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.

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.

The cracking during the drying process of thickened tailings stack is a critical issue impacting its stability. This study establishes a comprehensive analytical framework that encompasses both mechanism cognition and technical methodologies by systematically integrating multidimensional research findings. Research indicates that cracking results from the coupling effects of environmental parameters and process conditions. The environmental chamber, with its precise control over external conditions, has emerged as essential experimental equipment for simulating actual working environments. From a mechanical perspective, water evaporation induces volume shrinkage, leading to microcrack formation when local tensile stress surpasses the matrix's tensile strength, ultimately resulting in a network of interconnected cracks. This process is governed by the dual parameters of matric suction and tensile strength. In terms of theoretical modeling, the fracture mechanics model analyzes crack propagation laws from an energy dissipation standpoint, while the stress path analysis model emphasizes the consolidation shrinkage coupling effect. The tensile damage model is particularly advantageous for engineering practice due to its parameter measurability. In numerical simulation technology, the finite element method is constrained by the predetermined crack path, whereas the discrete element method can dynamically reconstruct the crack evolution process but encounters the technical challenge of large-scale multi-field coupling calculations. Research suggests that future efforts should focus on optimizing theoretical prediction models that account for the characteristics and cracking behavior of tailings materials. Additionally, it is essential to develop a comprehensive equipment system that integrates real-time monitoring, intelligent regulation, and data analysis. This paper innovatively proposes the establishment of a multi-scale collaborative research paradigm that integrates indoor testing, numerical simulation, and on-site monitoring. By employing data fusion technology, it aims to enhance the accuracy of crack predictions and provide both theoretical support and technical guarantees for the safety prevention and control of thickened tailings stacks throughout their entire life cycle.

An integrated constitutive model has been developed for rock-like materials, incorporating confinement-sensitive damage and bi-mechanism plasticity. The model aims to improve the capability of the conventional damage model in depicting the strengthening and brittle-to-ductile transitions that occur under both active and passive confinement conditions. A thermodynamic analysis of energy transformation and dissipation, considering both damage and plasticity, underpins the model's development. The model, rooted in damage-plastic theory, has been divided into two sub-models: (1) Confinement-Sensitive Model: This sub-model addresses the strengthening and ductility enhancements due to active confinement stress. It effectively captures the mechanical responses of rock-like materials under various levels of active confining stresses. (2) Endochronic Dilatancy Model: Based on endochronic theory, a separate dilatancy strain model is proposed, which effectively facilitates the interplay between lateral dilatancy and the growth of passive confining stress. Both sub-models, as well as the integrated model, have undergone validation using experimental data, including uniaxial tests, cyclic loading tests, actively confined tests, and passively confined tests of rock-like materials. These validations confirm the model's accuracy and reliability in predicting the mechanical behavior of rock-like materials under complex loading conditions.

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.

The unique optical properties of microplastic particles have a significant impact on atmospheric radiative forcing. Based on the generalized multi-particle Mie theory, this paper presents a comparative study of the extinction properties and absorption properties of single-component and mixed aerosol clusters composed of microplastics, dust, and black carbon in different structural forms and particle sizes. The results show that the structure, particle size, mixing arrangement, and orientation of aerosol particles containing microplastics will directly affect their optical properties. As the incident wavelength increases, significant differences are observed in the extinction and absorption cross-sections of microplastic and dust particle chains with different structures, although they exhibit similar trends. However, black carbon particle chains show a distinct variation pattern. In the mixed particle chains with different particle sizes, as the incident wavelength increases, the extinction and absorption cross-sections are significantly larger than those of the particle chains with the same particle size, indicating that the particle size has a remarkable influence on their optical properties. The different mixing forms and orientations of aerosol clusters also significantly affect their extinction and absorption cross-sections. These findings provide a new theoretical perspective for environmental optics and remote sensing monitoring of aerosols.

To better characterize the intricate coupled thermo-hydro-mechanical dynamic (THMD) response in twodimensional saturated soil and to enrich the research object of Green-Naghdi (G-N) generalized thermoelastic theory, this study innovatively combines the G-N generalized thermoelastic theory and Caputo's fractional order derivative, to obtain the new control equations, and to establish a new fractional order thermoelastic theoretical model. The article is solved by the normal mode analysis (NMA), which can eliminate the integration error and solve the complex fractional order partial differential control equations quickly at the same time. The effects of different boundary conditions of fractional order derivatives, porosity, frequency, and thermal conductivity coefficients on non-dimensional excess pore water pressure, temperature, vertical displacement, and vertical stress are also fully analyzed, and the distribution curves of high precision numerical solutions are given. The results show that the effect of frequency variation on each non-dimensional variable is obvious. The effects of fractional order derivatives, porosity and thermal conductivity coefficients on the non-dimensional variables vary depending on the boundary conditions. The results provide theoretical support for geotechnical and environmental engineering.

Roots can mechanically reinforce soils against landslides, but the impact of their typically random and complex distribution on this reinforcement is not well understood. Here, using a modelling approach based on homogenization theory, we aim to assess the effect of the randomness and complexity of root spatial distribution in soils on the mechanical properties of the soil-root composite and the resulting reinforcement. To do this, we modeled the soil-root composite as a three-dimensional (3D) soil column through which parallel roots penetrate vertically. The unit cell (UC) of the soil-root composites with a nonuniform root distribution was created based on the characteristics of root diameter distributions of Elymus dahuricus measured in the field, and the equivalent elastic modulus and strength parameters of the composites were calculated. The accuracy of the homogenization method was verified by direct shear tests with undisturbed soil-root samples. The results showed that the UC model of the soil-root composites could effectively predict its equivalent elastic parameters. A parametric analysis using the proposed homogenization model showed that roots can mobilize significant soil portions to resist deformation by increasing both the number and complexity of root distributions, even at the same root volume ratio. This makes the stress distribution in the soil more uniform and improves the shear strength of the soil-root composites. The presence of Elymus dahuricus roots significantly improved the shear strength of the soil-root composites, primarily due to an increase in cohesion of 23%. This study presents a new perspective on the development of a constitutive model for soil-root composites and highlights its potential value for engineering applications that use roots to reinforce soils.

This paper presents a novel micropolar-based hypoplastic model to reproduce the stress-strain relationship of face mask chips-sand mixtures (MSMs) and their localized deformation. Based on a critical state hypoplastic model, a non-polar hypoplastic model for MSMs is first developed with modifications and new features: (1) the cohesion induced by face mask chips is considered by introducing an additional stress tensor into the Cauchy stress tensor; (2) the initial stiffness variation in MSMs is described with a modified tangential modulus; and (3) the effective skeleton void ratio concept is introduced to capture the initial and critical void ratio variations in MSMs. The model is then extended to its micropolar terms by incorporating the micropolar theory, which includes an internal length parameter and a couple stress induced by particle rotation, with the advantage of overcoming the mesh dependency problem in the conventional finite element method (FEM) based simulations. Moreover, the new micropolar hypoplastic formulations are implemented into a FEM code. The onset and evolution of shear bands in MSMs are investigated by simulating a series of biaxial tests on both pure sand and MSMs. Numerical results are also compared to experimental observations, demonstrating that the developed micropolar hypoplastic model can adeptly capture the shear band propagation in MSMs and their mechanical responses.

This study investigated the dynamic properties of red mud (RM)-reinforced volcanic ash (VA) by dynamic triaxial tests. The effects of stress state (dynamic stress sigma d, confining stress sigma 3), dynamic frequency (f) and load waveform (F) on the accumulative plastic strain (epsilon p) have been investigated. The findings indicate a significant influence of the stress state on epsilon p. When sigma d reaches 120 kPa, the specimens exhibit insufficient strength, leading to shear failure. As sigma 3 increases, the dynamic stresses that lead to specimen destabilization also exhibit an upward trend. The effect of f on epsilon p is limited. The epsilon p does not exhibit a clear or consistent developing pattern with increasing f. As for the F, the epsilon p exhibited by the specimens subjected to sinusoidal wave loads is less than that observed under trapezoidal wave loads. Shakedown theory classifies deformation responses into plastic shakedown, plastic creep and incremental collapse. The epsilon p curve patterns of RM-reinforced VA exhibit plastic shakedown and incremental collapse without significant plastic creep characteristics under cyclic loading. A predictive model for epsilon p under cyclic loading is established, which has good predictability. This study presents a novel application of VA and RM, offering substantial research insights into waste recycling.