The permeability characteristics of tailings directly affect the position of the infiltration line of the tailings dam, which is the most critical factor affecting tailings dam failures. In order to fully analyze the essence of its permeability characteristics, computed tomography (CT) technology is used to analyze the structure of different types of tailings from a microscopic perspective and carry out microscopic seepage simulation. The results showed the following findings: (1) The porosity of viscous tailings ranges from 25 to 35%, the distribution of surface porosity along the height is relatively uniform, and the distribution is shown as having a certain discrete nature with the increase in particle size. (2) Compared with silty and sandy tailings, the surface of viscous tailings is smoother and more round, and the shape factor can reach 0.95; (3) The data gap between the simulation and the measurements by CT scanning technology is less than 10%, and the estimation of the permeability characteristics is feasible, with good applicability in the simulation of tailings seepage. (4) In the microscopic pore throat structure, the permeability characteristics of the tailings are more affected by the radius of the throat than the pore radius, and the exponential function relationship between the permeability coefficient and the porosity satisfies a high correlation. In this paper, the relationship between the microstructure and permeability characteristics of tailings is analyzed by CT technology; the permeability is simulated and calculated, and a permeability coefficient prediction model for tailings is proposed in combination with the experiment, which can provide a new idea and method for the study of the permeability characteristics of tailings.

This study aims to identify the difference in the mobilisation degree of RAP asphalt binder under three mixing techniques and its influences on the performance of recycled hot-mix asphalt mixture (HMA). Glass beads were selected to replace parts of fresh coarse aggregates, and to analyze the transfer of RAP binder using Fourier Transformation Infrared (FTIR) spectroscope analysis. Superpave Gyratory Compactor (SGC) and Hamburg Wheel-Track Device (HWTD) were used to evaluate the compaction property and the high-temperature performance of recycled HMA. Results showed that the relative percentage of reclaimed asphalt recovered (Rp) varied with the mixing techniques. The workability of recycled HMA is related to the mixing technique. The softer fresh asphalt binder is more capable of facilitating the mineral aggregates to form a stable skeleton structure. In addition, the transfer of RAP binder in recycled HMA may be an important factor influencing the skeleton structure.

To study the creep mechanical behavior of surrounding rock under the coupled effect of confining pressure unloading and deviatoric stress increase during the excavation of deep underground engineering, triaxial creep tests under stepwise unloading of confining pressure and loading of deviatoric stress were conducted using marble as the research object. The influences of different initial confining pressures, unloading amounts, and stress levels on the axial and circumferential creep deformation, creep rate, and failure characteristics of marble were systematically analyzed. The results indicate the following: (1) As the amount of confining pressure unloading increases, the creep failure stress of marble decreases significantly, and the test duration is markedly shortened. (2) Under conditions of small unloading amounts, the creep rate initially decreases and then increases with increasing stress levels, while under large unloading amounts, the creep rate monotonically increases with stress levels, indicating that confining pressure unloading significantly weakens the stability of the rock mass during creep. (3) Based on the test results, a three-dimensional non-stationary Nishihara creep model suitable for the stress path of stepwise confining pressure unloading and deviatoric stress loading was established. The model calculations agree well with the experimental data, effectively describing the entire creep process of marble under unloading conditions. The research findings can provide a reference for the long-term stability analysis of the surrounding rock after excavation in deep underground engineering.