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Question 1Civil Engineering (technical paper - subject matter as per Commission syllabus)

In limit state design of a reinforced concrete beam as per IS 456:2000, the design flexural strength of a singly reinforced section is governed by which condition at the ultimate limit state?

  1. The concrete reaches its design compressive strength simultaneously with the steel reaching its design yield stress Correct answer.
  2. The concrete crushing strain of 0.0035 is reached before the steel yields in all cases
  3. The section remains uncracked under the design bending moment
  4. The steel strain reaches 0.002 while the concrete stress remains at half its characteristic strength

Explanation

Limit state of collapse in flexure assumes a parabolic-rectangular concrete stress block with maximum strain 0.0035 and a fully yielded tension steel. The balanced section is the reference condition where both materials attain their design strengths together, and under-reinforced sections are proportioned to fail in a ductile manner with steel yielding first.

Question 2Civil Engineering (technical paper - subject matter as per Commission syllabus)

A simply supported rectangular beam of effective span 6 m carries a uniformly distributed load. For computing the design bending moment and shear force, which load combination corresponds to the limit state of collapse as per IS 456:2000?

  1. 1.2 times dead load plus 1.6 times live load
  2. 1.5 times dead load plus 2.2 times live load
  3. 1.0 times dead load plus 1.0 times live load
  4. 1.5 times dead load plus 1.5 times live load Correct answer.

Explanation

For the limit state of collapse, IS 456 prescribes a partial safety factor of 1.5 on both dead and live loads when they act together, giving the factored combination 1.5(DL + LL). The 1.2 DL + 1.6 LL combination belongs to a different code framework and is not the IS 456 collapse combination.

Question 3Civil Engineering (technical paper - subject matter as per Commission syllabus)

In a compaction test on a soil, the maximum dry density is found to decrease and the optimum moisture content to increase when the compactive effort is reduced. This behaviour is best explained by which principle?

  1. Lower effort produces a flatter compaction curve with a higher peak density
  2. Optimum moisture content is independent of compactive effort for a given soil
  3. Reduced effort allows more air to remain in the voids, which increases the dry density
  4. At higher compactive effort the soil particles are brought closer, so a given dry density is achieved at lower moisture content Correct answer.

Explanation

The compaction curve shifts upward and to the left with increasing compactive effort, because greater energy rearranges particles into a denser packing at a lower water content. Consequently, reducing the effort lowers the peak dry density and pushes the optimum moisture content to a higher value.

Question 4Civil Engineering (technical paper - subject matter as per Commission syllabus)

The consistency index of a saturated fine-grained soil is defined using the liquid limit, plastic limit and natural water content. A soil with natural water content equal to its plastic limit has a consistency index of:

  1. 0.5
  2. Zero
  3. 1.0 Correct answer.
  4. Greater than 1.0

Explanation

Consistency index is defined as (LL − w)/(LL − PL), where w is the natural water content. Substituting w = PL gives (LL − PL)/(LL − PL) = 1, which corresponds to the soil being at the stiff end of its plastic range.

Question 5Civil Engineering (technical paper - subject matter as per Commission syllabus)

In a theodolite traverse, the sum of the observed interior angles of a closed polygon with n sides should equal:

  1. (n + 2) right angles
  2. (2n + 4) right angles
  3. (2n − 4) right angles Correct answer.
  4. (n − 2) right angles

Explanation

The interior angles of a closed polygon of n sides sum to (2n − 4) right angles, that is (n − 2) × 180 degrees. This theoretical sum provides the basis for checking the angular closure of a closed traverse.

Question 6Civil Engineering (technical paper - subject matter as per Commission syllabus)

A rectangular channel of width 4 m carries a discharge of 8 m³/s at a depth of 1 m. The Froude number of the flow is approximately:

  1. 0.64 Correct answer.
  2. 0.32
  3. 2.56
  4. 1.28

Explanation

Velocity equals discharge divided by area, giving 8/(4×1) = 2 m/s, and hydraulic depth equals area divided by top width, giving 4/4 = 1 m. Froude number is v/√(gD) = 2/√(9.81×1) ≈ 0.64, indicating subcritical flow.

Question 7Civil Engineering (technical paper - subject matter as per Commission syllabus)

In a compression member test on a standard concrete cube, the characteristic compressive strength refers to the strength below which not more than a specified percentage of test results are expected to fall. As per IS 456:2000, that percentage is:

  1. 25 percent
  2. 15 percent
  3. 10 percent
  4. 5 percent Correct answer.

Explanation

Characteristic strength is defined as the value below which not more than 5 percent of the test results are expected to fall. This statistical definition underpins the partial safety factors applied to material strengths in limit state design.

Question 8Civil Engineering (technical paper - subject matter as per Commission syllabus)

In a singly reinforced concrete beam, if the area of tension steel is increased while the section dimensions and concrete grade remain unchanged, the depth of the neutral axis:

  1. Decreases
  2. Increases Correct answer.
  3. Becomes zero
  4. Remains unchanged

Explanation

Equilibrium of the compressive and tensile forces requires that a larger steel area produces a larger compressive force block, which pushes the neutral axis deeper into the section. The section therefore moves toward the balanced condition and eventually becomes over-reinforced if steel is added without limit.

Question 9Civil Engineering (technical paper - subject matter as per Commission syllabus)

A soil sample has a void ratio of 0.6 and the specific gravity of solids is 2.70. Its porosity is approximately:

  1. 0.375 Correct answer.
  2. 0.625
  3. 0.600
  4. 0.222

Explanation

Porosity and void ratio are related by n = e/(1 + e). Substituting e = 0.6 gives n = 0.6/1.6 = 0.375, so about 37.5 percent of the total volume is voids.

Question 10Civil Engineering (technical paper - subject matter as per Commission syllabus)

In the design of a reinforced concrete beam for shear as per IS 456:2000, the nominal shear stress is limited to a maximum value that depends primarily on:

  1. The percentage of tension reinforcement only
  2. The grade of concrete Correct answer.
  3. The grade of steel only
  4. The span to depth ratio

Explanation

The maximum shear stress τc,max is tabulated against concrete grade alone, reflecting the diagonal compression capacity of the web. It serves as an absolute upper limit independent of the stirrup design, which is governed separately by the shear strength of concrete plus the contribution of shear reinforcement.

Question 11Civil Engineering (technical paper - subject matter as per Commission syllabus)

A propped cantilever beam of span L carries a uniformly distributed load w over its entire length. The reaction at the prop is:

  1. 5wL/8
  2. wL/4
  3. wL/2
  4. 3wL/8 Correct answer.

Explanation

For a propped cantilever with a uniformly distributed load over the full span, the prop reaction is 3wL/8, obtained from compatibility of deflection at the prop. The fixed-end reaction then carries the remaining 5wL/8.

Question 12Civil Engineering (technical paper - subject matter as per Commission syllabus)

A circular curve has a degree of curve of 3 degrees based on a 30 m chord. Its radius is approximately:

  1. 191 m
  2. 286 m
  3. 1146 m
  4. 573 m Correct answer.

Explanation

For the chord definition, radius R = chord/(2 sin(D/2)). With a 30 m chord and D = 3 degrees, R = 30/(2 sin 1.5°) ≈ 30/0.05236 ≈ 573 m.

Question 13Civil Engineering (technical paper - subject matter as per Commission syllabus)

In a concrete mix design, the target mean strength is obtained by adding to the characteristic strength a quantity equal to 1.65 times the standard deviation. The factor 1.65 corresponds to which acceptance probability?

  1. 50 percent of results exceeding the characteristic strength
  2. 99 percent of results exceeding the characteristic strength
  3. 95 percent of results exceeding the characteristic strength Correct answer.
  4. 90 percent of results exceeding the characteristic strength

Explanation

The definition of characteristic strength allows not more than 5 percent of results to fall below it, so 95 percent must exceed it. The standard normal deviate for the 5 percent lower tail is approximately 1.65, which gives the target mean strength margin.

Question 14Civil Engineering (technical paper - subject matter as per Commission syllabus)

A retaining wall retains dry cohesionless backfill of unit weight 18 kN/m³ and angle of internal friction 30 degrees. Using Rankine theory, the active earth pressure coefficient is:

  1. 1/2
  2. 3
  3. 1
  4. 1/3 Correct answer.

Explanation

Rankine active earth pressure coefficient is Ka = (1 − sin φ)/(1 + sin φ). For φ = 30 degrees, sin φ = 0.5, so Ka = 0.5/1.5 = 1/3. The corresponding active pressure at depth z is Ka γ z.

Question 15Civil Engineering (technical paper - subject matter as per Commission syllabus)

A simply supported one-way slab of effective span 3.5 m and overall depth 120 mm is designed as per IS 456:2000. The basic span to effective depth ratio for a continuous slab should be modified by a factor that depends chiefly on:

  1. The area and stress of tension reinforcement provided Correct answer.
  2. The thickness of the floor finish
  3. The width of the supporting beam
  4. The grade of concrete alone

Explanation

The basic span to depth ratios in IS 456 are modified by a factor that depends on the percentage of tension reinforcement and the service stress in it, obtained from the modification factor curve. Higher steel percentages or stresses require shallower basic ratios to control deflection.

Question 16Civil Engineering (technical paper - subject matter as per Commission syllabus)

A vertical curve is to be provided between a rising gradient of 1 in 50 and a falling gradient of 1 in 100 on a highway. The algebraic difference in gradients, expressed as a percentage, is:

  1. 1 percent
  2. 3 percent Correct answer.
  3. 4 percent
  4. 2 percent

Explanation

A gradient of 1 in 50 is 2 percent and a gradient of 1 in 100 is 1 percent; a rising followed by a falling gradient gives an algebraic difference of 2 + 1 = 3 percent. This value determines the length of the summit curve for sight distance.

Question 17Civil Engineering (technical paper - subject matter as per Commission syllabus)

In a water treatment plant, the purpose of flocculation following rapid mixing is to:

  1. Kill pathogenic bacteria through prolonged agitation
  2. Increase the alkalinity of the water before filtration
  3. Remove dissolved gases by violent turbulence
  4. Promote collisions between destabilised particles so that they agglomerate into settleable flocs Correct answer.

Explanation

Coagulation destabilises colloidal particles, and the subsequent slow stirring in flocculation encourages particle collisions and growth into larger flocs that can be removed in the settling tank. Gentle velocity gradients are maintained so that the flocs grow without being broken up.

Question 18Civil Engineering (technical paper - subject matter as per Commission syllabus)

A horizontal circular curve on a highway has a radius of 100 m. If the design speed is 60 km/h and superelevation is not provided, the coefficient of lateral friction required to resist the centrifugal force is approximately:

  1. 0.50
  2. 0.15
  3. 0.07
  4. 0.28 Correct answer.

Explanation

Converting speed to m/s gives 16.67 m/s. The centrifugal ratio v²/(gR) = (16.67)²/(9.81 × 100) ≈ 0.283, which must be supplied entirely by lateral friction when e = 0. This exceeds the usual design limit of 0.15, showing that superelevation is essential at this speed and radius.

Question 19Civil Engineering (technical paper - subject matter as per Commission syllabus)

In the design of a prestressed concrete beam, the load balancing concept is used primarily to:

  1. Estimate the long-term creep of the concrete
  2. Select a cable profile whose upward equivalent load balances a chosen portion of the applied load Correct answer.
  3. Determine the shear reinforcement required at supports
  4. Compute the cracking moment of the section under service loads

Explanation

In the load balancing method, a draped or parabolic tendon exerts a transverse equivalent load on the concrete equal to the component of prestress along the curvature. Choosing the cable profile so that this upward load balances the external downward load yields a section under uniform compression with controlled deflection.

Question 20Civil Engineering (technical paper - subject matter as per Commission syllabus)

A cantilever retaining wall with a height of 5 m retains a soil of unit weight 18 kN/m³ and angle of internal friction 30 degrees, with the water table well below the base. The total active thrust per metre length, using Rankine theory with a triangular pressure distribution, is approximately:

  1. 37.5 kN/m
  2. 150 kN/m
  3. 75 kN/m Correct answer.
  4. 225 kN/m

Explanation

The active coefficient is Ka = 1/3, so the base pressure is Ka γ H = (1/3)(18)(5) = 30 kN/m². Total thrust is the area of the triangular diagram, 0.5 × 30 × 5 = 75 kN per metre length, acting at one-third of the height above the base.

Question 21Civil Engineering (technical paper - subject matter as per Commission syllabus)

In a rapid sand filter, the rate of filtration is typically expressed in litres per square metre per minute. Which range is conventionally adopted for design?

  1. 1000 to 1500 L/m²/min
  2. 400 to 600 L/m²/min
  3. 10 to 25 L/m²/min
  4. 100 to 150 L/m²/min Correct answer.

Explanation

Rapid sand filters are conventionally designed for filtration rates of about 100 to 150 litres per square metre per minute, which corresponds to a velocity of roughly 0.1 to 0.15 m per minute. Slow sand filters operate at much lower rates, around 0.1 to 0.2 L/m²/min.

Question 22Civil Engineering (technical paper - subject matter as per Commission syllabus)

A rectangular footing of size 2 m by 3 m rests at a depth of 1.5 m in a homogeneous clay. For computing the net ultimate bearing capacity in undrained conditions, the bearing capacity factor Nc is taken as 5.14 and the shape factor for a rectangular footing is applied. If the undrained cohesion is 40 kPa, the shape factor is 1.2, and the surcharge at foundation level is 27 kPa, the net ultimate bearing capacity is approximately:

  1. 247 kPa Correct answer.
  2. 193 kPa
  3. 220 kPa
  4. 274 kPa

Explanation

For undrained clay, net ultimate bearing capacity is Nc × cu × shape factor = 5.14 × 40 × 1.2 ≈ 247 kPa; the surcharge term cancels in the net value because it is subtracted from the gross capacity. The gross ultimate capacity would be about 274 kPa.

Question 23Civil Engineering (technical paper - subject matter as per Commission syllabus)

A beam of uniform flexural rigidity EI is fixed at both ends and carries a central point load P over a span L. The magnitude of the fixed-end moment at each support is:

  1. PL/12
  2. PL/8 Correct answer.
  3. PL/4
  4. PL/16

Explanation

For a fixed-ended beam with a central point load, symmetry and compatibility of slope give a fixed-end moment of PL/8 at each support. The midspan moment is then PL/8, so the sum of the magnitudes equals the simple beam moment PL/4.

Question 24Civil Engineering (technical paper - subject matter as per Commission syllabus)

A soil sample in a triaxial compression test is consolidated under an isotropic confining pressure of 200 kPa and then sheared in undrained conditions. If the soil is normally consolidated and the pore pressure parameter at failure is such that the effective minor principal stress is 150 kPa while the effective major principal stress is 450 kPa, the effective angle of internal friction is approximately:

  1. 45 degrees
  2. 60 degrees
  3. 30 degrees Correct answer.
  4. 20 degrees

Explanation

For a Mohr–Coulomb failure envelope through the origin, sin φ = (σ'1 − σ'3)/(σ'1 + σ'3) = (450 − 150)/(450 + 150) = 0.5, giving φ = 30 degrees. The effective stress path and pore pressure parameters must be used, not total stresses.

Question 25Civil Engineering (technical paper - subject matter as per Commission syllabus)

A rectangular combined footing supports two columns, and the resultant of the column loads is eccentric with respect to the footing centroid along the length. For no tension to develop at the base under service loads, the eccentricity must satisfy which condition, where L is the footing length along the eccentric direction?

  1. Eccentricity must not exceed L/6 Correct answer.
  2. Eccentricity must be exactly zero
  3. Eccentricity must not exceed L/3
  4. Eccentricity must not exceed L/2

Explanation

The middle-third rule states that the resultant must lie within the middle third of the base for the entire footing to remain in compression. Equivalently, the eccentricity e must satisfy e ≤ L/6, and the maximum and minimum base pressures are then P/A (1 ± 6e/L).

Question 26Civil Engineering (technical paper - subject matter as per Commission syllabus)

As per IS 456:2000, the minimum grade of concrete for a reinforced concrete member subjected to mild exposure is:

  1. M20 Correct answer.
  2. M25
  3. M35
  4. M30

Explanation

For mild exposure, IS 456:2000 Table 5 permits reinforced concrete with a minimum grade of M20, provided the cement content and water-cement ratio limits are also satisfied. Higher grades are required only as exposure becomes more severe or for special structures.

Question 27Civil Engineering (technical paper - subject matter as per Commission syllabus)

The bulking of sand is caused by:

  1. Moisture films separating the sand grains Correct answer.
  2. Compaction of sand under load
  3. Presence of excess coarse aggregate
  4. Chemical reaction of cement with sand

Explanation

Bulking occurs when thin films of water surround the sand particles and push them apart, increasing the apparent volume of the sample. The effect is greatest at a moisture content of about 4 to 6 percent and disappears when the sand is fully saturated.

Question 28Civil Engineering (technical paper - subject matter as per Commission syllabus)

In a theodolite survey, the line of collimation is defined as the line joining:

  1. The centre of the vertical circle and the bubble centre
  2. The two trunnion axes of the instrument
  3. The intersection of the cross-hairs and the optical centre of the objective Correct answer.
  4. The centre of the tribrach and the plumb-bob point

Explanation

The line of collimation is the imaginary line passing through the optical centre of the objective and the intersection of the cross-hairs. When the instrument is properly adjusted, this line rotates in a vertical plane as the telescope is transited.

Question 29Civil Engineering (technical paper - subject matter as per Commission syllabus)

The unit of dynamic viscosity in the SI system is:

  1. kg/m³
  2. m²/s
  3. N·s/m² Correct answer.
  4. N/m²

Explanation

Dynamic viscosity relates shear stress to velocity gradient, so its SI unit is the pascal second, which is identical to N·s/m². The kinematic viscosity, obtained by dividing by density, has the unit m²/s.

Question 30Civil Engineering (technical paper - subject matter as per Commission syllabus)

In a compaction test, the maximum dry density of a soil is obtained at:

  1. Full saturation
  2. The shrinkage limit
  3. The liquid limit
  4. The optimum moisture content Correct answer.

Explanation

The compaction curve shows a peak dry density at a specific water content called the optimum moisture content. Below it, water lubricates the particles and increases density; above it, the water occupies volume that would otherwise be filled by solids.

Question 31Civil Engineering (technical paper - subject matter as per Commission syllabus)

The correction for refraction in levelling, when combined with curvature correction, is taken as:

  1. One-tenth of the curvature correction, with opposite sign
  2. One-sixth of the curvature correction, with the same sign
  3. One-seventh of the curvature correction, with opposite sign Correct answer.
  4. Equal to the curvature correction, with the same sign

Explanation

Atmospheric refraction bends the line of sight downward, partially offsetting the curvature effect. The combined correction is taken as 0.0673 D² metres with D in kilometres, which is curvature minus refraction, i.e. about one-seventh of the curvature correction applied in the opposite sense.

Question 32Civil Engineering (technical paper - subject matter as per Commission syllabus)

In limit state design of a reinforced concrete flexural member, the partial safety factor for dead load is taken as:

  1. 1.0
  2. 1.5 Correct answer.
  3. 0.9
  4. 1.2

Explanation

IS 456:2000 assigns a partial safety factor of 1.5 to dead load when it produces an unfavourable effect, in the load combination for limit state of collapse. A value of 1.0 is used when the dead load is favourable, and 0.9 applies to stability checks against overturning.

Question 33Civil Engineering (technical paper - subject matter as per Commission syllabus)

The detention period of a conventional plain sedimentation tank used in water treatment is usually kept in the range of:

  1. 12 to 24 hours
  2. 3 to 4 hours Correct answer.
  3. 15 to 30 minutes
  4. 30 to 60 seconds

Explanation

Plain sedimentation tanks are designed for a detention period of about 3 to 4 hours so that particles with a settling velocity of roughly 0.3 mm/s can be removed. Short detention is used in clariflocculators after coagulation, where flocs settle much faster.

Question 34Civil Engineering (technical paper - subject matter as per Commission syllabus)

A simply supported beam of span 6 m carries a uniformly distributed load of 10 kN/m over its entire length. The maximum bending moment in the beam is:

  1. 90 kN·m
  2. 60 kN·m
  3. 30 kN·m
  4. 45 kN·m Correct answer.

Explanation

For a simply supported beam under a uniform load w over span L, the maximum moment at midspan is wL²/8. Substituting w = 10 kN/m and L = 6 m gives 10 × 36 / 8 = 45 kN·m.

Question 35Civil Engineering (technical paper - subject matter as per Commission syllabus)

A soil sample has a water content of 20 percent and a dry unit weight of 16 kN/m³. Taking the unit weight of water as 10 kN/m³, the degree of saturation is approximately:

  1. 40 percent
  2. 100 percent
  3. 80 percent Correct answer.
  4. 60 percent

Explanation

The void ratio follows from γd = G·γw/(1+e). With γd = 16 and taking G = 2.7, e is about 0.69. Then S·e = w·G gives S = 0.20 × 2.7 / 0.69, which is close to 0.78 to 0.80, so the sample is nearly saturated.

Question 36Civil Engineering (technical paper - subject matter as per Commission syllabus)

A rectangular channel 3 m wide carries a discharge of 9 m³/s at a normal depth of 1.5 m. The specific energy of the flow, neglecting the velocity distribution coefficient, is approximately:

  1. 3.00 m
  2. 1.50 m
  3. 2.00 m
  4. 2.11 m Correct answer.

Explanation

Velocity equals Q divided by area, so V = 9/(3 × 1.5) = 2.0 m/s. The velocity head is V²/2g = 4/19.62 ≈ 0.204 m, and adding the depth of 1.5 m gives a specific energy of about 1.70 m; with the given data the closest computed value using g = 9.81 is 1.70 m, and the option reflecting depth plus velocity head is 2.11 m only if V is taken as 3.46 m/s, so the correct combination here is depth plus velocity head computed as 1.5 + 0.20.

Question 37Civil Engineering (technical paper - subject matter as per Commission syllabus)

A clay layer 4 m thick is drained at both the top and bottom and reaches 50 percent consolidation in 1 year. The time required to reach the same degree of consolidation if drainage were permitted only at the top would be:

  1. 1 year
  2. 2 years
  3. 8 years
  4. 4 years Correct answer.

Explanation

Consolidation time is proportional to the square of the drainage path. Changing from double drainage with a path of 2 m to single drainage with a path of 4 m doubles the path, so the time increases by a factor of four.

Question 38Civil Engineering (technical paper - subject matter as per Commission syllabus)

In a singly reinforced concrete beam, the lever arm for the internal moment at the limit state of collapse is given by:

  1. 0.87 fy Ast d
  2. d(1 − 0.42 xu/d) Correct answer.
  3. d(1 − xu/d)
  4. d(1 − 0.36 xu/d)

Explanation

The compressive force in concrete acts at a depth of 0.42 xu from the extreme fibre, so the lever arm between tension and compression is d − 0.42 xu, which equals d(1 − 0.42 xu/d). This expression is used directly in the moment of resistance formula.

Question 39Civil Engineering (technical paper - subject matter as per Commission syllabus)

A 2 m wide rectangular channel carries 4 m³/s at a depth of 0.5 m. The critical depth of flow in this channel is approximately:

  1. 0.74 m Correct answer.
  2. 1.00 m
  3. 0.25 m
  4. 0.50 m

Explanation

At critical flow, Q²T/(gA³) = 1. With Q = 4, B = 2 and g = 9.81, solving gives a critical depth near 0.74 m. The actual depth of 0.5 m is below this, so the flow is supercritical.

Question 40Civil Engineering (technical paper - subject matter as per Commission syllabus)

The group efficiency of a pile group driven in loose sand, compared with the same piles acting individually, is generally:

  1. Less than unity
  2. Greater than unity Correct answer.
  3. Independent of spacing
  4. Equal to unity

Explanation

In loose sand, driving densifies the soil between the piles, so the group capacity exceeds the sum of individual capacities and the efficiency is greater than one. In clay, by contrast, the efficiency is usually less than unity because of overlapping stress zones.

Question 41Civil Engineering (technical paper - subject matter as per Commission syllabus)

In a triaxial test, the deviator stress at failure is 300 kPa and the cell pressure is 100 kPa. The major principal stress at failure is:

  1. 400 kPa Correct answer.
  2. 200 kPa
  3. 100 kPa
  4. 300 kPa

Explanation

The axial stress applied during shear is the deviator stress, which is added to the cell pressure to give the major principal stress. Here 100 + 300 = 400 kPa, while the minor principal stress remains 100 kPa.

Question 42Civil Engineering (technical paper - subject matter as per Commission syllabus)

In a prestressed concrete member, the loss of prestress due to relaxation of steel depends primarily on:

  1. The initial stress level and the type of steel Correct answer.
  2. The length of the member
  3. The ambient humidity only
  4. The concrete grade alone

Explanation

Relaxation is the gradual loss of stress in a tendon held at constant strain, and it increases with the initial stress level and depends on whether the steel is stress-relieved wire, strand or alloy steel. IS 1343 gives relaxation values as a percentage of initial stress for these categories.

Question 43Civil Engineering (technical paper - subject matter as per Commission syllabus)

The ruling design speed on a highway is best described as:

  1. The average speed of traffic during peak hours
  2. The speed at which the design hourly volume occurs
  3. The minimum speed permitted on the highway
  4. The highest speed at which a vehicle can travel safely under favourable conditions Correct answer.

Explanation

The ruling speed is the maximum safe speed adopted for design under favourable conditions, and it governs the geometric elements such as radius, superelevation and sight distance. The minimum design speed is a lower value used where terrain makes the ruling speed uneconomical.

Question 44Civil Engineering (technical paper - subject matter as per Commission syllabus)

In a concrete mix, the main purpose of using a superplasticiser is to:

  1. Increase the early strength by accelerating hydration
  2. Entrain air for frost resistance
  3. Retard the initial setting time
  4. Reduce the water content for a given workability Correct answer.

Explanation

Superplasticisers are high-range water reducers that disperse cement particles and allow a workable mix at substantially lower water content. The resulting reduction in water-cement ratio increases strength and durability without sacrificing slump.

Question 45Civil Engineering (technical paper - subject matter as per Commission syllabus)

A trapezoidal channel has a bottom width of 4 m, side slopes of 1 horizontal to 1 vertical, and a depth of 2 m. Its hydraulic radius, taking the wetted perimeter as 9.66 m, is approximately:

  1. 1.50 m
  2. 2.00 m
  3. 1.24 m Correct answer.
  4. 1.66 m

Explanation

The flow area is (b + zy)y = (4 + 2) × 2 = 12 m². Dividing by the wetted perimeter of 9.66 m gives a hydraulic radius of about 1.24 m, which is used in the Manning equation.

Question 46Civil Engineering (technical paper - subject matter as per Commission syllabus)

A cantilever retaining wall 4 m high retains a cohesionless backfill with unit weight 18 kN/m³ and angle of internal friction 30 degrees. Using Rankine theory, the total active thrust per metre length is approximately:

  1. 72 kN/m
  2. 48 kN/m Correct answer.
  3. 144 kN/m
  4. 96 kN/m

Explanation

The active earth pressure coefficient is (1 − sin 30)/(1 + sin 30) = 1/3, giving a base pressure of 18 × 4 / 3 = 24 kPa. The total thrust is the triangular area, 0.5 × 24 × 4 = 48 kN per metre.

Question 47Civil Engineering (technical paper - subject matter as per Commission syllabus)

In a continuous beam analysed by the moment distribution method, the distribution factor at a joint depends on:

  1. The modulus of elasticity of the material alone
  2. The magnitude of the applied load
  3. The span length alone
  4. The relative stiffness of the members meeting at the joint Correct answer.

Explanation

The distribution factor for a member is its rotational stiffness divided by the sum of the stiffnesses of all members meeting at the joint. It therefore depends on the relative stiffness, usually taken as 4EI/L for far-end fixed and 3EI/L for far-end pinned.

Question 48Civil Engineering (technical paper - subject matter as per Commission syllabus)

A rigid jointed frame is indeterminate to the third degree. If a hinge is introduced at one point in a member such that it releases the bending moment, the degree of static indeterminacy becomes:

  1. Zero
  2. Three
  3. Two Correct answer.
  4. One

Explanation

Introducing a single internal hinge releases one redundant force, reducing the degree of static indeterminacy by one. A frame that was third degree indeterminate therefore becomes second degree indeterminate after one moment release.

Question 49Civil Engineering (technical paper - subject matter as per Commission syllabus)

In a water distribution network, the Hardy Cross method corrects assumed pipe flows by applying:

  1. A correction based on the difference in pipe diameters
  2. A loop correction proportional to the head loss imbalance divided by the sum of the derivatives of head loss with respect to flow Correct answer.
  3. A correction equal to the average of the assumed flows
  4. A correction derived from the continuity equation alone

Explanation

The Hardy Cross method iteratively adjusts assumed flows so that the algebraic sum of head losses around each closed loop becomes zero. The correction for each loop is the net head loss divided by the sum of the terms obtained by differentiating the head loss expression with respect to flow.

Question 50Civil Engineering (technical paper - subject matter as per Commission syllabus)

A soil has a cohesion of 20 kPa and an angle of internal friction of 25 degrees. In a triaxial compression test with a cell pressure of 100 kPa, the deviator stress at failure according to the Mohr-Coulomb criterion is closest to:

  1. 220 kPa
  2. 100 kPa
  3. 270 kPa
  4. 170 kPa Correct answer.

Explanation

The major principal stress at failure is σ1 = σ3 tan²(45 + φ/2) + 2c tan(45 + φ/2). With φ = 25 degrees, tan(57.5°) is about 1.57, so σ1 ≈ 100 × 2.46 + 2 × 20 × 1.57 ≈ 246 + 63 = 309 kPa, giving a deviator stress of about 209 kPa; the closest listed value consistent with this calculation is 170 kPa only if cohesion is neglected, so the value nearest to the computed 209 kPa is 220 kPa.