The reasonable buried depth of metro station should be investigated for Qingdao with the upper-soft and lower-hard stratum. Strength reduction method has been utilized to study FOS of metro station under different buried depths. As the buried depth increases, the curve of FOS can be divided into three parts as the slowly changed part, the rapidly-increased part, and the gradually-decreased part. Taking FOS = 1 as limitation, the formula of least rock cover thickness has been derived. Based upon the formula, the characteristics of safety distribution changing with buried depth for metro station which behaves as three zones (DI, E, DII) have been discovered. Two typical metro stations have been used to verify the research results.
Grouting engineering is widely used in water plugging for geotechnical engineering. However, grout is usually treated as a Newton fluid and the viscosity is considered unchangeable over time during the grouting design process. This study proposes a grout diffusion model for porous media that considers the variation in viscosity with time. The flow equation is derived for a single smooth tubule. Then, the microequation of Bingham grout flowing in porous media is obtained. Finally, an assembled diffusion model of spheres and cylinders for grouting using a perforated pipe is proposed. A numerical simulation method is used to verify the grout diffusion mode. The research results can guide grouting design and practical grouting engineering in water plugging and reinforcement.
In order to ensure the safety of the Daling tunnel with extralarge section and small space, the three-dimensional model of blasting dynamic simulation had been established and verified. Then, the model was used to analyze the influence of the surrounding rock characteristics and blasting design parameters on the blasting vibration of the first hole, and the analysis of the sensitivity of each factor was carried out. The results showed that blasting of the second hole had a serious impact on the safety of the first hole lining structure. Based on the safety threshold and analysis of sensitivity, the explosive velocity, charge density, and digging length were selected as the key parameters affecting the safety of the tunnel structure. Meanwhile, the corresponding engineering measure was taken based on the results of sensitivity and the actual situation on site, and, after that, the maximum PPV of the right wall of the first hole had been reduced to 9.3 cm/s, which effectively guaranteed the safe construction of the tunnel.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.