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To investigate the creep characteristics of soft clay under true triaxial stress conditions, multistage loading creep tests using TSW-40 true triaxial apparatus were performed. The creep deformation characteristics, creep rate, and long-term strength of soft clay under a true triaxial stress path were studied. The results showed that the creep deformation and creep rate of soft clay increase with increasing major principal stress; the axial deformation is larger than the lateral deformation. The long-term strength and the equation for predicting the starting point of accelerated creep were obtained using the generalized shear stress. A four-element fractional-order creep (FFC) model based on the fractional Burgers creep model was established for soft clay and then extended to three dimensions. The model calculation results based on the parameters obtained using MATLAB’s Curve Fitting Toolbox were in good agreement with the experimental results. The comparison results showed that the 3D FFC model was more accurate at describing the entire creep curve of soft clay than the fractional Burgers model and the Burgers model, particularly regarding the accelerated creep characteristics. In conclusion, the results presented herein are expected to provide the scientific basis for determining soft clay creep instability under true triaxial stress conditions.

The surrounding rock stress release rate in a two-dimensional (2D) rock tunnel model and boundary problems in a three-dimensional (3D) rock tunnel model are the main factors that affect the results of modeling rock tunnels. We investigated the constraint effect of supporting structures and boundary effects of the 3D model based on the confinement convergence method. A rupturable lining unit was developed using FLAC3D to study the influence of the constraint effect on the surrounding rock stress release and influence range of the boundary effects. The results show that the 2D model stress release enhances the virtual support force generated by the support constraint effect by 3–5% of the initial rock stress. A comparison of field monitoring and numerical calculations of the Millin tunnel project shows that the 3D model boundary effect is nearly 1.5 times the tunnel span. The rupturable lining unit directly reflects the stress characteristics of concrete lining in practical engineering and provides support for the quantitative evaluation of tunnel engineering stability.

Silicon/carbon composite is one of the most potential high-capacity anode materials for lithium-ion batteries. The interface state between silicon and carbon of silicon/carbon composite is an important factor affecting its electrochemical performance. In this paper, Sin (n ≤ 6) clusters with different numbers of Si atoms are constructed on graphene as a structural unit of carbon material. The geometric configuration, structure stability and electronic property of Sin clusters adsorbed on graphene (Sin/Gr) are studied by the first-principles method based on density functional theory (DFT). The results show that when the number of Si atoms n ≤ 4, the Sin clusters are preferentially adsorbed on graphene in a two-dimensional configuration parallel to graphene. When n ≥ 5, the Sin clusters are preferentially adsorbed on graphene in a three-dimensional configuration. With the increase of the number of Si atoms n, the thermodynamic stability of Sin clusters on graphene decreases significantly, the interface binding strength between Sin clusters and graphene decreases, and the charge transfer between Sin clusters and graphene becomes less. At the same time, the storage capacity of Li atoms in Sin/Gr complex is also studied. Li atoms are mainly stored on the graphene surface near Sin clusters and around Sin clusters. The complex synergistic effect of Sin clusters and graphene enhances the thermodynamic stability of Li adsorption. When n ≤ 4, storing two Li atoms is beneficial to improving the thermodynamic stability of xLi-Sin/Gr system, and the thermodynamic stability decreases with the increase of Li atom number. When n ≥ 5, the thermodynamic stability of xLi-Sin/Gr system decreases with the increase of Li atom number. In the xLi-Si5/Gr system, the C-C bond and Si-Si bond are mainly covalent bonds, while the Li-C bond and Li-Si bond are mainly ionic bonds with certain covalent properties.

For the production safety of the tailings dam, a midterm tailings dam system stability assessment isneeded. With numerical methods, aiming at the specific examples of projects the seepage stability, the statics stability and the dynamics stability are calculated, Results show there is no infiltration of the overflow from the slope, little hydraulic gradient and seepage stability. Safety factors meet regulatory requirements and the dam is in static stability. Dynamic responses from the dam and liquefaction results of the dam show that the dam is stable. The study provides a comprehensive assessment of the stability line. The calculation with the numerical simulation of the tailings has a certain reference value and significance.

Widely building of the large span underground water seal oil caverns must gradually propose more stringent requirements of the design level of oil caverns. The large span underground water seal oil cavern not only needs to rely on the natural conditions of the buried groundwater, but must also relies on the water curtain hole installed around the cavern in a certain pressure to provide a stable water injection pressure to prevent oil leakage. The normal water curtain system can be improved to function more powerfully and economically. The improvement benefits from the theory of flow closed loop proposed and critical storage pressure given according to the theory. Details of the new water curtain system layout and its variable function according to requirement alternation are described. Taking a large domestic underground oil cavern as an example, comparison of seepage of fractured rock of different design is analyzed under the three-dimensional stress field using FLAC3D codes. Combining the relationship between the effective stress of infiltration formation and water pressure around the caverns, the analysis proves that the new layout not only meets the demand of water sealing effect and prevents oil leakage while reducing cavern inflow, but also improves the rock stability and engineering emergency safety.