Sediment transport is inherently a multi-phase phenomenon, encompassing grain-scale processes such as particle collisions and prolonged particle interactions with the fluid medium. While multi-phase models have garnered attention in the past decade, they still exhibit several limitations. Notably, these models struggle to accurately produce shear-induced volume changes and the consequent pore-pressure feedback, both of which play pivotal roles in subaqueous landslides. This study is dedicated to the development of an innovative multi-phase model for sediment transport, based on an Eulerian-Eulerian framework. The proposed model introduces a novel evolution equation specifically designed to determine the static solid pressure resulting from prolonged particle interactions. This equation effectively characterizes shear-induced volume changes in plane-shear configurations, addressing a critical limitation in existing models. Moreover, the newly devised multi-phase model demonstrates remarkable capabilities in capturing distinctive features associated with pore-pressure feedback, including the diverse collapse dynamics observed in granular columns with varying packing densities. Beyond theoretical advancement, this model finds practical applications in simulating waves generated by landslides and investigating the morphodynamics of gravel beaches. In summary, this research makes a significant contribution to the field of sediment transport by mitigating existing model limitations and providing a comprehensive framework for understanding the complexities of sediment motion, particularly in the context of subaqueous landslides.

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Keywords：Multi-phase model; Sediment transport; Pore-pressure feedback; Underwater landslide; Gravel beach.