A new empirical chart for rockburst analysis in tunnelling: Tunnelrockburst classification (TRC)

Abstract

Rockburst is defined as a phenomenon with immediate dynamic instability under excavation unloadingconditions of deep or high geostress areas. Inadequate knowledge and lack of characterizing informationprevent engineers and experts from achieving appropriate prediction results related to the rockburstbehaviour. In this study, a data set including 220 rockburst instances was collected for rockburst classi-fication via the geostatistical method. An update of the 2D graph, the tunnel rockburst classification (TRC)chart, was introduced based on analysing three indicators, namely, elastic energy index (Wet), tangentialstress in rock mass (rh), and uniaxial compressive strength (rc). Distribution and correlation of data weredrawn on 2D plot, and the boundaries of rockburst were distinguished according to the achieved inter-polate points by kriging method. Hierarchically, the validation phase was performed using an additionalset of 28 case histories obtained from several projects around the world. The results showed that the TRCchart with an average error percentage of 3.6% in the prediction of rockburst had a significant and effec-tive implementation in comparison to the exiting heuristic systems. Despite the initial character of theprediction, the described chart may be a helpful tool in the first steps of design and construction.