Sieve and Hydrometer Analysis-Civil Engineering Assignment Solution Sample

QUESTION

Sieve and Hydrometer Analysis

Introduction

The purpose of this lab is to classify a soil for engineering purposes. The grain sizes of a given soil mass is important. Sieve analysis is a method which determines the size and ranges of size in a soil expressed as a percentage of the total dry weight. Sieves are made of woven wires with square openings. The size designation for U.S. sieves uses 100mm to 6.3mm. To see more of the sieve sizes, refer to ASTM Standard: D-422. Another method use was the Hydrometer analysis test ASTM: D-422. This test normally used for determining the particle-size distribution of soil that’s finer than U.S. No. 200 sieve size(0.075mm). The lower limit of a particle size in this procedure is approximately 0.001mm. During the hydrometer analysis test the soil is put into water, as the soil interacts with the water it disperses and settle individually. It’s assumed that the soil particles are spheres, and by using Stokes’ law you can obtain the velocity of the particles.

Discussion of work

One of the Test methods used was the sieve analysis ASTM: D-422. The method was the ASTM 152-H type hydrometer analysis test. Deviations from the procedure were during lab. The steps that deviated were steps 1-3 which was done by the TA to allow adequate soaking time. On step 5 we were instructed to disregard all other references to the constant temperature bath. Instead we measured the temperatures as they changed. Step 12 We took our first reading at 30s instead of 15s. Step 14 we read only to the 30-minute mark. TA provided two more additional readings. For the combined sieve and hydrometer, we followed the procedure modification in section 5.6 (pp. 45-46). From the calculations of the graph for the sieve analysis since our Data didn’t have a value for D10 I just used the value from the lab book p.31 for calculation sake, this also skewed all the data. I didn’t know how to show the values for D10, D30, D60 graphically but I plotted what I could base off the information obtained in lab. For D10= 0.0016mm, D30 = 0.833mm, D60= 0.250mm. The Cu and Cc values are also skewed from these calculations. Cu =2.55, Cc = 28.32. Based off this information Cu is very large this indicates a well-graded soil. Since Cc is greater than 4, and Cc is not between 1 and 3 I cannot accurately determine the nature of this soil. Errors were from not taking a reading for D10 and this had a domino effect on the data, graphs, and values obtain. The hydrometer analysis test did not go any better. I didn’t combine the sieve analysis and the hydrometer analysis together because the data made no sense when I tried to interpret the results.

ANSWER

Sieve Analysis and Hydrometer Analysis

Introduction:

Grain size analysis is a method by which the proportion (gradation) of each grain size in a given soil sample is determined. This grain size distribution for coarse-grained soils can be determined by sieve analysis, while that for fine-grained soils has to be determined using hydrometer analysis. The grain size distribution for mixed soils with large deviation in sizes may be determined using combined sieve and hydrometer analysis.

Hydrometer analysis is a method of finding the proportions and distribution of soil particle sizes ranging from No. 200 (0.075 mm) sieve to 0.01 mm. The data is depicted on a semi log graph of percent finer vs. particle diameters. It is combined with data from the sieve analysis of material retained on No.200 (0.075 mm) sieve. The main objective of hydrometer analysis is to find the clay fraction (generally designated as the percent of particles finer than 0.002 mm). The hydrometer analysis also has its usefulness in identifying particle sizes less than 0.02 mm in frost susceptibility experiments for materials to be used in pavement subgrades. The test is performed when more than 20% material passes through No.200 sieve while 90% or more passes No. 4 (4.75 mm) sieve.

Objective:

To determine the grain size distribution (gradation) of coarse soil (not passing #200 sieve) using sieve analysis and using hydrometer analysis for finer soils.

Theory:

The grain size analysis is depicted using a semi log graph of percent finer versus particle size, also known as grain size distribution curve. A semi log graph needs to be used for the particle sizes so that both small and large diameters have nearly equal weight. Percent finer is plotted on the ordinate using arithmetic scale.

Using the grain size distribution curve, grain sizes of D10, D30 and D60 can be obtained, where ‘D’ refers to size or apparent diameter of soil particle and subscript (10, 30, 60) implies the percent that is smaller. For example, D10 = 0.16 mm implies that 10 percent of the sample particles are smaller than 0.16 mm. D10 size value is also known as effective size of the soil.

The coefficient of uniformity (C_u) gives the spread or range of the particle sizes, where

D60

C_u =

D10

The coefficient of curvature (C_c) gives the shape of the curve between D60 and D10 grain sizes, where

(D30)²

C_c =

D60 * D10

The sieve analysis test consists of passing the sample particles through a set of sieves arranged in a particular way and weighing the material retained on every sieve. Sieves are made of wires with square openings of specific sizes. Sieve analysis is done on material retained on the U. S. Standard No. 200 sieve. Following table lists the U. S. Standard sieve numbers along with their opening diameters.

U. S. Sieve Numbers and Associated Opening Sizes

Sieve No.	Opening Size (mm)	Sieve No.	Opening Size (mm)
4	4.75	35	0.500
5	4.00	40	0.425
6	3.35	45	0.355
7	2.80	50	0.300
8	2.36	60	0.250
10	2.00	70	0.212
12	1.70	80	0.180
14	1.40	100	0.150
16	1.18	120	0.125
18	1.00	140	0.106
20	0.85	200	0.075
25	0.71	270	0.053
30	0.60	400	0.038

Hydrometer analysis uses Stokes’ Law, which provides relationship among velocity of fall of particle spheres in any fluid, the diameter of the particle sphere, the specific weights of the fluid and the sphere, and fluid viscosity:

where,

v = velocity of sphere while falling (cm/s)

G_s = specific gravity of sphere

G_f = specific gravity of fluid

 = absolute, or dynamic, viscosity of the fluid (g /(cm * s))

D = diameter of the sphere (cm)

Solving it for D and putting specific gravity of water G_w,

D =  18  v / (G_s – G_w)

v = L / t

A =  18  / (G_s – G_w)

D = A L (cm) / t (min)

where 0.002 mm < D < 0.2 mm

Apparatus Required:

For Sieve Analysis:

1. Sieves, a bottom pan and a cover

2. A balance sensitive to 0.1g

3. Mortar and rubber pestle

4. Oven

5. Mechanical sieve shaker

6. Brush for cleaning sieves

For Hydrometer Analysis:

1. Hydrometer (152H model preferable)

2. Mixer

3. Two Sedimentation cylinder (1000mL)

4. Constant temperature bath

5. Deflocculating agent

6. Spatula

7. Beaker

8. Thermometer

9. Balance

10. Plastic squeeze bottle

11. No. 12 rubber stopper

Procedure:

For Sieve Analysis:

Sample preparation: The sample to be treated is first air-dried. Then the bigger aggregates present are thoroughly broken up using fingers or with mortar & pestle. The specimen to be tested needs to be large enough so that it can represent the soil in the field. However, it should be small enough not to overload the sieves. The size of a representative specimen depends on the maximum particle size present in the sample. Following table gives the guidelines for selecting the minimum sample weight.

Minimum Sample Weights for Sieve Analysis

Maximum size of particle(cm)	Minimum weight of sample (g)
7.5	6000
5.0	4000
2.5	2000
1.0	1000
Finer than No. 4 sieve	200
Finer than No.10 sieve	100

2. Collect a representative oven dried soil sample. Samples with largest particle size of No. 4 sieve opening (4.75 mm) should weigh about 500 grams. For soils with largest particle size greater than 4.75 mm, larger weights are required.

3. Break the sample into individual particles with a mortar & pestle. The aim is to divide bigger particles of the soil to individual particles and not to break the particles themselves.)

4. Find the mass of the sample upto 0.1g accuracy (W).

5. Arrange the sieves to form a stack. A sieve having larger opening is placed on top of a sieve having smaller opening. The sieve at the bottom is the No. 200. A bottom pan needs to be placed below the No. 200 sieve. The sieves commonly used in the stack are Nos. 4, 10, 20, 40, 60, 140 and 200. More sieves may be placed in between for more accuracy.

6. Pour the soil prepared in Step 3 into the stack of sieves from the top.

7. Place a cover on the top of the stack of sieves.

8. Put the stack of sieves on a sieve shaker for about 10 to 15 minutes.

9. Stop the sieve shaker and remove the stack of sieves.

10. Weigh the soil left on every sieve as well as the bottom pan.

If sufficient quantity of soil with silty fractions is retained on the No. 200 sieve, it needs to be washed. It is done by taking the No.200 sieve along with the soil left on it and pouring water through the sieve using a tap. When water passing through the sieve comes out clean, the flow of water is stopped. Transfer the soil retained on the sieve at the end of washing to porcelain evaporating dish by back washing. Put it in oven to dry to get a constant weight. Note the mass of the dry soil left on the No. 200 sieve. The difference between this mass and that left on the No. 200 sieve found in Step 10 is the mass of soil that has been washed away.

For Hydrometer Analysis:

Take 50 g of oven-dry, well-pulverized soil in a beaker.
Prepare a deflocculating agent. Usually a 4% solution of sodium hexametaphosphate (Calgon) is used. This can be prepared by adding 40 g of Calgon in 1000 cm³ of distilled water and mixing thoroughly.
Take 125 cm³ of the mixture prepared in Step 2 and add it to the soil taken in Step 1. This should be allowed to soak for about 8-12 hours.
Take a 1000-cm³ graduated cylinder and add to it 875 cm³ of distilled water plus 125 cm³ of deflocculating agent. Mix the solution well.
Put the cylinder (from Step 4) in a constant-temperature bath. Record the temperature T of the bath (°C).
Put the hydrometer in the cylinder (Step 5). Record the reading. (Note: The top of the meniscus should be read.) This is the zero correction F L., which can be positive or negative. Also observe the meniscus correction.
Using a spatula, mix the soil prepared in Step 3 thoroughly. Pour it into the mixer cup. (Note: During this process some soil may stick to the side of the beaker. Using the plastic squeeze bottle filled with distilled water, wash all the remaining soil in the beaker into the mixer cup.)
Add distilled water to the cup to make it about two-thirds full. Mix it for about 2 minutes using the mixer.
Pour the mix into the second graduated 1000-cm³ cylinder. Make sure that all of the soil solids are washed out of the mixer cup. Fill the graduated cylinder with distilled water to bring the water level up to the 1000-cm³ mark.
Secure a No. 12 rubber stopper on the top of the cylinder (Step 9). Mix the soil-water well by turning the cylinder upside down several times.
Put the cylinder into the constant-temperature bath next to the cylinder described in Step 5. Record the time immediately. This is cumulative time t = 0. Insert the hydrometer into the cylinder containing the soil-water suspension.
Take hydrometer readings at cumulative times t = 0.25, 0.5, 1, and 2 min. Always read the upper level of the meniscus.
Take the hydrometer out after 2 minutes and put it into the cylinder next to it (Step 5).
Hydrometer readings are to be taken at times t = 4, 8, 15, 30 minutes, 1, 2, 4, 8, 24, and 48 hours. For each reading, insert the hydrometer into the cylinder containing the soil-water suspension about 30 seconds before the reading is due. After the reading has been taken, remove the hydrometer and put it back into the cylinder next to it (Step 5).

Calculation:

For Sieve Analysis:

Description of soil: Sandy

Date: 2/05/19

Location: University of Alaska, Anchorage Geomatics Lab

Tested By (Group):

Sample No: A

Mass of oven dry sample (W): 351.47g

Sieve No.	Sieve opening (mm)	Mass of soil retained on each sieve (W_n)	Percent of mass retained on each sieve (R_n)	Cumulative percent retained,  R_n	Percent finer, 100 –  R_n
20	0.833	0.10	0.03	0.03	99.97
40	0.425	0.74	0.21	0.24	99.76
60	0.250	80.41	22.98	23.22	76.78
100	0.150	178.06	50.88	74.1	25.9
140	0.106	14.74	4.21	78.31	21.69
200	0.075	2.14	0.61	78.92	21.08


Bottom Pan	73.71	73.71

W1 =  W_n = 349.9

Mass loss during sieve analysis= (W – W1) X 100 / W = 0.45% (OK if less than 2%)

For Hydrometer Analysis:

Description of soil: Sandy

Sample No.: A

Location: University of Alaska, Anchorage Geomatics Lab

G_S: 2.65 Hydrometer Type: ASTM 152-H

Dry mass of soil M_S: 2.14 g Meniscus correction F_m: 1 Zero correction F_z: 7

Tested by:

Date: 2/12/19

Time (t, min.)	Hydrometer Reading (R)	Temperature of test T (C)	R_CP	Percent finer AR_CP100 / 50	R_CL	L (cm)	A	D (mm)
0.5	39		27.15	54.3	40	9.9
1	37.5		25.65	51.3	38.5	10.1
2	35	22	23.15	46.3	36	10.6	0.0133	0.0306
4	32	21	25.65	51.3	33	11.1	0.0135	0.0225
8	29.5	21	22.9	45.8	30.5	11.4	0.0135	0.0161
15	27.5	21	20.9	41.8	28.5	11.7	0.0135	0.0119
30	25	21	18.4	36.8	26	12.2	0.0135	0.0086

Note: Plot the percent finer versus grain size for both Hydrometer Method and Combined Method. Use arithmetic scale and vertical axis for percent finer and log scale and horizontal axis for grain size. This curve is called grain size distribution curve.

Graphs:

For Sieve Analysis:

For Hydrometer Analysis:

Interpretation:

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