week 9 Flashcards
What type of soil classifications exist?
Rock
Igneous rocks, such as granites, basalts which were formed as a result of solidification of molten material
Sedimentary rocks, such as sandstone, chalk and limestone, which were formed by deposition of granular material or sediment
Metamorphic rocks, such as slate which was formed as a result of heat or pressure acting on igneous or sedimentary rocks and changing the crystalline structure
Gravels & Sands
Typically grouped as coarse graded cohesion-less soils .06mm +
Move independently of each other
If treated can provide an adequate building base
Silts & Clays
Typically grouped as fine graded cohesionless soils < .06mm
Subject to changing moisture contents
Dry shrinkage and heave in wet weather
Peat & Organic Soils Large organic material Subject to large changes in compression resulting in decay from organic matter Generally not suitable for building Where is this most commonly found?
define contanimated ground
Any substance which is or could become toxic, corrosive, explosive flammable or radioactive and likely to be a danger to health and safety.
Before foundation types are decided, a number of factors regarding the structure and the site it is to be considered on will have to be considered. These include
Weight of the proposed structure Purpose of the structure Soil composition of the proposed site History of the proposed site Feasibility of costs
what is a foundation
Foundationsare the lower portion ofa buildingstructure that transfers its gravity loads to the earth.
Foundationsare generally broken into two categories: shallowfoundationsand deep foundations.
A tall/heavybuildingmust have a strong foundationif it is to stand for a long time. Basically Foundations act as the interface between loads of the building and the ground.
2 categories of foundatins
shallowfoundationsand deep foundatio
define raft foundation
Raft foundationis actually a thick concrete slab resting on a large area of soil reinforced with steel, supporting columns or walls and transfer loads from the structure to the soil. Usually, matfoundationis spread over the entire area of the structure it is supporting.
adv of raft foundation
Advantages of Raft Foundation:
Raft foundation is economic due to combination of foundation and floor slab.
It requires little excavation.
It can cope with mixed or poor ground condition.
neg of raft foundations
Disadvantages of Raft Foundation:
Raft foundation requires specific treatment for point loads.
Edge erosion occurs if not treated properly.
define pad foundations
Pad foundationsare a form of spread foundationformed by rectangular, square, or sometimes circular concrete ‘pads’ that support localised single-point loads such as structural columns, groups of columns or framed structures.
advantages of pad foundations
Advantages of Pad Foundations
Shallow foundations, so little excavation is required
Economic
Reinforcement for shear and tension can be added
Can be designed to accommodate a tight site
Easy design and
negatives of pad foundatin
Size of pad can be very large
Require bigger support for deep excavations
Weak against forces
Separated foundations
define strip foundation
Strip foundations(orstripfootings) are a type of shallowfoundationthat are used to provide a continuous, level (or sometimes stepped)stripof support to a linear structure such as a wall or closely-spaced rows of columns built centrally above them. Strip foundations are arguably the cheapest form of foundation available.
advantages of strip foundations
and neg
Conventional build method
Good amount of concrete thermal mass in floor.
Require simple excavation & simple formwork
Adapt to sloping sites
Cheap
Disadvantages
Generally requires good ground conditions
explain shallow foundation forms
Shallow foundations are typically used where the loads imposed by a structure are low relative to the bearing capacity of the surface soils.
Required to cope with point loads
Shapes of pad foundations can be varied to cope with site conditions
Raft foundations can be developed to become buoyant in some circumstances
Pad foundations
Strip foundations
Raft foundations
type of pad foundations
The location of such pads may include;
A series of discrete, well-separated pads.
Balanced base pads that support more than one point load.
Continuous pads, where there are a number of point loads close together
