Lecture 10: CE Applications Flashcards
CE applications of Geology
• Foundation • Excavation • Tunnelling • Dams and Reservoirs • Construction Materials • Slope Stability (Discussed in Geol Hazards as application and hazard)
COARSE GRAINED SOIL
– it means that majority of its particles are
bigger or on the coarser range of soil sizes
FINE GRAINED SOIL
– majority of the particles are on the finer side
COHESIONLESS SOIL
it means that the soil does not “stick”
together and cannot oppose pulling forces (think sand, if you try
to pull sand apart, there is no resistance and it just pulls apart)
COHESIVE SOIL
it means that the soil can oppose pulling forces
think clay, you can try to pull apart clay but it has resistance
The bottom part of a structure that serves to transfer the load of the structure to the Earth
Foundation
The soil/rock directly beneath the
foundation
Foundation Bed
The goal of a foundation
to transfer the load safely to the ground (ground does not give or collapse) and without too much
deformation (too much deformation means that the
purpose of the structure is no longer served efficiently)
2 limits in Designing Foundation
1 Strength Limit
2 Serviceability Limit
the limit when one part breaks due to
too much load.
Strength Limit
the limit related to the function
or useability of an object.
Serviceability Limit
For foundations, the relative parameters for strength limit and serviceability limits are
1 Foundation Capacity
2 Settlement
the maximum load that the foundation, based on its dimensions and soil supporting it, can carry
FOUNDATION CAPACITY
the amount of “sinking” that will happen to a
foundation (and hence the structure) once the loads of the structure are in place.
SETTLEMENT
2 Types of Settlement
1 Typical
2 Differential
settlement is the same for all points
of structure, hence the structure simply “sinks”.
Typical Settlement
settlement is different for different points of the structure, hence it may seem to “sink” and “rotate” at the same time.
Differential Settlement
Settlement that can lead to distortion damages to the structure
Differential
Settlement is not much of a limiting value when the foundation sits on_________
Rock
2 Parts of Settlement Foundation
1 Immediate
2 Consolidation
settlement that happens while
it is being constructed or immediately after
Immediate
settlement that happens over a long period of time. Way after the structure has been constructed, settlement still happens. This happens due to clays not allowing water to be expelled quickly, hence, it loses water over time, and as it does, it settles more.
Consolidation
DENSELY packed soils will allow __________ to happen compared to loosely packed soils.
less settlement
Is the ability of cay soils to hold water a good or a bad thing?
this is bad since it can take years before the building is able to force the water out in between clay minerals and this will result to settlement of clay over a long
period of time. This means that if your building is on clay, after a few years, you will find your building still sinking into the ground.
Why is long-time sinking a problem?
Because this is hard to remedy, compared to settlement that will be seen as you construct the
structure.
SHALLOW FOUNDATION
- Isolated Spread Footings
- Wall Footings
- Combined Footings
- Strap or Cantilevered Footings*
- Mat Foundation*
DEEP FOUNDATION
- Pile Foundation
- Driven Piles
- Bored Piles
- Pier/ Caisson Foundation
Foundations usually formed at shallow depths
Shallow Foundation
Shallow foundation is used when
- Material near the surface is strong enough for the structure
- While soil and rocks usually tend to be denser and stronger the deeper you go, this is not always the case. As such, it must be made sure that layers underneath the foundation bed are not weak as well.
1 footing for each column
Isolated Foundation
Continuous strip of footing supporting a wall of the structure.
Wall Footing
Footings with more than 1 column on them
Combined Footing
3 kinds of combined footings
(1) Rectangular
(2) Trapezoidal
(3) Strap/Cantilevered
2 separate spread footings and
then joined together by a strap beam
Strap footing
used to connect an eccentrically loaded
footing (footing where the load from the column is not located at the center of the footing) to another footing
Can also address differential Settlement
Strap Footing
Large foundation supporting more than 1 line of columns
Mat Footing
When is mat footing used?
Usually used when the soil is too weak but using (the more expensive) pile foundations proves to be uneconomical.
Used when the top layers are too weak to support the structure
Pile footing
2 types of Pile Footing
1 Driven
2 Bored
2 Ways Piles carries load
1 Skin Friction - friction on its sides
2 End Bearing Capacity -transferring the load on the other end