Past Questions — 2025

Slope stability is governed by the balance between shear strength (resisting force) and shear stress (driving force). Slope movement (landslides) is triggered when the driving force exceeds the resisting force. 1. **Excessive Rainfall**: Rainfall increases the pore water pressure within the soil or rock mass. According to Terzaghi's principle of effective stress (σ' = σ - u), an increase in pore water pressure (u) decreases the effective stress (σ'), which directly reduces the shear strength of the material, triggering failure. 2. **Earthquakes**: Seismic activity introduces dynamic horizontal and vertical forces (inertial forces) that increase the driving shear stress on the slope and can cause liquefaction in saturated sandy soils, leading to immediate slope failure. Why other options are incorrect: - **Vegetation growth**: Generally, vegetation stabilizes slopes by providing root reinforcement (increasing cohesion) and reducing pore water pressure through evapotranspiration. - **Rock mass only**: While rock masses can fail, they are the material being moved, not the 'trigger' itself. A trigger is an external event or change in condition. - **Clayey texture**: This is a material property (inherent characteristic), not a trigger. While clayey soils may be more prone to failure due to low permeability or swelling, the movement is triggered by an external factor like water infiltration.

In soil mechanics, the Degree of Saturation (S) is defined as the ratio of the volume of water (Vw) to the total volume of voids (Vv) in a soil mass, expressed as a percentage: S = (Vw / Vv) × 100%. 1. When S = 0%, the soil is considered 'dry', meaning there is no water in the voids. 2. When 0% < S < 100%, the soil is 'partially saturated', meaning the voids contain both air and water. 3. When S = 100%, the volume of water is exactly equal to the volume of voids (Vw = Vv). This means all the void spaces are completely filled with water, and there is no air present. This state is known as 'fully saturated'. Analysis of other options: - Option (a) is incorrect because a dry soil has S = 0%. - Option (c) is incorrect because the void ratio (e = Vv / Vs) depends on the arrangement of soil particles, not the presence of water. A soil can be 100% saturated while still having a significant void ratio. - Option (d) is incorrect because porosity (n = Vv / Vtotal) refers to the fraction of the total volume that consists of voids. Porosity cannot be 100% for a soil mass, as that would mean there are no solid particles present.

Precipitation is defined as any product of the condensation of atmospheric water vapor that falls under gravity from clouds. 1. Rain (Option a): This is liquid precipitation occurring when water droplets in clouds collide and grow large enough to fall to the earth. 2. Snow (Option b): This is frozen precipitation occurring when water vapor turns directly into ice crystals (deposition) and falls as flakes. 3. Hail (Option d): This is solid precipitation consisting of balls or irregular lumps of ice, formed by strong updrafts in thunderstorms. 4. Condensation (Option c): This is the physical process where water vapor (gas) changes into liquid water. While condensation is a necessary prerequisite for precipitation to occur (it forms the clouds), it is a phase change process, not a form of precipitation itself. Precipitation is the result of condensation, not the process of condensation.

In the context of construction materials and aggregate testing, it is crucial to distinguish between 'Toughness' and 'Hardness'. 1. **Toughness** is defined as the ability of an aggregate to resist failure under a sudden load or impact. The **Impact Test** (specifically the Aggregate Impact Test) is used to determine the toughness of aggregates. It measures the resistance to fragmentation under a falling weight. 2. **Aggregate Impact Value (AIV)** is the *result* or the *numerical value* derived from the Impact Test, rather than the name of the test itself. While closely related, the 'Impact Test' is the procedure used to determine toughness. 3. **Soundness Test** is used to determine the resistance of aggregates to weathering actions (such as freeze-thaw cycles or chemical reactions), not toughness. 4. **Los Angeles Abrasion Test** is used to determine the **Hardness** (resistance to surface wear and abrasion) of the aggregates, not their toughness. Therefore, the Impact Test is the correct procedure for determining toughness.

A gabion wall is a gravity retaining structure consisting of wire mesh baskets filled with rocks. Bulging at mid-height is a classic sign of structural instability within the baskets. 1. Why 'c' is correct: Gabions rely on the internal friction of the stones and the containment of the wire mesh. If the stones are not packed densely (uneven packing), they can shift under the lateral earth pressure, leading to voids and deformation. Furthermore, tie wires are essential to connect adjacent baskets and layers; if these are missing or insufficient, the baskets can move independently, causing the wall to bulge outward at the point of maximum pressure (typically mid-height). 2. Why 'a' is incorrect: Gabions are free-draining structures. Water passes through the voids between the stones, so hydrostatic pressure (too much water) is rarely the cause of bulging unless the filter fabric is completely clogged, which is not the primary structural issue described. 3. Why 'b' is incorrect: While steel corrosion can lead to the eventual failure of the wire mesh (bursting), bulging during construction is typically a result of poor workmanship (packing/tying) rather than long-term chemical degradation of the galvanized steel. 4. Why 'd' is incorrect: Gabion walls are dry-stone structures; they do not use cement. High cement content is irrelevant to the construction of a standard gabion wall.

In India, the Bureau of Indian Standards (BIS) defines the dimensions for modular bricks. A 'modular brick' is a brick whose dimensions are based on a module (standard unit) to ensure uniformity in construction. 1. **Standard Modular Size (excluding mortar):** The nominal size of a modular brick is 200 mm x 100 mm x 100 mm. However, this nominal size includes the mortar joints. The actual size of the brick itself (excluding mortar) is 190 mm x 90 mm x 90 mm. 2. **Nominal Size (including mortar):** When a 10 mm mortar joint is added to one side of the length, width, and height, the size becomes 200 mm x 100 mm x 100 mm. Analyzing the options: - Option (a) 190x90x80 mm is incorrect as the height is not 80 mm. - Option (b) 190x90x90 mm is the correct actual size of a modular brick. - Option (c) 200x100x100 mm is the nominal size (including mortar), whereas the question specifically asks for the size 'excluding mortar'. - Option (d) 230x110x70 mm refers to traditional/non-modular brick sizes used in some regions, not the standard modular size.

Run-off is the portion of precipitation that flows over the land surface rather than infiltrating into the soil. The relationship between run-off and the given options is as follows: 1. **Steeper slopes (Correct):** On a steep slope, the velocity of water flowing over the surface increases, and the time available for water to infiltrate into the ground decreases. Consequently, more water remains on the surface, leading to an increase in run-off. 2. **More vegetation cover (Incorrect):** Vegetation acts as a barrier that slows down the flow of water and increases the time available for infiltration. Roots also create pores in the soil, enhancing infiltration. Therefore, more vegetation decreases run-off. 3. **Highly permeable soil (Incorrect):** Permeability refers to the ability of soil to transmit water. Highly permeable soils (like sandy soils) allow water to seep into the ground quickly, which significantly reduces the amount of surface run-off. 4. **Higher infiltration (Incorrect):** Infiltration is the process by which water on the ground surface enters the soil. By definition, Run-off = Precipitation - Infiltration - Evapotranspiration. Therefore, as infiltration increases, run-off must decrease.

The Indian Standard (IS) Classification System for soils (IS 1498) is based on grain size distribution and plasticity characteristics. For fine-grained soils (silts and clays), the 'Plasticity Chart' is the primary tool used to classify the soil. This chart plots the Plasticity Index (PI) against the Liquid Limit (LL). The 'A-line' (defined by the equation PI = 0.73(LL - 20)) separates clays (above the line) from silts (below the line). Why other options are incorrect: - b. Ternary diagram: These are used for classifying coarse-grained soils based on the relative proportions of sand, gravel, and clay (e.g., in USCS or USDA systems for specific soil types), but the primary chart for the IS classification of fine soils is the plasticity chart. - c. Compaction curve: This is used to determine the Optimum Moisture Content (OMC) and Maximum Dry Density (MDD) of a soil, not for classification. - d. Permeability chart: Permeability is a property of soil, but there is no standard 'permeability chart' used as a basis for the IS classification system.

In civil engineering and hill road construction, different types of walls are used to stabilize slopes. 1. **Breast Wall (Option a):** A breast wall is a retaining wall constructed on the hill side of a road or slope to support the 'cut' portion of the hill. Its primary purpose is to prevent the soil or rock from sliding down onto the roadway. 2. **Toe Wall (Option b):** A toe wall is constructed at the base (toe) of a slope or embankment to prevent the sliding of the slope material and to protect the foot of the slope from erosion or sliding. 3. **Revetment Wall (Option c):** A revetment is a facing of stone, concrete, or other materials used to protect a slope (often in riverbanks or coastlines) from erosion caused by water or weathering, rather than supporting a vertical cut. 4. **Grouted Wall (Option d):** Grouting is a process of injecting fluid mortar into voids or cracks in soil or rock to strengthen it; it is a stabilization technique rather than a specific type of wall used to support a hill cut. Therefore, the wall specifically used to support the cut portion of a hill is the Breast Wall.

A crib wall is a type of retaining wall consisting of a network of interlocking prefabricated units (usually timber, concrete, or steel) that form a 'crate' or 'crib' which is then filled with granular material (like crushed stone or gravel). 1. Why Option (c) is correct: One of the primary aesthetic and functional advantages of crib walls is that the open structure allows for the planting of vegetation within the fill. Once the vegetation grows, the roots help bind the soil/fill, and the foliage covers the structure, allowing the wall to blend naturally into the landscape. 2. Why Option (a) is incorrect: While RCC panels can be used in some modular walls, crib walls are characterized by their open-grid framework rather than solid panels. 3. Why Option (b) is incorrect: Crib walls can be designed as permanent structures, especially when using treated timber or precast concrete. 4. Why Option (d) is incorrect: While they are stable, their primary design purpose is to resist lateral earth pressure, not wind. In fact, their open nature makes them less relevant to wind resistance compared to solid walls.

In civil engineering, specifically in the context of retaining structures, a 'breast wall' is a type of retaining wall built to support the face of an excavated slope or to prevent the soil from sliding down into a cutting (such as along a road or railway embankment). - Option (a) is incorrect because walls designed to withstand water pressure are typically called 'dam walls' or 'seawalls'. - Option (c) is incorrect because structures that hold foundations are generally referred to as 'footings' or 'pile caps'. - Option (d) is incorrect because protection from frost is achieved through 'frost depth' excavation or specific insulation techniques, not by a breast wall. Therefore, the primary purpose of a breast wall is to provide stability to an excavated slope face.

The fineness of cement refers to the size of the cement particles. Finer cement hydrates faster and generally provides higher early strength. There are two primary methods to determine fineness: 1) Sieve Analysis (using a 90-micron IS sieve) and 2) Air Permeability Method (Blaine's test). Among the given options, the Sieve Test is the correct method for determining fineness. Why other options are incorrect: - b. Soundness Test: This test is conducted to determine the ability of cement to retain its volume after hardening (checking for delayed expansion caused by free lime or magnesia), typically using the Le Chatelier apparatus or Autoclave test. - c. Consistency Test: This is a preliminary test (using the Vicat apparatus) to determine the amount of water required to create a cement paste of standard consistency, which is necessary before performing other tests like setting time and soundness. - d. Tensile Strength Test: This is generally performed on hardened concrete or steel, not on raw cement powder to determine its physical properties like fineness.

In soil mechanics, a compaction curve (or Proctor curve) is plotted by graphing the dry density of a soil sample against its moisture content for a constant compactive effort. As water is added to the soil, it acts as a lubricant, allowing soil particles to slide over each other and pack more closely, which increases the dry density. However, beyond a certain point, the water begins to occupy space that would otherwise be taken by soil solids, causing the dry density to decrease. The peak of this bell-shaped curve represents the Maximum Dry Density (MDD). The specific moisture content at which this peak occurs is known as the Optimum Moisture Content (OMC). Why other options are incorrect: - Option (a): The peak represents the optimum moisture content, not the 'maximum' moisture content (which would be the saturation point or liquid limit). - Option (c): The Zero Air Voids (ZAV) line is a theoretical line that represents 100% saturation; the compaction curve always stays to the left of the ZAV line and does not peak on it. - Option (d): The Liquid Limit is an Atterberg limit determined by a Casagrande or Cone penetrometer test, not by a compaction test.

Stability under loading in soil mechanics refers to the soil's ability to resist deformation (settlement) and shear failure. 1. **Well-graded soil**: A well-graded soil contains a wide variety of particle sizes. In such a distribution, smaller particles fill the voids between larger particles. This results in a denser packing arrangement, higher interlocking between grains, and a higher shear strength. Consequently, well-graded soils exhibit lower compressibility and higher stability under loading. 2. **Uniformly graded soil (Option c)**: These soils consist of particles of approximately the same size. This leads to larger void spaces and less interlocking between particles, making them more prone to settlement and less stable compared to well-graded soils. 3. **Higher void ratio (Option a)**: The void ratio is the ratio of the volume of voids to the volume of solids. A higher void ratio indicates a looser packing of soil particles, which generally leads to higher compressibility and lower stability. 4. **Plastic soil (Option d)**: Plasticity is a characteristic of fine-grained soils (like clays). While plasticity allows the soil to deform without cracking, highly plastic soils are often subject to significant consolidation settlement and lower shear strength compared to well-graded granular soils under typical loading conditions. Since both soils in the question have the same dry density, the deciding factor for stability is the grain size distribution. The well-graded soil provides the best mechanical interlocking and structural integrity.

Rainwater harvesting (RWH) is the process of collecting, filtering, and storing rainwater for future use or for recharging groundwater aquifers. 1. Rooftop collection (Option a) is a primary method of RWH where rain falling on roofs is collected via gutters and stored in tanks. 2. Recharge pits (Option c) are structures designed to direct rainwater into the ground to replenish the water table, which is a key component of groundwater harvesting. 3. Percolation tanks (Option d) are artificial ponds that hold rainwater, allowing it to seep slowly into the ground to recharge aquifers. In contrast, Irrigation from canals (Option b) involves the distribution of water from a river or reservoir through a network of man-made channels. This is a method of water distribution for agriculture, not a method of harvesting rainwater. Therefore, it does not fall under the definition of rainwater harvesting.

The design of water retaining structures requires special considerations to prevent leakage and cracking due to hydrostatic pressure and environmental conditions. 1. **IS 3370** is the specific Indian Standard code titled 'Code of Practice for Concrete Structures for Storage of Liquids'. It provides guidelines for the design and construction of water tanks, reservoirs, and other liquid-retaining structures, focusing on limiting crack widths and ensuring durability. Why other options are incorrect: - **IS 456** is the general 'Code of Practice for Plain and Reinforced Concrete'. While it provides the foundation for RCC design, it is not specific to water-retaining structures. - **IS 800** is the 'Code of Practice for General Construction in Steel'. It is used for structural steel design, not concrete water tanks. - **IS 13920** is the 'Ductile Design and Detailing of Reinforced Concrete Structures Subjected to Seismic Forces'. It focuses on earthquake resistance rather than liquid containment.

A crib wall is a type of retaining structure consisting of a cellular network of interlocking prefabricated units (usually timber or precast concrete) that are filled with granular material (crushed stone or gravel). 1. Why Option (c) is correct: Because crib walls are open-jointed and filled with granular material, they are highly permeable. This allows for excellent drainage and provides a medium where vegetation can grow through the structure. Once vegetation establishes itself, the roots help bind the soil and the foliage provides an aesthetically pleasing, natural appearance that blends with the environment. 2. Why Option (a) is incorrect: While RCC panels can be used in some modern modular walls, crib walls are traditionally defined by their 'crate-like' open structure. RCC panels are more characteristic of panel walls or diaphragm walls, not the defining advantage of a crib wall. 3. Why Option (b) is incorrect: Crib walls can be designed for both temporary and permanent applications. Their ability to be quickly assembled makes them useful for temporary works, but they are frequently used as permanent structures in landscaping and road embankments. 4. Why Option (d) is incorrect: Retaining walls are designed to resist lateral earth pressure, not wind. While they must be stable, 'resisting wind' is not a specific functional advantage or primary design goal of a crib wall compared to other retaining structures.

Permeability (hydraulic conductivity) refers to the ease with which a fluid (usually water) can flow through a porous medium. In soil mechanics, permeability is primarily governed by the size of the soil particles and the connectivity of the void spaces (pores). 1. **Gravel (Option b):** Consists of the largest particles among the choices. Large particles create large, interconnected void spaces, offering the least resistance to water flow. Therefore, gravel has the highest permeability. 2. **Silt (Option a):** Particles are smaller than sand and gravel. The smaller pore spaces significantly increase the resistance to flow, resulting in lower permeability than gravel. 3. **Clay (Option c):** Consists of the smallest particles (plate-like structure). Clay has very small pores and high surface tension/electrical charges that bind water, making it the least permeable soil (often acting as an aquiclude). 4. **Loam (Option d):** A mixture of sand, silt, and clay. While it has better permeability than pure clay, its permeability is significantly lower than that of clean gravel due to the presence of finer particles that fill the larger voids. According to Hazen's formula (k ∝ D₁₀²), the coefficient of permeability (k) is proportional to the square of the effective particle size (D₁₀). Since gravel has the largest D₁₀, it has the highest permeability.

Slope stability is fundamentally a balance between the driving forces (gravity, surcharge) that tend to cause the soil mass to slide and the resisting forces that oppose this movement. The primary resisting force in a soil mass is its shear strength. According to the Mohr-Coulomb failure criterion, shear strength is a function of cohesion (c) and the internal angle of friction (φ). If the shear stress induced along a potential failure plane exceeds the shear strength of the soil, the slope will fail. Why other options are incorrect: - a. Plasticity index: While it helps in classifying soil and predicting behavior (like swelling or shrinkage), it is not the direct resisting force against sliding. - b. Moisture content: Moisture content significantly affects shear strength (by increasing pore water pressure and reducing effective stress), but it is a variable that influences the strength, not the property that provides the stability itself. - d. Density index: Relative density affects the shear strength of granular soils, but it is a state parameter rather than the fundamental mechanical property that resists failure.

Varnish is a transparent, hard, protective finish or film primarily used in woodworking. It consists of a resin dissolved in a drying oil, alcohol, or turpentine. 1. Why Option (c) is correct: The primary purpose of varnish is to seal the surface of the material (usually wood) to protect it from moisture, scratches, and wear while enhancing the natural beauty of the grain by providing a glossy or semi-glossy finish. 2. Why Option (a) is incorrect: Varnish is typically transparent. If the goal is to change the color of the surface, 'stains' or 'paints' are used. 3. Why Option (b) is incorrect: Varnish is a surface coating. To fill gaps or holes in wood, 'wood fillers' or 'putty' are used. 4. Why Option (d) is incorrect: While some resins used in varnish have adhesive properties, the primary function of varnish as a building material is as a finish, not as a structural adhesive (like PVA glue or epoxy).

In cold weather concreting, the primary challenge is the slow rate of hydration of cement due to low temperatures. This leads to a delayed setting time and a slow gain in early strength, which can increase the risk of freezing and structural failure. Rapid Hardening Cement (RHC) is specifically designed to gain strength quickly at early ages. It achieves this through a higher proportion of Tricalcium Silicate (C3S) and a finer grinding of clinker. The increased rate of hydration in RHC generates more heat (heat of hydration), which helps counteract the low ambient temperatures of cold weather, ensuring the concrete sets and gains strength within a reasonable timeframe. Why other options are incorrect: - a. Ordinary Portland Cement (OPC): Its hydration rate is too slow in cold weather, leading to delayed strength gain. - b. Low Heat Cement: This cement is designed to minimize heat generation (used in mass concreting like dams) to prevent thermal cracking; using it in cold weather would further slow down the setting process. - d. Sulphate Resisting Cement: This is used in environments with high sulphate concentrations (like seawater or saline soils) to prevent chemical attack, not for temperature-related acceleration.

Paint consists of four main components: pigments, binders, solvents, and additives. 1. Pigments: These are finely ground solid particles. While some pigments provide color, 'anti-corrosive pigments' (such as red lead or zinc chromate) are specifically added to paints intended for metal surfaces. These pigments react chemically with the metal or create a barrier that prevents oxidation and rusting. 2. Binder: This is the resin or polymer that holds the pigment particles together and ensures the paint adheres to the surface. While it provides a physical barrier, the specific chemical prevention of rust is attributed to the pigment. 3. Solvent/Thinner: These are volatile liquids used to adjust the viscosity of the paint for application. They evaporate as the paint dries and do not provide any protective properties against rust. Therefore, the component specifically responsible for the anti-rusting property in metal paints is the pigment.

The correct answer is IS 456. Here is the detailed breakdown of the options provided: 1. **IS 456 (Plain and Reinforced Concrete - Code of Practice):** This is the primary Indian Standard code that provides the guidelines, requirements, and design specifications for the design and construction of reinforced concrete (RCC) and plain concrete structures in India. It covers everything from material properties and durability to limit state design of beams, slabs, columns, and footings. 2. **IS 875 (Code of Practice for Design Loads for Buildings):** This code is used to calculate the loads acting on a building (such as dead loads, imposed/live loads, wind loads, and snow loads). While it is used during the design process, it is a 'loading' code, not a 'concrete design' code. 3. **IS 800 (Code of Practice for General Construction in Steel):** This code provides the guidelines for the design of structural steelwork. It is not applicable to RCC design. 4. **IS 3370 (Code of Practice for Concrete Structures for Storage of Liquids):** This code provides specific guidelines for the design of water tanks and reservoirs. While it deals with concrete, it is a specialized code for liquid-retaining structures, whereas IS 456 is the general code for all RCC building design.

According to IS 383 (the Indian Standard specification for coarse and fine aggregates from natural sources), aggregates are classified based on their particle size. Fine aggregate is defined as the material that passes through a 4.75 mm IS sieve. Coarse aggregate is defined as the material that is retained on a 4.75 mm IS sieve. Analysis of options: - Option (a) is correct as it aligns with the standard definition of fine aggregates. - Option (b) describes the range for 'sand' specifically, but the general definition of fine aggregate is simply that it passes the 4.75 mm sieve. Material passing the 75-micron sieve is generally considered 'silt' or 'clay' and is treated as an impurity in aggregates. - Option (c) 10mm is a common size for coarse aggregates. - Option (d) 2.36mm is a size used for grading zones but not for the primary definition of fine aggregate.

Slope stabilization methods are generally categorized into short-term (temporary/immediate) and long-term (permanent/structural) measures. 1. **Shotcrete or Gunite (Option a):** This involves spraying concrete at high velocity onto a slope surface. It is primarily used as a short-term or immediate stabilization measure to prevent surface erosion, seal the face against weathering, and provide immediate confinement to the surface soil to prevent small-scale sloughing while more permanent measures are implemented. While it can be part of a permanent system, its primary function in initial slope stabilization is immediate surface protection. 2. **Soil Nailing (Option b):** This is a long-term reinforcement technique where steel tendons are inserted into the slope and grouted. It creates a coherent mass of reinforced soil and is designed for permanent stability. 3. **Toe Buttress (Option c):** This involves placing a heavy mass of material (like rockfill) at the toe of the slope to provide a resisting force against sliding. This is a structural, long-term stabilization method. 4. **Gabion Wall (Option d):** Gabions are wire mesh cages filled with rocks. They act as gravity retaining walls and are used for long-term stabilization and erosion control. Therefore, among the given options, shotcrete/gunite is the most appropriate answer for a short-term stabilization method.