This study employs the Discrete Element Method (DEM) to investigate the influence of initial fabric anisotropy on the cyclic liquefaction behavior of granular soils. Static and cyclic biaxial compression tests under undrained condition are simulated using two-dimensional elongated sharp-angled particles. Initial fabric anisotropy is introduced by considering a pre-defined inclined angle of elongated particles inside the sample. Results from the simulations reveal that varying fabric anisotropy affects the stress paths, resulting in a significant decrease in the maximum internal friction angle; however, the critical state internal friction angle is less affected. When subjected to cyclic loading, anisotropic samples exhibit distinct behavior influenced by initial fabric anisotropy. Comparison of the results with those of limited experiments in the literature confirms the simulations validity. The effective confining stress diminishes, leading to progressive liquefaction. The number of cycles required for initial liquefaction varies due to inherent anisotropy, and fabric anisotropy causes a shift in the concentration of compression or extension strains within the samples. Lower values of cyclic stress ratio amplifies the influence of inherent anisotropy on excess pore water pressure ratios. In addition to stress approach, the strain-based liquefaction resistance is also investigated by defining double amplitude strain values. It is found that when the double strain level is relatively small, the impact of inherent anisotropy becomes more noticeable. This study enhances the understanding of the role of initial fabric anisotropy in cyclic liquefaction behavior and provides insights for engineering design and mitigation strategies in seismic-prone areas.

In many densely populated cities, buried networks of urban services, such as facilities and sewage tunnels or sewer pipes are constructed adjacent to or beneath nearby building foundations. It is vital to consider the seismic interaction of shallow tunnels with these foundations in liquefiable deposits. In such circumstances, segmental tunnels are of interest due to being considered non-rigid structures, and their utilization has increased in shallow urban tunneling. Using a two-dimensional finite difference code, a shallow tunnel subjected to uplift pressures due to soil liquefaction is studied. An advanced constitutive model (PM4Sand) is employed in the numerical model along with a fully coupled Fluid-Solid solution to simulate soil liquefaction. First, a centrifuge laboratory model was used to validate the coupled hydrodynamic numerical simulations. Additionally, it allows for the use of real sand properties. The validation results indicated a good agreement between the numerical simulations and the centrifuge tests for tunnel uplift (maximum difference of 7 %) and the excess pore water pressure ratio (ru). Next, based on the results, segmentation of the tunnel lining was found to be effective in reducing ground surface uplift by 23 %. Then, a segmental tunnel lining with and without a five-story building on a combined footing foundation is considered under soil liquefaction. The interaction between the shallow foundation of the five-story building and the segmental lining highlights the significant influence of tunnel uplift on shear force, bending moment, tilting and rotation of the foundation and surface structure. Additionally, the presence of the foundation and surface structure leads to a reduction in tunnel uplift (by 29 %) and ground surface uplift (by 21 %). Lastly, a permeation grouting method has been utilized to mitigate seismic soil-surface structure-underground structure interaction (SSSSUSI) during liquefaction, resulting in a 90.7 % reduction.