The use of weathered phyllite waste slags generated from the excavation of cuttings and tunnels as roadbed filler material can effectively address issues related to filler scarcity, environmental protection, and cost. This study focused on weathered phyllite obtained from a highway expansion project in the Longnan Area of Gansu Province, China. Various experiments were conducted in a laboratory setting, including compaction, unconfined compressive strength (UCS), California bearing ratio (CBR), permeability, and disintegration tests, to investigate the response of mixtures with different gravel contents (GCs), ranging between 30 %-70 % by weight of weathered phyllite filler (WPF). The test results indicate the presence of a critical GC threshold. At 55 % GC, the WPF exhibits optimal compaction, the highest UCS and CBR values, and the lowest permeability and disintegration rates. Upon reaching this critical GC threshold, the phyllite gravels contact each other to form a skeletal structure, while fine grains fill the gaps within this structure to create a denser skeleton configuration. Coarse phyllite gravels are more prone to fragmentation into finer grains, which can effectively occupy large, medium, and small voids between particles. Consequently, the WPF exhibits enhanced structural density and improved mechanical and hydraulic properties. These findings provide a theoretical reference for the engineering application of phyllite in mountainous projects.

Changes in the pore-water environment have an obvious effect on the physical and mechanical properties of soil. Traditional consolidation theory has not considered the influence of the hydrochemical environment on the mechanical properties of soil. In order to investigate the mechanism of chemical action on geotechnical properties, in this study, one-dimensional compression tests and scanning electron microscope tests are carried out on soils prepared with different concentrations of NaCl solution. The mechanical characteristics reveal that the compression index shows a gradual decrease with an increase in pore-water salinity, and the structural yield stress of the soil increases gradually with the increase in pore-water salinity, reaching a maximum value of 50.34 kPa with a salt content of 5%. Conversely, the change in osmotic suction has minimal impact on the rebound index. Notably, the pore-water salinity primarily affects the intrinsic compression behavior of soft clays, as evidenced by an increase in the slopes of the sedimentary compression curve before yielding higher pore-water salinity. Combined with the analysis of microscopic test results, it is found that as the osmotic suction increases and the interparticle hydration capacity decreases, the soil particles change from a dispersed state to an aggregate state, leading to an increase in mesopores, and this increase indicates that the ability of the soils to resist the external loads also increases, which means an enhancement of the structural characteristic. In addition, the coefficient of permeability of the soil decreases as the consolidation pressure increases. Chemical consolidation produced by the increase in pore salt solution concentration causes a decrease in pore ratio, resulting in a smaller coefficient of permeability, and there exists a critical value for the effect of salt on the coefficient of permeability of the soil, which is related to the structural yield stress of the soil. This research provides a theoretical basis for the settlement prediction and the safety evaluation of soft ground in coastal areas.

This study investigates the pore water pressure and water content on a forested slope, focusing on the impact of canopy interception across various rainfall intensities. The study was performed on slopes in the Sukajaya Sub District of West Bogor, West Java, Indonesia, a region that encountered landslides in 2020. Soil hydraulic characteristics, soil textures, saturated water content, and soil moisture content at different pressures, were assessed at different slope locations and depths. The pore water pressure and water content change were simulated using the one-dimensional uniform (equilibrium) finite element model of water movement using the modified Richards and were executed with the HYDRUS 1D model across six scenarios of a combination of three rainfall events at two initial conditions of water content, contrasting bare and vegetated slopes of Maesopsis eminii, which exhibited 35% canopy interception. Findings demonstrate that bare soil attains saturation more rapidly, resulting in elevated pore water pressure and increased susceptibility to slope instability. Conversely, vegetated slopes have delayed saturation owing to canopy interception, which diminishes the volume of rainfall that reaches the soil. The results highlight the crucial function of vegetation in preserving slope stability by regulating soil water pressure and water content, particularly during intense rainfall events. This research enhances comprehension of how vegetated areas might reduce landslide hazards in high-rainfall environments.