Question

What is the deflection at the surface of flexible pavement due to a wheel load of 40 kN and a tyre pressue of $0.5MN/m^2$? (Assume modulus of elasticity of the pavement and subgrade as uniformly equal to 20 $MN/m^2$)

• A. 0.9 cm
• B. 0.3 cm
• C. 0.6 cm
• D. 1.2 cm

Answer 1

The correct option is C 0.6 cm

Tyre pressure = $\frac{Wheelload}{Area}$

$\Rightarrow p=\frac{P}{\pi a^2}$

$\Rightarrow a=\sqrt{\frac{40\times 1000}{3.14\times 0.5\times {10}^6}}=15.95cm$

Deflection = $\frac{1.5p.a}{E}$

$=\frac{1.5\times 0.5\times {10}^6\times 0.1595}{20\times {10}^6}=0.5986cm\approx 0.6cm$