Two-wall-in-one prefabricated underground continuous wall structure and construction method thereof

Abstract

A two-wall-in-one prefabricated underground continuous wall structure and a construction method thereof, wherein a plurality of vertically arranged suspension bars are anchored on the top of the prefabricated underground continuous wall unit, a bottom plate connecting groove is provided on the pit facing side of the prefabricated underground continuous wall unit at a position corresponding to a preset connecting position of the bottom plate, a steel bar connector is pre-embedded on the prefabricated underground continuous wall unit and in the bottom plate connecting groove, connecting notches arranged in the vertical direction and matching the size of the buttress column are provided on the opposite connecting sides of adjacent prefabricated underground continuous wall units, the bottom of the connecting notch is communicated with the bottom plate connecting groove, the horizontal steel bars in the prefabricated underground continuous wall unit extend from both sides of the prefabricated underground continuous wall unit within the range where the connecting notch is located, and the extended horizontal steel bars are arranged in the connecting notch to form reserved steel bars, and the bottom plate connecting groove and the connecting notch are filled with extruded boards. The wall quality after construction of the present invention meets the design requirements, while simplifying and standardizing the construction steps, thereby improving the quality of the continuous wall.

Description

Technical Field

[0001] The invention relates to a two-wall-in-one prefabricated underground continuous wall structure and a construction method thereof. Background Art

[0002] As a safety barrier for underground space development, foundation pit support projects have become diverse and expensive in the face of external factors such as complex urban surrounding environments, densely populated buildings, complex geological conditions, and abundant groundwater. As a temporary project, how can foundation pit support projects be safe, economical, and save construction time? This has brought huge challenges to various design and construction companies, especially when using traditional reverse construction methods. The cost of foundation pit support is expensive, the fragmented construction of the lower soil and shear walls leads to extremely low construction efficiency, and the large number of shear wall construction nodes leads to serious groundwater leakage. Although the traditional underground continuous wall support can achieve the integration of two walls, the existing underground continuous wall construction steps are to first dig a trench at the location where the continuous wall is to be laid, and then lay steel bars in the trench. Cage is cast and finally a continuous wall is formed. However, on the one hand, the bottom of the trench is not flat when the trench is excavated, resulting in inconsistent elevations at the top of the steel cage after it is placed on the bottom of the trench, causing a large error in the horizontal height of the steel connectors used to connect the bottom plate steel bars on the steel cage, affecting subsequent bottom plate construction. On the other hand, muddy water will remain in the trench when the trenching equipment is used to dig the trench, so direct casting will result in poor quality of underwater concrete pouring, which is prone to mud being trapped in the wall to form an infiltration channel and expose the steel bars on the wall, which not only affects normal use, but also seriously affects structural safety. Summary of the invention

[0003] To achieve the above object, the present invention first proposes a two-wall-in-one prefabricated underground continuous wall structure and a construction method thereof that simplifies and standardizes the construction steps and improves the quality of the continuous wall.

[0004] The present invention relates to a two-wall-in-one prefabricated underground continuous wall structure, comprising a prefabricated underground continuous wall unit, wherein a plurality of vertically arranged suspension bars are anchored on the top of the prefabricated underground continuous wall unit, a bottom plate connecting groove is provided on the pit facing side of the prefabricated underground continuous wall unit at a position corresponding to a preset connecting position of a bottom plate, a steel bar connector is pre-embedded on the prefabricated underground continuous wall unit and in the bottom plate connecting groove, and connecting notches arranged in a vertical direction and matching the size of buttress columns are provided on opposite connecting sides of adjacent prefabricated underground continuous wall units, the bottom of the connecting notch is communicated with the bottom plate connecting groove, the horizontal steel bars in the prefabricated underground continuous wall unit extend from both sides of the prefabricated underground continuous wall unit within the range of the connecting notch, and the extended horizontal steel bars are arranged in the connecting notch to form reserved steel bars, and the bottom plate connecting groove and the connecting notch are filled with detachable support members.

[0005] In this embodiment, the suspension bar is a U-shaped steel bar, and the central axis of the opening formed by the U-shaped part of the suspension bar is perpendicular to the prefabricated underground continuous wall unit.

[0006] In the present embodiment, the prefabricated underground continuous wall unit is also preset with a feed pipe, a wall bottom grouting pipe, a pit side grouting pipe and a soil side grouting pipe. The inlets of the feed pipe and the wall bottom grouting pipe are both arranged at the top of the prefabricated underground continuous wall unit, and the outlets are both arranged at the bottom of the prefabricated underground continuous wall unit. The inlet of the pit side grouting pipe is arranged at the top of the prefabricated underground continuous wall unit, and the outlet is arranged below the pit side and bottom plate connecting groove of the prefabricated underground continuous wall unit. The inlet of the soil side grouting pipe is arranged at the top of the prefabricated underground continuous wall unit, and the outlet is arranged below the soil side and bottom plate connecting groove of the prefabricated underground continuous wall unit.

[0007] In this embodiment, two of the feed pipes, the pit-facing side grouting pipes and the soil-facing side grouting pipes are provided, and the two feed pipes, the pit-facing side grouting pipes and the soil-facing side grouting pipes are symmetrically arranged with the length center of the prefabricated underground continuous wall unit as the symmetry axis, and the outlet of the wall bottom grouting pipe is set in the middle of the bottom surface of the prefabricated underground continuous wall unit.

[0008] In this embodiment, angle steel is pre-embedded in the area where the connection notch of the prefabricated underground continuous wall unit is located and on the corner connected to the connection notch on the connection side.

[0009] In this embodiment, a connection area is formed between the connection gaps of adjacent prefabricated underground continuous wall units, and buttress columns are cast in the connection area to connect the adjacent prefabricated underground continuous wall units.

[0010] In this embodiment, a vertically arranged expansion water stop strip is provided between the buttress column and the inner wall of the connecting notch.

[0011] The present invention also includes a construction method of a two-wall-in-one prefabricated underground continuous wall, using the above-mentioned two-wall-in-one prefabricated underground continuous wall structure, specifically comprising the following steps:

[0012] a. According to the design, a groove is excavated on the ground and at the location of the prefabricated underground continuous wall by a mechanical groove forming machine. The groove width should be 100-200mm greater than the thickness of the prefabricated wall, and the groove depth should be 300-500mm greater than the height of the prefabricated underground continuous wall unit;

[0013] b. Hoist the prefabricated underground continuous wall unit into the groove, insert the supporting steel beam into the suspension bar, arrange the supporting steel beam vertically with the prefabricated underground continuous wall unit, span the groove and support the two ends of the supporting steel beam on the guide wall, so that the prefabricated underground continuous wall unit is suspended in the groove by the supporting steel beam, and the elevation of the prefabricated underground continuous wall unit is adjusted and controlled by adjusting the height of the supporting steel beam, so that all prefabricated underground continuous wall units meet the elevation accuracy;

[0014] c. After the adjustment of the horizontal height and spacing of all prefabricated underground continuous wall units is completed, the concrete delivery conduit is inserted from the feed pipe of the prefabricated underground continuous wall unit to the bottom of the trench, and the first pouring of concrete is started. Then, the reserved wall bottom grouting pipe, pit side grouting pipe and soil side grouting pipe are used for secondary pressure grouting. Finally, the grouting pipe is inserted from the slot to carry out the third normal pressure grouting to fill the remaining gap. The third normal pressure grouting makes the concrete height in the trench reach the height of the top of the prefabricated underground continuous wall.

[0015] d. After the final setting of the concrete, excavate the foundation pit on the facing side of the precast underground continuous wall unit, then remove the concrete and filled extruded boards at the joints, connection gaps and bottom plate connection grooves of the precast underground continuous wall unit, weld steel sheets to seal between the adjacent precast underground continuous wall unit angles, and full welding is required. Buttress columns are arranged in the connection area formed by the connection gaps of adjacent precast underground continuous wall units.

[0016] In this embodiment, in step d, the specific arrangement method of the buttress columns is as follows: first, a steel cage is arranged in the connection area, and the reserved steel bars are bent when the steel cage is placed. After the steel cage is placed, the reserved steel bars are straightened. Before pouring the buttress columns, an expansion water stop strip is placed in the gap between the steel cage and the inner wall of the connection notch along the vertical direction, and finally concrete is poured in the connection area to form the buttress columns.

[0017] Compared with the prior art, the present invention has the following significant advantages:

[0018] 1. The prefabricated underground continuous wall unit of the present invention can be prefabricated in a factory. As the main load-bearing structure of the underground continuous wall, the prefabricated underground continuous wall unit can ensure the quality of the underground continuous wall body in the factory compared with on-site casting, and prevent the poor quality of underwater concrete casting caused by on-site casting;

[0019] 2. The prefabricated underground continuous wall unit uses the bottom plate connection groove as the dividing point. The steel bar connector in the bottom plate connection groove is used to connect with the bottom plate steel bar on the bottom plate of the underground structure. The part of the prefabricated underground continuous wall unit below the bottom plate connection groove is the length of the embedded section of the foundation pit support, and the part above the bottom plate connection groove is the height of the basement wall. When the prefabricated underground continuous wall unit is under construction, the groove depth is greater than the height of the prefabricated underground continuous wall unit. The prefabricated underground continuous wall unit is suspended in the groove through the cooperation of the suspension bar and the supporting steel beam, and does not contact the bottom of the groove. This facilitates the adjustment of the elevation of the prefabricated underground continuous wall unit, so that the elevation of the prefabricated underground continuous wall unit is not affected by the unevenness of the groove bottom, and ensures that the bottom plate connection groove on the prefabricated underground continuous wall unit is at the same horizontal height. This is convenient for the connection of the steel bar connector on the prefabricated underground continuous wall unit with the bottom plate steel bar on the bottom plate of the underground structure, ensures the convenience of construction, and improves the quality of construction;

[0020] 3. The prefabricated underground continuous wall units are provided with connection gaps, and the adjacent prefabricated underground continuous wall units are connected to each other through buttresses cast in situ in the connection gaps, so that the prefabricated underground continuous wall units are closely connected to ensure that the formed underground continuous wall meets the force requirements;

[0021] 4. A feed pipe is provided in the prefabricated underground continuous wall unit, so that the concrete delivery conduit can be directly dragged into the bottom of the trench through the feed pipe. On the one hand, pouring from bottom to top is realized through the feed pipe, so as to ensure the quality of pouring and reduce the generation of cavities and voids. On the other hand, by pouring from bottom to top, the concrete solidifies at the bottom of the prefabricated underground continuous wall unit to form a supporting structure, forming the foundation for supporting the prefabricated underground continuous wall unit, thereby improving the stability of the prefabricated underground continuous wall unit. In addition, a wall bottom grouting pipe, a pit side grouting pipe and a soil side grouting pipe are also provided in the prefabricated underground continuous wall unit. Secondary grouting is carried out through the reserved wall bottom grouting pipe, the pit side grouting pipe and the soil side grouting pipe, thereby further filling the gap between the prefabricated wall and the surrounding soil, further improving the stability of the prefabricated underground continuous wall unit, and restoring the bearing capacity of the soil.

[0022] In summary, the present invention combines the underground continuous wall and the basement shear wall into one, and at the same time meets the requirements of foundation pit support and main structure stress. The construction of the present invention adopts the form of hoisting and hanging, which can ensure the accuracy of the elevation of the prefabricated underground continuous wall unit. At the same time, through the feed pipe, the wall bottom grouting pipe, the pit side grouting pipe and the soil side grouting pipe, the gap between the bottom of the prefabricated underground continuous wall unit and the surrounding soil can be filled with concrete in a short time to restore the bearing capacity of the soil around the prefabricated wall, so that the wall quality finally meets the design requirements, and at the same time simplifies and standardizes the construction steps, thereby improving the quality of the continuous wall. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic structural diagram of the prefabricated underground continuous wall unit of the present invention.

[0024] Figure 2 This is a construction status diagram of the prefabricated underground continuous wall unit of the present invention.

[0025] In the attached figure: 1. Prefabricated underground continuous wall unit; 2. Connection notch; 3. Feed pipe; 4. Grouting pipe at the bottom of the wall; 5. Grouting pipe on the pit side; 6. Grouting pipe on the soil side; 7. Suspension reinforcement; 8. Bottom plate connection groove; 9. Reserved steel bars; 10. Buttress column; 11. Steel cage; 12. Angle steel; 13. Steel sheet; 14. Expansion water stop strip; 15. Reserved steel bars at the top. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0028] like Figure 1 , 2 As shown, the present invention provides a two-wall-in-one prefabricated underground continuous wall structure, including a prefabricated underground continuous wall unit 1, wherein the vertical steel bars in the prefabricated underground continuous wall unit 1 extend from the top of the prefabricated underground continuous wall unit to form a top reserved steel bar 15, and the top reserved steel bar 15 is used to connect with the upper structure, and the prefabricated underground continuous wall unit 1 is provided with a bottom plate connecting groove 8 on the facing pit side, and the bottom plate connecting groove 8 corresponds to the preset connection position of the bottom plate of the underground structure, and the bottom plate connecting groove 8 is a through groove, and a steel bar connector matching the bottom plate steel bar position is pre-embedded on the prefabricated underground continuous wall unit 1 and in the bottom plate connecting groove 8, and adjacent prefabricated underground continuous wall units are connected. A connecting notch 2 arranged in the vertical direction and matching the size of the buttress column 10 is provided on the connecting side opposite to the element 1, and the bottom of the connecting notch 2 is connected to the bottom plate connecting groove 8, and the connecting notch 2 connects the facing side of the prefabricated underground continuous wall unit 1 with the connecting side, and the horizontal steel bars of the prefabricated underground continuous wall unit 1 within the range of the connecting notch 2 extend from both sides of the prefabricated underground continuous wall unit 1 and are arranged in the connecting notch 2 to form reserved steel bars 9, and the bottom plate connecting groove 8 and the connecting notch 2 are filled with detachable support members, and the detachable support members fill the bottom plate connecting groove 8 and the connecting notch 2. In this embodiment, the detachable support members are extruded boards.

[0029] A plurality of vertically arranged suspension bars 7 are anchored on the top of the prefabricated underground continuous wall unit 1. The anchoring length, position and diameter of the suspension bars 7 are calculated according to the weight of the prefabricated underground continuous wall unit 1 to ensure that the suspension bars 7 can support the weight of the prefabricated underground continuous wall unit 1. The number of suspension bars 7 can be set according to the weight of the wall and the bearing capacity of the suspension bars 7. The suspension bars 7 are U-shaped steel bars. The central axis of the opening formed by the U-shaped part of the suspension bars 7 is perpendicular to the prefabricated underground continuous wall unit 1. The opening of the suspension bars 7 is larger than the supporting steel beam used for support, so that the supporting steel beam can pass through the suspension bars 7 conveniently.

[0030] The prefabricated underground continuous wall unit 1 is also preset with a feed pipe 3, a wall bottom grouting pipe 4, a pit-facing side grouting pipe 5 and a soil-facing side grouting pipe 6. The inlets of the feed pipe 3 and the wall bottom grouting pipe 4 are both arranged at the top of the prefabricated underground continuous wall unit 1, and the outlets are both arranged at the bottom of the prefabricated underground continuous wall unit 1. The inlet of the pit-facing side grouting pipe 5 is arranged at the top of the prefabricated underground continuous wall unit 1, and the outlet is arranged at the pit-facing side of the prefabricated underground continuous wall unit 1 and below the bottom plate connecting groove 8. The inlet of the side grouting pipe 6 is arranged at the top of the prefabricated underground continuous wall unit 1, and the outlet is arranged on the soil-facing side of the prefabricated underground continuous wall unit 1 and below the bottom plate connection groove 8; the feed pipe 3, the pit-facing side grouting pipe 5 and the soil-facing side grouting pipe 6 are each provided with two, and the two feed pipes 3, the pit-facing side grouting pipe 5 and the soil-facing side grouting pipe 6 are symmetrically arranged with the length direction center of the prefabricated underground continuous wall unit 1 as the symmetry axis, and the outlet of the wall bottom grouting pipe 4 is arranged in the middle of the bottom surface of the prefabricated underground continuous wall unit 1;

[0031] Angle steel 12 is pre-embedded in the area where the connection gap 2 of the prefabricated underground continuous wall unit 1 is located and on the corner connected to the connection gap 2 on the connection side. The angle steel 12 is arranged in the vertical direction and its length matches the length of the connection gap 2. The gap between adjacent prefabricated underground continuous wall units 1 and the part above the bottom plate connection groove 8 are sealed by welding steel sheets 13 between the angle steels 12. A connection area is formed between the connection gaps 2 of adjacent prefabricated underground continuous wall units 1. Buttress columns 10 are cast in the connection area to connect adjacent prefabricated underground continuous wall units 1. A steel cage 11 is arranged in the buttress columns 10. The reserved steel bars 9 in the prefabricated underground continuous wall unit 1 extend into the steel cage 11. A vertically arranged expansion water stop strip 14 is arranged between the buttress columns 10 and the inner wall of the connection gap 2.

[0032] The specific method for constructing a prefabricated underground continuous wall using the above-mentioned prefabricated underground continuous wall unit 1 is as follows:

[0033] a. According to the design, a groove is excavated on the ground and at the location of the prefabricated underground continuous wall by a mechanical groove forming machine. The groove width should be 100-200mm greater than the thickness of the prefabricated wall, and the groove depth should be 300-500mm greater than the height of the prefabricated underground continuous wall unit 1;

[0034] b. Hoist the prefabricated underground continuous wall unit into the groove, insert the supporting steel beam into the suspension bar, arrange the supporting steel beam vertically with the prefabricated underground continuous wall unit, the supporting steel beam spans the groove and the two ends of the supporting steel beam are supported on the guide wall, so that the prefabricated underground continuous wall unit is suspended in the groove by the supporting steel beam, and the prefabricated underground continuous wall unit does not contact the bottom of the groove, and the elevation of the prefabricated underground continuous wall unit is adjusted and controlled by adjusting the height of the supporting steel beam (for example, the height of the supporting steel beam can be adjusted by inserting a pad at the bottom of the supporting steel beam, and of course, the height of the supporting steel beam can be adjusted by other height adjustment methods in the prior art, which will not be listed here), so that all prefabricated underground continuous wall units meet the elevation accuracy;

[0035] c. When the horizontal height and spacing of all prefabricated underground continuous wall units are adjusted, the concrete delivery conduit is inserted from the feed pipe 3 of the prefabricated underground continuous wall unit to the bottom of the groove, and the first pouring of concrete is started. The pouring can be stopped when the first pouring of concrete covers the bottom plate connection groove 8, and then the reserved wall bottom grouting pipe, pit side grouting pipe and soil side grouting pipe are used for secondary pressure grouting. Finally, the grouting pipe is inserted from the groove to carry out the third normal pressure grouting to fill the remaining gap. The third normal pressure grouting makes the concrete height reach the top height of the prefabricated underground continuous wall, and the grouting is stopped;

[0036] d. After the final setting of the concrete, the foundation pit is excavated on the pit-facing side of the precast underground continuous wall unit, and then the concrete and filled extruded plates at the joints, connection gaps and bottom plate connection grooves of the precast underground continuous wall unit are removed, and steel sheets are welded to seal between the adjacent precast underground continuous wall unit angles. Full welding is required. In the connection area formed by the connection gaps of adjacent precast underground continuous wall units, steel cages are laid out. The reinforcement of the steel cages must meet the requirements of current specifications. When placing the steel cages, the reserved steel bars are bent first, and then the reserved steel bars are straightened after the steel cages are placed. At the same time, before pouring the buttresses, expansion waterstops are placed in the gap between the steel cages and the inner wall of the connection gaps along the vertical direction. Finally, concrete is poured in the connection area to form buttresses.

[0037] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the contents of the present invention's specification and drawings, or directly / indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A two-wall-in-one prefabricated underground continuous wall structure, comprising a prefabricated underground continuous wall unit (1), Features: A plurality of vertically arranged suspension bars (7) are anchored on the top of the prefabricated underground continuous wall unit (1); a bottom plate connection groove (8) is provided on the pit facing side of the prefabricated underground continuous wall unit (1); the bottom plate connection groove (8) corresponds to a preset connection position of the bottom plate of the underground structure; a steel bar connector is pre-embedded on the prefabricated underground continuous wall unit (1) and in the bottom plate connection groove (8); connecting notches (2) arranged in the vertical direction and matching the size of the buttress column (10) are provided on the opposite connecting sides of adjacent prefabricated underground continuous wall units (1); the bottom of the connecting notch (2) is communicated with the bottom plate connection groove (8); the prefabricated underground continuous wall unit (1) is provided with a plurality of vertically arranged suspension bars (7) on the pit facing side; the bottom of the connecting notch (2) is communicated with the bottom plate connection groove (8); the prefabricated underground continuous wall unit (1) is provided with a plurality of vertically arranged suspension bars (7) on the pit facing side; the bottom of the connecting notch (2) is communicated with the bottom plate connection groove (8); the prefabricated underground continuous wall unit (1) is provided with a plurality of vertically arranged suspension bars (7) on the top of the prefabricated underground continuous wall unit (1); ... The horizontal steel bars in the (1) extend from both sides of the prefabricated underground continuous wall unit (1) within the range where the connection notch (2) is located, and the extended horizontal steel bars are arranged in the connection notch (2) to form reserved steel bars (9), and the bottom plate connection groove (8) and the connection notch (2) are filled with detachable support members; after the concrete is finally set, the foundation pit is excavated on the pit facing side of the prefabricated underground continuous wall unit (1), the concrete and the detachable support members filled in the joints, connection notches (2) and bottom plate connection grooves (8) of the prefabricated underground continuous wall unit (1) are removed, and buttress columns (10) are arranged in the connection area formed by the connection notches (2) of adjacent prefabricated underground continuous wall units (1).

2. The two-wall-in-one prefabricated underground continuous wall structure according to claim 1, Features: The suspension bar (7) is a U-shaped steel bar, and the opening center axis formed by the U-shaped part of the suspension bar (7) is perpendicular to the prefabricated underground continuous wall unit (1).

3. The two-wall-in-one prefabricated underground continuous wall structure according to claim 2, Features: The prefabricated underground continuous wall unit (1) is also preset with a feed pipe (3), a wall bottom grouting pipe (4), a pit-facing side grouting pipe (5) and a soil-facing side grouting pipe (6); the inlets of the feed pipe (3) and the wall bottom grouting pipe (4) are both arranged at the top of the prefabricated underground continuous wall unit (1), and the outlets are both arranged at the bottom of the prefabricated underground continuous wall unit (1); the inlet of the pit-facing side grouting pipe (5) is arranged at the top of the prefabricated underground continuous wall unit (1), and the outlet is arranged below the pit-facing side and bottom plate connecting groove (8) of the prefabricated underground continuous wall unit (1); the inlet of the soil-facing side grouting pipe (6) is arranged at the top of the prefabricated underground continuous wall unit (1), and the outlet is arranged below the soil-facing side and bottom plate connecting groove (8) of the prefabricated underground continuous wall unit (1).

4. The two-wall-in-one prefabricated underground continuous wall structure according to claim 3, Features: The feed pipe (3), the pit-facing grouting pipe (5) and the soil-facing grouting pipe (6) are each provided with two, and the two feed pipes (3), the pit-facing grouting pipe (5) and the soil-facing grouting pipe (6) are symmetrically arranged with the length direction center of the prefabricated underground continuous wall unit (1) as the symmetry axis, and the outlet of the wall bottom grouting pipe (4) is arranged in the middle of the bottom surface of the prefabricated underground continuous wall unit (1).

5. The two-wall-in-one prefabricated underground continuous wall structure according to claim 4, Features: Angle steel (12) is pre-buried in the area where the connection notch (2) of the prefabricated underground continuous wall unit (1) is located and at the corner connected to the connection notch (2) on the connection side.

6. The two-wall-in-one prefabricated underground continuous wall structure according to claim 5, Features: A connection area is formed between the connection notches (2) of adjacent prefabricated underground continuous wall units (1), and buttress columns (10) are cast in the connection area to connect the adjacent prefabricated underground continuous wall units (1).

7. The two-wall-in-one prefabricated underground continuous wall structure according to claim 6, Features: A vertically arranged expansion water stop strip (14) is provided between the buttress column (10) and the inner wall of the connecting notch (2).

8. A construction method of a two-wall-in-one prefabricated underground continuous wall, using the two-wall-in-one prefabricated underground continuous wall structure according to any one of claims 3 to 7, Features: The steps include: a. Digging a trench on the ground at the location where the prefabricated underground continuous wall is to be laid out according to the design by using a mechanical trenching machine, wherein the trench width is greater than the thickness of the prefabricated wall and the trench depth is greater than the height of the prefabricated underground continuous wall unit (1); b. hoisting the prefabricated underground continuous wall unit (1) into the groove, inserting the supporting steel beam into the suspension bar (7), arranging the supporting steel beam vertically to the prefabricated underground continuous wall unit (1), the supporting steel beam spanning the groove and supporting the two ends of the supporting steel beam on the guide wall, so that the prefabricated underground continuous wall unit (1) is suspended in the groove by the supporting steel beam, and adjusting the height of the prefabricated underground continuous wall unit (1) by adjusting the height of the supporting steel beam, so that all prefabricated underground continuous wall units (1) meet the elevation accuracy; c. After the adjustment of the horizontal height and spacing of all prefabricated underground continuous wall units (1) is completed, the concrete delivery conduit is inserted from the feed pipe of the prefabricated underground continuous wall unit (1) to the bottom of the groove, and the first pouring of concrete is started. Then, the reserved wall bottom grouting pipe (4), the pit side grouting pipe (5) and the soil side grouting pipe (6) are used for secondary pressure grouting. Finally, the grouting pipe is inserted from the groove to carry out the third normal pressure grouting to fill the remaining gap. The third normal pressure grouting makes the concrete height in the groove reach the height of the top of the prefabricated underground continuous wall. d. After the concrete has finally set, a foundation pit is excavated on the pit facing side of the prefabricated underground continuous wall unit (1), and then the concrete and the filled detachable support members at the joints, connection gaps (2) and bottom plate connection grooves (8) of the prefabricated underground continuous wall unit (1) are removed, and steel sheets (13) are welded between the angle steels (12) of adjacent prefabricated underground continuous wall units (1) to seal, and full welding is adopted. Buttress columns (10) are arranged in the connection area formed by the connection gaps (2) of adjacent prefabricated underground continuous wall units (1).

9. The construction method of the two-wall-in-one prefabricated underground continuous wall according to claim 8, Features: In the step d, the specific arrangement method of the buttress column (10) is as follows: firstly, a steel cage (11) is arranged in the connection area, and when the steel cage (11) is placed, the reserved steel bars (9) are bent first, and after the steel cage (11) is placed, the reserved steel bars (9) are straightened, and before pouring the buttress column (10), an expansion water stop strip (14) is placed in the gap between the steel cage (11) and the inner wall of the connection notch (2) along the vertical direction, and finally concrete is poured in the connection area to form the buttress column (10).

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