Question

For a uniformly loaded rectangular area, the Newmark’s  influence factor given by ___________

(a) \(K= \left[\frac{20.20.4\sqrt{(0.2^2+0.4^2+1)}}{0.2^2+0.4^2+0.2^2 0.4^2+1}*\frac{0.2^2+0.4^2+2}{0.2^2+0.4^2+1}+tan^{-1}\frac{20.20.4\sqrt{(0.2^2+0.4^2+1)}}{0.2^2+0.4^2+0.2^2 0.4^2+1}\right] \)

(b) \(K=   \frac{1}{4π} \left[\frac{20.20.4\sqrt{(0.2^2+0.4^2+1)}}{0.2^2+0.4^2+0.2^2 0.4^2+1}*\frac{0.2^2+0.4^2+2}{0.2^2+0.4^2+1}+tan^{-1}\frac{20.20.4\sqrt{(0.2^2+0.4^2+1)}}{0.2^2+0.4^2+0.2^2 0.4^2+1}\right] \)

(c) \(K=   \frac{1}{4π}\)

(d) \(K=   \frac{q}{4π} \left[\frac{20.20.4\sqrt{(0.2^2+0.4^2+1)}}{0.2^2+0.4^2+0.2^2 0.4^2+1}*\frac{0.2^2+0.4^2+2}{0.2^2+0.4^2+1}+tan^{-1}\frac{20.20.4\sqrt{(0.2^2+0.4^2+1)}}{0.2^2+0.4^2+0.2^2 0.4^2+1}\right] \)

This question was posed to me during an internship interview.

My query is from Stress Distribution in division Stress Distribution of Geotechnical Engineering I

Answer 1

The correct choice is (b) \(K=   \frac{1}{4π} \left[\frac{20.20.4\sqrt{(0.2^2+0.4^2+1)}}{0.2^2+0.4^2+0.2^2 0.4^2+1}*\frac{0.2^2+0.4^2+2}{0.2^2+0.4^2+1}+tan^{-1}\frac{20.20.4\sqrt{(0.2^2+0.4^2+1)}}{0.2^2+0.4^2+0.2^2 0.4^2+1}\right] \)

Best explanation: The Newmark’s  influence factor for a uniformly loaded rectangular area of size a, b at depth z is given by,

 \(K=   \frac{1}{4π} \left[\frac{20.20.4\sqrt{(0.2^2+0.4^2+1)}}{0.2^2+0.4^2+0.2^2 0.4^2+1}*\frac{0.2^2+0.4^2+2}{0.2^2+0.4^2+1}+tan^{-1}\frac{20.20.4\sqrt{(0.2^2+0.4^2+1)}}{0.2^2+0.4^2+0.2^2 0.4^2+1}\right] \)

Where m=a/z

n=b/z.

m and n are interchangeable.