Simple calculation of strength of bearing layer

1. 2 is the weighted unit weight of soil and foundation

2. The main contents of building foundation include: physical properties of foundation soil and classification of rock and soil, stress in foundation, calculation of foundation deformation, shear strength and bearing capacity of soil, calculation principle of building foundation, shallow foundation design of natural foundation, foundation trench inspection and local treatment of foundation, soft soil foundation and pile foundation design
the pile foundation is deeply excavated, and the strength of bearing layer is high, which is more practical
the material used for box foundation is relatively large, which is the reason for its high cost. Due to the limitation of bearing layer strength, it is not very practical
strip foundation is commonly used for general good foundation because of its low cost and simple construction.

3. If the calculation is conservative, it can be considered as clay layer. It can also be weighted average, 0.1M for gravel layer and 0.1M for clay layer.

4. 1. Foundation bearing capacity 2. If the settlement needs to be calculated, the compression molus is needed. 3. If it is an elastic foundation beam plate, the foundation coefficient or deformation molus is also needed

5. The uniaxial compressive strength of moderately weathered rock is generally 50MPa, while that of strongly weathered rock is less than 10MPa. The bridge foundation is better to reach moderately weathered rock. If the thickness of strongly weathered rock reaches tens of meters, it can also be used as bearing stratum, but the pile end should be post grouted.

6. 1、 What is the bearing stratum
the so-called bearing stratum refers to the foundation with a bearing capacity of more than 2500kN / m ^ 2 and a value of N greater than 50 in principle. The uniformity of the bearing stratum can be evaluated by the mechanical property indexes besides the horizontal and vertical distribution of the soil. For example, the difference of the mechanical indexes of the samples taken from this stratum can be evaluated by the coefficient of variation of the statistical indexes
the design and construction drawings of a construction project should be designed according to the geological exploration report of the project. Generally, the one that can bear the upper load is called & quot; Bearing stratum;, The soil type of bearing stratum and the bearing pressure per square meter are stated in the geological exploration report. For example, it is indicated in the geological exploration report that the second layer can be used as the bearing stratum of shallow foundation, and the designer will calculate according to the type of the proposed house, For example, strengthening foundation is a way of foundation reinforcement.

Second, the development and current situation of foundation treatment methods
foundation treatment is to strengthen or improve the foundation soil according to the requirements of superstructure; Improve the bearing capacity of foundation soil to ensure the stability of foundation; Rece the settlement or uneven settlement of the house; Eliminate the collapsibility of wet loess; Improve the ability of anti liquefaction
with the development of construction and the full use of soft soil foundation, the old foundation treatment methods are improving day by day, and new foundation treatment methods are emerging. From mechanical compaction to chemical reinforcement, from shallow treatment to deep treatment, from general loose soil treatment to saturated cohesive soil treatment, there are many methods< Mechanical compaction includes mechanical compaction, heavy hammer compaction, vibration compaction and dynamic compaction
the mechanical compaction method uses flat roller, sheep foot roller and vibrating roller to compact the foundation soil, which is suitable for the construction of large area filled foundation
the heavy hammer compaction method is to use the lifting machinery to lift the heavy hammer to a certain height and then fall freely, and repeat the compaction, so as to form a layer of dense soil layer on the foundation surface. It is suitable for the foundation of cohesive soil, sandy soil, miscellaneous fill and layered fill whose groundwater level is more than 0.8m away from the surface. When the foundation soil is compacted, it should maintain the optimal water content to compact
the vibration compaction method is to use the vibration compaction machinery to proce a great vertical vibration force to compact the surface of the foundation, which is suitable for the loose miscellaneous fill and sand foundation with less clay particles and better water permeability
dynamic consolidation method is also called dynamic consolidation method. It is to lift the 8-40t heavy hammer to the height of 8-40m and drop it freely to tamp the soil strongly. This method is a new method developed on the basis of heavy hammer tamping method
2. Soil replacement cushion method
the soil replacement cushion method is to excavate the soft soil and replace the material with high strength. The cushion material can be sand, gravel, plain soil, lime soil, etc. the replaced cushion can be used as the bearing layer of the foundation because of its high strength, and the additional stress of the base diffuses downward through the cushion, so as to rece the additional stress acting on the soft underlying soil under the cushion, It is suitable for shallow treatment of soft foundation
3. Compaction method
compaction method is to form a hole in the soft foundation first, and then fill the hole with sand, stone, soil and other materials, and vibrate (squeeze, flush) the pile layer by layer, so that the pile can compact the surrounding soft soil or loose soil layer, and the soil and the pile form a composite foundation, so as to improve the bearing capacity of the foundation and rece the settlement
according to the different materials and construction methods used, there are soil or lime soil pile compaction method, sand pile compaction method and vibration flushing method
4. Drainage consolidation method
drainage consolidation method is a method that uses loading preloading and vacuum preloading to remove pore water, compress soil and complete a large amount of settlement before building construction. In recent years, it has been widely used in large area material storage yard, airport runway, oil tank engineering, embankment, earth dam and other foundations
there are usually surcharge preloading method and sand well surcharge preloading method
5. Chemical reinforcement method
chemical reinforcement method refers to a foundation treatment method that uses chemical slurry or cementant to improve the physical and mechanical properties of foundation soil through the principle of pressure or electroosmosis, grouting, pressing, high-pressure spraying or mixing, so as to make the slurry and soil particles cemented. At present, cement slurry, water glass slurry, acrylamide slurry and lignin slurry are used
silicification method, high pressure jet injection method, deep stirring method and powder jet stirring method are often used
among the above methods, the mechanical compaction method, heavy hammer compaction method, vibration compaction method and soil replacement cushion method belong to shallow foundation treatment method because of their shallow influence depth. For dynamic compaction method, compaction method, sand well surcharge preloading method, high-pressure jet grouting method, deep mixing method and so on, e to the deep influence of reinforcement treatment, it belongs to deep foundation treatment method.

7.

The specific judgment of the bearing layer at the construction site depends on what foundation the building structure adopts. If the foundation is shallow, the bearing capacity of the foundation is required to be higher. For example, it is very economical to live on an independent foundation, but the bearing capacity of the bearing layer is required to be higher

for general buildings, the piles are driven to full weathering. As for the more important buildings, they may be moderately or weakly weathered

the characteristic value of bearing capacity of bearing stratum is the conclusion of investigation report document provided by engineering geological investigation unit according to the requirements of investigation power of attorney. The combined value of the load effect on the building foundation structure is the result of the structural designer's overall mechanical analysis, which is distributed to the foundation and transferred to the available bearing layer

< H2 > development data

in the structural design of civil engineering, in the foundation design, the soil layer directly bearing the foundation load is called the bearing layer

in the calculation of soil mechanics, the pressure on the bearing stratum decreases continuously, and the pressure can be ignored after a certain depth, and the specific depth can only be known after calculation. The part under pressure is called the bearing layer, and the part below the bearing layer is called the underlying layer. In other words, according to the different loads, the bearing layer and the underlying layer are also different

8. Consult the local seismic historical data, relevant design specifications and geological exploration data.