A laboratory investigation on the effect of crushability on the interface parameters of Hormoz carbonated soil

Carbonated sands, also referred to as calcareous sediments, are a common type of soil in marine environments such as the West Australia Continental Platform, South China Sea, Persian Gulf and Oman sea and many parts of the world. During pile driving in such soils, imposed shear and volumetric strain to particles, crushing occurs which leads to change in the particle size distribution as well as interface properties of the soil-pile system. In this study, two types of sands (siliceous Firoozkooh-161 and carbonate Hormoz sand) and three types of materials (steel, wood and concrete) have been selected and were investigated using a direct shear and a tall oedometer apparatus for the prediction of the sand-pile interaction properties considering particle crushing. The smoothness and roughness of materials as well as soil relative density, and shearing rate on the interface properties were examined. Based on the results, smooth steel, wood at the direction of vessels, rough steel, smooth concrete, wood at the right angle to vessels, and rough concrete represent the lowest to the highest interface shear strength, respectively. Results revealed, increasing soil relative density leads to an increase in the interface friction angle. The results also emphasized that increasing the vertical stress leads to increasing in the breakage index both dense and loose states, however, the amount of particle increases with density. Particle crushing also decreases significantly when soil interact with smooth surfaces. Furthermore, increasing the shearing rate enhances the shear strength and reduces particle crushing. It also investigated that Hormoz sand compared to Firoozkooh sand exhibits a higher level of particle breakage due to the shape and texture of carbonated particles. Finally based on the achievements of this research, the limit values for skin friction bearing capacity of piles driven in carbonate and siliceous sands proposed in ARGEMA and API approach were examined.