Lecture 3 Flashcards
(17 cards)
Define Plasticity
The ability of a soil to undergo unrecoverable deformation at a constant volume without failing
Define Liquefaction
Transformation of a cohesionless material from a solid state to a liquid state due to increased pore pressure
What is Soil?
- A regolith with a layer of rock and mineral fragments
- Geologists say it’s a combination of mineral and organic matter
- Engineer’s say it’s an uncemented accumulation of mineral particles formed by the weathering of rocks and void space
The Soil Profile name the 5 horizons: “Only Amazing Earthworms Build Castles”
- O horizon, loose and partly decayed organic matter
- A horizon, mineral matter with humus
- E horizon, light coloured minerals, is the leaching where fine particles move down
- B horizon, accumulation zone for fine grain particles
- C horizon, parent material (partially altered rock)
Factor in Soil Formation…
- Parent material (it’s type)
- Time (how long weathering occurred)
- Climate
- Plants and Animals
- Topography
What is weathering?
The mechanical and chemical breakdown of Rocks exposed on the earth’s surface into smaller particles that may differ from original composition
What is erosion?
Detachment and transportation of surface particles due to
- gravity
- wind
- ice
- waves
- water
How can erosion by water be prevented?
Minimize clearing and grading, protect steep slopes, immediately stabilize exposed soils, and protect waterways
What is Mechanical weathering?
The process which a rock breaks into smaller and smaller pieces, each retaining the properties of the original material. Surface area is also increased
What is Chemical weathering?
Transformation of a rock into one or more new components
State the Porosity equation
n = Vv/Vt
State the void ratio equation
e = Vv/Vs
State the Bulk Density equation
p = Mt/Vt (kg/m^3)
State the moisture content formula
θw = Mw/Ms (%)
State the Degree of Saturation formula
Sr = Vw/Vv (N/m^3)
State the characteristics of clay
They have electrostatic attraction between particles, providing cohesiveness.
Some have repulsion to other clays, making them harder to compact.
Some hold water very strongly, expand, and exchange ions.
They are flat particles and can rearrange themselves in response to applied loads.
Define the LL, PL and SL
LL = the upper limit of water content for plastic behaviour
PL = the lower limit of water content for plastic behaviour
SL= the transition from plastic to solid behaviour
