Investigation of flow characteristics of landslide materials through pore space topology and complex network analysis

Abstract

Unlike embankments, earth dams, and other man-made structures, most landslide dams are formed by rapid accumulation of rock or debris rather than mechanical compaction; thus, they are loose and pose a great risk of seepage failure. Landslide materials usually have complex pore structures with randomly distributed pores of various sizes, making the flow and transport processes very complex. Aiming at these challenges, we have studied the influences of pore structure on the micro-and macroscale flow characteristics of landslide materials. First, landslide materials are simplified as spherical granular packings with wide grain size distributions. Then, we use finite difference method (FDM) and lattice Boltzmann method (LBM) to simulate the fluid flow through granular packings and calculate their permeability. We find that both the correlation between pore-scale velocity and throat diameters and the correlation between macroscopic permeability and average throat diameters follow a power-law scaling with an exponent close to 2, in agreement with the Hagen-Poiseuille equation for laminar flow in pipes, suggesting that the relationships in complex pore structures are conformed with the simple theory. Moreover, we propose a new method by combining pore networks and complex networks to characterize the pore structure. The network analysis illustrates that granular packings with different permeability display distinctive distributions of pore throat size and pore connectivity and their correlations. Compared with disassortative pore networks, assortative ones generally have higher permeability. Furthermore, pores with larger closeness centrality have higher flow efficiency that results in higher macroscopic permeability.