Question

The radius of relative stiffness of a rigid concrete pavement using the following data is ____ cm

(i) Modulus of elasticity of concrete$=3.0\times {10}^{5}kg/c{m}^2$
(ii) Thickness of pavement slab = 20 cm
(iii) Poisson's ratio = 0.15
(iv) Wheel load = 4100 kg
(v) Pressure applied to the plate load test at 1.25 mm displacement $=0.375kg/c{m}^2$

• A. 81.28
• B. 98.15
• C. 104.5
• D. 90.88

Answer 1

The correct option is D 90.88

We know,

$\text{Radius of relative stiffness,}l={\left[\frac{E{h}^3}{12k(1-{\mu }^2)}\right]}^{1/4}$

l = Radius of relative stiffness, cm
E = Modulus of elasticity of cement concrete, $=3\times {10}^{5}kg/c{m}^2$
h = Slab thickness, cm = 20 cm
k = Modulus of subgrade reaction $=0.375kg/c{m}^2/\text{deflection}$

$=\frac{0.375}{0.125}=3kg/c{m}^2$

$\therefore l={\left[\frac{3\times {10}^5\times {20}^3}{12\times 3\times (1-{0.15}^2)}\right]}^{1/4}=90.88cm$

$\therefore$ Radius of relative stiffness is 90.88 cm.