Flash floods are often responsible for deaths and damage to infrastructure. The objective of this work is to create a data-driven model to understand how predisposing factors influence the spatial variation of the triggering factor (rainfall intensity) in the case of flash floods in the continental area of Portugal. Flash floods occurrences were extracted from the DISASTER database. We extracted the accumulated precipitation from the Copernicus database by considering two days of duration. The analysed predisposing factors for flooding were extracted considering the whole basin where each occurrence is located. These factors include the basin area, the predominant lithology, drainage density, and the mean or median values of elevation, slope, stream power index (SPI), topographic wetness index (TWI), roughness, and four soil properties. The Random Forest algorithm was used to build the models and obtained mean absolute percentage error (MAPE) around 19%, an acceptable value for the objectives of the work. The median of SPI, mean elevation and the area of the basin are the top three most relevant predisposing factors interpreted by the model for defining the rainfall input for flash flooding in mainland Portugal.

This study quantifies the seismic fragility assessment of shallow-founded buildings in liquefiable and treated soils, enhanced by drainage and densification, considering both short-and long-term behaviors. A conceptual framework is proposed for developing seismic fragility curves based on engineering demand parameters (EDPs) of buildings subjected to various earthquake magnitudes. The framework for establishing seismic fragility curves involves three essential steps. First, nonlinear dynamic analyses of soil-building systems are performed to assess both the short-term response, which occurs immediately following an earthquake, and the longterm response, when excess pore water pressure completely dissipates, and generate a dataset of building settlements. The seismic responses are compared in terms of excess pore water pressure buildup, immediate and residual ground deformation, and building settlement to explore the dynamic mechanisms of soil-building systems and evaluate the performance of enhanced drainage and densification over short-and long-term periods. Second, 38 commonly used and newly proposed intensity measures (IMs) of ground motions (GMs) are comprehensively evaluated using five statistical measures, such as correlation, efficiency, practicality, proficiency, and sufficiency, to identify optimal IMs of GMs. Third, fragility curves are developed to quantify probability of exceeding various capacity limit states, based on structural damage observed in Taiwan, for both liquefaction-induced immediate and residual settlements of buildings under different levels of IMs. Overall, this study proposes a rapid and straightforward probabilistic assessment approach for buildings in liquefiable soils, along with remedial countermeasures to enhance seismic resilience.

This study investigates the seismic response of a reinforced concrete (RC) tunnel using two-dimensional plane strain finite element models calibrated and validated against experimental results. A comprehensive parametric study is then conducted to explore the influence of tunnel-soil flexibility ratio, soil relative density, Arias intensity of the input motion, and ground motion components on the seismic soil-structure interaction (SSI). The results demonstrated that the flexibility ratio and racking coefficient increase with overburden height, while soil deformations decrease. Acceleration amplification factors rise from the bottom soil to the ground surface, with dense soil showing higher amplification especially in the regions at and near the tunnel field. The horizontal amplification factor exhibits greater variability with increasing seismic energy intensity, and the effect of the vertical motion becomes more pronounced near the structure. The vertical amplification factor is lowest for the horizontal component, while the vertical and combined components exhibit higher values influenced by the presence of the tunnel with lower earthquake intensity. Soil relative density significantly influences the vertical and lateral pressures on the tunnel, with dense sand causing maximum vertical pressures on the top slab and walls. The vertical earthquake component has a greater impact on the tunnel's top slab pressure distribution than the horizontal component. Seismic bending moments are influenced by earthquake components, with the vertical component leading to the greatest positive bending moment values in the middle of the roof slab. Vertical soil deformation is significantly affected by the horizontal input motion component, whereas the vertical component minimally affects lateral soil deformation. These findings underscore the importance of capturing stress-strain response under cyclic loading, particularly near the tunnel crown, where complex stress interactions lead to increased variability in behavior.

Selecting the optimal intensity measure (IM) is essential for accurately assessing the seismic performance of the submarine shield tunnels in the layered liquefiable seabed. However, current research relies on simplistic ranking or filtering methods that neglect the different contributions of each evaluation criterion on IM's overall performance. To address this, this study begins by developing a numerical simulation method for nonlinear dynamic analysis, considering joint deformation, ocean environmental loads, and soil liquefaction, which is validated by experimental and theoretical methods. Subsequently, a fuzzy multiple criteria decision-making (FMCDM) method based on fuzzy probabilistic seismic demand models (FPSDM) is proposed, which integrates the fuzzy analytical hierarchical process (FAHP) for calculating weights and the fuzzy technique for order preference by similarity to ideal solution (FTOPSIS) for ranking IM alternatives. Finally, tunnel damage is classified into four states employing joint opening as the index for measuring damage, then the seismic fragility analysis is conducted. The results indicate that the optimal IM of a submarine shield tunnel situated in layered liquefiable seabed is sustained maximum velocity (SMV). Furthermore, the comparison between the fragility curves established using SMV and peak ground acceleration (PGA) reveals PGA, a frequently employed IM, notably undervaluing the seismic hazard.

Shallow subway tunnels in both the intermediate and far fields are significantly affected by Rayleigh surface waves, which typically induce substantial vertical seismic motion and exhibit high seismic destructiveness. However, current vulnerability assessments of underground tunnels primarily focus on body waves. This study aims to identify the optimal ground motion intensity measures (IMs) for evaluating the seismic fragility of shallow circular subway tunnels subjected to Rayleigh waves. A detailed dynamic analysis of soil-tunnel interaction is performed using the two-dimensional Finite Element Method, with particular emphasis on the influence of tunnel burial depth and site classification on the tunnel's response to Rayleigh waves. The input of Rayleigh wave motion is modeled by transforming the motion into a series of equivalent forces, applied through viscoelastic boundaries. This study examines 15 widely used ground motion IMs, with diameter deformation ratio (DDR) serving as the damage measure (DM). Linear regression analysis is conducted to explore the relationship between IMs and DDR. The optimal IMs are evaluated based on criteria including efficiency, practicality, proficiency, and correlation. The results indicate that for sites classified as Class III and IV, the optimal IM is root mean square velocity (vrms), while for Class II sites, spectral mean velocity (SMV) is more suitable. Fragility curves for shallow-buried tunnels in Class II, III, and IV sites are presented. These curves demonstrate that tunnels are most vulnerable to damage in Class II sites, followed by Class IV, and least vulnerable in Class III sites. In Class II sites, shallower tunnel depths are associated with increased seismic damage, while deeper tunnels in Class III and IV sites experience greater seismic damage. The primary factor influencing seismic damage to tunnels is the vertical relative deformation of the surrounding soil layers.

Seismic risk assessment is pivotal for ensuring the reliability of prefabricated subway stations, where selecting optimal intensity measures (IMs) critically enhances probabilistic seismic demand models and fragility analysis. While peak ground acceleration (PGA) is widely adopted for above-ground structures, its suitability for underground systems remains debated due to distinct dynamic behaviors. This study identifies the most appropriate IMs for soft soil-embedded prefabricated subway stations at varying depths through nonlinear finite element modeling and develops corresponding fragility curves. A soil-structure interaction model was developed to systematically compare seismic responses of shallow-buried, medium-buried, and deep-buried stations under diverse intensities. Incremental dynamic analysis was employed to construct probabilistic demand models, while candidate IMs (PGA, PGV, and vrms) were evaluated using a multi-criteria framework assessing correlation, efficiency, practicality, and proficiency. The results demonstrate that burial depth significantly influences IM selection: PGA performs optimally for shallow depths, peak ground velocity (PGV) excels for medium depths, and root mean square velocity (vrms) proves most effective for deep-buried stations. Based on these optimized IMs, seismic fragility curves were generated, quantifying damage probability characteristics across burial conditions. The study provides a transferable IM selection methodology, advancing seismic risk assessment accuracy for prefabricated underground infrastructure. Through a systematic investigation of the correlation between IM applicability and burial depth, coupled with the development of fragility relationships, this study establishes a robust technical framework for enhancing the seismic performance of subway stations, and provides valuable insights for seismic risk assessment methodologies in underground infrastructure systems.

Loess is a distinctly structured soil. Undisturbed loess is prone to geological hazards, such as liquefaction and landslides under dynamic loads. There are also problems such as the inhomogeneity, anisotropy, and disturbance of in situ sampling. An artificial structural loess is prepared to accurately display the dynamic characteristics of undisturbed loess. This study took artificial structural loess as the study object, through dynamic triaxial tests, analyzed the effects of the confining pressure (sigma 3), dry density (rho d), and cement content (D) on its dynamic strength. Then, a dynamic strength index model of artificial structural loess was established. Our results show that the dynamic strength of artificial structural loess rises with enhanced sigma 3, rho d, and D. The dynamic cohesion (cd) and dynamic friction angle (phi d) increased with the rise of rho d, and D. The dynamic strength of artificial structured loess is closer to that of undisturbed loess when the rho d is 1.60 g/cm3 and D is 2%. The R2 values of the phi d and the cd model were 0.97 and 0.98, respectively, fitting the dynamic strength index of artificial structural loess with different D, rho d, and sigma 3. Our study outcomes can serve as references and guides for engineering construction in loess areas.

Heavy metal contamination of the environment is increasing alarmingly due to increased anthropogenic activities. Among the various heavy metals, cadmium is a highly toxic heavy metal requiring urgent removal from soil. Strobilanthes alternata, a herbaceous terrestrial plant, has been reported to be an excellent plant for Cd phytostabilization. The present study investigated the effect of 25 ppm of 6-Benzylaminopurine (6-BAP) foliar sprays on the modulation of the physiological responses and elemental constitution in S. alternata grown in 250 mg/kg CdCl2 treated soil. The administration of 6-BAP effectively relieved the toxic effects of Cd by enhancing the total soluble sugar and alkaloid content of leaves by 56 and 250%, respectively, the total soluble protein content of roots by 27%, the phenolic content of roots and leaves by 9 and 10% respectively, and flavonoid content of roots and leaves by 53 and 6% respectively, in Cd-stressed S. alternata. Moreover, the 6-BAP-induced elevation of the thiol content of roots indicated amplified sequestration of Cd, thereby inflicting less damage to the aboveground portions of Cd + 6-BAP-treated plants. This inference was confirmed by SEM-EDX analysis, which revealed high Cd weight percentages in the roots of Cd + 6-BAP-treated plants. The ionomics and CHNS analysis confirmed that 6-BAP ascribable alterations in the elemental content and distribution helped the plant tolerate the adverse effects of Cd in S. alternata. Thus, the 6-BAP treatment could be used as a suitable and ecologically acceptable amendment to reduce Cd-induced damage and enhance the Cd phytostabilization potential in S. alternata.

In the processes of seismic design of underground structures, selecting a reasonable input ground motion is very important, which can cause severe damage to underground structures. To quantitatively evaluate the seismic damage potential of ground motions on multi-storey underground structures and solve the problem that single intensity measures are inadequate in accurately indicating the seismic damage potential of ground motions, this paper taking the input ground motions in the seismic design of underground structures as the research object, and constructing some composite intensity measures that can effectively characterize the damage potential of input ground motion. Firstly, considering that the underground structures in different characteristic period-type sites will exhibit different seismic responses under the same excitation, the soil-structure system is divided into four-period bands. Then, four representative periods are selected from four-period bands respectively, and the corresponding four soil-structure system numerical models are established. Subsequently, 40 ground motions are selected for elastoplastic numerical analysis, and the results of the numerical analysis were used as sample data to construct composite intensity measures corresponding to soil-structure systems in each period band using the partial least squares regression method. Finally, 100 additional ground motions were used to verify the correlation between the composite intensity measures and the seismic damage of underground structures. The results show that the correlation coefficient between the composite intensity measures and the seismic damage of multi-storey underground structures is better than those of commonly used single intensity measures.

The selection of representative ground motion intensity measure (IM) and structural engineering demand parameter (EDP) is the crucial prerequisite for evaluating structural seismic performance within the performance-based earthquake engineering (PBEE) framework. This study focuses on this crucial step in developing the probabilistic seismic demand model for two-story and three-span subway stations exposed to transverse seismic loadings in three different ground conditions. The equivalent linearization approach is used to simulate the shear modulus degradation and the increase in damping characteristics of the soil under seismic excitation. Nonlinear fiber beam-column elements are adopted to characterize the nonlinear hysteretic degradation of the subway station structure during seismic events. A total of 21 far-field ground motions are selected from the PEER strong ground motion database. Nonlinear incremental dynamic analyses (IDAs) are conducted to evaluate the seismic response of the subway station. A suite of 23 ground motion IMs is evaluated using the criteria of correlation, efficiency, practicality, and proficiency. Then, a multi-level fuzzy evaluation method is employed to integrate these evaluation criteria and determine the optimal ground motion IMs in different ground conditions. The peak ground acceleration and sustained maximum acceleration are demonstrated to be the optimal ground motion IM candidates for shallowly buried rectangular underground structures in site classes I, II, and III, while the root-mean-square displacement and compound displacement are found to be not suitable for this purpose.