**are defined as the foundation which laid at a depth equal to or less than its width.**

*Shallow foundations***of footing refer to the sinking of a foundation due to vertical deformation of the underlying soil.**

*Settlements*## What are the types of **Shallow Foundations**?

**Shallow Foundations**

The part of a building which is in contact with the earth and transfers the loads from superstructure to the soil underneath it is called the * foundation*.

*.*

**footing**- Shallow foundation
- Deep foundation

## 2 types of Shallow foundation

*shallow foundation***shear failures**foundation need be stationary

- Footings
- Raft foundation

- Spread footings
- Strap footings
- Combined footings

- Strip footings
- Isolated footings.

#### Isolated footings :

**footing**to the soil beneath are termed as Isolated footings.

#### Strip footings:

**walls**to the soil beneath.

#### Strapped footings:

**strap**.

#### Combined footings:

The footings holding two or higher columns when the areas needed for isolated footings would overlay are termed as combined footings.

By joining the column with another column, the load will uniformly be shared.

In plan, trapezoidal or rectangle will be the footing shape.

#### Raft Foundation:

**.**

*Mat foundations*## Bearing Capacity:

#### Ultimate bearing capacity

#### Net Ultimate bearing capacity

#### Net safe bearing capacity

#### Gross safe bearing capacity

#### Net secure settlement pressure

**Unit soil pressure or safe bearing pressure**is also called The net secure settlement pressure.

#### Net allowable bearing pressure

## Factors affecting bearing capacity

- Physical and engineering properties of the soil.
- Footing Shape, depth, size and the roughness.
- Groundwater table location
- Initial stresses, if any

#### Determination of ultimate bearing capacity by

## Types of Shear failures:

### Bearing capacity failures divided into three categories

- General shear failure
- Location shear failure
- Punching shear failure.

#### 1.General Shear failure

#### 2.Location shear failure

#### 3. Punching shear failure.

#### Water table effect on bearing capacity

Terzashi bearing capacity equation is determined based on the theory that the position of the groundwater table is at higher depth.

If the position of the groundwater table is at adjacent to the foundation base,

then the equation of bearing capacity requires to be done some modifications.

For * strip foundation*, Terzashi’s equation for bearing capacity is given by:

q ultimate=rDfNqRW1+CNc + 0.5rBNrRW2 ,

where RW1=(1+(W1Z/Df)) x 0.5 and RW2=(1+(W2Z/Df)) x 0.5

When ground water table location is at surface,then W1Z=0,RW1= 0.5,W2Z=0,RW2= 0.5

When ground water table location is at footing base,then W1Z=Df,RW1= 1,W2Z=0,RW2= 0.5

When groundwater table location is below footing base,

then W1Z=Df, RW1= 1, W2Z=Groundwater table depth, RW2=Equavialant value from the equation.

##### For **Square footing,**

**Square footing,**

q=rDfNq+CNc1.3+rBNr0.4,where B= footing side.

##### For** circular footing,**

**circular footing,**

q=rDfNq+CNc1.3+rBNr0.3,where B= footing diametre.

## Eccentrically loaded foundations:

## Settlement analysis:

### Settlements may be classified as

#### 1.Uniform or total settlement

**constant**settlement, then the foundation is said to have undergone a uniform settlement.

#### Factors which may result in the uniform settlement are:

#### 2.Non-uniform or differential settlement

**varied**settlement, then the foundation is said to have undergone a uniform settlement.

#### Factors which may result in the non-uniform settlement are:

## Settlements of shallow foundations:

### Shallow Foundation settlements under a load can be classified into:

#### 1.Immediate settlements or Elastic settlements (Si)

#### 2.Consolidation settlements

#### 3.Secondary consolidation settlements.

### Conclusion:

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