A support structure for a foundation pit excavated in stages

Abstract

This application relates to a support structure for phased excavation of foundation pits, belonging to the field of civil engineering construction technology. The support structure for phased excavation of foundation pits in this application includes a first support retaining wall, a second support retaining wall, and a third support retaining wall installed on the three sides of the foundation pit excluding the dividing piles. A first corner brace formed by reinforced concrete supports is installed between the first and second support retaining walls; a second corner brace formed by reinforced concrete supports is installed between the first and third support retaining walls; and a counterbracing formed by reinforced concrete supports is installed between the second and third support retaining walls, with the counterbracing adjacent to or close to the dividing piles. This application achieves a significant improvement in the bearing capacity and deformation resistance of the foundation pit support system, avoiding direct reliance on dividing piles or the first-phase basement structure for force transmission, thereby reducing construction difficulty and improving the safety and reliability of phased excavation construction.

Description

Technical Field

[0001] This application relates to the field of civil engineering construction technology, and in particular to a support structure for a staged excavation foundation pit. Background Technology

[0002] To meet the demands of urban development, many projects have adopted a phased development model. This model not only improves land utilization but also effectively alleviates the financial pressure and environmental impact of large-scale, one-time development. However, ensuring the coordination and safety between different phases of foundation pit development, especially when deep foundation pits are involved, becomes a crucial issue during the phased development of the same plot.

[0003] Currently, foundation pit construction typically employs a combination of bored piles and reinforced concrete supports to achieve its support function. When excavating foundation pits in phases on the same site, a row of dividing piles is installed at the boundary between adjacent phases. After the completion of the first phase and before the commencement of the second phase, one side of the dividing piles at the boundary is the existing basement structure, while the other side is the undeveloped soil structure. When excavating the second phase foundation pit, the conventional practice is to connect the reinforced concrete supports installed in the second phase foundation pit to one side of the dividing piles. However, since the first phase foundation pit is a basement structure, the shear strength of the dividing piles is insufficient to withstand the pressure from the reinforced concrete supports in the second phase foundation pit. Therefore, structural support is needed to transfer the load.

[0004] However, due to the complexity of the force transmission structure nodes and the susceptibility to stress concentration, the main structure is prone to failure. This is especially true in complex engineering projects such as deep foundation pits, where factors like groundwater variations and construction disturbances can cause earth pressure to exceed design values. Traditional support structures struggle to withstand excessive support forces, ultimately increasing the risk of structural failure. Therefore, a more reliable and efficient support solution is urgently needed to address this challenge. Utility Model Content

[0005] In order to improve the safety and reliability of the support structure in a phased excavation pit and reduce the construction difficulty, this application provides a support structure for a phased excavation pit.

[0006] The support structure for a phased excavation foundation pit provided in this application adopts the following technical solution:

[0007] A support structure for a phased excavation of a foundation pit includes a first support enclosure formed by a number of bored piles on one side of the foundation pit facing the dividing piles, a second support enclosure formed by a number of bored piles on one side of the foundation pit adjacent to the dividing piles, and a third support enclosure formed by a number of bored piles on the other side of the foundation pit adjacent to the dividing piles.

[0008] The second and third support fences are both located between the first support fence and the dividing pile, and the second and third support fences are arranged facing each other.

[0009] A first corner brace made of reinforced concrete is provided between the first support fence and the second support fence; a second corner brace made of reinforced concrete is provided between the first support fence and the third support fence.

[0010] The second and third support fences are provided with a bracing system made of reinforced concrete, which is adjacent to or close to the dividing pile.

[0011] The support structure in this application is mainly used for the support of foundation pits in the later stages of phased excavation. At this stage, the foundation pit contains the basement structure of the existing project, which has a relatively weak lateral shear bearing capacity, while the earth pressure on the sidewalls of the foundation pit excavated in the later stage is greater. The support structure in this application needs to bear these earth pressures and avoid transferring the force to the partition piles and the basement structure of the existing project as much as possible.

[0012] By adopting the above technical solution, the first, second, and third support retaining walls in this application together form a stable three-sided support system, effectively resisting the soil pressure on the sidewalls of the foundation pit. The first corner brace, second corner brace, and opposing brace form the internal support of the support structure, ensuring the stability and reliability of the entire support structure. Furthermore, the internal support structure is not connected to the partition piles, avoiding the use of the main basement structure for force transmission. This reduces the construction difficulty of the entire support structure and increases its safety factor. This design avoids the stress concentration problem caused by relying on partition piles for force transmission in traditional methods, significantly reducing the risk of structural failure and improving the safety and reliability of phased excavation of the foundation pit, thus possessing high economic and social value. Using the support structure in this application, during the later stages of foundation pit excavation, the partition piles can be broken down along with the earthwork excavation, and the basement structure can be directly connected to the previous basement structure without being affected by the partition piles, making construction more convenient.

[0013] Optionally, the top of the first, second, and third support fences is provided with an integral crown beam; the middle of the first, second, and third support fences is provided with an integral waist beam; the first, second, and third corner braces each have upper and lower layers; the upper-layer first, second, and third corner braces are all fixedly connected to the crown beam, and the lower-layer first, second, and third corner braces are all fixedly connected to the waist beam.

[0014] By adopting the above technical solutions, the installation of the capping beam and the waist beam enhances the overall stability of the first, second, and third support retaining walls, preventing displacement or deformation during the excavation of the foundation pit. The first corner braces, second corner braces, and counter-braces of the upper and lower layers are respectively fixed to the capping beam and the waist beam, forming a multi-layered support system, which further improves the load-bearing capacity and compressive strength of the support structure, ensuring safety and reliability during the excavation of the foundation pit.

[0015] Optionally, the first corner brace, the second corner brace, and the counter brace of the upper and lower layers are all fixed together by a number of column steel trusses; the bottom of the foundation pit is provided with column piles corresponding to the column steel trusses one by one, and the column steel trusses are fixed to the column piles.

[0016] By adopting the above technical solution, the first corner brace, the second corner brace, and the opposing brace are connected by a steel truss column to form an integral structure, enhancing the overall stability of the support structure and effectively distributing the loads acting on each support. The steel truss column is fixed to the piles at the bottom of the foundation pit, further transferring the vertical load to the depth of the foundation and reducing the risk of deformation of the support structure. This design not only improves the load-bearing capacity of the support system but also reduces the probability of structural failure caused by local stress concentration, thereby significantly improving the safety and reliability of the phased excavation process.

[0017] Optionally, the first and second corner braces are fixedly connected at one end near the first support fence; the other ends of the first and second corner braces are fixedly connected to the ends of the opposing braces through an auxiliary truss, the auxiliary truss is also formed by reinforced concrete support and the filling area of ​​the auxiliary truss is additionally provided with a plate strip.

[0018] By adopting the above technical solutions, the first and second corner braces and the opposing braces are integrated into one unit, working together to significantly improve the overall stability of the support structure; by strengthening the rigid connection of the entire internal support system, stress concentration points are dispersed, thereby effectively reducing the structural risks caused by excessive local stress.

[0019] Optionally, the bracing is arranged parallel to and spaced apart from the rows of dividing piles.

[0020] By adopting the above technical solution, the bracing can stably and reliably support the second and third retaining walls, while not transmitting pressure to the dividing piles, thus avoiding affecting the existing building structure.

[0021] Optionally, a first water-stop curtain is provided on the outer side of the first support enclosure, and a number of first high-pressure jet grouting piles are provided on the side of the first water-stop curtain away from the foundation pit. A number of rows of support steel pipes are inserted into the side of the first water-stop curtain near the foundation pit, and the support steel pipes are located between the first support enclosure and the first water-stop curtain.

[0022] By adopting the above technical solutions, the first water-stop curtain effectively blocks external water sources from entering the foundation pit, preventing groundwater infiltration from affecting the stability of the pit. The first high-pressure jet grouting pile further enhances the waterproof performance of the first water-stop curtain, ensuring that moisture in the surrounding soil is effectively isolated, and bearing and distributing soil pressure, thus improving the stability and reliability of the entire support structure. Rows of support steel pipes are inserted between the first support retaining wall and the first water-stop curtain, which not only improves the overall structural strength of the area but also provides additional support for the first support retaining wall, thereby better resisting lateral earth pressure. This combined protective measure significantly improves the safety and reliability of the foundation pit support structure.

[0023] Optionally, a second water-stop curtain is provided on the outer side of the second support enclosure, and a number of bored cast-in-place support piles are provided on the side of the second water-stop curtain away from the foundation pit. A second high-pressure jet grouting pile is provided between adjacent bored cast-in-place support piles for water-stopping and soil retention.

[0024] By adopting the above technical solutions, the second water-stop curtain can effectively prevent external water from seeping into the foundation pit, enhancing the overall waterproof performance of the foundation pit. The combined use of drilled cast-in-place support piles and the second high-pressure jet grouting piles further improves the water-stopping and soil-retaining effect, ensuring the stability of the soil around the foundation pit, reducing the impact of groundwater on the foundation pit construction, and thus improving the safety and reliability of the entire support structure.

[0025] Optionally, a third water-stop curtain is provided on the outside of the third support enclosure. The first, second, and third water-stop curtains are all formed using the mixed mixing wall type underground continuous wall construction method.

[0026] By adopting the above technical solution, a third water-stop curtain is set on the outside of the third support enclosure. The first, second and third water-stop curtains are all formed by the construction method of mixed mixing wall underground continuous wall, which can significantly improve the waterproof performance around the foundation pit, effectively prevent groundwater seepage, and enhance the overall stability of the foundation pit.

[0027] Optionally, the soil surface outside the foundation pit is hardened, and a water interception ditch is provided between the soil surface outside the foundation pit and the first, second, and third water-stop curtains. A concrete panel is also provided between the water interception ditch and the first, second, and third water-stop curtains, and the concrete panel is fixed to the soil by soil nails.

[0028] By adopting the above technical solutions, the hardening of the soil surface outside the foundation pit enhances the bearing capacity and waterproofing performance of the ground, effectively preventing rainwater or other water sources from seeping into the surrounding soil and reducing the impact of groundwater level fluctuations on the stability of the foundation pit. The intercepting ditch further intercepts and guides surface water flow, preventing water accumulation near the cutoff wall and thus mitigating soil pressure changes. The concrete panel, as an additional protective layer, not only strengthens the connection between the intercepting ditch and the cutoff wall but is also fixed to the soil with soil nails, forming a stable overall structure. This significantly improves the seepage prevention and deformation resistance of the entire support system, ensuring the safety and reliability of the foundation pit construction process.

[0029] In summary, this application includes at least one of the following beneficial technical effects:

[0030] 1. In this application, the first, second, and third support retaining walls together form a stable three-sided support system. The first corner brace, second corner brace, and opposing brace form the internal support of the support structure, ensuring the stability and reliability of the entire support structure. 2. The internal support structures in this application are not connected to the partition piles, avoiding the use of the main basement structure for force transmission. This reduces the construction difficulty of the entire support structure, increases its safety factor, and has high economic and social value. 3. The support structure in this application does not rely on partition piles. During the later excavation of the foundation pit, the partition piles can be broken down along with the earthwork excavation. Furthermore, the basement structure can be directly connected to the existing basement structure during construction, unaffected by the partition piles, making construction more convenient. Attached Figure Description

[0031] Figure 1 This is a top view structural diagram of the phased foundation pit in this application.

[0032] Figure 2 yes Figure 1 A magnified schematic diagram of the structure at point A in the middle.

[0033] Figure 3 yes Figure 1 Schematic diagram of the cross-sectional structure from K1 to K2.

[0034] Figure 4 This is a schematic diagram of the structure of the first corner brace, the second corner brace, and the counterbrace in this application.

[0035] Figure 5 This is a schematic diagram of the connection between the waist beam and the bored pile in this application.

[0036] In the picture:

[0037] 10. Drilled pile; 11. First retaining wall; 12. Second retaining wall; 13. Third retaining wall; 14. Crown beam; 15. Waist beam;

[0038] 20. First corner brace;

[0039] 30. Second corner brace;

[0040] 40. Support;

[0041] 50. Auxiliary trusses; 51. Plates and strips;

[0042] 60. Steel truss columns;

[0043] 70. Erected piles;

[0044] 80. The First Still Water Curtain;

[0045] 90. The second water-stopping curtain;

[0046] 100. The Third Water-Stopping Curtain;

[0047] 110. First high-pressure jet grouting pile;

[0048] 120. Second high-pressure jet grouting pile;

[0049] 130. Support steel pipe;

[0050] 140. Drilled cast-in-place support piles;

[0051] 150. Interception ditch;

[0052] 160. Concrete panel;

[0053] 170. Divider pile. Detailed Implementation

[0054] The following will be combined with the appendix Figure 1 -Appendix Figure 5 The technical solutions in the embodiments of this utility model are clearly and completely described herein. The described embodiments are only possible technical implementations of this utility model and not all possible implementations. Those skilled in the art can obtain other embodiments in conjunction with the embodiments of this utility model without creative effort, and these embodiments are also within the protection scope of this utility model.

[0055] Reference Figure 1 As shown, the support structure in this application is mainly used for the support of the later stage of excavation in a phased excavation project. At this stage, the early stage excavation pit contains the basement structure of the existing project, which has relatively weak lateral shear bearing capacity, while the soil pressure on the sidewalls of the later-excavated pit is greater. During the construction of the early stage excavation pit, a separator pile 170 is installed between the two stages of the excavation pit. The support structure in this application needs to bear the soil pressure on the sidewalls of the later-stage excavation pit and avoid transferring the force to the separator pile 170 and the existing basement structure as much as possible.

[0056] Reference Figure 1 and Figure 2As shown in the embodiment of this application, the support structure for the phased excavation of the foundation pit includes a first support enclosure 11, a second support enclosure 12, and a third support enclosure 13 respectively set on the three sides of the foundation pit other than the side of the dividing pile 170. The first support enclosure 11, the second support enclosure 12, and the third support enclosure 13 are all continuous wall structures formed by multiple bored cast-in-place piles 10 arranged at a certain interval. Each bored cast-in-place pile 10 can be made into a conventional steel cage or a prestressed steel cage according to actual needs to adapt to different geological conditions and bearing requirements. The first support fence 11 is located on the side of the foundation pit directly opposite the dividing pile 170. The second support fence 12 and the third support fence 13 are located on both sides of the first support fence 11 and the dividing pile 170, respectively. The second support fence 12 and the third support fence 13 are both located between the first support fence 11 and the dividing pile 170, and the second support fence 12 and the third support fence 13 are set directly opposite each other. The first support fence 11, the second support fence 12 and the third support fence 13 together form a stable three-sided support system, which effectively resists the soil pressure on the side wall of the foundation pit. A first corner brace 20, formed by reinforced concrete, is provided between the first support fence 11 and the second support fence 12; a second corner brace 30, also formed by reinforced concrete, is provided between the first support fence 11 and the third support fence 13; and a counter-brace 40, also formed by reinforced concrete, is provided between the second support fence 12 and the third support fence 13. The counter-braces 40 are adjacent to or close to the dividing piles 170. Preferably, the counter-braces 40 are arranged parallel to and spaced apart from the rows of dividing piles 170. Furthermore, the ends of the first corner brace 20 and the second corner brace 30 near the first support fence 11 are fixedly connected; the other ends of both the first corner brace 20 and the second corner brace 30 are fixedly connected to the ends of the counter-braces 40 via auxiliary trusses 50. The auxiliary trusses 50 are also formed by reinforced concrete, and the filling area of ​​the auxiliary trusses 50 is additionally provided with plate strips 51. The first corner brace 20, the second corner brace 30, and the counter-braces 40 form the internal support of the support structure, ensuring the stability and reliability of the entire support structure.

[0057] Reference Figure 2 , Figure 3 and Figure 4As shown, the tops of the first retaining wall 11, the second retaining wall 12, and the third retaining wall 13 are equipped with an integral capping beam 14; the middle sections of the first retaining wall 11, the second retaining wall 12, and the third retaining wall 13 are equipped with an integral waist beam 15; the first corner brace 20, the second corner brace 30, and the counter brace 40 each have upper and lower layers; the upper-layer first corner brace 20, the second corner brace 30, and the counter brace 40 are all fixedly connected to the capping beam 14, and the lower-layer first corner brace 20, the second corner brace 30, and the counter brace 40 are all fixedly connected to the waist beam 15. The capping beam 14 and the waist beam 15 enhance the overall stability of the first retaining wall 11, the second retaining wall 12, and the third retaining wall 13, preventing displacement or deformation during the excavation of the foundation pit. The first corner brace 20, the second corner brace 30, and the counter brace 40 of the upper and lower layers are respectively fixed to the cap beam 14 and the waist beam 15, forming a multi-layered support system. This improves the load-bearing capacity and compressive strength of the support structure, ensuring safety and reliability during the excavation of the foundation pit. Combined with... Figure 5 As shown, the waist beam 15 has a protruding structure that is embedded between two adjacent bored piles 10 to improve the stability and reliability of their connection.

[0058] Reference Figure 3 As shown, the first corner brace 20, second corner brace 30, and counter-brace 40 of the upper and lower layers are all fixedly connected together by several column steel trusses 60; at the bottom of the foundation pit, there are column piles 70 corresponding to the column steel trusses 60, and the column steel trusses 60 are fixedly connected to the column piles 70. In this application, the first corner brace 20, second corner brace 30, and counter-brace 40 are connected by column steel trusses 60 to form an integral structure, which enhances the overall stability of the support structure and effectively disperses the load acting on each support. The column steel trusses 60 are fixedly connected to the column piles 70 at the bottom of the foundation pit, further transferring the vertical load to the depth of the foundation and reducing the risk of deformation of the support structure.

[0059] Reference Figure 2 As shown, a first water-stop curtain 80 is installed on the outer side of the first support retaining wall 11. Several first high-pressure jet grouting piles 110 are installed on the side of the first water-stop curtain 80 away from the foundation pit. Several rows of support steel pipes 130 are inserted into the side of the first water-stop curtain 80 adjacent to the foundation pit. The support steel pipes 130 are located between the first support retaining wall 11 and the first water-stop curtain 80. A second water-stop curtain 90 is installed on the outer side of the second support retaining wall 12. Several bored cast-in-place support piles 140 are installed on the side of the second water-stop curtain 90 away from the foundation pit. Second high-pressure jet grouting piles 120 are installed between adjacent bored cast-in-place support piles 140 for water stop and soil retention. The third water-stop curtain 100 is set on the outside of the third support enclosure 13. Several rows of support steel pipes 130 can also be inserted on the side of the second water-stop curtain 90 and the third water-stop curtain 100 near the foundation pit. The first water-stop curtain 80, the second water-stop curtain 90 and the third water-stop curtain 100 are all formed by the mixed mixing wall type underground continuous wall construction method.

[0060] Reference Figure 3 As shown, the soil surface outside the foundation pit is hardened, and a water interception ditch 150 is provided between the soil surface outside the foundation pit and the first water-stop curtain 80, the second water-stop curtain 90 and the third water-stop curtain 100. A concrete panel 160 is also provided between the water interception ditch 150 and the first water-stop curtain 80, the second water-stop curtain 90 and the third water-stop curtain 100. The concrete panel 160 is fixed to the soil by soil nails.

[0061] Hardening the soil surface outside the excavation pit enhances its bearing capacity and waterproofing performance, effectively preventing rainwater or other water sources from seeping into the surrounding soil and reducing the impact of groundwater level fluctuations on the pit's stability. The intercepting ditch 150 further intercepts and guides surface water flow, preventing water accumulation near the cutoff wall and thus mitigating soil pressure variations. The concrete panel 160, as an additional protective layer, not only strengthens the connection between the intercepting ditch 150 and the cutoff wall but is also fixed to the soil with soil nails, forming a stable overall structure. This significantly improves the overall support system's seepage prevention and deformation resistance, ensuring the safety and reliability of the excavation pit construction process.

[0062] The implementation principle of this embodiment is as follows: The internal support structure formed by the first corner brace 20, the second corner brace 30, and the opposing brace 40 in this application is not connected to the partition pile 170, avoiding the use of the main basement structure for force transmission. This reduces the construction difficulty of the entire support structure and increases its safety factor. This design avoids the stress concentration problem caused by relying on the partition pile 170 for force transmission in traditional methods, significantly reducing the risk of structural failure and improving the safety and reliability of phased excavation of the foundation pit, thus possessing high economic and social value. Using the support structure in this application, the partition pile 170 can be broken down along with the earthwork excavation during the later stages of foundation pit excavation. Furthermore, the basement structure can be directly connected to the previous basement structure during construction, unaffected by the partition pile 170, making construction more convenient.

[0063] In this application, the first water-stop curtain 80, the second water-stop curtain 90, and the third water-stop curtain 100 effectively block external water sources from entering the foundation pit, preventing groundwater seepage from affecting the stability of the foundation pit. The first high-pressure jet grouting pile 110 and the second high-pressure jet grouting pile 120 further enhance the waterproof performance of the support structure, ensuring that moisture in the surrounding soil is effectively isolated, and bearing and sharing soil pressure, resisting lateral soil pressure, and improving the stability and reliability of the entire support structure. This combined protective measure significantly improves the safety and reliability of the foundation pit support structure.

[0064] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Identical components are represented by the same reference numerals. Therefore, all equivalent changes made to the structure, shape, and principle of this application should be covered within the scope of protection of this application.

Claims

1. A support structure for a staged excavation of a foundation pit, characterized in that, The first support enclosure (11) is formed by a number of bored piles (10) on one side of the foundation pit directly opposite the dividing pile (170), the second support enclosure (12) is formed by a number of bored piles (10) on one side of the foundation pit adjacent to the dividing pile (170), and the third support enclosure (13) is formed by a number of bored piles (10) on the other side of the foundation pit adjacent to the dividing pile (170). The second support fence (12) and the third support fence (13) are both located between the first support fence (11) and the dividing pile (170), and the second support fence (12) and the third support fence (13) are set facing each other; A first corner brace (20) formed by reinforced concrete is provided between the first support fence (11) and the second support fence (12); a second corner brace (30) formed by reinforced concrete is provided between the first support fence (11) and the third support fence (13); A bracing (40) made of reinforced concrete is provided between the second support fence (12) and the third support fence (13), and the bracing (40) is adjacent to or close to the dividing pile (170).

2. The support structure for phased excavation of the foundation pit according to claim 1, characterized in that, The top of the first support fence (11), the second support fence (12) and the third support fence (13) are provided with a crown beam (14) that is connected as one piece; the middle of the first support fence (11), the second support fence (12) and the third support fence (13) are provided with a waist beam (15) that is connected as one piece; the first corner brace (20), the second corner brace (30) and the counter brace (40) each have two layers, upper and lower; the first corner brace (20), the second corner brace (30) and the counter brace (40) located in the upper layer are all fixed to the crown beam (14), and the first corner brace (20), the second corner brace (30) and the counter brace (40) located in the lower layer are all fixed to the waist beam (15).

3. The support structure for phased excavation of the foundation pit according to claim 2, characterized in that, The first corner brace (20), the second corner brace (30), and the counter brace (40) of the upper and lower layers are all fixed together by several column steel trusses (60); the bottom of the foundation pit is provided with column piles (70) corresponding one-to-one with the column steel trusses (60), and the column steel trusses (60) are fixed to the column piles (70).

4. The support structure for a phased excavation pit according to claim 1, 2, or 3, characterized in that, The first corner brace (20) and the second corner brace (30) are fixedly connected at one end near the first support enclosure (11); the other ends of the first corner brace (20) and the second corner brace (30) are fixedly connected to the end of the opposing brace (40) through an auxiliary truss (50), the auxiliary truss (50) is also formed by reinforced concrete support and the filling area of ​​the auxiliary truss (50) is provided with a plate strip (51).

5. The support structure for a phased excavation pit according to claim 1, 2, or 3, characterized in that, The bracing (40) is arranged parallel to and spaced apart from the row of dividing piles (170).

6. The support structure for a phased excavation pit according to claim 1, 2, or 3, characterized in that, A first water-stop curtain (80) is provided on the outside of the first support enclosure (11). Several first high-pressure jet grouting piles (110) are provided on the side of the first water-stop curtain (80) away from the foundation pit. Several rows of support steel pipes (130) are inserted on the side of the first water-stop curtain (80) near the foundation pit. The support steel pipes (130) are located between the first support enclosure (11) and the first water-stop curtain (80).

7. The support structure for phased excavation of the foundation pit according to claim 6, characterized in that, A second water-stop curtain (90) is provided on the outside of the second support enclosure (12). Several bored cast-in-place support piles (140) are provided on the side of the second water-stop curtain (90) away from the foundation pit. A second high-pressure jet grouting pile (120) is provided between adjacent bored cast-in-place support piles (140) for water-stopping and soil retention.

8. The support structure for phased excavation of the foundation pit according to claim 7, characterized in that, The third support enclosure (13) is provided with a third water-stopping curtain (100) on the outside. The first water-stopping curtain (80), the second water-stopping curtain (90) and the third water-stopping curtain (100) are all formed by the mixed mixing wall type underground continuous wall construction method.

9. The support structure for phased excavation of the foundation pit according to claim 8, characterized in that, The soil surface outside the foundation pit is hardened, and a water interception ditch (150) is provided between the soil surface outside the foundation pit and the first water-stop curtain (80), the second water-stop curtain (90), and the third water-stop curtain (100). A concrete panel (160) is also provided between the water interception ditch (150) and the first water-stop curtain (80), the second water-stop curtain (90), and the third water-stop curtain (100). The concrete panel (160) is fixed to the soil by soil nails.

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