Raft foundations, also known as mat foundations, consist of a large concrete slab that supports multiple columns and walls, distributing load effectively across a larger area. Various types of raft foundations include flat plates, beam and slab constructions, box structures, and mats placed on piles, each designed for specific load conditions and column configurations. Additionally, the document discusses settlement types, causes of foundation movement, and methodologies for testing pile load capacity.

1. FOUNDATION
Prepared by
Gayathry satheesan

2. RAFT / MAT FOUNDATION
 Raft foundations (sometimes known as
Mat Foundations) are a large concrete slab
which can support a number of columns and
walls.
 The slab is spread out under the entire
building or at least a large part of it which
lowers the contact pressure compared to
the traditionally used strip or trench footings.

3. RAFT FOUNDATION

4. TYPES
 FLAT PLATE TYPE
 FLAT PLATE THICKENED UNDER COLUMN
 BEAM AND SLAB CONSTRUCTION
 BOX STRUCTURES
 MAT PLACED ON PILE

5. FLAT PLATE TYPE
 Mat of uniform thickness
 Used: when column load are light and spacing between
columns are small

6. FLAT PLATE THICKENED
 When column loads are heavy
 Portion of slab under column is thickened

7. BEAM AND SLAB
 The beam runs in two perpendicular direction and slab
provided between beams
 Columns are at intersection of beam
 Used: when large column spacing ad unequal column
load

8. BOX STRUCTURES
 A box is provided in which basement walls act as
stiffeners for mat
 Boxes are rigid frame consisting of slab and
basement wall
 Can resist high bending moment

10. MAT PLACED ON PILE
 Supported on pile

11. PILE FOUNDATION
Pile is a slender structural member made
of steel, wood or concrete
Pile is a type of deep foundation
Transfer the load to a greater distance

21. SHEET PILE

23. BATTER & FENDER PILE

28. CAISSON

47. SETTLEMENT OF
FOUNDATION
 The downward movement of foundation along with soil bed
due to load from building or any other load is called
settlement
 Two types:
 Uniform settlement
 Differential settlement
 CAUSES:
 Weight of superstructure
 Type of soil
 Increasing load of surrounding
 Excavation near foundation
 Vibration
 Elastic compression of underlying soil
 Ground movement
 Seasonal swelling or chemical action

49. PILE LOAD TEST
 THE MOST RELIABLE METHOD FOR DETERMINING THE
LOAD CARRYING CAPACITY OF PILE
 SET UP:
 Two anchor pile provided with anchor girder
 Test pile is installed between the anchor piles (similar to
installation of foundation pile
 Test pile should be at least 3B or 2.5 cm clear from anchor
pile
 Load applied by hydraulic jack resting on girder
 Measurements are taken with reference to a fixed point
 Test is conducted after rest period of 3 days (sandy soil) or
1 month(clay soil)

51. OBJECTIVE OF TEST