Transversely isotropic rocks (TIRs) are widespread in geological formations, and understanding their mechanical behavior is crucial for geotechnical and geoengineering applications. This study presents the development of a novel analog material that reproduces the directional mechanical properties of TIRs. The material is composed of quartz sand, mica flakes, and gelatin in adjustable proportions, allowing control over strength and stiffness anisotropy. Uniaxial compressive strength (UCS) and direct shear tests were conducted to evaluate mechanical responses across different anisotropy angles. Results show that the analog material replicates key features of natural TIRs, including directional variations in strength and fracture modes. In UCS tests, the anisotropy angle (beta) governs the transition between tensile and shear failure. In direct shear tests, the orientation angle (alpha) significantly affects shear strength. Higher gelatin concentrations increase cohesion and Young's modulus without changing the internal friction angle, while mica content reduces overall strength and stiffness. Comparisons with published data on sedimentary and metamorphic rocks confirm the mechanical representativeness of the material. Its simplicity, tunability, and reproducibility make it a useful tool for scaled physical modeling of anisotropic rock behavior in the laboratory. This approach supports the experimental investigation of deformation and failure mechanisms in layered rock masses under controlled conditions.

Climate change increases the frequency of extreme weather events, intensifying shallow flow-type landslides, soil erosion in mountainous regions, and slope failures in coastal areas. Vegetation and biopolymers are explored for ecological slope protection; however, these approaches often face limitations such as extended growth cycles and inconsistent reinforcement. This study investigates the potential of filamentous fungi and wheat bran for stabilizing loose sand. Triaxial shear tests, disintegration tests, and leachate analyses are conducted to evaluate the mechanical performance, durability, and environmental safety of fungus-treated sand. Results show that the mycelium enhances soil strength, reduces deformation, and lowers excess pore water pressure, with a more pronounced effect under undrained than drained conditions. Mycelium adheres to particle surfaces, forming a durable bond that increases cohesion and shifts the slope of the critical state line, significantly enhancing the mechanical stability of fungus-treated sand. The resulting strength parameters are comparable to those of soils reinforced with plant roots. Fungus-treated sand remains stable after 14 days of water immersion following triaxial shear tests, with no environmental risk from leachate. These findings demonstrated that fungal mycelium provides an effective and eco-friendly solution for stabilizing loose sand, mitigating shallow landslides, and reinforcing coastlines.

The widespread utilisation of vacuum-assisted prefabricated vertical drains (PVD) for managing clayey soft ground has led to the development of numerous consolidation models. However, these models have limitations when describing the filtration behaviour of soil under high water content conditions, without the formation of a particle network. To effectively address this issue, in this work, based on the compressional rheology theory, a two-dimensional axisymmetric model incorporating the compressive yield stress Py(phi) and a hindered setting factor r(phi) was developed to couple the filtration and consolidation of soil under vacuum preloading. A novel approach for determining the unified phi-Py-r relationships was introduced. The equation governing such fluid/solid and solid/solid interactions was solved using the alternative direction implicit (ADI) method, and the numerical solutions were validated against the 1-D filtration cases, 3-D laboratory model tests, and large-scale field trials. Further parametric analysis suggests that the radius of the representative unit and r(phi) exclusively affect the dewatering rate of the clayey slurry, while the gel point and Py(phi) influence both the dewatering rate and the final deformation.

Soils are generally considered anisotropic with respect to hydraulic conductivity, while the evolution of anisotropy condition is unknown for bare and vegetated soils. Therefore, the main goal of this study is to compare the anisotropic hydraulic conductivity of as-compacted, bare, and vegetated specimens. Accordingly, a series of 54 hydraulic conductivity tests were conducted in a custom-made cube triaxial permeameter. The as-compacted specimens were revealed isotropic because the loosely packed preparation procedure resulted in a dominant flocculent structure. However, a fivefold increase in the anisotropy ratio of bare specimens was measured along the isotropic loading path because of the induced surficial degradation zone formed by irrigation and desiccation processes as evident in preliminary observations and crack network analysis. The variations in anisotropy ratio vs. void ratio function of vegetated soil generally fall below the corresponding function of the bare soil. The function was revealed to have a crossed nature, varying from sub-isotropic to super-isotropic states, corresponding to the lower and upper bounds of 0.3 and 3, respectively. It was postulated that vegetation impacts the flow differently by reducing the potential of desiccation cracks, creating preferential flow through the propagation of primary roots and clogging flow channels by secondary roots.

Thermal damage mechanisms are crucial in reservoir stimulation for enhanced geothermal system (EGS). This study investigates the thermal damage mechanisms in granite samples from the Gonghe Basin, Qinghai, China. The granite samples were heated to 400 degrees C and then cooled in air, water, or liquid nitrogen. The physical and mechanical properties of the thermally treated granite were evaluated, and microstructural changes were analyzed using a scanning electron microscope (SEM) and computed tomography (CT). The results indicate that cooling with water and liquid nitrogen significantly enhances permeability and brittleness while reducing P-wave velocity, strength, and Young's modulus. Specifically, liquid nitrogen cooling increased granite permeability by a factor of 5.24 compared to the untreated samples, while reducing compressive strength by 13.6%. After thermal treatment, the failure mode of the granite shifted from axial splitting to a combination of shear and tension. Microstructural analysis revealed that liquid nitrogen-cooled samples exhibited greater fracture complexity than those cooled with water or air. Additionally, acoustic emission (AE) monitoring during damage evolution showed that liquid nitrogen cooling led to higher cumulative AE energy and a lower maximum AE energy rate, with numerous AE signals detected during both stable and unstable crack growth. The results suggest that liquid nitrogen induces a stronger thermal shock, leading to more significant thermal damage and promoting the development of a complex fracture network during EGS reservoir stimulation. This enhances both the heat exchange area and the permeability of the deep hot dry rock (HDR) in EGS reservoirs. The insights from this study contribute to a deeper understanding of thermal damage characteristics induced by different cooling media and provide valuable guidance for optimizing deep geothermal energy extraction. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Recent years have witnessed a burgeoning interest in sustainable, eco-friendly, and cost-effective construction materials for civil engineering projects. Soilcrete, an innovative blend of soil and cement, has gained significant acclaim for its versatility and effectiveness. It serves not only as grout for soil stabilization in corrosive environments like landfills and coastal regions but also as a reliable material for constructing structural elements. Understanding the mechanical properties of soilcrete is crucial, yet traditional laboratory tests are prohibitively expensive, time-consuming, and often imprecise. Machine learning (ML) algorithms present a superior alternative, offering efficiency and accuracy. This research focuses on the application of the adaptive neuro-fuzzy inference system (ANFIS) algorithm to predict the uniaxial compressive strength (UCS) of soilcrete. A total of 300 soilcrete specimens, crafted from two types of soil (clay and limestone) and enhanced with metakaolin as a pozzolanic additive, were meticulously prepared and tested. The dataset was divided, with 80% used for training and 20% for testing the model. Eight parameters were identified as key determinants of soilcrete's UCS: soil type, metakaolin content, superplasticizer content, shrinkage, water-to-binder ratio, binder type, ultrasonic velocity, and density. The analysis demonstrated that the ANFIS algorithm could predict the UCS of soilcrete with remarkable accuracy. By combining laboratory results with ANFIS model predictions, the study identified the optimal conditions for maximizing soilcrete's UCS: 11% metakaolin content, a 0.45 water-to-binder ratio, and 1% superplasticizer content.

In recent years, the rapid development of offshore exploration and coastal engineering has necessitated stringent requirements for foundation materials, particularly in complex geological environments. Cemented soils, widely used in large-scale offshore engineering projects, play a crucial role in ensuring the safety and stability of offshore structures. However, understanding the mechanical behavior of cemented sand, including its stress-strain relationship, strength characteristics, and long-term performance under different stress paths, remains a challenge. This study uses triaxial tests and discrete element method (DEM) simulations to investigate the mechanical properties of cemented sand, using offshore quartz sand as the aggregate and a gypsum plaster as the cementing agent. The results reveal that higher confining pressures and gypsum content significantly improve the peak and residual strength of cemented sand, while also increasing its brittleness. The particle-size increasing and natural curing results in increased strength, cohesion, and internal friction angle of cemented sand. The study also finds that the stress-strain relationship of cemented sand primarily shows a strain-softening behavior, but gradually transitions to strain-hardening behavior at higher gypsum contents. DEM simulation results show that the displacement of internal particles becomes more pronounced, with particle movement gradually shifting from the vertical to the lateral direction. The research provides a scientific foundation for offshore engineering design, ensuring the safe operation of structures under extreme marine conditions.

The integrity of an intact sample significantly depends on maintaining the water content of the extracted soil until laboratory testing. Particularly, when exposed to water, overconsolidated clays tend to absorb and volumetrically swell. Traditional methods, such as using wet porous disks, allow specimens to rapidly absorb available water upon contact, potentially altering the intact soil structure and thus its mechanical behavior. This means that unnecessary swelling of the clay specimens should be avoided during specimen preparation for soil element testing. This paper investigates the influence of cell pressure confinement during the introduction of water to drainage lines and initially dry filter stones on subsequent shear behavior through a series of controlled laboratory experiments that were conducted using reconstituted Ons & oslash;y clay specimens following ASTM D4767-11, Standard Test Method for Consolidated Undrained Triaxial Compression Test for Cohesive Soils guidelines. Various confining stresses were applied during initial flushing of the drainage lines: the swelling pressure inhibiting specimen expansion (120 kPa for OCR2 and 355 kPa for OCR4 specimens) and 5 kPa of mean effective stress allowing the specimen swelling. After consolidation, undrained shear compression tests were conducted, and the mechanical behavior was recorded, including stiffness, strength, and excess pore water pressure. Results revealed significant differences in mechanical behavior among specimens, suggesting that allowing free swelling of intact specimens could have detrimental effects on soil properties. This study underscores the importance of controlling swelling of overconsolidated specimens due to absorption and highlights the potential impact on soil shear behavior.

The exponential growth of tunnelling projects worldwide necessitates efficient management of excavated soil, particularly from Earth Pressure Balance Tunnel Boring Machines (EPB-TBMs). This study investigates the temporal evolution of mechanical properties in EPB-excavated soil, focusing on the conditioning process's impact. Through a comprehensive literature review, gaps in understanding the soil's transition from a liquid-like state back to its solid form are identified. Existing studies touch on mechanical property changes over time but lack detailed temporal analyses. Our research addresses this gap by examining the recovery of soil compactability over time, crucial for its reuse. By conducting modified Proctor tests at different time intervals post-conditioning, we elucidate the relationship between soil properties and conditioning parameters. Our findings reveal a direct correlation between recovery time and total water content, influenced by added water and foam injection ratio. We demonstrate that different conditioning parameter combinations yield similar immediate properties but divergent recovery times, which are crucial for logistical planning and environmental suitability. This study offers valuable insights into optimizing EPB-TBM excavation logistics, enhancing soil reuse efficiency, and advancing sustainability in civil engineering projects.

Shredded rubber from waste tyres has progressively been adopted in civil engineering due to its mechanical properties, transforming it from a troublesome waste into a valuable and low-cost resource within an eco-sustainable and circular economy. Granular soils mixed with shredded rubber can be used for lightweight backfills, liquefaction mitigation, and geotechnical dynamic isolation. Most studies have focused on sand-rubber mixtures. In contrast, few studies have been conducted on gravel-rubber mixtures (GRMs), primarily involving poorly-graded gravel. Poorly-graded gravel necessitates selecting grains of specific sizes; therefore, from a practical standpoint, it is of significant interest to examine the behaviour of well-graded gravel and shredded rubber mixtures (wgGRMs). This paper deals with wgGRMs. The results of drained triaxial compression tests on wgGRMs are analysed and compared with those on GRMs. Stress-strain paths toward the critical state and energy absorption properties are evaluated. The tested wgGRMs exhibit good shear strength and remarkable energy absorption properties; thus, they can be effectively utilised in several geotechnical applications.