A series of shear interface experiments on a type of loess and rough concrete interface under conditions of different initial water contents (16%, 21%, and 26%), dry densities (1.30 g/cm³, 1.52 g/cm³, 1.70 g/cm³) and normal stresses (50 kPa, 100 kPa, 200 kPa) were conducted to further understand shear deformation and strength characteristics of a loess and rough concrete interface combined with loess deformation monitoring method of gypsum powder line method. A discrete element method (DEM) model was then established, calibrated against the experimentally obtained shear stress–displacement curves, and run to investigate the shear deformation, contact force chain and fabric evolution processes at the microscopic level. The results show the following: (1) The shear deformation and strength behaviors of the loess and rough concrete interface were significantly impacted by the initial moisture content, dry density and normal stress. (2) The shear deformation of the loess increased with the increase in initial moisture content, and decreased with dry density and normal stress. (3) The shear strength of the loess and rough concrete interface increased with the increase in dry density and normal stress, and decreased with the increase in initial moisture content. (4) The evolution of the shear deformation, contact force chain and fabric of the loess-concrete rough interface were explored and analyzed from a microstructural perspective. This study contributes insights critical to construction of the pile-loess systems in Chinese Loess Plateau regions.

Solar radiation and snow accumulation are the two important factors impacting thermal states of the permafrost beneath embankments with asphalt pavement in the Arctic regions, which can threaten the stability of permafrost and thus operation safety. In this study, we adopted the numerical simulation method to evaluate and compare the cooling performance of the proposed three types of embankments, namely, grey near-infrared reflective coating embankment, sun/snow shield embankment, and grey near-infrared reflective coating–sun/snow shield embankment, thereby mitigating the effect of the solar radiation and snow accumulation in the Arctic regions. Results show that (1) the grey near-infrared reflective coating mainly cools permafrost underlying the asphalt pavement and cannot mitigate thermal imbalance issue of two sides in embankment (shady–sunny slope effect), while the sun/snow shield embankment mainly cools the permafrost under two side slopes and can significantly mitigate shady–sunny slope effect; (2) grey near-infrared reflective coating–sun/snow shield embankment can not only effectively cools the permafrost beneath the embankment but also addresses the shady–sunny slope effect; (3) these three proposed types of embankments can significantly increase the permafrost table under sunny slope by 25.25%, 72.41%, and 76.94%, under asphalt pavement by 70.85%, 65.02%, and 81.91%, and under shady slope by 41.07%, 63.40%, and 69.42%. This study contributes to the design, construction, and maintenance of permafrost embankments in Arctic regions.

The tensile strength of loess, a key mechanical parameter for crack-related failures, has not received much attention in previous research, with the literature demonstrating a lack of systematic studies. Therefore, in this study, the variations in the tensile strength, crack distribution, crack number, and internal stress of an undisturbed loess were studied in detail by combining the unconfined penetration test (UPT) and a discrete element method (DEM)-based simulation. The tensile strengths of undisturbed loess samples with different height–diameter ratios (1, 1.5, and 2) were investigated by using the UPT with loading plates of different diameters (12.86 mm, 15.56 mm, and 19.02 mm). DEM simulation was then conducted based on the experimental results. The results showed that (1) the tensile strength of undisturbed loess decreased with increased height–diameter ratio, while it increased with an increase in the diameters of the loading plates; (2) the DEM simulation allowed us to study the tensile characteristics of the undisturbed loess, and the simulated tensile strengths obtained via DEM simulation agreed with those determined via the UPT; (3) the distribution of internal stress and crack number in the DEM model were significantly influenced by the height–diameter ratio and loading plate diameter; (4) the number of cracks in the DEM model increased with an increase in the diameter of the loading plate, while the number of cracks first increased and then decreased with an increase in the height–diameter ratio. This study helps us to understand the variation in the tensile strengths of undisturbed loess samples from both macroscopic and microscopic perspectives. It is expected to serve as a reference for design, construction, and maintenance in engineering projects hinging upon the Loess Plateau region in China.

A series of (45 sets) true triaxial shear tests with controlled suction and under conditions of equal-b and equal-p are performed on unsaturated compacted loess. By incorporating the effects of matric suction in unsaturated loess and the influence of middle principal stress conditions, the characteristics of the stress–strain curve evolution, strength failure line and related strength parameters of the unsaturated compacted loess under complex stress paths are analyzed, and the applicability of different strength criteria is analyzed. The results indicated that both the matric suction and the middle principal stress condition have significant effects on the magnitude of shear stress. While matric suction exerts minimal effect on the configuration of the stress–strain curve, the middle principal stress condition markedly affects its shape. A function is established to approximately describe the correlation between the strength-related parameters and the middle principal stress coefficient. A comparison of the failure lines predicted with several strength criteria and the experimental data indicates that the experimental results of unsaturated compacted loess under a controlled suction state are consistent with the results of the predicted failure lines of the Lade–Duncan strength criterion. The findings can provide crucial theoretical support for engineering design and disaster prevention in loess regions.