Over the past two decades a number of main drainage and sewerage schemes constructed or currently under construction in coastal towns of LIbya have encountered a variety of ground problems. Locations involved are Tripoli, Benghazi, Tobruk, Derna and Misurata.
The geological setting of the work includes coastal dunes, sabkha deposits, terra rossa, limestone and marls—often with a capping of duricrust. Along the shore and in sabkha areas ground water is at or near sea-level, rising gradually inland. Thus, for a project serving large areas, excavation conditions vary significantly from place to place.
This paper describes in a geological context the construction methods adopted, with special reference to the works at Benghazi. Problems encountered include: culvert construction across soft sabkha deposits with a high water table; the penetration of caprock; high ground water inflows from karstic fissures; the provision of suitable materials for use as concrete aggregate and filter media.