The recurring occurrence of seismic hazards constitutes a significant and imminent threat to subway stations. Consequently, a meticulous assessment of the seismic resilience of subway stations becomes imperative for enhancing urban safety and ensuring sustained functionality. This study strives to introduce a probabilistic framework tailored to assess the seismic resilience of stations when confronted with seismic hazards. The framework aims to precisely quantify station resilience by determining the integral ratio between the station performance curve and the corresponding station recovery time. To achieve this goal, a series of finite element models of the soil-station system were developed and employed to investigate the impact of site type, seismic intensity, and station structural type on the dynamic response of the station. Then, the seismic fragility functions were generated by developing the relationships between seismic intensity and damage index, taking into account multidimensional uncertainties encompassing factors such as earthquake characteristics and construction quality. The resilience assessment was subsequently conducted based on the station's fragility and the corresponding economic loss, while also considering the recovery path and recoverability. Additionally, the impacts of diverse factors, including structural characteristics, site types, functional recovery models, and peak ground acceleration (PGA) intensities, on the resilience of stations with distinct structural forms were also discussed. This work contributes to the resilience-based design and management of metro networks to support adaptation to seismic hazards, thereby facilitating the efficient allocation of resources by relevant decision makers.

The excavation and maintenance of buried natural gas pipelines can lead to deformation and stress redistribution of the pipelines and even cause secondary damage to the pipes with issues. To clarify the impact of excavation unloading on buried pipelines, this study established a finite element three-dimensional pipe-soil model, investigated the mechanical response of pipelines under layered excavation and evaluated various parameters impacting the response. The parameters analyzed include the diameter-thickness ratio of the pipe, excavation length and width, thickness of top covering soil, elastic modulus of soil, specific weight of soil and initial displacement of the pipeline. The study results showed that the pipeline bulges upwards during excavation unloading, the pipe top in the middle is under tension, and the bottom of the pipe is under compression. Therefore, the axial stress and vertical displacement both increase first and then decrease, and they are distributed symmetrically along the pipeline axis; excavating the initially compressed pipeline leads to high strain areas in the pipeline and even local buckling. The response to slope excavation is more pronounced than that to straight trench excavation; the additional response of the pipeline increases with the increase of diameter-thickness ratio, excavation width, thickness of pipe top covering soil and specific weight of soil, but it decreases with the increasing soil elastic modulus. The additional response is closely related to excavation length and the initial displacement. The results of this study can provide a reference for pipeline construction, maintenance, and safety assessment.

The damage to microbial solidified engineering residue by freeze-thaw cycles increases the amount of material prone to wind erosion. Microbial solidification of engineering residue was carried out, and freeze-thaw cycle and indoor wind tunnel tests were conducted on the microbial solidified samples to reveal the interaction mechanism between different numbers of freeze-thaw cycles and the wind erosion degree. The test results showed that the larger the number of freeze-thaw cycles, the greater the mass loss of the microbial solidified engineering residue sample due to wind erosion and the lower the surface strength and surface thickness of the sample. However, the surface strength and surface thickness were relatively stable after more than 7 freeze-thaw cycles. The mass loss of the sample was 13 g after 9 freeze-thaw cycles at the maximum wind speed (15 m/s), higher than that of the sample exposed to no freeze-thaw cycles (6 g) but far lower than that of the undisturbed sample (3647 g). The results indicated that the microbial solidified engineering residue had high freeze-thaw resistance. The microbial solidified engineering residue was analyzed by computed tomography (CT) before and after the freeze-thaw cycles, and three-dimensional reconstruction was performed using digital image processing. The microstructure analysis showed that the freeze-thaw cycles did not change the content and spatial distribution of the microbial solidified products but reduced the ability to cement the microbial solidified products and the soil particles. The calcium carbonate inside the hard shell became more fragmented, the equivalent radius of the crystals and the stability of the hard shell decreased, and the porosity increased. However, the microbial solidified engineering residue exhibited high resistance to wind erosion and freeze-thaw cycles.