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Zhou Y.,Central South University | Zhou Y.,Hunan Key Laboratory of Mineral Resources Exploitation and Hazard Control for Deep Metal Mines | Deng H.,Central South University | Deng H.,Hunan Key Laboratory of Mineral Resources Exploitation and Hazard Control for Deep Metal Mines | And 3 more authors.
Minerals | Year: 2017

The utilization of cemented tailings/paste backfill (CPB) by the mining industry is becoming increasingly important. However, it has been difficult to analyze the economic usage of CPB for fine unclassified tailings. Therefore, the physical and chemical properties of fine unclassified tailings, sampled from the Sijiaying Mine, were first analyzed in this study. After this, active excitation of blast furnace slag was examined, with a cement mixture made up of slag, lime, plaster and cement being used to conduct the physicochemical evaluations and proportioning tests. These results were compared with those from ordinary cement. It was revealed that the cement mixture can effectively harden the unclassified tailings. The cement mixture specimens have good performance in early strength, with the seven-day strength being about twice as high as ordinary cement, which meets the requirements for efficient continuous mining. This strength was reduced after 10 days due to expansion and complicated reactions, with an average reduction of 11.8% after 28 days under recommended and better conditions. In addition, analysis of the microstructures was carried out to observe the hydration products and the change in strength. Furthermore, fluidity characteristics of the slurry were measured, with the slurry found to have a mass fraction of 70%–72% in addition to containing an ideal fluidity and a paste-like flow state. Considering the mining conditions, the aggregates with a tailings-cement ratio of 6:1 and a mass fraction of 70%–72% are recommended as high-strength CPB, which should be used for the surface layer and safety pillars. In addition, backfilling materials with a tailings-cement ratio of 15:1 and a mass fraction of 70%–72% are recommended as low-strength CPB, which should be used as ordinary CPB to achieve economic benefits. The application cases showed that the cement mixture is suitable for utilization of unclassified tailings with regards to safety, economics and efficiency. © 2017 by the authors.


Hu J.-H.,Hunan Key Laboratory of Mineral Resources Exploitation and Hazard Control for Deep Metal Mines | Hu J.-H.,Central South University | Lei T.,Hunan Key Laboratory of Mineral Resources Exploitation and Hazard Control for Deep Metal Mines | Lei T.,Central South University | And 4 more authors.
Journal of Central South University | Year: 2014

The pre-crack blast technology has been used to control the induction caving area in the roof. The key is to form the pre-crack seam and predict the effect of the seam. The H-J-C blast model was built in the roof. Based on the theories of dynamic strength and failure criterion of dynamic rock, the rock dynamic damage and the evolution of pre-crack seam were simulated by the tensile damage and shear failure of the model. According to the actual situation of No. 92 ore body test stope at Tongkeng Mine, the formation process of the pre-crack blast seam was simulated by Ansys/Ls-dyna software, the pre-crack seam was inspected by a system of digital panoramic borehole camera. The pre-crack seam was inspected by the system of digital panoramic borehole in the roof. The results of the numerical simulation and inspection show that in the line of centers of pre-hole, the minimum of the tensile stress reaches 20 MPa, which is much larger than 13.7 MPa of the dynamic tensile strength of rock. The minimum particle vibration velocity reaches 50 cm/s, which is greater than 30-40 cm/s of the allowable vibration velocity. It is demonstrated that the rock is destroyed near the center line and the pre-crack is successfully formed by the large diameters and large distances pre-crack holes in the roof. © 2014 Central South University Press and Springer-Verlag Berlin Heidelberg.


HU J.-H.,Central South University | HU J.-H.,Hunan Key Laboratory of Mineral Resources Exploitation and Hazard Control for Deep Metal Mines | YANG C.,Central South University | YANG C.,Hunan Key Laboratory of Mineral Resources Exploitation and Hazard Control for Deep Metal Mines | And 6 more authors.
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2016

Undercut is one kind of important spaces to place the mining blocks in the mass underground mining. This structure is also used as a compensation space during blasting. In the process of underground mining in the fragment orebody, it is important and critical to analyze the stability and blockage of the three-dimensional wedges created around the undercut space. The wedge stability is mainly controlled by factors including geometry (i.e., the size, shape and spatial location of the wedge and undercut), the strength (shear and tensile) of the discontinuities that created the wedge, and the stress distribution within the rock mass. The Unwedge software was used to conduct the orthogonal simulation tests (three factors and five levels) that considered different cross sections, trends, and plunges of the undercut space. The results demonstrate that the control value of the safety factor of wedge is set to be 1.2. The optimal parameters are determined in the undercut space, such as the blasting fragmentation, orientation of the fluid flow, and the equipment gradeability; the wedge stability can be evaluated in the light of the block images and continuous falling; the stability of the key block meets the needs of the undercut space, the parameters gained are reasonable and optimal. Cross section is 27°, trend is from 315° to 325° (it is 320° at in-suit test) and plunge is 5°. © 2016 The Nonferrous Metals Society of China

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