Asphalt concrete core wall rockfill dam (ACCD) is a type of dam that uses asphalt concrete core wall as the antiseepage structure and rockfill as the supporting structure. Under action of external loads and modulus differences, interface between the core wall and transition layer is prone to shear deformation, which may lead to excessive shear and tensile stresses in the core wall, and even cause cracks. This paper aims to reveal mechanical behaviors and interaction mechanism of the interface between the asphalt concrete core wall and the coarsegrained soil transition layer. Interface shear tests were conducted under five normal stresses and five shear rates condition using an interface shear test system. The shear stress-displacement behavior and shear strength behavior of the interface were analyzed. Influence of normal stress and shear rate on the shear behavior of the interface was discussed. Nuclear magnetic resonance (NMR) and high-pressure permeameter were used to test internal pores and permeability of the asphalt concrete after shear action. The effect of shear action on apparent damage, pore structure, and permeability of the asphalt concrete was discussed. The results indicated that the interface exhibited strain hardening behavior. The interface undergoes shear compaction deformation. The shear stress, displacement, strength was positively correlated with normal stress and shear rate. Shear action causes damage to the asphalt concrete within a depth range of 43 -52 mm from the surface. The damage lead to increase in porosity in the damage influence area. The porosity remains below 3 % after shear action. The shear action did not significantly affect the anti-seepage performance of the asphalt concrete.

Rapid permafrost degradation is observed in northern regions as a result of climate change and expanding economic development. Associated increases in active layer depth lead to thermokarst development, resulting in irregular surface topography. In Central Yakutia, significant areas of the land surface have been deteriorated by thermokarst; however, no mitigation or land rehabilitation efforts are undertaken. This paper presents the results of numerical modeling of the thermal response of permafrost to changes in the active layer hydrothermal regime using field data from the village of Amga, Republic of Sakha (Yakutia), and mathematical analysis. The results suggest that restoring a thick ice-enriched layer will require increasing the pre-winter soil moisture contents in order to increase the effective heat capacity of the active layer. Snow removal or compaction during the winter is recommended to maximize permafrost cooling. The thickness of the restored transition layer varies from 0.3 to 1.3 m depending on soil moisture contents in the active layer. The modeling results demonstrate that damaged lands can be restored through a set of measures to lower the subsurface temperatures. A combination of the insulating layer (forest vegetation) and the high heat capacity layer (transition layer) in the atmosphere-ground system would be more effective in providing stable geocryological conditions.