Coal mine rockburst is closely related to the complex geological structure. Understanding the criterion of the fault activation instability and the disaster-causing mechanism of rockburst under the influence of mining is the theoretical premise and important guarantee of safe and efficient coal mining. In this paper, based on the theory of key stratum, the mechanical model of fault slip instability in the normal fault during the hanging wall mining was established, and the instability criterion was derived. It is concluded that the fault slip instability of the hanging wall is mainly controlled by two factors: (1) the distance between coal seams and key stratum and (2) the distance between working face and fault. Moreover, these two factors have an inverse relation to the occurrence of rockburst. Subsequently, three conceptual models of rockburst induced by the fault stress transfer, stress concentration of coal pillars, and fault structural instability were proposed. Based on the rock mechanics theory, the rockburst carrier system model of “roof-coal seam-floor” near the fault was established. The mechanical essence of fault rockburst was obtained as follows: under the action of fault, the static load of fault coal pillar was increased and superimposed with the fault activation dynamic load, leading to high-strength rockburst disaster. Based on the occurrence mechanism of fault rockburst, the monitoring and prevention concept and technical measures were proposed in three aspects, including the monitoring and control of fault activation dynamic loads, the monitoring of high static load in fault coal pillar and stress release, and the strengthening roadway support. These prevention and control measures were verified in the panel 103down02 of the Baodian Coal Mine in engineering, and the effectiveness of these measures was proved.
To effectively monitor and control the severe mining-induced rockburst in deep fault area, the fault activation law and the mechanical essence of rockburst induced by crossing fault mining were studied through theoretical analysis, microseismic monitoring, field investigation, and other methods; numerical simulation was employed to verify the obtained fault activation law and the mechanical nature. First, the distribution of microseismic sources at different mining locations and the fault activation degree were analyzed. According to the microseismic frequency and the characteristics of the energy stage, the fault activation degree was divided into three stages: fault stress transfer, fault pillar stress behavior, and fault structure activation. It was determined that the impact disaster risk was the strongest in the stage of the fault pillar stress behavior. Based on the periodic appearance law of microseisms in fault area, three types of conceptual models of fault-type rockburst were proposed, and the rockburst carrier system model of “roof-coal seam-floor” in the fault area was established. The mechanical essence of fault-type rockburst was obtained as follows: under the action of fault structure, the static load of the fault coal pillar was increased and superimposed with the active dynamic load of the fault, leading to high-strength impact disaster. Finally, the prevention and treatment concepts of fault-type rockburst were proposed. The monitoring and prevention measures of fault-type rockburst were taken from two aspects: the monitoring and characterization of fault rockburst and weakening control of the high static load of the fault coal pillar and dynamic load of fault activation. The proposed concepts and technical measures have been verified in the working face 14310 of Dongtan Coal Mine with sound results. The research results have a guiding significance for the prevention and control of rockburst in a similar mining face under crossing fault mining.
In coal mining, the rockburst intensity triggered by the mine earthquake is often greater in the mining area, and the precursor information is more difficult to capture. In this paper, this kind of rockburst is called shock-type rockburst and studied as the research object. Based on the evolution process and the theoretical model of the carrier system, the energy criterion of the occurrence of shock-type rockburst was deduced based on the theories of mathematics and statistical physics. The results showed that the process of shock-type rockburst can go through four stages: inoculation stage, occurrence stage, development stage, and termination stage, and the secondary triggering phenomenon may occur in the occurrence stage. The theoretical model of the shock-type rockburst carrier system was constructed, and the key characteristic parameter of shock-type rockburst was put forward. Then, the energy of mine earthquake was quantitatively characterized in the form of kinetic energy of rock block. Through the combination of the two parameters, the energy criterion of shock-type rockburst was obtained as follows: once the energy of mine earthquake acting on the rockburst source area was 2%–9% of the static energy, shock-type rockburst can occur. Then, this criterion was verified by three typical cases. Finally, based on the distribution conditions of “red seam” overburden in the Yanzhou mining area of China, the secondary triggering principle of rockburst was expounded, that is, the secondary triggering principle of rockburst caused by the shear fracture and sliding settlement of “red seam” overburden. To sum up, a theoretical system for judging the instability of the shock-type rockburst carrier system was formed. This study provides a theoretical basis for earthquake prevention and disaster reduction in coal mining.
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