Damping plays a crucial role in the design of offshore wind turbine (OWT) monopile foundations. The soil damping of the monopile-soil system (MSS) represents the energy dissipation mechanism arising from the interaction between the pile and the soil. It is typically derived by back-calculating from the overall damping measured in the entire OWT structure. However, few studies have independently examined the soil damping in MSS, and the impact of key parameters such as pile diameter, pile embedded depth, cyclic load amplitude, and load eccentricity on the variation of soil damping in MSS remains unclear. This paper introduces an elastoplastic-damage constitutive model for the numerical simulation of the damping ratio variation in seabed soil and MSS. The model is implemented in ABAQUS software and validated against cyclic triaxial tests on stiff clay soil. On this basis, a three-dimensional finite element sensitivity study was conducted to elucidate the effect of these key parameters on the MSS damping ratio. The results of the study reveal that the MSS damping ratio exhibits a nonlinear and asymmetric trend as the loading cycles increase. The MSS damping ratio decreases with increasing pile diameter and embedded depth but increases with increasing lateral cyclic load amplitude and load eccentricity from the mudline.

This paper presents an efficient two-and-a-half dimensional (2.5D) numerical approach for analysing the long-term settlement of a tunnel-soft soil system under cyclic train loading. Soil deformations from train loads are divided into shear deformation under undrained conditions and volumetric deformation from excess pore water pressure (EPWP) dissipation. A 2.5D numerical model was employed to provide the dynamic stress state owing to the moving train load and the soil static stress state by the gravity effect for the determination of their accumulations. Then, an incremental computation approach combined with the initial strain approach in the framework of the 2.5D model was developed to compute the long-term deformation of the tunnel-soft soil system, considering the influence of the soil hardening due to EPWP dissipation. This approach helps to determine the distribution of the progressive settlement, transverse and longitudinal deformations in the tunnel-soil system, overcoming traditional limitations. A comparison of settlements computed using this approach with measured settlements of a shield tunnel in soft soil shows good agreement, indicating the effectiveness of the proposed approach in analysing train-induced progressive deformation of the tunnel-soil system.

Lining-soil systems are always designed to apply in the severe environment, including high temperature and impact loads. In this work, the thermo-hydro-mechanical responses of a lining-soil system are implemented under a sudden heating. To distinguish from previous works, the thermal contact resistance and the partition coefficient at the interface are considered. And the lining material is regarded as a continuous medium and the surrounding soil as a saturated porous medium. In the numerical part, the closed-form solutions pertaining to temperature, displacement, radial stress and pore water pressure are derived utilizing the Laplace transformation technique and its numerical inversion method. The rationality of the method is verified by comparison, and the effects of the thermal contact resistance, the partition coefficient, interfacial contact models and lining materials on each physical field are discussed. The results indicate that interfacial conditions have a significant impact on the heat transfer process of the lining-soil system.

Lunar-based equipment undertakes the task of movement and transportation in the construction of unmanned lunar base. In the process of moving, the mechanical legs of the equipment are influenced by the lunar soil with special mechanical properties. In order to avoid these uncertainties caused by the lunar soil and other lunar environmental conditions affecting the safety during the mission, a new robust control method with the form of sectionalized expression is proposed based on the dynamic model of the leg-soil system. Lyapunov second method is introduced to demonstrate that the proposed control method can maintain the stability of the leg-soil system successfully. In order to clarify the contact force in the dynamics model, CAS-1 lunar soil simulant that can accurately simulate real lunar soil is used in the calibration test to obtain the precise mechanical parameters. Simulation and experiment are also carried out to verify the proposed control method and the traditional control methods are introduced to make a comparison. Both the simulation and experiment results show that the proposed control method has a better control effect than traditional methods. The proposed method improves the accuracy by an average of 75.7% and 55.9% compared to the traditional methods and the error is limited to 0.2%. By maintaining the stability and accuracy of the leg-soil system, the stability of the lunar-based equipment is improved when performing construction tasks. This study lays the foundation for the construction of unmanned lunar base in advance.

Due to the widespread use of engineered nanomaterials (ENMs) for soil remediation and nano-enabled sustainable agriculture, there is a growing concern regarding the behavior and fate of ENMs released into soil systems in the presence of natural root exudates (REs). Herein, we investigate the influence of REs on the fate and ecological effect of ENMs from a comprehensive perspective. We summarize the key roles reported in the literature for REs in physical changes (e.g., adsorption, dispersion/aggregation), chemical changes (e.g., oxidation/redox reactions, and dissolution), and biotransformation of ENMs, which will further determine the ecological risk of ENMs in natural soil systems. Moreover, this review highlights the potential adverse effects of ENMs on different soil organisms (e.g., bacteria, plants, and eisenia foetida) in the presence of REs. The remaining unclear mechanisms (e.g., oxidative stress and DNA damage) of ENMs toxicity at the cellular level influenced by REs are reviewed and presented. Finally, the review concludes by addressing the current knowledge gaps and challenges in this field.

As the regulator of water and nutrient changes in the active layer after permafrost degradation, root signaling substances affect the plant-soil carbon allocation mechanism under climate warming, which is a key issue in the carbon source/sink balance in permafrost regions. To explore how plant root signaling substances regulate carbon allocation in plants and soils under permafrost degradation, the changes in carbon allocation and root signaling substances in the plants and soils of peatland in different permafrost regions at the time of labeling were studied by in situ C-13 labeling experiments. The results showed that the fixed C-13 of Larix gemlini, Carex schumidtii, and Sphagnum leaves after photosynthesis was affected by permafrost degradation. In regions with more continuous permafrost, the trend of the L. gemlini distribution to underground C-13 is more stable. Environmental stress had little effect on the C-13 accumulation of Vaccinium uliginosum. Nonstructural carbohydrates, osmotic regulatory substances, hormones, and anaerobic metabolites were the main root signaling substances that regulate plant growth in the peatlands of the three permafrost regions. The allocation of carbon to the soil is more susceptible to the indirect and direct effects of climate and environmental changes, and tree roots are more susceptible to environmental changes than other plants in isolated patches of permafrost regions. The physical properties of the soil are affected by climate change, and the allocation of carbon is regulated by hormones and osmotic regulators while resisting anoxia in the sporadic regions of permafrost. Carbon allocation in discontinuous permafrost areas is mainly regulated by root substances, which are easily affected by the physical and chemical properties of the soil. In general, the community composition of peatlands in permafrost areas is highly susceptible to environmental changes in the soil, and the allocation of carbon from the plant to the soil is affected by the degradation of the permafrost.

The accumulation of microplastics in agricultural soil brings unexpected adverse effects on crop growth and soil quality, which is threatening the sustainability of agriculture. Biochar is an emerging soil amendment material of interest as it can remediate soil pollutants. However, the mechanisms underlying biochar alleviated the toxic effects of microplastics in crops and soil were largely unknown. Using a common economic crop, peanut as targeted species, the present study evaluated the plant physiologica and molecular response and rhizosphere microbiome when facing microplastic contamination and biochar amendment. Transcriptome and microbiome analyses were conducted on peanut root and rhizosphere soil treated with CK (no microplastic and no biochar addition), MP (1.5% polystyrene microplastic addition) and MB (1.5% polystyrene microplastic+2% peanut shell biochar addition). The results indicated that microplastics had inhibitory effects on plant root development and rhizosphere bacterial diversity and function. However, biochar application could significantly promote the expressions of key genes associated with antioxidant activities, lignin synthesis, nitrogen transport and energy metabolism to alleviate the reactive oxygen species stress, root structure damage, nutrient transport limitation, and energy metabolism inhibition induced by microplastic contamination on the root. In addition, the peanut rhizosphere microbiome results showed that biochar application could restore the diversity and richness of microbial communities inhibited by microplastic contamination and promote nutrient availability of rhizosphere soil by regulating the abundance of nitrogen cycling-related and organic matter decomposition-related microbial communities. Consequently, the application of biochar could enhance root development by promoting oxidative stress resistance, nitrogen transport and energy metabolism and benefit the rhizosphere microecological environment for root development, thereby improved the plant-soil system health of microplastic-contaminated agroecosystem.