This paper documents field and laboratory testing performed on Sabkha at a project site located in the Middle East. Constructability of placing fill material on Sabkha was assessed to ensure that temporary structures could be built on the fill material overlying Sabkha. The field investigation included:
performing seventeen field Dynamic Cone Penetrometer (DCP) Tests to estimate shear strength parameters and Sabkha thickness,
excavating two test pits to collect composite Sabkha samples for geotechnical and chemical laboratory testing,
and conducting a field test pad to assess the required fill material thickness over Sabkha for stability of operating equipment. Laboratory testing indicated low shear strength parameters and a high concentration of chlorides and sulphates. Finally, field observations from the field test pad indicated that in order for equipment to operate in stable conditions during placement of the fill over Sabkha, the thickness of the fill material must not be less than 70 cm. Construction methodology for fill material placement over Sabkha was developed and applied for construction of temporary structures.
Sabkha is defined as a salt bearing arid climate deposit which consists of sand deposits mixed with silt and clay particles. Sabkha has:
low shear strength,
high soil compressibility, and
high concentration of chlorides and sulphates which are corrosive to concrete, steel, and other materials. Under climate changes, significant volume change occurs when naturally occuring gypsum undergoes hydration to form anhydrite and dehydration to reform gypsum again (Amin, 2004). Groundwater movement related to evaporation precipitates salts at or near the surface, and as a result, temporary cementation can take place in the upper layer, forming a surface crust. Permanent structures are not recommended to be constructed on Sabkha unless soil improvement, removal and replacement, or piling is considered.