????? ???????? Terrain analysis

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????? ????????Terrain analysis
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Reference

• Terrain analysis
• by Douglas S. Way

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Definition

• Processes of interpreting a geomorphological area
• To determine the effect of natural and man made
  features on engineering application
• Set of activities which leads to the
  classification compilation of terrain
  characteristics

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Landforms

• Land units have resulted from
• Constructional geological processes
• Destructional geological processes
• Have range of physical characteristics

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Factors on landform formations

• Age
• Climate
• Weathering
• Erosion

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Physical site factors

• These factors are identified from aerial
  photographs
• Topographic relief
• Drainage pattern
• Photographic color and tone
• Erosin gully analysis
• Land use and vegetation cover

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Objective of terrain analysis

• By using physical site factors to obtain the
  following
• Geology
• Rock type
• structures (fracture, fault )
• Soil
• Type
• Moisture
• Depth to bed rock
• Depth to water table

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Suitability of terrain analysis

• To draw boundaries between different rocks and
  soil units
• To identify the types of landform
• To evaluate the engineering properties of
  landforms and its suitability as
• Constructional material
• Foundations
• Ground water supply
• Excavation
• Building stones

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Terrain analysis ability

• Cover large area
• Help to identify and locate weak areas

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Type of landform Major features - plains -
Depressions - Plateaus - Mountains Minor
features
Mesas Hills
Butte Slopes
Canyon Alluvial fans
Valleys
Piedmont
Ridge
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Technical terms

• - Physiography genesis and evolution
• - Geomorphology form of earth, configuration of
  surface and change in evolution of landforms
• - Topography landform in cross-section

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Climate

• Characteristics
• Temperature
• Humidity
• Rainfall
• Frequency of climate change

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Arctic climate

• Rain is lt 10 / year
• Cold and dry
• No plants ( little moisture )
• Summer temperature is 4 C
• Winter temperature is -28 to -34 C

Type of weathering frost wedging
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Humid climate

• Rain lt 40 to 80 / yr
• Summer temp. is 10 to 27 C
• Winter temp. is 6 to 16 C
• Evaporation is less than rainfall

Type of weathering mechanical and chemical in
addition to frost wedging Soil develop deep
profiles Silica rich with high organic content
soil
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Tropical climate

• Rain lt 60 to 80 / yr
• Warm and cold
• Temperature is 21 32 C
• No big difference between winter and summer

Type of weathering chemical is more dominant
than mechanical ( high rain ) Soil with high
concentration of aluminum and iron oxides
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Arid climate

• Rain lt 20 / yr
• Warm and cold
• Summer temperature is 16 to 42 C
• Winter temp. is 6 to 32 C
• Evaporation exceeds rainfall

Type of weathering mechanical and chemical but
present at slow rate (low rainfall ) poly mineral
rocks( granite ) weather more rapidly than mono
mineral rocks (limestone) limestone and
sandstone form upland cliffs and cap rocks while
granite and metamorphic rocks occupy the more
weathered lowlands Soil free from organic and
more susceptible to wind erosion
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Weathering

• Act at the surface
• Decomposition and disintegration of rocks
• Two form of weathering mechanical and chemical

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Factors influenced weathering

• Rock hardness
• Mineral type
• Cement ( iron oxide )
• Chemical composition
• Differential expansion of colored minerals
• Rock jointing
• Climate
• Topography
• permeability

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Mechanical weatheringdisintegration) )

• By physical compression or splitting forces
• Broken rock of smaller pieces
• No mineral alteration
• Coarse and angular in general

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Pressure release

• Overburden material is removed
• Rock is exposed to surface by erosion or
  uplifting
• Develop fractures and cracks allow water , acids,
  ice, and roots to penetrate the rock and further
  disintegrate rock

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Crystal growth

• Growth of ice or salt crystals in cracks and
  pores of rock
• Water freezes, volume expands, exert a pressure (
  2100 tones/ft² )
• This force when repeated is shatter the rocks
• Water evaporate and salt crystal form in fractures

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Thermal expansion contraction

• By rapid heating and cooling in arid region
• exfoliation

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Root action

• Vegetation growth cause splitting forces in rocks
• Penetrate smallest cracks and cause water to
  enter

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• Chemical weathering
• ( decomposition )
• Rocks and minerals are broken down into very
  smaller units, alteration . Chemical compounds
  tend to break down into simpler and more stable
  one
• Greatest effect in warm and high humidity area
• New minerals, more stable and suited to the lower
  temperature and pressures in the earth surface
  are found
• Agents are water, oxygen carbon dioxides and
  organic acids

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Chemical activities 1- Oxidation Reaction
with O2 to form greater volume and lower density.
Red or brown stains is formed. This can take
place in rocks which contain iron with the
presence of water. The resulting ferric compounds
contain more oxygen than original compounds .
Slight oxidation produce the mineral hematite
(Fe2O3)
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2- Carbonation It is formed by the reaction
between carbonic acid and calcite to form calcium
and bicarbonate ions in solution. calcium
bicarbonate is about 30 times more soluble than
calcium carbonate
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3- Desilication The reaction of carbonic
acid with silicate compounds, the reaction of
this acid with feldspar mineral release clay
minerals, silica in solution So feldspar
weathers by this activities
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4- Hydration The combination of rock
minerals and water molecules which cause volume
expansion (about twice the original volume)
Anhydrite water Gypsum
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Susceptibility of rock to weathering

• Different type of rocks show various mode of
  weathering
• Igneous susceptible to chemical
• originate deep in the earth, not in harmony
  with surface

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sedimentary

• Consist of fragment previously weathered
• Relative weathering resistance depend on
  cementing agent
• Rocks are cemented by silica dominate their
  surrounding material

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Metamorphic rock

• Degree of resistance depend on
• Degree of metamorphism
• Original rock type
• structure

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Erosion

• Transportation of weathered material
• Down slope by mass wasting
• By fluvial
• By eolian processes

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The entire drainage pattern the gullies
(channelized flow), the tributaries, and the
major channels. high altitude photographs the
different patterns can indicate - Rock
types - soil - rock attitude - structure
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Drainage Pattern Types - Dendritic (most
common) - treelike branching - tributaries
join the gently curving main stream at acute
angles - homogeneous soil and rock and uniform
material - landforms of soft sedimentary
rocks, volcanic tuff, dissected glacial till and
dissected coastal plains
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Angular is a variation of dendritic or
trellis systems The faults, fractures or
jointing systems have modified the classic form.
Sharp, angular bends in the mainstream
Tributaries control by rock features. The
direction of angulations indicate the rock type
- sandstone develops jointing patterns -
limestone cleavage joints that intercept at
acute angles
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Rectangular patterns are variation of a
dendritic system - tributaries join the main
stream at right angle and form rectangular shapes
- controlled by bed rock jointing, foliations
or fracturing - stronger pattern, the thinner
the soil cover - forms in slate, schist - form
in gneiss, in resistive sandstone in arid climates
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Parallel Systems develop on homogeneous, gentle,
uniformly sloping surface and main stream may
indicate a fault or fracture - Tributaries join
stream at right angle - Landform of young coastal
plains - Large basalt flows Karst With surface
and subsurface drainage network - Result from
solution weathering of limestone - Few streams
ends in sinkholes - Scattered sinkholes
depressions - Some gullies lead into sinkholes
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Trellis Is modified dendritic forms with
parallel tributaries and short parallel gullies
occurring at right angles. - Indicate structure
not rock type - tilted, interbedded, sedimentary
rocks in which the main parallel channels follow
the strike of the beds
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Radial Is a circular network of almost
parallel channel flowing a way from a central
high - A major stream is found in point the
bottom of topographic features - volcanoes -
isolated hills - domelike landforms Annular De
velops on topography forms similar to those
associated with radial patters, but joints
control the parallel tributary - Sedimentary
domes - Granite domes
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Braided is found in alluvial plains in arid
regions - coarse soil Centripetal is variation
of radial - drainage directed downward toward a
central point - In basin or sinkhole - eroded
anticline or syncline Pinnate Is modified
dendritic patterns - indicate a high silt
content soil - found in loess - fine tex.
Flood plains Subdendritic Is complex
combination of rectangular and parallel dendritic
- Indicated different condition, rock type
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Internal Is not have of an integrated drainage
granular material, high permeability
porous rock materials in alluvium areas
beach ridges sand dunes Deranged In
nonintegrated drainage flat or undulating
surface high water table swamps
depressions, or lakes in flood plains, till
plains
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Intrusive rocks Landforms - Batholith
40mi2(60km2)area dome shaped Irregular
massave domed roof enlarges downward -
Stocks loss then 40mi2 similar to
batholiths - Laccolith leans shaped
concordant with surrounding rock structure
cause uplift - Sills similar to the laccolith
except no uplift Dikes enter a crack between
rock
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Intrusive rocks Tone light gray in acidic
rocks dark gray in basic rocks Drainage
Dendritic patterns Soil thin layer of residual
soil (2feet thick) SM with ML Trenching
Excavation of material for pipelines is expensive
to dig 6 feet deep trench
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Intrusive rock Construction material sand
is mixed with silt and clay not suitable
Aggregate is not recommended for use in
concrete Building stone is suitable,
excellent building stone Land slides may
occur due to fracturing and water Ground water
supply not sufficient as water supply Dam
construction Good areas for dam Foundation
high load bearing capacities
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Sedimentary rock The sediments originates
from Remnants of decomposes or disintegrated
igneous metamorphic or sedimentary rocks (clastic
rocks such as conglomerate, sandstone, shale)
Derived from chemical reactions (Limestone and
gypsum) Derived from organic sources like
coral
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• Characteristics of Sed. Rocks
• Diversity of their physical and engineering
  properties (strength, porosity, permeability)
• Numerous type of structures
• - Bedding
• - interbeding of different rocks flat, tilted
• - Solution cavities
• - Anticline / syncline
• - Uplifting cause drying and further jointing
  perpendicular to the bedding

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Sandstone Sandstone consolidated sand grains
(silica or orthoclase) form flat table rock of
equal elevation due to its bedding
Rugged topography due to its relative resistance
to weathering Interpretation of pattern elements
Tone light, banded Drainage angular or
rectangular Soil GM (silty gravel) GC
(clayey gravel) SM (silty sand) SC (clayey
sand)
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Sandstone Trenching may require blasting
seepage may occur Construction material Sand
good source from sand dunes Agg. From fair to
excellent Building stone strong sandstone is
good and important source of stone Ground
water very good aquifer Dam seepage
problem Foundation Mostly high load bearing
capacities
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Limestone Limestone is formed by processes
as 1- organic deposition (diatoms, coral) 2-
chemical precipitation ????? contains impurities
such as sand, silt or clay 3- chemical reactions
(Dolomite, replacement of Ca by
Mg) Weathering properties 1- weather by
chemical process as carbonation 2- water
dissolves limestone through joints and forms
channels and solution cavities 3- form
depression 4-form table rocks with vertical faces
??? ??? ???? ????? 5-coral form jagged cliff???
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Limestone Tone light gray uniform
banded Drainage Angler sail GM , ml
GC , CL Trenching may require blasting coral
power equipment Construction Material sand
not suitable Agg. Good
(limestone) poor
(coral) Building good
stone facing stone very
good-excellent Ground Water cam be found but
very hard Dam seepage due to
channel-cavities
channel-cavities
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Slate foliated meta. rock formed by heat
and pressure on shale has parallel foliation
planes (slaty cleavage) low grade of met am
orphism weathers very quickly by mechanical
means develops rugged topography with sharp
ridges
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Slate Tone uniform light gray Drainage
Rectangular Soil CM , silty clays Trenching
Easy with equipment Sand not suitable Aggregate
not suitable Facing stone not suitable Ground
water maybe available Dam construction not
suitable Foundation shallow fourdatim
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Schist Tone light faint parallel banding
Drainage rectangular angular Soil
ML,CL Trenching easy with power equipment Sand
not suitable Aggregate not suitable Building
stone not suitable Facing stone good Ground
water suitable in weathered and fractured Dam
seepage along fracture Foundation should take
care due to clay and schistosity
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Gneiss Tone Uniform light gray Drainage
rectangular angular Soil SM silty sand
clayey sand (SC),ML MH,CL and CH Trenching
heavy equipment and blasting Sand not
suitable Aggregate good to fair Facing stone
good to poor Ground water may occur in
fractured Dam suitable Foundation excellent
foundation material
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- Terrain evaluation is study of large area and
used in - planning - site investigation -
Objective - classification of the area into
terrain class - Engineering terrain class can
be studied - similar eng. Properties can be
assumed for similar class - Type of
classification PUCE Pattern Unit Component
Evaluation
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Basis of the PUCE - topography - underlying
rock and structure - soil and vegetation cover
PUCE operates of 4 levels as 1- Provinces 2-
Terrain Pattern 3- Terrain unit 4- Terrain
component
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Terrain pattern
Terrain unit (125000 or larger)
Terrain component (12500 or larger)
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Terrain provinces Terrain pattern Patterns
and units are described using, Aerial
photography Interpretation Field validation
1250000
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Process of terrain analysis 1- To classify
terrain on the basis of similarity or homogeneity
of certais properties, attributes 2- To assess
(qualitative) or evaluate (qualitative) like area
for the properties of the terrain that are
significant for the desired purpose
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PUCE class is composed repetitive association
????? ?????? of members of the next class in the
hierarchy ????? ???? a) aprovince consist of
association of terrain pattern b) a terrain
pattern consist of association of terrain units
c) a terrain units consists of a repetitive
association of terrain component
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The pattern and unites are describe using the
following criteria a) Slope categories Flat,
gently undulating area b) Soil categories
Shallow soil, sand, uniform soil, organic soil
c) Vegetation categories Grassland, open wood
land, forest area d) Land use categories
Forestry, unused area, recreation, urban
development
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Terrain classes A province - rock with
uniform age - determined from geology map of
scale 1250000 - Association of terrain patterns
A terrain pattern - uniform landscape -
Recurring ????? topography soil associations,
natural veg amplitude - characteristics drainage
pattern - uniform drainage density
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A terrain unit (area) - consist of a single land
form - characteristic soil and vegetation
formation A terrain component - A part from a
topography - Uniform underlying litho logy and
a uniform structure - a consistent association
of are class in the USC system - a
characteristic vegetation association
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Class ification nomenclature ????? ??? The
nomenclature used in PUCE system is numerical a)
Terrain components are allocated ????? eigh
digits b) Terrain units are allocated four
digits c) Terrain pattern are allocated three
digits d) Province are five digits
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Province (35.003) 35 carboniferous system .003
third recognized ???? province of carb. age
Terrain pattern 25/2 2 relicf amplitude to 75
m 5 Drainage density /2 second recogrize ????
pattern in the province Terrain unit 1.4.36
1.4 strongly undulating surface .3 clay soil
6 forest Terrain component 44203101 4 slope
major axis cor 4 slope major axis to 10º 2
slope major axis to 2º 03 soil profile 1 land
use forestry 01 vegetation
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