This study presents the interfacial shear properties of carbonate sands and carbonate gravels based on the direct shear tests. The results showed that the ultimate state friction angle of carbonate soil was related to relative density and particle size, whereas the phase transformation friction angle was almost a constant parameter which was larger than that of siliceous sand. The ratio of interfacial friction angle to the internal friction angle is ranged from 0.865 to 0.942. It could be useful to make the design in carbonate soil.


Understanding the interfacial shear strength characteristics of carbonate soil is critical to the infrastructure design, such as slop reinforcement, backfill-retaining wall, soil-anchor contact, and pile. Therefore, the interfacial shear characteristics play an important role in the capacity of infrastructure design.(Potyondy, 1961; Bosscher and Ortiz, 1987).

The interfacial shear characteristics have been studied by multiple methods. These studies have demonstrated that interfacial shear strength characteristics are influenced by many factors, such as the gradation, specimen density (Lopes and Ladeira, 1996), vertical stress (Ho et al., 2011), shear rates(Sweta and Hussaini, 2018), particle size (Vangla and Latha, 2015), morphological property of sand (Lashkari et al., 2020), and the roughness of contact surface (Han F et al., 2018).

Carbonate soil has unique characteristics of irregular shape, high porosity, and fragmentation. These properties made carbonate soil exhibit different physical and mechanical characteristics from terrigenous sediment. Therefore, understanding the interfacial shear characteristics of carbonate soil is important in offshore engineering. Recently, some studies have been conducted on interfacial shear characteristics of carbonate sand (Vangla and Latha, 2015; Wang et al., 2019; Shang et al., 2020).

However, most of the interfacial shear tests were performed on the carbonate soil under constant load conditions. In practice, the load could be applied rapidly, and even the sand may be in undrained condition, especially in the marine environment, such as pile driving, the foundation stability in storm surge. In these cases, sand was maintained in undrained conditions, and the volume of sand is considered as constant.

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