cn 301 chapter 2

8/11/2019 CN 301 Chapter 2

http://slidepdf.com/reader/full/cn-301-chapter-2 1/50

8/11/2019 CN 301 Chapter 2


GEO-ENVIRONMENTALENGINEERING

GEOTECHNICAL

ENGINEERING

ENVIRONMENTAL

ENGINEERING

8/11/2019 CN 301 Chapter 2


What do youunderstand about

rock?

8/11/2019 CN 301 Chapter 2


ROCK FORMATION PROCESS

1. IGNEOUS

ROCK

2. SEDIMENTARY

ROCK

3. METAMORPHICROCK

8/11/2019 CN 301 Chapter 2


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

8/11/2019 CN 301 Chapter 2


What do youunderstand about

Soil?

8/11/2019 CN 301 Chapter 2


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.

8/11/2019 CN 301 Chapter 2


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.

8/11/2019 CN 301 Chapter 2


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.

8/11/2019 CN 301 Chapter 2


8/11/2019 CN 301 Chapter 2


SOIL

Traditional definition: Material which nourishes andsupports growing plants; includes rocks, water, snow,air.

8/11/2019 CN 301 Chapter 2


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.

8/11/2019 CN 301 Chapter 2


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.

8/11/2019 CN 301 Chapter 2


8/11/2019 CN 301 Chapter 2


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.

8/11/2019 CN 301 Chapter 2


8/11/2019 CN 301 Chapter 2


Soil Forming Processes

Translocations

Transformations

Additions

Losses

8/11/2019 CN 301 Chapter 2


8/11/2019 CN 301 Chapter 2


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.

8/11/2019 CN 301 Chapter 2


Stages in the Formation of Soil

stage 1 stage 2

stage 3 stage 4

8/11/2019 CN 301 Chapter 2


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.

8/11/2019 CN 301 Chapter 2


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

8/11/2019 CN 301 Chapter 2


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

8/11/2019 CN 301 Chapter 2


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.

8/11/2019 CN 301 Chapter 2


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.

8/11/2019 CN 301 Chapter 2


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).

8/11/2019 CN 301 Chapter 2


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).

8/11/2019 CN 301 Chapter 2


SOIL

Component definition: Mixture ofmineral matter, organic

matter, water, and air.

8/11/2019 CN 301 Chapter 2


8/11/2019 CN 301 Chapter 2


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).

8/11/2019 CN 301 Chapter 2


ORGANIC

SURFACE SOIL

SUBSOIL

PARENT ROCK

8/11/2019 CN 301 Chapter 2


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.

http://en.wikipedia.org/wiki/Organic_matter

http://en.wikipedia.org/wiki/Topsoil

http://en.wikipedia.org/wiki/Soil_life


http://en.wikipedia.org/wiki/Bioturbation


http://en.wikipedia.org/wiki/Subsoil

http://en.wikipedia.org/wiki/Illuviation


http://en.wikipedia.org/wiki/Parent_rock

http://en.wikipedia.org/wiki/Parent_rock


http://en.wikipedia.org/wiki/Subsoil



http://en.wikipedia.org/wiki/Topsoil

http://en.wikipedia.org/wiki/Organic_matter

8/11/2019 CN 301 Chapter 2


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.

8/11/2019 CN 301 Chapter 2


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

8/11/2019 CN 301 Chapter 2


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

8/11/2019 CN 301 Chapter 2


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

8/11/2019 CN 301 Chapter 2


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.

8/11/2019 CN 301 Chapter 2


8/11/2019 CN 301 Chapter 2


USDA Textural Triangle

USDA – United States Agricultural Department

8/11/2019 CN 301 Chapter 2


Granular

Platy

Blocky

(Angular)(Subangular)

Wedge

Columnar Prismatic

Examples of Soil Structure

8/11/2019 CN 301 Chapter 2


Aspects of Soil Structure

The arrangement into aggregates of desirable shape and size

The stability of the aggregate

The configuration of the pores

8/11/2019 CN 301 Chapter 2


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

8/11/2019 CN 301 Chapter 2


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

8/11/2019 CN 301 Chapter 2


Important Note

All of these have a loosening effect on the soil, but they have noeffect on aggregate stability

8/11/2019 CN 301 Chapter 2


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

8/11/2019 CN 301 Chapter 2


Effects of Bulk Density

Engineering properties

Water movement

Rooting depth of plants

8/11/2019 CN 301 Chapter 2


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

8/11/2019 CN 301 Chapter 2


8/11/2019 CN 301 Chapter 2


Thank You

We

KNOW

Soil!

is naturally occurring solid inorganic (mostly)

8/11/2019 CN 301 Chapter 2


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

cn 301 chapter 2

Documents