TOPIC 2: TYPES OF FOUNDATION

WEEK 3

FACTORS AFFECTING FOUNDATION SELECTIONTYPE OF SHALLOW FOUNDATIONTYPE OF PILES AND CAPACITY. ADVANTAGES AND LIMITATIONS

Learning Outcomes

Student should be able to:

• Discuss criterias for foundation selection(CO2-PO10)

• Determine type of foundation(CO2-PO10)

FUNCTION OF A FOUNDATION

• To transmit load to the ground without bearing capacity failure and excessive settlement.

Bearing Pressure and Bearing Capacity Concept

Factors Affecting Foundation Selection

• Subsurface condition • Type and magnitude of loading• Type of structure• Constraint – vibration, noise• Cost• Time• Logistic

• Shallow Foundation

- pad footing, strip footing, raft foundation

Not more than 3m. A basement though may used shallow foundation if the ground is adequate.

Deep Foundation

Cast in situ pile, driven or jack in pile.

Deep Foundation

FUNCTION OF PILES

Transmit load to deeper depth underneath the structure when upper layer of soil too weak to support the load.

Resist horizontal force by bending.

Anchor a structure subjected to uplifting.

Hold a structure where the base is subjected to erosion.

Pile classification based on materials -       concrete piles – 150RC square pile structural capacity

250kN, 400x400 – 1980kN- Spun pile – 250mm diameter 460kN, 800mm diameter

3450kN

-       timber piles- 100kN bakau pile – 10kN, For Sustainability, Government Projects not allowed to use bakau pile.-       steel pile-       composite piles Pile classification based on installation-       Displacement piles : Driven piles, jacked pilesNon displacement piles : Bored pile, micropiles

PILE CLASSIFICATION

• Advantages and limitations of certain type of piles

Cost, availability, capacity, suitability for the ground strata, noise, vibration, machineries and rigs.

 Pile classification based on functions-       compression piles-       tension piles-       batter/rake piles – resist lateral load. Max inclination 4:1  Pile classification based on bearing-       end bearing piles-       friction piles-       partly end bearing and partly friction 

RAFT FOUNDATION

Covers the entire area under the structure, supporting several columns and walls

For low bearing capacityPockets of loose soilOr when individual spread footing covers more than 50% area.

TYPES OF RAFT FOUNDATION

Bearing Capacity of Raft Foundation

Case study: Foundation of KL Tower

Floating Foundation

Concept

Usage

Method of Construction

Water Proofing

Basement Construction

Cut and fill method

Secant Pile Wall

Diaphragm Wall