Past Questions — 2025

Landslide investigation requires understanding the subsurface geometry, the location of the failure plane (slip surface), and the monitoring of slope movement over time. 1. **Boreholes** are essential for extracting soil and rock samples to determine the geotechnical properties of the material and to identify the depth and nature of the sliding surface. 2. **Inclinometers** are specialized instruments installed within boreholes to measure the magnitude, direction, and rate of subsurface lateral displacement. They are the primary tool for detecting the exact depth at which a slope is shearing. Why other options are incorrect: - **Penetrometer (a):** While used for soil strength testing, it provides localized surface or shallow data and cannot track the deep-seated movement characteristic of landslides. - **Rain gauge (c):** This is a meteorological tool used to monitor rainfall (a trigger for landslides), but it is not a tool for investigating the physical stability or internal movement of the slope itself. - **Compass only (d):** A compass is used for mapping and orientation, but it cannot provide the subsurface data required for a technical landslide investigation.

The question asks for a wood product made by gluing thin layers of wood together. 1. **Plywood (Correct):** Plywood is an engineered wood product made from thin sheets of wood veneer (plies) that are glued together. Crucially, each layer is placed with its grain perpendicular to the grain of the next layer (cross-graining), which provides strength and stability in multiple directions. 2. **Particle board (Incorrect):** This is made from wood chips, sawmill shavings, or sawdust bonded together with a resin under heat and pressure. It consists of particles, not thin layers of wood. 3. **Block board (Incorrect):** 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 made of blocks, not thin layers of wood throughout. 4. **Fiberboard (Incorrect):** This is made by breaking down wood into fibers (essentially a pulp) and then pressing them into sheets using heat and glue. It is a homogeneous mass of fibers rather than distinct layers of wood veneer.

A gravity retaining wall is a structure that relies solely on its own self-weight (mass) to resist the lateral earth pressure exerted by the soil it is retaining. 1. **Stone masonry retaining wall (Option a):** These are constructed using heavy materials like stone or concrete. Because they have a large mass and a wide base, they use their own weight to prevent overturning and sliding. Therefore, it is a classic example of a gravity retaining structure. 2. **Reinforced soil wall (Option b):** These are composite structures where the soil is reinforced with geosynthetics or metallic strips to increase its shear strength. They rely on internal reinforcement rather than the mass of the wall itself. 3. **Anchored wall (Option c):** These walls use anchors (cables or rods) driven deep into the stable soil or rock behind the wall to provide additional stability. They rely on external tension members rather than self-weight. 4. **Sheet pile wall (Option d):** These are thin walls driven into the ground. They derive their stability from the passive resistance of the soil in front of the embedded portion of the pile, not from their own weight.

A crib wall is a type of retaining wall consisting of a cellular structure (a 'crib') made of interlocking units. These units are typically prefabricated and stacked in a criss-cross pattern to form a hollow cage, which is then filled with granular material (like crushed stone or gravel) to provide the necessary mass for stability. 1. Why Option (a) is correct: Historically, timber was the primary material used for crib walls due to its availability and ease of interlocking. In modern engineering, precast concrete units are widely used because they offer greater durability and resistance to decay compared to timber. 2. Why Option (b) is incorrect: Masonry (brick or stone) is used for gravity walls. A crib wall is specifically a cellular, open-frame structure, not a solid masonry wall. 3. Why Option (c) is incorrect: While steel may be used in some specialized reinforced earth structures, crib walls are defined by their modular, interlocking unit construction, not by steel reinforcement bars. 4. Why Option (d) is incorrect: Plastic cells are used in 'geocells' for soil stabilization, but standard crib walls are structural gravity-based systems made from heavier materials like concrete or timber to resist lateral earth pressure.

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.

The correct instrument for measuring precipitation (rainfall) is the Rain Gauge. It collects rainfall 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.

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 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: Vertical loads (the weight of the wall itself) actually help stabilize the wall against overturning and sliding; they are generally a stabilizing force rather than a cause of failure.

According to IS 383 (the Indian Standard code for coarse and fine aggregates from natural sources), aggregates are classified based on their particle size. 1. **Fine Aggregates**: These are defined as aggregates that pass through a 4.75 mm IS sieve. However, to distinguish 'fine aggregate' (sand) from 'silt' or 'clay' (which are considered deleterious materials in concrete), the definition specifies that they must be retained on a 75-micron (0.075 mm) sieve. Particles passing the 75-micron sieve are classified as silt or clay. 2. **Coarse Aggregates**: These are aggregates that are retained on a 4.75 mm IS sieve. Comparing the options: - Option (a) is partially correct but incomplete because it doesn't exclude the silt/clay fraction. - Option (b) provides the complete technical definition used in civil engineering standards. - Option (c) and (d) refer to sizes that do not define the boundary between fine and coarse aggregates.

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 geotechnical engineering and geology, slope movement (mass wasting) is categorized based on the type of material and the mechanism of movement. 1. **Slides (Option a):** This occurs when a distinct mass of rock or soil moves along a well-defined surface of rupture (e.g., translational or rotational slides). 2. **Falls (Option b):** This occurs when material detaches from a steep slope or cliff and descends primarily by free-fall, bouncing, or rolling. 3. **Flows (Option c):** This occurs when material moves as a viscous fluid, often saturated with water (e.g., mudflows, debris flows). **Lifts (Option d)** is not a recognized term for a type of slope movement. In engineering, 'lift' usually refers to the thickness of a layer of soil or concrete placed during construction (e.g., compacted lifts), but it does not describe a mechanism of slope failure or mass movement.

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 Pycnometer (a density bottle) is used. The process involves weighing the pycnometer when empty, when filled with soil and water, and when filled only with water. By calculating the mass of the soil solids and the mass of the water displaced by those solids, the specific gravity is determined. 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 to classify its plasticity. - d. Plate load test: A field test used to determine the ultimate bearing capacity of soil and the settlement characteristics of the ground.

The minimum depth of a shallow foundation is determined by the need to reach a soil stratum with sufficient bearing capacity (shear strength) to support the structural load without failure. Additionally, the depth of the water table is a critical governing factor because a high water table reduces the effective stress of the soil, thereby decreasing its shear strength and bearing capacity. Furthermore, the foundation must be placed below the frost line or the depth of seasonal moisture change to prevent heave or shrinkage. - Option (a) is incorrect because while the structure's load determines the required bearing capacity, the 'depth' itself is governed by the soil's properties at that depth. - Option (b) is incorrect because settlement criteria usually govern the 'maximum' allowable pressure or the 'size' of the footing rather than the 'minimum depth' of embedment. - Option (d) is incorrect because grain size is a characteristic of the soil that influences shear strength, but it is not the direct governing criterion for determining depth.

Relative density (also known as density index, $I_D$ or $D_r$) is a physical property used specifically for cohesionless or granular soils (like sands and gravels) to describe the degree of packing or compactness of the soil particles. It is defined as the ratio of the difference between the maximum and minimum void ratios to the difference between the minimum void ratio and the actual void ratio of the soil in its current state. Formula: $D_r = \frac{e_{max} - e}{e_{max} - e_{min}} \times 100\%$ Why other options are incorrect: - Option (a): Moisture content is measured by the water content ratio, not relative density. - Option (c): Relative density is not applicable to cohesive soils (clays) because their structure is dominated by surface chemistry and plasticity rather than simple mechanical packing of grains. - Option (d): Plasticity is measured by the Plasticity Index ($I_p$), which is the difference between the liquid limit and plastic limit.

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.

In soil mechanics, it is critical to distinguish between compaction and consolidation. 1. **Compaction** is an instantaneous process where soil is densified by the expulsion of air from the voids through mechanical means (such as rolling, ramming, or vibration). It is typically performed on unsaturated soils. 2. **Consolidation** is a time-dependent (long-term) process where soil is densified by the expulsion of pore water from saturated cohesive soils under a sustained static load. Evaluating the options: - **Option (a)** is incorrect because compaction is an almost instantaneous process, whereas consolidation is a long-term process. - **Option (b)** is correct because compaction specifically involves removing air from the soil voids using mechanical effort. - **Option (c)** is incorrect because the drainage of water is the defining characteristic of consolidation, not compaction. - **Option (d)** is incorrect because both processes generally lead to a decrease in void ratio, which typically results in a decrease (not increase) in permeability.

A gabion is a cage, cylinder, or box filled with rocks, concrete, or sometimes sand and soil, for use in civil engineering, road building, military applications, and erosion control. Specifically, in the context of retaining walls and slope stabilization, gabions consist of galvanized steel wire mesh baskets filled with hard, durable rocks or stones. Why other options are incorrect: - b. Clay soil: Clay is cohesive and lacks the internal friction and permeability required for gabion structures; filling them with clay would defeat the purpose of drainage and structural stability. - c. Bitumen: Bitumen is a binder used primarily in road surfacing (asphalt) and waterproofing, not as a filler for structural cages. - d. Cement mortar: While 'mattress' gabions exist, the defining characteristic of a standard gabion is its flexibility and permeability. Filling the baskets with cement mortar would turn the structure into a rigid concrete block, removing the primary advantages of gabions (such as permeability and the ability to settle without cracking).

A revetment wall (or revetment) is a protective facing, such as concrete blocks, riprap, or gabions, placed on a slope or riverbank to prevent erosion caused by the action of flowing water (scouring). Here is why the other options are incorrect: - a. Toe wall: A toe wall is a small wall constructed at the base (toe) of a larger retaining wall or embankment to prevent the soil from sliding out from the bottom. - c. Breast wall: A breast wall is typically a retaining wall built along the side of a road or railway embankment to support the soil and prevent it from sliding onto the track or road. - d. Anchor wall: An anchor wall is a type of retaining wall that uses anchors (cables or rods) driven deep into the stable ground behind the wall to provide additional stability against overturning.

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. Freshly felled trees contain a high percentage of water (free water and bound water). If used without seasoning, the timber is prone to warping, shrinking, cracking, and decay. By reducing the moisture content through air seasoning or kiln seasoning, the timber becomes more dimensionally stable, stronger, and more durable. Analysis of other options: - Option (a) Increase weight: Seasoning actually decreases the weight of timber because water is removed. - Option (c) Improve color: While seasoning may slightly alter the appearance, its primary engineering purpose is structural stability, not aesthetic color improvement. - Option (d) Make it fireproof: Seasoning does not make timber fireproof; in fact, dry timber may ignite more easily than green timber, although it does not change the inherent combustibility of the material.

Retaining walls are designed to resist the lateral earth pressure exerted by the soil behind them. When water accumulates behind the wall (due to rain or groundwater), it exerts an additional lateral force known as hydrostatic pressure. This pressure significantly increases the total load on the wall, which can lead to structural failure or overturning if not managed. Drainage systems (such as weep holes, perforated pipes, and granular filter material) are provided to allow water to escape, thereby relieving this hydrostatic pressure and ensuring the stability of the wall. Analysis of other options: - Option (a): Making soil heavier would increase the lateral pressure on the wall, which is undesirable. - Option (c): Drainage does not add cohesion; in fact, saturation usually reduces the effective shear strength of the soil. - Option (d): Drainage is used to manage water within the soil mass; it does not change the physical slope angle of the terrain.

According to Indian Standard (IS) specifications and general civil engineering standards for brick classification, bricks are categorized based on their compressive (crushing) strength. 1. First-Class Bricks: These are the highest quality bricks used for load-bearing walls. Their minimum average compressive strength should not be less than 10.5 N/mm². 2. Second-Class Bricks: These have a minimum compressive strength of 7.0 N/mm². 3. Third-Class Bricks: These have a minimum compressive strength of 3.5 N/mm². Comparing this to the options provided: - Option (a) 3.5 N/mm² corresponds to Third-Class bricks. - Option (b) 7.0 N/mm² corresponds to Second-Class bricks. - Option (c) 5.0 N/mm² does not align with standard class definitions. - Option (d) 10.5 N/mm² is the correct minimum requirement for First-Class bricks.

Artificial recharge is the process of augmenting the natural recharge of groundwater aquifers by intentionally directing surface water (such as rainwater, treated wastewater, or river water) into the ground. Step-by-step reasoning: 1. **Definition**: Artificial recharge involves the use of structures like recharge pits, shafts, or injection wells to move water from the surface into the saturated zone of an aquifer. 2. **Primary Goal**: The fundamental objective is to 'replenish' or 'refill' the groundwater table, especially in areas where extraction (pumping) exceeds natural recharge, leading to a drop in the water table. 3. **Evaluating Options**: - (a) Reduce surface water runoff: While reducing runoff is often a *method* or a *by-product* of recharge (by capturing water that would otherwise run off), it is not the ultimate 'objective'. The goal is what happens to that water after it is captured. - (b) Create open wells: Open wells are structures used to *extract* water; they are not the objective of recharging the aquifer. - (c) Replenish groundwater: This is the direct and primary objective of artificial recharge. - (d) Improve rainfall: Artificial recharge deals with water already present on the surface; it has no mechanism to influence atmospheric conditions or increase rainfall (which would be 'cloud seeding').

The water-cement (w/c) ratio is the ratio of the weight of water to the weight of cement used in a concrete mix. It is the primary factor determining the strength and durability of concrete. 1. **Abrams' Law**: According to the law established by Duff Abrams, the strength of concrete is primarily dependent on the water-cement ratio, provided the mix is workable. A lower w/c ratio generally leads to higher strength and lower permeability. 2. **General Construction Range**: For general construction work, the w/c ratio typically ranges between 0.40 and 0.60. A value of 0.5 is considered the standard 'middle-ground' or approximate value that balances strength, durability, and workability for general purposes. 3. **Analysis of Options**: - **0.3 (Option a)**: This is very low and typically used for high-strength concrete or specialized pre-cast elements. It often requires chemical admixtures (superplasticizers) to make the concrete workable. - **0.5 (Option b)**: This is the ideal approximate value for general construction, providing a good balance of strength and ease of placement. - **0.7 (Option c)**: This is too high for structural concrete. High water content leads to increased porosity, shrinkage cracks, and significantly reduced compressive strength. - **0.9 (Option d)**: This is excessively high and would result in very weak concrete with poor durability, unsuitable for almost any structural construction work.

The amount of rainwater that can be harvested from a roof is determined by the volume of water that falls on the surface and the efficiency with which that water is collected. The standard formula used for calculating rainwater harvesting potential is: Harvested Water = Catchment Area × Annual Rainfall × Runoff Coefficient. 1. Roof Area (Catchment Area): The horizontal projection of the roof surface that intercepts the rain. 2. Rainfall: The depth of precipitation over a specific period. 3. Runoff Coefficient: A dimensionless factor (ranging from 0 to 1) that accounts for losses due to evaporation, absorption by the roofing material, or leakage. For example, a concrete roof has a higher runoff coefficient (approx. 0.7-0.9) than a thatched roof. Why other options are incorrect: - a. Permeability of soil: This affects how water infiltrates the ground, but not how much is collected from an impermeable roof surface. - c. Catchment slope: While slope affects the velocity of runoff, the total volume of water harvested depends on the horizontal area, not the slope angle. - d. Groundwater table depth: This is relevant for well design or drainage, but it does not determine the amount of rain falling on a roof.

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.

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 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 chemical analysis, as they often cause discoloration or voids, but not the white crystalline deposits characteristic of efflorescence.