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# Soil Mechanics (381-400)

Updated: Apr 28, 2020

381. Phreatic line in an earth dam is

1. the topmost flow line with zero water pressure.

2. approximately a parabola

382. A soil has mass unit weight r, water content w (as ratio). The specific gravity

of soil solids = G, unit weight of water = r𝓌 , 'S', the degree of saturation of the soil

is given by 383. Shear failure of soils takes place when the angle of obliquity is maximum

384. A triaxial test was conducted on a granular soil. At failure σ₁/σ₃ = 4. The effective minor principal stress at failure was 100 kPa. The values of approximate Φ and the principal stress difference at failure are, respectively

37°and 300 kPa

385. In a Mohr's diagram, a point above Mohr's envelope indicates

imaginary condition

386. Consider the following statements:

Ranking's theory and Coulomb's theory give same values of coefficients of active

and passive earth pressures when

1. the retaining wall has a vertical back.

2. the backfill is cohesionless.

3. angle of slope of backfill is 0°.

4. angle of wall friction δ is 0°

387.

1. Any movement of retaining wall away from the fill corresponds to active

earth pressure condition.

388. A rectangular footing LxB is to be placed at a depth D below ground level such that D/B < 2.5. The factor N𝒸 to be used in deciding on the allowable bearing capacity for the footing as given by Skempton is calculated using the equation (where N c =NC for rectangular footing, N𝒸ₛ = N𝒸 at surface) 389. Consider the following statements associated with local shear failure of soils:

1. Failure is sudden with well-defined ultimate load.

2. Failure is preceded by large settlement.

390. Minimum centre to centre spacing of friction piles of diameter (D) as per BIS

code is 3D

391. A good quality undisturbed soil sample is one which is obtained using a sampling tube having an area ratio of 8%

392. Which one of the following tests cannot be done without undisturbed sampling? shear strength of clay

393. Consider the following statements: The Standard Penetration Test (SPT) in

soils is the most commonly used field test. SPT is used to determine

1. relative density of sands.

2. drained shear strength of fine loose sand

394. 395.

A.Stability of a clay foundation of an embankment, whose rate of construction is such that some consolidation occurs-Consolidated undrained test B. Initial stability of a footing on saturated clay- n-rained riaxial est C. Long-term stability of a slope in stiff, fissured clay-Drained triaxial test D. Foundation on soft marine clay deposits- Quick vane shear test

396. If an unconfined compressive strength of 4 kg/cm2 in the natural state of clay

reduces by four times in the remoulded state, then its sensitivity will be 4

397.In a direct shear test, the shear stress and normal stress on a dry sand sample at failure are 0.6 kg/cm² and 1 kg/cm² respectively. The angle of internal friction

of the sand will be nearly 31°

398.If an infinite slope of clay at a depth 5 m has cohesion of 1 t/m² and unit wt. of 2 t/m³ ,then the stability number will be 0.1

399.Which one of the following typical pressure distribution diagrams (Fig. 8.26)

represents the lateral pressure distribution on braced sheeting in stiff clay with temporary support, as given by Tschebotarioff? 400.Given that c = 2 t/m² , Φ = 0° and γ = 2t/m³ the depth of tension crack developing in a cohesive soil backfill would be 2 m