Progress and prospects of mining with backfill in metal mines in China

Mining is the foundation of modern industrial development.In the context of the“carbon peaking and carbon neutrality”era,countries have put forward the development strategy of“adhering to the harmonious coexistence of humans and nature.”The ongoing progress and improvement of filling mining technology have provided significant advantages,such as“green mining,safe,efficient,and low-carbon emission,”which is crucial to the comprehensive utilization of mining solid waste,environmental protection,and safety of re-mining.This review paper describes the development history of metal mine filling mining in China and the characteristics of each stage.The excitation mechanism and current research status of producing cementitious materials from blast furnace slag and other industrial wastes are then presented,and the concept of developing cementitious materials for backfill based on the whole solid waste is proposed.The advances in the mechanical characteristics of cemented backfill are elaborated on four typical levels:static mechanics,dynamic mechanics,mechanical influencing factors,and multi-scale mechanics.The working/rheological characteristics of the filling slurry are presented,given the importance of the filling materials conveying process.Finally,the future perspectives of mining with backfill are discussed based on the features of modern filling concepts to provide the necessary theoretical research value for filling mining.

A comparative investigation of the properties of coal-water slurries prepared from Australia and Shenhua coals

Two coal samples of similar rank were chosen from Australia and China to investigate the differences in Coal-Water Slurry （CWS） made from them. The effect of ash content and particle size gradation on these properties was also studied. Different grinding times were used when grinding the two coals and particle size analysis of these ground coals was used to select samples with a ＂double-peak＂ particle size distri- bution. All the ＂double-peak＂ samples were used to prepare a CWS. The concentration, viscosity, fluidity, and stability of each CWS were measured. The results show that the properties ofa CWS prepared from a coal sample with a ＂double-peak＂ size distribution are better than those CWS prepared from samples with a mono-modal particle distribution. The ash content of Australian coal is 21.72g higher than the ash content of Shenhua coal. The highest coal concentration in slurry from the Australia coal is 11.01% higher than in CWS from the Shenhua coat. The fluidity and stability of the CWS prepared from the Australian coal are both better than the fluidity and stability of slurry prepared from Shenhua coal. High ash content in the Australian coal imnroves the nulning results of a CWS made from it.

Experimental Research on Performances of Dry-grinding Fine Cement for Grouting

The performances of dry grinding fine cement (DFC) in grouting procedure were experimentally studied.The measurement of its fineness and simulated test for injectability showed that this DFC could be used to inject rock mass with micro fissure.In order to improve the grouting quality,the water cement ratio and discarding time of slurry should be controlled precisely.If the water cement ratio is over 2∶1 in slurry that is made from DFC,it is not suitable to grout.Finally,the influence of different mixing times on strength of hydrated cement made from the DFC is explained by microstructure analysis with SEM.

Laser processed micro-supercapacitors based on carbon nanotubes/manganese dioxide nanosheets composite with excellent electrochemical performance and aesthetic property

Micro-supercapacitors with excellent electrochemical performance and aesthetic property are realized using the carbon nanotubes/manganese dioxide nanosheets（CNTs/δ-MnO2） composite as electrodes.This CNTs/d-MnO2 nanocomposite is excellently compatible with the slurry dispensing process for electrode fabrication, and thus is conducive for preparing thick electrode films, which exhibits a specific capacitance of 257 F/g with an electrode thickness of 13μm. By involving laser-scribing technique, the electrode film can be patterned with a high resolution and fabricated into a planar micro-supercapacitor,showing the maximum energy density of 6.83 mWh/cm^3 at the power density of 154.3 mW/cm^3, and maintained a value of 2.71 mWh/cm^3 at the maximum power density of 2557.5 mW/cm^3. Considering the versatility of the laser-scribing technical platform, the micro-supercapacitors fabricated in this way exhibit excellent aesthetic property and can cater to various miniaturized wearable electronic applications. This technology opens up opportunities for facile and scalable fabrication of high performance energy devices with shape diversity and a meaning of art.