The Gaoloushan tunnel is a two-hole, deep-buried, extra-long rocky cross-ridge tunnel with a maximum depth of approximately 1,680 m. Due to the dual effects of tectonic stress and self-weight stress field, 90% of the tunnel body is subject to extremely high-stress and high-stress, and strong-moderate rock burst likely occurs in hard rocks, such as metamorphic sandstone and schist. To prevent human casualties and equipment damage caused by rock burst, this article investigates the layout of the multisource monitoring and early warning system for disasters in the Gaoloushan deep-buried tunnel. Early warning methods for potential destructive disasters and other ground pressure phenomena are also proposed by adopting important monitoring methods, such as microseismic monitoring, electromagnetic radiation monitoring, ground sound monitoring, surrounding rock stress monitoring, and acoustic emission monitoring. Therefore, this study has important significance and engineering application value for the prevention and control of rock burst disasters in deep-buried long tunnels.
Rock burst, a common phenomenon of rock stability in deep underground projects, is specifically manifested as the sudden, violent ejection and catapult of rocks into the excavation space. Rock burst likely results in damaged supporting equipment and deformed excavation profile, and even damaged engineering infrastructure, casualties, local earthquakes, surface collapse, and other disasters[1]. Rock burst is induced by internal and external factors, of which the former refers to the fact that when rock is sufficiently brittle, the elastic strain energy stored in the rock is enough to convert into kinetic energy for ejecting the rock when it is destroyed; and the latter refers to the redistribution and concentration of surrounding rock stress caused by the changes in the surrounding space environment during construction[2].
The mechanism of rock burst is complex, and many influencing factors exist. Determining whether rock burst will occur and quantitatively estimating the severity of rock burst are difficult. Gao[3] performed monitoring and early warning by using all-digital multichannel microseismic monitoring technology, developed a comprehensive quantitative scoring system on the basis of multimicroseismic parameters for the probability of rock burst, and conducted multiple effective rock burst monitoring and early warning. Wang[4] thoroughly analyzed the correlation among seismic wave velocity, seismic wave velocity gradient, and rock burst and initially established seismic wave velocity anomaly coefficient and wave velocity gradient coefficient as a model for evaluating the risk of rock burst. Zhang[5] monitored the whole process of roadway rock burst by using infrared thermal imaging camera and established a real-time early warning method on the basis of infrared spatiotemporal evolution to provide theoretical guidance for the establishment of early warning system for mining disasters. On the basis of the acoustic emission (AE) monitoring results and rock burst records, Lu[6] predicted and graded the rock burst of the Gaoligongshan tunnel and provided the criteria for predicting the AE rock burst of the tunnel. Jiang[7] proposed the design idea of an intelligent tunnel monitoring system on the basis of the Internet of Things; the corresponding technical system, which wirelessly transmitted various sensor information to the tunnel management center with the help of the Internet of Things technology, was also built to further realize the remote, real-time, and dynamic management of the tunnel. Liu[8] proposed a rock burst prediction method by combining rock mass structure analysis and electromagnetic radiation monitoring to predict the occurrence and intensity of rock burst on the basis of the changes in electromagnetic radiation energy and pulse. The combination was proven to be a feasible method for predicting rock burst during underground cavern construction. Ma[9] used microseismic monitoring technology as a rock burst monitoring and early warning method to reveal the relationship between the temporal and spatial evolution of microseisms and rock burst, including the 3S principle in seismology, as the basis for rock burst judgments. Four rock burst criteria were also proposed. Zhang[10] performed rock burst monitoring and early warning for deep-buried tunnel by microseismic monitoring technology in the construction of water diversion tunnels; the relationship between the temporal and spatial evolution of microseisms and rock burst was also preliminarily discussed, providing a new research idea for tunnel rock burst prediction. In view of the deficiency of existing research on rock burst monitoring, Zhang[11] conducted a uniaxial compression test and full ultrasonic monitoring of complete hard rock burst, analyzed its failure characteristics and the law of ultrasonic precursor, and discussed the prediction method of complete hard rock burst.
