Ground engineering solution for sabkha soil

Around one-third of the world's land surface falls within arid climate zones, where sabkha soils are a prominent feature. With their low shear strength and susceptibility to voids and subsidence, these soils present significant challenges for engineers. MOHAMED WEHBI* emphasises the importance of careful planning when constructing in these regions and explores the stabilisation methods to address these challenges.

- Mohamed Wehbi

SABKHA soils, which are common in rapidly urbanising regions like the Arabian Gulf, pose significant construction challenges that necessitate solutions to mitigate subsidence and ensure safe, durable land use.

Derived from the Arabic word for "salt flat", sabkha refers to flat, low-lying areas common in arid regions.

Sabkha soils are characterised by their loose, compressible nature, limited bearing capacity and extremely high salt content, with brine salinity levels up to six times higher than seawater. Their loose structure allows high water infiltration. When wet, the dissolution of salt-binding agents weakens the soil, causing it to collapse. Upon drying, salt crystallisation and re-crystallisation can result in heaving, further destabilising the ground.

The fragility of the soil structure, combined with the hydration-dehydration cycle, amplifies instability, making specialised engineering solutions essential for construction.

Sabkha soils are widespread along the Arabian Gulf coast, a region housing significant infrastructure such as petrochemical plants, residential complexes and recreation centres. Studies reveal that sabkha soil's collapse potential increases with greater applied loads and higher compaction fluid content.

With multi-billion-dollar investments being made in petrochemical and residential projects, the need for effective soil stabilisation methods has never been greater.

STABILISATION METHODS

Given the prevalence of sabkha soils and the impracticality of avoiding construction on them, soil stabilisation is a crucial consideration. Various methods have been explored to address these issues.

Mechanical stabilisation methods include preloading, stone columns and dynamic compaction.