$9\mathrm{.}7.$ A retaining wall having a smooth vertical back retains a dry,

cohesionless backfill. State, giving reasons, how the active earth pressure

exerted by the backfill will change in each of the following cases:

$($a$)$ the backfill becomes saturated due to capillary water, while the

ground water table remains below the base of the wall.

$($b$)$ the ground water table rises above the base, but there is no capillary

water.

$($c$)$ the given backfill is replaced by a cohesionless soil having :

$($i$)$ same unit weight but greater angle of internal friction.

$($ii$)$ same angle of internal friction but greater unit weight.

$($iii$)$ same usit weight and angle of internal friction, but having a small

apparent cohesion.