The document provides a summary of consolidation and 9 practice problems related to consolidation of soils. It begins with definitions of terms like settlement, change in void ratio, coefficient of consolidation. It then presents the practice problems related to calculation of void ratio, thickness change, coefficient of volume compressibility, time required for 50% consolidation based on coefficient of consolidation, estimation of settlement etc. It concludes with references for further reading on the topic of consolidation in geotechnical engineering.

1. 1
Geotechnical Engineering–I [CE-221]
BSc Civil Engineering – 4th Semester
by
Dr. Muhammad Irfan
Assistant Professor
Civil Engg. Dept. – UET Lahore
Email: mirfan1@msn.com
Lecture Handouts: https://groups.google.com/d/forum/2016session-geotech-i
Lecture # 21
10-Apr-2018

2. 2
CONSOLIDATION – SUMMARY
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For NCC
For OCC
If OCC is loaded beyond σp’
)10(009.0  LLCC Cr CC  1.0
Terzaghi & Peck (1948)

3. 3
Practice Problem #1
Practice Problem #2
A clay layer 10’ thick had initial void ratio 1.4 and LL = 60%. Find change
in thickness of clay layer if pressure is increased from 1 ton/ft2 to 1.52
ton/ft2.
A consolidation test was performed on a sample with initial dimensions of H
= 20 mm and ring diameter = 63 mm. At the end of test, the sample height
was 13.3 mm and the oven dry weight of soil was 78.3 g. Assuming Gs =
2.66, find:
(i) The initial void ratio, eo
(ii) Final void ratio, ef
(iii) Total sample strain εf

4. 4
Practice Problem #3
A saturated specimen of clay had undergone consolidation under a
pressure of 2 kg/cm2 in an oedometer test. Thickness of the specimen was
found to be 21.18 mm and its water content 12%. Subsequently with a
further increase in pressure 1 kg/cm2, the thickness of the specimen at the
end of 24 hours was reduced by 1.18 mm. From these data, compute the
coefficient of volume compressibility and compression index of the soil
assuming Gs = 2.7.

5. 5
Practice Problem #4
Practice Problem #5
At a certain depth below the foundation of a building there exists a clay layer of
thickness 10 m. Above and below the clay layer there are incompressible permeable
soils. In a consolidation test on the clay sample with drainage at top and bottom, a
sample with initial thickness 2.54 cm was compressed under a steady pressure. Half
of the final settlement took place in 10 minutes after the application of pressure.
Find how long it will take for the settlement of the building to reach 50% of its
ultimate value?
If the clay layer had drainage only from top, what would be the settlement time for
50% consolidation?
A clay layer, whose total settlement under a given loading is expected to be 12 cm
settles 3 cm at the end of 1 month after the application of load increment. How
many months will be required to reach a settlement of 6 cm? How much settlement
will occur in 10 months? Assume the layer to have double drainage.

6. 6
Practice Problem #6
How many days will be required by a clay stratum 5 m thick, draining at both
ends with an average value of coefficient of consolidation Cv = 40x10-4
cm2/sec to attain 50% of its ultimate settlement.

7. 7
Practice Problem #7
Given:
When the total pressure acting at mid height of a consolidating clay layer is
200 kN/m2, the corresponding void ratio of the clay is 0.98. When the total
pressure acting at the same location is 500 kN/m2, the corresponding void
ratio decreases to 0.81.
Required:
The void ratio of the clay if the total pressure acting at mid height of the
consolidating clay layer is 1000 kN/m2.

8. 8
Practice Problem #7

9. 9
Practice Problem #8
A stratum of normally loaded clay of 7m thick is located at a depth of 12m
below ground level. The natural moisture content of the clay is 43% and
its liquid limit is 48%. The specific gravity of the solid particles is 2.76.
The water table is located at a depth of 5m below the ground surface. The
soil is sand above the clay stratum. The submerged unit weight of the sand
is 11 kN/m3 and the same weighs 18kN/m3 above the water table. The bulk
unit weight of the clay is 19.5 kN/m3. The average increase in pressure at
the center of the clay stratum is 120 kN/m2 due to the weight of a building
that will be constructed on the sand above the clay stratum. Estimate the
expected settlement of the structure.

10. 10
Practice Problem #9

11. 11
Practice Problem #8

12. 12
CONCLUDED
REFERENCE MATERIAL
Principles of Geotechnical Engineering – (7th Edition)
Braja M. Das
Chapter #11
An Introduction to Geotechnical Engineering (2nd Edition)
By R. D. Holtz, W. D. Kovacs and T. C. Sheahan
Chapter #8 & 9