Design method and device for high-rise building raft foundation on soil-rock combined foundation

Abstract

The invention provides a method and a device for designing a raft foundation of a high-rise building on a soil-rock combined foundation. The method comprises the following steps of: transmitting an acting force to a raft based on the arrangement position of a vertical component; based on the acting force and geological survey data, whether the bearing capacity of the soil layer and the bed rock meets the design requirement of adopting a raft foundation or not is judged, and if yes, preliminary design parameters of a raft are determined; based on geological survey data, determining an estimated boundary between a soil layer and a bedrock at the elevation of the bottom plate; setting parameters of the mattress layer are determined based on the position of the pre-estimated boundary and the properties of the soil layer and the bedrock; and determining a foundation reaction and deformation checking calculation result of the high-rise building raft foundation based on the set parameters and the preliminary design parameters, and adjusting the set parameters and / or the preliminary design parameters when the foundation reaction and deformation checking calculation result does not meet requirements. By means of the compressibility of the mattress layer, deformation of the soil-rock combined foundation is coordinated, and differential settlement is effectively controlled.

Description

Technical Field

[0001] This invention relates to the field of high-rise building structural foundation design technology, specifically to a design method and device for a raft foundation for a high-rise building on a soil-rock composite foundation. Background Technology

[0002] In high-rise building foundation engineering, soil-rock composite foundations are a common and complex geological condition. The "Code for Design of Building Foundations" GB50007-2011 specifies that soil-rock composite foundations mainly include foundations with steep underlying bedrock slopes, foundations with densely exposed boulders, and foundations with large isolated boulders or individual exposed boulders. For foundations with mixed soil and rock without clear boundaries, local replacement or the installation of a cushion layer are commonly used in engineering. However, for soil-rock composite foundations with clear boundaries—that is, when the foundation base rests simultaneously on a continuous soil layer and a large area of ​​exposed hard bedrock—traditional design methods face significant challenges.

[0003] To ensure reliable and uniform bearing capacity, traditional designs often employ a hybrid support scheme combining localized natural foundations and localized pile foundations. In exposed bedrock areas, the raft foundation is placed directly on the bedrock as a natural foundation; in soil-covered areas, bored piles penetrate the soil to transfer the load to the underlying bedrock. While this scheme aims to unify the bearing stratum, it has significant theoretical and practical drawbacks: 1. The deformation mechanisms and stiffness of natural foundations (bedrock) and pile foundations are drastically different. Bedrock has extremely low compressibility, while pile foundations are affected by pile compression, pile tip sediment, and pile-soil interaction, resulting in complex and difficult-to-calculate settlement characteristics. When both support the same rigid raft foundation, the significant stiffness difference inevitably leads to differential settlement, generating additional stresses within the raft foundation that are difficult to accurately predict. 2. The individual pile stiffness of piles of varying lengths belongs to different mechanical systems than the subgrade coefficient of the natural bedrock. This makes it difficult to accurately assign and coordinate values ​​within the same raft foundation analysis model, leading to significant deviations between theoretical calculations and actual conditions, and making design adjustments difficult. 3. Part of the raft foundation is in direct contact with rigid bedrock, while another part is supported by rigid piles, creating a hard-on-hard support structure. In the soil-rock interface area, significant stress concentration exists within the raft foundation, posing a potential threat to structural safety. 4. Drilled pile construction with bedrock as the bearing stratum is difficult, inefficient, and costly. Furthermore, to control pile settlement and ensure coordination with natural foundation deformation, extremely strict requirements are placed on controlling the thickness of sediment at the pile bottom, further increasing construction difficulty and cost.

[0004] Therefore, there is an urgent need to provide a design method and device for raft foundations of high-rise buildings on soil-rock composite foundations, so as to achieve accurate calculation, convenient construction and economical and safe design of raft foundations for high-rise buildings on soil-rock composite foundations with clear boundaries. Summary of the Invention

[0005] In view of this, it is necessary to provide a design method and device for raft foundations of high-rise buildings on soil-rock composite foundations, in order to solve the technical problems of poor calculation accuracy and inconvenient construction of the traditional mixed support scheme of local natural foundation + local pile foundation in the existing technology.

[0006] To address the aforementioned technical problems, in a first aspect, the present invention provides a design method for a raft foundation of a high-rise building on a soil-rock composite foundation. The raft foundation of the high-rise building includes a raft slab and a cushion layer, and the soil-rock composite foundation includes a clearly defined soil layer and bedrock. The method includes: A structural calculation model is established based on the placement of the vertical components, and the force transmitted from the vertical components to the raft slab is determined based on the structural calculation model. Based on the forces and geological survey data, determine whether the bearing capacity of the soil layer and the bedrock meets the design requirements for a raft foundation. If it does, determine the preliminary design parameters of the raft foundation, which include planar dimensions, thickness and bottom elevation. Based on geological survey data, the estimated boundary between the soil layer and the bedrock is determined at the bottom elevation. The setting parameters of the mattress layer are determined based on the location of the estimated boundary line, the properties of the soil layer and the bedrock. The setting parameters include the mattress layer thickness and the mattress layer range. The mattress layer thickness in the bedrock area adjacent to the estimated boundary line is greater than the mattress layer thickness in other bedrock areas. Based on the setting parameters and the preliminary design parameters, the foundation reaction force and deformation verification results of the raft foundation of the high-rise building are determined. When the foundation reaction force and deformation verification results do not meet the requirements, the setting parameters and / or the preliminary design parameters are adjusted until the foundation reaction force and deformation verification results meet the requirements, and the setting parameters that meet the requirements are taken as the target setting parameters.

[0007] In one possible implementation, the mattress layer is made of graded sand and gravel, which includes medium-coarse sand and gravel, with a mass ratio of medium-coarse sand to gravel of 7:3, and the gravel has a particle size of less than or equal to 50 mm.

[0008] In one possible implementation, the compaction degree of the mattress layer is less than or equal to 0.9.

[0009] In one possible implementation, the thickness of the cushion layer in the bedrock area adjacent to the estimated boundary line is 450mm to 550mm, and the thickness of the cushion layer in other bedrock areas is 250mm to 350mm.

[0010] In one possible implementation, determining the foundation reaction and deformation verification results of the high-rise building raft foundation based on the setting parameters and the preliminary design parameters includes: Based on the setting parameters and the preliminary design parameters, determine the first subgrade coefficient of the soil layer and the second subgrade coefficient of the bedrock for which the cushion layer is set; The foundation reaction and deformation verification results of the raft foundation of the high-rise building are determined based on the first subgrade coefficient and the second subgrade coefficient.

[0011] In one possible implementation, the method further includes: The actual bedrock coefficient of the bedrock for which the mattress layer is set was determined based on in-situ experiments; When the difference between the actual bed coefficient and the second bed coefficient is greater than the preset difference, the setting parameters and / or the preliminary design parameters are adjusted.

[0012] In one possible implementation, the method further includes: Obtain the actual boundary line between the soil layer and the bedrock after on-site construction excavation; Determine whether the actual boundary line is inconsistent with the estimated boundary line; If there is a discrepancy, the setting parameters of the mattress layer are updated based on the actual boundary line, and the target setting parameters are determined based on the updated setting parameters.

[0013] In one possible implementation, the method further includes: Obtain the shear stress of the raft foundation of the high-rise building adjacent to the estimated boundary line, and configure shear reinforcement based on the shear stress.

[0014] In one possible implementation, the high-rise building raft foundation further includes a brick formwork and a foundation cushion layer, wherein the brick formwork is disposed between the soil layer and the cushion layer, and the foundation cushion layer is disposed between the cushion layer and the raft slab.

[0015] Secondly, the present invention also provides a design device for a raft foundation of a high-rise building on a soil-rock composite foundation. The raft foundation of the high-rise building includes a raft slab and a cushion layer, and the soil-rock composite foundation includes a clearly defined soil layer and bedrock. The device includes: The force determination unit is used to establish a structural calculation model based on the layout position of the vertical members, and to determine the force transmitted from the vertical members to the raft slab based on the structural calculation model. The preliminary design parameter determination unit is used to determine whether the bearing capacity of the soil layer and the bedrock meets the design requirements for using a raft foundation based on the forces and geological survey data. If they do meet the requirements, the preliminary design parameters of the raft foundation are determined. The preliminary design parameters include planar dimensions, thickness and bottom elevation. The estimated boundary line determination unit is used to determine the estimated boundary line between the soil layer and the bedrock at the bottom elevation based on geological survey data. A mattress layer setting parameter determination unit is used to determine the setting parameters of the mattress layer based on the location of the estimated boundary line, the properties of the soil layer and the bedrock. The setting parameters include mattress layer thickness and mattress layer range. The mattress layer thickness in the area where the bedrock is located adjacent to the estimated boundary line is greater than the mattress layer thickness in other bedrock areas. The verification unit is used to determine the foundation reaction force and deformation verification results of the high-rise building raft foundation based on the setting parameters and the preliminary design parameters. When the foundation reaction force and deformation verification results do not meet the requirements, the setting parameters and / or the preliminary design parameters are adjusted until the foundation reaction force and deformation verification results meet the requirements, and the setting parameters that meet the requirements are used as the target setting parameters.

[0016] The beneficial effects of this invention are as follows: The design method for raft foundations of high-rise buildings on soil-rock composite foundations provided by this invention sets up a cushion layer in the bedrock area. Utilizing the compressibility of the cushion layer, it changes the traditional hard-on-hard support state, achieving soft support, thereby fundamentally coordinating the deformation of the soil-rock composite foundation and effectively controlling differential settlement. Simultaneously, this invention sets the cushion layer thickness in the bedrock area near the estimated boundary line to be greater than the cushion layer thickness in other bedrock areas, achieving zoned support settings. This further eliminates the root cause of differential settlement between the bedrock and soil layers, making the raft foundation settlement more uniform. This ensures that the determined stress highly matches the actual stress conditions, improving the accuracy of stress calculation, eliminating stress concentration problems, and improving structural safety.

[0017] Furthermore, this invention completely avoids the highly difficult and costly process of drilling and grouting piles in hard bedrock. The construction process of the cushion layer is simple, the quality is easy to control, the overall construction cycle is greatly shortened, the comprehensive cost is significantly reduced, and it has outstanding economic benefits.

[0018] Furthermore, this invention verifies the setting parameters based on the foundation reaction force and deformation calculation results, ensuring the accuracy of the final target setting parameters and greatly improving the quality and reliability of the project. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1A schematic flowchart of an embodiment of the design method for raft foundation of high-rise buildings on soil-rock composite foundation provided by the present invention; Figure 2 A flowchart illustrating an embodiment of the present invention for determining the calculation results of foundation reaction force and deformation; Figure 3 This is a schematic flowchart of an embodiment of the present invention for verifying target setting parameters based on actual boundary lines; Figure 4 A raft foundation plan for a high-rise building; Figure 5 for Figure 4 AA cross-section view; Figure 6 for Figure 4 BB cross-section; Figure 7 for Figure 4 CC cross-section; Figure 8 This is a schematic diagram of an embodiment of the design device for a raft foundation of a high-rise building on a soil-rock composite foundation provided by the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0022] It should be understood that the schematic drawings are not drawn to scale. The flowcharts used in this invention illustrate operations implemented according to some embodiments of the invention. It should be understood that the operations in the flowcharts may be implemented out of order, and steps without logical contextual relationships may be reversed or performed simultaneously. Furthermore, those skilled in the art, guided by the content of this invention, may add one or more other operations to the flowcharts, or remove one or more operations from the flowcharts. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities may be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0023] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0024] This invention provides a design method and apparatus for a raft foundation for a high-rise building on a soil-rock composite foundation. The raft foundation for the high-rise building includes a raft slab and a cushion layer, and the soil-rock composite foundation includes a clearly defined soil layer and bedrock.

[0025] Specifically, high-rise buildings refer to residential buildings with 10 or more floors or a building height greater than 28 meters, as well as other civil buildings with a building height greater than 24 meters.

[0026] The definitions of soil-rock composite foundations with and without clear boundaries are as follows: A soil-rock composite foundation with clear boundaries refers to a foundation where, at the bottom elevation, there is a relatively clear and continuous boundary line between continuous soil layers and continuous bedrock layers. The foundation is clearly divided into two main parts: the soil area and the bedrock. A soil-rock composite foundation without clear boundaries refers to a foundation where the soil layers contain a large number of rock fragments, pebbles, or isolated rocks, but the rocks are not connected into large areas; instead, they are interspersed and interwoven with the soil, without a clear and continuous boundary line.

[0027] The following sections provide a detailed description of the design method and apparatus for raft foundations of high-rise buildings on soil-rock composite foundations in the embodiments of the present invention.

[0028] Figure 1 A schematic flowchart illustrating an embodiment of the design method for raft foundations of high-rise buildings on soil-rock composite foundations provided by the present invention is shown below. Figure 1 As shown, the design methods for raft foundations of high-rise buildings on soil-rock composite foundations include: S101. Establish a structural calculation model based on the layout of vertical members, and determine the force transmitted from the vertical members to the raft slab based on the structural calculation model.

[0029] Vertical components include, but are not limited to, reinforced concrete columns, steel columns, and structural walls.

[0030] S102. Based on the force and geological survey data, determine whether the bearing capacity of the soil layer and bedrock meets the design requirements for using a raft foundation. If it does, determine the preliminary design parameters of the raft foundation, including the planar dimensions, thickness and bottom elevation.

[0031] It should be understood that when the bearing capacity of the soil and bedrock does not meet the design requirements for raft foundations, it means that the bearing capacity of the soil-rock composite foundation cannot meet the requirements of high-rise buildings. In this case, designers need to carry out additional special designs, which are not within the scope of discussion of the embodiments of this invention.

[0032] S103. Based on geological survey data, determine the estimated boundary between the soil layer and the bedrock at the bottom elevation.

[0033] Determining the estimated boundary line based on geological exploration data is a mature engineering geological interpretation technique, which will not be elaborated here.

[0034] S104. Determine the setting parameters of the cushion layer based on the location of the estimated boundary line, the properties of the soil layer and the bedrock. The setting parameters include the thickness and range of the cushion layer. Among them, the thickness of the cushion layer in the bedrock area adjacent to the estimated boundary line is greater than the thickness of the cushion layer in other bedrock areas.

[0035] The adjacent estimated boundary line refers to the area that is less than the set distance from the estimated boundary line. The set area can be set or adjusted based on the actual engineering scenario, and no specific limitation is made here.

[0036] S105. Based on the setting parameters and preliminary design parameters, determine the foundation reaction force and deformation verification results of the raft foundation of high-rise buildings. If the foundation reaction force and deformation verification results do not meet the requirements, adjust the setting parameters and / or preliminary design parameters until the foundation reaction force and deformation verification results meet the requirements, and take the setting parameters that meet the requirements as the target setting parameters.

[0037] When the results of the foundation reaction and deformation verification meet the requirements, the setting parameters at this time will be used as the target setting parameters.

[0038] Specifically, the deformation verification results include, but are not limited to, the results of the raft slab's punching shear and shear resistance.

[0039] It should be understood that the design method for raft foundations of high-rise buildings on soil-rock composite foundations in this embodiment of the invention can be implemented in any device based on the design method for raft foundations of high-rise buildings on soil-rock composite foundations. Specifically, the design method for raft foundations of high-rise buildings on soil-rock composite foundations is stored in the device as a pre-programmed program. When the device is started, the program is called, and the design method for raft foundations of high-rise buildings on soil-rock composite foundations is implemented.

[0040] Compared with existing technologies, the design method for raft foundations of high-rise buildings on soil-rock composite foundations provided in this invention sets up a cushion layer in the bedrock area. Utilizing the compressibility of the cushion layer, it changes the traditional hard-on-hard support state, achieving soft support, thereby fundamentally coordinating the deformation of the soil-rock composite foundation and effectively controlling differential settlement. Simultaneously, this invention sets the cushion layer thickness in the bedrock area near the estimated boundary line to be greater than the cushion layer thickness in other bedrock areas, achieving zoned support settings. This further eliminates the root cause of differential settlement between the bedrock and soil layers, making the raft foundation settlement more uniform. This ensures that the determined stress closely matches the actual stress conditions, improving the accuracy of stress calculations and eliminating stress concentration problems, thus enhancing structural safety.

[0041] Furthermore, the embodiments of the present invention completely avoid the highly difficult and costly process of drilling and grouting piles in hard bedrock. The construction process of the cushion layer is simple, the quality is easy to control, the overall construction cycle is greatly shortened, the comprehensive cost is significantly reduced, and it has outstanding economic benefits.

[0042] Furthermore, the embodiments of the present invention verify the setting parameters based on the foundation reaction force and deformation calculation results, ensuring the accuracy of the final target setting parameters and greatly improving the quality and reliability of the project.

[0043] To ensure that the mattress layer has a suitable compression modulus and deformation capacity, in some embodiments of the present invention, the mattress layer material is graded sand and gravel, which includes medium and coarse sand and gravel, with a mass ratio of medium and coarse sand to gravel of 7:3, and the particle size of the gravel is less than or equal to 50 mm.

[0044] Among them, medium and coarse sand refers to a mixture of medium and coarse sand, while coarse and medium sand refer to the types of sand specified in national standards or industry specifications based on fineness modulus.

[0045] This invention employs a 7:3 mass ratio of medium-coarse sand to gravel, creating a rational particle skeleton and filling structure. This ratio allows the material to combine the compactness of sand with the skeletal function of gravel, resulting in a moderate and stable deformation modulus. This allows for both compressive deformation to coordinate differential settlement between soil and rock, and sufficient bearing capacity to effectively diffuse stress. Secondly, limiting the maximum gravel size to no more than 50mm prevents material segregation and ensures the uniformity of the overall properties of the cushion layer; it also avoids the concentration of excessively large particles during compaction, which could affect construction quality. Furthermore, the graded sand and gravel are common building materials, lowering the implementation threshold and cost.

[0046] To further control the construction quality of the mattress layer, in a specific embodiment of the present invention, the compaction degree of the mattress layer is less than or equal to 0.9.

[0047] Among them, the compaction degree is a key parameter for measuring the density and deformation of filling materials. In this embodiment of the invention, by setting the compaction degree of the mattress layer to be less than or equal to 0.9, the basic requirements of the standard for the density of the mattress layer can be met, and the requirements for adjusting the subgrade coefficient and deformation capacity of the bedrock area can also be met by controlling the compaction degree.

[0048] To further improve the overall deformation consistency of the raft slab, in some embodiments of the present invention, the thickness of the cushion layer in the bedrock area adjacent to the estimated boundary line is 450mm~550mm, and the thickness of the cushion layer in other bedrock areas is 250mm~350mm.

[0049] This invention differentiates the thickness of the cushion layer in the bedrock area near the estimated boundary line from the thickness of the cushion layer in other bedrock areas. This actively forms a deformation buffer zone at the junction where the stiffness changes abruptly between the soil layer and the bedrock, making the foundation support change from stiffness to a gradual change, effectively eliminating stress concentration and significantly reducing differential settlement.

[0050] It should be noted that the thickness of the cushion layer can be adaptively selected based on the relative deformation capacity of the bedrock and soil layers. Specifically, a higher value should be used when the relative deformation capacity difference is large, and a lower value should be used when the relative deformation capacity difference is small.

[0051] In some embodiments of the present invention, such as Figure 2 As shown, step S105, which involves determining the foundation reaction force and deformation verification results of the raft foundation of a high-rise building based on the set parameters and preliminary design parameters, includes: S201. Determine the first subgrade coefficient of the soil layer and the second subgrade coefficient of the bedrock for which the cushion layer is set based on the setting parameters and preliminary design parameters.

[0052] Specifically, the first subgrade coefficient can be obtained directly from geological exploration data. The second subgrade coefficient is an equivalent value that takes into account the compression deformation of the cushion layer, and it is determined based on the design thickness of the cushion layer and the deformation modulus after compaction.

[0053] S202. Based on the first and second subgrade coefficients, determine the ground reaction force and deformation verification results of the raft foundation of high-rise buildings.

[0054] The specific process for determining the foundation reaction force and deformation verification results is as follows: establish a finite element model of the raft foundation of the high-rise building, assign the first foundation coefficient and the second subgrade coefficient to the mesh, perform finite element simulation, and obtain the foundation reaction force and deformation verification results.

[0055] This invention, by introducing a first and second subgrade bed coefficient for each zone, enables the establishment of a computational model in conventional foundation design software that accurately reflects the non-uniformity of foundation stiffness. The physical meanings of the model parameters are clearly defined (deformation modulus and thickness of the mattress layer). When the verification results do not meet the requirements, rapid optimization can be achieved by adjusting the setting parameters and / or preliminary design parameters, making the design process efficient and controllable.

[0056] In practical applications, a discrepancy may arise between the second subgrade coefficient determined during the design phase and the actual subgrade coefficient after construction. To avoid this technical problem leading to inaccurate target setting parameters, in some embodiments of the present invention, the design method for raft foundations of high-rise buildings on soil-rock composite foundations further includes: The actual bedrock coefficient of the bedrock for which the mattress layer is set was determined based on in-situ experiments; When the difference between the actual subgrade coefficient and the second subgrade coefficient is greater than the preset difference, adjust the setting parameters and / or preliminary design parameters.

[0057] The preset difference can be set or adjusted according to the actual application scenario, and no specific limitation is made here.

[0058] The embodiments of the present invention verify the second subgrade coefficient based on the actual subgrade coefficient, which can ensure the final calculation results are consistent with the actual scenario, and greatly improve the accuracy and reliability of the design method of raft foundation for high-rise buildings on soil-rock composite foundation.

[0059] Furthermore, since geological exploration data is obtained based on point boreholes, the estimated boundary lines determined by these boreholes may contain errors. To further improve the accuracy of target setting parameters, in some embodiments of the present invention, such as... Figure 3 As shown, the design method for raft foundations of high-rise buildings on soil-rock composite foundations also includes: S301. Obtain the actual boundary line between the soil layer and the bedrock after on-site construction excavation; S302. Determine whether the actual boundary line is inconsistent with the estimated boundary line; S303. If there is a discrepancy, update the setting parameters of the mattress layer based on the actual boundary line, and determine the target setting parameters based on the updated setting parameters.

[0060] This invention, through the implementation of an excavation-comparison-dynamic adjustment process, enables the design method to adapt to changes in geological conditions, thereby ensuring the accuracy of the parameters for setting the cushion layer.

[0061] In other words, by performing dual verification on the estimated boundary line and the second bed coefficient, the embodiments of the present invention enable the design method to have the ability to self-verify and self-adjust, thereby improving the reliability and robustness of the design method.

[0062] It should be noted that during the design review, provided that the bearing capacity and deformation requirements of the specifications are met, the thickness of the raft slab and the foundation elevation, which have a significant impact on subsequent on-site construction, can be left unchanged. Only the concrete strength grade and reinforcement of the raft slab need to be adjusted according to the measured boundary between the soil layer and the bedrock and the foundation deformation parameters.

[0063] The embodiments of the present invention coordinate differential settlement of soil and rock by setting a cushion layer, which changes the support conditions of the foundation, but it cannot completely eliminate the stiffness difference. Therefore, in actual engineering applications, shear stress still exists at the soil-rock boundary.

[0064] To further improve the rationality and accuracy of raft foundations for high-rise buildings, in some embodiments of the present invention, the shear stress of the raft foundation of the high-rise building near the estimated boundary line is obtained, and shear reinforcement is configured based on the shear stress.

[0065] The embodiments of the present invention provide a safety redundancy for the determined raft foundation of high-rise buildings by configuring shear-resistant reinforcement based on shear stress, thereby further improving construction quality and safety.

[0066] At the boundary between soil and rock, there is a construction challenge: if there is no support between the loose cushion layer and the adjacent soil slope, the slope will collapse, causing the cushion layer to mix with the soil and making it impossible to form a cushion layer of uniform thickness and material as required by the design.

[0067] To address this technical problem, in a specific embodiment of the present invention, the raft foundation of a high-rise building further includes a brick formwork, which is disposed between the soil layer and the mattress layer.

[0068] In this embodiment of the method, the brick formwork acts as a sturdy, vertical temporary retaining wall, precisely separating the earthwork and the bedding layer. This ensures that the bedding layer in the bedrock can be filled and compacted according to the designed shape and thickness. It also provides a safe and stable working surface for subsequent bedding layer laying and compaction operations.

[0069] To prevent damage or contamination of the mattress layer during subsequent construction, in a specific embodiment of the present invention, the raft foundation of a high-rise building also includes a foundation mattress layer, which is disposed between the mattress layer and the raft foundation.

[0070] The foundation pad can be C15 concrete.

[0071] The foundation padding layer provided in this embodiment of the invention serves to isolate and protect the mattress layer, ensuring its integrity during subsequent construction.

[0072] Specifically, the relationship between the mattress layer and the base layer is as follows: the mattress layer extends 100mm beyond the edge of the base layer in the exposed bedrock area. This arrangement ensures complete coverage by the mattress layer, prevents hard spots from being exposed, and also prevents the mattress layer material from being squeezed out at the edges.

[0073] It should be noted that if there are local areas in the soil layer where the bearing capacity of the foundation does not meet the requirements and there are conditions to excavate and replace the soil, C15 concrete 11 can be used for replacement to improve the local foundation bearing capacity of the soil layer.

[0074] In one specific embodiment of the present invention, such as Figure 4-7 As shown, the unique relationship between the numbers and components is as follows: 1. Raft foundation of high-rise building; 2. Vertical component; 3. Estimated boundary line; 4. Actual boundary line; 5. Area where the local foundation bearing capacity of the soil layer does not meet the requirements and can be excavated and replaced; 6. Brick formwork; 7. Cushion layer in other bedrock areas; 8. Cushion layer in bedrock areas adjacent to the estimated boundary line; 9. Foundation cushion layer; 10. Shear reinforcement; 11. C15 concrete.

[0075] In summary, the design method for raft foundations of high-rise buildings on soil-rock composite foundations proposed in this invention avoids the use of partial natural foundations + partial bored pile foundations in such buildings. Instead, it adopts a design method of natural soil-rock composite foundation + integral cushion layer in the bedrock zone, and uses transition treatment in the cushion layer at the exposed soil-rock interface to reduce differential deformation. Simultaneously, shear reinforcement measures are implemented at the corresponding soil-rock interface during raft foundation design to ensure structural safety. The structural concept is clear, the force transmission path is direct, the theoretical calculations for the raft foundation match the actual situation well, construction is convenient, the cost is economical, and safety is controllable. Verified through engineering practice, it can be widely used.

[0076] On the other hand, embodiments of the present invention also provide a design device for raft foundations of high-rise buildings on soil-rock composite foundations, such as... Figure 8 As shown, a design device 800 for a raft foundation of a high-rise building on a soil-rock composite foundation is provided. The raft foundation of the high-rise building includes a raft slab and a cushion layer. The soil-rock composite foundation includes clearly defined soil layers and bedrock. The device includes: Force determination unit 801 is used to establish a structural calculation model based on the layout position of vertical members, and to determine the force transmitted from the vertical members to the raft slab based on the structural calculation model. The preliminary design parameter determination unit 802 is used to determine whether the bearing capacity of the soil layer and bedrock meets the design requirements for using a raft foundation based on the force and geological survey data. If it does, the preliminary design parameters of the raft foundation are determined. The preliminary design parameters include planar dimensions, thickness and bottom elevation. The estimated boundary line determination unit 803 is used to determine the estimated boundary line between the soil layer and the bedrock at the bottom elevation based on geological survey data. The mattress layer setting parameter determination unit 804 is used to determine the setting parameters of the mattress layer based on the location of the estimated boundary line, the properties of the soil layer and the bedrock. The setting parameters include the mattress layer thickness and the mattress layer range; wherein, the mattress layer thickness in the bedrock area adjacent to the estimated boundary line is greater than the mattress layer thickness in other bedrock areas. The verification unit 805 is used to determine the foundation reaction force and deformation verification results of the raft foundation of high-rise buildings based on the setting parameters and preliminary design parameters. When the foundation reaction force and deformation verification results do not meet the requirements, the setting parameters and / or preliminary design parameters are adjusted until the foundation reaction force and deformation verification results meet the requirements, and the setting parameters that meet the requirements are used as the target setting parameters.

[0077] The design device 800 for raft foundations of high-rise buildings on soil-rock composite foundations provided in the above embodiments can realize the technical solutions described in the above embodiments of the design method for raft foundations of high-rise buildings on soil-rock composite foundations. The specific implementation principles of each module or unit can be found in the corresponding content in the above embodiments of the design method for raft foundations of high-rise buildings on soil-rock composite foundations, and will not be repeated here.

[0078] Those skilled in the art will understand that all or part of the processes of the methods described in the above embodiments can be implemented by a computer program instructing related hardware (such as a processor, controller, etc.), and the computer program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a disk, optical disk, read-only memory, or random access memory, etc.

[0079] The above provides a detailed description of the design method and device for a raft foundation of a high-rise building on a soil-rock composite foundation provided by the present invention. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A design method for raft foundations of high-rise buildings on soil-rock composite foundations, characterized in that, A raft foundation for a high-rise building includes a raft slab and a cushion layer; a soil-rock composite foundation includes clearly defined soil layers and bedrock; the method includes: A structural calculation model is established based on the placement of the vertical components, and the force transmitted from the vertical components to the raft slab is determined based on the structural calculation model. Based on the forces and geological survey data, determine whether the bearing capacity of the soil layer and the bedrock meets the design requirements for a raft foundation. If it does, determine the preliminary design parameters of the raft foundation, which include planar dimensions, thickness and bottom elevation. Based on geological survey data, the estimated boundary between the soil layer and the bedrock is determined at the bottom elevation. The setting parameters of the mattress layer are determined based on the location of the estimated boundary line, the properties of the soil layer and the bedrock. The setting parameters include the mattress layer thickness and the mattress layer range. The mattress layer thickness in the bedrock area adjacent to the estimated boundary line is greater than the mattress layer thickness in other bedrock areas. Based on the setting parameters and the preliminary design parameters, the foundation reaction force and deformation verification results of the raft foundation of the high-rise building are determined. When the foundation reaction force and deformation verification results do not meet the requirements, the setting parameters and / or the preliminary design parameters are adjusted until the foundation reaction force and deformation verification results meet the requirements, and the setting parameters that meet the requirements are taken as the target setting parameters.

2. The design method for raft foundations of high-rise buildings on soil-rock composite foundations according to claim 1, characterized in that, The mattress layer is made of graded sand and gravel, which includes medium and coarse sand and gravel. The mass ratio of the medium and coarse sand to the gravel is 7:3, and the particle size of the gravel is less than or equal to 50 mm.

3. The design method for raft foundations of high-rise buildings on soil-rock composite foundations according to claim 1, characterized in that, The compaction degree of the mattress layer is less than or equal to 0.

9.

4. The design method for raft foundations of high-rise buildings on soil-rock composite foundations according to claim 1, characterized in that, The thickness of the cushion layer in the bedrock area adjacent to the estimated boundary line is 450mm~550mm, and the thickness of the cushion layer in other bedrock areas is 250mm~350mm.

5. The design method for raft foundations of high-rise buildings on soil-rock composite foundations according to claim 1, characterized in that, The determination of the foundation reaction force and deformation verification results of the high-rise building raft foundation based on the set parameters and the preliminary design parameters includes: Based on the setting parameters and the preliminary design parameters, determine the first subgrade coefficient of the soil layer and the second subgrade coefficient of the bedrock for which the cushion layer is set; The foundation reaction and deformation verification results of the raft foundation of the high-rise building are determined based on the first subgrade coefficient and the second subgrade coefficient.

6. The design method for raft foundations of high-rise buildings on soil-rock composite foundations according to claim 5, characterized in that, The method further includes: The actual bedrock coefficient of the bedrock for which the mattress layer is set was determined based on in-situ experiments; When the difference between the actual bed coefficient and the second bed coefficient is greater than the preset difference, the setting parameters and / or the preliminary design parameters are adjusted.

7. The design method for raft foundations of high-rise buildings on soil-rock composite foundations according to claim 1, characterized in that, The method further includes: Obtain the actual boundary line between the soil layer and the bedrock after on-site construction excavation; Determine whether the actual boundary line is inconsistent with the estimated boundary line; If there is a discrepancy, the setting parameters of the mattress layer are updated based on the actual boundary line, and the target setting parameters are determined based on the updated setting parameters.

8. The design method for raft foundations of high-rise buildings on soil-rock composite foundations according to claim 1, characterized in that, The method further includes: Obtain the shear stress of the raft foundation of the high-rise building adjacent to the estimated boundary line, and configure shear reinforcement based on the shear stress.

9. The design method for raft foundations of high-rise buildings on soil-rock composite foundations according to claim 1, characterized in that, The raft foundation of the high-rise building also includes a brick formwork and a foundation pad, wherein the brick formwork is disposed between the soil layer and the pad layer, and the foundation pad is disposed between the pad layer and the raft slab.

10. A design device for a raft foundation of a high-rise building on a soil-rock composite foundation, characterized in that, The raft foundation of a high-rise building includes a raft slab and a cushion layer; the soil-rock composite foundation includes clearly defined soil layers and bedrock; the device includes: The force determination unit is used to establish a structural calculation model based on the layout position of the vertical members, and to determine the force transmitted from the vertical members to the raft slab based on the structural calculation model. The preliminary design parameter determination unit is used to determine whether the bearing capacity of the soil layer and the bedrock meets the design requirements for using a raft foundation based on the forces and geological survey data. If they do meet the requirements, the preliminary design parameters of the raft foundation are determined. The preliminary design parameters include planar dimensions, thickness and bottom elevation. The estimated boundary line determination unit is used to determine the estimated boundary line between the soil layer and the bedrock at the bottom elevation based on geological survey data. A mattress layer setting parameter determination unit is used to determine the setting parameters of the mattress layer based on the location of the estimated boundary line, the properties of the soil layer and the bedrock. The setting parameters include mattress layer thickness and mattress layer range. The mattress layer thickness in the area where the bedrock is located adjacent to the estimated boundary line is greater than the mattress layer thickness in other bedrock areas. The verification unit is used to determine the foundation reaction force and deformation verification results of the high-rise building raft foundation based on the setting parameters and the preliminary design parameters. When the foundation reaction force and deformation verification results do not meet the requirements, the setting parameters and / or the preliminary design parameters are adjusted until the foundation reaction force and deformation verification results meet the requirements, and the setting parameters that meet the requirements are used as the target setting parameters.

Images