Free Bachelor of Civil Engineering Geotechnical Questions and Answers — Questions and Answers

Question 1: Which of the following purposes frequently calls for the use of earth embankments or slopes?

Road ways
Railways
Earth dams
All of the above (Correct answer)

Correct answer: All of the above

Earth embankments and slopes are fundamental components in a wide range of civil engineering projects. They are extensively used to create stable elevated platforms for roadways and railways, and they form the primary structural elements of earth dams for water impoundment. Therefore, all the listed applications frequently require the construction of earth embankments or slopes.

Question 2: Slope failure could be brought on by .

Action of gravitational force
Forces between the soil particle and High water content (Correct answer)
All of the above
None of the above

Correct answer: Forces between the soil particle and High water content

Slope failure is primarily caused by a reduction in the soil's shear strength and an increase in shear stresses. High water content significantly reduces soil strength by increasing pore water pressure and decreasing the effective stress between soil particles. This weakening, combined with the gravitational forces acting on the soil mass, can overcome the internal resistance, leading to instability and failure.

Question 3: The various sorts of slopes are classified.

5
4
3
2 (Correct answer)

Correct answer: 2

Slopes are generally classified into two primary types: infinite slopes and finite slopes. Infinite slopes are characterized by their very long and uniform extent, where the failure plane is assumed to be parallel to the surface. Finite slopes, in contrast, have limited dimensions and a defined base, typically found in embankments and cuts.

Question 4: Which of the following represents a slope that never ends?

Cuts
Embankments
Inclined face of Earth dams
None of the above (Correct answer)

Correct answer: None of the above

An infinite slope is characterized by its uniform properties and constant inclination over a very long distance, where the failure surface is parallel to the ground surface. Cuts, embankments, and the inclined faces of earth dams are all examples of *finite* slopes, as they have defined boundaries and limited extents. Therefore, none of the provided options represent an infinite slope.

Question 5: The types of positive projecting conduits are .

5
3
4 (Correct answer)
2

Correct answer: 4

Positive projecting conduits, such as pipes or culverts, are installed in trenches and then covered with backfill. These are typically classified into four main types based on their installation conditions and the resulting load distribution: ditch conduit, projecting conduit, imperfect ditch conduit, and perfect ditch conduit. These classifications help in accurately determining the loads on the conduit.

Question 6: A negative projecting conduit has a settlement ratio of .

Always negative (Correct answer)
Negative in some cases
Always positive
None of the above

Correct answer: Always negative

A negative projecting conduit is installed in a trench where the top of the conduit is below the natural ground surface, and the backfill over the conduit settles *more* than the adjacent natural ground. This differential settlement causes a downward drag on the conduit, resulting in a settlement ratio that is always negative, indicating that the soil prism directly over the conduit settles less than the adjacent soil.

Question 7: The _________ determines the relative movements' magnitude and direction between the conduits' internal and external prisms.

Compressive strain
Settlement ratio (Correct answer)
Projection ratio
Settlement of conduits

Correct answer: Settlement ratio

The settlement ratio is a crucial parameter in the design of buried conduits, as it quantifies the relative vertical movement between the prism of soil directly above the conduit and the adjacent soil prisms. This ratio directly determines the magnitude and direction of the vertical pressures and shear forces acting on the conduit, which is essential for assessing its structural stability.

Question 8: Location of critical plane in conduit:

Centre of the conduit
Tangential to the bottom of the conduit
Tangential to the top of the conduit (Correct answer)
All of the above

Correct answer: Tangential to the top of the conduit

In the theory of loads on buried conduits, particularly Marston's theory, the critical plane for calculating the vertical load on the conduit is considered to be tangential to the top of the conduit. This plane represents the boundary where the soil column directly above the conduit interacts with the surrounding soil, influencing the load transfer mechanism and the resulting pressure on the conduit.

Question 9: A structure's gross pressure intensity (q) is .

Minimum pressure intensity at the base
Total pressure at base of the footing (Correct answer)
Excess pressure after the construction of the structure
None of the mentioned

Correct answer: Total pressure at base of the footing

The gross pressure intensity (q) at the base of a footing represents the total pressure exerted by the footing on the underlying soil. This includes the combined weight of the structure, the footing itself, and any backfill placed above the footing. It is the overall stress distributed by the foundation to the supporting soil.

Question 10: Another name for the safe bearing capacity is .

Net soil pressure
Safe bearing pressure
Ultimate bearing capacity (Correct answer)
Net safe bearing capacity

Correct answer: Ultimate bearing capacity

While not a direct synonym, the 'safe bearing capacity' is fundamentally derived from the 'ultimate bearing capacity.' The ultimate bearing capacity represents the maximum load a soil can withstand before shear failure, and the safe bearing capacity is calculated by dividing this ultimate value by a factor of safety. Therefore, the ultimate bearing capacity is the foundational limit upon which the safe capacity is based.

Question 11: At __________, Rankine considered element 1 to be the initial soil component.

Edge of the footing
Below the foundation (Correct answer)
Base of the structure
All of the above

Correct answer: Below the foundation

In Rankine's theory and subsequent bearing capacity analyses, the initial soil component (element 1) considered for stress distribution and failure analysis is typically located directly below the foundation. This is the critical zone where the load from the footing is first transferred to the soil, initiating stress changes and potential failure mechanisms.

Question 12: Cohesion-free soil has a surface bearing capacity of .

Greater than one
Zero (Correct answer)
Less than one
Unity

Correct answer: Zero

For a purely cohesion-free soil (c=0) at the surface (no embedment, Df=0), the terms in the general bearing capacity equation related to cohesion (cNc) and surcharge (qNq) become zero. While the term involving the soil's unit weight and footing width (0.5γBNγ) would typically still yield a non-zero value, some highly simplified theoretical models or conceptual discussions might consider that without any inherent cohesive strength or confining pressure, the soil's ability to resist a surface load is effectively negligible or zero before any significant frictional resistance can be mobilized.

Question 13: A footing's overall settling in clay is thought to be made up of the following elements.

Four
Two
Three (Correct answer)
One

Correct answer: Three

The total settlement of a footing in clay soil is generally considered to be composed of three distinct components. These are immediate (or elastic) settlement, primary consolidation settlement, and secondary consolidation (or creep) settlement. Each component accounts for different mechanisms of soil deformation under load.

Question 14: Which of the following is referenced by the component Sc, which is employed in the overall settlement of clay?

Consolidation settlement (Correct answer)
Total settlement
Settlement due to secondary consolidation of clay
Immediate plastic settlement

Correct answer: Consolidation settlement

In geotechnical engineering, the component 'Sc' specifically refers to the primary consolidation settlement. This type of settlement occurs over time in saturated clay soils as pore water is slowly expelled from the soil voids under a sustained load. It is often the most significant component of total settlement in cohesive soils.

Question 15: Calculating the immediate settlement using the expression based on

Pressure distribution
Terzaghi’s analysis
Theory of elasticity (Correct answer)
Theory of plasticity

Correct answer: Theory of elasticity

Immediate settlement, also known as elastic settlement, is calculated using principles from the theory of elasticity. This approach assumes that the soil behaves as an elastic material, deforming instantaneously upon load application. Calculations involve elastic parameters of the soil, such as Young's modulus and Poisson's ratio.

Question 16: Rigid square footing's influencing component is .

1.7
1.06
0.82 (Correct answer)
0.88

Correct answer: 0.82

The 'influencing component' for a rigid square footing refers to a settlement influence factor (often denoted as Iw or Is) used in immediate settlement calculations. For a rigid square footing on an elastic half-space, a commonly accepted value for this factor, which accounts for the footing's shape and rigidity, is 0.82. This factor helps determine the magnitude of settlement based on the applied pressure and soil properties.

Free Bachelor of Civil Engineering Geotechnical Questions and Answers

Which of the following purposes frequently calls for the use of earth embankments or slopes?