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Tanah (soil / turbah)

dwzwy-geologi-2008 1

Assoc Prof Dr. Wan Zuhairi Yaacob

Program Geologi

UKM

Definasi

• Geologist

• Engineer

• Soil scientist

• Pedologist


Soil Scientist


Geologist !!!

dwzwy-geologi-2008

The importance of soil (tanah)

• Natural resource for plant growth

• Erosion – environmental degradation

• Source of sediment

• Filter for groundwater

• Bearing material

• Construction material

• Land-use planning

• Waste Management

• Evaluate natural hazards

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dwzwy-geologi-2008

KISAH PEMBUNUHAN PERTAMA

• Kenapa mayat manusia di tanam dalamtanah?

• Kisah QABIL membunuh HABIL (semak Al-

Quran, Al Maidah ayat 31)

“kemudian Allah menyuruh seekor burung gagak menggali-gali dibumi untuk memperlihatkan kepada Qabil bagaimana diaseharusnya menguburkan mayat saudaranya”

-- manusia banyak belajar dari alam

-- jangan segan mengambil pelajaran dari yang lebih rendahtingkatan pengetahuannya.

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dwzwy-geologi-2008

SOILROCKweathering

The breaking down of various

types of rocks into smaller pieces

through mechanical and chemical

processes.

RESIDUAL SOIL

-formed in place

-cover the rock surface

-cold / cool area

= fairly thin; slow weathering

-hot / warm area

= thick; rapid weathering.

TRANSPORTED SOIL

1. Alluvial or fluvial = running water

(estuarine deposits)

2. Glacial = glacier

3. Aeolian = wind action

NON-INDURATED (SOFT) ROCKS

-referred as soil by engineers

-Eg. Oxford clay; Kajang Formation

(Primary minerals)

(Secondary minerals)

6

Physical

Biological

chemical


NON-INDURATED (SOFT) ROCKS

“soil to me but rock to you”

dwzwy2007 8

Fresh Granit (Grade I)

Weathered Granit

(Grade III-IV)

dwzwy2007 9

dwzwy2007 10

Kadar luluhawa beberapa mineral pembentuk batuan

• S.S. Goldich (1938)

– Mencadangkan siri

luluhawa mineral

pembentuk batuan

– Di permukaan bumi; olivine

dan Ca-plagioclase

feldspar sangat mudah

terluluhawa

– Quartz dan muscovite mica

adalah sukar terluluhawa

(inert)

dwzwy-geologi-2008

Soil Horizons

• Vertical and horizontal

movements of materials in soil

create distinct layering;

parallel to surface –

collectively known as soil

profile

• The layers are called zones /

horizons.

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dwzwy-geologi-2008

Soil

horizons

Descriptions Colour

O Highly concentrated organic matter

(Plant litter and other organic material)

Dark

brown/black

A Zone of leaching (eluviation)

•Contains both organic and resistant mineral material

•Leaching – process of dissolving, washing, or draining earth

materials by water.

•Moves clay and other material such as iron & calcium to B

Light

black/brown

E Zone of leaching

•Resulting from leaching of clay, Ca, Mg, Al2O3 and Fe2O3 to B

•Light in colour; less organic material than O & A

Light

colored

(white)

B Zone of accumulation (illuviation)

Enriched in clay, iron oxides, Si, CO3

Red

(iron/Al

oxides)

C Parent material partly altered by weathering process

R Unaltered parent material

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dwzwy-geologi-2008

Soil Profile

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Soil chronosequences

(kronojujukan tanah)

• Sama seperti kronojujukan

batuan (penentuan usia

relatif batuan)

• Penentuan usia relatif

berdasarkan kepada

pemerhatian di lapangan

• Digabungkan dengan C

dating (14C) – numerical

dating



the leached

zone thickens

with time

a redder color

and becomes

dark red in

10,000 years

(zone of

accumulation –

iron)

Soil chronosequences

(kronojujukan tanah)

Penkelasan tanah

(Soil classification )

• Soil Science

– Soil taxonomy

– US Dept. of Agriculture triangle

• Engineering

– Unified soil classification (USC)


• Soil Science

– Soil taxonomy

– US Dept. of Agriculture textural triangle


Loam: 40% silt ; 40% sand; 20% clay

US Dept. of Agriculture standard textural triangle

• Engineering– Unified soil

classification

(USC)


dwzwy-geologi-2008

Engineering properties of soils

• The most important : Soil = solid + liquid + gas

1. Texture (Tekstur – saiz butiran tanah)

2. Plasticity (keplastikan) - water content of soil

3. Strength (kekuatan); resistance to deformation

- Bergantung kpd “cohesion” & “friction”

4. Sensitivity (kesensitifan); change in soil

strength from disturbances (vibration /

excavation) – liquifaction

5. Compressibility (Kebolehpadatan); soils

tendency to consolidate (decrease in volume);

settlement

21

Plastic limit


PI = LL – PL

PI (<5%) = cause problems; easily change from solid to liquid state

PI (>35%) = potential to expand and contract

Panos

Paolo

6. Erodibility (hakisan);

7. Permeability (ketertelapan); finer grained

materials are less permeable

8. Corrosion potential (kekaratan); tendency to

corrode materials and structures, esp. metals,

laid in the ground

9. Ease of excavation (pengorekan)

- Common excavation ; rippable ; blasting / rock cutting

10.and shrink-swell potential (kembang-kecut).clays absorb water and expand "fat clays.“

Eg. Montmorillonite; bentonite; smectite


Engineering properties of soils

Soil texture (Tekstur tanah)

• Bergantung kepada peratusan bahagian

pasir; lodak dan lempung.

• Boleh ditentukan di lapangan & makmal


Stones and cobbles are bigger than 64 mm

Gravel is from 2 mm to 64 mm

Sand is from .05 to 2 mm

Silt is from .002 to .05 mm

Clay is less than .002 mm.

dwzwy2004

Soil Classification Calculator

http://www.tulsamastergardeners.org/black

box/soil_clas_calc.htm

dwzwy2004

Mechanical analysis of soil

• Determination of the size range

of particles.

• Sieve analysis

– Particle > 0.075mm

• Hydrometer

– Particle <0.075mm

Sedigraph

• Particle Size Analyser (micromeritics SediGraph III)


dwzwy2004

Sampel

(Wet sieving 2mm; 63 um; pan)

> 63um <63um

Sieve analysis Sedimentation

analysis

Pasir kerikil Lempung/clay

lodak/silt

Ayakan basah

Ayakan kering

(dry sieving)hydrometer

dwzwy2004

Sand and Gravel

Sand & fine gravel

Silt, Sand and gravel

Silt and fine sand

Silt = 95-31 = 64%

31% clay

5% sand

* Name the fractions for soil A, B, C and D?

** What is the percentage of silt for soil D?

*** Which one is poorly graded curve?

**** Which one is well graded curve?

Universal Soil Loss Equation (USDA)


meaning, soil erosion is a function of the following factors:

A = average annual soil loss

R = erosive impact by rainfall (energy and intensity of rainfall)

K = soil erodibility factor (coarse grains need more energy to

transport, clay is cohesive and takes more energy to erode)

L = slope length factor (long slopes gather more water and

greater erosive flow velocity)

S = slope angle factor (water flows faster down steeper slopes)

C = the soil cover factor (soil cover; cover crops)

P = support practice factor (erosion control practice/contouring)

A = f (R,K,L,S,C,P)

Kira berapa nilai A, sekiranya semua faktor/parameter yang digunakan ialah 1 ?

dwzwy :: 2009-2010

Your good friend has the opportunity to buy this riverside land in a beautiful

canyon at a good price. She wants to build a log cabin on the site. Knowing

some geology. What should you tell her?

31

Latihan Berkumpulan

(Boleh print dari website)

25hb Januari 2010

(sebelum jam 11am)

TAMAT


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