Particle characteristics (particle shape and size), along with relative density, significantly influence the frictional characteristics and liquefaction behavior of granular materials, particularly sand. While many studies have examined the individual effects of particle shape, gradation, and relative density on the frictional characteristics and liquefaction behavior of sand, they have often overlooked the combined effects of these soil parameters. In this study, the individual effect of these three soil parameters on the strength characteristics (angle of internal friction) and liquefaction resistance has been quantified by analyzing the data available in the literature. A novel dimensionless parameter, the 'packing index (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha $$\end{document}),' was developed to account for the bulk characteristics (relative density - RD) and grain properties (gradation, represented by the coefficient of uniformity (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$C_u$$\end{document}), and particle shape represented by the shape descriptor regularity (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\rho $$\end{document})) of the granular soils. Through statistical analysis, a power law-based equation was proposed and validated to relate the cyclic resistance ratio (CRR) and angle of internal friction (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\phi $$\end{document}) with the packing index. Finally, an approach to assess the liquefaction resistance was detailed considering the intrinsic soil parameters, aiming to bridge the gap between field observations and laboratory analysis to facilitate a comprehensive understanding of soil behavior under cyclic loading.

Liquefaction poses a potential threat to the safety, serviceability and stability of shield tunnels during seismic events. This study investigates the seismic response of shield tunnels in liquefiable soils employing a fully coupled dynamic effective stress analysis model. The model accounts for the nonlinear mechanical behavior of the shield tunnel structure and incorporates the advanced bounding surface elastoplastic PM4Sand and PM4Silt models integrated with Biot u - p formulation to simulate the constitutive behavior of liquefiable and nonliquefiable soil layers. The seismic performance of shield tunnel -liquefiable soil system is evaluated considering ground motions with different characteristics in the transverse direction. The numerical results reveal the significant effects of ground motion frequency content and seismic intensity on the liquefaction triggering, the tunnel deformation and the internal forces of segmental joints. The soil -structure dynamic interaction and the soil shear dilatancy characteristics greatly influence the generation of the earthquake -induced excess pore water pressure and post -liquefaction shear strains. It is observed that the soil contact pressures on the left and right springlines of the tunnel experience larger increase compared to the contact pressure on the tunnel crown and invert. This observation suggests that the soil could cause racking deformation on both sides of the tunnel structure towards the center. Besides, the deformations and mechanical behaviors of the segmental joints around the tunnel left and right feet and the right springline are notably higher than at other joints in the saturated deposits. Furthermore, it is found that ground motion characterized by low -frequency contents, amplifies the seismic response of the soil and the tunnel when compared to the ground motions with high or moderatefrequency contents.

BackgroundEarthen heritage sites have high cultural and scientific value. However, most of earthen heritage sites have been severely damaged and are in urgent need of restoration. To address this issue, a novel rockbolt, bamboo-steel composite rockbolt (BSCR), was proposed and widely employed in earthen site protection. However, the research on the anchorage mechanism of BSCR lags behind engineering practice, particularly with regard to its behavior under the coupled effect of tensile and shear stress.Case PresentationIn this study, based on centrifugal test results, a numerical model was established and validated and a comparative analysis of the anchorage mechanism between conventional rockbolt (CR) and BSCR was also conducted. Various parameters, including rockbolt diameter, bending stiffness, inclination angle, and length, were systematically investigated to elucidate their influence on protective efficacy.ConclusionBSCR has a larger diameter and bending stiffness, and is superior to CR in protecting earthen heritage sites. In addition, reducing the rockbolt inclination angle and increasing the number of rockbolt layers can reduce slope deformation caused by the coupling effect of tensile and shear stress. Increasing the length of BSCR can enhance the stability of the anchored slopes; however, due to the influence of the effective anchorage length of the rockbolt, excessively extending the rockbolt length is inefficient. These research results provide valuable insights into the application of BSCR in earthen site protection and can provide a reference for further research on its anchorage mechanism under complex stress conditions.