Large-scale irregular deep foundation pit support system and construction method

Abstract

This invention relates to a support system and construction method for large-scale, irregularly shaped deep foundation pits, comprising the following steps: constructing dewatering wells on both the inner and outer sides of the excavation area of ​​the foundation pit; manufacturing lattice columns using adjustable, standardized jigs, constructing bored piles within the foundation pit, and casting the lower end of the lattice columns onto the bored piles; sloping and excavating the first layer of soil in the foundation pit, and reinforcing the soil on the sidewalls of the foundation pit; setting up a horizontal support system; excavating the foundation pit layer by layer downwards, and pouring sealing concrete at the upper end of the steel casing; constructing the main structure within the foundation pit, and sealing the dewatering wells; removing recyclable anchor cables and cutting and dismantling the horizontal supports section by section. The beneficial effects of this invention are: the double sealing plate combined with reinforcing wire mesh on the outer side of the dewatering well steel casing effectively improves the sealing performance of the outer side of the steel casing; the porous metal plate and pressure relief pipe on the inner side of the steel casing effectively prevent micro-expansion cement mortar from being squeezed out of the steel casing, thus improving the sealing effect.

Description

Technical Field

[0001] This invention relates to the construction of foundation pit support systems, and more particularly to a support system and construction method for large-scale irregular deep foundation pits. Background Technology

[0002] When carrying out foundation pit excavation and support construction, the traditional construction method is to excavate in layers and construct the support system layer by layer. However, this construction method also has some problems. For example, to reduce the height of the external support structure while ensuring the safety of the foundation pit construction, a slope excavation method is adopted. However, this method requires a large working surface, which is difficult to meet when the working space is limited and the foundation pit has an irregular shape. During the foundation pit excavation, the concrete internal supports are fixed by lattice columns, but lattice columns generally have problems such as low manufacturing precision and long manufacturing time. After the structural construction in the foundation pit is completed, the concrete internal supports of the foundation pit need to be removed. The traditional removal method is to erect a scaffold under the concrete internal supports to temporarily support the concrete internal supports to be removed, and then cut and remove the concrete internal supports in sections. When the concrete internal supports are high above the ground, a higher scaffold needs to be erected. The scaffold is prone to instability and failure, and it requires more manpower and resources, increasing construction costs. To avoid the impact of groundwater during foundation pit excavation, dewatering wells are set up to pump out groundwater. However, some dewatering wells located inside the foundation pit generally have problems with poor sealing and difficulty in sealing off leaks later. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a support system and construction method for large-scale irregular deep foundation pits.

[0004] The construction method for this large-scale, irregularly shaped, deep foundation pit support system includes the following construction steps:

[0005] Step 1: Mark out the plan position of the foundation pit on the ground, construct the outer support structure along the edge of the foundation pit, and construct dewatering wells inside and outside the excavation area of ​​the foundation pit.

[0006] Step 2: Use an adjustable, standardized formwork to manufacture lattice columns, construct bored piles in the foundation pit, and cast the lower end of the lattice column onto the bored piles.

[0007] Step 3: Excavate the first layer of soil in the foundation pit with a slope and reinforce the soil on the side walls of the foundation pit;

[0008] Step 4: Insert recyclable anchor cables into the sidewalls of the foundation pit, construct horizontal ring beams and horizontal supports along the outer support structure, and tension the recyclable anchor cables to form a horizontal support system;

[0009] Step 5: Excavate the foundation pit layer by layer downwards, and at the same time construct the horizontal support system layer by layer according to the method described in Step 4 until the design depth of the foundation pit is reached; drive steel casings with pressure relief pipes into the dewatering wells in the foundation pit, and pour bottom sealing concrete at the upper end of the steel casings.

[0010] Step 6: Pump out groundwater through the pressure relief pipe until the bottom sealing concrete reaches the design strength, then construct the main structure inside the foundation pit and seal the dewatering well;

[0011] Step 7: Slide and erect the attached safety operation platform on the horizontal ring beam, and remove the recyclable anchor cable and cut and remove the horizontal support section by section based on the attached safety operation platform.

[0012] Preferably, in step one, the external support structure is a bored pile or a diaphragm wall.

[0013] Preferably, in step two, the adjustable prefabricated frame includes a rotating main shaft, a fixed rotating shaft, a telescopic half-shaft, telescopic support legs, limiting angle steel, and guide pulleys. One end of the rotating main shaft is supported on the fixed rotating shaft, and the middle and the other end are supported on the telescopic half-shaft. Four limiting angle steels are arranged circumferentially along the rotating main shaft, and several are arranged longitudinally. Two guide pulleys are arranged horizontally, and several are arranged longitudinally. The limiting angle steel and guide pulleys are fixed to the rotating main shaft by telescopic support rods. When manufacturing the lattice column, the length of the telescopic support rods is adjusted according to the size of the lattice column so that the distance between the limiting angle steels is equal to the side length of the lattice column. Then, the lattice column angle steel is placed on the limiting angle steel, and connecting steel plates are welded to the lattice column angle steel. Then, the length of the telescopic support rods is adjusted to support the manufactured lattice column on the guide pulleys. The telescopic half-shafts are alternately contracted and retracted to slide the lattice column out of the rotating main shaft along the guide pulleys.

[0014] As a preferred embodiment, the specific method for reinforcing the soil of the pit sidewall in step three is as follows: excavate the first layer of pit soil, drive inclined steel pipe piles and vertical steel pipe piles into the soil of the pit sidewall, spray a layer of concrete surface layer on the surface of the pit sidewall, and pour the tail ends of the inclined steel pipe piles and vertical steel pipe piles into the concrete surface layer.

[0015] Preferably, in step four, the end of the horizontal support is connected to the horizontal ring beam. First, the reinforcing bars of the horizontal ring beam and the horizontal support are tied. Then, the side formwork of the horizontal ring beam and the horizontal support is erected, and a track is placed on the surface of the horizontal ring beam. A lifting ring is placed on the surface of the horizontal support. The track and the lifting ring are spot-welded to the reinforcing bars of the horizontal ring beam and the horizontal support, respectively. Then, concrete is poured into the formwork and vibrated to compact it. After the concrete of the horizontal ring beam and the horizontal support reaches the design strength, the recyclable anchor cable is tensioned and anchored using anchor blocks. The lifting rings are evenly spaced along the length of the horizontal support.

[0016] Preferably, in step five, a steel casing is driven into the dewatering well located inside the foundation pit, and a pressure relief pipe is inserted into the steel casing. Then, an upper sealing plate and a lower sealing plate are welded to the upper end of the steel casing, and a layer of reinforcing wire mesh is laid between the upper and lower sealing plates. Then, bottom sealing concrete is poured between the upper and lower sealing plates. The upper and lower sealing plates are flush with the upper and lower surfaces of the bottom sealing concrete, respectively, and annular flow plates are provided on the upper and lower sealing plates.

[0017] Preferably, in steps five and six, the pressure relief pipe passes through the center of the upper sealing plate; the pressure relief pipe is equipped with multiple perforated metal plates, and the upper end of the pressure relief pipe is equipped with a rubber sealing plug; before the bottom sealing concrete reaches the design strength, groundwater is continuously pumped out through the pressure relief pipe; after the bottom sealing concrete reaches the design strength, the main structure in the foundation pit is constructed, and then a sleeve valve grouting pipe is inserted from the pressure relief pipe to inject micro-expansion cement mortar into the steel sleeve of the dewatering well, and then the pressure relief pipe is sealed with a rubber sealing plug.

[0018] Preferably, in step seven, the suspended dismantling support includes an L-shaped clamp, a hydraulic strut, a guide pulley, and a steel wire rope. One end of the hydraulic strut is hinged to the L-shaped clamp, and the guide pulley is installed at the other end of the hydraulic strut. An attached safety operating platform is erected on the pre-embedded track of the horizontal ring beam, and the recyclable anchor cable is dismantled using the attached safety operating platform. One end of the steel wire rope is tied to the lifting ring of the horizontal support, and the other end is tied to the lattice column. Then, the horizontal support is cut section by section, and the L-shaped clamp is inserted into the cutting seam and fixed to the horizontal support using expansion bolts. The steel wire rope is supported on the guide pulley, and then the horizontal support is cut again. The cut concrete blocks are then lowered to the bottom of the pit. After each section of concrete block is dismantled, the suspended dismantling support is moved towards the lattice column. The horizontal support is cut and dismantled section by section in the above manner.

[0019] Preferably, in step seven, the attached safety operating platform is supported on the pre-embedded track by a sliding bearing plate, the sliding bearing plate is provided with a counterweight, and a flip hinge is provided between the sliding bearing plate and the attached safety operating platform.

[0020] The support system for large, irregularly shaped deep foundation pits is obtained by any of the methods described above.

[0021] The beneficial effects of this invention are:

[0022] 1) The adjustable and standardized jig proposed in this technology can be used to process and manufacture lattice columns of different structural dimensions, while ensuring the manufacturing accuracy of the lattice columns, reducing the difficulty of welding operations, and shortening the manufacturing cycle.

[0023] 2) The outer side of the steel casing of the dewatering well is equipped with double sealing plates and reinforced steel wire mesh, which can effectively improve the sealing performance of the outer side of the steel casing; the inner side of the steel casing is equipped with a perforated metal plate and pressure relief pipe, which can effectively prevent the micro-expansion cement mortar from being squeezed out from the steel casing and improve the sealing effect.

[0024] 3) The horizontal supports are dismantled in sections and blocks. The existing lattice columns and horizontal supports are used to set up a hanging dismantling scaffold. The cut concrete blocks are then hoisted to the bottom of the pit without the need for scaffolding, which can effectively reduce the amount of on-site work and lower construction costs.

[0025] 4) Anchor cable retrieval operations rely on an attached safety work platform. The work platform can slide along the pre-buried track, which can effectively improve the efficiency of anchor cable retrieval operations while ensuring the safety of workers.

[0026] 5) Inclined and vertical steel pipe piles were driven into the soil of the first-level foundation pit sidewalls, which effectively ensured the support effect of the foundation pit sidewalls under the limited space conditions and prevented the foundation pit from collapsing during construction. Attached Figure Description

[0027] Figure 1 This is a flowchart of the construction method of the present invention;

[0028] Figure 2 This is a schematic diagram of the deep foundation pit support system structure;

[0029] Figure 3 yes Figure 2 Schematic diagram of the anchor cable recovery operation platform at node A;

[0030] Figure 4 This is a schematic diagram of the welding and positioning of the sealing plate for the dewatering well;

[0031] Figure 5 This is a schematic diagram of well sealing and anchor cable recovery.

[0032] Figure 6 This is a schematic diagram of grouting and sealing of dewatering wells;

[0033] Figure 7 This is a schematic diagram showing the completion of the grouting and sealing operation of the dewatering well;

[0034] Figure 8 This refers to the process of dismantling the internal support suspension. Figure 1 ;

[0035] Figure 9 yes Figure 8 Detailed drawing of the dismantling and installation of the hanger at node B;

[0036] Figure 10 This refers to the process of dismantling the internal support suspension. Figure 2 ;

[0037] Figure 11 This refers to the process of dismantling the internal support suspension. Figure 3 ;

[0038] Figure 12 This refers to the process of dismantling the internal support suspension. Figure 4 ;

[0039] Figure 13 It is an adjustable, standardized tire frame;

[0040] Figure 14 This is a detailed view of a portion of the adjustable, standardized tire frame;

[0041] Figure 15 This is a schematic diagram of the assembly and construction of lattice columns;

[0042] Figure 16 This is a schematic diagram of the lattice column assembly and disassembly.

[0043] Figure 17 This is a schematic diagram of a lattice column structure.

[0044] Markings in the diagram: 11-Ground surface, 12-Foundation pit, 13-Inclined steel pipe pile, 14-Vertical steel pipe pile, 15-Concrete surface layer, 16-External support structure, 21-Drilled cast-in-place pile, 22-Lattice column, 23-Horizontal support, 24-Lifting ring, 25-Horizontal ring beam, 26-Recoverable anchor cable, 27-Anchor, 28-Railway, 29-Attached safety operating platform, 210-Flip hinge, 211-Counterweight block, 212-Sliding bearing plate, 31-Dewatering well, 32-Steel casing, 33-Upper sealing plate, 34-Lower sealing plate, 35-Circular ring Flow plate, 36-Bottom sealing concrete, 37-Porous metal plate, 38-Pressure relief pipe, 39-Sleeve valve grouting pipe, 310-Micro-expansion cement mortar, 311-Rubber sealing plug, 312-Reinforcing wire mesh, 41-L-shaped clamping plate, 42-Hydraulic strut, 43-Guide pulley, 44-Wire rope, 45-Expansion bolt, 46-Cutting seam, 47-Concrete block, 51-Rotating spindle, 52-Fixed rotating shaft, 53-Telescopic half shaft, 54-Telescopic strut, 55-Limiting angle steel, 56-Guide pulley, 61-Lattice column angle steel, 62-Connecting steel plate. Detailed Implementation

[0045] The present invention will be further described below with reference to embodiments. The description of the embodiments below is only for the purpose of helping to understand the present invention. It should be noted that those skilled in the art can make several modifications to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0046] Example 1

[0047] As one example, such as Figures 1 to 17As shown, the construction method for this large-scale, irregularly shaped deep foundation pit support system includes the following construction steps:

[0048] Step 1: Mark out the plan position of the foundation pit 12 on the ground 11, construct the outer support structure 16 along the edge of the foundation pit 12, and construct dewatering wells 31 inside and outside the excavation area of ​​the foundation pit 12.

[0049] Step 2: Manufacture the lattice column 22 using an adjustable prefabricated jig. Adjust the length of the telescopic strut 54 according to the size of the lattice column 22 so that the distance between the limiting angle steels 55 is equal to the side length of the lattice column 22. Then place the lattice column angle steel 61 on the limiting angle steel 55 and weld the connecting steel plate 62 on the lattice column angle steel 61. Then adjust the length of the telescopic strut 54 to support the manufactured lattice column 22 on the guide pulley 56. Alternately contract and retract the telescopic half shaft 53 to slide the lattice column 22 out from the rotating main shaft 51 along the guide pulley 43. Construct the bored pile 21 in the foundation pit and pour the lower end of the lattice column 22 onto the bored pile 21.

[0050] Step 3: Excavate the first layer of foundation pit 12 and drive inclined steel pipe piles 13 and vertical steel pipe piles 14 into the soil of the side wall of foundation pit 12. Then spray a layer of concrete surface layer 15 on the surface of the side wall of foundation pit 12 and pour the tail ends of inclined steel pipe piles 13 and vertical steel pipe piles 14 into the concrete surface layer 15.

[0051] Step 4: Insert recyclable anchor cables 26 into the side wall of the foundation pit 12, and then construct the horizontal ring beam 25 and horizontal support 23 closely adjacent to the outer support structure 16. The end of the horizontal support 23 is connected to the horizontal ring beam 25. First, tie the steel bars of the horizontal ring beam 25 and the horizontal support 23, and then set up the side formwork of the horizontal ring beam 25 and the horizontal support 23. Place the track 28 on the surface of the horizontal ring beam 25 and the lifting ring 24 on the surface of the horizontal support 23. The track 28 and the lifting ring 24 are spot welded to the steel bars respectively. Then, pour concrete into the formwork and vibrate it to make it dense. After the concrete of the horizontal ring beam 25 and the horizontal support 23 reaches the design strength, tension the recyclable anchor cables 26 and use anchors 27 to tension and anchor the recyclable anchor cables 26.

[0052] Step 5: Excavate the soil of the foundation pit 12 downwards, and construct the horizontal support system inside the foundation pit 12 according to the method described in Step 4. The support system is constructed one layer at a time according to the principle of excavating one layer at a time until the foundation pit is excavated to the design depth. Drive a steel casing 32 into the dewatering well 31 located inside the foundation pit 12, and insert a pressure relief pipe 38 into the steel casing 32. Then weld the sealing plate 33 and the lower sealing plate 34 to the upper end of the steel casing 32. Then pour the bottom sealing concrete 36 of the foundation pit 12, and lay a layer of reinforcing wire mesh 312 between the upper sealing plate 33 and the lower sealing plate 34.

[0053] Step 6: Before the bottom sealing concrete 36 reaches the design strength, continue to pump out groundwater through the pressure relief pipe 38. After the bottom sealing concrete 36 reaches the design strength, construct the main structure inside the foundation pit 12. Then, insert the sleeve valve grouting pipe 39 into the pressure relief pipe 38 and inject micro-expansion cement mortar 310 into the steel sleeve 32 of the dewatering well 31. Then, use the rubber sealing plug 311 to seal the pressure relief pipe 38.

[0054] Step 7: Erect an attached safety operation platform 29 on the pre-embedded track 28 of the horizontal ring beam 25, and remove the recyclable anchor cable 26 based on the attached safety operation platform 29; tie one end of the wire rope 44 to the lifting ring 24 of the horizontal support 23, and the other end to the lattice column 22; then cut the horizontal support 23 section by section, and insert the L-shaped clamp 41 of the hanging dismantling bracket into the cutting seam 46, and fix it to the horizontal support 23 with expansion bolts 45, support the wire rope 44 on the guide pulley 43 of the hanging dismantling bracket, and then continue to cut the horizontal support 23, and lower the cut concrete block 47 to the bottom of the pit. After each section of concrete block 47 is removed, move the hanging dismantling bracket towards the lattice column 22, and cut and dismantle the horizontal support 23 section by section in the above manner.

[0055] Example 2

[0056] As another embodiment, this embodiment two proposes a more specific construction method for a large-scale irregular deep foundation pit support system based on embodiment one.

[0057] In step one, the external support structure 16 can be a bored pile or a diaphragm wall.

[0058] In step two, the adjustable fixed-shape jig includes a rotating main shaft 51, a fixed rotating shaft 52, a telescopic half shaft 53, a telescopic support leg 54, a limiting angle steel 55, and a guide pulley 56. One end of the rotating main shaft 51 is supported on the fixed rotating shaft 52, and the middle and the other end are supported on the telescopic half shaft 53. Four limiting angle steels 55 are arranged circumferentially along the rotating main shaft 51, and several are arranged longitudinally. Two guide pulleys 56 are arranged horizontally, and several are arranged longitudinally. The limiting angle steels 55 and the guide pulleys 56 are fixed to the rotating main shaft 51 by the telescopic support rod 54.

[0059] In step four, the lifting rings 24 are evenly spaced along the length of the horizontal support 23.

[0060] In step five, the upper sealing plate 33 and the lower sealing plate 34 are flush with the upper and lower surfaces of the bottom sealing concrete 36, respectively, and the upper sealing plate 33 and the lower sealing plate 34 are respectively provided with annular flow plates 35.

[0061] In steps five and six, the pressure relief pipe 38 passes through the center of the upper sealing plate 33; the pressure relief pipe 38 is provided with multiple perforated metal plates 37, and the upper end of the pressure relief pipe 38 is provided with a rubber sealing plug 311.

[0062] In step seven, the suspended dismantling support includes an L-shaped clamp 41, a hydraulic strut 42, a guide pulley 43, and a steel wire rope 44. One end of the hydraulic strut 42 is hinged to the L-shaped clamp 41, and the guide pulley 43 is installed at the other end of the hydraulic strut 42. One end of the steel wire rope 44 is tied to the lifting ring 24, and the other end is tied to the lattice column 22. The steel wire rope 44 is supported on the guide pulley 43.

[0063] The attached safety operation platform 29 is supported on the pre-embedded track 28 by a sliding bearing plate 212. The sliding bearing plate 212 is provided with a counterweight 211, and a flip hinge 210 is provided between the sliding bearing plate 212 and the attached safety operation platform 29.

[0064] It should be noted that the parts in this embodiment that are the same as or similar to those in Embodiment 1 can be referred to each other, and will not be repeated in this application.

[0065] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

Claims

1. A construction method for a large-scale, irregularly shaped deep foundation pit support system, characterized in that, The construction steps include the following: Step 1: Mark out the plan position of the foundation pit on the ground, construct the outer support structure along the edge of the foundation pit, and construct dewatering wells inside and outside the excavation area of ​​the foundation pit. Step 2: Manufacture the lattice column using an adjustable, standardized formwork. Construct bored piles within the foundation pit, and cast the lower end of the lattice column onto the bored piles. The adjustable, standardized formwork includes a rotating main shaft, a fixed rotating shaft, a telescopic half-shaft, telescopic struts, limiting angle steel, and guide pulleys. One end of the rotating main shaft is supported on the fixed rotating shaft, while the middle and the other end are supported on the telescopic half-shaft. Four limiting angle steels are arranged circumferentially along the rotating main shaft, and several are arranged longitudinally. Two guide pulleys are arranged horizontally, and several are arranged longitudinally. Each limiting angle steel and guide pulley is fixed to the rotating main shaft by telescopic struts. When making the lattice column, the length of the telescopic struts is adjusted according to the size of the lattice column so that the distance between the limiting angle steels is equal to the side length of the lattice column. Then the lattice column angle steel is placed on the limiting angle steel, and connecting steel plates are welded on the lattice column angle steel. Then the length of the telescopic struts is adjusted to support the manufactured lattice column on the guide pulley. The telescopic half shaft is alternately contracted and retracted to slide the lattice column out of the rotating main shaft along the guide pulley. Step 3: Excavate the first layer of soil in the foundation pit with a slope and reinforce the soil on the side walls of the foundation pit; Step 4: Insert recyclable anchor cables into the sidewalls of the foundation pit, construct horizontal ring beams and horizontal supports along the outer support structure, and tension the recyclable anchor cables to form a horizontal support system; Step 5: Excavate the foundation pit layer by layer downwards, and at the same time construct the horizontal support system layer by layer according to the method described in Step 4 until the design depth of the foundation pit is reached; drive steel casings with pressure relief pipes into the dewatering wells in the foundation pit, and pour bottom sealing concrete at the upper end of the steel casings. Step 6: Pump out groundwater through the pressure relief pipe until the bottom sealing concrete reaches the design strength, then construct the main structure inside the foundation pit and seal the dewatering well; Step 7: Slide and erect an attached safety operating platform on the horizontal ring beam. Using this platform, dismantle the recyclable anchor cables and cut and dismantle the horizontal supports segment by segment. The suspended dismantling support includes an L-shaped clamp, hydraulic struts, guide pulleys, and wire ropes. One end of the hydraulic strut is hinged to the L-shaped clamp, and the guide pulley is installed at the other end of the hydraulic strut. Erect the attached safety operating platform on the pre-embedded track of the horizontal ring beam and use it to dismantle the recyclable anchor cables. Tie one end of the wire rope to the lifting ring of the horizontal support and the other end to the lattice column. Then cut the horizontal supports segment by segment, inserting the L-shaped clamp into the cutting seam and fixing it to the horizontal support using expansion bolts. Support the wire rope on the guide pulley, and continue cutting the horizontal support. Lower the cut concrete blocks to the bottom of the pit. After each section of concrete block is removed, move the suspended dismantling support towards the lattice column. Continue cutting and dismantling the horizontal supports segment by segment in the same manner.

2. The construction method of the large-scale irregular deep foundation pit support system according to claim 1, characterized in that, In step one, the external support structure is a bored pile or a diaphragm wall.

3. The construction method of the large-scale irregular deep foundation pit support system according to claim 1, characterized in that, In step three, the specific method for reinforcing the soil of the pit sidewall is as follows: excavate the first layer of pit soil, drive inclined steel pipe piles and vertical steel pipe piles into the soil of the pit sidewall, spray a layer of concrete surface layer on the surface of the pit sidewall, and pour the tail ends of the inclined steel pipe piles and vertical steel pipe piles into the concrete surface layer.

4. The construction method of the large-scale irregular deep foundation pit support system according to claim 1, characterized in that, In step four, the end of the horizontal support is connected to the horizontal ring beam. First, the reinforcing bars of the horizontal ring beam and the horizontal support are tied. Then, the side formwork of the horizontal ring beam and the horizontal support is erected, and a track is placed on the surface of the horizontal ring beam. A lifting ring is placed on the surface of the horizontal support. The track and the lifting ring are spot-welded to the reinforcing bars of the horizontal ring beam and the horizontal support, respectively. Then, concrete is poured into the formwork and vibrated to compact it. After the concrete of the horizontal ring beam and the horizontal support reaches the design strength, the recyclable anchor cable is tensioned and anchored using anchor blocks. The lifting rings are evenly spaced along the length of the horizontal support.

5. The construction method of the large-scale irregular deep foundation pit support system according to claim 1, characterized in that, In step five, a steel casing is driven into the dewatering well located inside the foundation pit, and a pressure relief pipe is inserted into the steel casing. Then, an upper sealing plate and a lower sealing plate are welded to the upper end of the steel casing, and a layer of reinforcing wire mesh is laid between the upper and lower sealing plates. Then, bottom sealing concrete is poured between the upper and lower sealing plates. The upper and lower sealing plates are flush with the upper and lower surfaces of the bottom sealing concrete, respectively, and annular flow plates are provided on the upper and lower sealing plates.

6. The construction method of the large-scale irregular deep foundation pit support system according to claim 1, characterized in that, In steps five and six, the pressure relief pipe passes through the center of the upper sealing plate; the pressure relief pipe is equipped with multiple perforated metal plates, and the upper end of the pressure relief pipe is equipped with a rubber sealing plug; before the bottom sealing concrete reaches the design strength, groundwater is continuously pumped out through the pressure relief pipe; after the bottom sealing concrete reaches the design strength, the main structure in the foundation pit is constructed, and then the sleeve valve grouting pipe is inserted from the pressure relief pipe to inject micro-expansion cement mortar into the steel sleeve of the dewatering well, and then the pressure relief pipe is sealed with a rubber sealing plug.

7. The construction method of the large-scale irregular deep foundation pit support system according to claim 4, characterized in that, In step seven, the attached safety operating platform is supported on the pre-embedded track by a sliding bearing plate. The sliding bearing plate is equipped with a counterweight, and a flip hinge is provided between the sliding bearing plate and the attached safety operating platform.

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