Support system and construction method for basement-sized foundation pit

Abstract

The application discloses a supporting system and a construction method in the technical field of basement construction, and relates to the technical field of construction. The supporting system comprises a large foundation pit supporting structure located at the periphery of a large foundation pit, a small foundation pit supporting structure located at the periphery of a small foundation pit, and the crown beam of the large foundation pit is higher than the crown beam of the small foundation pit; the large foundation pit is further provided with an inclined throwing supporting structure for assisting the construction of the small foundation pit; and the small foundation pit is provided with a small foundation pit concrete supporting beam for the construction of the small foundation pit. In the construction method, the small foundation pit supporting and excavation process comprises the following steps: constructing the small foundation pit supporting structure, constructing the basement bottom plate in the large foundation pit, removing the large foundation pit concrete supporting beam, constructing the inclined throwing supporting structure, constructing the small foundation pit concrete supporting beam, excavating the earthwork, constructing the basement bottom plate in the small foundation pit, and pouring the support plate, etc. The application can avoid the influence of the construction of the small foundation pit on the existing buildings in the periphery, and the supporting structure and the corresponding construction process can adapt to the coastal geological environment, so that the safety of the entire supporting system is ensured.

Description

Technical Field

[0001] This invention relates to the field of basement construction technology, specifically to a support system and construction method for basement pits of various sizes. Background Technology

[0002] With the rapid development of my country's economy, the development and utilization of urban underground space has become an important part of urban infrastructure construction. Large-scale development of urban underground space inevitably involves construction near existing buildings and structures, giving rise to numerous new geotechnical engineering problems. In the current construction process of buildings, the structural strength of the foundation pit and the degree of impact on surrounding buildings are important indicators for assessing the quality of foundation pit construction.

[0003] In some deep foundation pit projects for coastal buildings, the influence of silty geological environments and the constraints of existing urban rail structures present significant challenges. These challenges include the lack of sufficient space for slope protection, the construction of smaller foundation pits on the periphery of existing large pits, and, in some cases, the lower height of the support structure for the larger pit compared to the smaller pit. Relying solely on the internal concrete supports of the smaller pits is insufficient to guarantee structural stability. Ensuring the safety and stability of new foundation pits while simultaneously controlling ground movement caused by excavation and keeping the impact on the surrounding environment within permissible limits has become a major challenge for industry professionals.

[0004] Therefore, there is a need for a support structure that can provide stable support during the construction of both large and small foundation pits. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a support system and construction method for basement pits of various sizes.

[0006] The technical solution of this invention is as follows:

[0007] A support system for basement excavations of varying sizes, wherein the smaller excavation is located on the periphery of the larger excavation, characterized in that...

[0008] The large foundation pit is surrounded by a large foundation pit support structure, and the small foundation pit is surrounded by a small foundation pit support structure. The height of the large foundation pit capping beam in the large foundation pit support structure is less than the height of the small foundation pit capping beam in the small foundation pit support structure.

[0009] The large foundation pit is also equipped with a sloping support structure to assist the construction of the small foundation pit. The two ends of the sloping support structure abut against the capping beam of the large foundation pit and the basement floor slab inside the large foundation pit, respectively.

[0010] The small foundation pit is equipped with a small foundation pit concrete support beam for the construction of the small foundation pit. The two ends of the small foundation pit concrete support beam abut against the small foundation pit cap beam and the large foundation pit cap beam, respectively.

[0011] According to the present invention based on the above scheme, the small foundation pit support structure includes the small foundation pit capping beam and small foundation pit support piles located below the small foundation pit capping beam; the large foundation pit support structure includes the large foundation pit capping beam and large foundation pit support piles located below the large foundation pit capping beam.

[0012] According to the present invention based on the above scheme, the basement floor slab in the large foundation pit that abuts against the lower end of the inclined support structure is at the same height as the basement floor slab in the small foundation pit.

[0013] According to the present invention based on the above scheme, the inclined support structure includes an inclined steel pipe support, a first support component, and a second support component. The upper end of the inclined steel pipe support is connected to the capping beam of the large foundation pit through the first support component, and its lower end is connected to the basement floor slab inside the large foundation pit through the second support component.

[0014] Furthermore, the first support component includes a first support base and a first embedded connector pre-embedded in the first support base. The first support base is fixedly connected to the capping beam of the large foundation pit, and the first embedded connector is fixedly connected to the inclined steel pipe support.

[0015] Furthermore, the second support component includes a reaction pier, a second pre-embedded connector fixed within the reaction pier, and a movable end of a prestressed steel pipe joint connecting the second pre-embedded connector and the inclined steel pipe support.

[0016] Furthermore, the reaction pier includes a steel reinforcement assembly and a second concrete block cast inside and outside the steel reinforcement assembly. One longitudinal section of the second concrete block is trapezoidal, and the lateral inclination angle of the trapezoid facing the inclined steel pipe support is greater than the lateral inclination angle of the inclined steel pipe support. The longitudinal section of the other side of the second concrete block is an isosceles trapezoid.

[0017] On the other hand, a construction method for a support system for basement pits of varying sizes is characterized by the following steps: after completing the support and excavation of the large pit, the small pit is then supported and excavated. The support and excavation process for the small pit includes:

[0018] S1, Support structure for small foundation pit during construction;

[0019] S2. Complete the construction of the basement floor slab connected to the inclined support structure within the large foundation pit;

[0020] S3. Remove the concrete support beams of the large foundation pit inside the large foundation pit;

[0021] S4. Constructing a sloping support structure within a large foundation pit;

[0022] S5. Construct concrete support beams for the small foundation pit within the small foundation pit;

[0023] S6. Determine the excavation sequence of the small foundation pit according to the on-site construction environment and carry out the excavation.

[0024] S7. Construct the basement floor slab within the excavated small foundation pit, ensuring that the basement floor slab is connected to the support structure of the large foundation pit.

[0025] S8. Cast the replacement support plate between the basement floor slab and the support structure of the small foundation pit.

[0026] According to the present invention based on the above-described scheme, step S4 specifically includes:

[0027] S41. A first support component is installed at the capping beam of the large foundation pit support structure, and a second support component is installed on the basement floor slab connected to the inclined support structure.

[0028] S42. Configure the connecting parts of the inclined steel pipe support according to the length;

[0029] S43. Fix both ends of the inclined steel pipe support to the first support component and the second support component respectively.

[0030] According to the present invention described above, the invention is characterized by further including a step for removing each support:

[0031] A1. Remove the concrete support beams for the small foundation pit;

[0032] A2. Remove the inclined support structure inside the large foundation pit;

[0033] A3. Destroy the large foundation pit support structure that affects the construction of the same floor slab in the large and small foundation pits, and leave a void in the large foundation pit support piles in the remaining large foundation pit support structure in the same floor slab.

[0034] A4. Pour the basement floor slab for the reserved voids.

[0035] According to the above-described scheme, the beneficial effects of this invention are as follows: This invention can support the construction of large foundation pits using a large foundation pit support structure, and support the construction of small foundation pits using a sloping support structure and a small foundation pit support structure. This allows for the completion of small foundation pit construction after the existing large foundation pit construction is finished, while avoiding disturbance and deformation of the surrounding soil layers and preventing the impact of small foundation pit construction on existing buildings. Furthermore, the support structure and corresponding construction process of this invention can adapt to coastal geological environments, ensuring the safety of the entire support system. Attached Figure Description

[0036] Figure 1 This is a top view of the construction system of the present invention;

[0037] Figure 2 This is a schematic diagram showing the distribution of the two-story basement area and the one-story basement area in this invention;

[0038] Figure 3 for Figure 1 A magnified view of a portion of the image;

[0039] Figure 4 for Figure 3 Sectional view of 1-1;

[0040] Figure 5 This is a schematic diagram of the upper connection position of the inclined support structure in this invention;

[0041] Figure 6 This is a schematic diagram of the lower connection position of the inclined support structure in this invention;

[0042] Figure 7 This is a schematic diagram of the reaction pier in this invention;

[0043] Figure 8 for Figure 7 Side sectional view;

[0044] Figure 9 This is a schematic diagram of the structure of the second embedded steel plate in this invention;

[0045] Figure 10 This is a schematic diagram of the side structure of the second embedded steel plate in this invention;

[0046] Figure 11 This is a schematic diagram showing the distribution of construction procedures in this invention.

[0047] In the figure, the labels for each item are as follows:

[0048] A. Large foundation pit; B. Small foundation pit; C. Land boundary line;

[0049] a. Second basement area; a1. Second basement boundary; b. First basement area; b1. First basement boundary;

[0050] 100. Support structure for large foundation pits; 110. Support piles for large foundation pits; 120. Cap beam for large foundation pits;

[0051] 200. Small foundation pit support structure; 210. Small foundation pit plain concrete pile; 220. Small foundation pit support cast-in-place pile; 230. Small foundation pit capping beam; 240. Support bored pile; 250. High-pressure jet grouting water-stopping pile;

[0052] 300. Concrete support beams for large foundation pits;

[0053] 400. Concrete support beam for small foundation pit; 410. Beam bottom cushion layer;

[0054] 500. Inclined support structure; 510. Inclined steel pipe support; 520. First support component; 5211. First concrete block; 5212. Reinforcing mesh; 5221. First embedded steel plate; 5222. Reinforcing bar; 530. Second support component; 5310. Reaction pier; 5311. First threaded steel bar; 5312. Second threaded steel bar; 5313. Closed-loop hoop; 5314. Second concrete block; 5321. Second embedded steel plate; 5322. Embedded anchor bar; 5330. Movable end of prestressed steel pipe joint;

[0055] 610. First-floor basement slab of the large foundation pit; 620. Replacement support slab of the large foundation pit; 630. Backfill area;

[0056] 710. The foundation slab of the first-floor basement of the small foundation pit;

[0057] 810. Shotcrete access road; 820. Temporary excavation access road;

[0058] 910. Drainage ditch; 920. Safety railing; 930. Pipe trench. Detailed Implementation

[0059] The present invention will now be further described with reference to the accompanying drawings and embodiments:

[0060] When facing the specific challenge of constructing a deep foundation pit near the sea, especially when there are existing buildings or other construction sites nearby, the technical requirements for deep foundation pit construction are high and the construction is extremely difficult. Specifically, large-scale development of urban underground space inevitably involves construction near existing buildings and structures. When constructing a new foundation pit, it is necessary not only to ensure the safety and stability of the pit itself, but also to control the movement of nearby strata caused by the excavation, and to ensure that the impact on the surrounding environment is within an acceptable range. Therefore, foundation pit construction in this situation faces enormous challenges.

[0061] by Figure 1 Taking the construction environment shown as an example, the surrounding environment of this foundation pit construction is as follows: To the north of the site, from south to north, are a sightseeing road, a border road, and a waterway; to the south is the foundation pit of a two-story basement under construction; to the east is a tunnel working shaft, relatively close to the boundary line; and to the west is the construction site. There is a 930mm concrete pipe trench next to the sightseeing road on the north side of the foundation pit, but no pipelines are installed inside. The overall geological conditions for construction are: the fill layer on the north side is relatively thick and contains many stones; the silt layer is also thick; the groundwater level is relatively high; and the groundwater on the site is connected to the waterway on the north side. Therefore, the entire foundation pit development faces enormous challenges.

[0062] like Figures 1 to 10As shown, the excavation of a new deep foundation pit disturbs the surrounding soil, causing deformation, which is then transmitted to adjacent structures. This disrupts the original stress balance of the structures, leading to deformation under the redistribution of ground stress, and consequently causing deformation in existing structures. Therefore, to ensure the safety and stability of the foundation pit itself while controlling the movement of nearby strata caused by excavation and keeping its impact on the surrounding environment within acceptable limits, this invention proposes a support system for basement foundation pits of varying sizes. This system utilizes a combined internal and external support structure to reduce the impact of small foundation pit excavation on nearby coastlines and existing basements, while simultaneously ensuring the safety of the foundation pit's support system.

[0063] This support system for basement excavations includes a large excavation pit A and a small excavation pit B, with the small excavation pit B located outside the large excavation pit A. This embodiment is based on the completed excavation of the large excavation pit A and the construction of the lower floor slab. Specifically, the large excavation pit A contains a two-story basement area a (with the floor slab already constructed) and a one-story basement area b (not yet constructed).

[0064] During the excavation of the large foundation pit, a large foundation pit support structure 100 is installed around the perimeter of the large foundation pit A. Inside the large foundation pit support structure 100, there is a partial first-floor basement area b, the inner edge of which is the boundary line a1 of the second-floor basement. After the excavation of the large foundation pit A and the construction of the outer wall of the support piles, a small foundation pit B is excavated. A small foundation pit support structure 200 is installed around the perimeter of the small foundation pit B. Inside the small foundation pit support structure 200 is a first-floor basement area b, and the inner edge of the small foundation pit support structure 200 is the boundary line b1 of the first-floor basement. The challenge faced by this invention is that the height of the large foundation pit capping beam 120 in the large foundation pit support structure 100 is less than the height of the small foundation pit capping beam 230 in the small foundation pit support structure 200. Relying solely on the small foundation pit support structure 200 and the concrete supports inside the small foundation pit B is insufficient to support the perimeter of the small foundation pit B. Simultaneously, the perimeter of the small foundation pit B has existing building structures, is adjacent to the land boundary line C, and has no space for slope protection.

[0065] The support system for basement pits of varying sizes includes: a large pit concrete support beam 300 located within the large pit and used for its construction; a sloping support structure 500 located within the large pit and used to assist in the construction of smaller pits; and a small pit concrete support beam 400 located within the small pit and used for its construction. This invention primarily utilizes the small pit support structure 200, the sloping support structure 500, and the small pit concrete support beam 400 to provide support during the construction of smaller pits. Specifically, the two ends of the large pit concrete support beam 300 abut against the large pit support structure 100; the two ends of the sloping support structure 500 abut against the large pit capping beam 120 and the basement floor slab within the large pit, respectively; and the two ends of the small pit concrete support beam 400 abut against the small pit capping beam 230 and the large pit capping beam 120, respectively. A 100mm thick beam bottom pad layer 410 is also provided on the underside of the small pit concrete support beam 400.

[0066] The large foundation pit support structure 100 is an existing support structure, which includes a large foundation pit capping beam 120 and large foundation pit support piles 110 located below the large foundation pit capping beam 120. In this embodiment, the elevation of the large foundation pit capping beam 120 is 1.7m.

[0067] The small foundation pit support structure 200 includes a small foundation pit capping beam 230 and small foundation pit support piles located below the small foundation pit capping beam 230. In this embodiment, the elevation of the small foundation pit capping beam 230 is 2.5m, which has a certain height difference with the large foundation pit capping beam 120, so that the two ends of the large foundation pit concrete support beam 300 are connected to the large foundation pit capping beam 120 and the small foundation pit capping beam 230 respectively, forming a certain inclination angle. In the specific construction process, the small foundation pit support piles include interlocking pile sections and non-interlocking pile sections. The interlocking pile sections of the small foundation pit support piles include several small foundation pit plain concrete piles 210, and small foundation pit support cast-in-place piles 220 are provided between two adjacent small foundation pit plain concrete piles 210; the non-interlocking pile sections of the small foundation pit support piles include several support bored piles 240, and high-pressure jet grouting water-stopping piles 250 are provided between two adjacent support bored piles 240.

[0068] The basement floor slab in the large foundation pit, which abuts against the lower end of the inclined support structure 500, is at the same height as the basement floor slab in the small foundation pit. Specifically, in this embodiment, within the large foundation pit, the elevation of the second-floor basement area is -9.9m, and the elevation of the first-floor basement area (here, the elevation after the completion of the first-floor basement floor slab 610 of the large foundation pit) is -2.0m; within the small foundation pit, the elevation after excavation is -2.6m, and the elevation after the completion of the basement floor slab in the small foundation pit is also -2.0m.

[0069] Please see Figures 3 to 10The inclined support structure 500 includes an inclined steel pipe support 510 (using ∅610x16 steel pipe), a first support component 520, and a second support component 530. The upper end of the inclined steel pipe support 510 is connected to the large foundation pit cap beam 120 through the first support component 520, and its lower end passes through the large foundation pit concrete support beam 300 and is connected to the basement floor slab inside the large foundation pit through the second support component 530.

[0070] Specifically, the first support component 520 includes a first support base and a first embedded connector pre-embedded in the first support base. The first support base is fixedly connected to the large foundation pit cap beam 120, and the first embedded connector is fixedly connected to the inclined steel pipe support 510. The connection with the large foundation pit cap beam 120 is achieved through the first support base, and the fixation of the inclined steel pipe support 510 to the first support base is achieved through the first embedded connector.

[0071] The first support includes a steel mesh 5212 and a first concrete block 5211 cast inside and outside the steel mesh 5212 and formed. The lower apex angle of the first concrete block 5211 is an acute angle (in this embodiment, the included angle is 17° to 23°), so that the outer side of the first concrete block 5211 contacts the cap beam 120 of the large foundation pit, and its inner side slopes downward and contacts the first pre-embedded connector.

[0072] The first embedded connector includes a first embedded steel plate 5221 and a reinforcing bar 5222 welded to the side of the first embedded steel plate 5221. The reinforcing bar 5222 passes through the first support seat and extends into the capping beam 120 of the large foundation pit. The angle between the reinforcing bar 5222 and the first embedded steel plate 5221 located below it is an acute angle (this acute angle is complementary to the lower apex angle of the first concrete block 5211).

[0073] Specifically, the second support component 530 includes a reaction pier 5310, a second pre-embedded connector fixed in the reaction pier 5310, and a movable end 5330 of a prestressed steel pipe joint connecting the second pre-embedded connector and the inclined steel pipe support 510. The reaction pier 5310 is fixed on the basement floor of the large foundation pit and provides support force for the inclined steel pipe support 510. The second pre-embedded connector is used to connect the reaction pier 5310 and the movable end 5330 of the prestressed steel pipe joint, and the movable end 5330 of the prestressed steel pipe joint is used to provide support force for the inclined steel pipe support 510.

[0074] The reaction pier 5310 includes a reinforcing steel assembly and a second concrete block 5314 cast inside and outside the reinforcing steel assembly. One longitudinal section of the second concrete block 5314 is trapezoidal, and the angle of inclination of the side facing the inclined steel pipe support 510 is greater than the angle of inclination of the side facing the inclined steel pipe support 510. The longitudinal section of the other side of the second concrete block 5314 is an isosceles trapezoid. The side facing the inclined steel pipe support 510 is perpendicular to the extension direction of the inclined steel pipe support 510. The reinforcing steel assembly includes several first threaded steel bars 5311 arranged side-by-side, several second threaded steel bars 5312 arranged side-by-side, and a closed-loop hoop 5313 located inside the first threaded steel bars 5311 and second threaded steel bars 5312. The plane containing the first threaded steel bars 5311 is perpendicular to the plane containing the second threaded steel bars 5312.

[0075] The second embedded connector includes a second embedded steel plate 5321 and an embedded anchor bar 5322 welded to the side of the second embedded steel plate 5321 and embedded in the reaction pier 5310. The embedded anchor bar 5322 is perpendicular to the surface of the second embedded steel plate 5321.

[0076] In one specific embodiment, the perimeter of the small foundation pit is provided with a drainage ditch 910 for drainage, a safety railing 920 for protection, and a cable trench 930 for cable laying. The heights of the drainage ditch 910, safety railing 920, and cable trench 930 are all higher than the top of the capping beam 230 of the small foundation pit. In addition, in order to carry out excavation work in the corresponding area, an excavation channel is also provided along the outer edge of the small foundation pit. Specifically, a shotcrete channel 810 is provided around the perimeter of the small foundation pit, and a temporary excavation channel 820 is provided near the outer edge of the shotcrete channel 810 and the outer side of the small foundation pit.

[0077] like Figures 1 to 11 As shown, the present invention also provides a construction method for the above-mentioned support system for basement pits of various sizes, specifically for the excavation process of small pits. Please refer to [link to details]. Figure 11 After the support and excavation of the large foundation pit are completed, the support and excavation of the small foundation pit are carried out.

[0078] The process of supporting and excavating small foundation pits includes:

[0079] S1, Construction small foundation pit support structure 200.

[0080] For areas with abundant adjacent rockfill, interlocking piles are used for construction, while non-interlocking piles are used in other areas. Specifically, when constructing the small foundation pit support piles for the interlocking pile section, plain concrete piles 210 are constructed first, followed by reinforced concrete cast-in-place piles 220. When constructing the small foundation pit support piles for the non-interlocking pile section, bored piles 240 are constructed first, followed by high-pressure jet grouting water-stopping piles 250 between the piles.

[0081] S2. Complete the construction of the basement floor slab connected to the inclined support structure 500 in the large foundation pit.

[0082] This refers to the construction of the basement slab 610 of the first floor of the large foundation pit. Before construction, a replacement support slab 620 is constructed in this target area of ​​the large foundation pit. Then, stone powder or excavated soil is backfilled and compacted to form a backfill area 630. Finally, the basement slab 610 of the first floor of the large foundation pit is laid. Preferably, C25 concrete is used to pour and form a 600mm thick replacement support slab 620.

[0083] The basement floor slab 610 of the large foundation pit is at the same height as the basement floor slab 710 of the small foundation pit, both being -2.0m.

[0084] S3. Remove the 300mm concrete support beam of the large foundation pit inside the large foundation pit.

[0085] S4. Construct a 500mm inclined support structure within the large foundation pit. Specifically, this includes:

[0086] S41. A first support component 520 is installed at the position of the large foundation pit capping beam 120 of the large foundation pit support structure 100, and a second support component 530 is installed on the basement floor slab connected to the inclined support structure 500.

[0087] S42. Configure the connecting parts of the inclined steel pipe support 510 according to its length, specifically including the steel pipe support, fixed head, and hinged head. After connection, apply prestress, with a prestress of 50KN applied to each support beam; in addition, wedge the pad in the hinged head and weld the support end firmly.

[0088] S43. Fix both ends of the inclined steel pipe support 510 to the first support component 520 and the second support component 530 respectively.

[0089] During the later dismantling process, the inclined steel pipe support 510 was removed first, followed by the removal of the first support assembly 520 and the second support assembly 530 on both sides. Specifically, the support stress was first released, the flexible ends were loosened, and the supports were dismantled one by one from both sides towards the middle, and then lifted out of the pit.

[0090] S5. Construct a 400mm concrete support beam for the small foundation pit within the small foundation pit.

[0091] S6. Determine the excavation sequence of the small foundation pit according to the on-site construction environment and carry out the excavation.

[0092] After the strength of each support structure reaches the design requirements, the earthwork excavation in the small foundation pit is carried out. During the excavation process, it is carried out in layers and sections. The foundation layer and the bottom slab are constructed in a timely manner at the bottom slab position after the excavation reaches the bottom.

[0093] During the excavation of the small foundation pit, it is essential to continuously monitor the deformation data of the pit. Specific monitoring content includes:

[0094] (1) Observation of horizontal displacement and settlement at the top of the pit: The horizontal displacement is set at the top of the pile, and the settlement point is set at the top of the monitoring pit support structure to monitor the change of horizontal displacement as the pit is excavated and used.

[0095] (2) Settlement observation of pit top and building: Set up on the top of the slope and building to monitor the ground settlement changes of the pit top and building as the pit is excavated and used.

[0096] (3) Groundwater level monitoring.

[0097] (4) Deep horizontal displacement monitoring: The hole depth inside the installed support pile shall not be less than the depth of the pile bottom.

[0098] (5) Support stress monitoring: Installed in the waist beam and support for monitoring the stress of steel bars.

[0099] (6) Monitoring of column settlement.

[0100] S7. Construct the basement floor slab within the excavated small foundation pit, ensuring that the basement floor slab is connected to the large foundation pit support structure 100.

[0101] S8. Pour the replacement support plate between the basement floor slab and the small foundation pit support structure 200mm inside the small foundation pit.

[0102] The replacement support plate is 400mm thick, and its strength is the same as that of the basement floor slab of the small foundation pit.

[0103] In addition, the construction method of the present invention also includes the step of removing each support:

[0104] A1. Remove the 400mm concrete support beam for the small foundation pit;

[0105] A2. Remove the inclined support structure within the large foundation pit (500 mm).

[0106] A3. Destroy the large foundation pit support structure 100 that affects the construction of the same floor slab in the large and small foundation pits, and leave a cavity in the large foundation pit support pile 110 of the remaining large foundation pit support structure 100 in the same floor slab.

[0107] A4. Pour the basement floor slab for the reserved voids.

[0108] This invention utilizes a 500mm inclined support structure and a 200mm small foundation pit support structure to support the surrounding small foundation pit. This ensures the pit's own safety and stability while controlling the impact of small foundation pit construction on adjacent buildings (urban rail). Furthermore, the aforementioned structure and process significantly reduce construction costs and shorten the construction period, effectively controlling the impact of deep foundation pit construction on adjacent urban rail, thus achieving good economic benefits.

[0109] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

[0110] The present invention has been described above with reference to the accompanying drawings. Obviously, the implementation of the present invention is not limited to the above-described manner. Any improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A support system for basement excavations of varying sizes, wherein the smaller excavation is located on the periphery of the larger excavation, characterized in that, The large foundation pit is surrounded by a large foundation pit support structure, and the small foundation pit is surrounded by a small foundation pit support structure. The height of the large foundation pit capping beam in the large foundation pit support structure is less than the height of the small foundation pit capping beam in the small foundation pit support structure. The large foundation pit support structure includes the large foundation pit capping beam and large foundation pit support piles located below the large foundation pit capping beam; the small foundation pit support structure includes the small foundation pit capping beam and small foundation pit support piles located below the small foundation pit capping beam. The large foundation pit is also equipped with a sloping support structure to assist the construction of the small foundation pit. The two ends of the sloping support structure abut against the capping beam of the large foundation pit and the basement floor slab in the large foundation pit, respectively. The basement floor slab in the large foundation pit that abuts against the lower end of the sloping support structure is at the same height as the basement floor slab of the small foundation pit. The inclined support structure includes an inclined steel pipe support, a first support assembly, and a second support assembly. The upper end of the inclined steel pipe support is connected to the capping beam of the large foundation pit through the first support assembly, and its lower end is connected to the basement floor slab inside the large foundation pit through the second support assembly. The first support assembly includes a first support base and a first embedded connector pre-embedded in the first support base. The first support base is fixedly connected to the capping beam of the large foundation pit, and the first embedded connector is fixedly connected to the inclined steel pipe support. The second support assembly includes a reaction pier, a second embedded connector fixed in the reaction pier, and a movable end of a prestressed steel pipe joint connecting the second embedded connector to the inclined steel pipe support. The small foundation pit is equipped with a small foundation pit concrete support beam for the construction of the small foundation pit. The two ends of the small foundation pit concrete support beam abut against the small foundation pit cap beam and the large foundation pit cap beam, respectively.

2. The support system for basement pits of various sizes according to claim 1, characterized in that, The reaction pier includes a steel reinforcement assembly and a second concrete block cast inside and outside the steel reinforcement assembly. One longitudinal section of the second concrete block is trapezoidal, and the lateral inclination angle of the trapezoid facing the inclined steel pipe support is greater than the lateral inclination angle away from the inclined steel pipe support. The longitudinal section of the other side of the second concrete block is an isosceles trapezoid.

3. A construction method for a support system for basement pits of various sizes as described in claim 1, characterized in that, After completing the support and excavation of the large foundation pit, the smaller foundation pits are then supported and excavated. The support and excavation process for the smaller foundation pits includes: S1, Support structure for small foundation pit during construction; S2. Complete the construction of the basement floor slab connected to the inclined support structure within the large foundation pit; S3. Remove the concrete support beams of the large foundation pit inside the large foundation pit; S4. Constructing a sloping support structure within a large foundation pit; S5. Construct concrete support beams for the small foundation pit within the small foundation pit; S6. Determine the excavation sequence of the small foundation pit according to the on-site construction environment and carry out the excavation. S7. Construct the basement floor slab within the excavated small foundation pit, ensuring that the basement floor slab is connected to the support structure of the large foundation pit. S8. Cast the replacement support plate between the basement floor slab and the support structure of the small foundation pit.

4. The construction method for the support system for basement pits of various sizes according to claim 3, characterized in that, Step S4 specifically includes: S41. A first support component is installed at the capping beam of the large foundation pit support structure, and a second support component is installed on the basement floor slab connected to the inclined support structure. S42. Configure the connecting parts of the inclined steel pipe support according to the length; S43. Fix both ends of the inclined steel pipe support to the first support component and the second support component respectively.

5. The construction method for the support system for basement pits of various sizes according to claim 3, characterized in that, It also includes the steps for dismantling each support: A1. Remove the concrete support beams for the small foundation pit; A2. Remove the inclined support structure inside the large foundation pit; A3. Destroy the large foundation pit support structure that affects the construction of the same floor slab in the large and small foundation pits, and leave a void in the large foundation pit support piles in the remaining large foundation pit support structure in the same floor slab. A4. Pour the basement floor slab for the reserved voids.

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