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Chapter 3
- 1. BACHELOR OF QUANTITYSURVEYING (HONS) BLD 60104 CONSTRUCTION TECHNOLOGY 1 By Azrina Md Yaakob Azrina.MdYaakob@taylors.edu.my CHAPTER 3 FOUNDATIONS
- 2. • A structureforming the foundation of a building or other construction. • Include foundations, ground beams, ground floor columns and ground floor slab 1.0 SUB-STRUCTURE
- 4. 2.0 FOUNDATIONS • Thebase on which a building rests • To safely transfer the load of a building to a suitable soil • Types of load: A) dead load –concrete structure, walls, timber structure, roof covering & other permanent components of a building B) live load –non-permanent fixtures & fittings (tables, chairs, etc) C) wind load
- 6. 2.1 DETERMINING FOUNDATIONSYSTEM • Type & bearing capacity of soil • Building design • Types of foundation
- 7. 2.1.1 TYPE OFSOIL COHESIVE SOILS • Fine grained particles are closely integrated and stick together Particle size ranges between 0.06mm or less • The level of cohesiveness depends on the size, shape and water level • When its wet, it is soft and when its dry it becomes hard • Has a high level of moisture content • Always experiences shrinkage and extension process • The increasing of water level can caused soil strengths to differ • Therefore the depth of the foundation should be constructed at least 1m from the earth surface • High level of water content can caused difficulty in earth excavation which will flood the construction site • E.g- clay and silt
- 9. 2.1.1 TYPE OFSOIL NON-COHESIVE SOIL • The soil particles are not sticking to each other • The particle size ranges between 0.06mm200mm • Non-cohesive soils has a high value for a construction site • Water are easy to flow out because of its hollow particle • E.g- gravel, sands,
- 10. 2.2 TYPE OFFOUNDATIONS Site Investigation Pad/Isolated Foundation Strip Foundation Trench Foundation Raft Foundation Pile Foundation
- 11. 2.2 DEEP ANDSHALLOW FOUNDATION DEEP Tr a n s f e r l o a d t o subsoil some distance below the ground floor of a building Depth > 3m below finished level Pile SHALLOW Transfer load to subsoil at a point near to the ground floor of a building Strips, raft, footing
- 12. 2.2.1 STRIP FOUNDATION • A continuous strip of concrete provides a continuous ground bearing under the load bearing walls • Placed centrally under the walls & composed with plain concrete to a mix of 1:3:6 by volume… (what is 1:3:6?) • Thickness not < 150mm • Buildings up to 4 storey high
- 14. 2.2.2 TRENCH FOUNDATION • More economical than strip foundation to depth of 900mm or more in shrinkable clay soil & with brickwork below ground • In reducing the width of trench, quantity of excavation, backfill and surplus soil removal also reduced • deeper foundation provides greater resistance to fracture from unequal settlement • Time saving because of the quicker completion with concrete trench fill
- 16. 2.2.3 PAD/ ISOLATEDFOUNDATION • To support & transmit loads from piers & columns • 1:2:4 • Most economic plan shape: square • Thickness: not < the projection from column or 150mm • Size of foundation can be reduced by adding steel reinforcement towards the bottom of foundation running in both directions
- 19. 2.3.4 RAFT FOUNDATION • Cover the whole area of building & usually extend beyond it • RC slab up to 300mm thick; thicken under load bearing wall • Best suited for use on soft natural ground / mining areas • Used when column / other structural loads are close together • Act as single unit, thus eliminating differential settlement • Expensive • Ways to protect the raft: A) laying concrete paving around the building B) deepening the edge beam C) laying a field drain in a filled trench
- 22. 2.3.4.1 USAGE OFRAFT FOUNDATION • The structural loads are high or the soil condition so poor that spread footings would be exceptionally large. As a general rule of thumb, if spread footings would cover more than 50% of the building footprint area, a mat or some type of deep foundation will usually be more economical. • The soil is very erratic & the structural loads are erratic. Thus, prone to excessive differential settlements. The structure continuity and flexural strength of a mat will bridge over these irregularities. • The lateral loads are not uniformly distributed through the structure and thus may cause differential horizontal movements • The bottom of the structure is located below the groundwater table, so waterproofing is an important concern. Because raft are monolithic, they are much easier to waterproof. The weight of the mat also helps resist hydrostatic uplift forces from the groundwater.
- 24. 2.3.5 PILE FOUNDATION • A group of piles that supports a superstructure • Used with multi storey buildings • To transmit load through weak & unstable soil conditions • Pile + pile caps = pile foundation • Pile cap will connect the piles together & distributes the superstructure loads the layer beneath • Pile is a load-bearing member made of timber, steel, concrete or a combination of these materials, usually forced into the ground to transfer the load to underlying soil or rock layers when the surface soils at a proposed site are too weak or compressible to provide enough support
- 26. 2.3.5.1 TYPES OFPILING MATERIAL Timber Pile Steel Pile
- 27. 2.3.5.1 TYPES OFPILING MATERIAL Concrete Pile
- 29. 2.3.5.2 USAGE OFPILE FOUNDATION • inadequate bearing capacity of shallow foundations • to prevent uplift force • to reduce excessive settlement The capacity of soil to support the loads applied to the ground Consolidation -soils decrease in volume when stress is applied to a soil that causes the soil particles to pack together more tightly
- 30. 2.3.5.3 TYPE OFLOAD TRANSFER Combination of End Bearing and Friction Pile Friction Pile End Bearing Pile
- 31. END BEARING PILE • The shaft passes through soft deposits • The base rests on bedrocks / penetrates dense sand / gravel • Pile acts as column
- 32. FRICTION PILE • Embeddedin cohesive soil, often firm clay • Obtains its support mainly by the adhesion or ‘skin friction’ of the soil on the surface of the shaft • The load is transferred to the adjoining soil by friction between the pile and the surrounding soil.
- 36. COMBINATION PILE • apile may pass through a fairly soft soil that provides frictional resistance and then into a form layer which develops a load-carrying capacity by both end bearing and friction over a rather short length of embedment
- 37. TUTORIAL 3 • Ina table form, compare and contrast the types of foundation available in construction. • Item to be included in the tables are: ü Suitability ü Advantages ü Disadvantages ü Cost Requirements: You should prepare in table form. Please state your name, student ID and title. (Individual)