What principles should be met in the design of the foundation

The design of the foundation shall comply with the following provisions:

1. The foundation calculation of all buildings shall meet the relevant provisions of the bearing capacity calculation.

2. Buildings with design grades of Grade A and Grade B should be designed according to the deformation of the foundation.

3. When a building with a design grade of C has one of the following circumstances, it should be deformed for verification.

The characteristic value of the bearing capacity of the foundation is less than 130kpa, and the building is complex.

When there is a ground load on the foundation and its vicinity or the load difference of adjacent foundations is large, which may cause excessive uneven settlement of the foundation.

When there is an eccentric load on a building on a weak foundation.

When adjacent buildings are close to each other and may be tilted.

When there is a large thickness or uneven thickness of fill soil in the foundation, and its self-weight consolidation is not completed.

Ground type. From the perspective of on-site construction, the foundation can be divided into natural foundation and artificial foundation. The foundation is the rock and soil bearing layer under the pressure under the foundation.

The natural foundation is a natural soil layer that can meet the requirements of bearing all the loads of the foundation in a natural state and does not need to be reinforced by man, which saves the project cost and does not need to be manually treated.

A natural foundation is a natural soil layer in which the foundation can be placed directly without the need to treat the foundation. It is divided into four main categories: rock, gravel soil.

Sandy soil, cohesive soil.

The principle of foundation treatment design is "to adapt to local conditions, use local materials, protect the environment and conserve resources". This is stipulated in the general provisions of JGJ79-2012 "Technical Specification for Foundation Treatment", and the following figure is for reference.

Hope it helps.

The design of foundation treatment should follow the following principles:

1. Must have sufficient information.

It includes two geological data and information on the superstructure.

1) Geological data.

Geological data include the mechanical properties of each layer of soil, the spatial (including vertical and horizontal) distribution of soil layers, and the flow law of groundwater.

In the analysis of geological data, special attention should be paid to the origin of soil quality and the influence of regional characteristics on the mechanical properties of soil, and the influence of soil particularity on the proposed building should be paid attention to special soils, such as newly sedimentary soil, collapsible soil, liquefied soil, etc.

2) Superstructure data.

Each type of structure has different ability to adapt to settlement and allowable deformation value, and these structural factors must be considered when selecting a foundation treatment solution. The complexity of the building will also have different requirements for foundation treatment, for example, for buildings with simple body shape and good overall structural rigidity, the settlement of the building is mainly controlled; For buildings with integrated main podiums, the impact of differential settlement must be taken into account in the foundation treatment plan.

2. Technical rationality.

The rationality of the foundation treatment technical scheme is to adopt reasonable reinforcement measures according to the requirements of different buildings for bearing capacity and deformation, according to the soil conditions that need to be treated, so as to meet the functional requirements of the building.

The rationality of the foundation treatment technical scheme should take into account the geological conditions, the use function of the building, the type of structure, the load distribution, the hazards that may be caused by uneven settlement, and groundwater and other factors, and carry out a comprehensive analysis.

3. Technical feasibility of construction.

The technical feasibility of the construction, including the pertinence of the construction plan and the selection of equipment to change the mechanical properties of the soil and the degree to which the environmental conditions are allowed. The foundation treatment scheme to improve the bearing capacity of the foundation can choose the composite foundation scheme with different solidifications, and the foundation treatment scheme to eliminate sand liquefaction can choose the foundation treatment methods such as strong compaction and vibroflotation.

At the same time, the selected foundation treatment scheme should be carried out under the conditions that the surrounding environment allows, such as the strong compaction method can not be used in the dense area of underground pipelines, and the vibrating immersed pipe construction method cannot be selected in the populated residential area.

4. Economy.

The economics of any foundation treatment solution should be taken into account. The economics of the foundation treatment scheme are integrated into the technical rationality and construction technical feasibility. That is to say, under the premise of satisfying the technical rationality and construction feasibility, the economy of the foundation treatment scheme is very important.

5. It is necessary to have the concept of superstructure-foundation-foundation interaction.

With the increase of the height of the building, the increase of the depth of the underground structure, and the emergence of the integrated structure of the main group of buildings and the building form of large chassis and multi-tower, the determination of the foundation treatment scheme should not only focus on improving the bearing capacity of the foundation, eliminating liquefaction, eliminating collapsibility, reducing deformation, etc., but also use the concept of superstructure-foundation-foundation joint action to evaluate the effect of the superstructure load on the foundation, and reasonably select the foundation treatment scheme.

1. The load effect (base compressive stress) acting on the foundation shall not exceed the allowable bearing capacity of the foundation or the characteristic value of the bearing capacity of the foundation, so as to ensure that the building does not cause overall damage or affect the normal use due to insufficient bearing capacity of the foundation, and has sufficient safety reserves to prevent the overall damage;

2. The foundation settlement shall not exceed the allowable value of the foundation deformation to ensure that the building is not damaged or affected by the deformation of the foundation;

3. The retaining wall, slope and foundation ensure that there is sufficient safety reserve to prevent instability and damage.

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1. The foundation of the same structural unit should not be set on a foundation with a completely different nature;

2. The same structural unit should not be partially natural foundation and partly pile foundation; When different foundation types are used or the buried depth of the foundation is significantly different, corresponding measures should be taken in the relevant parts of the foundation and superstructure according to the settlement difference of the two parts of the foundation at the first time;

3. When the foundation is soft cohesive soil, liquefied soil, and newly filled soil into serious uneven soil, corresponding measures should be taken according to the uneven settlement of the foundation and other adverse effects.

The soil or rock mass that supports the foundation is called the foundation, and the foundation is the structural component that transmits the various actions that the structure bears to the foundation. It must be satisfied: the load effect acting on the foundation shall not exceed the allowable bearing capacity of the foundation or the characteristic value of the bearing capacity of the foundation; The foundation settlement shall not exceed the allowable value of the foundation variation; The foundation must have sufficient safety reserves to prevent instability and damage.

The principle of foundation treatment design is "to adapt to local conditions, use local materials, protect the environment and conserve resources".

See JGJ79-2012 "Technical Specification for Foundation Treatment" for general provisions, the following figure is for reference.

Hope it helps.

The principles of foundation design are as follows.

When carrying out the foundation design, it is necessary to fully consider the geotechnical conditions of the building site and the foundation according to the use and design level of the building, the building layout and the type of superstructure, and combine the requirements of the construction period and cost to reasonably select the foundation plan. Common foundation solutions include: shallow foundations on natural foundations or artificial foundations; deep foundation; Combination of deep and shallow foundations (such as pile-to-raft, pile-to-box foundation, etc.).

Generally speaking, the shallow foundation on the natural foundation is convenient for construction, the construction period is short, and the cost is low, if it can meet the strength and deformation requirements of the foundation, it should be preferred.

According to the requirements of foundation calculation, according to the complexity of the foundation, the scale and functional characteristics of the building, and the degree to which the building may be damaged or affected by the normal use due to the foundation problem, the Code for the Design of Building Foundation Foundation divides the foundation design into three design levels. According to the design grade of the foundation foundation of the building and the degree of influence of the deformation of the foundation on the superstructure under the action of long-term load, the foundation design shall comply with the following provisions:

1. The foundation calculation of all buildings shall meet the relevant provisions of the bearing capacity calculation.

2. Buildings with design grades A and B should be designed according to foundation deformation;

3. The design grade of the building within the scope of the "Code for the Design of Building Foundation Foundation" can not be deformed for the building, if there is one of the following circumstances, the deformation calculation should still be done: 1) The characteristic value of the bearing capacity of the foundation is less than 130kpa, and the building is complex; 2) When there is a ground load on the foundation and its vicinity or the foundation load difference of the adjacent section is large, which may cause excessive uneven settlement of the foundation; 3) When there is eccentric load on the building on the weak foundation; 4) When the adjacent buildings are too close together and may be tilted; 5) There is a large thickness or uneven thickness of the fill in the foundation, and its self-weight consolidation is not completed.

4. The stability of high-rise buildings, high-rise structures and retaining walls that are often subjected to horizontal loads, as well as buildings and structures built on or near slopes, should be checked;

5. Stability check should be carried out for foundation pit engineering;

6. When the groundwater is shallow and there is a problem of floating in the basement or underground structure of the building, the anti-floating calculation should be carried out.

Increasing the research on the foundation of the building can improve the stability of the entire building on the basis. Because China is a country with a large land and abundant resources, there are huge differences in geological conditions in various places, and the selection of scientific and reasonable foundation treatment technology can improve the construction efficiency of housing construction and reduce the cost of construction.

When carrying out foundation design, it is necessary to fully consider the geotechnical conditions of the building site and foundation according to the use and design grade of the building, the building layout and the type of superstructure, and reasonably select the foundation scheme in combination with the requirements of the construction conditions, construction period, cost and other aspects.

1. Requirements for foundation calculation.

Obtain a master plan of the building with topography and coordinates, understand the structure and function of each building, the type of foundation to be used and the depth of embedding, and the requirements for the foundation design. Then, the building foundation was investigated to find out the meteorological and engineering geological conditions of the site. The geotechnical samples in the survey area were sent to the laboratory for geotechnical physical and mechanical index statistics, combined with in-situ testing, to determine the geotechnical parameters required for the design.

To find out the groundwater burial, it is necessary to check the water level change range and change law when the foundation pit is designed, and find out the situation of the low water reservoir. Whether the water quality and soil layer will corrode the building materials should be judged, and the groundwater characteristics, chemical composition, burial depth and dynamics of the building environment should be understood before construction, and the changes in the soil and groundwater construction will affect the project, and reasonable prevention and control measures should be adopted. For deep foundation pit excavation, it is necessary to calculate and support the geotechnical parameters for design, and study and analyze the surrounding influencing factors such as natural precipitation and foundation pit excavation.

2. Provisions on load values.

In the design of long and short pile composite foundation, the general design idea is that the bearing capacity and deformation calculation are calculated according to the formula of the bearing capacity of the long pile and the short pile composite foundation respectively, and then the bearing capacity of the long and short pile composite foundation is calculated according to the interpile soil of the long pile composite foundation, and then the deformation calculation is carried out.