SOIL MECHANICS

UNIT 1

INTRODUCTION

Nature of Soil - Problems with soil - phase relation - sieve analysis - sedimentation analysis û

Atterberg limits - classification for engineering purposes - BIS Classification system û Soil

compaction - factors affecting compaction û field compaction methods and monitoring.

DESCRIPTIVE QUESTIONS (6 OR 12 MARKS)

1. Soil Phase Relationships & Inter relationships with diagram

2. Sieve Analysis Explanation

3. Sedimentation Analysis Explanation

4. Consistency Limits Explanation with Diagram

5. Uses/ Importance of Consistency Limits

6. Classification of Soils as per BIS û Step by Step Procedure

7. Lab Classification of Fine Grained Soil (Plasticity Chart)

8. Boundary Classification of Soils

9. Factors Affecting Compaction

10. Effect of Compaction on Soil Properties

11. Field Compaction Methods

12. Field Compaction Control (Procter Needle Method)

13. Relationship between Water Content and Dry Density

14. Comparison between Standard and Modified Proctors Test PROBLEM TYPES

1. Calculation of Degree of Saturation of natural soil sample (Pg. No. 31 û Example 2.21)

2. Calculation of Water Content, Voids Ratio, Specific Gravity & Dry Density of saturated soil

(Pg. No. 36 = Problem 2)

3. Core Cutter Based Problem (Pg. No. 22 = Example 2.3)

4. Compacted Soil Based Problem (Pg.No.35 = Example 2.35) & (Pg. No. 36 = Problem 3)

5. Embankment Fill up Problem (Pg.No.26 = Example 2.11) & (Pg. No. 36 = Problem 3)

6. Paraffin Wax Based Problem (Pg.No.36 = Example 2.22)

7. Relative Density Calculation Problem (Pg.No.23 = Example 2.4)

8. Calculation of Specific Gravity, Volumetric Shrinkage & Shrinkage Parameters

(Pg. No. 69 = Example 3.6)

9. Calculation of Shrinkage Limit & Shrinkage Ratio (Pg.No.71 = Example 3.9)

10. Soil Comparison based on Indices (Pg. No.125 = Example 4.2)

11. Soil Classification based on data (Pg. No 125 = Example 4.1)

12. Compaction Lab Test Problem (Pg. 419 = Example 17.1)

2 MARK QUESTIONS

1. What is soil?

2. What are the main stages in formation of soil?

3. Define soil mechanics.

4. Draw the soil three phase diagram for saturated, dry and partially saturated soils

5. Define water content

6. Define void ratio

7. Define porosity

8. Define specific gravity

9. Define density of soil. Mention the types.

10. Define soil index (or) relative density (or) density index (or) degree of density

11. For what soils is relative density used? Why?

12. Mention any four soil phase inter relationships.

13. Derive from fundamentals the relation between porosity and voids ratio.

14. Derive from fundamentals the relation between dry and bulk density in terms of water

content.

15. What are the index properties of soil?

16. Mention any four methods for determination of water content.

17. Mention any four methods to determine field density of soil.

18. Mention any four methods to determine specific gravity of soil.

19. What is particle size analysis of soils?

20. What are the stages or types of particle size analysis? Which test is not affected by

temperature?

21. What is Stoke's Law?

22. What is combined sieve and sedimentation analysis?

23. Define effective size in particle analysis. Give examples.

24. Define Cc & Cu in mechanical analysis of soils.

25. How would you classify soils based on Cu & Cc?

26. Sketch typical particle size distribution curves for well graded and poorly graded soils.

27. Sketch typical particle size distribution curves for uniformly graded and gap graded soils.

28. If uniformity coefficient of soil is twice, the coefficient of curvature, calculate the ratio

between D 60 and D 30

29. A sieve analysis test has the results D 10 = 0.093 mm, D 30 = 0.25 mm, D 60 = 0.51 mm.

Calculate the coefficients. Is it a uniformly graded soil?

30. What is consistency of soils? What are the states of consistency?

31. Define liquid limit, plastic limit and shrinkage limit 32. Define flow index, consistency index, toughness index, plasticity index and shrinkage

index

33. Differentiate between the following (a) Density & Density Index (b) Liquid Limit &

Liquid Index (c) Plastic Limit & Plastic Index

34. What are the main uses of Atterberg limits?

35. What are the limitations of Atterberg limits?

36. What are the various soil classification systems?

37. What is the need for classification of soils?

38. How is A line used to distinguish clays?

39. Distinguish between GP & GW, SC & SM soils

40. As per BIS system, when is dual symbols used for classification?

41. Mention the limitations of BIS Classification system

42. Differentiate between compaction and consolidation

43. Write a short note on compaction of soils.

44. How is degree of compaction ensured in the fields?

45. Indicate the various types of rollers used for various soils.

46. List the factors influencing compaction of soil

47. Why does dry density decrease with increasing water content when the soil is compacted

on the west side of OMC?

48. What is meant by OMC (optimum moisture content)?

49. Classify the soil having the following properties as per BIS : Fraction passing 75 micron

sieve : 60%, Liquid limit : 19%, Plastic limit : 14%

50. The shrinkage limit of a soil is 12%. The soil is dried from its initial water content of 8%

to the dry state. Calculate the percentage of volume change in this process.

SOIL MECHANICS

UNIT 2

SOIL WATER AND WATER FLOW

Soil water û Various forms û Influence of clay minerals û Capillary rise û Suction - Effective

stress concepts in soil û Total, neutral and effective stress distribution in soil - Permeability û

Darcy's Law- Permeability measurement in the laboratory û quick sand condition - Seepage û

Laplace Equation - Introduction to flow nets ûproperties and uses - Application to simple

problems.

DESCRIPTIVE QUESTIONS (6 OR 12 MARKS)

1. Soil Suction and Factors

2. Stress distributions in Submerged, Saturated & Partially Saturated Soils

3. Factors Affecting Permeability

4. Lab Methods of Determining Permeability û Constant Head Test

5. Lab Methods of Determining Permeability û Falling Head Test PROBLEM TYPES

1. Variations in Soil Stresses (Pg. No. 172 û Example 6.13)

2. Constant Head Test (Pg. No. 191 = Example 7.1) (Pg. No. 193 = Example 7.4)

3. Falling Head Test (Pg. No. 191 = Example 7.2) (Pg. No. 204 = Problem 6 )

4. Temperature Rise Problems (Pg.No.192 = Example 7.3)

5. Stratified Layers Problem (Pg.No.199 = Example 7.12)

6. Quick Sand Problems (Pg.No. 226 = Example 9.3) (Pg.No.227 = Example 9.5)

2 MARK QUESTIONS

1. What are the various forms of soil water?

2. Mention the clay minerals influencing water in soils.

3. Define structural water, adsorbed water and capillary water.

4. Mention any four factors influencing capillarity in water.

5. Write the relation between capillary rise and temperature.

6. Define capillary tension of soil.

7. Define capillary potential and soil suction.

8. If the pF of a soil is 2.8, calculate the capillary height and potential of the soil.

9. Mention any four factors affecting soil suction.

10. What are the methods of measurement of soil suction?

11. Write a brief note on shrinkage and swelling of soils.

12. What is meant by frost boil and frost heave in soils?

13. Explain slaking of clays.

14. Explain bulking of sand.

15. What is capillary siphoning?

16. Define effective, neutral and total pressure in soils.

17. Diagrammatically illustrate effective, neutral and total pressure in soils.

18. What happens to effective stress when water table rises due to rain?

19. The depth of water in a river was 10m during one month of 2010.If the saturated unit

weight of the soil is 9.81 KN/m2, find the effective stress at a depth of 10m below the

riverbed.

20. Define permeability and percolation.

21. What do you understand by laminar flow?

22. Mention any four factors affecting permeability/hydraulic conductivity.

23. What is the flow per unit area through a soil with hydraulic gradient unity?

24. Define seepage and seepage velocity.

25. What is Darcy law? State its expression.

26. Mention the validity or limitation of Darcy Law.

27. State Allen Hazen's formula & Loudon formula for calculating permeability.

28. Give the empirical correlation between permeability & particle size (Allen Hazen)

29. Estimate the permeability coefficient of a soil having effective particle size 0.2 mm.

30. Mention the various lab and field methods for determining permeability.

31. Differentiate constant head and variable head tests.

32. Why is falling head permeability test preferred to constant head method for finding

coefficient of permeability of fine grained soils 33. Mention the formula for constant head and variable head methods.

34. Distinguish between discharge and seepage velocity.

35. The void ratio of a soil is 1.0 and the superficial velocity through the soil is 1 x 10

û5

cm/s.

Find the seepage velocity.

36. The discharge and seepage velocities of a soil are 1 x 10-3 cm/s and 2 x 10-3 cm/s. Find

the void ratio of the soil.

37. Find the critical hydraulic gradient of a sandy soil with w = 34% and G = 2.64.

38. List the assumptions made in Laplace equation.

39. Write down the Laplace equation.

40. What is quicksand condition?

41. Write the equation for quicksand flow.

42. Define flownets.

43. Mention any two applications of flownet.

44. State any two properties of flownet.

45. What is phreatic line?

SOIL MECHANICS

UNIT 3

3. STRESS DISTRIBUTION, COMPRESSIBILITY AND SETTLEMENT 10

Stress distribution in soil media û Boussinesque formula û stress due to line load and Circular

and rectangular loaded area - approximate methods - Use of influence charts û Westergaard

equation for point load - Components of settlement - Immediate and consolidation settlement -

Terzaghi's one dimensional consolidation theory û governing differential equation - laboratory

consolidation test û Field consolidation curve û NC and OC clays - problems on final and time

rate of consolidation

DESCRIPTIVE QUESTIONS (6 OR 12 MARKS)

1. Boussinesque Analysis

2. Stress Formula for Point,Line,Rectangular & Circular Loads

3. Stress Distribution in Soils û Isobar, Vertical & Horizontal Distribution

4. Westergaard Formula

5. Newmark's Influence Chart

6. Terzaghi's one dimensional consolidation theory & equation

7. Consolidation û Spring Analogy

8. Lab Consolidation Test

9. Calculation of Coefficient of Consolidation

10. Virgin Compression Curve û NC & OC clays û Compression Index

PROBLEM TYPES

1. Intensity of Stress due to Point Load (Pg. No.302 = Example 13.1)

2. Stress due to Point Load by Boussinesque & Westergaard Methods

(Pg. No. 324 = Problem 3 & 4)

3. Stress due to Line Loads (See Attachment)

4. Stress due to Rectangular Loads (Pg.No.314 = Example 13.3)

5. Stress due to Circular Loads (Pg.No.321 = Example 13.7)

6. Equivalent Point Load Method (Pg.No.314 = Example 315)

7. Settlement Based Problems of Clay Layer û Profile Given

(Pg.No.374 = Example 15.20 & Pg.No.377 = Example 15.24

& Pg.No.370 = Example 15.14 & Pg.No.373 = Example 15.18)

8. Settlement based on Overburden Pressure (Pg.No.363 = Example 15.6)

9. Time required for Settlement Problems

(Pg.No. 372 = Example 15.16) (Pg.No.361 = Example 15.1)

10. Vertical Pressure Change Based Problems

(Pg.No.367 = Example 15.11)

2 MARK QUESTIONS

1. Write the equilibrium equation of stress distribution in soils.

2. List the assumptions made in Boussinessque theory

3. Write the relation between modulus of elasticity of soil and vertical stress of soil.

4. What is the fundamental difference in Boussinesque & Westergaard theories?

5. Compare the Boussinesque & Westergaard coeffecients with a neat sketch.

6. State Boussinesque & Westergaard coeffecients for point loads.

7. Define geostatic stress. Write the formula for its computation.

8. Determine the geostatic stress for a soil with unit weight 16.5 kN/m

2

, K o = 0.5 at a depth

of 2m.

9. What is meant by isobar?

10. Explain the concept of pressure bulb.

11. Draw a neat sketch to represent stress distribution horizontally in soils.

12. Draw a neat sketch to represent stress distribution vertically in soils.

13. Briefly explain equivalent point load method.

14. Briefly explain Newmark's influence chart method.

15. Briefly explain Fenske's Chart.

16. For what type of soils is Newmark's method used?

17. What is meant by influence diagram? What is its use in soil mechanics?

18. Mention any four approximate methods for stress distribution.

19. Discuss the limitations of approximate methods of stress distribution analysis.

20. What is contact pressure?

21. Explain initial consolidation, primary consolidation and secondary consolidation

22. Explain one dimensional consolidation and three dimensional consolidation.

23. Differentiate between compaction and consolidation.

24. Define settlement of soils

25. State the components of settlement and their predominant soil type.

26. Mention the assumptions made in Terzaghi's theory of one dimensional consolidation.

27. Obtain the differential equation of one dimensional consolidation.

28. Mention the solutions proposed to one dimensional consolidation differential equation.

29. State the limitations in Terzaghi's one dimensional consolidation theory.

30. Mention the methods to determine the voids ratio in lab consolidation test.

31. Define Compression Index

32. Define coefficient of consolidation and coefficient of compressibility.

33. What are the fitting methods for calculation of coefficient of consolidation?

34. Mention any four causes for pre consolidation or over consolidation. 35. Define pre consolidation pressure. How is it determined?

36. Distinguish between NC and OC soils.

37. Why is the compressibility of OC clays less than NC clays?

38. Find the ratio between the time for 100% consolidation and 50% consolidation.

39. A soil sample consolidating in a ring of diameter 60 mm has a thickness of 18.9 mm at a

particular stage. Find the void ratio at this stage if the mass of dry soil is 78 g and specific

gravity of solids is 2.65.

40. The void ratio of clay is 1.58 at compression index of 0.8 and pressure of 180 kN/m

2

.

Calculate the voids ratio at a pressure of 240 kN/m

2

.

SOIL MECHANICS

UNIT 4

SHEAR STRENGTH

Shear strength of cohesive and cohesionless soils - Mohr - Coulomb failure theory û Saturated

soil and unsaturated soil (basics only) - Strength parameters - Measurement of shear strength,

direct shear, Triaxial compression, UCC and Vane shear tests ûTypes of shear tests based on

drainage and their applicability - Drained and undrained behaviour of clay and sand û Stress path

for conventional triaxial test.

DESCRIPTIVE QUESTIONS (6 OR 12 MARKS)

1. Mohr Coulomb Failure Theory

2. Direct Shear Test

3. Triaxial Compression Test

4. Stress Path for Traiaxial Compression Test

4. UCC û Unconfined Compression Test

5. Vane Shear Test

6. Drained and Undrained behaviour of clay and sand PROBLEM TYPES

1. Triaxial Compression Test based problems

(Pg. No.448 = Example 18.9) (Pg. No.449 = Example 18.10)

(Pg. No. 446 = Example 18.6) (Pg. No.480 = Example 18.39)

2. Direct Shear Test based problems based on Mohr Circle

(Pg. No. 475 = Example 18.29)

3. Embankment Type Problem

(Pg.No. 471 = Example 18.19) (Pg.No.455 = Example 18.12)

4. Vane Shear Test Type Problems

(Pg.No. 451 = Example 18.11)

5. Major and Minor Principal Stress

(Pg.No. 473 = Example 18.25)

2 MARK QUESTIONS

1. Define shear strength of soils.

2. How does soil derive shear strength? or What are the factors influencing shear strength?

3. Write a brief note on Mohr's circle.

4. Mention the shear strength parameters of sand and clay.

5. Differentiate shear strength parameters based on total and effective stress.

6. What is the role of pore pressure in shear strength of soils?

7. Mention the various tests available for measurement of shear strength.

8. Define principal plane and principal stress.

9. What are the limitations of Mohr Coulomb Theory?

10. Give the Coulomb's shear strength equation.

11. Define (a) drained consolidated (b) undrained unconsolidated (c) undrained consolidated

conditions.

12. What is the main cause of soil shear failure?

13. Write a brief note on (a) Advantages of Direct Shear Test (b) Limitations of Direct Shear

Test and (c) Need for Direct shear Test.

14. Write a brief note on (a) Advantages of Triaxial Compression Test (b) Limitations of

Triaxial Compression Test and (c) Need for Triaxial Compression Test.

15. Write a brief note on (a) Advantages of Vane Shear Test (b) Limitations of Vane Shear

Test and (c) Need for Vane Shear Test.

16. Write a brief note on (a) Advantages of UCC Test (b) Limitations of UCC Test and (c)

Need for UCC Test.

17. Define stress path of soils.

18. Draw the Mohr circle at failure and strength envelope corresponding to unconfined

compression test.

19. Draw the Mohr circle at failure and strength envelope corresponding to direct shear test.

20. Find the angle made by failure plane with major principal plane using Mohr's circle and

strength envelope.

21. What is effective stress failure envelope?

22. What is the role of friction in shear strength of clays?

23. The strength of a saturated clay is 200 kPa in UCC. If a cell pressure of 100 kPa is

maintained on a similar specimen in unconsolidated undrained test, find the deviator

stress at which the sample will fail.

24. For a granular soil with effective stress 200 KN/m

2

and angle of internal friction 30

o

,

compute the maximum shear strength.

25. In a triaxial test on a cohesionless soil sample, with cell pressure of 20kPa, the failure

was observed at 40kPa. Compute the angle of internal friction.

SOIL MECHANICS

UNIT 5

SLOPE STABILITY

Slope failure mechanisms - Modes - Infinite slopes - Finite slopes û Total and effective stress

analysis - Stability analysis for purely cohesive and C- soils - Method of slices û Modified

Bishop's method - Friction circle method - stability number û problems û Slope protection

measures.

DESCRIPTIVE QUESTIONS (6 OR 12 MARKS)

1. Definition and Method of Location of Critical Slip Circle

2. Method of Slices û Explanation and Derivation

3. Friction Circle method û Explanation and Derivation

4. Modified Bishops method û Explanation and Derivation

5. Different Ways of Failure of Finite Slope with Sketches

6. Taylor's Stability Number & Chart - Expression PROBLEM TYPES

1. Cutting of Soil Problem based on Taylor's Stability Number

(Pg. No.625 = Example 23.8)

2. Infinite Slope û Factor of Safety

(Pg. No. 607 = Example 23.2) (Pg. No. 608 = Example 23.3)

3. Infinite Slope û Critical Height

(See Attachment)

4. Embankment Based Problems- Maximum Side Slope & Factor of Safety

(Pg.No. 627 = Example 23.12) (Pg.No. 628 = Example 23.13)

5. Slip Circle Method Problem

(Pg.No. 626 = Example 23.10) (Pg.No.628 = Example 23.14)

6. Canal Running Full & Rapidly drawndown problem

(See Attachment)

2 MARK QUESTIONS

1. Define slope and slide.

2. Mention the major reasons for the failure of slopes.

3. What are the types of slopes? Give examples.

4. Differentiate finite and infinite slopes.

5. Mention the components of stability analysis of slopes.

6. State the types of failure surfaces.

7. Mention the two ways by which a finite slope will fail.

8. Mention any four methods for analysis of stability of slopes.

9. What is meant by factor of safety and stability number?

10. What is difference between stability number and stability factor?

11. Mention four slope protection measures.

12. Mention the suitable method for stability analysis of slopes in saturated clay and sand.

13. Which is the most critical stability problem for earth dam?

14. Write a brief note on Taylor's stability number.

15. Write a brief note on Friction Circle method.

16. Compare the factor of safety of infinite slope with sandy and clayey soils.

17. An infinite sand mass has b 20 kN/m3 and is just stable at a slope of 30

o

. If the entire

mass is inundated and ends up below the water table, will the slope remain stable?

18. What is the maximum depth of vertical cut that can be made in a purely cohesive soil of

UCC strength 32 KPa and unit weight 16 kN/m

3

. Taylor's stability number for this case is

0.261.

19. A long natural slope of cohesionless soil is inclined at 12o to the horizontal. Taking angle

of internal friction as 30

o

, determine the factor of safety of the slope.

20. A clayey soil has UCC strength 25 kN/m

2

and 19 kN/m

3

. If the stability number is

0.064, calculate the critical height of the slope.

# Soil mechanics question bank

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