Study on Ratio Optimization and Diffusion-Gelation Process of Polymer Grouting Materials for Fracture Filling in Underground Mines.

The existence of fissures poses a serious threat to the safe production of underground mines, and this paper investigates a polymer grouting material for filling fissures in underground mines. To optimise the ratio of polymer grouting materials, this paper designed 16 test groups using the orthogonal test method to find the most reasonable slurry ratio. In order to study the gel diffusion process of polymer slurry in the fissure and to explore the changes of various parameters of the slurry after injection, simulated grouting tests were carried out, and the distribution laws of viscosity, pressure, and diffusion distance of the slurry were discussed. The findings indicate that when the proportion of ethylenediamine polypropylene oxide tetrol: glycerol polyether: catalyst: foam stabiliser is 10:8:0.5:0.4, the polymer grouting material has excellent compressive strength, and the maximum compressive strength can reach 12.31 MPa. Prior to reaching the gel time point, the viscosity of the polymer slurry was nearly constant, which is basically maintained at 0.772 Pa·s under normal temperature and pressure, but after reaching the gel time point, it abruptly rose. As the slurry mass increased, so did the penetration distance and pressure; in the simulated grouting test, when the slurry mass was 400 g, the maximum diffusion distance of the slurry reached 39 cm. Conversely, as the fracture pore size increased, the diffusion distance and pressure of the slurry decreased. Along the diffusion path, the slurry pressure progressively drops, but this change is not synchronised with the diffusion distance's change. This work can serve as a reference for the configuration of polymer slurry and aid in comprehending the diffusion law of the slurry within the fissure.

A comprehensive analysis on the source-exposure and diffusion rule of VOCs for end-life vehicles dismantling activities.

In recent years, the rapid development of technology has posed significant challenges to the waste management practices of the retired vehicle industry. How to minimize the environmental impact during the recycle process of scrap vehicle has emerged as a prevalent and pressing concern. This study employed statistical analysis and positive matrix factorization (PMF) model to assess the origin of Volatile Organic Compounds (VOCs) at a scrap vehicle dismantling location situated in China. The quantification of potential hazards to human health arising from identified sources was achieved through the integration of source characteristics with exposure risk assessment. In addition, fluent simulation was employed to examine the spatiotemporal dispersion of the pollutant concentration field and velocity profile. The findings of the study revealed that the activities of parts cutting, disassembling air conditioning and refined dismantling were responsible for 89.98 %, 84.36 %, and 78.63 % of the total air pollution accumulation, respectively. Additionally, it should be noted that the aforementioned sources accounted for 59.40 %, 18.44 %, and 4.86 % of the aggregate non-cancer risk. The cumulative cancer risk was determined to be the disassembling air conditioning process, with a contribution of 82.71 %. Meanwhile, the average concentration of VOC in soil around the disassembling air conditioning area is 8.4 times higher than the background value. The simulation revealed that pollutants were primarily dispersed within the factory at a height ranging from 0.75 m to 2 m, which corresponds to the human respiratory zone and the concentration of pollutants in the vehicle cutting area was observed to exceed normal levels by over 10 times. These findings of this study may serve as a foundation for improving of environmental protection measures of industrialization.

CFD simulation of multi-phase and multi-component diffusion of air-dust-gas in a fully mechanized mining face.

To explore the rule of airflow-dust-gas dispersion and interaction in a fully mechanized mining face, the airflow current vector, the dust trajectory, and the gas spatial distribution were numerically simulated by Fluent. The results show that under the influence of airflow, respiratory dust diffuses to the leeward side of each dust-producing point and footway space and forms a high-concentration (peak concentration 2000 mg/m3) dust mass at 2 m on the leeward side of the advancing support. Gas tends to accumulate near the coal cutter drum, the roof, and the return air corner of the mining face, and the peak concentration exceeds the lower limit of explosion. Near the rear drum of the coal cutter and at the advancing support, considering that the gas and coal dust concentrations are both high and dust and gas can reduce each other's explosion limit, serious gas and coal dust explosions are extremely likely to occur in the presence of a fire source, which may result in serious consequences. Therefore, the two areas can be regarded as key areas of gas and coal dust explosion prevention and control.