A CONCEPTUAL MODEL OF ENVIRONMENTAL, GEOLOGICAL AND GEO-TECHNICAL RESPONSE OF DREDGED SEDIMENT FILLS TO GEO-DISTURBANCES IN LOWLANDS

Abstract

In mineralogical evolution of clays, amongst the weathering phenomena, hydrolysis is very
important. Clay minerals of 2/1 type, which first appear, are silica-rich with two tetrahedral silica sheets. The
1/1 clay minerals that follow have but one tetrahedral sheet and the last, gibbsite, has none at all. It is
important to consider temperate and tropical environments. The kaolinite-gibbsite association is mostly
characteristic of tropical environments. When all the silicates disappear to the gain of gibbsite, it is called
total hydrolysis. Kaolinite and gibbsite are stable products in tropical environment. In temperate
environment, weathering is often halted at the stage of 2/1 minerals (for example montmorillonite). This
weathering can continue with kaolinite. In both cases it is partial hydrolysis only. This shows that the tropical
environment is the only one to accumulate large quantities of gibbsite. In temperate climate only small
amount of gibbsite is produced. In this paper a conceptual model of three layer system consisting of kaolinite,
illite and montmorillonite is considered with symbols K, I, M respectively. The Geo- disturbance caused by
dredging varies from pocket to pocket in the soil profile. The permutations and combinations of placed
dredged materials are considered with different combinations of the three clay types (KIM). All possible
combinations will yield 24 different Geo-Technical sequences. The above analysis is applied to important
lowland Geo-technology problems in coastal areas such as sub-grade in pavement construction, land
reclamation and fills to contribute to marine multi-inter-disciplinary research.