soil Flashcards
commonly refers
to the analysis of a soil
sample to determine the
characteristics, composition,
content, reactivity etc.
SOIL TESTING
soil test
It is usually done by a
geotechnical engineer before
the start of a construction.
soil test
importance of soil testing
Soil testing determines and identify the type of foundation needed.
Helps avoiding resting foundations on poor soil or inadequate depth.
Helps identify corrosive soil, identify soil liquefaction possibilities during an earthquake.
Determines not only the bearing capacity of the soil, but it also determines the rate of settlement of the soil. This rate determine the rate of the structure stabilization on the soil.
also called moisture content, is
the quantity of water contained in a material, such as
soil.
water content
It is the ratio of mass of water to mass of soil which is
expressed in percentage.
water content
methods to calculate water content
oven drying
calcium carbide
a thermogravimetric method
(loss on drying) in which the
sample is dried for a defined
period of time at constant
temperature.
oven drying
simplest and the most
commonly adopted method for
the determination of water
content.
oven drying
oven drying apparatus
Thermostatically controlled oven
maintained at a temperature of 110 ±
5oC
- Weighing balance, with an accuracy
of 0.04% of the weight of the soil taken - Air-tight container made of non-
corrodible material with lid - Tongs
oven drying procedure
Clean the container, dry it and weigh it with the lid (Weight ‘W1’).
Take the required quantity of the wet soil specimen in the container and weigh it with the lid (Weight ‘W2’).
Place the container, with its lid removed, in the oven till its weight becomes constant (Normally for 24hrs.).
When the soil has dried, remove the container from the oven, using tongs.
Find the weight ‘W3’ of the container with the lid and the dry soil sample.
method known as Rapid
Moisture Meter, in which the soil
sample undergoes a chemical
reaction where the water turns
into acetylene gas, thereby
producing pressure.
calcium carbide method
It is a simple and FAST method
for the determination of water
content.
calcium carbide method
calcium carbide apparatus
Metallic Pressure Vessel
* Counterpoised Balance
* Scoop
* Steel Balls
* Calcium Carbide Reagent
calcium carbide samples
Sand - No special preparation. Coarse powders may be ground
and pulverized.
Cohesive and plastic soil - Soil is tested with addition of steel ball in
the pressure vessels.
The test requires about 6g, 26g or 200g of sample.
calcium carbide method procedures
Set up the balance, place the sample in the pan till the mark on the balance arm matches with the index mark.
Check that the cup and the body are clean.
Hold the body horizontally and gently deposit the levelled, scoop-full of the absorbent (Calcium Carbide) inside the chamber.
Transfer the weighed soil from the pan to the cup.
Hold the cup and chamber horizontally, bringing them together without disturbing the sample and the absorbent.
Clamp the cup tightly into place. If the sample is bulky, reverse the above placement, that is, put the sample in the chamber and the absorbent in the cup.
In the case of clayey soils, place all 4 steel balls (3 smaller and 1 bigger) in the body along with the absorbent.
Shake the unit up and down vigorously in this position for about 15 seconds.
Hold the unit horizontally, rotating it for 10 seconds, so that the balls roll around the inner circumference of the body.
Rest for 20 seconds.
Repeat the above cycle until the pressure gauge reading is constant and note the reading. Usually, it takes 4 to 8 minutes to achieve constant reading. This is the water content (m) obtained on a wet mass basis.
Finally, release the pressure slowly by opening the clamp screw and taking the cup out, empty the contents, and clean the instrument with a brush.
an actual test that helps engineers
understand soil properties and their suitability
for different construction projects.
particle size distribution test
sieve analysis (soil)
This procedure involves preparing a representative sample of the soil by drying it, breaking up clods, and removing debris.
The sample is soaked in water with a dispersive agent for 10 to 12 hours.
The sample is washed through a 4.75mm sieve, and the retained material is oven-dried and sieved through 20mm and 10mm sieves.
The portion passing through the 4.75mm sieve is oven-dried, riffled, and about 200g taken.
This sample is then washed through a 75μm sieve with distilled water, and the material retained on the sieve is collected and dried in an oven.
The dried soil sample is sieved through 2mm, 600μm, 425μm, and 212μm sieves, and the soil retained on each sieve is weighed.
another method for conducting the particle size distribution test.
hydrometer analysis
the soil particles is suspended in water and then use a hydrometer to measure the density of the suspension at different time intervals.
hydrometer analysis
used to analyze the soil particle size if
the soil passing 75μm is 10% or more.
hydrometer analysis
The mechanical and hydrometer analysis results are plotted on a
semi-log graph with a particle size as the abscissa (log
scale) and a percentage smaller than the specified diameter as
the ordinate.`
known as the upper plastic limit, is the
water content at which the soil changes from the liquid state
to a plastic state. It is the minimum moisture content at which
a soil flows upon application of very small shear force.
liquid limit
methods in determining liquid limit
casagrande method
cone penetration method
casagrande method apparatus
Casagrande Apparatus
* 425 μm IS Sieve
* Grooving Tool
* Weighing Scale
* Oven
* Mixing Bowl
* Spatula
casagrande method procedures
Weigh about 120 g of air-dried soil passing through 425 μm IS Sieve.
Mix the soil sample with distilled water in a mixing bowl to form a uniform paste.
Take a portion of the paste and place it in the Casagrande Cup and level it using spatula.
Cut a groove in the center of the soil paste using a grooving tool.
Turn the crank of the apparatus and count the number of blows until the soil paste will come into contact.
Collect a portion of the sample of the soil using the spatula.
Change the water content of the paste by adding more water and mix it thoroughly.
Repeat the procedures 3 to 7 at least three times to obtain at least 3 samples.
Determine the water content of the (three) samples using any method of water content determination.
Draw the flow curve between log N and W, and determine the Liquid Limit of the soil that corresponds to N=25.
the water content at the change from a plastic to a semi-solid state. This test involves repeatedly rolling a soil sample into a thread until it reaches a point where it crumbles. Standard test methods are ASTM D4318 and AASHTO T 90.
plastic limit
essential to ascertain the plasticity index of the soil.
plastic limit
plastic limit apparatus
Porcelain Evaporating Dish - about 12 cm in
diameter
* Glass Plate - 10mm thick and 45 cm2 or larger
* Spatula or Pill Knife - about 2cm wide and
about 10 to 13cm long
* Brass Rod - 3mm in diameter and 10cm long
* Balance - must be sensitive to the extent of
0.01 g
* 425-micron Sieve
* Plastic Limit Rolling Device - allows for
accurate results in testing for the plastic limit
of cohesive soils. The patented design
delivers consistent and repeatable
performance
plastic limit procedures
Take about 20 gm of thoroughly mixed portion of the material passing through 425-micron I.S. sieve obtained in accordance with I.S. 2720 (Part 1)- 1983
Mix it thoroughly with distilled water in the evaporating dish till the soil mass becomes plastic enough to be easily molded with fingers.
Allow it to season for sufficient time (for 24 hrs.) to allow water to permeate throughout the soil mass.
Take about 8 gm of this plastic soil mass and roll it between fingers and glass plate with just sufficient pressure to roll the mass into a thread of uniform diameter throughout its length. The rate of rolling shall be between 80 and 90 strokes per minute.
Continue rolling till you get a thread of 3 mm diameter.
Knead the soil together to a uniform mass and re-roll.
Continue the process until the thread crumbles when the diameter is 3 mm.
Collect the pieces of the crumbled thread in air tight container for moisture content determination as described in IS:2720 (Part 2)-1973.
Repeat the test to at least 3 times and take the average of the results calculated to the nearest whole number.
