Resembling brown wheat flour in shape, colour and texture, sabkha is a heterogenous saline soil, which is silky smooth and evaporates with the pleasant breezes.

There are two types of sabkhas: coastal, which appeared throughout the ages as a result of sea water evaporation and lowering of its level, and inland sabkha, caused by movements of the earth's crust due to winds, hurricanes, and other natural factors. The lands affected by the sabkha are no longer suitable for cultivation, not even for the construction of residential buildings or roads. Engineers, construction workers and geo-technicians have faced serious problems due to the soil’s fragility and inability to bear the pressure of construction loads.

On this topic, researcher Omaima Al-Shirawi of the Agricultural and Marine Sciences College conducted a study to develop solutions for the use of lands containing high levels of sabkha. Two techniques were used to improve the properties of the Omani sabkha soil and increase its strength: surface mixing of soil and deep mixing using the ordinary Portland cement and salinity-resistant cement, with or without the addition of cement kiln dust – a cost-effective leftover residue of cement during manufacturing.

Samples of sabkha soil from the Azaiba neighbourhood in Muscat underwent testing using two methods: surface mixing, i.e., dry mixing of the soil with ordinary Portland cement and salinity-resistant cement, both with or without cement dust. The samples were examined in three stages: first after 7 days, the second after 14 days and the third after 28 days. In the first sample, the soil was mixed with 100% Portland cement, the second sample was mixed with 50% Portland cement and cement dust, and the third sample was mixed with salinity-resistant cement and cement kiln dust, each at 50%.

Regarding deep mixing, a mixture of water and cement was added to the soil to determine its bearing strength after completion of the experiments. The unconfined compressive strength test was applied to the samples in the three stages (7, 14 and 28 days).

The results indicated that the two soil mixing techniques may be favourable for enhancing the results of the Omani sabkha soil strength. The unconfined compressive strength test supports such techniques in many construction applications. In addition, the surface soil mixing technique can enhance sabkha soil’s strength and mechanical properties, making it suitable for paving the base layers of roads. The tests also demonstrated that the deep soil mixing proved to be highly effective in improving soil quality, enabling it for use in various construction projects, including roads and residential or commercial buildings.

The study recommended examining all types of sabkha soil before determining which technique to use since the mineral composition, size and weight of the structure and the depth of the sabkha play pivotal roles in selecting the most suitable approaches to reinforce the sabkha and establish resilient structures atop it.