MAT AND PILE FOUNDATION

NOROZ FIAZ MALGHANI

Mat/Raft Foundation

A mat foundation is a thick reinforced concrete slab supporting arrangement of column's or walls in a row and transmitting the load into the soil. It is use to support storage tanks, industrial equipment's , chimney's and various structure.

WHY IT IS USED The spread footings cover over 50% of the foundation area because of large

column load. The soil is soft with a low bearing capacity. When the expenses of deep foundation is higher than raft foundation. Walls of the structure are so close that individual footings would overlap

TYPES OF MAT FOUNDATION

Flat plate mat Plate thickened under column's Rigid frame mat Piled mat Two way beam and slab Plate with pedestal

PRESSURE DISTRIBUTION IN MAT FOUNDATION

A mat supported on strong bed rock transmit the load in a relatively area column's. The pressure distribution on raft/mat foundation as shown in fig.If the mat rests on stiff or compact soil, the mat distribute the load to the sub soil in larger area as shown in fig.If the mat rests on weak soil the pressure distribution on the mat tends to be uniform as shown in fig

PROCEDURE 1. SOIL TEST2. SHORE PILE CONSTRUCTION3. EXCAVATION4. REINFORCEMENT5. CC LAYER CONSTRUCTION6. LEVELING & DRESSING7. COLOUMN POSITIONING8. FORM WORK9. CONCRETE WORK10. CURING

SOIL TEST

Bearing capacity of soil Classification of soil Moisture content Ground water level Appropriation and depth of mat

SHORE PILE CONSTRUCTION

Shore piles support the surrounding loads and prevent the surrounding soil from breaking in at the time of construction

PLACING OF REINFORCEMENT

A batch of horizontal reinforcement placing; Another batch of reinforcement placement to to complete the

bottom mesh; Columns rod placement; Vertical rod placement over bottom mesh to hold the upper

mesh; Upper mesh placement

FORM WORK Form work is a mold or open box, like container into which fresh concrete is

poured and compacted. When the concrete is set, the form work is removed and a solid mass is

produced in the shape of the inner face of the form work. The top of the form work is normally left open. False work is the necessary support system that hold the formwork in the

correct position.

TYPES OF FORM WORK

Timber form work Plastic form work Steel form work

CASTING Start from one end Layer basis casting Side basis casting

LEVELING

After casting the whole mat area leveling is essential to be ensured That the thickness of the mat slab is same all over the area.

TYPES OF CURING Shading concrete work Steam curing Ponding method Sprinkling of water Covering concrete surface with gunny bags

ADVANTAGES OF MAT/RAFT FOUNDATION

Raft foundation is economic due to combination of foundation& floor slab Require little excavation Can cope with mixed and poor ground condition It reduces different settlement.

DISADVANTAES OF MAT FOUNDATION It require specific treatment for point loads. Edge erosion occur if not treated properly

PILE FOUNDATION

Pile foundation is a special kind of deep foundation, where the depth of the foundation is much greater than the width of the foundation

Today, pile foundation is much more common than any other type of deep foundation

USES It is used where the soil is compressible, It is used where the soil is water logged It is used when stratum of required bearing capacity is at greater

depth

MAJOR USES OF PILES : To carry vertical compression loads, To resist uplift loads To resist horizontal or inclined loads

CLASSIFICATION OF PILES1. BASED ON THE FUNCTION End bearing pile Friction pile compaction pile Sheet pile Batter pile Tension pile fender pile and dolphins

2. BASED ON THE MATERIAL& COMPOSITION Concrete pile Timber pile Steel pile Composite pile: concrete& timber concrete& steel3. BASED ON THE METHOD OF INSTALLATION; Driven pile cast-in situ pile Driven and cast-in-situ pile

SELECTION OF PILES

FACTOR GOVERNING THE SELECTION OF PILES

They are: Length of the pile in relation to the load and type of soil, Characters of the structure, Availability of the materials, types of loading, Factor causing deterioration, Ease of maintenance, Estimated cost of types of pile, taking into account the initial cost, life expectancy and

cost of maintenance Availability of funds.

Prepared By NOROZ FIAZ MALGHANI CIVIL ENGINEER