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DFCCIL’21 CE: Daily Practice Quiz. 29-July-2021

Quiz: Civil Engineering
Exam: DFCCIL-JE
Topic: MISCELLANEOUS

Each question carries 1 mark
Negative marking: 1/4 mark
Time: 8 Minutes

Q1. Clay can be described as:
(a) Aquifer
(b) Aquitard
(c) Aquiclude
(d) None of these

Q2. Bentonite is a material obtained due to the weathering of
(a) limestone
(b) quartzite
(c) volcanic ash
(d) shales

Q3. A soil has bulk density of 22 kN/m³ and water content 10%. The dry density is
(a) 20 kN/m³
(b) 15 kN/m³
(c) 18 kN/m³
(d) 19 kN/m³

Q4. Inorganic soil with low compressibility is represented by
(a) MH
(b) SL
(c) ML
(d) CH

Q5. For a homogeneous earth dam 50 m high having 2 m free broad, a flow net was constructed and the results were: Number of potential drops = 2.4 Number of flow channels = 0.4. If coefficient of permeability of the dam material is 3 x 10-3 cm/sec, the discharge per metre length of dam, is
(a) 12 x 10-5 m^3 \/sec
(b) 24 x 10-3 m^3 \/sec
(c) 6 x 10-5 m^3 \/sec
(d) 24 x 10-5 m^3 \/sec

Q6. If σ0′ and σ’ represent initial and increased pressure ; e0 and e void ratios corresponding to initial and increased pressure ; and Cc the compression index (dimensionless), then, the virgin compression curve as expressed by Terzaghi empirical formula is
(a) e = e0 + Cc log10 σ’/σ0′
(b) e = e0 – Cc log10 σ’/σ0′
(c) e0 = e – Cc log10 σ’/σ0′
(d) e0 = e + Cc log10 σ0’/σ’

SOLUTION

S1. Ans.(c)
Sol. Aquiclude are geological formation or stratum of impervious material which do not allow of water. Clay is an example of aquiclude.

S2. Ans.(c)
Sol. Bentonite is obtained due to the weathering of volcanic ash containing high percentage of clay mineral and montmorillonite.

S3. Ans.(a)
Sol. Given,
γ_b=22 kN\/m^3
w=10%=0.1
γ_d= ?
γ_d=γ_b/(1+w)
=22/(1+0.1)
=22/1.1
▭(γ_d=20 kN\/m^3 )
S4. Ans.(c)
Sol. fine grain soil classification according to compressibility –
Compressibility Water content Symbol
Low compressible W_L<35% L
Intermediate compressible 35%< W_L<50% I
High compressible W_L>50% H

In ML = inorganic silt with low compressibility
S5. Ans.(d)
Sol. Given,
Coefficient of permeability (k) = 3×10^(-3) cm\/sec = 3×10^(-5) m\/sec
Height of water head (H) = 50-2=48 m.
No. of potential drop (N_d )=2.4
No. of flow channels (N_F) = 0.4
Now,
Discharge per meter length of dam(q) = KH NF/Nd
=3×10^(-5)×48×0.4/2.4
=24×10^(-5) m^3 \/sec

S6. Ans.(b)
Sol. the virgin compression curve as expressed by Tarzaghi empirical formula is
▭(e=e_o-C_C log_10 σ^’/(σ_0^’ ) )
Where e = void ratio corresponds to increased pressure
e_O = Void ratio corresponds to initial pressure
C_C = compression index
σ^’= increased pressure
σ_0^’ = initial pressure

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