High stress and strong excavation disturbance are the main causes of dynamic disasters, rock burst in deep hard rocks, and are more frequent and violent than those in shallow, which seriously restricts the deep mining. Given rock burst encountered in deep mining of Lingnan metal mines, the optimized triaxial cyclic loading and unloading tests are designed to characterize the performance of rock failure and to evaluate the rock burst proneness. The correlation between elastic energy index and damage evolution is built, and rock burst proneness in each status is analyzed; furthermore, the dissipation energy in the failure process of deep rocks is explicated. In this paper, the law that the elastic energy index via damage increases is drawn. In terms of the dynamic disaster conditions in the deep rock, the identification approach for the damage zone of the rock burst is established.

In order to scientifically evaluate the thermal environment of the deep stope and its influencing factors, research was conducted on the thermal environment in Sanshandao Gold Mine, the theoretical calculations and structural analysis of heat release from 8 types of heat sources in the three sub-levels of -930 m, -945 m, and -960 m were carried out, and quantitative characterization was made on the influential degree of comprehensive heat release on the thermal environment, and it was clear that the heat release from the surrounding rock and mechanical and electrical equipment were the main parts at the deep mining site and the proportion of heat release from other heat sources is basically stable. Then, through the analysis of the influence factors of heat sources in the mining site, 17 evaluation indexes of the influence factors of the mining site thermal environment were sorted out, and the indexes’ weight was calculated based on the entropy weighting method, and it was learned that the largest weight of the influence on the thermal environment factors in a single excavation working face was the water gushing in the roadway. The TOPSIS method was used to comprehensively analyze and rank the thermal damage degree in the three middle sections. The results show that the degree of thermal damage in the -960 m is more severe than that in the -930 m and -945 m. This will provide some basic basis for the evaluation and prevention of thermal damage in deep mining projects, and is of great significance for improving mine production efficiency.

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Purpose: Macro synthetic steel fibers were incorporated into the concrete material as a toughening agent to improve the corrosion and cracking resistances of concrete in a sulfate-containing service environment. Design/methodology/approach: To study the basic mechanical properties of this system, an accelerated concrete degradation test was designed to evaluate the influence of the sulfate ions on the concrete. A three-point bending test was carried out in the laboratory to evaluate the fracture toughness. The thickness of the damaged concrete layer and changes of microstructure of the degraded concrete were monitored by using ultrasound, scanning electron microscopy and X-ray diffraction detection methods. Findings: The results showed that compared to the performance of ordinary concrete, in an exposure environment containing sulfate ions, the structure compactness of macro synthetic steel fiber concrete was improved, degradation resistance to the sulfate solution was enhanced and the fracture resistance performance was improved significantly. Originality/value: The thickness of the degradation layer on the macro synthetic steel fiber concrete was less than a half of that of ordinary concrete in the sulfate environment, and was generally unchanged with increase in the sulfate concentration. Through micro-structural analysis, it was confirmed that macro synthetic steel fiber improved the compactness of the concrete structure, inhibiting access of sulfate ions to the interior of the concrete and thereby reducing the degree of sulfate degradation to the concrete.