Mechanics of Soils-2marks

7/28/2019 Mechanics of Soils-2marks

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UNIT-1

INTRODUCTION

1) Define soil mechanics2) Write the typical engineering behavior of

a) Coarse-grained soils

b) Silt

c)Clays

3) What do you understand by residual soils andtransported soils?

4) What are the three basic factors whichinfluence the characteristics of a transportedsoil? What factors determine the characteristicsof a residual soil?

5) Draw the phase diagram for partially saturated,saturated, dry condition.

6) Write the following terms:

a) Relation between ws ,w and w

b) Relation between e and n

c)Relation between e, w, Gs and s

d) Bulk unit weight ,t in terms of Gs ,e, w andw

e) Saturated unit weight , sat in terms of Gs ,eand w


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f) Dry unit weight , d in terms of Gs ,e and w

g) Submerged unit weight , in terms of Gs,eand w

h) Relation between , d and w

i) Relation between d , Gs , w and na

7) How water content can be determined?

8) Explain the quick laboratory method ofdetermining water content?

9) What are the methods to determine in situ unitweight?

10) What is meant by sphericity?

11) What is meant by terminal velocity?

12) Define the following terms.

a) Water content, degree of saturation, aircontent.

b) Percentage air voids, Bulk unit weight

c)Well -graded and poorly- graded soil.

d) Uniformly graded and gap graded soil.

e) Coefficient of uniformity & curvature.

f) Atterberg limits.

g) Plastic limit, liquid limit, shrinkage limit.

h) Shrinkage ratio.


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13) What is flow curve? Where it is used?

14) What is the difference between:

a) Porosity and void ratiob) Saturated unit weight and submerged unit

weight

c)Dry unit weight and unit weight of soils

d) Specific gravity of soils and mass specificgravity

15) Give the grain size ranges of different soiltypes according to IS:1498(1970)

16) How do you use the field identification tests toidentify the major soil types?


a) Liquidity index and relative consistency

b) Flow index and toughness index

c)Sensitivity , activity and thixotropy

d) Undisturbed and remolded soil

18) What are the conditions to be satisfied toclassify sand as well graded?

19) What is the consistency of the soils, if a) wN>wL b) wL > wN > wP c) wP > wN

20) What is the value ofIP if the soil is not plastic?


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21) What happens when a non plastic soil issubmerged in water?

22) What is the significance of shrinkage limit?

23) Does sand soil experiences shrinkage? Doesclay?

24) What are the differences between compactionand consolidation?

25) What are the factors affecting compaction?

26) Draw the following curvesa) Compaction curve for sands

b) Effect of compaction on structure

c)Effect of compaction on compressibility

d) Effect of stress-strain behavior

27) What kind of improvement of the engineeringproperties of a soil mass can be brought aboutthrough compaction?

28) Explain the shape of the compaction curve of acohesive soil in terms of the development ofwater films around the particles

29) List the different methods of applyingcompaction to a soil in the field and in thelaboratory.

30) What is meant by optimum moisture content?


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31) What causes reduction in the value of drydensity of soil beyond optimum moisturecontent?

32) Give an account of the differences in soilcharacteristics such as structure, permeabilityupon saturation, shear strength, stress-strainbehavior, compressibility and swelling when it iscompacted on the dry side of OMC and wet sideof OMC?

33) For the following projects, would you prefer to

compact the soil on the dry side of OMC or onwet side of OMC? Give reasons.

a) Homogenous earth dam

b) Core of an earth dam

c)Sub grades for highways

d) Earth fills34) Define the following terms:

a) Relative density or density index

b) Relative compaction

c)Zero air voids density

d) 95% Of proctor density

35) Compare the compactive energy in the I.S.heavy compaction test to that in the I.S. lightcompaction test.


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36) What is the ratio of the compactive energy inthe I.S. heavy compaction test to that in the I.S.light compaction test?

37) What type of soils are best compacted by useof the following compacting equipment?

a) Smooth wheel rollers

b) Rubber tyred rollers

c)Pneumatic tyred rollers

d) Sheepsfoot rollerse) Vibratory rollers

38) Can water content of a soil be more than100%? Justify your answer.

39) The void ratio of a soil is zero when the soil isfully saturated. Justify your answer

40) Is the consistency limits are determined forsoils in their remolded sate? Justify your answer

41) How is the compaction controlled by the use ofthe proctors needle?

42) Is Zero air voids density can attain inpractice? justify your answer

43) Is vibroflotation technique will be effectivefor all types of soil? justify your answer

44) Will efficiency of compaction improves withincrease in compactive effort?


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45) During compaction, soil always remainsunsaturated. Justify your answer

46) What is porosity of the given soil if its void ratio

is 0.57.

47) A soil sample with specific gravity of soils 2.70has a mass specific gravity of 1.84.Assuming thesoil to be perfectly dry, determine the void ratio.

48) If dry and saturated unit weights of a soil are18kN/m3 and 20 kN/m3 respectively, what is its

unit weight at 50% saturation?49) The dry density of a soil and its specific gravity

of solids are respectively 18 g/cc and 2.7 .findthe moisture content required to have 100%saturation.

50) If uniformity coefficient of a soil is twice itscoefficient of curvature, find the ratio betweenD60 and D30 .

51) A 100 cm3 volume of soil contains 27 cm3 ofvoids. if the volume of soils is 73 cm3 ,Determineits void ratio.

52) The mass specific gravity of a soil equals1.64.the specific gravity of soil is 2.7. Determine

the void ratio under the assumption that the soilsare perfectly dry.

53) The liquid limit and plastic limit of a soil sampleare 110% and 18%. Find the plasticity index.


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54) Classify the soil having the following propertiesas per BIS:

Fraction passing 75 micron sieve=65%

Liquid limit=19%

Plastic limit=14%

55) A soil with Liquidity index of -0.20 has a liquidlimit of 56% and plasticity index of 20%.what isits natural water content? What is the nature ofthis soil?


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UNIT-2

SOIL WATER AND WATER

1) List the different types of soil water.

2) Define effective pressure.

3) What are the factors that influence the heightof capillary rise in soils?

4) What is meant by apparent cohesion?

5) What is the most significant consequence ofcapillarity on soil behavior?

6) What is meant by neutral stress andintergranular stress?

7) Define hygroscopic moisture.

8) Differentiate between:

a) Pore water pressure and effectivestress

b) Positive pore water pressure andnegative pore water pressure


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c)Pressure head and piezometric head

d) Hydrostatic pressure and seepagepressure

9) Explain gravitational water and held water.

10) Obtain the expression for the critical hydraulicgradient necessary for a quick condition todevelop by using (a) total stress approach (b)effective stress approach

11) Why is there more likelihood of quick

condition in sands than in clays?

12) State the condition for Quick sandphenomenon.

13) Show that it is impossible to drown in quicksand.

14) Quick sand phenomenon is common inpervious coarse sands and gravels. Justify youranswer

15) Is the effect of capillary saturation is toincrease the effective stress? Justify youranswer

16) Will decrease in water table increases the

effective stress? Justify your answer

17) Is total stress in soil is greater than theeffective stress? Justify your answer

18) What is meant by hydraulic gradient?


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19) The lower bound velocity of turbulent flow isabout 6.5 times the upper bound velocity oflaminar flow? Explain.

20) Write the relation between seepage velocityand discharge velocity.

21) Write the expression for the radius of influence.

22) Give five examples of problem in soilengineering where knowledge of permeabilityof soils is essential.


a) Laminar flow and turbulent flow

b) One dimensional flow, two dimensionalflow and three dimensional flow.

c)Confined flow and unconfined flow

d) Seepage velocity and superficialvelocity

e) Constant and falling head permeabilitytest

24) List out the laboratory and field tests todetermine the coefficient of permeability.

25) Give the relationship between coefficient ofpermeability and coefficient of percolation.

26) What is the influence of void ratio on thecoefficient of permeability?


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27) State Alllen Hazen formula for permeability ofsoils?

28) List the factors that influence permeability of

soils and mention the manner in which they doso.

29) State Darcys law.

30) Comment on the validity of Darcys law forsoils

31) Relate the various methods of determination of

k with the soil types for which they are bestsuited.

32) How does flow through a soil change theeffective stress?

33) What is meant by effective stress?

34) The velocity of flow defined by the Darcys lawis only a fictitious velocity. Justify your answer

35) Is the boundary velocity of flow betweenlaminar and turbulent flow is about 1 cm/s?Justify your answer

36) Coefficient of permeability increases astemperature rises. Justify your answer.

37) In fine grained soils, the capillary rise is lesscompared to coarse grained soil. justify youranswer


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38) Why falling head permeability test is bettersuited for measuring the permeability of finesands and silts?

39) State true or false for the following and justifyyour answer

a) Darcys law of flow through soils isvalid for flow through gravels andpebbles

b) Oedometer tests are usually used to

determine the permeability of lowpermeability soils.

c)Seepage velocity is always greater thansuperficial velocity of flow

d) Coefficient of permeability is equal tosuperficial velocity of flow under ahydraulic gradient equal to unity.

40) Determine the effective stress of soil at adepth of 4m below ground when water tablerises up to the ground level. The saturated unitweight of soil is 22kN/m3

41) In a laboratory constant head permeabilitytest, a cylindrical sample 100mm in diameter

and 150mm high is subjected to an upwardflow ml (cm3)/min. The head loss over thelength of the sample is measured to be360mm.calculate the Coefficient ofpermeability in m/s


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UNIT-3

STRESS DISTRIBUTION

1) State the assumptions implied in use of theboussinesqs theory to determine the verticalstress in a soil due to a point load and discusstheir validity.


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2) For the application of the theory of elasticity toestimate vertical stresses in soils, is itnecessary for the soil to be truly elastic?

3) For a sedimentary soil deposit, which solutionis more appropriate - boussinesqs orwestergaards? Why? State the assumptionsinvolved in westergaards theory.

4) What do you understand by the terms:

a) Isobar, pressure bulb, Isochrones.

b) Line load, strip load and trapezoidal load.

c)Two -to-one load distribution and 30 degreedistribution.

5) What is the basis of the construction of theNewmarks influence chart? How it is used?

6) What is influence chart and influence value?

7) A 2m thick deposit of soil weighing 15 kN/m3 isplaced over a large area .if the increase invertical stress at 1m depth is 30 kN/m2, theincrease in vertical stress at 2m depth 15kN/m2.

8) The theoretical maximum value of Poissons

ratio for saturated clay undergoing no volumechange when stressed is 0.5. Justify youranswer


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9) New mark chart can be used to determine thevertical stress at a point even if the point liesoutside the loaded area. Justify your answer

10) For carved clay, use of westergaardequation is more appropriate than theboussinesq equation for determining thevertical stress. Justify your answer

11) Boussinesq theory indicates values ofvertical stresses which are always larger than

Westergaards. Justify your answer12) If a loaded area has its sides at least equal

to one third the depth at which the verticalstress is required, the disturbed load can betreated as an equivalent point load acting atthe centroid of the area.

13) How is consolidation different fromcompaction?

14) What do you understand by the followingterms:

a) Immediate settlement, Primaryconsolidation, Secondary consolidation.

15) Differentiate between:a) Coefficient of compressibility and

Coefficient of volume decrease

b) Underconsolidated, normally consolidation,over consolidation soils.


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c)Compression index, swelling index andrecompression index.

d) Coefficient of consolidation and degree of

consolidation

e) Laboratory consolidation curve and fieldconsolidation curve

f) Initial compression ratio, Primarycompression ratio, secondary compressionratio.

g) Pore water pressure and excess pore waterpressure.

16) Which soil parameters can be taken as ameasure of

a) Magnitude of compression

b) Rate of consolidation

c)Degree of over- consolidation

17) Under what conditions does secondaryconsolidation become important?

18) How do you obtain a time-settlementrelationship for a clay stratum?

19) Give a few causes of preconsolidation insoils.

20) How do you extrapolate the fieldconsolidation curve from the laboratoryconsolidation curve?


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21) If coefficient of volume compressibility isequal to half of coefficient of compressibility ofsoil, find its void ratio.

22) How do you determine immediatesettlement of sand?

23) Coefficient of compressibility is constantfor a clay layer. Justify your answer.

24) Compressibility of soil decreases as theeffective stress increases. Justify your answer.

25) The over consolidation ratio of a fielddeposit of clay cannot be less than 1. Justifyyour answer

26) Terzaghis consolidation theory does nottake into account the compressibility of porewater and soil solids. Justify your answer.

UNIT-4

SHEAR STRENGTH

1) List of few important problems in soilengineering where knowledge of shearstrength is essential.

2) Define shear strength of a soil .Is it possible

to tabulate the values of shear strength fordifferent soils?

3) What does the Mohr circle of stressrepresent?


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4) How do you utilize the property of the pole(origin of planes) to obtain useful informationfrom the Mohr circle of stress?


a) Non-linear stress strain relation

b) Work hardening material

c)Work-softening material

d) Elasto-plastic material. Use diagrams forillustration.

6) How do we define failure in soils? Accordingto Mohr coulomb criterion, how is the failureplane is recognized and how is shear strengthdefined?


a) UU test

b) CU test

c)CD test

d) UC test

8) Give one example each of use of UU strength,CU strength and CD strength in engineeringpractice.


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9) Show, for a normally consolidated, saturatedsoil, the failure envelopes in terms of totalstress and effective stress (where applicable)

for the UC, UU, CU and CD tests.10) Draw the failure envelopes foe an over

consolidated soil for the CU test and point outthe important divergences from a normallyconsolidated soil.

11) What is the meaning of the following terms:

a) Peak and residual shear strength of claysoils

b) Peak and ultimate angle of shearingresistance of sands

c)Angle of repose

d) Critical void ratio of a sand

e) Liquefaction phenomenon in sands

12) What is the significance of the pore pressurecoefficients? Illustrate the answer by anexample?

13) Define the pore pressure parameters

14) How are the pore pressure parameters A andB are determined?

15) What is a stress path? Show the stress pathsESP and TSP for the different triaxial sheartests.


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16) From the kf line .how are c, parametersdetermined?

17) Mention any two advantages of direct shear

test.

18) How shear test is classified based ondrainage conditions?

19) Sketch coulomb and Mohrs failure envelope.

20) Name the different types of triaxialcompression test.

21) For which type of soils , the following testscan be done

a) Vane shear test

b) UCC test

22) A purely cohesive soil sample of cohesion

25kPa is subjected to a cell pressure of100kPa in a triaxial test. Will the sample failby shear? Justify your answer

23) A soil sample of diameter 38mm and length80mm is subjected to drained test .if thevolume of water collected in burette is 8 x 103

mm

3

and the change in length is 8mm atincipient failure condition, find the modifiedarea of the sample.


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24) Find the angle made by failure plane withmajor principal plane using Mohrs circle andstrength envelope.

25) Determine the value of cohesion ,if theunconfined compressive strength of clay is600KN/m2

26) List different tests to determine shearstrength parameters.

27) If angle of failure plan in triaxial compression

test with respect to x-axis will be 60 degree.Determine angle of internal friction

28) What is deviator stress? How it is related tomajor and minor principle stresses?

29) How is Mohr coulomb equation modifiedfor purely cohesive soils?

30) What are the advantages of triaxialcompression test?

31) Under what circumstances vane shear testis used?

32) What are the limitations of direct sheartest?

33) Sensitivity of clay can never be less than 1.Justify your answer.


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34) A sand with its void ratio higher than itscritical void ratio increases in volume whensheared. Justify your answer.

35) Moist sand can exhibit some cohesion.Justify your answer.


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UNIT-5

STABILITY OF SLOPES

1) Define the various factors of safety used inthe analysis of stability of slopes

2) What are the probable types of failure ofaslope?

3) What is meant by an infinite slope?4) What is the criterion for the stability of an

infinite slope in sand?

5) What is the effect of seepage parallel to theslope on the factor of safety?

6) List the factors affecting the factor of safety

of an infinite slope in clay soil.7) What is the difference between the total

stress and effective stress methods ofstability analysis?


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8) Mention conditions where the effective stressanalysis can be conveniently used.

9) What is Taylors stability number? How do

you use the stability chart?

10) How is simplified bishops method differentfrom the conventional Swedish circle method?Is it s total stress or an effective stressanalysis? Does it give a higher or lower factorof safety as compared to the conventionalmethod?

11) How is bishops rigorous analysis differentfrom his simplified method?

12) With neat sketch define the types of failure offinite slopes

13) Write any two assumptions made in Swedishcircle method

14) Define finite and infinite slope

15) What are the critical conditions for thestability of slopes?

16) A soil sample of diameter 38mm and length80mm is subjected to drained test .if the

volume of water collected in burette is 8x10

3

mm3 and the change in length is 8mm atincipient failure condition, find the modifiedarea of the sample.


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17) The factory of safety of an infinite slope ofcohesion less soil is independent of the heightof the embankment. Justify your answer.

18) The side slopes of a canal are more criticalwhen there is a sudden drawdown rather thanwhen the canal is running full. Justify youranswer.

19) Name the different types of slopes

20) What is the effect of tension cracks in the

stability analysis of slopes?21) Determine the FOS against sliding for the soil

whose angle of internal friction will be 30degree and slope angle is 15 degree.

22) When do you prefer Swedish circle method ofanalysis?

23) What do you understand by factor of safetywith respect to shear Strength? Give anexpression.

24) Write any two assumptions made in Frictioncircle method.

25) How do you test the stability of slopes of an

earthen dam?26) What are the three conditions for which

stability analysis of an earth dam is carriedout?


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27) Taylors stability charts are based on thefriction circle method using total stressanalysis. Justify your answer.

28) In the Swedish circle method of analysis, theinters lice forces are ignores for all slices.Justify your answer.

29) Simplified bishops method gives a lower FOSthan the conventional method .why? Justifyyour answer.

30) For long term stability of slopes.Effectivestress method must be used. Why? Justifyyour answer.


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ASSIGNMENT-5

STABILITY OF SLOPES

1) Explain the following finite slope analysis indetail with neat sketch

a) Swedish circle methodb) Friction circle method

c)Bishops simplified method

2) Explain stability of slopes of earth dam withthe following conditions

a) At the end of construction

b) At the end of a sudden drawdown

c)After a long time, when a state of equilibriumis reached.

3) a) Determine the FOS with respect tocohesion if an embankment 25m high andhaving a slope of 40 degree is subjected to

sudden drawdown.(c=40kN/m2 ,sat =18kN/m3

b) Determine the FOS with respect tocohesion for a submerged embankment 25m


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high and having a slope of 40 degree.( c=40kN/m2 ,sat =18 kN/m3

c)Determine the FOS with respect to shear

strength 25m high and having a slope of 40degree.( c=40kN/m2 ,sat =18 kN/m3

4) a) An embankment is inclined at an angle of35 degree and its height is 15m.The angle ofshearing resistance is 18 degree and thecohesion intercept is 180 kN/m2 .The unitweight of soil is 20 kN/m3 .If the Taylors

stability number is 0.06,find the factor ofsafety with respect to cohesion.

b) Find the FOS of an infinite slope ofcohesion less soil of an angle of internalfriction 36 degrees and slope angle in 30degrees.

5) A cutting 7m deep is to be made in clay havinga unit weight of 19 kN/m3 and an average cohesionof 20 kN/m2 .A rock stratum exists at a depth of12m below the ground surface .what is the safeslope angle if a factor of safety of 1.25 isconsidered necessary?


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Mechanics of Soils-2marks

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