The hydraulic effect of plant roots reduces precipitation infiltration and enhances shallow slope stability. However, after root death and decay, soil permeability increases while water-retention capacity decreases. The time-varying mechanisms governing the hydraulic properties of root-soil composites after root decay remain unclear. This study examines the evolution of soil pore structure following root decay. A time-varying soil water retention curve (SWRC) model was developed to characterize changes in water-retention capacity. Additionally, a time-varying saturated infiltration coefficient model and a permeability coefficient prediction model were established to describe variations in hydraulic properties. A one-dimensional soil column infiltration test was conducted on root-soil composites at different stages of root decay to investigate the time-dependent changes in hydraulic properties. The reliability of the proposed models was validated using experimental results. The findings indicate the following: After root death, root biomass, diameter, length, and number decreased with increasing decay time, stabilizing after four months. Root decay led to a reduction in root volume ratio, which altered soil structure and enhanced the permeability of root-soil composites. Longer decay periods increased soil porosity, modifying the soil water characteristic curve and reducing water-retention capacity. Creeping roots decayed more significantly than fibrous roots due to their distinct morphological traits, making changes in hydraulic properties more pronounced in the topsoil. Therefore, plant root decay negatively affects soil hydraulic properties by continuously altering soil pore structure. These findings provide a crucial foundation for understanding the time-dependent mechanisms of hydraulic property variations in root-soil composites during plant root decay.

Geosynthetics are widely used in civil engineering reinforcements owing to their high strength, acceptable toughness, and ease of transportation. However, traditional geosynthetics do not have the capability to monitor damage inside the soil. Therefore, in this paper, a new sensor-enabled piezoelectric geobelt (SPGB) is developed to measure the deformation of reinforced-soil structures. In-soil drawing tests are conducted to investigate the sensing performance of the SPGB. Variations in the voltage and impedance signals of the SPGB with the drawing displacement under different damage conditions are investigated. The results show that with the increase of drawing displacement, SPGB undergoes tensile deformation followed by pullout damage. In tensile deformation, the signal response of SPGB is related to strain. As the strain increases, the output voltage first increases and then decreases, and the impedance gradually decreases. In the pullout damage phase, the signal response of SPGB is related to the contact area between SPGB and soil. As the drawing displacement increases, the contact area between SPGB and soil gradually decreases, the output voltage gradually decreases, and the impedance gradually increases. Therefore, the SPGB, as a sensor- enabled geosynthetic, provides a reinforcing function to the soil body and simultaneously performs in-soil catastrophe identification.

Designers often assume a rigid foundation for buildings in seismic zones, believing it ensures safety during earthquakes. However, this assumption may neglect important factors, such as soil-structure interaction (SSI) and the potential for collisions between adjacent buildings. This study investigates the effect of dynamic SSI on the seismic pounding response of adjacent buildings. A nonlinear finite-element analysis was performed on three cases: bare buildings, buildings with linear fluid viscous dampers (LFVDs), and buildings with nonlinear fluid viscous dampers (NFVDs). The dynamic contact technique, in which contact surfaces with both the contactor and target, was employed to mimic the mutual pounding. Key seismic response parameters, including acceleration, displacement, inter-story drift, and pounding forces, were analyzed. The results showed that dynamic SSI significantly affects the seismic performance of adjacent buildings, altering the number, timing, and intensity of collisions. In some cases, SSI increased inter-story drifts beyond code-permissible limits, indicating that relying on a rigid foundation assumption could lead to unsafe structural designs. Additionally, SSI had a notable impact on the forces in NFVDs, highlighting the need for careful design considerations when using these devices. The study further investigates the effect of soil flexibility on the performance of nearby structures under different seismic excitations, focusing on the NFVDs case with a 10 % damping ratio. Incremental Dynamic Analysis (IDA) and fragility analysis were conducted to assess performance under seismic excitations, focusing on three performance levels: Immediate Occupancy (IO), Life Safety (LS), and Collapse Prevention (CP). While SSI had minimal impact on the more flexible buildings, it significantly affected the more rigid building, particularly at LS and CP levels, making it more vulnerable to damage compared to buildings on rigid foundations. These findings underscore the importance of incorporating SSI in seismic design to ensure structural safety.

The present document presents a review on the use of the finite element software package CODE_BRIGHT to simulate reinforced soil structures (RSS). RSS are composed of longitudinal steel or polymeric materials, placed orthogonal to the main stress direction in a soil mass, acting as tension-bearing elements. A common application of RSS is in retaining structures, in the form of reinforced soil walls (RSWs). RSW are usually designed with analytical methods, which have limited capabilities when predicting a structure's deformation response. To improve on this, the use of numerical tools allows to quantify the stress-strain response of complex, compound structures, such as RSWs. Several factors must be considered when modelling RSS, including reinforcement response, which can be non-linear under several circumstance (including time- and temperature-dependencies), soil-reinforcement interaction, soil-structure interaction, and soil response, all of which can be affected by the presence of moisture. Using laboratory measured data, the individual response of reinforcements (e.g., creep elongation), as well as the compound behaviour of soil-reinforcement material (e.g., pullout response) can be simulated to explore individual and compound response. Depending on the modelled phenomena, numerical simulations may include 2D and 3D representations. For full-scale reinforced soil walls, the stress-strain response within the soil mass, reinforcements, concrete facing panels, and connections can be studied in magnitude and distribution. Details regarding special considerations of how to model such structures with CODE_BRIGHT and other commercially available software are provided. Insights on the thermo-hydraulic repone of RSWs are covered. Advantages, limitations and future lines of research in the use of CODE_BRIGHT are explored.

The study investigates the interaction between geogrids and two distinct granular backfill materials, Yamuna sand and coal mine overburden through a combination of laboratory experiments and numerical simulations. It evaluates the physical and mechanical properties of coalmine overburden and Yamuna sand, and the pullout performance of geogrid embedded in both materials. A large-scale pullout box was utilised to conduct the experiments, and the results showed that coalmine overburden offers higher pullout resistance than Yamuna sand. The effect of physical parameters such as elasticity of geogrid, geogrid geometry and angle of inclination were analysed using the discrete element method. The pullout resistance of geogrids mainly depends on the elastic properties of the material. The study also shows the existence of an optimum spacing between longitudinal and transverse ribs.

Understanding the volume change behavior of deep-water sediments is essential for the safety design of deep-water engineering structures. In this study, the volume change behaviors of marine sediments from the South China Sea were studied through oedometer and isotropic compression tests. Scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) tests have been conducted to investigate the microstructure evolution of two types of sediments under loads. The experimental results showed that the structural anisotropy of intact specimens is more pronounced in oedometer tests with the increase of stress, however, depolarization occurs in the isotropic consolidation test. The volume change after yield in the oedometer and isotropic consolidation tests comes from inter-aggregate pore variations associated with the adjustment of the soil fabric. The reconstituted specimen presents a more uniform distribution of pores than that of the intact specimen, and the macropores are more easily compressed for the reconstituted specimen than those of the intact specimen. With increasing stress, the oedometer compression and isotropic consolidation curves of intact specimens gradually approach those of the reconstituted specimen. The deformation mechanism under high stresses is that soil particles are reoriented and the variation of micropores.

This paper presents a data-driven model updating framework to estimate the operational parameters of a laterally-impacted pile. The goal is to facilitate the estimation of soil-pile interaction parameters such as the mobilized mass and stiffness, as well as geometrical data such as embedded pile length, using output-only information. Accurate knowledge of mass, stiffness, and pile embedded length is essential for understanding foundation behavior when developing digital-twin models of structures for the purpose of damage detection. The method first employs subspace identification to determine modal parameters and quantifies their uncertainties using output-only data. The covariance matrix adaptation evolution strategy (CMA-ES), a stochastic evolutionary algorithm, is subsequently used to update the model. The effectiveness of the approach is demonstrated through its application to numerical models in this paper, to quantify errors, and subsequently to data from a documented full-scale field test of a pile subjected to an impact load. The work underscores the potential of statistical updating in advancing the accuracy and reliability of soil-structure interaction parameter estimation for systems where only output data might exist.

The development of soil structure, characterized by fractal geometry, improves plant-rooting development and improves water retention, drainage, and air permeability. However, due to this function to increase fertility, excessive intensive cultivation contributes to environmental load. The amount of nitrogen in rivers in agricultural watersheds is significantly related to the surplus nitrogen in the watershed, and since the nitrogen load increases with the increase in the crop field proportion, it is important to manage the surplus nitrogen in crop field. On the other hand, since wetlands have reduced the surplus nitrogen in the watershed through the purification of nitrate nitrogen in river water, it is possible to reduce the environmental load by optimizing land use. Replacing a part of chemical fertilizer application with organic fertilizer application increased soil organic carbon and contribute to the prevention of global warming without reducing crop yield. In Japanese grasslands, the annual application of 3.5tC ha-1 of compost offset greenhouse gas emissions. Furthermore, the continuous use of compost mitigated soil acidification and suppressed N2O emissions. I investigated the impact of greenhouse gas emissions associated with agricultural development on permafrost and peat soils, which are the world's soil carbon reservoirs. In eastern Siberia, disturbance of taiga forests caused permafrost melting and increased CH4 emissions. Drainage of peatland reduced CH4 emissions, but increased CO2 and N2O emissions due to peat decomposition, which was exacerbated by the application of chemical fertilizers. It was essential to keep the groundwater level at -20 cm to -40 cm to suppress greenhouse gas emissions. Environmental load means that soil health is being damaged. It is necessary to develop agricultural techniques to maintain and restore soil health. In particular, organic matter management can restore soil structure by increasing soil organic matter, and also reduce the amount of chemical fertilizer used, which has the effect of reducing greenhouse gas emissions. On the other hand, excessive continuous use of organic fertilizer can increase nitrogen loads. It has been pointed out that the relationship between cover crops and tillage is also important for organic matter management. Regional research is increasingly essential.

To study the failure mechanism of paleosol landslides, taking the paleosol of a landslide body in Yan'an as an example, scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), and conventional triaxial tests were used to obtain particle composition, microstructure scanning results, T2 spectral distribution, and stress-strain curves under different freeze-thaw cycles. The results showed that with the increase of freeze-thaw cycles, the number of micropores in paleosol increased to 70.5% and stabilized, while the number of micropores decreased to 18.4%, mesopores decreased to 7.5%, macropores decreased to 3.6%, and eventually stabilized. The fractal dimension of pore shape distribution in paleosol increases along a convex curve to 1.42. The T2 spectrum presents three stepped small peaks, with the peak spectral area of relaxation time ranging from 0.01 ms to 3.16 ms being the largest, indicating that small pores dominate. As the number of freeze-thaw cycles increases, the peak area of smaller relaxation times expands, indicating that freeze-thaw cycles have destroyed the structure of paleosols and generated a large number of tiny pores. Under conditions of higher confining pressure and lower moisture content, when there are fewer freeze-thaw cycles, the strain corresponds to higher stress. The freeze-thaw cycle makes the stress-strain curve of paleosol harder, indicating that the original structure is damaged and the new structure appears as disordered particles.

To address the long-term settlement of embankments over structured soft soil during the in-service stage, artificial structured soils with different interparticle bonding strengths and initial void ratios were prepared, and repeated triaxial loading tests were conducted to investigate the effects of bonding strength, initial void ratio, stress amplitude and cycle number on the accumulative deformation characteristics. The results show that the relationship between the accumulative plastic strain and cycle number can be classified into stable, critical and destructive types, and an empirical relationship between the stress sensitivity and dynamic stress ratio is established. Furthermore, two different empirical models for accumulative plastic strain are presented that incorporate soil structure. Reasonable agreement between the model predictions and the experimental results for different natural soft soils demonstrate that the proposed models can accurately capture the accumulative deformation behaviour of structured soils. In addition, considering the accumulated plastic deformation of soil subjected to cyclic loading as static creep, a simplified method for calculating three-dimensional cyclic accumulative deformation is proposed by implementing the proposed model in a finite-element simulation utilizing an implicit stress integration algorithm. Finally, the effects of the dynamic stress level and structural strength on the accumulative deformation are analyzed. This has important implications in controlling the long-term settlement of embankment in soft soil area.