Lesson 1: Soil Formation Flashcards
the uncemented aggregate of mineral grains and decayed organic matter (solid particles) with liquid and gas in the empty spaces between the solid particles
soil
used as a construction material in various civil engineering projects and it supports structural foundations
soil
what are the properties of soil?
- origin
- grain-size distribution
- ability to drain water
- compressibility
- shear strength
- load-bearing capacity
branch of science that deals with the study of the physical properties of soil and the behavior of soil masses subjected to various types of forces
soil mechanics
subdiscipline of civil engineering that involves natural
materials found close to the surface of the earth; it includes the application of the principles of soil mechanics and rock mechanics to the design of foundations, retaining structures, and earth materials
geotechnical engineering
what are the application of principles of soil mechanics to
engineering problem?
- highway retaining wall
- building basement walls
- bridge abutments
- earth dam
- waterfront bulkhead
what are the examples of geotechnical systems?
- dams
- tunnels
- excavations
- slope stabilization
- earth retaining structures
- subgrade support
- ground improvements
- foundation for buildings
give 2 examples of geotechnical failures
- leaning Tower of Pisa
- failure of Transcona Grain Elevator
chemical elements that constitute rocks
minerals
the aggregation of minerals into a hard mass
rocks
materials that are derived from the weathering of rocks
soils
average particle diameter of the soil at the 10th percentile or 10% of the particles are smaller that this diameter size
effective particle size (D-subscript-10)
average particle diameter of the soil
average particle diameter (D-subscript-50)
numerical measure of uniformity
uniformity of coefficient (C-subscript-u)
measure of the shape of the particle distribution curve (coefficient of gradation/ coefficient of concavity)
coefficient of curvature (C-subscript-c)
weathering of rock
soil
process of which rocks are broken into pieces by physical force (e.g. water, wind, waves or ice and frost)
mechanical weathering
process of chemical decomposition of the original rock
chemical weathering
what are the 3 basic types of rocks?
- igneous rock
- sedimentary rock
- metamorphic rock
soils that are formed by the weathered products at their place of origin; these soils retain many of the elements that comprise the parent rock
residual soil
the composition of these soils depends on the environment under which they were transported and is often different from the parent rock
transported soil
categories of transported soil:
soils from landslides or mudflows
colluvial or gravity transported
categories of transported soil:
formed by deposition in quiet lakes
lacustrine
categories of transported soil:
transported by running water & deposited along streams
alluvial
categories of transported soil:
formed by transportation and deposition from glaciers
glacial
categories of transported soil:
transported & deposited by wind
aeolian
categories of transported soil:
formed by deposition in the seas
marine
crystalline materials and make up the solids constituent of a soil
minerals
what are the two classifications of minerals?
*chemical composition
*structure
most minerals of interest to geotechnical engineers are composed of _____ and _____, two of the most abundant elements on earth
- oxygen
- silicon
the principal mineral of coarse- grained soils; it is hard and composed of silicon dioxide (SiO2) in colored, colorless, and transparent hexagonal crystals
quartz
the particles of coarse-grained soil are naturally _____
angular
complex aluminum silicates made of two distinct structural units
clay minerals
composed of silica sheet
silicon tetrahedron
composed of octahedral sheet/ gibbsite (Al) sheet or brucite (Mg) sheet
alumina octahedron
what are the three clay minerals?
- kaolinite
- illite
- montmorillonite
clay mineral that consists of repeating layers of elemental silica gibbsite sheets in 1:1 lattice; the layers are held together by hydrogen bonding and occurs as platelets
kaolinite
clay mineral that is commonly used in paints, paper and in pottery and pharmaceutical industries
kaolinite
(OH)8Al4Si4O10
kaolinite
kaolinite family that has hydrated and tubular structure; (OH)8Al4Si4O10 * 4H2O
halloysite
clay mineral that consists of gibbsite sheets bonded to two silica sheets - one at the top and another at the bottom, also bonded by potassium ions
illite
illite sometimes called _____
clay mica
clay mineral that has a structure similar to that of illite - one gibbsite sheet sandwiched between two silica sheets; there is
isomorphous substitution of magnesium and iron for aluminum in the octahedral sheets; potassium ions are not present as in illite and large amount of water attracted into the space between the layers
montmorillonite
clay mineral that expands on contact with water and highly reactive clay
montmorillonite
montmorillonite is also called _____
smectite
(OH)4Al4Si8O20 * nH2O
montmorillonite
part montmorillonite family that is used as drilling mud, in slurry trench walls, stopping leaks
bentonite
during deposition, the mineral particles are arranged into structural frameworks that we call _____
soil fabric
common type of soil fabric where particles tend to orient parallel to one another
flocculated structure (saltwater environment)
common types of soil fabric where particles oriented in perpendicular manner
flocculated structure (freshwater environment)
common type of soil fabric that occurs when majority of the
particles orient parallel to one another
dispersed structure
what are the three major categories of particle shape?
- bulky particles
- flaky particles
- needle-shaped particles
a particle shape that is mostly formed by mechanical
weathering of rock and minerals
bulky particles
described as angular, sub-angular, rounded, and sub-rounded
bulky particles
a particle shape with very low sphericity, predominantly clay minerals
flaky particles
a particle shape that is less common than the two other particle types; examples are some coral deposits and attapulgite clays
needle-shaped particles
what are the three types of soil according to its particle size?
- gravel
- sand
- silt and clay
soil type:
pieces of rocks with occasional particles of quartz, feldspar, and other minerals
gravel
soil type:
mostly made of quartz and feldspar
sand
soil type:
consists of very fine quartz grain, mostly flake-shape microscopic and submicroscopic particles of mica, clay mineral and others
silt and clay
what are the coarse-grained soil?
- gravel (G)
- sand (S)
a coarse-grained soil described as rounded and/or angular bulky hard rock, coarsely divided
gravel (G)
a coarse-grained soil described as rounded and/or angular bulky hard rock, finely divided
sand (S)
grain size of gravel: >75 mm
coarse
grain size of gravel: 4.75 mm-19 mm
fine
grain size of sand: 2.0 mm-4.75mm
coarse
grain size of sand: 0.425 mm-2.0 mm)
medium
grain size of sand: 0.075 mm-0.425 mm
fine
what are the fine-grained soil (also called fines)?
- silt (M)
- clay (C)
a fine-grained soil described the particle size between clay and sand; nonplastic or very slightly plastic, exhibits little or no strength when dried; easily brushed off when dried
silt (M)
a fine-grained soil described the particles as smooth and mostly clay minerals; greasy and sticky when wet; exhibits plasticity and significant strength when dried; water reduces strength
clay (C)
what is the grain size of silt (M)?
0.002 mm-0.075 mm
what is the grain size of clay (C)?
<0.002 mm
determination of size range of particles present in a soil,
expressed as % of the total dry weight
mechanical analysis of soil
mechanical analysis method for particle sizes larger than 0.075 mm in diameter
sieve analysis
mechanical analysis method for particle sizes smaller than 0.075 mm in diameter
hydrometer analysis
a method that consists of shaking the soil sample through a set of sieves that have progressively smaller openings
sieve analysis
a method based on the principle of sedimentation of soil grains in water
hydrometer analysis
sieve number for 4.75 mm
4
sieve number for 2 mm
10
sieve number for 0.84 mm
20
sieve number for 0.425 mm
40
sieve number for 0.25 mm
60
sieve number for 0.106 mm
140
what are the parameters for particle size distribution curve?
- effective size (D-subscript-10)
- uniformity coefficient (C-subscript-u)
- coefficient of gradation (C-subscript-C)
- sorting coefficient (S-subscript-0)
a parameter for particle size distribution curve where the diameter in the particle-size distribution curve corresponding to 10% finer; good measure to estimate the hydraulic conductivity and drainage through soils
effective size (D-subscript-10)
a parameter for particle size distribution curve defined as (C-subscript-60) over (C-subscript-10)
uniformity coefficient (C-subscript-u)
a parameter for particle size distribution curve defined as (C-subscript-30) squared over (C-subscript-60) x (C-subscript-10)
coefficient of gradation (C-subscript-C)
a parameter for particle size distribution curve defined as another measure of uniformity and is generally encountered in geologic works, expressed as: the square root of (D-subscript-75) over (D-subscript-25)
sorting coefficient (S-subscript-0)
what are the different types of particle-size distribution curve?
- curve I (poorly graded)
- curve II (well graded)
- curve III (gap graded)
a type of particle-size distribution curve that represents a type of soil in which most of the soil grains are the same size
curve I (poorly graded)
a type of particle-size distribution curve that represents a soil in which particle sizes are distributed over a wide range
curve II (well graded)
uniformity coefficient (Cu) for gravel
> 4
uniformity coefficient (Cu) for sand
> 6
uniformity coefficient (Cu) for sand and gravel
between 1 and 3
a type of particle-size distribution curve where soil might have a combination of two or more uniformly graded fractions
curve III (gap graded)
