Ensuring the accuracy of free-field inversion is crucial in determining seismic excitation for soil-structure interaction (SSI) systems. Due to the spherical and cylindrical diffusion properties of body waves and surface waves, the near-fault zone presents distinct free-field responses compared to the far-fault zone. Consequently, existing far-fault free-field inversion techniques are insufficient for providing accurate seismic excitation for SSI systems within the near-fault zone. To address this limitation, a tailored near-fault free-field inversion method based on a multi-objective optimization algorithm is proposed in this study. The proposed method establishes an inversion framework for both spherical body waves and cylindrical surface waves and then transforms the overdetermined problem in inversion process into an optimization problem. Within the multi-objective optimization model, objective functions are formulated by minimizing the three-component waveform differences between the observation point and the delayed reference point. Additionally, constraint conditions are determined based on the attenuation property of propagating seismic waves. The accuracy of the proposed method is then verified through near-fault wave motion characteristics and validated against real downhole recordings. Finally, the application of the proposed method is investigated, with emphasis on examining the impulsive property of underground motions and analyzing the seismic responses of SSI systems. The results show that the proposed method refines the theoretical framework of near-fault inversion and accurately restores the free-field characteristics, particularly the impulsive features of near-fault motions, thereby providing reliable excitation for seismic response assessments of SSI systems.

In this study, the effect of near-field and far-field ground motions on the seismic response of the soil pile system is investigated. The forward directivity effect, which includes a large velocity pulse at the beginning of the velocity time history of the ground motion is the most damaging phenomenon observed in near-field ground motions. To investigate the effect of near-field and far-field ground motions on the seismic response of a soil-pile system, a three-dimensional model consisting of the two-layer soil, liquefiable sand layer over dense sand, and the pile is utilized. Modeling is conducted in FLAC 3D software. The P2P Sand constitutive model is selected for sandy soil. Three fault-normal near-field and three far-field ground motion records were applied to the model. The numerical results show that near field velocity pulses have a considerable effect on the system behavior and sudden huge displacement demands were observed. Also, during the near-field ground motions, the exceeded pore water pressure coefficient (Ru) increases so that liquefaction occurs in the upper loose sand layer. Due to the pulse-like ground motions, a pulse-like relative displacement is created in response to the pile. Meanwhile the relative displacement response of the pile is entirely different due to the energy distribution during the far-field ground motions.

A utility tunnel is an infrastructure that consolidates multiple municipal pipeline systems into a shared underground passage. As long linear structures inevitably cross different soils, this paper aims to accurately assess the seismic damage to a shallow-buried utility tunnel in a non-homogeneous zone by employing a viscous-spring artificial boundary and deriving the corresponding nodal force equations. The three-dimensional model of the utility tunnel-soil system is established using finite element software, and a plug-in is developed to simulate the three-dimensional oblique incidence of SV waves with a horizontal non-homogeneous field. In this study, the maximum interstory displacement angle of the utility tunnel is used as the damage indicator. Analysis of structural vulnerability based on IDA method using PGA as an indicator of seismic wave intensity, which considers the angle of oblique incidence of SV waves, the type of seismic waves, and the influence of the nonhomogeneous field on the seismic performance of the utility tunnel. The results indicate that the failure probability of the utility tunnel in different soil types increases with the incident angle and PGA. Additionally, the failure probability under the pulse wave is higher than that under the non-pulse wave; Particular attention is given to the states of severe damage (LS) and collapse (CP), particularly when the angle of incidence is 30 degrees and the PGA exceeds 0.6g, conditions under which the probability of failure is higher. Additionally, the failure probability of the non-homogeneous zone is greater than that of sand and clay; the maximum interlayer displacement angle increases with the incident angle, accompanied by greater PGA dispersion, indicating the seismic wave intensity. The maximum inter-layer displacement angle increases with the incident angle, and the dispersion of the seismic wave intensity indicator (PGA) becomes greater. This paper proposes vulnerability curves for different working conditions, which can serve as a reference for the seismic design of underground structures.

Iron pipes connected by bell-spigot joints are utilized in buried pipeline systems for urban water and gas supply networks. The joints are the weak points of buried iron pipelines, which are particularly vulnerable to damage from excessive axial opening during seismic motion. The axial joint opening, resulting from the relative soil displacement surrounding the pipeline, is an important indicator for the seismic response of buried iron pipelines. The spatial variability of soil properties has a significant influence on the seismic response of the site soil, which subsequently affects the seismic response of the buried iron pipeline. In this study, two-dimensional finite element models of a generic site with explicit consideration of random soil properties and random mechanical properties of pipeline joints were established to investigate the seismic response of the site soil and the buried pipeline, respectively. The numerical results show that with consideration of the spatial variability of soil properties, the maximum axial opening of pipeline joints increases by at least 61.7 %, compared to the deterministic case. Moreover, in the case considering the variability of pipeline-soil interactions and joint resistance, the spatial variability of soil properties remains the dominant factor influencing the seismic response of buried iron pipelines.

Destructive earthquakes result in significant damage to a wide variety of buildings. The resulting damage data is crucial for evaluating the seismic resilience of buildings in the region and investigating urban resilience. Field damage data from 38 destructive earthquakes in Sichuan Province were collected, classified, and statistically analysed according to the criteria of the latest Chinese seismic intensity scale for evaluating building damage levels. Meanwhile, the construction features and seismic damage characteristics of these buildings were also examined. These results facilitated the development of a damage probability matrix (DPM) for various building typologies, such as raw-soil structures (RSSs), stone-wood structures (SWSs), brick-wood structures (BWSs), masonry structures (MSs), and reinforced concrete frame structures (RCFSs). The damage ratio was employed as the parameter for vulnerability assessment, and a comprehensive analysis was performed on the differences in damage levels among all buildings in various intensity zones and time frames. Furthermore, the DPMs were further refined by simulating additional data from high-intensity zones to more accurately represent the seismic resistance of existing buildings in multiple-intensity zones. Vulnerability prediction models were developed using the biphasic Hill model, which elucidates varying damage trends across different construction typologies. Finally, empirical fragility curves were established based on horizontal peak ground acceleration (PGA) as the damage indicator. This study is based on multiple seismic damage samples from various regions, accounting for the influence of earthquake age. The DPMs, representative of the regional characteristics of Sichuan Province, were developed for different building types. Furthermore, multidimensional vulnerability regression models and empirical fragility curves are established based on these DPMs. These models and curves provide a theoretical foundation for seismic disaster scenario simulations and the seismic capacity analysis of buildings within Sichuan Province.

The entrance of permafrost tunnels in cold regions is particularly vulnerable to frost damage caused by complex thermal-hydro-mechanical (THM) interactions in unsaturated frozen soils. The effects of temperaturedependent volumetric strain variations across different stratum materials on heat and moisture transport are often neglected in existing THM coupling models. In this study, a novel THM coupled model for unsaturated frozen soil integrating volumetric strain correction is proposed, which addresses bidirectional interactions between thermal-hydraulic processes and mechanical responses. The model was validated through laboratory experiments and subsequently applied to the analysis of the Yuximolegai Tunnel. The results indicate that distinct layered ice-water distribution patterns are formed in shallow permafrost under freeze-thaw cycles, driven by bidirectional freezing and water migration. Critical mechanical responses were observed, including a shift in maximum principal stress from the invert (1.40 MPa, frozen state) to the crown (5.76 MPa, thawed state), and periodic lining displacements (crown > invert > sidewalls). Frost damage risks are further quantified by the spatial-temporal zoning of ice-water content-sensitive regions. These findings advance unsaturated frozen soil modeling and provide theoretical guidance for frost-resistant tunnel design in cold regions.

Soil-steel composite bridges (SSCBs) are commonly utilized as overpasses. In the majority of existing studies, the transverse structural performance of SSCBs is primarily focused on, while neglecting their longitudinal structural performance. The aims of this paper are to clarify the longitudinal properties and compensate for the paucity of research on the longitudinal structural performance of SSCBs. In current study, field tests were conducted on a SSCB case bridge in a mining area, both in the construction stage and post-construction stage. Subsequently, longitudinal differences in the structural settlements, deformations, and hoop strains were analyzed. Additionally, a refined three-dimensional finite element model was developed and verified to analyze the transfer behavior of soil pressure above the structure along the longitudinal direction. The results indicate that in the construction stage, the difference in the soil-covered height primarily account for the differences in structural performances along the longitudinal direction. At the end of backfilling, the settlements, deformations, and hoop strains in the middle are all greater than those in the end sections. In the post-construction stage, further developments of longitudinal structural characteristics occur due to creep deformation of the foundation soil and disturbances from mining trucks. One year after construction, the structural characteristics have stabilized. The maximum settlement reaches -1.014 m and the maximum settlement difference reaches 0.365 m. The differential settlement ratio, at 0.62 %, remains within the 1 % limit specified in the CHBDC code. Due to longitudinal settlement differences, the soil pressure in the higher settlement zone is transferred to the lower settlement zone by the longitudinal soil arching effect, which benefits the load-bearing capacity of SSCBs.

This study investigates the influence of wood pellet fly ash blended binder (WABB) on the mechanical properties of typical weathered granite soils (WS) under a field and laboratory tests. WABB, composed of 50 % wood pellet fly ash (WA), 30 % ground granulated blast furnace slag (GGBS), and 20% cement by dry mass, was applied at dosages of 200-400 kg/m3 to four soil columns were constructed at a field site deposited with WS. After 28 days, field tests, including coring, standard penetration tests (SPT), and permeability tests, revealed enhanced soil cementation and reduced permeability, indicating a denser soil matrix. Unconfined compressive tests (UCT) and free-free resonant column (FFRC) tests on field cores at 28 and 56 days, compared with laboratory specimens and previously published data, demonstrated strength gains 1.2-2.1 times higher due to field-induced stress. The presence of clay minerals influenced the WABB's interaction and microstructure development. Correlations between seismic waves, small-strain moduli, and strength were developed to monitor in-situ static and dynamic stiffness gain of WABB-stabilized weathered granite soils.

Rapid urbanization and industrial growth in China have increased brownfield site reclamation, the sustainable remediation for urban transformation and enhancing ecosystem services. However, traditional brownfield safety assessment strategies impose unnecessary costs since excessive remediation. Herein, a comprehensive system integrated by soil self-purification, potential ecological risks and human health risks is developed to investigate the safety of brownfield sites. Indices, including soil environmental loading capacity (SELC), and Nemerow integrated pollution index (NIPI), were introduced to assess heavy metals (HMs) pollution. Results show that 72.05% of the sites are identified as moderate pollution, where Cd, As, and Cr(VI) are at heavy pollution, incorporating soil self-purification. The average values of potential ecological risk (PERI) reached 6615.00, posing a significant damage to the local ecosystem, and Cd was identified as main ecological hazards in the study sites. Furthermore, the health risk assessment shows that children's health risks are higher than that of adults, with non-carcinogenic risk to children (2.60) and adults (0.41), and carcinogenic risk to children (2.30 x 10-3) and adults (1.12 x 10-4). Utilizing a multi-index decision-making approach, it is determined that 19.30% of the site exhibit high-risk values, between concentration screening (11.40%) and risk screening (83.30%) base on single-indices. The study sheds light on the comprehensive assessment of brownfield site safety.

Post-grouted shafts (PGDS) and stiffened deep cement mixed (SDCM) shafts reinforce the surrounding soils with cement to enhance the bearing capacity of shaft foundations, and their applications are becoming increasingly widespread. Field tests involving two post-grouted shafts and two stiffened deep cement mixing shafts were conducted at the bridge foundations projects, analyzing the vertical bearing performance of the shafts with cement-stabilized soil enhancement. Additionally, numerical simulations were performed to establish calculation models for single shaft and groups of drilled shafts, PGDS, and SDCM shafts, enabling a comparative analysis of their bearing capacity performance within the identical strata. The results indicate that the post- grouted shaft demonstrated significant bearing deformation capacity, as confirmed by field tests. After grouting, the ultimate bearing capacities of DS1 and DS2 improved by 124.5 % and 110.9 %, respectively. In both single and group modeling shaft foundations, the post-grouted shafts demonstrated the highest bearing deformation characteristics, followed by the identical- size stiffened deep cement mixed shaft, while the long-core SDCM shafts and the ungrouted shafts exhibited the weakest performance. Due to interaction effects among group shafts, the total bearing capacity of the group shafts is not simply the sum of the individual shafts. Specifically, the reduction factor for group shaft capacity ranges from 0.68 to 0.79 at the Baoying Large Bridge site, while at the Yangkou Canal Bridge site, it varies from 0.66 to 0.85. The findings of this study provide valuable insights for practical engineering applications.