GEOLOGI E0505
TEKNIK KERJALAPANGAN
GEOLOGI 2
(GEOLOGIC FIELD TECHNIQUE 2)
E0504
Kandungan Kursus:
Pengenalan kepada teknik lapangan
berasaskan geologi eksplorasi (kajian
subpermukaan); peralatan asas, pengambilan
data lapangan (soil logging), pengelasan dan
penerangan tanih, air bawah tanah dan
perolehan data air bawah tanah, maintenance
dan keselamatan.
EKSPLORASI
SUBPERMUKAAN
• Kaedah Eksplorasi Subpermukaan:
• Terdapat dua operasi yang terlibat bagi mendapatkan
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sampel dari subpermukaan: penggerudian dan
penyampelan.
Penggerudian melibatkan proses membuat lubang,
dan selepas itu pensampelan dan pengukuran
berkaitan kajian subpermukaan boleh dilakukan.
Proses membuat lubang boleh melalui beberapa
kaedah. Semua kaedah pembuatan lubang mestilah
dibuat log dan diberi keterangan menggunakan
piawaian spt United Soil Classification System (USCS).
EKSPLORASI
SUBPERMUKAAN
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Peralatan Asas Penggerudian:
1. Test pits
2. Auger holes
3. Drill holes
• Terdapat beberapa kaedah dan alat digunakan
bergantung kepada keperluan kajian.
EKSPLORASI
SUBPERMUKAAN
• Objektif dan Kepentingan Eksplorasi:
• Maklumat subpermukaan diperlukan dalam merancang
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dan membina tapak untuk struktur kejuruteraan dan
untuk memantau kesan ke atas sekitaran.
Kerja-kerja kejuruteraan yg memerlukan maklumat
subpermukaan antaranya adalah:
Earth fill, rock fill, empangan, terowong, jambatan,
bangunan, lebuhraya, levees, pelabuhan, stesen
janakuasa dan subway, perlombongan, underground
storage utk gas dan cecair, pelupusan sisa, sanitary
landfill, dan eksplorasi minyak dan gas.
EKSPLORASI
SUBPERMUKAAN
• Maklumat yg diperlukan antaranya adalah: depth to
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bedrock, nature of the soil, groundwater conditions, soil
strength, and bedrock strength.
Perancangan Kajian Subpermukaan:
1. Reconnaissance
 Office Reconnaissance
 Field Reconnaissance
• 2. Subsurface Exploration
 Methods of drilling
 Sampling methods
EKSPLORASI
SUBPERMUKAAN
• 1. Reconnaissance
• - iaitu kerja awalan yg diperlukan sebelum dijalankan
penggerudian dan pensampelan. Terdapat 2 fasa:
a. Office Reconnaissance
Terdapat beb langkah dalam fasa ini:
 Review of design plans
 Review of engineering reports
 Review of published information or open file geologic reports
 Topographic maps
 Geologic maps
 Aerial photographs
 Well log data
EKSPLORASI
SUBPERMUKAAN
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b. Field Reconnaissance
Terdapa dua objektif:
1) to view the site and record information
Perkara yg diperhati di lapangan:
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Proposed location of structure
Topography and vegetation
Surface soils, gullying and natural slopes
Surface and subsurface water
Geology of the site
EKSPLORASI
SUBPERMUKAAN
• 2) utk mendapat maklumat bagi drill crew
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mencapai boring program.
Perkara yg diperlu diketahui:
 How to get to the site
 Where to drill
 Type of equipment required
 What difficulties will likely occur
KAEDAH
PENGGERUDIAN
• Kaedah membuat lubang:
• 1. Cable tool well drilling
• Digunakan terutamanya utk penggerudian
telaga air. Chisel bit dihentak ke tanah
dengan mengangkat dan menjatuhkannya.
• 2. Wash boring: Lubang gerudi ditusuk oleh
tindakan basuhan oleh kombinasi water jet
dan chopping oleh mata gerudi.
KAEDAH
PENGGERUDIAN
• Steel casing digunakan bagi membukakan
lubang gerudi. Rincisan (cuttings) dibawa ke
permukaan oleh air basuhan melalui annulus.
• 3. Rotary Drilling: Drill rod diputar dan
pelbagai drill bit diguna untuk memotong
tanih atau batuan. Rincisan dibawa ke
permukaan oleh air basuhan.
KAEDAH PENGGERUDIAN
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Empat prosidur kaedah berputar utama
untuk penggerudian eksplorasi:
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auger boring with solid auger stems,
auger boring with hollow-stem augers,
rotary drilling with roller bits, dan
Coring of soil or rock.
Auger boring
Rotary drilling
Rotary drilling
SAMPLING METHODS
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Sampel diperoleh utk tujuan pengecaman
dan pengelasan tanih dan batuan.
Undisturbed sampel: diguna untuk wet
and dry density determination, triaxial,
shear or unconfined compression test, and
permeability and consolidation test.
Dengan itu pembungkusan, pengangkutan
dan storan utk undisturbed sampel adalah
perlu.
SAMPLING METHODS
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Disturbed sample: soil structure tidak
maintained dan ia hanya diguna utk
penerangan dan pengelasan tanih.
Undisturbed sample collection
SAMPLING METHODS
• Kaedah Pensampelan:
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Standard Penetration Test (SPT):
Sampler ini, apabila dikeluarkan drp drill
rod, split kepada dua bahagian utk
mendedah turus tanih diperoleh semasa
operasi penusukan.
The split-spoon sampler attached ke drill
rod dan ditusuk ke tanah oleh a series of
blows from the drop hammer.
Sample sampler
SAMPLING METHODS
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The sample is advanced in three
increments of 6 in. (150mm) with the
number of blows recorded.
The N value is the sum of the last two
increments, in this case,12, and it
represents the number of blows per foot.
The SPT or N values diguna untuk sebagai
indication of density or consistency of the
soil.
SAMPLING METHODS
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Pushed Tube Sampling: pushed barrel or
thin-walled tube sampling diguna utk tanih
atau batuan lembut bagi mendapat
undisturbed sample. A thin-walled tube is
forced into the soil, using the static force
from the weight of drilling rig.
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Rotary coring: diguna untuk mendapat
sampel tanih dan batuan dengan
menggunakan core bit.
Pushed Tube Sampling
PREPARATION OF BOREHOLE LOGS
• Penyediaan Borehole Logs:
• Borehole log yang lengkap secara tipikal
mengandungi maklumat berikut:
1. Nama projek dan tarikh
2. Borehole identification, ketinggian dan
lokasi
3. Kaedah penggerudian dan penyampelan
4. Rate of drilling progress
PREPARATION OF BOREHOLE LOGS
5. Lokasi coring runs, sampel, dan in situ
tests
6. Description of ground water level
7. Detailed geologic description of the soil or
rock samples.
Pengelasan dan Penerangan Tanih
• Geologic classification of materials:
• Bedrock is a general term that includes any of the
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generally indurated or crystalline materials that make
up the Earth's crust.
Surficial Deposits are the relatively younger
materials occurring at or near the Earth's surface
overlying bedrock. They occur as two major classes:
(1) transported deposits and (2) residual deposits
formed in place as a result of weathering processes.
Pengelasan dan Penerangan Tanih
• Kajian tanih yang dijalankan untuk tujuan kejuruteraan
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dijelaskan mengikut Unified Soil Classification System
(USCS).
All soil classification descriptions for particle sizes
less than No. 4 sieve size are to be in metric units.
• Terminologi utk tanih:
• Cobbles and boulders—particles retained on a 3•
inch (75-mm) U.S. Standard sieve.
Gravel—particles of rock that will pass a 3-in (75-mm)
sieve and is retained on a No. 4 (4.75-mm) sieve.
Pengelasan dan Penerangan Tanih
• Sand—particles of rock that will pass a No. 4 (4.75o
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mm) sieve and is retained on a No. 200 (0.075-mm or
75-micrometer [μm]) sieve.
• Coarse sand—passes No. 4 (4.75-mm) sieve and
is retained on No. 10 (2.00-mm) sieve.
• Medium sand—passes No. 10 (2.00-mm) sieve
and is retained on No. 40 (425-μm) sieve.
• Fine sand—passes No. 40 (425-μm) sieve and is
retained on No. 200 (0.075-mm or 75-μm) sieve.
Pengelasan dan Penerangan Tanih
• Clay—passes a No. 200 (0.075-mm or 75-μm) sieve.
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Soil has plasticity within a range of water contents
and has considerable strength when air-dry.
Silt—passes a No. 200 (0.075-mm or 75-μm) sieve.
Soil is nonplastic or very slightly plastic and that
exhibits little or no strength when air-dry.
Pengelasan Tanih
• Group Names and Group Symbols.
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GW - Well graded gravel
GP - Poorly graded gravel
GM - Silty gravel
GC - Clayey gravel sand
SW - Well graded sand
SP - Poorly graded sand
SM - Silty sand
SC - Clayey sand
CL - Lean clay
ML - Silt
OL - Organic clay
Pengelasan Tanih
• Dual Symbols.—Dual symbols separated by a hyphen are used
in laboratory classification of soils and in visual classification
when soils are estimated to contain 10 percent fines. A dual
symbol (two symbols separated by a hyphen, e.g., GP-GM, SWSC, CL-ML) should be used to indicate that the soil has the
properties of a classification where two symbols are required.
• Borderline Symbols.—Borderline symbols are used when soil
properties indicate the soil is close to another classification
group. Two symbols separated by a slash, such as CL/CH,
SC/CL, GM/SM, CL/ML, should be used to indicate that the soil
has properties that do not distinctly place the soil into a specific
group.
Pengelasan Tanih
• Identification Criteria for Fine-Grained Soils.—The tests for
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identifying properties of fines are dry strength, dilatency,
toughness, and plasticity.
Procedures and Criteria for Visual Classification
of Coarse-Grained Soils
The soil is classified as a WELL GRADED GRAVEL (GW), or as
a WELL GRADED SAND (SW), if a wide range of particle sizes
and substantial amounts of the intermediate particle sizes are
present.
The soil is classified as a POORLY GRADED GRAVEL (GP) or
as a POORLY GRADED SAND (SP) if the material is
predominantly one size (uniformly graded) or the soil has a wide
range of sizes.
Pengelasan Tanih
• Checklist for the description of soil
classification and identification:
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Group name and symbol
Percent gravel, sand, and/or fines
Percent by volume of cobbles and boulders
Particle size
Gravel - fine, coarse
Sand - fine, medium, coarse
Particle angularity: angular subangular subrounded rounded
Particle shape: flat elongated flat and elongated
Pengelasan Tanih
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Maximum particle size or dimension
Hardness of coarse sand and larger particles
Plasticity of fines: nonplastic low medium high
Dry strength: none low medium high very high
Dilatancy: none slow rapid
Toughness: low medium high
Color (when moist)
Odor (if organic or unusual)
Moisture: dry moist wet
Reaction with HCL: none weak strong
Pengelasan Tanih
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Maximum particle size or dimension
Hardness of coarse sand and larger particles
Plasticity of fines: nonplastic low medium high
Dry strength: none low medium high very high
Dilatancy: none slow rapid
Toughness: low medium high
Color (when moist)
Odor (if organic or unusual)
Moisture: dry moist wet
Reaction with HCL: none weak strong
Pengelasan Tanih
• Checklist for the description of in-place conditions In-place
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conditions:
Consistency (fine-grained soils only): very soft soft firm hard
very hard
Cementation: weak moderate strong
Structure: stratified laminated fissured slickened lensed
homogeneous
Geologic interpretation and/or local name, if any
Additional comments and description
Presence of roots or root holes
Presence of mica, gypsum, etc.
Surface coatings
Caving or sloughing of excavation
Excavation difficulty
Pengelasan Tanih
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Example 1: CLAYEY GRAVEL WITH SAND AND COBBLES
(GC)—Approximately 50 percent fine to coarse,
sub-rounded to subangular gravel; approximately
30 percent fine to coarse, subrounded sand;
approximately 20 per-cent fines with medium plasticity,
high dry strength, no dilatancy, medium toughness; weak
reaction with HCl; original field sample had about
5 percent (by volume) subrounded cobbles, maximum size
150 mm.
IN-PLACE CONDITIONS: firm, homogeneous, dry,
brown.
GEOLOGIC INTERPRETATION: alluvial fan.
Abbreviated symbol is (GC)sc.
Soil Logging
• Soil investigations conducted for engineering
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purposes that use test pits, auger and drill
holes, or other exploratory methods are
logged and described according to the
Unified Soil Classification System (USCS).
Test pits dan auger holes boleh di log
menggunakan form spt di Figure 1-1.
Contoh log spt di Figure 1-2, 1-3 dan 1-4.
Soil Logging
• Arahan umum untuk log format dan
keterangan.
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Capitalize the group name.
Describe plasticity of fines as:
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Approx. 30% fines with high plasticity
Approx. 605 fines with low to medium plasticity
Approx. 10% nonplastic fines
 Give results of hand test
 Use “reaction with HCL”