methodology
TRANSCRIPT
SOIL ERODIBILITY STUDY ALONG PENCALA RIVER – SOIL 1
METHODOLOGY
To achieve the objective of the study which are to investigate relationship between the
slope failure case at Sungai Pencala with erodibility of the soil, increase awareness and
knowledge on relationship soil erosion with the slope failure, conduct test for the soil sample to
get the relationship between failure factor with soil to identify the solution to prevent soil
erodibility issues some test and data collection will be carry out.
The research work is mainly a laboratory experimental based. Site surveys will be along the
critical area of Sungai Pencala river for the purpose of the slope physical inventory and soil
sampling. Hand auger will be use to extract the soil at about 0.5 to 1.0 m below original ground
level at slope crest, slope face and toe of each slope. The samples will preserve into three
different tighten plastic bags for further laboratory testing. Figure 2 shows the flowchart of the
propose tests and activities involve.
Figure 2: Methodology Flowchart
Feasibility Study
Site Inventory
Soil Sampling
Laboratory Test Classification By
Particle Sizes
Sieve Analysis Test Hydrometer Test
SOIL ERODIBILITY STUDY ALONG PENCALA RIVER – SOIL 2
SOIL CLASSIFICATION TESTS
All the representative soil samples will be test and classified according to BS1377:1990. The
standard soil classifications by particle size and soil permeability test will conduct as shown by
Figure 3 and in figure 4 is the sample of standard form for sieve analysis test.
SOIL PARTICLE SIZE DISTRIBUTION TEST – SIEVE ANALYSIS TEST
In order to categorize the soil for engineering purposes, one needs to know the
distribution of the grain sizes in the given soil mass. Soil sieve analysis or also known as particle
size distribution is the method used to determine the grain size distribution of soil samples. The
sieves are made of woven wires with square openings. Note that the test sieve number increases
whereby the size of opening decreases.
In other words, the particle size distribution is used for gravel and sand size (coarse)
particles, which can be separated into different size ranges with a series of sieves of standard
aperture openings. Soil sieving cannot be used for the very much smaller silt and clay (fine)
particles. For this reason, the sedimentation procedures are used instead and most common
would be the hydrometer test of soil – to determine the distribution of the finer particles.
Particle size distribution testing can range from a simple sieving test on the clean gravel
and sand, then to elaborate composite tests on clay-silt-sand-gravel mixtures. The test procedures
for different types of materials are similar in principle but vary in detail and description in
separate manner. The most difficult type of material to deal with is that referred as the ‘boulder
clay’ which treats as special case. As a result of the grain size distribution of soil, it is possible to
whether the soil consists of predominantly gravel, sand, silt or clay sizes. Moreover, the
possibility to see the soil being limited extent in which the particles size is likely used to control
the engineering properties.
SOIL ERODIBILITY STUDY ALONG PENCALA RIVER – SOIL 3
The Standard Reference for Sieve analysis
D422 of ASTM – Standard Test Method for Particle Size Analysis of Soils
Clause 9.2 (for wet test) or 9.3 (for dry test) of BS1377: Part 2: 1990
The Required Equipment for soil Sieve Analysis
Stack of Sieves (including the pan and cover)
Electronic balance (the weight accuracy up to 0.01 g)(figure 5)
Rubber pestle and Mortar (for crushing the soil if lumped or conglomerated)
Mechanical sieve shaker (electrical powered) (figure 3)
Drying Oven with temperature up to 110°C(figure 6)
The benefits of soil grading for Engineering Construction Works
Data obtained from grain size distribution curves is used in the design of filters for earth
dams and to determine suitability of soil for road construction, air field, and etc.
Information obtained from particle size distribution test can be used to predict soil water
movement although permeability tests are more generally used.
The drainage characteristics of the ground are to the large extent dependent upon the
proportion of fines (clay and silt) present in the soil.
Some of the construction situations that having poor ground conditions can be improved
by dynamic compaction and the particle size analysis could give the indication of the
feasibility of the process.
SOIL ERODIBILITY STUDY ALONG PENCALA RIVER – SOIL 4
Test Procedure:
Sieve Analysis:
(1) Write down the weight of each sieve as well as the bottom pan to be used in the analysis.
(2) Record the weight of the given dry soil sample.
(3) Make sure that all the sieves are clean, and assemble them in the ascending order of sieve
numbers (#4 sieve at top and #200 sieve at bottom). Place the pan below #200 sieve
Carefully pour the soil sample into the top sieve and place the cap over it.
(4) Place the sieve stack in the mechanical shaker and shake for 10 minutes.
(5) Remove the stack from the shaker and carefully weigh and record the weight of each
sieve with its retained soil. In addition, remember to weigh and record the weight of the
bottom pan with its retained fine soil.
The particle size distribution is one of the must have soil testing and done in the
laboratory. Not only is the soil samples tested, but also to other construction materials like
aggregates.
SOIL ERODIBILITY STUDY ALONG PENCALA RIVER – SOIL 5
Figure 3: Stack of sieves Figure 4: Sieve Analysis test form
Figure 5: Electronic Balance Figure 6: Drying Oven
SOIL ERODIBILITY STUDY ALONG PENCALA RIVER – SOIL 6
HYDROMETER TEST
Hydrometer test as in figure 7 is the procedure generally adopted for determining the
particle-size distribution in the soil for the fraction for that is finer than sieve size 0.075 mm. The
lower limit of the particle size determined by this procedure is about 0.001 mm. In soil
hydrometer testing, the soil sample is dispersed in water. In the dispersed state in the water, the
soil particle will settle individually. All the data collect will be fulfill in the standard form for
hydrometer analysis test as in figure 8.
It is assumed that the soil particles are spheres, and its velocity can be given by the
Stoke’s Law. The 152 H type hydrometer of ASTM D422 will be used. If the soil hydrometer is
suspended in water in which the soil is dispersed, it will measure the specific gravity of the soil-
water suspension at the depth L. The depth L is called as effective depth.
In this method a density hydrometer of special design is used to measure the density of
the soil, pre-treated in a suspension in water at various intervals of time. From these
measurements the distribution of particle sizes in the silt range (60 to 2 µm) can be assessed. The
hydrometer test is not usually performed in less than 10% of the soil material passes the 63 µm
sieve pan.
This method can give results which are sufficiently accurate for most engineering
purposes. The techniques are less exacting than those required for the pipette method. The
hydrometer test method has the additional advantage that it can be performed without much
difficulty in a small field laboratory. If the main central laboratory also uses this procedure, the
results obtained by both are directly comparable.
Soil hydrometer used for testing of soil density in technical standard of BS1377: Part 2:
1990 specified in clause 9.5.2.1. An essential requirement is that the scale reading is graduated to
indicate density in g/cm³ or g/ml at scale intervals of 0.0005 g/cm³. In technical standard of
ASTM D422, the 2 types of hydrometer are specified; reference as 151 H or 152 H in ASTM
Specification E 100. The hydrometer test can be performed without any individual calibration.
SOIL ERODIBILITY STUDY ALONG PENCALA RIVER – SOIL 7
Other apparatus needed for performing the hydrometer test are:
Glass measuring cylinder with 1000ml marked and 360 mm high; 2 nos.
Water distiller (figure 9)
Sodium Carbonate/ Sodium Hexametaphosphate(figure 10)
Stop-watch reading to 1 second for time measures.
Glass rod about 400 mm long and 12 mm diameter.
Thermometer covering the range of zero to 50°C with reading to 0.5°C.
Constant-temperature bath capable of being maintained at 25°C ± 0.5°C with deep
enough for immersing the sedimentation cylinders to the 1000 ml mark.
Hydrometer Analysis:
(1) Take the fine soil from the bottom pan of the sieve set, place it into a beaker, and add 125 mL
of the dispersing agent (sodium hexametaphosphate (40 g/L)) solution. Stir the mixture until the
soil is thoroughly wet. Let the soil soak for at least ten minutes.
(2) While the soil is soaking, add 125mL of dispersing agent into the control cylinder and fill it
with distilled water to the mark. Take the reading at the top of the meniscus formed by the
hydrometer stem and the control solution. A reading less than zero is recorded as a negative (-)
correction and a reading between zero and sixty is recorded as a positive (+) correction. This
reading is called the zero correction. The meniscus correction is the difference between the top of
the meniscus and the level of the solution in the control jar (Usually about +1). Shake the control
cylinder in such a way that the contents are mixed thoroughly. Insert the hydrometer and
thermometer into the control cylinder and note the zero correction and temperature respectively.
(3) Transfer the soil slurry into a mixer by adding more distilled water, if necessary, until mixing
cup is at least half full. Then mix the solution for a period of two minutes.
SOIL ERODIBILITY STUDY ALONG PENCALA RIVER – SOIL 8
(4) Immediately transfer the soil slurry into the empty sedimentation cylinder. Add distilled
water up to the mark.
(5) Cover the open end of the cylinder with a stopper and secure it with the palm of your hand.
Then turn the cylinder upside down and back upright for a period of one minute. (The cylinder
should be inverted approximately 30 times during the minute.)
(6) Set the cylinder down and record the time. Remove the stopper from the cylinder. After an
elapsed time of one minute and forty seconds, very slowly and carefully insert the hydrometer
for the first reading.
(Note: It should take about ten seconds to insert or remove the hydrometer to minimize any
disturbance, and the release of the hydrometer should be made as close to the reading depth as
possible to avoid excessive bobbing).
(7) The reading is taken by observing the top of the meniscus formed by the suspension and the
hydrometer stem. The hydrometer is removed slowly and placed back into the control cylinder.
Very gently spin it in control cylinder to remove any particles that may have adhered.
(8) Take hydrometer readings after elapsed time of 2 and 5, 8, 15, 30, 60 minutes and 24 hours
The hydrometer test is among the sedimentation theory which based on the fact that
large particles in the liquid settle more quickly than small particles, by assuming all the particles
have similar densities and shapes.(http://www.soiltestequipment.com/hydrometer-test-
%E2%80%93-the-density-of-soil/)
SOIL ERODIBILITY STUDY ALONG PENCALA RIVER – SOIL 9
Figure 7: Hydrometer analysis measuring cylinder Figure 8: Hydrometer Analysis form
Figure 9: Water distiller Figure 10: Sodium Carbonate
SOIL ERODIBILITY STUDY ALONG PENCALA RIVER – SOIL 10
DESIGN STUDIES
All the data collected from both particle distribution size test and hydrometer test will be
apply by using ROM software to produce a result that can measure the soil erodibility level and
able to predicting landslide risk base on the sample from each soil erosion occurrence was taken
and its grading characteristic identified. Using Bouyancos, the value of Erodibility Index (EI)
can be obtained. From the EI value, a new equation which is modified from Bouyancos equation
was developed successfully. This new equation is named as ‘ROM’ (after the name of
researchers, ROSLAN & MAZIDAH) equation. The equation is then used to get the new value
of EI for ROM, thus leading to the establishment of ‘ROM’ Scale which indicates the degree of
soil erosion tragedy.( International Research Centre on Disaster Prevention (IRCDIP), Universiti
Teknologi MARA, 2011)
‘ROM’ equation (EIROM) = % Sand + % Silt
2 (% Clay)
This software will generate a ROM scale rule graph in figure 4 and particle distribution
graph in figure 5 automatically after fulfill the Microsoft excel base standard form for both
particle distribution size and hydrometer test.
Base from the soil physical, it being conclude that the higher different between the
colloidal and sand percentages with clay percentages will effect high Erodibility index (EI). The
result that obtain from particle size distribution graph and ROM ruler finally can categorize the
soil characteristic in soil critical table that measure the level of soil erodibility as in figure 6.
SOIL ERODIBILITY STUDY ALONG PENCALA RIVER – SOIL 11
Figure 4 : ROM Ruler
Figure 5: Particle size distribution graph
SOIL ERODIBILITY STUDY ALONG PENCALA RIVER – SOIL 12
Figure 6: Soil Erodibility Scale
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