Study on rockburst control of deep-buried tunnel by combining advanced stress release borehole and hydraulic fracturing

Abstract

Rockbursts are a common geological hazard during the construction of deep-buried tunnels and seriously threaten the safety of workers. To control rockbursts, first, during the construction of the Hanjiang-to-Weihe River Diversion Project, advance stress release borehole (ASRB) tests were conducted in each of the three different depth tunnel sections where rockbursts occur frequently. Then, microseismic (MS) monitoring technology was used to monitor the microfracture information inside the surrounding rock in real- time during the excavation process. The effectiveness of ASRBs for rockburst control was evaluated by comparing the counts, MS energies and rockburst levels in the drilled and adjacent undrilled sections. The results showed that the ASRBs did not provide the expected pressure relief effect in every tunnel section. In rock masses with higher in- situ stress, the ASRBs did not form a pressure relief zone and instead led to local stress concentration and increased the risk of rockbursts. Finally, this study proposed rockburst control technology for deep-buried tunnels using a combination of ASRBs and hydraulic fracturing (HF) and verified the feasibility of the technology using numerical simulation methods. In addition, the effects of parameters such as the diameter, number and location of ASRBs on the effectiveness of HF in controlling rockbursts are discussed in this study. The rockburst control measures proposed in this study have significance for the construction of deep-buried tunnels.