Construction method for arranging underground garage for existing building based on open caisson

Abstract

The invention discloses a construction method for arranging an underground garage for an existing building based on an open caisson, and belongs to the field of building construction. According to the method, an open caisson is arranged between two adjacent existing buildings, the two ends of the cross section of the open caisson in the length direction are semicircular channels, the two sides of the cross section of the open caisson in the width direction are a plurality of arch walls continuously protruding outwards, and standard knots are formed between the opposite arch walls on the two sides. The construction method comprises the steps that the plane size of the open caisson is determined according to existing building foundation arrangement and spacing; a working pit extending to the position below the existing building is excavated; a first section of open caisson is poured in the working pit, so that the arch wall is located below the foundation beam; foundation soil is excavated, and the open caisson sinks and is poured and lengthened through the dead weight of the open caisson and the downward pressure of the existing building; the sinking and lengthening steps are repeated, and a temporary channel and a floor slab are manufactured; and the working pit is backfilled after construction is completed. According to the method, counter-force beams are omitted, floor slabs are manufactured synchronously to improve the open caisson strength and reduce the water and soil pressure influence, material transfer is achieved through the semicircular channels, and construction is efficient, safe and reliable.

Description

Technical Field

[0001] This invention relates to the field of building construction, and in particular to a construction method for setting up underground parking garages in existing buildings based on caissons. Background Technology

[0002] In many office or residential buildings, storage rooms are typically located directly beneath the building, while underground parking is usually installed around the perimeter. For existing buildings without underground parking, caisson technology is often used to add three-dimensional mechanical parking garages. Traditional caisson technology is a deep foundation excavation technique that involves excavating soil within the caisson to lower the shaft. The shaft is then continuously extended at ground level until the design elevation is reached.

[0003] Using caissons to create underground spaces around existing buildings, the caisson walls act as supports, reducing the impact of earthwork excavation on the existing structures. However, when the caisson has a large cross-section and the soil is hard, it is difficult to achieve sinking by relying solely on the caisson's own weight to overcome the lateral resistance between the caisson's outer wall and the soil.

[0004] Patent ZL202510239646.3 discloses a method for constructing underground space in the vicinity of existing buildings using caissons. This method involves setting up a reaction beam between two adjacent existing buildings and using jacks to assist in the caisson's sinking. However, when the two existing buildings are far apart, the reaction beam requires a large cross-sectional size. Furthermore, existing caissons use a vertically connected cylinder to transport excavated soil to the ground surface. The caisson's base slab and horizontal beams and slabs of each level also need to be transported to the construction surface via the vertically connected cylinder. When the cylinder is deep, transportation becomes difficult. Since the horizontal pressure generated by water and soil is proportional to the square of the caisson depth, when there are many caisson layers and the cylinder is deep, it is challenging to bear this horizontal load solely through the transverse walls of the connecting sections of a continuous arched composite section caisson. Summary of the Invention

[0005] This invention addresses the problems of current construction methods that use reaction beams to press down on caissons, which require increasing the length and cross-sectional dimensions of the reaction beams when the existing building has a large span, as well as the high water and soil pressure. It provides a construction method for setting up underground parking garages for existing buildings based on caissons.

[0006] To solve the above problems, the technical solution adopted by the present invention is a construction method for setting up an underground parking garage for existing buildings based on a caisson. The caisson is set between two adjacent existing buildings. The cross-section of the caisson is set as a semi-circular channel at both ends in the length direction and as multiple continuously outwardly protruding arch walls on both sides in the width direction. The standard section of the caisson is formed between the opposite arch walls on both sides. The construction method includes the following steps: S1. Determine the planar dimensions of the caisson according to the foundation layout and spacing of the existing buildings; S2. According to the dimensions of the caisson, excavate a working pit between the existing buildings, and the working pit extends to the bottom of the existing buildings on both sides. S3. Pour the first section of the caisson in the working pit, with the arch walls on both sides of the caisson located below the foundation beams of the existing buildings on both sides; S4. Excavate the foundation soil below the caisson, and use the caisson's own weight and the downward pressure of the existing buildings on both sides to make the caisson sink; S5. Pour the extension above the caisson; S6. Repeat steps S4-S5 to complete the construction of the caisson to the set depth. Each time the extension is completed, a temporary passage connecting the bottom and top of the caisson is made in the semi-circular channel; during multiple extensions, floor slabs are periodically made in the standard sections; S7. After completing the construction of the caisson to the set depth, backfill the working pit between the top of the caisson and the bottom of the existing buildings. This construction method utilizes the continuous arched shape of the caisson, placing the arch wall beneath the existing building. The existing building directly applies downward pressure to the arch wall, eliminating the need for reaction beams. During the caisson construction, the floor slabs of the underground building and the ramps between adjacent floor slabs are constructed simultaneously, creating a frame-like infill structure inside the caisson. This not only improves the strength of the caisson and greatly reduces the impact of external water and soil pressure on it, but also eliminates the need for separate floor slab construction later. Furthermore, the existing semi-circular passageway of the caisson serves as a transfer channel for foundation soil and equipment, solving the problem of inconvenient vertical transfer at great depths.

[0007] As a preferred implementation of a construction method for setting up underground parking garages for existing buildings based on caissons, in step S6, the foundation soil is transported out via a ramp, and building materials are transported in. The transfer of foundation soil and building materials is directly achieved via the ramp, eliminating the need for additional vertical transportation facilities. This completely solves the problem of inconvenient vertical transfer in the construction of deep caissons, while simplifying the transportation process, reducing safety hazards during transfer, and significantly improving construction efficiency.

[0008] As a preferred implementation scheme for a construction method of setting up an underground parking garage for an existing building based on a caisson, the existing building includes multiple independent foundations. Each independent foundation is a columnar structure embedded in the ground. Multiple independent foundations are arranged at both ends and the middle of a foundation beam, with equal spacing between adjacent foundations. The upper end of each independent foundation is connected to the foundation beam. In step S1, the number of standard sections corresponds to the number of independent foundations, with one standard section between every two adjacent independent foundations. The semi-circular passage is located on the outside of the existing building. The one-to-one arrangement of standard sections and independent foundations ensures precise adaptation between the caisson structure and the existing building's foundation load-bearing system, avoiding local disturbance to the independent foundations during construction. The semi-circular passage, located on the outside of the building, does not occupy the core construction space between buildings while meeting the vehicle passage requirements between the upper and lower levels of the underground parking garage, maximizing the use of open space resources between existing buildings.

[0009] As a preferred implementation scheme for a construction method of setting up an underground parking garage for an existing building based on a caisson, the distance between the arch feet of the two arch walls is the length L of the standard section, and the distance between the outer edges of the two existing buildings is K, satisfying KL≥200mm; the spacing between the two ends of the same arch wall is the width B of the standard section, and B is equal to the spacing between two adjacent foundation beams in the existing building; the arch height of the arch wall is... A 200mm safety distance effectively prevents planar collisions between the caisson and the outer edge of the existing building, ensuring foundation stability; the B-value being consistent with the spacing of the foundation beams makes the caisson more evenly stressed; the precisely calculated arch height ensures that the arch wall is in the optimal stress state, fully utilizing the compressive strength of the material, reducing the amount of reinforcement, lowering building material costs, and ensuring the stress coordination between the arch wall and the foundation beams.

[0010] As a preferred implementation scheme for the construction method of setting up underground parking garages for existing buildings based on caissons, the arch crown of the arch wall is located below the foundation beam. In step S4, jacks are installed between the arch crown of the arch wall and the foundation beam, and the caisson is pressed down using the jacks. By actively applying downward pressure with the help of the jacks, combined with the self-weight of the caisson and the downward pressure of the existing building, the triple force works together to overcome the lateral resistance between the outer wall of the caisson and the soil, solving the problem of difficult sinking when the caisson cross-section is large and the soil is hard, greatly accelerating the sinking speed of the caisson and shortening the construction period.

[0011] As a preferred implementation scheme for constructing underground parking garages for existing buildings based on caissons, during construction, settlement monitoring is conducted on the side of the existing building adjacent to the working pit. In step S7, based on the settlement depth of the existing building, jacks are used to lift the existing building, and micro-expansion concrete is filled between the top of the caisson and the bottom of the existing building. After the micro-expansion concrete has cured to the required strength, the jacks are removed, and the original jack positions are filled with micro-expansion concrete. Real-time settlement monitoring can promptly detect potential settlement hazards in the existing building, the jack lifting can accurately correct settlement displacement, and the filling and compaction of micro-expansion concrete ensures a tight connection between the caisson and the bottom of the existing building, avoiding gaps that could lead to structural deformation later, forming a stable support system, and ensuring the long-term structural safety of the existing building.

[0012] As a preferred implementation scheme for a construction method of setting up an underground parking garage for an existing building based on a caisson, in step S6, when constructing the floor slab, a connecting wall is simultaneously constructed between adjacent standard sections. The upper and lower edges of the connecting wall are connected to the floor slab, and a connecting door is provided on the connecting wall. The connecting wall and the floor slab form an integral frame structure, which significantly improves the overall rigidity and lateral displacement resistance of the caisson and enhances its resistance to water and soil pressure. The connecting door enables spatial connection between the standard sections, which not only facilitates the passage of personnel and equipment during construction but also meets the vehicle passage requirements when the underground parking garage is in use, without the need for additional tunnel excavation later.

[0013] As a preferred implementation scheme for constructing underground parking garages for existing buildings based on caissons, in step S6, a steel beam is installed at regular intervals between the inner and outer walls of the semi-circular passage. Temporary slabs are laid on the steel beams to form a temporary passage for transporting foundation soil and equipment. When constructing the floor slabs, steel bars are tied above the temporary slabs and concrete is poured to form a permanent ramp connecting the upper and lower floor slabs. After the concrete has cured, the steel beams and temporary slabs are removed and transported to the upper caisson for repeated construction and reuse. The temporary passage is constructed quickly, ensuring the continuity of foundation soil and equipment transportation and solving the problem of deep transportation. The temporary slabs also serve as formwork for the later pouring of the permanent ramp, eliminating the repetitive process of formwork construction, saving formwork costs, and the steel beams and slabs can be reused, reducing construction costs and achieving efficient connection between temporary facilities and permanent structures.

[0014] As a preferred implementation of a construction method for setting up underground parking garages in existing buildings based on caissons, the temporary paving slab includes multiple temporary inclined slabs, with a temporary flat plate on top of the inclined slabs, flush with the top of the caisson. The temporary inclined slabs adapt to the slope requirements of the ramp, and the temporary flat plate is flush with the top of the caisson, ensuring smooth driving for construction vehicles entering and exiting the caisson, reducing bumps and safety risks during transportation, while improving transfer efficiency and ensuring the orderly progress of construction.

[0015] As a preferred implementation scheme for constructing underground parking garages for existing buildings based on caissons, during settlement monitoring, if the settlement depth exceeds the set depth, the jacking pressure is increased to support the existing building through the caisson. After backfilling with micro-expansion concrete, if voids appear between the independent foundation and the foundation soil, pressure grouting is injected into these voids. When settlement exceeds the standard, increasing the jacking pressure, with the caisson as support, quickly curbs the settlement of the existing building and prevents the potential for further damage. Pressure grouting effectively fills the voids between the independent foundation and the foundation soil, restores the bearing capacity of the foundation, prevents secondary settlement of the building, and further strengthens the collaborative support system between the existing building and the caisson.

[0016] As can be seen from the above technical solutions, the beneficial effects of this invention are as follows: This construction method constructs the caisson arch wall beneath the existing building, eliminating the need for additional reaction beams. It utilizes the downward pressure from the existing building in conjunction with the caisson's own weight, combined with active pressure from jacks. This triple force synergistically overcomes the lateral resistance of the caisson's outer wall, efficiently solving the sinking problem when the caisson has a large cross-section and hard soil, significantly shortening the construction period. The caisson dimensions are precisely matched to the existing building foundation layout, the number of standard sections corresponds to the independent foundation, and a safety distance of KL≥200mm ensures foundation stability. The arch wall parameters are optimized to achieve the best stress state, fully utilizing the material's compressive strength, reducing reinforcement requirements and building material costs, while maximizing the use of open space between buildings. The caisson construction is combined with the construction of the internal building space after the caisson is completed, with floor slabs and connecting walls being constructed simultaneously during construction. This design forms an overall frame structure, significantly improving the rigidity and lateral displacement resistance of the caisson, and enhancing its resistance to water and soil pressure. The connecting door and the outer semi-circular passage meet the needs of the underground parking garage without requiring additional excavation. A transfer channel is formed using the existing caisson passage and temporary steel beams and slabs. The temporary slabs also serve as permanent ramp formwork and are reusable, completely solving the problem of inconvenient vertical transfer at great depths. This simplifies the process and saves on formwork and construction costs. The temporary inclined slabs and the temporary flat slabs flush with the top of the caisson ensure smooth and efficient transportation. Through full-process settlement monitoring and the dual application of jacks, potential hazards can be quickly contained when settlement exceeds the standard, and precise jacking and correction can be achieved. Combined with micro-expansion concrete backfilling and void pressure grouting, a stable support system is formed, preventing structural deformation and secondary settlement, and ensuring the long-term structural safety of the existing building. Attached Figure Description

[0017] To more clearly illustrate the technical solution of this patent, the drawings used in the description will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this patent. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1This is a structural diagram of the existing building before construction, as shown in a specific embodiment of the present invention.

[0019] Figure 2 This is a top view of the caisson in a specific embodiment of the present invention.

[0020] Figure 3 This is a cross-sectional view in the main view direction during the pouring of the first section of the caisson in a specific embodiment of the present invention.

[0021] Figure 4 This is a cross-sectional view from the side during the pouring of the first section of the caisson in a specific embodiment of the present invention.

[0022] Figure 5 This is a cross-sectional view from the side during the sinking of the caisson in a specific embodiment of the present invention.

[0023] Figure 6 This is a cross-sectional view of the floor slab from the rear side in a specific embodiment of the present invention.

[0024] Figure 7 This is a schematic diagram of the temporary channel in a specific embodiment of the present invention.

[0025] Figure 8 This is a sectional view from the side after construction is completed in a specific embodiment of the present invention.

[0026] Explanation of main figure symbols 00. Existing building, 01. Caisson, 02. Foundation, 1. Standard section, 2. Semicircular passage, 3. Arch wall, 4. Working pit, 5. Floor slab, 6. Ramp, 7. Independent foundation, 8. Foundation beam, 9. Jack, 10. Connecting wall, 11. Connecting door, 12. Steel beam, 13-1. Temporary inclined plate, 13-2. Temporary flat plate, 14. Pad block. Detailed Implementation

[0027] To make the objectives, features, and advantages of this patent more apparent and understandable, the technical solutions of this patent will be clearly and completely described below with reference to the accompanying drawings of the specific embodiments. Obviously, the embodiments described below are only some embodiments of this patent, and not all embodiments. Based on the embodiments of this patent, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this patent.

[0028] like Figure 1-8As shown, a construction method for setting up an underground parking garage for an existing building based on a caisson is disclosed. The caisson 01 is set between two adjacent existing buildings 00. The cross-section of the caisson 01 is configured as a semi-circular channel 2 at both ends in the length direction, and multiple continuously outwardly protruding arch walls 3 on both sides in the width direction. The standard section 1 of the caisson 01 is formed between the two opposing arch walls 3. The construction method includes the following steps: S1. Determine the plan dimensions of caisson 01 based on the foundation layout and spacing of existing building 00; The existing building 00 includes multiple independent foundations 7, each of which is a columnar structure embedded in the ground. Multiple independent foundations 7 are arranged at both ends and the middle of the foundation beam 8, and the spacing between adjacent independent foundations 7 is equal. The upper end of the independent foundation 7 is connected to the foundation beam 8. The number of standard sections 1 corresponds to the number of independent foundations 7, and a standard section 1 is set between every two adjacent independent foundations 7. The semi-circular passage 2 is located on the outside of the existing building 00, which can realize vehicle passage between upper and lower floors. The distance between the arch feet of the two arch walls 3 is the length L of the standard section 1, and the distance between the outer edges of the two existing building 00s is K, satisfying KL≥200mm to avoid planar conflict between the caisson 01 and the foundation of the existing building 00; the distance between the two ends of the same arch wall 3 is the width B of the standard section 1, and B is equal to the distance between two adjacent foundation beams 8 in the existing building 00; the arch height of the arch wall 3 is... This size design ensures that the arch wall 3 is in the optimal stress state, giving full play to the compressive strength of the material; The outer arch wall in the third span must be located directly below the foundation beam in the eighth span. Based on this principle, the specific value of L should be reasonably calibrated. S2. According to the dimensions of the caisson 01, excavate the working pit 4 between the existing buildings 00. The working pit 4 is excavated to the bottom of the foundation (to avoid further excavation affecting the stability of the foundation) and extends to the bottom of the existing buildings 00 on both sides; the vertical distance from the bottom of the foundation to the bottom of the foundation beam 8 is used as the space for pouring the caisson 01 and placing the jacks 9. S3. Pour the first section of caisson 01 in the working pit 4. The height of the first section of caisson 01 is the net height from the bottom of the foundation beam 8 to the bottom of the working pit 4 minus the height of the jack 9. The bottom of the outer wall of caisson 01 is constructed with a cutting edge to facilitate cutting into the soil. Reinforcing bars are tied along the outer wall edge of caisson 01, formwork is erected, and concrete is poured. Lap reinforcement bars for extending the wall are left at the top of the wall. After the caisson 01 is poured, ensure that the arch walls 3 on both sides of caisson 01 are located below the foundation beams 8 of the existing buildings 00 on both sides. The foundation beams 8 need to be checked for bearing capacity. If the bearing capacity is insufficient, the beams need to be reinforced. S4. Excavate the foundation soil below the caisson 01 and use the weight of the caisson 01 itself and the downward pressure of the existing buildings 00 on both sides to make the caisson 01 sink. The arch of the arch wall 3 is located below the foundation beam 8. A jack 9 is installed between the arch of the arch wall 3 and the foundation beam 8. The jack 9 is used to press down the caisson 01, and the pressing process is carried out simultaneously with the excavation process. When the piston of the jack 9 completes one stroke, the piston retracts. A pad block 14 of one stroke height is inserted between the jack 9 and the foundation beam 8 to ensure that the jack 9 continues to press down the caisson 01 until the first section of the caisson 01 is submerged in the bottom of the working pit 4. S5. Cast the extension above the caisson 01, and use the lapped steel bars reserved at the top of the wall to connect the walls during the extension process; S6. Repeat steps S4-S5 to complete the construction of the caisson 01 at the set depth. Each time it is extended, a temporary passage connecting the bottom and top of the caisson 01 is made in the semi-circular passage 2. During multiple extensions, floor slabs 5 are periodically made in the standard section 1. As the caisson 01 is extended, after the opening at the top of the caisson 01 is closed by the floor slab 5, the foundation soil is transported out via the ramp 6 and building materials are transported in. When constructing floor slab 5, a connecting wall 10 is constructed between adjacent standard sections 1. The upper and lower edges of the connecting wall 10 are connected to floor slab 5 to form an overall load-bearing system. A connecting door 11 is provided on the connecting wall 10 to allow vehicles and personnel to pass through the garage. A steel beam 12 is installed at regular intervals between the inner and outer walls of the semicircular passage 2. The two ends of the steel beam 12 are inserted into the reserved holes in the inner and outer walls of the semicircular passage 2. Temporary slabs are laid on the steel beam 12 to form a temporary passage for transporting foundation soil and equipment. When constructing the floor slab 5, steel bars are tied above the temporary slabs and concrete is poured to form a permanent ramp 6 connecting the upper and lower floor slabs 5. After the concrete has cured to the design strength, the steel beam 12 and the temporary slabs are removed and transported to the upper caisson 01 for repeated construction and use. The temporary paving includes multiple temporary inclined slabs 13-1, and a temporary flat plate 13-2 is provided on the top of the temporary inclined slabs 13-1. The temporary flat plate 13-2 is flush with the top of the caisson 01, forming a complete temporary passage for construction vehicles to enter and exit. As the caisson 01 is continuously extended upward, the temporary inclined slabs 13-1 are continuously extended upward, and the temporary flat plate 13-2 moves forward synchronously until the construction of this layer of caisson 01 is completed. S7. After the construction of the caisson 01 at the set depth is completed, stop the excavation, first set the bottom plate of the caisson 01, and then backfill the working pit 4 between the top of the caisson 01 and the bottom of the existing building 00. During construction, settlement monitoring is conducted on the side of the existing building 00 adjacent to the working pit 4. Based on the settlement depth of the existing building 00, jack 9 is used to lift the existing building 00. If the foundation settlement of the existing building 00 exceeds the specification requirements during the sinking of the caisson 01, the existing building 00 can be lifted again by jack 9 after the caisson 01 has reached the bottom and been sealed, so that the foundation of the original building can be completely restored to its original elevation. Micro-expansion concrete is filled between the top of the caisson 01 and the bottom of the existing building 00, and on both sides of the caisson 01 and the foundation beam 8 near the jack 9. After the micro-expansion concrete has cured to the required strength, the jack 9 is removed and the original position of the jack 9 is filled with micro-expansion concrete. When conducting settlement monitoring, if the settlement depth exceeds the set depth, the jacking pressure of jack 9 is increased to form a jacking system for the existing building 00 supported by caisson 01, controlling the settlement within the allowable range of the specifications; after backfilling with micro-expansion concrete, if a void appears between the independent foundation 7 and the foundation soil, pressure grouting is performed in the void, ultimately forming a system in which caisson 01 and the original foundation jointly support the building.

[0029] As can be seen from the above embodiments, the advantages of this invention are as follows: In this construction method, the dimensions of the caisson 01 are precisely matched with the foundation layout of the existing building 00, and the optimized arch height puts the arch wall in the best stress state, which can give full play to the compressive strength of the material, reduce the amount of reinforcement, and save building material costs; with the synergistic effect of the self-weight of the existing building 00 and the downward pressure of the jacks, combined with the cutting edge design of the caisson 01, the lateral resistance of the outer wall of the caisson 01 can be effectively overcome, solving the sinking problem when the caisson 01 has a large cross-section and hard soil, and significantly shortening the construction period; during construction, the floor slabs and connecting walls are made simultaneously to form an overall frame structure, which, combined with the horizontal support of the semi-circular passage and ramp, significantly improves the lateral displacement resistance of the caisson 01 and effectively resists water and soil pressure and the additional load of the existing building 00; the semi-circular passage is reused The passageway, connecting door, and temporary paving plank serve as a construction transfer channel. The temporary paving plank also doubles as permanent ramp formwork and can be reused, solving the problem of inconvenient vertical transfer at great depths and eliminating the need for additional formwork fabrication and transportation facility construction, thus improving construction efficiency and reducing costs. Through full-process settlement monitoring and the bidirectional application of jacks, combined with micro-expansion concrete backfilling and void pressure grouting, the settlement of the existing building 00 can be precisely controlled, avoiding safety hazards caused by foundation disturbance, forming a stable system jointly supported by the caisson 01 and the original foundation, ensuring the long-term structural safety of the existing building 00. At the same time, the design of the semi-circular passageway and connecting door meets the usage requirements of the underground parking garage, and the corresponding arrangement of standard sections and independent foundations maximizes the use of the open space between buildings, achieving efficient connection between construction and usage functions.

[0030] The above description of the disclosed embodiments enables those skilled in the art to implement or use this patent. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this patent. Therefore, this patent is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A construction method for setting up an underground parking garage for an existing building based on a caisson, wherein the caisson (01) is set between two adjacent existing buildings (00), the cross-section of the caisson (01) is set as a semi-circular channel (2) at both ends in the length direction, and multiple continuously outwardly protruding arch walls (3) are set on both sides in the width direction, and a standard section (1) of the caisson (01) is formed between the two opposing arch walls (3), characterized in that, The construction method includes the following steps: S1. Determine the plan dimensions of the caisson (01) based on the foundation layout and spacing of the existing building (00); S2. Based on the dimensions of the caisson (01), excavate a working pit (4) between the existing buildings (00), with the working pit (4) extending to the bottom of the existing buildings (00) on both sides; S3. The first section of the caisson (01) is poured in the working pit (4). The arch walls (3) on both sides of the caisson (01) are located below the foundation beams (8) of the existing buildings (00) on both sides. S4. Excavate the foundation soil below the caisson (01) and use the weight of the caisson (01) itself and the downward pressure of the existing buildings (00) on both sides to make the caisson (01) sink. S5. Cast an extension above the caisson (01); S6. Repeat steps S4-S5 to complete the construction of the caisson (01) at the set depth. Each time it is extended, a temporary passage connecting the bottom and top of the caisson (01) is made in the semi-circular passage (2). During multiple extensions, floor slabs (5) are periodically made in the standard section (1). S7. After completing the construction of the caisson (01) at the set depth, backfill the working pit (4) between the top of the caisson (01) and the bottom of the existing building (00).

2. The construction method for setting up underground parking garages for existing buildings based on caissons according to claim 1, characterized in that, In step S6, the foundation soil is transported out via ramp (6) and building materials are transported in.

3. The construction method for setting up underground parking garages for existing buildings based on caissons according to claim 1, characterized in that, The existing building (00) includes multiple independent foundations (7), each of which is a columnar structure embedded in the ground. Multiple independent foundations (7) are arranged at both ends and the middle of the foundation beam (8), and the spacing between adjacent independent foundations (7) is equal. The upper end of the independent foundation (7) is connected to the foundation beam (8). In step S1, the number of standard sections (1) corresponds to the number of independent foundations (7), and a standard section is provided between every two adjacent independent foundations (7). The semi-circular channel (2) is located on the outside of the existing building (00).

4. The construction method for setting up underground parking garages for existing buildings based on caissons according to claim 3, characterized in that, The distance between the arch feet of the two arch walls (3) is the length L of the standard section (1), and the distance between the outer edges of the two existing buildings (00) is K, satisfying KL≥200mm; the distance between the two ends of the same arch wall (3) is the width B of the standard section (1), and B is equal to the distance between two adjacent foundation beams (8) in the existing building (00); the arch height of the arch wall (3) is .

5. The construction method for setting up underground parking garages for existing buildings based on caissons according to claim 1, characterized in that, The arch of the arch wall (3) is located below the foundation beam (8). In step S4, a jack (9) is set between the arch of the arch wall (3) and the foundation beam (8) to press down the caisson (01).

6. The construction method for setting up underground parking garages for existing buildings based on caissons according to claim 1, characterized in that, During the construction process, settlement monitoring is carried out on the side of the existing building (00) adjacent to the working pit (4). In step S7, based on the settlement depth of the existing building (00), the existing building (00) is lifted by jacks (9), and micro-expansion concrete is filled between the top of the caisson (01) and the bottom of the existing building (00). After the micro-expansion concrete has solidified to the strength requirement, the jacks are removed and the original jack positions are filled with micro-expansion concrete.

7. The construction method for setting up underground parking garages for existing buildings based on caissons according to claim 1, characterized in that, In step S6, when the floor slab (5) is being made, a connecting wall (10) is being made between adjacent standard sections (1). The upper and lower edges of the connecting wall (10) are connected to the floor slab (5) respectively, and a connecting door (11) is provided on the connecting wall (10).

8. The construction method for setting up underground parking garages for existing buildings based on caissons according to claim 1, characterized in that, In step S6, a steel beam (12) is installed at regular intervals between the inner and outer walls of the semi-circular passage (2). Temporary slabs are laid on the steel beams (12) to form a temporary passage for transporting foundation soil and equipment. When making the floor slab (5), steel bars are tied above the temporary slabs and concrete is poured to form a permanent ramp (6) connecting the upper and lower floor slabs (5). After the concrete has cured, the steel beams (12) and temporary slabs are removed and transported to the upper caisson (01) for repeated construction and use.

9. The construction method for setting up underground parking garages for existing buildings based on caissons according to claim 8, characterized in that, The temporary paving includes multiple temporary inclined plates (13-1), and a temporary flat plate (13-2) is provided on the top of the temporary inclined plate (13-1). The temporary flat plate (13-2) is flush with the top of the caisson (01).

10. The construction method for setting up underground parking garages for existing buildings based on caissons according to claim 6, characterized in that, When conducting settlement monitoring, if the settlement depth exceeds the set depth, the top pressure of the jacks is increased, and the existing building (00) is supported by the caisson (01); after backfilling with micro-expansion concrete, if a gap appears between the independent foundation (7) and the foundation soil, pressure grouting is performed in the gap.

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