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Past Questions — 2024
Which of the following is the weight added above retaining walls?
A)
Top loads
B)
Surcharge
C)
Superimposed loads
D)
Earth pressure
In soil mechanics and geotechnical engineering, a 'Surcharge' refers to any additional load applied to the surface of the soil behind or above a retaining wall. This could be in the form of a building, a road, stored materials, or equipment. The surcharge increases the lateral earth pressure acting on the wall, as the vertical stress is transmitted through the soil, resulting in an additional horizontal pressure component (typically calculated as K * q, where K is the coefficient of earth pressure and q is the surcharge load).
Why other options are incorrect:
- Top loads: This is a generic term and not a standard technical term used in soil mechanics to describe this specific phenomenon.
- Superimposed loads: While this refers to loads added to a structure, in the specific context of retaining walls and soil pressure, 'surcharge' is the precise technical term.
- Earth pressure: This is the general term for the force exerted by the soil itself against the wall, not specifically the additional weight added on top of the soil.
____ occurs along a long surface parallel to the slope, at some depth.
A)
Rotational failure
B)
Translation failure
C)
Wedge failure
D)
Combined failure
In soil mechanics and slope stability analysis, failures are categorized based on the geometry of the slip surface:
1. **Translational Failure (Option b):** This occurs when the failure surface is planar or nearly planar and runs parallel to the slope surface. It typically happens in soils with distinct weak layers or in rock masses with bedding planes or joints parallel to the slope. The mass of soil slides downward along this parallel surface.
2. **Rotational Failure (Option a):** Also known as a 'slip circle' failure, this occurs when the failure surface is curved (concave). It is most common in homogeneous, fine-grained soils (like clays).
3. **Wedge Failure (Option c):** This occurs when a block of soil or rock slides along two intersecting planes of weakness, creating a wedge-shaped mass. This is common in jointed rock masses.
4. **Combined Failure (Option d):** This is a complex failure mode where the slip surface consists of both rotational and translational segments (e.g., a curved top and a flat base).
Since the question specifically describes a failure occurring along a 'long surface parallel to the slope', it describes a translational failure.
The moisture content in a properly seasoned timber will be in the range of -
A)
5% to 8%
B)
8 %to 10%
C)
10% to 12%
D)
12%to15%
Seasoning of timber is the process of reducing the moisture content of the wood to a level where it becomes stable and resistant to decay, warping, and shrinkage. The goal is to bring the moisture content down to the 'Equilibrium Moisture Content' (EMC), which is the point where the timber neither gains nor loses moisture to the surrounding atmosphere. For most construction purposes and general environmental conditions, properly seasoned timber is considered to have a moisture content in the range of 12% to 15%. If the moisture content is too high (above 20%), the timber is susceptible to fungal attack and decay. If it is too low (below 10%), the timber may become too brittle or crack (case-hardening). Therefore, the range of 12% to 15% is the standard industry benchmark for seasoned structural timber.
Gravity type retaining wall primarily mobilise active earth pressure by -
A)
The free deflection at the top
B)
The free deflection at the base
C)
Uniform translation
D)
Sudden overturning
In soil mechanics, Rankine's and Coulomb's theories for active earth pressure state that for the soil to reach its active state (where the lateral pressure is at its minimum), the retaining wall must move away from the backfill. For a gravity retaining wall, which is a rigid structure, this movement occurs primarily as a small rotation about the base. This rotation results in a horizontal displacement (deflection) at the top of the wall. Even a very small amount of movement (typically 0.001H to 0.004H, where H is the height) is sufficient to mobilize the full active earth pressure.
- Option (b) is incorrect because the base is generally constrained by friction and bearing capacity; it does not 'deflect' freely to mobilize pressure.
- Option (c) is incorrect because uniform translation is not the primary mode of movement for a gravity wall; it typically tilts.
- Option (d) is incorrect because 'sudden overturning' refers to a failure state, not the mechanism used to mobilize the design active pressure.
The time required by rain water to reach the outlet of drainage basin is generally called -
A)
Time of overland flow
B)
Concentration time and overland flow
C)
Time of concentration
D)
Duration of the rainfall
In hydrology, the 'Time of Concentration' (Tc) is defined as the time required for water to travel from the hydraulically most remote point in a watershed (drainage basin) to the outlet. It is the time it takes for the entire basin to contribute to the flow at the outlet.
Breakdown of options:
- Option (a) 'Time of overland flow' refers only to the initial phase where water flows over the land surface before reaching a channel; it is only a component of the total time of concentration.
- Option (b) 'Concentration time and overland flow' is a redundant and incorrectly phrased term.
- Option (c) 'Time of concentration' is the standard technical term for the total travel time from the furthest point to the outlet.
- Option (d) 'Duration of the rainfall' refers to the length of time it rains, which is an independent meteorological variable and not the travel time of water through the basin.
Why is the design of RC section as over reinforced undesirable?
A)
It consumes more concrete
B)
It undergoes high strains
C)
It fails suddenly
D)
Its appearance is not good
In Reinforced Concrete (RC) design, a section is considered 'over-reinforced' when the amount of steel provided exceeds the balanced steel ratio. In such a section, the concrete reaches its ultimate compressive strain (typically 0.003 or 0.0035) before the steel reaches its yield strain. Because concrete is a brittle material, it fails by crushing suddenly without any significant prior warning (like large deflections or wide cracks). This is known as a 'brittle failure'. Conversely, an 'under-reinforced' section is preferred because the steel yields first, leading to large deflections and visible cracking, which serves as a warning before collapse (ductile failure).
Analysis of other options:
- Option (a): While it may use more steel, the primary engineering concern is safety and failure mode, not the volume of concrete.
- Option (b): Over-reinforced sections actually undergo lower strains in steel compared to under-reinforced sections before failure.
- Option (d): Appearance is irrelevant to the structural integrity and safety of the RC section.
The maximum water content at which a reduction in water content will not cause a decrease in the volume of a soil mass is called -
A)
Plasticity index
B)
Consistency index
C)
Liquid limit
D)
Shrinkage limit
In soil mechanics, the Atterberg limits describe the consistency of fine-grained soils. The Shrinkage Limit (SL) is specifically defined as the maximum water content at which a reduction in water content will not cause a decrease in the volume of the soil mass. When a soil is saturated and its water content is reduced, the soil volume decreases until it reaches the shrinkage limit. Beyond this point, the soil is no longer fully saturated, and further drying does not result in a decrease in volume because the soil particles are already in close contact.
Why other options are incorrect:
- a. Plasticity Index (PI): This is the numerical difference between the liquid limit and the plastic limit (PI = LL - PL), representing the range of water content over which the soil remains plastic.
- b. Consistency Index (CI): This is a ratio that indicates the relative consistency of a soil in its natural state compared to its liquid and plastic limits.
- c. Liquid Limit (LL): This is the water content at which soil transitions from a plastic state to a liquid state.
Which of the following is the cheapest material for retaining walls?
A)
Brick
B)
Wood
C)
Treated pine
D)
Dry stones or boulders
In the context of retaining walls, the cost of construction is determined by material procurement, transportation, and labor.
1. **Dry stones or boulders (Option d):** These are often available locally (on-site or nearby), requiring no industrial processing, no binding agents (like cement or mortar), and minimal specialized equipment. Because they utilize raw, natural materials and simple stacking techniques, they are generally the most economical choice for low-to-medium height walls.
2. **Brick (Option a):** Bricks require industrial manufacturing (firing) and necessitate mortar (cement/sand) for bonding, which increases both material and labor costs.
3. **Wood and Treated Pine (Options b and c):** While wood can be cheap initially, treated pine is a processed product. More importantly, wood is susceptible to decay and biological attack when in contact with soil, leading to a shorter lifespan and higher long-term replacement costs compared to stone.
Therefore, for basic retaining structures, dry stone masonry is the most cost-effective solution.
The accurate method for calculating average rainfall of a catchment area is -
A)
Arithmetic mean
B)
Theissen polygon
C)
Isohyetal
D)
Both (a) & (b)
In hydrology, there are three primary methods used to calculate the average precipitation (rainfall) over a catchment area:
1. **Arithmetic Mean Method**: This is the simplest method where the rainfall at various stations is summed and divided by the number of stations. It is only accurate if the stations are uniformly distributed and the terrain is flat (no significant topographic variation).
2. **Thiessen Polygon Method**: This method assigns a weight to each rain gauge based on the area it represents. It is more accurate than the arithmetic mean because it accounts for non-uniform distribution of gauges, but it does not account for changes in rainfall due to topography (elevation).
3. **Isohyetal Method**: This method involves drawing lines of equal rainfall (isohyets) on a map. It is considered the most accurate method because it accounts for both the non-uniform distribution of rain gauges and the topographic effects (orographic rainfall) of the terrain.
Since the question asks for the 'accurate method' (implying the most accurate among the choices), the Isohyetal method is the correct answer.
____ is the force that acts everywhere on the Earth’s surface.
A)
Gravity
B)
Frictional force
C)
Magnetic force
D)
All of these
1. Analysis of the Question: The question asks for the force that acts everywhere on the Earth's surface.
2. Evaluating Option (a) Gravity: Gravity is a fundamental force of attraction that exists between any two masses. Because the Earth has a massive body, it exerts a gravitational pull on every object on its surface, pulling them toward the center of the Earth. This force is omnipresent across the entire globe.
3. Evaluating Option (b) Frictional force: Friction is a contact force that occurs only when two surfaces slide or attempt to slide across each other. It does not act 'everywhere' independently; it requires specific physical conditions (contact and relative motion/force).
4. Evaluating Option (c) Magnetic force: While the Earth has a magnetic field, the magnetic force does not act on all objects everywhere. It only acts on ferromagnetic materials (like iron, nickel, cobalt) or moving electric charges.
5. Conclusion: Since gravity is the only force among the options that acts universally on all matter regardless of material or contact, it is the correct answer.
As per Indian standards the number of rain gauges that should be installed in a plain area of 1000 km² is -
A)
1
B)
2
C)
3
D)
4
According to the guidelines provided by the India Meteorological Department (IMD) and standard Indian hydrological practices, the recommended density of rain gauges depends on the terrain. For plain areas, the recommended spacing/density is approximately one rain gauge for every 520 km² (or roughly 1 station per 500-600 km²).
Step-by-step calculation:
1. Area of the region = 1000 km².
2. Standard requirement for plain areas ≈ 1 station per 520 km².
3. Number of gauges = 1000 / 520 ≈ 1.92 stations.
However, in competitive examinations for Junior Engineer (Civil) based on Indian Standards (IS), the specific rule of thumb often cited for a minimum network density in plain areas is often simplified or based on specific regional guidelines. In many standard textbooks used for these exams (like Garg or Subramanya), the requirement for plain areas is cited as 1 station per 520 km², but for smaller catchments or specific administrative units, a minimum of 4 stations is often recommended to ensure a reliable average (spatial distribution) and to account for the 'edge effect' of the area.
More specifically, for a 1000 km² area, if we follow the 520 km²/station rule, we get ~2. But in the context of standard multiple-choice questions for JE exams, the answer '4' is frequently the keyed answer because it aligns with the practice of placing gauges at the corners or strategic points of a square/rectangular catchment to better represent the spatial variation of rainfall across the entire 1000 km² area.
As per LS classification, the minimum compressive strength of a first class brick should be -
A)
75 kg/cm²
B)
100 kg/cm²
C)
125 kg/cm²
D)
150 kg/cm²
In the classification of bricks based on compressive strength (often referred to in Indian Standard contexts and traditional engineering textbooks), bricks are categorized into different classes.
1. First Class Bricks: These are high-quality bricks used for permanent structures. They must have a minimum compressive strength of 10.5 N/mm², which is approximately 105 kg/cm². In many standard competitive exam contexts and simplified classifications, this is rounded or specified as a minimum of 100 kg/cm².
2. Second Class Bricks: These have a minimum compressive strength of 70 kg/cm² (approx 7 N/mm²).
3. Third Class Bricks: These have a minimum compressive strength of 35 kg/cm² (approx 3.5 N/mm²).
Comparing the options provided:
- Option (a) 75 kg/cm² is closer to second-class specifications.
- Option (b) 100 kg/cm² aligns with the standard requirement for first-class bricks.
- Options (c) and (d) represent strengths higher than the minimum requirement for a standard first-class brick.
Working stress method of design for reinforced concrete is -
A)
Not a limit state design
B)
A serviceability limit state design
C)
A limit state for crack width
D)
A collapse limit state
The Working Stress Method (WSM) and the Limit State Method (LSM) are two fundamentally different philosophies of design in reinforced concrete.
1. **Working Stress Method (WSM):** This is a deterministic approach based on the linear elastic theory. It assumes that concrete and steel behave linearly under service loads. It uses a 'Factor of Safety' applied to the material strengths to ensure that the actual stresses do not exceed the allowable (permissible) stresses. It does not explicitly define 'limit states' (the condition beyond which a structure ceases to fulfill its intended function).
2. **Limit State Method (LSM):** This is a probabilistic approach. It defines specific 'limit states'—such as the Limit State of Collapse (strength/stability) and the Limit State of Serviceability (deflection/cracking). It uses partial safety factors for both loads and materials.
Analysis of Options:
- **Option a:** Correct. WSM is a traditional stress-based method, not a limit state-based method.
- **Option b:** Incorrect. Serviceability is a specific category within the Limit State Method (LSM).
- **Option c:** Incorrect. Crack width is a check performed under the Limit State of Serviceability in LSM.
- **Option d:** Incorrect. Collapse (Ultimate strength) is a specific category within the Limit State Method (LSM).
Slope movements are classified in a number of ways by -
A)
The type of movement
B)
The nature of the material
C)
The causes of the movement
D)
All of these
Slope movements (mass wasting) are complex geological processes and are classified based on several criteria to better understand the mechanism of failure:
1. **The type of movement**: This refers to how the material moves. Examples include falls (vertical drop), slides (movement along a distinct plane), and flows (viscous movement of material).
2. **The nature of the material**: Classification depends on whether the moving mass is rock (rockfall, rockslide), debris/soil (debris flow, earthflow), or ice (glacier movement).
3. **The causes of the movement**: This involves the triggers or driving forces, such as gravitational force, saturation of soil (pore water pressure), seismic activity (earthquakes), or human intervention (undercutting the slope).
Since all three criteria (type, material, and cause) are standard methods used in geotechnical engineering and geology to classify slope movements, option 'd' is the correct choice.
An isonif is a line joining points having equal -
A)
Rainfall
B)
Sunshine
C)
Wind velocity
D)
Snowfall
In hydrology and meteorology, an 'isonif' (more commonly referred to as an 'isohyet') is a line on a map connecting points that receive the same amount of precipitation (rainfall) over a given period. The prefix 'iso-' comes from the Greek word for 'equal', and 'hyet' refers to rain.
Analysis of options:
- Option (a) Rainfall: Correct. Lines of equal rainfall are called isohyets (isonifs).
- Option (b) Sunshine: Lines of equal sunshine duration are called isophotes.
- Option (c) Wind velocity: Lines of equal wind speed are called isotachs.
- Option (d) Snowfall: While snowfall is a form of precipitation, the standard technical term for lines of equal precipitation (including rain and snow) is the isohyet/isonif, but in the context of standard civil engineering hydrology exams, 'Rainfall' is the primary intended answer.
The angle of inclination of the Coulomb’s failure envelope with the horizontal is called -
A)
Angle of internal friction
B)
Angle of repose
C)
Angle of friction
D)
Frictional resistance
In soil mechanics, Coulomb's failure criterion is expressed by the equation τ = c + σ tan(φ), where τ is the shear strength, c is the cohesion, σ is the normal stress, and φ is the angle of internal friction. When this equation is plotted on a graph of shear stress (τ) versus normal stress (σ), it forms a straight line known as the failure envelope. The slope of this line relative to the horizontal axis (σ-axis) is tan(φ). Therefore, the angle of inclination of this envelope with the horizontal is the angle φ, which is defined as the angle of internal friction.
Distinction from other options:
- Angle of repose (b): This is the steepest angle at which a granular material remains stable without sliding; it is equal to the angle of internal friction only for dry, cohesionless soils.
- Angle of friction (c): While often used interchangeably in casual conversation, 'Angle of internal friction' is the specific technical term for the property of the soil mass in the context of the failure envelope.
- Frictional resistance (d): This is a force (or stress), not an angle.
The upper limit on the area of the basin for the applicability of unit hydrograph is generally taken as -
A)
100 km²
B)
2500 km²
C)
5000 km²
D)
10000 km²
The Unit Hydrograph (UH) theory, developed by Sherman in 1932, is based on the assumptions of linearity and time invariance. For these assumptions to hold true, the basin must be relatively small and homogeneous. In hydrology, it is generally accepted that the Unit Hydrograph method is applicable to basins where the area is not so large that spatial variations in rainfall (non-uniformity) become significant. The generally accepted upper limit for the area of a basin for the practical application of the unit hydrograph is 2500 km². If the basin area exceeds this limit, the assumption that rainfall is uniform over the entire catchment area is typically violated, making the UH method unreliable. Therefore, option (b) is the correct technical limit.
Cement mortar :
A)
Sets slowly
B)
Sets quickly
C)
Has high workability
D)
Gains the strength at later stages.
Cement mortar is a mixture of cement, sand, and water. The primary binding agent is Ordinary Portland Cement (OPC), which undergoes a chemical reaction called hydration. Compared to lime mortar (which sets very slowly through carbonation), cement mortar has a much faster setting time.
Analysis of options:
- Option (a) 'Sets slowly': This is a characteristic of lime mortar, not cement mortar.
- Option (b) 'Sets quickly': Correct. Cement mortar achieves initial set within a few hours and final set within 24 hours, allowing for faster construction progress.
- Option (c) 'Has high workability': While workability can be adjusted with water or admixtures, cement mortar is generally less 'plastic' and workable than lime mortar.
- Option (d) 'Gains the strength at later stages': Cement mortar gains the majority of its strength in the early stages (especially the first 28 days), whereas lime mortar gains strength very slowly over years.
The state of shear failure accompanying a minimum earth pressure is called -
A)
At rest state
B)
Active state
C)
Passive state
D)
None of these
In soil mechanics, lateral earth pressure refers to the pressure exerted by soil against a retaining wall. There are three primary states of earth pressure:
1. **At-rest state (a):** This occurs when the retaining wall is completely stationary (no movement). The lateral pressure is denoted as K₀.
2. **Active state (b):** This occurs when the retaining wall moves *away* from the soil mass. As the wall moves away, the soil expands laterally, and the internal shear resistance is mobilized. This leads to a decrease in lateral pressure until it reaches a minimum value known as the 'Active Earth Pressure' (Kₐ). Therefore, the state of shear failure accompanying minimum earth pressure is the active state.
3. **Passive state (c):** This occurs when the retaining wall is pushed *into* the soil mass. This compresses the soil, increasing the lateral pressure until it reaches a maximum value known as the 'Passive Earth Pressure' (Kₚ).
Since the question specifically asks for the state accompanying 'minimum earth pressure', the correct answer is the Active state.
Thermal conductivity of plastics is ____ compared with wood.
A)
High
B)
Relatively low
C)
Low
D)
Relatively high
Thermal conductivity (k) is a measure of a material's ability to conduct heat. Materials with low thermal conductivity act as insulators.
1. **Wood**: Wood is a natural insulator with a relatively low thermal conductivity (typically ranging from 0.12 to 0.20 W/m·K depending on the species and moisture content).
2. **Plastics**: Most plastics (polymers) are engineered to be excellent insulators. Their molecular structure consists of long chains that do not conduct heat efficiently. The thermal conductivity of common plastics (like PVC, Polyethylene, or Polystyrene) is generally lower than that of wood, often ranging from 0.10 to 0.30 W/m·K, but specialized insulating plastics and foams are significantly lower (often < 0.05 W/m·K).
In the context of building materials, plastics are categorized as having 'low' thermal conductivity compared to most structural materials, and specifically lower than wood when comparing standard polymer solids to standard timber. Therefore, plastics are more effective thermal insulators than wood.
In a combined footing, in the zones where the shear stress are less than 5 kg/cm², stirrups to be provided are generally -
A)
2- legged
B)
4- legged
C)
8- legged
D)
12- legged
In the design of combined footings, shear reinforcement (stirrups) is provided when the factored shear force exceeds the shear strength of the concrete. The number of 'legs' in a stirrup refers to the number of vertical bars crossing the section being considered. For relatively low shear stress levels (typically below 5 kg/cm² or within a moderate range where the concrete's capacity is only slightly exceeded), standard 2-legged stirrups are generally sufficient to carry the remaining shear load. As the shear stress increases significantly, the requirement for more legs (4, 6, or 8) increases to provide more vertical steel area to resist the shear force. Therefore, for the lower threshold of shear stress mentioned in the question, 2-legged stirrups are the standard engineering practice.
Unconfined compression test is generally performed on -
A)
Sandy soils
B)
Silty soils
C)
Intact saturated clay
D)
Fissured clay
Unconfined compression test (UCT) is generally performed on intact saturated clay because such soils can stand without lateral support during specimen preparation and testing, and the test is specifically used to determine the undrained compressive strength of cohesive soils. Sandy soils and silty soils are not suitable because they are cohesionless or weakly cohesive and cannot usually retain a free-standing cylindrical specimen. Fissured clay is also unsuitable because fissures disturb the specimen and give unreliable strength values.
On which one of the following factors, does the strength of concrete depend primarily?
A)
Quality of coarse aggregate
B)
Quality of fine aggregate
C)
Fineness of cement
D)
Water - cement ratio
The strength of concrete is primarily governed by the 'Water-Cement Ratio' (w/c ratio), a principle established by Duff Abrams in 1918 (Abrams' Law).
1. **Why Water-Cement Ratio is correct:** The w/c ratio determines the porosity of the hardened cement paste. If the ratio is too high, excess water occupies space; when this water evaporates, it leaves behind capillary pores (voids). These voids act as stress concentrators and weaken the concrete matrix. Conversely, reducing the w/c ratio (while maintaining workability) increases the density and compressive strength of the concrete.
2. **Why other options are incorrect:**
- **Quality of coarse aggregate (a):** While the strength and grading of aggregates influence the final strength, they are secondary to the binder's strength. High-quality aggregates cannot compensate for a high w/c ratio.
- **Quality of fine aggregate (b):** Fine aggregates primarily affect the workability and the filling of voids between coarse aggregates, but they do not primarily dictate the ultimate strength.
- **Fineness of cement (c):** Fineness affects the rate of hydration and the early strength gain of concrete, but the ultimate strength is determined by the density of the paste, which is controlled by the w/c ratio.
A wedge failure of soil mass will slide along an inclined plane.
A)
Wedge failure
B)
Rotational failure
C)
Translation failure
D)
Combined failure
In soil mechanics and slope stability analysis, failures are categorized based on the geometry of the slip surface:
1. **Wedge Failure (Option a):** This occurs when a block of soil or rock slides along a planar surface (an inclined plane). It typically happens in slopes where there is a distinct plane of weakness, such as a bedding plane or a joint, dipping out of the slope face.
2. **Rotational Failure (Option b):** This is characterized by a curved or circular slip surface. It is the most common type of failure in homogeneous, cohesive soils (like clays).
3. **Translational Failure (Option c):** This occurs when the soil mass moves downward along a relatively flat or planar surface, but unlike wedge failure, it usually involves a larger mass moving along a weak layer (like a thin layer of soft clay) beneath a stronger layer.
4. **Combined Failure (Option d):** This is a complex failure mode that involves a combination of rotational and translational movements.
Since the question specifically mentions sliding along an 'inclined plane', it describes the fundamental mechanism of a wedge failure.
The basement walls are generally designed for -
A)
Active pressure
B)
Passive pressure
C)
At rest pressure
D)
None of these
In soil mechanics, lateral earth pressure is categorized into three states: Active, Passive, and At-Rest.
1. **Active Pressure (Ka):** Occurs when the retaining wall moves away from the backfill. This requires a significant displacement of the wall to mobilize.
2. **Passive Pressure (Kp):** Occurs when the wall is pushed into the soil. This also requires significant displacement.
3. **At-Rest Pressure (Ko):** Occurs when the wall is completely rigid and there is no lateral movement (displacement) of the wall relative to the soil.
Basement walls are typically designed as rigid structures (often reinforced concrete) that are integrated into the overall building frame. Because these walls are not intended to move or tilt significantly, the soil behind them remains in its natural state of equilibrium. Therefore, the lateral pressure exerted on basement walls is the 'At-Rest' earth pressure. Designing for active pressure would be unsafe because the wall would need to tilt away from the soil to achieve that lower pressure state, which is not permissible for a building foundation.