Formation mechanism of micro-seismicity difference between rockbursts in deep-seated parallel tunnels

Abstract

Deep-seated parallel tunnels are highly susceptible to rockbursts owing to the geological environment and engineering disturbances caused by adjacent tunnel excavations. However, accurately predicting these is challenging. The temporal and spatial characteristics of microseismic (MS) events and rockbursts in parallel tunnels can be jointly analyzed owing to their similar occurrence environments. However, although the left and right tunnels exhibited similar rockburst features during the construction of the Gaoloushan highway tunnel, noticeable differences in the MS events were observed. To clarify the cause of this phenomenon, the mechanisms of the influences of the buried depth, rock mass structure, hydrogeological conditions, construction parameters, blasting disturbance, and other factors on the MS activities of the left and right tunnels were investigated. Our findings suggested that the original geological occurrence environments, including the buried depth, rock mass structure, and hydrogeological conditions, were the primary reasons for the MS differences between the left and right tunnels. There was no obvious correspondence between the tunneling speed and evolution of the MS events. The influences of the section change and blasting on the MS anomaly were restricted by the geological environment and surrounding rocks. The results provide valuable insights into the effects of geological conditions and construction parameters on the formation mechanisms of rockbursts and MS events and may assist in developing an effective early warning strategy, as well as in preventing and controlling rockbursts in parallel tunnels or tunnel groups.