Showing posts with label SOIL MECHANICS. Show all posts
Showing posts with label SOIL MECHANICS. Show all posts
Soil Mechanics and Foundation Engineering MCQ

Soil Mechanics and Foundation Engineering MCQ

civil

Soil Mechanics and Foundation Engineering Multiple Choice Questions :-

1. Residual soils are formed by
A. glaciers
B. wind
C. water
D. none of the above
Answer: D

2. Water content of soil can
A. never be greater than 100 %
B. take values only from 0 % to 100 %
C. be less than 0 %
D. be greater than 100 %
Answer: D

3. Which of the following types of soil is transported by gravitational forces ?
A. loess
B. talus
C. drift
D. dune sand
Answer: B

4. A fully saturated soil is said to be
A. one phase system
B. two phase system with soil and air
C. two phase system with soil and water
D. three phase system
Answer: C

5. Valid range for S, the degree of saturation of soil in percentage is
A. S>0
B. S<0
C. 0<S<100
D. 0 < S < 100
Answer: D

6. Constant head permeameter is used to test permeability of
A. silt
B. clay
C. coarse sand
D. fine sand
Answer: C

7. A soil has a bulk density of 22 kN/m3 and water content 10 %. The dry density of soil is
A. 18.6 kN/m3
B. 20.0 kN/m3
C. 22.0 kN/m3
D. 23.2 kN/m3
Answer: B

8. If the voids of a soil mass are full of air only, the soil is termed as
A. air entrained soil
B. partially saturated soil
C. dry soil
D. dehydrated soil
Answer: C

9. Valid range for n, the percentage voids, is
A. 0<n<100
B. 0<n<100
C. n>0
D. n<0
Answer: A

10. Select the correct statement.
A. Unit weight of dry soil is greater than unit weight of wet soil.
B. For dry soils, dry unit weight is less than total unit weight.
C. Unit weight of soil increases due to submergence in water.
D. Unit weight of soil decreases due to submergence in water.
Answer: D

11. Voids ratio of a soil mass can
A. never be greater than unity
B. be zero
C. take any value greater than zero
D. take values between 0 and 1 only
Answer: C

12. If the volume of voids is equal to the volume of solids in a soil mass, then the values of porosity and voids ratio respectively are
A. 1.0 and 0.0
B. 0.0 and 1.0
C. 0.5 and 1.0
D. 1.0 and 0.5
Answer: C

13. When the degree of saturation is zero, the soil mass under consideration represents
A. one phase system
B. two phase system with soil and air
C. two phase system with soil and water
D. three phase system
Answer: B

14. Select the correct range of density index,ID
A. lD>0
B. ID>0
C. 0 < lD < 1
D. 0 < ID < 1
Answer: D

15. If the degree of saturation of a partially saturated soil is 60%, then air content of the soil is
A. 40%
B. 60%
C. 80%
D. 100%
Answer: A

16. If the water content of a fully saturated soil mass is 100%, then the voids ratio of the sample is
A. less than specific gravity of soil
B. equal to specific gravity of soil
C. greater than specific gravity of soil
D. independent of specific gravity of soil
Answer: B

17. The ratio of volume of voids to the total volume of soil mass is called
A. air content
B. porosity
C. percentage air voids
D. voids ratio
Answer: B

18. Relative density of a compacted dense sand is approximately equal to
A. 0.4
B. 0.6
C. 0.95
D. 1.20
Answer: C

19. If the sand in-situ is in its densest state, then the relative density of sand is
A. zero
B. 1
C. between 0 and 1
D. greater than 1
Answer: B

20. Which of the following methods is most accurate for the determination of the water content of soil ?
A. oven drying method
B. sand bath method
C. calcium carbide method
D. pycnometer method
Answer: A

21. For proper field control, which of the following methods is best suited for quick determination of water content of a soil mass ?
A. oven drying method
B. sand bath method
C. alcohol method
D. calcium carbide method
Answer: D

22. A pycnometer is used to determine
A. water content and voids ratio
B. specific gravity and dry density
C. water content and specific gravity
D. voids ratio and dry density
Answer: C

23. Stoke’s law is valid only if the size of particle is
A. less than 0.0002 mm
B. greater than 0.2 mm
C. between 0.2 mm and 0.0002 mm
D. all of the above
Answer: C

24. In hydrometer analysis for a soil mass
A. both meniscus correction and dispersing agent correction are additive
B. both meniscus correction and dispersing agent correction are subtractive
C. meniscus correction is additive and dispersing agent correction is subtractive
D. meniscus correction is subtractive and dispersing agent correction is additive
Answer: C

25. The hydrometer method of sedimentation analysis differs from the pipette analysis mainly in
A. the principle of test
B. the method of taking observations
C. the method of preparation of soil suspension
D. all of the above
Answer: B

26. Which of the following is a measure of particle size range ?
A. effective size
B. uniformity coefficient
C. coefficient of curvature
D. none of the above
Answer: B

27. Which of the following statements is correct?
A. Uniformity coefficient represents the shape of the particle size distribution curve.
B. For a well graded soil, both uniformity coefficient and coefficient of curvature are nearly unity.
C. A soil is said to be well graded if it has most of the particles of about the same size
D. none of the above
Answer: D

28. Uniformity coefficient of a soil is
A. always less than 1
B. always equal to 1
C. equal to or less than 1
D. equal to or gi eater than 1
Answer: D

29. According to Atterberg, the soil is said to be of medium plasticity if the plasticity index PI is
A. 0 < PI < 7
B. 7<PI< 17
C. 17<PI<27
D. PI>27
Answer: B

30. If the natural water content of soil mass lies between its liquid limit and plastic limit, the soil mass is said to be in
A. liquid state
B. plastic state
C. semi-solid state
D. solid state
Answer: B

32. When the plastic limit of a soil is greater than the liquid limit, then the plasticity index is reported as
A. negative
B. zero
C. non-plastic (NP)
D. 1
Answer: B

33. Toughness index is defined as the ratio of
A. plasticity index to consistency index
B. plasticity index to flow index
C. liquidity index to flow index
D. consistency index to liquidity index
Answer: B

34. If the plasticity index of a soil mass is zero, the soil is
A. sand
B. silt
C. clay
D. clayey silt
Answer: A

35. The admixture of coarser particles like sand or silt to clay causes
A. decrease in liquid limit and increase in plasticity index
B. decrease in liquid limit and no change in plasticity index
C. decrease in both liquid limit and plasticity index
D. increase in both liquid limit and plasticity index
Answer: C

36. Select the correct statement.
A. A uniform soil has more strength and stability than a non-uniform soil.
B. A uniform soil has less strength and stability than a non-uniform soil.
C. Uniformity coefficient does not affect strength and stability.
D. Uniformity coefficient of a poorly graded soil is more than that of a well graded soil.
Answer: B

38. The water content of soil, which represents the boundary between plastic state and liquid state, is known as
A. liquid limit
B. plastic limit
C. shrinkage limit
D. plasticity index
Answer: A

39. Which of the following soils has more plasticity index ?
A. sand
B. silt
C. clay
D. gravel
Answer: C

40. At liquid limit, all soils possess
A. same shear strength of small magnitude
B. same shear strength of large magnitude
C. different shear strengths of small magnitude
D. different shear strengths of large magnitude
Answer: A

41. If the material of the base of the Casagrande liquid limit device on which the cup containing soil paste drops is
softer than the standard hard rubber, then
A. the liquid limit of soil always increases
B. the liquid limit of soil always decreases
C. the liquid limit of soil may increase
D. the liquid limit of soil may decrease
Answer: A

42. According to IS classification, the range of silt size particles is
A. 4.75 mm to 2.00 mm
B. 2.00 mm to 0.425 mm
C. 0.425 mm to 0.075 mm
D. 0.075 mm to 0.002 mm
Answer: D

43. Highway Research Board (HRB. classification of soils is based on
A. particle size composition
B. plasticity characteristics
C. both particle size composition and plasticity characteristics
D. none of the above
Answer: C

44. Inorganic soils with low compressibility are represented by
A. MH
B. SL
C. ML
D. CH
Answer: C

45. Sand particles are made of
A. rock minerals
B. kaolinite
C. illite
D. montmorillonite
Answer: A

46. The clay mineral with the largest swelling and shrinkage characteristics is
A. kaolinite
B. illite
C. montmorillonite
D. none of the above
Answer: C

47. Dispersed type of soil structure is an arrangement comprising particles having
A. face to face or parallel orientation
B. edge to edge orientation
C. edge to face orientation
D. all of the above
Answer: A

48. Effective stress is
A. the stress at particles contact
B. a physical parameter that can be measured
C. important because it is a function of engineering properties of soil
D. all of the above
Answer: C

49. Rise of water table above the ground surface causes
A. equal increase in pore water pressure and total stress
B. equal decrease in pore water pressure and total stress
C. increase in pore water pressure but decrease in total stress
D. decrease in pore water pressure but increase in total stress
Answer: A

50. The total and effective stresses at a depth of 5 m below the top level of water in a swimming pool are respectively
A. zero and zero
B. 0.5 kg/cm2 and zero
C. 0.5 kg/cm2 and 0.5 kg/cm2
D. 1.0 kg/cm2 and 0.5 kg/cm2
Answer: B

51. If the water table rises upto ground surface, then the
A. effective stress is reduced due to decrease in total stress only but pore water pressure does not change
B. effective stress is reduced due to increase in pore water pressure only but total stress does not change
C. total stress is reduced due to increase in pore water pressure only but effec-tive stress does not change
D. total stress is increased due to de-crease in pore water pressure but effective stress does not change
Answer: B

53. Quick sand is a
A. type of sand
B. flow condition occurring in cohesive soils
C. flow condition occurring in cohesionless soils
D. flow condition occurring in both cohesive and cohesionless soils
Answer: A

54. The hydraulic head that would produce a quick condition in a sand stratum of thickness 1.5 m, specific gravity 2.67 and voids ratio 0.67 is equal to
A. 1.0m
B. 1.5 m
C. 2.0 m
D. 3m
Answer: B

55. Physical properties of a permeant which influence permeability are
A. viscosity only
B. unit weight only
C. both viscosity and unit weight
D. none of the above
Answer: C

56. Select the correct statement.
A. The greater the viscosity, the greater is permeability.
B. The greater the unit weight, the greater is permeability.
C. The greater the unit weight, the smaller is permeability.
D. Unit weight does not affect per-meability.
Answer: B

57. Effective stress on soil
A. increases voids ratio and decreases permeability
B. increases both voids ratio and permeability
C. decreases both voids ratio and permeability
D. decreases voids ratio and increases permeability
Answer: C

58. If the permeability of a soil is 0.8 mm/sec, the type of soil is
A. gravel
B. sand
C. silt
D. clay
Answer: B

59. Which of the following methods is more suitable for the determination of permeability of clayey soil ?
A. constant head method
B. falling head method
C. horizontal permeability test
D. none of the above
Answer: B

60. Which of the following methods is best suited for determination of permeability of coarse-grained soils ?
A. constant head method
B. falling head method
C. both the above
D. none of the above
Answer: A

61. Due to a rise in temperature, the viscosity and the unit weight of the percolating fluid are reduced to 60% and 90% respectively.
If other things remain constant, the coefficient of permeability
A. increases by 25%
B. increases by 50%
C. increases by 33.3%
D. decreases by 33.3%
Answer: B

62. Coefficient of permeability of soil
A. does not depend upon temperature
B. increases with the increase in temperature
C. increases with the decrease in temperature
D. none of the above
Answer: B

63. The average coefficient of permeability of natural deposits
A. parallel to stratification is always greater than that perpendicular to stratification
B. parallel to stratification is always less than that perpendicular to stratification
C. is always same in both directions
D. parallel to stratification may or may not be greater than that perpendicular to stratification
Answer: A

64. The total discharge from two wells situated near to each other is
A. sum of the discharges from individual wells
B. less than the sum of the discharges from individual wells
C. greater than the sum of the discharges from individual wells
D. equal to larger of the two discharges from individual wells
Answer: B

65. The flownet for an earthen dam with 30 m water depth consists of 25 potential drops and 5 flow channels. The coefficient of permeability of dam material is 0.03 mm/sec. The discharge per meter length of dam is
A. 0.00018 nrVsec
B. 0.0045 m3/sec
C. 0.18m3/sec
D. 0.1125m3/sec
Answer: A

66. The most suitable method for drainage of fine grained cohesive soils is
A. well ppint system
B. vacuum method
C. deep well system
D. electroosmosis method
Answer: D

67. Total number of stress components at a point within a soil mass loaded at its boundary is
A. 3
B. 6
C. 9
D. 16
Answer: C

Soil Mechanics and Foundation Engineering Interview Questions

76. The slope of isochrone at any point at a given time indicates the rate of change of
A. effective stress with time
B. effective stress with depth
C. pore water pressure with depth
D. pore water pressure with time
Answer: C

77. Within the consolidation process of a saturated clay
A. a gradual increase in neutral pressure and a gradual decrease in effective pressure takes place and sum of the two is constant
B. a gradual decrease in neutral pressure and a gradual increase in effective pressure takes place and sum of the two is constant
C. both neutral pressure and effective pressure decrease
D. both neutral pressure and effective pressure increase
Answer: B

78. The value of compression index for a remoulded sample whose liquid limit is 50% is
A. 0.028
B. 0.28
C. 036
D. 0.036
Answer: B

79. Which one of the following clays behaves like a dense sand ?
A. over-consolidated ciay with a high over-consolidation ratio
B. over-consolidated clay with a low over-consolidation ratio
C. normally consolidated clay
D. under-consolidated clay
Answer: A

80. Coefficient of consolidation of a soil is affected by
A. compressibility
B. permeability
C. both compressibility and permeability
D. none of the above
Answer: C

81. Degree of consolidation is
A. directly proportional to time and inversely proportional to drainage path
B. directly proportional to time and inversely proportional to square of drainage path
C. directly proportional to drainage path and inversely proportional to time
D. directly proportional to square of drainage path and inversely proportional to time
Answer: B

82. Time factor for a clay layer is
A. a dimensional parameter
B. directly proportional to permeability of soil
C. inversely proportional to drainage path
D. independent of thickness of clay layer
Answer: B

84. Clay layer A with single drainage and coefficient of consolidation Cv takes 6 months to achieve 50% consolidation. The time taken by clay layer B of the same thickness with double drainage and coefficient of consolidation Cv/2 to achieve the same degree of consolidation is
A. 3 months
B. 6 months
C. 12 months
D. 24 months
Answer: A

85. Coefficient of consolidation for clays normally
A. decreases with increase in liquid limit
B. increases with increase in liquid limit
C. first increases and then decreases with increase in liquid limit
D. remains constant at all liquid limits
Answer: A

86. Direct measurement of permeability of the specimen at any stage of loading can be made
A. only in fixed ring type consolido-meter
B. only in floating ring type consolido-meter
C. both (A. and (B.
D. none of the above
Answer: A

87. Compressibility of sandy soils is
A. almost equal to that of clayey soils
B. much greater than that of clayey soils
C. much less than that of clayey soils
D. none of the above
Answer: C

88. Select the correct statement.
A. coefficient of compressibility of an over-consolidated clay is less than that of a normally consolidated clay
B. coefficient of compressibility of an over-consolidated clay is greater than that of a normally consolidated clay
C. coefficient of compressibility is cons-tant for any clay
D. none of the above
Answer: A

89. Coefficient of compressibility is
A. constant for any type of soil
B. different for different types of soils and also different for a soil under different states of consolidation
C. different for different types of soils but same for a soil under different states of consolidation
D. independent of type of soil but depends on the stress history of soil
Answer: B

90. The ultimate consolidation settlement of a structure resting on a soil
A. decreases with the increase in the initial voids ratio
B. decreases with the decrease in the plastic limit
C. increases with the increase in the initial voids ratio
D. increases with the decrease in the porosity of the soil
Answer: A

91. The ultimate consolidation settlement of a soil is
A. directly proportional to the voids ratio
B. directly proportional to the compression index
C. inversely proportional to the compression index
D. none of the above
Answer: B

92. A normally consolidated clay settled 10 mm when effective stress was increased from 100 kN/m2 to 200 kN/ m2. If the effective stress is further increased from 200 kN/ m2 to 400 kN/ m2, then the settlement of the same clay is
A. 10 mm
B. 20 mm
C. 40 mm
D. none of the above
Answer: A

93. Coarse grained soils are best compacted by a
A. drum roller
B. rubber tyred roller
C. sheep’s foot roller
D. vibratory roller
Answer: D

94. With the increase in the amount of compaction energy
A. optimum water content increases but maximum dry density decreases
B. optimum water content decreases but maximum dry density increases
C. both optimum water content and maximum dry density increase
D. both optimum water content and maximum dry density decrease[ES 93]
Answer: B

95. The maximum dry density upto which any soil can be compacted depends upon
A. moisture content only
B. amount of compaction energy only
C. both moisture content and amount of compaction energy
D. none of the above
Answer: C

97. For better strength and stability, the fine grained soils and coarse grained soils are compacted respectively as
A. dry of OMC and wet of OMC
B. wet of OMC and dry of OMC
C. wet of OMC and wet of OMC
D. dry of OMC and dry of OMC where OMC is optimum moisture content
Answer: B

98. Select the incorrect statement.
A. Effective cohesion of a soil can never have a negative value.
B. Effective angle of internal friction for coarse grained soils is rarely below 30�.
C. Effective angle of internal friction for a soil increases as state of compact-ness increases.
D. Effective angle of internal friction is a complicated function of mineralogy and clay size content.
Answer: A

99. For a loose sand sample and a dense sand sample consolidated to the same effective stress
A. ultimate strength is same and also peak strength is same
B. ultimate strength is different but peak strength is same
C. ultimate strength is same but peak strength of dense sand is greater than that of loose sand
D. ultimate strength is same but peak
Answer: C

100. The shear strength of a soil
A. is directly proportional to the angle of internal friction of the soil
B. is inversely proportional to the angle of internal friction of the soil
C. decreases with increase in normal stress
D. decreases with decrease in normal stress
Answer: D

101. In a consolidated drained test on a normally consolidated clay, the volume of the soil sample during shear
A. decreases
B. increases
C. remains unchanged
D. first increases and then decreases
Answer: A

102. Skempton’s pore pressure coefficient B for saturated soil is
A. 1
B. zero
C. between 0 and 1
D. greater than 1 [CS 95]
Answer: A

103. Shear strength of a soil is a unique function of
A. effective stress only
B. total stress only
C. both effective stress and total stress
D. none of the above
Answer: A

104. In a deposit of normally consolidated clay
A. effective stress increases with depth but water content of soil and un-drained strength decrease with depth
B. effective stress and water content increase with depth but undrained strength decreases with depth
C. effective stress and undrained strength increase with depth but water content decreases with depth
D. effective stress, water content and undrained strength decrease with depth
Answer: C

105. Select the incorrect statement.
Effective angle of shearing resistance
A. increases as the size of particles increases
B. increases as the soil gradation im-proves
C. is limited to a maximum value of 45�
D. is rarely more than 30� for fine grained soil
Answer: C

106. Unconfmed compressive strength test is
A. undrained test
B. drained test
C. consolidated undrained test
D. consolidated drained test
Answer: A

107. A cylindrical specimen of saturated soil failed under an axial vertical stress of 100kN/m2 when it was laterally unconfmed. The failure plane was inclined to the horizontal plane at an angle of 45�.
The values of cohesion and angle of internal friction for the soil are respectively
A. 0.5 N/mm2 and 30�
B. 0.05 N/mm2 and 0�
C. 0.2 N/mm2 and 0�
D. 0.05 N/mm2 and 45�
Answer: B

109. The angle that Coulomb’s failure envelope makes with the horizontal is called
A. cohesion
B. angle of internal friction
C. angle of repose
D. none of the above
Answer: A

111. If a cohesive soil specimen is subjected to a vertical compressive load, the inclination of the cracks to the horizontal is
A. 90�
B. 45�
C. 22.5�
D. 0�
Answer: B

112. Select the incorrect statement.
A. In a direct shear box test, the plane of shear failure is predetermined.
B. Better control is achieved on the drainage of the soil in a triaxial compression test.
C. Stress distribution on the failure plane in the case of triaxial compression test is uniform.
D. Unconfined compression test can be carried out on all types of soils.
Answer: D

113. If the shearing stress is zero on two planes, then the angle between the two planes is
A. 45�
B. 90�
C. 135�
D. 225�
Answer: B

114. In the triaxial compression test, the application of additional axial stress (i.e. deviator stress) on the soil specimen produces shear stress on
A. horizontal plane only
B. vertical plane only
C. both horizontal and vertical planes
D. all planes except horizontal and vertical planes
Answer: D

116. In a triaxial compression test when drainage is allowed during the first stage (i. e. application of cell pressure) only and not during the second stage (i.e. application of deviator stress at constant cell pressure), the test is known as
A. consolidated drained test
B. consolidated undrained test
C. unconsolidated drained test
D. unconsolidated undrained test
Answer: B

120. During the first stage of triaxial test when the cell pressure is increased from 0.10 N/mm2 to 0.26 N/mm2, the pore water pressure increases from 0.07 N/mm2 to 0.15 “N/mm2. Skempton’s pore pressure parameter B is
A. 0.5
B. -0.5
C. 2.0
D. – 2.0
Answer: A

121. Sensitivity of a soil can be defined as
A. percentage of volume change of soil under saturated condition
B. ratio of compressive strength of unconfined undisturbed soil to that of soil in a remoulded state
C. ratio of volume of voids to volume of solids
D. none of the above
Answer: B

122. Rankine’s theory of earth pressure assumes that the back of the wall is
A. plane and smooth
B. plane and rough
C. vertical and smooth
D. vertical and rough
Answer: C

123. The coefficient of active earth pressure for a loose sand having an angle of internal friction of 30� is
A. 1/3
B. 3
C. 1
D. 1/2
Answer: A

124. The major principal stress in an element of cohesionless soil within the backfill of a retaining wall is
A. vertical if the soil is in an active state of plastic equilibrium
B. vertical if the soil is in a passive state of plastic equilibrium
C. inclined at 45� to the vertical plane
D. none of the above
Answer: A

126. The effect of cohesion on a soil is to
A. reduce both the active earth pressure intensity and passive earth pressure intensity
B. increase both the active earth pressure intensity and passive earth pressure intensity
C. reduce the active earth pressure in-tensity but to increase the passive earth pressure intensity
D. increase the active earth pressure in-tensity but to reduce the passive earth pressure intensity [GATE 99]
Answer: C

127. A retaining wall 6m high supports a backfill with a surcharge angle of 10�. The back of the wall is inclined to the vertical at a positive batter angle of 5�. If the angle of wall friction is 7�, then the resultant active earth pressure will act at a distance of 2 m above the base and inclined to the horizontal at an angle of
A. 7�
B. 10�
C. 12�
D. 17�
Answer: C

128. Coefficient of earth pressure at rest is
A. less than active earth pressure but greater than passive earth pressure
B. greater than active earth pressure but less than passive earth pressure
C. greater than both the active earth pressure and passive earth pressure
D. less than both the active and passive earth pressures
Answer: B

137. Bishop’s method of stability analysis
A. is more conservative
B. neglects the effect of forces acting on the sides of the slices
C. assumes the slip surface as an arc of a circle
D. all of the above
Answer: C

138. Allowable bearing pressure for a foundation depends upon
A. allowable settlement only
B. ultimate bearing capacity of soil only
C. both allowable settlement and ultimate bearing capacity
D. none of above
Answer: C

142. The rise of water table below the foundation influences the bearing capacity of soil mainly by reducing
A. cohesion and effective angle of shearing resistance
B. cohesion and effective unit weight of soil
C. effective unit weight of soil and effective angle of shearing resistance
D. effective angle of shearing resistance
Answer: B

143. Terzaghi’s general bearing capacity formula for a strip footing
(C Nc + y D Nq + 0.5 Y NTB. gives
A. safe bearing capacity
B. net safe bearing capacity
C. ultimate bearing capacity
D. net ultimate bearing capacity where C = unit cohesion
Y =unit weight of soil D = depth of foundation B = width of foundation N� Nq, NY = bearing capacity factors
Answer: C

144. Terzaghi’s bearing capacity factors Nc, Nq and Nr are functions of
A. cohesion only
B. angle of internal friction only
C. both cohesion and angle of internal friction
D. none of the above
Answer: B

145. In the plate loading test for determining the bearing capacity of soil, the size of square bearing plate should be
A. less than 300 mm
B. between 300 mm and 750 mm
C. between 750 mm and 1 m
D. greater than 1 m
Answer: B

146. Select the incorrect statement.
A. Bearing capacity of a soil depends upon the amount and direction of load.
B. Bearing capacity of a soil depends on the type of soil.
C. Bearing capacity of a soil depends upon shape and size of footing.
D. Bearing capacity of a soil is indepen-dent of rate of loading.
Answer: A

147. A 600 mm square bearing plate settles by 15 mm in plate load test on a cohesionless soil under an intensity of loading of 0.2 N/ram2. The settlement of a prototype shallow footing 1 m square under the same intensity of loading is
A. 15 mm
B. between 15 mm and 25 mm
C. 25 mm
D. greater than 25 mm
Answer: B

148. A 300 mm square bearing plate settles by 15 mm in a plate load test on a cohesive soil when the intensity of loading is 0.2 N/mm2. The settlement of a prototype shallow footing 1 m square under the same intensity of loading is
A. 15 mm
B. 30 mm
C. 50 mm
D. 167 mm
Answer: C

149. Rise of water table in cohesionless soils upto ground surface reduces the net ultimate bearing capacity approximately by
A. 25%
B. 50%
C. 75%
D. 90%
Answer: B

150. Contact pressure beneath a rigid footing resting on cohesive soil is
A. less at edges compared to middle
B. more at edges compared to middle
C. uniform throughout
D. none of the above
Answer: B

151. In active state of plastic equilibrium in a non cohesive soil with horizontal ground surface

A. major principal stress is horizontal
B. minor principal stress is vertical
C. major principal stress is vertical
D. minor and major principal stresses are equally inclined to horizontal.
Answer: C

152. The reduction in volume of soil due to squeezing out of water from the voids, is termed

A. primary consolidation
B. primary compression
C. primary time effect
D. all the above.
Answer: D

153. �Drift� is the material picked up, mixed, disintegrated, transported and redeposited by

A. wind
B. gravitational force
C. glaciated water
D. all the above.
Answer: C

154. The consistency index of a soil is defined as the ratio of

A. liquid limit plus the natural water content to the plasticity index of the soil
B. liquid limit minus the natural water content to the plasticity index of the soil
C. natural water content of a soil minus plastic limit to the plasticity index of the soil
D. natural water content of a soil plus its plastic limit to the plasticity index of the soil.
Answer: B

155. A clay subjected to pressure in excess to its present over-burden, is said to be

A. pre-compressed
B. pre-consolidated
C. over-consolidated
D. all the above.
Answer: D

156. Pick up the correct statement from the following:

A. The void ratio in soils is defined as the ratio of the volume of voids to the volume of solids
B. The porosity of a soil is defined as the ratio of the volume of voids to the gross volume of the soil
C. The bulk density of a soil is defined as the unit weight of the soil
D. The dry density of a soil is defined as weight of solids to the total volume of the soil
E. All the above.
Answer: E

157. The shear strength of a soil

A. increases with an increase in the normal stress
B. is proportional to the cohesion of the soil
C. is generally known as the strength of the soil
D. is proportional to the tangent of the angle of internal friction
E. all the above.
Answer: E

158. The property of a soil which permits water to percolate through it, is called

A. moisture content
B. permeability
C. capillarity
D. none of these.
Answer: B

159. The triaxial apparatus is usually used for

A. unconsolidated-undrained test
B. consolidated-undrained test
C. drained test
D. all the above tests.
Answer: D

160. A pycnometer is used to determine

A. voids ratio
B. dry density
C. water content
D. density index.
Answer: C

161. Soils containing organic matters

A. are of spongy nature
B. swell with decrease of moisture
C. shrink with increase of moisture content
D. none of these.
Answer: A

162. A soil not fully consolidated under the existing over-burden pressure, is called

A. pre-consolidated
B. normally consolidated
C. under-consolidated
D. none of these.
Answer: C

163. The angle of internal friction is maximum for

A. angular-grained loose sand
B. angular-grained dense sand
C. round-grained dense sand
D. round-grained loose sand
E. clays.
Answer: B

164. A grillage foundation

A. is provided for heavily loaded isolated columns
B. is treated as spread foundation
C. consists of two sets of perpendicularly placed steel beams
D. all the above.
Answer: D

165. The plasticity of fine soils may be assessed by means of

A. dry strength test
B. toughness test
C. dilatancy test
D. all of these.
Answer: D

166. The density of soil can be increased

A. by reducing the space occupied by air
B. by elastic compression of soil grains
C. by expelling water from pores
D. All the above.
Answer: D

167. The length/diameter ratio of cylindrical specimens used in triaxial test, is generally

A. 1
B. 1.5
C. 2
D. 2.5
E. 3
Answer: C

168. Pick up the correct statement from the following:

A. The object of classifying soils is to arrange them into groups according to their properties and behaviour
B. A soil classification system is meant to provide an accepted and systematic method of describing the various types of soils eliminating personal factors
C. The first category of soil classification is based on grain size of the soil
D. The second category of soil classification is based on fine as well as coarse grains
E. All the above.
Answer: E

169. The bearing capacity of a soil depends upon

A. size of the particles
B. shape of the particles
C. cohesive properties of particles
D. internal frictional resistance of particles
E. all the above.
Answer: E

170. A direct shear test possesses the following disadvantage:

A. A relatively thin thickness of sample permits quick drainage
B. A relatively thin thickness of sample permits quick dissipation of pore pressure developed during the test
C. As the test progresses the area under shear, gradually changes
D. none of these.
Answer: C

171. Through a point in a loaded soil mass, there exists n typical planes mutually orthogonal on which the stress is wholly normal and no shear stress acts, if n is

A. 1
B. 2
C. 3
D. 4
Answer: C

172. The pressure that builds up in pore water due to load increment on the soil, is termed

A. excess pore pressure
B. excess hydrostatic pressure
C. hydrodynamic pressure
D. all the above.
Answer: D

173. The ratio of emax and emin of silty sand, is

A. 2.0
B. 5
C. 3.0
D. 3.5
E. 4.0
Answer: C

174. A flow net may be utilised for the determination of

A. exit gradient
B. seepage
C. hydrostatic pressure
D. seepage pressure
E. all the above.
Answer: E

175. The neutral stress in a soil mass is

A. force per neutral area
B. force per effective area
C. stess taken up by the pore water
D. stress taken up by solid particles.
Answer: C

176. If voids ratio is 0.67, water content is 0.188 and specific gravity is 2.68, the degree of saturation of the soil, is

A. 25%
B. 40%
C. 60%
D. 75%
Answer: D

177. If water content of a soil is 40%, G is 2.70 and void ratio is 1.35, the degree of saturation is

A. 70%
B. 75%
C. 80%
D. 85%
E. 90%
Answer: C

178. On wetting, cohesive soils,

A. loose permeability
B. gain shear strength
C. loose elasticity
D. decrease their shear strength.
Answer: D

179. Which one of the following statements is true for Mohr-Coulomb envelope ?

A. Coulomb suggests that the relationship between shear strength and normal stress, is adequately represented by the straight line
B. The generalised Mohr theory suggests that, though the shear stress depends on the normal stress, the relation is not linear
C. Coulomb and Mohr suggest that a definite relationship exists among the principal stress and the angle of internal friction
D. For an ideal pure friction material, the straight line passes through the origin.
E. All the above.
Answer: E

180. A structure is erected on an impervious clay whose thickness is 12 m. Drainage is possible both at upper and lower surfaces. Coefficient of consolidation is 0.015 cm2 per minute. For attaining 50% consolidation with a time factor 0.20, the number of days required

A. 3233
B. 3123
C. 33331
D. 3313
Answer: C

181. Pick up the correct statement from the following:

A. The range of water content between the liquid limit and plastic limit, is called plasticity index.
B. The ratio of the liquid limit minus the natural water content to the plasticity index of soils, is called consistency index
C. The ratio of natural water content minus its plastic limit to its plasticity index is called liquidity index
D. The ratio between plasticity index and flow index (i.e. slope of flow curve in case of liquid limit), is called toughness index
E. All the above.
Answer: E

182. �Talus� is the soil transported by

A. wind
B. water
C. glacier
D. gravitational force.
Answer: D

183. A triaxial shear test is prefered to direct shear test, because

A. it can be performed under all three driange conditions with complete control
B. precise measurement of pore pressure and change in volume during test, is not posible
C. stress distribution on the failure plane, is non uniform
D. none of these.
Answer: A

184. Pick up the correct statement from the following:

A. When stress decreases, void, ratio decreases
B. When stress decreases, coefficient of permeability decreases
C. When stress decreases, coefficient of volume change decreases
D. When stress decreases void ratio, co-effi-cients of per-meability and volume change decrease.
Answer: D

185. Chemical weathering of soil is caused due to

A. oxidation
B. carbonation
C. hydration
D. leaching
E. all the above.
Answer: E

186. Hydrometer readings are corrected for:

A. temperature correction
B. meniscus correction
C. dispersing agent correction
D. meniscus and dispersing agent corrections
E. temperature, meniscus and dispersing agent corrections.
Answer: E

187. Tergazhi�s theory of one dimensional consolidation assumes

A. soil is homogeneous and fully saturated
B. water and soil particles are incompressible
C. deformation of the soil, is entirely due to change in volume
D. Darcey�s law for the velocity of flow of water through soil, is perfectly valid
E. all the above.
Answer: E

188. The specific gravity of Calcite is

A. 2.65
B. 2.72
C. 2.85
D. 2.90
Answer: B

189. The ratio of volume of air voids to the volume of total voids, is known as

A. air content
B. percentage air voids
C. percentage voids
D. porosity.
Answer: A

190. A plane inclined at an angle f to the horizontal at which the soil is expected to stay in the absence of any lateral support, is known as

A. natural slope line
B. repose line
C. the f line
D. all the above.
Answer: D

191. Tergazhi�s theory of one dimensional consolidation assumes

A. load is applied in one direction
B. coefficient of permeability is constant
C. excess pore water drains out only in the vertical direction
D. time lag in consolidation is due entirely to permeability
E. all the above.
Answer: E

192. Pick up the correct statement from the following:

A. The dry density reduces by addition of water after attaining optimum moisture content
B. The line joining the peak of three moisture content graphs obtained by using three compactive energies, is called line of optimus
C. Well graded coarse grained soils can be compacted to a very high density as compared to fine grained soils
D. All the above. .
Answer: D

193. A soil mass is said to be in plastic equilibrium if

A. it is stressed to maximum
B. it is on the verge of failure
C. it is in plastic stage
D. it starts flowing.
Answer: B

194. Pick up the correct statement from the following:

A. The permeability of the coarse-grained soils may be reduced by grouting.
B. The process of injecting fluids (i.e. grouts) into the pores space of the soil, is called grouting.
C. The grouting increases the soil strength.
D. All the above.
Answer: D

195. A soil sample of mass specific gravity 1.92, has a moisture content 30%. If the specific gravity of solids is 2.75, the void ratio, is

A. 0.858
B. 0.860
C. 0.862
D. 0.864
Answer: C

196. The ratio of the weight of water to the weight of solids in a given mass of soil, is known

A. porosity
B. specific gravity
C. void ratio
D. water content.
Answer: D

197. During seepage through a soil, direction of seepage is always

A. parallel to equipotential lines
B. perpendicular to stream lines
C. perpendicular to equipotential lines
D. none of these.
Answer: C

198. The property of a soil which allows it to be deformed rapidly without rupture, elastic rebound and also a volume change, is known

A. porosity
B. plasticity
C. permeability
D. ductility.
Answer: B

199. The slip at critical angle, is generally known

A. d 1-line
B. rupture plane
C. slip plane
D. all the above.
Answer: D

200. Pick up the cohesive soil from the following:

A. Red earth
B. Clay
C. Black cotton soil
D. Compacted ground.
Answer: C

201. Pile foundations are generally preferred to for

A. bridge foundations
B. sky scrapper buildings
C. residential buildings
D. runways.
Answer: B

202. The angle of internal friction of clays, is usually

A. 0� to 5�
B. 5� to 20�
C. 20� to 30�
D. 30� to 45�
Answer: B

203. The specific yield of soil depends upon

A. compaction of stratum
B. distribution of pores
C. shape and size of particles
D. all the above.
Answer: D

204. Pick up the correct statement from the following:

A. Coefficient of compressibility is the decrease in void ratio per unit increase of pressure
B. The percent settlement at any time is called degree of consolidation
C. Time factor is a dimensionless quantity
D. The initial curve on either side of the point of unloading and reloading is called �virgin curve�
E. All the above.
Answer: E

205. �Loess� is silty clay formed by the action of

A. water
B. glacier
C. wind
D. gravitational force.
Answer: C

206. The maximum possible value nf dry density is referred to as

A. dry density
B. zero air voids
C. saturation dry density
D. all the above.
Answer: D

207. Failure of a slope occurs only when total shear force is

A. equal to total shearing strength
B. greater than total shearing strength
C. less than total shearing strength
D. none of these.
Answer: B

208. Pick up the correct statement from the following:

A. A soil having pH value more than 7 is an acidic soil
B. A soil having pH value less than 7 is an acidic soil
C. A soil having pH value more than 7 is an alkaline soil
D. A soil containing chemicals for the manufacture of portland cement is preferred.
Answer: B

209. Cohesionless soil is

A. sand
B. silt
C. clay
D. clay and silt.
Answer: A

210. The shearing force acting along the slice of a curved surface of slippage, causes the soil to slide

A. down at the centre
B. down at the toe
C. upward at the centre
D. none of these.
Answer: A

211. The seepage exit gradient in a soil is the ratio of

A. total head to the length of seepage
B. flow line to slope
C. head upstream to that at downstream
D. head loss to the length of the seepage
E. none of these.
Answer: D

212. Sedimentation analysis is based on the assumption:

A. soil particles are spherical
B. particles settle independent of other particles
C. walls of the jar do not affect the settlement .
D. all the above.
Answer: D

213. The maximum pressure which a soil can carry without shear failure, is called

A. safe bearing capacity
B. net safe bearing capacity
C. net ultimate bearing capacity
D. ultimate bearing capacity.
Answer: A

214. For general engineering purposes, soils are classified by

A. particle size classification system
B. textural classification system
C. High Way Research Board (HRB), classification system
D. unified soil classification system.
Answer: D

215. If there is no impervious boundary at the bottom of a hydraulic structure, stream lines tend to follow :

A. a straight line
B. a parabola
C. a semi-ellipse
D. a semi-circle.
Answer: C

216. The change of moisture content of soils, changes the

A. value of the angle of repose
B. amount of compaction required
C. cohesive strength of soil
D. all the above.
Answer: D

217. A failure wedge develops if a retaining wall

A. moves away from the backfill
B. moves towards the backfill
C. sinks downwards
D. stresses equally by vertical and horizontal forces.
Answer: A

218. For determining the ultimate bearing capacity of soil, the recommended size of a square bearing plate to be used in load plate test should be 30 to 75 cm square with a minimum thickness of

A. 5 mm
B. 10 mm
C. 15 mm
D. 20 mm
E. 25 mm
Answer: E

219. The water content in a soil sample when it continues to loose weight without loosing the volume, is called

A. Shrinkage limit
B. Plastic limit
C. liquid limit
D. semi-solid limit.
Answer: A

220. When a cohesionless soil attains quick condition, it looses

A. shear strength
B. bearing capacity
C. both (a) and (b)
D. neither (a) nor (6).
Answer: C

221. Pick up the correct definition from the following:

A. The lateral pressure exerted by the soil when the retaining wall moves away from the back fill, is generally known as active earth pressure of the soil
B. The lateral pressure exerted by the soil when the retaining wail moves towards the soil, is generally known as �Passive earth pressure of the soil�
C. The lateral pressure exerted by the soil when the retaining wall has no movement relative to the back fill, is known as �earth pressure at rest of the soil�
D. All the above.
Answer: D

Test for Moisture on soil or Determination of Water Content on soil

Test for Moisture on soil or Determination of Water Content on soil

Test for Moisture content on soil or Determination of Water Content on soil

Following test conducted on soil for determination of water content or Moisture

1 Oven Drying Method 2 Sand Bath Method 3 Alcohol Method 4 Calcium Carbide Method 5 Pycnometer test 6 Radiation Method 7 Torsion Balance Method

Oven Drying Method

Oven drying method is the most accurate and simplest method for water content determination. In this method complete drying of soil sample occur and water content in sample is calculated accurately by a maintained temperature in the oven ( 105° C to 110° C) for 24 hours. Note: For highly organic soils a low temperature of about 60° C is preferable. If Gypsum is present, the temperature should not be more than 80° C but for a long time.

Table of Contents

 

The Oven Drying Method is used to determine the water content in a specific soil.

This method is necessary to understand the bearing capacity as well as the probable settlement of the soil. It is carried out in the laboratory itself.

 


 

  1. Apparatus Required  

i. Thermostatically controlled oven maintained at a temperature of 110 ± 5oC

ii. Weighing balance, with an accuracy of 0.04% of the weight of the soil taken 

iii. Air-tight container made of non-corrodible material with a lid

iv. Tongs

 


 

  2. Quantity of Soil Required for Water Content Determination  

Size of particles more than 90% of passingMinimum Quantity ( grams)
425-micron sieve25
2 mm sieve50
4.25 mm sieve200
10 mm sieve300
20 mm sieve500
40 mm sieve1000

 


 

  3. Procedures in Oven Drying Method of Soil  

The procedure for the oven drying method can be listed as follows:

i. The air-tight container along with its lid must be first weighed(W1).

ii. The specimen sample is then taken in the container, and the weight of a container along with the lid and sample is taken, say W2.

iii. Then, the container is left in the oven. The specimen is dried to a constant weight at temperatures ranging from 105 to 110 degrees Celsius for about 16 to 24 hours.

iv. The container, along with the lid and the dried sample, are finally weighed(W3).

v. The moisture content is then calculated using the following formula:

W= [ (W2-W3) / (W3-W1) ] * 100

Where,

W1= Weight of the container with a lid in grams

W2= Weight of the container with lid and wet sample in grams

W3= Weight of the container with lid and dry sample in grams

Note: To get an accurate value, a minimum of three soil samples should be taken to test, and average water content should be taken as a result. 

 


 

  4. Observations and Calculations of Oven Dry Method  

Sl. No.Observations and CalculationsDetermination No.
123
Observation
1Container No.
2Weight of empty container (W1)
3Weight of container + soil (W2)
4Weight of container + dry soil (W3)
Calculations
5Weight of water Mw= M2 – M3
6Weight of solids, Ms= M3 – M1
7Water content= (5)/(6)x100

 


 

  5. Result of Oven Dry Method  

Water content of the given soil sample = ______%

 


 

  6. Precautions in Oven Drying Method  

a. Temperature of the oven should be maintained between (105°-110°)C.

b. Wait to cool for the dry soil in a container to remove from the oven ( or use tongs).

c. For accurate calibration, the thermostat should be kept on checking regularly.

 

INTERPRETATION OF FLOWNET - IN SOIL MECHANICS

INTERPRETATION OF FLOWNET - IN SOIL MECHANICS

INTERPRETATION OF FLOW NET - IN SOIL MECHANICS :


FLOW RATE:

Let the total head loss across the flow domain be ΔH, that is, the difference between upstream and downstream water level elevation. 
Then the head loss (Δh) between each consecutive pair of equipotential lines is 
  • ∆h = ∆H/Nd 
where Nd is the number of equipotential drops, 
that is = the number of equipotential lines minus one. 
  • Therefore, Δh = ΔH/Nd 
From Darcy’s law, the flow rate is 
  • q= k.H.Nf /Nd 
where Nf is the number of flow channels (number of flow lines minus one).
The ratio N f /N d is called the shape factor. Finer discretization of the flow-net by drawing more flow lines and equipotential lines does not significantly change the shape factor. 
 

Hydraulic Gradient:

  • You can find the hydraulic gradient over each curvilinear square by dividing the head loss by the length, L.that is,
  • i= ∆h/L 
  • You should notice that L is not constant. Therefore, the hydraulic gradient is not constant. 
  • The maximum hydraulic gradient occurs where L is a minimum; that is, 
  • Imax =∆h / Lmin 
  • where L min is the minimum length of the cells within the flow domain. 
  • Usually, L min occurs at exit points or around corners, and it is at these points that we usually get the maximum hydraulic gradient.  

Critical Hydraulic Gradient:

  • We can determine the hydraulic gradient that brings a soil mass (essentially, coarse-grained soils) to static liquefaction. 
  • Static liquefaction, called quicksand condition, occurs when the seepage stress balances the vertical stress from the soil. The critical hydraulic gradient, i cr , is
  •  icr = (G-1) /1+e) 
  • where G s is specific gravity of the soil particles, and e is the void ratio. 
  • Since G s is constant, the critical hydraulic gradient is solely a function of the void ratio of the soil. 
  • In designing structures that are subjected to steady-state seepage, it is absolutely essential to ensure that the critical hydraulic gradient cannot develop.  

Pore Water Pressure Distribution:

 

Uplift Forces:

Lateral and uplift forces due to groundwater flow can adversely affect the stability of struc- tures such as dams and weirs. The uplift force per unit length (length is normal to the xz plane) is found by calculating the porewater pressure at discrete points along the base (in the x direction,) and then finding the area under the porewater pressure distribu- tion diagram  

IMPORTENT Terms:

  • 1. A flow-net is a graphical representation of a flow field that satisfies Laplace’s equation and comprises a family of flow lines and equipotential lines. 
  • 2. From the flownet, we can calculate the flow rate, the distribution of heads, pore- water pressures, and the maximum hydraulic gradient. 
  • 3. The critical hydraulic gradient should not be exceeded in design practice.

 

SUMMARY:

  • The governing equation for flow of water through soils is Laplace’s equation. 
  • A graphical technique, called flownet sketching, was used to solve Laplace’s equation.
  • A flownet consists of a network of flow and equipotential lines. 
  • From the flow-net, we can calculate the flow rate, the distribution of heads, pore-water pressures, and the maximum hydraulic gradient.
PHASES OF SOIL INVESTIGATION WORK

PHASES OF SOIL INVESTIGATION WORK

PHASES OF A SOILS INVESTIGATION 

 
The scope of a soils investigation depends on 
  • The type, size, and importance of the structure; 
  • The client and Economy; 
  • The engineer’s familiarity with the soils at the site; and 
  • Local building codes. 
Structures that are sensitive to settlement such as machine foundations and high-use buildings usually require a more thorough soils investigation than a foundation for a house. A client may wish to take a greater risk than normal to save money and set limits on the type and extent of the site investigation.
     You should be cautious about any attempt to reduce the extent of a soils investigation below a level that is desirable for assuming acceptable risks for similar projects on or within similar ground conditions. 
    If the geotechnical engineer is familiar with a site, he/she may undertake a very simple soils investigation to confrm his/ her experience. Some local building codes have provisions that set out the extent of a site investigation. 
It is mandatory that a visit be made to the proposed site. 

A soils investigation has following components. 

  • The first component is done prior to design. 
  • The second component is done during the design process. 
  • The third component is done during construction. 
  • The second and third components are needed for contingencies. 
  • The first component is generally more extensive and is conducted in phases. 
 

Phases of SOIL INVESTIGATION are as follows: 

  • 1. DESK STUDY
  • 2.PRELIMINARY RECONNAISSANCE OR A SITE VISIT
  • 3.DETAILED SOIL EXPLORATION
  • 4.LABORATORY TESTING
  • 5.WRITE A REPORT
 

Phase I.  DESK STUDY

This phase is sometimes called “desk study.” It involves collection of available information such as a site plan; type, size, and importance of the structure; loading conditions; previous geotechnical reports; maps, including topographic maps, aerial photo- graphs, still photographs, satellite imagery, and geologic maps; and newspaper clippings. An assortment of maps giving geology, contours and elevations, climate, land use, aerial photos, regional seismicity, and hydrology are available on the Internet. Geographical information system (GIS)—an integration of software, hardware, and digital data to capture, manage, analyze, and display spatial information— can be used to view, share, understand, question, interpret, and visualize data in ways that reveal relationships, patterns, and trends. GIS data consist of discrete objects such as roads and continuous fields such as elevation. These are stored either as raster or vector objects. Google Earth can be used to view satellite imagery, maps, terrain, and 3D structures. You can also create project maps using Google Earth. 
 

Phase II. PRELIMINARY RECONNAISSANCE OR A SITE VISIT

 

Preliminary reconnaissance or a site visit to provide a general picture of the topography and geology of the site. It is necessary that you take with you on the site visit all the information gathered in Phase I to compare with the current conditions of the site. Your site visit notes should include: 
  • ■ Photographs of the site and its neighborhood. 
  • ■ Access to the site for workers and equipment. 
  • ■ Sketches of all fences, utility posts, driveways, walkways, drainage systems, and so on. 
  • ■ Utility services that are available, such as water and electricity. 
  • ■ Sketches of topography including all existing structures, cuts, flls, ground depression, ponds, and so on. 
  • ■ State of any existing building at the site or nearby. Your notes should include exterior and interior cracks, any noticeable tilt, type of construction (e.g., brick or framed stucco building), evidence of frost damage, molds, and any exceptional features. 
  • ■ Geological features from any exposed area such as a road cut. 
  • ■ Occasionally, a few boreholes, trenches, and trial pits may be dug to explore the site. 
 

Phase III. DETAILED SOIL EXPLORATION

Detailed soils exploration. The objectives of a detailed soils exploration are: 
■ To determine the geological structure, which should include the thickness, sequence, and extent of the soil strata. 
■ To determine the groundwater conditions. 
■ To obtain disturbed and undisturbed samples for laboratory tests. 
■ To conduct in situ tests. 
 

Phase IV.  LABORATORY TESTING

Laboratory testing. The objectives of laboratory tests are: 
■ To classify the soils. 
■To determine soil strength, failure stresses and strains, stress–strain response, permeabilities, compactibility, and settlement parameters.
Not all of these may be required for a project. 
 

Phase V. WRITE A REPORT

Write a report. The report must contain a clear description of the soils at the site, methods of exploration, soil strati-graphy, in situ and laboratory test methods and results, and the location of the groundwater. You should include information on and/or explanations of any unusual soil, water-bearing stratum, and any soil and groundwater conditions such as frost susceptibility or waterlogged areas that may be troublesome during construction. 
 
Key points 
1. A soils investigation is necessary to determine the suitability of a site for its intended purpose. 
2. A soils investigation is conducted in phases. Each phase affects the extent of the next phase. 
3. A clear, concise report describing the conditions of the ground, soil stratigraphyStratigraphy is a branch of Geology and the Earth Sciences that deals with the arrangement and succession of strata, or layers, as well as the origin, composition and distribution of these geological strata., soil parameters, and any potential construction problems must be prepared for the client
 
 
 
Index Properties and Key Parameter of Soil - Civil Engineering

Index Properties and Key Parameter of Soil - Civil Engineering

Index Properties and Parameters of Soil 

DEFINITIONS OF BASIC KEY TERMS OF SOIL

Index Properties of Soil  

Water Content

Water content (w) is the ratio of the weight of water to the weight of solids.often expressed as a percentage

Index Properties of Soil 

Void Ratio

Void ratio (e) is the ratio of the volume of void spaces to the volume of solids.The void ratio is usually expressed as a decimal quantity.
 

Index Properties of Soil

 Porosity

Porosity (n) is the ratio of the volume of voids to the total volume of soil. 
 

Index Properties of Soil

 Degree of Saturation

Degree of saturation (S) is the ratio of the volume of water to the volume of voids. 
 

Index Properties of Soil

 Bulk Unit weight

Bulk unit weight (γ) is the weight density, that is, the weight of a soil per unit volume. 
 

Index Properties of Soil

 Saturated Unit Weight

Saturated unit weight (γsat) is the weight of a saturated soil per unit volume. 
 

Index Properties of Soil

 Dry Unit Weight

Dry unit weight (γd) is the weight of a dry soil per unit volume. 
 

Index Properties of Soil 

 Effective Unit Weight

 Effective unit weight (γ′) is the weight of a saturated soil submerged in water per unit volume. 


Index Properties of Soil

 Relative Density

Relative density (Dr) is an index that quantifes the degree of packing between the loosest and densest state of coarse-grained soils. 
 

Index Properties of Soil

 Density Index

Density index (Id) is a similar measure (not identical) to relative density. 
 

Index Properties of Soil

 Unit Weight

Unit weight ratio or density ratio (Rd) is the ratio of the unit weight of the soil to that of water. 
 

Index Properties of Soil

 Swell Factor

Swell factor (SF) is the ratio of the volume of excavated material to the volume of in situ material (sometimes called borrow pit material or bank material). 
 

Index Properties of Soil

 Liquid Limit

Liquid limit (LL) is the water content at which a soil changes from a plastic state to a liquid state. 
 

Index Properties of Soil 

 Plastic Limit

Plastic limit (PL) is the water content at which a soil changes from a semisolid to a plastic state. 
 

Index Properties of Soil

 Shrinkage Limit

Shrinkage limit (SL) is the water content at which a soil changes from a solid to a semisolid state without further change in volume. 
 

Index Properties of Soil

 Plasticity Index

Plasticity index (PI) is the range of water content for which a soil will behave as a plastic material (deformation without cracking). 
 

Index Properties of Soil

 Liquidity Index

Liquidity index (LI) is a measure of soil strength using the Atterberg limits (liquid and plastic limits based on test data). 
 

Index Properties of Soil

 Shrinkage Index

Shrinkage index (SI) is the range of water content for which a soil will behave as a semisolid (deformation with cracking).

 

 

Basic Definitions and Simple Tests on Soil Mechanics

Basic Definitions and Simple Tests on Soil Mechanics

Basic Definitions and Simple Tests on Soil Mechanics


Introduction

This page discuss some of the basic definitions and simple tests used throughout the subject.

  • The phase diagram is a simple, diagrammatic representation of a real soil.
  • The phase diagram is also known as block diagram.
  • A soil mass consists of solid particles, water and air, which are segregated and placed separately, known as three-phase system.
  • A three-phase system becomes a two-phase system when the soil is absolutely dry (solids + air) or when the soil is fully saturated (solids + water).
  • In phase diagram, volumes are represented on the left side, whereas weights are represented on the right side.



Volumetric Relationships

In total, there are fi ve volumetric relationships. These are as follows:

1. Void ratio (e):

  • It is defi ned as the ratio of volume of voids to volume of solids.
  • Range: e > 0
  • e = Vv/Vs
  • For some soils, it may have a value even greater than unity.
  • The void ratio of coarse grained soils is, generally, smaller than that of a fi ne-grained soil.

2. Porosity (n):

  • It is defined as the ratio of volume of voids to the total volume.
  • n Vv/V
  • Range: 0 < n < 1
  • Also called ‘percentage voids’.
  • Both porosity and void ratio are the measure of the degree of denseness (or looseness) of soil. Relationship between n and e:
  • e = n /(n-1)
  • n = e /(e+1)

3. Degree of saturation (Sr ):

  • It is defined as the ratio of volume of water to the volume of voids, in soil.
  • It is expressed as a percentage.
  • Sr = Vw/Vv
  • Range: 0 ≤ S ≤ 100%
  • For dry soil, V w = 0 ⇒ S = 0
  • For saturated soil, V w = V v ⇒ S = 100%

4. Percentage air voids (na ):

  • It is defined as the ratio of volume of air to total volume, of soil.
  • na=Va/V
  • Range: 0 ≤ n a ≤ n

5. Air content (ac ):

  • It is defined as the ratio of volume of air to the volume of voids, in soil.
  • ac=Va/Vv
  • Range: 0 ≤ a c ≤ 100%
  • For dry soil, V a = V v ⇒ a c = 100%
  • For saturated soil, V a = 0 ⇒ a c = 0
  • Relationships between a c , n a , n and s:
  • ac + S =1
  • na= n*ac
Soil Structure and Clay Mineralogy

Soil Structure and Clay Mineralogy

Soil Structure and Clay Mineralogy

Soil Structure

  • Geometric arrangement of soil particles with respect to one another is known as soil structure.
  • Depending upon the particle size and mode of formation, the following types are found.

Single Grained Structure

  • Found in coarse grained soils, like gravel, sand.
  • The major cause for formation is gravitational force. Here the surface forces are negligible.
  • Under the influence of gravitational forces, the grains will assume a particle to particle contact referred to as single grained structure.

Single grained structure may be loose or dense as shown below.

  • (a) Loosest state
  • (b) Densest state
Single Grained Structure


Honey-comb Structure

  • It is possible for fine sands or silts.
  • Both gravitational force and surface force are responsible.
  • Such a structure can support loads, only under static conditions.
  • Under vibrations and shocks, the structure collapses and large deformations take place.
Honey-comb Structure

Flocculated Structure

  • This structure occurs in clays.
  • Clay particles have a negative charge on surface and a positive charge on edges and flocculated structure occurs when there is an edge-to-face orientation.
  • A flocculated structure is formed when there is a net attractive force between the particles.
  • Soils with flocculent structure have a high void ratio and water content and, also have a low compressibility, a high permeability and high shear strength.


Flocculated Structure


Dispersed Structure

  • A dispersed develops in clays that have been reworked or remolded.
  • Remoulding converts ‘edge-to-face’ orientation to ‘face- to-face’ orientation.
  • Dispersed structure is formed when there is a net repulsive force between particles.
  • Have low shear strength, high compressibility and low permeability.

Dispersed Structure

Composite Structure

  • A composite structure in the form of coarse grained skeleton or clay-matrix is formed when soil contains different types of soil particle
Composite Structure


Clay Mineralogy

  • Important clay minerals kaolinite, Illite, montmorillonite and halloysite, are present in clays.
  • In coarse grained soils, like gravel, sand, rock minerals like quartz, feldspar, mica, etc., are present.

Kaolinite Mineral

  • One molecule of kaolinite mineral is made of one silica sheet and one gibbsite sheet.
  • Various such molecules are joined by hydrogen bonds.
  • These show less change in volume due to changes in moisture content.
  • Kaolinite is thus the least active of clay minerals.
  • Example: China clay

Illite Mineral

  • One molecule of Illite is made of two silica sheets and one gibbsite sheet, but in silica sheet, silicon atom is replaced by aluminum atom.
  • Various such molecules are joined together by ionic bond (potassium ion).
  • These shows medium swelling and shrinkage properties.
  • Example: Alluvial soil.

Montmorillonite Mineral (Also Called ‘Smectite’)

  • One molecule of montmorrilonite mineral is made of two silica sheets and one gibbsite sheet.
  • Gibbsite sheet is sandwiched between silica sheets.
  • Various such molecules are loosely bonded through water.
  • These soils show high volume changes on moisture variation (i.e., large swelling and large shrinkage).
  • Example: Black cotton soils, bentonite soil.


Diffuse Double Layer and Adsorbed Water

  • Clay particles usually carry a negative charge on their surface.
  • Because of net negative charge on the surface, the clay particles attract cations, such as potassium, calcium and sodium, from the moisture present in the soil to reach equilibrium.
  • The layer extending from the clay particle surface to the limit of attraction is known as a diffuse double layer.
  • The water held in the zone of the diffuse double layer is known as adsorbed water or oriented water.
  • The plasticity characteristics of clay are due to the presence of adsorbed water.
  • Clays using non-polar liquid, such as kerosene in place of water, does not show any plasticity characteristics.
  • The thickness of adsorbed water layer is about 10–15 A°for colloids, but may be up to 200 A° for silts.