Question

If the load is at the surface of subgrade, the elastic strain is ________

(a) \(∆=\frac{pa}{E} 1.5\)

(b) \(∆=\frac{3pa^2}{2E} 2.5\)

(c) \(∆=\frac{a^2}{2E} 3\)

(d) \(∆=\frac{pa^2}{2E} 3.5\)

This question was posed to me in an interview.

My doubt is from Stresses in Flexible Pavements in portion Design of Flexible & Rigid Pavement of Geotechnical Engineering II

Answer 1

Right choice is (a) \(∆=\frac{pa}{E} 1.5\)

Best explanation: When the Poisson’s ratio is 0.5, the elastic strain ∆ is given by,

\(∆=\frac{pa}{E} F_B,\) and at the surface, z=0,

∴ FB=1.5

Hence, \(∆=\frac{pa}{E} 1.5.\)