A new method for risk assessment of pillar recovery operation

Safe pillar recovery operations can result in better miner safety and more efficient recovery of ore reserves. Several parameters influence on safety of pillar recovery operation. Each of these parameters is able to reduce safety of operation and cause to detrimental effects during pillar recovery. In this paper, by emphasizing ground control aspects, the most important technical parameters influencing on safety of pillar recovery are introduced and the role of them is described. Then, a new method is presented by combining all of these parameters to assess overall risk of pillar recovery operation in pre-developed room and pillar mines. The proposed method involves calculating the PR-Risk (Pillar Recovery-Risk) indicator. PR-Risk value is between 0 and 100 that based on overall risk of pillar recovery operation divides into four categories: low, medium, high, and very high. PR-Risk is an important indicator for predicting the safety of pillar recovery operation and based on it decision can be made about the safe implementation of operation. Finally, the overall risk of pillar recovery operation in main panel of Tabas Central Mine, located in the mid eastern of Iran, is assessed by use of proposed method in this paper. PR-Risk value in this panel was obtained 51 that show overall risk of operation is medium. Moreover, based on individual assessment of parameters, for the safe implementation of operation and reduction of related risks, reinforcement of roof prior to beginning of operation and partial pillar extraction have been suggested as the most efficient controlling measures.     

Development of Regenerated Cellulose/Citric Acid Films with Ionic Liquids

Nowadays, the importance of green and biodegradable plastics as viable substitutes for non-degradable petroleum-based materials is felt more than ever. Regenerated cellulose (RC) as a potential candidate suffers from poor processability and inferior properties, limiting its wide applications. In this study, it is demonstrated that citric acid (CA) enhances physical, mechanical, and thermal properties of RC films, due to RC-citric acid compatibility. 1-ethyl-3-methylimidazolium chloride (EMIMCl) as a green ionic liquid was employed for the processing of RC. The optimum properties in terms of thermal stability, mechanical strength, contact angle, water uptake, and oxygen permeability were achieved at 10 wt% of CA. However, further incorporation of CA adversely affected the film properties. This behaviour was explained by the crosslinking and plasticizing effects of CA. Furthermore, in vitro cytotoxicity test demonstrated that RC/CA films are cytocompatible, suggesting the potential advantage of using these biopolymeric films for biomaterial and biological applications.