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.

Seismic fragility denotes the probabilities of a system exceeding some prescribed damage levels under a range of seismic intensities. Classical seismic fragility studies in slope engineering usually construct fragility functions by making some assumptions for fragility curve shape, and always neglect spatial variability of soil materials. In this study, an assumption-free method on the basis of probability density evolution theory (PDET) is proposed for seismic fragility assessment of slopes. The random input earthquakes and spatially-variable soil parameters in slope are simultaneously quantified. By the proposed method, assumption-free fragility curves of a slope are established without limiting the fragility curve shape. The obtained fragility results are also compared with those from two classic parametric fragility methods (linear regression and maximum likelihood estimation) and Monte Carlo simulation. The results demonstrate that the proposed assumption-free method has potential to gives more rigorous and accurate fragility results than classical parametric fragility analysis methods. With the proposed method, more reliable fragility results can be obtained for slope seismic risk assessment.

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.

Landslides, which are a type of process-based geological hazard, exhibit stagewise characteristics that serve as important guidance for the prevention and mitigation of slope engineering disasters. The cross-correlation and randomness of soil parameters can influence the evolution of landslide characteristics. This paper, based on the spatial variability of slope soil parameters, combines copula theory and the material point method (MPM) to establish a Monte Carlo-random material point method considering the cross-correlation of soil parameters. This resulting method is called copula-RMPM. It investigates the probability distributions of slope instability and landslide large deformation characteristics, such as sliding distance, landslide thickness, collapse range, and volume of sliding mass. The results indicated that in the study of soil parameter characteristics, failure probability increases with increased correlation coefficient. Also, failure probability showed a positive correlation with the variability coefficient of cohesion and internal friction angle, with failure probability being more sensitive to the variability coefficient of the internal friction angle. The landslide large deformation characteristics generally follow the normal distribution; they exhibit significant fluctuations in sliding distance and sliding mass area despite the relatively small variability coefficient. Compared with the results of random field simulation of soil parameters, the probability of landslide large deformation characteristics obtained by deterministic soil parameters is often lower. Therefore, the probability distribution of landslide large deformation characteristics obtained by the Monte Carlo-random material point method considering the cross-correlation of soil parameters is more meaningful for engineering guidance.

The delayed breakage of particles significantly affects the long-term mechanical properties of rockfill materials. This study examines the effects of particle strength dispersion on the distribution of time-dependent strength using fracture mechanics and probabilistic methods. Subsequently, the distribution of normalized maximum contact force (NMCF), defined as the ratio of the maximum contact force to instantaneous strength, for specimens with uniform particle size is derived using extreme value theory and Discrete Element Method (DEM). Based on this analysis, the probabilities of delayed breakage in rockfill specimens over various time intervals are calculated using a joint probability delayed breakage criterion. The feasibility of the proposed method is validated by comparing theoretical calculation with DEM triaxial creep simulation results that accounted for particle breakage. The findings offer innovative tools and theoretical insights for understanding and predicting the particle delayed breakage behavior of rockfill materials and for developing macro-micro creep crushing constitutive models.

PurposeThis paper aims to develop a probabilistic framework which combines uncoupled cofferdam stability analysis, random forest and Monte Carlo simulation for cofferdam reliability analysis.Design/methodology/approachThe finite element method and limit equilibrium method are used to calculate the seepage field and stability of cofferdam, respectively. Sufficient training and validating random samples are generated to obtain a random forest surrogate model with acceptable accuracy. The calibrated random forest model combined with MCS is used to conduct cofferdam reliability analysis. The proposed methodology is illustrated using a typical cofferdam model.FindingsThe numerical simulation results demonstrate that a larger pore water pressure leads to a lower stability of the cofferdam and vice versa. The increase in the slope angle significantly reduces the stability of cofferdam on the corresponding side, while the stability of cofferdam on the other side is mainly affected by the internal pore water pressure. The increase in the width and height of the reverse pressure platform significantly enhances the stability of cofferdam, and the changes in the angle of the reverse pressure platform affect the stability of cofferdam to some extent. The probability of failure (Pf) of cofferdam increases gradually with increasing vertical and horizontal scales of fluctuation, coefficient of variation, and cross-correlation coefficient when the degradation degree of soil properties is low. It is worth noting that the effect of vertical and horizontal scales of fluctuation, coefficient of variation, and cross-correlation coefficient on the Pf of cofferdam changes significantly when degradation coefficient decreases to a critical value.Practical implicationsA geotechnical engineer could use the proposed method to perform cofferdam reliability analysis.Originality/valueThe reliability of cofferdam can be efficiently and accurately studied using the proposed framework.

Paleoliquefaction investigations are crucial for assessing seismic hazard potential and identifying regions susceptible to liquefaction, which is essential for seismic risk-sensitive land-use planning. This research aimed to identify paleoliquefaction sites by reviewing documented descriptions of the damages and ground deformations in Bangladesh during three significant historical earthquakes: the Bengal Earthquake (1885), the Great Assam Earthquake (1897), and the Srimangal Earthquake (1918). A paleoliquefaction map for Bangladesh was generated, locating the paleoliquefaction sites during these three major historical earthquakes. In addition, Standard Penetration Test (SPT) blow count and Down-hole Seismic Tests (DST) were conducted at selected locations to assess the Liquefaction Potential Index (LPI) by using deterministic (simplified) and probabilistic procedures. The results confirmed a high likelihood of liquefaction during future large-magnitude earthquakes. The research outcome will help to distinguish and characterize Bangladesh's susceptible regions to soil liquefaction during potential earthquakes in the future and is recommended for consideration in large-scale construction or development plans.

Strength anisotropy and heterogeneous rotated anisotropy are prevalent phenomena in natural slopes. Previous studies have underscored their significance in slope stability analysis. However, in previous slope stability analyses, the effects of strength anisotropy and heterogeneous rotated anisotropy on slope stability were studied separately, without considering their coupled effect. This paper aims to propose a probabilistic analysis framework of slope stability considering the coupled effect of strength anisotropy and heterogeneous rotated anisotropy. Through an undrained clay slope case, the proposed probabilistic analysis framework is examined. The influence of strength anisotropy and heterogeneous rotated anisotropy on slope stability is investigated. The results show that the proposed probabilistic analysis framework of slope stability considering the coupled effect of strength anisotropy and heterogeneous rotated anisotropy is effective. Both strength anisotropy and heterogeneous rotated anisotropy have an important influence on slope stability. Furthermore, the statistics of safety factor including mean value, coefficient of variation, and reliability index, vary with the strength anisotropy coefficient, the heterogeneous anisotropy coefficient, and the rotational angle. The smaller the strength anisotropy coefficient, the larger the heterogeneous anisotropy coefficient, and the smaller the reliability index. The rotational angle of strata corresponding to the minimum and maximum values of the slope reliability index is sensitive to the strength anisotropy coefficient, but not to the heterogeneous anisotropy coefficient.

The slope has an adverse effect on the ultimate bearing capacity of shallow foundations. Due to inherent variability in soil properties and geometric factors of slopes, designing a foundation on slopes is a perplexing and challenging task. The spatial variation in the soil's shear strength property is commonly ignored by the designers to avoid complexity in design. Shear strength property in real scenarios increases along the depth and simultaneously it poses spatial variability. This kind of randomness is modelled using a non-stationary random field. The proposed study aims to evaluate the probabilistic bearing capacity of strip footing on spatially varying slopes. The probabilistic bearing capacity factor is analyzed for different influential factors like geometry and footing placements, correlation distances and coefficient of variation of soil properties. Slopes exhibiting nonstationary characteristics contribute to remarkable differences in the bearing capacity of footing as compared to the stationary condition. The study highlights that the geometry factors, footing placements, soil spatial variability and most importantly the increasing trend of soil strength play a critical role in the bearing capacity and risk of failure of a footing. High variations in the failure probability can be observed even after considering safety factors.

In order to further study the dynamic response and damage status of the subway station structure and promote the development of the TOD (transit-oriented development) mode structure system, this paper proposes a calibration method for the seismic performance index limit of the subway station complex structure in TOD mode. Taking a practical project in the Beijing city sub-center station integrated transport hub as the research background, the nonlinear analysis model of soil-structure interaction under different site types is established. Firstly, the limit value of the interstory drift ratio is determined by the pushover loading method of the inverted triangular distributed load for the three-dimensional numerical model. Secondly, different types of seismic waves are selected to analyze the seismic vulnerability of the simplified two-dimensional numerical model, and the exceedance probability of different damage states of the structure is quantitatively analyzed. By analyzing the pushover curve, the maximum interstory drift ratio limits corresponding to the five damage states of the subway station complex structure are 0.14%, 0.32%, 0.66%, and 1.12%, respectively. Under different site types and different types of seismic waves, the seismic response law of subway station structures in TOD mode is different. Using different types of ground motion as the input, the mean and discreteness of different IDA curve clusters are quite different. The near-field pulse-type ground motion has a greater impact on the ground motion of the structural system under the Class II site, and the far-field long-period ground motion has a greater impact on the structure under the Class III site. Damage decreases with the increase in the equivalent shear wave velocity of the site, that is, the harder the site's soil is, the less susceptible the structural system is to damage by underground motion. The established seismic vulnerability curve and seismic damage probability table can effectively evaluate the seismic performance of subway station complex structure in TOD mode. The research results can provide a valuable reference for the seismic performance evaluation of similar underground structures.