Foundation pit retaining structure for soft soil foundation and its construction method

Abstract

The present invention discloses a foundation pit retaining structure for soft soil foundation and its construction method. The structure includes multiple first steel piles and second steel piles that are arranged at intervals along the perimeter of the foundation pit and inserted into the soft soil foundation. A horizontal longitudinal connecting steel beam is detachably connected to the tops of two adjacent first steel piles. There is a steel bracket fixed to the side wall of each respective first steel pile vertically below both ends of the horizontal longitudinal connecting steel beam. The bottom in the middle of the length of the horizontal longitudinal connecting steel beam is detachably connected to the tops of two inclined steel connecting columns, and the bottom end of each inclined steel connecting column abuts against its respective steel bracket. A collar beam and a soil retaining and water blocking wall composed of a metal corrugated plate assembly and inserted into the soft soil body are detachably connected between two adjacent second steel piles. There is a rigid connection structure composed of multiple steel strand anchorages and connecting steel pipes between every two rows of steel piles. The inner and outer rows of piles of the present invention have good integrity, strong bearing capacity, good safety performance, relatively small project quantity, and relatively low construction cost.

Description

Technical Field

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

[0002] The foundation composed of soft soil is a soft soil foundation, which is widely distributed in the southern coastal areas, inland rivers and lakes of China. For the foundation pit retaining structure of soft soil foundation, the more commonly used ones are diaphragm walls or row piles plus cement mixing piles that enclose a circle around the foundation pit. The row piles are a circle or a row of reinforced concrete piles formed around the foundation pit to retain soil, and the cement mixing piles generally interlock with adjacent piles to retain water; there are also cases where a circle or a row of reinforced concrete piles are used to retain soil and water. In order to enhance the bearing capacity of the retaining structure against lateral soil pressure and provide the safety performance for construction excavation, those skilled in the art have continuously improved the support structure and support method in the foundation pit retaining structure.

[0003] At first, it was changed from the original horizontal internal support to inclined internal support. However, due to the existence of inclined internal support, there are still disadvantages such as obstructing the excavation of foundation pit soil, requiring waiting for curing time and waiting for the completion of support construction, which affect the construction progress and construction efficiency.

[0004] In recent years, a double-row pile structure has gradually been adopted to replace the internal support in the foundation pit, that is, to replace the horizontal internal support and the inclined internal support.

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

[0006] The Chinese patent website discloses a retaining structure of a double-row pile foundation pit of reinforced concrete piles. Between the inner and outer rows of reinforced concrete piles, that is, a circle of reinforced concrete piles close to the foundation pit and a circle of reinforced concrete piles far from the foundation pit and located in the soil around the foundation pit, a reinforced concrete connecting body is used 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 around. A trench dozens to hundreds of meters long and five to more than ten meters deep in a circle has a large amount of work, a long construction period, a slow construction speed, and low construction efficiency; the construction costs such as the hourly rate of equipment and the wages of workers are relatively high; the consumption of building materials is large and the material cost is relatively high; and after the retaining mission of the foundation pit retaining structure is completed, its connection structure cannot be disassembled, so the steel cannot be reused. Summary of the Invention

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

[0008] One technical solution of the present invention is to provide a foundation pit retaining structure for soft soil foundation, including a first soil retaining and water blocking wall formed by adjacent plain cement soil mixing piles that are mutually occluded and are away from the foundation pit.

[0009] The foundation pit retaining structure for soft soil foundation of the present invention further includes multiple first steel piles that are arranged at intervals along the periphery of the foundation pit inside the first soil retaining and water blocking wall and are inserted into the soft soil foundation. A horizontal longitudinal connecting steel beam is detachably connected to the tops of two adjacent first steel piles. There is a steel corbel fixed on the opposite side walls of their respective first steel piles vertically below both ends of the horizontal longitudinal connecting steel beam. The bottom in the middle of the length of the horizontal longitudinal connecting steel beam is detachably connected to the tops of two inclined steel connecting columns. The bottom end of each inclined steel connecting column abuts against its respective steel corbel, so that a circle of first steel piles is connected into a whole.

[0010] The foundation pit retaining structure for soft soil foundation of the present invention further includes multiple second steel piles that are arranged at intervals along the outer periphery of the foundation pit edge and are inserted into the soft soil foundation. The second steel piles are detachably connected with at least one circle of purlins, so that a circle of second steel piles is connected into a whole.

[0011] A metal corrugated plate assembly inserted into the soft soil foundation is detachably connected between two adjacent second steel piles to form a soil retaining and water blocking unit. The soil retaining and water blocking units extend along the outer periphery of the foundation pit edge to form a second soil retaining and water blocking wall.

[0012] A horizontal transverse connecting steel beam is detachably connected to the tops of the first steel pile and the second steel pile in each pair of steel piles. The first steel pile and the second steel pile in each pair of steel piles each have at least one through hole along the vertical depth. At least one connecting steel pipe inserted horizontally from inside the foundation pit is accommodated in the corresponding through holes of the first steel pile and the second steel pile in each pair of steel piles. There is a steel strand movably sleeved in a plastic pipe inside each connecting steel pipe. The U-shaped inner ends of the steel strand and the plastic pipe are accommodated in the U-shaped groove of a bullet-shaped concrete body. The middle part of the steel strand is placed inside the connecting steel pipe. There is a grouting pipe for grouting inside the connecting steel pipe. The solidified grout, the U-shaped part of the plastic pipe and the bullet-shaped concrete body form an internal anchoring head. The two outer ends of the steel strand on the foundation pit side and the anchor are formed into an external anchoring head.

[0013] After adopting the above structure, the foundation pit retaining structure for soft soil foundation of the present invention has the following advantages:

[0014] The foundation pit retaining structure of the soft soil foundation of the present invention comprises an outer first retaining wall formed by a plain cement soil mixing pile away from the foundation pit and an inner second retaining wall formed by a metal corrugated plate assembly connected by a second steel pile, and has a good double-layer retaining effect. Two circles of steel piles are directly inserted into the soft soil foundation, and the first steel piles of the circle away from the foundation pit are connected to each other at the top by an inclined steel connecting column to form a whole. The second steel piles of the circle on the foundation pit side are connected to form a whole by a circle of surrounding purlins or multiple circles of surrounding purlins on the foundation pit side. In particular, the top horizontal horizontal connecting steel beams and at least one anchoring steel strand and connecting steel pipes are used to rigidly connect the two rows of steel piles, that is, each pair of first steel piles and second steel piles. The above structure constitutes the foundation pit retaining structure of two circles rigidly connected as a whole. The foundation pit retaining structure of the soft soil foundation of the present invention realizes that under the premise that there is no horizontal inward support or oblique inward support in the foundation pit, it still has a strong bearing capacity against the lateral pressure of the soil and a very high safety performance.

[0015] The construction of the foundation pit retaining structure of the present invention does not require digging trenches. Only at the positions of the ground markings, such as the positions of several circles of construction lines marked with lime, a circle of first retaining walls composed of adjacent plain cement soil mixing piles interlocking with each other is constructed, and then two rows of steel piles are inserted and screwed on site to be connected into a whole. Compared with digging trenches that are dozens or hundreds of meters long and about one meter wide and pouring reinforced 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 small, the construction efficiency is relatively high, and the construction costs such as equipment shift fees and workers' wages are relatively low.

[0016] 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, reduces the material cost of the foundation pit retaining structure, and greatly saves steel resources.

[0017] Furthermore, the steel bracket is welded to the vertical middle or lower part of each first steel pile, so that a circle of the vertical middle or vertical lower part of the first steel pile is connected as a whole. After adopting the above structure, the first steel piles can form a circle of wholes in addition to the top part, and the middle or lower part can also form a circle of wholes, further ensuring that the foundation pit retaining structure has a strong bearing capacity to resist the lateral pressure of the soil and has a high safety performance.

[0018] Furthermore, the steel corbel is composed of two parallel vertical steel plates. Each inclined steel connecting column is made of an H-shaped steel. The web at the bottom end of the H-shaped steel is shorter than the two flange plates at the bottom end of the H-shaped steel. The bottom end face of the web of the H-shaped steel at the bottom end of the inclined steel connecting column is placed on the horizontal top surfaces of the two vertical steel plates of each steel corbel. The width dimension of each steel corbel is narrower than the width dimension between the two flange plates at the bottom end of the H-shaped steel of the inclined steel connecting column. The two flange plates at the bottom end of the H-shaped steel of each inclined steel connecting column are located outside the two parallel vertical steel plates of the steel corbel. The top end of each inclined steel connecting column is screwed to the middle of the length of the channel web of the horizontal longitudinal connecting steel beam through a connecting block, multiple bolts and multiple nuts. After adopting the above structure, there is a good butting effect between the bottom end of each inclined steel connecting column and the steel corbel, ensuring the good integrity of the first steel piles in a circle, further ensuring the technical effects that the foundation pit retaining structure has a strong bearing capacity against lateral soil pressure and a high safety performance; and when the first steel piles need to be pulled out, the resistance of the steel corbel is very small.

[0019] Furthermore, the metal corrugated plate assembly includes two metal corrugated plates with the same shape and size. Each metal corrugated plate is a metal corrugated plate formed by connecting multiple vertical flat plates and multiple vertical angle plates at intervals. Between the two metal corrugated plates, there are multiple vertical long strip-shaped metal plates extending vertically and parallel to each other. Each pair of vertical flat plates of the two metal corrugated plates is screwed and fixed to a vertical long strip-shaped metal plate through multiple bolts and multiple nuts. The angles of the multiple vertical angle plates of the two metal corrugated plates are all away from the vertical long strip-shaped metal plate to form an outer arch structure for bearing lateral soil pressure; adjacent two vertical long strip-shaped metal plates are connected by multiple horizontal steel connecting rods arranged vertically. There are horizontal steel connecting strips at the top and bottom of the metal corrugated plate for connecting each vertical long strip-shaped metal plate and the metal corrugated plate, making the metal corrugated plate assembly form a rigid whole. After adopting the above structure, the metal corrugated plate assembly not only has a good function of retaining soil and water, but also has good rigidity and integrity, has good jacking-in ability, and also has good ability to resist lateral soil pressure, further ensuring the technical effects that the foundation pit retaining structure has a strong bearing capacity against lateral soil pressure, a high safety performance and good waterproof performance.

[0020] Furthermore, the detachable connection structure between the metal corrugated plate assembly and the second steel pile is as follows: on the opposite side walls of two adjacent second steel piles, a vertical insertion steel is respectively fixed. The insertion notch of the vertical insertion steel faces away from the foundation pit, and the height dimension of the vertical insertion steel is equal to or greater than the height dimension of the metal corrugated plate assembly. The outer sides of the vertical long strip metal plates on both sides of the metal corrugated plate assembly are fixed to the inner side of the web of a vertical channel steel. The side plate close to the foundation pit on both sides of the vertical channel steel is vertically inserted into the notch of the vertical insertion 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 not only convenient for the insertion and installation of the metal corrugated plate assembly and the second steel pile, but also convenient for disassembly during subsequent recycling, further ensuring the technical effects of high construction efficiency, low construction cost, good waterproof performance and good resistance to lateral soil pressure of the foundation pit retaining structure.

[0021] Furthermore, both ends of each horizontal longitudinal connecting steel beam are screwed to two first steel piles by connecting blocks and multiple screws; the middle bottom of each horizontal longitudinal connecting steel beam is screwed to the tops of two inclined steel connecting columns by connecting blocks, multiple bolts and multiple nuts; the inclined steel connecting columns are the inclined steel connecting columns that are disassembled after the construction of the main building of the foundation pit is completed and pulled out by an inclined pulling device; the first steel piles are the first steel piles that are disassembled from the steel strands and connecting steel pipes, and after the construction of the main building of the foundation pit is completed, the horizontal transverse connecting steel beams, horizontal longitudinal connecting steel beams are disassembled, the inclined steel connecting columns are pulled out, and then pulled out by a vertical pulling device; the metal corrugated plate assembly is the metal corrugated plate assembly that is disassembled from the purlin and pulled out integrally by a vertical pulling device after the construction of the main building of the foundation pit is completed; the steel strands, connecting steel pipes and the side purlin of the foundation pit are the steel strands, connecting steel pipes and the side purlin of the foundation pit that are disassembled layer by layer from the bottom to the top after the outer anchor heads are disassembled layer by layer from the bottom to the top by using the replacement bracing construction steps during the process of constructing the main building in the foundation pit from the bottom to the top and pulled out by a horizontal pulling device; the second steel piles are the second steel piles that are disassembled from the steel strands, connecting steel pipes and the side purlin of the foundation pit, and after the construction of the main building of the foundation pit is completed, the top purlin is disassembled, the metal corrugated plate assembly is pulled out, and then pulled out by a vertical pulling device. After adopting the above structure, all the steel components constituting the foundation pit retaining structure of the present invention can be gradually disassembled during the construction process of the main building of the foundation pit and completely disassembled after the main building of the foundation pit is completely completed, and can be recycled for repeated use, greatly reducing the consumption of building materials, greatly reducing the material cost of the foundation pit retaining structure, and greatly saving steel resources.

[0022] Furthermore, both the first steel pile and the second steel pile adopt H-shaped steel, the webs of each pair of H-shaped steel are parallel to each other, and the through holes are all arranged on the webs. After adopting the above structure, the mechanical properties of the steel piles are better and the construction is more convenient, further ensuring the technical effect of high construction efficiency of the foundation pit retaining structure of the present invention.

[0023] Further, in each pair of steel piles, the first steel pile and the second steel pile are each provided with respective first through holes and second through holes at intervals of several meters vertically downward from the top along the depth of the foundation pit. The first through hole is a tapered hole for axially limiting the inner end of the connecting steel pipe. The inner end of the connecting steel pipe is matched with the tapered hole and has a smaller end close to the soil-cement mixing pile and a larger part away from the soil-cement mixing pile. The second through hole is a straight through hole for passing through the connecting steel pipe. After adopting the above structure, the vertical connection of the two rows of steel piles is more firm, the integrity is better, the insertion and disassembly of the steel pipes are convenient, reliable and fast, further ensuring that the foundation pit retaining structure has a strong bearing capacity against lateral soil pressure, high safety performance and high construction efficiency.

[0024] Another technical problem to be solved by the present invention is to provide a construction method for a foundation pit retaining structure in soft soil foundation, which has good integrity between the inner and outer rows of piles, strong bearing capacity, good safety performance, relatively small engineering quantity and relatively low construction cost.

[0025] Another technical solution of the present invention is to provide a construction method for a foundation pit retaining structure in soft soil foundation, and construct the foundation pit retaining structure in any of the above technical solutions, including the following construction steps:

[0026] (1) On the pre-scored positions on the surface of the soft soil foundation far from the foundation pit around the foundation pit, use a pile driver to construct a first soil retaining and water blocking wall formed by the interlocking of adjacent soil-cement mixing piles.

[0027] (2) Fix respective steel corbels on the left and right sides of each first steel pile at a predetermined vertical height in advance. On the pre-scored positions on the soft soil foundation far from the foundation pit inside the first soil retaining and water blocking wall around the foundation pit, use a pile driver to insert multiple first steel piles at intervals around the foundation pit into the soil to a predetermined depth.

[0028] (3) Use the power head of a pile driver capable of adjusting the inclination angle to insert respective inclined steel connecting columns obliquely downward from the middle of the distance between two adjacent first steel piles, and make the bottom end of each inclined steel connecting column abut against its respective steel corbel. Then, detachably connect the top ends of the two inclined steel connecting columns to the bottom plate of a horizontally longitudinal connecting steel beam, and then detachably connect the two ends of the horizontally longitudinal connecting steel beam to the top ends of their respective first steel piles.

[0029] (4) Weld respective vertical plug-in steels for inserting metal corrugated plate assemblies on the left and right sides of each second steel pile in advance. On the pre-scored positions on the soft soil foundation outside the edge of the foundation pit, use a pile driver to insert multiple second steel piles at intervals around the foundation pit into the soft soil foundation to a predetermined depth.

[0030] (5) Use a crane to lift the prefabricated and welded metal corrugated plate assembly with vertical channel steel to the insertion point, and then use the power head of the pile driver to insert the metal corrugated plate assembly with vertical channel steel into the soft soil foundation along the vertical insertion steel of two adjacent second steel piles until the predetermined depth to form a soil and water retaining unit. Then, construct the soil and water retaining units one by one along the outer perimeter of the foundation pit to form a second soil and water retaining wall around the perimeter;

[0031] (6) Connect one or more laps of purlins to the second steel piles in a detachable manner, and the multiple laps of purlins are distributed along the vertical height;

[0032] (7) Use the power head of the horizontal pile driver to horizontally 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 and axially limit it. 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 is cured, tension and anchor the two free ends of the steel strand on the foundation pit side with anchors to form an external anchor head.

[0033] After adopting the above construction steps, the construction method of the foundation pit retaining structure for the soft soil foundation of the present invention has the following advantages:

[0034] The foundation pit retaining structure for the soft soil foundation constructed by the construction method of the present invention includes an outer first soil and water retaining wall composed of a circle of cement-soil mixing piles far from the foundation pit and an inner second soil and water retaining wall composed of metal corrugated plate assemblies connected by second steel piles. The double-layer wall has good soil and water retaining effects. Two circles of steel piles are directly inserted into the soft soil foundation. For the first circle of steel piles far from the foundation pit, in addition to being connected at the top, there are inclined steel connecting columns connecting the first steel piles in this circle into a whole. The second circle of steel piles on the foundation pit side is connected into a whole by a circle or multiple circles of purlins on the foundation pit side. In particular, between the two rows of steel piles, that is, between each pair of the first steel pile and the second steel pile, there are horizontal transverse connecting steel beams at the top and at least one anchor steel strand and connecting steel pipe for rigid connection. The above structure forms an integral foundation pit retaining structure with two circles of rigid connection. The foundation pit retaining structure for the soft soil foundation of the present invention realizes strong bearing capacity against lateral soil pressure and high safety performance without horizontal or inclined internal supports in the foundation pit.

[0035] The construction method of the present invention does not require trenching. Only at the positions of several construction lines marked on the ground, such as marked with lime, a first retaining and water-blocking wall composed of adjacent plain cement soil mixing piles biting each other is constructed first, and then two rows of steel piles are inserted and screwed on-site. Compared with digging trenches dozens of meters or hundreds of meters long and about one meter wide and casting reinforced concrete piles and reinforced concrete connectors on-site, the engineering quantity is relatively small, the construction period is relatively short, the construction speed is relatively fast, the labor intensity is relatively small, the construction efficiency is relatively high, and the construction costs such as the shift fee of equipment and the wages of workers are relatively low.

[0036] Furthermore, the construction method of the foundation pit retaining structure for soft soil foundation of the present invention further includes the following construction steps:

[0037] (8) During the construction of the main building in the foundation pit from bottom to top, the external anchor heads are disassembled layer by layer from bottom to top by using the replacement bracing construction steps, all the steel strands and all the connecting steel pipes are pulled out layer by layer by using the horizontal pulling equipment, and one or more circles of the retaining beams on the foundation pit side that can be disassembled are manually disassembled layer by layer in the foundation pit, and multiple retaining beams of each circle are lifted away by a crane, and at the same time, they are replaced by the temporary supports of the main building.

[0038] (9) After the construction of the main building in the foundation pit is completed, the two ends of the horizontal cross-connecting steel beam are manually disassembled from the detachable joints at the tops of the first steel pile and the second steel pile in each pair of steel piles on the ground one by one, and the horizontal cross-connecting steel beam is lifted away by a crane.

[0039] (10) All the metal corrugated plate components fixed with vertical channel steel are pulled out vertically one by one by using the vertical pulling equipment.

[0040] (11) All the second steel piles are pulled out one by one by using the vertical pulling equipment.

[0041] (12) The two ends of the horizontal longitudinal connecting steel beam are manually disassembled from the multiple connecting screws at the top ends of their respective first steel piles on the ground one by one, the multiple bolts and nuts at the middle of the horizontal longitudinal connecting steel beam and the top ends of the two inclined steel connecting columns are disassembled, and the horizontal longitudinal connecting steel beam is lifted away by a crane.

[0042] (13) All the inclined steel connecting columns are pulled out one by one by using the inclined pulling equipment.

[0043] (14) All the first steel piles are pulled out one by one by using the vertical pulling equipment.

[0044] After adopting the above construction steps, all the steel components that make up the foundation pit retaining structure of the present invention can be gradually removed during the construction process of the main building of the foundation pit. They will be completely removed after the completion of the main building of the foundation pit for recycling and reuse, which greatly reduces the consumption of building materials, significantly reduces the material cost of the foundation pit retaining structure, and greatly saves steel resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 is a top-sectional structural schematic diagram of the foundation pit retaining structure of the soft soil foundation of the present invention (the vertical insertion steel shows the structure of the second embodiment; the channel steel side block is not shown in the figure).

[0046] Figure 2 is Figure 1 an enlarged structural schematic diagram of A in (the vertical insertion steel also shows the structure of the second embodiment; the channel steel side block is shown in the figure).

[0047] Figure 3 is a structural schematic diagram of the first steel pile and the second steel pile of the present invention connected by a horizontal transverse connecting steel beam, a connecting steel pipe and a steel strand (only one connecting steel pipe is schematically shown; the heights of the first steel pile, the second steel pile and the metal corrugated plate assembly are also schematic, and the height-omitting drawing method is adopted. The following Figure 6 , Figure 8 , Figure 9 , Figure 10 , Figure 11 is the same).

[0048] Figure 4 is Figure 3 a horizontal sectional structural schematic diagram at the center of the connecting steel pipe in.

[0049] Figure 5 is Figure 4 a top-sectional structural schematic diagram at the second through hole of the second steel pile in.

[0050] Figure 6 is Figure 5 a front view structural schematic diagram of.

[0051] Figure 7 is Figure 4 a top-sectional structural schematic diagram at the first through hole of the first steel pile in.

[0052] Figure 8 is Figure 7 a front view structural schematic diagram of.

[0053] Figure 9 is Figure 2 a front-sectional structural schematic diagram of the inclined steel connecting column in connected to the horizontal longitudinal connecting steel beam and the steel bracket of two adjacent first steel piles.

[0054] Figure 10 is a schematic longitudinal sectional view of the corrugated metal plate assembly in the present invention along the width direction.

[0055] Figure 11 is a schematic longitudinal sectional view of the corrugated metal plate assembly in the present invention along the thickness direction (only showing the connecting screws and not showing the vertical channel steel).

[0056] Figure 12 is a schematic cross-sectional view of the part below the top horizontal steel connecting bar of the corrugated metal plate assembly in the present invention.

[0057] Figure 13 is a schematic cross-sectional view of the upper and lower joints of the corrugated metal plate assembly in the present invention when it needs to be lengthened, with the outer surface spliced corrugated metal plates.

[0058] Figure 14 is a schematic top view of the first embodiment of the vertical plug-in steel in the present invention.

[0059] Figure 15 is Figure 4 an enlarged schematic view of B in

[0060] As shown in the figure: 1. Foundation pit, 2. Cement-soil mixing pile, 3. First retaining and water-blocking wall, 4. First steel pile, 5. Second steel pile, 6. Connecting steel pipe, 7. Waling, 8. Corrugated metal plate assembly, 9. Inner anchoring head, 10. Channel steel side block, 11. One side plate close to the foundation pit, 12. Opposite side wall of the second steel pile, 13. Outer anchoring head, 14. Steel strand, 15. Vertical angle steel, 16. Horizontal transverse connecting steel beam, 17. Bullet-shaped concrete body, 18. Plastic pipe, 19. Grouting pipe, 20. U-shaped groove, 21. Second through hole, 22. First through hole, 23. First bolt, 24. First nut, 25. Horizontal longitudinal connecting steel beam, 26. Inclined steel connecting column, 27. Steel corbel, 28. Opposite side wall of the first steel pile, 29. Horizontal steel connecting rod, 30. Top horizontal steel connecting bar, 31. Vertical long-strip metal plate, 32. Second bolt, 33. Bottom horizontal steel connecting bar, 34. Vertical channel steel, 35. Connecting screw, 36. Vertical angle-shaped plate, 37. Vertical flat plate, 38. Second nut, 39. Corrugated metal plate, 40. Metal connecting corrugated plate, 41. Steel connecting block, 42. Notch, 43. C-shaped groove, 44. Vertical C-shaped steel, 45. Vertical steel plate; 46. Second retaining and water-blocking wall, 47. End, 48. Part far from the cement-soil mixing pile. Detailed implementation manners

[0061] 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 on the present invention. In addition, the technical features involved in the following specific embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0062] As Figures 1 - 15 shown.

[0063] The foundation pit retaining structure for soft soil foundation of the present invention includes a first soil retaining and water blocking wall 3 which is away from the foundation pit 1 and is formed by the mutual engagement of adjacent plain cement soil mixing piles 2.

[0064] The foundation pit retaining structure for soft soil foundation of the present invention further includes a plurality of first steel piles 4 which are arranged at intervals along the periphery of the foundation pit 1 inside the first soil retaining and water blocking wall 3 and are inserted into the soft soil foundation. A horizontal longitudinal connecting steel beam 25 is detachably connected to the tops of two adjacent first steel piles 4. There is a steel corbel 27 fixed, such as by welding, on the opposite side walls 28 of the respective first steel piles directly below the two ends of the horizontal longitudinal connecting steel beam 25. The bottom of the middle of the length of the horizontal longitudinal connecting steel beam 25 is detachably connected to the tops of two inclined steel connecting columns 26. The bottom end of each inclined steel connecting column 26 abuts against its respective steel corbel 27, so that a circle of first steel piles 4 is connected into a whole. The steel corbel 27 is fixed on the outer side walls of two first steel piles 4 such as H-shaped steel. For two adjacent first steel piles 4, as Figure 9 shown, it can be called the opposite side wall 28 of the first steel pile.

[0065] The foundation pit retaining structure for soft soil foundation of the present invention further includes a plurality of second steel piles 5 which are arranged at intervals along the outer periphery of the edge of the foundation pit 1 and are inserted into the soft soil foundation. At least one circle of purlins 7 is detachably connected to the second steel piles 5, so that a circle of second steel piles 5 is connected into a whole. The purlin 7 is also called a steel beam. It is preferably to use multiple circles of purlins 7. For example, there can be a circle of purlins 7 at the top of a circle of second steel piles 5, which is used to replace the reinforced concrete coping beam in the prior art. The advantage is that it can be disassembled and recycled. There can be a circle of purlins 7 fixed on the second steel piles 5 on the side of the foundation pit 1 at the middle or lower part in the vertical direction of the second steel piles 5. The purlin 7 can be made of channel steel or H-shaped steel. The purlin 7 and the second steel pile 5 can be screwed together with a plurality of screws; of course, they can also be welded, and it is also very easy to disassemble by cutting with an oxygen cutting device when disassembly is required.

[0066] It is not difficult to understand that the meaning of "a plurality of" in the plurality of screws in the present invention is broad, and can refer to several, more than a dozen, dozens or hundreds, etc.

[0067] It is not difficult to understand that except at the turning points, the spaced arrangement of the first steel piles 4 and the second steel piles 5 refers to an equally spaced arrangement, and the four turning points are symmetrically arranged relative to the center point of the foundation pit 1.

[0068] The described steel corbel 27 can be welded to the upper part of each first steel pile 4 vertically, so that the upper parts of a circle of first steel piles 4 vertically are connected into a whole. Of course, the described steel corbel 27 is preferably welded to the middle or lower part of each first steel pile 4 vertically, so that the middle or lower part of a circle of first steel piles 4 vertically is connected into a whole.

[0069] As Figure 1 , Figure 2 shown, the described steel corbel 27 can be formed by welding two parallel vertical steel plates 45 to the first steel pile 4. Each inclined steel connecting column 26 can adopt an H-shaped steel. The web at the bottom end of the H-shaped steel is shorter than the two flange plates at the bottom end of the H-shaped steel. The bottom end face of the web at the bottom end of the H-shaped steel of the inclined steel connecting column 26 is placed on the horizontal top faces of the two vertical steel plates 45 of each steel corbel 27. Of course, the top faces of the two vertical steel plates 45 can also be inclined, that is, inclined from the outside to the side wall of the first steel pile 4, so that the effect of the bottom end face of the web at the bottom end of the H-shaped steel pressing against the steel corbel 27 is better. The width dimension of each steel corbel 27 can be narrower than the width dimension between the two flange plates at the bottom end of the H-shaped steel of the inclined steel connecting column 26. The two flange plates at the bottom end of the H-shaped steel of each inclined steel connecting column 26 are located outside the two parallel vertical steel plates 45 of the steel corbel 27, so that the pressing effect is better. The top end of each inclined steel connecting column 26 is screwed to the middle of the length of the channel steel web of the horizontal longitudinal connecting steel beam 25 through a connecting block, multiple bolts and multiple nuts. For example, the top end of each inclined steel connecting column 26 is screwed to the middle of the length of the channel steel web of the horizontal longitudinal connecting steel beam 25 through a steel connecting block 41, multiple first bolts 23 and multiple first nuts 24 in one-to-one correspondence.

[0070] As Figures 1 - 8 , Figure 15 shown.

[0071] In the foundation pit retaining structure of the soft soil foundation of the present invention, the top of the first steel pile 4 and the top of the second steel pile 5 in each pair of steel piles are detachably connected with a horizontal transverse connecting steel beam 16. Each of the first steel pile 4 and the second steel pile 5 in each pair of steel piles has at least one through hole along the vertical depth. At least one connecting steel pipe 6 inserted horizontally from the foundation pit 1 is accommodated in the corresponding through holes of the first steel pile 4 and the second steel pile 5 in each pair of steel piles. There is a steel strand 14 movably sleeved in a plastic pipe 18 in each connecting steel pipe 6. The U-shaped inner end of the steel strand 14 and the U-shaped inner end of the plastic pipe 18 are accommodated in the 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. There is a grouting pipe 19 for grouting in the connecting steel pipe 6. The solidified grout, the U-shaped part of the plastic pipe 18 and the bullet-shaped concrete body 17 form an internal anchoring head 9. The two outer ends of the steel strand 14 on the foundation pit 1 side and the anchor are formed into an external anchoring head 13.

[0072] Among a circle of first steel piles 4 and a circle of second steel piles 5, every two or each pair can be on the same straight line, and this straight line forms a 90° angle with the purlin 7. The same straight line can be understood in this way. For example, Figures 4 - 8 As shown, the same point of the first steel pile 4 and the second steel pile 5 is on the same straight line, just like the axes of the second through hole 21 and the first through hole 22 described below are on the same straight line. Figure 6 The left vertex of the second steel pile 5 in Figure 8 is on the same straight line as the left vertex of the first steel pile 4 in Figure 6 The right vertex of the second steel pile 5 in Figure 8 is on the same straight line as the right vertex of the first steel pile 4 in Figure 1 etc. The 90° angle, for example, in Figure 1 the axis of the connecting steel pipe 6 at the straight edge of the foundation pit 1 forms a 90° angle with the purlin 7, and the axes of the connecting steel pipes 6 at the four turning points also form a 90° angle with the purlin 7. The difference is that the connecting steel pipes 6 at the turning points are not parallel to the adjacent two connecting steel pipes 6 but form a 45° angle with each other.

[0073] Both the first steel pile 4 and the second steel pile 5 can be made of H-shaped steel, and the webs of each pair of H-shaped steels are parallel to each other. The through holes are all arranged on the webs.

[0074] In each pair of steel piles, the first steel pile 4 and the second steel pile 5 are each provided with their own first through hole 22 and second through hole 21 vertically along the depth of the foundation pit 1 from the top down every few meters, such as 3 meters, 4 meters or 5 meters. For example, Figure 4 、 Figure 7 、 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 has a smaller end 47 close to the end of the soil-cement mixing pile 2, that is, the diameter of the end 47 is small, and a larger part 48 away from the soil-cement mixing pile, that is, the diameter of this part is large. For example, Figure 4 、 Figure 5 、 Figure 6 As shown, the second through hole 21 is a straight through hole for passing through the connecting steel pipe 6.

[0075] For example, Figure 1 、 Figure 2 、 Figure 10 、 Figure 11 、 Figure 12 、 Figure 13 As shown.

[0076] Adjacent two second steel piles 5 are detachably connected to a metal corrugated plate assembly 8 inserted into the soft soil foundation to form a soil and water retaining unit. The soil and water retaining units extend around the outer periphery of the foundation pit 1 to form a circle of second soil and water retaining walls.

[0077] The metal corrugated plate assembly 8 includes two metal corrugated plates 39 with the same shape and size. Each metal corrugated plate 39 is composed of multiple vertical flat plates 37 and multiple vertical angular plates 36 connected at intervals. The vertical flat plates 37 and the vertical angular plates 36 are connected to each other on the side. As Figure 2 , Figure 12 shown, specifically, the side of the first vertical flat plate 37 is connected to the side of the first vertical angular plate 36, then to the side of the second vertical flat plate 37, then to the side of the second vertical angular plate 36, then to the side of the third vertical flat plate 37, then to the side of the third vertical angular plate 36, then to the side of the fourth vertical flat plate 37, then to the side of the fourth vertical angular plate 36, and then to the side of the fifth vertical flat plate 37 to form an integral metal corrugated plate 39. Between the two metal corrugated plates 39, there are multiple vertically elongated metal plates 31 extending vertically and parallel to each other along the metal corrugated plates 39. Each pair of vertical flat plates 37 of the two metal corrugated plates 39 is screwed and fixed to a vertically elongated metal plate 31 through multiple bolts and nuts. For example, each pair of vertical flat plates 37 of the two metal corrugated plates 39 is screwed and fixed to a vertically elongated metal plate 31 through multiple bolts such as the second bolt 32 and multiple nuts such as the second nut 38. The angles of the multiple vertical angular plates 36 of the two metal corrugated plates 39 are all away from the vertically elongated metal plates 31 to form an outer arch structure for bearing the lateral pressure of the soil body. Adjacent vertically elongated metal plates 31 are connected by multiple horizontally arranged steel connecting rods 29 arranged vertically, such as by welding. There are horizontal steel connecting strips connecting each vertically elongated metal plate 31 and the metal corrugated plate 39 at the top and bottom of the metal corrugated plate 39, that is, the top horizontal steel connecting strip 30 and the bottom horizontal steel connecting strip 33, so that the metal corrugated plate assembly 8 forms a rigid whole. The bottom horizontal steel connecting strip 33 can be in a triangular shape with a larger upper part and a smaller lower part that is beneficial for drilling.

[0078] The depth of the metal corrugated plate assembly 8 can match or be slightly deeper than the depth of the foundation pit 1, such as 5 meters, 10 meters, 15 meters, etc. The vertical height of each metal corrugated plate 39 can be a complete piece, or two or three pieces spliced up and down, etc. Figure 13 The cross-sectional view shows the structure of the metal corrugated plate assembly 8 when it needs to be lengthened, and a metal connecting corrugated plate 40 is spliced on the outer surface of each metal corrugated plate 39 at the upper and lower joints.

[0079] The detachable connection structure between the metal corrugated plate assembly 8 and the second steel pile 5 can be as follows: On the opposite side walls 12 of two adjacent second steel piles, a vertical insertion steel is fixed (such as welded) respectively. The insertion notch of the vertical insertion steel faces away from the foundation pit 1, and the height dimension of the vertical insertion steel can be equal to or greater than the height dimension of the metal corrugated plate assembly 8. The outer sides of the vertical strip-shaped metal plates 31 on both sides of the metal corrugated plate assembly 8 are fixed (such as welded or screwed with multiple connecting screws 35) to the inner side of the web of a vertical channel steel 34. The side plate 11 of the vertical channel steel 34 close to the foundation pit on both sides is vertically inserted into the notch of the vertical insertion steel, and the height dimension of the vertical channel steel 34 can be equal to or greater than the height dimension of the metal corrugated plate assembly 8. The vertical insertion steel is fixed (such as welded) on the outer side walls of the two second steel piles 5. For two adjacent second steel piles 5, as Figure 1 such as 2, Figure 14 shown, it can be called the opposite side walls 12 of the second steel pile.

[0080] such as Figure 14 shown, the first embodiment of the vertical insertion steel: A vertical C-shaped steel 44 with a notch 42 is welded on the opposite side walls 12 of the second steel pile. The side length of the vertical C-shaped steel 44 close to the foundation pit 1 is long, and the other side is short to form the notch 42. The side plate 11 of the vertical channel steel 34 close to the foundation pit on both sides is vertically inserted into the C-shaped groove 43 of the vertical C-shaped steel 44.

[0081] such as Figure 1 、 Figure 2 shown, the second embodiment of the vertical insertion steel: A vertical angle steel 15 is welded on the opposite side walls 12 of the second steel pile. The opening of the vertical angle steel 15 faces away from the foundation pit 1. The side plate 11 of the vertical channel steel 34 close to the foundation pit on both sides is vertically inserted onto the horizontal plate of the vertical angle steel 15. A channel steel side stopper 10 for preventing the vertical channel steel 34 inserted onto the horizontal plate of the vertical angle steel 15 from disengaging from the horizontal plate away from the foundation pit 1 can be welded on the side of the horizontal plate of the vertical angle steel 15 away from the foundation pit 1.

[0082] such as Figures 1 - 9 、 Figure 14 、 Figure 15As shown, both ends of each horizontal longitudinal connecting steel beam 25 are screwed to two first steel piles 4 by connecting blocks and a plurality of screws; the middle bottom of each horizontal longitudinal connecting steel beam 25 is screwed to the top ends of two inclined steel connecting columns 26 by connecting blocks, a plurality of bolts and a plurality of nuts. For example, the middle bottom of each horizontal longitudinal connecting steel beam 25 can be screwed to the top ends of two inclined steel connecting columns by a steel connecting block 41, a plurality of bolts such as the first bolt 23 and a plurality of nuts such as the first nut 24. The inclined steel connecting column 26 is an inclined steel connecting column 26 that is removed after the construction of the main building of the foundation pit is completed and is pulled out by an inclined pulling device. The first steel pile 4 is a first steel pile 4 that removes the steel strand 14 and the connecting steel pipe 6, and after the construction of the main building of the foundation pit is completed, removes the horizontal transverse connecting steel beam 16 and the horizontal longitudinal connecting steel beam 25, pulls out the inclined steel connecting column 26, and is pulled out by a vertical pulling device. The metal corrugated plate assembly 8 is a metal corrugated plate assembly 8 that is removed after the construction of the main building of the foundation pit is completed and is pulled out integrally by a vertical pulling device. The steel strand 14, the connecting steel pipe 6 and the side retaining wall of the foundation pit are the steel strand 14, the connecting steel pipe 6 and the retaining wall of the foundation pit that are manually removed after the outer anchor head 13 is removed layer by layer from bottom to top by the replacement bracing construction step during the process of constructing the main building from bottom to top in the foundation pit 1 and are pulled out by a horizontal pulling device. The second steel pile 5 is a second steel pile 5 that removes the steel strand 14, the connecting steel pipe 6 and the side retaining wall of the foundation pit, and after the construction of the main building of the foundation pit is completed, removes the top retaining wall, pulls out the metal corrugated plate assembly 8 and is pulled out by a vertical pulling device.

[0083] As Figures 1 - 15 shown.

[0084] The construction method of the foundation pit retaining structure of the soft soil body of the present invention constructs the foundation pit retaining structure in any one of the above technical solutions, including the following construction steps:

[0085] (1) At the pre-scored positions on the surface of the soft soil foundation far from the foundation pit 1 around the foundation pit, a first soil retaining and water retaining wall 3 composed of adjacent cement-soil mixing piles 2 biting each other is constructed by a pile driver.

[0086] (2) Fix the respective steel corbels 27 by welding at the predetermined vertical heights on the left and right sides of each first steel pile 4 in advance. At the pre-scored positions on the soft soil foundation far from the foundation pit 1 inside the first soil retaining and water retaining wall 3 around the foundation pit, a plurality of first steel piles 4 are inserted into the soil at intervals along the perimeter of the foundation pit to a predetermined depth by a pile driver. If the depth of one H-shaped steel is not enough, another one or two can be welded on the ground after inserting one, and correcting the verticality of the first steel pile 4, i.e., the H-shaped steel, inserted into the soft soil is a conventional technique and will not be elaborated. The following connection and correction of the second steel pile 5, i.e., the H-shaped steel, are the same.

[0087] (3) Use the power head of a pile driver that can adjust the tilt angle to insert the respective inclined steel connecting columns 26 obliquely downward from the middle of the distance between two adjacent first steel piles 4 to the side, and make the bottom end of each inclined steel connecting column 26 abut against its respective steel corbel 27. For example, make the bottom end face of the web of the inclined steel connecting column 26 of the H-shaped steel abut against the top surface of the steel corbel 27 formed by two vertical steel plates 45. Then detachably connect the top ends of the two inclined steel connecting columns 26 to the bottom plate of a horizontally arranged longitudinal connecting steel beam 25, and then detachably connect the two ends of the horizontally arranged longitudinal connecting steel beam 25 to the top ends of their respective first steel piles 4. For example, use multiple first bolts 23 and multiple first nuts 24 to be screwed through a steel connecting block 41, and then detachably connect the two ends of the horizontally arranged longitudinal connecting steel beam 25 to the top ends of their respective first steel piles 4, such as using multiple screws to be screwed through a steel connecting block. It is not difficult to understand that construction workers can use equipment and auxiliary tools to insert the bottom end of the inclined steel connecting column 26 into the soft soil foundation, insert it on the top surface of the steel corbel 27 and press it tightly, and make the two wing plates located on the two outer sides of the steel corbel 27, which can be successfully completed during the actual construction process.

[0088] (4) Weld the respective vertical insertion steels for inserting the metal corrugated plate assembly 8, such as vertical C-shaped steels 44, to the left and right sides of each second steel pile 5 in advance. At the pre-scored positions on the soft soil foundation outside the edge of the foundation pit 1, use a pile driver to insert multiple second steel piles 5 at intervals along the outer perimeter of the foundation pit 1 into the soft soil foundation to a predetermined depth.

[0089] (5) Use a crane to lift the metal corrugated plate assembly 8 that has been prefabricated and welded with vertical channel steels 34 to the insertion position, and then use the power head of a pile driver to insert the metal corrugated plate assembly 8 welded with vertical channel steels 34 along the vertical insertion steels of two adjacent second steel piles 5, such as vertical C-shaped steels 44, into the soft soil foundation until the predetermined depth to form a soil and water retaining unit. Then construct the soil and water retaining units one by one along the outer perimeter of the edge of the foundation pit 1 to form a second soil and water retaining wall 46.

[0090] (6) Detachably connect one or more laps of waling beams 7 to the second steel piles 5, and the multiple laps of waling beams 7 are distributed along the vertical height. For example, detachably connect one lap of waling beam 7, such as a channel steel, to the top of the H-shaped steel of one lap of second steel piles 5 to replace the reinforced concrete coping beam, and detachably connect one lap of waling beam 7, such as a channel steel or H-shaped steel, to the middle and lower parts respectively. The top one can be screwed with screws, and the middle and lower ones can be welded. When it needs to be disassembled, use oxygen cutting to cut it.

[0091] It is not difficult 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. Excavate the foundation pit 1 on the side of the inserted second steel piles 5 and the second soil and water retaining wall 46 of the foundation pit 1. You can insert the connecting steel pipe 6, install the external anchor head 13 and the waling beam 7 while excavating the soil until reaching the bottom surface of the foundation pit 1.

[0092] (7) Use the power head of the horizontal pile driver to horizontally insert the connecting steel pipe 6 connected with the steel strand 14, the plastic pipe 18 and the bullet-shaped concrete body 17 from one side of the foundation pit 1 into the second through hole 21 of the second steel pile 5, the soft soil foundation and the first through hole 22 of the first steel pile 4, and axially limit it. 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, tension and anchor the two free ends of the steel strand 14 on one side of the foundation pit 1 with anchors to form an external anchor head 13.

[0093] The construction method of the foundation pit enclosure structure of the soft soil body of the present invention further includes the following construction steps:

[0094] (8) During the construction process of the main building in the foundation pit 1 from bottom to top, adopt the replacement support construction steps to disassemble the external anchor head 13 layer by layer from bottom to top, use the horizontal pulling equipment to pull out all the steel strands 14 and all the connecting steel pipes 6 layer by layer, and manually disassemble the detachable connections such as dismounting screws or gas cutting welding of one or more circles of the retaining beams 7 on one side of the foundation pit 1 layer by layer in the foundation pit, and use a crane to lift away multiple retaining beams 7 in each circle, and at the same time replace them with the temporary support of the main building. It is not difficult to understand that the replacement support construction steps are construction steps familiar to construction personnel in the field. The temporary support is generally not taken out again.

[0095] (9) After the construction of the main building in the foundation pit 1 is completed, manually disassemble the detachable connections at both ends of the horizontal transverse connecting steel beam 16 with the tops of the first steel pile 4 and the second steel pile 5 in each pair of steel piles on the ground one by one, such as dismounting screws, and use a crane to lift away the horizontal transverse connecting steel beam 16.

[0096] (10) Use the vertical pulling equipment to vertically pull out all the fixed metal corrugated plate assemblies 8 welded with vertical channel steels 34 one by one.

[0097] (11) Use the vertical pulling equipment to pull out all the second steel piles 5 one by one.

[0098] (12) Manually disassemble the screws at both ends of the horizontal longitudinal connecting steel beam 25 with the top of the respective first steel pile 4 on the ground one by one, disassemble the multiple bolts and multiple nuts at the middle of the horizontal longitudinal connecting steel beam 25 and the tops of the two inclined steel connecting columns 26, such as disassembling the multiple first bolts 23 and multiple first nuts 24 at the middle of the horizontal longitudinal connecting steel beam 25 and the tops of the two inclined steel connecting columns, and use a crane to lift away the horizontal longitudinal connecting steel beam 25.

[0099] (13) Use the oblique pulling equipment to pull out all the inclined steel connecting columns 26 one by one. It is not difficult to understand that the pulling inclination directions of two adjacent inclined steel connecting columns 26 are opposite.

[0100] (14) Use a vertical pulling device to pull out all the first steel piles 4 one by one.

[0101] It is not difficult to understand that:

[0102] The construction sequence of steps (9), (10), (11) and steps (12), (13), (14) is not very strict. Specifically, steps (9), (10), (11) can be constructed first, and then steps (12), (13), (14); or steps (12), (13), (14) can be constructed first, and then steps (9), (10), (11); or steps (9), (10), (11) and steps (12), (13), (14) can be constructed simultaneously.

[0103] It is not difficult to understand that after all the building construction in the foundation pit 1 is completed, that is, after the retaining mission of the foundation pit retaining structure is completed, the said foundation pit retaining structure is abandoned. Therefore, all the steel materials are recycled and reused.

[0104] The parts, structures, quantities, etc. not marked above are not shown in the drawings. The drawings are only schematic. If there are inconsistencies between the drawings and the text description, or inconsistencies between the drawings themselves, the text description shall prevail.

[0105] The above is only the preferred embodiment of the present invention and is not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A foundation pit retaining structure for soft soil foundation, comprising a first soil retaining and water blocking wall formed by adjacent plain cement soil mixing piles that are mutually occluded and are away from the foundation pit; characterized in that: It further comprises a plurality of first steel piles that are arranged at intervals along the perimeter of the foundation pit inside the first soil retaining and water blocking wall and are inserted into the soft soil foundation. A horizontal longitudinal connecting steel beam is detachably connected to the tops of two adjacent first steel piles. There is a steel bracket fixed on the opposite side walls of their respective first steel piles vertically below both ends of the horizontal longitudinal connecting steel beam. The bottom of the middle of the length of the horizontal longitudinal connecting steel beam is detachably connected to the tops of two inclined steel connecting columns. The bottom end of each inclined steel connecting column abuts against its respective steel bracket, so that a circle of first steel piles is connected into a whole; It further comprises a plurality of second steel piles that are arranged at intervals along the outer perimeter of the foundation pit edge and are inserted into the soft soil foundation. The second steel piles are detachably connected with at least one circle of purlins, so that a circle of second steel piles is connected into a whole; A metal corrugated plate assembly inserted into the soft soil foundation is detachably connected between two adjacent second steel piles to form a soil retaining and water blocking unit. The soil retaining and water blocking units extend along the outer perimeter of the foundation pit edge to form a second soil retaining and water blocking wall; A horizontal transverse connecting steel beam is detachably connected to the tops of the first steel pile and the second steel pile in each pair of steel piles; both 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. At least one connecting steel pipe inserted horizontally from inside the foundation pit is accommodated in the corresponding through holes of the first steel pile and the second steel pile in each pair of steel piles. A steel strand is movably sleeved in a plastic pipe inside each connecting steel pipe. The U-shaped inner ends of the steel strand and the plastic pipe are accommodated in the U-shaped groove of a bullet-shaped concrete body. The middle part of the steel strand is placed inside the connecting steel pipe. There is a grouting pipe for grouting inside the connecting steel pipe. The solidified grout, the U-shaped part of the plastic pipe and the bullet-shaped concrete body form an internal anchoring head. The two outer ends of the steel strand on the foundation pit side and the anchor fittings form an external anchoring head.

2. The foundation pit retaining structure for soft soil foundation according to claim 1, characterized in that: The steel brackets are welded to the middle or lower part of the vertical direction of each first steel pile, so that the middle or lower part of the vertical direction of a circle of first steel piles is connected into a whole.

3. The foundation pit retaining structure for soft soil foundation according to claim 1, characterized in that: The steel brackets are composed of two parallel vertical steel plates. Each inclined steel connecting column is made of an H-shaped steel. The web of the bottom end of the H-shaped steel is shorter than the two wing plates of the bottom end of the H-shaped steel. The bottom end face of the web of the bottom end of the H-shaped steel of the inclined steel connecting column is placed on the horizontal top surfaces of the two vertical steel plates of each steel bracket. The width dimension of each steel bracket is narrower than the width dimension between the two wing plates at the bottom end of the H-shaped steel of the inclined steel connecting column. The two wing plates at the bottom end of the H-shaped steel of each inclined steel connecting column are located outside the two parallel vertical steel plates of the steel bracket; the top end of each inclined steel connecting column is screwed to the middle of the length of the web of the channel steel of the horizontal longitudinal connecting steel beam through a connecting block, a plurality of bolts and a plurality of nuts.

4. The foundation pit retaining structure for soft soil foundation according to claim 1, wherein: The metal corrugated plate assembly comprises two metal corrugated plates with the same shape and size. Each metal corrugated plate is composed of multiple vertical flat plates and multiple vertical angular plates connected at intervals. Between the two metal corrugated plates, there are multiple vertical strip-shaped metal plates extending vertically and parallel to each other. Each pair of vertical flat plates of the two metal corrugated plates are screwed and fixed to a vertical strip-shaped metal plate through multiple bolts and nuts. The angles of the multiple vertical angular plates of the two metal corrugated plates are all away from the vertical strip-shaped metal plate, thus forming an outer arch structure for bearing the lateral pressure of the soil body. Adjacent two vertical strip-shaped metal plates are connected by multiple horizontal steel connecting rods arranged vertically. There are horizontal steel connecting strips at the top and bottom of the metal corrugated plates to connect each vertical strip-shaped metal plate and the metal corrugated plate, making the metal corrugated plate assembly form a rigid whole.

5. The foundation pit retaining structure for soft soil foundation according to claim 4, characterized in that: The detachable connection structure between the metal corrugated plate assembly and the second steel pile is as follows: on the opposite side walls of two adjacent second steel piles, a vertical plug-in steel is respectively fixed. The plug-in notch of the vertical plug-in steel faces away from the foundation pit. 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 strip-shaped metal plates on both sides of the metal corrugated plate assembly are fixed to the inner side of the web of a vertical channel steel. 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. The height dimension of the vertical channel steel is equal to or greater than the height dimension of the metal corrugated plate assembly.

6. The foundation pit retaining structure for soft soil foundation according to claim 1, characterized in that: Both ends of each horizontal longitudinal connecting steel beam are screwed to two first steel piles by connection blocks and multiple screws; the middle bottom of each horizontal longitudinal connecting steel beam is screwed to the tops of two inclined steel connecting columns by connection blocks, multiple bolts and nuts; the inclined steel connecting columns are the inclined steel connecting columns that are removed after the construction of the main building of the foundation pit is completed and are pulled out by an inclined pulling device; the first steel piles are the first steel piles that are removed from the steel strands and connecting steel pipes, and after the construction of the main building of the foundation pit is completed, the horizontal transverse connecting steel beam, the horizontal longitudinal connecting steel beam are removed, the inclined steel connecting columns are pulled out, and are pulled out by a vertical pulling device; the metal corrugated plate assembly is the metal corrugated plate assembly that is removed from the top purlin after the construction of the main building of the foundation pit is completed and is pulled out integrally by a vertical pulling device; the steel strands, connecting steel pipes and the side purlin of the foundation pit are the steel strands, connecting steel pipes that are removed layer by layer from the bottom to the top after the outer anchor heads are removed layer by layer in the process of constructing the main building from the bottom to the top in the foundation pit by using the replacement bracing construction steps and are pulled out by a horizontal pulling device, and the side purlin of the foundation pit that is manually removed; the second steel piles are the second steel piles that are removed from the steel strands, connecting steel pipes and the side purlin of the foundation pit, and after the construction of the main building of the foundation pit is completed, the top purlin is removed, the metal corrugated plate assembly is pulled out, and is pulled out by a vertical pulling device.

7. The foundation pit retaining structure for soft soil foundation according to claim 1, characterized in that: Both the first steel pile and the second steel pile adopt H-shaped steel. The webs of each pair of H-shaped steel are parallel to each other, and the through holes are all arranged on the webs.

8. The foundation pit retaining structure for soft soil foundation according to claim 1, characterized in that: In each pair of steel piles, the first steel pile and the second steel pile are each provided with respective first through holes and second through holes vertically along the depth of the foundation pit at intervals of several meters from the top downwards. The first through hole is a tapered hole for axially limiting the inner end of the connecting steel pipe. The inner end of the connecting steel pipe is matched with the tapered hole and has a smaller end close to the cement-soil mixing pile and a larger part far from the cement-soil mixing pile. The second through hole is a straight through hole for passing through the connecting steel pipe.

9. A construction method for the foundation pit retaining structure of a soft soil foundation, which constructs the foundation pit retaining structure according to any one of claims 1-8, including the following construction steps: (1) On the pre-scored positions on the surface of the soft soil foundation far from the foundation pit around the foundation pit, use a pile driver to construct a first soil retaining and water blocking wall formed by the interlocking of adjacent cement-soil mixing piles. (2) Fix respective steel corbels on the left and right sides of each first steel pile at a predetermined vertical height in advance. On the pre-scored positions on the soft soil foundation far from the foundation pit inside the perimeter of the first soil retaining and water blocking wall, use a pile driver to insert multiple first steel piles at intervals around the foundation pit into the soil to a predetermined depth. (3) Use the power head of a pile driver capable of adjusting the inclination angle to insert respective inclined steel connecting columns obliquely downward from the middle of the distance between two adjacent first steel piles to the side, and make the bottom end of each inclined steel connecting column abut against its respective steel corbel. Then, detachably connect the top ends of the two inclined steel connecting columns to the bottom plate of a horizontally arranged longitudinal connecting steel beam, and then detachably connect the two ends of the horizontally arranged longitudinal connecting steel beam to the top ends of their respective first steel piles. (4) Weld respective vertical insertion steels for inserting metal corrugated plate assemblies on the left and right sides of each second steel pile in advance. On the pre-scored positions on the soft soil foundation outside the edge of the foundation pit, use a pile driver to insert multiple second steel piles at intervals around the foundation pit into the soft soil foundation to a predetermined depth. (5) Use a crane to lift the metal corrugated plate assembly prefabricated and welded with vertical channel steels to the insertion position, and then use the power head of a pile driver to insert the metal corrugated plate assembly welded with vertical channel steels into the soft soil foundation along the vertical insertion steels of two adjacent second steel piles until a predetermined depth to form a soil retaining and water blocking unit. Then, construct the soil retaining and water blocking units one by one along the outside perimeter of the edge of the foundation pit to form a second soil retaining and water blocking wall. (6) Detachably connect one or more laps of purlins to the second steel piles, and the multiple laps of purlins are distributed along the vertical height. (7) Use the power head of a horizontal pile driver to horizontally insert a connecting steel pipe connected with a steel strand, a plastic pipe, and a 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 and axially limit it. 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, tension and anchor the two free ends of the steel strand on the foundation pit side with anchors to form an external anchor head.

10. According to the construction method for the foundation pit retaining structure of a soft soil foundation described in claim 9, the following construction steps are further included: (8) During the construction of the main building from bottom to top in the foundation pit, the external anchor heads are disassembled layer by layer from bottom to top using the replacement bracing construction steps, all the steel strands and all the connecting steel pipes are pulled out layer by layer using a horizontal pulling device, and one or more laps of the retaining beams on the foundation pit side with detachable connections are manually disassembled layer by layer in the foundation pit, and multiple retaining beams in each lap are lifted away by a crane, and at the same time, they are replaced by the temporary supports of the main building; (9) After the construction of the main building in the foundation pit is completed, the two ends of the horizontal cross-connecting steel beam are manually disassembled from the detachable connections at the tops of the first steel pile and the second steel pile in each pair of steel piles on the ground, and the horizontal cross-connecting steel beam is lifted away by a crane; (10) All the metal corrugated plate components fixed with vertical channel steels are pulled out vertically one by one using a vertical pulling device; (11) All the second steel piles are pulled out one by one using a vertical pulling device; (12) The two ends of the horizontal longitudinal connecting steel beam are manually disassembled from the multiple connecting screws at the top ends of their respective first steel piles on the ground, the multiple bolts and multiple nuts at the middle of the horizontal longitudinal connecting steel beam and the top ends of the two inclined steel connecting columns are disassembled, and the horizontal longitudinal connecting steel beam is lifted away by a crane; (13) All the inclined steel connecting columns are pulled out one by one using an inclined pulling device; (14) All the first steel piles are pulled out one by one using a vertical pulling device.

Images