Determination Of Consolidation Properties Of Soil Assignment

Determination of Consolidation Properties of soil (Oedometer Test)
In geotechnical engineering, an oedometer test is an investigation carried
out to measure consolidation properties of soil. The deformation response
is measured on a sample of soil under different loads. Experimental
results are used in predicting the deforming response of soil with respect
to the effective stress.
Mesri and Feng (2014) argue the compressive characteristics of soil are
found by the consolidation analysis (Oedometer test) of soil and are
essential in the construction of any structure being built on a
compressible soil.
Apparatus
 Consolidation apparatus
 Consolidation cell
 Displacement transducer
 Loading device
 Porous disc
Procedure
Specimen preparation
The test specimen was cut from an undisturbed soil sample with a ring
diameter 75.00 mm and ring height 19.00 mm. The surfaces of the
sample (top and bottom) were trimmed using a palette knife until they
flushed and levelled with the surfaces of the ring i.e. both the top and
bottom.
Test procedure
1. The specific gravity of the soil particles, the weight of the cutting
ring with and without the sample and the initial moisture content of
the sample were recorded.
2. The first porous disc was placed in the consolidation cell dry. The
ring with the specimen on top of the porous disc was placed with
filter paper against each face of the sample. The top porous disc
was placed, and then the loading cap into the cell. The assembled
consolidation cell was placed in position on the oedometer press.
The oedometer was adjusted to bring the load transmitting beam
into contact with the loading cap. The displacement transducers
were positioned to monitor any vertical movement.
3. Within 3 minutes of pressure being applied to the soil sample, the
cell was filled with water so that the sample was submerged.

4. The loading apparatus was set up and the vertical load to the
sample was applied. A load was then applied and the change in the
sample thickness was measured using the displacement transducer.
5. The load was increased in increments, each increment being held
constant for 1 day, and each applied stress being double that of the
preceding stage.
6. The load was removed and swelling allowed for 24 hours. After the
final decrement, the final height and weight of the sample were
measured after removing the load and the hanger.
7. The final moisture content was then determined”
Results
Initial Final
Moisture
Content
16% Moisture
Content
16%
Bulk Density 2.04 Mg/m3 Bulk Density 2.39 Mg/m3
Dry Density 1.76 Mg/m3 Dry Density 2.06 Mg/ m3
Void Ratio 0.508 Void Ratio 0.2870
Degree of
Saturation
83.5% Degree of
Saturation
147.77%
Pressure (Loading
Stages)(kPa)
Volume
Compressibility
Coefficient
(mv)(m2/MN)
Consolidation
Coefficient (Cv)(m2/yr)
0
50 0.79 5.24
100 1.00 5.48
200 0.19 1.68
400 0.12 5.11
50 -0.07
Calculations

Initial bulk density:
ρ=m0 ×1000
A × H0
= 171.12× 1000
4414.9 ×19.0 =2.04 Mg
m3
Initial dry density:
ρd =( 100
100+W ) ρ= ( 100
100+16 )2.04=1.76 Mg
m3
Initial voids ratio:
e0= Gs
ρd
−1= 2.65
1.76 −1=0.506
Equivalent height of the solid particles:
Hs = H0
1−e0
= 19.0
1−0.506 =38.46 mm
Coefficient volume compressibility:
M v= ( H1−H2
H1 ) ( 1000
p2− p1 )= ( 19−12.6
19 )( 1000
400−50 )=0.96 m2
MN
Final Void Ratio:
ef =wf ×Gs=0.424
Discussion
According to Civilseek (no date) “The type of curves representing
consolidation test results is e versus log stress, e versus log t, e versus
square root t, av versus log pressure, cv versus log pressure curves”
Tables 1, 2 and 3 represent some typical results obtained from a
consolidation test and figures 1 and 2 represent the corresponding plots.
The Coefficient volume compressibility M v was found to be 0.96 m2 / MN
and the final void ratio of 0.424 and the consolidation coefficient is also
adequate.