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CPD SEMINAR ON CLASSIFICATION OF ROAD MATERIALS AND IDENTIFICATION OF INDEGINOUS
QUARRIES
Engr. Zahid Arif, Secretary C&W Department
December 11, 2012
By
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SEQUENCE OF PRESENTATION
INTRODUCTION
IMPORTANCE OF THE SUBJECT
SOIL CLASSIFICATION
SPECIFIED PARAMETERS OF SUB BASE & BASE
MATERIALS
IDENTIFICATION OF INDEGINOUS QUARRIES
QUESTION & ANSWER SESSION3
IMPORTANCE OF THE SUBJECT
Selection of specified materials through:
Visual inspection
Laboratory tests
Economizing the construction cost
Identification of local quarries
Effective supervision and monitoring of developmental projects
Selection of suitable site for Building projects
SOIL CLASSIFICATION
SOIL CLASSIFICATION Soil is defined as a conglomeration consisting of a wide
range of relatively smaller particles derived from a parent rock through mechanical weathering processes of water abrasion, freeze-thaw cycles, temperature changes, and chemical weathering processes like oxidation and carbonation. The density of soil mass can range from very hard to very soft.
Classification is the laboratory-based process of grouping soils with similar engineering characteristics into various categories.
The AASHTO system (M 145) is commonly used for grouping of soils into various categories having similar load carrying capacity for subgrade design of highway projects.
Engineering Classification of Soils
Cassagrande apparatus
WentworthScale
“Gravel”75-2 mm
“Sand”2-0.075 mm
“Silt and Clay”< 0.075 mm
“Cobbles” 75 – 300 mm ( 3 in – 12 in)
Particle Size Definitions
“Boulders” > 300mm(>12 inches)
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Grain Size definitions
Boulders Cobbles Gravel Sand Silt and Clay
Coarse Fine Coarse FineMedium
300 mm
75 mm
19 mm
(No.4)
4.75 mm
(No.10)
2.0 mm
(No.40)
0.425 mm
(No.200)
0.075 mm
Parameters of Soil Classification
For grouping of Soil in various categories, the following soil characteristics are required to be determined first:
Liquid Limit Plastic Limit Plasticity Index (PI)
As water content increases, the shear strength of soil decreases.
Status changes with the increase in Water Content
Liquid Limit Soil is practically a liquid in this
state
Shows minimal shear strength
Defined as the moisture content required to close a distance of 0.5 inch along the bottom of a groove after 25 blows of the liquid limit device.
Plastic Limit Water content at which the soil
becomes plastic Less water content than liquid
limit Wide range of shear strengths
at plastic limit Defined as the moisture
content at which the soil begins to crumble when rolled into 1/8” dia threads
Plasticity Index (PI)
Difference between Liquid Limit and Plastic Limit
Important measure of plastic
behavior
Example:
Liquid Limit = 24%Plastic Limit 14 %
Plasticity Index = 24 – 14 = 10 %
In general….
PI Degree of Plasticity
0 Non-plastic1-5 Slightly plastic5-10 Low plasticity10-20 Medium plasticity20-40 High plasticity40+ Very high plasticity
Procedure for AASHTO Classification
Developed in 1929 as the Public Road Administration Classification Systemmodified by the Highway Research Board (1945)
COARSE-GRAINED SOIL (Sand & Gravel)
STEPS
Determine the percentage of soil passing the #200 sieve
Determine the percent passing the #10 and #40 sieves for Sub grouping.
Determine the liquid limit and plasticity index
THEN, determine soil group or subgroup from Table - 1
For coarse-grained soils (gravel and sand), determine the percent passing #10, #40, and #200 sieves.
CobbleGravelVery Coarse to Medium SandFine/Very Fine SandSilt/Clay
3 in#10#40
#200
#10
#40
#200
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Table-1 : AASHTO Classification for Coarse-grained Soil
FINE-GRAINED SOIL (Silt & Clay)
STEPS
Determine the percentage of soil passing the #200 sieve
Determine the liquid limit and plasticity index
THEN, determine soil group or subgroup from Table - 2
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Table-2 : AASHTO Classification for Fine-grained Soil
To evaluate the quality of a soil as a highway subgrade material, a number called the group index (GI) is also incorporated alongwith the groups and subgroups of the soil.
The group index is written in parenthesis after the group or subgroup designation.
GI is given by the following general Equation: GI = (F-35)[0.2+0.005(LL-40)] + 0.01(F-15) (PI-
10)
Group Index usually reflects the relative strength of material, where low values have greater shear strength
GROUP INDEX
e.g: A-7-5(9)
Determination of Group Index
Example ProblemExamples
Solution
SOFT ROCKThe rock which can be cut by the blade of a 200 HP Bull Dozer is classified as a Soft Rock.
MEDIUM ROCKThe rock which cannot be cut by the blade of a 200 HP Bull Dozer is classified as a Medium Rock.
HARD ROCKThe rock which cannot be cut by the Ripper of a 200 HP Bull Dozer is classified as a Hard Rock.
Engineering Classification of Rocks
SUB BASE
“SUB BASE is the structural layer of road pavement consisting of NATURAL or processed aggregates placed above the Sub grade” The material should comply with the following quality requirements:
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MATERIAL REQUIREMENTS FOR SUB BASE MATERIALS
GRADING REQUIREMENTS
US STANDARD SEIVE SIZE PERCENT PASSING
CLASS A CLASS B
2½” 100 -
2” 90-100 100
1” 50-80 55-85
⅜”- 40-70
No. 4 35-70 30-60
No. 10 - 20-50
No. 40 - 10-30
No. 200 2-8 5-15
QUALITY PARAMETERS
(i) CBR value @ 98% Compaction >50 %(ii) Los Angles Abrasion Value < 50 %(iii) Liquid Limit < 25(iv) Plasticity Index < 6(v) Oversize < 5 %(vi) Sand Equivalent = 25 min 28
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AGGREGATE BASE COURSE
“AGGREGATE BASE COURSE is the basic structural layer of flexible pavement consisting of a mixture of various sizes of crushed Aggregates ranging from 2” to material passing sieve #200”
The material should fulfill the following suitability parameters:
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MATERIAL REQUIREMENTS FOR AGGREGATE BASE COURSE
GRADING REQUIREMENT
US STANDARD SEIVE SIZE PERCENT PASSING
CLASS A CLASS B
2” 100 100
1” 60-80 75-95
⅜” 30-65 40-75
No. 4 25-55 30-60
No. 10 15-40 20-50
No. 40 8-20 12-25
No. 200 2-8 5-10
PHYSICAL PROPERTIES AND QUALITY PARAMETERS
i. Los Angles Abrasion Value < 40 %ii. SOUNDNESS with NA2SO4 <12 %iii. SAND EQUIVALENT < 45 %iv. L.L = 25 % (Max) v. P.I = 6% (Max)vi. CBR at 100 % compaction > 80 % vii. Laminated Particles <15% (By Volume)viii. Round particles < 10 %
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WATER BOUND MACADAM BASE
WBM is the base layer consisting of clean crushed stone
mechanically interlocked by rolling and voids filled with screening materials with assistance of water.
Fine aggregate (also called chocked materials) consists of
crushed stone screenings free from clay lumps with specified gradation.
Following are the quality requirements of WBM and screening
materials :
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GRADING REQUIREMENT
US STANDARD SEIVE SIZE
PERCENT PASSING
CLASS A CLASS B CLASS C
4” 100 - -
3½” 90-100 - -
3” - 100 -
2½” 25-60 90-100 100
2” - 25-75 90-100
1½” 0-15 0-15 35-70
1” - - 0-15
3/4 in 0-5 0-5 0-5
1/2 in - - -
FILLER MATERIAL OR SCREENINGS : Physical Requirements of Coarse Aggregate
SIZE % Passing 3/8” (9.5mm) 100 Los Angles Abrasion value = Max 45%No. 4 (4.75 mm) 85-100 L.L = 25 % (Max) No. 100 (0.15 mm) 10-30 P.I = 6 (Max) CBR >80% Flakiness Index = Max 15% Soundness with (Na2SO4 ) = Max 45%
MATERIAL REQUIREMENTS FOR WBM
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IDENTIFICATION OF INDIGENIOUS QUARRIES
Based on the above characteristics, the following local quarries have been identified for road materials on various District level:
Baisai (Peshawar) for aggregate and WBM
Zangali Khwar(Peshawar) for Sub Base material
Nizampur and Lawrencepur for Coarse Sand
Watarh nullah (Nowshera) for Sub Base material
Palai (Malakand Agency) for aggregate and WBM
Khyali River bed material for filter layers and Granular
backfill
Pir Sabaq (Nowshera) for aggregate and WBM
Sawal Dhair(Mardan) for aggregate and WBM
Pizzu (Sarai Naurang) for aggregate and WBM
Kurram River bed material(Bannu) for filter, Base & Sub
Base.
Margalla (Islamabad) for aggregate and WBM.
THANK YOU
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