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8/11/2019 CN 301 Chapter 2
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8/11/2019 CN 301 Chapter 2
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GEO-ENVIRONMENTALENGINEERING
GEOTECHNICAL
ENGINEERING
ENVIRONMENTAL
ENGINEERING
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What do youunderstand about
rock?
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ROCK FORMATION PROCESS
1. IGNEOUS
ROCK
2. SEDIMENTARY
ROCK
3. METAMORPHICROCK
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Summarize
Igneous Rock
MagmaMetamorphic
Rock
SedimentaryRock
Soil
Mt
Mt C
M
W
W
W
I
M
W =Weathering M =Metamorphosis Mt =Melting I = Indurations
C = CoolingPyroclastic Ejection
Pyroclastic Ejection
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What do youunderstand about
Soil?
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SOIL
Minerals which have a common bondfluid particles are weak or non-binding.
It is formed from rock weathering results.
There are voids which consist of
air and water among the particles.
Supportive role to the load structures built on it.
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The term Soil has various meanings, depending upon thegeneral field in which it is being considered.
To a Pedologist ... Soil is the substance existing on theearth's surface, which grows and develops plant life.
To a Geologist ..... Soil is the material in the relative thinsurface zone within which roots occur, and all the rest of thecrust is grouped under the term ROCK irrespective of its
hardness.
*To an Engineer .... Soil is the un-aggregated or un-cemented deposits of mineral and/or organic particles orfragments covering large portion of the earth's crust.
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Soils are a mixture of different things; rocks, minerals, and dead, decayingplants and animals. Soil can be very different from one location to another,
but generally consists of organic and inorganic materials, water and air.
The inorganic materials are the rocks that have been broken into smallerpieces. The size of the pieces varies. It may appear as pebbles, gravel, or as
small as particles of sand or clay.
The organic material is decaying living matter. This could be plants or
animals that have died and decay until they become part of the soil. Theamount of water in the soil is closely linked with the climate and othercharacteristics of the region.
The amount of water in the soil is one thing that can affect the amount ofair. Very wet soil like you would find in a wetland probably has very little
air.
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SOIL
Traditional definition: Material which nourishes andsupports growing plants; includes rocks, water, snow,air.
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SOIL
Soil Taxonomy definition: Collection of natural bodies ofthe earth’s surface, in places modified or evenmade by man or earthy materials, containingliving matter and supporting or capable of
supporting plants out of doors. Its upper limit is air or shallow water and itslower limit is the depth to which soilweathering has been effective.
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SOIL
As a portion of the landscape: Collection of naturalbodies occupying portions of the earth’s surfacethat support plants and that have properties dueto the integrated effect of climate and living
matter, acting upon parent material, asconditioned by relief, over periods of time.
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SOIL FORMATION
Soils are formed by the disintegration of rock
material of the earth’s relatively deeper crust,which itself is formed by the cooling ofvolcanic magma. The stability of crystallinestructure governs the rock formation.
As the temperature falls, new and often morestable minerals are formed. For instance, oneof the most abundant minerals in soils knownas quartz acquires a stable crystallinestructure when the temperature drops below573oC.
The intermediate and less stable minerals(from which quartz has evolved) lendthemselves to easy disintegration during theformation of soils.
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Soil Forming Processes
Translocations
Transformations
Additions
Losses
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Chemical Weathering
Can transformed hard rock
minerals into soft, easily erodable
matter.
Chemical reactions induced by
exposure to oxygen, water and
chemicals.
Agents:
- Oxidation, Reduction,
Carbonation, Leaching,
Hydration, Desilication,
Hydrolisis, Chelation, cation
exchange between the rock
mineral surface and the
surrounding medium.
SOIL FORMATION PROCESS Soil material is the product of rock.The geological process that produce soil is WEATHERING (Chemical andPhysical/Mechanical).
Physical Weathering
Physical breakdown of rocks and
minerals.
Agents:
- The erosive action of rain, ice,
wind, hail, glaciers etc (frost
action)
- Thermal expansion and
contraction from day to day and
season to season (heat cold)
- Landslides and rockfalls
- Activities of plants, animals and
humans.
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Stages in the Formation of Soil
stage 1 stage 2
stage 3 stage 4
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GROUPS O SOIL
ORGANIC SOIL
Land on whichthere is a layer
on the surface ofthe earth
Contain organicsubtances
The thickness ofthe soil usuallydoes not exceed500 mm
RESIDUAL SOIL
Formed by the
weatheringprocess
Material formedby disintegration
of underlyingparent rock orpartiallyinduratedmaterial.
TRANSPORTED
SOIL
Materialtransported anddeposited by
running water,air, wind,glaciers, gravityetc.
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The types of soil that formed from weathering andtransportation process.
Organic Soil
- Organic matter originates from plant or animalremains, the end product of which known as humus, acomplex mixture of organic compounds.
- A feature of topsoil, occurring in the upper layer (>0.5
m thickness). Alluvial Soil (water-laid), Aeolian (wind-laid), glacial
(ice-transported)
- particles are brought into contact with the stream bedand with each other and so are abraded.
- Erosion Agents: water, glacier, or gravity.
Residual Soil
- Soils that have not been transported.
- Weathering process (chemical and physical)
S il F i F t
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Soil Forming Factors
1. Parent material: The primary material from which the soil is
formed. Soil parent material could be bedrock,organic material, an old soil surface, or a depositfrom water, wind, glaciers, volcanoes, or material
moving down a slope.
2. Climate:
Weathering forces such as heat, rain, ice, snow,
wind, sunshine, and other environmental forces,break down parent material and affect how fastor slow soil formation processes go. Amount ofmoisture available, temperature, chemicalreaction speed and rate of plant growth
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Soil Forming Factor Cont’d
3. Organisms present:All plants and animals living in or on the soil
(including micro-organisms and humans). Theamount of water and nutrients, plants needaffects the way soil forms.
4. Topography:
The location of a soil on a landscape canaffect how the climatic processes impact it.Soils at the bottom of a hill will get morewater than soils on the slopes, and soils onthe slopes that directly face the sun will bedrier than soils on slopes that do not.
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Soil Forming Factor Cont’d 5. Time:
All of the above factors assert themselves over time, oftenhundreds or thousands of years. Soil profiles continually changefrom weakly developed to well developed over time.
Varies for soils in different climates, locations.
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Soil Composition
While a nearly infinite variety of substances may be found insoils, they are categorized into four basic components: minerals,organic matter, air and water.
Most introductory soil textbooks describe the ideal soil (ideal forthe growth of most plants) as being composed of 45% minerals,25% water, 25% air, and 5% organic matter. In reality, thesepercentages of the four components vary tremendously.
Soil air and water are found in the pore spaces between the solidsoil particles. The ratio of air-filled pore space to water-filled porespace often changes seasonally, weekly, and even daily,depending on water additions through precipitation, throughflow, groundwater discharge, and flooding.
The volume of the pore space itself can be altered, one way or theother, by several processes. Organic matter content is usuallymuch lower than 5% in South Carolina (typically 1% or less).Some wetland soils, however, have considerably more organicmatter in them (greater than 50% of the solid portion of the soilin some cases).
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SOIL COMPOSITION
While a nearly infinitevariety of substances
may be found in soils,they are categorized into
four basic components:minerals, organic matter,
air and water.
Most introductory soiltextbooks describe theideal soil (ideal for the
growth of most plants) asbeing composed of 45%minerals, 25% water, 25%
air, and 5% organicmatter. In reality, thesepercentages of the four
components varytremendously.
Soil air and water are found in the pore spacesbetween the solid soil particles. The ratio of air-
filled pore space to water-filled pore space oftenchanges seasonally, weekly, and even daily,depending on water additions through
precipitation, through flow, groundwaterdischarge, and flooding.
The volume of the pore space itself can bealtered, one way or the other, by several
processes. Organic matter content is usuallymuch lower than 5% in South Carolina
(typically 1% or less). Some wetland soils,
however, have considerably more organic matterin them (greater than 50% of the solid portion ofthe soil in some cases).
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SOIL
Component definition: Mixture ofmineral matter, organic
matter, water, and air.
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SOIL HORIZON
If you were to begin digging into a mature soil, you wouldnotice that the color, texture, and other properties of thesoil changed as you went deeper. If you were to dig deepenough, you would see that the soil appeared to be invery distinct layers. These layers, known as soil horizons,
occur because of the different chemical and biologicalprocesses that take place in these zones.
Depending upon the type of soil, there can be up to 5
different horizons. These are denoted by the letters O, A,B, C, and E. Not all soils will have these horizons, withsome immature soils having none. Most soils have at leastthree of these (A, B, and C).
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ORGANIC
SURFACE SOIL
SUBSOIL
PARENT ROCK
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O) Organic matter: Litter layer of plant residues inrelatively undecomposed form.
A) Surface soil: Layer of mineral soil with mostorganic matter accumulation and soil life. This layereluviates (is depleted of) iron, clay, aluminum,organic compounds, and other soluble constituents.When eluviation is pronounced, a lighter colored"E" subsurface soil horizon is apparent at the base
of the "A" horizon. A-horizons may also be theresult of a combination of soil bioturbation andsurface processes that winnow fine particles frombiologically mounded topsoil. In this case, the A-horizon is regarded as a "biomantle".
B) Subsoil: This layer accumulates iron, clay,
aluminum and organic compounds, a processreferred to as illuviation.
C) Parent rock: Layer of large unbroken rocks. Thislayer may accumulate the more soluble compounds.
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D horizons are not universally distinguished, butin the Australian system refer to "any soilmaterial below the solum that is unlike the solumin general character, is not C horizon, and cannotbe given reliable designation… [it] may berecognized by the contrast in pedologicorganization between it and the overlying
horizons" (MacDonald et al., 1990, p. 106).
R horizons basically denote the layer of partiallyweathered bedrock at the base of the soil profile.Unlike the above layers, R horizons largelycomprise continuous masses (as opposed toboulders) of hard rock that cannot be excavatedby hand. Soils formed in situ will exhibit strongsimilarities to this bedrock layer.
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FUNDAMENTAL PROPERTIES OF SOIL
Soil Texture (Particle Size and Shape)
Soil Structure
i. Cohesionless Soils (gravel, sand and silt) – singlegrained
ii. Cohesive Soils (clay soils) – its’ mineralogy andis a controlling factor determining the shapes, sizes,and surface characteristics of a particle in a soil.
Soil color
Bulk density
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4 Major Types of Soils
[Note: Sand, silt, and clay are collectively referred to as the fine earth fraction ofsoil. They are <2 mm in diameter. Larger soil particles are referred to as rockfragments and have their own size classes (pebbles, cobbles, and boulders).
CLAY
Fine-grained soil
Kaolin group
1. Kaolinite
2. Halloysite
Montmorilonite
group
Illite group
SILT
Organic / Inorganic
Silt
Fine-grained soil with
little or no plasticity.
SAND
Coarse grained soil
They are cohesionless
aggregates of rounded
subangular or angular
fragments of more or
less unaltered rocks or
mineral.
Particles of size from
0.075 to 4.75 mm
sand.
Size from 4.75 -80
mm as gravel.
GRAVEL
Coarse grained soil
Individiual particles
that are large enough
to be view without
magnification
T bl f P ti l G i Si
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Table of Particle Grain Size
ORGANIZATION
PARTICLE GRAIN SIZE (mm)
GRAVEL SAND SILT CLAY
AASHTO 76.2 to 2 2 to 0.07
5
0.075 to 0.
002 <0.002
ASTM 76.2 to 4.
75
4.75 to 0.
075 Fines: 0.075
AASHTO – American Association of State highway and Transportation OfficialsASTM
– American Society for Testing and Materials
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The particle size
classification systems also
provide range for particles>76.2 mm, known as Cobblesand Boulders.
In general, cobbles rangefrom 76.2 – 400 mm.
Particles larger than 400 mmare considered boulders.
Coarse-grained Soil >65% Sandand gravel – the soil name
based on the particle sizespresent.
Fine-grained Soil >35% silt and
clay sizes it is based onbehavioral characteristics.
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USDA Textural Triangle
USDA – United States Agricultural Department
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Granular
Platy
Blocky
(Angular)(Subangular)
Wedge
Columnar Prismatic
Examples of Soil Structure
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Aspects of Soil Structure
The arrangement into aggregates of desirable shape and size
The stability of the aggregate
The configuration of the pores
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Factors that Affect Aggregate Stability
Kind of clay
Chemical elements associated with the clay
Nature of the products of decomposition or organic matter
Nature of the microbial population
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Factors that Affect Soil Structure
Kind of clay
Amount of organic matter
Freezing and thawing
Wetting and drying
Action of burrowing organisms
Growth of root systems of plants
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Important Note
All of these have a loosening effect on the soil, but they have noeffect on aggregate stability
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Bulk Density
Determined by dividing the weight of oven-dry soil in grams byits volume in cubic centimeters
The variation in bulk density is due largely to the difference intotal pore space
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Effects of Bulk Density
Engineering properties
Water movement
Rooting depth of plants
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Soil Color
Indicator of different soil types
Indicator of certain physical and chemical characteristics
Due to humus content and chemical nature of the ironcompounds present in the soil
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Thank You
We
KNOW
Soil!
is naturally occurring solid inorganic (mostly)
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A mineral is naturally occurring, solid, inorganic (mostly),has a fixed chemical formula and has an orderly
crystalline structure.
Most minerals contain twoor more elements, 8account for nearly 98% ofthe rocks and minerals:
Oxygen 46%
Silicon 27.72%
Aluminium 8.13%
Iron 5%
Calcium 3.63%
Sodium 2.83%
Potassium 2.59%
Magnesium 2.09%
The most common rocks-formingminerals can be divided into threebroad groups:
1. The carbonates, sulfates and oxides
2. The rock-forming silicate materials
3. The common ore mineral
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