Smith Albert Edu world : 2016

Monday, May 23, 2016

Electrical Machines - Mixed Bag

Answer the following in brief:
1. Why do round rotor synchronous generators have small diameters and large axial length of core?
2. Why does open circuit synchronous machine have curved shape?
3. Do slot harmonics affect the torque-speed curve of a three-phase induction motor?
4. Why are brushes of a d.c. machine made of carbon?
5. Why are interpoles used in a d.c. machines?
6. What is the all-day efficiency of a transformer?
7. Why are core-type transformer used in high-voltage circuits?
8. How are iron losses in a transformer made very small?

Answers
1. Synchronous generators of round rotor types are designed mostly of 2 pole type running al 3000 rpm. They are designed for lower values of diameter in order to limit the centrifugal forces which have a profound influence on the design, to get the designed value of ${D^2}L$ for a given output. the length of core is therefore required to be kept large.

2. The o.c.c. of a synchronous machine have a curved shaped because of saturation of magnetic core. At low values If when iron is unsaturated. the o.c.c. is almost linear but high values of If magnetic core gels saturated, hence the o.c.c. becomes curved.

3. A three phase winding carrying a sinusoidal currents produces harmonics of the order of n = 6N $\pm$ 1, N is an integer. The movement of the harmonics is with or against the direction of the rotation depending upon the sign. These harmonics produce torque of the same, general torque slip shape as that of fundamental but with synchronous speed corresponding to that harmonics. Thus, the torque slip characteristics will get affected.

4. The function of brushes is to collect current from commutator.

5. Inter poles are used in d.c. machines to balance or to nullify the effect of cross-magneting component of armature reaction field.

6. All Day Efficiency = output in kWh in 24 hours/input in kWh in 24 hours

7. High voltage transformers are designed with core type construction because this provides easy maintenance and tappings can be provided more conveniently.

8. Transformers are having been made of core of superior quality and thin laminations, has lesser eddy current losses and having selecting a soft magnetic material will have low hysteresis loss and hence iron losses can be made small.

(These questions are taken from AMIE exams.)

Tuesday, May 17, 2016

Electrical Machines - Mixed Bag

Answer the following in brief:
1. Why is in a normal synchronous machine Xq smaller than Xd?
2. Resistance of dampers for synchronous generators is lower than that of dampers for synchronous motors. Why?
3. What is meant by an infinite bus?
4. Distribution transformers are designed for lower iron losses. Why?
5. What are the functions of transformer oil?
6. Do we use laminations for all iron parts of an electrical machine. If not, why?
7. Explain why in an induction motor a high value of rotor resistance is preferred at starting?
8. Why is an ordinary induction motor not started at normal voltage?
9. Why is the rotor core loss almost absent in normal operating condition of an induction motor?
10. Why is star-delta starter not suitable for high voltage induction motor?

Answers

The quadrature axis reactance in a salient pole machine is smallest than the direct axis reactance, because a given current component in that axis gives rise to smaller flux, the reluctance of the magnetic path including the interpolar spaces.
In synchronous generators, damper winding is provided to suppress the negative sequence field and to damp the oscillations when the machine starts hunting, hence, damper winding has lowest value. In synchronous motors the function of damper winding is to provide starting torque and to develop damping power when the machine starts hunting hence, it is designed to have high resistance.
The terminal voltage and its frequency is held constant independent of load drawn from the bus. then the bus is called infinite bus.
Distribution transformer are kept on for 24 hours even if load is there or not. hence continuously iron losses takes place, therefore these are designed for low value of iron losses.
Functions of transformer oil are (a) To create insulation to insulated conductors and coils. (b) To provide cooling medium to dissipate or carryover heat to the tank walls.
We make use of laminations for those iron pans only in which fluctuations of flux takes place. For all those parts, where, there are no fluctuations, no eddy currents are included, hence laminations arc not provided.
By adding external resistance to the rotor circuit, the starting torque of the motor is increased as a result of improved power factor.
An ordinary motor if. started at normal voltage, will draw very high starting current, which may be 5 to 7 times the full load current and hence motor may be damaged.
In normal operating conditions of an induction motor, frequency of induced rotor emf and hence, rotor current is small. This will have very small value of iron losses because hysteresis and copper losses are both dependent on frequency.
Star-delta starter is not suitable for voltage exceeding 3000 V because of the excessive number of stator turns needed for delta connection.

(Author is associated with www.amiestudycircle.com)

Friday, May 13, 2016

Soil Mechanics - Permeability of Soil

Q.1. In terms of permeability of soil, following statement is true

(a) clays>silts>sands

(b) silts>sands>clays

(d) none of these

Q.2. Match List-I with List-II and select correct answer by using the codes given below the lists.

List-I

A. Gravels

B. Sand

C. Silt

D. Clays

List-II

1. 10^-7 cm/sec.

2. 10^-6 cm/sec.

3. 10^-1 cm/sec.

4. 10 cm/sec.

(a) A1,B2,C3,D4

(b) A3,B4,C1,D2

(d) A2,B4,C3,D1 (IES 1992)

Q.3. Constant head permeameter is used to test permeability of

(a) silt

(b) clay

(d) fine sand

Q.4. Falling head permeameter is used to test permeability of

(a) silt

(b) clay

(d) all these

Q.5. For practically impervious type of soil, the coefficient of permeability is determined using

(a) variable head test

(b) constant head test

(d) pumping test (IES 1993)

Q.6. Using falling head permeameter, value of permeability(k) is determined from the formula

(a) $\frac{{a.L}}{{A({t_2} - {t_1})}}.{\log _e}\frac{{{h_2}}}{{{h_1}}}$

(b) $\frac{{a.L}}{{A({t_2} - {t_1})}}.{\log _e}\frac{{{h_1}}}{{{h_2}}}$

(d) $\frac{{a.L}}{{A({t_2} - {t_1})}}.{\log _{10}}\frac{{{h_2}}}{{{h_1}}}$

Where t₂ - t₁ is the time taken for the head to fall from h₁ to h₂, A is cross-sectional area of sample, a is cross-sectional area of the standpipe and L is height of sample.

Q.7. If during a permeability test on a soil sample with a falling head permeameter, equal time intervals are noted for drop of head from h₁ to h₂ and again from h₂ to h₃, then which one of the following relations would hold good?

(a) h₁² = h₂h₃

(b) h₂² = h₁h₃

(d) none of these (IES 1995)

Q.8. In an unconfined flow pumping test, acquifer is

(a) underlain by permeable stratum

(b) underlain by impermeable stratum

(d) none of these

Q.9. In a confined flow pumping test, acquifer is

(a) underlain by impermeable stratum

(b) underlain by permeable stratum

(d) contained between impermeable strata, above and below

Q.10. In an unconfined flow pumping set, pumping generates a radial flow

(a) towards the filter well

(b) beyond filter well

(d) towards impermeable stratum

Answers:

1. c

2. c

3. c

4. d

5. d

6. b

7. b

8. b

9. d

10. a

Tuesday, April 26, 2016

Soil Mechanics - Classification of Soils

Q.1. Soils transmitted by the wind are called
(a) alluvial soil
(b) residual soil
(c) aeolin soil
(d) marine soil (AMIE Summer2000)

Q.2. A fine-grained soil transported by water and deposited at the bottom of the lake is
(a) lacustrine soil
(b) alluvial soil
(c) loess
(d) dune sand (IES 1996, AMIE Summer98)

Q.3. Match List I with List II and select the correct answer using the codes given below the lists:
List I (Type of Soil)
A. Lacustrine soil
B. Alluvial soil
C. Aeolin soil
D. Marine soil

List II (Mode of transportation and deposition)
1. Transportation by the wind
2. Transportation by running water
3. Deposited at the bottom of lakes
4. Deposited in sea water

(a) A1,B2,C3,D4
(b) A3,B2,C1,D4
(c) A3,B2,C4,D1
(d) A1,B3,C2,D4 (IES 1995)

Q.4. The description �sandy silty clay� signifies that
(a) the soil contains unequal proportions of three constituents such that sand > silt > clay
(b) the soil contains equal proportions of sand, silt and clay
(c) the soil contains unequal proportions of the three constituents such that clay > silt > sand
(d) there is no information regarding the relative proportions of the three (GATE 1992)

Q.5. The shape of clay particle is usually
(a) angular
(b) flaky
(c) tubular
(d) rounded (GATE 1997)

Q.6. The swelling nature of black cotton soil is primarily due to the presence of
(a) Kaolinite
(b) Illite
(c) Montmorillonite
(d) Vermiculite (GATE 1993)

Q.7. The consistency of a saturated cohesive soil is affected by
(a) particle size distribution
(b) density index
(c) coefficient of permeability
(d) water content (GATE 1995)

Q.8. According to IS code, size of particles of silt will be between
(a) 0.075 mm and 4.75 mm
(b) 0.002 mm and 0.075 mm
(c) 0.001 mm and 0.06 mm
(d) 0.075 mm and 0.275 mm (AMIE Summer2000)

Q.9. Coefficient of curvature(Cc) is defined as
(a) $\frac{{{D_{30}}{D_{10}}}}{{{D_{60}}^2}}$
(b) $\frac{{{D_{10}}^2}}{{{D_{60}}{D_{30}}}}$
(c) $\frac{{{D_{30}}^2}}{{{D_{60}}{D_{10}}}}$
(d) $\frac{{{D_{60}}^2}}{{{D_{30}}{D_{10}}}}$

Q.10. Coefficient of uniformity(Cu) is
(a) D60/D10
(b) D10/D60
(c) D60/D30
(d) D60.D10 (AMIE Summer98)

Answers
1. c
2. a
3. b
4. c
5. b
6. c
7. d
8. b
9. c
10. a

Wednesday, April 20, 2016

Soil Mechanics - Classification of Soils

Q.1. In soil classification, SP stands for
(a) well-graded soil
(b) poorly graded sands
(c) well graded sands
(d) inorganic clay (AMIE Summer99)

Q.2. Based on grain distribution analysis, the D10, D30 and D60 values of a given soil are 0.23 mm, 0.3 mm, and 0.41 mm respectively. As per IS code, the soil classification will be
(a) SW
(b) SP
(c) SM
(d) SC (IES 2001)

Q.3. In soil classification, MH stands for
(a) inorganic silts of high compressibility
(b) organic silt of high compressibility
(c) well graded clay
(d) poorly graded clay (AMIE Summer99)

Q.4. Match list I(different types of soil) with List II(group symbols of I.S. classification) and select answer using codes given below the lists.
List I
A. Well graded gravel-sand mixture with little or no fines
B. Poorly graded sands or gravelly sand with little or no fines
C. Inorganic silts and very fine sands or clayey silts with low plasticity
D. Inorganic clays of high plasticity
List II
1. ML
2. CH
3. GW
4. SP
(a) A3,B1,C4,D2
(b) A3,B4,C1,D2
(c) A2,B4,C1,D3
(d) A2,B1,C4,D3 (IES 1994)

Q.5. A soil has a liquid limit of 45% and lies above the A-line when plotted on a plasticity chart. The group symbol of the soil as per IS soil classification is
(a) CH
(b) CI
(c) CL
(d) MI (IES 1997)

Q.6. Match List-I(soils) with List-II(group symbols) and select the correct answer using the codes given below the lists:

List-I
A. clayey gravel
B. clayey sand
C. organic clay
D. silty sand

List-II
1. SM
2. OH
3. SC
4. GC
(a) A3,B4,C2,D1
(b) A4,B3,C1,D2
(c) A4,B3,C2,D1
(d) A3,B4,C1,D2 (IES 2000)

Q.7. Consider the following statements in the context of aeolian soils:
1. The soil has low density and low compressibility.
2. The soil is deposited by the wind.
3. The soil has large permeability.
Of these statements
(a) 1,2 and 3 are correct
(b) 2 and 3 are correct
(c) 1 and 3 are correct
(d) 1 and 2 are correct (IES 1997)

Q.8. The structure of clay mineral as represented in the following figure is

(a) Illite
(b) montmorillonite
(c) silica
(d) rock

Q.9. The structure of clay mineral as represented in the following figure is of

(a) Illite
(b) montmorillonite
(c) silica
(d) rock

Q.10. When the product of rock weathering are not transported as sediments but remained in place, the soil is
(a) alluvial soil
(b) residual soil
(c) glacial soil
(d) aeolian soil

Answers:

1. b

2. b

3. a

4. b

5. b

6. c

7. b

8. a

9. b

10. b

Friday, April 15, 2016

Soil Mechanics - Soil Classification

Q.1. For a soil sample, degree of shrinkage is less than 5%. The quality of the soil sample is
(a) poor
(b) very poor
(c) medium good
(d) good

Q.2. A soil having particles of nearly the same size is known as
(a) well graded
(b) uniformly graded
(c) poorly graded
(d) gap graded (GATE 1995)

Q.3. The particles size distribution curves are extremely useful for the classification of
(a) fine grained soils
(b) coarse grained soils
(c) both coarse grained and fine grained soils
(d) silts and clays (GATE 1996)

Q.4. Unified soil classification is based on
(a) grain size
(b) plasticity
(c) both(a) and (b)
(d) neither (a) nor (b)

Q.5. A soil is described by GP. the soil is
(a) silty soil
(b) inorganic soil
(c) poorly graded gravel
(d) low plasticity organic silt

Q.6. A soil is described by CI. The soil is
(a) poorly graded soil
(b) silty soil
(c) inorganic clay*
(d) none of these

Q.7. A soil is described as ML. The soil is
(a) well graded soil
(b) plastic fines soil
(c) peat
(d) low plasticity silt

Q.8. In Unified soil classification system, primary letters M, O and Pt stand for
(a) clay, sand and peat respectively
(b) organic, silt and peat
(c) silt, organic and peat
(d) none of these

Q.9. In Unified soil classification system, secondary letter M stands for
(a) well graded
(b) poorly graded
(c) Non-plastic fines
(d) low plasticity

Q.10. In Unified soil classification system, secondary letter
(a) W stands for well graded
(b) C stands for plastic fines
(c) L stands for low plasticity
(d) all of the above

Answer:
1. d
2. b
3. c
4. c
5. c
6. c
7. d
8. c
9. c
10. d

Friday, April 8, 2016

Soil Mechanics - Basic Concepts

Q.1. If activity number of a soil sample is greater than 1.40, the soil would be
(a) active
(b) subjected to volume change
(c) both (a) and (b)
(d) neither (a) nor (b)

Q.2. If plasticity index is greater than 17%, the soil is
(a) plastic
(b) less plastic
(c) highly plastic
(d) stiff

Q.3. Data for a given soil sample is: Liquid limit = 60 %; Plastic limit = 30%; Flow index = 27. Toughness index of the soil will be
(a) 1.11
(b) -1.11
(c) 0.9
(d) -0.9

Q.4. Liquid index of a soil in semi-solid state would be
(a) 0
(b) 1
(c) >1
(d) negative

Q.5. Liquid index of a soil in solid state would be
(a) 0
(b) 1
(c) >1
(d) negative

Q.6. Liquid index of a soil in very stiff state, would be
(a) 0
(b) 1
(c) >1
(d) <0
Q.7. Liquidity index of a soil sample in soft state will be equal to
(a) 0
(b) 1
(c) <1
(d) >1

Q.8. Liquid index of a soil sample in liquid state(when disturbed) will be equal to
(a) 0
(b) 1
(c) <1
(d) >1

Q.9. The maximum possible value of Group Index for a soil is
(a) 20
(b) 30
(c) 40
(d) 50 (GATE 1991)

Q.10. When the natural moisture content of a soil is equal to its plastic limit, its liquidity index is equal to
(a) 0%
(b) 50%
(c) 75%
(d) 100% (AMIE Summer2000)

Answer:
1. c
2. c
3. a
4. d
5. d
6. a
7. b
8. d
9. a
10. a

Thursday, March 17, 2016

Soil Mechanics - Basic Concepts

Q.1. Activity of a clay is given by
Activity = N/clay formation(%), here N stands for
(a) liquidity index
(b) plasticity index
(c) flow index
(d) none of these (AMIE Summer99)

Q.2. Lists I and II contain respectively terms and expressions related to soil classifications. Match the two lists and select the correct answer using the codes given below.

List I
A. Activity number
B. Liquidity index
C. Sensitivity

List II
1. $\frac{{Liquid\,\lim it - water\,content}}{{plasticity\,index}}$
2. $\frac{{plasticity\,index}}{{percentage\, < \,2\,microns}}$
3. (Natural water content - plastic limit)/plasticity index
4. Unconfined compressive strength of undisturbed soil sample divided by unconfined compressive strength of remoulded soil sample
(a) A1,B3,C4
(b) A1,B2,C3
(c) A3,B2,C1
(d) A2,B3,C4 (IES 1993)

Q.3. The plasticity index and the percentage of grain size finer than 2 microns of a clay sample are 25 and 15 respectively. Its activity ratio is
(a) 2.5
(b) 1.67
(c) 1.0
(d) 0.6 (IES 2001)

Q.4. 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
(a) 1
(b) 2
(c) 4
(d) 8 (IES 1999)

Q.5. A soil has a liquid limit of 60%; plastic limit of 35% and shrinkage limit of 20% and it has a natural moisture content of 50%. The liquidity index of soil is
(a) 1.5
(b) 1.25
(c) 0.6
(d) 0.4 (IES 1996)

Q.6. A soil has plasticity index equal to 34%. It has 23% particles having size less than 2 micron.Its activity number would be
(a) 0.67
(b) 1.48
(c) -0.12
(d) none of these

Q.7. The liquid limit and plastic limit of a sample are 65% and 29% respectively. The percentage of the soil fraction with grain size finer than 0.002 mm is 24. The activity ratio of the soil sample is
(a) 0.5
(b) 1.00
(c) 1.50
(d) 2.00 (IES 1995)

Q.8. In a soil sample, dia. of 60% size = 0.0060 mm and dia of 10% size = 0.0005 mm. Its uniformity coefficient will be
(a) 12
(b) .83
(c) 0.08
(d) none of these

Q.9. Data for a given soil sample is: liquid limit = 49.1%; Plastic limit = 26.5 % and natural water content is 45.6%. Consistency index of the soil would be
(a) 0.845
(b) 0.1545
(c) 6.45
(d) none of these

Q.10. A sample of soil has the following properties:
Liquid limit = 45%
Plastic limit = 25%
Shrinkage Limit = 17%
Natural Moisture Cont. = 30%
The consistency index of soil is
(a) 15/20
(b) 13/20
(c) 8/20
(d) 5/20 (IES 1994)

Answer:

1. b

2. d

3. b

4. c

5. c

6. d

7. c

8. a

9. b

10. b

(Author is associated with www.amiestudycircle.com)

Saturday, March 12, 2016

Soil Mechanics - Basic Concepts

Q.1. On flow curve, liquid limit is water content corresponding to
(a) 10 blows
(b) 15 blows
(c) 25 blows
(d) 50 blows

Q.2. The following data were obtained from a liquid limit test conducted on a soil sample.

Liquid limit would be
(a) 63.1
(b) 62.8
(c) 61.9
(d) 60.6 (GATE 2002)

Q.3. $\frac{{{w_2} - {w_1}}}{{{{\log }_{10}}{N_1} - {{\log }_{10}}{N_2}}}$ is called
(a) toughness index
(b) liquidity index
(c) consistency
(d) flow index
Where N stands for the number of blows and w stands for water content.

Q.4. $\frac{{{w_n} - {w_p}}}{{{I_p}}}$ is called
(a) liquidity index
(b) flow index
(c) liquidity index
(d) consistency index
Where wn is natural water content.

Q.5. $\frac{{{w_1} - {w_n}}}{{{I_p}}}$ is called
(a) toughness index
(b) liquidity index
(c) consistency index
(d) flow index
where Ip is plasticity index. wl is water content at liquid limit. (GATE 1997)

Q.6. ${w_n} - {w_p}$ is called
(a) plasticity index
(b) toughness index
(c) flow index
(d) none of these
Where wn is natural water content. wp is water content at plastic limit.

Q.7. A soil sample contains wn = 62%, wl = 24% and wp = 28%. Plasticity index will be
(a) 34%
(b) -0.12
(c) 1.48
(d) none of these

Q.8. A soil sample contains wn(natural water content) = 62%, wl(water content at liquid limit) = 24% and wp(water content at plastic limit) = 28%. Liquidity index will be
(a) 34%
(b) -0.12
(c) -0.24
(d) +0.12

Q.9. A soil has a liquid limit of 40% and plasticity index of 20%. The plastic limit of the soil is
(a) 20%
(b) 30%
(c) 40%
(d) 60% (IES 2000)

Q.10. The Atterberg limits of a clay are 38%, 27% and 24.5%. Its natural water content is 30%. The clay is in
(a) solid state
(b) semi solid state
(c) liquid state
(d) plastic state (GATE 1994)

Answers

1. c

2. c

3. d

4. c

5. c

6. a

7. a

8. b

9. a

10. d
(Author is associated with www.amiestudycircle.com)

Friday, March 11, 2016

Soil Mechanics - Basic Concepts

Q.1. The standard plasticity chart to classify fine-grained soils shown in the given figure:

The area marked �X� represents
(a) silt of low plasticity
(b) clay of high plasticity
(c) organic soil of medium plasticity
(d) clay of intermediate plasticity (IES 1996)

Q.2. Water content at the boundary between plastic state and liquid state of a given soil sample is called
(a) liquid limit
(b) plastic limit
(c) shrinkage limit
(d) none of these

Q.3. The moisture content of a clayey soil is gradually decreased from a large value. What will be the correct sequence of the occurrence of the following limits?
1. Shrinkage limit
2. Plastic limit
3. Liquid limit
Select the correct answer using the codes given below:
(a) 1,2 and 2
(b) 1,3 and 2
(c) 3,2 and 1
(d) 3,1 and 2 (IES 1997)

Q.4. In a liquid state, shear strength of a soil is
(a) infinite
(b) 1
(c) <1
(d) 0

Q.5. The soil can be moulded in any shape in
(a) liquid state
(b) solid state
(c) plastic state
(d) natural state

Q.6. The soil loses its plasticity in
(a) liquid state
(b) solid state
(c) semi-solid state
(d) natural state

Q.7. At shrinkage limit, when water content is further reduced in a soil sample, volume of soil
(a) decreases
(b) increases
(c) remains unaltered
(d) first increases then decreases (GATE 1998)

Q.8. When a graph is plotted between number of blows(N) on log scale on x-axis and water content on y-axis, we get
(a) plasticity index curve
(b) toughness index curve
(c) consistency index curve
(d) flow curve

Q.9. Plasticity index divided by Flow index is called
(a) toughness index
(b) liquidity index
(c) flow index
(d) consistency index (GATE 1999)

Q.10. The relative ease with which a soil can be deformed is called
(a) liquidity
(b) plasticity
(c) consistency
(d) none of these

Answers

1. c

2. a

3. c

4. d

5. c

6. c

7. c

8. d

9. a

10. c

(The author is associated with www.amiestudycircle.com)

Thursday, March 10, 2016

Soil Mechanics - Basic Concepts

Q.1. In a soil sample, at a certain point, there is no reduction in volume even by reducing water content. Water content at this point is called
(a) shrinkage ratio
(b) saturation limit
(c) liquidity limit
(d) shrinkage limit (AMIE Winter99)

Q.2. In a soil sample, at a certain point, there is no reduction in volume even by reducing water content. In this situation, space left behind due to reduction of water content is filled by
(a) water
(b) air
(c) both air and water
(d) none of these

Q.3. Shrinkage limit(ws) is
(a) $\frac{{({W_1} - {W_d}) - {\gamma _w}({V_1} - {V_d})}}{{{W_d}}}x100\%$
(b) $\frac{{{\gamma _w}}}{{{\gamma _d}}} - \frac{1}{G}$
(c) e/G
(d) all these
Where W1 is weight of ordinary soil, Wd is weight of dried sample, V1 is original volume, V2 = Vd is volume of sample at shrinkage limit and ${\gamma _d}$ is dry unit weight.

Q.4. A soil sample has a shrinkage limit of 10% and specific gravity of soil solids as 2.7. The porosity of the soil at shrinkage limit is
(a) 21.2%
(b) 27%
(c) 73%
(d) 78.8% (IES 1995)

Q.5. A clay sample has a void ratio of 0.50 in dry state and specific gravity of solids = 2.70. Its shrinkage limit will be
(a) 12%
(b) 13.5%
(c) 18.5%
(d) 22% (IES 1996)

Q.6. The ratio of given change in volume expressed as percentage of dry volume, to the corresponding change in water, is called
(a) Degree of saturation
(b) shrinkage limit
(c) submerged unit weight
(d) shrinkage ratio

Q.7. Water content at the boundary between solid state and semi solid state of a soil sample is called
(a) liquid limit
(b) plastic limit
(c) shrinkage limit
(d) none of these

Q.8. Water content at the boundary between semi-solid state and plastic state in a soil sample is called
(a) liquid limit
(b) plastic limit
(c) shrinkage limit
(d) none of these

Q.9. The equation of A-line in plasticity chart is
(a) Ip = 0.73(wL - 20)
(b) Ip = 0.93(wL - 20)
(c) Ip = 1.73(wL - 20)
(d) none of these (GATE 1995)

Q.10. The values of liquid limit and plasticity index for soils having common geological origin in a restricted locality usually define
(a) A zone above A-line
(b) A straight line parallel to A-line
(c) A straight line perpendicular to A-line
(d) points may be anywhere in the plasticity chart (GATE 1999)

Answers

1. d

2. d

3. d

4. a

5. b

6. d

7. c

8. b

9. a

10. b

Tuesday, March 8, 2016

Soil Mechanics - Basic Concepts

Q.1. If a soil sample of weight 0.18 kg having a volume of ${10^{ - 4}}$ ${m^3}$ and dry unit weight of 1600 kg/ ${m^3}$ is mixed with 0.02 kg of water then the water content in the sample will be
(a) 30%
(b) 25%
(c) 20%
(d) 15% (IES 1999)

Q.2. The void ratio and specific gravity of a soil are 0.65 and 2.72 respectively. The degree of saturation in % corresponding to water content is
(a) 65.3
(b) 20.9
(c) 83.7
(d) 54.4 (GATE 2001)

Q.3. Given that W1 is the weight of empty Pycnometer, W2 is the weight of Pycnometer and dry soil, W3 is the weight of Pycnometer, soil and water and W4 is the weight of Pycnometer and water. The specific gravity of the solids is given by
(a) $\frac{{{W_2}}}{{({W_4} - {W_2})}}$
(b) $\frac{{({W_2} - {W_1})}}{{({W_3} - {W_4}) - ({W_2} - {W_1})}}$
(c) $\frac{{{W_2}}}{{({W_3} - {W_4})}}$
(d) $\frac{{({W_2} - {W_1})}}{{[({W_2} - {W_1}) - ({W_3} - {W_4})]}}$ (IES 1995)

Q.4. Relative density of a natural granular soil is
(a) $\frac{{{e_{\max }} - e}}{{{e_{\max }} - {e_{\min }}}}x100\%$
(b) $\frac{{{e_{\max }} + e}}{{{e_{\max }} + {e_{\min }}}}x100\%$
(c) $\frac{{{e_{\max }} - e}}{{{e_{\max }}}}x100\%$
(d) $\frac{{{e_{\max }}}}{{{e_{\max }} - {e_{\min }}}}x100\%$
Where emax is void ratio of soil in densest condition, emin is void ratio of soil in loosest condition, e is in place void ratio.

Q.5. Relative density of a natural granular soil is
(a) $\frac{{{\gamma _d}_{,\max }}}{{{\gamma _d}}}x\frac{{{\gamma _d} - {\gamma _d}_{,\min }}}{{{\gamma _{d,\max }} - {\gamma _{d,\min }}}}x100\%$
(b) $\frac{{{\gamma _d}_{,\max }}}{{{\gamma _d}}}x\frac{{{\gamma _d}}}{{{\gamma _{d,\max }} - {\gamma _{d,\min }}}}x100\%$
(c) $\frac{{{\gamma _d}_{,\max }}}{{{\gamma _d}}}x\frac{{{\gamma _d}_{,\min }}}{{{\gamma _{d,\max }} - {\gamma _{d,\min }}}}x100\%$
(d) $\frac{{{\gamma _d}_{,\max }}}{{{\gamma _d}}}x\frac{{{\gamma _d} - {\gamma _d}_{,\min }}}{{{\gamma _{d,\max }}}}x100\%$
Where ${\gamma _{d\max }}$ is dry unit weight of soil in densest condition, ${\gamma _{d\min }}$ is dry unit weight of soil in loosest condition, ${\gamma _d}$ is in place dry unit weight.

Q.6. The natural void ratio of a sand sample is 0.6 and its density index is 0.6. If its void ratio in the loosest state is 0.9, then the void ratio in the densest state will be
(a) 0.2
(b) 0.3
(c) 0.4
(d) 0.5 (IES 2001)

Q.7. Which one of the following represents relative density of saturated sand deposit having moisture content of 25%, if maximum and minimum void ratio of sand are 0.95 and 0.45 respectively and specific gravity of sand particles is 2.6?
(a) 40%
(b) 50%
(c) 60%*
(d) 70% (IES 2002)

Q.8. The void ratios at the densest, loosest and the natural states of a sand deposit are 0.2, 0.6 and 0.4, respectively. The relative density of the deposit is
(a) 100%
(b) 75%
(c) 50%
(d) 25% (GATE 2002)

Q.9. Water content at the boundary of semi-solid state and solid state in a soil element is called
(a) shrinkage ratio
(b) saturation limit
(c) liquidity limit
(d) shrinkage limit*

Q.10. Which one of the following phase diagrams represents a clay at its shrinkage limit?
(a)

AIR

WATER

SOLIDS

(b)

WATER

SOLIDS

(c)

AIR

SOLIDS

(d)

WATER

AIR

SOLIDS

(IES 2001)

Answers:
1. b
2. c
3. d
4. a
5. a
6. c
7. c
8. c
9. d
10. b