Geotechnical characteristics of a selected shallow marine area considered for quay wall construction

Abstract

Quay wall defense systems are useful marine structures for berthing of vessels and other marine operations. Before quay-walls are constructed in shallow marine areas, there is need for adequate subsurface investigation to ensure proper design and construction of quay-walls that will be able to satisfactorily support the facilities they are intended for. This research work focuses on subsurface investigation involving the geotechnical characterization of soil in a selected shallow marine area in the Niger Delta area of Nigeria. Percussion rigs were used for both the on-land and over-the-water borings. A total of seven (7) on-land and six (6) over-the-water borings, all to a depth of 40 m each below existing ground level and sea bed respectively, were carried out. Field and laboratory tests were performed in order to effectively characterize the soils. Stratigraphy of on-land borings showed soft fibrous organic peaty clay layer, underlain below by silty sands and clays. Beneath this layer to the end of boring is well-graded sands and gravels. The borings over-water had a very soft to soft clay layer underlain by silty-sand, being underlain by poorly-graded sands and well-graded sands to the limits of the borings. Deep foundation systems employing reinforced concrete piles to depths (coinciding with the sandy horizon) were recommended for the on-land piles, reinforced hollow cylindrical steel piles for piers and piles for offshore landing jetties, and concrete sheet piles for shore protection works. This will form the ballasts for mooring of cargo vessels for conveying oil and gas final products.