Triaxial compression tests were carried out on artificially structured soil samples at confining pressures of 25, 37.5, 50, 100, 200, and 400 kPa. A binary-medium constitutive model for artificially structured soils is proposed based on the experimental results, the disturbed state concept (DSC), and homogenization theory. A new constitutive model for artificially structured soils was formulated by regarding the structured soils as a binary medium consisting of bonded blocks and weakened bands. The bonded blocks are idealized as bonded elements whose deformation properties are described by elastic materials, and the weakened bands are idealized as frictional elements whose deformation properties are described by the Lade-Duncan model. By introducing the structural parameters of breakage ratio and local strain coefficient, the nonuniform distribution of stress and strain within a representative volume element can be given based on the homogenization theory of heterogeneous materials. The methods fo...

A new gradation equation that can describe the particle-size distribution curves of soils with continuous gradation is presented. The results obtained for a large amount of test data from soil gradations prove that the equation is applicable over a wide range of soils, including rockfill, gravel, sand, and clay. Three parameter determination methods are proposed, with the optimization method yielding the best results. The possible values of the parameters m and b in the proposed equation were intensively investigated, and the suggested ranges of the parameters were found to be b < 1 and m > 0. However, for most soils, these parameters have values of –4 < b < 1 and 0 < m < 12. The study of the features of the gradation equation and the resulting curves in P-logd coordinates revealed that the parameter b determines the gradation curve shape. If b ≤ 0.5, the gradation curve is hyperbolic, and if 0.5 < b < 1, the curve is sigmoidal. The parameter m determines the gradation curve slope, which increases with increasing m. Several soil gradations used in earth-rockfill dams worldwide were investigated to summarize the gradation characteristics, and the results revealed that the values of the parameters b and m for the rockfill fall within a narrow range. The proposed equation is more convenient for expressing the soil gradation and makes it possible to quantitatively describe the relationship between the mechanical properties of the rockfill and the gradation.

Landslide dam is one of the main types of barrier dams, whose structure is loose and stability is poor. Once seepage failure occurs, it will threaten the life and property safety of downstream people. The particle composition and depositing characteristics of the dam are key influence factors in evaluating the seepage safety of landslide dams, which are also the primary considerations to carry out model tests. Based on previous studies, combined with the results of field investigations and indoor model tests, the depositing characteristics of landslide dams and advances in model tests for seepage failure are summarized, and the existing problems are discussed. Results show that the depositing characteristics of the landslide dam are related to the lithology of landslides, sliding path, bank slope structure, etc. The failure modes and processes of landslide dams are varied from depositing characteristics, particle size compositions to hydraulic conditions. For the landslide dams with high permeability zones, their failure can be attributed to the progressive cycle of piping and downstream dam slope collapse. While designing a model test, experimenters should not only consider the dynamic flow similarity but also determine the particle size distribution of the dam soils according to the relationship between particle size and particle movement. Finally, it is proved that the grading entropy can comprehensively reflect the gradation characteristics of the landslide dam as well as the change in gradation in the fine particle erosion process, which can be used to predict the permeability and internal stability of dam particles. Combined with other information, the failure mode and process of landslide dam can be predicted. The research results can provide references for the experimental research of landslide dam.