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RESEARCH PAPER

Monotonic and Cyclic Behavior of Salt-Encrusted Flat (Sabkha) Soil Ahmed Alnuaim1

•

Naif Alsanabani1 • Abdulhafiz Alshenawy1

Received: 23 May 2020 / Revised: 20 July 2020 / Accepted: 11 August 2020 Ó Iran University of Science and Technology 2020

Abstract Sabkha (salt-encrusted flat) soils are problematic because they lose strength due to wetting, and they have liquefaction potential. These soils are spread in North Africa, Australia, and most of the Eastern Province of Saudi Arabia. Owing to a lack of experimental studies, the cyclic behavior of sabkha soils is relatively unknown. The monotonic and cyclic behaviors of sabkha soil were studied based on effective stress (50, 100, and 150 kPa) and cyclic stress ratio (CSR) (0.15, 0.35, and 0.65) using cyclic triaxial and bender element tests. Results indicate that the sabkha exhibits ductile behavior with the cohesion value of 9.33 kPa and a friction angle of 33°. The maximum shear moduli are 18,900, 49,500, and 63,500 kPa for effective confining pressures of 50, 100, and 150 kPa, respectively. Furthermore, the shear modulus tended to decrease with shear strain for different cyclic stress ratios. On the other hand, the damping ratio depends on the level of the cyclic stress ratio. At a cyclic stress ratio of 0.15, the damping ratios remained constant with shear strain. For a cyclic stress ratio of 0.65, the damping ratios decreased with shear strain. However, at a cyclic stress ratio of 0.35, the damping ratio varied with shear strain depending on effective stress. Keywords Shear strain  Shear modulus  Damping ratio  Sabkha

1 Introduction Sabkha (salt-encrusted flat) soils are loose to medium dense and are problematic because they lose strength due to wetting. Sabkha has high dissolved salt concentrations, and a high liquefaction potential. Sabkha soil is widespread in semi-arid regions, such as North Africa, Australia, and parts of Saudi Arabia (Eastern, Western and South regions) [1]. Because of the rapid increases in the development, urbanization, and industrial activity of the Eastern Province of Saudi Arabia, the monotonic and cyclic behaviors of sabkha soil plays a role in the geotechnical and seismic design of foundation structures. Cyclic behavior is represented by the dynamic properties and liquefaction potential

& Ahmed Alnuaim [email protected] Naif Alsanabani [email protected] Abdulhafiz Alshenawy [email protected] 1

of soil. For analyzing dynamic problems such as vibration amplitude, foundation resonance, and seismic analysis, both shear modulus (G) and damping ratio (D) are required. A number of studies have focused on the characteristics of sabkha soils in terms of geology, structure, and volume changes [2–7]. Furthermore, many studies have examined the characteristics of the chemical stabilization of sabkha soil [8–11]. The behavior of deep foundations in sabkha soil was studied numerically by [12], whereas the seismic response of sabkha soil in Jubail was carried out by [13