Difficulties related to seepage are frequently encountered in tunnel design and construction, especially in deep-buried tunnels. Nowadays, analytical solutions of steady seepage fields for deep-buried tunnel usually assume that the surrounding rock mass is homogeneous. In this study, analytical solutions of a steady seepage field for a deep-buried tunnel with grouting ring considering anisotropic flow are proposed. The proposed analytical solutions are verified by numerical simulations and parameter analysis are carried out. Results show that the seepage field of surrounding rocks around the deep buried circular tunnel is no longer uniformly distributed and presents elliptical distribution. The change of permeability coefficient of the lining structure has a great influence on the hydraulic head when the difference between permeability coefficient of lining structure and surrounding rock is not very large. The results show that the size of the grouting ring has more significant influence on the grouting effect.

Viscosity reducer is used to reduce the high viscosity of drilling fluid containing bentonite as a continuous phase. However, the viscosity of drilling fluid increases and the rheology of the drilling fluid deteriorates at high temperature, causing problems such as reduction in rate of penetration and bit balling. As a core component, drilling fluids with bad rheology seriously affect the further development of drilling engineering, especially at high temperatures. Therefore, there is an urgent need for viscosity reducer suitable for high temperature. In this study, a high temperature-resistant viscosity reducer for water-based drilling fluid was prepared. The rheological parameters of drilling fluids containing 0, 0.5, 1, 1.5 wt% viscosity reducer after aging at different temperatures were evaluated. The results showed that the rheological parameters, such as apparent viscosity, yield point, plastic viscosity, and gel strength decreased within 200℃. Otherwise, filtration volume of 1.8 and 2.2 g/cm³ compound drilling fluids containing 1 wt% viscosity reducer was less than 10 ml. And its resistance to Na+ contamination reached saturation, that is, 36% NaCl solutions. The mechanism of viscosity reduction was also investigated by Fourier transform infrared and X-ray diffraction. Viscosity reducer adsorbed on the clay particles and destroyed the network structure formed by the clay particles while releasing free water.

Epoxy resin is regarded as a reliable option for coating advanced materials owing to its outstanding strength, adhesion, and stability. However, its relatively weak toughness compared to common materials has limited its application. In this study, the toughness of epoxy resin was enhanced by incorporating bamboo fibers, and a novel polymer coating material for bamboo-fiber-reinforced epoxy resin was developed. Different fiber pretreatment methods were employed to address the issue of poor interfacial performance between bamboo fibers and epoxy resin, aiming to optimize its performance as an advanced material coating. The effects of curing agents, fiber mesh sizes, fiber contents, and fiber pretreatment methods on the mechanical properties of the fiber-modified resin composites were investigated. The findings indicate that the JH45 and T31 curing agents were more effective in promoting the homogeneous dispersion of fibers within the epoxy resin. Additionally, bamboo fibers modified with KH550 exhibited enhanced interfacial properties: the tensile strength of the composite demonstrated a respective increase of 31.1% and 27.0% compared to untreated fibers. Increasing the mesh size proved advantageous for improving tensile properties, albeit potentially impacting the compressive properties. Particularly noteworthy was the significantly enhanced interfacial compatibility between bamboo fibers treated with the silane coupling agent KH550 and the epoxy resin. Analysis using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD) revealed that treating bamboo fibers with sodium hydroxide effectively enhanced bonding at the fiber–resin interface. This enhancement was attributed to the combined effects of bamboo fiber hydrolysis and delamination reactions. The silane coupling agent promoted the chemical reaction between bamboo fibers and epoxy resin through grafting, thereby strengthening the cross-linking property of the composites. These findings offer valuable insights into the design and fabrication of natural-fiber-reinforced polymer composites suitable for coating advanced materials.

The development and utilization of urban underground space (UUS) have emerged as critical strategies to address the challenges posed by urban population growth and land resource depletion. Accurate prediction of UUS demand serves as the cornerstone for scientifically planning underground space and promoting sustainable urban development. In this study, statistical analysis methods were used to investigate the relationship between potential driving factors and UUS demand based on collected data from 16 cities in China. The identification of primary driving factors involves correlation, path, and determination coefficient analyses. Subsequently, univariate regression, multiple linear regression, and LASSO regression methods are employed to construct prediction models for UUS demand. Additionally, the link between historical data and UUS demand in each city was studied separately. The findings reveal that GDP per km² and GDP per capita comprehensively capture the influence of urban population, economy, and transportation on UUS demand. Notably, GDP per km² makes the most significant contribution to the proposed regression models, followed by GDP per capita. The application of LASSO regression proves effective in selecting potential factors while maximizing data utilization, presenting itself as a valuable auxiliary tool for UUS planning.

Temperature is the fundamental variable used in artificial ground freezing (AGF) design to assess the frozen curtain’s state and carry out an analysis of its mechanical behavior. Therefore, it is important to appropriately understand the temperature variation in the soil during freezing and thawing throughout the construction process of AGF. In this paper, a soil physical state analysis model was established to obtain the one-dimensional distribution curve of the soil temperature field and the temperature variation curve of the soil with temporal, which can be used to explore the soil temperature characteristics during the construction of AGF, so as to scientifically evaluate the physical state of frozen soil and reduce the construction risk. The soil can be divided into three zones during the construction process of AGF, namely the frozen zone, the frozen fringe, and the unfrozen zone. Additionally, Hangzhou muddy silty clay was selected for the indoor model test to verify the correctness of the analytical model. The results show the following: (1) Due to the influence of the latent heat of the phase change, the physical state and temperature of the soil on both sides of the frozen fringe are not the same. It is not appropriate to use the same temperature index to judge whether the soil is frozen or thawed in the project. (2) For Hangzhou muddy silty clay, the freezing index is −1 °C, and the thawing index is 0.9 °C. The research results can provide some guidance for the judgment of the soil state during the AGF of subway cross passages.