Study on the influence laws of geology and stress on the occurrence time of rockburst in deep-buried borehole-blasting tunnels

Abstract

Rockburst occurrence time in deep-buried borehole-blasting tunnels is characterized by significant temporal clustering. Revealing the geological and stress influence laws is a prerequisite for accurate warning and risk control. In this study, a 3D excavation model is constructed, and the surrounding-rock damage variable RFD is introduced. Two time-series characterization indicators are defined: the principal stress change rate and the geometric characteristics of surroundingrock damage. Through orthogonal tests, Pearson correlation, ridge regression, and linear regression, we investigate the influence of in-situ stress, rock-mass mechanical parameters, and spatial geometric parameters on rockburst time. Results show that rockburst excavation-lag time is jointly controlled by these two indicators, which both exhibit a strong positive correlation with it. Specifically, as in-situ stress, the angle between in-situ stress direction and tunnel axis, and brittleness coefficient increase, the principal stress change rate decreases, leading to earlier rockbursts. As uniaxial compressive strength increases, the principal stress change rate increases, delaying rockbursts. As the angle between structural planes and the maximum principal stress and the spacing of structural planes increase, the geometric characteristics of damage increase, also delaying rockbursts. These findings can provide theoretical support for warning, prevention, and control of immediate rockbursts in deep-buried tunnels.