Engineering Classification of Soils

Report
CPD SEMINAR ON
CLASSIFICATION OF ROAD MATERIALS
AND IDENTIFICATION OF INDEGINOUS
QUARRIES
By
Engr. Zahid Arif, Secretary C&W
Department
December 11, 2012
2
SEQUENCE OF PRESENTATION

INTRODUCTION

IMPORTANCE OF THE SUBJECT

SOIL CLASSIFICATION

SPECIFIED PARAMETERS OF SUB BASE & BASE
MATERIALS

IDENTIFICATION OF INDEGINOUS QUARRIES

QUESTION & ANSWER SESSION
3
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
Particle Size
Definitions
“Boulders”
> 300mm
(>12 inches)
“Cobbles”
75 – 300 mm
( 3 in – 12 in)
“Gravel”
75-2 mm
“Sand”
2-0.075 mm
“Silt and Clay”
< 0.075 mm
Wentworth
Scale
Grain Size definitions
Boulders
Gravel
Cobbles
Coarse
300
mm
75
mm
19
mm
Sand
Fine
Coarse
Medium
(No.4) (No.10)
4.75
mm
Silt and Clay
2.0 mm
Fine
(No.40) (No.200)
0.425
mm
0.075
mm
10
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
1-5
5-10
10-20
20-40
40+
Non-plastic
Slightly plastic
Low plasticity
Medium plasticity
High plasticity
Very high plasticity
Procedure for AASHTO
Classification
Developed in 1929 as the Public Road Administration Classification System
modified 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.
Cobble
#10
3 in
Gravel
#10
Very Coarse to Medium Sand
#40
Fine/Very Fine Sand
#200
Silt/Clay
#40
#200
Table-1 : AASHTO Classification for Coarse-grained Soil
19
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
Table-2 : AASHTO Classification for Fine-grained Soil
21
GROUP INDEX
 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. e.g: A-7-5(9)
 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
Determination of Group Index
Examples
Example Problem
Solution
Engineering Classification of Rocks
 SOFT ROCK
The rock which can be cut by the blade of a 200 HP Bull Dozer is
classified as a Soft Rock.
 MEDIUM ROCK
The rock which cannot be cut by the blade of a 200 HP Bull Dozer is
classified as a Medium Rock.
 HARD ROCK
The rock which cannot be cut by the Ripper of a 200 HP Bull Dozer
is classified as a Hard Rock.
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:
27
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 28
29
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:
30
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 %
31 31
32
33
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 :
34
MATERIAL REQUIREMENTS FOR WBM
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 :
SIZE
3/8” (9.5mm)
No. 4 (4.75 mm)
No. 100 (0.15 mm)
% Passing
100
85-100
10-30
Physical Requirements of Coarse Aggregate
Los Angles Abrasion value
L.L
P.I
CBR
Flakiness Index
Soundness with (Na2SO4 )
= Max 45%
= 25 % (Max)
= 6 (Max)
>80%
= Max 15%
= Max 45%
35
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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.
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THANK YOU
38

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