Search

Currently, the dynamic behavior of high-speed long-runout landslides triggered by earthquakes remains unclear due to the complexity of such phenomena. Degradation in the shear strength of rock masses is considered a primary factor contributing to the high velocities and long runout distances of these landslides. In this study, the strength degradation induced by changes in rock joint morphology is analyzed considering a numerical model of the Donghekou landslide, by using discontinuous deformation analysis (DDA). First, an exponential joint roughness degradation function (i.e., JRCm) that depends on displacement is incorporated with the nonlinear Barton–Bandis (B–B) shear strength criterion, and this modified B–B criterion is combined with the DDA. Moreover, a virtual joint is introduced in the DDA to model the propagation of cracks in intact rock masses, in order to simulate the dynamic phenomenon of earthquake-induced landslides. Subsequently, this improved DDA (IDDA) is validated via simulations of a shear test and a sliding block over an inclined plane. Finally, the IDDA is employed to simulate the Donghekou landslide, which was induced by the 2008 Wenchuan earthquake in China. Furthermore, the entire dynamic process of the landslide, including crack propagation, instability, initiation, and motion, is depicted. The simulated deposit patterns obtained via the IDDA are in good agreement with the results of field investigations. The simulation results also prove that the IDDA can reflect key movement behaviors of Donghekou landslide and that the degradation of rock joints significantly influences the long runout distance and high velocity of sliding mass. [ABSTRACT FROM AUTHOR]

Uranium-contaminated wastewater associated with uranium (U) mining and processing inevitably releases into soil environment. In order to assess the risk of U wastewater contamination to groundwater through percolation, U adsorption and transport behavior in a typical red soil in South China was investigated through batch adsorption and column experiments, and initial pH and carbonate concentration were considered of the high-sulfate background electrolyte solution. Results demonstrated that U adsorption isotherms followed the Freundlich model. The adsorption of U to red soil significantly decreased with the decrease of the initial pH from 7 to 3 in the absence of carbonate, protonation-deprotonation reactions controlled the adsorption capacity, and lnCs had a linear relationship with the equilibrium pH (pHeq). In the presence of carbonate, the adsorption was much greater than that in the absence of carbonate owing to the pHeq values buffered by carbonate, but the adsorption decreased with the increase of the carbonate concentration from 3.5 to 6.5 mM. Additionally, the breakthrough curves (BTCs) obtained by column experiments showed that large numbers of H+ and CO32− competed with the U species for adsorption sites, which resulted in BTC overshoot (C/C0 > 1). Numerical simulation results indicated that the BTCs at initial pH 4 and 5 could be well simulated by two-site chemical non-equilibrium model (CNEM), whereas the BTCs of varying initial carbonate concentrations were suitable for one-site CNEM. The fractions of equilibrium adsorption sites (f) seemed to correlate with the fractions of positively charged complexes of U species in solution. The values of partition coefficients (kd′) were lower than those measured in batch adsorption experiments, but they had the same variation trend. The values of first-order rate coefficient (ω) for all BTCs were low, representing a relatively slow equilibrium between U in the liquid and solid phases. In conclusion, the mobility of U in the red soil increased with the decrease of the initial pH and with the increase of the initial carbonate concentrations. [ABSTRACT FROM AUTHOR]

• Ion irradiation effects on a reduced activation ferritic/martensitic steel CLF-1 have been investigated by TEM analysis and nanoindentation tests. • It is confirmed the increase of <100>-type dislocation loops with the increasing irradiation temperature. These lattice defects induced irradiation hardening. • Lattice swelling after Fe ion irradiation at 500°C was observed, which was induced by nano-sized cavities around the dislocation loops and along dislocation lines. A kind of reduced-activation ferritic-martensitic steel, CLF-1, was developed by the Southwestern Institute of Physics, China, as a candidate structural material for fusion and fourth-generation fission reactors. This work reports the results from the nanoindentation and transmission electron microscopy study performed on this steel after irradiation with 2.75 MeV Fe11+ ions up to 1 and 10 dpa at temperatures of 300 - 500 °C. An increase in hardness was observed in the damaged layer of samples irradiated at 400 °C, while the samples irradiated at 500 °C exhibited a softening of the damaged layer. The hardening can be primarily, although not exclusively, attributed to the increase of <100>-type dislocation loops observed at the increasing irradiation temperature. Nano-sized cavities around the dislocation loops and along dislocation lines were also observed, explaining the lattice swelling after irradiation at 500°C. The research results provide a valuable reference for the development of irradiation-hardening-resistant Fe-Cr alloys for advanced nuclear energy systems. [ABSTRACT FROM AUTHOR]

• Three novel N,N -dimethyldithiocarbamoyl modified pillararenes were prepared. • This is the first example of CH 3 Hg+ extraction by pillararene-based materials. • High extraction efficiency (%E > 99%) and selectivity (SF > 690) were achieved. • A rather low THg (3.45 ppb) was found in extraction raffinate of spiked river water. • Spectroscopy studies and DFT calculation provide insights into extraction mechanism. Pillararenes, a rising star in macrocyclic chemistry, are recognized as promising organic materials for metal ion separation. Herein, three novel pillar[5]arenes (1a-c) appended with N,N -dimethyldithiocarbamoyl groups were designed for highly efficient extraction of aqueous mercury. This work represents the first case of using pillararene-based materials for organic mercury removal, and rather low Hg(II) residue (3.45 ppb) was found in the extraction raffinate of mercury spiked river water after being treated with the as-prepared extractants, which is a rare example of solvent extraction systems that meet the waste water discharge standard (<5 ppb). The extraction performance of the extractant materials was evaluated under different acidities, equilibrium time and sodium nitrate concentrations. High extraction efficiency (>99%) and selectivity (SF Hg/M > 690) were achieved under the optimum condition, and the near quantitative stripping after two contacts enable regeneration of the ligands as well as mercury recovery. The stoichiometric ratio between ligands and Hg2+ was ascertained to be 1:1 from the slope analysis method and mass spectroscopy. Investigation of the extracted species by NMR, IR, EXAFS techniques and DFT simulation reveals that the C=S moieties of the ligands play a crucial role in metal complexation. It is noted that the as-prepared extractants show excellent recovery and removal ability towards mercury using simulated samples. After extraction by 1c , the total Hg(II) in spiked river samples was reduced to lower than 5 ppb, the maximum tolerable concentration set by China for industrial waste water. This study demonstrates the potential application of N,N -dimethyldithiocarbamoyl modified pillararenes as functional materials for aquatic mercury remediation. [ABSTRACT FROM AUTHOR]