Geotechnical · MCQ practice Soil Consolidation MCQs – Part 2
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Part 2 of 2 Question 16 Medium
The pore water pressure in the soil sample of a consolidometer test is ______.
A maximum at bottom B maximum at center C maximum at top D minimum at center
Answer: B. maximum at center
The oedometer sample drains through porous stones at top and bottom (double drainage), so excess pore pressure is zero at the faces and highest at mid-height.
Question 17 Medium
The coefficient of compressibility of soil is the ratio of ______.
A stress to strain B strain to stress C stress to settlement D rate of loading to that of settlement
Answer: B. strain to stress
\(a_v = \Delta e/\Delta\sigma'\): a deformation (change in void ratio) per unit stress, i.e. strain to stress.
Question 18 Easy
Coefficient of consolidation is used for calculating:
A time rate of settlement B total settlement C preconsolidation pressure D stress in soil
Answer: A. time rate of settlement
\(t = T_v d^2 / c_v\): the coefficient of consolidation controls how fast settlement happens.
Question 19 Easy
The relation between coefficient of consolidation Cᵥ, time factor Tᵥ, drainage path d and time t is given by:
A Cᵥ = d²Tᵥ / t B Cᵥ = d²t / Tᵥ C Cᵥ = tTᵥ / d² D Cᵥ = Tᵥ / (t·d²)
Answer: A. Cᵥ = d²Tᵥ / t
From \(T_v = c_v t/d^2\): \(c_v = T_v d^2 / t\).
Question 20 Easy
In consolidation, time factor is defined as:
A Cᵥt / d² B Cᵥ²t / d C Cᵥt² / d D Cᵥt² / d²
Answer: A. Cᵥt / d²
\(T_v = c_v t / d^2\), a dimensionless number.
Question 21 Medium
The ultimate consolidation settlement of a structure resting on a soil:
A decreases with the increase in the initial void ratio B decreases with the decrease in the plastic limit C increases with the increase in the initial void ratio D increases with the decrease in the porosity of the soil
Answer: A. decreases with the increase in the initial void ratio
\(\Delta H = \frac{C_c H}{1+e_0}\log(\sigma'_f/\sigma'_0)\): with \(C_c\) and the other terms fixed, \(\Delta H \propto 1/(1+e_0)\), so it decreases as \(e_0\) increases.
Question 22 Easy
The rate of consolidation:
A increases with decrease in temperature B increases with increase in temperature C is independent of temperature D All the above
Answer: B. increases with increase in temperature
Warmer water is less viscous, so permeability and cv increase and consolidation proceeds faster.
Question 23 Easy
For a routine consolidation test in the laboratory, the thickness of the specimen is:
A 10 mm B 20 mm C 40 mm D 60 mm
Answer: B. 20 mm
IS 2720 (Part 15) uses a specimen 60 mm in diameter and 20 mm thick.
Question 24 Medium
The consolidation time for soils:
A increases with increasing compressibility B decreases with increasing permeability C is independent of the stress change D All of the above
Answer: D. All of the above
\(t = T_v d^2/c_v\) with \(c_v = k/(m_v\gamma_w)\): time rises with compressibility (mv ), falls with permeability (k), and does not depend on the size of the stress increment.
Question 25 Easy
The coefficient of consolidation is measured in:
A cm²/g B cm²/sec C g/cm²/sec D g-cm/sec
Answer: B. cm²/sec
\(c_v = T_v d^2/t\): Tv is dimensionless, so cv has units of length²/time, e.g. cm²/sec.
Part 2 of 2