According to Rankine's formula, minimum depth of foundations, is
A
$$\frac{{\text{P}}}{{\text{w}}} \times {\left( {\frac{{1 + \sin \varphi }}{{1 - \sin \varphi }}} \right)^2}$$
B
$$\frac{{\text{P}}}{{\text{w}}} \times {\left( {\frac{{1 - \sin \varphi }}{{1 + \sin \varphi }}} \right)^2}$$
C
$$\frac{{\text{P}}}{{2{\text{w}}}} \times {\left( {\frac{{1 - \sin \varphi }}{{1 + \sin \varphi }}} \right)^2}$$
D
$$\frac{{\text{P}}}{{\text{w}}} \times \frac{{1 + \sin \varphi }}{{1 - \sin \varphi }}$$
Correct Answer: $$\frac{{\text{P}}}{{\text{w}}} \times {\left( {\frac{{1 - \sin \varphi }}{{1 + \sin \varphi }}} \right)^2}$$
