Prefabricated single-layer wall underground structure and construction method thereof

Abstract

The present application relates to the technical field of underground engineering, and particularly relates to a fabricated single-layer wall underground structure and a construction method thereof, which comprises a prefabricated bottom plate, a prefabricated top plate and a prefabricated underground continuous wall, the inner side of the bottom of the prefabricated underground continuous wall is provided with a groove, and the two ends of the prefabricated bottom plate are connected with the grooves on the two sides of the prefabricated underground continuous wall through first cast-in-place connecting joints; the two ends of the prefabricated top plate are respectively supported on the two sides of the prefabricated underground continuous wall and connected through second cast-in-place connecting joints. The prefabricated underground continuous wall is both the enclosure structure in the foundation pit excavation stage and the side wall of the main structure, and bears the lateral water and soil pressure from the foundation pit excavation to the main structure use stage, thereby reducing the engineering cost, reducing the construction process and shortening the construction period; and the prefabricated bottom plate and the prefabricated underground continuous wall and the prefabricated top plate and the prefabricated underground continuous wall are connected in the mode of cast-in-place joints, and the joint parts have sufficient strength, stiffness and good waterproof performance.

Description

Technical Field

[0001] This invention relates to the field of underground engineering technology, specifically to a prefabricated single-layer wall underground structure and its construction method. Background Technology

[0002] Underground structures such as tunnels constructed using the open-cut method include the foundation pit retaining structure and the main structure. If the main structure is constructed using prefabricated construction methods, the foundation pit retaining structure is mostly cast in place. For water-rich strata, the retaining structure is usually a diaphragm wall, and it only serves as a retaining structure during the construction phase. The load-bearing capacity of the retaining structure is not considered during the normal use of the tunnel structure. The shortcomings of this structural type and construction method are firstly that the retaining structure is abandoned after construction, and its retaining effect during the normal use of the structure is not considered, resulting in resource waste and environmental pollution. Secondly, a trench needs to be left between the retaining structure and the tunnel sidewalls, resulting in wasted space and increased earthwork excavation. Summary of the Invention

[0003] The purpose of this invention is to provide a prefabricated single-layer wall underground structure that can reduce project costs, reduce construction procedures, shorten construction period, and at the same time ensure that the joints between the prefabricated underground continuous wall and the prefabricated bottom slab and top slab have sufficient strength, rigidity and good waterproof performance.

[0004] To achieve the above objectives, the technical solution of the present invention is a prefabricated single-layer wall underground structure, including a prefabricated base slab and a prefabricated top slab, and also including a prefabricated underground continuous wall. The inner side of the bottom of the prefabricated underground continuous wall is provided with a groove. The two ends of the prefabricated base slab are connected to the grooves on the prefabricated underground continuous walls on both sides of the base slab through a first cast-in-place connection joint. The two ends of the prefabricated top slab are respectively supported on the prefabricated underground continuous walls on both sides of the base slab and are connected through a second cast-in-place connection joint.

[0005] As one embodiment, the first cast-in-place connection joint includes a pre-embedded steel plate embedded in the groove, a first steel profile connected to the pre-embedded steel plate, a second steel profile embedded in the end of the precast base plate, and concrete poured between the groove and the precast base plate; the first steel profile is connected to the second steel profile.

[0006] As one embodiment, a step is provided on the inner side of the top of the precast underground continuous wall, a positioning hole is provided at the end of the precast top slab, the end of the precast top slab is supported on the step, and the second cast-in-place connection joint includes a positioning steel column whose bottom is embedded in the horizontal surface of the step, whose top is inserted into the positioning hole, and micro-expansion concrete poured between the positioning steel column and the positioning hole.

[0007] As one implementation method, a cast-in-place roof slab is provided on the precast roof slab, and the positioning steel column passes through the positioning hole and extends into the cast-in-place roof slab.

[0008] As one implementation method, the side facade of the step is provided with a steel bar joint, which is connected to the steel bars in the positioning steel column and the cast-in-place roof slab.

[0009] As one implementation method, a lower section of a prefabricated intermediate partition wall is connected to the prefabricated base plate, and an upper section of a prefabricated intermediate partition wall is connected to the prefabricated top plate. The lower section of the prefabricated intermediate partition wall and the upper section of the prefabricated intermediate partition wall are connected by a mortise and tenon joint.

[0010] As one implementation method, the lower section of the prefabricated partition wall is prefabricated integrally with the prefabricated base plate, and the upper section of the prefabricated partition wall is prefabricated integrally with the prefabricated top plate.

[0011] The present invention also provides a construction method for the above-mentioned prefabricated single-layer wall underground structure, comprising the following steps:

[0012] S1. Construct the guide wall for the underground continuous wall and reinforce the strata on both sides of the guide wall with grouting.

[0013] S2. Excavate the soil in the trench of the underground continuous wall in sections and use mud slurry to protect the wall. After the trench of each underground continuous wall is completed, backfill the trench with silty soil.

[0014] S3. Fill the groove reserved at the bottom of the precast diaphragm wall with foam material, install the precast diaphragm wall in sections, and after the precast diaphragm wall is installed in place, replace the silty soil in the trench by grouting, and construct the top cap beam of the wall.

[0015] S4. Excavate the foundation pit in layers and sections, and erect supports;

[0016] S5. After leveling the bottom of the foundation pit, construct a concrete cushion layer, then install the precast base plate, and remove the foam material from the groove of the precast underground continuous wall.

[0017] S6. The first cast-in-place connection joint between the precast base slab and the precast underground continuous walls on both sides;

[0018] S7. Install the precast top slab and connect the precast top slab to the precast underground continuous walls on both sides using the second cast-in-place connection joint;

[0019] S8. Remove the supports and backfill with soil.

[0020] As one of the implementation methods, the precast base plate has a second steel profile pre-embedded at the end during the manufacturing process, and the precast underground continuous wall has a pre-embedded steel plate pre-embedded at the bottom of the groove during the manufacturing process; in step S6, the first steel profile is fixed on the pre-embedded steel plate, then the first steel profile is connected to the second steel profile, then the joint template is erected, and concrete is poured to form a cast-in-place connection joint.

[0021] As one implementation method, the precast diaphragm wall has a step reserved at the top during construction, and a positioning steel column is pre-embedded on the horizontal surface of the step and a steel bar joint is reserved on the side elevation of the step. The precast top slab has a positioning hole reserved at the end during construction. In step S7, the positioning holes at both ends of the precast top slab are respectively fitted onto the positioning steel column on the precast diaphragm wall, micro-expansion concrete is poured into the positioning hole, and then the steel bar joint is connected to the positioning steel column and the steel bar of the cast-in-place top slab. Finally, the cast-in-place top slab is poured.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The prefabricated underground continuous wall of the present invention is both a retaining structure in the foundation pit excavation stage and a side wall of the main structure, which reduces the project cost, reduces the construction procedures, and shortens the construction period.

[0024] (2) The precast base slab and the precast underground continuous wall, as well as the precast top slab and the precast underground continuous wall, are connected by cast-in-place joints. The joints have sufficient strength and rigidity and good waterproof performance, meeting the structural requirements for waterproof indicators.

[0025] (3) The top slab of the present invention adopts a composite structure of "precast components + cast-in-place reinforced concrete". The composite top slab is composed of precast components in the lower layer and cast-in-place concrete in the upper layer. It does not require on-site formwork and support, and can also improve the waterproof performance and overall load-bearing performance of the top slab.

[0026] (4) The construction method of the present invention is simple and can improve construction efficiency and construction quality. Before lowering the precast underground continuous wall, silty soil is backfilled in the underground continuous wall trench, so that the precast underground continuous wall is relatively stable during the lowering process. After the precast underground continuous wall is installed in place, the silty soil is replaced and reinforced by grouting to improve the stability of the precast underground continuous wall. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of backfilling silty soil into the trench after the diaphragm wall is constructed, according to an embodiment of the present invention.

[0029] Figure 2 This is a schematic diagram of the installation and positioning of the prefabricated underground continuous wall in an embodiment of the present invention;

[0030] Figure 3 This is a schematic diagram of the excavation and support erection of the foundation pit in an embodiment of the present invention;

[0031] Figure 4 This is a construction diagram of the concrete cushion layer and precast base slab in an embodiment of the present invention;

[0032] Figure 5 This is a construction schematic diagram of the first cast-in-place connection joint between the precast base slab and the precast underground continuous wall in an embodiment of the present invention;

[0033] Figure 6 This is a schematic diagram of the first cast-in-place connection joint in an embodiment of the present invention;

[0034] Figure 7 for Figure 6 AA view;

[0035] Figure 8 This is a construction diagram of the precast roof slab in an embodiment of the present invention;

[0036] Figure 9 This is a construction schematic diagram of the cast-in-place roof slab in an embodiment of the present invention;

[0037] Figure 10 This is a schematic diagram of the second cast-in-place connection joint between the precast roof slab, the cast-in-place roof slab and the precast underground continuous wall in an embodiment of the present invention;

[0038] Figure 11 for Figure 10 BB view;

[0039] Figure 12 This is a schematic diagram illustrating the removal of supports and backfilling in an embodiment of the present invention;

[0040] In the diagram: 1. Guide wall; 2. Grouting reinforcement; 3. Silt soil; 4. Precast diaphragm wall; 5. Groove; 6. Step; 7. Crown beam; 8. Support; 9. Concrete cushion; 10. Precast base slab; 11. Lower section of precast intermediate partition wall; 12. Concrete; 13. Channel steel; 14. Embedded steel plate; 15. Embedded bolt; 16. I-beam; 17. Precast top slab; 18. Upper section of precast intermediate partition wall; 19. Cast-in-place top slab; 20. Positioning steel; 21. Positioning hole; 22. Micro-expansion concrete; 23. Rebar joint. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0043] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0044] Example 1

[0045] like Figure 12 As shown, this embodiment provides a prefabricated single-layer underground wall structure, including a prefabricated base slab 10 and a prefabricated top slab 17, as well as a prefabricated diaphragm wall 4. The inner side of the bottom of the prefabricated diaphragm wall 4 is provided with a groove 5. The two ends of the prefabricated base slab 10 are connected to the grooves 5 on the prefabricated diaphragm walls 4 on both sides via a first cast-in-place joint. The two ends of the prefabricated top slab 17 are respectively supported on the prefabricated diaphragm walls 4 on both sides and connected via a second cast-in-place joint. In this embodiment, the prefabricated diaphragm wall 4 serves as both the retaining structure during the excavation stage and the side wall of the main structure, bearing the lateral water and soil pressure during the excavation stage, the main structure construction stage, and the main structure usage stage. This reduces project costs, construction procedures, and construction period. Furthermore, the prefabricated base slab 10 and the prefabricated diaphragm wall 4, as well as the prefabricated top slab 17 and the prefabricated diaphragm wall 4, are connected by cast-in-place joints. The joints not only have good waterproofing but also high rigidity and reasonable stress distribution.

[0046] In the optimized embodiment, the first cast-in-place connection joint includes a pre-embedded steel plate 14 embedded in the groove 5, a first steel profile connected to the pre-embedded steel plate 14, a second steel profile embedded at the end of the precast base slab 10, and concrete 12 poured between the groove 5 and the precast base slab 10; the first steel profile is connected to the second steel profile. In this embodiment, the joint between the precast base slab 10 and the precast underground continuous wall 4 is a stress concentration point with complex stress. Using a cast-in-place steel-concrete joint not only enhances the strength and rigidity of the joint but also provides good structural waterproofing.

[0047] Furthermore, the precast base slab 10 and the concrete 12 are connected by a tongue and groove joint to improve the waterproof performance at the connection between the precast base slab 10 and the concrete 12. A waterstop strip can also be added at the tongue and groove joint to further enhance the waterproof performance.

[0048] As one implementation method, such as Figure 6 and Figure 7 As shown, the first steel profile is an I-beam 16 with one end welded to the pre-embedded steel plate 14 on site, and the second steel profile is a channel steel 13 with one end pre-embedded in the precast base plate 10. The channel steel 13 is provided on both sides of the web of the I-beam 16, and the channel steel 13 on both sides is arranged back to back. The web of the I-beam 16 is welded to the web of the channel steel 13 on both sides on site, which reduces the assembly difficulty between the precast base plate 10 and the precast underground continuous wall 4 and facilitates the connection between the precast base plate 10 and the side walls of the precast underground continuous wall 4.

[0049] Furthermore, several embedded bolts 15 are welded onto the embedded steel plate 14. The embedded bolts 15 are embedded in the concrete 12, so that the concrete 12 is reliably connected to the precast underground continuous wall 4.

[0050] Optimize the above embodiments, such as Figure 10 and Figure 11 As shown, a step 6 is provided on the inner side of the top of the precast diaphragm wall 4, and a positioning hole 21 is provided at the end of the precast top slab 17. The end of the precast top slab 17 is supported on the step 6. The second cast-in-place connection joint includes a positioning steel column whose bottom is embedded in the horizontal surface of the step 6, whose top is inserted into the positioning hole 21, and micro-expansion concrete 22 poured between the positioning steel column and the positioning hole 21. In this embodiment, the precast top slab 17 is accurately positioned on the precast diaphragm wall 4 by cooperating with the positioning steel column and the positioning hole 21, and the positioning steel column is firmly fixed in the positioning hole 21 by filling the space between the positioning steel column and the positioning hole 21 with micro-expansion concrete 22.

[0051] The positioning steel column can be a positioning steel 20. The positioning steel 20 is preferably a square steel, and the outer circle of the square steel matches the positioning hole 21, so as to achieve accurate positioning of the precast top plate 17. Micro-expansion concrete 22 is poured in the square steel and between the square steel and the positioning hole 21.

[0052] In this embodiment, the top slab can be a precast top slab 17 or a composite top slab. As one implementation, a composite top slab is used. Specifically, a cast-in-place top slab 19 is provided on the precast top slab 17, and the positioning steel column passes through the positioning hole 21 and extends into the cast-in-place top slab 19. A reinforcing steel frame is pre-embedded in the precast top slab 17, and part of the reinforcing steel frame extends into the cast-in-place top slab 19 and is effectively connected to the reinforcing steel in the cast-in-place top slab 19, ensuring that the precast top slab 17 and the cast-in-place top slab 19 are subjected to force as a whole, improving their overall integrity. Furthermore, a reinforcing steel joint 23 is reserved on the side facade of the step 6. The reinforcing steel joint 23 is connected to the positioning steel column and the reinforcing steel in the cast-in-place top slab 19, ensuring that the connection between the top slab and the precast diaphragm wall 4 is a rigid joint. The top slab and the precast diaphragm wall 4 are connected by a cast-in-place joint, resulting in good waterproofing, high rigidity, and reasonable stress distribution at the joint. In this embodiment, the top plate can be a flat top or an arched top. Ideally, the composite top plate adopts a flat arched structure, which is reasonable in terms of stress distribution and also facilitates the reasonable transfer of the arch load to the side walls on both sides.

[0053] The prefabricated single-layer wall underground structure of this embodiment can be used in underground structures such as subway tunnels, underground passages, and integrated utility tunnels. It can be used in underground structures without partition walls or in underground structures with partition walls. As one implementation, a prefabricated lower section 11 of a prefabricated intermediate partition wall is connected to the prefabricated base slab 10, and a prefabricated upper section 18 of a prefabricated intermediate partition wall is connected to the prefabricated top slab 17. The lower section 11 of the prefabricated intermediate partition wall and the upper section 18 of the prefabricated intermediate partition wall are connected by a tenon joint to form an underground structure with partition walls.

[0054] Ideally, the lower section 11 of the prefabricated partition wall is prefabricated integrally with the prefabricated base plate 10, and the upper section 18 of the prefabricated partition wall is prefabricated integrally with the prefabricated top plate 17, reducing on-site splicing work and improving construction efficiency.

[0055] Example 2

[0056] This embodiment provides a construction method for a prefabricated single-layer underground wall structure as described in Embodiment 1. During fabrication, the prefabricated underground continuous wall 4 has a pre-reserved groove 5 at the bottom and a pre-reserved step 6 at the top. An embedded steel plate 14 is pre-embedded at the bottom of the groove 5, and pre-embedded bolts 15 are welded onto the embedded steel plate 14. Positioning steel columns are pre-embedded on the horizontal surface of the step 6, and steel bar joints 23 are pre-reserved on the side elevation of the step 6. During fabrication, the prefabricated base slab 10 has second steel profiles pre-embedded at both ends, and the prefabricated top slab 17 has positioning holes 21 pre-reserved at both ends. This construction method includes the following steps:

[0057] S1. Construct the guide wall 1 for the underground continuous wall, and reinforce the strata on both sides of the guide wall 1 by grouting to form the grouting reinforced body 2;

[0058] S2. Excavate the soil within the trench for the diaphragm wall in sections, and use mud slurry for wall protection. After each section of the diaphragm wall is completed, backfill the trench with silty soil 3 to facilitate the lowering of the precast diaphragm wall 4. This also makes the precast diaphragm wall 4 relatively stable within the trench, improving the stability of the precast diaphragm wall 4 during the lowering process. Figure 1 As shown;

[0059] S3. Fill the grooves 5 of the precast diaphragm wall 4 with foam material to protect the embedded steel plates 14 and embedded bolts 15 in the grooves 5; install the precast diaphragm wall 4 in sections. After the precast diaphragm wall 4 is installed in place, replace the silty soil 3 in the trench by grouting, and construct the top cap beam 7 of the wall. Figure 2 As shown;

[0060] Among them, grouting pipes are pre-embedded on both sides of the bottom of the precast underground continuous wall 4. Grouting is injected into the trench through the grouting pipes, which can replace and reinforce the silty soil 3 in the trench, thereby improving the stability of the underground continuous wall.

[0061] S4. Excavate the foundation pit in layers and sections, and erect supports 8, such as Figure 3 As shown; among them, support 8 can be steel support, with connectors pre-embedded during the construction of cap beam 7, and the ends of the steel support can be detachably connected to the connectors on cap beam 7, so that the steel support can be removed after the main structure is completed for reuse and cost reduction.

[0062] S5. The soil at the bottom 0.5m of the foundation pit is excavated manually. After leveling the bottom of the foundation pit, a concrete cushion layer 9 is constructed using C15 concrete, followed by the installation of the precast base slab 10. After the precast base slab 10 is in place, the foam material in the groove 5 of the precast diaphragm wall 4 is removed. For structures with a central partition wall, the precast base slab 10 and the lower section 11 of the precast central partition wall are installed, as follows: Figure 4 As shown;

[0063] S6, the first cast-in-place connection joint between the precast base slab 10 and the precast underground continuous walls 4 on both sides, such as Figure 5 As shown;

[0064] The specific construction method of the first cast-in-place connection joint is as follows: First, weld the first steel profile on the pre-embedded steel plate 14, then weld the second steel profile on the precast base plate 10 to the first steel profile, then erect the joint template, and pour concrete 12 between the groove 5 and the precast base plate 10 to form a cast-in-place connection joint.

[0065] S7. Install the precast roof slab 17, such as Figure 8 As shown, the precast top slab 17 is connected to the precast underground continuous walls 4 on both sides using a second cast-in-place connection joint; for those with a central partition wall, the precast top slab 17 and the upper section 18 of the precast central partition wall are installed; for those with a composite structure of precast top slab 17 and cast-in-place top slab 19, the cast-in-place top slab 19 is poured last, as shown. Figure 9 As shown;

[0066] The specific construction method of the second cast-in-place connection joint is as follows: First, the precast top slab 17 is hoisted into place, and the positioning holes 21 at both ends of the precast top slab 17 are respectively fitted onto the positioning steel columns on the precast underground continuous wall 4. Then, micro-expansion concrete 22 is filled into the gap between the positioning steel 20 and the positioning hole 21, and the positioning steel 20 is firmly fixed in the positioning hole 21. When the top slab adopts a composite structure, after filling the micro-expansion concrete 22, the precast top slab 17 is also used as the formwork for the cast-in-place top slab 19. The steel bar joint 23 reserved at the top of the precast underground continuous wall 4 is connected to the steel bars of the positioning steel column and the cast-in-place top slab 19. Finally, the cast-in-place top slab 19 is poured.

[0067] S8. Remove the supports and backfill the soil above the top slab, such as... Figure 12 As shown.

[0068] The construction method of this embodiment is simple, and the precast underground continuous wall 4 is connected to the precast base slab 10 and the precast underground continuous wall 4 to the top slab by cast-in-place joints. The joints have sufficient strength and rigidity and good waterproof performance, which meets the requirements of the structure for waterproof indicators. It is especially suitable for situations where both the retaining structure and the main structure are precast components in water-rich strata, which can effectively improve construction efficiency and project quality.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A prefabricated single-layer wall underground structure, comprising a prefabricated base slab and a prefabricated top slab, characterized in that: It also includes a precast diaphragm wall, the inner side of which has a groove. The two ends of the precast base slab are connected to the grooves on the precast diaphragm walls on both sides via a first cast-in-place joint. The two ends of the precast top slab are respectively supported on the precast diaphragm walls on both sides and connected via a second cast-in-place joint. The first cast-in-place joint includes a pre-embedded steel plate embedded in the groove, a first steel profile connected to the pre-embedded steel plate, a second steel profile embedded in the end of the precast base slab, and concrete poured between the groove and the precast base slab. The first steel profile is connected to the second steel profile. The inner side of the top of the precast diaphragm wall has a step, and the end of the precast top slab has a positioning hole. The end of the precast top slab is supported on the groove. On the aforementioned steps, the second cast-in-place connection joint includes a positioning steel column whose bottom is pre-embedded on the horizontal surface of the steps and whose top is inserted into the positioning hole, and micro-expansion concrete poured between the positioning steel column and the positioning hole; a cast-in-place top slab is provided on the precast top slab, and the positioning steel column passes through the positioning hole and extends into the cast-in-place top slab; a steel bar joint is reserved on the side facade of the steps, and the steel bar joint is connected to the steel bars in the positioning steel column and the cast-in-place top slab; a lower section of a precast intermediate partition wall is connected to the precast bottom slab, and an upper section of a precast intermediate partition wall is connected to the precast top slab, and the lower section of the precast intermediate partition wall and the upper section of the precast intermediate partition wall are connected by a tenon joint; the lower section of the precast intermediate partition wall is integrally precast with the precast bottom slab, and the upper section of the precast intermediate partition wall is integrally precast with the precast top slab.

2. A construction method for a prefabricated single-layer wall underground structure as described in claim 1, characterized in that, Includes the following steps: S1. Construct the guide wall for the underground continuous wall and reinforce the strata on both sides of the guide wall with grouting. S2. Excavate the soil in the trench of the underground continuous wall in sections and use mud slurry to protect the wall. After the trench of each underground continuous wall is completed, backfill the trench with silty soil. S3. Fill the groove reserved at the bottom of the precast diaphragm wall with foam material, install the precast diaphragm wall in sections, and after the precast diaphragm wall is installed in place, replace the silty soil in the trench by grouting, and construct the top cap beam of the wall. S4. Excavate the foundation pit in layers and sections, and erect supports; S5. After leveling the bottom of the foundation pit, construct a concrete cushion layer, then install the precast base plate, and remove the foam material from the groove of the precast underground continuous wall. S6. The first cast-in-place connection joint between the precast base slab and the precast underground continuous walls on both sides; S7. Install the precast top slab and connect the precast top slab to the precast underground continuous walls on both sides using the second cast-in-place connection joint; S8. Remove the supports and backfill with soil.

3. The construction method as described in claim 2, characterized in that: During the fabrication of the precast base slab, a second steel profile is pre-embedded at the end. During the fabrication of the precast underground continuous wall, a pre-embedded steel plate is pre-embedded at the bottom of the groove. In step S6, the first steel profile is fixed on the pre-embedded steel plate, and then the first steel profile is connected to the second steel profile. Then, the joint template is erected, and concrete is poured to form the first cast-in-place connection joint.

4. The construction method as described in claim 2, characterized in that: During the fabrication of the precast diaphragm wall, a step is pre-reserved at the top, and positioning steel columns are pre-embedded on the horizontal surface of the step. Rebar joints are pre-reserved on the side elevation of the step. Positioning holes are pre-reserved at the ends of the precast top slab during fabrication. In step S7, the positioning holes at both ends of the precast top slab are respectively fitted onto the positioning steel columns on the precast diaphragm wall. Micro-expansion concrete is poured into the positioning holes. Then, the rebar joints are connected to the positioning steel columns and the rebars of the cast-in-place top slab. Finally, the cast-in-place top slab is poured.

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