Geocells are three-dimensional, interconnected cellular geosynthetics widely used to enhance the overall strength of soils. Their foldable structure can cause variations in pocket shape during installation, depending on the extent of extension. Understanding the impact of these shape variations is essential for optimizing reinforcement efficiency and reducing the associated geocell application costs. The aspect ratio, defined as the ratio of the cell's transverse (welded) axis to the longitudinal (wall summit) axis, is proposed to evaluate the degree of extension of the most commonly utilized honeycomb-shaped geocell. A coupled continuum-discontinuum numerical method was employed to investigate the behavior of honeycomb-shaped geocell reinforced soils across various aspect ratios under confined compressive loading. The simulation results indicate that a geocell with an aspect ratio of 1.0 exhibits optimal reinforcement efficiency, and whereas reinforcement efficiency decreases as the aspect ratio deviates from 1.0 causing pocket geometries to flatten. The superior performance of rounded geocells is attributed to their enhanced ability to promote load-bearing in strong contact subnetworks. This results in denser packing structures, higher contact force anisotropy from a microscopic perspective, and greater confinement capacity against deformation from a macroscopic perspective.

Frozen soils exhibit unique mechanical behavior due to the coexistence of ice and unfrozen water, making experimental studies essential for engineering applications in cold regions. This review comprehensively examines laboratory investigations on frozen soils under static and dynamic loadings, including uniaxial and triaxial compression, creep, direct shear, and freeze-thaw (F-T) cycle tests. Key findings on stress-strain characteristics, failure mechanisms, and the effects of temperature and time are synthesized. Advancements in microstructural analysis techniques, such as computed tomography (CT), scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), and mercury intrusion porosimetry (MIP), are also summarized to elucidate the internal structural evolution of frozen soils. While significant progress has been made, further efforts are needed to better replicate complex environmental and loading conditions and to fully understand the interactions between multiple influencing factors. Future research should focus on developing novel experimental techniques, establishing standardized testing protocols, and creating a comprehensive database to enhance data accessibility and advance frozen soil research. This review provides critical insights into frozen soil mechanics and supports validating constitutive models and numerical simulations, aiding infrastructure design and construction in cold regions.

The main problem in expansive soil treatment with steel slag (SS) is the relatively slow hydration reaction that occurs during the initial period. To circumvent this, SS-treated expansive soil activated by metakaolin (MK) under an alkaline environment was investigated in this study. Based on a series of tests on the engineering properties of the treated soil, it can be reported that SS could enhance the strength and compressibility of expansive soil, with strength increasing by approximately 108 % for SS contents exceeding 10 % compared to 3 % lime-treated soil, and the compression index reducing by 20 %. Further addition of MK plays a dual role, enhancing strength for higher SS content while excessive MK leads to strength reduction due to insufficient pozzolanic reactions and hydration product transformation. Expansive and shrinkage behaviors are notably improved, with a 5 % increase in SS content reducing the free swelling ratio by 0.66 %-5.9 %, and the combination of 15 % SS and 6 % MK achieving a nearly 300 % reduction in the linear shrinkage ratio. Microstructural analysis confirms the formation of hydration gels, densification of the soil structure, and reduced macropores, validating the enhanced mechanical and shrinkage resistance properties of the SS-MK-treated expansive soil. Additionally, to develop predictive models for mechanical and the content of hardening agents (SS and MK), the experimental data are processed utilizing a backpropagation neural network (BPNN). The results of BPNN modeling predict the mechanical properties perfectly, and the correlation coefficient (R) approaches up to 0.98.

Soil-steel composite bridges (SSCBs) are commonly utilized as overpasses. In the majority of existing studies, the transverse structural performance of SSCBs is primarily focused on, while neglecting their longitudinal structural performance. The aims of this paper are to clarify the longitudinal properties and compensate for the paucity of research on the longitudinal structural performance of SSCBs. In current study, field tests were conducted on a SSCB case bridge in a mining area, both in the construction stage and post-construction stage. Subsequently, longitudinal differences in the structural settlements, deformations, and hoop strains were analyzed. Additionally, a refined three-dimensional finite element model was developed and verified to analyze the transfer behavior of soil pressure above the structure along the longitudinal direction. The results indicate that in the construction stage, the difference in the soil-covered height primarily account for the differences in structural performances along the longitudinal direction. At the end of backfilling, the settlements, deformations, and hoop strains in the middle are all greater than those in the end sections. In the post-construction stage, further developments of longitudinal structural characteristics occur due to creep deformation of the foundation soil and disturbances from mining trucks. One year after construction, the structural characteristics have stabilized. The maximum settlement reaches -1.014 m and the maximum settlement difference reaches 0.365 m. The differential settlement ratio, at 0.62 %, remains within the 1 % limit specified in the CHBDC code. Due to longitudinal settlement differences, the soil pressure in the higher settlement zone is transferred to the lower settlement zone by the longitudinal soil arching effect, which benefits the load-bearing capacity of SSCBs.

Despite the complexity of real earthquake motions, the incident wavefield excitation for soil-structure interaction (SSI) analysis is conventionally derived from one-dimensional site response analysis (1D SRA), resulting in idealized, decoupled vertically incident shear and compressional waves for the horizontal and vertical components of the wavefield, respectively. Recent studies have revealed potentially significant deviation of the 1D free-field predictions from the actual three-dimensional (3D) site response and obtained physical insights into the mechanistic deficiencies of this simplified approach. Particularly, when applied to vertical motion estimation, 1D SRA can lead to consistent overprediction due to the refraction of inclined S waves in the actual wavefield that is not correctly accounted for in the idealized vertical P wave propagation model. However, in addition to the free-field site response, seismic demands on structures and non-structural components are also influenced by the dynamic characteristics of the structure and SSI effects. The extent to which the utilization of vertically propagating waves influences the structural system response is currently not well understood. With the recent realization of high-performance broadband physics-based 3D ground motion simulations, this study evaluates the impact of incident wavefield modeling on SSI analysis of representative building structures based on two essential ingredients: (1) realistic spatially dense simulated ground motions in shallow sedimentary basins as the reference incident motions for the local SSI model and (2) high-fidelity direct modeling of the soil-structure system that fully honors the complexity of the incident seismic waves. Numerical models for a suite of archetypal two-dimensional (2D) multi-story building frames were developed to study their seismic response under the following incident wavefield modeling conditions: (1) SSI models with reference incident waves from the 3D earthquake simulation, (2) SSI models with idealized vertically incident waves based on 1D SRA, and (3) conventional fixed-base models with base translational motions from 1D SRA. The impact of these modeling choices on various structural and non-structural demands is investigated and contrasted. The results show that, for the horizontal direction, the free-field linear and nonlinear site amplification and subsequent dynamic filtering of the base motions within the structure can be reasonably captured by the assumed vertically propagating shear waves. This leads to generally fair agreements for structural demands controlled by horizontal motions, including peak inter-story drifts and yielding of structural components. In contrast, vertical seismic demands on structures are overpredicted in most cases when using the 1D wavefields and can result in exacerbated structural damage. Special attention should be given to the potentially severe vertical floor accelerations predicted by the 1D approach due to the combined effects of fictitious free-field site amplification and significant vertical dynamic amplification along the building height. This can pose unrealistic challenges to seismic certification of acceleration-sensitive secondary equipment necessary for structural and operational functionality and containment barrier design of critical infrastructures. It is also demonstrated that vertical SSI effects can be more significant than those in the horizontal direction due to the large vertical structural stiffness and should be considered in vertical floor acceleration assessments, especially for massive high-rise buildings.

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 study focuses on the architectural and structural analysis of the Justinian Bridge, an ancient stone arch bridge dating from the Byzantine era, located on Turkey's Sakarya (Sangarius) River. The research examines the structural configuration of the bridge and integrates its architectural background with data derived from comprehensive analyses. Experimental geophysical investigations were employed to assess the bridge's structural behavior, particularly considering the depths of the piers embedded in alluvial soil layers. The studies provided valuable data on the geometric and hydraulic properties of the bridge piers. The bridge's natural vibration frequencies and mode shapes were determined using a three-dimensional finite element model under four different boundary conditions. The results revealed that natural vibration frequencies are sensitive to soil properties. Time history analysis, incorporating ten sets of ground motion data, evaluated the bridge's dynamic response to earthquake loads. The damage distribution on the bridge body was determined and compared with the stresses obtained from the numerical analysis. The numerical results accurately show the damaged areas of the bridge. The findings provide valuable insights into the safety of historic stone arch bridges and serve as an essential reference for future conservation efforts.

Natural marine clays exhibit distinct dynamic behavior compared to remolded counterparts due to their inherent structural properties. Dynamic and static triaxial tests were conducted on both marine clay types to evaluate stress-strain behavior, double amplitude strains, pore water pressure, and dynamic elastic modulus, as well as post-cyclic strength attenuation. The results indicate that due to the structural properties, the effective stress path of undisturbed samples is more ductile than that of remolded samples. Also, there is a clear inflection point in the strain development curve of undisturbed samples. The structure exerts a certain degree of restraint on the strain development of the undisturbed samples, and has a distinct impact on the variation of pore water pressure at varying dynamic stress levels. Both marine clay types exhibited gradual reductions in dynamic elastic modulus and marked undrained strength attenuation. Critically, the attenuation of dynamic elastic modulus in undisturbed samples aligned with post-cyclic strength loss, while remolded samples exhibited greater dynamic elastic modulus loss relative to strength degradation. These findings clarify the role of soil structure in cyclic response and strength degradation, offering insights for the long-term stability assessment of structures and disaster mitigation in marine clay engineering.

A microstructural rock model based on the distinct element method employing the Subspring Network contact model with rigid, Breakable, Voronoi-shaped grains (SNBV model) is proposed. The model consists of a mesh (3D Voronoi tessellation) of rigid, breakable, Voronoi blocks. The SNBV model is a microstructural rock model because it is a discrete model that can mimic rock microstructure at the grain scale. SNBV material mimics the microstructure of angular, interlocked, breakable grains with interfaces that may have an initial gap and can sustain partial damage. The model embodies the microstructural features and damage mechanisms that occur at the grain scale: initial microcrack fabric; heterogeneity-induced local tension; and intergranular and transgranular damage. The heterogeneity-induced local tension can be introduced in a controlled fashion that is not tied directly to the shape and packing of the grains and the interface stiffnesses. The synthetic material exhibits behavior during direct-tension and triaxial compression tests that matches the behavior of compact rock. The material can be calibrated to match the standard material properties and characteristic stresses of pink Lac du Bonnet granite. The material properties consist of Young's modulus and Poisson's ratio corresponding with uniaxial compression and Young's modulus corresponding with direct tension, as well as tensile strength, crack-closure stress, crack-initiation stress, secondary crack-initiation stress to mark the onset of grain breakage, crack-damage stress, and compressive strengths up to 4 MPa confinement. The model is suitable for studying the grain-scale micromechanics of brittle rock fracture.

Erosion and seepage control is a prime concern for embankments, dams, and other hydraulic structures constructed with alluvial sandy soil due to its highly porous characteristics. Permeation grouting has been a popular solution for controlling seepage situations in such structures. In this study, unconfined compression tests and triaxial tests were performed to determine the strength properties of grouted alluvial sandy soil located in the Ganges-Brahmaputra-Meghna delta. A simple method was devised to prepare cylindrical grouted samples with water-cement ratios (W/C) of 2:1, 3:1, 4:1, and 5:1. Here, unconfined compressive strength test results revealed that the highest compressive strength of the grouted sandy soil samples was achieved at the 2:1 W/C ratio at all curing ages. Different failure patterns are observed for different W/C samples during unconfined compressive tests. Furthermore, triaxial tests were conducted on the grouted samples prepared at the 2:1 W/C ratio under consolidated undrained conditions. Dilation occurred during the volume change, and the pore pressure decreased with increasing confining stress. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy were conducted to discern the microstructural behavioral changes and the chemical characteristics of the grouted sandy samples, respectively. Here, SEM images revealed a reduction in porosity with decreasing W/C ratio and increasing curing age. Permeation grouting leads to a reduction in permeability without disturbing the soil microstructure. Therefore, permeation grouting is a very effective technique for improving the mechanical behavior of grouted alluvial sand.