Microseismic early warning of surrounding rock mass deformation in the underground powerhouse of the Houziyan hydropower station, China

Early warning of surrounding rock mass deformation and failure is of great significance for an underground powerhouse and remains a challenge in rock engineering. The microseismic (MS) monitoring technique was adopted for surrounding rock mass deformation forecasting in the underground powerhouse of the Houziyan hydropower station. By analysing the evolution laws of multiple MS parameters, including the MS event count, the energy release, the energy index, the apparent volume, the dominant frequency, the b value, and the fractal dimension, typical abnormal variations prior to a large deformation were obtained, and these MS parameters were found to behave differently. The MS event count appeared with escalating fluctuation as the energy demonstrated a gradually accelerating increase, while the energy index sharply increased with a stable increase of the cumulative apparent volume. Moreover, the dominant frequency, the b value, and the fractal dimension decreased. Accordingly, these MS abnormalities can be regarded as indicators prior to a large deformation of surrounding rock mass. A comprehensive analysis of these MS parameters could allow for better warning and risk assessment of surrounding rock mass deformation and failure in underground caverns.