This study explores the impact of granular materials with varying moisture contents and particle sizes, as well as block materials with different volumes and layer strengths, on landslide fragmentation, motion, and deposit. The experimental results show that as particle size increases, the maximum dam height (Hmax) and width (Wmax) increase, while the minimum dam height (Hmin) decreases, indicating an improvement in the stability of landslide dams. Larger particle sizes are less sensitive to changes in moisture content. Additionally, moisture content inhibits Wmax, with mixed particle-size materials showing a greater reduction compared to single particle-size materials. As Wmax increases, the maximum dam length (Lmax) decreases exponentially. Sliding time (Ts), deposition time (Td), and total time (T) decrease as particle size increases. For mixed particle-size materials, a more continuous particle size distribution further reduces Ts, Td, and T. Block material experiments show that with increasing block volume, Wmax, Lmax, and Hmax increase significantly, with corresponding increases in Ts, Td, and T. When the strength of the lower layer material decreases, Wmax and Hmax decrease, while Ts, Td, and T increase. Conversely, when the lower layer material strength increases, the opposite effect is observed. Frictional energy loss (Ef) is the primary energy loss pathway, with both total energy loss and Efdecreasing with increasing particle size. Localized energy losses are mainly due to terrain collisions, independent of moisture content.

High-latitude permafrost, including hydrate-bearing frozen ground, changes its properties in response to natural climate change and to impacts from petroleum production. Of special interest is the behavior of thermal conductivity, one of the key parameters that control the thermal processes in permafrost containing gas hydrate accumulations. Thermal conductivity variations under pressure and temperature changes were studied in the laboratory through physical modeling using sand sampled from gas-bearing permafrost of the Yamal Peninsula (northern West Siberia, Russia). When gas pressure drops to below equilibrium at a constant negative temperature (about -6(degrees)C), the thermal conductivity of the samples first becomes a few percent to 10% lower as a result of cracking and then increases as pore gas hydrate dissociates and converts to water and then to ice. The range of thermal conductivity variations has several controls: pore gas pressure, hydrate saturation, rate of hydrate dissociation, and amount of additionally formed pore ice. In general, hydrate dissociation can cause up to 20% thermal conductivity decrease in frozen hydrate-bearing sand. As the samples are heated to positive temperatures, their thermal conductivity decreases by a magnitude depending on residual contents of pore gas hydrate and ice: the decrease reaches similar to 30% at 20-40% hydrate saturation. The thermal conductivity decrease in hydrate-free saline frozen sand is proportional to the salinity and can become similar to 40% lower at a salinity of 0.14%. The behavior of thermal conductivity in frozen hydrate-bearing sediments under a pressure drop below the equilibrium and a temperature increase to above 0 C-degrees is explained in a model of pore space changes based on the experimental results.