Shallow foundations are foundations with small depths limited to the width of the footing. They spread loads from the superstructure over a larger area of soil to reduce stress intensity to a level the soil can safely support. Shallow foundations are classified as isolated or combined footings. Isolated footings support single walls or columns, while combined footings support two or more columns and come in shapes like rectangular, trapezoidal, or T-shaped. Mat foundations are used for soils with very low bearing capacity, forming a single, continuous raft to support the entire structure.

1. SHALLOW FOUNDATION
PRESENTED BY:- SHARIQ AHMED
B.ARCH. 3RD YEAR
THEORY OF STRUCTURES

2. FOUNDATION
THE FOUNDATION CAN BE DEFINED AS THE
SUBSTRUCTURE WHICH INTERFACES THE
SUPERSTRUCTURE AND THE SUPPORTING GROUND.
ITS PURPOSE IS TO TRANCEFER ALL LOADS FROM THE
SUPERSTRUCTURE TO THE GROUND SAIFLY AND
PROVIDE STABLE BASE TO THE SUPERSTRUCTURE.

3. SHALLOW FOUNDATION
IT HAS SMALLER DEPTH LIMITED TO
THE WIDTH OF FOOTING.
• IT SPREADS THE LOAD FROM
SUPERSTRUCTURE ON A LARGER AREA
OF SOIL SO THAT STRESS INTENSITY IS
REDUCED TO A VALUE WHICH CAN BE
CARRIED SAIFLY BY SOIL.
•

4. CLASSIFICATION
SHALLOW FOOTING IS CLASSIFIED INTO TWO TYPES :ISOLATED FOOTING


IT SUPORTS ONE WALL
OR ONE COLUMN.
A WALL FOOTING IS A
CONTINUOUS STRIP,
EITHER FLAT OR
STEPPED WHICH
DISTRIBUTES THE LOAD
OF WALL TO THE SOIL.
COMBINED FOOTING


A COMBINED FOOTING
SUPPORTS TWO OR
MORE COLUMNS.
THEY ARE FURTHER
CLASSIFIED AS THOSE
WHICH SUPPORT TWO
COLUMNS AND THOSE
WHICH SUPPORT MORE
THEN TWO COLUMNS.

5. 

AN ISOLATED FOOTING
SUPPORTING A SINGLE
COLUMN IS COMUNLY
USED WHERE THE
LOADS ON COLUMNS
ARE SMALL AND
COLUMNS ARE NOT
CLOSELY SPACED.
THEY ARE SQUARE,
RECTANGULAR,
CIRCULER, OR OF
OTHER SHAPES.

COMBINED FOOTING
SUPPORTING TWO
COLUMNS MAY BE
USED FOR COLUMNS
ON PROPERTY LINES.

6. EXAMPLES FOR ISOLATED FOOTING
FOOTING FOR WALL.
FOOTING FOR COLUMN

8. COMBINED FOOTING FOR TWO COLUMN
COMBINED RECTANGULAR FOOTING
COMBINED TRAPEZOIDAL FOOTING

9. COMBINED FOOTING FOR TWO COLUMN
T-SHAPED FOOTING
STRAP FOOTING

10. Secondary Factors Affecting Foundation
Choice

Construction access, methods & site
conditions

Environmental factors

Building Codes & Regulations

Impact on surrounding structures

Construction schedule

Construction risks

11. SUITABLE FOOTING


AN ISOLATED FOOTING FOR COLUMN ON PROPERTY
LINE WOULD EXTEND BEYOND IT WHICH CAN BE
AVOIDED BY COMBINING SUCH FOOTING WITH THAT
OF INTERIOR COLUMN.
SUCH FOOTING CAN BE OF SHAPES LIKE
RECTANGULAR, TRAPEZOIDAL OR T-SHAPED IN PLAN
OR MAY CONSIST OF ISOLATED FOOTINGS
CONNECTED WITH A NARROW BEAM.

12. 
WHEN THE BEARING CAPACITY OF SOIL IS LOW,
RESULTING IN LARGE AREA OF FOOTING AND THE
COLUMNS ARE CLOSELY SPACED SO THAT
NORMALLY DESIGNED ISOLATED FOOTING SHALL
APPROACH EACH OTHER, CONTINUOUS STRIP
FOOTING SUPPORTING MORE THEN TWO
COLUMNS IN A ROW ARE PROVIDED.

13. GRID FOUNDATION
SUCH STRIP
FOOTINGS
PROVIDED IN
BOTH DIRECTIONS
ARE KNOWN AS
GRID
FOUNDATION.

14. MAT FOUNDATION
FOR VERY LOW BEARING
CAPACITY OF SOIL, THE
STRIP OR ISOLATED
FOOTING MERGE
RESULTING IN THE MAT
FOUNDATION .
• IT IS A SINGLE LARGE
CONTINUOUS FOOTING
SUPPORTIN THE ENTIRE
STRUCTURE.
• IT ALSO REDUCES THE
DIFFERENTIAL
SETTLEMENT BETWEEN
THE COLUMS.
•
BEAM AND SLAB SYSTEM AMD PLATE WITH
PEDESTAL
PLATE THICKENED UNDER COLUMN AND FLAT PLATE

15. EXAMPLES OF MAT FOUNDATION