Construction method for optimizing shear resistance of inclined strut of underground diaphragm wall foundation pit

Abstract

The invention relates to the field of underground engineering, in particular to a method for optimizing the shear resistance of an inclined strut of a foundation pit of an underground diaphragm wall, which comprises the following steps: S1, manufacturing a reinforcement cage; s2, structural part construction; s3, a foundation pit is excavated; s4, manufacturing a steel enclosing purlin; s5, erecting a steel enclosing purlin; and S6, the steps of S3-S5 are repeated until excavation is conducted to the bottom of the foundation pit, construction is completed, construction is guided, in the construction operation process, firstly, due to the unique steel enclosing purlin manufacturing and erecting mode, the shear resistance of the inclined strut can be effectively improved, and secondly, due to the guided construction of the six construction steps, the shear resistance of the inclined strut can be effectively improved. The construction efficiency can be effectively improved, and the effects that the supporting working performance of the inclined supporting section can be improved to a certain extent, the construction rhythm of the embedded steel plate part is accelerated, a supporting system is rapidly closed, and the foundation pit deformation risk is effectively controlled are achieved.

Description

Technical Field

[0001] The present application relates to the field of underground engineering, and in particular to a construction method for optimizing the shear resistance of diagonal braces of an underground continuous wall foundation pit. Background Art

[0002] Underground continuous wall is a commonly used underground structure engineering technology, usually used for deep foundation pit support, groundwater control, and permanent enclosure structure of underground buildings. It forms a continuous and solid underground wall by excavating a trench on the ground and pouring reinforced concrete in the trench. The underground continuous wall has high strength and stability, can effectively resist soil pressure and groundwater pressure, and ensure the safety of foundation pits and underground structures. With the influence of multiple factors such as the south-to-Beijing water supply, the increase in groundwater extraction and drainage control, and the increase in rainfall in Beijing over the years, the underground water level in Beijing continued to rise from 2014 to 2023. The difficulty and safety of underground engineering construction are closely related to groundwater. High water pressure will not only increase the lateral pressure of the enclosure structure, but also increase the risk of leakage during the construction of the enclosure structure under the influence of groundwater. In order to better control the hydrogeological risks of underground engineering construction, underground continuous wall support and water blocking technology are widely used in Beijing rail transit engineering foundation pit projects. From 2013 to 2018, a total of 39 open-cut stations were built in Beijing's rail transit projects, of which 16 were underground continuous wall stations, accounting for 41%. From 2018 to 2023, a total of 26 open-cut stations were built, of which 19 were underground continuous wall stations, accounting for 73.1%. It can be seen that underground continuous walls have become the preferred enclosure structure type for open-cut stations.

[0003] The technology and process of underground continuous walls are mature. Compared with retaining piles, underground continuous wall retaining structures have greater rigidity and better water-stopping performance, and have obvious advantages in deformation control and groundwater control. However, due to the constraints of structural functions and site conditions, it is necessary to set up complex structural shapes such as expanded ends and variable sections. Due to its complex structural shape, in order to improve the overall stress performance of the local retaining structure, integral steel purlins are often set to improve the overall working performance of the diagonal bracing section support, so as to avoid point stress causing large deformation of the underground continuous wall foundation pit retaining structure or uneven stress on the prestressed wall causing deflection, which in turn causes risks such as deformation of the underground continuous wall and joint leakage, endangering the safety of the foundation pit and surrounding environment.

[0004] From the above-mentioned related technologies, it can be seen that the existing steel purlins with diagonal bracing can adapt to the construction requirements to a certain extent. However, in the related technologies, firstly, due to the constraints of construction technology, construction level and other factors, it is almost impossible to fully weld the steel purlins and the embedded steel plates during actual construction. They are often welded by steel tie bars, and the steel purlins and underground continuous walls in the area without embedded steel plates are filled with crushed stone concrete to ensure close contact. The horizontal component of the diagonal bracing relies on the local welding connection between the steel purlins and the embedded steel plates and the friction resistance between the steel purlins and the underground continuous walls to provide restraint force, which has low reliability. In the actual construction process, there are risks such as insufficient diagonal bracing, large deformation of the retaining structure and even cracking. Secondly, the embedded steel plates in the walls of the diagonal bracing sections need to be chiseled and reinforced by welding, which takes a long construction period. The deformation of the retaining structure due to the time effect of the foundation pit is uncontrollable, and the risks are prominent. Therefore, a method for optimizing the working performance of the diagonal bracing of the underground continuous wall foundation pit is urgently needed to improve the supporting performance of the diagonal bracing section, speed up the construction rhythm of the embedded steel plate part, realize the rapid closure of the support system, and play a role in effectively controlling the deformation risk of the foundation pit. Summary of the invention

[0005] In order to improve the supporting performance of the diagonal bracing section, speed up the construction pace of the embedded steel plate part, realize the rapid closure of the supporting system and effectively control the risk of foundation pit deformation, the present application provides a construction method for optimizing the shear performance of the diagonal bracing of the underground continuous wall foundation pit.

[0006] The present application provides a construction method for optimizing the shear resistance of diagonal braces of underground continuous wall foundation pits, which adopts the following technical solutions: A construction method for optimizing the shear resistance of diagonal braces of an underground continuous wall foundation pit, comprising the following steps: S1. Fabrication of steel cage: On-site staff fabricate the steel cage according to the design requirements; S2, construction of structural parts, construction of guide wall, underground continuous wall, crown beam, etc. in sequence; S3, excavation of foundation pit: after the completion of S2, the foundation pit is excavated to a specified elevation according to the design requirements; S4. Fabrication of steel perimeter purlins. On-site staff fabricate steel perimeter purlins according to design requirements. S5. Erection of steel perimeter purlins: Erection of steel perimeter purlins to the designed elevation; S6. Repeat S3 to S5 until the excavation reaches the bottom of the foundation pit and the construction is completed.

[0007] By adopting the above technical scheme, the settings of S1, S2, S3, S4, S5, and S6 provide a systematic optimization construction method to ensure that the shear resistance of the diagonal brace is optimized, and the optimization is carried out according to the construction steps of this application. In addition to optimizing the shear resistance of the diagonal brace, the construction efficiency can also be improved. This application has the effect of improving the supporting working performance of the diagonal brace section to a certain extent, speeding up the construction rhythm of the embedded steel plate part, realizing the rapid closure of the support system, and playing a role in effectively controlling the risk of foundation pit deformation.

[0008] Optionally, in S1, corrugated steel plates and foam plates are pre-embedded for the erection of steel purlins in S5.

[0009] By adopting the above technical solution, corrugated steel plates and foam plates are pre-embedded during the erection of steel purlins, which can enhance the connection strength between the purlins and the underground walls and improve the overall stability.

[0010] Optionally, in S3, each time the foundation pit is excavated, the excavation should be carried out to 0.5m below the specified elevation.

[0011] By adopting the above technical solution, each excavation is carried out to 0.5m below the specified elevation, which can ensure the stability of the soil and avoid the risk of collapse caused by excessive excavation. This control method helps to maintain the safety and stability of the foundation pit.

[0012] Optionally, S3 further includes chiseling out the foam plate and cleaning the corrugated steel plate.

[0013] By adopting the above technical solution, the construction efficiency can be effectively improved and sufficient preparation can be made for subsequent construction.

[0014] Optionally, in S4, during the manufacturing process of the steel perimeter purlin, a V-shaped fixing plate is welded to the back of the steel perimeter purlin, and the V-shaped fixing plate is installed tightly against the steel perimeter purlin.

[0015] By adopting the above technical solution and welding a V-shaped gusset plate on the back of the steel purlin, the rigidity and strength of the purlin can be increased, its stress-bearing performance can be improved, and the overall shear resistance can be improved.

[0016] Optionally, micro-expansive cement is also filled between the V-shaped gusset plate and the steel purlin.

[0017] By adopting the above technical solution and filling with micro-expanding cement, it helps to enhance the bonding force between the two, prevent the structure from deformation due to water intrusion or temperature changes, and improve shear strength and stability.

[0018] Optionally, in S5, the steel purlin is prestressed during installation.

[0019] By adopting the above technical solution and prestressing treatment, the stability of the purlin when subjected to stress can be improved, its bearing capacity can be enhanced, and deformation can be reduced, thereby effectively improving the shear resistance.

[0020] Optionally, the corrugated steel plate is embedded in the concrete protective layer.

[0021] By adopting the above technical solution, the corrugated steel plate is buried in the concrete protective layer, which can improve its corrosion resistance and extend its service life, while ensuring its effectiveness in the structure and avoiding the external environment from affecting its performance.

[0022] Optionally, the cross-sectional size of the corrugated steel plate is set to 1000mmx1000mm.

[0023] By adopting the above technical solution, sufficient strength and stability are provided. Appropriate size design can improve its force performance and ensure better shear resistance.

[0024] Optionally, the foam board is fixed by tying wire and / or iron wire.

[0025] By adopting the above technical solution, the stability of the foam board can be effectively enhanced, the displacement of the foam board during the construction process can be avoided, and the construction quality and shear resistance of the subsequent structure can be ensured.

[0026] In summary, the present application includes at least one of the following beneficial technical effects: 1. The setting of S1, S2, S3, S4, S5, and S6 provides a systematic optimization construction method to ensure that the shear resistance of the diagonal brace is optimized, and the optimization is carried out according to the construction steps of this application. In addition to optimizing the shear resistance of the diagonal brace, it can also improve the construction efficiency. This application has the effect of improving the support performance of the diagonal brace section to a certain extent, speeding up the construction rhythm of the embedded steel plate part, realizing the rapid closure of the support system, and playing a role in effectively controlling the risk of foundation pit deformation; 2. By pre-setting the corrugated steel plate and the foam plate, the connection strength between the purlin and the underground wall can be enhanced, and the overall stability can be improved. Secondly, the foam plate can be chiseled out and the corrugated steel plate can be cleaned, which can effectively improve the construction efficiency and make full preparations for the subsequent construction; 3. V-shaped gussets can increase the stiffness and strength of the purlin, improve its stress-bearing performance, and thus improve the overall shear resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a flowchart of a construction method for optimizing the shear performance of diagonal braces of an underground continuous wall foundation pit according to an embodiment of the present application.

[0028] Figure 2 It is a schematic diagram of S1 in the construction method of this application.

[0029] Figure 3 It is a schematic diagram of S2 in the construction method of this application.

[0030] Figure 4 yes Figure 3 Magnified view of area A.

[0031] Figure 5 It is a schematic diagram of S3 in the construction method of this application.

[0032] Figure 6 It is a schematic diagram of S4 in the construction method of this application.

[0033] Figure 7 It is a schematic diagram of S5 in the construction method of this application.

[0034] Figure 8 It is a front view of the embedded corrugated steel plate in the embodiment of the present application.

[0035] Fig. 9 It is a top view of the steel purlin and steel support in the embodiment of the present application, which is mainly used to show the position of the V-shaped gusset plate.

[0036] Fig.10 It is a top view of the underground continuous wall in the embodiment of the present application, which is mainly used to show the position of the steel cage (foam board, corrugated steel plate).

[0037] Fig.11 After removing the foam board, Fig. 9 and Fig.10 Schematic diagram of the assembly.

[0038] Description of reference numerals: 1. Steel purlin; 2. Corrugated steel plate; 3. Foam board; 4. V-shaped gusset plate. DETAILED DESCRIPTION

[0039] The following is combined with Figure 1-11 This application is described in further detail.

[0040] It should be noted that, in the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicating orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0041] Here, it is necessary to further elaborate on the technical background of this application in order to understand the creative work of this application. In the actual construction process, the applicant of this application found that the diagonal bracing section of the foundation pit adopts the method of welding the steel purlin and the embedded steel plate in the underground continuous wall to ensure the force effect of the diagonal bracing and avoid the slip of the steel purlin due to shear. However, due to the existence of a concrete protective layer of about 5 cm thick outside the embedded steel plate, the embedded steel plate cannot be closely attached to the steel purlin after chiseling, and the width of the embedded steel plate is consistent with the width of the steel purlin. During the construction process, due to the installation of the steel purlin and the installation deviation of the embedded steel plate, the two are not at the same elevation. Even after the welding treatment, the shear resistance effect is poor, and because the closure time of the diagonal bracing section is as long as 3 to 5 days, the deformation exceeds the limit during the excavation of the foundation pit, which increases the difficulty of on-site safety risk control.

[0042] The embodiment of the present application discloses a construction method for optimizing the shear resistance of the diagonal brace of an underground continuous wall foundation pit, comprising S1, manufacturing a steel cage; S2, construction of structural members; S3, excavation of the foundation pit; S4, manufacturing a steel purlin 1; S5, erection of a steel purlin 1; S6, repeating S3-S5 until the excavation reaches the bottom of the foundation pit and the construction is completed. A total of six steps are provided to guide the construction. During the construction operation, firstly, due to the unique steel purlin 1 manufacturing and erection mode of the present application, the shear resistance of the diagonal brace of the present application can be effectively improved. Secondly, due to the guidance of the six construction steps of the present application, the construction efficiency can be effectively improved. The present application has the ability to improve the supporting working performance of the diagonal brace section to a certain extent, speed up the construction rhythm of the embedded steel plate part, realize the rapid closure of the support system, and play a role in effectively controlling the deformation risk of the foundation pit.

[0043] Specifically, the present application discloses a construction method for optimizing the shear performance of diagonal braces of an underground continuous wall foundation pit, comprising the following steps: S1. Fabrication of steel cage: On-site staff fabricate the steel cage according to the design requirements.

[0044] Regarding S1, according to the design requirements, it is necessary to select the steel bars. In the embodiment of the present application, the steel bars used can be high-strength steel bars such as HRB400 and HRB500. After the material selection is completed, the steel bars need to be processed, and the processing includes steel bar cutting and steel bar bending. The specific processing process needs to be strictly constructed according to the design requirements and drawings. After the steel bars are processed, the steel cage is assembled. The steel cage assembly is to tie and weld the steel bars after cutting and bending. Usually, the longitudinal steel bars are assembled first, and then the stirrups are tied. The stiffening bars are reasonably arranged according to the design requirements to ensure the stability of the steel cage. After the steel cage is assembled, it is also necessary to set the reinforcement according to the actual engineering needs. The reinforcement is used to strengthen the overall stiffness of the steel cage to prevent deformation during hoisting or concrete pouring. After the reinforcement is set, it is necessary to set the external protective pads of the steel cage to ensure that the steel cage can maintain a uniform concrete protective layer thickness during concrete pouring, and fix plastic or cement pads on the outside of the steel cage. After completing the above steps, the quality inspection of the steel cage is required, mainly to check the size of the steel cage, the spacing between steel bars, the binding and welding quality, and whether the arrangement of the stiffening bars meets the design requirements. It is also necessary to check whether the pads are firmly fixed.

[0045] Furthermore, in the embodiment of the present application, in S1 , the corrugated steel plate 2 and the foam plate 3 are pre-embedded for the erection of the steel perimeter purlin 1 in S5 .

[0046] First, the corrugated steel plate 2 is embedded in the concrete structure of the underground continuous wall. Its main function is to provide a reserved connection surface when the steel purlin 1 is erected, thereby enhancing the shear resistance between the purlin and the underground continuous wall. The corrugated design of the corrugated steel plate 2 can increase the contact area between the wall and the steel purlin 1, thereby effectively improving the friction and connection strength of the contact surface. The corrugated structure of the corrugated steel plate 2 increases the irregularity of the surface, improves the friction and bite force between the steel purlin 1 and the wall, thereby enhancing the shear resistance of the diagonal bracing system. The corrugated steel plate 2 can provide a more stable installation foundation for the steel purlin 1 to prevent the steel purlin 1 from displacement or sliding due to soil pressure or other external forces. The corrugated steel plate 2 is embedded in step S1, which can provide a precise installation position for the subsequent installation of the steel purlin 1, reducing the operation steps of secondary reinforcement or positioning on site.

[0047] Secondly, the pre-embedded foam board 3 is mainly used to provide a buffer space that is easy to remove when erecting the steel purlin 1. The foam board 3 can be used as a temporary isolation layer during the construction of the steel purlin 1, which is convenient for the erection of the purlin in step S5. Due to the lightweight characteristics of the foam board 3, it can be easily chiseled out without damaging the wall and the corrugated steel plate 2. When the steel purlin 1 is installed, the foam board 3 needs to be chiseled out, so as to ensure that the steel purlin 1 is in direct contact with the concrete and corrugated steel plate 2 of the underground continuous wall, forming a tighter structural connection and avoiding inclusions affecting the connection effect. The foam board 3 is arranged between the contact surface between the wall and the steel purlin 1, and plays a temporary support and protection role during the installation process. When it is chiseled out, the steel purlin 1 is in direct contact with the wall, ensuring a stable connection and avoiding position displacement or sliding of the steel purlin 1 during installation.

[0048] In general, the high friction performance of the corrugated steel plate 2 and the isolation effect of the foam plate 3 ensure that the steel purlin 1 can be in close contact with the wall after erection, reducing the possibility of sliding and dislocation of the steel purlin 1, thereby enhancing the shear resistance of the entire foundation pit diagonal bracing system. The foam plate 3 plays a temporary supporting and filling role before the installation of the steel purlin 1, and is easy to chisel out during installation, while the corrugated steel plate 2 ensures that a high-strength connection is formed between the steel purlin 1 and the underground continuous wall after installation, ensuring the stability of the steel purlin 1.

[0049] Meanwhile, the corrugated steel plate 2 is embedded in the concrete protective layer. The cross-sectional size of the corrugated steel plate 2 is set to be.

[0050] The corrugated steel plate 2 is buried in the concrete protective layer, which can improve its corrosion resistance and extend its service life, while ensuring its effectiveness in the structure and avoiding the external environment from affecting its performance. The setting of 1000mmx1000mm provides sufficient strength and stability. Appropriate size design can improve its force performance and ensure better shear resistance.

[0051] At the same time, the foam board 3 is fixed by tying wires and / or iron wires.

[0052] The method of tying wire or iron wire can effectively enhance the stability of the foam board 3, avoid displacement of the foam board 3 during construction, ensure the construction quality and shear resistance of the subsequent structure, and also facilitate the removal of the foam board 3 during the subsequent construction process.

[0053] S2. Construction of structural parts: construction of guide wall, underground continuous wall, crown beam, etc. in sequence.

[0054] Regarding S2, the construction of the guide wall includes the steps of laying out and measuring, excavating the guide wall foundation, pouring concrete, setting up the steel cage, etc.; the construction of the underground continuous wall includes the steps of excavating the trench, mud wall protection, installing the steel cage, pouring concrete, handling the mud, etc.; the construction of the crown beam includes the steps of laying out and measuring, steel bar binding, crown beam construction, etc. This is relatively well known to those skilled in the art, so it will not be described in detail in the embodiments of this application.

[0055] S3, foundation pit excavation. After S2 is completed, the foundation pit will be excavated to the specified elevation according to the design requirements.

[0056] Regarding S3, each time the foundation pit is excavated, it should be excavated to 0.5m below the specified elevation.

[0057] During the excavation process, construction workers need to always pay attention to monitoring the excavation depth. When the design elevation is reached, continue to excavate 0.5 meters to ensure that there is a certain soil layer at the bottom of the foundation pit as support. In general, by excavating in layers and excavating 0.5 meters below the specified elevation each time, the risks that may arise during the excavation of the foundation pit can be effectively reduced to ensure construction safety. At the same time, this method helps to maintain the stability of the foundation pit and lays a good foundation for the subsequent installation of the steel cage and concrete pouring.

[0058] Furthermore, S3 also includes chiseling away the foam plate 3 and cleaning the corrugated steel plate 2 .

[0059] When the foam board 3 is embedded in the early stage (step S1), it is mainly used as a temporary support material when the steel purlin 1 is erected. When the foundation pit is excavated to a certain depth, the foam board 3 needs to be chiseled off so that the subsequent structure can directly contact the concrete wall and the corrugated steel plate 2. After the foam board 3 is chiseled off, the steel purlin 1 can directly contact closely with the underground continuous wall or the corrugated steel plate 2, reducing the gap and avoiding local weaknesses caused by loose contact. This ensures the stability of the steel purlin 1 during erection. If the foam board 3 is not chiseled off in time, there will be a weak layer between the steel purlin 1 and the wall, resulting in stress concentration at certain specific points, which may cause local deformation or structural failure. By chiseling off the foam board 3, the steel purlin 1 can be evenly contacted with the wall, dispersing the stress and reducing the risk of excessive local pressure. The foam board 3 is elastic and soft, and retaining the foam board 3 may affect the precise positioning of the steel purlin 1. After the foam board 3 is removed, the position of the steel purlin 1 can be adjusted more accurately to ensure that it is installed in the correct position according to the design requirements.

[0060] As a key structural element for enhancing shear resistance, the corrugated steel plate 2 will be partially covered by concrete or contaminated by impurities such as mud and dust during concrete pouring. Before installing the steel purlin 1, the corrugated steel plate 2 must be cleaned to ensure that its surface is clean and free of debris. The corrugated steel plate 2 needs to be tightly combined with the steel purlin 1 or other structural members. Cleaning the surface can remove mud, dust or concrete residue, ensuring that the steel purlin 1 can directly contact the steel plate surface, increasing friction and structural bonding. Cleaning the corrugated steel plate 2 can ensure the effectiveness of the corrugated shape. If the surface of the steel plate is covered with concrete or impurities, the effective contact area of ​​the corrugation will be reduced, reducing its shear resistance. Cleaning the corrugated steel plate 2 can restore the full functionality of the corrugated structure and enhance the shear resistance of the entire diagonal bracing system.

[0061] Through the implementation of the above two steps, the shear performance of the entire underground continuous wall foundation pit diagonal bracing system has been effectively improved, while ensuring safety and structural accuracy during the construction process.

[0062] S4. Fabrication of steel perimeter purlin 1: On-site staff fabricate steel perimeter purlin 1 according to design requirements.

[0063] Regarding S4, during the manufacturing process of the steel purlin 1, a V-shaped gusset plate 4 is welded to the back of the steel purlin 1, and the V-shaped gusset plate 4 is installed closely to the steel purlin 1.

[0064] The steel purlin 1 needs to bear the pressure from the soil and structural loads in the support system, and is prone to bending and deformation. By welding a V-shaped plate 4 on the back of the steel purlin 1, the bending resistance of the steel purlin 1 can be significantly increased. The shape of the V-shaped plate 4 enables it to effectively disperse stress when bearing vertical and horizontal loads, preventing excessive deformation of the steel purlin 1. The V-shaped plate 4 is installed closely to the steel purlin 1, which increases the overall stiffness of the structure and greatly improves the bearing capacity and deformation resistance of the steel purlin 1. The increase in stiffness helps the purlin to remain stable when subjected to large external forces, thereby improving the overall performance of the foundation pit support structure. Through the reinforcement of the V-shaped plate 4, the cross-sectional geometry of the steel purlin 1 is optimized, making it more stable when subjected to shear force, which helps to improve the overall shear resistance of the steel purlin 1 and enhance the safety of the entire foundation pit support system. The close installation between the V-shaped plate 4 and the steel purlin 1 helps prevent the steel purlin 1 from twisting when subjected to force. The steel purlin 1 without additional reinforcement is prone to twisting when subjected to lateral force, causing instability of the overall structure. The design and close installation of the V-shaped plate 4 can effectively avoid this phenomenon, enhance the stability of the structure, and ensure that the steel purlin 1 can still maintain its shape and load-bearing capacity under complex working conditions. By standardizing the welding of the V-shaped plate 4 to the back of the steel purlin 1 in the factory or construction site, the on-site installation work can be simplified. During the installation process, the construction personnel only need to fix the prefabricated steel purlin 1 to the underground continuous wall and other structures, without the need for complex reinforcement or adjustment, which improves the construction efficiency and accuracy.

[0065] Furthermore, the space between the V-shaped gusset plate 4 and the steel purlin 1 is filled with slightly expansive cement.

[0066] Filling micro-expansive cement between the steel purlin 1 and the V-shaped gusset plate 4 can eliminate gaps, enhance the close connection between the two, improve the shear and deformation resistance of the overall structure, and effectively prevent slippage. Its anti-corrosion and durability properties can extend the life of the structure, while reducing stress concentration by evenly dispersing stress. The construction process is simple, and the self-expansion properties of micro-expansive cement can also ensure the quality of the connection and improve the stability and safety of the entire foundation pit support system.

[0067] S5. Erect steel perimeter purlin 1 to the designed elevation.

[0068] Regarding S5, the steel purlin 1 is prestressed during erection.

[0069] The advantage of prestressing the steel purlin 1 during erection is that it can apply controlled stress in advance, reduce deformation and stress concentration caused by subsequent external loads, thereby improving the bending and shearing resistance of the steel purlin 1 and increasing the stability and bearing capacity of the structure. At the same time, prestressing can also reduce structural looseness or fatigue during long-term use, extend service life, and improve overall safety.

[0070] S6. Repeat S3 to S5 until the excavation reaches the bottom of the foundation pit and the construction is completed.

[0071] The implementation principle of a construction method for optimizing the shear resistance of an underground continuous wall foundation pit diagonal brace in an embodiment of the present application is as follows: the settings of S1, S2, S3, S4, S5, and S6 provide a systematic optimization construction method to ensure that the shear resistance of the diagonal brace is optimized, and the optimization is performed according to the construction steps of the present application. In addition to optimizing the shear resistance of the diagonal trough, the construction efficiency can also be improved. The present application has the ability to improve the supporting working performance of the diagonal brace section to a certain extent, speed up the construction rhythm of the embedded steel plate part, and achieve rapid closure of the support system, playing a role in effectively controlling the risk of foundation pit deformation.

[0072] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A construction method for optimizing the shear performance of diagonal bracing of underground continuous wall foundation pit, characterized in that: The following steps are involved: S1. Fabrication of steel cage: On-site staff fabricate the steel cage according to the design requirements; S2, construction of structural parts, construction of guide wall, underground continuous wall, crown beam, etc. in sequence; S3, excavation of foundation pit: after the completion of S2, the foundation pit is excavated to a specified elevation according to the design requirements; S4. Fabrication of the steel perimeter purlin (1): On-site staff fabricate the steel perimeter purlin (1) according to design requirements; S5. Erecting the steel perimeter purlin (1): Erecting the steel perimeter purlin (1) to the designed elevation; S6. Repeat S3 to S5 until the excavation reaches the bottom of the foundation pit and the construction is completed.

2. A construction method for optimizing the shear performance of diagonal braces of underground continuous wall foundation pit according to claim 1, characterized in that: In the S1, corrugated steel plates (2) and foam plates (3) are pre-buried for the installation of the steel purlins (1) in the S5.

3. The construction method for optimizing the shear resistance of diagonal braces of underground continuous wall foundation pit according to claim 1 is characterized in that: In S3, each time the foundation pit is excavated, the excavation should be carried out to 0.5m below the specified elevation.

4. The construction method for optimizing the shear performance of diagonal braces of underground continuous wall foundation pit according to claim 2 is characterized in that: The step S3 also includes chiseling away the foam plate (3) and cleaning the corrugated steel plate (2).

5. The construction method for optimizing the shear performance of diagonal braces of underground continuous wall foundation pit according to claim 1 is characterized in that: In S4, during the manufacturing process of the steel purlin (1), a V-shaped gusset plate (4) is welded to the back of the steel purlin (1), and the V-shaped gusset plate (4) and the steel purlin (1) are tightly installed.

6. A construction method for optimizing the shear resistance of diagonal braces of underground continuous wall foundation pit according to claim 5, characterized in that: Micro-expansive cement is also filled between the V-shaped gusset plate (4) and the steel purlin (1).

7. The construction method for optimizing the shear performance of diagonal braces of underground continuous wall foundation pit according to claim 1 is characterized in that: In S5, the steel purlin (1) is prestressed during installation.

8. The construction method for optimizing the shear resistance of diagonal braces of underground continuous wall foundation pit according to claim 2 is characterized in that: The corrugated steel plate (2) is pre-buried in the concrete protective layer.

9. The construction method for optimizing the shear performance of diagonal braces of underground continuous wall foundation pit according to claim 2, characterized in that: The cross-sectional dimensions of the corrugated steel plate (2) are set to 1000 mm x 1000 mm.

10. The construction method for optimizing the shear performance of diagonal braces of underground continuous wall foundation pit according to claim 2, characterized in that: The foam board (3) is fixed by means of tying wires and / or iron wires.

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