Investigation of Rockburst Mechanisms and Rockburst Prediction  Using Numerical Modeling Methods
Creators: Wang, Jun
Publisher: name: University of Alberta Library
Year: 2023

<p>Rockburst is a sudden rock failure characterized by the breaking up and expulsion of rocks from their surroundings, accompanied by a violent release of energy. Due to its unpredictability and high intensity, rockburst is one of the most hazardous geological disasters. It has caused thousands of injuries and fatalities and significant economic losses to mine enterprises. To date, great efforts have been devoted to the investigation of mechanisms, risk evaluation and prediction, and prevention and mitigation of rockbursts. However, there is no effective way to control rockbursts completely because the phenomenon is very complex and is influenced by many factors. Hence, the rockburst mechanisms in some conditions remain unclear, and current methods and indicators fail to predict rockbursts in many cases.<br>
The objective is to reveal rockburst mechanisms and develop a systematic method and a new stiffness-based indicator for predicting rockburst risks. Compared with other methods, such as physical simulation and field tests, the numerical modeling method has the advantages of low cost, safety, time-saving, and flexibility. More importantly, it can provide more information and simulate the complex mechanical behaviour of rocks and rock masses under different conditions. This can visualize the “real” world in underground mining for researchers and engineers to tackle various rock mechanics problems (e.g., rockburst). Thus, numerical modeling is employed as the primary research approach. <br>
This thesis consists of seven chapters. Chapter 1 presents the research background, problem statement, research objectives and methodologies, and outlines the thesis organization. Chapter 2 provides a literature review of rockburst-related studies based on research objectives. A systematic numerical modeling framework for studying rockburst mechanisms and other rockburst-related problems is established based on the summary and analysis of the literature. In Chapter 3, following the proposed numerical modeling framework, a three-dimensional (3D) finite difference method (FDM) model is established via fast lagrangian analysis of continua in three dimensions (FLAC3D) using the “5.5” rockburst event in the Zofiówka Coal Mine as a case example to reveal the rockburst source mechanism of driving roadways in close-distance coal seam mining conditions. The results suggest that the superposition of multiple excavation-induced stresses of roadways provides an environment for stress concentration. The side abutment stress induced by mining in the upper coal seam has a “strengthening” effect to rockburst occurrence. The great deviatoric stress induced by complex excavating situations is another important exterior cause. A strict calibration procedure should be implemented before using indicators to predict rockburst potential. Thus, a systematic method that can reasonably select and use rockburst indicators is proposed to predict the location and magnitude of rockbursts. Chapter 4 adopted an improved global-local modeling approach to study strainburst damage mechanisms. The results suggest that the strainburst damage mechanism for the study site combines three types of damage: rock ejection, rock bulking, and rockfall, which agrees well with in situ observations confirming the rationality and capability of the modeling approach. The principles to control and mitigate strainburst damage are also proposed. In Chapter 5, instead of conventional drop tests, the performance of yielding rockbolts (D-bolt and Roofex) during remotely triggered and self-initiated strainbursts was systematically evaluated via building a two-dimensional (2D) distinct element method (DEM) model of a deep roadway using a universal distinct element code (UDEC). The results suggest that the yielding rockbolt with high strength and deformation capacity (e.g., D-bolt) has a better performance in controlling rockburst damage. The support effects can be significantly improved by increasing the bolt number and supplementing cables and surface retaining elements (e.g., steel arch). In Chapter 6, a new rockburst indicator, called strainburst stiffness factor (SSF), is proposed and developed to predict strainburst risks based on the analysis of stiffness differences. The prediction results of SSF successfully match with the 5.5” rockburst event in the Zofiowka Coal Mine and the “11.28” rockburst event in the Jinping II Hydropower Station, validating the effectiveness of SSF. Chapter 7 presents the thesis summary, conclusions, research contributions, and future work. <br>
This study revealed rockburst mechanisms and developed a systematic method and a new stiffness-based indicator for predicting rockburst risks. The outcomes of this PhD study can contribute to understanding rockburst mechanisms and effectively predicting rockburst risks for improving the safety of workers and production in burst-prone mines. </p>