This document discusses raft/mat foundations, including: - A raft foundation is a thick reinforced concrete slab that supports columns and transmits loads into the soil. It is used for structures with large or uneven column loads. - Types of raft foundations include flat plate, thickened under columns, beam and slab, box structures, and mats on piles. - Construction involves soil testing, excavation, reinforcement placement, forming, concrete pouring, and curing. Raft foundations are economic and reduce differential settlement but require treatment for point loads.

1. RAFT/MAT
FOUNDATION
SUBMITTED TO :- SUBMITTED BY:-
MR. HARPINDERPAL SINGH KAMAL BHATIA
GU-2015-0376-L

2. CONTENTS
 INTRODUCTION
 NECESSITY OF RAFT FOUNDATION
 TYPES OF RAFT FOUNDATION
 CONSTRUCTION PROCEDURE
 MERITS & DEMERITS

3. RAFT FOUNDATION
 A mat foundation is a thick reinforced concrete slab
supporting arrangement of columns or walls in a
row and transmitting the load into the soil.
 It is used to support storage tanks, industrial
equipments, chimney`s and various structures.

4. WHY IT IS
USED/NECESSITY
 The spread footings covers over 50% of the
foundation area because of large column load.
 The soil is soft with low bearing capacity.
 When the expenses of deep foundation is higher
than the raft foundation.
 Walls of the structure are so close that individual
footings would overlap.

5. TYPES OF MAT
FOUNDATION
 FLAT PLATE TYPE
 FLAT PLATE THICK UNDER
COLUMNS
 BEAM AND SLAB CONSTRUCTION
 BOX STRUCTURES
 MATS PLACED ON PILES

6. FLATE PLATE TYPE
A mat of uniform thickness is provided. This is
most suitable when the column loads are relatively
light and the spacing of columns is relatively small
and uniform.

7. FLAT PLATE THICK UNDER
COLUMNS
When the column loads are heavy, this type is more
suitable than the flat plate type.
A portion of slab under the column is thickened to
provide enough thickness for negative bending
moment.

8. BEAM & SLAB
CONSTRUCTION
 The beams run in two perpendicular directions and
a slab is provided between the beams.
 This type suitable when the bending stresses are
high because of large column spacing and unequal
column loads.

9. BOX STRUCTURES
 A box structure is provided in which the basement
walls act as stiffeners for the mat.
 This type of mat foundation can resist very high
bending stresses.

10. MATS PLACED ON PILES
 The mat is supported on piles in this type of
construction.
 This type of mat foundation is used where the soil
is highly compressible and water table is high.
 This type of construction reduces the settlement
and also control the buoyancy.

11. CONSTRUCTION PROCEDURE
 SOIL TEST
 EXCAVATION
 REINFORCEMENT
 LEVELING & DRESSING
 COLOUMN POSITIONING
 FORM WORK
 CONCRETE WORK
 CURING

12. SOIL TEST
 Bearing capacity of soil
 Classification of soil
 Moisture content
 water table

13. EXCAVATION

14. PLACING REINFORCEMENT
 A batch of horizontal reinforcement
placing
 Another batch of reinforcement
placement to complete the bottom
mesh
 Columns rod placement
 Vertical rod placement over bottom
mesh to hold the upper mesh
 Upper mesh placement

16. FORM WORK
 Timber form work
 Plastic form work
 Steel form work

17. PLACING OF CONCRETE

18. CURING
the process of maintaining the moisture and
temperature conditions of concrete for
hydration reaction to normally so that
concrete develops hardened properties over
time.

19. MERITS OF MAT FOUNDATION
Raft foundation is economic due to
combination of foundations & floor
slab.
Require little excavation.
Can cope with mixed and poor ground
condition.
It reduces different settlement.

20. DEMERITS
It require specific treatment for point
loads.
Edge erosion occur if not treated
properly.

21. THANKS