**Correct Answer: Erosion of subsoil by high velocity of seepage flow**

**Explanation:** Piping in soils occurs when water infiltrating through the soil creates high-velocity seepage flow. This flow can erode and remove fine soil particles, forming channels or pipes within the soil mass. This phenomenon is particularly problematic in dam construction and can lead to soil instability.

**Correct Answer: cm/sec**

**Explanation:** The coefficient of permeability represents the rate at which water can flow through soil. It is expressed in units of length per time, and common units include cm/sec. This unit indicates the distance water can travel through the soil in one second.

**Correct Answer: Gravel**

**Explanation:** Permeability is influenced by the particle size of soil. Gravel, with its larger particles, generally has the highest permeability among the options listed. Larger particles create more interconnected void spaces, allowing water to flow more easily through the soil.

**Correct Answer: Clayey**

**Explanation:** The falling head permeability test is suitable for soils with low permeability, such as clayey soils. In this test, the water level in a standpipe falls over time as water permeates through the soil sample. It is particularly effective for soils with slower permeability.

**Correct Answer: Sand**

**Explanation:** The coefficient of permeability of 0.08 cm/sec suggests that the soil has a moderate permeability, characteristic of sandy soils. Sand has larger particles compared to clay or silt, allowing water to move more freely through the soil.

**Correct Answer: Proportional to the coefficient of permeability**

**Explanation:** The quantity of seepage is directly proportional to the coefficient of permeability. Higher permeability allows more water to flow through the soil, leading to an increased quantity of seepage.

**Correct Answer: Proportional to the total head loss**

**Explanation:** The quantity of water seeping through a soil is proportional to the total head loss, which includes both the head at the upstream and the head at the downstream. The greater the total head loss, the larger the quantity of seepage.

**Correct Answer: Pumping test**

**Explanation:** Conducting a pumping test in situ is an effective way to determine the permeability of a soil deposit. This test involves pumping water from or into a well and monitoring the water level changes over time, providing valuable information about in situ permeability.

**Correct Answer: Condition in which a cohesionless soil loses its strength because of upward flow of water**

**Explanation:** Quick sand refers to a condition where a cohesionless soil, often sand, loses its strength due to the upward flow of water. In this state, the soil behaves like a liquid, and structures built on or in it can sink or collapse.

**Correct Answer: 1.5m**

**Explanation:** The head required for the quick condition in a sand stratum depends on specific gravity and voids ratio. In this case, the head required is calculated to be 1.5m. This indicates the depth of water needed to induce the quick condition in the specified soil.

**Correct Answer: (G-1)/(1+e)**

**Explanation:** The critical exit gradient is defined by the expression (G-1)/(1+e), where G is the specific gravity of soil particles and e is the void ratio. This critical exit gradient is a crucial factor in analyzing seepage conditions in soil mechanics.

**Correct Answer: All of the above**

**Explanation:** The critical exit gradient may occur under various conditions, including when flow is in an upward direction, when seepage pressure is in an upward direction, and when effective pressure is zero. These conditions are critical in terms of seepage and soil stability.

**Correct Answer: Increases with an increase in the specific gravity**

**Explanation:** The critical exit gradient increases with an increase in the specific gravity of soil particles. Specific gravity is a measure of the density of soil particles, and higher values lead to a higher critical exit gradient.

**Correct Answer: Increases with a decrease in void ratio**

**Explanation:** The critical exit gradient increases as the void ratio of the soil decreases. The void ratio is a measure of the porosity of the soil, and lower porosity corresponds to a higher critical exit gradient.

**Correct Answer: Perpendicular to equipotential line**

**Explanation:** The direction of seepage in a soil is perpendicular to the equipotential lines. Equipotential lines represent points in the soil with equal total head, and water tends to flow from higher to lower total head perpendicular to these lines.

**Correct Answer: Perpendicular to equipotential line**

**Explanation:** The seepage force in the soil is perpendicular to the equipotential lines. This force is a result of the hydraulic gradient and is exerted in the direction perpendicular to the equipotential lines.

**Correct Answer: Exit gradient**

**Explanation:** The seepage force is proportional to the exit gradient. The exit gradient is the change in total head per unit length and plays a crucial role in determining the force exerted by seeping water in the soil.

**Correct Answer: Head loss**

**Explanation:** The seepage force is proportional to the head loss. The head loss represents the change in total head between the upstream and downstream points, and this factor influences the magnitude of the seepage force.

**Correct Answer: All of the above**

**Explanation:** A flow net is a graphical representation of equipotential lines and flow lines in a soil mass. It can be used to determine various parameters, including seepage flow rate, hydrostatic pressure, and seepage pressure, providing valuable insights into the behavior of water flow in the soil.

**Correct Answer: The space between two adjacent flow lines**

**Explanation:** The flow path or flow channel is the space between two adjacent flow lines in a flow net. It represents the pathway through which water flows in the soil. The flow lines indicate the direction of flow, and the channels between them are critical in understanding the seepage pattern in the soil.

**Correct Answer: Intersecting lines at 90°**

**Explanation:** Flow lines and equipotential lines in a flow net intersect at 90 degrees. This orthogonal intersection is a key characteristic of flow nets, aiding in the graphical representation and analysis of seepage patterns in soils.

**Correct Answer: Flow lines and equipotential lines intersect orthogonally**

**Explanation:** In a flow net, flow lines (representing the direction of flow) and equipotential lines (connecting points of equal head) intersect at right angles, orthogonally. This characteristic simplifies the analysis of seepage patterns.

**Correct Answer: Positive hydrostatic pressure**

**Explanation:** The phreatic line is the line within a dam section where the hydrostatic pressure is positive. It represents the boundary above which water pressure is sufficient to cause seepage.

**Correct Answer: q = KH(Nf/Nd)**

**Explanation:** The discharge (q) through the complete flow is given by q = KH(Nf/Nd), where K is the coefficient of permeability, H is the total hydraulic head difference, Nf is the total number of flow channels, and Nd is the total number of potential drops.

**Correct Answer: An equipotential line**

**Explanation:** The upstream (u/s) face of an earthen dam is represented by an equipotential line in a flow net. Equipotential lines connect points with the same total head.

**Correct Answer: The top flow line**

**Explanation:** The phreatic line corresponds to the top flow line in a flow net. It represents the boundary above which seepage occurs and below which the soil is saturated.

**Correct Answer: Draw flow net**

**Explanation:** The electrical analogy method is a technique used to draw flow nets. It involves representing the flow of water in soil by analogies to the flow of electricity in a network of resistors.

**Correct Answer: Parabola**

**Explanation:** The top flow line in seepage flow through an earthen dam often has the shape of a parabola. This shape is a result of the flow pattern and is a characteristic feature in flow net analysis.

**Correct Answer: Parabolic**

**Explanation:** In an earthen dam, the phreatic line is often represented as a parabolic line in a flow net. This parabolic shape is a consequence of the seepage flow pattern.

**Correct Answer: Three-dimensional structure**

**Explanation:** A dam is a three-dimensional structure, as it has length, width, and height. This three-dimensional nature is considered in the analysis of seepage and stability of dams.

**Correct Answer: q = k.s**

**Explanation:** Kozeny’s parabola is used to represent the flow net in a dam. The seepage flow rate (q) per unit length is given by the product of the coefficient of permeability (k) and the focal length of Kozeny’s parabola (s).

_{x}k

_{z}

_{x}k

_{z})

_{x}k

_{z})

^{1.5}

_{x}k

_{z})

^{2}

**Correct Answer: k’ = √(k _{x} k_{z})**

**Explanation:** For anisotropic soils with different permeabilities in different directions (k_{x} and k_{z}), the modified coefficient of permeability (k’) is given by the square root of their product.

**Correct Answer: Laminar**

**Explanation:** Seepage flow through a porous medium is generally laminar, especially in soils. This is characterized by smooth and continuous flow paths without significant mixing.

_{s}, and Darcy’s velocity, v, are related as

_{s}/n

_{s}= v/n

_{s}= v.n

_{s}= n/v

**Correct Answer: v _{s} = v/n**

**Explanation:** The seepage velocity (v_{s}) is related to Darcy’s velocity (v) by the porosity (n) of the soil. The relationship is v_{s} = v/n.

**Correct Answer: Linear when plotted on semi-log paper**

**Explanation:** The pressure-void ratio curve typically exhibits a linear relationship when plotted on semi-logarithmic paper. This type of plotting is used to represent a wide range of values more conveniently.

**Correct Answer: Optimum moisture content (OMC)**

**Explanation:** The Standard Proctor test is conducted to determine the Optimum Moisture Content (OMC) and Maximum Dry Density (MDD) of a soil, which is crucial for compaction purposes.

**Correct Answer: Decreasing void ratio**

**Explanation:** The primary objective of soil compaction is to decrease the void ratio, leading to increased soil density and improved engineering properties such as strength and stability.

**Correct Answer: Optimum moisture content**

**Explanation:** The maximum dry density of a soil occurs at the Optimum Moisture Content (OMC), which represents the moisture content at which the soil can be compacted most effectively.

**Correct Answer: Air**

**Explanation:** Compaction helps in removing air voids from the soil, resulting in increased soil density and improved engineering properties.

**Correct Answer: Decreases OMC**

**Explanation:** An increase in compaction effort typically decreases the Optimum Moisture Content (OMC) while increasing the Maximum Dry Density (MDD) of the soil.

**Correct Answer: Any of the above**

**Explanation:** The compaction process can involve various methods, including rolling, tamping, and vibration, depending on the type of soil and the project requirements.

**Correct Answer: Rammer**

**Explanation:** In congested areas, where space is limited, a rammer is a suitable type of compaction equipment for both cohesive and cohesionless soils.

**Correct Answer: Vibrofloatation**

**Explanation:** Vibrofloatation is effective for compacting cohesionless soils with large thickness, providing improved compaction in such conditions.

**Correct Answer: Vibration**

**Explanation:** Vibration is often the most effective method for compacting sand, ensuring better soil densification and stability.

**Correct Answer: 15%**

**Explanation:** The optimum moisture content for silt is typically around 15%, representing the moisture content at which the soil can be compacted most effectively.

**Correct Answer: Penetration resistance to control field compaction**

**Explanation:** The plasticity needle or Proctor needle is used to measure penetration resistance, helping to control field compaction during construction.

**Correct Answer: 45cm**

**Explanation:** In the modified Proctor test, the drop height of the rammer is 45cm, which is a standard height used for compaction.

**Correct Answer: Stabilization**

**Explanation:** Stabilization involves improving the engineering properties of soil to enhance its stability and performance in construction applications.

**Correct Answer: Proper grading**

**Explanation:** Mechanical stabilization involves improving soil properties through proper grading, ensuring an optimal mix of particle sizes for enhanced stability.

**Correct Answer: Soil stabilization**

**Explanation:** Cement stabilization is commonly used for stabilizing soil, improving its strength and durability, and making it suitable for various construction applications.

**Correct Answer: Any of the above**

**Explanation:** Various admixtures such as cement, lime, or bitumen can be used in soil stabilization to improve its properties for construction purposes.

**Correct Answer: Hydrated lime**

**Explanation:** Clays containing organic matter can be stabilized by adding a small percentage of hydrated lime, which helps enhance their engineering properties.

**Correct Answer: 90°**

**Explanation:** When the shearing stress is zero on two planes, the angle between the two planes is 90 degrees.

**Correct Answer: Consolidation**

**Explanation:** Consolidation is the process involving the gradual expulsion of pore water under long-term static load, resulting in compression of the soil.

**Correct Answer: Terzaghi**

**Explanation:** Consolidation theory was enunciated by Karl Terzaghi, a pioneering figure in soil mechanics and geotechnical engineering.

**Correct Answer: Gradual expulsion of pore water**

**Explanation:** Consolidation is a gradual process involving the expulsion of pore water from the soil under long-term static loads.

**Correct Answer: Increases with an increase in temperature**

**Explanation:** The rate of consolidation generally increases with an increase in temperature.

**Correct Answer: Sands**

**Explanation:** Sands typically undergo faster consolidation when subjected to a static load compared to clays or silty soils.

**Correct Answer: Coefficient of consolidation**

**Explanation:** The square root of time fitting method is used to calculate the coefficient of consolidation in geotechnical engineering.

_{c}and the liquid limit (LL) of normally loaded clays of low to medium sensitivity is

_{c}= 0.009(LL-10%)

_{c}= 0.009(10%-LL)

_{c}= 0.09{1/LL(-10%)}

_{c}= 0.1(LL-25%)

**Correct Answer: C _{c} = 0.009(LL-10%)**

**Explanation:** This empirical relationship expresses the compression index (C_{c}) in terms of the liquid limit (LL) for normally loaded clays of low to medium sensitivity.

_{v}, the coefficient of consolidation C

_{v}, the length of the drainage path d, and time t is given by

_{v}= C

_{v}.d

^{2}/ t

_{v}= C

_{v}.t / d

^{2}

_{v}= C

_{v}.t / d

_{v}= C

_{v}.t

^{2}/ d

^{2}

**Correct Answer: T _{v} = C_{v}.t / d^{2}**

**Explanation:** The relationship between time factor (T_{v}), coefficient of consolidation (C_{v}), length of drainage path (d), and time (t) is given by T_{v} = C_{v}.t / d^{2}.

**Correct Answer: Air**

**Explanation:** Compression of soils occurs rapidly when voids are occupied by air, which is more compressible than water.

**Correct Answer: Degree of consolidation**

**Explanation:** The degree of consolidation is the ratio of settlement at any time to the final settlement, expressing the extent of consolidation that has occurred.

**Correct Answer: Overconsolidated soil**

**Explanation:** Overconsolidated soil has experienced higher pressures in the past than the current overburden pressure.

**Correct Answer: Underconsolidated soil**

**Explanation:** Underconsolidated soil has not fully settled under the existing overburden pressure.

**Correct Answer: Normally consolidated soil**

**Explanation:** Normally consolidated soil has settled fully under the existing overburden pressure.

**Correct Answer: Both (a) and (b) of the above**

**Explanation:** Overconsolidation can occur due to the weight of removed ice sheets or landslides.

**Correct Answer: Relieve pressure in impervious layers**

**Explanation:** Bleeder wells are used to relieve pressure in impervious layers and control seepage in dams.

**Correct Answer: Effective stress**

**Explanation:** Effective stress is the difference between total stress and pore water pressure in a soil mass.

**Correct Answer: Stress shared by the particles of the soil**

**Explanation:** Effective stress in a soil represents the stress shared by the solid particles of the soil, and it is equal to the difference between total stress and pore water pressure.

**Correct Answer: Stress shared by the pore water**

**Explanation:** The neutral stress in a soil mass is the stress carried by the pore water within the soil.

**Correct Answer: Force per unit effective area**

**Explanation:** The total stress in a soil is the total force applied per unit area, considering both the solid particles and the pore water.

**Correct Answer: Ultimate shear stress**

**Explanation:** The strength of a soil is commonly identified by its ultimate shear strength, representing the maximum shear stress the soil can withstand.

**Correct Answer: Increases with normal stress**

**Explanation:** The shear strength of a soil typically increases with an increase in normal stress applied to the soil.

**Correct Answer: All of the above**

**Explanation:** The shear strength of a soil is influenced by cohesion, angle of friction, and normal stress.

**Correct Answer: Effective stress only**

**Explanation:** Shear strength is primarily related to effective stress, which accounts for the stress carried by the soil skeleton.

**Correct Answer: Directly to the tangent of the angle of internal friction**

**Explanation:** Shear strength is proportional to the tangent of the angle of internal friction.

**Correct Answer: All of the above**

**Explanation:** Shear strength in the laboratory is determined through tests such as unconfined shear test, triaxial shear test, and direct shear test.

**Correct Answer: Both (a) and (b) of the above**

**Explanation:** Shear resistance in soils is due to both intergranular friction and cohesion/adhesion between soil particles.

**Correct Answer: Cohesion**

**Explanation:** In an undrained condition, the shear strength of plastic clay is primarily due to cohesion.

**Correct Answer: Normal stress**

**Explanation:** The shearing strength of cohesionless soil is influenced by normal stress, which is the force applied perpendicular to the shear plane. The normal stress plays a crucial role in determining the resistance of the soil to shearing forces. Other factors, such as particle arrangement, shape, and size, also contribute to the overall shearing strength of cohesionless soils.

_{u}. of saturated clay tested in unconfined compression is given in terms of unconfined compressive strength q

_{u}as

_{u}= 1/2 q

_{u}

_{u}= q

_{u}

_{u}= 2q

_{u}

_{u}2/3 q

_{u}

**Correct Answer: C _{u} = 1/2 q_{u}**

**Explanation:** The relationship between undrained shear strength (C_{u}) and unconfined compressive strength (q_{u}) in saturated clay under unconfined compression is expressed by C_{u} = 1/2 q_{u}.

**Correct Answer: Unconfined compression test**

**Explanation:** The unconfined compression test is commonly recommended for testing the shear strength of saturated clay. This test involves applying axial load to a cylindrical soil specimen without confining pressure, providing insights into the undrained shear strength of the clay.

**Correct Answer: Decrease their shear strength**

**Explanation:** Cohesive soils, such as clays, often experience a decrease in shear strength upon wetting. This is attributed to factors like swelling and changes in pore water pressure, which can lead to a reduction in the soil’s ability to resist shear forces.

**Correct Answer: Plastic and also compressible**

**Explanation:** Cohesive soils, like clays, exhibit plastic behavior and are compressible. Their plasticity is characterized by the ability to undergo deformation without rupture, and their compressibility is evident in volume changes under applied loads.

**Correct Answer: 2**

**Explanation:** The length/diameter ratio of cylindrical specimens used in a triaxial test is generally maintained at 2 for standard testing procedures. This ratio ensures that the test results are representative and reliable for evaluating soil behavior under different stress conditions.

**Correct Answer: All of the above**

**Explanation:** The triaxial apparatus is versatile and can be used for various tests, including unconsolidated-untrained tests, consolidated-untrained tests, and drained tests. This flexibility makes it a valuable tool for studying different aspects of soil mechanics.

**Correct Answer: Clays/cohesive soils**

**Explanation:** The vane shear test is specifically designed for in-situ determination of the undrained shear strength of intact fully saturated cohesive soils, including clays. It involves rotating a vane blade in the soil and measuring the torque required for shearing.

^{2}(45 + Φ/2) is called

**Correct Answer: Flow value**

**Explanation:** The value NΦ, defined as tan^{2} (45 + Φ/2), is commonly referred to as the flow value. It is utilized in geotechnical engineering to assess the flow characteristics of cohesionless soils, providing insights into their behavior under different conditions.

**Correct Answer: Does not carry maximum shear stress**

**Explanation:** The failure plane in soil mechanics does not necessarily carry the maximum shear stress. The location and orientation of the failure plane depend on factors such as soil type, stress conditions, and the presence of water. The determination of failure planes is crucial for understanding soil stability and designing foundations and slopes.

**Correct Answer: C = q/2**

**Explanation:** The shear strength of cohesive soil (C) is commonly expressed as half of the unconfined compressive strength (q), and the relationship is represented by C = q/2.

**Correct Answer: 5-20°**

**Explanation:** The angle of internal friction for clayey soils typically falls in the range of 5-20°. This low angle is indicative of the cohesive nature of clay, which doesn’t exhibit significant frictional characteristics.

**Correct Answer: 27-33°**

**Explanation:** Silty sands generally have an angle of internal friction in the range of 27-33°. This range reflects the intermediate frictional characteristics of soils containing a significant proportion of silt in addition to sand.

_{d}

_{d}

_{d}

_{d}

**Correct Answer: 30 + 0.15 D _{d}**

**Explanation:** The angle of internal friction for granular soils with less than 5% silt content can be determined by the expression 30 + 0.15 D_{d}, where D_{d} is the percentage of silt.

_{1}and σ

_{3}are major principal stress and τ is the shear stress on these planes

_{1}-σ

_{3})+τ

_{1}-σ

_{3})+τ]

_{1}-σ

_{3})}

^{2}+τ

^{2}]

_{1}-σ

_{3})+τ

^{2}]

**Correct Answer: √[{1/2(σ _{1}-σ_{3})}^{2}+τ^{2}]**

**Explanation:** The radius of Mohr’s stress circle is calculated as √[{1/2(σ_{1}-σ_{3})}^{2}+τ^{2}]. This represents the distance from the center of the circle to the Mohr-Coulomb failure envelope.

**Correct Answer: Dilatancy**

**Explanation:** Dilatancy is the phenomenon where dense sand tends to expand or dilate when subjected to shearing loads. This behavior is characterized by an increase in volume and is opposite to thixotropy, where a material becomes less viscous over time.

**Correct Answer: 45°**

**Explanation:** The angle between the maximum shear stress plane (Mohr-Coulomb failure plane) and the horizontal plane is 45° according to Mohr’s circle of stress. This is a fundamental principle in soil mechanics.

**Correct Answer: Remoulding less**

**Explanation:** The difference between the undisturbed shear strength of soil and its remoulded shear strength is referred to as remoulding less. This phenomenon is associated with changes in soil structure and properties during the process of remoulding.

**Correct Answer: Major principal plane**

**Explanation:** The major principal stress occurs on the plane where the stress is maximum. This is a fundamental concept in stress analysis, and the major principal stress is represented by σ_{1}.

**Correct Answer: Dense sand, loose sand, and clay**

**Explanation:** The stress-strain curves A, B, and C correspond to dense sand, loose sand, and clay, respectively. Each curve represents the material’s response to applied stress, illustrating variations in stress and strain for different types of soils.

## FAQs on Soil Mechanics MCQs for Civil Engineers

### ▸ What is soil mechanics in civil engineering?

Soil mechanics is a branch of civil engineering that deals with the behavior of soil and its applications in construction. It involves studying the physical properties of soil, its classification, and the principles of stress, strain, and shear strength. For more detailed MCQs on soil mechanics, visit gkaim.com.

### ▸ How can I prepare for Soil Mechanics MCQs for civil engineering exams?

To prepare for Soil Mechanics MCQs, you should focus on understanding key concepts such as soil properties, compaction, consolidation, and slope stability. Practicing a variety of MCQs and reviewing detailed solutions will also be beneficial. Explore comprehensive MCQs on this topic at gkaim.com.

### ▸ What are the fundamental concepts covered in Soil Mechanics MCQs?

Fundamental concepts covered in Soil Mechanics MCQs include soil classification, compaction, permeability, consolidation, shear strength, and earth pressure theories. Each of these topics is crucial for designing stable foundations and structures. Visit gkaim.com for detailed MCQs and explanations.

### ▸ Where can I find reliable MCQs on Soil Mechanics?

Reliable MCQs on Soil Mechanics can be found on educational websites like gkaim.com. These sites offer a variety of questions with detailed explanations to help you understand the concepts thoroughly and prepare for exams effectively.

### ▸ What are the types of soil tests commonly included in Soil Mechanics MCQs?

Common soil tests included in Soil Mechanics MCQs are Atterberg limits, Proctor compaction test, permeability test, triaxial shear test, and consolidation test. Understanding these tests and their applications is essential for civil engineers. Detailed MCQs on these tests are available at gkaim.com.

### ▸ How does soil compaction affect construction projects?

Soil compaction increases the density of soil, which improves its load-bearing capacity and reduces settlement issues. Properly compacted soil ensures the stability and longevity of structures. For MCQs related to soil compaction and its impact, visit gkaim.com.

### ▸ Why is understanding soil permeability important for civil engineers?

Understanding soil permeability is crucial for designing effective drainage systems and ensuring the stability of structures. Permeability determines how easily water can flow through soil, affecting foundation design and soil stability. Find more about soil permeability in the MCQs at gkaim.com.

### ▸ What is the significance of shear strength in soil mechanics?

Shear strength is a critical property of soil that determines its ability to resist sliding or failure under load. It is essential for designing stable foundations and slopes. Detailed MCQs on shear strength and its significance can be found at gkaim.com.

### ▸ How do consolidation and settlement affect building foundations?

Consolidation and settlement affect building foundations by causing gradual deformation under load. Understanding these processes helps in designing foundations that minimize settlement and ensure structural stability. Explore MCQs on consolidation and settlement at gkaim.com.

### ▸ What are the applications of soil mechanics in civil engineering projects?

Applications of soil mechanics in civil engineering include foundation design, slope stability analysis, earth retaining structures, and pavement design. It helps in predicting and improving the performance of these structures. Visit gkaim.com for detailed MCQs on the applications of soil mechanics.