(a) Compare the application of 'straight blade' and 'angle blade' of bulldozers for earthwork in a construction project. Determine the unit cost (₹/m³) for pushing the soil by a bulldozer for a canal construction project using the following data :

(

Question

(a) Compare the application of 'straight blade' and 'angle blade' of bulldozers for earthwork in a construction project. Determine the unit cost (₹/m³) for pushing the soil by a bulldozer for a canal construction project using the following data :

(i) Bulldozer cost = ₹ 4,000 per hour

(ii) Wages of operator = ₹ 150 per hour

(iii) Rated moldboard capacity in loose volume (blade load) = 4 cum

(iv) Swell factor for the soil = 1·25

(v) Hauling distance = 50 m

(vi) Operating time per hour for the bulldozer = 50 minutes

(vii) Forward speed of the bulldozer = 3 kmph

(viii) Reverse speed of the bulldozer = 6 kmph

(ix) Gear shifting time = 0·3 minute

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(b) Answer the following in brief :

(i) Why is it advantageous to use ferrocement when the structural member is in tension?

(ii) What are the advantages of using ferrocement over reinforced concrete?

(iii) What are the advantages of using ferrocement in marine structures?

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(c) The speed and delay study was conducted by floating car method during different round trips on a stretch of 3 km State highway. The data of the study is given below :

| Trip Number | Number of Vehicles | | |
| | In Opposite Direction | Overtaking | Overtaken |
| 1 | 140 | 30 | 16 |
| 2 | 130 | 22 | 17 |
| 3 | 180 | 18 | 19 |

Given that the floating car is moving at a constant speed of 30 kmph, calculate the following :

(i) Traffic stream variables for different trips

(ii) Speed-density and volume-density relationship

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UPSC Answer Check · Accepted Answer

Begin with a comparative analysis of straight blade versus angle blade bulldozers for part (a), followed by systematic numerical calculation of unit cost using the given operational parameters. For part (b), provide concise, technically precise answers on ferrocement properties and applications. For part (c), apply the floating car method equations to derive traffic stream variables and establish the Greenshields relationships. Allocate approximately 40% of effort to part (a) given its 20 marks, 30% to part (b) for 15 marks, and 30% to part (c) for 15 marks.
- Part (a): Comparison of straight blade (U-blade for heavy digging, crowding, short hauls) versus angle blade (side casting, ditching, spreading, longer hauls) with specific construction applications
- Part (a): Correct calculation of production rate considering blade load, swell factor, cycle time (forward haul + reverse return + gear shifting), and operating efficiency
- Part (a): Accurate unit cost computation by combining ownership/operating costs with hourly production output
- Part (b): Ferrocement's tensile advantage due to high specific surface area of mesh reinforcement, crack control, and distributed micro-cracking behavior
- Part (b): Ferrocement advantages over RC—thinner sections, no cover requirements, impermeability, impact resistance, and suitability for prefabrication
- Part (b): Marine applications—corrosion resistance of galvanized mesh, resistance to chloride penetration, repairability, and performance in splash zones
- Part (c): Correct application of floating car method equations: traffic volume, average travel time, and mean speed calculations for each trip
- Part (c): Derivation of speed-density (linear) and volume-density (parabolic) relationships using fundamental diagram principles

Dimension	Weight	Max marks	Excellent	Average	Poor
Concept correctness	20%	10	Demonstrates precise understanding of bulldozer blade mechanics, ferrocement composite behavior under tension, and fundamental traffic flow theory; correctly identifies that straight blades excel in crowding/pushing while angle blades enable side casting; recognizes ferrocement's crack bridging mechanism and distributed reinforcement action	Shows basic familiarity with equipment types and material properties but misses nuanced distinctions in blade applications or oversimplifies ferrocement behavior; traffic theory concepts partially correct but may confuse space mean speed with time mean speed	Confuses blade types or their applications; fundamentally misunderstands ferrocement as merely thin RC; applies incorrect traffic stream relationships or misidentifies the floating car method purpose
Numerical accuracy	20%	10	All calculations error-free: correct swell factor application (bank volume = loose volume/1.25), accurate cycle time summation (50m at 3 kmph = 1 min, return at 6 kmph = 0.5 min, plus 0.3 min shifting = 1.8 min cycle), proper hourly production, and unit cost; traffic calculations yield consistent q, k, v values across trips with correct arithmetic	Minor computational errors in one sub-part (e.g., incorrect speed conversion, missed gear shifting time, or swell factor applied incorrectly); traffic volume calculations approximately correct but rounding errors affect final relationships	Major errors in multiple calculations: wrong cycle time components, omitted operating efficiency factor, incorrect cost summation, or fundamental errors in floating car equations leading to impossible traffic values
Diagram quality	15%	7.5	Clear schematic diagrams for part (a) showing straight blade (U-shape, no tilt) versus angle blade (tilted position, side discharge); for part (c), accurate fundamental diagrams of speed-density (linear decreasing) and flow-density (parabolic) with properly labeled axes, units, and key points (jam density, optimum density, free-flow speed)	Diagrams present but lack precision in blade geometry representation or traffic diagram scaling; axes labeled but missing units or critical points not marked	No diagrams provided where essential for explanation; or diagrams fundamentally incorrect (e.g., wrong curve shapes, mislabeled relationships, confusing blade types)
Step-by-step derivation	25%	12.5	Systematic presentation: for (a) explicit formula for cycle time, production rate, and cost per m³ with all substitutions shown; for (c) clear derivation of traffic volume from floating car equations, followed by calculation of density and speed for each trip, then regression/estimation of Greenshields parameters (uf and kj) for the relationships	Steps shown but some shortcuts taken; intermediate values not always stated; traffic relationships stated without showing how uf and kj were determined from the three data points	Final answers only with no derivation; or disorganized calculation sequence making verification impossible; missing critical steps like swell factor conversion or cycle time breakdown
Practical interpretation	20%	10	Contextualizes bulldozer selection for Indian canal projects (e.g., CWC guidelines, soil types in alluvial plains); relates ferrocement to actual applications (ferrocement boats in Kerala, water tanks, silos); interprets traffic results for highway capacity and level of service implications for state highway planning	Generic statements about equipment efficiency or material benefits without specific Indian context; traffic results presented numerically without interpretation for highway management	No practical relevance drawn; calculations remain abstract numbers without connection to construction economics, material selection decisions, or traffic engineering applications

Q4

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