Btech Aktu Geotechnical Engineering KCE-501 Short Question, Quantum Book Pdf

Learn about Geotechnical Engineering B.Tech AKTU Quantum Book Short Question Notes. Investigate the fundamentals of foundation design, geotechnical analysis, and soil mechanics for sturdy and durable construction projects.

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Unit-I: Origin and Classification of Soil (Short Question)

Q1.  Define origin of soil. 

Ans. Soils are formed by weathering of rocks and minerals at or near the earth’s surface by either: 

• i. Physical disintegration due to the action of natural or mechanical agents,
• ii. Chemical decomposition due to the action of chemical agents. 

Q2. Illustrate the different methods of soil formation. 

Ans. Following are the two methods of soil formation:

1. Physical Disintegration: lt is due to :

i. Temperature changes.                                 ii. Abrasion.

iii. Wedging action of ice                                 iv. Spreading of roots of plants.  

2. Chemical Decomposition: It includes : 

i. Hydration.                                                     ii. Carbonation.

iii. Oxidation.                                                   iv. Leaching. 

v. Hydrolysis. 

Q3. What is muck? 

Ans. Fine particles and highly degraded organic debris are combined to form muck. It has a silky consistency and is a deep shade of black. 

Q4. Draw the figure of element separated soil into three phases.  

Ans. 

Q5. Write methods to determine the water content.  

Ans. Following are the methods which are used to determine the water content: 

i. Oven dry method.                                       ii. Sand bath method.

iii. Alcohol method.                                         iv. Calcium carbide method.  

v. Radiation method, etc.  

Q6. Define the term consistency. 

Ans. Consistency is a phrase that is used to qualitatively characterise the degree of hardness of a soil using terms like soft, medium, firm, stiff, or hard. It shows how easily a soil can deform in relation to other soils.

Q7. Define bulk unit weight. Write the relation between bulk unit weight and dry unit weight. 

Ans. Bulk Unit Weight: It is defined as the total weight per unit total volume. Thus, 

Q8. Define Consistency limits. 

Ans. Consistency Limits (Atterberg Limits): Atterberg limits are also referred to as the liquid limit, plastic limit, and shrinkage limit. The water content at which a change in soil behaviour occurs from a liquid to a plastic state, a plastic state to a semisolid state, and a semisolid state to a solid state is known as the shrinkage limit.

Q9. What is liquid limit ?

Ans. Liquid Limit (w_L): It is the soil’s water content, which may be determined using any defined process, at which the soil is essentially in a liquid state yet has negligible barrier to flow.

Q10. Define plastic and shrinkage limit. 

Ans. i. Plastic Limit: It is described as the amount of water at which a soil would just start to disintegrate if rolled into a thread about 3 mm in diameter.

ii. Shrinkage Limit: The maximum water content at which a reduction in moisture content does not result in a reduction in the volume of the soil mass is known as this water content. With full saturation of the soil mass, it is also the lowest value of water content.

Q11. What are the basic structural units of clay minerals ?

Ans. Structure of Clay Minerals: Structure of clay minerals are built of two fundamental crystal sheets: 

• 1. Tetrahedral or silica sheet.
• 2. Octahedral or Alumina sheet. 

Q12. Briefly explain single grain structure. 

Ans. Gravitational forces predominate over surface forces in bulky grains that make up cohesionless soils like gravel and sand. When these soils are deposited, the particles gravitationally pull themselves to the equilibrium location. Every particle interacts with those around it. Single-grained structure is the name given to the resulting soil structure.

Q13. Briefly explain the flocculant grain structure. 

Ans. When there is a net attractive force between particles, flocculant structure is created. Clays have flocculated structure. The kind and concentration of clay particles as well as the amount of salts in the water affect how much a clay deposit will flocculate. 

Q14. What is relative consistency ?

Ans. The ratio of a soil’s plasticity index to the difference between its liquid limit and its natural water content is known as the relative consistency (I_c) or consistency index.

Q15. Explain index properties of soil. 

                              OR

Define index properties of soil. 

Ans. Index Properties of Soil: The procedure used to categorize a soil is known as a classification test. The numerical outcomes of such tests are referred to as the soil’s index properties. These are divided into two following categories : 

• 1. Soil grain properties. 
• 2. Soil aggregate properties. 

Q16. What is relative density or density index ?

Ans. A cohesionless soil’s relative density (I_D) is calculated as the difference between the void ratios in the loosest and densest states divided by the difference between the void ratios in the soil’s natural state.

Q17. Write down the expressions for coefficient of uniformity and coefficient of curvature.

Ans.

Q18. Define flow index.  

Ans. The ordinate of the water content on the natural scale against the number of blows on the log scale yields the flow index, which is the slope of the flow curve. It is given by, 

Q19. How will you define the toughness index ?

Ans. Toughness index is defined as the ratio of plasticity index to flow index.

Q20. What is effective size ? 

Ans.  Effective size is the diameter in the grain size distribution curve corresponding to 10 % finer. 

Q21. Explain fineness modulus.  

Ans.  The fineness modulus measures the proportion of fine soil to coarse soil. For instance, if 5% clay and 2% silt are present in a coarse soil, the fineness modulus will be equivalent to 7%.

Q22. The void ratio of soil sample is 1, determine the corresponding porosity of the soil sample.  

Ans. Given: Void ratio, e = 1

To Find: Porosity. 

Unit-II: Soil Hydraulics (Short Question)

Q1. What do you understand by effective stress ? 

Ans. The difference between the total stress and the pore water pressure is referred to as effective stress. It is an abstract quantity and expressed as.

Q2. What is neutral stress in soil grains ?

Ans. The stress borne by the pore water, which is constant in all directions, is referred to as neutral stress. This is denoted by the letter u and is also known as pore water pressure. This will be equal to y 𝛄_w Z ata depth below the water table.  

Q3. State the Darcy’s law. 

Ans. As per Darcy’s law for laminar flow in saturated soils, velocity (v) of flow is directly proportional to hydraulic gradient (i). 

Q4. Explain the coefficient of permeability.

Ans. It is described as the flow rate that would occur at a given hydraulic gradient. Coefficient of permeability,

Q5. What are the limitations of Darcy’s law ? 

Ans. The limitations of Darcy’s law as follows : 

• i. If the soil flow is laminar, it is valid.
• ii. Colloidal clay is not an eligible candidate.
• iii. There should be a roughly linear relationship between the velocity and the hydraulic gradient.

Q6. What is permeability?

Ans. Permeability is the quality of a soil that allows water (or any other liquid) to pass through it. 

Q7. What are the different characteristics of flownet ?

Ans. The characteristics of flownet can be summarized as under:

• i. A flow line and an equipotential line should intersect at a right angle.
• ii. Discharge (𝜟q) between any two adjacent flow lines is constant and the drop of head (𝜟h) between the two adjacent equipotential lines is constant. 

Q8. Define analogy method by Laplace equation.

Ans.

• i. The electrical analogy technique is predicated on the idea that Ohm’s law, which regulates the flow of electricity in a conducting medium, is equivalent to Darcy’s law, which rules the flow of water through soils.
• ii. According to the analogy, the current’s relationship to voltage drop is analogous to how seepage’s relationship to heat dissipation is.
• iii. The boundary conditions of an electrical model are created to resemble those of the soil model. By connecting the locations of equal voltage, the equipotential lines are formed.
• iv. The building of the flow net in the model uses the flow pattern that was acquired from the electrical model.

Q9. List the factors affecting permeability of soils. 

Ans. Following are the factors that affect the permeability of soils: 

 i. Particle size.                            ii. Structure of soil mass.

iii. Shape of particles.                  iv. Void ratio. 

v. Properties of water.                 vi. Degree of saturation.  

vii. Adsorbed water.                    viii. Impurities in water.

Q10. What do you mean by hydraulic conductivity ? 

Ans. A characteristic of soil and rocks called hydraulic conductivity explains how easily a fluid, usually water, can pass through pore spaces or cracks.

Q11. Define the term quick sand condition. 

Ans. A stage is finally reached where the effective stress is lowered to zero as a result of the upward flow of water. Quick sand condition refers to the state in which things have developed.

Q12. Define critical gradient. 

Ans. The hydraulic gradient at which the effective stress becomes zero is known as the critical gradient (i_e). 

Q13. What are the preventive measures from the piping failures ?

Ans. The following measures generally adopted to prevent piping failures:

• i. Increasing the path of percolation. 
• ii. Reducing seepage. 
• iii. Providing drainage filter. 
• iv. Loaded filter. 

Q14. What is the exit gradient ?

Ans. Exit Gradient: The hydraulic gradient at the downstream end of the flow line, where percolating water escapes into the free water at the downstream, is known as the exit gradient. It can be calculated as

Q15. Compute the range for capillary rise in silt deposits. Assume value of void ratio as 0.7.

Ans. Given: Void ratio, e =0.7

To Find: Range of capillary rise.

Unit-III: Soil Compaction and Consolidation (Short Question)

Q1. What do you mean by soil compaction ?

Ans. Compaction is the term used to describe the mechanical forcing of soil particles together. In general, compaction enhances the soil’s shear strength.

Q2. Design the term relative compaction.

Ans.  The ratio of the dry density in the field to the maximum dry density is known as the relative compaction or percent compaction 

Q3. Give the IS specification for light and heavy compaction test.

                                                              OR

What is weight of hammer, height of drop, number of layers as per IS-2720 part VIl in heavy compaction test ?

Ans. Following test: are the IS specification for light and heavy compaction: 

• i. The mould must have a capacity of 1000 cc for both light and heavy compaction, measuring 100 mm in diameter and 127.3 mm in height.
• ii. For light compaction, the hammer should weigh 2.6 kg and fall from a height of 310 mm onto three levels, giving each layer the customary 25 blows.
• iii. For heavy compaction, the hammer should weigh 4.89 kg and descend from a height of 450 mm on five layers, giving each layer the customary 25 blows.

Q4. What is the recommendation of US Army corps for protective filters? 

Ans. The filter specifications are given below:

Q5. What are the factors affecting compaction ? 

Ans. The dry density of the soil is increased by compaction. The increase in the dry density depends upon the following factors: 

• i. Water factors. 
• ii. Amount of compaction. 
• iii. Type of soil. 
• iv. Method of compaction. 

Q6. What are the methods for compaction used in field ? 

Ans. For soil compaction in fields, various techniques are utilised. The method chosen will depend on the type of soil, the needed maximum dry density, and economic factors.

• i. Tamping. 
• ii. Rollin
• iii. Vibrating.

Q7. Write down the stages of the consolidation process. 

Ans. The consolidation of a soil deposit can be divided into three stages:

• i. Initial consolidation. 
• ii. Primary consolidation. 
• iii. Secondary consolidation.

Q8. Define coefficient of compressibility. 

Ans. 

Q9. What is the coefficient of volume change?

Ans. 

Q10. Discuss the factors affecting the time factor and degree of consolidation. 

Ans. The time factor (T_v) and degree of consolidation depends upon: 

• i. Thickness of clay layer. 
• ii. Number of drainage faces. 
• iii. Coefficient of permeability. 
• iv. Coefficient of consolidation. 
• v. Magnitude of consolidation pressure. 

Q11.  What is pre-consolidated stress ?

Ans. The most effective stress that the soil can undergo before consolidating is known as pre-consolidation stress. With the effective stress in its current state, this stress is recognised in compression.

Q12. Give the expression for the determination of time factor (T_v).

Ans. Time factor is calculated as:

Unit-IV: Stress Distribution in Soil and Shear Strength (Short Question)

Q1. Define the shear strength of soil.  

Ans. It may be described as the highest level of resistance provided by shear stresses before to failure.

Q2. Write down the various tests for determining the shear strength of soil.

Ans. The following tests are available for determining the shear strength of soil 

1. Laboratory Test:

i. Direct shear test.                                   ii. Triaxial compression test.

iii. Unconfined compression test.             iv. Laboratory vane shear test.

v. Torsion test.                                          vi. Ring shear test. 

2. Field Test: 

i. Vane shear test.                                    ii. Penetration test.

Q3. Discuss the advantages of direct shear test.

Ans. The test has several advantages. Some of them are as follows: 

• i. It is quick, cheap, and easy.
• ii. When the shear strength along fissures or other chosen planes is required, samples can be sheared along preset planes.

Q4. Give the disadvantages of direct shear test.

Ans. Following are the disadvantages of direct shear test:

• i. The test’s failure plane is always horizontal, however it may not be the sample’s weakest plane.
• ii. Because the shear box does not have a way to measure pore water pressure, it is impossible to calculate effective stresses from an undrained test.

Q5. What is platen or end effect in shearing strength ?

Ans. A flat plate, particularly one that applies or absorbs pressure, has platen shearing strength.

Q6. Explain in brief about stress isobar or isobar diagram. 

                                                      OR

Explain the isobar.  

Ans. An “isobar” is a line or stress contour that connects all points below the ground’s surface when the vertical pressure is constant. The pressure bulb is another name for the isobar of stress because of its bulbous shape.

Q7. Define undrained shearing strength.  

Ans. The term “undrained shear strength” refers to a fine-grained soil’s shear strength when it is not drained. 

Q8. What are the limitations of coulomb’s theory?

Ans. Limitations of Coulomb’s Theory: 

• i. The impact of the intermediate primary stress is disregarded.
• ii. According to this idea, the failure envelope roughly corresponds to a straight line that may have a slight curve for overconsolidated clays.
• iii. The normal and shear stresses on the plane of failure do not always have a fixed relationship for particular clays. Such soils cannot be covered by this idea.
• iv. This theory states that the shear strength of pure clays remains constant with depth. But in actuality, a slight increase is seen.

Q9. Write down the assumptions of Boussinesq equation theory. 

Ans. Following are the assumption of Boussinesq theory:

• i. The soil mass is an elastic continuum with a constant value for the elasticity modulus (E), meaning that the ratio of stress to strain is also constant.
• ii. The soil is homogeneous, meaning that it has the same characteristics throughout.
• iii. The soil is isotropic, meaning that it has the same characteristics in all directions.
• iv. The soil mass is semi-infinite, meaning that it extends in all directions, including downhill and laterally, to infinity.
• v. Before the load is applied, the soil is weightless and devoid of residual strains.

Q10. What are the assumptions of Westergaard’s theory ? 

Ans. Following are the assumptions of Westergaard’s theory:

• i. The soil has some limitless elasticity.
• ii. Soil is made up of a large number of thin, horizontal layers of an infinitely hard material that are spaced tightly together.
• iii. The rigid material permits only the downward deformation of mass in which horizontal deformation is zero.

Unit-V: Earth Pressure and Stability of Slopes (Short Question)

Q1. Define the term earth pressure.  

Ans. The soil that is kept in place at a slope that is steeper than it can support due to its shearing strength pulls on the retaining wall. The term “earth pressure” refers to this force.  

Q2. Classify the lateral earth pressure. 

Ans. The three categories of lateral earth pressure are: 

i. At rest earth pressure.                       ii. Active pressure.                       iii. Passive pressure.

Q3. Draw pressure distribution diagram for submerged soil mass.

Ans. 

Q4. What are the limitations of Rankine theory ? 

Ans. Following are the limitations in Rankine theory:

• i. The retained soil might not always be free of cohesiveness.
• ii. The back of the wall isn’t usually vertical.
• iii. Because the wall’s back is never smooth, friction forms.

Q5. Give the factors affecting of coefficient of earth pressure. 

Ans. Coefficient of earth pressure depends upon: 

• i. The angle of back of soil, 
• ii. The soil wall friction value, 
• iii. The angle of backfill. 

Q6. Define slope. Where it is used? 

Ans. An unsupported sloping surface of a soil mass is referred to as an earth slope. For the construction of railway embankments, highway embankments, earth dams, canal banks, levees and many other structures, earth slopes are created.

Q7. What are the assumptions made for the analysis of slopes? 

Ans. The following assumptions are generally made for slopes:

• i. It is believed that the stress system is two-dimensional. The third direction’s stresses are assumed to be zero. 
• ii. It is assumed that the Coulomb equation for shear strength is applicable and the strength parameters and 𝝓 are known. 

Q8. Explain factor of safety with respect to cohesion.

Ans. The factor of safety with respect to cohesion is the ratio of the available cohesion intercept (f_c) and the mobilized cohesion intercept  (c_m)

Q9. What do you understand by factor of safety with respect to friction ?

Ans. The ratio of the available frictional strength to the mobilised frictional strength is the safety factor for friction.

Q10. What are different types of slope failures ?

Ans. Following are the various types of slope failures:

i Rotational failure                                             ii. Translational failure. 

iii. Compound failure.                                        iv. Wedge failure. 

v. Miscellaneous failure.  

Q11. Give the expression for stability number.

Ans. The stability number is inversely proportional to the permitted height and directly proportional to the required cohesiveness.

Stability number is a dimensionless quantity. 

Q12. Define stability factor.  

Ans. Stability factor is the reciprocal of the stability number.  

Q13. What is the most critical circle ?

Ans. The circle which gives the minimum factor of safety is the most critical circle. 

Q14. How can you improve the stability of slopes ?

Ans. These are following measures which improve stability of slopes : 

• i. Flattening the slope lightens the bulk that is leaning to one side. It may be applied wherever practical.
• ii. Consolidation through supercharging, electro-osmosis, or other processes improves slope stability.
• iii. Increased slope stability is achieved through grouting and the injection of cement or other substances into particular zones.
• iv. Soil stabilization contributes to slopes becoming more stable.

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