Construction method for efficient support changing system of deep and large foundation pit

Abstract

The invention relates to a construction method for an efficient support changing system of a deep and large foundation pit, aiming at the problem of water seepage of a secant pile of the foundation pit, on the basis of cement stone blocking and secondary grouting, water in foundation soil is drained into a water diversion pipe through a horizontally arranged water diversion pipe, and water pressure balance in the pipe is realized by utilizing atmospheric pressure through a vertically lengthened water diversion pipe; a water pumping device is arranged in an auxiliary mode to achieve dynamic adjustment, and the foundation pit secant pile leakage blocking effect is greatly improved; a traditional concrete beam support is replaced with the hoop type profile steel inner support, the problem that the slenderness ratio and the stress ratio of a steel pipe column exceed the limit in the deep foundation pit excavation process is effectively solved, meanwhile, the site construction efficiency is greatly improved, and the safety of foundation pit supporting and an upper structure is guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of foundation and basic engineering, and in particular relates to a construction method of a high-efficiency support replacement system for a deep and large foundation pit. Background Art

[0002] With the continuous development of cities and the improvement of construction technology, the utilization of underground space is becoming more and more common, the excavation depth of foundation pits is increasing, the distance between the side walls of foundation pits and surrounding buildings (structures) is getting smaller and smaller, the difficulty of foundation pit construction is increasing, and the problems that need to be solved are also increasing.

[0003] For example: pit support interlocking piles are widely used in pit support projects because they have both support and water-stopping functions, require less construction space, and are more economical than underground continuous walls. However, engineering and technical defects are inevitable during the construction process, or because of the complexity of the site's geological conditions, the pit interlocking piles fail to act as a water-stopping curtain, and water leakage often occurs between the interlocking piles. Another example: During the excavation of deep foundation pits, the slenderness ratio and stress ratio of steel pipe columns exceed the limit. For safety reasons, the existing technology sets traditional concrete beams for support, but it requires excavation layer by layer and brick slag backfilling. It also involves the disadvantages of reserved holes for formwork and template assembly and disassembly, which seriously affects construction efficiency. Another example: The construction of steel pipe diagonal braces at the bottom of the foundation pit usually sets the reaction pier on the cast bottom plate, which makes it difficult to cast the foundation pit bottom plate in one go, and the overall waterproofness of the bottom plate and the molding quality of the bottom plate concrete are greatly reduced.

[0004] In view of this, there is an urgent need to invent a construction method for an efficient support replacement system for deep and large foundation pits which has strong stability, high transfer efficiency, simple installation and operation, and outstanding economic and technical benefits. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for constructing a high-efficiency support replacement system for a deep and large foundation pit.

[0006] This deep and large foundation pit high-efficiency support replacement system construction method includes the following steps:

[0007] S1. Set grouting holes on the ground above the leaking point of the foundation pit water-stop curtain for grouting, and set a water diversion pipe at the leaking point to pump out water;

[0008] S2. Build safety protection passages layer by layer from the bottom of the foundation pit;

[0009] S3. Install the steel pipe inner support at the steel purlin position in the foundation pit, and apply prestressing tension and lock;

[0010] S4. Install steel inner supports between the local steel tube concrete columns in the foundation pit as temporary support structures.

[0011] S5. Install the steel transition section through the pile cap pier, and install the foundation pit steel diagonal brace on the top of the steel transition section;

[0012] S6. Continue to excavate the reserved soil in the foundation pit, use the lattice column system in the foundation pit to install the hanging construction platform, and cast the cast-in-place base slab concrete in one go.

[0013] Preferably, in step S1, the foundation pit water-stop curtain is supported by interlocking piles formed by cast-in-place piles and plain concrete compaction piles, grouting holes are set on the ground above the local pile joint leakage points for grouting, and the leakage points are treated by hole expansion and excavation, and filled with cement stones. At the same time, water diversion pipes are set horizontally between the pile joints, and the exposed pipe openings inside and outside the foundation pit are connected upward to the pit top, and the seepage water in the pipe is pumped into the pit top drainage ditch by a pit top pump; exhaust holes are set between adjacent grouting holes.

[0014] Preferably, in step S1, a water diversion hole is provided at the end of the horizontal section of the water diversion pipe, a water pipe is provided in the vertical section of the water diversion pipe, and the water pipe is connected to a water pump.

[0015] Preferably, in step S2, scaffolding cross bars and scaffolding vertical bars are set up layer by layer from the bottom of the foundation pit to form the main support body of the safety protection channel, and assembled steel steps, steel guardrails and rainproof colored steel plates are installed layer by layer simultaneously, and are anchored and connected to the foundation pit channel steel waist beam through the connecting fasteners at the end of the scaffolding cross bars.

[0016] Preferably, in step S3, auxiliary prestressed lifting ropes are installed at both ends of the steel pipe inner support, tensioning end plates and flexible joint ends are provided at the ends of the steel pipe inner support, steel strands are passed between the tensioning end plates and flexible joint ends at both ends, and prestressed tensioning and locking are applied; the prestressed lifting ropes are respectively sleeved on both ends of the steel pipe inner support, and connected to the embedded hooks arranged on the cast-in-place piles on both sides; the tensioning end plates are provided with reserved holes for steel strands at equal intervals in the circumferential direction.

[0017] Preferably, in step S4, steel hoops are provided at both ends of the inner support of the steel section, and the steel hoops are installed on the steel tube concrete column. The steel hoops at both ends are connected into a whole through a steel support beam in the middle, which are used to replace part of the main beam steel bars and are cast in the main beam as a permanent structure; two sets of upper and lower limit rings are provided on the surface of the steel tube concrete column, and the steel hoops are arranged between the upper and lower limit rings through connecting bolts.

[0018] Preferably, in step S4, the inner support of the steel section includes a steel hoop, a hoop connecting section and a steel support beam, and the single-side steel hoop is provided with a hoop connecting section, and the hoop connecting section is connected and fixed to the steel support beam by anchor bolts through left and right connecting plates.

[0019] Preferably, in step S4, the inner support of the steel section includes a steel hoop, a hoop connecting section and a steel support beam, and the single-side steel hoop is provided with a hoop connecting section, and the hoop connecting section is connected and fixed to the steel support beam by anchor bolts through left and right connecting plates.

[0020] Preferably, in step S6, after the installation of the foundation pit steel diagonal braces is completed, the reserved soil of the foundation pit continues to be excavated, the bottom plate steel bars of the cast-in-place bottom plate are tied after the base is treated, and the main reinforcement of the bottom plate is welded to the steel transition section, and the hanging construction platform is provided with hanging plates hung on the lattice columns around, and the top surface of the hanging construction platform is provided with hooks around, and prestressed hanging ropes are installed between the hooks and the lattice columns, and the hanging construction platform is used to cast the cast-in-place bottom plate concrete in one time.

[0021] The beneficial effects of the present invention are:

[0022] 1) The present invention has developed a water pressure balancing technology for the drainage of the top of the pit through the diversion hole and the water diversion pipe. To solve the seepage problem of the foundation pit interlocking piles, on the basis of cement stone sealing and secondary grouting, the water in the foundation soil is drained into the water diversion pipe through a horizontally arranged water diversion pipe, and the water pressure in the pipe is balanced by using atmospheric pressure by vertically extending the water diversion pipe. An auxiliary pumping device is set to realize dynamic adjustment, which greatly improves the seepage sealing effect of the foundation pit interlocking piles.

[0023] 2) The present invention has developed a permanent and temporary combined steel internal support construction technology, which uses hoop-type steel internal supports to replace traditional concrete beam supports, effectively solving the problem of excessive slenderness ratio and stress ratio of steel pipe columns during deep foundation pit excavation, while greatly improving on-site construction efficiency and ensuring the safety of foundation pit support and superstructure.

[0024] 3) The present invention has developed a one-time casting technology for the steel diagonal brace replacement bottom plate, and through the pre-buried steel transition section, the pile cap reaction seat is able to penetrate the bottom plate without leaving a hole, thereby realizing the one-time casting and forming of the foundation pit bottom plate, effectively improving the overall waterproofness of the bottom plate and the forming quality of the bottom plate concrete. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the seepage plugging structure of the bite pile in the present invention;

[0026] Figure 2 It is a schematic diagram of the installation of the water diversion pipe in the present invention;

[0027] Figure 3 This is a schematic diagram of the installation of the transverse steel support in the present invention;

[0028] Figure 4 The present invention Figure 3 Middle AA section;

[0029] Figure 5 It is a schematic diagram of the permanent and temporary combined steel inner support structure in the present invention;

[0030] Figure 6 The present invention Figure 5 Middle AA section;

[0031] Figure 7 This is a front view of the foundation pit safety protection channel structure of the present invention;

[0032] Figure 8 It is a side view of the foundation pit safety protection channel structure of the present invention;

[0033] Fig. 9 This is a schematic diagram of the installation of the hanging construction platform in the present invention;

[0034] Fig.10 It is a schematic diagram of the installation of the steel diagonal brace of the foundation pit bottom plate in the present invention.

[0035] In the figure: 1-foundation soil; 2-plain concrete compaction pile; 3-cast-in-place pile; 4-water diversion pipe; 5-cement stone; 6-water diversion hole; 7-grouting hole; 8-air outlet; 9-water pump; 10-water pipe; 11-drainage ditch; 12-crown beam; 13-embedded hook; 14-prestressed suspension rope; 15-flexible joint end; 16-tensioning end plate; 17-lateral steel support; 18-steel strand; 19-anchor end; 20-foundation pile; 21-reserved reinforcement; 22-steel tube concrete column; 23-connecting bolt; 24-steel bracket Hoop; 25-limiting ring; 26-connecting plate; 27-anchor bolt; 28-hoop connecting section; 29-steel support beam; 30-assembled steel step; 31-scaffolding cross bar; 32-scaffolding upright; 33-steel guardrail; 34-rainproof colored steel plate; 35-channel steel waist beam; 36-connecting fastener; 37-lattice column; 38-hanging plate; 39-construction platform; 40-hook; 41-steel diagonal brace; 42-steel transition section; 43-waterstop steel plate; 44-cast-in-place bottom plate; 45-pile cap pier; 46-waterproof membrane. DETAILED DESCRIPTION

[0036] The present invention is further described below in conjunction with embodiments. The description of the following embodiments is only used to help understand the present invention. It should be noted that for ordinary persons in the art, without departing from the principle of the present invention, the present invention can also be modified in some ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0037] Embodiment 1

[0038] As an embodiment, the construction method of the deep and large foundation pit high-efficiency support replacement system includes the following steps:

[0039] S1. Treatment of seepage plugging of interlocking piles in foundation pit support: The foundation pit water-stop curtain is supported by interlocking piles formed by reinforced concrete bored piles and plain concrete bored piles. Grouting holes 7 are set on the ground above the local pile joint leakage points for grouting, and the leakage points are treated by hole expansion and filled with cement stones 5. At the same time, water diversion pipes 4 are set horizontally between the pile joints, and the exposed pipe openings inside and outside the foundation pit are connected upward to the pit top. The seepage water in the pipe is pumped into the pit top drainage ditch 11 by the pit top water pump 9.

[0040] S2. Construction of the safety protection passage of the foundation pit: Scaffolding cross bars 31 and scaffolding vertical bars 32 are constructed layer by layer from the bottom of the foundation pit to form the main support body of the safety protection passage. Simultaneously, the bottom assembled steel steps 30, steel guardrails 33 and top rainproof colored steel plates 34 are installed layer by layer, and the scaffolding cross bars 31 are connected to the foundation pit channel steel waist beam 35 through the fasteners 36 at the end.

[0041] S3. Installation of prestressed auxiliary steel pipe internal supports outside the pit: Install the steel pipe internal supports at the position of the steel purlin in the pit of the foundation pit. After the steel pipe internal supports are stable, auxiliary prestressed suspension ropes 14 are installed at both ends. At the same time, the tensioning end plates 16 of the pipe body at the flexible joint end 15 and the anchor end 19 are used to pass the steel strands 18, and prestressed tensioning and locking are applied.

[0042] S4. Installation of permanent and temporary combined steel inner supports for foundation pit: Steel inner supports are installed between the steel tube concrete columns 22 in the local foundation pit as temporary support structures. The steel inner supports have steel hoops 24 at both ends, which are installed on the steel tube concrete columns 22. The steel hoops 24 at both ends are connected as a whole by a steel support beam 29 in the middle. Later, the steel inner supports replace part of the main beam steel bars and are cast in the main beam as a permanent structure.

[0043] S5. Installation of foundation pit steel diagonal brace 41 through bottom plate reinforcement: Pre-cast concrete pile cap pier 45 on the top of foundation pile 20 at the bottom of foundation pit, install steel transition section 42 as reaction support for steel diagonal brace 41 through pile cap pier 45, and then use the top of steel transition section 42 to install foundation pit steel diagonal brace 41.

[0044] S6. Overall pouring of the bottom plate of the hanging construction platform 39: After the installation of the steel diagonal braces 41 of the foundation pit is completed, the reserved soil of the foundation pit is continued to be excavated. After the base is processed, the bottom plate steel bars are tied, and the main reinforcement of the bottom plate is welded to the steel transition section 42. Subsequently, the hanging construction platform 39 is installed using the lattice column 37 system in the foundation pit, and the hanging construction platform 39 is used to cast the concrete of the bottom plate of the foundation pit in one time.

[0045] Embodiment 2

[0046] As another embodiment, this embodiment 2 proposes, on the basis of the embodiment 1, a more specific construction method of a high-efficiency support replacement system for a deep and large foundation pit:

[0047] In step S1 , exhaust holes are provided between adjacent grouting holes 7 .

[0048] A water diversion hole 6 is provided at the end of the horizontal section of the water diversion pipe 4 , and a water pipe 10 is provided in the vertical section of the water diversion pipe 4 , and the water pipe 10 is connected to a water pump 9 .

[0049] In step S3 , the prestressed suspension ropes 14 are respectively sleeved on both ends of the support inside the steel pipe, and connected to the pre-buried hooks 13 arranged on the cast-in-place piles 3 on both sides.

[0050] The tensioning end plate 16 is provided with reserved holes for the steel strands 18 at equal intervals in the circumferential direction.

[0051] In step S4 , two sets of upper and lower limiting rings 25 are provided on the surface of the steel tube concrete column 22 .

[0052] The inner support of the steel section is mainly composed of a steel hoop 24, a hoop connecting section 28 and a steel support beam 29. The steel hoop 24 is fixed in the limiting ring 25 of the steel tube concrete column 22 by connecting bolts 23. The single-sided steel hoop 24 is provided with a hoop connecting section 28, and the hoop connecting section 28 is connected and fixed to the steel support beam 29 by anchor bolts 27 through the left and right connecting plates 26.

[0053] In step S5 , an annular water-stopping steel plate 43 is disposed in the middle of the steel transition section 42 , and is buried in the outer surface of the inner section of the bottom plate and is covered with a waterproof coiled material 46 .

[0054] In step S6 , the hanging construction platform 39 is provided with hanging plates 38 that can be hung on the lattice column 37 , and the top surface is provided with hanging hooks 40 , and the prestressed hanging rope 14 is installed between the hanging hook 40 and the lattice column 37 .

[0055] It should be noted that the parts in this embodiment that are the same or similar to those in the first embodiment can be referenced to each other and will not be described in detail in this application.

[0056] Embodiment 3

[0057] As another embodiment, this embodiment 3 proposes, based on the embodiments 1 and 2, that this deep and large foundation pit efficient support replacement system, such as Figure 1 and Figure 2 As shown, it includes a foundation pit water-stop curtain. A grouting hole 7 is arranged on the ground above the leaking point of the foundation pit water-stop curtain, and a water diversion pipe 4 is arranged in the leaking point along the horizontal direction.

[0058] A safety protection passage is set up at the bottom of the foundation pit, steel pipe internal supports are installed at the position of the steel purlin of the foundation pit, and steel internal supports are installed between 22 steel pipe concrete columns in the foundation pit. Foundation piles 20 are arranged at the bottom of the foundation pit, and concrete pile cap piers 45 are cast on the top of the foundation piles 20. Steel transition sections 42 are installed on the pile cap piers 45, and foundation pit steel diagonal braces 41 are installed on the top of the steel transition sections 42; a hanging construction platform 39 is installed between the lattice columns 37 in the foundation pit.

[0059] The foundation pit water-stop curtain includes cast-in-place piles 3 and plain concrete compaction piles 2, which are interlocked and connected with each other, and grouting holes 7 are arranged on the ground above the leakage points of the pile joints of the cast-in-place piles 3 and the plain concrete compaction piles 2. A water diversion pipe 4 is arranged in the horizontal direction inside the leakage points of the pile joints of the cast-in-place piles 3 and the plain concrete compaction piles 2, and the gap between the water diversion pipe 4 and the foundation pit water-stop curtain is filled with cement stones 5. The pipe mouth of the water diversion pipe 4 is connected upward to the top of the pit, and a water pump 9 is arranged on the top of the pit. A drainage ditch 11 is arranged on the foundation soil 1 outside the foundation pit, and the water pump 9 is used to pump the seepage water in the water diversion pipe 4 into the drainage ditch 11; an exhaust hole is arranged between adjacent grouting holes 7.

[0060] A water diversion hole 6 is provided at the end of the horizontal section of the water diversion pipe 4 , and a water pipe 10 is provided in the vertical section of the water diversion pipe 4 , and the water pipe 10 is connected to a water pump 9 .

[0061] Embodiment 4

[0062] As another embodiment, this embodiment 4 proposes a more specific high-efficiency support replacement system for deep and large foundation pits based on the embodiment 3, such as Figures 3 to 10 As shown: It also includes safety protection passages, steel pipe internal supports and steel section internal supports.

[0063] like Figure 7 and Figure 8 As shown, the safety protection passage includes a scaffolding cross bar 31, a scaffolding vertical pole 32, an assembled steel step 30, a steel guardrail 33 and a rainproof colored steel plate 34. The end of the scaffolding cross bar 31 is anchored and connected to the foundation pit channel steel waist beam 35 through a connecting fastener 36.

[0064] like Figure 3 and Figure 4 As shown, auxiliary prestressed suspension ropes 14 are installed at both ends of the steel pipe inner support, and tensioning end plates 16 and flexible joint ends 15 are set at the ends of the steel pipe inner support. Steel strands 18 are passed between the tensioning end plates 16 and the flexible joint ends 15 at both ends, and prestressed tension locking is applied; the prestressed suspension ropes 14 are respectively sleeved on both ends of the steel pipe inner support, and are connected to the embedded hooks 13 set on the cast-in-place piles 3 on both sides; the tensioning end plates 16 are circumferentially and evenly spaced with reserved holes for the steel strands 18.

[0065] like Figure 5 and Figure 6 As shown, steel hoops 24 are provided at both ends of the inner support of the steel section, and the steel hoops 24 are installed on the steel tube concrete column 22. The steel support beam 29 is used in the middle to connect the steel hoops 24 at both ends into a whole; two sets of upper and lower limit rings 25 are provided on the surface of the steel tube concrete column 22, and the steel hoop 24 is arranged between the upper and lower limit rings 25 through the connecting bolts 23.

[0066] The inner support of the steel section includes a steel hoop 24, a hoop connection section 28 and a steel support beam 29. The single-side steel hoop 24 is provided with a hoop connection section 28, and the hoop connection section 28 is connected and fixed to the steel support beam 29 by anchor bolts 27 through left and right connecting plates 26.

[0067] like Fig.10 As shown, an annular water-stop steel plate 43 is arranged in the middle of the steel transition section 42, a cast-in-place bottom plate 44 is cast above the pile cap pier 45, and some sections of the steel transition section 42 are buried in the cast-in-place bottom plate 44. The outer surface of the steel transition section 42 section buried in the cast-in-place bottom plate 44 is wrapped with a waterproof membrane 46.

[0068] like Fig. 9 As shown, the hanging construction platform 39 is provided with hanging plates 38 hung on the lattice columns 37, and the top surface of the hanging construction platform is provided with hooks 40. Prestressed hanging ropes 14 are installed between the hooks 40 and the lattice columns 37. The hanging construction platform 39 is used for the pouring construction of the cast-in-place bottom plate 44 in the foundation pit.

[0069] It should be noted that the parts in this embodiment that are the same or similar to those in Embodiment 3 can be referenced to each other and will not be described in detail in this application.

[0070] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

Claims

1. A construction method for an efficient support replacement system for a deep and large foundation pit, characterized in that: The following steps are involved: S1. Set grouting holes on the ground above the leaking point of the foundation pit water-stop curtain for grouting, and set a water diversion pipe at the leaking point to pump out water; S2. Build safety protection passages layer by layer from the bottom of the foundation pit; S3. Install the steel pipe inner support at the steel purlin position in the foundation pit, and apply prestressing tension and lock; S4. Install steel inner supports between the local steel tube concrete columns in the foundation pit as temporary support structures. S5. Install the steel transition section through the pile cap pier, and install the foundation pit steel diagonal brace on the top of the steel transition section; S6. Continue to excavate the reserved soil in the foundation pit, use the lattice column system in the foundation pit to install the hanging construction platform, and cast the cast-in-place base slab concrete in one go.

2. The high-efficiency support replacement system construction method for deep and large foundation pits according to claim 1 is characterized in that: In step S1, the foundation pit water-stop curtain is supported by interlocking piles formed by cast-in-place piles and plain concrete compaction piles, grouting holes are set on the ground above the local pile joint leakage points for grouting, and the leakage points are treated by hole expansion and excavation, and filled with cement stones. At the same time, water diversion pipes are set horizontally between the pile joints, and the exposed pipe openings inside and outside the foundation pit are connected upward to the pit top, and the seepage water in the pipe is pumped into the pit top drainage ditch by a pit top pump; exhaust holes are set between adjacent grouting holes.

3. The high-efficiency support replacement system construction method for deep and large foundation pits according to claim 2 is characterized in that: In step S1, a water diversion hole is arranged at the end of the horizontal section of the water diversion pipe, a water pipe is arranged in the vertical section of the water diversion pipe, and the water pipe is connected to a water pump.

4. The high-efficiency support replacement system construction method for deep and large foundation pits according to claim 1 is characterized in that: In step S2, scaffolding cross bars and scaffolding vertical bars are set up layer by layer from the bottom of the foundation pit to form the main support body of the safety protection channel, and assembled steel steps, steel guardrails and rainproof colored steel plates are installed layer by layer simultaneously, and are anchored and connected to the foundation pit channel steel waist beam through the connecting fasteners at the end of the scaffolding cross bars.

5. The high-efficiency support replacement system construction method for deep and large foundation pits according to claim 1 is characterized in that: In step S3, auxiliary prestressed lifting ropes are installed at both ends of the steel pipe inner support, tensioning end plates and flexible joint ends are set at the ends of the steel pipe inner support, steel strands are passed between the tensioning end plates and flexible joint ends at both ends, and prestressed tension locking is applied; the prestressed lifting ropes are respectively sleeved on both ends of the steel pipe inner support, and connected with embedded hooks set on the cast-in-place piles on both sides; the tensioning end plates are circumferentially provided with reserved holes for steel strands at equal intervals.

6. The high-efficiency support replacement system construction method for deep and large foundation pits according to claim 1 is characterized in that: In step S4, steel hoops are provided at both ends of the inner support of the steel section. The steel hoops are installed on the steel tube concrete column. The steel hoops at both ends are connected into a whole through a steel support beam in the middle, which is used to replace part of the main beam steel bars and is cast in the main beam as a permanent structure; two sets of upper and lower limit rings are provided on the surface of the steel tube concrete column, and the steel hoops are arranged between the upper and lower limit rings through connecting bolts.

7. The high-efficiency support replacement system construction method for deep and large foundation pits according to claim 6 is characterized in that: In step S4, the inner support of the steel section includes a steel hoop, a hoop connecting section and a steel support beam. The single-side steel hoop is provided with a hoop connecting section, and the hoop connecting section is connected and fixed to the steel support beam by anchor bolts through left and right connecting plates.

8. The high-efficiency support replacement system construction method for deep and large foundation pits according to claim 6 is characterized in that: In step S4, the inner support of the steel section includes a steel hoop, a hoop connecting section and a steel support beam. The single-side steel hoop is provided with a hoop connecting section, and the hoop connecting section is connected and fixed to the steel support beam by anchor bolts through left and right connecting plates.

9. The high-efficiency support replacement system construction method for deep and large foundation pits according to claim 1 is characterized in that: In step S6, after the installation of the foundation pit steel diagonal brace is completed, the reserved soil of the foundation pit continues to be excavated. After the base is processed, the bottom plate steel bars of the cast-in-place bottom plate are tied, and the main reinforcement of the bottom plate is welded to the steel transition section. Hanging plates hung on the lattice columns are arranged around the hanging construction platform, and hooks are arranged around the top surface of the hanging construction platform. Prestressed hanging ropes are installed between the hooks and the lattice columns. The hanging construction platform is used to cast the cast-in-place bottom plate concrete in one time.

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