Q$.5($a$)$ Identify the main problem affecting the design of piles founded in karst formation. $(6$ marks$)$

$($b$)$ A circular pile is driven into two layers of saturated clay with undrained shear strength given in Figure Q$\mathrm{.}5($a$).$

$($i$)$ Calculate the end bearing capacity $(Q_p)$ of the pile using the Meyerhof's method with reference to Chart Q$.5$ on page $9.$

$(5$ marks$)$

$($ii$)$ Calculate the skin resistance $($Qs$)$ of the pile by means of the $$ method. $(8$ marks$)$

$($iii$)$ Using a Factor of Safety of three $(3),$ estimate the net allowable pile load capacity $(Q_{\text{a}\text{l}\text{l}}).$

$(6$ marks$)$

Figure Q$\mathrm{.}5($a$)$ Pile driven into clay