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Within the clear definition of a quick clay as being a soil which has a sensitivity greater than 30 and a remoulded strength less than 0.5 kPa, a general model for quick clay development is presented, based on the influences of various material properties and natural processes on the sensitivity and remoulded strength. The influences are separated according to depositional requirements and post‐depositional factors and according to whether the influence is to increase the undisturbed strength or to decrease the remoulded strength. Depositional factors are the requirements for a flocculated structure and the dominance of low activity minerals. Post‐depositional factors are cementation and slow load increase, which increase the undisturbed strength, and little consolidation, leaching and dispersants, which decrease the remoulded strength. The application of the model to marine, brackish water and freshwater sediments is discussed.

The sedimentary and evaporative environment that has prevailed on the southern shores of the Arabian (Persian) Gulf region, has produced salt encrusted flat areas known as 'sabkha', along the coast and in some nearby depressions.In this paper the morphology, development, mineralogy and hydrology of coastal sabkhas have been briefly reviewed. Geotechnical properties and problems associated with sabkha deposits have been described.The authors' general view of sabkha as cemented and uncemented layers of varying thickness and properties has been confirmed by a limited field study in terms of pits and boreholes carried out near Dhahran, Saudi Arabia. Calcium carbonate and more recent diagenetic minerals such as gypsum serve as the primary cementing agents.Laboratory experiments aimed at simulating the development of cementation in sabkha material, by chemically precipitating calcium carbonate and calcium sulphate within pluviated sand samples, have shown that marked increase in static penetration resistance is exhibited with the addition of 2-5% precipitate (by weight of sand) as compared to uncemented sands. The results also demonstrate the potential advantages of using static cone pentrometers in the field to assess the strength and layering of sabkha. Coastal Sabkha Morphology and developmentThe coastal sabkha plains generally lie above the high tide level and slope gently seaward at approximately 0.4 m per km (Evans et al. 1969). At their

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