(a) Compare the application of 'straight blade' and 'angle blade' of bulldozers for earthwork in a construction project…

Blade comparison and unit cost Straight and angle blades both push soil, but they differ in geometry and use. A straight blade, or U-blade, has a rigid straight moldboard, higher rated capacity, and is best for heavy digging, crowding, and short hauls where large bank volumes must be moved quickly, such as canal embankment filling. An angle blade, or A-blade, can be swung to the side, has slightly lower capacity, and is preferred for side casting, ditching, spreading, cleaning, and shaping; it is useful for canal banks, side slopes and longer hauls where material must be cast to one side. The straight blade is less flexible but more productive for direct pushing; the angle blade is more versatile for finishing and side casting.

For the cost, hourly cost = 4000 + 150 = ₹4150. Forward time = 50 m / 50 m/min = 1.0 min; reverse time = 50 m / 100 m/min = 0.5 min; gear shifting = 0.3 min. Cycle time = 1.8 min. With 50 min operating time per hour, cycles = 50/1.8 = 27.78. Bank volume per load = 4/1.25 = 3.2 m³. Production = 27.78 × 3.2 = 88.9 bank m³/hr. Unit cost = 4150/88.9 = ₹46.7 per bank m³ (about ₹37.4 per loose m³).

Ferrocement (i) In tension, ferrocement is advantageous because its closely spaced thin wire mesh has high specific surface area, giving many small cracks and high bond. Tension is shared by numerous wires, crack widths are controlled, and the member remains ductile even in thin sections where conventional bars would be ineffective. (ii) Over reinforced concrete, ferrocement allows thinner sections, needs little or no conventional cover, is more impermeable, has better impact and fatigue resistance, can be prefabricated easily, and is repairable. Its fine mesh distributes stresses, reducing large cracks and improving durability. (iii) In marine structures, galvanized or corrosion-resistant mesh resists chloride attack, thin dense sections limit crack penetration, and the material performs well in splash zones. It is repairable, suitable for seawalls, breakwaters, pipes, tanks and marine platforms, and maintains integrity where conventional concrete cover may spall.

Floating car method Floating car time = 3/30 hr = 0.1 hr = 6 min. Let N be opposite-direction vehicles and D be the absolute difference between overtaking and overtaken vehicles. For the two-way stretch, stream speed is v = 30(N-D)/(N+D), volume per direction q = (N-D)/(2 × 0.1), density k = q/v, and travel time t = 3/v.

Trip 1: N=140, D=|30-16|=14. v=30×126/154=24.55 kmph; q=126/0.2=630 veh/hr; k=630/24.55=25.67 veh/km; t=3/24.55=7.33 min. Trip 2: N=130, D=|22-17|=5. v=30×125/135=27.78 kmph; q=125/0.2=625 veh/hr; k=22.50 veh/km; t=6.48 min. Trip 3: N=180, D=|18-19|=1. v=30×179/181=29.67 kmph; q=179/0.2=895 veh/hr; k=30.17 veh/km; t=6.07 min.

The computed density-speed pairs are (25.67,24.55), (22.50,27.78), (30.17,29.67), and the density-volume pairs are (25.67,630), (22.50,625), (30.17,895). Plotting these gives the speed-density and volume-density relationships. In the Greenshields idealisation, speed-density is linear, v = Vf(1 - k/Kj), and volume-density is parabolic, q = Vf k(1 - k/Kj); a straight-line fit to the k-v points gives Vf at k=0 and Kj at v=0.

Thus, for canal earthwork, a straight blade is preferred for high-capacity short-haul pushing, while an angle blade is preferred for side casting, ditching and spreading; the bulldozer unit cost is about ₹46.7 per bank m³.