Study on monitoring and control of rock burst in deep hard rock based on bolt pre-tightening force

Aiming at the insufficiency of rockburst monitoring and prevention and control research in deep hard rock,a rockburst monitoring method for the pre-tightening force of bolt was proposed,the monitoring system of the pre-tightening force of bolt was developed,a biaxial compression test of anchor specimens was carried out,and the pre-tightening force of bolt and plate were analyzed,and the anchor spacing design methodology for rockburst prevention and control was determined. The results show that the pre-tightening force of bolt is highly sensitive to the micro-deformation of hard rock,and has a good correspondence with the evolution process of rockburst deformation,damage and fracture,and can be predicted by monitoring the pre-tightening force of bolt;compared with the instantaneous rockburst,time delayed rockburst is characterized by multiple obvious sudden increase peaks in the pre-tightening force of bolt. With the increase of depth of the anchored surrounding rock,the anchor prestress continues to decay and the influence range increases. With the increase of the pressure spread angle,the faster the anchor prestress decays with depth and the more obvious the increase of the influence range. The critical depth is defined,and the critical depth formula is given,and the optimized formula of the spacing of the anchor plate is derived based on the critical depth,and the anchor pre-stressing(tightening) force principle used for designing the spacing of the anchors is put forward to get the optimized spacing of the design of the anchor plate,and the design method highlights the control on the shallow part of the surrounding rock,and is particularly applicable to the design of the shallow control and prevention for the surrounding rock hazards such as the rockburst;The contact between the anchor plate and the surface of the surrounding rock affects the anchoring effect. It should be ensured that the anchor plate is in full contact with the surface of the surrounding rock,to ensure that the pre-tightening force of bolt is effectively transmitted and exerted effect to the surface of and the inner of the surrounding rock through the plate. The research results have good guidance and reference significance for prestressing anchor anchorage mechanism,rockburst monitoring,prediction and forecasting,prevention and control. © 2024 Academia Sinica. All rights reserved.