chapter 3 building foundation

Building Foundation is an underground structure that directly in contact with the soil and spread the load of building to the ground so as to limit the soil settlement of the building. In certain circumstances, it is also to withstand the wind pressure.

Spread the load of building structures to the broader and stronger area.

Spreading the load with uniform and constantly (avoid differential settlement)

To strongly hold the frame of building, especially in high-rise buildings

Prepare a hard and flat surface

Located in a safe place and to distribute all loads such as dead load, live load and wind load in an appropriate manner.

Sufficient in depth Resistant to sulfate attack

Shallow foundation Strip Pad Raft

Deep Foundation Piling Hollow basement, caisson

Good foundation design is to ensure that the structure load including the mass of foundation distributed by:

Economical Safe No movement during or after

construction

Site Investigation Magnitude and distribution of loads from

the structure is divided by dead load, life load and vibration (dynamic loading) and also wind pressure.

Overall total of settlement and the differential settlement

Foundation Types Allowable bearing pressure value of load

Pressure distribution under foundation calculation

Analysis of settlement Foundation material Structure design working drawing

Ultimate bearing capacity Safe bearing capacity

Load bearing strength is determined by the following :

a) Ranking Analysis b) Penetration Test c) Persumptive value

Increase the depth of foundationsoil compaction:

a. Vibration b. Preloading c. Water flowing d. Grouting

Definition: Downward vertical movement due to the load pressure on them. Divided into two

a) Immediate settlement-occur when the soil is imposed by the load from soil elastic deformation where it does not change the water content

b) Consolidation Settlement-reduction in the volume of soil due to water flowing out from the grain cavities.

Structure pressure to the ground Changes in soil water content The vibration caused by impact piling,

blasting and heavy machinery. Expansion and contraction of soil Movement / soil erosion Other causes, such as soil digging in

the nearby area

Definition: the relative settlement between one part of the building to the other part of building and cause the stress that can result building to crack or collapse

Differences in soil layers in a single site The difference in the load structure Large load area The time difference between the

construction of other parts of the building

Differences in site conditions.

Use raft foundation with a thick slab Use deeper underground space to

reduce pressure on soil. Transfer load to the stronger and not

easily compressible soil with the foundation applied such as piles, caisson, etc.

Method of repair of soil - increase in soil strength

Condition and soil strength The nature and type of building The total loads of building Surrounding area Cost