TOPIC 2: TYPES OF FOUNDATION WEEK 3 FACTORS AFFECTING FOUNDATION SELECTION TYPE OF SHALLOW FOUNDATION TYPE 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 piles Non displacement piles : Bored pile, micropiles

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 capacity Pockets of loose soil Or 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