The backfilling mining method can effectively solve the environmental and safety problems caused by mining. It is the key technology to realize green mining. Scientific development has accelerated the pace of research on the rational utilization of mine solid waste and improved the research level of backfilling technology. The development history of the backfilling mining method is introduced in the present paper, and it is determined that roof-contacting backfilling is the key technology of mine-solid-waste backfilling mining. This paper introduces three calculation methods of similar roof-contacted backfilling rates. In this paper, the relationship between the characteristics of backfilling slurry made from solid waste from mines and the roof-contacted backfilling rate is systematically analyzed, such as the flow law in stope (gravity gradient), bleeding shrinkage, and natural sedimentation of backfilling slurry. It is pointed out that the characteristics of the stope, such as washing-pipe water, water for the leading way, filling pipeline, and shape of the backfilling stope, are closely related to the roof-contacted backfilling rate. The influential relationship between objective factors, such as human factors, limited auxiliary leveling measures, and backfilling “one-time operation” in the backfilling process, and high-efficiency top filling are considered, and a schematic diagram of the influencing top-filling rate and structure is drawn. At the same time, this paper summarizes the improvement measures of roof connection from three aspects. These include the use of expansive non-shrinkable materials, forced roof-contacted technology, and strengthening management level. It is pointed out that the roof-contacted filling technology is still facing severe challenges, and the research on the backfilling connection technology needs to be strengthened.
Adding basalt fiber into concrete can significantly improve its mechanical properties. In order to explore the influence of basalt fiber content on the uniaxial compressive strength and splitting tensile strength of concrete and the mechanism of fiber action, this paper conducts compressive and splitting tensile tests on three kinds of basalt fiber concrete specimens with different fiber content and obtains the relationship between the macro mechanical properties and the fiber content. At the same time, with the help of CT scanning equipment and digital image processing technology, the microstructure of basalt fiber concrete with three groups of fiber content is reconstructed, and the pore, crack, and fiber distribution are quantitatively described using the calculation and processing function of the Avizo reconstruction software. The results show that when the optimal fiber content is 3 kg/m3, the improvement rates of uniaxial compressive strength and splitting tensile strength are 31.9% and 23.7%, respectively. The network structure formed by fiber in concrete has the best compactness and the least number of pores, with an average sphericity of 0.89 and an average pore volume of 20.26 μm3. Through analysis, it was found that the initial defects of basalt fiber concrete exist in the form of pores, and the addition of basalt fiber will destroy the large pore size of concrete, change the pore size distribution, and increase the average sphericity; The distribution of the fiber in the concrete is a three-dimensional network, and the distribution of the fiber in the initial defect distribution area is parallel to the direction of pore arrangement.
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