Research on the Law of Large-Scale Deformation and Failure of Soft Rock Based on Microseismic Monitoring

Abstract

Based on the existing Canadian ESG microseismic monitoring system, a mobile microseismic monitoring system for a soft rock tunnel has been successfully constructed through continuous exploration and improvement to study the large-scale nucleation and development of microfractures in the soft rock of the Yangshan Tunnel. All-weather, continuous real-time monitoring is conducted while the tunnel is excavated through drilling and blasting, and the waveform characteristics of microseismic events are analysed. rough the recorded microseismic monitoring data, the variation characteristics of various parameters (e.g., the temporal, spatial, and magnitude distributions of the microseismic events, the frequency of microseismic events, and the microseismic event density and energy) are separately studied during the process of large-scale deformation instability and failure of the soft rock tunnel. e relationship between the deterioration of the rock mass and the microseismic activity during this failure process is consequently discussed. e research results show that a microseismic monitoring system can be used to detect precursors; namely, the microseismic event frequency and energy both will appear "lull" and "active" periods during the whole failure process of soft rock tunnel. Two peaks are observed during the evolution of failure. When the second peak occurs, it is accompanied by the destruction of the surrounding rock. e extent and strength of the damage within the surrounding rock can be delineated by the spatial, temporal, and magnitude distributions of the microseismic events and a microseismic event density nephogram. e results of microseismic analysis confirm that a microseismic monitoring system can be used to monitor the largescale deformation and failure processes of a soft rock tunnel and provide early warning for on-site construction workers to ensure the smooth development of the project.

Rockburst prediction and early warning for a highway tunnel excavated by TBM based on microseismic monitoring

“…One of the most obvious features of the MS event waveform is its short duration, generally only a few tenths of a second or so. The characteristic of small amplitude is also an important criterion for distinguishing effective MS signals (Chen et al, 2018). The phase features of MS events include arrival time, waveform, amplitude, period, etc., while the data extracted from MS events mainly include the arrival time and phase features of the MS P-and S-waves.…”