01-02-2013, 11:24 AM
Soil Stabilization or soil modification:
Soil Stabilization.pdf (Size: 1.97 MB / Downloads: 159)
ABSTRACT
Every structure, be it a building, a tower, a bridge or a road is founded on soil and takes into account the properties of the other important materials used in its construction. For better performance and for longer durability, it is imperative to select the materials based on their best properties. To ensure that, several laboratory tests are to be carried out for every material and they are to be checked against the prescribed set of values as per the Indian Standard specifications and norms.
This report consist of various stages and methods of the laboratory testing of materials used in construction of roads as well as building with the help of advanced technology and latest equipment.
STANDARD PROCTOR TEST
OBJECTIVE:
Determination of MDD and OMC by Standard Proctor Compaction Test as per Indian Standard
Code : IS : 2720 (Part VII) 1980-87
THEORY:
Compaction of soil is a mechanical property by which the soil particles are constrained to be
packed more closely together by reducing the air voids. Soil compaction causes decrease in air
voids and consequently an increase in dry density. This may result in increase in shearing
strength. The possibility of future settlement or compressibility decrease and also the tendency
for subsequent changes in moisture content decreases. Degree of compaction is usually
measured quantitatively by dry density.
Increase in dry density of soil due to compaction mainly depends on two factors:
The amount of moisture content in soil
The amount of compaction
In practical for all types of soil it is found that with increase in compaction in respect of
increasing moisture content; the dry density first increases and then decreases. This indicates
that under a given compactive effort every soil has optimum moisture content (OMC) at which
the soil attains maximum dry density.
In laboratory various types of compacting equipment are available for compaction of soil as per
the test methods used for determining are available for compaction of soil as per the test
methods used for determining the moisture density relationship of soil. Usually dynamic
compaction test are adopted in laboratory namely Proctor Test.
For construction of highways, airports, and other structures, it is often necessary to compact soil
to improve its strength. Proctor (1933) developed a laboratory compaction test procedure to
determine the maximum dry unit weight of compaction of soils, which can be used for
specification of field compaction. This test is referred to as the Standard Proctor Compaction
Test. It is based on compaction of soil fraction passing 4.75 mm sieve.
APPARATUS:
i) Cylindrical Metal Mould fitted with a detachable base plate and removable collar.
ii) Tray
iii) Balances : one of capacity 10 kg, sensitive to 1 g and other of 200 g capacity sensitive to
0.01 g.
iv) Oven : thermostatically controlled with interior of non-corroding Material to maintain
temperature between 105°C and 110°C.
v) Container : any suitable non-corrodible airtight container to determine the water content
for tests conducted in the laboratory.
vi) Steel Straightedge : a steel straightedge about 30 cm in length and having one bevelled
edge.
vii) Sieve : 4.75-mm and 20-mm IS sieves
viii) Mixing Tools : miscellaneous tools, such as tray or pan, spoon, trowel and spatula, or a
suitable mechanical device for thoroughly mixing the sample of soil with additions of
water.
ix) A metal rammer having 5cm dia circular face and weight 2.6 kg
PROCEDURE:
i) About 3 kg of dry soil in total is taken after passing through IS 2.36 mm sieve. The sample
should be mixed thoroughly with a suitable amount of water depending on the soil every time
may be measured in a jar graduated in ml.
ii) Enough water is added to the specimen to bring the moisture content to about 9% less than
the estimated OMC for clayey soil. The processed soil water mixture is thoroughly. The wet soil
is compacted into compacted into the mould in 3 equal layers, each layer being given 25 blows
of the 2.6 kg rammer dropped from a height of 310 mm above the soil. The blow should be
uniformly distributed over the surface of each layer. Each layer of compacted soil is scored with
a spatula before placing the soil for the succeeding layer. The amount of soil used should be
just sufficient to fill the mould leaving about 6mm to be struck off on the top after compacting the
final layer.
ii) The collar is removed and the compacted soil is levelled off to the top of the mould by mean
of the straight edge. The mould and the soil is then weight. The soil is taken in an air tight
container from the cut surface. The moisture content of this representative sample is determined
by finding the wet weight keeping in oven, at 105-1100 C and finding the dry weight after
24 hours.
iv) This procedure is repeated 5 to 6 times using fresh part of soil sample and after adding
higher water content then the preceding specimen every time until the weight of the soil sample
decease.