$13\mathrm{.}1$ Figure P$13\mathrm{.}1$ shows a drilled shaft in sand. Determine the maximum load that can be allowed on it$.$ Assume ${}^{\text{'}}=0\mathrm{.}6{}^{\text{'}}$ and allow a factor of safety of $4.$ Use Berezantzev et al$.\text{'}$s Eq$.(13\mathrm{.}18)$ for computing the point load. What fraction of the load$-$carrying capacity is derived from the shaft?

FIGURE P$13\mathrm{.}1$