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.

Earthquake-induced soil liquefaction poses significant risks to the stability of geotechnical structures worldwide. An understanding of the liquefaction triggering, and the post-failure large deformation behaviour is essential for designing resilient infrastructure. The present study develops a Smoothed Particle Hydrodynamics (SPH) framework for earthquake-induced liquefaction hazard assessment of geotechnical structures. The coupled flowdeformation behaviour of soils subjected to cyclic loading is described using the PM4Sand model implemented in a three-phase, single-layer SPH framework. A staggered discretisation scheme based on the stress particle SPH approach is adopted to minimise numerical inaccuracies caused by zero-energy modes and tensile instability. Further, non-reflecting boundary conditions for seismic analysis of semi-infinite soil domains using the SPH method are proposed. The numerical framework is employed for the analysis of cyclic direct simple shear test, seismic analysis of a level ground site, and liquefaction-induced failure of the Lower San Fernando Dam. Satisfactory agreement for liquefaction triggering and post-failure behaviour demonstrates that the SPH framework can be utilised to assess the effect of seismic loading on field-scale geotechnical structures. The present study also serves as the basis for future advancements of the SPH method for applications related to earthquake geotechnical engineering.

Tunnels buried in liquefiable soils are prone to liquefaction-induced uplift damage during strong earthquakes. Studying the parameters that affect the liquefaction-induced uplift of tunnels is crucial for enhancing the seismic resilience of tunnels, minimizing potential damage, and ensuring the safety of critical infrastructure during strong earthquakes. This study investigates the effects of tunnel diameter (D), burial depth (H), and amplitude of input shaking at the base of the soil layer (amax) on the liquefaction-induced uplift of circular tunnels using numerical simulation. A comprehensive parametric study was conducted to investigate the effect of the H/D ratio and the value of amax on the dynamic responses, such as uplifts and internal forces in the lining of the tunnel. Using the numerical results, an empirical function was proposed to estimate the liquefaction-induced uplift of circular tunnels buried in liquefiable, loose soils. Finally, the results predicted by the proposed function were compared with those of a shaking table test and a centrifuge experiment. It has been demonstrated that the burial depth of a tunnel has the greatest impact on its seismic performance. Under identical input motion, increasing the burial depth of a tunnel with a 5-m diameter from 5 to 10 m resulted in a 270% increase in uplift and increased the internal forces in the tunnel lining, noticeably.

Past earthquakes have revealed that damage to sheet -pile walls under saturated conditions is closely linked to excess pore water pressure buildup in the surrounding soil. Nonlinear effective stress analysis (ESA) is commonly employed to assess the seismic performance of sheet -pile walls in liquefiable soils, incorporating constitutive models for liquefaction simulation. However, ESA results are sensitive to uncertainties in input parameters, model calibration, and modeling techniques. Dynamic centrifuge tests conducted in the Liquefaction Experiments and Analysis Project (LEAP) offer valuable insights into important response mechanisms and validate ESA. Seven centrifuge tests on a cantilevered sheet -pile wall model showed that liquefaction did not occur in the backfill near the wall due to net seaward wall displacement but did occur farther away. In addition, the mechanism of wall displacement was mainly due to the shear deformation of the softened backfill, with the displacement magnitude depending on the relative density of soil, peak ground acceleration of base motion, and wall displacement during gravity loading. Nonlinear ESA was performed for three centrifuge tests using FLAC2D and the PM4Sand constitutive model for soil. Gravity analysis captured static wall displacement and initial stress distribution in the soil. Two calibrations of the PM4Sand model were pursued at the element level: C1 calibration for liquefaction strength and C2 calibration for liquefaction strength and the post -liquefaction shear strain accumulation rate. System -level simulations showed similar liquefaction behavior as observed in the tests for both calibrations. However, the C2 calibration provided closer predictions of wall displacements, while the C1 calibration (default for PM4Sand) resulted in larger and more conservative displacements. Overall, the PM4Sand model performed well with minimal calibration, making it suitable for nonlinear ESA of sheet -pile walls.

Featured Application The conclusions of this article can be used to predict the uplift of tunnels or underground structures induced by soil liquefaction considering vertical earthquake motion.Abstract The uplift of underground structures induced by soil liquefaction can damage underground structure systems. Numerical simulations have shown that uplift is positively correlated with the energy of horizontal input motion. However, the effects of vertical input motion on uplift have not been studied comprehensively in the past. Previous studies on the vertical motion concluded that the effects of vertical motion on uplift depend on the overall characteristics of earthquake motion. These motion characteristics have only been studied separately in previous studies. A comprehensive study to explore the interactions and overall effects of these characteristics on the uplift of underground structures is essential. In this study, the FLAC program with the PM4Sand model was used as a numerical tool to explore the effects of vertical input motion on the uplift of underground structures. The numerical model was calibrated using centrifuge test results, and 48 earthquake motions were selected as input motions to study the effects of the overall characteristics of earthquake motions on the uplift of underground structures. The simulation results show that the frequency content characteristics of horizontal and vertical motion are the major factors affecting the uplift magnitude and the responses of liquefiable soils. However, most simulation cases show that the inclusion of vertical motion causes a 10% difference in the tunnel uplift, compared to cases without vertical motion.

Liquefaction occurs in saturated sandy and silty soils due to transient and repetitive seismic loads. The result is a loss of soil strength caused by increased pore pressure. In this study, the response of buried pipes in the Iskenderun region during the earthquakes centered in the subprovinces of Pazarc & imath;k and Elbistan in Kahramanmara & scedil;, Turkey, on 6 February 2023, has been investigated utilizing numerical analyses using geological data from two different areas. The effects of shallow and deep rock layers, pipe diameter, burial depths, and boundary conditions have been evaluated. In the analyses, records from two stations located in Iskenderun during the Pazarc & imath;k, Kahramanmara & scedil; earthquake have been utilized, taking into account records from shallow rock (station no. 3116) and thick soil layers (station no. 3115), as determined from shear wave velocities. Modeling conducted using station 3116 records has revealed the effect of shallow rock layers on pipe displacement, indicating less damage in areas where the rock layer is close to the surface. The pipe uplift risk is higher when the bedrock is deep, and the overlying soil layer is liquefiable (station no. 3115). It has been determined that depth to bedrock significantly influences upward movement of the pipe. In the areas where the bedrock is deep, expanding the boundary conditions has helped reduce the effects of settlements outside the pipe, preventing the occurrence of pipe uplift. Increasing the pipe diameter has increased the amount of uplift. The analysis results are consistent with field observations.

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.