Purpose / Importance:

• To determine the type of foundation.
• To determine design parameter for the foundation such bearing capacity and allowable soil bearing pressure.
• To calculate potential settlement of foundation.
• To determine expansion potential at the site.
• To investigate the stability of slope and their effect on adjacent structure.
• To investigate possible way of improving the soil to increase the foundation bearing capacity.

Types of foundation:

A. Shallow foundation

• Width greater than its depth.
• Located just below the lower part of wall or column which it support.

Types of shallow foundation:

1. Strip / Continuous footing

• Provided for load bearing wall.
• L>B.

2. Spread / Isolated footing

• Circular, square or rectangular slab of uniform thickness.

3. Combined footing

• Supports two or more columns in row.
• Preferred in limited space.

4. Strap / Cantilever footing

• Two or more footing connected by beam.

5. Mat / Raft foundation

• Consist of large slab supporting number of column and walls.

B. Deep foundation

• Depth is greater than width.
• Distributes load from super-structure vertically rather than laterally.

Types of deep foundation:

1. Pile foundation

• Column made of wood, steel, concrete of RCC.
• Embedded into the ground to transmit the load of the structure to a hard stratum or compressed soil.

2. Pier foundation

• A cast insitu pile greater than 0.6 m diameter is termed as pier.
• Consists of cylindrical column of large diameter to support and transfer load.

3. Well foundation

• Well is a type of cassion.
• Suitable for soil containing large boulders.

1.2 Factors affecting choice of foundation

• Function of structure.
• Cost of foundation.
• Sub-surface condition of soil.
• Boundry criteria.
• Bearing capacity of soil.
• Types of load of super structure and other load acting on foundation.

1.3 Introduction to machine foundation

• Foundation provided below the super strucutre of a vibrating and rotating machine for installation is called machine foundation.
• Includes the studies of vibration of foundation soil system transmitted by wave energy.
• Used for supporting turbines, large electric motor and generator.
• Wave energy transmitted through the underlined soil from the foundation should not cause harmful effects to machine, structure of people.

1.4 Types of machine foundation

1. Block foundation

• Consists of a pedestal resting on a footing.
• It has large mass and smaller natural frequency.
• Provided for compressor and reciprocating engine.

2. Box or caisson’s foundation

• Use for lighter foundation.
• It has smaller mass and higher natural frequency.

3. Wall type foundation

• Consist of well-column and beam slab.
• Steam turbines are provided with wall type foundation.

1.5 Types of machine

1. High speed machine

• Turbo generator and rotary compressor fall in this category.
• Speed ranging from 3000 to 10000 rpm.

2. Low speed machine

• Compressor and reciprocating engine comes in this category.
• Speed is smaller than 600 rpm.

3. Impact type machine

• Produce impact loading.
• Speed is usually 60 to 150 blows per minute.

References:

• Terzaghi, Karl and peck, R.B. John Wiley.(1967). Soil mechanics in engineering practice, New York.
• Arora K.R. (1997). Soil Mechanics and foundation engineering, India: Standard Publisher Distribution.

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