Past Questions — 2025

In Reinforced Concrete Cement (RCC) design, 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: A column is considered short if its slenderness ratio is less than a specific limit (typically 12 according to IS 456:2000). Short columns primarily fail due to direct crushing of the material. 2. Slender (Long) Columns: A column is considered slender if its slenderness ratio exceeds the limit. These columns 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 a parameter for circular columns; it is a component used to calculate the slenderness ratio, but not the defining criterion on its own. - d. Material type: Both short and slender columns can be made of the same material (e.g., concrete); the classification is a geometric property related to stability.

In hydrology, the water balance equation for precipitation considers various 'losses'—processes that remove water from the surface or prevent it from becoming surface runoff. 1. Interception (Option a): This occurs when precipitation is caught by vegetation or structures before it reaches the soil surface. 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 that reduces surface runoff. 3. Evaporation (Option d): This is the process by which water changes from a liquid to a gas and returns to the atmosphere. Along with transpiration (forming Evapotranspiration), it is a key loss. Extraction (Option c) is not a standard hydrological term used to describe the natural losses of precipitation. While 'extraction' might refer to human activities (like pumping groundwater), it is not a categorized natural loss process in the precipitation-runoff cycle. Therefore, it is the correct answer as it is NOT a loss from precipitation.

According to IS 383 (the Indian Standard specification for coarse and fine aggregates from natural sources for concrete), 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) is incorrect because while fine aggregates are generally retained on a 75-micron sieve (material passing 75 microns is considered 'silt' or 'clay'), the primary defining boundary for 'fine aggregate' is the 4.75 mm sieve. - Option (c) and (d) are incorrect as 10mm and 2.36mm are specific sieve sizes used for grading and classification of coarse aggregates or specific sand zones, but they do not define the general boundary between fine and coarse aggregates.

Step-by-step reasoning: 1. **Polyethylene (PE)**: Specifically High-Density Polyethylene (HDPE) and Linear Low-Density Polyethylene (LLDPE), these plastics are widely used for water storage tanks because they are chemically inert, non-toxic, durable, and resistant to corrosion and UV radiation. They are food-grade materials, making them safe for potable water. 2. **Bakelite**: This is a thermosetting phenol-formaldehyde resin. It is hard, brittle, and heat-resistant, typically used for electrical switches, handles of cooking utensils, and telephone casings, not for large water storage containers. 3. **PVC (Polyvinyl Chloride)**: While PVC is extensively used for water pipes and fittings due to its rigidity and strength, it is generally not used for the main body of large domestic water storage tanks because it is more brittle than polyethylene and can be more difficult to mold into large, seamless tank shapes. 4. **Nylon**: This is a polyamide used primarily for fibers, textiles, gears, and mechanical parts due to its high strength and wear resistance. It is not used for water storage tanks as it is expensive and not the optimal material for such applications. Therefore, Polyethylene is the most appropriate material for making water storage tanks.

The specific gravity (G) of soil solids is defined as the ratio of the unit weight of the soil solids to the unit weight of distilled water. To determine this, a device that can accurately measure the mass of a known volume of liquid and the mass of soil solids displaced by that liquid is required. A Pycnometer (or a density bottle) is specifically designed for this purpose. Why other options are incorrect: - a. Triaxial apparatus: Used to determine the shear strength parameters (cohesion and angle of internal friction) of soil under controlled drainage and pressure conditions. - c. Casagrande apparatus: Used to determine the Liquid Limit (LL) of a soil sample as part of Atterberg limits testing. - d. Plate load test: A field test used to determine the ultimate bearing capacity of soil and the settlement characteristics of the ground.

In Reinforced Concrete Design (RCC), the 'Limit State Method' defines a limit state as a condition beyond which a structure ceases to fulfill the function for which it was designed. There are two primary categories of limit states: 1. **Limit State of Collapse (Strength):** This ensures the safety of the structure against failure (collapse) due to loads. It deals with strength, stability, and ultimate failure (e.g., flexure, shear, torsion). 2. **Limit State of Serviceability:** This ensures that the structure remains functional and usable under normal working loads. It focuses on the comfort of users and the appearance of the structure. The primary criteria under this limit state are: - **Deflection:** Ensuring the structure does not sag excessively. - **Cracking:** Ensuring cracks are within permissible limits to prevent corrosion and maintain aesthetics. - **Vibration:** Ensuring the structure does not vibrate excessively under dynamic loads. **Analysis of other options:** - **Option a (Collapse):** This ensures the structure does not fail catastrophically, but a structure can be safe from collapse yet be unusable due to excessive sagging or cracking. - **Option c (Durability):** While durability is essential for the lifespan of a structure, it is often considered a subset or a requirement to achieve serviceability over time, rather than the primary limit state defining 'usability' in standard RCC codes (like IS 456). - **Option d (Flexural strength):** This is a specific strength parameter falling under the Limit State of Collapse, not a general limit state for usability.

Lubrication is essential in construction equipment to reduce friction, wear, and heat between moving mechanical parts. 1. **Grease (Option a):** Grease is a semi-solid lubricant consisting of a thickening agent (usually soap) and a lubricating oil. It is widely used in construction machinery for joints, bearings, and open gears because it stays in place (adheres to the surface) better than liquid oils, providing long-term protection against wear and contamination from dust and water. 2. **Diesel (Option b):** Diesel is a fuel used to power internal combustion engines. While it is a hydrocarbon, it lacks the viscosity and additive properties required to act as an effective lubricant; using it as a lubricant would lead to rapid wear and tear of components. 3. **Cement slurry (Option c):** Cement slurry is a mixture of cement and water used in construction for grouting or lubrication of piles during driving (in specific geotechnical contexts), but it is not a mechanical lubricant for equipment parts. In fact, once it hardens, it would seize any moving part. 4. **Paint (Option d):** Paint is a protective coating used to prevent corrosion and provide aesthetic appeal. It is not a lubricant and would actually increase friction if applied to moving mechanical interfaces.

Relative density (Dr), also known as compactness or density index, is a measure used specifically for cohesionless (granular) soils, such as sands and gravels. It describes the degree of packing of the soil particles relative to its loosest and densest possible states. Mathematically, it is expressed as: Dr = (e_max - e_nat) / (e_max - e_min) Where: - e_max is the void ratio of the soil in its loosest state. - e_min is the void ratio of the soil in its densest state. - e_nat is the natural void ratio of the soil in situ. Why other options are incorrect: - Option (a): Moisture content is measured by the water content ratio (w), not relative density. - Option (c): Relative density is not applicable to cohesive soils (like clays) because their structure is governed by electrochemical forces and plasticity rather than simple mechanical packing. For cohesive soils, the Liquidity Index or Plasticity Index is used. - Option (d): Plasticity is a property of cohesive soils measured by the Atterberg limits (Liquid Limit, Plastic Limit), not by relative density.

In soil mechanics, the Atterberg limits define the critical water contents of a fine-grained soil. 1. **Plastic Limit (PL):** This is defined as the water content at which a soil transitions from a semi-solid state to a plastic state. In laboratory testing, it is specifically determined as the water content at which a soil thread, rolled to a diameter of 3.2 mm (1/8 inch), just begins to crumble. Therefore, option (b) is the correct definition. 2. **Analysis of other options:** - **Option (a):** The water content at which soil becomes semi-solid is the transition point between the plastic and semi-solid states, but the 'Plastic Limit' is the boundary itself. The state below the plastic limit is semi-solid. - **Option (c):** The water content at which soil begins to flow is known as the **Liquid Limit (LL)**. - **Option (d):** The water content when soil is completely dry is simply 0% moisture content, which is not a defined Atterberg limit.

Step-by-step reasoning: 1. **Analysis of the Requirement**: The question asks for a structure specifically designed to protect riverbanks from erosion caused by the flow of water. 2. **Evaluating Option (b) Revetment wall**: A revetment is a facing of stone, concrete, or other materials placed on a bank or shoreline to protect it from erosion caused by wave action or currents. It acts as a protective layer (armoring) that prevents the soil from being washed away by the river flow. This directly matches the question's requirement. 3. **Evaluating Option (a) Toe wall**: A toe wall is a wall constructed at the base (toe) of a slope or a larger retaining wall to prevent the sliding or scouring of the base. While it helps in stability, it is not the primary structure used for overall bank erosion protection. 4. **Evaluating Option (c) Breast wall**: A breast wall is a retaining wall built across a slope or at the edge of a road/embankment to prevent the soil from sliding down. It is typically used for slope stability rather than protecting against hydraulic erosion from a river. 5. **Evaluating Option (d) Anchor wall**: An anchor wall is a type of retaining wall that uses anchors (cables or rods) driven into the ground to provide additional stability against overturning. It is a structural design for stability, not a specific erosion protection measure for riverbanks. Conclusion: The revetment wall is the correct technical term for a structure providing protection against erosion along riverbanks.

The Plate Load Test is a standard field test used to determine the ultimate bearing capacity of soil and the settlement characteristics of the soil under a given load. In this test, a steel plate is placed on the soil surface or at a specific depth and loaded using a hydraulic jack until the soil fails or a specific settlement is reached. Why other options are incorrect: - a. Core Cutter Test: This is used to determine the in-situ bulk density (unit weight) of cohesive soils. - c. Vane Shear Test: This is used to determine the undrained shear strength of soft, saturated clays, not the overall bearing capacity of various soil types. - d. Pycnometer Test: This is a laboratory test used to determine the specific gravity of soil solids.

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 to limit state design. 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), but it does not provide the design rules for the RCC members themselves. 3. **IS 800 (Code of Practice for General Construction in Steel):** This code provides the guidelines for the design of structural steelwork, not reinforced concrete. 4. **IS 3370 (Code of Practice for Concrete Structures for Storage of Liquids):** This is a specialized code specifically for the design of water tanks and liquid-retaining structures, rather than general RCC building design.

Step-by-step reasoning: 1. Analysis of Geology: The problem specifies 'impermeable geology'. In such areas, natural infiltration of rainwater into the aquifer is restricted, leading to a lack of natural groundwater replenishment. 2. Problem Identification: Declining groundwater levels indicate that the rate of extraction exceeds the rate of natural recharge. 3. Evaluating Solutions: To combat declining levels in impermeable or semi-impermeable terrain, 'Artificial Recharge' is required. This involves man-made structures (like percolation tanks, recharge shafts, or recharge wells) that bypass impermeable surface layers to direct water directly into the permeable aquifer zones. 4. Evaluating Options: Option (b) Open wells and Option (c) Deep borewells are methods of extraction, not replenishment; using them further would accelerate the decline of groundwater levels. Option (d) Rooftop irrigation is a water-use method, not a groundwater recharge method. Therefore, artificial recharge structures are the only viable engineering solution to increase the water table in this scenario.

A retaining wall is a structure designed to hold back soil or other materials that would otherwise move due to gravity. The primary engineering purpose of a retaining wall is to resist the 'lateral earth pressure' exerted by the soil behind it, preventing slope failure or landslides and allowing for the creation of level terraces in hilly terrain. Analysis of other options: - Option (a) 'Support roofing' is the function of beams, columns, or load-bearing walls, not retaining walls. - Option (c) 'Anchor piles' refers to a foundation technique; while some retaining walls use anchors (anchored walls), the wall's primary purpose is not to anchor the piles themselves. - Option (d) 'Store water' is the function of tanks, reservoirs, or dams. While some retaining walls may be designed for hydrostatic pressure, their primary definition relates to earth retention.

Step-by-step reasoning: 1. **Plywood**: This is an engineered wood product made by gluing together thin layers of wood veneers. These layers (plies) are glued with their grains oriented perpendicular to each other (cross-graining), which provides high strength, stability, and resistance to splitting. 2. **Particle board**: This is made from wood chips, sawmill shavings, or sawdust bonded together with a resin under heat and pressure. It does not consist of 'thin layers' of wood veneers. 3. **Block board**: This consists of a core of solid wood strips (blocks) sandwiched between two layers of veneer. While it uses veneers on the surface, the core is not made of thin layers glued together, but rather solid blocks. 4. **Fiberboard (MDF/HDF)**: This is made by breaking down wood residuals into fibers, combining them with wax and resin, and forming panels under high temperature and pressure. It is a homogeneous material rather than a layered veneer product. Therefore, the product specifically defined by gluing thin layers (veneers) together is Plywood.

In slope stability analysis, the Factor of Safety (FoS) is a measure of the stability of a soil slope against failure. Failure occurs when the shear stress ($ au$) acting along a potential failure surface exceeds the shear strength ($s$ or $ au_f$) of the soil. Therefore, the Factor of Safety is defined as the ratio of the resisting forces (shear strength) to the driving forces (shear stress). Mathematically: FoS = (Available Shear Strength) / (Mobilized Shear Stress). Why other options are incorrect: - Option (a): The ratio of active to passive pressure is used in the design of retaining walls to check for stability against sliding or overturning, but it is not the definition of the factor of safety for slope stability. - Option (b): Weight and height are parameters used to calculate stresses, but their ratio does not define the stability factor. - Option (d): Cohesion is a component of shear strength (according to Mohr-Coulomb theory), and the slope angle affects the driving stress, but their direct ratio is not the definition of the factor of safety.

The runoff coefficient (C) is a dimensionless coefficient used in the Rational Method (Q = CiA) to represent the fraction of rainfall that becomes surface runoff. It depends on the permeability of the surface. 1. Concrete surfaces are considered 'impervious' or 'impermeable,' meaning they allow very little to no water to infiltrate into the ground. 2. Because infiltration is negligible, most of the precipitation that falls on a concrete surface becomes runoff. 3. Typical values for the runoff coefficient for concrete range from 0.80 to 0.95, depending on the smoothness and condition of the surface. Analysis of options: - Option (a) 0.1: Typical for sandy soils or heavily forested areas with high infiltration. - Option (b) 0.3: Typical for lawns or parks. - Option (c) 0.85 - 0.95: Correct for impervious surfaces like concrete and asphalt. - Option (d) 1.2: Impossible, as the runoff coefficient cannot exceed 1.0 (you cannot have more runoff than the total rainfall received).

The hydrological cycle is governed by the principle of conservation of mass. For a given catchment area or a specific volume of the earth's atmosphere/crust over a specific time interval, the inflow must equal the outflow plus the change in storage. 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 is a tool for analysis, not the governing equation of the entire cycle. - c. Darcy's law: This describes the flow of a fluid through a porous medium (like soil), which is only a small part of the hydrological cycle (infiltration/groundwater flow). - 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 term 'Water Budget Equation' is the standard terminology used to represent the cycle's balance.

Water tanks are liquid-retaining structures that require high durability and low permeability to prevent leakage and protect reinforcement from corrosion. According to standard engineering practices and codes (such as IS 456 and IS 3370), concrete used for water-retaining structures must be dense and high-strength to ensure water-tightness. 1. **Durability Requirements**: Water tanks are often exposed to severe environmental conditions or aggressive chemicals in water. High-grade concrete (M30 and above) provides a denser matrix with fewer interconnected pores, reducing the permeability of the concrete. 2. **Crack Control**: Higher grades of concrete, when combined with appropriate reinforcement and design (as per IS 3370), help in controlling crack widths, which is critical for liquid-retaining structures. 3. **Comparison with other options**: - M10 and M15 are lean concretes used for leveling courses or PCC (Plain Cement Concrete) and lack the strength and density required for structural water tanks. - M20 is a general-purpose grade for basic RCC work but is generally considered insufficient for the stringent permeability and durability requirements of specialized water-retaining structures. Therefore, M30 or above is the standard recommendation for ensuring the longevity and functionality of water tanks.

In rainwater harvesting systems for household use, the storage tank must be made of materials that are durable, non-toxic, and do not leach harmful chemicals into the water. 1. **HDPE (High-Density Polyethylene)**: This is a food-grade plastic that is corrosion-resistant, lightweight, and does not react with water, making it ideal for potable water storage. 2. **Reinforced Concrete**: This is a traditional and highly durable material for large-scale storage. When properly cured and sealed (often with food-grade liners or waterproof coatings), it provides excellent structural stability and keeps water cool. Why other options are incorrect: - **Asbestos (a)**: Asbestos is a known carcinogen and is strictly prohibited for use in drinking water systems due to health risks. - **Lead (b)**: Lead is a toxic heavy metal that causes lead poisoning; it must never be used for storing drinking water. - **Uncoated Iron (d)**: Uncoated iron is highly susceptible to corrosion (rusting) when in contact with water, which contaminates the water and leads to structural failure of the tank.

Seasoning of timber is the process of reducing the moisture content (sap) of the wood to a level that is in equilibrium with the environment in which the timber will be used. 1. Why Option (b) is correct: Freshly felled timber contains a large amount of water. If used immediately, this water evaporates over time, leading to shrinkage, warping, cracking, and susceptibility to fungal attacks. Seasoning removes this excess moisture, thereby increasing the strength, durability, and dimensional stability of the wood. 2. Why other options are incorrect: - Option (a): Seasoning actually decreases the weight of the timber because water is removed. - Option (c): While seasoning might slightly alter the appearance, its primary engineering purpose is structural stability, not aesthetic color improvement. - Option (d): Seasoning does not make timber fireproof; in fact, dry timber may ignite more easily than green (wet) timber, although it is more stable for construction.

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. It achieves this through a higher tricalcium silicate (C3S) content and a finer grinding of the clinker, which accelerates the hydration process and generates more heat of hydration. This internal heat helps maintain the temperature of the concrete mix, ensuring that the concrete sets and gains sufficient strength rapidly even in cold environments. Analysis of other options: - Ordinary Portland Cement (OPC): Its hydration rate slows down significantly in cold weather, making it less ideal than RHC for rapid strength gain. - Low Heat Cement: This cement is designed to minimize the heat of hydration to prevent thermal cracking in mass concrete (like dams). Using it in cold weather would be counterproductive as it would further slow down the setting process. - Sulphate Resisting Cement: This is used in environments with high sulphate concentrations (like coastal areas or certain soils) to prevent chemical attack; it does not specifically address cold weather hydration issues.

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., rubber, cellulose, DNA) or synthetic (man-made). 4. Since PVC is produced through a chemical process (polymerization) in industrial plants and does not occur naturally in the environment, it is classified as 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 homogeneous plastic. (b) Natural polymers occur in nature; PVC is man-made. (d) Ceramics are inorganic, non-metallic solids (e.g., bricks, glass); PVC is an organic plastic.

Hairline cracks appearing soon after construction in concrete structures, especially water tanks, are typically 'plastic shrinkage cracks' or 'drying shrinkage cracks'. 1. **High Water-Cement (w/c) Ratio**: A high w/c ratio increases the amount of evaporable water in the concrete mix. As this excess water evaporates, the volume of the concrete decreases, leading to shrinkage. Since the structure is restrained, this shrinkage manifests as hairline cracks. 2. **Improper Curing**: Curing is essential to maintain moisture for the hydration of cement. If curing is inadequate, the surface dries out rapidly, leading to differential shrinkage between the surface and the core of the concrete, which triggers cracking. Why other options are incorrect: - **Option a (Low cement grade)**: While cement grade affects strength, it is not the primary driver of immediate hairline shrinkage cracks; shrinkage is more closely tied to the water content and curing process. - **Option c (Use of reinforcement)**: Reinforcement is intended to control cracking and provide tensile strength. Its presence generally reduces the width of cracks rather than causing them. - **Option d (Rapid shuttering removal)**: Removing formwork too early typically leads to structural sagging, deflection, or large structural cracks due to the concrete not having reached sufficient strength to support its own weight, rather than widespread hairline shrinkage cracks.

Step-by-step reasoning: 1. Water absorption refers to the ability of an aggregate to absorb water into its internal pore structure. 2. In a concrete mix, the 'effective water' is the water available to lubricate the aggregates and hydrate the cement paste, which directly determines the workability (slump) of the mix. 3. If aggregates with high water absorption are used without adjusting the mix design (i.e., without adding extra water to compensate for what the aggregate absorbs), the aggregates will soak up a portion of the mixing water. 4. This reduction in free water leads to a drier mix, significantly reducing the workability of the concrete, making it difficult to place and compact. 5. While compressive strength and durability can be affected indirectly if the mix is poorly compacted due to low workability, the most immediate and direct property affected by the absorption of mixing water is the workability. 6. Initial setting time is primarily a property of the cement and chemical admixtures, not the water absorption of the aggregate.