Landslide dams are common worldwide, especially in tectonically active mountain regions, which are usually caused by natural hazards, such as mountain collapse, earthquakes, and mudslides. Landslide dams are mainly composed of loose soil and fragmented rocks with grain size spanning several orders of magnitude (Sun et al., 2016). The blockage of river channels by landslide dams results in raising water in upstream areas. With the increase in the water level of the dammed lake, the loose dam body will collapse catastrophically, causing anomalous destructive flood waves and posing a significant threat to downstream life and properties (Peng & Zhang, 2012). Therefore, the study of landslide dams and their consequences has acquired significant relevance in scientific research to predict and prevent landslide dam collapse. Many factors influencing the stability of landslide dams have been studied comprehensively, such as dam geometry (Chen et al., 2015), grains composition (Okeke & Wang, 2016), angle of dam downstream face (Gregoretti et al., 2010), and permeability (Shi et al., 2018). Among these factors, permeability is considered one of the critical factors affecting the stability of landslide dams (Costa & Schuster, 1988). The high permeability area of the loose dam body will increase the infiltration, which could cause seepage failure immediately (Shi et al., 2015).Previous studies on the hydraulic properties of landslide materials have revealed that the grain size distribution of the dam accumulation has significant impact on the seepage stability of landslide dams (Okeke & Wang, 2016;Zhu et al., 2020). The effect of grain shapes on permeability has also been investigated via laboratory tests (Wei et al., 2021) and numerical simulations (Garcia et al., 2009;Torskaya et al., 2014). The relationship between pore structure and hydraulic properties of landslide materials has not been fully understood, mainly due to the challenges in characterizing the pore structure of landslide materials. The complex pore structure originates from the quick deposits of landslide materials composed of poorly graded soils and fragmented rocks. The existing test results have shown 1∼2 orders of magnitude permeability variation for approximately the same porosity.