This set of Soil Mechanics Multiple Choice Questions & Answers (MCQs) focuses on “Drainage and Dewatering – Shallow and Deep Well System”.
1. The soil deposits may be divided into _________ classes according to consolidation theory.
a) 1
b) 2
c) 3
d) 4
View Answer
Explanation: The soil deposits may be divided into three classes according to consolidation theory. The three classes are pre-consolidated, normally consolidated and under consolidated soils.
2. A clay is not said to be ___________ if it has been subjected to a pressure in excess of its present overburden pressure.
a) normally consolidated
b) pre-consolidated
c) over- consolidated
d) pre- compressed
View Answer
Explanation: A normally consolidated specimen is one which has never been subjected to an effective pressure greater than the existing overburden pressure. Thus, a clay is said to be pre-consolidated, over- consolidated or pre- compressed if it has been subjected to a pressure in excess of its present overburden pressure.
3. Pre-consolidated pressure is the pressure subjected in ________
a) past
b) present but not future
c) future but not present
d) present but not past
View Answer
Explanation: Pre-consolidated pressure is the pressure subjected in the past. It is a overburden pressure to which a soil has been subjected and under which it got consolidated. An example can be glaciers on soil which got melted.
4. The temporary over burden pressure to which a soil has been subjected and under which it got consolidated is known as ________
a) normally consolidation pressure
b) pre- consolidation pressure
c) under- consolidation pressure
d) pre- compression pressure
View Answer
Explanation: The temporary over burden pressure to which a soil has been subjected and under which it got consolidated is known as pre- consolidation pressure. Pre-consolidated pressure is the pressure subjected in the past.
5. The example of pre-consolidation pressure is _____________
a) ice sheet or glacier
b) desert soil
c) sea soil
d) marine soil
View Answer
Explanation: Since the pre-consolidation pressure is known as the temporary over burden pressure to which a soil has been subjected and under which it got consolidated, ice sheet or glacier is an example of it. This is because the glaciers put a lot load on the soil before its melt.
6. A soil that is not fully consolidated is called ___________
a) normally consolidated
b) pre-consolidated
c) over- consolidated
d) under-consolidated
View Answer
Explanation: If the initial vertical effective stress is greater than the pre-consolidated stress then the soil will be under consolidated soil. It means that the soil is still in the process of consolidating under a previously applied load. Therefore, a soil that is not fully consolidated is called under-consolidated.
7. ___________ soil has never been subjected to an effective pressure greater than existing over-burden pressure and has completely consolidated.
a) normally consolidated
b) pre-consolidated
c) under- consolidated
d) pre- compressed
View Answer
Explanation: A soil that has never experienced a vertical effective stress that was greater than its present vertical effective stress is called a normally consolidated (NC) soil.
8. In case of normally consolidated and pre-consolidated soils, it is not fully consolidated under existing over-burden pressure.
a) True
b) False
View Answer
Explanation: In case of normally consolidated and pre-consolidated soils, it is fully consolidated under existing over-burden pressure. Whereas the under-consolidated soil is the one that has not fully consolidated.
9. To find pre-consolidation pressure, __________ sample is used.
a) undisturbed clay
b) disturbed clay
c) gravel
d) sand gravel
View Answer
Explanation: To find the pre-consolidation pressure, undisturbed clay is used. The disturbed samples can have drastic effects on the pre-consolidation pressure. The effect of sample disturbance on the values of pre-consolidation pressure can be shown by using Schmertmann method.
10. To find pre-consolidation pressure, __________ relationship in graph is plotted.
a) voids ratio and effective pressure
b) effective pressure and total pressure
c) effective pressure and pore pressure
d) total pressure and total pressure
View Answer
Explanation: To find pre-consolidation pressure, voids ratio and effective pressure relationship in graph is plotted.
11. To find pre-consolidation pressure, __________ graph is used.
a) hexagonal paper
b) semi-log graph
c) log-log graph
d) normal probability paper
View Answer
Explanation: To find pre-consolidation pressure, semi-log graph is used. In this type, the voids ratio is plotted in a linear scale and the effective pressure or the applied pressure is plotted in the logarithmic scale.
12. In finding pre-consolidation pressure, initial portion of curve resembles ___________
a) recompression curve of remolded sample
b) swelling curve
c) expansion curve
d) laboratory virgin curve
View Answer
Explanation: In finding pre-consolidation pressure, initial portion of curve is flat and resembles the recompression curve of the remolded sample.
13. In finding pre-consolidation pressure, the lower portion of the curve is ________________
a) parabolic curve
b) swelling curve
c) expansion curve
d) straight line
View Answer
Explanation: In finding pre-consolidation pressure, the lower portion of the curve approximates to a straight line.
14. Who founded the method of determination of pre-consolidation pressure?
a) Casagrande
b) Appuswamy
c) Falcon India
d) Darcy
View Answer
Explanation: Casagrande in 1936 gave the empirical method for finding the per-consolidation pressure. He selected a point in the graph that has the minimum radius and drew tangents to it. The bisecting point gives the pre-consolidation pressure.
15. In determination of pre-consolidation pressure, ___________ point of virgin curve is selected.
a) maximum curvature
b) maximum radius
c) minimum curvature
d) initial point
View Answer
Explanation: The point A of maximum curvature or minimum radius is selected and horizontal line AB is drawn. Tangent AC is drawn and also the bisector AD. The straight portion of the virgin curve is extended back to meet the bisector at point P. The point P corresponds to pre-consolidating pressure.
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