A subway transfer node area deep foundation pit construction method

Abstract

This application relates to the field of deep foundation pit construction technology, and particularly to a method for constructing deep foundation pits in a subway transfer node area. The transfer node area includes an enlarged section, a pipeline relocation section, and a main connecting section. A temporary partition is set on the side of the main connecting section to separate the transfer node area from the main section of the first subway line. The enlarged section adopts a concrete support system, while the pipeline relocation section and the main connecting section adopt a hybrid support system of concrete and steel supports. The deep foundation pit construction method includes: Step S1: Traffic diversion and pipeline relocation; Step S5: Foundation pit excavation and support: The foundation pit excavation and support adopts a combination of vertical layering and longitudinal segmentation. The longitudinal segmentation sequence is the enlarged section, the main connecting section, and the pipeline relocation section. When excavating and supporting the foundation pit of the pipeline relocation section, the temporary partition at the corresponding depth is removed simultaneously to avoid idle work and greatly shorten the overall construction time.

Description

Technical Field

[0001] This application relates to the field of deep foundation pit construction technology, and in particular to a method for constructing deep foundation pits in subway transfer node areas. Background Technology

[0002] With the rapid development of subway lines in China, the number of complex working conditions, such as subway line intersections, increased depth, and proximity to existing municipal roads and pipelines, is gradually increasing. Correspondingly, the support system for foundation pits is also becoming more complex. Commonly used systems include concrete supports and steel supports. Concrete supports have the advantages of high rigidity, can be arranged over long distances in a plane, and have fewer restrictions on the arrangement. The disadvantage is that the construction time is longer. Steel supports have the advantages of being able to apply prestress to actively control deformation. The disadvantage is that they have lower rigidity and are limited in the arrangement. In current construction, concrete supports and steel supports are often combined to form a support system to adapt to support areas of different sizes and support strength requirements. However, there is currently no reasonable precedent to follow on how to adjust the construction sequence in combination with the setting of the support system to improve construction speed and save construction costs.

[0003] Therefore, there is a need to provide an improved technical solution that addresses the shortcomings of the existing technology. Summary of the Invention

[0004] The purpose of this application is to provide a method for constructing deep foundation pits in subway transfer node areas to solve or alleviate the problems existing in the prior art.

[0005] To achieve the above objectives, this application provides the following technical solution:

[0006] A method for constructing a deep foundation pit in a subway transfer node area, wherein the transfer node area includes an enlarged section, a pipeline relocation section, and a main connection section;

[0007] A temporary partition is provided on the side of the main connecting section to separate the transfer node area from the main section of the first subway line. The first subway line includes the transfer node area and the main section. The first subway line and the second subway line cross and connect at the expansion section. A permanent cover plate structure is provided on the top of the pipeline relocation section for pipeline relocation.

[0008] The expansion section adopts a concrete support system, while the pipeline relocation section and the main connection section adopt a hybrid support system of concrete and steel support.

[0009] The deep foundation pit construction method includes:

[0010] Step S1: Traffic diversion and pipeline relocation;

[0011] Step S5, Excavation and Support of Foundation Pit: The excavation and support of the foundation pit adopts a combination of vertical layering and longitudinal segmentation. The longitudinal segmentation is in the following order: expansion section, main connection section, and pipeline relocation section. When excavating and supporting the foundation pit of the pipeline relocation section, the temporary partitions at the corresponding depth are removed simultaneously.

[0012] In the above-described method for constructing deep foundation pits in a subway transfer node area, preferably, the support system of the expanded section includes a total of six concrete supports arranged sequentially from top to bottom; the support system of the pipeline relocation section and the main connection section includes a total of seven concrete supports and steel supports arranged alternately from top to bottom.

[0013] The above-described method for constructing deep foundation pits in subway transfer node areas is preferably...

[0014] The expanded section passes under an existing municipal road; along the direction of the existing municipal road, a temporary cover structure is installed on top of the area where the expanded section passes under the existing municipal road;

[0015] The support system of the second subway line extends along its own axis to the underside of the temporary cover structure and intersects with the support system of the enlarged section;

[0016] The deep foundation pit construction method includes:

[0017] Step S3: Construction of temporary cover structure.

[0018] In the above-described method for constructing a deep foundation pit in a subway transfer node area, preferably, the enlarged section, the pipeline relocation section, and the main connecting section are sequentially and continuously arranged along the direction of the first subway line; the temporary cover structure is located on the top of the enlarged section at the end furthest from the pipeline relocation section.

[0019] The above-described method for constructing a deep foundation pit in a subway transfer node area, preferably, includes a support system for the enlarged section comprising diagonal bracing connecting adjacent sides of the enlarged section and straight bracing connecting opposite sides of the enlarged section.

[0020] The enlarged section includes an inclined bracing area with inclined bracing, a straight bracing area with straight bracing, and an unsupported area without support. The inclined bracing area is located at the end of the enlarged section away from the pipeline relocation section, the straight bracing area is located at the end closer to the pipeline relocation section, and the unsupported area is located between the inclined bracing area and the straight bracing area.

[0021] Step S5 further includes: when excavating the foundation pit of the enlarged section, first excavate the unsupported area, then excavate the inclined support area, and finally excavate the straight support area.

[0022] The support system of the second subway line is intersected with the diagonal bracing of the expanded section.

[0023] In the above-described method for constructing deep foundation pits in subway transfer node areas, preferably, each support includes multiple support components, and adjacent support components are connected by connecting beams.

[0024] In the above-described method for constructing deep foundation pits in a subway transfer node area, preferably, the excavation depth of the foundation pit for the second subway line is less than the excavation depth of the foundation pit for the first subway line.

[0025] The support system of the second subway line includes a total of five concrete supports installed from top to bottom; the support depth of each support of the second subway line is consistent with the support depth of the first to fifth supports of the enlarged section, the main connection section, and the pipeline relocation section.

[0026] In the above-described method for constructing a deep foundation pit in a subway transfer node area, preferably, the first support of the second subway line extends along its axial direction and passes under the temporary cover structure.

[0027] In the above-described method for constructing deep foundation pits in a subway transfer node area, preferably, the sixth support depth of the enlarged section is located between the sixth and seventh support depths of the main connection section and the pipeline relocation section.

[0028] As described above, in any of the deep foundation pit construction methods for subway transfer node areas, preferably, the bottom plate of the permanent cover plate structure is located between the first support and the second support of the pipeline relocation section.

[0029] Step S5 further includes: no longer constructing the first support at the permanent cover plate structure.

[0030] Compared with the closest prior art, the technical solution of this application has the following beneficial effects:

[0031] Different support systems are designed according to the different functional requirements of the expansion section, pipeline relocation section, and main connection section to achieve cost savings. Considering the long construction and curing time of concrete supports, the concrete support construction of the expansion section is carried out first, so that the construction of other areas can be carried out simultaneously during the concrete curing period to avoid idle work. The main connection section is then constructed, followed by the pipeline relocation section. Again, based on the consideration of avoiding idle work, the construction of the pipeline relocation section can be carried out simultaneously during the concrete support curing or steel support pressurization of the main connection section. Furthermore, the removal of the temporary partition on one side of the main connection section is treated as another parallel procedure for the pipeline relocation section construction, which greatly shortens the overall construction time. Attached Figure Description

[0032] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. Wherein:

[0033] Figure 1 This is a schematic diagram of the first support plan of the deep foundation pit in a subway transfer node area according to some embodiments of this application;

[0034] Figure 2 This is a schematic diagram of the second support plan for a deep foundation pit in a subway transfer node area, provided according to some embodiments of this application.

[0035] Figure 3 This is a schematic diagram of the third support plan of the deep foundation pit in a subway transfer node area according to some embodiments of this application;

[0036] Figure 4 This is a schematic diagram of the fourth support plan of the deep foundation pit in a subway transfer node area according to some embodiments of this application;

[0037] Figure 5 This is a schematic diagram of the fifth support plan of the deep foundation pit in a subway transfer node area according to some embodiments of this application;

[0038] Figure 6 This is a schematic diagram of the sixth support plan of the deep foundation pit in a subway transfer node area according to some embodiments of this application;

[0039] Figure 7 This is a schematic diagram of the seventh support plan of the deep foundation pit in a subway transfer node area according to some embodiments of this application.

[0040] Explanation of reference numerals in the attached figures:

[0041] 1. First subway line; 2. Second subway line; 3. Expansion section; 4. Pipeline relocation section; 5. Main connection section; 6. Main section; 7. Temporary cover plate structure; 8. Permanent cover plate structure; 9. Diagonal bracing area; 10. Unbraced area; 11. Straight bracing area; 12. Connecting beam; 13. Lattice column; 14. Diaphragm wall; 15. Temporary partition. Detailed Implementation

[0042] The present application will now be described in detail with reference to the accompanying drawings and embodiments. Various examples are provided by way of explanation and not by way of limitation. In fact, those skilled in the art will recognize that modifications and variations can be made to the present application without departing from the scope or spirit thereof. For example, a feature shown or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. Therefore, it is desirable that the present application encompass such modifications and variations that fall within the scope of the appended claims and their equivalents.

[0043] In the following description, the terms "first / second / third" are used merely to distinguish similar objects and do not represent a specific order of objects. It is understood that "first / second / third" may be interchanged in a specific order or sequence where permitted, so that the embodiments of this application described herein can be implemented in an order other than that illustrated or described herein.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used herein is for the purpose of describing embodiments of this disclosure only and is not intended to limit this disclosure.

[0045] In the description of this application, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and do not require that this application be constructed and operated in a specific orientation, and therefore should not be construed as limiting this application. The terms "connected," "linked," and "set up" used in this application should be interpreted broadly. For example, they can refer to fixed connections or detachable connections; direct connections or indirect connections through intermediate components; wired connections, radio connections, or wireless communication signal connections. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0046] The following will be combined with the appendix Figure 1-7 The present invention provides a more detailed description of a deep foundation pit construction method for a subway transfer node area.

[0047] A method for constructing deep foundation pits in a subway transfer node area, the transfer node area including an enlarged section 3, a pipeline relocation section 4, and a main connection section 5;

[0048] A temporary partition 15 is installed on the side of the main connecting section 5 to separate the transfer node area from the main section 6 of the first metro line 1; the first metro line 1 includes the transfer node area and the main section 6, and the first metro line 1 and the second metro line 2 are intersected and connected in the expansion section 3; a permanent cover structure 8 is installed on the top of the pipeline relocation section 4 for pipeline relocation.

[0049] The expansion section 3 adopts a concrete support system, while the pipeline relocation section 4 and the main connection section 5 adopt a hybrid support system of concrete and steel support.

[0050] Deep foundation pit construction methods include:

[0051] Step S1: Traffic diversion and pipeline relocation;

[0052] Step S5, Excavation and Support of Foundation Pit: The excavation and support of foundation pit adopts a combination of vertical layering and longitudinal segmentation. The longitudinal segmentation sequence is as follows: expansion section 3, main connection section 5, and pipeline relocation section 4. When excavating and supporting the foundation pit of pipeline relocation section 4, the temporary partition 15 at the corresponding depth is removed simultaneously.

[0053] As the intersection connecting the first subway line 1 and the second subway line 2, the extended section 3 connects to the second subway line 2 on one side. Compared with the pipeline relocation section 4 and the main connection section 5, which have complex shapes and larger areas, the extended section 3 has higher requirements for the support strength of the support system. Concrete supports meet the support requirements of the extended section 3 due to their excellent support strength and less restriction on the layout. However, concrete supports have a long construction and curing time, high cost, and no recycling function. In order to save money and improve construction efficiency, a hybrid support system of concrete and steel supports is adopted for the pipeline relocation section 4 and the main connection section 5, which have weaker support strength requirements and more regular shapes.

[0054] Meanwhile, due to the long construction and curing time of concrete supports, the construction of the expanded section 3 is carried out first when arranging the construction. The excavation and support construction of the foundation pit of the main connecting section 5, and even the pipeline relocation section 4, are treated as parallel procedures for the concrete support curing of the expanded section 3, in order to avoid idle work. Similarly, since the construction of the pipeline relocation section 4 is after the construction of the main connecting section 5, the excavation and support construction of the foundation pit of the pipeline relocation section 4 are also treated as parallel procedures for the concrete support curing or steel support pressurization of the main connecting section 5. At the same time, since the construction rhythm of the pipeline relocation section 4 and the main connecting section 5 is basically consistent, after the construction of the main connecting section 5 is completed, the construction of the pipeline relocation section 4 is not yet finished. The subsequent construction is treated as a parallel procedure for the removal of the temporary partition 15 of the corresponding depth set on one side of the main connecting section 5, so as to fully realize the overlapping construction and greatly save construction time.

[0055] In a specific embodiment of the present invention

[0056] The pipeline relocation in step S1 includes the construction of the permanent cover structure 8. The permanent cover structure 8 is constructed using the cut-and-cover method. The cut-and-cover method construction needs to be combined with traffic diversion and pipeline relocation requirements, and is carried out according to the following construction steps: perimeter retaining structure of the permanent cover structure 8; construction of temporary steel structure column foundations; construction of temporary steel structure columns; excavation of shallow foundation pit in the area of ​​the permanent cover structure 8; construction of temporary column top steel beams; construction of the top slab structure; permanent relocation of pipelines to the designed location; excavation of the foundation pit and erection of inter-column supports and steel supports; construction of the bottom slab structure; construction of side walls, central columns, and central slab structures and removal of corresponding supports; construction of side walls and central columns to form an integral structure with the top slab structure.

[0057] Deep foundation pit construction methods also include:

[0058] Step S2, Construction of Diaphragm Wall 14: C35 P6 underwater concrete is used. The construction sequence is as follows: guide wall construction, mud preparation, trench excavation, reinforcement cage fabrication and hoisting, tremie pipe installation, underwater concrete pouring, mud circulation and treatment, and waterproofing treatment of the diaphragm wall joints. Guide wall construction is a crucial preparatory step for diaphragm wall 14 construction. Its main functions are to guide the trenching, control the elevation, control the verticality and position of the trench sections, and position the reinforcement cage, preventing trench collapse and load-bearing. The guide wall is 2.0m high and 200mm thick, with a spacing of 1050mm between the two guide walls. The design strength grade of the guide wall concrete is C20. The quality of the mud directly affects the stability of the trench wall during diaphragm wall 14 trenching construction. The main components of the drilling mud are bentonite, CMC, soda ash, and water. The mud mix ratio is determined based on the geological conditions and the sediment at the bottom of the borehole. The mud is mixed using a high-speed rotary mixer. The mixed mud should be placed in the storage tank and allowed to stand for at least 24 hours to allow the bentonite particles to fully hydrate and expand, ensuring the quality of the mud. During trenching, the unit trench sections are constructed using an intermittent skip-work method to avoid affecting adjacent sections that have already been filled with concrete. Specifically, the single holes at both ends of the trench section are excavated first, or the first hole is excavated and then a certain distance is skipped before the second hole is excavated, leaving a certain width of unexcavated soil between the two single holes. This allows the grab bucket to be subjected to balanced force when excavating single holes, effectively correcting deviations and ensuring the verticality of the trench. The reinforcing cage is hoisted in sections. To ensure the safety of the reinforcing cage during hoisting, the hoisting points need to be locally reinforced. Specifically, the shorter reinforcing cage section is hoisted first, followed by the longer reinforcing cage section. The steel cage is hoisted using a double-crane lifting system and straightened in mid-air. The hoisting is directed by an experienced crane operator. Concrete pouring must be continuous and not interrupted for a long time to maintain the uniformity of the concrete. The concrete pouring elevation of the trench section should be no less than 500-600mm higher than the design elevation of the top of the wall.

[0059] Step S4, Construction of tension piles, temporary columns and dewatering wells:

[0060] Step S41, Construction of tension piles and temporary columns: The lower part of the temporary columns uses bored cast-in-place piles with a diameter of 1200mm and a length of 25m, which also serve as tension piles for the foundation. The top of the piles is located at the bottom of the main structure's base slab. The main reinforcement bars of the steel cage are anchored into the main structure's base slab for ≥40d. The upper part of the temporary columns uses steel lattice columns 13 with a cross-sectional dimension of 600×600mm. Steel lattice columns 13 are constructed by welding four L200×20mm equilateral angle steel bars and four 540×350×12@750mm gusset plates. The top of steel lattice columns 13 is located at the bottom of the first concrete support, and the bottom of steel lattice columns 13 is inserted 4m into the bottom of the foundation pit.

[0061] Step S42, Dewatering Well Construction: Dewatering wells are used. Dewatering treatment is carried out 15 days before the excavation of the foundation pit, continuing until the main structure's top slab and capping beam are completed. After the first layer of concrete support is completed, a platform is erected for the dewatering wells in the pit to ensure continuous operation. Based on the excavation conditions, the dewatering depth for each excavation layer is controlled to be 1.5m below the bottom of the current excavation layer. During the pumping process, flow rate and water level data of each pumping well should be recorded. Due to the depth of the foundation pit excavation, drainage from the pit becomes more difficult during rainy seasons, especially after the second layer of excavation. Sump pits and drainage ditches around the pit are used for pumping. Drainage ditches and retaining walls are installed around the pit, and rainwater grates are installed on top of the drainage ditches to collect and discharge atmospheric precipitation into the municipal stormwater pipes. The sealing of the dewatering wells began after the construction of the main structure's top slab and capping beam was completed. During the construction of the station's main structure, the dewatering wells were in continuous dewatering operation, continuously pumping water from the bottom of the foundation pit to keep the water level below 1.5m from the bottom of the foundation pit.

[0062] In step S5, the vertical layer thickness of the foundation pit excavation does not exceed 2.0m, and each layer is excavated twice. First, the middle part is excavated and the reserved counterweight soil on both sides is removed. The longitudinal section length, that is, the section length along the direction of the first subway line 1, does not exceed 20m. Among them, the longitudinal length of the enlarged section 3 is 51m, the longitudinal length of the pipeline relocation section 4 is 18m, and the longitudinal length of the main connection section 5 is 14m.

[0063] The support system of the expansion section 3 includes a total of six concrete supports installed sequentially from top to bottom; the support system of the pipeline relocation section 4 and the main connection section 5 includes a total of seven concrete and steel supports installed alternately from top to bottom.

[0064] In a specific embodiment of the present invention, the cross-sectional dimensions of the six concrete supports of the enlarged section 3, from top to bottom, are: 1.0*1.0m, 1.2*1.2m, 1.2*1.3m, 1.2*1.7m, and 1.2*1.7m; the types and cross-sectional dimensions of the seven supports of the pipeline relocation section 4 and the main connection section 5, from top to bottom, are: concrete support (1.0*1.7m), steel support (φ609mm), concrete support (1.2m*1.2m), steel support (φ800mm), concrete support (1.2*1.7m), steel support (φ800mm), and steel support (φ800mm).

[0065] In step S5, taking the support construction of pipeline relocation section 4 and main connection section 5 as an example, it includes:

[0066] (1) Construction of the first concrete support: Remove the hardened road above the foundation pit, remove construction waste and materials, and excavate the foundation pit in sections to 5cm below the first concrete support. Construct the cap beam, the first concrete support and the retaining wall.

[0067] (2) Construction of the second steel support: After the strength of the cap beam and the first concrete support reaches the design requirements, the excavation of the foundation pit is carried out in sections and layers to 50cm below the second steel support, the second steel support is erected and the pre-loaded axial force is applied;

[0068] (3) Construction of the third concrete support: After the second steel support is erected and the pre-loaded axial force is applied, continue to excavate in sections and layers to 5cm below the third concrete support, and construct the cushion layer and the third concrete support.

[0069] (4) Construction of the fourth steel support: After the strength of the third concrete support reaches the design requirements, continue to excavate in sections and layers to 50cm below the fourth steel support, erect the fourth steel support and apply pre-stressed axial force;

[0070] (5) Construction of the fifth concrete support: After the fourth steel support is erected and the pre-loaded axial force is applied, continue to excavate in sections and layers to 5cm below the fifth concrete support, and construct the cushion layer and the fifth concrete support.

[0071] (6) Construction of the sixth steel support: After the strength of the fifth concrete support reaches the design requirements, continue to excavate in sections and layers to 50cm below the sixth steel support, erect the sixth steel support and apply pre-stressed axial force;

[0072] (7) Construction of the seventh steel support: (7) After the sixth steel support is erected and the pre-loaded axial force is applied, continue to excavate in sections and layers to 50cm below the seventh steel support, erect the seventh steel support and apply the pre-loaded axial force;

[0073] After the seventh steel support is erected and pre-loaded with axial force, the excavation is carried out in sections and layers to 300mm above the bottom of the pit, and finally, the excavation is carried out manually to the bottom of the pit.

[0074] The extended section 3 passes under the existing municipal road; along the direction of the existing municipal road, a temporary cover structure 7 is set on the top of the area where the extended section 3 passes under the existing municipal road;

[0075] The support system of the second subway line 2 extends along its own axis to the underside of the temporary cover structure 7 and intersects with the support system of the enlarged section 3.

[0076] Deep foundation pit construction methods include:

[0077] Step S3, temporary cover structure 7 construction.

[0078] In a specific embodiment of the present invention, the support system of the second subway line 2 is extended along its axial direction to the underside of the temporary cover structure 7, and together with the support system of the enlarged section 3, it serves as a support, which not only enhances the stability of the temporary cover structure 7, but also facilitates construction arrangements.

[0079] In step S3, the construction of the temporary cover structure 7 specifically includes: construction of the foundation of the temporary steel structure column; construction of the temporary steel structure column; excavation of the shallow foundation pit in the area of ​​the temporary cover structure 7; construction of the steel beam on top of the temporary column; and construction of the top slab structure.

[0080] The expansion section 3, pipeline relocation section 4, and main connection section 5 are set up sequentially and continuously along the first subway line 1.

[0081] The temporary cover structure 7 is set on top of the end of the enlarged section 3 that is away from the pipeline relocation section 4.

[0082] Since the temporary cover structure 7 is set at the top of the end of the expanded section 3 away from the pipeline relocation section 4, and the support system of the second subway line 2 extends along its axis to the bottom of the temporary cover structure 7, the second subway line 2 and the first subway line 1 intersect at the end of the expanded section 3 away from the pipeline relocation section 4 in an L-shaped structure.

[0083] The support system of the enlarged section 3 includes diagonal braces connecting adjacent sides of the enlarged section 3 and straight braces connecting opposite sides of the enlarged section 3;

[0084] The enlarged section 3 includes an inclined bracing area 9 with inclined bracing, a straight bracing area 11 with straight bracing, and an unsupported area 10 without support. The inclined bracing area 9 is located at the end of the enlarged section 3 away from the pipeline relocation section 4, the straight bracing area 11 is located at the end closer to the pipeline relocation section 4, and the unsupported area 10 is located between the inclined bracing area 9 and the straight bracing area 11.

[0085] Step S5 also includes: when excavating the foundation pit of the enlarged section 3, first excavate the unsupported area 10, then excavate the inclined support area 9, and finally excavate the straight support area 11.

[0086] The support system of the second subway line 2 is intersected with the diagonal bracing of the expanded section 3.

[0087] Since the second subway line 2 and the first subway line 1 intersect in an L-shaped structure at the end of the expansion section 3 away from the pipeline relocation section 4, concrete diagonal bracing must be used at the end of the expansion section away from the pipeline relocation section 4 to match the corresponding structural shape and meet the layout and strength requirements. Specifically, since one side of the expansion section 3 is connected to the second subway line 2, there is a lack of support points for the straight bracing in this area. In order to ensure the support strength, diagonal bracing can only be used. At the same time, since the diagonal bracing has a large span, the support stiffness requirement is high, so concrete diagonal bracing is selected.

[0088] During the excavation of the foundation pit, since the inclined support area 9 is located at the end of the expanded section 3 away from the pipeline relocation section 4, and a temporary cover structure 7 is installed on top, and the expanded section 3 is close to the existing road, the soil removal route is restricted. In order to avoid the impact on the existing road and to ensure the soil removal route, the soil excavation of the unsupported area 10 is carried out first. Since the concrete support of the inclined support area 9 is longer, the required curing time is longer than that of the straight support area 11. In order to meet the need for traffic above the temporary cover structure 7 as soon as possible, after the soil excavation of the unsupported area 10 is completed in layers, the soil excavation of the inclined support area 9 is carried out in layers, and finally the soil excavation of the straight support area 11 is carried out in layers. The soil of the inclined support area 9 needs to be transported from the site to the unsupported area 10 before being transported out. The above excavation method also conforms to the characteristics of basin excavation, which can minimize the deformation of the retaining structure.

[0089] For the excavation at or above the bottom of the capping beam, ordinary excavators are used to directly remove the soil. For the excavation from the bottom of the capping beam to a depth of 10m below the original ground level, five DX230LC excavators are used in relay to excavate the soil in the foundation pit. The excavators on the upper and lower steps work together to transport the soil to the next platform. The excavator on the top step directly loads the soil onto trucks for transport. For the excavation from 10m below the original ground level to the bottom of the foundation pit, DX230LC and PC60 excavators are used in combination to excavate the soil in the foundation pit. The excavators on the upper and lower steps work together to transport the soil to the next platform. A hydraulic grab bucket is used to load the soil onto trucks for transport.

[0090] Each support consists of multiple support components. To further increase the support strength, adjacent support components are connected by connecting beams 12.

[0091] The excavation depth of the foundation pit for the second subway line 2 is less than that for the first subway line 1.

[0092] The support system of the second subway line 2 includes a total of five concrete supports installed from top to bottom; the support depth of each support of the second subway line 2 is consistent with the support depth of the first to fifth supports of the enlarged section 3, the main connection section 5, and the pipeline relocation section 4.

[0093] In a specific embodiment of the present invention

[0094] The excavation depths for the first to fifth supports of the expanded section 3, pipeline relocation section 4, main connection section 5, and the second subway line 2 are set as follows: the excavation depth between the original ground and the first support is 1.8m; the excavation depth between the first and second supports is 6.3m; the excavation depth between the second and third supports is 6.3m; the excavation depth between the third and fourth supports is 3.9m; and the excavation depth between the fourth and fifth supports is 3.9m.

[0095] To further enhance the stability of the temporary cover structure 7, the first support of the second subway line 2 extends along its axis and passes under the temporary cover structure 7.

[0096] In a specific embodiment of the present invention, the planar arrangement of the supporting components of the second to fifth supports of the second subway line 2 is consistent; the planar arrangement of the supporting components of the second to fifth concrete supports of the expanded section 3 is consistent; the planar arrangement of the supporting components of the second and fourth concrete supports of the pipeline relocation section 4 is consistent; the planar arrangement of the supporting components of the first, second, and fourth concrete supports of the main connecting section 5 is consistent; and the planar arrangement of the supporting components of the third, fifth, to seventh steel supports of the pipeline relocation section 4 and the main connecting section 5 is consistent. Specifically, the first support of the second subway line 2 extends axially and passes under the temporary cover structure 7; the length of the diagonal brace of the first concrete support of the expanded section 3 is shortened due to the passing under of the first support of the second subway line 2; and the arrangement of the first concrete support of the pipeline relocation section 4 is adjusted due to the installation of the permanent cover structure 8.

[0097] Since the support system of the second subway line 2 no longer extends along its axis to below the temporary cover structure 7 from the fifth support below, the corresponding side of the enlarged section 3 is no longer connected to the second subway line 2. By adjusting the arrangement of the diagonal bracing in the diagonal bracing area 9 and increasing the number of connecting beams 12, based on the high support strength of concrete support, the depth of the sixth support of the enlarged section 3 is located between the sixth and seventh support depths of the main connection section 5 and the pipeline relocation section 4, so as to reduce construction procedures, shorten construction time, and reduce construction costs while meeting the support strength requirements.

[0098] In a specific embodiment of the present invention

[0099] For the expanded section 3: the excavation depth between the fifth and sixth supports is 6.2m; the excavation depth between the sixth support and the bottom of the pit is 4.03m.

[0100] For pipeline relocation section 4 and main connection section 5: the earthwork excavation depth between the fifth and sixth supports is 3.6m; the earthwork excavation depth between the sixth and seventh supports is 3.0m; and the earthwork excavation depth between the seventh support and the bottom of the foundation pit is 3.63m.

[0101] The base plate of the permanent cover plate structure 8 is located between the first and second supports of the pipeline relocation section 4;

[0102] Step S5 also includes: the first support will no longer be constructed at 8 locations of the permanent cover structure.

[0103] In a specific embodiment of the present invention, since the bottom plate of the permanent cover plate structure 8 is located between the first support and the second support of the pipeline relocation section 4, the permanent cover plate structure 8 itself can play a supporting role as a supporting structure. The first support of other areas of the pipeline relocation section 4, except for the permanent cover plate structure 8, is connected to the side of the permanent cover plate structure 8.

[0104] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for constructing deep foundation pits in subway transfer node areas, characterized in that, The transfer node area includes an expansion section, a pipeline relocation section, and a main connection section. A temporary partition is set on the side of the main connecting section to separate the transfer node area from the main section of the first subway line. The first subway line includes the transfer node area and the main section. The first subway line and the second subway line are intersected and connected at the expansion section. A permanent cover plate structure is installed on the top of the pipeline relocation section for pipeline relocation. The expansion section adopts a concrete support system, while the pipeline relocation section and the main connection section adopt a hybrid support system of concrete and steel support. The deep foundation pit construction method includes: Step S1: Traffic diversion and pipeline relocation; Step S2, construction of the diaphragm wall; Step S4: Construction of anti-tension piles, temporary columns and dewatering wells; Step S5, Excavation and Support of Foundation Pit: The excavation and support of the foundation pit adopts a combination of vertical layering and longitudinal segmentation. The longitudinal segmentation is in the following order: enlargement section, main connection section, and pipeline relocation section. When excavating and supporting the foundation pit of the pipeline relocation section, the temporary partitions at the corresponding depth are removed simultaneously. The expanded section passes under an existing municipal road; along the direction of the existing municipal road, a temporary cover structure is installed on top of the area where the expanded section passes under the existing municipal road; The support system of the second subway line extends along its own axis to the underside of the temporary cover structure and intersects with the support system of the enlarged section; The deep foundation pit construction method includes: Step S3, temporary cover plate structure construction; The expansion section, pipeline relocation section, and main connecting section are arranged sequentially and continuously along the first subway line; the temporary cover plate structure is located on the top of the expansion section at the end away from the pipeline relocation section. Each support consists of multiple support components, and adjacent support components are connected by connecting beams.

2. The method for constructing deep foundation pits in subway transfer node areas according to claim 1, characterized in that, The support system of the expansion section includes a total of six concrete supports arranged sequentially from top to bottom; the support system of the pipeline relocation section and the main connection section includes a total of seven concrete supports and steel supports arranged alternately from top to bottom.

3. The method for constructing deep foundation pits in subway transfer node areas according to claim 1, characterized in that, The support system of the enlarged section includes diagonal braces connecting adjacent sides of the enlarged section and straight braces connecting opposite sides of the enlarged section. The enlarged section includes an inclined bracing area with inclined bracing, a straight bracing area with straight bracing, and an unsupported area without support. The inclined bracing area is located at the end of the enlarged section away from the pipeline relocation section, the straight bracing area is located at the end closer to the pipeline relocation section, and the unsupported area is located between the inclined bracing area and the straight bracing area. Step S5 further includes: when excavating the foundation pit of the enlarged section, first excavate the unsupported area, then excavate the inclined support area, and finally excavate the straight support area. The support system of the second subway line is intersected with the diagonal bracing of the expanded section.

4. The method for constructing deep foundation pits in subway transfer node areas according to claim 1, characterized in that, The excavation depth of the foundation pit for the second subway line is less than that for the first subway line. The support system of the second subway line includes a total of five concrete supports installed from top to bottom; the support depth of each support of the second subway line is consistent with the support depth of the first to fifth supports of the enlarged section, the main connection section, and the pipeline relocation section.

5. The method for constructing deep foundation pits in subway transfer node areas according to claim 4, characterized in that, The first support of the second subway line extends along its axis and passes under the temporary cover structure.

6. The method for constructing deep foundation pits in subway transfer node areas according to claim 4, characterized in that, The sixth support depth of the expanded section is located between the sixth and seventh support depths of the main connection section and the pipeline relocation section.

7. A method for constructing deep foundation pits in a subway transfer node area according to any one of claims 1-6, characterized in that, The base plate of the permanent cover plate structure is located between the first and second supports of the pipeline relocation section; Step S5 further includes: no longer constructing the first support at the permanent cover plate structure.

Images