Subgrade soil test, by Micotol

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1

Sieve AnalysisTest Procedure

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2Sieve Sizes in Descending Order

• 75 mm (3 in.)

• 63 mm (2-1/2 in.)

• 50 mm (2 in.)

• 37.5 mm (1-1/2 in.)

• 25.0 mm (1 in.)

• 19.0 mm (3/4 in.)

• 12.5 mm (1/2 in.)

• 9.5 mm (3/8 in.)

• 4.75 mm (No. 4)

• 2.36 mm (No. 8)

• 1.18 mm (No. 16)

• 600 μ m (No. 30)

• 300 μ m (No. 50)

• 150 μ m (No. 100)

• 75 μ m (No. 200)

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3Sieve Analysis Test Procedure

Prepare the sample Fine Aggregate

Select a representative sample of approximately 500 g from material that has been thoroughly dried at a temperature of 110 ± 5 ° C (230 ± 9 °F).

Weigh the sample and record its mass to the nearest 0.1 g.

Coarse Aggregate

Dry the sample in an oven to a constant mass, and then allow cooling to room temperature.

Record the total dry mass of the sample to the nearest gram.

Minimum mass of samples required in each sieve sizes from 9.5mm to 75mm are as shown below

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4 Sieve Analysis Test ProcedureStep 1- Sample preparation

Step 2- Arrange sieves in descending order from largest opening to the smallest

Step 3- Pour the prepared aggregate onto the top sieve;

Step 4- Shake the sieves either using mechanical sieve shaker or hand shake

Step 5- weigh mass retained in each sieves

Step 6- Calculate % retained

Step 7- Calculate cumulative % retained

Step 8- Calculate % passed

Step 9- Calculate fineness modules

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5

Atterberg Limit TestsTest Procedure for Liquid limit (Casagrande)

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6 Introduction This method describes the procedure for determining the plasticity index of

fine-grained soils. This includes all soils having more than 50% of its particles passing a No. 400 mm.

The plasticity index of a soil is the numerical difference between its liquid and plastic limits.

The lowest water content determined by the following procedure at which the soil remains plastic is the plastic limit.

The water content determined by the following procedure at which the soil passes from a plastic state to a liquid state is the liquid limit.

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7 Procedure of Liquid Limit Test Adjust the liquid limit

device by means of the adjustment plate on the device and the gauge on the handle of the grooving tool. Adjust so the center of the wear point on bottom of cup is lifted exactly 1 cm above the base.

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8 Procedure of Liquid Limit Test Place approximately 100 grams of prepared soil in the

evaporating dish and add 15 to 20 ml of water and mix water thoroughly with the soil .

Place mixture in the cup over the spot where the cup rests on the base and spread into place with as few strokes as possible to a depth of 10 mm.

Divide the soil in the cup with a firm stroke of the grooving tool along the diameter through the centerline of the cam follower.

Turn the crank to raise and drop the cup twice per second until the two sides of the grooved sample come in contact at the bottom of the groove for a distance of 12.5 mm.

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9 Procedure of Liquid Limit Test Record the number of blows.

If the number of blows is between 15 and 40, take a representative sample of the soil in the cup for moisture content.

If the number of blows is outside the range of 15 to 40, transfer the soil from the cup to the evaporating dish. Adjust the moisture content by mixing, with or without the addition of water and repeat the test until the blows fall within the range of 15 -40 blows.

Repeat the test and obtain a second moisture sample.

Oven dry the samples at 110oC to a constant weight and weigh after cooling.

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10 Calculation Record the numerical difference between the wet and dry weight as

weight of moisture.

The "weight of moisture" divided by the "dry weight of sample" and multiplied by one hundred is the percent moisture.

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11 CalculationThe moisture content and corresponding number of blows for the two liquid limit determinations is used to calculate the liquid limit (wL) at 25 blows. Adjust the moisture content of the sample by dividing by a denominator selected from the following chart:

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12 Calculation Calculate the liquid limit for each test and average the results as

shown in the following example.

Test 1 2

Blows 19 31

Moisture 33.79 31.50

Test 1: WL(25 blows)= = 32.6%

Test 2: WL (25 blows)= = 32.4%

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13

Atterberg Limit TestsTest Procedure for Plastic limit

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14Procedure of Plastic Limit Test

Place approximately 20 grams of the prepared soil in evaporating dish and thoroughly mix with water until the mass becomes plastic enough to be shaped into a ball.

Take approximately 8 to 12 grams of the moistened soil and form into a uniform mass roughly elliptical in shape.

Roll the ball of soil by hand on the rolling surface with just enough pressure to form an elongated thread as rolling proceeds.

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15Procedure of Plastic Limit Test

If the soil can be rolled to a thread 3 mm thick without crumbling, amass it and re -roll it.

Repeat rolling and amassing until the soil crumbles under slight pressure required for rolling. Crumbling may occur when the soil has a diameter greater than 3 mm, however, this is considered a satisfactory end point, provided the soil has been previously rolled into a 3 mm thread.

Gather portions of the crumbled soil and place in a tared aluminum can and weigh, then oven dry at 110oC to a constant weight and weigh again after cooling.

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16 Calculation of Plastic Limit

Record the difference between the wet and dry weights as the weight of moisture.

Calculate the plastic limit Wp by dividing the "weight of moisture" by the "dry weight of sample" and multiply by 100.

Plastic Limit (Wp) = x 100

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17Compaction TestStandard and Modified Proctor test

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18Compaction Test

Soil is air dried, pulverized & passed thru #4 sieve. Separated into 4 to 6 samples. Adjust the water content of each sample by adding water.

Using the proctor mould (1/30th cubic foot) place & compact soil in 3 layers.

Each layer should receive 25 drops of the compaction hammer.

After the last layer, use a straight edge to trim the excess soil leveling to the top of the mould.

Determine the weight of the mould with the compacted moist soil.

Extrude from mould and collect a sample for water content determination.

Repeat for each sample over a range of moisture contents.

After collecting all pertinent weights, calculate dry density and plot vs. water content

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19

CBR (California Bearing Ratio) Test

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20California Bearing Ratio Test Procedure

California bearing ratio test is the ratio of force per unit area required to penetrate a soil mass with standard circular piston at the rate of 1.25 mm/min, to that required for the corresponding penetration of standard material or (Crushed Stone).

CBR = * 100

Sample Preparation

Prepare the remolded specimen at Proctors maximum dry density or any other density at which CBR is required.

Maintain the specimen at optimum moisture content or field moisture as required.

The material used should pass 20mm Sieve but should be retained on 4.75mm

Prepare the specimen either by static or dynamic compaction.

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Dynamic Compaction Take 4.5 to 5.5Kg of soil and mix thoroughly with the required water (OMC)

Fix the extension Collar and the base plate to the mould,

Insert the spacer disc over the base, and place the filter paper over the spacer disc.

Compact the mix soil in the mould either using light compaction or heavy compaction.

Light Compaction: - Compact the soil in 3 equal layers, each layer being given 55 blows by the 2.6Kg rammer

Heavy Compaction: - Compact the soil in 5 equal layers, each layer being given 55 blows by the 4.89Kg rammer

Remove the collar and trim off the soil

Turn the mould upside down and remove the base plate and the spacer disc

Weigh the mould with compacted soil and determine the bulk density and dry density

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Observation & Recording Optimum water content (%)

Weight of mould + Compacted specimen (gm)

Weight of empty Mould (gm)

Weight of Compacted Specimen (gm)

Volume of Specimen (cm2)

Bulk density g/cc

Dry density g/cc

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Light Compaction Calculate the weight of the wet soil at the required water content to give desired density

when occupying standard specimen volume in the mould from the expression

W = Desired dry density * ( 1+w ) V

W = Weight of wet soil

w = Desired Water Content

V = Volume of Specimen in the mould = 2250cm3

Take the weight W (calculated as above) of the mix soil and place it in the mould

Place a filter paper and the displacer disc on the top of soil.

Keep the mould assembly in static loading frame and compact by pressing the displacer disc till the level of disc reaches the top of the mould.

Keep the load for some time and then release the load, remove the displacer

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The test may be conducted for soaked as well as unsoaked conditions, if the sample is soaked, (for both light and heavy compactions), put a filter paper on the top of the soil and place the adjustable stem and perforated plate on the top of filter paper.

Put annular weights to produce a surcharge equal to weight of base material and pavement expected in actual construction, each 2.5kg weight is equivalent to 7cm construction.

A minimum of 2 weights should be used

Immerse the mould assembly and weights in a tank of water and soak it for 96hours and remove the mould for compaction test.

Observations and recordings for light compaction

Dry density gm/cc

Moulding water Content

Wet weight of the compacted soil, gm

Period of soaking 96hrs (4days)

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Procedure for Penetration test Set the stress and strain dial gauge to read zero,

Place the mould assembly with the surcharge weight on the penetration test machine, but in no case in excess of 4kg so that full contact of the piston on the sample is established.

Apply the load on the Piston so that the penetration rate is about 1.25mm/min

Record the load readings at penetration of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 7.5, 10, 12.5mm

Note the maximum load and corresponding penetration if it occurs for a penetration less than 12.5mm

Detach the mould from the loading equipment.

Take about 20 to 50 gm. of soil from the top 3cm layer and determine the moisture content.

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Interpretation and Recording If the initial portion of the curve (load vs Penetration) is concave upwards, apply

correction by drawing a tangent to the curve at the point of greatest slope and shift the origin.

Find and record the correct load reading corresponding to each penetration.

CBR = * 100

PT = Corrected test load corresponding to the chosen penetration from the load penetration curve

PS = Standard load for the same penetration

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27California Bearing Ratio Test ProcedureInterpretation and RecordingPenetration of crushed stone and the corresponding load that causes the penetration

The CBR values are usually calculated for penetration of 2.5mm and 5mm.

Generally the CBR value of 2.5mm will be grater than that at 5mm and in such a case the former (2.5mm CBR value) should be taken as a design CBR.

If CBR for 5mm exceeds that for 2.5mm, the test shall be repeated.

If Identical results follow, the CBR corresponding to 5mm penetration should be taken for design.

Penetration of plunger (mm)

Standard load (Kg)

2.5 1370

5.0 2055

7.5 2630

10.0 3180

12.5 3600

Subgrade soil test, by Micotol

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