Sieve analysis

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KNS 2591 CIVIL ENGINEERING LABORATORY 3 FACULTY OF ENGINEERING

UNIVERSITI MALAYSIA SARAWAK

LAB S2 : SIEVE ANALYSIS

THEORY :

The method covers the quantitative determination of the particle size distribution in a soil from the coarse sand size to the clay size.

OBJECTIVE :

The objective of the test is to determine the grain-size distribution of soil by sieve analysis.

RESULTS / ANALYSIS :

1. The mass retained on each sieve is obtained by subtracting the sieve mass from the sieve mass +

retained soil. These values are recorded on the data sheet under column headed "Mass Retained”.

2. Now this column of masses (including that in the pan) is summed and the mass obtained are

compared.

3. The percent retained on each sieve is computed by dividing the weight retained on each sieve by the

original sample mass. This is valid, since any material passing the No.200 sieve will pass any sieve

above it in the stack.

4. The percent passing (or percent finer) is computed by starting with 100 percent and subtracting the

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5. Each individual should make a semi logarithmic plot of particle size versus percent finer, using the

graph on the data sheet. If less than 12 percent passes the No. 200 sieve, compute CU and Cc and

show on the graph.

Preparation Dried Sample + Tray

(g)

1192.81

Tray (g) 692.66

Dried Sample (g) 500.15

CALCULATION :

C = ( Total mass sample before sieve-Total mass sample after sieve )12

= ( 500.15-500.09 )12

= 0.005 g

BS Test Sieve Mass Retained (g) Corrected Mass (g) %

Retained Passing% Max Load(g)

14 mm 4.15 4.155 0.83 99.17 1500

10 mm 13.28 13.285 2.66 96.51 1000

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3.35 mm 40.68 40.685 8.13 81.99 400 1.18 mm 60.60 60.605 12.12 69.87 100 600 μm 70.44 70.445 14.08 55.79 75 425 μm 52.80 52.805 10.56 45.23 75 300 μm 69.81 69.815 13.96 31.27 50 212 μm 45.88 45.885 9.17 22.10 50 150μm 50.45 50.455 10.09 12.01 40 63 μm 49.46 49.465 9.89 2.12 25 mass passing 63 μm 10.61 10.615 2.12 0 Total 500.09 500.15 100.00 Notes :

% Retained = Corrected Mass Retainedml x 100 C = Mass Retained/Total Mass Sample

Corrected Mass = Mass Retained + C % Passing = 100 - Σ % Retained

Thus, the graph of particle size (mm) versus percent finer is plotted as shown below.

Coefficient of Uniformity Cu

This is the indicator of the spread of the range of the grain sizes and is defined as

10 60

D D Cu=

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Cu = 0.70 mm

0.15 mm Cu = 4.67

Coefficient of Curvature Cc

This is the measure of the shape of curve between D60 and D10 grain sizes, defined as

Cc = (0.29 mm ) 2

(0.70 mm x 0.15 mm)

Cc = 0.80

DISCUSSION :

Sieve analysis is one type of mechanical analysis which determines the size range of particles present in a soil, expressed as a percentage of the total dry weight or mass. Sieve analysis consists of shaking the soil sample through a set of sieves that have progressively smaller openings. The results of sieve analysis are generally expressed as the percentage of total weight of soil that passed through different sieve.

From the results, the total mass sample after sieving is smaller than the total mass before sieving where 0.06 g of soil is missing. This is probably because the small particles of soil is missing during the sieves are being vibrated.

( )

(

10 60

)

2 30 D D D Cc × =

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Therefore, the total mass is corrected by adding the mass retained with the corrected mass of soil.

CONCLUSION :

The objective to determine the grain-size distribution of soil by sieve analysis is achieved. The soil tested is sandier as 13.96% of soil is retained in the 300μm sieve.

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HYDROMETER ANALYSIS

THEORY :

The method covers the quantitative determination of the particle size distribution in a soil from the coarse sand size to the clay size.

OBJECTIVE :

The objective of the test is to determine the grain-size distribution of soil by hydrometer method.

RESULTS / ANALYSIS :

Table 1 Hydrometer Test Data

1 2 3 4 5 6 7 8 9 10 Date Time of readin g Elapse d Time (min) Temp. (To_C) Readin_g Rh’ Rh’+ Cm = Rh Effectiv e Depth HR (mm) Particle Diamet er D (mm) Rh’-R’ o =Rd Percenta ge finer than D

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K(%)

• t is the elapsed time from the start of sedimentation (min) • T ,the temperature of the suspension at that time (°C)

• Rh is the hydrometer reading at the upper rim of the meniscus, consisting of the decimal part only

with the decimal point moved three places to the right

• For example, a hydrometer reading of 1.0325 would be recorded as an R,, value of 32.5

• Cm is the meniscus correction

• HR is the effective depth (mm) corresponding to Rh obtained from the

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• D is the equivalent particle diameter

• Ro is the hydrometer reading at the upper rim of the meniscus in the dispersant solution (mm)

• K is the percentage by mass of particles less than D • Rd is the modified hydrometer reading

1. The true hydrometer reading Rh (mm) is calculated, from the equation: Rh = Rh’ + Cm

Where C is the meniscus correction and R’h is the observed hydrometer reading. Enter the values in

column 6 of Table 1.

2. The effective depth, HR (mm) is obtained, at which the density of the suspension is measured,

corresponding to the reading, Rh, from the hydrometer scale calibration curve, either by reading off

from the curve or by calculation from its equation. The value of HR isentered in column 7 of

Table1.

3. The equivalent particle diameter, D (mm) is calculated, from equation

where,

η is the dynamic viscosity of water at the test temperature (m.Pa.s) shown in Table 2

HR is the effective depth at which the density of the suspension is measured (mm);

ρs is the particle density (Mg/m3); t is the elapsed time (min);

0.005531 is a constant.

Record the value of D, calculated from each set of readings, as shown in column 8 in Table 1.

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4. The modified hydrometer reading, Rd,is calculated from the equation: Rd = R,, - Ro

where;

R'o is the hydrometer reading at the upper rim of the meniscus in the dispersant solution. The value of Rd is entered as shown in column 9 of Table 1.

5. The percentage by mass, K is calculated, of particles smaller than corresponding equivalent particle

diameter, D (mm), from the equation;

Where,

m is the mass of the dry soil used (g)

The value K is entered corresponding to each value of D as shown in column 10 of Table 1.

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Hydrometer Calibration and Sample Data

Weight of hydrometer = 70.0 g Volume of hydrometer, Vh = 70.0 ml L = 241.0 mm N = 10.0 mm h = 158.0 mm Hydrometer No. 1 Meniscus Correction Cm 0.5 mm Reading in dispersant Ro 0.5 mm Calibration equation HR = 193.7 – 3.85 Rh

Dry mass of soil M 50.08 gram

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measured/assumed Viscosity of water at 25o_C Η 0.891 m.Pa.s Calibration of Hydrometer Scale mark (g/cm3) Reading Rh Distance from lowest mark d (mm) d + N = H (mm) HR 1.030 30 12.6 22.6 92.2 1.025 25 18.5 28.5 98.1 1.020 20 37.0 47.0 116.6 1.015 15 56.0 66.0 135.6 1.010 10 75.0 85.0 154.6 1.005 5 94.0 104.0 173.6 1.000 0 114.1 124.1 193.7 0.995 -5 133.0 143.0 212.6

Data Collection and Calculation

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D ate Time of readin g Elapse d Time (min) Temp . (T˚C) Readin g Rh’ Rh’ + Cm = Rh Effectiv e Depth HR (mm) Particle Diamete r D (mm) Rh’-R’o = Rd Percenta ge finer than D K (%) 9/8 9.00a m 0 25 13.0 13.5 141.73 - 12.5 39.64 9.02a m 2 25 10.0 10.5 153.28 0.0351 9.5 30.13 9.04a m 4 25 6.5 7.0 166.75 0.0259 6.0 19.03 9.06a m 6 25 1.5 2.0 186.00 0.0223 1.0 3.17 9.08a m 8 25 -1.5 -1.0 197.55 0.0199 -2.0 -6.34 9.16a m 16 25 -2.5 -2.0 201.40 0.0142 -3.0 -9.51 9.30a m 30 25 -3.5 -3.0 205.25 0.0105 -4.0 -12.69 10.00a m 60 25 -4.0 -3.5 207.18 0.0074 -4.5 -14.27 1 0/8 9.00a m 1440 25 -4.5 -4.0 209.10 0.0015 -5.0 -15.86 CALCULATION : Formula used: Particle size,

(

)

t H D s t 1 005531 . 0 − = ρ η

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Percentage finer,

(

)

d s s _R m K 1 100 − = ρ ρ

Thus, the graph of effective depth, HR versus reading, Rh is plotted as below.

From the graph above, the equation of the line is HR = 193.7 – 3.85 Rh.

Thus, the graph of percentage finer (%) versus particle diameter (mm) is plotted as shown below.

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DISCUSSION :

Hydrometer analysis is one of the mechanical analysis to determine the size range of particles present in a soil. Hydrometer analysis is based on the principle of sedimentation of soil grains in water. When a soil specimen is dispersed in water, the particles settle at different velocities, depending on their shape, size and weight.

Hydrometer analysis takes longer time due to the waiting for the sediments of smaller soils particles. Some errors such as defects on equipment and parallax error (personal error during taking reading) may occur during experiment and these will affect the result of the experiment

After the soil sample gone through the procedures of this Hydrometer Analysis, data is taken for plotting the grain size distribution graph. From the graph, we can see that this soil sample is considered as poorly graded.

CONCLUSION :

The objective to determine the grain-size distribution of soil by hydrometer method is achieved. The sample of soil in this laboratory test is poorly graded.