shallow foundation

SHALLOW FOUNDATION

Done by:Aditya Raj Pradhan BE/10575/2014Rishikesh Prabhakar BE/10667/2014

Lowest part of a structure Provides a base for the super structure Transmits the load on the structure including the

dead weight of the structure itself to the soil below.

Foundation

Deep foundations Shallow foundations

Types of Foundation:

Foundation placed immediately lowest part of

the super structure. Used to distribute the structural load over a

wide horizontal area at a shallow depth below the ground level.

According to Terzaghi, a foundation is shallow if its depth is equal to or less than its width.

Shallow Foundation

Spread footing Combined footing Mat or raft footing

Types of Shallow Foundations

Structural members are used to support columns and walls and to transmit their loads to their loads to the soil.

Spread footing

Wall footings Reinforced Concrete footings Inverted arch Footing Column Footings

Types of Spread footing

Wall footing

Supports wall that may either be bearing or non bearing walls.

Required to support direct concentric loads.

Used in low rise buildings.

Reinforced Concrete

Footing Relatively heavy

loading than wall footing.

Bearing capacity of soil is low.

Reinforcing steel is placed in the bottom of the footing in a direction perpendicular to the wall.

Inverted arch footing

Used to resist sideways, inwards loads.

Used in conjunction with retaining walls.

Column Foundation

Most economical type of footing

Used when columns are spaced at relatively long distances.

Carries heavy load Used to support single

column. Distribute the load

uniformly.

Usually supports two or three columns not in a

row. Used when two columns are so close that

single footings cannot be used or when one column is located at or near a property line.

Combined footings

Combined Footing

Two columns are close together causing overlap of adjacent isolated footings.

Soil bearing capacity is low causing overlap of adjacent isolated footings.

Procedure of

Combined Footing

Consist of a thick reinforced concrete slab

covering the entire area of the bottom of the structure (like a floor).

Raft/ Mat Foundation

Base soil has low bearing capacity or Column load are so large that more than 50%

of the area covered by conventional spread footing.

Resist unequal settlement due to earthquake. Quickness of construction work.

Raft Foundation

Different types of

Raft

Spread footers being installed is too shallow (2-3 feet

below), which does not eliminate the effects of expansive soil.

Foundation repair will last longer than a week as the excavations are made and the concrete will have to be cured before the holes can be refilled.

A huge amount of earthwork is to be done in mat foundation

If the shoring system cannot resist the pressure of outside land, then the structure surrounding the area may be damaged by deflection of soil.

Ground water may come out when earthwork is done. Limited to dealing with point loads.

Limitations of Shallow Foundation

Quick process compared to others

construction work. Economically cheaper. Can resist ground water absorption. Damage due to earthquake is lesser than any

other type of foundation. Consist of reinforced concrete slab which is

more thicker than footing foundation. Prevents unequal settlements.

Advantages of shallow foundation