Coursework - design of foundations and foundations in residential and public buildings

Contents

Contents

1. Design Input

2. Assessment of geotechnical conditions

3. Define Loads

4. Calculation of shallow tape foundations

5. Calculation of sediment of strip foundations of shallow foundation

6. Calculation of pile foundations

7. Calculation of the tape pile pile

8. Economic comparison of foundation options

9. List of literature used

1. Input for Course Engineering

Cipher VI-B-C

DL Planning Layer

WL groundwater level

1,2,3 - soil layer numbers counting from the planned elevation

Building Variant - C.

5-storey 25-apartment block section.

Structural diagram - transverse and longitudinal bearing walls with support of floor panels along the contour;

external walls - red brick = 640 mm;

internal walls - load-bearing railway panels = 380 mm;

floors - solid LG panels = 160 mm;

partitions - gypsum concrete = 80 mm;

balconies - steel plates = 100 mm;

roof - a national railway with a cold attic;

roof - roll-free;

floors - linoleum, ceramic tiles.

Basement is located between axes G-Z and 110. Basement height - at the student's choice; basement walls of blocks = 600 mm.

Assessment of geotechnical conditions and soil properties

The construction site is located in Volgograd. Geological section in Figure 2.

According to the task, the following variant of soil bedding was issued: 1 - sandy soil, absolute bottom elevation - 3.1m, layer thickness - 3.1m; 2 - sandy soil, absolute elevation of the sole is 6.1m, layer thickness is 3.0m; 3 - dusty-clay soil, absolute elevation 16.6, layer thickness 10.5 m.

Groundwater level (WL) is located at elevation - 5.1m. The waters are not aggressive.

For reasonable selection of acceptable options of bases and foundations, as well as depth of foundation laying based on the results of engineering and geological surveys, we will conduct a comprehensive assessment of engineering and geological conditions of the site.

Source Data

Layer 1. (Model No. 10)

1. Particle content larger than 0.5 mm - 77% - coarse sand

Conclusion: soil cannot serve as a natural basis

Layer 2. (Model No. 34)

1. The content of particles is larger than 0.25 mm - 63.3% - medium-sized sand (Table 1, Annex I). [4]

d10=0,096; d60 = 0,474 Cu = non-uniform sand.

2. Determine the soil porosity factor

4. Determine the degree of soil humidity

Conclusion: soil cannot serve as a natural basis

Layer 3. (Model No. 71)

1. We determine the number of ductility of the soil

2. Determine the soil porosity factor

(Table 3, Annex II). [1]

3. We determine the density of soils in dry state

4. Determine the degree of soil humidity

wet soil

5. Determine soil density in suspended state

7. Yield index

(refractory soil) (Table 5, Annex II). [4]

8. We determine the porosity coefficient of the soil at its humidity at the flow boundary

9. We determine the indicator P.

10. R0 = 234 MPa (Table 6, Annex II). [4]

Conclusion: soil can serve as a natural basis.

Define Loads

We define loads for 4 sections that differ in cargo areas.

Fig.2 (a) b)

Load application diagrams to foundations:

a) along axes A and 1

b) along axes D and 4

a) shallow foundation with soil replacement; b) pile foundation.

a) b)

On the recommendation of the manager, due to the unsuitability of the soils of the first and second layers for use as a natural base, we replace the soils with more reliable ones. Gravel-dried soils with R0 = 400 MPa were selected. Two types of foundations were also chosen: a strip prefabricated from railway blocks and a hanging pile.

Next, we calculate these foundations.

Option # 1. strip assembly of LG shallow-laying units

According to the design requirements, it is necessary to lay the foundation to a depth of 1.6 meters.

By the depth of seasonal freezing of soils for Volgograd, we find the coefficient Mt = 26.3 (Table 10, Annex II). [4]

Standard freezing depth

Design freezing depth of the 1st soil layer

We accept the depth of foundation laying satisfying all the above conditions, namely d = 1,6 m.

We calculate the foundation along the axis G.

We determine the approximate area of the foundation foot: We accept A = 1.2m2

We calculate the weight of 1m of the foundation length

Determine the weight of 1m of soil length on foundation cutting

kN

Find the average pressure on the foundation bottom

We define the design resistance of the bearing layer.

(Table 4.5, 4.4 c.89.90). [5]

The main condition P = 378.6kPa < R = 419kPa, and the underpressure in the base is 9%, which is less than the required 10%, therefore, we will accept a prefabricated slab with a width of b = 1.2m as a foundation pad.

We calculate the foundation along axis 1.

We determine the approximate area of the foundation foot: We accept A = 1.2m2

We calculate the weight of 1m of the foundation length

Determine the weight of 1m of soil length on foundation cutting

kN

Then, and the eccentricity value in the level of the foundation floor will be

Therefore, the foundation can be considered as centrally compressed.

Find the average pressure on the foundation bottom

We define the design resistance of the bearing layer.

The main condition P = 310, 5kPa < R = 317, 5kPa, and the underpressure in the base is 2.2%, which is less than the required 10%, therefore, we will accept a prefabricated slab b = 1 .2m as a foundation pad.

We calculate the foundation along the axis A.

We determine the approximate area of the foundation foot: We accept A = 1.4m2

We calculate the weight of 1m of the foundation length

Determine the weight of 1m of soil length on foundation cutting

kN

Then, and the eccentricity value in the level of the foundation floor will be

Therefore, the foundation can be considered as centrally compressed.

Find the average pressure on the foundation bottom

We define the design resistance of the bearing layer.

(Table 4.4, 4.5 p. 89.90). [5]

The main condition P = 298, 5kPa < R = 325kPa, and the underpressure in the base is 8%, which is less than the required 10%, therefore, we will accept a prefabricated slab with a width of b = 1 .4m as a foundation pad.

We calculate the foundation along axis 4.

We determine the approximate area of the foundation foot: We accept A = 1.2m2

We calculate the weight of 1m of the foundation length

Determine the weight of 1m of soil length on foundation cutting

kN

Then, and the eccentricity value in the level of the foundation floor will be

Therefore, the foundation can be considered as centrally compressed.

Find the average pressure on the foundation bottom

We define the design resistance of the bearing layer.

The main condition P = 288kPa < R = 317, 5kPa, and the underpressure in the base is 9.3%, which is less than the required 10%, therefore, we will accept a prefabricated slab b = 1 .2m as a foundation pad.

10. Calculation of sediment of strip foundation of shallow foundation

11. Next, for this version of foundations, we will calculate the sediment along the most loaded axis.

Calculation of sediment along the D axis

Using the data on the soil conditions of the construction site, we find the values ​ ​ of the epure of vertical stresses from the action of the own weight of the soil.

on the surface of the earth:

foundation sediment. (Axis D)

at the foundation floor level:

at the contact level of the 1st and 2nd layers, we may not calculate, since we replaced them by obtaining 1 layer.

in the first layer at groundwater level

at the contact level of the 2nd and 3rd layers

at the contact level of the 2nd and 3rd layers

at the floor level of layer 3

According to the obtained data, we build vertical stress and auxiliary stress epures.

For the tape foundation, the ratio To avoid interpolation according to Table 1.2, we set the ratio, then the height of the elementary soil layer will be (Table 1.2, c.19). [5]

Let's build an epic of additional vertical stresses from the external load in the thickness of the base of the calculated foundation using the data of Table 1.2. All calculations are given in tabular form:

Next, we calculate the foundation settlement, neglecting the difference in the deformation modulus at the boundary of the soil layers, taking into account that this assumption will slightly affect the calculation results:

As per Table 4.3 for residential buildings with brick bearing walls the value of the maximum permissible settlement. In this case, therefore, the basic calculation condition for the second group of limit states is satisfied.

Option # 2. Strip pile foundation

In this embodiment, friction pile is accepted.

We calculate the pile along the axis G.

We will accept 2 piles per 1 meter of foundation. Define allowable load per pile

We accept a pile with a section size of 250x250 mm and a length of 6 m, which satisfies 207.7 < 650 kN in material strength. Piles of other sizes are clearly irrational for a load of 207.7 kN.

Pile cross-sectional area

Perimeter

Top of pedestal is accepted at elevation -1.3m

When the pile is embedded in the pile pile by 0.1m and the point height is 0.25m, the depth of pile immersion from the ground surface is

For medium humidity loam, refer to Table 10.2. According to Table 10.1, for piles submerged with diesel hammers, we find the value of the coefficients of soil working conditions under the lower end of the pile and along the side surface. The thickness of the soil cut by the pile is divided into layers with a thickness of not more than 2 m.

We find the bearing capacity of one pile:

According to the current norms, piles and pile foundations are calculated according to the bearing capacity of soils of bases by the formula

We will find the weight of the foundation blocks and the pedestal, which falls on 1 m of length:

Soil weight on cuttings

Total load per pile is

Calculate the pile along axis A.

We will accept 2 piles per 1 meter of foundation. Define allowable load per pile

We accept a pile with a section size of 250x250 mm and a length of 6 m, which satisfies 207.7 < 650 kN in material strength. Piles of other sizes are clearly irrational for a load of 207.7 kN.

Pile cross-sectional area

Perimeter

Top of pedestal is accepted at elevation -1.3m

When the pile is embedded in the pile pile by 0.1m and the point height is 0.25m, the depth of pile immersion from the ground surface is

For medium humidity loam, refer to Table 10.2. According to Table 10.1, for piles submerged with diesel hammers, we find the value of the coefficients of soil working conditions under the lower end of the pile and along the side surface. The thickness of the soil cut by the pile is divided into layers with a thickness of not more than 2 m.

Calculation of the tape pile pile

In the calculation of belt pile-bars, they are considered as a multi-span continuous beam. Moments on supports and in span are determined.

After determining the reference and span moments, the required

We accept 2⌀12 AIII (= 2, 26sm2) on supports.

Economic comparison of accepted foundations

Possible options for foundations were discussed above. We consider direct costs and labor intensity according to enlarged indicators (Table 13, Annex II [4])

For both the costs and labor costs, option No. 2 is more economical. Therefore, we accept pile tape foundations for development.

List of literature used:

1. SNiP 2.01.0785. Loads and impacts. Gosstroy of the USSR, 1986

2. SNiP 3.02.0187. Earthworks, foundations and foundations, Gosstroy of the USSR, 1987

3. SNiP 2.02.0385. Pile foundations, M, 1986 – 48 pages.

4. Khasauov Yu.M. Methodological guidelines for the development of a course project in the discipline "Foundations and Foundations." Ch.1 - Nalchik. KBSU, 1998 65s.

5. . Berlinov M.V. Foundations and foundations. Textbook for universities M.: Higher School, 1988

6. Shvetsov G.I. Foundations and foundations. Handbook M.: Higher School, 1991

7. Designer Reference Book. Foundations, foundations and underground structures .//Under the common. Ed. E.A. Sorochana and Yu.G. Trofimenkova. – M.; 1988 – 415 pages.

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