This study presents a novel micromorphic continuum model for sand-gravel mixtures with low gravel contents, which explicitly accounts for the influences of the particle size distribution, gravel content, and fabric anisotropy. This model is rigorously formulated based on the principle of macro-microscopic energy conservation and Hamilton's variational principle, incorporating a systematic analysis of the kinematics of coarse and fine particles as well as macro-microscopic deformation differentials. Dispersion equations for plane waves are derived to elucidate wave propagation mechanisms. The results demonstrate that the model effectively captures normal dispersion characteristics and size-dependent effects on wave propagation in these mixtures. In long-wavelength regimes, wave velocities are governed by macroscopic properties, whereas decreasing wavelengths induce interparticle scattering and multiple reflections, attenuating velocities or inhibiting waves, especially when wavelengths approach interparticle spacing. The particle size, porosity, and stiffness ratio primarily influence the macroscopic average stiffness, exhibiting consistent effects on dispersion characteristics across all wavelength domains. In contrast, the particle size ratio and gravel content simultaneously influence both macroscopic mechanical properties and microstructural organization, leading to opposing trends across different wavelength ranges. Model validation against experiments confirms its exceptional predictive ability regarding wave propagation characteristics, including relationships between lowpass threshold frequency, porosity, wave velocity, and coarse particle content. This study provides a theoretical foundation for understanding wave propagation in sand-gravel mixtures and their engineering applications.

The delayed breakage of particles significantly affects the long-term mechanical properties of rockfill materials. This study examines the effects of particle strength dispersion on the distribution of time-dependent strength using fracture mechanics and probabilistic methods. Subsequently, the distribution of normalized maximum contact force (NMCF), defined as the ratio of the maximum contact force to instantaneous strength, for specimens with uniform particle size is derived using extreme value theory and Discrete Element Method (DEM). Based on this analysis, the probabilities of delayed breakage in rockfill specimens over various time intervals are calculated using a joint probability delayed breakage criterion. The feasibility of the proposed method is validated by comparing theoretical calculation with DEM triaxial creep simulation results that accounted for particle breakage. The findings offer innovative tools and theoretical insights for understanding and predicting the particle delayed breakage behavior of rockfill materials and for developing macro-micro creep crushing constitutive models.

The city of A & iuml;n T & eacute;mouchent, located in northwest Algeria at the westernmost part of the Lower Cheliff Basin, has experienced several moderate earthquakes, the most significant of which occurred on 22 December 1999 (Mw 5.7, 25 fatalities, severe damage). In this study, ambient noise measurements from 62 sites were analyzed using the horizontal-to-vertical spectral ratio (HVSR) method to estimate fundamental frequency (f0) and amplitude (A0). The inversion of HVSR curves provided sedimentary layer thickness and shear wave velocity (Vs) estimates. Additionally, four spatial autocorrelation (SPAC) array measurements refined the Rayleigh wave dispersion curves, improving Vs profiles (150-1350 m/s) and sediment thickness estimates (up to 390 m in the industrial zone). Vs30 and vulnerability index maps were developed to classify soil types and assess liquefaction potential within the city.

In this work, the dispersion characteristic equation of cylindrical tunnels in elastic saturated soil is established. We use the pipe-in-pipe model as a frame to model the tunnel lining as a cylindrical shell and the surrounding soil as a saturated porous medium. Based on the Stokes-Helmholtz vector decomposition theorem, the Biot wave equation is successfully decoupled, and parametric analytic expressions of the displacement field and stress field are obtained. Finally, we apply boundary conditions at the interface to determine the dispersion characteristic equation, which controls the tunnel vibration. The effects of tunnel length, wall thickness, and radius on natural vibration frequency are discussed with numerical examples, and the results are compared with those obtained using elastic relations. Finally, the maximum vibration damage of a tunnel lining structure and the surrounding soil under a harmonic load is determined by using a stable natural frequency; this provides a reference for environmental protection.

The fall armyworm (FAW), Spodoptera frugiperda, a major pest in maize production, was assessed for its temporal and spatial distribution in maize fields during both the dry and rainy seasons of 2021 and 2022 in two agroecological regions in Benin (zone 6 and 8). Zone 6 (AEZ 6) called zone of terre de barre (Southern and Central Benin) consisted of ferralitic soils, a Sudano-Guinean climate (two rainy seasons alternating with two dry seasons) with a rainfall ranging between 800 and 1400 mm of rainfall per year; while zone 8 (AEZ 8) called fisheries region (Southern Benin is characterized by coastal gleysols and arenosols with a Sudano-Guinean climate and a rainfall of 900-1400 mm of rainfall per year. In this study, 30 and 50 maize plants were randomly sampled using a W pattern during the dry and rainy seasons, respectively. Larval density, larval infestation rates, and damage severity were monitored over time. Taylor's power law and the mean crowding aggregation index were applied to evaluate the dispersion patterns of the larvae. The results indicate a higher larval infestation rate and larval density in AEZ 8 compared to AEZ 6 during the dry season. In the rainy season, while the percentage of damaged plants was higher in AZE 8, no significant differences in larval density between the two zones were observed. The dispersion analysis revealed moderate aggregation (aggregation index = 1.25) with a basic colony of 2.08 larvae, i.e., an average initial cluster of 2.08 larvae observed per plant, reflecting the aggregation oviposition behavior of FAW. This study provides valuable monitoring data on the FAW's distribution, offering insights for further research on population dynamics and developing predictive models for integrated pest management strategies.

Dispersive soil has poor engineering geological properties, which can lead to various geological hazards in practical engineering projects. This study utilizes guar gum, an eco-friendly biopolymer with great potential in soil improvement, to improve dispersive soils in western Jilin. Guar gum powder was added to the dispersive soil at dry mass ratios of 0%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 4%, and 5%, and cured for 1, 3, 7, 14, and 28 days. The improvement effect was comprehensively evaluated by dispersion identification test, unconfined compressive strength test before and after immersion, disintegration test, matric suction test, and permeability test. The mechanism of guar gum in improving dispersive soil was further explained from the microscopic point of view by particle size analysis, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results showed that more than 1.5% guar gum proportion was effective in eliminating soil dispersion. The cured soil had the best mechanical properties at 3.0% guar gum content. With the incorporation of guar gum, the hydrophysical properties of the soil were also improved. Guar gum wraps around soil particles, forming bridges through the hydrogel. Additionally, it fills the voids in the soil, leading to a denser aggregation of the soil particles. In conclusion, guar gum, as an environmentally friendly biopolymer, has a positive effect on the improvement of dispersive soils. The research results will provide theoretical guidance for engineering construction in dispersive soil areas.

Vegetation barriers are an important environmental characteristic of spent fuel road transportation accidents. Spent fuel vessels may be affected by force majeure factors during transportation, which leads to damage to spent fuel assemblies and containers and can cause radionuclides to gradually release from assemblies to vessels to the external environment. In this work, considering the growth periods of coniferous vegetation barriers and vessel type, a radionuclide dispersion model based on computational fluid dynamics (CFD) was established by adding a decay term and a pressure loss term. The simulations showed that, first, compared to the small (Type-II) vessel, the effects of fluid flow around the large vessel (Type-I) have a more significant impact on radionuclide dispersion. The backflow around the Type-I vessel causes leaked radionuclides to disperse towards the vessel, and the larger the vessel is, the more significant the rise of the leaked radionuclide plume tail will be due to the increased negative pressure gradient area. Moreover, the area contaminated exceeding the maximum allowable concentration by radioactivity for the Type-I vessel is reduced gradually with the growth of coniferous vegetation barriers due to the weakening of the backflow effect by growing vegetation. Second, compared to vegetation barriers of 15 years and 23 years, the horizontal distance exceeding the maximum allowable concentration of the leaked I-131 dispersion from Type II vessels near vegetation barriers for 12 years is the longest. The older the vegetation barrier is, the shorter the horizontal dispersion range, and the shape of radionuclide dispersion gradually transforms from flat to semicircular with vegetation barrier growth, but this could cause a greater radioactive accumulation effect near the leakage point, and the maximum concentration of leaked I-131 reached 0.54 kBq center dot m(-3) for leaked radionuclides from the Type II vessel under vegetation barriers of 23 years. In addition, improvement suggestions based on the proposed method are presented, which will enable the Standards Institutes to apply the research methodologies described herein across various scenarios. Environmental Implication: Compared to nonradioative pollutants, radioactive pollutants are intercepted by vegetation barriers and then migrate to the soil through leaves, stems, and roots, which can contaminate the surrounding environment. Considering the effects of vessel type and coniferous vegetation growth, a radionuclide dispersion model based on CFD was established. Suggestions for decontaminating radioactive pollution areas have been proposed based on the simulation results of hypothetical scenarios. The scenario applicability improvements based on the proposed model could assist relevant Standards Institutes to making improving measures.

In recent years, graphene oxide (GO) has been widely used in various fields owing to its high specific surface area and rich oxygen-containing functional groups. Adding an appropriate amount of GO (about 0.01-0.1 wt%) is beneficial to strengthen the soft soil foundation, which can improve the mechanical properties of the geopolymers, promote the hydration reaction, and improve the pore structure. The main mechanisms include the distortion effect, intercalation effect, template effect, bridge effect, active catalytic effect, adsorption cementation effect, and nucleation effect. Currently, GO research on cement materials mainly focuses on mortar and concrete and pays less attention to geotechnical engineering fields, such as cement soil. Therefore, to fully understand the unique advantages of GO, to clarify the method and mechanism of GO strengthening soft soil foundations, and to expand its application in geotechnical engineering, we briefly summarise the characterisation methods, dispersion of GO, analyse the influence of the single incorporation of GO on the mechanical properties of geopolymers, and discuss its microscopic mechanism. The environmental and safety effects are also discussed. Finally, the problems existing in the current research are analysed and future research directions are discussed.

A series of laboratory tests were conducted to investigate the properties of fiber-reinforced underwater flowable solidified soil (UFSS) as a novel material for scour protection in marine structures. The tests included flowability, underwater anti-dispersion, unconfined compressive strength (UCS), and anti-scour resistance. Results showed that adding fibers reduced UFSS's flowability and significantly enhanced its underwater anti-dispersion, exhibiting a similar trend with increasing fiber content. Increasing fiber length initially decreased and then increased flowability, with the opposite trend for anti-dispersion. The least favorable fiber lengths for flowability were 6 mm for PVA fiber and 9 mm for both basalt and glass fibers, whereas these lengths were optimal for antidispersion. Fibers improved both UCS and anti-scour resistance of UFSS, with both properties first increasing and then decreasing as fiber content and length increased. Excessive fiber content or length reduced both properties. In this study, the optimal fiber content for improving UCS was 0.3% for PVA and 0.2% for basalt and glass fibers, with an optimal length of 6 mm for all three. An empirical exponential relationship between UCS, critical scour resistance velocity, and critical scour shear stress at typical times (t = 3 h, 5 h) was established for rapid prediction of UFSS's anti-scour resistance.

Monotonously stratified porous medium, where the layered medium changes its hydraulic conductivity with depth, is present in various systems like tilled soil and peat formation. In this study, the flow pattern within a monotonously stratified porous medium is explored by deriving a non-dimensional number, Fhp, from the macroscopic Darcian-based flow equation. The derived Fhp theoretically classifies the flow equation to be hyperbolic or parabolic, according to the hydraulic head gradient length scale, and the hydraulic conductivity slope and mean. This flow classification is explored numerically, while its effect on the transport is explored by Lagrangian particle tracking (LPT). The numerical simulations show the transition from hyperbolic to parabolic flow, which manifests in the LPT transition from advective to dispersive transport. This classification is also applied to an interpolation of tilled soil from the literature, showing that, indeed, there is a transition in the transport. These results indicate that in a monotonously stratified porous medium, very low conducting (impervious) formations may still allow unexpected contamination leakage, specifically for the parabolic case. This classification of the Fhp to the flow and transport pattern provides additional insight without solving the flow or transport equation only by knowing the hydraulic conductivity distribution.