Question

For four free standing pile group having arc tan value of 18.3, the efficiency as per Converse Labarre formula, would be

• A. 76%
• B. 78%
• C. 80%
• D. 82%

Answer 1

The correct option is C 80%

Efficiency by Converse Labarre formula

${\eta }_g=1-\frac{\varphi }{90}\left[\frac{m(n-1)+n(m-1)}{mn}\right]$

Given m = n = 2

For four free standing pile group

$\varphi =arctan\left(\frac{d}{s}\right)=18.3$

${\eta }_g=1-\frac{18.3}{90}\left[\frac{2\times 1+2\times 1}{2\times 2}\right]$

$=0.797\underset{–}{\sim }80\%$