Revisiting the strainburst intensity of roadways in coal mines: Theory and case study

Strainburst is a type of severe dynamic hazard frequently encountered in underground excavation, involving violent rock ejection. It is caused by the release of elastic strain energy stored in the surrounding rocks. Hence, the burst energy criterion is crucial for evaluating the strainburst intensity. In this study, using a damage model of roadway strainbursts, a new critical energy storage density index for strainburst initiation was proposed, and a novel assessment criterion for the bursting intensity of strainburst-prone roadways was established. The results showed that an increase in coal brittleness results in decreases in critical stress of the strainburst and bursting intensity of the surrounding rocks. When the rock strength increases, the critical stress of the strainburst occurrence and bursting intensity of the surrounding rocks increase accordingly. Additionally, an increase in roadway support’s bearing capacity improves the critical stress of the strainburst occurrence and the energy storage capacity of the surrounding rocks. Although a large roadway excavation size does not affect the critical stress threshold of the strainburst occurrence, it has a significant effect on the bursting intensity of the surrounding rocks. For the Xinjie mining area, the theoretical energy release density of the roadway is calculated as 5.63 × 10 7 J/m for a strainburst-prone coal seam with a uniaxial compressive strength of 30.8 MPa. Verification was performed using two in situ rockburst cases, where the theoretical bursting energy release values Q are 2.82 × 10 5 J and 1.13 × 10 6 J for actual roadway failure lengths of 5 m and 20 m, respectively, with calculation error of 8.46%-25.98%. • A new burst energy criterion for assessing the bursting intensity of roadway strainbursts after their occurrence is provided. • The proposed energy density index describes the energy storage limit, which is directly related to the rock properties, support stress, and excavation size. • The influence of the support strength on the bursting intensity of roadway strainbursts was quantified at the roadway scale.