Particle gradation effect on the shear-dilatancy of granular soils was studied through a series of drained triaxial tests using the discrete element and finite difference methods (PFC3D-FLAC3D). Spherical particles with different coefficients of uniformity Cu and median particle sizes D50 were assembled to exclude the strong size-shape correlation in natural sands. Four groups of Cu and four groups of D50 at the same void ratio ecprior to shearing, and seven more groups with the same void ratio e0 prior to isotropic compression were tested. Various mechanical behaviors were analyzed, including the stress-strain response, the stress-dilatancy response, friction angle, and fabric anisotropy. Cu significantly influences the peak friction angle, the maximum dilation angle, and the anisotropies of normal contact force and contact normal, whereas these are almost independent of D50. The contribution of the maximum rate of dilation to the excess friction angle is largely independent of Cu and D50 for spherical particles. (c) 2024 The Society of Powder Technology Japan. Published by Elsevier BV and The Society of Powder Technology Japan. All rights are reserved, including those for text and data mining, AI training, and

Plastics within municipal solid waste (MSW) are non-degradable. As MSW continues to degrade, the relative content of plastics rises, and particle gradation may also change. Moreover, throughout the landfilling process, MSW is subjected to various stress conditions, potentially influencing its mechanical properties. This study explored the effects of varying plastic contents, different particle gradations, and distinct stress paths on the mechanical properties of MSW, and consolidated drained triaxial tests of 42 groups of reconstituted MSW specimens were conducted. The results showed that there was an optimal plastic content of 6-9 % for MSW, where the shear strength of MSW was higher than that of MSW with other plastic contents. When the stress path changed from TC45 to TC72, the optimal plastic content of MSW changed from 6 % to 9 %. As the plastic content increased, both the cohesion and internal friction angle of the MSW initially increased, then subsequently decreased. The impact of plastic content on cohesion was more pronounced than on the internal friction angle, especially at larger strains. Under various stress paths, MSW with distinct particle size distributions demonstrated diverse stress-strain behaviors. Traditional criteria for evaluating well-graded conditions in soils are not suitable for MSW. The effect of gradation on the cohesion of MSW is essentially due to the predominant role of fiber content; the relationship between gradation and the internal friction angle in MSW is complex and correlates closely with the content of both coarse and fine particles, as well as fibers. This study serves as an essential reference for predicting deformations in landfills and analyzing the stability of landfill slopes.

Particle gradation is an important feature of granular materials, which has a significant influence on the mechanical properties of soil. Several dynamic compaction (DC) tests for mono-sized dry sand samples and a well-graded dry sand sample were modeled using discrete element method. The effect of particle gradation on crater depth was analyzed as well as coordination number, porosity and contact stress from a microscopic view. It is indicated that the change rates of dynamic stress, coordination number and porosity of the well-graded sample were greater than the results from the mono-sized samples. For the mono-sized samples and the well-graded sample, the differences in dynamic contact stress, coordination number and porosity became larger as the distance of measurement point from ground surface increased. The results also demonstrate from a microscopic view that the well-graded soil and the mono-sized soil with smaller particle size were more prone to become dense under DC. This study at a grain level is helpful to understand the microscopic mechanism of DC and has a certain guiding significance to the construction of DC.

Hydro -thermal coupling is the essence of the freeze -thaw process, and theoretical studies of this coupled process have been hot topics in the field of frozen soil. Darcy's law of unsaturated soil water flow, heat conduction theory, and relative saturation and solid -liquid ratio are based on this paper. According to the principle that the cumulative curve of particle gradation of canal foundation soil is similar to soil -water properties. A soil -water characteristic curve is derived using the cumulative particle gradation curve. VG model is then used to fit soil -water characteristic curves to obtain the canal foundation soil's hydraulic characteristic parameters, and the established hydro -thermal coupling model is modified to reflect canal foundation soil hydro -thermal evolution more objectively. A closed system one-way freezing test method is used to verify the feasibility of the proposed method in this part. The results show that the optimal parameters of the VG model of the subsoil are a = 0.06, n = 1.2, and m = 0.17, and the temperature and water fields obtained from the simulation are in good agreement with the measured data, showing the utility of the hydro -thermal coupling model in predicting hydraulic parameters. Analysis of the multi -field interaction mechanism and dynamic coupling process of the canal foundation soil during freezing and thawing. This has great importance for preventing freezing damage in canals and protecting agricultural safety.

Soil-rock mixture (SRM) is a special geomaterial that is composed of soil and a certain percentage of rock blocks with various sizes and strengths. It has high structural strength and renewable resources that are used as filler in subgrade, construction material and embankment dams. However, the mechanical properties of the soil-rock mixture are sophisticated owing to the complicated interaction between soil and rock particles. Previously, many experimental investigations were conducted to focus on shear behaviours and the influencing factors of SRM. Yet, limited work has been done to underline the effect of particle size distribution towards SRM shear strength parameters. Thus, this study conducted an SRM shear test with three different kinds of gradation and rock block percentages. Various soil densities, porosities and different framework structures have resulted from different rock particle concentrations. From the results, the well-graded SRM shows a non-linear trend of cohesion value while uniformly graded and gap- graded SRMs shows contradicting trend respectively. The result and analysis in this study are especially useful in analysing its influence on the shear strength parameters of SRM with different rock block percentages.