Awarded as the best online publication by CIDC
The ground conditions in hillsides of Hong Kong normally consist of colluvium overlying weathered and fresh rock. The groundwater flow in sloping ground may involve both perched and main water flow. As permeability of soil tends to decrease with depth, groundwater flow may take place in the upper aquifer which contains a perched water table.
The presence of pile groups below groundwater level hinders the flow of groundwater, leading to an increase on groundwater level. For major development in hillsides with plenty of deep foundations, the effect of rise in water table is sever. The increase in water table owing to damming effects of pile groups decreases the stability of slopes by reduction of shear strength of soils and may eventually cause slope failures.
This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.