A method for constructing an underground space in the peripheral area of an existing building by using a caisson

Abstract

A method for constructing underground space in the surrounding area of existing buildings by using a caisson, belonging to the technical field of caisson construction, includes setting a caisson construction area between existing buildings, and constructing anti-pulling piles in the internal area of the caisson to be constructed; constructing a reaction beam so that the reaction beam is fixedly connected with the anti-pulling piles, and both ends of the reaction beam are fixedly connected with the existing buildings, using the weight of the existing buildings as the reaction force to assist the sinking of the caisson; after the construction of the reaction beam is completed, constructing the caisson, and setting anti-pulling piles in the caisson, which can improve the stress state of the reaction beam, reduce its cross-section, and in areas with high groundwater levels, the anti-pulling piles at the lower part of the caisson can also be used as anti-floating components of the caisson, and the anti-pulling piles in the caisson can be used as part of the columns of the basement, effectively reducing the cost. The anti-pulling piles are set in the caisson, and compared with those set near the outer wall of the caisson, they have higher bearing capacity and can better play their role.

Description

Technical Field

[0001] The present invention relates to the technical field of caisson construction, and particularly to a method for constructing an underground space in the surrounding area of an existing building by using a caisson. Background Art

[0002] A large number of existing buildings do not have underground parking lots designed. With the increase in the number of cars, there has emerged the problem of difficult parking. For existing buildings without designed underground parking lots, caisson technology is mostly used to add a three-dimensional mechanical garage. The traditional caisson technology sinks the caisson shaft by excavating the soil in the caisson, and the shaft is continuously extended on the ground until the design elevation.

[0003] However, when the cross-section of the caisson is large and the soil is relatively hard, it is very difficult to sink the caisson only by relying on its own weight to overcome the lateral resistance between the outer wall of the caisson and the soil. Currently, there has emerged a method for sinking a reaction force static pressure caisson (such as the publication number CN108487280B). Anchor piles / anti-pull piles, etc. are arranged around the caisson to be constructed. There are several cross beams located above the caisson on the pile tops. Reserved holes are arranged on the cross beams, and pull-through jacks are correspondingly arranged on each reserved hole. The reaction force frame of the anchor pile cross beam is used in cooperation with the jacks to provide the sinking force and the upward pulling force for the caisson.

[0004] In the existing method for sinking a reaction force static pressure caisson, the anti-pull piles are arranged closely along the outer peripheral side of the caisson (in order to avoid too much eccentricity when the jacks load the caisson). The sinking of the caisson will weaken the bearing capacity of the anti-pull piles, and the reaction force of the caisson sinking completely depends on the anti-pull piles and the cross beams on their tops, which is extremely likely to cause difficulties in sinking the caisson. Moreover, after the bearing capacity of the anti-pull piles is weakened, excessive deformation, cracks or even fractures may occur in the pile body when bearing the reaction force of the caisson sinking; in addition, in areas with a high groundwater level, the anti-floating bearing capacity of the caisson usually cannot meet the requirements. Summary of the Invention

[0005] In order to solve the technical problems in the above-mentioned background art that in the existing method for sinking a reaction force static pressure caisson, the anti-pull piles are arranged closely along the outer peripheral side of the caisson, the sinking of the caisson will weaken the bearing capacity of the anti-pull piles, which is extremely likely to cause difficulties in sinking the caisson and damage to the pile body, the present invention provides a method for constructing an underground space in the surrounding area of an existing building by using a caisson.

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

[0007] The present invention provides a method for constructing an underground space in the surrounding area of an existing building by using a caisson, specifically as follows:

[0008] Set a caisson construction area in the area between existing buildings, and construct anti-pulling piles in the internal area of the caisson to be constructed as the mid-span supports of the reaction beam, which can effectively share the load borne by the reaction beam, enhance the bearing capacity and stability of the reaction beam, reduce its cross-sectional size, and provide a reliable support structure for subsequent construction. In addition, the anti-pulling piles can also be used as anti-floating components during the use of the caisson and as vertical support components inside the caisson;

[0009] Construct the reaction beam so that the reaction beam is fixedly connected to the anti-pulling piles, and both ends of the reaction beam are fixedly connected to the existing buildings. Use the weight of the existing buildings as the reaction force to assist the caisson in sinking;

[0010] After the construction of the reaction beam is completed, construct the caisson. Use the caisson to develop the underground space of the existing buildings. The caisson can reduce the impact of earth excavation on the existing buildings;

[0011] Backfill after the caisson construction is completed, which can restore the ground form of the construction area, make the area available for normal use, and at the same time protect the caisson and enhance the stability of the entire underground space structure.

[0012] Preferably, the depth of the anti-pulling piles exceeds the bottom elevation of the caisson to be constructed, which can make the anti-pulling piles better take root in the stable soil layer, provide stronger anti-pulling force and support force, and effectively prevent the caisson from floating or settling unevenly during construction and use. The design bearing capacity of the anti-pulling piles should not only meet the anti-pulling support reaction force for the reaction beam, but also the part of the anti-pulling piles below the caisson bottom plate provides the anti-floating bearing capacity during the normal use of the caisson, and the part above the bottom plate meets the bearing capacity of the vertical bearing components (basement columns) inside the caisson.

[0013] Preferably, the top of the reaction beam is flush with the outdoor ground, so that the pouring and other operations of the caisson are carried out below the ground level, and the connection points of the reaction beam and the existing buildings do not enter the interior, thus minimizing the impact on the residents of the existing buildings to the greatest extent.

[0014] Preferably, the specific process of caisson construction is as follows:

[0015] Excavate the ground between existing buildings to the bottom elevation of the building foundation to form a working pit for caisson construction. Excavating to the bottom elevation of the building foundation to form a working pit provides sufficient space for caisson construction, facilitates subsequent caisson pouring and sinking operations, and can effectively control the influence range of construction on the existing building foundation;

[0016] Carry out the pouring construction of the first section of the caisson. Install a jack between the top of the first section of the caisson and the reaction beam, excavate the soil inside the first section of the caisson, and at the same time use the jack to press the first section of the caisson;

[0017] After the first section of the open caisson sinks to the bottom of the working pit, the second section of the open caisson is constructed and sunk above the first section of the open caisson. The soil inside the open caisson is continuously excavated and the open caisson is continuously extended until the designed elevation of the bottom of the open caisson is reached. By installing jacks between the top of the open caisson and the reaction beam and using the jacking force of the jacks to assist the sinking of the open caisson, the soil friction and other resistances during the sinking process of the open caisson can be effectively overcome, enabling the open caisson to sink.

[0018] Preferably, when excavating the working pit, the ground near the existing building is reserved to facilitate the travel of the residents of the existing building.

[0019] Preferably, a working face is reserved on the outside of the open caisson to be constructed in the working pit as the working space for workers to bind steel bars, formwork, and pour concrete for the open caisson, facilitating the construction of the open caisson.

[0020] Preferably, the height of the first section of the open caisson is the net height from the reaction beam to the bottom of the working pit minus the height of the jacks to be installed. The bottom of the first section of the open caisson is constructed into a cutting edge to facilitate the open caisson to cut into the soil.

[0021] Preferably, a hanging basket is installed at a position on the reaction beam close to the inner side of the outer wall of the open caisson to provide a working face inside the excavated open caisson, facilitating subsequent operations such as steel bar binding and formwork support.

[0022] Preferably, after the open caisson sinks to the designed elevation of the bottom of the open caisson, the open caisson is sealed at the bottom, and components are constructed inside the open caisson to make full use of the underground space of the existing building.

[0023] Preferably, when there is an open space on the opposite side of the existing building, a construction area for the open caisson is set on one side of the existing building, and anti-pulling piles are constructed in the internal area of the open caisson to be constructed;

[0024] After the construction of the anti-pulling piles is completed, the reaction beam is constructed, such that one end of the reaction beam is fixedly connected to the adjacent existing building; the other end of the reaction beam extends a set length in the direction away from the open caisson to be constructed, and a soil stacking plate is constructed on the top of the extended end beam of the reaction beam. The soil excavated from the open caisson is stacked on the soil stacking plate, and the existing building cooperates with the weight of the stacked soil to provide the reaction force for the open caisson, giving full play to the role of the stacked soil. Moreover, in the initial stage of the sinking of the open caisson, the sinking resistance is small and the amount of excavated soil is small; in the later stage of the sinking of the open caisson, the sinking resistance becomes larger, and at this time the amount of excavated soil becomes larger, which can effectively combine the technological characteristics of the open caisson and reduce the cost.

[0025] It can be seen from the above technical solutions that the advantages of the present invention are as follows:

[0026] 1. Install anti - uplift piles inside the open caisson. This not only serves as the support for the reaction beam, improves the stress state of the reaction beam, reduces the cross - section of the reaction beam, but also in areas with high groundwater levels, the anti - uplift piles at the lower part of the open caisson can act as anti - floating components of the open caisson. The anti - uplift piles inside the open caisson can serve as partial columns of the basement, effectively reducing costs. The anti - uplift piles installed inside the open caisson have higher bearing capacity compared to those installed near the outer wall of the open caisson, can better play their role, and both ends of the reaction beam are fixedly connected to the existing building, using the weight of the existing building as the reaction force to better assist the sinking of the open caisson.

[0027] 2. The depth of the anti - uplift pile exceeds the elevation of the bottom slab of the open caisson to be constructed, which can enable the anti - uplift pile to better take root in the stable soil layer, provide stronger anti - uplift force and support force, and effectively prevent the open caisson from floating or uneven settlement during construction and use. Therefore, the designed bearing capacity of the anti - uplift pile should not only meet the anti - uplift support reaction force for the reaction beam, but also the part of the anti - uplift pile below the bottom slab of the open caisson provides anti - floating bearing capacity during the normal use of the open caisson, and the part above the bottom slab meets the bearing capacity of the vertical load - bearing components (basement columns) inside the open caisson.

[0028] 3. The top of the reaction beam is flush with the outdoor ground, enabling the pouring of the open caisson and other operations to be carried out below the ground level, and the connection points of the reaction beam with the existing building will not enter the interior, thus minimizing the impact on the residents of the existing building to the greatest extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0030] Figure 1 is a plan view of the foundation and wall before adding underground space between strip - foundation buildings;

[0031] Figure 2 is an elevation view of the foundation and wall before adding underground space between strip - foundation buildings;

[0032] Figure 3 is a plan view of constructing anti - uplift piles in the area between strip - foundation buildings;

[0033] Figure 4 is an elevation view of constructing anti - uplift piles in the area between strip - foundation buildings;

[0034] Figure 5 is a plan view of constructing the reaction beam between strip - foundation buildings and excavating the soil to the elevation of the foundation bottom;

[0035] Figure 6 It is an elevation schematic diagram of constructing a reaction beam between strip foundation buildings and excavating the soil to the bottom elevation of the foundation.

[0036] Figure 7 It is a plan schematic diagram of casting the first section of the caisson between strip foundation buildings and installing jacks.

[0037] Figure 8 It is an elevation schematic diagram of casting the first section of the caisson between strip foundation buildings and installing jacks.

[0038] Figure 9 It is a plan schematic diagram of excavating the soil inside the caisson between strip foundation buildings and gradually sinking the caisson.

[0039] Figure 10 It is an elevation schematic diagram of excavating the soil inside the caisson between strip foundation buildings and gradually sinking the caisson.

[0040] Figure 11 It is an elevation schematic diagram of the caisson sinking to the designed elevation between strip foundation buildings.

[0041] Figure 12 It is an elevation schematic diagram of sealing the bottom of the caisson and constructing each layer of beam and slab between strip foundation buildings.

[0042] Figure 13 It is a plan schematic diagram of using the soil heap outside the strip foundation building to provide reaction force for the caisson.

[0043] Figure 14 It is an elevation schematic diagram of using the soil heap outside the strip foundation building to provide reaction force for the caisson.

[0044] Figure 15 It is a plan schematic diagram of using the caisson to develop the underground space between independent foundation buildings.

[0045] Figure 16 It is an elevation schematic diagram of using the caisson to develop the underground space between independent foundation buildings.

[0046] The components represented by each reference numeral in the figure are as follows:

[0047] 1. Wall; 2. Strip foundation; 3. Outdoor ground; 4. Uplift pile; 5. Reaction beam; 6. Working pit; 7. Existing soil; 8. Jack; 9. First section of caisson; 10. Soil inside caisson; 11. Second section of caisson; 12. Suspended basket; 13. Designed elevation of caisson bottom; 14. Bottom sealing; 15. Beam and slab; 16. Top beam and top slab; 17. Soil heap plate; 18. Soil heap; 19. Independent foundation; 20. Column. Detailed implementation manners

[0048] To make the objectives, features, and advantages of the present invention more apparent and understandable, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the specific embodiments. Obviously, the embodiments described below are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments in this patent, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of this patent.

[0049] Embodiment 1

[0050] In a typical implementation manner of the present invention, as Figure 1 - Figure 2 shown, a method for constructing an underground space in the surrounding area of an existing building using a caisson is proposed, specifically as follows:

[0051] A caisson construction area is set in the area between existing buildings, and in the internal area of the caisson to be constructed, tension piles 4 are constructed to serve as the mid-span supports of the reaction beam 5. There are various types of existing buildings, such as Figure 3 and Figure 4 shown, strip foundation existing buildings (the upper structure is a wall 1); as Figure 15 and Figure 16 shown, independent foundation existing buildings (the upper structure is a column 20).

[0052] Specifically, since the distance between the areas between existing buildings is relatively large, the span of the reaction beam 5 with the existing building foundation as the end supports is relatively large, the force is unreasonable, and the cross-sectional size of the reaction beam 5 is also relatively large. Therefore, in the internal area of the caisson to be constructed and on the axis of the reaction beam 5 to be constructed, one or more tension piles 4 are set according to the span of the reaction beam 5 to serve as the mid-span supports of the reaction beam 5, which can effectively improve the mechanical properties of the reaction beam 5 and reduce its cross-sectional size; in addition, the tension piles 4 can also serve as anti-floating members during the use of the caisson and at the same time as vertical support members in the caisson.

[0053] The tension piles 4 can be cast in place on site by means of bored cast-in-place piles, etc. Specifically, start the hole-forming equipment and carry out hole-forming construction according to the designed pile diameter, pile depth, and verticality. After the hole reaches the designed depth, carry out hole cleaning operations to remove the sediment at the bottom of the hole and impurities in the mud, improve the bearing capacity of the pile tip, use a crane to vertically lift the steel reinforcement cage and slowly lower it into the hole, pour concrete, and after the concrete pouring is completed, promptly clean the floating slurry and excess concrete at the pile head to make the concrete surface at the pile top flat.

[0054] The depth of the uplift pile 4 should exceed the elevation of the bottom slab of the caisson to be constructed (i.e., the designed elevation of the caisson bottom 13), so that the designed bearing capacity of the uplift pile 4 should not only meet the requirement of providing the uplift support reaction for the reaction beam 5, but also the part of the uplift pile 4 below the caisson bottom slab should provide the anti-floating bearing capacity during the normal use of the caisson, and the part above the bottom slab should meet the bearing capacity of the vertical load-bearing members (basement columns) in the caisson.

[0055] After the construction of the uplift pile 4 is completed, construct the reaction beam 5 so that the reaction beam 5 is located between the existing buildings to provide a downward reaction force for the sinking of the caisson. The reaction beam 5 is fixedly connected to the uplift pile 4, and both ends of the reaction beam 5 are fixedly connected to the existing buildings.

[0056] To utilize the weight of the existing buildings, such as Figure 5 and Figure 6 As shown, when the existing building is an existing building with a strip foundation, both ends of the reaction beam 5 extend into the wall 1 on the side of the existing building close to the caisson. Specifically, a hole is opened in the wall 1 perpendicular to the direction of the reaction beam 5, and the bound support steel cage is inserted into the hole. The steel cage of the reaction beam 5 is bound and connected to the support steel cage, and then concrete is poured; at the position of the uplift pile 4, the longitudinal bars of the uplift pile 4 should be anchored into the reaction beam 5, and they form an integral body after the concrete is poured.

[0057] In this embodiment, the underground space of the existing building is developed by using the caisson. The caisson can reduce the impact of earth excavation on the existing building. At the same time, using the weight of the existing building as a reaction force can help the caisson sink.

[0058] Such as Figure 15 and Figure 16 As shown, when the existing building is an existing building with an independent foundation, the reaction beam 5 is arranged on both sides of the column 20 and the uplift pile 4. The reaction beam 5 clamps the column 20 and the uplift pile 4 and is fixedly connected as an integral body. Specifically, steel bars are implanted on both sides of the column 20, and at the same time, the steel bars extend into the interior of the reaction beam 5. For the uplift pile 4, the longitudinal bars of the uplift pile 4 are bent and then anchored into the reaction beam 5 on both sides from both sides. The steel cage of the reaction beam is bound, and concrete is poured to form an integral body.

[0059] It should be noted that the top of the reaction beam 5 should be flush with the outdoor ground 3, so that the pouring and other work of the caisson can be carried out below the ground level, and the connection points of the reaction beam 5 and the existing building will not enter the interior, thus minimizing the impact on the residents of the existing building to the greatest extent.

[0060] It can be understood that the number of the reaction beams 5 needs to be determined comprehensively according to the reaction force required for the caisson to sink, the length and width of the caisson section, and the situation of the wall 1 (or column 20) of the existing building. Specifically, there are no excessive restrictions here.

[0061] After the reaction force beam 5 is constructed, construct the caisson.

[0062] Specifically, as Figure 6 shown, excavate the ground between the existing buildings to the bottom elevation of the building foundation (i.e., the strip foundation 2 or the independent foundation 19) (exceeding the base elevation will affect the safety of the building), and form a working pit 6 for the caisson construction to provide sufficient space for the fabrication of the caisson.

[0063] Among them, in order to ensure the travel of the residents of the existing buildings, retain the ground at a set distance close to the existing buildings, that is, the existing soil mass 7 close to the existing buildings. In this embodiment, the ground with a width of 1 m close to the existing building 1 is retained.

[0064] Reserve a working face with a set width on the outside of the caisson to be constructed in the working pit. In this embodiment, reserve a working face with a width of about 1 m as the working space for workers to bind steel bars, formwork, and pour concrete for the caisson, facilitating the progress of the caisson construction work.

[0065] First, carry out the pouring construction of the first-stage caisson 9. Specifically, bind steel bars, set up formwork along the outer wall edge line of the caisson, and pour concrete, and reserve lapping steel bars for connecting the second-stage caisson 11 at the top of the caisson. The height of the poured first-stage caisson 9 is the net height from the reaction force beam 5 to the bottom of the working pit 6 minus the height of the jack 8 to be installed. As Figure 8 shown, the bottom of the first-stage caisson 9 is constructed into a cutting edge to facilitate the caisson to cut into the soil mass.

[0066] After the wall concrete of the first-stage caisson 9 reaches the design strength, install the jack 8 between the top of the first-stage caisson 9 and the reaction force beam 5 above it. Then, excavate the soil in the first-stage caisson 9. While excavating the soil in the first-stage caisson 9, use the jack 8 to jack up the first-stage caisson 9, so that the jacking work of the jack 8 and the soil excavation process are carried out synchronously. When the piston of the jack 8 completes a stroke, the piston retracts, and a cushion block with a stroke height is inserted between the jack 8 and the reaction force beam 5 to ensure that the jack 8 continues to press down the caisson. Repeat the above operations until the first-stage caisson 9 sinks into the bottom of the working pit 6.

[0067] After the first-stage caisson 9 sinks into the bottom of the working pit 6, continue to bind steel bars, set up formwork, and pour concrete above the first-stage caisson 9, so as to fixedly connect the second-stage caisson 11 above the first-stage caisson 9 to extend the first-stage caisson 9. Among them, in order to provide a working face in the excavated caisson, install a hanging basket 12 at a position on the reaction force beam 5 close to the inner side of the outer wall of the caisson.

[0068] As Figure 10 - Figure 11As shown, continuously excavate the soil 10 inside the open caisson and continuously extend the open caisson until the designed elevation 13 of the bottom of the open caisson is reached. Among them, when there is groundwater in the sinking depth of the open caisson, artificial dewatering needs to be carried out in advance to ensure the smooth progress of soil excavation and sinking.

[0069] As Figure 12 shown, after the open caisson sinks to the designed elevation 13 of the bottom of the open caisson, seal the bottom 14 of the open caisson and carry out the construction of components inside the open caisson.

[0070] Specifically, lay a steel mesh at the bottom of the open caisson and pour concrete to complete the bottom sealing 14 work of the open caisson. It should be particularly noted that waterproof treatment is carried out at the connection between the bottom slab of the open caisson and the uplift resistance pile 4. After the bottom sealing 14, dewatering can be stopped. After the bottom sealing is completed, gradually complete the construction of each layer of beam-slab 15, top beam and top slab 16 inside the open caisson, as well as vertical components such as basement columns and walls. The reaction beam 5 can be used as part of the top beam, and the uplift resistance pile 4 can be used as part of the basement column to save costs.

[0071] Finally, backfill the working pit 6 to restore the ground.

[0072] In this embodiment, the uplift resistance pile 4 is arranged inside the open caisson. It can not only serve as the support of the reaction beam 5, improve the stress state of the reaction beam 5, and reduce the cross-section of the reaction beam 5, but also in areas with high groundwater levels, the uplift resistance pile 4 at the lower part of the open caisson can also be used as the anti-floating component of the open caisson. The uplift resistance pile 4 inside the open caisson can be used as part of the columns of the basement, effectively reducing the cost. The uplift resistance pile 4 is arranged inside the open caisson, which has higher bearing capacity and can better play its role compared with being arranged near the outer wall of the open caisson.

[0073] Embodiment 2

[0074] In another typical implementation manner of the present invention, a method for constructing an underground space in the surrounding area of an existing building by using an open caisson is proposed. Compared with Embodiment 1, the difference is that there is an open space on the opposite side of the existing building, and one end of the reaction beam 5 cannot be fixedly connected to the existing building. Specifically as follows:

[0075] Set an open caisson construction area on one side of the existing building, and construct the uplift resistance pile 4 in the internal area of the open caisson to be constructed, so as to serve as the mid-span support of the reaction beam 5. There are various types of existing buildings, such as Figure 3 and Figure 4 shown, an existing building with a strip foundation (the superstructure is a wall 1); as Figure 15 and Figure 16 shown, an existing building with an independent foundation (the superstructure is a column 20).

[0076] After the construction of the uplift resistance pile 4 is completed, as Figure 13 and Figure 14As shown in the figure, a construction reaction beam 5 is provided, with one end of the reaction beam 5 fixedly connected to an adjacent existing building. The other end of the reaction beam 5 extends a set length away from the to-be-constructed caisson, and a soil stacking plate 17 is constructed on the top of the extended end of the reaction beam 5. The soil excavated from the caisson is stacked on the soil stacking plate 17, and the reaction force is provided by the weight of the stacked soil 18 and the existing building to ensure the sinking of the caisson. The reaction beam 5 is fixedly connected to the anti-pulling pile 4.

[0077] The existing building and the weight of the stacked soil 18 cooperate to provide the reaction force for the caisson, giving full play to the role of the stacked soil 18. Moreover, in the initial stage of the caisson sinking, the sinking resistance is small and the amount of excavated soil is small; in the later stage of the caisson sinking, the sinking resistance becomes larger, and at this time the amount of excavated soil becomes larger, which can effectively combine the technological characteristics of the caisson and reduce the cost.

[0078] It should be noted that the top of the reaction beam 5 should be flush with the outdoor ground 3, so that the work such as the pouring of the caisson is carried out below the ground level, and the connection point between the reaction beam 5 and the existing building will not enter the interior, thus minimizing the impact on the residents of the existing building to the greatest extent.

[0079] After the construction of the reaction beam 5 is completed, the caisson is constructed.

[0080] Specifically, the ground between the existing buildings is excavated to the bottom elevation of the building foundation (i.e., the strip foundation 2 or the independent foundation 19) (exceeding the base elevation will affect the safety of the building), forming a working pit 6 for the construction of the caisson to provide sufficient space for the fabrication of the caisson.

[0081] Among them, in order to ensure the travel of the residents of the existing building, the ground at a set distance from the existing building is reserved, that is, the existing soil 7 near the existing building. In this embodiment, the ground with a width of 1 m near the existing building is reserved.

[0082] A working surface with a set width is reserved on the outside of the to-be-constructed caisson in the working pit. In this embodiment, a working surface with a width of about 1 m is reserved as the working space for workers to bind steel bars, formwork, and pour concrete for the caisson, facilitating the construction work of the caisson.

[0083] First, the pouring construction of the first-stage caisson 9 is carried out. After the wall concrete of the first-stage caisson 9 reaches the design strength, a jack 8 is installed between the top of the first-stage caisson 9 and the reaction beam 5 above it. Then, the soil is excavated in the caisson, and while the soil is being excavated in the caisson, the caisson is jacked by the jack 8, so that the jacking work of the jack 8 is synchronized with the soil excavation process. When the piston of the jack 8 has completed one stroke, the piston retracts, and a pad block with a stroke height is inserted between the jack 8 and the reaction beam 5 to ensure that the jack 8 continues to press down the caisson. The above operations are repeated until the first-stage caisson 9 sinks into the bottom of the working pit 6.

[0084] After the first-section open caisson 9 sinks into the bottom of the working pit 6, reinforce bars are continuously tied, formwork is supported, and concrete is poured above the first-section open caisson 9, so as to fixedly connect the second-section open caisson 11 above the first-section open caisson 9 to lengthen the first-section open caisson 9. Among them, in order to provide a working surface inside the open caisson after excavation, a hanging basket 12 is installed at a position on the reaction beam 5 close to the inner side of the outer wall of the open caisson.

[0085] The soil 10 inside the open caisson is continuously excavated, and the open caisson is continuously lengthened until the designed elevation 13 of the bottom of the open caisson is reached. After the open caisson sinks to the designed elevation 13 of the bottom of the open caisson, the bottom sealing 14 of the open caisson is carried out, and the construction of components is carried out inside the open caisson.

[0086] Specifically, a steel mesh is laid at the bottom of the open caisson and concrete is poured to complete the bottom sealing 14 work of the open caisson. It should be particularly noted that the connection between the bottom slab of the open caisson and the uplift resistance pile 4 is waterproofed. After the bottom sealing 14, the dewatering can be stopped. After the bottom sealing is completed, the construction of each layer of beam slab 15, top beam and top slab 16, and vertical components such as basement columns and walls inside the open caisson is gradually completed. The reaction beam 5 can be used as part of the top beam, and the uplift resistance pile 4 can be used as part of the basement column to save costs.

[0087] Finally, the working pit 6 is backfilled to restore the ground surface.

[0088] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for constructing an underground space in the surrounding area of ​​an existing building using a caisson, characterized in that: The details are as follows: A caisson construction area is set up between existing buildings, and anti-pullout piles (4) are constructed in the inner area of ​​the caisson to be constructed to serve as mid-span supports for the reaction beam (5); Constructing a reaction beam (5) such that the reaction beam (5) is fixedly connected to the pull-out pile (4), and both ends of the reaction beam (5) are fixedly connected to the existing building, and the top of the reaction beam (5) is flush with the outdoor ground (3); After the reaction beam (5) is constructed, the caisson is constructed; Backfill is carried out after the caisson construction is completed.

2. The method for constructing an underground space in the surrounding area of ​​an existing building by using a caisson according to claim 1, characterized in that: The depth of the anti-pull pile (4) exceeds the bottom plate elevation of the caisson to be constructed.

3. The method for constructing an underground space in the surrounding area of ​​an existing building by using a caisson according to claim 1, characterized in that: The specific process of caisson construction is as follows: Excavating the ground between the existing buildings to the bottom elevation of the building foundation to form a working pit for the construction of the caisson (6); Performing pouring construction of the first section caisson (9), installing a jack (8) between the top of the first section caisson (9) and the reaction beam (5), excavating earth in the first section caisson (9), and simultaneously using the jack (8) to press the first section caisson (9); After the first section caisson (9) is sunk into the bottom of the working pit (6), the second section caisson (11) is constructed above the first section caisson (9) and is sunk, and the earthwork (10) in the caisson is continuously excavated and the caisson is continuously extended until the designed elevation (13) of the caisson bottom is reached.

4. The method for constructing an underground space in the surrounding area of ​​an existing building by using a caisson according to claim 3, characterized in that: When excavating the working pit (6), the ground near the existing building is retained.

5. The method for constructing an underground space in the surrounding area of ​​an existing building by using a caisson according to claim 3, characterized in that: A working surface is reserved on the outside of the caisson to be constructed in the working pit (6).

6. The method for constructing an underground space in the surrounding area of ​​an existing building by using a caisson according to claim 3, characterized in that: The height of the first section caisson (9) is the net height from the reaction beam (5) to the bottom of the working pit (6) minus the height of the jack (8) to be installed, and the bottom of the first section caisson (9) is constructed to form a blade angle.

7. The method for constructing an underground space in the surrounding area of ​​an existing building by using a caisson according to claim 3, characterized in that: A hanging basket (12) is installed on the reaction beam (5) at a position close to the inner side of the outer wall of the caisson.

8. The method for constructing an underground space in the surrounding area of ​​an existing building by using a caisson according to claim 3, characterized in that: After the caisson sinks to the designed elevation of the caisson bottom (13), the caisson bottom is sealed (14) and components are constructed in the caisson.

9. The method for constructing an underground space in the surrounding area of ​​an existing building by using a caisson according to claim 1, characterized in that: When the opposite side of the existing building is an open space, a caisson construction area is set up on one side of the existing building, and anti-pullout piles (4) are constructed in the inner area of ​​the caisson to be constructed; After the construction of the pull-out piles (4) is completed, a reaction beam (5) is constructed so that one end of the reaction beam (5) is fixedly connected to an adjacent existing building; the other end of the reaction beam (5) is extended by a set length in a direction away from the caisson to be constructed, and an earth pile board (17) is constructed on the top of the extended end beam of the reaction beam (5), and the soil excavated from the caisson is piled on the earth pile board (17).

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