This set of Soil Mechanics Assessment Questions and Answers focuses on “Determination of Coefficient of Consolidation – 2”.

1. The graph is plotted with the procedure of square root of time fitting method. The line B is drawn that its abscissa at every point is ______ times that of line A.

a) 1.40

b) 1.30

c) 1.15

d) 0

View Answer

Explanation: When the graph is plotted with the procedure of square root of time fitting method. The line B is drawn that its abscissa at every point is 1.15 times that of line A. The line B is drawn from R

_{c}, instead of the initial reading R

_{0}.

2. The average drainage path for the pressure increment is calculated from the formula of ______

a) \(d=\frac{1}{2} \left[\frac{H_{‘}-H_f}{2}\right] \)

b) \(d=\frac{1}{2} \left[\frac{H_{‘}}{2}\right] \)

c) \(d=\frac{1}{2} \left[\frac{H_{‘}-H_f}{4}\right] \)

d) \(d=\frac{1}{2} \left[\frac{H_f-H_{‘}^{’}}{2}\right] \)

View Answer

Explanation: The average drainage path for the pressure increment is calculated from the formula of,

\(d=\frac{1}{2} \left[\frac{H_{‘}-H_f}{2}\right] \)

where, H

_{1}=initial height of the specimen under initial load

and H

_{f}=final height of the specimen under final load.

3. The logarithm of time fitting method was suggested by ______

a) Terzaghi

b) Taylor

c) Darcy

d) A.Casagrande

View Answer

Explanation: The logarithm of time fitting method was suggested by A.Casagrande in 1930. The use of square root of fitting method was suggested by Taylor in 1948. Darcy did his research in the permeability of soils.

4. In logarithm of time fitting method, the graph is drawn on a ____________

a) radial graph

b) linear graph

c) semi-log plot

d) log-log plot

View Answer

Explanation: In logarithm of time fitting method, the graph is drawn on a in which the degree of consolidation (U) or the dial readings (R) are plotted in the linear scale and the logarithm of time (log t) in the log scale.

5. The logarithm of time fitting method is based on the characteristic of ______________

a) U and T_{v}

b) U and log_{10}T_{v}

c) T_{v}

d) log_{10}T_{v}

View Answer

Explanation: The logarithm of time fitting method is based on the characteristic of U and log

_{10}T

_{v}in the intersection of the tangent at the point of inflection and the asymptote of the lower portion is at the ordinate of 100% U.

6. The primary consolidation is from _____________

a) R_{100} to R_{f}

b) R_{10} to R_{c}

c) R_{1} to R_{c}

d) R_{c} to R_{100}

View Answer

Explanation: The consolidation from R

_{c}to R

_{100}is the primary consolidation. The dial reading R

_{100}is given by extending the straight portion of curve to meet the point of 100% consolidation.

7. The secondary consolidation is from __________

a) R_{10} to R_{f}

b) R_{100} to R_{f}

c) R_{c} to R_{100}

d) R_{f} to R_{100}

View Answer

Explanation: The consolidation from R

_{100}to R

_{f}is the secondary consolidation. Usually the secondary consolidation in most of the problems is neglected because of the time it takes to consolidate.

8. For logarithm of time fitting method, the coefficient of consolidation is detained from ________

a) \(c_v=\frac{(T_v)_{70} d^3}{t_{70}} \)

b) \(c_v=\frac{(T_v)_{80} d^2}{t_{80}} \)

c) \(c_v=\frac{(T_v)_{90} d^4}{t_{90}} \)

d) \(c_v=\frac{(T_v)_{50} d^2}{t_{50}} \)

View Answer

Explanation: For logarithm of time fitting method, the coefficient of consolidation is detained from,

\(c_v=\frac{(T_v)_{50} d^2}{t_{50}}\)

where, c

_{v}=coefficient of consolidation

(T

_{v})

_{50}=time factor corresponding to 50% consolidation

t

_{50}=elapsed time for 50% consolidation

d=average drainage path for pressure increment.

9. From the coefficient of consolidation and coefficient of volume change, the coefficient of permeability is found by equation ____________

a) k=m_{v} γ_{v}

b) k=C_{v} γ_{v}

c) k=C_{v} m_{v} γ_{v}

d) k=C_{v} m_{v}

View Answer

Explanation: The coefficient of consolidation is given by the formula,

\(C_v=\frac{k}{m_vγ_v}\). Therefore, on rearranging the equation,

∴ k=C

_{v}m

_{v}γ

_{v}.

10. From the coefficient of consolidation and coefficient of compressibility, the coefficient of permeability is found by equation __________

a) \(k=\frac{γ_w}{1+e_o} \)

b) \(k=\frac{C_v a_v Aγ_w}{1+e_o} \)

c) \(k=\frac{a_v γ_w}{1+e_o} \)

d) \(k=\frac{C_v a_v γ_w}{1+e_o} \)

View Answer

Explanation: Since the coefficient of permeability is given by the equation,

k=C

_{v}m

_{v}γ

_{w}—————–(1)

The coefficient of volume change is given by,

\(m_v=\frac{a_v}{1+e_0},\) therefore substituting in (1),

\(k=\frac{C_v a_v γ_w}{1+e_o} \).

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