Well Constructions at Sea

Abstract

For the purpose of groundwater investigation, relating to the dry dock construction, two types of wells with 31m length having different screen diameters,100mm and 200mm, were constructed in the sea bed at the depth of 11∼ 12m. These wells must have the cut-off structure to eliminate the sea water and unexpected strata water.
Bentonite-cement mixture was utilized for a triple-tube 100mm diameter well to cut off water above the aimed strata. For the same reason, mortar was utilized for a double-tube 200mm diameter well. The wells were sustained by platform and piles to avoid the damage of cut-off structure due to oscillatory motions produced by tides and ocean waves.
Pumpages were stable during full-pumping after the well construction. The observed water levels in these wells without pumping were higher than tidal levels, and the peaks of well water level were observed later than those of tide level. According to these facts, and observations during the construction, it was concluded that these wells were appropriately planed and constructed to investigate the groundwater at the sea bed.