] The first connecting hole includes, but is not limited to, bolt holes and pin holes, and the second connecting hole includes, but is not limited to, rivet holes. Correspondingly, the fastening component can be a bolt or a rivet.

[0074] In the embodiments of this application, such as Figure 5 As shown, the upper end of the L-shaped angle steel 5 permanently embedded in section 201 is provided with a first bolt hole 401 for anchoring the steel plate, while the lower end may not have a bolt hole. Figure 6 As shown, the L-shaped angle steel 5 of standard section 202 is symmetrically provided with first bolt holes 401 for anchoring and connecting steel plates at both ends.

[0075] like Figure 7 As shown, the L-shaped angle steel 5 of the floor slab transition section 203 is symmetrically provided with first bolt holes 401 for anchoring the steel plate; as Figure 9 As shown, the lower end of the L-shaped angle steel 5 of the top fixing section 205 is provided with a first bolt hole 401 for anchoring the steel plate.

[0076] In this embodiment, bolts are passed sequentially through the connecting holes of the connecting steel plate and the L-shaped angle steel 5, and the bolts are tightened with nuts. This allows the permanently embedded section 201, the standard section 202, the floor slab transition section 203, and the top fixed section 205 to be firmly spliced ​​into a steel lattice column structure 2.

[0077] In one embodiment, the top of the L-shaped angle steel 5 of the permanently embedded section 201, the top and bottom of the L-shaped angle steel 5 of the standard section 202, the top and bottom of the L-shaped angle steel 5 of the floor slab transfer section 203, the top and bottom of the L-shaped angle steel 5 of the support beam transfer section 204, and the bottom of the L-shaped angle steel 5 of the top fixing section 205 are all provided with first connecting holes, and the connecting steel plate is provided with second connecting holes corresponding to the first connecting holes;

[0078] The fastening assembly passes through the second connection hole and the first connection hole, and sequentially splices together the permanently embedded section 201, at least one standard section 202, at least one floor slab transition section 203, at least one support beam transition section 204, and the top fixed section 205.

[0079] In the embodiments of this application, such as Figure 5 As shown, the upper end of the L-shaped angle steel 5 permanently embedded in section 201 is provided with a first bolt hole 401 for anchoring the steel plate 3, while the lower end may not have a bolt hole. Figure 6 As shown, the L-shaped angle steel 5 of standard section 202 is symmetrically provided with first bolt holes 401 at both ends for anchoring and connecting the steel plate 3.

[0080] like Figure 7 , Figure 8 As shown, the L-shaped angle steel 5 of the floor slab transfer section 203 and the support beam transfer section 204 are symmetrically provided with first bolt holes 401 for anchoring the steel plate 3. Figure 9 As shown, the lower end of the L-shaped angle steel 5 of the top fixing section 205 is provided with a first bolt hole 401 for anchoring the steel plate 3.

[0081] In this embodiment, bolts are passed sequentially through the connecting holes of the connecting steel plate and the L-shaped angle steel, and the bolts are tightened with nuts. This allows the permanently embedded section 201, standard section 202, floor slab transition section 203, support beam transition section 204, and top fixed section 205 to be firmly spliced ​​into a steel lattice column structure 2.

[0082] In an optional embodiment, a bolt hole reinforcing protrusion may be provided inside the bolt hole of the L-shaped angle steel 5. Taking the top fixing section 205 as an example, the bottom of the top fixing section 205 is connected to the top of the floor slab transition section 203 via a connecting steel plate, bolts, and nuts. Therefore, as... Figure 10 As shown, a first bolt hole reinforcing protrusion 401a can be provided inside the first bolt hole 401 of the L-shaped angle steel 5 corresponding to the connecting section of the top fixing section 205. During subsequent basement structure construction, such as... Figure 8 , Figure 12 As shown, a support platform needs to be installed on the top fixed section 205. Therefore, as... Figure 11 As shown, a first bolt hole reinforcing protrusion 401a can be provided inside the first bolt hole 401 of the L-shaped angle steel 5 corresponding to the support platform section of the top fixed section 205.

[0083] By setting a first bolt hole reinforcing protrusion 401a inside the bolt hole of the L-shaped angle steel 5, the connection between each segment of the steel lattice column structure 2 and the bolts and nuts through the connecting steel plates can be made more secure.

[0084] In an optional embodiment, such as Figure 12 As shown, the connecting steel plate 3 is provided with second bolt holes 402 corresponding to each segment, such as... Figure 13 As shown, a second bolt hole reinforcing protrusion 402a may be provided on the outer side of the second bolt hole 402.

[0085] By setting a second bolt hole reinforcing protrusion 402a on the outside of the second bolt hole 402 of the connecting steel plate 3, the connection between each segment of the steel lattice column structure and the bolts and nuts through the connecting steel plate can be made more secure.

[0086] like Figures 1-20 As shown, the construction of the prefabricated steel lattice columns for foundation pit support includes the following steps:

[0087] (1) Determine the number and length of each segment of the steel lattice column structure 2 according to the basement structure, select each segment of the steel lattice column structure 2 through finite element simulation, and then splice each segment of the steel lattice column structure 2 into the steel lattice column structure 2.

[0088] (2) After the basement column pile 104 is poured, the steel lattice column structure is sunk so that the lower end of the permanent embedded section 201 is embedded in the column pile 104. The sinking depth of the steel lattice column structure is controlled by the long-distance laser positioning control method.

[0089] More specifically, when using the long-distance laser positioning control method to control the sinking depth of the steel lattice column structure, a laser instrument 701 and a fixed ruler 703 are respectively set up on opposite sides of the foundation pit area. The laser instrument 701 is set up on a base 702 with a known elevation. During the sinking process of the steel lattice column structure 2, a horizontal laser line 704 is emitted by the laser instrument 701. The horizontal laser line 704 is calibrated and its elevation is determined by the fixed ruler 703. Based on the elevation of the horizontal laser line 704, the sinking depth of the steel lattice column structure 2 is controlled by moving the ruler 705.

[0090] (3) Excavate the construction positions of the support beams 101 of each floor of the basement from top to bottom in the basement foundation pit, and excavate the pit 101b at the bottom of the construction position of the support beams 101 of each floor to accommodate the support platform 206. Install the support platform 206 on the top fixed section 205 and the support beam transition section 204, and wrap the top fixed section 205 and the support beam transition section 204 with foam paper 207. Construct the support beams 101 of each floor from top to bottom, and bury the top of the top fixed section 205 into the corresponding support beam 101, so that the support beam transition section 204 passes through the corresponding support beam 101, and the support platform 206 supports the corresponding support beam 101.

[0091] (4) Excavate the construction position of the basement floor slab 103 in the basement foundation pit, then construct the floor slab 103, and set a reserved post-pouring hole 103a at the permanent embedded section 201 to expose the connection joint between the permanent embedded section 201 and the standard section 202 so that the standard section 202 above the permanent embedded section 201 can be removed without damage in the future.

[0092] (5) Wrap foam paper 207 around the floor slab transfer joint 203. Construct the floor slabs 102 of each basement level from bottom to top at the construction position of the floor slabs 102 below the support beams 101 of each level, and make the floor slab transfer joint 203 penetrate the corresponding floor slabs 102. After the construction of each basement floor slab 102 is completed and the concrete of the floor slab 102 reaches the required strength, remove the basement support beams 101 layer by layer and transfer the load of the support beams 101 to the floor slabs 102.

[0093] (6) Remove the connecting steel plate 3 and fastening components between the top floor slab transition section 203 and the top fixed section 205 of the basement, then remove the top fixed section 205, and then remove the floor slab transition sections 203, standard sections 202 and support beam transition sections 204 of each floor of the basement from top to bottom, and repair the reserved post-pouring hole 103a formed on the bottom slab 103 and the post-pouring hole formed on the floor slab 102 after removal.

[0094] More specifically, when dismantling the floor slab transition section 203, standard section 202, and support beam transition section 204 of each basement floor, remove the connecting steel plate 3 and fastening components between the floor slab transition section 203 and the standard section 202, without removing the L-shaped angle steel 5 of the floor slab transition section 203. Anchor the suspension rod 202a on the lacing plate 6 at the top of the standard section 202. Then remove the connecting steel plate 3 and fastening components at the lower end of the support beam transition section 204. Next, remove the L-shaped angle steel 5 of the floor slab transition section 203. Using a forklift to support the suspension rod 202a, invert the standard section 202 and the support beam transition section 204 together in the preset direction.

[0095] When repairing the reserved post-cast hole 103a formed on the base slab 103 and the post-cast hole formed on the floor slab 102, the bottom surface of the reserved post-cast hole 103a on the base slab 103 is flush with the bottom surface, the protruding steel lattice column structure 2 is cut off, the surface of the reserved post-cast hole 103a on the base slab is roughened and cleaned, and then repair concrete 103b is poured into the reserved post-cast hole 103a on the base slab 103 to fill the reserved post-cast hole 103a on the base slab 103; a baffle is set at the bottom of the post-cast hole on the floor slab 102, and then repair cement mortar 102a is poured into the post-cast hole on the floor slab 102 to fill the post-cast hole on the floor slab 102.

[0096] like Figure 14 As shown, for a single-story basement, the construction method for prefabricated steel lattice columns used for foundation pit support includes the following steps:

[0097] S10. Based on the location of the supporting beam, floor slab, basement floor slab, foundation pit ground, the embedment depth of the steel lattice column structure into the column piles, and the height of the basement floors, determine the length and quantity of each segment of the steel lattice column structure. Determine the model and size of the relevant components of the steel lattice column structure through finite element simulation. Produce all segments and related components in the factory or transport them from the previous construction site. Assemble all segments and related components to obtain the steel lattice column structure 2.

[0098] All segments and related components produced in the factory or transported from the previous construction site need to be pre-assembled to ensure that the assembly accuracy and the dimensions of the assembled structure meet the requirements.

[0099] In this embodiment, the determination of the model and size of the relevant components of the steel lattice column structure is achieved by using commercial finite element software to simulate the most unfavorable working conditions of foundation pit support and earthwork excavation, and to obtain the maximum axial force, shear force and moment at the intersection of the steel lattice column structure and the support beam; the model of the steel lattice column structure and the support platform is selected based on the maximum axial force, shear force and moment of the node, and the high-strength bolts 4 and bolt hole sizes for anchoring the components are designed; the specific design calculations refer to the "Code for Design of Steel Structures" GB 50017.

[0100] For a single-story basement, the steel lattice column structure is assembled sequentially from a permanently embedded section 201, a standard section 202, a floor slab transition section 203, and a top fixed section 205.

[0101] S20. After the concrete pouring of the column pile is completed, the steel lattice column structure is lowered into the column pile so that the bottom of the permanent embedded section 201 is embedded in the column pile.

[0102] Among them, column piles are a type of pile structure that is deeply buried underground. Their main function is to transfer the load generated by the foundation pit support structure to the ground, ensuring the stability and safety of the building.

[0103] In this embodiment, the construction of the column pile typically includes steps such as drilling, cleaning the hole, placing the reinforcing cage, and pouring concrete. Before the concrete of the column pile solidifies, the assembled steel lattice column structure is sunk into the column pile, so that the bottom of the permanently embedded section 201 is embedded in the column pile.

[0104] S30. Excavate downwards to the bottom elevation of the first support beam at the location of the first support beam. Dig a pit for installing the support platform below the first support beam and at the top fixed section. Install the support platform on the top fixed section. Wrap the top fixed section with foam paper 207. Perform formwork, tie steel bars, and pour concrete on the ground at the bottom elevation of the first support beam to form the first support beam, so that the top of the top fixed section is buried in the first support beam. The location of the first support beam is the support beam with the largest height among the multiple support beam locations.

[0105] Formwork erection is a preparatory step before concrete pouring, aiming to create a space for concrete pouring and ensure the concrete maintains the correct shape and dimensions during pouring and hardening. Specifically, formwork erection includes surveying and setting out, formwork installation, and formwork fixing.

[0106] Among them, steel bars are the main part of concrete structures that bear tensile forces, and tying steel bars is an important step to ensure the strength of the structure.

[0107] Among them, pouring concrete involves pouring concrete material into a formwork to form a concrete structure with a specific shape and size.

[0108] In the embodiments of this application, such as Figure 1 , Figure 15 As shown, a pit 101b is dug below the first ground depth 101a and near the top fixed section. A support platform is installed on the top fixed section to support the first support beam. Foam paper 207 is wrapped around the top fixed section to facilitate its removal later.

[0109] S40. Excavate down to the bottom elevation of the basement floor slab, tie steel bars and pour concrete on the ground at the basement floor slab elevation to form the basement floor slab 103, and set a reserved post-pouring hole 103a at the permanent embedded section 201 to expose the connection joint between the permanent embedded section 201 and the standard section 202, so as to remove the standard section 202 above the permanent embedded section 201 without damage in the future.

[0110] The top of the permanently embedded section 201 is located below the upper surface of the basement floor slab 103, and the part below the top is located inside the column pile.

[0111] In this embodiment, the excess concrete of the column pile 104 is removed at a position 200mm-300mm above the bottom surface 105 of the foundation pit. A box-shaped formwork with dimensions of 800mm×800mm×350mm is made at the position of the steel lattice column structure 2, 200mm-300mm below the elevation of the upper surface of the basement floor slab 103. This allows for the pre-reserved post-pouring hole 103a with a depth of 200mm-300mm to be reserved at the position of the steel lattice column structure 2 when the basement floor slab 103 is poured with concrete, so that the standard section 202 permanently embedded above the section 201 can be removed without damage in the future.

[0112] S50. After the concrete of the basement floor slab 103 has hardened to the required strength, foam paper 207 is wrapped around the floor slab transfer joint that penetrates the basement floor slab. Formwork is then erected, steel bars are tied, and concrete is poured at the corresponding basement structural columns, beams, basement floor slabs, and the locations between the basement floor slab and the maintenance structure to form the basement floor slab and the replacement support structure. The floor slab transfer joint 203 penetrates the basement floor slab. After the concrete has reached the required strength, the support beam above the basement floor slab is removed, and the load of the support beam is transferred to the first basement floor slab.

[0113] In the embodiments of this application, such as Figure 1 As shown, basement floor 102 is obtained by setting up formwork, tying reinforcing bars, and pouring concrete at the locations of basement structural columns, beams, first basement floor slab, and between the first basement floor slab and the maintenance structure.

[0114] By applying the embodiments of this application, the first support beam, the basement floor slab, and the first basement floor slab are constructed sequentially. Then, the first support beam is removed, and the supporting force provided by the support beam is converted into the supporting force provided by the basement floor slab. The top fixed section of the steel lattice column, the floor slab transition section 203, and the standard section 202 can be gradually removed, the opening can be repaired, and the construction of the first basement floor can be completed.

[0115] For a two-story basement, the construction method for using prefabricated steel lattice columns for foundation pit support includes the following steps:

[0116] S100. Based on the location of the supporting beam, floor slab, basement floor slab, foundation pit ground, the embedment depth of the steel lattice column structure into the column piles, and the height of the basement floors, determine the length and quantity of each segment of the steel lattice column structure. Use finite element simulation to determine the model and size of the relevant components of the steel lattice column structure. Produce all segments and related components in the factory or transport them from the previous construction site. Assemble all segments and related components to obtain the steel lattice column structure.

[0117] In the embodiments of this application, step S100 can refer to step S10, and will not be repeated here.

[0118] For a two-story basement, the steel lattice column structure is assembled from a permanently embedded section 201, a standard section 202, a floor slab transfer section 203, a support beam transfer section 204, and a top fixed section.

[0119] S200. After the concrete for the column pile is poured, the steel lattice column structure is lowered into the column pile so that the bottom of the permanent embedded section 201 is embedded in the column pile.

[0120] In the embodiments of this application, step S200 can refer to step S20, and will not be repeated here.

[0121] S300, such as Figure 15 , Figure 16 As shown, the excavation proceeds downwards to the bottom elevation of the first support beam. A pit for installing the support platform is excavated below the first support beam and at the top fixed section. The support platform is installed on the top fixed section, and foam paper 207 is wrapped around the top fixed section. Formwork is erected, reinforcing bars are tied, and concrete is poured at the bottom elevation of the first support beam to form the first support beam, so that the top of the top fixed section is embedded in the first support beam. The position of the first support beam is the support beam with the largest height among the multiple support beam positions.

[0122] In the embodiments of this application, step S300 can refer to step S30, and will not be repeated here.

[0123] S400, such as Figure 15 , Figure 16 As shown, the excavation process involves removing soil and rock from the foundation pit down to the top surface of the second support beam, then excavating downwards from the location of the first support beam to the bottom elevation of the second support beam. A pit is then dug at the transition section of the support beam to install the support platform. The support platform is installed on the transition section of the support beam, and foam paper 207 is wrapped around the transition section of the support beam that passes through it. Formwork is then erected, steel bars are tied, and concrete is poured at the bottom elevation of the second support beam to form the second support beam, allowing the transition section to pass through the second support beam. The location of the second support beam is the support beam whose height is only less than that of the first support beam among multiple support beam locations.

[0124] In this embodiment of the application, a support platform is installed on the support beam transition section 204. The support platform is used to support the second support beam. Foam paper 207 is wrapped around the support beam transition section 204 to facilitate the removal of the support beam transition section 204 later.

[0125] S500. Continue to excavate the soil and rock in the foundation pit until the bottom surface of the basement floor slab is at the elevation. Tie steel bars and pour concrete on the ground at the elevation of the basement floor slab to form the basement floor slab 103, so that the top of the permanent embedded section 201 is embedded in the basement floor slab 103.

[0126] In the embodiments of this application, step S500 can refer to step S40, and will not be repeated here.

[0127] S600, such as Figure 17As shown, the basement structure construction, support replacement, and support removal are carried out. Foam paper 207 is wrapped around the floor slab transfer joint that penetrates the first basement floor slab. Formwork is erected, reinforcing bars are tied, and concrete is poured at the corresponding basement structural columns, beams, the first basement floor slab, and the locations between the first basement floor slab and the maintenance structure to form the first basement floor slab and the support structure. The floor slab transfer joint 203 penetrates the first basement floor slab. After the concrete reaches its required strength, the support beams above the first basement floor slab are removed, transferring the load of the support beams to the first basement floor slab.

[0128] In the embodiments of this application, step S600 can refer to step S50, and will not be repeated here.

[0129] S700, such as Figure 17 As shown, foam paper 207 is wrapped around the floor slab transfer joint 203 corresponding to the location of the second basement floor slab. Formwork is erected, steel bars are tied, and concrete is poured at the corresponding basement structural columns, beams, the location of the second basement floor slab, and the location between the second basement floor slab and the maintenance structure to form the second basement floor slab, so that the second floor slab transfer joint 203 penetrates through the second basement floor slab. After the concrete reaches its age strength, the support beam above the second basement floor slab is removed, and the load of the support beam is transferred to the second basement floor slab. The location of the second basement floor slab is the basement floor slab location whose height is only greater than that of the first basement floor slab location among multiple basement floor slab locations.

[0130] In the embodiments of this application, such as Figure 2 As shown, the second basement floor slab is obtained by setting up formwork, tying reinforcing bars, and pouring concrete at the location of the second basement floor slab.

[0131] In the embodiments of this application, the first support beam, the second support beam, the basement floor slab, the first basement floor slab, and the second basement floor slab are constructed sequentially. After the construction of the first basement floor slab is completed, the support beams above the floor slab are removed, and the load of the support beams is transferred to the first basement floor slab. Then the second basement floor slab is constructed. After the construction of the second basement floor slab is completed, the support beams above the floor slab are removed, and the load of the support beams is transferred to the second basement floor slab.

[0132] Finally, the top fixing sections of the steel lattice columns were gradually removed, the openings were repaired, and the construction of the basement floors was completed.

[0133] For basements with three or more floors, the specific construction process can be referred to in steps S100 to S700. The construction is carried out in the order of support beams, basement floor slabs, and basement floor slabs. The supporting force provided by the support beams is converted into the supporting force provided by the basement floor slabs. The top fixing sections of the support beams and steel lattice columns are gradually removed, the openings are repaired, and the construction of the multi-story basement floors is completed.

[0134] Following step S10, the following specific step S101 is also included:

[0135] S101. A laser instrument and a fixed ruler are set up on opposite sides of the foundation pit area. The laser instrument is set up on the base. During the sinking process of the steel lattice column structure, a horizontal laser is emitted by the laser instrument. The horizontal laser is calibrated and its elevation is determined by the fixed ruler. According to the elevation of the horizontal laser, the sinking depth of the steel lattice column structure 2 is controlled by moving the ruler, so that the bottom of the permanently embedded section 201 is inserted into the column pile.

[0136] In the embodiments of this application, such as Figure 18 As shown, the sinking depth of the steel lattice column structure 2 is controlled by a long-distance laser positioning method. Specifically, a laser instrument 701 is set up on a base 702 with a known elevation. A horizontal laser line 704 is emitted by the laser instrument 701. The horizontal laser line 704 is calibrated and its elevation is determined by a fixed ruler 703. Based on the elevation of the horizontal laser line 704, the sinking depth of the steel lattice column structure 2 is controlled by moving the ruler 705. This achieves precise control of the sinking depth of the steel lattice column structure within the foundation pit area. Compared with the existing theodolite control, the operation is more convenient and the construction difficulty of controlling the sinking depth of the steel lattice column structure is greatly simplified.

[0137] Following step S50, the following steps S51 to S52 are also included:

[0138] S51. After the first support beam is removed, remove the connecting steel plate 3 and fastening components between the top of the first floor slab transition section 203 and the bottom of the top fixed section 205 to remove the top fixed section 205.

[0139] S52. Remove the connecting steel plate 3 and fastening components between the bottom of the first floor transition section 203 and the top of the standard section 202. Without pulling out the L-shaped angle steel 5 of the first floor transition section 203, anchor the suspension rod 202a on the lacing plate 6 at the top of the standard section 202. Use a forklift to support the suspension rod 202a so that the standard section 202 is laid upside down in the preset direction to remove the first floor transition section 203 and the standard section 202.

[0140] In this embodiment, the connection between the standard section 202 and the floor slab transition section 203 avoids the first basement floor slab, and the connection between the floor slab transition section 203 and the top fixed section 205 avoids the first basement floor slab. The top fixed section 205, the floor slab transition section 203 and the standard section 202 are removed sequentially from top to bottom, thus achieving the non-destructive removal of the standard section 202, the floor slab transition section 203 and the top fixed section 205.

[0141] In one embodiment, after step S52, in which the standard section 202 is inverted in a preset direction by using a forklift to support the suspension rod 202a to remove the first floor slab transition section 203 and the standard section 202, the following steps S521~S522 are further included:

[0142] S521. The bottom surface of the reserved post-pouring hole 103a of the basement floor slab 103 is flush with the basement floor slab 103. The protruding part of the steel lattice column structure is cut off, the surface of the reserved post-pouring hole 103a of the basement floor slab 103 is roughened and cleaned, and then the repair concrete 103b of the basement floor slab is poured to fill the reserved post-pouring hole 103a of the basement floor slab 103.

[0143] S522. A baffle is installed below the post-cast hole that penetrates the second basement floor slab of the steel lattice column structure, and repair cement mortar 102a is poured above the first basement floor slab to fill the post-cast hole of the first basement floor slab.

[0144] In the embodiments of this application, such as Figure 20 As shown, repair concrete 103b is poured on the basement floor slab, and repair cement mortar 102a is poured on top of the first basement floor slab.

[0145] By filling in the reserved post-pouring holes in the basement floor slab and the first basement floor slab, the integrity and stability of the basement structure can be ensured, preventing structural damage or safety accidents caused by the holes.

[0146] Following step S700, the following steps S710~S730 are also included:

[0147] S710. After all the supporting beams have been removed, remove the connecting steel plate 3 and fastening components between the top of the first floor slab transition section 203 and the bottom of the top fixed section 205 to remove the top fixed section 205.

[0148] S720. Remove the connecting steel plate 3 and fastening components between the bottom of the first floor slab transition section 203 and the top of the standard section 202. Without pulling out the L-shaped angle steel 5 of the first floor slab transition section 203, anchor the suspension rod 202a on the lacing plate 6 at the top of the standard section 202. Remove the connecting steel plate 3 and fastening components between the bottom of the support beam transition section 204 and the top of the second floor slab transition section 203. Pull out the L-shaped angle steel 5 of the first floor slab transition section 203. Use a forklift to support the suspension rod 202a so that the standard section 202 is laid upside down in the preset direction to remove the first floor slab transition section 203, the standard section 202, and the support beam transition section 204.

[0149] S730. Remove the second support beam. After the second support beam is removed, remove the connecting steel plate 3 and fastening components between the bottom of the second floor slab transition section 203 and the top of the standard section 202. Without pulling out the L-shaped angle steel 5 of the second floor slab transition section 203, anchor the suspension rod 202a on the lacing plate 6 at the top of the standard section 202. Use a forklift to support the suspension rod 202a so that the standard section 202 is laid upside down in the preset direction to remove the second floor slab transition section 203 and the standard section 202.

[0150] In the embodiments of this application, such as Figure 19 As shown, after all the supporting beams are removed, the steel lattice column structure is dismantled section by section from top to bottom. First, the high-strength bolts 4 connecting the upper end of the first floor slab transition section 203 to the connecting steel plate are removed, and the top fixing section 205 is removed. Then, the high-strength bolts 4 connecting the lower end of the first floor slab transition section 203 to the standard section 202 are removed. At this time, the L-shaped angle steel 5 of the first floor slab transition section 203 is not pulled out, as it serves as support for the dismantling of the lower standard section 202 and the supporting beam transition section 204. Then, the standard section 202 and the supporting beam transition section 204 are dismantled as a whole. First, the suspension rod 202a is anchored at the upper end of the standard section 202, then the high-strength bolts 4 connecting the lower end of the supporting beam transition section to the connecting steel plate 3 are removed, and then the standard section 202 is dismantled. The high-strength bolts 4 connecting the floor slab transition section 203 and the connecting steel plate are laid upside down on one side of the support beam transition section. The L-shaped angle steel 5 of the first floor slab transition section 203 is pulled out. The standard section 202 and the support beam transition section 204 are laid upside down in the preset direction by using a forklift to support the suspension rod 202a, so as to achieve the safe dismantling of the first floor slab transition section 203, the standard section 202 and the support beam transition section 204. This process is repeated until the lowest standard section 202 is dismantled. All sections except the permanently embedded section 201 can be dismantled without damage and reused. Compared with the traditional construction method of dismantling steel lattice column structure by gas cutting, it is not only more efficient, but also does not require the use of dangerous devices such as gas cutting, which greatly improves the safety of dismantling steel lattice column structure.

[0151] In one embodiment, after step S730, in which the floor slab transition section 203 and standard section 202 are inverted in a preset direction by using a forklift to support the suspension rod 202a to remove the second floor slab transition section 203 and standard section 202, the following steps S731~S732 are further included:

[0152] S731. Cut off the protruding steel lattice column structure of the reserved post-pouring hole 103a of the basement floor slab, roughen and clean the surface of the reserved post-pouring hole 103a of the basement floor slab, and then pour the repair concrete 103b of the basement floor slab to fill the reserved post-pouring hole 103a of the basement floor slab.

[0153] S732. A baffle is installed below the post-cast hole in the steel lattice column structure that penetrates the first basement floor slab and the second basement floor slab. Repair cement mortar 102a is poured above the first basement floor slab and the second basement floor slab to fill the post-cast hole in the first basement floor slab and the second basement floor slab.

[0154] In the embodiments of this application, such as Figure 20 As shown, repair concrete 103b is poured on the basement floor slab, repair cement mortar 102a is poured on the top of the first basement floor slab, and repair cement mortar 102a is poured on the top of the second basement floor slab.

[0155] By filling in the reserved post-pouring holes in the basement floor slab 103, the post-pouring holes in the first basement floor slab and the second basement floor slab, the integrity and stability of the basement structure can be ensured, and the damage to the basement structure or safety accidents caused by the holes can be prevented.

[0156] In one embodiment, such as Figures 21-23 As shown, the support platform 206 includes a first fixing plate 206a, a second fixing plate 206b, a stiffening rib 206c, and a support plate 206d. One end of the first fixing plate 206a is vertically welded to one end of the bottom surface of the second fixing plate 206b. The stiffening rib 206c is vertically welded to the bottom surface of the second fixing plate 206b and perpendicularly welded to the surface of the first fixing plate 206a. The support plate 206d is anchored to the top surface of the second fixing plate 206b. The first fixing plate 206a is detachably connected to the L-shaped angle steel 5. The support beam 101 is supported on the support plate 206d.

[0157] More specifically, the first fixing plate 206a and the second fixing plate 206b are welded together on their short sides; the stiffening rib 206c is welded to the second fixing plate 206b and perpendicularly welded to the first fixing plate 206a; the support plate 206d is disposed on the second fixing plate 206b and anchored to the second fixing plate 206b by bolts; a third bolt hole 206e for anchoring the support plate 206d is provided on the second fixing plate 206b on one side of the stiffening rib 206c. A fourth bolt hole 206g corresponding to the second fixing plate 206b is provided on the plate 206d. A third bolt hole 206e for anchoring the support platform 206 to the support beam transition section 204 and the top fixing section 205 is provided on the first fixing plate 206a on the other side of the stiffening rib 206c. A third bolt hole reinforcing protrusion 206f is provided on the side of the stiffening rib 206c for the third bolt hole 206e. A nut embedding hole 206h is provided at the bolt hole of the support plate 206d.

[0158] In this embodiment of the application, through the joint cooperation of the first fixing plate 206a, the second fixing plate 206b, the stiffening rib 206c and the support plate 206d, the support platform 206 installed on the top fixing section 205 can support the first support beam 101, and the support platform installed on the support beam transition section 204 can support the second support beam 101.

[0159] Based on the characteristic that the steel lattice column structure passes through the support beam 101, floor slab 102, and column pile 104, this invention divides the steel lattice column structure into five types of standard segments: permanently embedded segment 201, standard segment 202, floor slab transition segment 203, support beam transition segment 204, and top fixed segment 205. The segments are connected by high-strength bolts 4, and the connection nodes avoid the support beam 101, floor slab 102, and column pile 104. After the basement structure construction is completed and the support beam 101 is removed, except for the permanently embedded segment 201, the other segments can be removed without damage, which greatly improves the reusability of the steel lattice column structure and effectively reduces material costs. The floor slab transition section 203 uses a combination of four L-shaped angle steels and connecting steel plates, and the L-shaped angle steel 5 at the floor slab is wrapped with foam paper 207. No openings need to be reserved when the floor slab is poured. The steel lattice column structure is poured integrally with the floor slab. The overall bending length of the steel lattice column structure will not increase significantly due to the removal of the supporting beams. This effectively avoids the increased cost caused by the increase in bending length in traditional construction methods, which would lead to instability of the support structure or the use of larger steel lattice column structures.

[0160] The bolt holes are equipped with reinforcing protrusions to ensure that they are designed according to the required load-bearing capacity, guaranteeing sufficient load-bearing capacity for the high-strength bolt 4 connection nodes between each segment. Furthermore, the load-bearing capacity requirement for the high-strength bolt 4 connection nodes between each segment is more than 1.5 times the vertical load-bearing capacity of the steel lattice column structure. These connection nodes possess sufficient strength and damage resistance, ensuring they can be reused multiple times without failure. The sinking depth of the steel lattice column structure 2 is controlled using a long-distance laser positioning method. Utilizing a laser instrument with known benchmark elevation, the sinking depth of all steel lattice column structures in the foundation pit is precisely controlled by emitting horizontal laser lines and a scale. Compared to traditional theodolite control, this method is more convenient and significantly simplifies the construction difficulty of controlling the sinking depth of the steel lattice column structure.

[0161] Remove the high-strength bolts 4 connecting the lower end of the floor slab transition section 203 to the connecting steel plate. Do not remove the L-shaped angle steel of the floor slab transition section 203 at this time, as it will serve as a support for the removal of the lower standard section 202 and the support beam transition section 204. Then, remove the standard section 202 and the support beam transition section 204 as a whole. First, anchor the suspension rod 202a on the lacing plate 6 at the upper end of the standard section 202. Then, remove the high-strength bolts 4 connecting the lower end of the support beam transition section to the connecting steel plate. Next, remove the high-strength bolts 4 connecting the floor slab transition section 203 to the connecting steel plate on one side of the standard section 202 and the support beam transition section 204. Pull out the L-shaped angle steel 5 of the upper floor slab transition section 203. Use a forklift to support the suspension rod 202a so that the standard section 202 and the support beam transition section 204 are laid upside down in the preset direction, thus achieving the safe removal of the floor slab transition section 203, the standard section 202, and the support beam transition section 204. Compared with the traditional gas cutting method for dismantling steel lattice column structures, this invention not only has high dismantling efficiency, but also does not require the use of dangerous devices such as gas cutting, which greatly improves the safety of dismantling steel lattice column structures.

[0162] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A prefabricated steel lattice column for foundation pit support, characterized in that: Including a top fixed section (205), a standard section (202), a floor slab transition section (203), a support beam transition section (204), and a permanently embedded section (201), each basement floor is equipped with a standard section (202), and each basement floor slab (102) is equipped with a floor slab transition section (203). A support beam transition section (204) is correspondingly installed on the support beam (101) between two adjacent basement floors. The standard section (202), support beam transition section (204), and floor slab transition section (203) between two adjacent basement floors are detachably connected from top to bottom via connecting steel plates (3) and fastening components. A top fixed section (205) is correspondingly embedded on the support beam (101) at the top of the basement. The top fixed section (205), the floor slab transition section (203) at the top of the basement, and the standard section (202) at the top of the basement are detachably connected from top to bottom via connecting steel plates (3) and fastening components. A permanent embedded section (201) is embedded in the column pile (104). The permanent embedded section (201) and the standard section (202) of the basement bottom are detachably connected by connecting steel plates (3) and fastening components. The top fixed section (205) and the support beam transition section (204) are both provided with support platforms (206). The support beam (101) is supported on the corresponding support platform (206). The support platform (206) includes a first fixed plate (206a) and a second fixed plate. (206b), stiffening rib (206c) and support plate (206d), one end of the first fixed plate (206a) is vertically welded to one end of the bottom surface of the second fixed plate (206b), the stiffening rib (206c) is vertically welded to the bottom surface of the second fixed plate (206b) and perpendicularly welded to the surface of the first fixed plate (206a), the support plate (206d) is anchored to the top surface of the second fixed plate (206b), and the support beam (101) is supported on the support plate (206d).

2. The prefabricated steel lattice column for foundation pit support according to claim 1, characterized in that: The permanent embedded section (201), standard section (202), support beam transfer section (204), floor slab transfer section (203) and top fixed section (205) all include four L-shaped angle steels (5) arranged symmetrically in pairs. The two adjacent L-shaped angle steels (5) in the permanent embedded section (201) and standard section (202) are detachably connected by a gusset plate (6).

3. The prefabricated steel lattice column for foundation pit support according to claim 2, characterized in that: The L-shaped angle steel (5) has a first connecting hole at its end and a second connecting hole on the connecting steel plate (3). The L-shaped angle steel (5) is detachably connected to the connecting steel plate (3) through the fastening components, the first connecting hole, and the second connecting hole.

4. The prefabricated steel lattice column for foundation pit support according to claim 2, characterized in that: The first fixing plate (206a) is detachably connected to the L-shaped angle steel (5).

5. A construction method for prefabricated steel lattice columns for foundation pit support as described in claim 1, characterized in that, Includes the following steps: The number and length of each segment of the steel lattice column structure (2) are determined according to the basement structure. The segment of the steel lattice column structure (2) is selected through finite element simulation. Then, the segments of the steel lattice column structure (2) are spliced ​​together to form the steel lattice column structure (2). After the basement column piles (104) are poured, the steel lattice column structure is sunk so that the lower end of the permanent embedded section (201) is embedded in the column pile (104). The sinking depth of the steel lattice column structure is controlled by the long-distance laser positioning control method. The construction positions of the support beams (101) of each floor of the basement are excavated from top to bottom in the basement foundation pit. At the bottom of the construction position of each support beam (101), a pit (101b) is excavated to accommodate the support platform (206). The support platform (206) is installed on the top fixed section (205) and the support beam transition section (204). Foam paper (207) is wrapped on the top fixed section (205) and the support beam transition section (204). The support beams (101) of each floor are constructed from top to bottom. The top of the top fixed section (205) is buried in the corresponding support beam (101). The support beam transition section (204) passes through the corresponding support beam (101). The support platform (206) supports the corresponding support beam (101). The construction location of the basement floor slab (103) is excavated in the basement foundation pit, and then the floor slab (103) is constructed. A reserved post-pouring hole (103a) is set at the permanent embedded section (201) to expose the connection joint between the permanent embedded section (201) and the standard section (202) so that the standard section (202) above the permanent embedded section (201) can be removed without damage in the future. Foam paper (207) is wrapped around the floor slab transfer joint (203). The floor slabs (102) of each basement floor are constructed from bottom to top at the construction position of the floor slab (102) below the support beam (101) of each floor. The floor slab transfer joint (203) passes through the corresponding floor slab (102). After the construction of each basement floor slab (102) is completed and the concrete of the floor slab (102) reaches the required strength, the basement support beam (101) is removed layer by layer, and the load of the support beam (101) is transferred to the floor slab (102). Remove the connecting steel plate (3) and fastening components between the basement top floor slab transfer section (203) and the top fixed section (205), then remove the top fixed section (205), and then remove the floor slab transfer sections (203), standard sections (202) and support beam transfer sections (204) of each basement floor in sequence from top to bottom, and repair the reserved post-pouring hole (103a) formed on the bottom slab (103) and the post-pouring hole formed on the floor slab (102) after removal.

6. The construction method of the prefabricated steel lattice column for foundation pit support according to claim 5, characterized in that, The long-distance laser positioning control method is used to control the sinking depth of the steel lattice column structure, including the following steps: A laser instrument (701) and a fixed ruler (703) are set up on opposite sides of the foundation pit area. The laser instrument (701) is set up on a base (702) with a known elevation. During the sinking process of the steel lattice column structure (2), a horizontal laser line (704) is emitted by the laser instrument (701). The horizontal laser line (704) is calibrated and its elevation is determined by the fixed ruler (703). Based on the elevation of the horizontal laser line (704), the sinking depth of the steel lattice column structure (2) is controlled by moving the ruler (705).

7. The construction method of the prefabricated steel lattice column for foundation pit support according to claim 5, characterized in that, When dismantling the floor slab transfer joints (203), standard joints (202), and support beam transfer joints (204) on each basement floor, the following steps are included: Remove the connecting steel plate (3) and fastening components between the floor slab transition section (203) and the standard section (202), without pulling out the L-shaped angle steel (5) of the floor slab transition section (203), and anchor the suspension rod (202a) on the lacing plate (6) at the top of the standard section (202). Then remove the connecting steel plate (3) and fastening components at the lower end of the support beam transition section (204), and then pull out the L-shaped angle steel (5) of the floor slab transition section (203). Using a forklift to support the suspension rod (202a), the standard section (202) and the support beam transition section (204) are laid upside down together in the preset direction.

8. The construction method of the prefabricated steel lattice column for foundation pit support according to claim 5, characterized in that, When repairing the reserved post-cast hole (103a) formed on the base slab (103) and the post-cast hole formed on the floor slab (102), the following steps are included: The bottom surface of the reserved post-pouring hole (103a) on the flat bottom plate is cut off, the protruding steel lattice column structure (2) is removed, the surface of the reserved post-pouring hole (103a) on the bottom plate is roughened and cleaned, and then repair concrete (103b) is poured into the reserved post-pouring hole (103a) on the bottom plate to fill the reserved post-pouring hole (103a) on the bottom plate. A baffle is installed at the bottom of the post-cast hole on the floor slab (102), and then repair cement mortar (102a) is poured into the post-cast hole on the floor slab (102) to fill the post-cast hole on the floor slab (102).

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