Xiaokang Guo

Ensuring the stability of the excavation face is essential for tunnel excavation. Existing limit equilibrium models mainly adopt two-dimensional wedge mechanisms to estimate the minimum support force for tunnels, which cannot accurately represent the failure characteristics of practical tunnels. To address this limitation, a three-dimensional logarithmic spiral sliding model is developed based on the limit equilibrium method and strength reduction technique. The model introduces an equivalent area approach to represent heterologous sections and establishes the global moment equilibrium equation using the slice method. Taking the Huashansong tunnel as a case study, a parametric analysis is conducted on the reinforcement performance of end-anchored and fully bonded rock bolts. The results indicate that the diameter, strength, and density of bolts affect the stability of the excavation face, and the No. 11 end-anchored bolt and No. 37 fully bonded bolt are recommended. Furthermore, numerical simulation shows that the maximum extrusion deformation of the excavation face decreases from 11.57 mm without bolts to 9.13 mm and 8.46 mm for the No. 11 end-anchored bolt and No.37 fully bonded bolt, while tunnel convergence deformation decreases from 4.06 mm to 3.42 mm and 3.23 mm, respectively. The application of the No. 37 fully bonded bolt in the Huashansong tunnel controls the extrusion deformation and convergence deformation within 9.25 mm and 4.47 mm, ensuring the stability and economy of the tunnel excavation.

Offshore wind power is a new trend in renewable energy development. However, during the operation of offshore wind turbines, the rock-socketed monopile foundation is subjected to long-term cyclic loads, which will cause the seawater to erode the rock around the monopile foundation and reduce the ultimate end-bearing capacity. There is no suitable rock mass classification for evaluating the quality of marine bedrock and no theoretical method for accurately calculating the ultimate end-bearing capacity of the monopile foundation. Therefore, based on the existing rock mass classification, an ocean rock mass classification (OMR) that is applicable to marine bedrock is proposed. The ratings of four geological indices (R₁, R₂, R₃, and R₄) in the OMR classification are reset by the analysis hierarchy process and modified according to the geological conditions of marine bedrock. Then, an accelerated test of seawater erosion is used over 60 days to simulate seawater erosion for up to 12 years to determine the adjustment factor for the effect of time, F_t, in the OMR classification. Based on the OMR classification, a theoretical calculation method of the ultimate end-bearing capacity of the offshore wind monopile foundation under the overall sliding failure mode of rock mass is proposed. The theoretical calculation method was employed for offshore wind engineering, and the reliability of the theoretical calculation and three-dimensional numerical simulation was validated. The results show that the theoretical and numerical results for the ultimate end-bearing capacity without seawater erosion are similar to the measured results, with a relative error of less than 9%. The theoretical results are always larger than the numerical results, with a relative error of less than 7%. Finally, the theoretical and numerical results were used to guide the design and construction of an offshore wind turbine. The offshore wind turbine has been operating for 8 years, and its displacement is 15.3 mm, which is less than the numerical result of 16.94 mm.

This study takes a new Shidao tunnel where the left line constructing in weak rock mass as a case study, and the effect of the new constructing tunnel on the existed tunnel are studied by the numerical analysis. High-precision field investigations are conducted to provide accurate parameters for the numerical model. The modified generalized Zhang-Zhu (GZZ) constitutive model is applied, and the numerical analysis results containing horizontal convergence displacement of side walls of the new constructing tunnel and a longitudinal crack in existed tunnel are validated by real-time monitoring. The vertical displacement of the vault, the horizontal displacement of the adjacent side wall, the plastic zone of the new constructing tunnel are studied. The effect of the new constructing tunnel on the existed tunnel is studied by analyzing the vertical displacement of the vault and the horizontal displacement of the adjacent side wall of the existed tunnel. During the constructing process of new tunnel, the maximum width variation of longitudinal crack is less than 0.3 mm. The maximum vertical displacement of the vault is less than 1 mm, and the maximum horizontal displacement of the adjacent side wall is less than 0.5 mm for the existed tunnel. Finally, the effects of tunnel spacing between new constructing and existed tunnels and geological condition represented by geological strength index (GSI) are investigated. The result shows that the maximum vertical displacements of the vault and the maximum horizontal displacement of adjacent side wall can reach −10.4 mm and −4.9 mm respectively when tunnel spacing is 0.5 d (d is actual spacing). When GSI is increased from 15 to 30, the maximum vertical displacement of the vault is reduced obviously.

A novel, regioselective protocol for the synthesis of diphenylmethane derivatives has been developed by using iron-­catalyzed Friedel-Crafts reaction of arenes with benzyl thiocyanates. In the presence of FeBr₃, a variety of benzyl thiocyanates underwent the reaction with arenes to selectively afford the corresponding diarylmethane derivatives in moderate to high yields.