← Junior Engineer
Past Questions
Aggregates occupy around ____ percent of the volume of concrete.
A)
70 - 80
B)
60 - 70
C)
80-90
D)
50-60
Concrete is a composite material consisting primarily of cement, water, and aggregates (fine and coarse). Aggregates act as the filler material and provide the bulk of the concrete's volume and strength. In a typical concrete mix, aggregates (sand and crushed stone/gravel) occupy approximately 70% to 80% of the total volume. The remaining 20% to 30% is occupied by the cement paste (cement and water), which fills the voids between the aggregate particles and binds them together. Options b, c, and d are incorrect because 60-70% is too low for standard structural concrete, 80-90% would leave insufficient room for the binding paste to ensure workability and strength, and 50-60% is far below the standard volumetric composition of concrete.
The plies in plywood are so placed that the grains of each ply are -
A)
Parallel to each other
B)
At right angles to one another
C)
45° oblique to adjacent grain
D)
Not constrained by any consideration
Plywood is a manufactured wood product made from thin layers of wood veneers (plies) glued together. The fundamental characteristic of plywood is that the grain of each successive layer is placed perpendicular (at right angles) to the grain of the layer immediately above and below it. This technique is known as 'cross-graining'.
Why this is done:
1. Dimensional Stability: Wood expands and contracts significantly more across the grain than along the grain. By alternating the grain direction, the expansion of one layer is restrained by the stability of the adjacent layer, reducing overall shrinkage and swelling.
2. Strength: It provides uniform strength in both longitudinal and transverse directions, eliminating the inherent weakness of natural wood along its grain.
3. Resistance to Splitting: Cross-graining prevents the material from splitting or cracking along a single grain line.
Analysis of other options:
- Option (a) Parallel: If grains were parallel, the material would behave like a single piece of solid wood, retaining all the weaknesses (like splitting) and lacking the stability of plywood.
- Option (c) 45° oblique: While some specialized composites exist, standard structural plywood uses 90° (right angles) to maximize stability and strength.
- Option (d) Not constrained: The orientation of grains is the most critical engineering consideration in the manufacturing of plywood.
The decrease in the volume of a soil mass, expressed as a percentage of the dry volume of the soil mass, when water content is reduced from a given percentage to the shrinkage limit is called -
A)
Linear shrinkage
B)
Volumetric shrinkage
C)
Plastic limit
D)
Shrinkage limit
The question describes the definition of Volumetric Shrinkage.
1. **Volumetric Shrinkage (VS)**: This is defined as the decrease in volume of a soil mass, expressed as a percentage of the dry volume, when the water content is reduced from a given percentage (usually the initial water content or the liquid limit) to the shrinkage limit. The formula is: VS = [(V1 - V2) / V2] × 100, where V1 is the initial volume and V2 is the dry volume (volume at shrinkage limit).
2. **Why other options are incorrect**:
- **Linear Shrinkage (a)**: This is the decrease in the linear dimensions (length) of a soil pat, expressed as a percentage of the dry length, when the water content is reduced to the shrinkage limit. It is a 1D measurement, whereas the question asks for volume (3D).
- **Plastic Limit (c)**: This is the water content at which a soil transitions from a semi-solid to a plastic state (specifically, when a thread of soil can no longer be rolled to 3mm diameter without crumbling).
- **Shrinkage Limit (d)**: This is the specific water content below which no further decrease in volume occurs, regardless of further drying. It is a point/value of water content, not a measure of volume decrease.
Efflorescence of bricks is due to -
A)
Excessive burning of bricks
B)
High silt content in brick clay
C)
High porosity of bricks
D)
Soluble salts present in parent clay
Efflorescence is the appearance of a white powdery deposit on the surface of bricks or mortar. This phenomenon occurs when soluble salts (such as sodium sulfates, potassium sulfates, or magnesium sulfates) are present in the brick clay or the water used for mixing. When the brick absorbs moisture, these salts dissolve and migrate to the surface via capillary action. As the water evaporates, the salts crystallize and leave behind the characteristic white powder.
Analysis of other options:
- (a) Excessive burning: This typically leads to the brick becoming brittle, distorted, or over-burnt (bloated), but does not cause efflorescence.
- (b) High silt content: Excessive silt can lead to shrinkage cracks and reduced strength, but it is not the chemical cause of efflorescence.
- (c) High porosity: While high porosity allows water to move more easily (facilitating the transport of salts), it is not the 'cause' of efflorescence; the salts themselves are the cause. A porous brick without soluble salts will not exhibit efflorescence.
Soil classification is done on the basis of -
A)
Plasticity of soil
B)
Grain size distribution
C)
Soil type
D)
Both (a) & (b)
Soil classification systems, most notably the Unified Soil Classification System (USCS) and the Indian Standard Soil Classification System (ISSCS), categorize soils based on two primary physical properties:
1. Grain Size Distribution (Option b): This is used to distinguish between coarse-grained soils (gravel and sand) and fine-grained soils (silt and clay). Sieve analysis and hydrometer analysis are used to determine the distribution of particle sizes.
2. Plasticity of Soil (Option a): For fine-grained soils, the grain size alone is insufficient for classification. Therefore, Atterberg limits (Liquid Limit and Plastic Limit) are used to determine the plasticity index, which helps distinguish between silts (low plasticity) and clays (high plasticity).
Since both the size of the particles and the plasticity characteristics are essential for a complete and accurate soil classification, option (d) is the correct choice.
The strength envelope of a pure cohesive soil is -
A)
Vertical
B)
Horizontal
C)
Inclined
D)
Curvilinear
The shear strength of soil is defined by the Mohr-Coulomb failure criterion: 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. For a 'pure cohesive soil' (such as saturated clay), the angle of internal friction (φ) is zero. Substituting φ = 0 into the equation, we get τ = c. This means the shear strength is constant and independent of the normal stress applied to the failure plane. When plotted on a graph of shear stress (τ) versus normal stress (σ), the resulting failure envelope is a straight line parallel to the σ-axis, which is a horizontal line.
- Option (a) Vertical: This would imply infinite strength for zero normal stress, which is physically impossible.
- Option (c) Inclined: This occurs in c-φ soils (like sands or silty clays) where φ > 0.
- Option (d) Curvilinear: This occurs in some specialized soil types or under specific loading conditions, but not for the standard definition of pure cohesive soil.
The minimum depth for all foundations below the natural ground level is -
A)
500mm
B)
400mm
C)
600mm
D)
550mm
In civil engineering and building construction standards (such as those outlined in various National Building Codes and standard specifications like IS codes), the minimum depth of foundation is specified to ensure the stability of the structure and to protect the foundation from environmental factors such as seasonal moisture changes, frost action, and surface erosion. For general small-scale structures or residential buildings, the standard minimum depth for foundations below the natural ground level (NGL) is typically taken as 500 mm. This depth ensures that the foundation rests on a relatively stable layer of soil and is sufficiently buried to avoid disturbance from surface activities and weather-induced soil shrinkage or swelling. Options b, c, and d are incorrect as they do not align with the standard minimum requirement of 500mm generally adopted in technical specifications for basic foundations.
The surface runoff is due to -
A)
Initial rain
B)
Residual rain
C)
Residual rain in the net supply interval
D)
All of these
In hydrology, surface runoff occurs when the rate of precipitation exceeds the infiltration capacity of the soil. When rain begins, the initial portion of the rainfall is used to satisfy the soil moisture deficit (filling the pores of the dry soil) and is absorbed through infiltration. This is known as the 'initial loss'. Only the rainfall that occurs after the soil has reached its saturation point or after the infiltration capacity has been exceeded is available to flow over the land surface as runoff. This remaining portion of the rainfall is termed as 'residual rain' or 'excess rainfall'. Therefore, surface runoff is specifically caused by the residual rain that cannot be absorbed by the ground. Option (a) is incorrect because initial rain is primarily absorbed. Option (c) is a misapplication of terminology from irrigation (net supply interval) to general hydrology.
When specific information about the density of snowfall is not available, the water equivalent of snowfall is taken as -
A)
50%
B)
30%
C)
10%
D)
90%
In hydrology, the 'water equivalent of snowfall' refers to the depth of liquid water that would result if the snow melted completely. Snow density varies significantly depending on temperature and moisture content (ranging from very light powder to heavy, wet snow). However, in the absence of specific site data or density measurements, a standard empirical rule of thumb is used in engineering practice. The general assumption is that the water equivalent of snow is approximately 10% of the depth of the snowfall (a 10:1 ratio). For example, 10 cm of snowfall is typically assumed to yield 1 cm of liquid water. Therefore, option (c) is the standard accepted value for general calculations when specific density information is unavailable.
Hydrograph is a graphical representation of -
A)
Surface runoff
B)
Groundwater flow
C)
Rainfall
D)
None of these
A hydrograph is a graph showing the rate of flow (discharge) versus time past a specific point in a river, channel, or catchment. It represents the response of a watershed to a rainfall event. Specifically, it plots the surface runoff (discharge) resulting from precipitation.
- Option (a) is correct because the hydrograph specifically tracks the discharge of surface runoff over time.
- Option (b) is incorrect because groundwater flow is typically analyzed via potentiometric maps or groundwater hydrographs (which are different from the standard storm hydrograph used in surface hydrology).
- Option (c) is incorrect because a graphical representation of rainfall over time is called a 'Hyetograph'.
- Option (d) is incorrect as option (a) is the standard definition.
As per IS code, maximum permissible differential settlement on clayey soil is -
A)
35
B)
40
C)
60
D)
50
In soil mechanics and foundation engineering, differential settlement refers to the difference in settlement between two adjacent foundations. Excessive differential settlement can lead to structural cracking or failure. According to standard Indian Standard (IS) guidelines and general geotechnical practice for structures on clayey soils, the maximum permissible differential settlement is typically limited to 50 mm (or 1/500 of the span for certain structural elements) to prevent structural damage. While specific limits can vary based on the type of structure (e.g., residential vs. industrial), 50 mm is the widely accepted benchmark value used in competitive examinations for general clayey soil conditions. Options a, b, and c (35, 40, 60) do not align with the standard permissible limit specified in the general IS code guidelines for this context.
A cement of average composition requires about ____ of water by mass for chemical reaction.
A)
35%
B)
45%
C)
15%
D)
25%
The chemical reaction between cement and water is known as hydration. For the complete chemical hydration of Ordinary Portland Cement (OPC), the theoretical amount of water required is approximately 23% to 25% by mass of the cement. This water is chemically bound into the cement paste to form calcium silicate hydrate (C-S-H) gel and calcium hydroxide. In practical construction, a higher water-cement ratio (typically 0.40 to 0.60) is used, not because it is all needed for the chemical reaction, but to provide sufficient workability for placing and compacting the concrete. Therefore, the specific amount required for the 'chemical reaction' alone is roughly 25%.
Direct runoff is made up of -
A)
Overland flow only
B)
Surface runoff, infiltration and evaporation
C)
Surface runoff only
D)
Surface runoff, prompt interflow and channel precipitation
Direct Runoff is defined as the portion of precipitation that reaches the stream channel without first infiltrating into the soil to become groundwater (baseflow). It consists of several components:
1. Surface Runoff (Overland Flow): Water that flows over the land surface directly into the channel.
2. Prompt Interflow: Water that infiltrates the soil but moves laterally through the upper soil layers quickly enough to contribute to the storm hydrograph peak.
3. Channel Precipitation: Rain that falls directly onto the surface of the stream channel.
Analysis of other options:
- Option (a) is incomplete because it ignores interflow and direct precipitation.
- Option (b) is incorrect because infiltration and evaporation are 'losses' from the precipitation; they do not contribute to runoff.
- Option (c) is incomplete as it only considers surface flow.
As compared to working stress method of design, limit state method takes concrete to -
A)
A higher stress level
B)
A lower stress level
C)
The same stress level
D)
Sometimes higher but generally lower stress level
The Working Stress Method (WSM) is a conservative approach based on the linear elastic theory. It assumes that concrete and steel behave linearly under service loads and uses a large 'Factor of Safety' applied to the material strengths to ensure that the actual stresses never exceed a small fraction of the ultimate strength. Consequently, WSM utilizes only a small portion of the material's capacity.
In contrast, the Limit State Method (LSM) is a semi-probabilistic approach. It considers the actual non-linear behavior of concrete up to its ultimate failure (limit state of collapse). LSM uses partial safety factors for both loads (increasing them) and materials (decreasing them), but it allows the concrete to be stressed much closer to its actual ultimate compressive strength (typically 0.447 fck in IS 456:2000) compared to the very low permissible stresses used in WSM. Therefore, LSM allows the concrete to be taken to a significantly higher stress level, resulting in more economical and slender sections.
The thickness of base slab of a retaining wall generally provided, is -
A)
width of the stem at the bottom
B)
one-third of the width of the stem at the bottom
C)
one-fourth of the width of the steam at the bottom
D)
twice the width of the steam at the bottom.
In the design of retaining walls (specifically cantilever retaining walls), the base slab must be sufficiently rigid to distribute the load to the soil and resist shear forces. A common empirical rule of thumb used in structural engineering for the preliminary design of the base slab thickness is to keep it approximately equal to the thickness (width) of the stem at its base. This ensures that the junction between the stem and the base is robust and can handle the high bending moments and shear forces occurring at that critical section.
- Option (a) is the standard empirical guideline.
- Options (b) and (c) would result in a base slab that is too thin, leading to potential shear failure or excessive deflection.
- Option (d) would lead to an over-designed, uneconomical structure without providing significant additional structural benefit in most standard soil conditions.
Given that d = Effective depth, b = width and D= overall depth, the maximum area of compression reinforcement in a beam is -
A)
0.4 bd
B)
0.04 bD
C)
0.12 bd
D)
0.12 bD
According to the Indian Standard code for reinforced concrete design (IS 456:2000), there are specific limits on the amount of reinforcement provided in a beam to ensure ductile failure and prevent congestion of steel.
1. **Minimum Reinforcement**: The minimum area of tension reinforcement is specified to prevent sudden failure upon cracking.
2. **Maximum Reinforcement**: To ensure that the beam is not 'over-reinforced' (which would lead to a brittle failure of concrete before the steel yields), the code limits the maximum area of reinforcement.
3. **Compression Reinforcement**: For doubly reinforced beams, the maximum area of compression reinforcement is limited to 4% of the gross cross-sectional area of the concrete.
Mathematically, this is expressed as:
Maximum Area of Compression Steel (Asc,max) = 0.04 × b × D
Where:
- b = width of the beam
- D = overall depth of the beam
Comparing this to the options:
- Option (a) 0.4 bd is far too high (40% of effective area).
- Option (b) 0.04 bD matches the IS 456 limit (4% of gross area).
- Option (c) 0.12 bd refers to the maximum tension reinforcement limit in some contexts (though usually 4% is the general limit for both, 0.12 is sometimes cited in older codes or specific conditions for tension steel, but not for compression steel).
- Option (d) 0.12 bD is too high for compression reinforcement.
An infinite slope represents the inclined face of -
A)
An earth dam
B)
An embankment
C)
An excavation
D)
A natural high hill
In soil mechanics, an 'infinite slope' is a theoretical model used to analyze the stability of a slope where the failure surface is parallel to the ground surface and the extent of the slope is very large in the horizontal direction compared to the depth of the failure plane.
1. **Why 'A natural high hill' is correct**: Natural hills or mountains often have slopes that extend over vast distances with a relatively constant inclination. In such cases, the boundary effects of the crest (top) and toe (bottom) of the slope are negligible, making the 'infinite slope' assumption mathematically applicable for calculating the factor of safety against sliding.
2. **Why other options are incorrect**:
- **Earth dams (a)** and **Embankments (b)** are man-made structures with finite dimensions. They have specific geometries (crest width, slope length, and base width) where the failure surfaces are typically curved (circular or non-circular) rather than parallel to the surface. These are analyzed as 'finite slopes'.
- **Excavations (c)** usually involve vertical or near-vertical cuts where the stability is governed by lateral earth pressure and the depth of the cut, not by a parallel failure plane across an infinite surface.
Slope failure may take place due to -
A)
Gravitational forces
B)
Seepage forces
C)
Earthquake
D)
All of these
Slope failure occurs when the shear stress acting on a failure surface exceeds the shear strength of the soil. Several factors contribute to this imbalance:
1. Gravitational forces: This is the primary driving force. The weight of the soil mass creates a downslope component of force that attempts to pull the material downward.
2. Seepage forces: When water flows through a slope, it exerts a drag force (seepage force) in the direction of flow. Additionally, increased pore water pressure reduces the effective stress between soil particles, thereby decreasing the shear strength of the soil.
3. Earthquake: Seismic activity introduces dynamic horizontal and vertical accelerations. These inertial forces increase the driving force and can cause liquefaction in saturated sandy soils, leading to sudden slope failure.
Since all three factors can independently or collectively trigger a slope failure, the correct option is 'All of these'.
For the purpose of designs per IS : 456 deflection of RC slab or beam is limited to -
A)
0.2 % of span
B)
0.25 % of span
C)
0.4% of span
D)
0.45 % of span
According to IS 456:2000 (the Indian Standard code of practice for Plain and Reinforced Concrete), the deflection of beams and slabs is controlled to ensure the serviceability and aesthetic appearance of the structure.
1. Final Deflection: The final deflection (including the effects of temperature, shrinkage, and creep) of all beams and slabs should generally not exceed Span/250.
2. Calculation: Span/250 is equivalent to (1/250) * 100 = 0.4% of the span.
3. However, for the purpose of design and limiting the deflection that occurs after the partition or other services are installed, the limit is often specified as Span/500 for the deflection occurring after the erection of partitions and other services.
4. In the context of standard competitive exam questions based on IS 456, when asked for the general limit for 'design' purposes regarding the deflection of RC members to avoid damage to partitions, the value is often cited as Span/500, which is 0.2% of the span.
Comparing the options:
- Option (a) 0.2% of span = Span/500 (Limit for deflection after partition installation).
- Option (c) 0.4% of span = Span/250 (General limit for total deflection).
In most technical examinations for Junior Engineer (Civil), when these specific options are provided, the intended answer refers to the more stringent limit of Span/500 (0.2%) to prevent cracking of non-structural elements.
The shear test that is more suitable in the field is -
A)
Direct shear
B)
Triaxial shear
C)
Unconfined compression
D)
Vane shear
The question asks for the shear test most suitable for 'in the field' (in-situ) application.
1. **Vane Shear Test (Option d):** This is specifically designed as an in-situ test. A vane is pushed into the soil (typically soft to medium clays) and rotated. The torque required to shear the soil is measured, allowing for the calculation of the undrained shear strength. Because it is performed directly in the ground, it avoids the 'disturbance' associated with sampling and transporting soil to a lab.
2. **Direct Shear Test (Option a):** This is a laboratory test where a soil sample is placed in a shear box. It cannot be performed in the field.
3. **Triaxial Shear Test (Option b):** This is the most versatile and accurate laboratory test for determining shear strength parameters (c and φ) under controlled drainage and pressure conditions. It requires complex laboratory equipment.
4. **Unconfined Compression Test (Option c):** This is a simplified laboratory test (a special case of the triaxial test where confining pressure is zero) used for cohesive soils. It requires an undisturbed sample to be taken to a lab.
Therefore, the Vane Shear test is the only option among the four that is primarily used as a field test.
____ is the property of the soil which allows passage of fluid through it.
A)
Capillarity
B)
Permeability
C)
Laminar flow
D)
Shrinkage
Step-by-step reasoning:
1. **Definition of Permeability**: In soil mechanics, permeability (or hydraulic conductivity) is defined as the property of a soil mass that allows water or other fluids to flow through its interconnected voids (pores).
2. **Evaluating Option (a) Capillarity**: Capillarity is the ability of a liquid to flow in narrow spaces without the assistance of, or even in opposition to, external forces like gravity. While it involves fluid movement, it is a phenomenon of surface tension, not the general property of allowing fluid passage.
3. **Evaluating Option (c) Laminar flow**: Laminar flow describes a specific *type* of fluid motion (smooth, parallel layers) that typically occurs in soils (following Darcy's Law), but it is a characteristic of the flow itself, not a property of the soil material.
4. **Evaluating Option (d) Shrinkage**: Shrinkage is the reduction in volume of a soil mass upon the loss of moisture, which is a volume-change property, not a fluid-passage property.
Conclusion: Permeability is the correct technical term for the soil's capacity to transmit fluids.
The standard Symon’s type rain gauge has a collecting area of diameter -
A)
12.7cm
B)
10cm
C)
5.08 cm
D)
25.4cm
The Symons' rain gauge is a non-recording type rain gauge widely used in India (standardized by the India Meteorological Department - IMD). According to the standard specifications for a Symons' rain gauge, the collecting funnel has a diameter of 12.7 cm (which is equivalent to 5 inches). The collected water is then passed into a receiver bottle.
Analysis of options:
- Option (a) 12.7 cm: This is the standard diameter for the IMD Symons' rain gauge.
- Option (b) 10 cm: Incorrect; not a standard specification for this gauge.
- Option (c) 5.08 cm: Incorrect; this is 2 inches, which is too small for standard precipitation measurement.
- Option (d) 25.4 cm: Incorrect; this is 10 inches, which is larger than the standard Symons' gauge diameter.
Doubly reinforced beams are recommended when -
A)
The depth of the beam is restricted
B)
The breadth of the beam is restricted
C)
Both depth and breadth are restricted
D)
The shear is high
A doubly reinforced beam is a concrete beam reinforced with steel in both the tension and compression zones.
1. **Why it is used:** In a singly reinforced beam, the moment of resistance is limited by the maximum depth of the neutral axis (to ensure a ductile failure). If the external bending moment exceeds the moment of resistance of a balanced section for a given size, the engineer has two choices: increase the dimensions of the beam or provide compression reinforcement.
2. **The 'Restricted Depth' Scenario:** In many architectural or structural designs, the overall depth (d) of the beam is restricted due to headroom requirements or aesthetic constraints. When the depth cannot be increased to accommodate the required moment of resistance, compression steel is added to increase the load-carrying capacity without increasing the beam's size.
3. **Analysis of other options:**
- **Option b:** Restricting the breadth usually leads to stability issues (lateral buckling) but doesn't fundamentally necessitate compression steel in the same way depth restrictions do.
- **Option c:** While both might be restricted, the primary driver for switching from singly to doubly reinforced is the limitation on the effective depth (d), as the moment capacity is proportional to d².
- **Option d:** High shear is addressed by providing shear reinforcement (stirrups), not by adding compression reinforcement to the longitudinal section.
The design of retaining wall assumes that the retained earth -
A)
Is dry
B)
Is free from moisture
C)
Consists of granular particles
D)
All of these
In the basic design of retaining walls, particularly when applying Rankine's or Coulomb's theories of earth pressure, the standard assumption is that the retained soil is a cohesionless, granular material (such as sand or gravel).
1. Why 'Consists of granular particles' is correct: The fundamental formulas for active and passive earth pressure coefficients (Ka and Kp) are derived based on the internal friction angle (φ) of granular soils. Cohesionless soils are the baseline for these theories because their behavior is predictable based on friction alone.
2. Why 'Is dry' and 'Is free from moisture' are incorrect: While designers often start with a dry soil analysis for simplicity, the design of a retaining wall does NOT assume the soil is always dry. In fact, professional engineering design must account for the worst-case scenario, which includes saturated soil and hydrostatic water pressure. If a wall were designed assuming the soil is always dry, it would likely fail during rainfall due to the added weight of water and the loss of effective stress. Therefore, 'dryness' is a condition for a specific calculation, not a general assumption of the design theory itself.
3. Why 'All of these' is incorrect: Since options (a) and (b) are not fundamental assumptions of the general design theory (and are often dangerously incorrect in practice), 'All of these' cannot be the correct choice.
In passive case, the wall moves -
A)
Towards the backfill
B)
Away from backfill
C)
No movement at all
D)
Downwards
In soil mechanics, the lateral earth pressure exerted by a soil mass against a retaining wall depends on the movement of the wall. There are three primary states of earth pressure:
1. **At-Rest State**: The wall is stationary; there is no movement. The pressure is denoted as K0.
2. **Active State**: The wall moves **away** from the backfill. This causes the soil to expand horizontally, reducing the lateral pressure to its minimum value (Ka).
3. **Passive State**: The wall is pushed **towards** the backfill. This compresses the soil mass, causing the lateral pressure to increase significantly until it reaches a maximum value (Kp).
Since the question asks for the 'passive case', the wall must be moving into the soil (towards the backfill) to mobilize the passive resistance of the soil.