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Past Questions
Which of the following is used to calculate rainwater harvested from a roof?
A)
Permeability of soil
B)
Roof area x rainfall x runoff coefficient
C)
Catchment slope
D)
Groundwater table depth
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.
Timber is seasoned to-
A)
Increase weight
B)
Reduce moisture content
C)
Improve color
D)
Make it fireproof
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.
Rainwater harvesting does not include-
A)
Rooftop collection
B)
Irrigation from canals
C)
Recharge pits
D)
Percolation tanks
Rainwater harvesting (RWH) is the process of collecting, filtering, and storing rainwater for future use or for recharging groundwater.
1. Rooftop collection (Option a): This is a primary method of RWH where rain falling on the roof is collected via gutters and pipes and stored in tanks.
2. Recharge pits (Option c): These are artificial pits designed to direct rainwater into the ground to replenish the water table, which is a core component of groundwater harvesting.
3. Percolation tanks (Option d): These are small reservoirs that hold rainwater, allowing it to slowly seep (percolate) into the ground to recharge aquifers.
In contrast, Irrigation from canals (Option b) involves the distribution of water from a river or a large 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 equation representing the hydrological cycle is known as-
A)
Hydrograph equation
B)
Water budget equation
C)
Darcy’s law
D)
Continuity equation
The hydrological cycle is governed by the principle of conservation of mass. For a given catchment area or a specific volume of control, the change in storage is equal to the difference between the total inflow and 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 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), specifically relating flow rate to hydraulic gradient; it is a subset of groundwater hydrology, not the overall 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 and the hydrological cycle, the term 'Water Budget Equation' is the standard and specific terminology used.
Which is a recommended tank material for household rainwater storage?
A)
Asbestos
B)
Lead
C)
HDPE or reinforced concrete
D)
Uncoated iron
In rainwater harvesting systems for household use, the storage tank must be made of materials that are durable, non-toxic, and resistant to corrosion to ensure the water remains potable and safe for consumption.
1. **HDPE (High-Density Polyethylene)**: This is a food-grade plastic that is lightweight, durable, and does not leach harmful chemicals into the water. It is widely recommended for domestic water storage.
2. **Reinforced Concrete**: This is a standard engineering material for large-scale or permanent household storage. When properly cured and sealed (to prevent seepage), it provides excellent structural stability and keeps the 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 can leach into the water, causing severe neurological damage (lead poisoning).
- **Uncoated Iron (d)**: Uncoated iron is highly susceptible to corrosion (rusting) when in contact with water, which contaminates the water with iron oxides and leads to structural failure of the tank.
The crushing strength of first-class bricks should not be less than-
A)
3.5 N/mm²
B)
7.0 N/mm²
C)
5.0 N/mm²
D)
10.5 N/mm²
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.
The main objective of artificial recharge is to-
A)
Reduce surface water runoff
B)
Create open wells
C)
Replenish groundwater
D)
Improve rainfall
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').
Which of the following woods is most resistant to termite attack?
A)
Pine
B)
Teak
C)
Cedar
D)
Sal
In the context of construction materials and timber engineering, resistance to termites and decay is primarily determined by the presence of natural oils, resins, and the density of the wood.
1. **Sal (Shorea robusta):** Sal is a heavy, hard, and durable hardwood. It contains high concentrations of natural resins and tannins that make it highly resistant to termite attacks and fungal decay. It is widely used in heavy construction, railway sleepers, and door frames specifically because of its superior durability in harsh conditions.
2. **Teak (Tectona grandis):** While Teak is highly prized for its durability and natural oils that resist water and rot, in many comparative engineering standards for termite resistance in the Indian subcontinent, Sal is often rated higher for structural resistance against subterranean termites due to its extreme density.
3. **Cedar:** Cedar is naturally resistant to decay and insects, but it is a softwood and generally lacks the structural density and extreme termite resistance of Sal.
4. **Pine:** Pine is a softwood and is generally very susceptible to termite attacks and decay unless chemically treated.
Therefore, among the given options, Sal is recognized as the most resistant to termite attack.
Which of the following is commonly used as a lubricant in construction equipment?
A)
Grease
B)
Diesel
C)
Cement slurry
D)
Paint
Step-by-step reasoning: 1. Definition of a lubricant: A lubricant is a substance used to reduce friction between two moving surfaces, preventing wear and tear and heat buildup. 2. Evaluating Option (a) Grease: Grease is a semi-solid lubricant consisting of a thickening agent and a base oil. It is specifically designed to adhere to moving parts (like bearings, joints, and gears) in heavy construction equipment, providing long-lasting lubrication and protection against contaminants. 3. Evaluating Option (b) Diesel: Diesel is a fuel used to power internal combustion engines; it is not used as a lubricant because it lacks the viscosity and additive properties required to reduce friction between mechanical parts. 4. Evaluating Option (c) Cement slurry: This is a mixture of cement and water used for grouting or bonding; it hardens over time and would cause mechanical parts to seize if used as a lubricant. 5. Evaluating Option (d) Paint: Paint is a protective or decorative coating; it is not a lubricant and would act as a contaminant in mechanical assemblies. Therefore, grease is the only appropriate lubricant among the choices.
Compaction differs from consolidation in that compaction is-
A)
A long-term process
B)
Due to expulsion of air under mechanical effort
C)
Due to drainage of water
D)
Due to increase in permeability
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.
Which parameter is defined as the volume of voids to the volume of solids in a soil mass?
A)
Porosity
B)
Void ratio
C)
Degree of saturation
D)
Water content
In soil mechanics, the phase relationship of a soil mass is defined by several key parameters. The correct answer is determined as follows:
1. **Void Ratio (e):** It is defined as the ratio of the volume of voids (Vv) to the volume of solids (Vs). Formula: e = Vv / Vs. This matches the definition provided in the question.
2. **Porosity (n):** It is the ratio of the volume of voids (Vv) to the total volume of the soil mass (Vt). Formula: n = Vv / Vt. While similar to void ratio, the denominator is the total volume, not the volume of solids.
3. **Degree of Saturation (S):** It is the ratio of the volume of water (Vw) to the volume of voids (Vv), expressed as a percentage. Formula: S = (Vw / Vv) × 100%.
4. **Water Content (w):** Also known as moisture content, it is the ratio of the weight of water (Ww) to the weight of solids (Ws). Formula: w = (Ww / Ws) × 100%.
Therefore, the parameter defined as the volume of voids to the volume of solids is the Void Ratio.
Drainage behind retaining walls is provided to-
A)
Make soil heavier
B)
Relieve hydrostatic pressure
C)
Add cohesion
D)
Reduce slope angle
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.
Silica in brick earth is responsible for-
A)
Plasticity
B)
Preventing cracking and shrinkage
C)
Improving color
D)
Binding material
Brick earth consists of several constituents, primarily silica, alumina, lime, iron oxide, and magnesia.
1. **Silica (SiO2):** Silica is the primary constituent of brick earth. Its main function is to prevent cracking, shrinking, and warping during the drying and burning process. However, if silica is present in excess, the bricks may lose plasticity and become brittle.
2. **Alumina (Al2O3):** This is responsible for the **plasticity** of the clay, allowing the brick to be molded into shape. Excess alumina causes the brick to shrink and crack during drying.
3. **Iron Oxide:** This acts as a flux to fuse the particles and is primarily responsible for the characteristic **red color** of the brick.
4. **Lime (CaO):** Lime helps in the fusion of silica and acts as a **binding material** to some extent, but excess lime causes the brick to disintegrate (efflorescence).
Therefore, since the question asks specifically about the role of silica, the correct answer is that it prevents cracking and shrinkage.
The factor of safety in slope stability analysis is defined as the ratio of-
A)
Active to passive pressure
B)
Weight to height of slope
C)
Shear strength to shear stress
D)
Cohesion to slope angle
In slope stability analysis, the Factor of Safety (FoS) is a dimensionless ratio used to determine the stability of a soil or rock slope. It is defined as the ratio of the resisting forces (or strengths) to the driving forces (or stresses) acting along a potential failure surface. Specifically, it is the ratio of the available shear strength of the soil (the maximum resistance the soil can offer) to the actual shear stress acting on the failure plane (the stress tending to cause the slope to slide).
Mathematically: FoS = (Available Shear Strength) / (Mobilized Shear Stress).
- If FoS > 1, the slope is stable.
- If FoS = 1, the slope is in a state of limiting equilibrium (critical).
- If FoS < 1, the slope is unstable and will fail.
Analysis of other options:
- Option (a): Active and passive pressures are used in retaining wall design, not as the general definition of slope stability FoS.
- Option (b): Weight and height are parameters used to calculate stresses, but their ratio does not define the factor of safety.
- Option (d): Cohesion is a component of shear strength, and the slope angle affects the shear stress, but their direct ratio is not the definition of FoS.
Which is not a component of surface water?
A)
Rivers
B)
Aquifers
C)
Lakes
D)
Reservoirs
Surface water refers to any body of water found on the Earth's surface, including natural and man-made sources.
1. Rivers (Option a): These are natural flowing watercourses on the surface of the earth. They are a primary component of surface water.
2. Lakes (Option c): These are large bodies of surface water surrounded by land. They are a primary component of surface water.
3. Reservoirs (Option d): These are artificial lakes created by dams to store surface water for human use. They are considered surface water bodies.
4. Aquifers (Option b): An aquifer is an underground layer of water-bearing permeable rock, gravel, sand, or silt from which groundwater can be extracted. Because aquifers are located beneath the earth's surface, they are a component of 'Groundwater', not 'Surface Water'.
Therefore, aquifers are not a component of surface water.
A normally consolidated clay will exhibit-
A)
High compressibility
B)
Very low permeability
C)
Low compressibility
D)
High shear strength
A normally consolidated (NC) clay is a soil that has never been subjected to a pressure higher than the current effective overburden pressure. In soil mechanics, NC clays are characterized by their tendency to undergo significant volume reduction (consolidation) when additional loads are applied.
1. **Why 'High compressibility' is correct**: Because the soil is at its maximum historical stress, any increase in load will lead to a significant decrease in void ratio, resulting in high compressibility compared to over-consolidated (OC) clays.
2. **Why 'Very low permeability' is incorrect**: While clays generally have low permeability, this is a characteristic of the material (clay) regardless of whether it is normally consolidated or over-consolidated. The question asks specifically what a *normally consolidated* clay will exhibit relative to its state.
3. **Why 'Low compressibility' is incorrect**: Low compressibility is a characteristic of over-consolidated clays, which have been subjected to higher pressures in the past and are therefore 'stiffer'.
4. **Why 'High shear strength' is incorrect**: Normally consolidated clays typically have lower shear strength compared to over-consolidated clays of the same composition because they have a looser structure and higher void ratio.
Which foundation is suitable when the bearing stratum lies at a greater depth?
A)
Pile foundation
B)
Mat foundation
C)
Spread footing
D)
Grillage foundation
In soil mechanics and foundation engineering, foundations are categorized into shallow and deep foundations.
1. **Pile Foundation (Deep Foundation):** When the surface soil or the immediate layers have low bearing capacity and the strong, stable bearing stratum (hard rock or dense sand) lies at a significant depth, deep foundations like piles are used. Piles transfer the load to the deeper, stronger strata through skin friction or end-bearing. Therefore, it is the correct choice when the bearing stratum is at a greater depth.
2. **Mat/Raft Foundation (Shallow Foundation):** This is used when the soil bearing capacity is low or the column loads are very high, spreading the load over the entire area of the building. However, it is still considered a shallow foundation and is not used to reach deep strata.
3. **Spread Footing (Shallow Foundation):** This is the most common type of shallow foundation used when the bearing stratum is located at a shallow depth. It distributes the load of a single column over a wider area.
4. **Grillage Foundation (Shallow Foundation):** This consists of beams of steel sections used to distribute heavy concentrated loads over a larger area of soil. It is typically used for heavy steel columns and is not intended for reaching deep bearing strata.
A retaining wall fails mainly due to-
A)
Wind pressure
B)
Lateral earth pressure
C)
Snow accumulation
D)
Vertical dead loads
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.
Losses from precipitation do not include:
A)
Interception
B)
Infiltration
C)
Extraction
D)
Evaporation
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. Together 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. While 'extraction' might refer to human activities (like pumping groundwater), it is not a component of the natural precipitation loss cycle in the context of hydrology exams. Therefore, it is the correct answer as it is NOT a loss from precipitation.
Toe walls are constructed at-
A)
Top of hill slopes
B)
Below foundation
C)
Bottom of slopes to prevent scouring
D)
On bridges
A toe wall is a protective structure constructed at the base (the 'toe') of a slope, embankment, or retaining wall. Its primary engineering purpose is to provide stability to the slope and protect the base from erosion or 'scouring' caused by water flow or soil movement. By reinforcing the bottom of the slope, the toe wall prevents the slope from sliding or being undercut, which would otherwise lead to the failure of the entire embankment.
Analysis of other options:
- Option (a) is incorrect because structures at the top of slopes are typically called 'crest walls' or 'coping'.
- Option (b) is incorrect because while a toe wall is part of the foundation system of a slope, it is not constructed 'below' the foundation; it is the lowest part of the visible structural support.
- Option (d) is incorrect because while bridges have foundations (like abutments), a 'toe wall' specifically refers to slope stabilization rather than a general bridge component.
The triaxial shear test provides information about-
A)
Plasticity
B)
Shear strength under controlled drainage
C)
Specific gravity
D)
Consolidation characteristics
The triaxial shear test is one of the most versatile and widely used methods for determining the shear strength parameters (cohesion 'c' and angle of internal friction 'φ') of soil. Its primary advantage over other tests (like the direct shear test) is the ability to control the drainage conditions and the pore water pressure. Depending on how the drainage valves are operated, the test can be conducted as an Unconsolidated Undrained (UU) test, a Consolidated Undrained (CU) test, or a Consolidated Drained (CD) test.
Why other options are incorrect:
- a. Plasticity: This is determined using Atterberg limits tests (Liquid Limit, Plastic Limit).
- c. Specific gravity: This is determined using a pycnometer or a density bottle.
- d. Consolidation characteristics: These are determined using an oedometer (consolidation test) to find the compression index and coefficient of consolidation.
Which property is most affected when aggregate with high water absorption is used without accounting for it?
A)
Initial setting time
B)
Workability
C)
Compressive strength
D)
Durability
Step-by-step reasoning: 1. Water-Cement Ratio: The workability of concrete is primarily governed by the amount of free water available in the mix to lubricate the aggregates and facilitate flow. 2. Effect of Absorption: Aggregates with high water absorption act like sponges. If these aggregates are used in a dry state without adjusting the mixing water (accounting for absorption), they will absorb a significant portion of the mixing water intended for the cement paste. 3. Impact on Workability: This reduction in 'free water' leads to a stiffer mix, significantly reducing the slump and overall workability of the concrete, making it difficult to place and compact. 4. Analysis of other options: (a) Initial setting time is primarily a property of the cement chemistry and water temperature, not aggregate absorption. (c) Compressive strength is affected by the water-cement ratio; however, if the aggregate absorbs water, the effective w/c ratio actually decreases, which might theoretically increase strength but would make the concrete unworkable and prone to honeycombing (which then lowers strength). The most immediate and direct property affected is workability. (d) Durability is a long-term property; while absorption can affect it, the immediate impact during mixing is on workability.
Which is a suitable foundation for a retaining wall?
A)
Clay bed
B)
Loose sand
C)
Compacted granular base
D)
Silty soil
A retaining wall is subject to significant lateral earth pressure and vertical loads, which can lead to failure through sliding, overturning, or bearing capacity failure. To ensure stability, the foundation must have high shear strength and low compressibility.
1. **Compacted granular base (Correct):** Granular materials (like crushed stone or well-graded gravel) provide high bearing capacity, excellent drainage (reducing hydrostatic pressure), and minimal settlement when properly compacted. This provides the most stable platform for the wall's base slab.
2. **Clay bed (Incorrect):** Clay is cohesive and compressible. It is prone to long-term consolidation settlement and can lose strength when saturated, increasing the risk of wall tilting or failure.
3. **Loose sand (Incorrect):** Loose sand has low bearing capacity and is highly susceptible to settlement and liquefaction under certain conditions. It must be compacted to be suitable.
4. **Silty soil (Incorrect):** Silty soils are often unstable, highly compressible, and sensitive to moisture changes, making them poor foundations for heavy structural loads like retaining walls.
Which soil type is best suited for the core of an earthen dam?
A)
Gravel
B)
Coarse sand
C)
Clayey soil
D)
Silty sand
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 could otherwise lead to piping failure or structural instability.
1. **Clayey Soil (Correct):** Clay has very low hydraulic conductivity (permeability) due to its small particle size and cohesive nature. This makes it the ideal material for the core to minimize seepage losses and maintain the stability of the dam.
2. **Gravel (Incorrect):** Gravel is highly permeable. While it is excellent for the 'shell' of a dam to provide structural stability and drainage, it cannot stop water flow.
3. **Coarse Sand (Incorrect):** Like gravel, coarse sand has high permeability and would allow significant water leakage, making it unsuitable for a core.
4. **Silty Sand (Incorrect):** While less permeable than coarse sand, silty sand still lacks the impermeability and cohesion of clay, making it an inferior choice for the core.
The unit weight of soil is defined as-
A)
Weight of water per unit volume
B)
Weight of solids per unit volume
C)
Weight of soil mass per unit volume
D)
Weight of solids per unit weight
In soil mechanics, the unit weight (also known as bulk density when expressed as mass) is defined as the total weight of a soil sample (which includes the weight of the solid particles and the weight of the water filling the voids) divided by the total volume of that sample. Mathematically, it is expressed as γ = W / V, where W is the total weight of the soil mass and V is the total volume.
Analysis of options:
- Option (a) refers to the unit weight of water (γw).
- Option (b) refers to the dry unit weight (γd), which considers only the weight of solids.
- Option (c) is the correct general definition of unit weight (bulk unit weight).
- Option (d) is dimensionally incorrect as it describes a ratio of weights rather than a weight per unit volume.