Test Name: GRAIN SIZE ANALYSIS (HYDROMETER ANALYSIS)

EXPERIMENT 4 , Test Name: GRAIN SIZE ANALYSIS (HYDROMETER ANALYSIS) , soil and foundation

EXPERIMENT 4 , Test Name: GRAIN SIZE ANALYSIS (HYDROMETER ANALYSIS) , soil and foundation

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Purpose

This test is performed to determine the percentage of different grain sizes contained within a soil.

The hydrometer method is used to determine the distribution of the finer particles

Equipment

1. Cleaning brush,

2. Mixer (blender),

3. 152H Hydrometer,

4. Sedimentation cylinder,

5. Control cylinder,

6. Thermometer,

7. Beaker,

8. Timing device

Test Name: GRAIN SIZE ANALYSIS (HYDROMETER ANALYSIS)

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Test Procedure

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 hexameta phosphate (40 g/L)) solution. Stir the mixture until the soil is thoroughly wet. Let the soil soak for at least ten minutes.

2. 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.

3. Immediately transfer the soil slurry into the empty sedimentation cylinder. Add distilled water up to the mark. 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.)

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).

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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.

Take hydrometer readings after elapsed time of 2 and 5, 8, 15, 30, 60 minutes and 24 hours

Data Analysis

  1. Apply meniscus correction to the actual hydrometer reading.

2. From Table 1, obtain the effective hydrometer depth L in cm (for meniscus corrected reading).

3. For known Gs of the soil (if not known, assume 2.65 for this lab purpose), obtain the value of K from Table 2.

4. Calculate the equivalent particle diameter by using the following formula:

Where t is in minutes, and D is given in mm.

5. Determine the temperature correction CT from Table 3.

6. Determine correction factor “a” from Table 4 using Gs.

7. Calculate corrected hydrometer reading as follows:

8. Calculate percent finer as follows:

Where : WS is the weight of the soil sample in grams.

9. Adjusted percent fines as follows

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                            F200 = % finer of #200 sieve as a percent

10. Plot the grain size curve D versus the adjusted percent finer on the semilogarithmic sheet.

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EXAMPLE DATA

Date Tested: MAY 8 , 2022

Tested By: HM Class, Group D

Project Name: HM Lab

Sample Number: A ,B

Visual Classification of Soil: Brown Clayey to silty sand, traces fine gravel

     Weight of Container:           198.5 gm

     Wt. Container+Dry Soil:      722.3 gm

     Wt. of Dry Sample:              523.8 gm

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