Soil Mechanics - Compressibility of Soil, Consolidation & Compaction

1. In case of single drainage, the maximum distance that water has to travel to reach a drainage face(length of longest drainage path) is equal to
(a) thickness of clay layer
(b) double the thickness of clay layer
(c) half the thickness of clay layer
(d) none of these

2. The identical clay samples of the same size, designed as “A” and “B” are subjected to consolidation tests under identical loading conditions. Drainage takes place through one face in sample “A” and through both faces in sample “B”. 50% consolidation of sample “A” occurs in 10 minutes. The time required for 50% consolidation to occur in sample “B” will be
(a) 40 minutes
(b) 10 minutes
(c) 5 minutes
(d) 2.5 minutes (IES 1995)

3. A clay layer 5 m thick in field takes  300 days to attain 50% consolidation with condition of double drainage. If the same clay layer is underlain by hard  rock then the time taken to attain 50% consolidation will be
(a) 300 days
(b) 600 days
(c) 900 days
(d) 1200 days (IES 1996)
Hint: {T_v} = \frac{{{C_v}t}}{{{H^2}}}

4. A saturated clay layer with double drainage takes 5 years to attain 90% degree of consolidation under a structure. If the same layer were to be single drained, what would be the time(in years) required to attain the same consolidation under the same loading conditions?
(a) 10
(b) 15
(c) 20
(d) 25 (IES 2001)
Hint: \frac{{{t_2}}}{{{t_1}}} = {\left( {\frac{{{d_2}}}{{{d_1}}}} \right)^2}

5. In Terzaghi’s theory, non dimensional factors is/are
(a) drainage path
(b) time factor(Tv)
(c) degree of consolidation
(d) all these

6. Time factor({T_v}) is given by
(a) {T_v} = \frac{{{C_v}t}}{H}
(b) {T_v} = \frac{t}{H}  
(c) {T_v} = \frac{{{C_v}}}{H}  
(d) {T_v} = \frac{{{C_v}t}}{{{H^2}}}
Where {C_v} is coefficient of consolidation and H is the maximum distance that water has to travel to reach a drainage face.

7. A standard Oedometer test in the laboratory indicated that a 0.02 m thick clay specimen took 0.5 day to undergo 90% primary consolidation. How many days will a 2 m thick layer of identical clay sandwitched between sand layers and subjected to an identical stress increment take to undergo the same?
(a) 100 days
(b) 500 days
(c) 5000 days
(d) 10,000 days (GATE 1992)

8. Degree of consolidation(or consolidation ratio) is given as
(a) \frac{{{u_i} - {u_z}}}{{{u_i}}}
(b) \frac{{{u_z} - {u_i}}}{{{u_i}}}  
(c) {u_i} - {u_z}  
(d) none of these
Where {u_i} is initial excess pore water pressure.

9. Time factor({T_v}) is directly proportional to
(a) time elapsed(t)
(b) coefficient of consolidation, {C_v}
(c) maximum distance that water has to travel to reach a drainage face, H
(d) all these

10. Time factor {T_v} = (\pi /4){U^2}  when
(a) U  > 50%
(b) U ≤ 60%
(c) U > 60%
(d) U ≤ 50%


    1. (a)    2. (d)    3. (d)    4. (b)    5. (d)
    6. (d)    7. (c)    8. (a)    9. (a)    10. (b)

These questions are taken from the book "Objective Questions (Civil Engineering)". The Kindle edition of this book is available at just ₹ 99/- only! 


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