shallow foundation
TRANSCRIPT
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