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SOIL TEST AND SURVEY



4-1 Test for particle size

Different soil has different characteristics affecting the

performance of each individual soil by moisture content

(MC) and density(ρ).



There are several kinds of physical tests that have

been developed to measure soil performance issued

and recommended by AASHTO

(American Association of State Highway and

Transportation Officials) and ASTM (American Society

for Testing and Materials.)



THE SIEVE ANALYSIS

Is the process being used to determine the particles sizesof gravel and fine aggregates.

A sample of the material is thoroughly dried and shaken

through series of sieves ranging from course to fine.

The amount on each sieve is weighed and recorded.



The AASHTO standard sieve sizes for soil aggregates

are presented as follows:Sieve no. in inches (“) By no. opening in millimeters (mm)

2 50

1 -1/2 37.5

1 25.0

3/4 19.0

3/8 9.50

4 4.75

10 2.0

40 .425

200 .075

Material finer than No. 200 sieve (.075 mm) is not feasible in determining the particles sizes

Instead, these are determined by observing the rate at which the grains settle through liquid

or gas.



Under the stoke’s law

“ the rate of settlement of solid through a given liquid or

gas is proportional to the square of the diameters of thesolid.”

The AASHTO method as specified is called hydrometer test

AASHTO designation T-88



hydrometer test

1. Sample of the material passing No. 10 sieve is mixed thoroughly with water

and dispersing agent that dissipate any electrolytic bonds in the sample that

might cause flocculation and accelerate settlement.

2. After 12 hours, the mixture is agitated making all particles suspended in water.

3. The mixture is then placed in a graduated flask, allowing the solid to settle

under the pull of gravity.

4. The bigger particles settle first, followed by the smaller then the smallest one.

The specific gravity of the liquid decreases. The changes are recorded by

special hydrometer and read at prescribed intervals.

5. Change in specific gravity is related to the grain size of the material by stoke’s

law.

6. Careful control of temperature and other possible variable is strictly observedto obtain satisfactory test results.



4-2 test to evaluate the effect of moisture

consistency of soil varies from semi solid to plastic

then, to liquid if water content is increased.

Consistency is the term used to describe the degree of firmness

(e.g. soft, medium, firm, or hard) of a soil.



1. LIQUID LIMIT TEST (LLT)

2. PLASTIC LIMIT TEST (PLT)

3. PLATIC INDEX TEST (PIT)

4. SHRINKAGE TEST (ST)

5. HAND FEEL TEST (HFT)

6. SAND EQUIVALENT TEST (SET)

test to evaluate the effect of moisture



LIQUID LIMIT TEST

The AASHTO designation T-89 on liquid limitsignifies the percentage of moisture at which the sample

changes by decreasing the water from liquid to plastic

state.



When the sample is wet than the

liquid limit, a grooved sample ofthe soil in a cup will flow whenlightly jarred 25 times. On theother hand, if the sample is jarred

at the liquid limit, water separatesthe soil particles just wide enoughto remove the soil mass shearingstrength. Several tests on each

sample are required to reach themoisture content wherein thegroove in the sample is required toclose at exactly 25 blows.



Sample problem:

The following results were obtained from a liquid limit test on a

clay using the casagrande cup device. Use the graph in figure.

What is the liquid limit of this clay?

No. of blows 12 20 28 32

Water content (%) 47.1 42.3 38.6 37.5



Another example: “CE board exam nov . 1998”

The results of the liquid limit and plastic limit tests areshown in figure SM-3. Which of the following most nearly

gives the liquid limit (LL) of the soil:

A. LL = 36% B. LL = 26% C. LL = 65% D. LL = 52%



Answer:



PLASTIC LIMIT TEST

AASHTO Designation T-90

signifies the percentage of moisture wherein the samplechanges with lowering wetness from plastic to semi-solid

condition.



At this stage, the soil mortar starts to crumble when rolled into

threads 1/8” diameter. Additional water will make the soil

plastic, but sands are non-plastic material that its non-plastic

limit cannot be determined.



PLASTIC INDEX TEST

AASHTO Designation T-91is defined as the numerical difference between its liquid limitand its plastic limit.

PI = LL-PL It is also referred to as the percentage of dry weight. In some

combination, it measures:

a.) the fitness and shapes of the soil particles.

b.) the interplay of the attractive forces tending to hold the claymineral flakes together.

c.) the thickness and velocity of the water film and,

d.) the quantity and electrical charges of the cations.



Example: “CE board exam may 2003”

The following data were obtained from the atterberg limits test

for a soil.

Liquid limit = 41.0%

Plasticity limit = 21.1%

What is the plasticity index of the soil?

Solution:

PI = LL-PL

PI = 41.0% - 21.1%

PI = 19.9%



SHRINKAGE TEST

Shrinkage test measures the changes in volume and weightthat occur as partly mixture of soil and water (except No. 40).

Sample is dried from the near liquid limit to constant weight of

110°C. The results are stated in terms of shrinkage limit,

volumetric change, and lineal shrinkage.

SL = [(m1 - m2)/ m2] – [(V1 - V2)/m2](ρ w)

higher value of shrinkage factor showed that the soil will give

more trouble and problem. The volume of a certain soil

increases when it absorbs water. Soils that are suitable for sub-

grade and base course are those that expand very little when

moistened. And those that swell more are considered as poor

materials. A common soil specimen requires volume change

limit of 1% for base coarse materials.



SAMPLE PROBLEM:

Following are the results of a shrinkage limit test:

Initial volume of soil in saturated state (V1)= 24.6 cc

Final volume of soil in a dry state (V 2)= 15.9 cc

Initial mass in a saturated sate (m1) = 44 gFinal mass in a dry state (m2) = 30.1 g

Determine the shrinkage limit of the soil?

Solution: note: (ρ w) = 1 grm/cc

SL = [(m1 - m2)/ m2] – [(V1 - V2)/m2](ρw)

SL =[(44 – 30.1)/ 30.1 ] – [(24.6 – 15.9)/30.1](1) = 0.1728 or 17.18%



HAND FEEL TEST Experienced soil Engineer employ the “ hand feel test” to

approximately predict the plasticity index of the soil. The testmay include:

a.) thread toughness at moisture content approximating theplastic limit.

b.) the air-dried strength.

c.) Dilatancy - the tendency of a substance to become more viscousor solid when affected by an outside force or agitation.



SAND EQUIVALENT TEST

AASHTO Designation T-176is for field determination of the presence of undesirablequantities of clay like materials in soil.

Aggregate mixture is based on the volume, rather than the on

weight.The sand equivalent is the ratio between the height of the sandcolumn (laboratory experiment test) and the combined heightof sand and expanded saturated clay expressed in percentage.

Higher values of sand equivalent indicate superior materials.The allowable moving average value from the Californiaspecification is 21 for sub base, 31 for aggregate base and 45-50for aggregates of various type asphalt concrete and 76 forconcrete sand.



4-3 density test of soil

The density of soil or weight per cubic foot

varies with the peculiarities of the soil itself,

the moisture contents, and the compacteddevice plus the method of their use. The

standard weight of soil per cubic foot cannot

be fixed, but should be determined inparticular instance.



The main variables in the soil proper are:1. Specific gravity of the soil particles that may vary from 2.0 to

3.3 that is normally between 2.5 and 2.8.

2. Particle size distribution of the soil. A mass composed ofentirely spheres of one size in the densest possible conditionwill contain 75% solid and 25%. The smaller the sphere inthe mass the higher the percentage of the solid, hence,particle size distribution may greatly affect density.

3. Grain shape of soil particles. Sharp angular particles will resistshifting from loose to a compacted state. Flaky particles insoil will decrease its density because they are difficult tocompact.



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