FIELD IDENTIFICATION AND CLASSIFICATION OF SOIL
Submitted by
Md. Saydul Islam
Student ID: 161015
Submitted to
Dr. Md. Kamal Hossain
Professor,
Department of Civil Engineering, DUET
And
Md. Ariful Islam
Assistant Professor,
Department of Civil Engineering, DUET
Department Of Civil Engineering
Dhaka University of Engineering & Technology,
Gazipur-1707
Dhaka University of Engineering & Technology,
Gazipur-1707
Department Of Civil Engineering
Course No.
: CE-3302
Credit: 0.75
Course Name : Geotechnical Engineering – I Sessional
Date of Allocation
Experiment No.
Experiment Name
07/12/2020
Date of Submission
19/12/2020
: 01
: Field Identification and classification of soil
Submitted to
Dr. Md. Kamal Hossain
Professor,
Department of Civil Engineering, DUET
And
Md. Ariful Islam
Assistant Professor,
Department of Civil Engineering, DUET
Submitted by
Md. Saydul Islam
Year/Semester: 3/2
Section: A
Student ID: 161015
1. Introduction
Soils are usually classified into coarse and fine-grained soil depending on their
particle size. Some simple tests are used to identification of these major soil
components. These tests are known as identification tests. The sample should be
identified first on the basis by visual inspection and certain simple tests can be
performed in the field.
Soils are farther classified as gravel, sand, silt and clay. Gravel and sand are known
as coarse-grained soils, silt and clay as fine-grained soils.
According to ASTM classification of different soils on the basis of particle size are
as bellow
Gravel
Coarse Sand
Medium Sand
Fine Sand
Fines (silt and clay)
> 4.75 mm
2.00 – 4.75 mm
0.425 – 2.00 mm
0.075 – 0.425 mm
< 0.075 mm
Gravel: Coarse-grained soil, cohesion less, does not possess plasticity, high
permeability.
Sand: Coarse-grained soil, cohesion less, does not possess any plasticity. Also subdivided as coarse, medium and fine. Permeability varies, generally is high for
medium and coarse sand.
Silt: Bulky, fine-grained particles. The least plastic varieties consist primarily of
very fine rounded particles.
Clay: Flaky shape, plastic, cohesion, ability to adsorb ions, very fine particle.
By visual inspection may get the idea of whether the soil contains more than or less
50% of visible particles. If it contains more than 50% of visible particles then the
soil is classified as coarse grained soil and if the soil contains less than 50% of
visible particles then the soil is classified as fine grained soil.
The coarse grained soils such as gravel and sand can be separate through visual
inspection but fine-grained soil such as silt and clay can not separate by visual
inspection. Using some simple field test can separate silt and clay. These test are as
follows:
1.
2.
3.
4.
5.
Sedimentation
Dilatancy or Shaking Test
Dry Strength Test
Ribbon Test
Plasticity Test
1.1 Objectives
i) To identify coarse and fine-grained soil
ii) To identify gravel, sand, silt and clay
2. Materials and Methodology
2.1 Materials
Apparatus:
 Spoon
 Jar or beaker
Materials:
 Soil sample
 Water
2.2 Methodology
By visual inspection for separating gravel and sand,
For Silt and clay separation performing following identification test:
1. Sedimentation Test:
a) A spoonful of the collected soil sample is dispersed or mixed with water in a
jar or beaker and after shaking allowed to settle on a flat surface.
b) Gravel and sand will settle almost immediately to the bottom and fine sand
will take about 1 to 2 minutes to settle.
c) Silt particles usually settle in 15 to 60 min. whereas clay particles will
remain in suspension for at least several hours or may remain even for
several days.
2. Dilatancy or Shaking Test
It describes the permeability as rapid, slow, or none. The higher the silt content, the
lower would be the permeability characteristics.
Observation:
a) Glossy Surface – indicates moisture has risen to the surface.
b) Quick reaction - soil contains silt or very fine sand.
c) Slow reaction – soil contains silt, clay.
d) Not glossy surface – soil contains large amount of clay.
3. Dry Strength Test
It provides a basis for describing the strength as very low, low, medium, high, or
very high. A clay fragment can be broken with great effort, whereas a silt fragment
crushes easily. The higher the clay content, the higher would be the dry strength.
Observation:
a) Easily powdered – low dry strength (Fine sand or silt)
b) Considerable pressure is required – medium dry strength (silt and some clay)
c) Lump cannot be powdered – high dry strength (appreciate amount of clay)
4. Ribbon Test
By Ribbon test can separate silt and clay. This test performed by mixing water with
soil to make it workable and pressing it slowly between the thumb and index figure
finger to make a ribbon like shape of about 3 mm thick and as long as it can be
formed before it breaks itself under its own weight.
Observation:
a) Longer than 100 mm - soil contains high amount of clay.
b) Break before reached length 100 mm – silt
5. Plasticity Test
By plasticity test can separate silt and clay. This test performed by mixing water to
make saturated soil and roll the soil pat into long threads of diameter as small as 3
mm.
Observation:
a) If make 3mm dia threads without cracking – soil contains high clay.
b) If crack form – soil contains silt.
3. Data Analysis:
3.1 Observed data from test
i) Dry strength test: Need Low pressure to powder
ii) Sedimentation Test :
a) Total thickness: 50+5 = 55mm
b) Thickness immediately after start of sedimentation: 7mm
c) Thickness after 1-2 minutes : 2 mm
d) Thickness after one hours: 34mm
e) Remaining thickness: 12mm
iii) Shaking Test: Glossy surface visible
iv) Ribbon Test: Possible to make 3mm thick ribbon more than 100mm long
v) Plasticity Test: 3mm dia thread without cracking.
3.2 Sample calculation:
For Sedimentation Test:
a) Gravel and sand 7 mm thickness =
b) Fine sand 2 mm thickness =
c) Silt particles 34 mm thickness =
d) Clay particles 12 mm thickness =
This soil is mainly fine-grained which contain large amount of silt.
4. Results and Discussion
4.1 Results:
i) Dry strength test: Low dry strength (Fine sand or silt)
ii) Sediment test: Mainly fine-grained which contains large amount of silt.
iii) Shaking test: soil contains silt or very fine sand
iv) Ribbon test: soil contains high amount of clay
v) Plasticity test: soil contains high amount of clay particle
4.2 Discussion
From this experiment we obtained identification of soil which is the first step in
any geotechnical engineering project. It also identifies and describes the subsoil
condition. For example as soon as a ground is identified as gravel, engineer can
immediately form some ideas on the nature of problems that might be encountered
in a tunneling project. In contrast, a soft clay ground is expected to lead to other
types of design and construction considerations. Therefore, it is useful to have a
systematic procedure for identification of soils even in the planning stages of a
project. The results obtained from this experiment help to progress further work of
a project. These experiments are simple and get idea or result quickly. The
property of a coarse grained material mass depends also on the uniformity of the
sizes of the grains. Well-graded sand is more stable for a foundation base as
compared to a uniform or poorly graded material. From these test we get the idea
of the uniformity of soil.
5. Conclusion
This Experiment is very simple and easy. But in the pandemic situation of Covid 19 we could not perform this test in physically. For this reason we have some lack
of experience about this experience. After this pandemic situation we want to
perform this test physically in the laboratory.
Reference
[1] GEOTECHNICAL ENGINEERING - I SESSIONAL, Department of Civil
Engineering, Dhaka University of Engineering and Technology.
[2] Geotechnical Engineering Sessional-I (Lab Manual), Department of Civil
Engineering, Ahsanullah University of Science and Technology.
[3] CEE 4442 Geotechnical Engineering Lab, Department of Civil Engineering,
Islamic University of Technology,
[4] Online source