Past Questions — 2025

A normally consolidated (NC) clay is a soil that has never been subjected to a pressure higher than the current existing overburden pressure. In soil mechanics, NC clays are characterized by their tendency to undergo significant volume reduction (settlement) when additional loads are applied, which is defined as high compressibility. Analysis of options: - Option (a) High compressibility: Correct. NC clays have a higher compression index (Cc) compared to overconsolidated clays, making them highly compressible under new loads. - Option (b) Very low permeability: While clays generally have low permeability, this is a characteristic of the material (clay) rather than the consolidation state (normally consolidated vs. overconsolidated). Therefore, it is not the defining behavior of an NC clay specifically. - Option (c) Low compressibility: Incorrect. This describes overconsolidated (OC) clays, which have already been compressed by higher pressures in the past and thus resist further compression. - Option (d) High shear strength: Incorrect. NC clays typically have lower shear strength compared to overconsolidated clays of the same composition because they have a looser structure and higher water content.

Workability of concrete refers to the ease with which it can be mixed, transported, placed, and compacted without segregation. 1. **Slump Test (Option a):** This is the most common field test used to measure the consistency and workability of fresh concrete. It involves filling a conical mold (slump cone) with concrete and measuring the vertical subsidence (slump) after the mold is removed. A higher slump indicates higher workability. 2. **Compression Test (Option b):** This test is performed on hardened concrete (usually cubes or cylinders) to determine its compressive strength, not its workability. 3. **Tensile Test (Option c):** Concrete is naturally weak in tension. Tensile tests (like the split tensile test) are used to determine the tensile strength of hardened concrete. 4. **Flexural Test (Option d):** This test is used to determine the modulus of rupture or the bending strength of concrete beams, which is a property of hardened concrete.

The durability of aggregates refers to their ability to resist disintegration due to environmental factors such as freeze-thaw cycles or chemical reactions. 1. **Soundness Test (Correct):** This test is specifically designed to evaluate the resistance of aggregates to volume changes caused by weathering. It involves immersing the aggregates in solutions of sodium sulfate or magnesium sulfate. If the aggregate disintegrates or expands significantly, it is considered 'unsound,' indicating poor durability. 2. **Fineness Modulus Test (Incorrect):** This is a measure of the average particle size of the aggregate (primarily for fine aggregates) and is used for grading purposes, not durability. 3. **Shape Test (Incorrect):** This evaluates the geometry of the particles (e.g., flaky or elongated). While shape affects workability and strength, it is not a measure of long-term durability against weathering. 4. **Water Absorption Test (Incorrect):** This measures the amount of water an aggregate can absorb into its pores. While high absorption can correlate with poor durability (especially in freeze-thaw conditions), the test itself measures porosity/absorption, whereas the Soundness Test directly measures the resulting durability/disintegration.

India's climate is dominated by the monsoon system. The vast majority of the annual precipitation (approximately 75% to 90% in many regions) occurs during the Southwest Monsoon season, which typically lasts from June to September. This is caused by the seasonal reversal of winds, where moisture-laden winds blow from the Indian Ocean toward the landmass. Why other options are incorrect: - a. Cyclones: While cyclones cause heavy rainfall, they are seasonal and localized primarily to the coastal regions (East and West coasts) and do not contribute to the bulk of the national annual precipitation. - c. Snowfall: Snowfall is restricted to the Himalayan regions and high-altitude areas, representing a very small fraction of total precipitation. - d. Convection storms: These occur locally (such as pre-monsoon showers or 'Mango showers'), but they are sporadic and do not provide the volume of water that the monsoon system delivers.

In civil engineering and hill road construction, different types of walls are used to stabilize slopes. 1. **Breast Wall (Correct):** A breast wall is a retaining wall constructed on the hill side of a road or path to support the cut slope of the hill. Its primary purpose is to prevent the soil or rock from sliding down onto the roadway. 2. **Toe Wall:** A toe wall is constructed at the base (toe) of a slope or embankment to prevent the slope from sliding outwards or to protect the foot of the slope from erosion. It supports the 'toe' rather than the 'cut portion' of the hill. 3. **Revetment Wall:** A revetment is a facing of stone, concrete, or other materials used to protect a slope from erosion (often by water), but it is generally a surfacing layer rather than a structural wall designed specifically to support a cut hill slope. 4. **Grouted Wall:** This refers to a wall where grout (a fluid form of concrete) is injected into voids or joints to strengthen the structure or soil; it is a method of stabilization rather than a specific type of wall used for hill cuts.

A retaining wall is a structure specifically designed to resist the horizontal pressure of soil, waste materials, or water. The primary force acting on a retaining wall is the 'Lateral Earth Pressure,' which is the pressure exerted by the soil mass behind the wall. Failure typically occurs when this lateral pressure exceeds the wall's capacity to resist it, leading to failure modes such as sliding, overturning, or bearing capacity failure of the foundation. Why other options are incorrect: - a. Wind pressure: While wind can act on the exposed face of a wall, it is negligible compared to the massive force of the soil it is designed to hold. - c. Snow accumulation: Snow may add a small amount of surcharge load, but it is not the primary cause of failure for the structure as a whole. - d. Vertical dead loads: The dead load (weight of the wall itself) actually helps in stabilizing the wall against overturning and sliding; it is a stabilizing force rather than a primary cause of failure.

The primary purpose of the core in an earthen dam is to act as an impermeable barrier to prevent water from seeping through the dam body, which would otherwise lead to internal erosion (piping) and potential failure. 1. **Clayey Soil (Correct):** Clay has very low hydraulic conductivity (permeability) due to its small particle size and the electrochemical properties of clay minerals. This makes it the ideal material for the core to minimize seepage losses. 2. **Gravel (Incorrect):** Gravel has very high permeability and is used in the 'shell' of the dam to provide structural stability and drainage, not for the core. 3. **Coarse Sand (Incorrect):** Like gravel, coarse sand is highly permeable and cannot prevent water seepage. 4. **Silty Sand (Incorrect):** While less permeable than coarse sand, silty sand still allows significant water flow compared to clay and is more susceptible to piping failure if used as a core.

In soil mechanics, the unit weight (denoted by γ) is a fundamental property defined as the total weight of a soil sample (including the weight of solids and the weight of water in the voids) divided by the total volume of that sample. The formula is γ = W / V, where W is the total weight and V is the total volume. Analysis of options: - Option (a) refers to the unit weight of water (γw), not the soil. - Option (b) refers to the 'dry unit weight' (γd) specifically, which is only one type of unit weight and does not define 'unit weight' in general terms. - Option (c) is the general and correct definition of bulk unit weight, encompassing the entire soil mass. - Option (d) is dimensionally incorrect as it describes a ratio of weight to weight (dimensionless), whereas unit weight must be weight per unit volume.

Step-by-step reasoning: 1. **Polyethylene (PE)**: This is a thermoplastic polymer known for its excellent chemical resistance, durability, and non-toxicity. Specifically, High-Density Polyethylene (HDPE) and Linear Low-Density Polyethylene (LLDPE) are the industry standards for manufacturing water storage tanks because they are food-grade, resistant to corrosion, and can be molded into large, seamless containers. 2. **Bakelite**: This is a thermosetting plastic. It is brittle and used primarily for electrical switches, handles of cooking utensils, and telephone casings due to its heat resistance. It is not suitable for large water tanks. 3. **PVC (Polyvinyl Chloride)**: While PVC is widely used in plumbing for water pipes and fittings, it is generally not used for the main body of large domestic water storage tanks because it is more rigid and prone to cracking under certain environmental stresses compared to polyethylene. 4. **Nylon**: This is a polyamide used primarily for fibers, gears, and mechanical parts due to its high strength and wear resistance. It is not used for water storage tanks due to cost and material properties. Therefore, Polyethylene is the most appropriate material for water storage tanks.

Step-by-step reasoning: 1. The question asks for a wood product made by gluing thin layers of wood together. 2. Plywood is a structural material made from thin sheets of wood veneer (plies) that are glued together. Crucially, the grain of each layer is typically rotated 90 degrees relative to the next (cross-graining), which provides strength and stability in multiple directions. 3. Analyzing other options: (a) Particle board is made from wood chips, shavings, and sawdust bonded with resin. (b) Block board consists of a core of softwood strips (blocks) sandwiched between two layers of veneer. (d) Fiberboard (like MDF) is made from wood fibers combined with wax and resin and pressed under heat. Therefore, only plywood fits the description of being composed of thin layers (veneers) glued together.

The resistance of wood to termite attack is primarily determined by the presence of natural oils, resins, and extractives within the heartwood. 1. **Teak (Tectona grandis):** Teak is globally renowned for its exceptional durability and resistance to termites and decay. This is due to the high concentration of natural oils and silica present in its heartwood, which act as a chemical deterrent and physical barrier against pests. 2. **Sal (Shorea robusta):** While Sal is a very hard and durable timber often used for railway sleepers and heavy construction, it is generally considered slightly less resistant to certain types of termite attacks compared to the natural oil-rich composition of Teak. 3. **Cedar:** Cedar contains natural oils that make it resistant to decay and some insects, but it is a softer wood and generally less resistant to aggressive termite species than Teak. 4. **Pine:** Pine is a softwood and is highly susceptible to termite attacks and fungal decay unless it is chemically treated (pressure-treated). Therefore, among the given options, Teak is the most resistant to termite attack.

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. The formula is: S = (Vw / Vv) × 100%. 1. When S = 0%, the soil is completely dry (no water in the voids). 2. When 0% < S < 100%, the soil is partially saturated (voids contain both air and water). 3. When S = 100%, the volume of water is exactly equal to the volume of voids (Vw = Vv), meaning all the void spaces are completely filled with water. This state is known as a 'fully saturated soil'. 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 amount of water filling those voids. A saturated soil still has voids; they are just filled with water. - Option (d) is incorrect because porosity (n = Vv/V) is a physical property of the soil structure. Porosity cannot be 100% for a soil mass, as that would imply there are no solid particles present.

To determine the most suitable stone for heavy engineering structures like bridge piers, we must evaluate the mechanical properties required for such structures: high compressive strength, high durability, low porosity, and resistance to weathering and abrasion. 1. **Granite (Option c):** Granite is an igneous rock characterized by a coarse-grained crystalline structure. It possesses exceptionally high compressive strength and hardness. Because it is non-porous and highly resistant to chemical weathering and water penetration, it is the ideal choice for heavy-duty foundations, bridge piers, and abutments that must withstand massive loads and constant exposure to water. 2. **Limestone (Option a):** While used in construction, limestone is a sedimentary rock that is generally softer than granite and can be susceptible to chemical weathering (especially by acidic rain/water), making it less ideal for heavy-load bearing piers in varying environments. 3. **Laterite (Option b):** Laterite is a soil-like rock rich in iron and aluminum. It is relatively soft when quarried and hardens upon exposure to air, but it lacks the structural strength and density required for heavy engineering works like bridge piers. 4. **Marble (Option d):** Marble is a metamorphic rock primarily used for ornamental and architectural purposes due to its aesthetic appeal. It is softer than granite and can react with acids, making it unsuitable for heavy structural engineering applications. Therefore, Granite is the most suitable material due to its superior strength and durability.

The design of water tanks requires concrete that is not only structurally sound but also 'watertight' to prevent leakage and protect the reinforcement from corrosion. According to IS 3370 (the Indian Standard code of practice for concrete structures for storage of liquids), the permeability of concrete must be minimized. Higher grades of concrete (M30 and above) have a denser microstructure with fewer interconnected pores, which significantly reduces permeability and increases durability against chemical attacks and seepage. - M10 and M15 (Options a and d) are lean mixes used for leveling courses or PCC, and are far too porous for liquid-retaining structures. - M20 (Option b) is a general-purpose grade for RCC but is generally considered insufficient for the strict durability and impermeability requirements of water tanks. - M30 or above (Option c) ensures the necessary density and strength to maintain water-tightness and long-term serviceability.

A gabion is a cage, cylinder, or box filled with rocks, concrete, or sometimes sand and soil, used in civil engineering for retaining walls, erosion control, and slope stabilization. Specifically, gabion structures consist of double-twisted hexagonal wire mesh baskets that are filled with hard, durable rocks or stones. Why other options are incorrect: - b. Clay soil: Clay is cohesive and lacks the structural strength and permeability required for gabion walls. Gabions are designed to be free-draining to reduce hydrostatic pressure. - c. Bitumen: Bitumen is a binder used primarily in road construction (asphalt) and waterproofing; it is not a filler material for structural cages. - d. Cement mortar: Adding cement mortar would turn the structure into a rigid masonry wall, defeating the primary purpose of a gabion, which is flexibility and permeability (the ability to settle and drain water).

To understand why option (b) is correct, we must distinguish between the two fundamental processes of volume reduction in soil mechanics: Compaction and Consolidation. 1. **Compaction**: This is an instantaneous process where soil is densified by applying mechanical energy (such as rolling, ramming, or vibration). The primary mechanism is the expulsion of **air** from the void spaces between soil particles. It is typically performed on unsaturated soils. 2. **Consolidation**: This is a time-dependent (long-term) process that occurs in saturated cohesive soils (like clay). It involves the gradual expulsion of **pore water** from the soil voids under a sustained static load, leading to a decrease in volume. Evaluating the options: - **Option (a)**: Incorrect. Compaction is an almost instantaneous process, whereas consolidation is a long-term process. - **Option (b)**: Correct. Compaction occurs due to the expulsion of air under mechanical effort. - **Option (c)**: Incorrect. The drainage of water is the defining characteristic of consolidation, not compaction. - **Option (d)**: Incorrect. Both processes generally lead to a decrease in void ratio, which typically results in a decrease (not increase) in permeability.

Landslides are broadly classified based on two primary criteria: the type of material involved and the nature/speed of the movement. 1. **Type of Movement**: This distinguishes how the mass moves. For example: - **Falls**: Abrupt detachment of rocks. - **Slides**: Movement along a distinct failure surface (Rotational or Translational). - **Flows**: Material moves as a viscous fluid (Debris flows, Mudflows). - **Spreads**: Lateral movement of a coherent mass over a ductile layer. 2. **Speed of Movement**: Landslides are categorized by their velocity, ranging from extremely slow (creep) to extremely rapid (rockfalls or debris avalanches). Why other options are incorrect: - **a. Location only**: While location is important for mapping, it is not a basis for scientific classification of the landslide mechanism. - **c. Height of slope**: Slope height may influence the potential energy or scale of a landslide, but it does not define the classification of the landslide type. - **d. Rainfall amount**: Rainfall is a common 'trigger' or cause of landslides, but the classification refers to the physical behavior of the mass, not the trigger that caused it.

Efflorescence refers to the formation of a white crystalline powdery deposit on the surface of bricks or concrete. This occurs when water dissolves soluble salts present within the brick material; as the water migrates to the surface and evaporates, the salts are left behind. The efflorescence test is specifically designed to determine the amount of these soluble salts (such as sodium, potassium, and magnesium salts) present in the brick. Why other options are incorrect: - a. Sulphates: While some soluble salts are sulphates, the test detects all soluble salts, not just sulphates. - c. Clay content: Clay content is determined by the composition analysis of the raw material, not by an efflorescence test. - d. Organic impurities: Organic impurities are typically identified by the color of the brick after burning or through specific chemical tests, as they cause discoloration or holes in the brick.

The hydrological cycle is governed by the principle of conservation of mass. For a given catchment area or a specific volume of the atmosphere/earth, the change in storage is equal to the difference between the total inflow and the total outflow. This is mathematically expressed as: Inflow - Outflow = Change in Storage. This fundamental relationship is known as the Water Budget Equation. Why other options are incorrect: - a. Hydrograph equation: A hydrograph is a plot of discharge versus time at a specific point in a river; it describes the response of a watershed to a rainfall event, not the overall cycle. - c. Darcy's law: This describes the flow of fluid through a porous medium (like soil) and is used to calculate groundwater discharge, not the entire hydrological cycle. - d. Continuity equation: While the water budget equation is a specific application of the continuity equation (conservation of mass), in the context of Hydrology, the specific term used to represent the cycle's mass balance is the 'Water Budget Equation'.

The water-cement (w/c) ratio is the ratio of the weight of water to the weight of cement used in a concrete mix. According to Abram's Law, the strength of concrete is primarily dependent on the w/c ratio; a lower ratio generally leads to higher strength and durability, while a higher ratio increases porosity and reduces strength. 1. **Option (a) 0.3**: This is a very low w/c ratio. While it produces high-strength concrete, it results in a very stiff mix with very low workability, making it difficult to place and compact without the use of high-range water-reducing admixtures (superplasticizers). It is not typical for 'general' construction. 2. **Option (b) 0.5**: This is considered the standard or approximate range for general construction work. It provides a balanced compromise between adequate workability (ease of placement) and sufficient compressive strength and durability for most structural elements. 3. **Option (c) 0.7**: This ratio is too high for structural concrete. It leads to excessive bleeding, segregation, and high permeability, which significantly reduces the strength and durability of the concrete. 4. **Option (d) 0.9**: This is an extremely high ratio, typically resulting in very weak concrete that is unsuitable for any structural purpose. Therefore, for general construction purposes, a w/c ratio of approximately 0.4 to 0.6 is typically used, making 0.5 the most appropriate choice among the given options.

In hydrology, the water balance equation for a catchment area considers precipitation as the input and various 'losses' as the outputs that prevent precipitation from becoming surface runoff. 1. Interception (Option a): This is the process where precipitation is caught by vegetation or structures before it reaches the ground. It is a primary loss from precipitation. 2. Infiltration (Option b): This is the process by which water on the ground surface enters the soil. It is a major loss component in the hydrological cycle. 3. Evaporation (Option d): This is the process by which water changes from liquid to gas and returns to the atmosphere. Along with transpiration (Evapotranspiration), it is a key loss. Extraction (Option c) is not a standard hydrological term used to describe the natural losses of precipitation from a watershed. While 'extraction' might refer to human activities (like pumping groundwater), it is not categorized as a natural loss process from precipitation in the context of the hydrological cycle. Therefore, it is the correct answer as it is NOT a loss from precipitation.

Step-by-step reasoning: 1. PVC stands for Polyvinyl Chloride. 2. Chemically, it is a polymer made from the monomer vinyl chloride. 3. Polymers are categorized as either natural (e.g., cellulose, rubber, DNA) or synthetic (man-made). 4. Since PVC is produced through a chemical process called polymerization in industrial plants, it is a synthetic polymer. 5. Evaluating other options: (a) Composite materials are combinations of two or more distinct materials (e.g., reinforced concrete); PVC is a single chemical compound. (b) Natural polymers occur in nature; PVC does not. (d) Ceramics are inorganic, non-metallic solids (e.g., bricks, tiles); PVC is an organic plastic material.

The correct instrument for measuring rainfall is the Rain Gauge. It collects precipitation over a specific period, and the depth is measured in millimeters (mm) or inches. Analysis of other options: - a. Evaporimeter: Used to measure the rate of evaporation of water from a surface. - c. Barometer: Used to measure atmospheric pressure. - d. Anemometer: Used to measure wind speed and direction.

In masonry construction, mortar is the primary binding material used to fill the joints between individual masonry units (such as bricks or stones). Its primary functions are to bond the units together, distribute the load evenly across the wall, and seal the joints against air and water penetration. Reasoning for other options: - Grout (a): While similar to mortar, grout is a fluid mixture used primarily to fill voids in concrete masonry units (CMUs) or to inject into cracks in existing structures; it is not the standard material for filling joints during the laying of masonry. - Putty (c): Putty is used for filling small holes, cracks, or smoothing surfaces (usually in woodwork or plastering) before painting; it lacks the structural strength required for masonry joints. - Cement paste (d): This is a mixture of only cement and water. It is too prone to shrinkage and lacks the volume stability and workability provided by the aggregate (sand) found in mortar, making it unsuitable for filling masonry joints.

In Reinforced Concrete Design (RCC), columns are classified as 'short' or 'slender' based on their slenderness ratio. The slenderness ratio is defined as the ratio of the effective length of the column to its least lateral dimension. 1. Short Columns: These are columns where the slenderness ratio is low (typically less than 12 according to IS 456:2000). Short columns primarily fail due to crushing of the material under axial load. 2. Slender (Long) Columns: These are columns with a high slenderness ratio. They are prone to buckling before the material reaches its ultimate crushing strength. Why other options are incorrect: - (a) Cross-sectional shape: While the shape affects the moment of inertia, the classification of 'short' vs 'slender' depends on the ratio of length to dimension, not the shape itself. - (b) Diameter: Diameter is only applicable to circular columns and is only one part of the slenderness ratio calculation; it cannot define a column as short on its own without knowing the length. - (d) Material type: Both short and slender columns can be made of the same material (e.g., concrete); the classification is geometric, not material-based.