The density-moisture curves for five crushed sandstone particle mixtures, with different grain size distribution curves, were determined by a standard compaction test. The values of the maximum dry density and optimum moisture content, deduced from the compaction tests, range from 2.04 to 2.11 g/cm³ and from 7.56 to 10.11%, respectively. The variations of the maximum dry density and optimum moisture content of the mixtures, with the median particle size, gravel content, uniformity coefficient and curvature coefficient, were analysed. The grain size distribution curve for each tested material after compaction was analysed by a standard sieve analysis test for the purpose of analysing the particle crushing. Testing results indicate that the difference in the grain size distribution curves after compaction, for the tested materials with the same original particle size distribution curve and different water contents, is very small. The average relative breakage was therefore used to evaluate the particle crushing. The effects of the factors, such as the median particle size, gravel content, uniformity coefficient and curvature coefficient, on the average relative breakage, were analysed based on the testing data.

In this study, the size effect on the tensile properties of compacted clay was investigated by using deep beam specimens. The equation for calculating tensile strength considering the effect of specimen thickness was established based on the results of finite element analyses. By using deep beams, Brazilian discs, and three-point bending beams, the tensile strength of compacted clay was tested to verify the rationality of deep beam specimens. Furthermore, differences in the tensile properties of deep beams of different sizes (widths of 50, 75, 100, and 125 mm) were explored. The results showed a significant size dependence of the peak load and peak displacement. As the specimen size increased, the tensile strength of the soil exhibited a linearly decreasing trend, whereas the energy required for tensile damage gradually increased. The Bažant size effect model was used to predict the strengths of compacted clays, and a peak load prediction model that considers the structural parameters of the specimens was developed.

Rock slope instability is a prevalent geological hazard that imposes significant adverse impacts on engineering activities. Although existing studies have focused on homogeneous rock slopes, the theoretical models for quantifying the stability of soft-hard interbedded anti-inclined slopes remain underdeveloped, primarily due to the complex force transfer mechanisms involved. This study proposed a novel theoretical model for the stability analysis of soft-hard interbedded anti-inclined slopes under rainfall conditions. The framework models stratified rock layers as layered cantilever beams with material heterogeneity. Based on the principle of deformation compatibility, it comprehensively accounted for interlayer force transfer and strength degradation resulting from differential deformations among rock layers. Furthermore, it integrated the critical instability length induced by the self-weight of rock layers to determine the fracture depth. The proposed method was validated against engineering case studies and physical model tests, with error falling within an acceptable range. Compared to existing theoretical methods, the proposed method provided a more realistic representation of the slope’s stress field. The analysis results demonstrate that rainfall not only reduces the inclination angle of the failure surface but also leads to an approximate 30% decrease in the safety factor. The proposed theoretical model is particularly useful for quickly calculating the stability of soft-hard interbedded anti-inclined rock slope under rainfall conditions, compared to complex and time-consuming numerical simulation calculations.