Shallow cut-and-cover underground structures, such as subway stations, are traditionally designed as rigid boxes (moment-resisting connections between the main structural members), seeking internal hyperstaticity and high lateral (transverse) stiffness to achieve important seismic capacity. However, since seismic ground motions impose racking drifts, this proved rather prejudicial, with great structural damage and little resilience. Therefore, two previous papers proposed an opposite strategy seeking low lateral (transverse) stiffness by connecting the structural elements flexibly (hinging and sliding). Under severe seismic inputs, these structures would accommodate racking without significant damage; this behaviour is highly resilient. The seismic resilience of this solution was numerically demonstrated in the well-known Daikai station (Kobe, Japan) and a station located in Chengdu (China). This paper is a continuation of these studies; it aims to extend, deepen, and ground this conclusion by performing a numerical parametric study on these two stations in a wide and representative set of situations characterised by the soil type, overburden depth, engineering bedrock position, and high- and lowlateral-stiffness of the stations. The performance indices are the racking displacement and the structural damage (quantified through concrete damage variables). The findings of this study validate the previous remarks and provide new insights.

The thermo-mechanical (TM) behaviour of the energy pile (EP) group becomes more complicated in the presence of seepage, and the mechanism by which seepage impacts the EP group remains unclear.In the current work, a 2 x 2 scale model test bench of EP group was set up to investigate the TM behaviour of EP group with seepage. The test results indicate that the heat exchange performance of EP group with seepage can be significantly enhanced, but also leads to obvious differences in the temperature distribution of pile and surrounding soil along the seepage direction, and thus causes evident differences in the mechanical properties between the front pile and the back pile in pile group. Compared with the parallel connection form, the thermal performance of EP group with the series connection form is slightly attenuated. However, the mechanical properties of various piles in the EP group differ significantly. Under the action of seepage, the mechanical balance properties of various piles in the forward series form are optimal, followed by the parallel form, and the reverse series form is the least optimal. A 3-D CFD model was established to further obtain the influence of seepage and arrangement forms on EP group. The findings indicate that seepage can not only mitigate thermal interference between distinct piles but also expedite the process of heat transfer from pile-soil to reach a state of stability. Concurrently, the thermal migration effect induced by seepage will be superimposed along the seepage direction, resulting in the elevation of thermal interference of each pile along the seepage direction, and the superposition of thermal migration effect increases with the time. Under the same seepage condition, the cross arrangement can enhance the thermal performance of EP group, optimize the temperature distribution of pile and soil, and thus the imbalance of mechanical properties among pile groups can be reduced. In addition, the concepts of thermal interference coefficient and heat exchange rate per unit soil volume are introduced to facilitate a more precise evaluation of the thermal interference degree of each pile in the pile group and the heat exchange performance under different pile arrangement forms.The standard deviation and mean value in the statistical method are used to evaluate the equilibrium of mechanical properties of pile group, which is more intuitive to compare the differences in mechanical properties of pile groups under different working conditions.

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.

The physical and mechanical characteristics of saline soil are significantly influenced by salt content, with macro- and mesoscopic mechanical properties closely correlated. This study investigates the strength and deformation behaviors of saturated saline sand through indoor triaxial shear testing under varying confining pressures and salt contents. The key innovation lies in developing a coupled finite element and discrete element analysis model to simulate the mesoscopic behavior of saline sand under triaxial shear stress state. Flexible boundary conditions were applied, and appropriate contact models for salt-sand interactions were selected. By adjusting mesoscopic parameters, stress-strain curves and variations in porosity, coordination number, particle displacement, and contact force chains were analyzed. The study further explores shear band development and shear failure mechanisms by examining relative particle displacement and the breaking of contact force chains. Additionally, the influence of salt particle size on the overall strength of the DEM model was assessed. The findings provide valuable insights into the internal structural changes of saline sand during shear deformation, contributing to a better understanding of its mechanical behavior in engineering applications.

The breakage phenomenon has gained attention from geotechnical and mining engineers primarily due to its pivotal influence on the mechanical response of granular soils. Numerous researchers performed laboratory tests on crushable soils and incorporated the corresponding effects into numerical simulations. A systematic review of various studies is crucial for gaining insight into the current state of knowledge and for illuminating the required developments for upcoming research projects. The current state-of-the-art study summarizes both experimental evidence and numerical approaches, particularly focusing on discrete element simulations and constitutive models used to describe the behavior of crushable soils. The review begins by exploring particle breakage quantification, delving into experimental evidence to elucidate its influence on the mechanical behavior of granular soils, and examining the factors that affect the breakage phenomenon. In this context, the accuracy of various indices in estimating the extent of breakage has been assessed through ten series of experiments conducted on different crushable soils. Furthermore, alternative breakage indices are suggested for constitutive models to track the evolution of particle crushing under continuous shearing. Regarding numerical modeling, the review covers different approaches using the discrete element method (DEM) for simulating the behavior of crushable particulate media, discussing the advantages and disadvantages of each approach. Additionally, different families of constitutive models, including elastoplasticity, hypoplasticity, and thermodynamically based approaches, are analyzed. The performance of one model from each group is evaluated in simulating the response of Tacheng rockfill material under drained triaxial tests. Finally, new insights into the development of constitutive models and areas requiring further investigation utilizing DEM have been highlighted.

This study investigates the influence of unsymmetrical surcharge on the piles of a bridge located in a coastal soft soil area, aiming to elucidate the deformation characteristics of the piles. The impact of some key parameters, including soft soil properties and unsymmetrical surcharge, on pile deformations is evaluated through 3D finite element numerical analysis and parameter sensitivity analysis. The results show that unsymmetrical surcharge significantly influences the displacement of both the piles and the surrounding soil, with both being affected by the soil arching effect. The parameter sensitivity analysis reveals that Poisson's ratio of the soft soil, and the stiffness of the piles have minimal impact on horizontal displacement. In contrast, the elastic modulus, cohesion, and internal friction angle of the soft soil, as well as the height and slope of the unsymmetrical surcharge, have significant effects on the piles. When the unsymmetrical surcharge is applied parallel or perpendicular to the bridge, the parallel surcharge has a relatively minor impact on the pile. The horizontal displacement of the pile follows an exponential relationship with L/B, D/h, and B/d. A functional relationship can be established between these parameters to predict the pile's horizontal displacement.

As lunar exploration advances, the development of durable and sustainable lunar surface architecture is increasingly critical, with a particular focus on material selection and manufacturing processes. However, current technologies and designs have yet to deliver an optimal solution. This study presented an innovative designs pattern for laser-sintered lunar soil bricks, namely a sintered glass outer layer and a core composed of lunar soil particles. For structural reinforcement purposes, a combined system of columns and slabs was implemented to improve the overall strength characteristics. This approach leverages the low thermal conductivity of lunar regolith particles in conjunction with the thermal stability, radiation resistance, and mechanical strength characteristics of glass. In this case, our simulations of heat conduction demonstrated a marked improvement in the thermal insulation properties of the new lunar soil bricks. The low thermal conductivity of lunar regolith effectively serves as an insulating layer, while the column, plate and glass outer layer, with their higher thermal conductivity, enable rapid thermal response across the entire structure and enhance spatial heat transfer uniformity. We further investigated the influence of structural variations on heat transfer mechanisms, revealing that the thickness of the glass layer exclusively modulates the heat transfer rate without altering its spatial distribution. Additionally, comparative analysis of all designed samples demonstrated that the novel sample displays superior thermal insulation properties, reduces average energy consumption by three quarters, and maintains adequate mechanical strength, alongside the proposal of a suitable assembly and construction methodology. Consequently, we believe that glassy composites exhibit substantial potential for space construction. These findings offer valuable insights and recommendations for material design in lunar surface construction.

The shear stress-shear displacement relationship and shear strength parameters at the pipe-soil interface are crucial for calculating jacking force. To investigate these properties, a series of tests were performed using a large-scale direct shear device to examine the shear mechanics of the steel-sand interface under various conditions. The effects of particle size, normal stress, and slurry concentration on shear performance were analyzed macroscopically. Additionally, the evolution of interface micro-behavior was studied using discrete element software PFC 2D. The experimental results indicate that the particle size of the sand has a significant impact on the shear stress-shear displacement curve of the interface, with smaller particle sizes requiring greater shear stress to achieve stability during shear. The strain-softening degree of sand is affected by normal stress. The shear stress-shear displacement curve is more significantly affected by particle size with the increase of normal stress. By considering different slurry concentrations, it is observed that both the shear stress and the sliding friction coefficient reached a minimum value at a concentration of 14%. The numerical simulation results indicate that particle motion causes changes in the distribution of particle structures. The distribution of particle force chains is relatively dispersed before shear. Particles move vigorously toward the shear interface, and force chains primarily concentrate on the shear interface during shear. Shear stress is transmitted through particle movement, and particle displacement causes shear dilation within the contact zone. Particles essentially cease moving toward the shear interface, and the force chains no longer change once the shear band is formed.

The aim of this study is to reveal the influence of frozen soil anisotropy and thermal-hydraulic-mechanical coupling effects on the frost heave deformation behavior of sheet pile walls (SPWS) through numerical simulation and experimental verification. In this research, a thermal-hydraulic-mechanical (THM) model of frozen soils is improved by integrating the anisotropic frost deformation firstly. Then, considering the shear characteristics of soil-structure interface, a finite element analysis of SPWS during freezing is conducted based on the proposed THM model. The simulation results are then validated by a small-scale simulation test. The results shown that, the pile is subjected to large bending moments and normal stress at the junction between the embedded and the cantilever section. Embedment depth of pile is suggested to set be 1/3 to 1 time the overall lenth, which having a greater effect on antiing the frost deformation. Numerical simulation considering the anisotropic of frozen soil is closer to the experimental results than traditional calculation methods. The THM numerical method can well characterize the directional relationship between temperature gradient and pile deformation. In seasonal frozen soil areas, deformation numerical simulation that can be further developed by considering the effects of multiple freeze-thaw cycles in subsequent research.

This paper uses a simplified assessment method based on the excavated-induced ground movement to examine the coupling effect between adjacent excavations during construction. The finite element numerical model is established to simulate and analyze the deformation of adjacent excavations at each stage of construction. Distinct construction sequences are employed to explore the dissimilarities in the deformation characteristics of the surrounding soil and envelope after excavation. The results indicate that when adjacent excavations are excavated simultaneously, their interactions affect the soil and envelopes' deformation. The maximum ground settlement occurs at a certain distance from the edge of the excavation. As the excavation depth increased, the enclosure exhibited a more pronounced deformation. The deformation of the enclosure structure can be significantly inhibited by the spatial effect at the corners of the excavation. When adjacent pits are constructed in different construction sequences, the enclosure structure on the first constructed excavation often experiences greater deformation than on the later constructed excavation.