Rockburst Risk Discrimination And Forecast Based On Microseismic Monitoring

Deep buried tunnels are becoming more and more common in water conservancy,hydropower,transportation,mining and other projects,and the geological problems caused by high ground stress,high temperature and high water pressure under the action of excavation disturbance are becoming more and more prominent.The rock burst has a huge impact on the safety of construction personnel and equipment.The potential threat is one of the recognized worldwide problems in deep rock engineering.Therefore,it is of great significance to the safety of on-site construction to carry out relevant research on the problem of rockburst and promote the development of rockburst prevention work.In this paper,based on the background of Lingnan project of Qinling water delivery tunnel in Shaanxi Province Yinhanjiwei project,the microseismic monitoring technology was applied to the prevention of rockbursts.It mainly carried out the following works:(1)The rockburst monitoring work on the excavation face of Lingnan drill-and-blast method and TBM method based on microseismic monitoring technology is carried out.After continuous exploration,optimization and improvement,a rockburst monitoring system completely separated from TBM is successfully constructed.The monitoring system makes the rockburst monitoring and TBM excavation mutually unaffected,greatly reducing the failure rate of the rockburst monitoring system,and fully guarantees the continuity and integrity of the rockburst monitoring data.The monitoring system is easy to install,operates stably,and has a low failure rate,which is very suitable for promotion and application in similar projects.(2)Over 20 months of rockburst monitoring has been performed on the working faces excavated by the drill-and-blast method and the TBM method:from January 1st to August 25th,2017,the No.4 branch hole excavated by the drill-and-blast method is counted for 18 times in total,of which 15 times are predicted accurately,accounting for 83.3%,and the remaining 3 times failed to predict in advance or the prediction level is lower.From September 8th,2017 to September 30th,2018,the Lingnan TBM working face excavated by TBM method is counted for rockburst in total 177 times,of which 161 times are predicted accurately,accounting for 90.96%,and the remaining 16 times fail to predict in advance or the prediction level is lower.The monitoring results are well received by all parties involved in the construction,and the monitoring data is used as an important reference for the determination of excavation and support parameters.(3)Carrying out comparative monitoring tests of different microseismic monitoring systems for the same microseismic event,the rockburst risk identification indicators based on microseisms with "energy as main factor,frequency,magnitude and concentration as auxiliary factors" are summarized,which not only simplifies the discrimination difficulty,but also facilitates the understanding and application of all parties involved in the construction,and is conducive to the further promotion and application of rockburst monitoring based on microseismic monitoring technology.Through the comparative analysis of monitoring data and on-site feedback,the indicator is quantified gradually,which promotes the development of quantitative determination of rockburst risk level.(4)An abnormal alarm system of rockburst monitoring data is developed.When the rockburst monitoring data is abnormal,the alarm information can be pushed through the PC end and WeChat end at the same time,so that the technicians can know and intervene immediately,greatly reducing the processing period.After preliminary application in the field,the abnormal alarm system of rockburst monitoring data can shorten the time period of data processing and fault maintenance by more than 50%.(5)Based on the quantified rockburst risk identification index,an automatic rockburst risk level discrimination system is developed,which can give the rockburst risk level in real time based on the waveform processing results of microseismic events,and push the relevant information in real time through the PC end and wechat client.The system can reduce the risk discrimination error of rockburst caused by human factors to a certain extent,and improve the objectivity of rockburst risk discrimination,and lay the foundation for the introduction of artificial intelligence in the next step.After preliminary application in the field,the automatic discrimination system of rockburst risk level is in good agreement with the judgment result of experienced technicians.