a) Both A and R are true and R is the correct
explanation of A
b) Both A and R are true but R is not a correct
explanation of A
c) A is true but R is false
d) A isfalse but R is true
421. Assertion A : At depth Z below the surface of a submerged soil, water
pressure is γ𝓌 Z and it is the stress caused by the water which is called the "neutral stress".
Reason R : The water pressure acts equally in all directions and transmits the
same fully on grain to grain contact causing compression in the soil.
422. Assertion A : The safe height (2Z₀) to which an unsupported vertical cut in clay can be made is 4C/γ
Reason R : Active earth pressure of cohesive backfill shows that the negative
pressure (tension) is developed at top level. This tension decreases to zero at
depth Z₀ and total net pressure up to a depth 2Z₀ is zero a
423. Assertion A : Negative skin friction will act on piles in filled up soils, which should be considered in design of pile foundations.
Reason R : The filled up soils start consolidating and develop a drag force on
the pile a
424. Assertion A : Constant-head permeability test is not used for fine-grained soils.
Reason R :The lesser the permeability of the soil, lesser is the discharge
425. Assertion A : In box shear test, the failure plane is predetermined and is
Reason R : The shear stress is applied in the vertical direction
426. Assertion A : In the case of sand deposits with uniform density, N values are found to increase with depth.
Reason R : Overburden pressure increases with depth below ground level.
427. Assertion A : In the case of unconfmed compression test, Mohr's circle passes
through the origin.
Reason R : The major principal stress is zero.
428. Assertion A : Permeability continues to decrease with the increase in dry density of a compacted soil.
Reason R : Soil particles in water surroundings may be mutually attracted or
429. Assertion A : For a fully saturated soil, the pore pressure parameter is equal to
Reason R : The compressibility of water is much smaller than the coefficient
of volume compressibility.
430. Assertion A : Wash boring is recom mended to obtain undisturbed soil sample above ground water table.
Reason R : In wash boring, water pumped through the hollow drill rods
emerges through the ports of the chopping bit carrying disintegrated soil fragment. d
431. Assertion A : Terzaghi's theory of consolidation considers only primary
Reason R : Secondary consolidation takes place only at the end of the primary
432. Assertion A : Mohr's circle for unconfmed compression test passes
through the origin.
Reason R : In an unconfmed compression test, the axial stress is equal to confining stress c
433. Assertion A : Secondary consolidation takes place at a rate much slower than that of primary consolidation..
Reason R : There is dissipation of excess pore water pressure during secondary consolidation. a
434. Assertion A : The ratio of operating frequency of machine 'f and natural
frequency of foundation soil system 4fₙ should be either less than 0.5 or more than 1.5.
Reason R : The high amplitude caused during resonance (f = fₙ) would damage
the delicate parts of the machine. a
435. Assertion A : When a saturated soil mass is subjected to consolidation, its volume at any instant is related to the total stress.
Reason R : Total stress is equal to the sum of the effective stress and pore water
436. Assertion A : Highly plastic swelling type of clay can be best stabilized by
using lime as admixture.
Reason R : Absorption of water by lime in the soil improves its shear
437. Assertion A : The load carrying capacity of bored cast in-situ pile in a sandy soil is much less than that of a driven pile of similar dimensions.
Reason R : A drive pile generates much more point bearing resistance than a
bored pile a
438. Assertion A : The phenomenon of quicksand occurs mostly in coarse sands
Reason R : Quicksand condition does not occur in clayey soils as their cohesion
holds the grains together even under upward flow at critical hydraulic gradient