A foundation pit retaining structure for soft soil foundation and construction method thereof

Abstract

The present invention discloses a foundation pit retaining structure for a soft soil foundation and a construction method thereof. The structure includes a plurality of first steel piles spaced apart from the foundation pit and arranged along the periphery of the foundation pit and inserted into the soft soil foundation. Two adjacent first steel piles are connected to a first metal corrugated plate assembly inserted into the soft soil foundation element and continue to form a first retaining wall. The structure also includes a plurality of second steel piles spaced apart along the periphery of the foundation pit and inserted into the soft soil foundation. Two adjacent second steel piles are detachably connected to a second metal corrugated plate assembly inserted into the soft soil foundation and continue to form a second retaining wall. A horizontal cross-connecting steel beam is detachably connected to the top of the first steel pile and the top of the second steel pile in each pair of steel piles. A plurality of steel strands and a connecting steel pipe connection structure are provided between each pair of steel piles. The present invention provides good integrity between the inner and outer rows of piles, strong bearing capacity, good safety performance, relatively small engineering workload, and relatively low construction cost.

Description

Technical Field

[0001] The invention relates to the technical field of foundation pit retaining system construction, in particular to a foundation pit retaining structure for a soft soil foundation and a construction method thereof. Background Art

[0002] Soft soil foundations are widely distributed along the southern coast of my country and along inland rivers and lakes. The most common retaining structures for soft soil foundations are underground diaphragm walls or rows of piles and concrete mixing piles, which form a circle around the pit. A row of piles is a ring or row of reinforced concrete piles formed around the pit to retain soil. Cement-soil mixing piles typically interlock with adjacent piles to retain water; a circle or row of reinforced concrete piles can also be used to retain soil and water. To enhance the retaining structure's bearing capacity against lateral soil pressure and ensure safety during construction and excavation, those skilled in the art are continually improving the support structures and methods used in the pit retaining structure.

[0003] Initially, the original horizontal inward support was changed to an inclined inward support. However, due to the existence of the inclined inward support, it still had disadvantages such as hindering the excavation of the foundation pit soil, requiring waiting for curing time and waiting for the support construction to be completed, thus affecting the construction progress and efficiency.

[0004] In recent years, double-row pile structures have gradually been used to replace the support in the foundation pit, that is, to replace the horizontal inward support and the inclined inward support.

[0005] The double-row pile structure generally uses a shoulder-pole type connecting beam on the top of the reinforced concrete piles, that is, on the ground, to connect the respective top pressure beams on the top of the double-row piles. However, this structure can only ensure the integrity of the top, but cannot meet the needs of strong bearing capacity and strong safety performance such as resisting the lateral pressure of the soil at the vertical depth of the reinforced concrete piles near the foundation pit.

[0006] A Chinese patent website discloses a retaining structure for a double-row foundation pit of reinforced concrete piles. Reinforced concrete connectors are used between the inner and outer rows of reinforced concrete piles, i.e., a circle of reinforced concrete piles close to the foundation pit and a circle of reinforced concrete piles located away from the foundation pit and in the soil around the foundation pit, to connect the inner and outer rows of reinforced concrete piles into a whole. This retaining structure has good overall performance, but trenches need to be excavated all around. A circle of trenches is tens to hundreds of meters long and five to more than ten meters deep. The project volume is large, the construction period is long, the construction speed is slow, and the construction efficiency is low. The construction costs such as equipment shift fees and workers' wages are high. The consumption of building materials is large, and the material cost is high. Moreover, after the retaining mission of the foundation pit retaining structure is completed, its connection structure cannot be dismantled, so the steel cannot be reused. Summary of the Invention

[0007] A technical problem to be solved by the present invention is to provide a foundation pit retaining structure for a soft soil foundation, which has good integrity between the inner and outer rows of piles, strong bearing capacity, good safety performance, relatively small engineering volume and relatively low construction cost.

[0008] A technical solution of the present invention is to provide a foundation pit retaining structure for soft soil foundation.

[0009] The invention comprises a plurality of first steel piles spaced apart from the foundation pit and arranged along the periphery of the foundation pit and inserted into the soft soil foundation. Two adjacent first steel piles are detachably connected to a rigid integral first metal corrugated plate assembly inserted into the soft soil foundation to form an earth-retaining and water-retaining unit. The earth-retaining and water-retaining unit extends along the periphery to form a circle of first earth-retaining and water-retaining walls. A circle of first purlins is detachably connected to the top of the circle of first steel piles.

[0010] The present invention provides a foundation pit retaining structure for a soft soil foundation, further comprising a plurality of second steel piles spaced apart along the periphery of the foundation pit and inserted into the soft soil foundation, wherein two adjacent second steel piles are detachably connected to a rigid integral second metal corrugated plate assembly inserted into the soft soil foundation to form an earth-retaining and water-retaining unit, wherein the earth-retaining and water-retaining unit extends along the periphery of the foundation pit to form a circle of second earth-retaining and water-retaining walls; a circle of second steel piles is detachably connected to at least one circle of second surrounding purlins;

[0011] The top of the first steel pile and the top of the second steel pile in each pair of steel piles are detachably connected to a horizontal transverse connecting steel beam; the first steel pile and the second steel pile in each pair of steel piles have at least one through hole along the vertical depth, and at least one connecting steel pipe inserted horizontally from the foundation pit is accommodated in the through hole corresponding to the first steel pile and the second steel pile in each pair of steel piles, and each connecting steel pipe has a steel strand that is movably fitted in a plastic pipe, and the U-shaped inner end of the steel strand and the U-shaped inner end of the plastic pipe are accommodated in a U-shaped groove of a bullet-shaped concrete body, and the middle part of the steel strand is placed in the connecting steel pipe, and there is a grouting pipe for grouting in the connecting steel pipe, and the solidified slurry, the U-shaped part of the plastic pipe and the bullet-shaped concrete body constitute an inner anchor head, and the two outer ends of the steel strand on the foundation pit side and the anchor constitute an outer anchor head.

[0012] After adopting the above structure, the foundation pit retaining structure of soft soil of the present invention has the following advantages:

[0013] The present invention provides a foundation pit retaining structure for a soft soil foundation, comprising an outer first retaining wall formed of first steel piles and a rigid first corrugated metal plate assembly, located away from the foundation pit, and an inner second retaining wall formed of second steel piles and a rigid second corrugated metal plate assembly, achieving a double-layer retaining effect. Two circles of steel piles are directly inserted into the soft soil foundation, and the first steel piles in one circle and the second steel piles in one circle are connected to each other by a rigid corrugated metal plate assembly, in addition to being connected to each other at the top by surrounding purlins. In particular, the two rows of steel piles, i.e., each pair of first and second steel piles, are rigidly connected at the top by a horizontal transverse connecting steel beam, at least one anchoring steel strand, and a connecting steel pipe. The above structure constitutes a two-circle rigidly connected foundation pit retaining structure as a whole. Even without horizontal or oblique inward supports within the foundation pit, the structure still has a strong bearing capacity against lateral soil pressure and a high safety performance.

[0014] The construction of the foundation pit retaining structure of the present invention does not require digging trenches. It only requires inserting two rows of steel piles on site and screwing them together on site at the positions of the ground markings, such as the positions of the construction lines marked with lime. Compared with digging trenches that are tens to hundreds of meters long and about one meter wide and pouring steel concrete piles and reinforced concrete connectors on site, the engineering workload is relatively small, the construction period is relatively short, the construction speed is relatively fast, the labor intensity is relatively low, the construction efficiency is relatively high, and the construction costs such as equipment shift fees and workers' wages are relatively low.

[0015] After the construction of the foundation pit building is completed, the detachable steel can be recycled for reuse, which reduces the consumption of building materials, lowers the material cost of the foundation pit retaining structure, and greatly saves steel resources.

[0016] Furthermore, the first corrugated metal plate assembly and the second corrugated metal plate assembly each include two corrugated metal plates of the same shape and size, each corrugated metal plate is composed of a plurality of vertical flat plates and a plurality of vertical angle plates connected at intervals, and a plurality of vertical long metal plates extending vertically along the corrugated metal plates and parallel to each other are sandwiched between the two corrugated metal plates, each pair of vertical flat plates of the two corrugated metal plates is screwed and fixed to a vertical long metal plate by a plurality of bolts and a plurality of nuts, and the corners of the multiple vertical angle plates of the two corrugated metal plates are all away from the vertical long metal plates to form an external arch structure that bears the lateral pressure of the soil; the two adjacent vertical long metal plates are connected by a plurality of horizontal steel connecting rods arranged vertically, and the top and bottom of the corrugated metal plates are provided with horizontal steel connecting bars connecting each vertical long metal plate and the corrugated metal plate, so that the first corrugated metal plate assembly and the second corrugated metal plate assembly constitute a rigid whole. After adopting the above structure, the metal corrugated plate assembly not only has a good function of water retaining wall, but also has good rigidity and integrity, good downward insertion ability, and good ability to resist lateral pressure of soil, which further ensures that the foundation pit retaining structure has a strong bearing capacity to resist lateral pressure of soil and has high safety performance and good waterproof performance.

[0017] Furthermore, the detachable connection structure between the first metal corrugated plate assembly and the first steel pile, and the detachable connection structure between the second metal corrugated plate assembly and the second steel pile are both: a vertical plug-in steel is fixed on the opposite side walls of the two adjacent first steel piles and the opposite side walls of the two adjacent second steel piles, the plug-in notch of the vertical plug-in steel faces the side away from the foundation pit, and the height dimension of the vertical plug-in steel is equal to or greater than the height dimension of the metal corrugated plate assembly; the outer sides of the vertical long metal plates on both sides of the first metal corrugated plate assembly and the second metal corrugated plate assembly are fixed to the inner side of the web of a vertical channel steel, and the side plate close to the foundation pit on both sides of the vertical channel steel is vertically plugged into the notch of the vertical plug-in steel, and the height dimension of the vertical channel steel is equal to or greater than the height dimension of the metal corrugated plate assembly. After adopting the above structure, it is convenient to connect and install the metal corrugated plate assembly with the first steel pile and the second steel pile, and it is also convenient to disassemble for subsequent recycling, which further ensures the technical effects of high construction efficiency, low construction cost and good waterproof and resistance to lateral pressure of soil of this foundation pit retaining structure.

[0018] Furthermore, the structure of the vertical splicing steel is as follows: the vertical U-shaped steel with a notch is welded on the opposite side wall of the first steel pile and also on the opposite side wall of the second steel pile. The vertical U-shaped steel has a longer side close to the foundation pit and a shorter side close to the foundation pit to form a notch. The side plate close to the foundation pit on both sides of the vertical channel steel is vertically spliced ​​into the U-shaped groove of the vertical U-shaped steel. After the vertical splicing steel adopts the above specific structure, the side plate close to the foundation pit on both sides of the vertical channel steel is vertically spliced ​​into the U-shaped groove of the vertical U-shaped steel, making it more convenient to splice the vertical channel steel connected with the vertical metal plate assembly and the vertical U-shaped steel, the splicing structure is more solid and reliable, the retaining effect of soil and water is better, and the ability to resist lateral pressure of the soil is better.

[0019] Furthermore, the structure of the vertical splice steel is as follows: the vertical angle steel is welded to the opposite side wall of the first steel pile and also to the opposite side wall of the second steel pile, the opening of the vertical angle steel faces away from the foundation pit, the side plate of the vertical channel steel close to the foundation pit is vertically spliced ​​to the horizontal plate of the vertical angle steel, and a channel steel side block is welded on the side of the horizontal plate of the vertical angle steel away from the foundation pit to prevent the vertical channel steel spliced ​​to the horizontal plate of the vertical angle steel from detaching from the horizontal plate toward the side away from the foundation pit. After adopting the above structure, another specific structure of vertical splice steel is provided, which also has the technical effects of convenient splicing, reliable splicing, good soil and water retaining effect, and good ability to resist horizontal soil pressure. Compared with the first specific structure of vertical splice steel, it can relatively save steel.

[0020] Furthermore, the first and second steel piles are both constructed of H-shaped steel, with the webs of each pair of H-shaped steels parallel to each other, and the through holes are all provided on the webs. This structure improves the mechanical properties of the steel piles and facilitates construction, further ensuring the high efficiency of the construction of the foundation pit retaining structure.

[0021] Furthermore, the first and second steel piles in each pair of steel piles are provided with respective first and second through holes every few meters vertically from the top downward along the depth of the foundation pit. The first through holes are tapered holes for axially limiting the inner end of the connecting steel pipe. The inner end of the connecting steel pipe matches the tapered hole and is smaller at the end away from the foundation pit and larger at the part close to the foundation pit. The second through holes are straight through holes for passing through the steel pipe. With the above structure, the vertical connection between the two rows of steel piles is more secure and integrated, and the insertion and removal of the steel pipe are convenient, reliable, and quick, further ensuring that the foundation pit retaining structure has a strong bearing capacity against lateral soil pressure and has high safety performance and high construction efficiency.

[0022] Furthermore, the first metal corrugated plate component is the first metal corrugated plate component that is pulled out as a whole by disassembling the horizontal horizontal connecting steel beam and the first purlin after the construction of the main building of the foundation pit is completed, and using a vertical pulling device; the first steel pile is the first steel pile that is pulled out as a whole by disassembling the steel strand and the connecting steel pipe, and using a vertical pulling device after the construction of the main building of the foundation pit is completed, and using a vertical pulling device; the second metal corrugated plate component is the second purlin that is pulled out as a whole by disassembling the top circle after the construction of the main building of the foundation pit is completed, and using a vertical pulling device The second metal corrugated plate assembly is pulled out as a whole; the steel strands and the connecting steel pipes and the second purlin on the side of the foundation pit are the steel strands and the connecting steel pipes that are pulled out by the horizontal pulling device after the external anchor heads are removed layer by layer from bottom to top in the process of constructing the main building in the foundation pit; the second steel piles are the second steel piles that are pulled out by the vertical pulling device after the steel strands, the connecting steel pipes and the second purlin on the side of the foundation pit are removed and the second purlin on the top is removed after the construction of the main building of the foundation pit is completed. After the above structure is adopted, all the steel components constituting the foundation pit retaining structure of the present invention can be gradually dismantled during the completion of the main building of the foundation pit, and can be completely dismantled after the main building of the foundation pit is completed. They can be recycled for reuse, i.e., reused, which greatly reduces the consumption of building materials, greatly reduces the material cost of the foundation pit retaining structure, and greatly saves steel resources.

[0023] Another technical problem to be solved by the present invention is to provide a construction method for a foundation pit retaining structure for a soft soil foundation, in which the inner and outer rows of piles have good integrity with each other, strong bearing capacity, good safety performance, relatively small engineering volume and relatively low construction cost.

[0024] Another technical solution of the present invention is to provide a construction method for a foundation pit retaining structure on a soft soil foundation, wherein the construction of the foundation pit retaining structure in any of the above technical solutions comprises the following construction steps:

[0025] (1) Welding respective vertical plug-in steels for inserting the first metal corrugated plate assembly on the left and right sides of each first steel pile in advance, and using a pile driver to insert multiple first steel piles into the soft soil foundation at predetermined depths along the periphery of the foundation pit at pre-marked positions on the surface of the soft soil foundation away from the foundation pit;

[0026] (2) A crane is used to lift the first metal corrugated plate assembly that has been prefabricated and welded with vertical channel steel to the insertion point, and then the power head of the pile driver is used to insert the first metal corrugated plate assembly that has been welded with vertical channel steel into the soft soil foundation along the vertical insertion steel of two adjacent first steel piles to a predetermined depth to form a retaining and water-retaining unit, and then the retaining and water-retaining units are constructed one by one along the four sides to form a circle of first retaining and water-retaining walls;

[0027] (3) A circle of first purlins is detachably connected to the top of a circle of first steel piles;

[0028] (4) Welding respective vertical plug-in steels for plugging in the second metal corrugated plate assembly on the left and right sides of each second steel pile in advance, and using a pile driver to insert multiple second steel piles into the soft soil foundation at predetermined depths along the periphery of the foundation pit at pre-marked positions on the surface of the soft soil foundation outside the foundation pit;

[0029] (5) Use a crane to lift the second metal corrugated plate assembly that has been prefabricated and welded with vertical channel steel to the plug-in location, then use the power head of the pile driver to insert the second metal corrugated plate assembly that has been welded with vertical channel steel into the soft soil foundation along the vertical plug-in steel of two adjacent second steel piles to a predetermined depth to form a retaining soil and water retaining unit, and then construct the retaining soil and water retaining units one by one along the outer periphery of the foundation pit to form a circle of second retaining soil and water retaining walls;

[0030] (6) One or more circles of second purlins are detachably connected to the second steel piles, and the multiple circles of second purlins are distributed along the vertical height;

[0031] (7) Use the power head of a horizontal pile driver to insert the connecting steel pipe connected with the steel strand, plastic pipe and bullet-shaped concrete body into the second through hole of the second steel pile, the soft soil foundation and the first through hole of the first steel pile from the foundation pit side and limit it axially. Then use the grouting pipe in the connecting steel pipe to inject cement slurry into the gap between the inner end of the connecting steel pipe and the bullet-shaped concrete body. After the cement slurry solidifies, tighten the two free ends of the steel strand on the foundation pit side with anchors and anchor them into an external anchor head.

[0032] After adopting the above construction steps, the construction method of a foundation pit retaining structure for a soft soil foundation of the present invention has the following advantages:

[0033] The present invention discloses a foundation pit retaining structure constructed by a soft soil foundation construction method, comprising an outer retaining wall formed of first steel piles and a rigid first corrugated metal plate assembly, located away from the foundation pit, and an inner retaining wall formed of second steel piles and a rigid second corrugated metal plate assembly, achieving a double-layer retaining effect. Two circles of steel piles are directly inserted into the soft soil foundation, and the first steel piles in one circle and the second steel piles in one circle are connected to each other by a rigid corrugated metal plate assembly, in addition to being connected at the top by surrounding purlins. In particular, the two rows of steel piles, i.e., each pair of first and second steel piles, are rigidly connected at the top by a horizontal transverse connecting steel beam, at least one anchoring steel strand, and a connecting steel pipe. The above structure forms a two-circle rigidly connected foundation pit retaining structure as a whole. Without horizontal or oblique inward supports within the foundation pit, the foundation pit retaining structure for soft soil of the present invention has a strong bearing capacity against lateral soil pressure and a high safety performance.

[0034] A construction method of the present invention does not require digging trenches. It only requires inserting two rows of steel piles on site and screwing them together on site to connect them into a whole at the positions of the construction lines marked on the ground, such as a few circles marked with lime. Compared with digging trenches of dozens or hundreds of meters long and about one meter wide and pouring steel concrete piles and reinforced concrete connectors on site, the project volume is relatively small, the construction period is relatively short, the construction speed is relatively fast, the labor intensity is relatively low, the construction efficiency is relatively high, and the construction costs such as equipment shift fees and workers' wages are relatively low.

[0035] Furthermore, the construction method of a foundation pit retaining structure for soft soil of the present invention further includes the following construction steps:

[0036] (8) During the construction of the main building in the foundation pit from bottom to top, the external anchor heads are dismantled layer by layer from bottom to top using the replacement support construction step and all the steel strands and all the connecting steel pipes are pulled out layer by layer using the transverse pulling equipment. One or more circles of the detachably connected second purlins on the foundation pit side are manually dismantled layer by layer in the foundation pit, and multiple second purlins in each circle are lifted away by a crane and replaced with temporary supports of the main building at the same time;

[0037] (9) After the construction of the main building of the foundation pit is completed, the detachable connections between the two ends of the horizontal cross-connecting steel beam and the top of the first steel pile and the top of the second steel pile in each pair of steel piles are manually dismantled on the ground one by one, and the horizontal cross-connecting steel beam is lifted away by a crane;

[0038] (10) Using a vertical drawing device to vertically pull out all the second metal corrugated plate components piece by piece;

[0039] (11) Use vertical pulling equipment to pull out all the second steel piles one by one;

[0040] (12) dismantling the first purlin and vertically pulling out all the first corrugated metal plate assemblies piece by piece using a vertical pulling device;

[0041] (13) Use vertical pulling equipment to pull out all the first steel piles one by one.

[0042] After adopting the above construction steps, all the steel components constituting the foundation pit retaining structure of the present invention can be gradually dismantled during the completion of the main construction of the foundation pit, and can be completely dismantled after the main construction of the foundation pit is completed, so as to be recycled and reused, which greatly reduces the consumption of building materials, greatly reduces the material cost of the foundation pit retaining structure, and greatly saves steel resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a schematic top-sectional view of the structure of a foundation pit retaining structure for a soft soil foundation according to the present invention (the vertical plug-in steel shows the structure of the second embodiment; the channel steel side blocks are not shown).

[0044] Figure 2 yes Figure 1 The enlarged structural diagram of A in the middle (the vertical plug-in steel shows the structure of the second embodiment; the channel steel side block is shown).

[0045] Figure 3 This is a schematic diagram of the structure in which the first steel pile and the second steel pile are connected via a horizontal cross-connecting steel beam, a steel pipe and a steel strand (only one steel pipe is shown; the heights of the first steel pile, the second steel pile and the metal corrugated plate assembly are also schematic, and the height is omitted. Figure 7 、 Figure 8 、 Figure 9 、 Figure 10 Same).

[0046] Figure 4 yes Figure 3 Schematic diagram of the horizontal cross-section structure at the center of the steel pipe.

[0047] Figure 5 yes Figure 4 Schematic diagram of the top cross-sectional structure of the second through hole of the second steel pile.

[0048] Figure 6 yes Figure 4 Schematic diagram of the top cross-sectional structure of the first through hole of the first steel pile.

[0049] Figure 7 yes Figure 5 Schematic diagram of the front view structure.

[0050] Figure 8 yes Figure 6 Schematic diagram of the front view structure.

[0051] Figure 9 It is a schematic diagram of the longitudinal cross-sectional structure of the metal corrugated plate assembly in the present invention along the width direction.

[0052] Figure 10 It is a schematic diagram of the longitudinal cross-sectional structure of the metal corrugated plate assembly in the present invention along the thickness direction.

[0053] Figure 11 It is a schematic cross-sectional structural diagram of the portion below the top horizontal steel connecting strip of the metal corrugated plate assembly of the present invention.

[0054] Figure 12 It is a schematic cross-sectional structural diagram of the outer surface spliced ​​metal corrugated plates at the upper and lower joints when the metal corrugated plate assembly in the present invention needs to be extended.

[0055] Figure 13 This is a schematic top view of the structure of the first embodiment of the vertical splicing steel in the present invention.

[0056] Figure 14 Yes Figure 4 Schematic enlarged structure diagram of B in

[0057] As shown in the figure: 1. Foundation pit, 2. First steel pile, 3. Second steel pile, 4. First metal corrugated plate assembly, 5. Second metal corrugated plate assembly, 6. Connecting steel pipe, 7. Second purlin, 8. Inner anchor head, 9. Channel steel side block, 10. One side plate close to the foundation pit, 11. Opposite side wall of the first steel pile, 12. Opposite side wall of the second steel pile, 13. Outer anchor head, 14. Steel strand, 15. Vertical angle steel, 16. Horizontal transverse connecting steel beam, 17. Concrete body in the shape of a bullet head, 18. Plastic pipe, 19. Grouting pipe, 20. U-shaped groove, 21. Second through hole, 22. First through hole, 23. Horizontal steel connecting rod, 24. Top horizontal steel connecting strip, 25. Vertical long strip metal plate, 26. Bolt, 27. Bottom horizontal steel connecting strip, 28. Vertical channel steel, 29. Connecting screw, 30. Vertical angle plate, 31. Vertical flat plate, 32. Nut, 33. Metal corrugated plate, 34. Metal connecting corrugated plate, 35. Notch, 36. C-shaped groove, 37. Vertical C-shaped steel, 38. First soil and water retaining wall, 39. Second soil and water retaining wall, 40. End part, 41. Part close to the foundation pit. Specific embodiments

[0058] The specific embodiments of the present invention will be further described below in conjunction with the accompanying drawings. It should be noted here that the description of these specific embodiments is used to help understand the present invention, but does not constitute a limitation to the present invention. In addition, the technical features involved in the various specific embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0059] As Figures 1-14 shown.

[0060] A foundation pit retaining structure for soft soil foundation of the present invention includes multiple first steel piles 2 that are spaced apart along the periphery of the foundation pit 1 and inserted into the soft soil foundation, and two adjacent first steel piles 2 are detachably connected to a first metal corrugated plate assembly 4 that is inserted into the soft soil foundation and is a rigid whole to form a soil and water retaining unit, and the soil and water retaining units extend along the outer periphery of the foundation pit edge to form a circle of first soil and water retaining walls 38. The tops of a circle of first steel piles 2 are detachably connected, for example, by screwing a circle of first purlins with multiple screws.

[0061] The present invention provides a foundation pit retaining structure for soft soil, further comprising a plurality of second steel piles 3 spaced apart along the outer periphery of the foundation pit 1 and inserted into the soft soil. Two adjacent second steel piles 3 are detachably connected to a rigid integral second metal corrugated plate assembly 5 inserted into the soft soil foundation to form a retaining and water-retaining unit. The retaining and water-retaining unit extends along the outer periphery of the foundation pit to form a circle of second retaining and water-retaining walls 39. A circle of second steel piles 3, such as an H-shaped steel, is detachably connected, for example, with a plurality of screws, to at least one circle of second purlins 7. Preferably, multiple circles of second purlins 7 are used, such as a circle of second steel piles 3 having a circle of second purlins 7 at the top to replace the reinforced concrete top beam of the prior art, so as to be recyclable and reusable. A circle of second purlins 7 fixed to the second steel piles 3 on the side of the foundation pit 1 may be provided at the vertical middle or lower portion of the second steel piles 3. The second purlin 7 can be made of channel steel or H-shaped steel, and the purlin 7 and the second steel pile 3 can be screwed together with multiple screws. Of course, welding is also possible. When disassembly is required, it can be easily disassembled by cutting with oxygen cutting equipment. The first purlin and the second purlin 7 are both called steel beams.

[0062] It is easy to understand that the meaning of "a plurality" in the plurality of screws in the present invention is broad, and refers to several, dozens, dozens or hundreds, etc.

[0063] It is not difficult to understand that, except for the turning points, the spacing settings of the first steel pile 2 and the second steel pile 3 refer to equal distance spacing settings, and the four turning points are symmetrically set relative to the center point of the foundation pit 1.

[0064] The present invention provides a foundation pit retaining structure for soft soil, wherein the top of the first steel pile 2 and the top of the second steel pile 3 in each pair of steel piles are detachably connected, for example, by screwing a plurality of screws to a horizontally connecting steel beam 16 . The first steel pile 2 and the second steel pile 3 in each pair of steel piles have at least one through hole along the vertical depth, and at least one connecting steel pipe 6 inserted horizontally from the foundation pit 1 is accommodated in the through hole corresponding to the first steel pile 2 and the second steel pile 3 in each pair of steel piles. Each connecting steel pipe 6 contains a steel strand 14 that is movably fitted in a plastic pipe 18. The U-shaped inner end of the steel strand 14 and the U-shaped inner end of the plastic pipe 18 are accommodated in a U-shaped groove 20 of a bullet-shaped concrete body 17. The middle part of the steel strand 14 is placed in the connecting steel pipe 6. A grouting pipe 19 for grouting is contained in the connecting steel pipe 6. The solidified slurry, the U-shaped part of the plastic pipe 18 and the bullet-shaped concrete body 17 constitute an internal anchor head 8, and the two outer ends of the steel strand 14 on the foundation pit 1 side and the anchor constitute an external anchor head 13. Each pair of the first steel piles 2 and the second steel piles 3 can be on the same straight line, which is at a 90° angle to the second purlin 7. The same straight line can be understood as follows: Figure 4-Figure 8 As shown, the same point of the first steel pile 2 and the second steel pile 3 are on the same straight line, and the axis of the second through hole 21 and the first through hole 22 described below are on the same straight line. Figure 7 The left vertex of the second steel pile 3 in Figure 8 The left vertices of the first steel pile 2 are on the same straight line. Figure 7 The right vertex of the second steel pile 3 in Figure 8 The right apex of the first steel pile 2 is on the same straight line. The 90° angle, such as Figure 1 The axis of the connecting steel pipe 6 at the straight side of the middle foundation pit 1 is at a 90° angle to the second purlin 7, and the axis of the connecting steel pipe 6 at the four turns is also at a 90° angle to the second purlin 7. The difference is that the connecting steel pipe 6 at the turn is not parallel to the two adjacent connecting steel pipes 6 but is at a 45° angle to each other.

[0065] The first steel piles 2 and the second steel piles 3 are preferably made of H-shaped steel, the webs of each pair of H-shaped steels are parallel to each other, and the through holes are all provided on the webs of the H-shaped steels.

[0066] The first steel pile 2 and the second steel pile 3 in each pair of steel piles are provided with respective first through holes 22 and second through holes 21 every several meters, such as 3 meters, 4 meters or 5 meters, vertically from the top downward along the depth of the foundation pit 1. Figure 4 、 Figure 6 、 Figure 8 As shown, the first through hole 22 is a tapered hole for axially limiting the inner end of the connecting steel pipe 6. The inner end of the connecting steel pipe 6 is matched with the tapered hole and is smaller at the end 40 away from the foundation pit 1 and larger at the part 41 close to the foundation pit. Figure 4 、 Figure 5 、 Figure 7 As shown, the second through hole 21 is a straight through hole for passing through the connecting steel pipe 6.

[0067] like Figure 1 、 Figure 2 、 Figure 9 、 Figure 10 、 Figure 11 、 Figure 12 、 Figure 13 shown.

[0068] The first corrugated metal plate assembly 4 and the second corrugated metal plate assembly 5 each include two corrugated metal plates 33 of the same shape and size. Each corrugated metal plate 33 is composed of a plurality of vertical flat plates 31 and a plurality of vertical angled plates 30 connected at intervals. The vertical flat plates 31 and the vertical angled plates 30 are connected to each other at the side. Figure 2 、 Figure 11 、 Figure 13As shown, in detail, the side of the first vertical flat plate 31 is connected to the side of the first vertical angled plate 30, and then connected to the side of the second vertical flat plate 31, and then connected to the side of the second vertical angled plate 30, and then connected to the side of the third vertical flat plate 31, and then connected to the side of the third vertical angled plate 30, and then connected to the side of the fourth vertical flat plate 31, and then connected to the side of the fourth vertical angled plate 30, and then connected to the side of the fifth vertical flat plate 31 to form an integral metal corrugated plate 33. Between the two corrugated metal sheets 33 are multiple vertically parallel long metal sheets 25 extending vertically along the sheets 33. Each pair of vertical flat plates 31 of the two corrugated metal sheets 33 is bolted to one of the vertical long metal sheets 25 using multiple bolts 26 and nuts 32. The corners of the multiple vertical angle plates 30 of the two corrugated metal sheets 33 are all oriented away from the vertical long metal sheets 25, forming an external arch structure that bears the lateral pressure of the soil. Adjacent vertical long metal sheets 25 are connected by multiple horizontal steel connecting rods 23 arranged vertically, such as by welding. Horizontal steel connecting bars 24 and 27 connect each vertical long metal sheet 25 at the top and bottom of the corrugated metal sheets 33, forming a rigid unit with the first corrugated metal sheet assembly 4 and the second corrugated metal sheet assembly 5. The bottom horizontal steel connecting bar 27 can be in the shape of a triangle, with a larger top and a smaller bottom, to facilitate drilling.

[0069] The depth of the first corrugated metal plate assembly 4 and the second corrugated metal plate assembly 5 can match the depth of the foundation pit 1 or be slightly deeper, such as 5 meters, 10 meters, 15 meters, etc. The vertical height of each corrugated metal plate 33 can be a complete piece, or two or three pieces spliced ​​together. Figure 12 It shows a cross-sectional structural diagram of the upper and lower connections when the first metal corrugated assembly 4 and the second metal corrugated plate assembly 5 need to be extended, using a metal connecting corrugated plate 34 spliced ​​onto the outer surface of each metal corrugated plate 33.

[0070] The detachable connection structure between the first corrugated metal plate assembly 4 and the first steel pile 2, and the detachable connection structure between the second corrugated metal plate assembly 5 and the second steel pile 3 can both be as follows: a vertical plug-in steel is fixed to the opposite side walls 11 of two adjacent first steel piles and the opposite side walls 12 of two adjacent second steel piles, respectively, with the plug-in notch of the vertical plug-in steel facing the side away from the foundation pit 1, and the height dimension of the vertical plug-in steel can be equal to or greater than the height dimension of the corrugated metal plate assembly. The outer sides of the vertical long metal plates 25 on both sides of the first corrugated metal plate assembly 4 and the second corrugated metal plate assembly 5 are fixed to the inner side of the web of a vertical channel steel 28, such as by screwing or welding with multiple connecting screws 29. The side plate 10 of the two side plates of the vertical channel steel 28, which is closer to the foundation pit, is vertically plugged into the notch of the vertical plug-in steel. The height dimension of the vertical channel steel 28 can be equal to or greater than the height dimension of the corrugated metal plate assembly. The vertical plug-in steel is fixed, for example, by welding, on the outer side walls of the two first steel piles 2 and the two second steel piles 3. For two adjacent first steel piles 2, the two opposite side walls can be referred to as the opposite side walls 11 of the first steel piles; for two adjacent second steel piles 3, the two opposite side walls can be referred to as the opposite side walls 12 of the second steel piles.

[0071] like Figure 13 As shown, a first embodiment of vertical splice steel is shown: a vertical U-shaped steel 37 with a notch 35 is welded to the opposite side wall 12 of the second steel pile. The side of the vertical U-shaped steel 37 closest to the foundation pit 1 is longer, and the other side is shorter, forming the notch 35. The side plate 10 of the vertical channel steel 28 closest to the foundation pit is vertically spliced ​​into the U-shaped groove 36 of the vertical U-shaped steel 37. The above uses the second steel pile 3 as an example. The first steel pile 2 can also adopt the same structure of the first embodiment of vertical splice steel.

[0072] like Figure 1 、 Figure 2 As shown, a second embodiment of vertical splice steel is shown: vertical angle steel 15 is welded to the opposite side wall 11 of the first steel pile, with the opening of the vertical angle steel 15 facing away from the foundation pit 1. The side plate 10 of the two side plates of the vertical channel steel 28, which is closer to the foundation pit, is vertically spliced ​​to the horizontal plate of the vertical angle steel 15. A channel steel side block 9 can be welded to the side of the horizontal plate of the vertical angle steel 15 away from the foundation pit 1 to prevent the vertical channel steel 28, which is spliced ​​to the horizontal plate of the vertical angle steel 15, from detaching from the horizontal plate away from the foundation pit 1. The above is based on the first steel pile 2 as an example. The second steel pile 2 can also adopt the same structure of the second embodiment of vertical splice steel.

[0073] It is readily understood that the first steel pile 2 may employ one of the above embodiments of vertically spliced ​​steel, while the second steel pile 3 may employ another embodiment of vertically spliced ​​steel. However, it is preferred that both the first and second steel piles 2 and 3 employ the first embodiment of vertically spliced ​​steel, or that both the first and second steel piles 2 and 3 employ the second embodiment of vertically spliced ​​steel.

[0074] like Figure 3-Figure 8 、 Figure 13 、 Figure 14 As shown, the first corrugated metal plate assembly 4 is the first corrugated metal plate assembly 4 that is pulled out as a whole using a vertical pulling device after the horizontal transverse connecting steel beam 16 and the first purlin are disassembled after the construction of the main building of the foundation pit is completed. The first steel pile 2 is the first steel pile 2 that is pulled out as a whole using a vertical pulling device after the steel strand 14 and the connecting steel pipe 6 are disassembled and the construction of the main building of the foundation pit is completed, and the horizontal transverse connecting steel pipe 16, the first purlin, and the first corrugated metal plate assembly 4 are disassembled. The second corrugated metal plate assembly 5 is the second corrugated metal plate assembly 5 that is pulled out as a whole using a vertical pulling device after the construction of the main building of the foundation pit is completed after the top circle of the second purlin 7 is disassembled. The steel strands 14 and the connecting steel pipes 6 and a circle of second purlins 7 on the side of the foundation pit 1 are extracted using a horizontal pulling device after the outer anchor heads 13 are removed layer by layer from bottom to top using a bracing replacement construction step during the construction of the main building from bottom to top within the foundation pit. The second steel piles 3 are extracted using a vertical pulling device after the steel strands 14, the connecting steel pipes 6, and the second purlins 7 on the side of the foundation pit are removed, and after the construction of the main building of the foundation pit is completed, the top second purlin 7 is removed, and the second metal corrugated plate assembly 5 is extracted.

[0075] like Figures 1-13 shown.

[0076] The present invention provides a construction method for a foundation pit retaining structure in soft soil, which comprises the following construction steps:

[0077] (1) Vertical connecting steels, such as vertical H-shaped steels 37 with notches 35, for inserting the first metal corrugated plate assembly 4 are welded to the left and right sides of each first steel pile 2 in advance. A pile driver is used to insert multiple first steel piles 2 into the soft soil foundation at predetermined depths at predetermined positions on the surface of the soft soil foundation away from the foundation pit 1. If the depth of one H-shaped steel is insufficient, another or two more H-shaped steels can be welded to the ground after one H-shaped steel is inserted. Correcting the verticality of the first steel piles 2, i.e., H-shaped steels, inserted into the soft soil foundation is a conventional technique and will not be described in detail. The same applies to the lengthening and correction of the second steel piles 3, i.e., H-shaped steels.

[0078] (2) A crane is used to lift the first metal corrugated plate assembly 4 that has been prefabricated and welded with vertical channel steel 28 to the plug-in position, and then the power head of the pile driver is used to connect the first metal corrugated plate assembly 4 that has been welded with vertical channel steel 28 along the vertical plug-in steel of the two adjacent first steel piles 2, such as the vertical U-shaped steel 37, into the soft soil foundation until it reaches a predetermined depth to form a retaining and water-retaining unit, and then the retaining and water-retaining units are constructed one by one along the four sides to form a circle of first retaining and water-retaining walls 38.

[0079] (3) A detachable connection is made at the top of a circle of first steel piles 2, such as by screwing a circle of first purlins with multiple screws.

[0080] (4) Vertical connecting steels such as vertical U-shaped steels 37 with notches 35 for inserting the second metal corrugated plate assembly 5 are welded on the left and right sides of each second steel pile 3 in advance. A pile driver is used to insert multiple second steel piles 3 into the soft soil foundation at predetermined depths at predetermined positions on the surface of the soft soil foundation outside the foundation pit 1.

[0081] (5) A crane is used to lift the second metal corrugated plate assembly 5 which is prefabricated and welded with vertical channel steel 28 to the plug-in position, and then the power head of the pile driver is used to insert the second metal corrugated plate assembly 5 which is welded with vertical channel steel 28 into the soft soil foundation along the vertical plug-in steel of the two adjacent second steel piles 3, such as the vertical U-shaped steel 37, to a predetermined depth to form a retaining soil and water retaining unit, and then the retaining soil and water retaining units are constructed one by one along the outer side of the edge of the foundation pit 1 to form a circle of second retaining soil and water retaining walls 39.

[0082] (6) One or more circles of second purlins 7 are detachably connected to the second steel piles 3, and the multiple circles of second purlins 7 are distributed along the vertical height. For example, the top of the H-shaped steel of a circle of second steel piles 3 can be detachably connected to a circle of second purlins 7 such as channel steel to replace the reinforced concrete top beam of the existing technology, and the middle and lower parts can be detachably connected to a circle of second purlins 7 such as channel steel or H-shaped steel. The top second purlin 7 can be screwed, and the middle and lower second purlins 7 can be welded. When disassembly is required, they can be cut by oxygen cutting.

[0083] (7) Use the power head of a horizontal pile driver to insert the connecting steel pipe 6 connected with the steel strand 14, the plastic tube 18 and the bullet-shaped concrete body 17 from the side of the foundation pit 1 horizontally into the second through hole 21 of the second steel pile 3, the soft soil foundation and the first through hole 22 of the first steel pile 2, and limit the axial position such as the axial position of the tapered hole and the tapered part of the connecting steel pipe 6. Then use the grouting pipe 19 in the connecting steel pipe 6 to inject cement slurry into the gap between the inner end of the connecting steel pipe 6 and the bullet-shaped concrete body 17. After the cement slurry solidifies, tighten the two free ends of the steel strand 14 on the side of the foundation pit 1 with anchors and anchor them into the external anchor head 13.

[0084] It is easy to understand that the soft soil foundation described in the present invention refers to the soft soil foundation outside the foundation pit 1 or outside the edge of the foundation pit 1, which is located around the foundation pit 1. The foundation pit 1 is excavated on the side of the foundation pit 1 where the second steel piles 3 and the second retaining wall 39 are inserted. The connecting steel pipes 6 can be inserted and the external anchor heads 13 and the second surrounding purlins 7 can be installed while digging until the bottom surface of the foundation pit 1 is reached.

[0085] The construction method of a foundation pit retaining structure of soft soil of the present invention further includes the following construction steps:

[0086] (8) During the construction of the main building from bottom to top in the foundation pit, the external anchoring head 13 is dismantled layer by layer from bottom to top using the replacement support construction step and all the steel strands 14 and all the connecting steel pipes 6 are pulled out layer by layer using the transverse pulling device. One or more circles of the detachably connected second purlins 7 on the side of the foundation pit 1 are manually dismantled layer by layer in the foundation pit, and the multiple second purlins 7 in each circle are lifted away by a crane and replaced with temporary supports of the main building. It is not difficult to understand that the replacement support construction step is a construction step familiar to construction personnel in this field. The temporary supports are generally not removed.

[0087] (9) After the construction of the main building of the foundation pit is completed, the detachable connections between the two ends of the horizontal transverse connecting steel beam 16 and the top of the first steel pile 2 and the top of the second steel pile 3 in each pair of steel piles are manually disassembled one by one on the ground, such as removing screws, and the horizontal transverse connecting steel beam 16 is lifted away by a crane.

[0088] (10) Use vertical drawing equipment to vertically pull out all the second metal corrugated plate components 5 piece by piece.

[0089] (11) Use vertical pulling equipment to pull out all the second steel piles 3 one by one.

[0090] (12) Dismantle the first purlin and use a vertical pulling device to vertically pull out all the first metal corrugated plate assemblies 4 piece by piece.

[0091] (13) Use vertical pulling equipment to pull out all the first steel piles 2 one by one.

[0092] It is not difficult to understand:

[0093] The construction order of steps (10), (11) and steps (12), (13) is not very strict. Specifically, steps (10) and (11) can be constructed first, and then steps (12) and (13); steps (12) and (13) can also be constructed first, and then steps (10) and (11); steps (10) and (11) can also be constructed simultaneously with steps (12) and (13).

[0094] After the construction of the buildings in the foundation pit 1 is completed, that is, after the retaining mission of the foundation pit retaining structure is completed, the foundation pit retaining structure is discarded and all steel components can be dismantled for reuse.

[0095] The above unmarked parts, structures, quantities, etc. are not shown in the drawings. The drawings are for illustration only. If there is any discrepancy between the drawings and the text description, the text description shall prevail.

[0096] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A foundation pit retaining structure for soft soil foundation, characterized by: The invention comprises a plurality of first steel piles spaced apart from the foundation pit and arranged along the periphery of the foundation pit and inserted into the soft soil foundation. Two adjacent first steel piles are detachably connected to a rigid integral first metal corrugated plate assembly inserted into the soft soil foundation to form an earth-retaining and water-retaining unit. The earth-retaining and water-retaining unit extends along the periphery to form a circle of first earth-retaining and water-retaining walls. A circle of first purlins is detachably connected to the top of the circle of first steel piles. The system further comprises a plurality of second steel piles spaced apart along the periphery of the foundation pit and inserted into the soft soil foundation, wherein two adjacent second steel piles are detachably connected to a rigid second corrugated metal plate assembly inserted into the soft soil foundation to form a retaining unit, wherein the retaining unit extends along the periphery of the foundation pit to form a circle of second retaining walls; and each circle of second steel piles is detachably connected to at least one circle of second purlins. The first corrugated metal plate assembly and the second corrugated metal plate assembly each comprise two corrugated metal plates of identical shape and size, each corrugated metal plate comprising a plurality of vertical flat plates and a plurality of vertical angled plates connected at intervals; the corners of the plurality of vertical angled plates of the two corrugated metal plates are all away from the vertical long strip metal plates to form an outer arch structure that bears the lateral pressure of the soil; The detachable connection structure between the first corrugated metal plate assembly and the first steel pile, and the detachable connection structure between the second corrugated metal plate assembly and the second steel pile are both as follows: a vertical plug-in steel is fixed on the opposite side walls of two adjacent first steel piles and on the opposite side walls of two adjacent second steel piles, the plug-in notch of the vertical plug-in steel faces the side away from the foundation pit, and the height dimension of the vertical plug-in steel is equal to or greater than the height dimension of the corrugated metal plate assembly; the outer sides of the vertical long metal plates on both sides of the first corrugated metal plate assembly and the second corrugated metal plate assembly are fixed to the inner side of the web of a vertical channel steel, and the side plate of the two side plates of the vertical channel steel close to the foundation pit is vertically plugged into the notch of the vertical plug-in steel, and the height dimension of the vertical channel steel is equal to or greater than the height dimension of the corrugated metal plate assembly; The top of the first steel pile and the top of the second steel pile in each pair of steel piles are detachably connected to a horizontal transverse connecting steel beam; the first steel pile and the second steel pile in each pair of steel piles have at least one through hole along the vertical depth, and at least one connecting steel pipe inserted horizontally from the foundation pit is accommodated in the through hole corresponding to the first steel pile and the second steel pile in each pair of steel piles, and each connecting steel pipe has a steel strand movably fitted in a plastic pipe, the U-shaped inner end of the steel strand and the U-shaped inner end of the plastic pipe are accommodated in a U-shaped groove of a bullet-shaped concrete body, the middle part of the steel strand is placed in the connecting steel pipe, and a grouting pipe for grouting is provided in the connecting steel pipe, the solidified slurry and the U-shaped part of the plastic pipe and the bullet-shaped concrete body constitute an inner anchor head, and the two outer ends of the steel strand on the foundation pit side and the anchor constitute an outer anchor head; The first and second steel piles in each pair of steel piles are provided with respective first and second through holes every few meters vertically from the top downward along the depth of the foundation pit. The first through holes are tapered holes for axially limiting the inner end of the connecting steel pipe. The inner end of the connecting steel pipe matches the tapered hole and is smaller at the end away from the foundation pit and larger at the part close to the foundation pit. The second through holes are straight through holes for passing through the steel pipe. The first steel pile and the second steel pile are both made of H-shaped steel, the webs of each pair of H-shaped steels are parallel to each other, and the through holes are all arranged on the webs.

2. The foundation pit retaining structure for soft soil foundation according to claim 1, characterized in that: Multiple vertical long metal plates extending vertically along the metal corrugated plates and parallel to each other are sandwiched between the two metal corrugated plates. Each pair of vertical flat plates of the two metal corrugated plates is screwed and fixed to a vertical long metal plate by multiple bolts and multiple nuts. The corners of the multiple vertical angle plates of the two metal corrugated plates are all away from the vertical long metal plates to form an external arch structure that bears the lateral pressure of the soil; the two adjacent vertical long metal plates are connected by multiple horizontal steel connecting rods arranged vertically, and there are horizontal steel connecting bars connecting each vertical long metal plate and the metal corrugated plate at the top and bottom of the metal corrugated plate, so that the first metal corrugated plate assembly and the second metal corrugated plate assembly form a rigid whole.

3. The foundation pit retaining structure for soft soil foundation according to claim 1, characterized in that: The structure of the vertical spliced ​​steel is as follows: a vertical U-shaped steel with a notch is welded on the opposite side wall of the first steel pile and also on the opposite side wall of the second steel pile. The vertical U-shaped steel has a longer side close to the foundation pit and a shorter side to form a notch. The side plate close to the foundation pit on both sides of the vertical channel steel is vertically inserted into the U-shaped groove of the vertical U-shaped steel.

4. The foundation pit retaining structure for soft soil foundation according to claim 1, characterized in that: The structure of the vertical plug-in steel is as follows: the vertical angle steel is welded on the opposite side wall of the first steel pile and also on the opposite side wall of the second steel pile. The opening of the vertical angle steel faces away from the foundation pit. The side plate close to the foundation pit on both sides of the vertical channel steel is vertically plugged into the horizontal plate of the vertical angle steel. A channel steel side block is welded on the side of the horizontal plate of the vertical angle steel away from the foundation pit to prevent the vertical channel steel plugged into the horizontal plate of the vertical angle steel from detaching from the horizontal plate toward the side away from the foundation pit.

5. The foundation pit retaining structure for soft soil foundation according to claim 1, characterized in that: The first metal corrugated plate component is a first metal corrugated plate component that is pulled out as a whole by vertical pulling equipment after the horizontal horizontal connecting steel beam and the first purlin are dismantled after the construction of the main building of the foundation pit is completed; the first steel pile is a first steel pile that is pulled out as a whole by vertical pulling equipment after the steel strand and the connecting steel pipe are dismantled, and the horizontal horizontal connecting steel beam, the first purlin and the first metal corrugated plate component are dismantled after the construction of the main building of the foundation pit is completed; the second metal corrugated plate component is a first steel pile that is pulled out as a whole by vertical pulling equipment after the top circle of the second purlin is dismantled after the construction of the main building of the foundation pit is completed The second metal corrugated plate component is pulled out; the steel strands and the connecting steel pipes and the second purlin on the foundation pit side are obtained by removing the external anchor heads layer by layer from bottom to top in the foundation pit using the support replacement construction steps, and then using horizontal pulling equipment to pull out the steel strands and the connecting steel pipes and the second purlin on the foundation pit side that are manually disassembled; the second steel piles are obtained by removing the steel strands, the connecting steel pipes and the second purlin on the foundation pit side, and then removing the second purlin on the top after the construction of the main building of the foundation pit is completed, and then pulling out the metal corrugated plate component and using vertical pulling equipment to pull out the second steel piles.

6. A method for constructing a foundation pit retaining structure on a soft soil foundation, comprising the following steps: (1) Weld the respective vertical plug-in steels for plugging the first metal corrugated plate assembly on the left and right sides of each first steel pile in advance, and use a pile driver to insert multiple first steel piles into the soft soil foundation at predetermined depths along the periphery of the foundation pit at pre-marked positions on the surface of the soft soil foundation away from the foundation pit; (2) Use a crane to lift the first metal corrugated plate assembly that has been prefabricated and welded with vertical channel steel to the plug-in location, then use the power head of the pile driver to insert the first metal corrugated plate assembly that has been welded with vertical channel steel into the soft soil foundation along the vertical plug-in steel of two adjacent first steel piles to a predetermined depth to form a retaining and water-retaining unit, and then construct the retaining and water-retaining units one by one along the four sides to form a circle of first retaining and water-retaining walls; (3) A circle of first purlins is detachably connected to the top of a circle of first steel piles; (4) Weld the respective vertical plug-in steels for plugging the second metal corrugated plate assembly on the left and right sides of each second steel pile in advance, and use a pile driver to insert multiple second steel piles into the soft soil foundation at predetermined depths along the periphery of the foundation pit at pre-marked positions on the surface of the soft soil foundation outside the foundation pit; (5) Use a crane to lift the second metal corrugated plate assembly that has been prefabricated and welded with vertical channel steel to the plug-in location, then use the power head of the pile driver to insert the second metal corrugated plate assembly that has been welded with vertical channel steel into the soft soil foundation along the vertical plug-in steel of the two adjacent second steel piles to a predetermined depth to form a retaining soil and water retaining unit, and then construct the retaining soil and water retaining units one by one along the outer periphery of the foundation pit to form a circle of second retaining soil and water retaining walls; (6) One or more circles of second purlins are detachably connected to the second steel piles, and the multiple circles of second purlins are distributed along the vertical height; (7) Use the power head of the horizontal pile driver to insert the connecting steel pipe connected with the steel strand, plastic pipe and bullet-shaped concrete body from the foundation pit side into the second through hole of the second steel pile, the soft soil foundation and the first through hole of the first steel pile and limit it axially. Then use the grouting pipe in the connecting steel pipe to inject cement slurry into the gap between the inner end of the connecting steel pipe and the bullet-shaped concrete body. After the cement slurry solidifies, tighten the two free ends of the steel strand on the foundation pit side with anchors and anchor them into an external anchor head.

7. The construction method of a foundation pit retaining structure for a soft soil foundation according to claim 6 further comprises the following construction steps: (8) During the construction of the main building in the foundation pit from bottom to top, the external anchor heads are dismantled layer by layer from bottom to top using the replacement support construction steps and all the steel strands and all the connecting steel pipes are pulled out layer by layer using the transverse pulling equipment. One or more circles of the detachable second purlins on the foundation pit side are manually dismantled layer by layer in the foundation pit, and multiple second purlins in each circle are lifted away by a crane and replaced with temporary supports of the main building; (9) After the construction of the main building of the foundation pit is completed, the detachable connections between the two ends of the horizontal cross-connecting steel beam and the top of the first steel pile and the top of the second steel pile in each pair of steel piles are manually dismantled on the ground one by one, and the horizontal cross-connecting steel beam is lifted away by a crane; (10) Using vertical drawing equipment to vertically pull out all the second metal corrugated plate components piece by piece; (11) Use vertical pulling equipment to pull out all the second steel piles one by one; (12) Dismantle the first purlin and use vertical pulling equipment to pull out all the first metal corrugated plate components piece by piece; (13) Use vertical pulling equipment to pull out all the first steel piles one by one.

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