Ozone is widely used for water treatment because of its strong oxidation ability. However, the efficiency of ozone in groundwater remediation is limited because of its relatively low solubility and rapid decomposition in the aqueous phase. Methods for increasing the stability of ozone within the subsurface are drawing increasing attention. Micro-nano-bubbles (MNBs), with diameters ranging from tens of nanometres to tens of micrometres, present rapid mass transfer rates, persist for a relatively long time in water, and transport with groundwater flow, which significantly improve gas concentration and provide a continuous gas supply. Therefore, MNBs show a considerable potential for application in groundwater remediation. In this study, the characteristics of ozone MNBs were examined, including their size distribution, bubble quantity, and zeta potential. The mass transfer rate of ozone MNBs was experimentally investigated. Ozone MNBs were then used to treat organics-contaminated water, and they showed remarkable cleanup efficiency. Column tests were also conducted to study the efficiency of ozone MNBs for organics-contaminated groundwater remediation. Based on the laboratory tests, field monitoring was conducted on a trichloroethylene (TCE)-contaminated site. The results showed that ozone MNBs can greatly improve remediation efficiency and represent an innovative technology for in situ remediation of organics-contaminated groundwater.

An accurate modeling of soil-structure interfaces is very important in order to obtain realistic solutions of many soil-structure interaction problems. To study the mechanical characteristics of soil-structure interface, a series of direct shear tests were performed. A charged-coupled-device camera was used to observe the sand particle movements near the interface. It is shown that two different failure modes exist during interface shearing. Elastic perfect-plastic failure mode occurs along the smooth interface, while strain localization occurs in a rough interface accompanied with strong strain-softening and bulk dilatancy. To describe the behavior of the rough interface, this paper proposes a damage constitutive model with ten parameters. The parameters are identified using data from laboratory interface shear tests. The proposed model is capable of capturing most of the important characteristics of interface behavior, such as hardening, softening, and dilative response. The interface behaviors under di...

The engineering properties of tailings are important for the safety evaluation and engineering design of tailing dams. In the present study, laboratory experiments were performed to investigate the geotechnical properties of four different tailings, including two iron tailings (coarse and fine) and two copper tailings (coarse and fine). Compared to the copper tailings, the iron tailings showed higher compressibility, lower permeability, lower strength, and lower cyclic resistance. With the decrease in void ratio, the coefficient of consolidation almost kept constant for the fine iron tailings, whereas for the fine copper tailings, the coefficient of consolidation gradually increased. Under cyclic loading, the accumulation of pore water pressure was faster in the fine tailings than that in the coarse tailings. The cyclic resistance ratios (CRR) of the four tailings were found to be comparable with previous report data on other metal tailings, and the consolidation stress showed little impact on CRR. The laboratory tests provided useful information to understand the geotechnical behaviors of mine tailings including seepage, deformation, strength, as well as seismic responses.