Geotechnical behaviour of saline sabkha soils

Abstract

The behaviour of salt-cemented sabkha soil was investigated by considering the effect of brine and distilled water on its properties. Laboratory and field testing programmes were conducted to examine the effect of soaking and leaching on the structure, compressibility, collapse, permeability, load-carrying capacity and settlement of sabkha soil. Results indicate that the percolation of distilled water through the sabkha causes destruction of the natural cementation, leading to collapse, increase in permeability, reduction in strength and increase in settlement. Dissolution and leaching of halite, gypsiferous and calcarenite cements occur, leaving the quartz particles covered by a thin loose mat of illitic clay with large voids. The collapse deformation of sabkha is inclusively linked to the ambient salt complex, which determines the structural properties of the soil and promotes the development of collapse on wetting. The soaking of sabkha produces practically negligible collapse; leaching causes a significant collapse due to the softening, dissolution and effusion of salts from the soil skeleton. Le comportement d'un sol de Sabkha cimenté par du set a été étudié au travers de l'effet de la circulation d'une saumure ou d'une eau distillée sur ses propriétés. Des programmes d'essais réalisés en laboratoire et in-situ ont permis d'examiner l'influence d'une immersion et d'un lessivage sur la texture, l'effondrement dû à la compressibilité des minéraux, la perméabilité, la charge admissible et le tassement du sol. Les résultats montrent qu'une percolation d'eau distillée dans la Sabkha induit une destruction de la cimentation naturelle qui se traduit par un effondrement du sol, une augmentation de la perméabilité, une diminution de la résistance et un accroissement du tassement. La dissolution et le lessivage des minéraux halitiques, gypseux et calcaires constitutifs du ciment font que les particules de quartz ne sont plus recouvertes que par une couche d'illites mince, peu dense et a larges vides. La déformation par effondrement de la Sabkha est à relier au complexe salin présent qui, parce qu'il régit les propriétés texturales du sol, favorise le développement d'effondrements lors de l'humidification. Si l'effondrement résultant d'une immersion est quasiment négligeable, it ne l'est plus lors d'un lessivage et devient même important en raison du ramollissement, de la dissolution et de l'effusion des sels du squelette solide.

Cement-Stabilization of Sabkha Soils from Al-Auzayba, Sultanate of Oman

“…along the Arabian Gulf coast) (Ismael 2000;Abduljauwad and Al-Amoudi 1995;Akili 1981) They are formed due to the drop in sea level during the Quaternary and Recent Ages followed by evaporation. Environmental activities such as wind, temperature and biological activities all contributed to the formation of sabkha.…”

Cropland Soil Salinization and Associated Hydrology: Trends, Processes and Examples

“…Salt precipitation, especially subflorescence precipitation, greatly affects soil mechanical properties as salt crystallization may lead to soil cementation that holds sand and silt particles together and increases the shear strength and stiffness of soil during the drying process [42,43]. On the other hand, in cohesive soils, subflorescence salt crystallization may enhance weathering processes and reduce soil aggregate stability as the crystallized salt at the pores applies pressure against the pore walls that leads to disaggregation [44,45].…”

“…On the other hand, in cohesive soils, subflorescence salt crystallization may enhance weathering processes and reduce soil aggregate stability as the crystallized salt at the pores applies pressure against the pore walls that leads to disaggregation [44,45]. Naturally, salt precipitation in the soil pores changes the soil's hydrological properties and reduces percolation and evaporation processes as it reduces matrix porosity, permeability and vapour diffusivity [40,43,46,47]. Salt precipitation as efflorescent salt crust has a weaker effect on the physical properties of the soil-matrix itself, as crystallization takes action above the soil surface.…”

“…This process is the cause of the formation of many of the salinized soils found in dry areas around the world [43,[76][77][78], with an estimated total area of about 350 × 10 4 km 2 [9]. An example of soil salinization in an agricultural region, due to the presence of shallow and salty groundwater can be seen in the Gerar wash basin in the Northern Negev desert, Israel (Figure 3).…”

Capillary effect in salt-cemented media of particle sizes

“…Laboratory examinations of salt cementation have included the soaking behavior, leaching on the structure, collapse, and hydraulic conductivity of a salt-cemented soil (Abduljauwad and Al-Amoudi, 1995). Furthermore, the small strain stiffness of a particulate medium cemented by salt has been investigated by using wave based methods (Truong et al, 2009).…”