Effect of branch roadways on dynamic disaster-causing and energy dissipation characteristics of outburst gas-solid two-phase flow

Coal and gas outbursts are complex, dynamic phenomena in coal mining. Outburst two-phase flow (OTPF) poses a serious threat to the safety of underground equipment and operators during an outburst. In this study, by means of physical simulation test, the dynamic disaster characteristics of OTPF in roadway with and without branches were discussed. The experimental results showed that pulverized coal flow was initially shaped like an arc-shaped jet. The average migration velocity of OTPF under non-branched right-angle turning roadway (L-Rd) was larger than under branched right-angle turning roadway (F-Rd). In the straight section, the mass of pulverized coal under L-Rd was generally larger than under F-Rd, whereas in the turning section, the opposite was observed. The branch roadway enhanced the flow capacity of outburst pulverized coal in main roadway. An alternating pattern of strong and weak impact forces was observed. The impact dynamic disaster-causing intensity of F-Rd increased by 33.4% compared to L-Rd in the straight section and by 19.2% in the turning section. The impact force was generally higher under F-Rd relative to L-Rd, indicating that the branch roadway increased the disaster-causing risk of OTPF in main roadway. Moreover, the static pressure was generally lower under F-Rd relative to L-Rd, indicating that the branch roadway weakened the static pressure damage in the main roadway. The findings of this study hold significant value for the design of mine roadways and the establishment of emergency shelters.