The K & uuml;& ccedil;& uuml;k & ccedil;ekmece-Avc & imath;lar corridor of the D100 highway constitutes a critical component of Istanbul's transportation infrastructure. Given its strategic importance, ensuring its operational continuity following the anticipated major Istanbul earthquake is imperative. The aim of this study was to investigate the liquefaction-induced geotechnical risks threatening the K & uuml;& ccedil;& uuml;k & ccedil;ekmece-Avc & imath;lar segment of the D100 highway. Initially, the study area's liquefaction susceptibility was assessed through Liquefaction Potential Index mapping. Subsequently, post-liquefaction ground displacements were quantified using semi-empirical methodologies and advanced numerical analyses focused on representative critical sections. Numerical simulations incorporated various constitutive models for liquefiable soils, enabling a comparative assessment against semi-empirical estimations. The results revealed that semi-empirical approaches systematically overestimated the lateral displacements relative to numerical predictions. Moreover, the analyses highlighted the sensitivity of model outcomes to the selection of constitutive parameters, underscoring the necessity for careful calibration in modeling liquefiable layers. Despite considering the most conservative displacement values from numerical analyses, findings indicated that the D100 highway is likely to experience substantial damage, potentially leading to extended service disruptions following the projected seismic event.

On May 1, 2024, a small embankment collapse occurred in the early hours of the morning on the Meida Highway in Meizhou City, Guangdong Province, resulting in 48 fatalities. The small-scale collapse caused massive casualties and garnered widespread attention. In detail, there is a significant lack of precipitation at the time of the 51 Meida collapse disaster, lagging 10 h behind the peak precipitation. The collapse occurs on a mountainous slope, with a hollow catchment area located above the embankment. Multiple potential streams converge in the area, contributing to the water flow towards the slope. Within the western zone of the Lianhua Mountain fault, the collapse area is crossed by fault lines at approximately 800 m on the upper side and 650 m on the lower side. Bedrock fractures formed by faults act as water conduits. The combination of catchment topography and potential faults enriches the water around the embankment slope, contributing to its instability. The disaster site is situated within granite formations. The refilling soil, composed of weathered granite, exhibits poor hydro-mechanical properties, making the slope particularly susceptible to failure due to the effects of multi-source water infiltration. A key insight from this research is that potentially unstable embankment slopes should be identified by considering the interaction between multi-source water and soil/rock. Greater emphasis should be placed on factors such as fault development and hollow topography above the slope, which influence the effects of multi-source water. These factors should be quantified in future studies to improve the assessment of unstable highway slopes in mountainous regions. The findings and strategies outlined in this study can serve as a valuable reference for assessing both embankment and natural slopes in mountainous areas.

Soil with high liquid limit is often encountered in southern China, which is unsuitable for direct use as embankment fill. Current soil reinforcement methods entail high carbon emissions, necessitating mitigation for a low-carbon future. In this study, a reconstituted soil is reconstituted to simulate the soil with high liquid limit from the site of the reconstruction and expansion project for the Zhangshu-Ji'an Highway in Jiangxi, China. This reconstituted soil was reinforced using steel slag, varying in grain sizes and employing two mixing methods. The mechanical characteristics of the pure and reinforced soil were examined by a series of monotonic and cyclic triaxial tests. The results indicate that decreasing the grain size of steel slag increases the monotonic shear strength and leads to a decrease in the permanent strain under cyclic loading, regardless of the mixing methods. The reduction in grain size of steel slag increases the total frictional surface area, thereby enhancing soil strength and resistance to deformation. Compared to the samples by uniform mixing with the steel slag, the samples by layered mixing results in a greater shear strength and a more significant permanent strain, because the concentrated steel slag grains and reconstituted soil particles produce greater friction and more significant compressibility, respectively. Overall, smaller grains of the steel slag by uniform mixing are more effective for reinforcing weak soil with high liquid limit, as it provides a higher monotonic strength and a lower permanent deformation, and reduces rapid energy dissipation under cyclic loading, compared to layered mixing.

Seismic risk expresses the expected degree of damage and loss following a catastrophic event. An efficient tool for assessing the seismic risk of embankments is fragility curves. This research investigates the influence of embankment's geometry, the depth of rupture occurrence, and the underlying sandy soil's conditions on the embankment's fragility. To achieve this, the response of three highway embankments resting on sandy soil was examined through quasi-static parametric numerical analyses. For the establishment of fragility curves, a cumulative lognormal probability distribution function was used. The maximum vertical displacement of the embankments' external surface and the fault displacement were considered as the damage indicator and the intensity measure, respectively. Damage levels were categorized into three qualitative thresholds: minor, moderate, and extensive. All fragility curves were generated for normal and reverse faults, as well as the combination of those fault types (dip-slip fault). Finally, the proposed curves were verified via their comparison with those provided by HAZUS. It was concluded that embankment geometry and depth of fault rupture appearance do not significantly affect fragility, as exceedance probabilities show minimal differences (<4%). However, an embankment founded on dense sandy soil reveals slightly higher fragility compared to the one founded on loose sand. Differences regarding the probability of exceedance of a certain damage level are restricted by a maximum of 7%.