If E is the modulus of elasticity of cement concrete, μ is the Poisson's ratio for concrete, h is the slab thickness, and k is the subgrade modulus.
The radius of relative stiffness (ℓ) for rigid pavement is given by ____
1
\( {\left[ {\frac{{E{h^3}}}{{12\;k\left( {1 - {\mu ^2}} \right)}}} \right]^{1/4}}\)
2
\( {\left[ {\frac{{E{h^4}}}{{12\;k\left( {1 - {\mu ^2}} \right)}}} \right]^{1/3}}\)
3
\( {\left[ {\frac{{E{h^4}}}{{12\;k\left( {1 - {\mu }} \right)^2}}} \right]^{1/3}}\)
4
\( {\left[ {\frac{{E{h^2}}}{{12\;k\left( {1 - {\mu }} \right)^2}}} \right]^{1/4}}\)