Soft soil subgrades often present significant geotechnical challenges under cyclic loading conditions associated with major infrastructure developments. Moreover, there has been a growing interest in employing various recycled tire derivatives in civil engineering projects in recent years. To address these challenges sustainably, this study investigates the performance of granular piles incorporating recycled tire chips as a partial replacement for conventional aggregates. The objective is to evaluate the cyclic behavior of these tire chip-aggregate mixtures and determining the optimum mix for enhancing soft soil performance. A series of laboratory-scale, stress-controlled cyclic loading tests were conducted on granular piles encased with combi-grid under end-bearing conditions. The granular piles were constructed using five volumetric proportions of (tire chips: aggregates) (%) of 0:100, 25:75, 50:50, 75:25, and 100:0. The tests were performed with a cyclic loading amplitude (qcy) of 85 kPa and a frequency (fcy) of 1 Hz. Key performance indicators such as normalized cyclic induced settlement (Sc/Dp), normalized excess pore water pressure in soil bed (Pexc/Su), and pile-soil stress distribution in terms of stress concentration ratio (n) were analyzed to assess the effectiveness of the different mixtures. Results indicate that the ordinary granular pile (OGP) with (25 % tire chips + 75 % aggregates) offers an optimal balance between performance and sustainability. This mixture reduced cyclic-induced settlement by 86.7 % compared to the OGP with (0 % TC + 100 % AG), with only marginal losses in performance (12.3 % increase in settlement and 2.8 % reduction in stress transfer efficiency). Additionally, the use of combi-grid encasement significantly improved the overall performance of all granular pile configurations, enhancing stress concentration and reducing both settlement and excess pore water pressure. These findings demonstrate the viability of using recycled tire chips as a sustainable alternative in granular piles, offering both environmental and engineering benefits for soft soil improvement under cyclic loading.

Gravelly soils, characterized by a distinctive combination of coarse gravel aggregates and fine soil matrix, are widely distributed and play a crucial role in geotechnical engineering. This study investigates the mechanical behavior of gravelly soil subjected to simulated freeze-thaw (F-T) cycles using triaxial compressive strength tests. The long-term deviatoric stress response of specimens with varying gravel content and initial water content was analyzed under three distinct effective confining pressures (100, 200, and 300 kPa) across different F-T cycles. The results indicate that compressive strength is significantly influenced by gravel content, initial water content, and confining pressure. Notably, the rate of increase in deviatoric stress does not exhibit a proportional rise under confining pressures of 200 kPa and 300 kPa after 40 F-T cycles. However, a direct correlation is observed between deviatoric stress and increasing confining pressure (100, 200, and 300 kPa) over 2-, 4-, and 6-day intervals, this effect is more pronounced at higher confining pressures. The deviatoric stress peaks at different strain thresholds depending on the applied confining pressure; furthermore, no evident strain-softening behavior is observed across the tested conditions. These findings suggests that higher confining pressure inhibits particle displacement and interlocking failure, thereby reducing both the void ratio and axial strain within the soil matrix. Overall, these insights enhance our understanding of the complex interactions among gravel content, water content, confining pressure, and freeze-thaw effects, contributing to the understanding of the compressive strength evolution in gravelly soils under cyclic environmental loading.

The distinct particle breakage characteristics of calcareous sand can induce extra settlement in calcareous sand foundations, posing a significant challenge to the safety of island and reef engineering. To explore the particle breakage, settlement characteristics and internal stress variations of calcareous sand foundations, the laboratory loading tests for calcareous sand foundations with different particle gradations were conducted. Particle Image Velocimetry (PIV) technology and tactile pressure sensor systems were also utilized. The study reveals that the tested calcareous sand foundations have differential settlements subjected to external loading, which has a strong relationship with the particle breakage. It is found that the nonuniform internal stresses between the sand particles can induce different degrees of the particle breakage, which in turn changes internal stresses and redistribution of particle positions in calcareous sands, and further causes the uneven settlement of the foundation. The degree of uneven settlement in calcareous sand foundations increases with an increase of external load and decreases with an increase of the coefficient of uniformity Cu for calcareous sands. During creep, the vertical and lateral stresses on the inter-particle contacts within the calcareous sand foundation exhibit an overall trend of decrease in weak forces and increase in strong forces. This continuous increase in strong forces results in a growth of creep deformation in calcareous sand foundation, while the degree of differential settlement in the foundation decreases with the progression of creep.

This paper investigates the mechanisms of rock failure related to axial splitting and shear failure due to hoop stresses in cylindrical specimens. The hoop stresses are caused by normal viscous stress. The rheological dynamics theory (RDT) is used, with the mechanical parameters being determined by P- and S-wave velocities. The angle of internal friction is determined by the ratio of Young's modulus and the dynamic modulus, while dynamic viscosity defines cohesion and normal viscous stress. The effect of frequency on cohesion is considered. The initial stress state is defined by the minimum cohesion at the elastic limit when axial splitting can occur. However, as radial cracks grow, the stress state becomes oblique and moves towards the shear plane. The maximum and nonlinear cohesions are defined by the rock parameters under compressive strength when the radial crack depth reaches a critical value. The efficacy and precision of RDT are validated through the presentation of ultrasonic measurements on sandstone and rock specimens sourced from the literature. The results presented in dimensionless diagrams can be utilized in microcrack zones in the absence of lateral pressure in rock masses that have undergone disintegration due to excavation. (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-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

In this research, an energy formulation is proposed for the evaluation of pore pressure generation, incorporating the influence of the initial state of static stresses, both normal and shear, prior to cyclic loading. The proposed model focuses on obtaining a law of evolution of pore pressures under cyclic loading in saturated soils regardless of their susceptibility or not to liquefaction. The energy approach developed in this research extends previous energy based models developed for granular soils (susceptible to liquefaction and without initial static shear stress) incorporating: a) the integration in the formulation and interpretation of both the work dissipated and consumed during the dynamic process; b) the normalization of the formulation considering initial static stresses both normal and shear; c) obtaining and validating the model parameters with conventional tests of cyclic shearing equipment. The proposed model was validated with 116 cyclic simple shear tests under different in situ vertical effective stresses and different combinations of static and cyclic shear stresses. However, the model can be easily calibrated for other soils with cyclic simple shear tests without static shear stress, widely used in laboratories with dynamic equipment.

The increasing level of cadmium (Cd) contamination in soil due to anthropogenic actions is a significant problem. This problem not only harms the natural environment, but it also causes major harm to human health via the food chain. The use of chelating agent is a useful strategy to avoid heavy metal uptake and accumulation in plants. In this study, randomized design pot experiment was conducted to evaluate potential role of malic acid (MA) and tartaric acid (TA) foliar spray to mitigate Cd stress in Spinacia oleracea L plants. For Cd stress, S. oleracea plants were treated with CdCl2 solution (100 mu M). For control, plants were given distilled water. One week after Cd stress, MA and TA foliar spray was employed at concentration of 100 and 150 mu M for both. The results of this study revealed that Cd stress (100 mu M) significantly reduced growth attributes, photosynthetic pigments and related parameters and gas exchange attributes. Cadmium stress also stimulated antioxidant defense mechanism in S. oleracea. Cd stressed plants had elevated levels of Cd metal ions in root and consumable parts (i.e. leaves) and caused severe oxidative damages in the form of increased lipid peroxidation and electrolytic leakage. MA and TA supplements at both low and high levels (100 and 150 mu M) effectively reversed the devastating effects of Cd stress and improved growth, photosynthesis and defense related attributes of S. oleracea plants. These supplements also prevented excessive accumulation of Cd metal ions as indicated by lowered Cd metal contents in MA and TA treated plants. These findings demonstrated that MA and TA treatments can potentially reduce Cdl induced phytotoxicity in plants by reducing its uptake and enhancing photosynthesis and defense related parameters.

One of the most successful techniques used to increase structural capacity and sustainability in highway construction is cement stabilization. Despite its reported advantages, some disadvantages such as sensitivity to overloading and reflection cracking normally accompany this technique. The aim of this paper is to investigate the effect of recycled steel fibers inclusion on compressive properties of cement-stabilized granular material and to identify the implications of such reinforcement on pavement responses and economic benefits in terms of pavement thickness. The study was undertaken from both laboratory and theoretical points of view. Laboratory investigation was conducted in terms of unconfined compressive strength (UCS), modulus of elasticity and Poisson's ratio. The results indicated that incorporation of fibers reduces density and UCS of the composite while stiffness modulus and Poisson's ratio were found to be increased as a result of such modification. The failure pattern observations revealed better intactness and integrity of specimens as fiber content increased. From a UCS point of view, the use of lower fiber content (0.25% by volume of aggregate) produced better properties. However, the reduction in the UCS due to reinforcement inclusion can be considered small compared with the reported improvement in tensile properties. Furthermore, incorporating fiber in a cement-stabilized base helps to reduce the tensile strains at the bottom of both asphalt surface and cemented base layers and also compressive strain on the top of subgrade. Finally, reinforcing cement-stabilized aggregate with fibers from consumed tires will ensure reduction of the required thickness of cemented base layer and/or overlying and underlying pavement layers.

Soil metal pollution is a global issue due to its toxic nature affecting ecosystems and human health. This has become a concern since metals are non-biodegradable and toxic. Most of the reclamation methods currently used for soils rely on the use of physical and chemical means, which tend to be very expensive and result in secondary environmental damage. However, microbe-aided phytoremediation is gaining attention as it is an ecofriendly, affordable, and technically advanced method to restore the ecosystem. It is essential to understand the complex interaction between plants and microbes. The primary function of plant growth-promoting bacteria (PGPB) is to stimulate plant development, aid in metal elimination, and reduce their bioavailability in the soil. These microbes regulate phytohormones, stimulate processes such as phytoextraction and phyto-stabilization, and improve the uptake of essential nutrients, such as nitrogen and phosphorus. PGPBs secrete a range of enzymes and chemicals, fix nitrogen, solubilize minerals, increase the bioavailability of nutrients under diverse biological environments with high salinities, excessive metal-contaminated soil, and organic pollutants, increase the soil fertility and help in the reclamation of agriculture and regenerate the native flora. The integration of CRISPR-Cas9 gene-editing technology with microbialaided phytoremediation and the use of genetically modified microbes with nanomaterials further enhance the efficacy of the approaches in polluted environments for sustainable restoration of the soil.

In practical engineering, soil strength displays characteristics of spatial heterogeneity and anisotropy. Neglecting these characteristics complicates reliably evaluations of slope stability. Therefore, this study conducts an in-depth analysis of slope stability considering the spatial heterogeneity and anisotropy of soil strength. First, improvements were made to the existing spatial heterogeneity model and the original Casagrande anisotropy model to enhance their universality and practicality. Next, the spatial heterogeneity and anisotropy of soil strength were coupled and incorporated into the Mohr-Coulomb (M-C) strength criterion using an improved tensile-shear mode. Subsequently, within the framework of the limit equilibrium (LE) theory, a calculation mode of slip surface stress was employed to replace the conventional assumption mode of inter-slice force. This was achieved by constructing slip surface stress functions and introducing the concept of the local factor of safety for the slip surface, along with stress constraint conditions at the ends of the slip surface. This approach integrates the combined mechanisms of tension-shear and compression-shear, as well as the progressive failure modes of slopes. Finally, based on the overall mechanical equilibrium conditions satisfied by the sliding body, a rigorous LE solution for slope stability was established, accounting for the characteristics of the spatial heterogeneity and anisotropy in soil strength. Through comparative analysis of specific examples, the feasibility and effectiveness of the proposed method were validated. Additionally, this research can also be applied to thoroughly elucidate the slope failure mechanism influenced by the spatial heterogeneity and anisotropy of soil strength.

Climate change not only leads to high temperatures, droughts, floods, storms and declining soil quality, but it also affects the spread and mutation of pests and diseases, which directly influences plant growth and constitutes a new challenge to food security. Numerous hormones like auxin, ethylene and melatonin, regulate plant growth and development as well as their resistance to environmental stresses. To mitigate the impact of diverse biotic and abiotic stressors on crops, single or multiple phytohormones in combination have been applied. Melatonin is a multifunctional signaling molecule engaged in the development and stress response of plants. In the current review, we discuss the synthesis and action of melatonin, as well as its utilization for plant resistance to different stresses from the perspective of practical application. Simultaneously, we elucidate the regulatory effects and complex mechanisms of melatonin and other plant hormones on the growth of plants, explore the practical applications of melatonin in combination with other phytohormones in crops. This will aid in the planning of management strategies to protect plants from damage caused by environmental stress.