Layer-adding construction method for basement with existing box type foundation and multi-layer frame structure

Abstract

The invention discloses a storey-adding construction method for a basement with an existing box type foundation and a multi-layer frame structure, and belongs to the technical field of constructional engineering and city renewing.The storey-adding construction method comprises the following steps that S1, storey-adding buildings of the existing basement are evaluated; s2, underground diaphragm wall construction; s3, reinforcing the existing basement storey-adding building foundation; s4, the overground structure of the existing basement storey-adding building is reinforced; s5, foundation underpinning construction is conducted; s6, earth excavation is conducted at the storey-adding position of the existing basement; s7, construction of a storey-adding foundation bottom plate; and S8, layer-adding underpinning column and top plate construction. According to the storey-adding construction method for the basement with the box type foundation and the multi-layer frame structure, storey-adding transformation is conducted on the basement of an existing building, the usable area of the building is effectively increased, the construction efficiency is improved, the influence on the surrounding environment is reduced, and the urban development and the ever-increasing space requirements of people are met.

Description

Technical Field

[0001] The present invention belongs to the technical field of construction engineering and urban renewal, and particularly relates to a construction method for adding floors to a basement of an existing box-type foundation multi-story frame structure. Background Art

[0002] Urban land resources are scarce, and how to expand building space within limited land has become a critical issue in the construction industry. Adding floors to existing buildings, particularly multi-story frame structures with box foundations, effectively increases the building's usable area and space utilization without requiring additional construction land, making it a key approach to alleviating urban land shortages.

[0003] Box foundations have been widely used in multi-story frame structures due to their excellent bending stiffness and good seismic performance, providing reliable protection for the stability and safety of buildings. However, when adding floors to basements of this type of structure, many technical difficulties and challenges are faced. Since adding floors will change the load distribution and transfer path of existing buildings, it is necessary not only to fully consider the stability and safety of the existing structure, but also to accurately control multiple links such as foundation reinforcement and structural verification. Existing construction technologies such as direct floor addition, load transfer addition, and outer structure addition are difficult to effectively solve the problem of disturbance to the existing structure during construction and the reliability problem of the connection between the old and new structures in the scenario of adding floors to the basement. There are shortcomings such as high construction risks and difficulty in ensuring structural safety. They cannot fully meet the increasingly stringent quality and safety requirements of urban development for basement floor addition construction.

[0004] Therefore, a more scientific, safe and efficient construction method is urgently needed to achieve reliable floor-adding reconstruction of existing box-type foundation multi-story frame structure basements. Summary of the Invention

[0005] The purpose of the present invention is to provide a construction method for adding floors to an existing box-type foundation multi-story frame structure basement. This method effectively increases the usable area of ​​the building, improves construction efficiency, and reduces the impact on the surrounding environment by adding floors to the basement of an existing building, thereby meeting the growing space needs of urban development and people.

[0006] To achieve the above-mentioned object, the present invention provides a construction method for adding a floor to a basement of an existing box-type foundation multi-story frame structure, comprising the following steps:

[0007] S1. Pre-construction assessment: determine whether to add a floor to the basement of an existing building, make a floor addition decision based on functional needs, and obtain design requirements and site geological conditions;

[0008] S2. Based on the design requirements and on-site geological conditions obtained in S1, use trenching machinery to construct underground continuous walls; and carry out water-stop curtain and pile construction at the existing building where additional floors are to be added;

[0009] S3. Calculate the original building foundation and determine the reinforcement plan for the building's ground floor and original foundation based on the foundation type, current bearing capacity, and load requirements for additional floors;

[0010] S4. Carry out structural stress and deformation calculation analysis for the existing building to be constructed, identify weak points in the superstructure during construction and perform secondary reinforcement;

[0011] S5. Arrange anchor static piles under the existing foundation according to the design in S3. Using the deadweight of the existing building as the reaction force, connect the pile driving equipment to the foundation via anchor rods and press the piles into the pile body section by section until the designed bearing layer is reached.

[0012] S6. Excavate the earthwork of the area where the additional floor is to be added in layers;

[0013] S7. After excavation reaches the bottom elevation of the added floor, the raft slab of the added basement foundation is poured;

[0014] S8. Carry out the casting construction of frame columns and top plates within the height range of the added storey. After the strength of the columns reaches the design requirements, cut and remove the anchor static pressure piles at the added storey.

[0015] Preferably, in S2, the water-stop curtain adopts the bite pile technology, and the adjacent piles bite each other to form a continuous water-stop barrier. The pile rows are selected from cast-in-place piles or prefabricated piles according to the geological conditions. The verticality, pile diameter and pile spacing of the piles are strictly controlled during the construction process.

[0016] Preferably, in S3, if the original building has an independent foundation, it is reinforced by increasing the bottom area of ​​the foundation and adding foundation beams; if it is a raft foundation, a reinforced concrete surface layer is added to the original raft or anchor static pressure piles are used for reinforcement, and the reinforcement construction is carried out in coordination with the underpinning pile construction.

[0017] Preferably, in S5, during the construction of anchor static pressure piles, pile driving equipment is used to press the piles in sections, controlling the pile driving force and the depth of penetration into the soil. The steel bars supporting the ground beam are connected to the anchor rods of the anchor static pressure piles, and the ground beam is connected to the ground connecting wall.

[0018] Preferably, in S6, the depth of each layer of earthwork excavation does not exceed 2m, and a level and a total station are used to monitor the excavation depth. Settlement observation points and tilt monitoring points are arranged on existing buildings, and high-precision measuring instruments are used to monitor deformation in real time and set early warning values.

[0019] Preferably, in S7, the foundation raft slab concrete is poured in layers and vibrated in layers, commercial concrete is used, the slump is controlled, and the vibrating rod is prevented from touching the anchor static pressure pile during the pouring process.

[0020] Preferably, in S8, the frame columns and top slab concrete are poured and then cured. When the column strength reaches not less than 75% of the design strength, the anchor static pressure piles are removed using cutting equipment, and the structure is inspected and analyzed after removal.

[0021] Therefore, the present invention adopts the above-mentioned existing box-type foundation multi-story frame structure basement floor construction method. Compared with the prior art, the present invention has the following significant beneficial effects:

[0022] (1) The present invention effectively increases the usable area of ​​a building by adding floors to the basement of an existing building, and adopts scientific and reasonable construction techniques and processes to enhance the earthquake resistance and durability of the building;

[0023] (2) The present invention ensures the safety of the original structure by reinforcing the original building foundation and ground structure and combining it with a replacement construction method, while improving the stability of the entire building, thereby extending the service life of the building;

[0024] (3) The present invention shortens the construction period, reduces construction costs, and improves economic benefits by optimizing the construction process. In the process of adding layers, the groundwater level and earth excavation depth are strictly controlled to protect the ecological environment and achieve sustainable development.

[0025] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a process diagram of the construction method for adding a floor to a basement with a multi-story frame structure having an existing box-type foundation according to the present invention. Figure 1 (a) is the construction process diagram of foundation pit support-ground diaphragm wall. Figure 1 (b) is the reinforcement process diagram of the building bottom floor and the original foundation. Figure 1 (c) in the figure is the foundation replacement construction process drawing. Figure 1 (d) is the underground soil excavation process diagram. Figure 1 (e) in the figure is the newly added basement floor pouring process diagram. Figure 1 (f) is the newly added casting process drawing of the basement top slab and structural columns;

[0027] Figure 2 This is a schematic diagram of the arrangement of supporting ground beams, connecting anchor static pressure piles, and ground-connected walls in the construction method for adding floors to a basement with a multi-story frame structure having an existing box-type foundation according to the present invention. Figure 2 (a) is a plan view. Figure 2 (b) is a schematic elevation view.

[0028] Reference numerals

[0029] 1. Replacement of foundation piles; 2. Anchor static pressure piles; 3. Piling rows; 4. Existing foundation columns. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used in the present invention should be the common meanings understood by people with ordinary skills in the field to which the present invention belongs.

[0031] Example 1

[0032] like Figure 1 As shown, the method for constructing a basement floor increase in a multi-story frame structure with an existing box-type foundation of the present invention comprises the following steps:

[0033] S1. Pre-construction assessment includes: a detailed investigation of the historical data of existing buildings, including original design drawings, construction records, and modifications during use, to understand their structural systems, foundation forms, material strength, and other information; and an on-site inspection of existing buildings to examine the current state of the structures and assess damage and deformation.

[0034] Determine to add a floor to the basement of an existing building, combine the functional requirements of the added floor, such as commercial, warehousing, etc., comprehensively consider the surrounding environment and geological conditions of the building, use professional structural analysis software to simulate the mechanical properties after the addition, make scientific and reasonable decisions on the addition of floors, clarify key parameters such as the scale and layout of the added floors, and obtain design requirements and on-site geological conditions.

[0035] S2. Based on the design requirements in S1 and the on-site geological conditions, trenching machinery is used to construct the underground continuous wall (ground-connected wall). Precisely control the verticality, depth, and width of the trench, place a steel cage within the trench, and then pour concrete to form a continuous underground wall. The ground-connected wall serves the dual purpose of water stopping and foundation pit support, preventing groundwater seepage and pit sidewall collapse, creating a safe environment for subsequent construction. Water-stop curtains and pile rows are constructed in the area where the existing building is to be added.

[0036] The water-stop curtain adopts the bite pile technology. Adjacent piles bite each other to form a continuous water-stop barrier. The piles in row 3 are cast-in-place piles or prefabricated piles according to the geological conditions. The verticality, pile diameter and pile spacing of the piles are strictly controlled during the construction process.

[0037] If there is a need for 3 rows of piles, cast-in-place piles or precast piles will be used at the corresponding locations for 3 rows of piles. Water-stopping measures, such as high-pressure jet-jet water-stop curtains, will be properly installed between the piles to ensure an effective water-stopping and support system. This is mainly used for excavation support and groundwater control in the added-story areas, preventing groundwater from flowing into the foundation pit of the added-story building during excavation, creating a safe and dry working environment for subsequent excavation and foundation construction.

[0038] S3. Conduct detailed structural calculations on the original building foundation and determine the reinforcement plan for the building's ground floor and original foundation based on the foundation type (e.g., independent foundation, raft foundation, etc.), current bearing capacity, and load requirements for additional floors.

[0039] If the original building has an independent foundation, it can be reinforced by increasing the bottom area of ​​the foundation and adding foundation beams. If it is a raft foundation, a reinforced concrete surface layer can be added to the original raft or anchor static pressure piles 2 can be used for reinforcement. The reinforcement construction is carried out in coordination with the underpinning pile construction.

[0040] At the same time, in conjunction with the construction of underpinning piles, the positions of underpinning piles are set in advance at appropriate locations to prepare for the subsequent foundation underpinning, enhance the bearing capacity of the original foundation, and ensure the structural stability during the construction of the additional floors. Strengthening the original building foundation can enhance its bearing capacity and ensure the stability and safety of the original structure during the construction of the additional floors.

[0041] S4. Analyze the structural stress and deformation of the existing building to be constructed, identify weak areas in the superstructure during construction, and implement secondary reinforcement. Use finite element analysis software and other tools to simulate and analyze the stress and deformation of the existing building superstructure during various stages of the additional floor construction (such as excavation and loading of the new structure).

[0042] Focus on weak areas prone to stress concentration, such as beam-column joints and inter-floor connections. Perform secondary reinforcement by pasting carbon fiber cloth, adding steel plate hoops or increasing component reinforcement to improve the overall stiffness and bearing capacity of the structure and prevent safety issues such as cracking and excessive deformation of the upper structure during the floor-adding construction process.

[0043] By performing structural stress and deformation calculation analysis, safety problems caused by stress changes in the upper structure during the construction of additional floors can be effectively prevented, ensuring the stability of the overall building structure during construction.

[0044] S5, such as Figure 2 As shown, according to the solution in S3, anchor static piles 2 are arranged below the existing foundation column 4. Using the deadweight of the existing building as the reaction force, the pile driving equipment is connected to the foundation through anchor rods, and the pile body is pressed into the pile body section by section until it reaches the designed bearing layer;

[0045] During the construction of the anchor static pressure pile 2, the pile driving equipment is used to press the pile into the ground section by section, controlling the pile driving force and the depth of the pile into the ground. The steel bars supporting the ground beam are reliably connected to the anchor rods of the anchor static pressure pile 2, and the ground beam is effectively connected to the ground wall.

[0046] A supporting ground beam is set on the top of the anchor static pressure pile 2 and is associated with the underpinning platform 1. The ground beam is connected to the anchor static pressure pile 2 and the ground connection wall. The pile row 3 can be used as a part of the ground connection wall to form a stable load transfer system. The additional layer load is transferred to the deep foundation through the anchor static pressure pile 2, ensuring that the existing foundation remains stable after excavation.

[0047] By building a new load transfer system, it is ensured that the foundation pile will not be significantly deformed after excavation, providing a stable foundation support for subsequent construction;

[0048] S6. Excavate the earthwork in the area where the additional layers are to be added in layers and sections. The excavation depth of each layer is determined based on the design requirements and soil stability, and generally does not exceed 2 meters. Use excavators and other equipment for excavation operations, and equip measuring instruments such as levels and theodolites to monitor the excavation depth and foundation pit slope displacement in real time.

[0049] During construction, continuous drainage efforts were implemented. Drainage ditches and sump wells were installed around the foundation pit, and groundwater was pumped out promptly using water pumps to keep the pit dry. Settlement observation points and tilt monitoring points were installed on existing buildings. High-precision measuring instruments were used to monitor deformation in real time and set early warning levels. If deformation data approached the warning level, excavation was immediately halted, the cause analyzed, and appropriate reinforcement or adjustment measures implemented to prevent damage to existing building structures caused by excavation.

[0050] S7. After excavation reaches the designed bottom elevation of the additional floor, clean the foundation pit and lay the concrete cushion. Tie the steel bars according to the design requirements and arrange the bearing and distribution steel bars of the foundation raft, while taking care to avoid the anchor static pressure pile 2.

[0051] Install and reinforce the formwork to ensure it does not deform or leak during the concrete pouring process. Use commercial concrete for pouring, control the concrete slump within an appropriate range, and adopt a layered pouring and vibrating method. Use an inserted vibrator to ensure the concrete is dense. During the vibration process, the vibrator rod must not touch the anchor static pressure pile 2 to ensure the quality of the foundation raft construction and provide a reliable foundation for the additional floor.

[0052] S8. After completing the basement floor construction, build the formwork support system for the frame columns and top plate. The formwork should be made of materials that meet the strength and rigidity requirements, and the support system should ensure sufficient stability.

[0053] Tie the steel bars of the frame columns and top slab according to the designed reinforcement. After acceptance, pour the concrete. Pour the concrete from one end to the other, pouring the frame columns first and then the top slab. Use a flat vibrator to vibrate the top slab concrete to ensure that the concrete is dense.

[0054] When the concrete strength of the frame columns reaches no less than 75% of the design strength (depending on the design requirements), cutting equipment is used to remove the two anchor static pressure piles that exceed the design height in the added story area. Protective measures are taken during the cutting process to avoid damage to the surrounding structure. After removal, the structure is inspected and analyzed to ensure that the newly added concrete columns accurately align vertically with the first-floor columns. Structural calculations and construction measures are used to ensure that both are properly stressed, so that the added story and the existing building form a synergistic, integrated structure.

[0055] At this point, the main structure construction of the additional floor has been completed, and the additional floor renovation of the basement of the existing building has been realized.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A construction method for adding floors to a basement with a multi-story frame structure having an existing box-type foundation, characterized in that: The following steps are involved: S1. Pre-construction assessment: determine whether to add a floor to the basement of an existing building, make a floor addition decision based on functional needs, and obtain design requirements and site geological conditions; S2. Based on the design requirements and on-site geological conditions obtained in S1, use trenching machinery to construct underground continuous walls; and carry out water-stop curtain and pile construction at the existing building where additional floors are to be added; S3. Calculate the original building foundation and determine the reinforcement plan for the building's ground floor and original foundation based on the foundation type, current bearing capacity, and load requirements for additional floors; S4. Carry out structural stress and deformation calculation analysis for the existing building to be constructed, identify weak points in the superstructure during construction and perform secondary reinforcement; S5. Arrange anchor static pressure piles under the existing foundation according to the design plan in S3; Using the deadweight of the existing building as the reaction force, the pile driving equipment is connected to the foundation through anchor rods, and the pile is pressed into the body section by section until it reaches the designed bearing layer; S6. Excavate the earthwork of the area where the additional floor is to be added in layers; S7. After excavation reaches the bottom elevation of the added floor, the raft slab of the added basement foundation is poured; S8. Carry out the casting construction of frame columns and top plates within the height range of the added storey. After the strength of the columns reaches the design requirements, cut and remove the anchor static pressure piles at the added storey.

2. The construction method for adding a floor to a basement with a multi-story frame structure of an existing box-type foundation according to claim 1 is characterized in that: In S2, the water-stop curtain adopts the interlocking pile technology, in which adjacent piles interlock with each other to form a continuous water-stop barrier. The pile rows are selected from cast-in-place piles or prefabricated piles according to the geological conditions. The verticality, pile diameter and pile spacing of the piles are strictly controlled during the construction process.

3. The construction method for adding a floor to a basement with a multi-story frame structure of an existing box-type foundation according to claim 1 is characterized in that: In S3, if the original building has an independent foundation, it is reinforced by increasing the bottom area of ​​the foundation and adding foundation beams; if it is a raft foundation, a reinforced concrete surface layer is added to the original raft or anchor static pressure piles are used for reinforcement. The reinforcement construction is carried out in coordination with the underpinning pile construction.

4. The construction method for adding a floor to a basement with a multi-story frame structure of an existing box-type foundation according to claim 1 is characterized in that: In S5, during the construction of anchor static pressure piles, pile driving equipment is used to press them in sections, controlling the pile driving force and the depth of penetration into the soil. The steel bars supporting the ground beam are connected to the anchor rods of the anchor static pressure piles, and the ground beam is connected to the ground connection wall.

5. The construction method for adding a floor to a basement of a multi-story frame structure with an existing box-type foundation according to claim 1 is characterized in that: In S6, the depth of each layer of earthwork excavation does not exceed 2m. Level instruments and total stations are used to monitor the excavation depth. Settlement observation points and tilt monitoring points are arranged on existing buildings. High-precision measuring instruments are used to monitor deformation in real time and set early warning values.

6. The construction method for adding a floor to a basement of a multi-story frame structure with an existing box-type foundation according to claim 1 is characterized in that: In S7, the foundation raft slab concrete is poured in layers and vibrated in layers. Commercial concrete is used to control the slump and avoid the vibrating rod from touching the anchor static pressure pile during the pouring process.

7. The construction method for adding a floor to a basement of a multi-story frame structure with an existing box-type foundation according to claim 1 is characterized in that: In S8, the frame columns and top slabs are cured after concrete pouring. When the column strength reaches no less than 75% of the design strength, the anchor static pressure piles are removed using cutting equipment. After removal, the structure is inspected and analyzed.

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