THE COOPER UNION
Albert Nerken School of Engineering
Soil Mechanics Laboratory
Experiment No. 1 - Sample Preparation For Experiments 2 Through 5

To separate from a sample of whole soil at its natural moisture content, those sieve fractions and size ranges necessary for the performance of Experiments 2-5.

 

1) "Soil Testing for Engineers" by T. W. Lambe - Chapter I.

2) "Engineering Properties of Soils and Their Measurements" - 4th edition by Joseph E. Bowles.

3) A.S.T.M. Standards, 1978, Part 19; Designation D421-58, D2216-71, D2216-66.

 

1) Triple-beam balance (sensitive to 0.1 gm.)

2) Electronic top-loading balance (sensitive to 0.01 gm.)

3) Seven clean one-pint, and two two-quart Mason jars, with covers.

4) Testing Sieves: U. S. Standard Series, No. 4, 10 and 40.

5) Mortar and rubber-covered pestle.

6) Miscellaneous apparatus:

  1. sieve pans,
  2. sieve brushes,
  3. evaporating dishes,
  4. spatulas,
  5. large metal pan with bottle, etc.

7) Sodium Hexametaphosphate, 0.4N concentration.

1) Take two, two-quart jars of whole soil at its natural moisture content and separate the entire quantity on a No. 4 sieve into a +No. 4 (+ indicates material larger than a particular sieve opening or size) fraction and a -No. 4 (- indicates material finer than a particular sieve opening or size) fraction using the following procedure:

a) Set up a No. 4 sieve and a pan.

b) Take approximately one-quarter of a jar of the whole soil and gently grind it in a mortar using a rubber covered pestle. Make certain that no individual, discrete grains are crushed; the grinding action is intended to break down aggregations, or accumulations of grains. Particles obviously larger than the No. 4 sieve opening can be picked out and put aside in an evaporating dish.

c) Transfer the remaining material from the mortar to the No. 4 sieve, and using a stiff brush and the fingers work it through the sieve. Remember that a sieve is a measuring instrument and avoid exerting any great force on the screen while working the material through it; excessive force will permanently warp the mesh, increasing the size of the opening and reducing the value of the sieve as a measuring instrument. Be extremely careful to see that every soil grain retained on this sieve is a discrete particle and not an aggregation. This condition is very common in soils having plastic fine fractions, and if grinding in the mortar from (b) was not sufficiently thorough, it will probably be necessary to examine many grains individually by attempting to crush them between the fingers, to properly test for this condition.

d) Remove the +No. 4 material and set it aside with that from (b).

e) Empty the sieve pan containing the -No. 4 material into a clean, two-quart jar.

f) Repeat parts (a) to (e) for the contents of the two, two-quart jars of whole soil.

2) This -No. 4 material constitutes the material for Experiment No. 5, Step No. 1. Place this material in a two-quart jar and label it as "-# 4 - Experiment No. 5". The +No. 4 material from the two, two-quart jars, should be placed in a one-pint jar and labelled as "+#4 - Experiment No. 5".

3) Take one, one-quart jar of whole soil at its natural moisture content and separate the entire quantity on a No. 4 and a No. 10 sieve into a +No. 4 fraction, a -No. 4 to +No. 10 fraction, and a -No. 10 fraction, using the following procedure:

a) Set up a No. 4 and a No. 10 sieve and a sieve pan.

b) Step 1 (b).

c) Step 1 (c).

d) Step 1 (d).

e) Follow the procedure of part (c) for the material retained on the No. 10 sieve; observe the caution mentioned in (c) even more diligently, since the soil grains are much smaller in size and the detection of these aggregations will be more difficult.

f) Remove the No. 10 sieve and set aside the -No. 4 to +No. 10 material in another evaporation dish.

g) The sieve pan now contains the -No. 10 material; leave it in this pan.

h) Repeat parts (a) to (g) for the contents of the one quart jar.

4) Transfer the -No. 4 to +No. 10 material of step 3 (f) and the +No. 4 material of step 3 (d) into separate one-pint jars labeling the former material as "-#4 to +#10 - Experiment No. 3" and labeling the latter material as "+#4 - Experiment No. 3".

5) Weigh the -No. 10 material on a triple-beam balance to 0.1 gm. and record this weight in Table 2 on Data Sheet A of Experiment No. 3.

6) Transfer this -No. 10 material to a one-pint jar and label it as "-#10 - Experiment No.3".

7) Steps 3, 4, 5, & 6 constitute the materials for Experiment No. 3, Steps l and 2 (a-h).

8) Record the weight of a crystallizing dish and watch glass in Table 1 on Data Sheet A of Experiment No. 3.

9) From the jar of -No. 10 material of step 6 select a representative sample of approximately 50 grams; place in the weighed crystallizing dish and watch glass and weigh the container plus soil sample on an electronic top loading balance to 0.01 gm. Record this weight in Table 1.

10) Remove the watch glass and place beneath the crystallizing dish and put both, together with the sample, in the electric oven at 110oC. If some soil has adhered to the watch glass, place the glass beside the crystallizing dish in the oven. Samples must be dried to a constant weight which, for clays and clay soils usually requires no less than 12 hours for samples weighing 50 grams or less and no less than 24 hours for samples weighing 100 to 200 grams. the laboratory. [NOTE: If the experiment is being performed during a regularly scheduled lab session, the soil will be allowed to dry until the next meeting of the laboratory.]

11) After drying to constant weight, remove the crystallizing dish and watch glass from the oven, and cover the soil sample with the watch glass so that it will not absorb moisture from the atmosphere. Place the container in a dessicator to cool; remove after cooling to room temperature, and weigh to 0.01 gm. on the electronic top loading balance. Record the weight in Table 1.

12) Compute the moisture content and record in Table 1.

13) Steps 8-12 constitute the procedure of Experiment No. 3, Steps 3-9.

14) Record the weight of an evaporating dish in Table 5 on Data Sheet B of Experiment 3.

15) From the jar of -No. 10 material of step 6, select a representative sample of approximately 75 grams, place in the weighed evaporating dish and-weigh the dish plus soil on the electronic top loading balance to 0.01 gm. Record this weight in Table 5 on Data Sheet B of Experiment No. 3.

16) Add sufficient distilled water to the evaporating dish to cover the soil samples with approximately 1/4 inch of water; stir until the soil is thoroughly wetted.

17) Add 100 ml. of the dispersing agent to this soil-water mixture, stir thoroughly and transfer the entire soil-water mixture to a one-pint jar; screw on the cap, but do not tighten the cap, to create air-tightness. This will, of course, prevent evaporation and contamination from dust while permitting the chemical reaction to take place under atmospheric temperature and pressure. Be careful that in this transferral not a single drop of this soil-water mixture is lost since the soil sample itself represents a definite weighed quantity from Step 15. A wash bottle or syringe filled with distilled water is a very convenient device for making this transferral. Label the jar: "-#10 Experiment No. 3 - Hydrometer Analysis".

18) Allow the soil-water mixture to soak for at least 18 hours.

19) Steps 14-18 constitute the procedures of Experiment No. 3, Steps 14-17.

20) From the jar of -No. 10 material of step 6 select a representative sample of approximately 75 grams. Place this sample in a one pint jar and label it: "-#10 - Experiment No. 2 - Specific Gravity".

21) From the jar of -No. 10 material of step 6 select a representative sample of approximately 100 grams.

22) Using a sieve brush and the fingers, work this material through the No. 40 sieve. Observe the caution of 3(e). Discard the +No. 40 material.

23) Transfer the -No. 40 material to a one-pint jar and label it: "-#40 - Experiment No. 4".

24) Repeat steps 21-23 until a sample of about 225 grams has been obtained. This soil constitutes the material for several parts of Experiment No. 4.

25) Retain any -No. 10 material remaining from step 6 in a separate jar, should any parts of experiments 2-5 have to be repeated.