Project of foundation design

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HO CHI MINH CITY

UNIVERSITY OF TECHNOLOGY AND EDUCATION

PROJECT OF FOUNDATION DESIGN

INSTRUCTOR: DR. NGUYEN VAN CHUNG

STUDENT ID: 20149103

HKI 2023-2024

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

TABLE CONTENTS

CHAPTER I: SOIL INVESTIGATION...4

1. Soil investigation formular and definition...4

2. Choose the depth of the foundation...44

3. Determine size of foundation...45

4. Calculation of reinforcement...53

CHAPTER III: STRIP FOUNDATION DESIGN...57

1. Calculation data...57

2. Calculation strip foundation...59

3. Check size of foundation...62

4. Check stability condition...63

5. Check the anti-slip forces condition...64

6. Check condition strength...65

7. Check settlement condition...66

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

8. Check punching shear...69

9. Internal calculation of the strip foundation...70

10.Calculate the reinforcement...73

11. Calculate the reinforcement in foundation slab...74

CHAPTER IV: PILE FOUNDATION DESIGN...78

1. Calculation data...80

2. Calculation pile foundation...84

3. Choose size of foundation...84

4. Determine the load capacity of the pile...86

5. Determine the number of pile and arrangement the pile...92

6. Check the bearing capacity of pile...93

7. Check the load capacity of the pile...94

8. Check the stability and settlement of the pile foundation...95

9. Check the settlement condition of the foundation...97

10. Design pile cap...99

11. Calculation reinforcement for pile cap

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

CHAPTER I: SOIL INVESTIGATION1. Soil investigation formular and definition:

1.1. Statistical theory:

- Geological survey records for foundation design with a large number of boreholes and number of soil samples in a large soil layer. The problem is these soil layers we have to choose is the target to represent the background.

- Initially, when drilling, sampling was based on the observation of color change, the degree of grain that we divided each layer of soil.

- According to TCVN 9362-2012, it is called a geotechnical layer when the set of values having its mechanical properties must have a sufficiently small coefficient of variation . Therefore, we must exclude the samples with data disparate with large mean values for a geological unit.

- So geological statistics is a very important job in the calculation of the foundation.

1.2. Division of geological units1.2.1. Coefficient of Variation

We rely on coefficient of variation unary division: - The coefficient of variation v is determined by the formula:

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

- In there:

Average value of a feature: Mean square deviation: The mean square deviation:

When checking to eliminate gross errors for double criteria such as adhesion

as follows:

is the eigenvalue of eigenvalues in the same soil layer. n: number of test samples of quantity A in the same soil layer.

1.3. Rule for the exclusion of raw errors

- In the sample set of a soil layer with coefficient of variation [], the opposite is achieved then we have to exclude data with large or small errors.

- In which []: the largest coefficient of variation, look up Table 1 depending on each

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

following formula | - A | ≥ Vσ . In which deviation is estimated:�cm

1.4. Standard value of soil characteristics1.4.1. Standard values of single indicators

- Standard values of all single parameters (physical parameters such as humidity, bulk weight volume, plasticity index, viscosity, ... and mechanical parameters such as total

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

strain modulus, compressive strength, …) is the average of the individual test results Ā after, excluding gross errors.

1.4.2. Standard value of dual indicators:

- The standard values of the dual criteria of unit adhesive force (c) and internal friction angle () are made according to the method of least squares of the linear relationship of normal stress and stress. the extreme contact of the equivalent shearii

experiments:

- The standard unit adhesive force c and the friction angle in the standard tctc are determined by the following formula:

- If the above formula can be calculated c < 0, then choose c = 0 and recalculatetctc

according to the formula:

1.5. Calculating soil characteristics1.5.1. Calculation value of single indicators

- In order to improve the safety for the stability of the load-bearing foundation, some stability calculations of the foundation are carried out with the calculation characteristics.

- The calculated value of single criteria is determined by the following formula:

In there:

Atc is the standard value of the features under consideration. The factor of safety on soil is determined by the formula: - The accuracy index is determined by the formula:

In there:

tα is the coefficient that depends on the confidence probability Dynamic coefficient is determined according to item 1.2.1

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

When calculating the background by intensity (TTGH I), α = 0.95 When calculating the background according to strain (TTGH II), α = 0.85 - The minimum number of a certain criterion experiment with each engineering geological unit needs to be ensured is 6.

- If within the scope of engineering geology unit there are less than 6 samples, the calculated values of their criteria are calculated according to the method of minimum average and average maximum:

- The choice of calculation according to one of the two formulas depends on the criteria that increase the safety of the works.

1.5.2. Calculation value of double indicators

- The calculated value of the double criteria is determined according to the following formula:

In there:

Atc is the standard value of the features under consideration. - For double criteria such as: stick force c and coefficient of friction tg.

We have the formula: = t να

The coefficient of variation is determined according to the following formulas: and

The mean square deviation is determined according to the following formula: When calculating the background by intensity (TTGH I), α = 0.95

When calculating the background according to strain (TTGH II), α = 0.85 Note:

To find the standard and calculated values of c and , it is necessary to determine not less than 6 values of for each value of normal pressure .

When finding the calculated value c, uses the total number of experiments to do n.

Degree of freedom

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

- The computed features according to TTGH I and TTGH II have values in the range:

- Depending on the specific design case, we take the sign (+) or the sign (-) to ensure more safety.

- When calculating the background according to the intensity and stability, we take the calculated characteristics according to TTGH I (in the larger range = 0.95).

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

- When calculating the background according to the deformation, we take the calculated characteristics according to TTGH II (in the range less than = 0.85).

- Soil properties: Clay mixed Lateric gravel, yellow brown – pink brown-red brown, hard plastic state.

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

a) Determine the standard value:Empty factor by load class

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

The above sample set is selected

Empty factor by load class

No Drillhole Modelnumbe

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

b) Determine the standard value:

()

Empty factor by load class

No Drillhole numberModel Depth

Empty factor e corresponding to the load class

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

=> So all of the samples in layer 4 are selectedb) Determine the standard value:

()

c) Determine the value according to limit state I:

With limit state I then the confidence probability . Look up the table we get

d) Determine the value according to limit state II:

With the limit state II then the confidence probability . Look up the table we get

Empty factor by load class

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

Empty factor e corresponding to the load class

Friction angle and stick force

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

- Soil properties: Clay and Laterite gravel grit, white gray - red brown - yellow brown, hard and soft plastic state.

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

- Soil properties: Heavy phase clay, yellow brown - white grey, hard and soft plastic

- Soil properties: Heavy phase clay - clay mixed sand, yellow-brown - white grey, hard plastic state.

Soil properties: Heavy phase clay clay mixed sand, yellow brown – pink brown -white grey, hard plastic state.

- Soil properties: Mixed sand, yellow brown - pink brown white grey.

3.1. Geological statistics of soil layer 1:3.1.1. Single target statistics:

Bulk density:

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

=> So the sample set is selected

No. numberModel Depth Empty factor e corresponding to the load class P ((0-25) (25-50) (50-100) (100-200)

3.1.2. Empty factor by load class e:3.1.3. Multiple target statistics:

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

a) Check statistics:

= > Accepted the sample test.

b) Determine the value according to limit state:

0.01387 =>

3.2. Geological statistics of soil layer 2:3.2.1. Single target statistics:

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

=> So the sample set is selected

=> So the sample set is not selected

=> So the sample set is not selected3.2.2. Empty factor by load class e:

No. numberModel Depth (25-50)Empty factor e corresponding to the load class P ((50-100) (100-200) (200-400)

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

3.2.3. Mutiple target statistics:

= > Accepted the sample test.

b) Determine the value according to limit state:

0.212 =>

3.3. Geological statistics of soil layer 3a:3.3.1. Single target statistics:

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

=> So the sample set is selected

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

=> So the sample set is selected

=> So the sample set is not selected

=> So the sample set is selected

a) Determine the value according to limit state I:

With limit state I then the confidence probability . Look up the table we get

-b) Determine the value according to limit state II:

With the limit state II then the confidence probability . Look up the table we get

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

3.3.2. Empty factor by load class e:3.3.3. Multiple target statistics:

3.4. Geological statistics of soil layer 3:3.4.1 Single target statistics:

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

=> So the sample set is selected

=> So the sample set is not selected

=> So the sample set is selected

=> So the sample set is not selected

No numberModel Depth (25-50)Empty factor e corresponding to the load class P ((50-100) (100-200) (200-400)

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

3.4.2. Empty factor by load class e:3.4.3. Multiple target statistics:

3.5. Geological statistics of soil layer 4a:3.5.1 Single target statistics:

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

=> So the sample set is selected

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

=> So the sample set is selected

=> So the sample set is not selected

No numberModel Depth (25-50)Empty factor e corresponding to the load class P ((50-100) (100-200) (200-400)

3.4.2. Empty factor by load class e:3.4.3. Multiple target statistics:

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

3.4. Geological statistics of soil layer 3:3.4.1 Single target statistics:

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

→ This is satisfied settlement condition.

3.8. Check the anti-slip forces condition:

Slippage force:

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

Anti-slip force:

Friction force between the soil and the bottom of the foundation. Active pressure coefficient of layer 3:

Active pressure at depth z:

Passive pressure of the layer 3:

Total active soil pressure:

Total passive soil pressure:

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

→ This is satisfied slip condition.

3.9. Check punching shear:

We have

The area of an approximate punching surface (rectangular):

Maximum calculation pressure at the foundation:

Minimum calculation pressure at the foundation:

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

Figure 2.3: Punching shear cross-section:

4. Calculation of reinforcement:4.1. Section 1-1:

Figure 2.4: Schematic of reinforcement according to l

The calculation diagram is console beam under trapezoidal load , we convert it to evenly distributed load :

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

Moment at the foot of the column :

The area of reinforcement:

Choose with area of a steel bar: Number of steel bar:

→ Choose 12 steel bars Distance between each bar:

4.2. Section 2-2:

Figure 2.5: Schematic of reinforcement according to b

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

Moment at the foot of the column :

The area of reinforcement:

Choose with area of a steel bar: Number of steel bar:

→ Choose 10 steel bars Distance between each bar:

→ Choose a= 250 mm → Choose short-edge steel L:

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

CHAPTER 3: STRIP FOUNDATION DESIGN

1.4.Geological cross – section:

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Project of Foundation DesignInstructor: Dr Nguyen Van Chung

Figure 3.1. Section drill hole

2. Calculation strip foundation

2.1.Choose the depth of the foundation:

The foundation is placed in a layer of soil that is good for construction.

The foundation bottom is at least 0.2 m from the boundary of the layer (soft soil) with the good soil layer

The foundation bottom must be at least 0.5m higher than the groundwater level. Based on geological data, the thickness of the first layer is 8.3m it is very reasonable

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Project of foundation design

<b>PROJECT OF FOUNDATION DESIGN</b>

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