Name:

1. Which of the following is not the assumption of one dimensional consolidation?

• consolidation is occurring under small changes in effective stress
• Stoke's law is valid
• volume of soil solids is constant
• flow occurs on account of excess pore water pressure
• The soil particles and water are incompressible
2. During the consolidation process of a saturated soil, what will happen to the degree
of saturation of the soil?
• It will increase.
• It will decrease.
• It will remain constant.
• It will behave randomly.
• It will be related to the applied load.
3. The main objective of consolidation test on soil is to determine ________.
• water content
• optimum moisture content and maximum dry density
• liquid limit
• coefficient of compressibility
• degree of saturation

4. In saturated soils, the initial consolidation is mainly due to ___________.

• relocation of soil particles
• compression of solid particles
• compression of air in voids
• expulsion of air in voids
• compression of water molecules

5. Consolidation time of a soil sample

• increases with a decrease in permeability.
• increases with an increase in permeability.
• does not related to permeability
• increases with a decrease in compressibility.
• increases with a decrease in a unit weight of soil

6. The elastic settlement of rigid foundation-----

• equals to the elastic settlement of flexible foundation
• equals to 0.93 of the elastic settlement of flexible foundation
• equals to 1.5 of the elastic settlement of flexible foundation
• equals to double the elastic settlement of flexible foundation
• equals to three times the elastic settlement of flexible foundation
7. The contact pressure distribution under a rigid footing on a cohesive soil would be:
• Uniform throughout
• Zero at edges and maximum at centre
• Maximum at edges and minimum at centre
• Zero at centre and maximum at edges
• Non uniform
8. In Terzaghi’s piston and spring analogy, the grain structure was represented by:
• water
• piston
• cylinder
• valve
• spring
9. In the spring cylinder analogy model of consolidation, at the moment of applying the
load P and the valve is closed----------
• ∆𝑢 = 0
• ∆𝒖 = 𝑷⁄𝑨
• ∆𝑢 > 𝑃⁄𝐴
• ∆𝑢 < 𝑃⁄𝐴
• None of the above
10. In the spring analogy of consolidation, cylinder is filled with water up to bottom of
piston and spring carries 10 units of load. If external two units of load is applied and
the valve is partly opened, then the effective pressure σ’ and hydrodynamic
pressure u is given by ___________
• σ’=0, u=12
• σ’=10+∆σ’, u=2-∆σ’
• σ’=10, u=2
• σ’=12, u=0
• σ’=12, u=2
Name
1. Pick - out the INCORRECT assumption of terzaghi’s theory of consolidation of
soils.
• Soil is laterally confined, and the consolidation takes place only in axial direction.
• Drainage of water occurs in vertical direction
• The soil is homogenous and isotropic
• There is unique relationship between the volumetric strain and the effective stress
and this relationship remains constant during the load increment
• The soil is fully saturated
2. The decrease in the volume of soil mass under stress is known as
• compression
• compressibility
• tension
• consolidation
• expansion
3. In comparison to the elastic settlement of flexible foundation,
the elastic settlement of rigid foundation is
• less
• more
• equal
• not related
• less or more (could be any)
4. The elastic settlement distribution under a flexible footing on a cohesive soil would
be:
• Uniform throughout
• Zero at edges and maximum at centre
• Maximum at edges and minimum at centre
• Zero at centre and maximum at edges
• Non uniform
5. The compression resulting from a long- term static load and consequent escape of
pore water is
• compression
• compressibility
• tension
• consolidation
• swelling ____________
6. In the spring cylinder analogy model of consolidation, the spring represents-----
• skeleton of soil
• pore water
• air voids
• water
• all of the above
7. In the spring cylinder analogy model of consolidation, after applying the load P and
opening the valve, ------
• all the load will be carried by water in cylinder
• all the load will be carried by spring
• the load will be carried by both water and spring
• the water will be dissipated
• excess pore water will be zero
8. In the spring analogy of consolidation, cylinder is filled with water up to bottom of
piston and spring carries 10 units of load. If external two units of load is applied and
the valve closed, then the effective pressure σ’ and hydrodynamic pressure u is given
by ___________
• σ’=0, u=12
• σ’=0, u=0
• σ’=10, u=2
• σ’=12, u=0
• σ’=2, u=0

9. Excess pore pressure is also known as ___________

• seepage pressure
• hydrodynamic pressure
• effective pressure
• total pressure
• net pressure
10. For a dry soil mass of 180.4 g, specific gravity 2.68 and cross-sectional area of
specimen as 50 cm2, find the height of solids Hs.
• 13.45 mm
• 14 mm
• 17 mm
• 19.5 mm
• 15.5 mm
Name:

1. The property of soil mass pertaining to its susceptibility to decrease in volume under
pressure is ____________
• compression
• compressibility
• tension
• consolidation
• Expansion
2. The contact pressure distribution under a rigid footing on a cohesion less soil would
be:
• Uniform throughout
• Zero at edges and maximum at centre
• Maximum at edges and minimum at centre
• Zero at centre and maximum at edges
• Non uniform
3. In the spring cylinder analogy model of consolidation, the spring represents-----
• pore water
• air voids
• soil mass
• water
• all of the above
4. in a clay layer drained at top and bottom as the result of an added stress ∆𝝈,
at time equals zero

• ∆𝒖 = ∆𝝈, 𝒂𝒏𝒅 ∆𝝈 = 𝟎

• ∆𝑢 < ∆𝜎, 𝑎𝑛𝑑 ∆𝜎  > 0
• ∆𝑢 = 0, 𝑎𝑛𝑑 ∆𝜎 = ∆𝜎 
• ∆𝑢 > ∆𝜎, 𝑎𝑛𝑑 ∆𝜎  > 0
• ∆𝑢 > ∆𝜎, 𝑎𝑛𝑑 ∆𝜎  < 0

5. If the specimen height H is 24mm and height of solids Hs is 13.45mm, then find the
voids ratio.
1. 0.843
2. 0.786
3. 0.432
4. 0.356
5. 0.650
6. What is not found by the consolidation test data?
• the voids ratio and the coefficient of its volume change
• coefficient of consolidation
• the specific gravity of the soil particles
 • coefficient of compressibility
• coefficient of permeability
7. In consolidation experiment where H initial height of the specimen, 𝐻𝑠 the height of
solids, and Hv the initial height of voids, then void ratio of the speciemen can be
calculated from------
• Hv/Hs
• (H-Hv)/Hs
• Hv/(H-Hs)
• Hv-Hs
• None of these
8. Which one of the following is the part of assumptions made by Terzaghi while
developing the mathematical statement of the consolidation process?
1. The soil is non-homogeneous
2. The soil particles and water are incompressible
3. The soil is partially saturated
4. Coefficient of permeability is variable during consolidation
5. Darcy's law is not valid
9. The reduction in volume of soil which is due to squeezing out of water from the voids
is __________

• effective pressure
• primary consolidation
• secondary consolidation
• elastic settlement
• none of these

10. During the consolidation process of a saturated soil, what will happen to the water
content of the soil?
• It will increase.
• It will decrease.
• It will remain constant.
• It will behave randomly.
• It will be related to the applied load.
 Al-Iraqia University-College of Engineering

Civil Engineering Department

Soil Mechanics II

Typical answers for time rate of consolidation

Prof Dr Nesreen Kurdy Al-Obaidy

1. The degree of consolidation at a distance z at any time t where 𝐮𝐳 excess pore water
pressure at time t, is
𝒖 −𝒖
• 𝑼𝒛 = 𝒐𝒖 𝒛
𝒐
𝑢
• 𝑈𝑧 = 𝑢𝑧
𝑜
• 𝑈𝑧 = 𝑢𝑧 − 𝑢0
• 𝑈𝑧 = (𝑢𝑧 + 𝑢0 )/2
𝑢
• 𝑈𝑧 = 1 + 𝑢𝑧
𝑜
2. The time factor Tv for a clay layer does not depend on------
• coefficient of consolidation
• time
• compressibility index
• drainage path
• depth of the clay layer
3. The time factor Tv for a clay layer depends on------
• coefficient of consolidation
• time
• depth of the clay layer
• drainage path
• All of the mentioned above
4. The time factor Tv for a clay layer depends on------
• coefficient of consolidation
• time
• Degree of consolidation
• drainage path
• All of the mentioned above
5. For degree of consolidation ranging between 0% and 60%, Time factor can be
calculated according to-----
• 𝑇𝑣 = 1.781 − 0.933log⁡(100 − 𝑈%)
𝝅 𝑼% 𝟐
• 𝑻𝒗 = 𝟒 (𝟏𝟎𝟎)
 𝜋 𝑈% 2
• 𝑇𝑣 = 2 (100)
𝜋 𝑈% 3
• 𝑇𝑣 = 4 (100)
• 𝑇𝑣 = 1.781 + 0.933log⁡(100 − 𝑈%)
6. For degree of consolidation more than 60%, Time factor can be calculated
according to-----
• 𝑇𝑣 = 1.781 + 0.933log⁡(100 − 𝑈%)
𝜋 𝑈% 2
• 𝑇𝑣 = 4 (100)
𝜋 𝑈% 2
• 𝑇𝑣 = 2 (100)
𝜋 𝑈% 3
• 𝑇𝑣 = 4 (100)
• 𝑇𝑣 = 1.781 − 0.933log⁡(100 − 𝑈%)
7. ---------- proposed the first theory to consider the rate of one-dimensional
consolidation for saturated clay soils

• Taylor
• Skempton
• Terzaghi
• Darcy
• Newton
8. During consolidation, the rate of change in the volume of the soil element is
• equal to the rate of change in the volume of voids
• equal to the rate of change in the volume of solids
• the rate of change in the total volume from solids and voids
• not equal to the rate of change in the volume of voids
• none of these
9. The mathematical expression of the assumption (soil solids are incompressible)
means
𝜕𝑉
• 𝜕𝑡𝑣=0
𝝏𝑽𝒔
• =𝟎
𝝏𝒕
𝜕𝑒
• =0
𝜕𝑡
𝜕𝑒
• 𝑉𝑆 𝜕𝑡 =0
• None of these
10. When the degree of consolidation is 30%, about how much is the time factor?
• 0.0515
• 0.0707
• 0.0 915
• 1.0219
• 0.1843
 Explanation
𝝅 𝑼% 𝟐 𝝅 𝟑𝟎 𝟐
30% degree of consolidation (between 0% and 60%), 𝑻𝒗 = ( ) 𝑻𝒗 = 𝟒 (𝟏𝟎𝟎) =
𝟒 𝟏𝟎𝟎
𝟎. 𝟎𝟕𝟎𝟕

11. If the time required for 20% consolidation of a clay layer is 6.4 days. What is the
time required to reach 40% consolidation
• 30.1days
• 9.21 days
• 25.6 days
• 14.44 days
• 5.2 days
𝑡1 𝑈12 6.4 202
= = 2 𝒕𝟐 = 25.6. days
Explanation 𝑡2 𝑈22 𝑡2 40

12. The time required for 50% consolidation of a 20-mm-thick clay layer (drained at
both top and bottom) in the laboratory is 120 sec. How long (in seconds) will it take
for a 2-m-thick clay layer of the same clay in the field under the same pressure
increment to reach 50% consolidation? In the field, there is a rock layer at the
bottom of the clay.
• tfield =8,064,000 sec
• tfield =6,164,000 sec
• tfield =4,800,000 sec
• tfield =3,184,000 sec
• tfield =7,164,000 sec
Explanation
120 𝑠𝑒𝑐 𝑡𝑓𝑖𝑒𝑙𝑑
𝑡𝑙𝑎𝑏 𝑡𝑓𝑖𝑒𝑙𝑑 =
= 2 2 (2𝑚)2
2
𝐻𝑑𝑟(𝑙𝑎𝑏) 𝐻𝑑𝑟(𝑓𝑖𝑒𝑙𝑑) 0.020 m
( 2 )

𝑡𝑓𝑖𝑒𝑙𝑑 = 4,800,000 sec

 Al-Iraqia University-College of Engineering

Civil Engineering Department

Soil Mechanics II

Typical answers quiz2/a by Prof Dr Nesreen Kurdy Al-Obaidy

1. According to the Terzaghi's theory of one-dimensional consolidation, the direction of

load applied is _________.
• in three directions
• in two directions
• in one direction only
• at any direction
• none of these
2. During the consolidation process of a saturated soil, what will happen to the water
content of the soil?
• It will increase.
• It will decrease.
• It will remain constant.
• It will behave randomly.
• It will be related to the applied load.
3. in a clay layer drained at top and bottom as the result of an added stress ∆𝝈, at time
equals zero
• ∆𝒖 = ∆𝝈, 𝒂𝒏𝒅 ∆𝝈 = 𝟎
• ∆𝑢 < ∆𝜎, 𝑎𝑛𝑑 ∆𝜎  > 0
• ∆𝑢 = 0, 𝑎𝑛𝑑 ∆𝜎 = ∆𝜎 
• ∆𝑢 > ∆𝜎, 𝑎𝑛𝑑 ∆𝜎  > 0
• ∆𝑢 > ∆𝜎, 𝑎𝑛𝑑 ∆𝜎  < 0

4. For an Over-consolidated soil, ------

• a small change in void ratio will occur
• a large change in the void ratio
• the 𝑒 − 𝑙𝑜𝑔 𝜎 ` relationship is practically linear with a steeper slope.
• the effective pressure applied ≥ the maximum effective past overburden pressure
• none of these

5. The primary consolidation settlement for a soil strata of thickness H that has fully
consolidated, a pressure increment ∆σ’ with respect to mv is given by ___________
• Sc=mv H
• Sc =H ∆σ’
• Sc =mv ∆σ’
• Sc =mv H ∆σ’
• None of these
 6. In a semi-logarithmic plot, the virgin compression curve becomes---------
• straight line
• parabolic curve
• hyperbolic curve
• elliptical curve
• none of these
7. The value of a compression index for a remolded sample, whose liquid limit is 50%,
is-------
• 0.36
• 0.048
• 0.036
• 0.17
• 0.28
Explanation: Cc=0.007(LL%-10) =0.007(50-10)=0.007(40)=0.28
8. What is the soil in the consolidation test?
• restrained vertically
• restrained laterally
• not restrained laterally
• not restrained
• None of these
9. If the final height of specimen Hf is 13.45 mm and final voids is 0.864, then the change
of voids ratio ∆e with respect to ∆H is ____________
• ∆e=0.139 ∆H
• ∆e=0.123 ∆H
• ∆e=0.178 ∆H
• ∆e=0.148 ∆H
• ∆e=0.156 ∆H

∆𝒆 ∆𝒆 𝟏+𝒆𝒐 𝟏+0.864
Explanation:𝑺𝒄 = 𝟏+𝒆 𝑯 ∆H = 𝟏+𝒆 𝑯 ∆𝒆 = ∆H ∆𝒆 = ∆H =
𝒐 𝒐 𝑯 13.45
0.139∆H

10. If coefficient of volume change is 0.291 m2/MN, ∆e=0.1 and the initial voids ratio is
0.72, then find the change in effective pressure.
• 200 KN/𝐦𝟐
• 50 KN/m2
• 300 KN/m2
• 100 KN/m2
• 150 KN/m2
∆𝑒 0.1
𝑎𝑣 ∆𝜎 ∆𝜎
Explanation 𝑚𝑣 = 𝑚𝑣 = 𝟎. 𝟐𝟗𝟏 =
1+𝑒𝑜 1+𝑒𝑜 1+0.72

𝑀𝑁
∆𝜎  = 0.2 = 200 KN/m2
m2