Study on Rockburst Proneness Evaluation and Prevention and Control Countermeasures of Over-kilometer Shaft

Abstract

In view of the problem of rockburst in over-kilometer shaft, based on 220 rockburst cases at home and abroad, combined with forward and backward cloud generator to determine the each rockburst proneness evaluation index belongs to the certainty and reasonable numerical characteristics of each rockburst level. Indexes weight are determined by using the improved CRITIC method. An improved multidimensional normal cloud-critic rockburst proneness evaluation model is proposed. Compared with the evaluation results of the entropy weight method-cloud model and the cloud model for rockburst proneness based on the index distance and the uncertainty measure, which verifies the effectiveness of the model. At the same time, the magnitude of σ θ/σ c is obtained plays a dominant role in the occurrence degree of rockburst. Based on this, taking elastic strain energy, average energy release rate and plastic zone volume as evaluation indexes, the rockburst prevention and control countermeasures with reducing σ θ/σ c and energy release rate as the core are put forward: optimizing bore speed, implementing stress release holes on palm surface and bolt-shotcrete support. Optimizing bore speed can reduce the average energy release rate of surrounding rock; Uniform arrangement of stress release holes around the palm surface can effectively reduce the stress concentration behind the palm surface, and form a large low-pressure crushing zone around it. By bolt-shotcrete support, the energy release rate of surrounding rock of shaft wall can be reduced. The above three methods are jointly implemented to effectively prevent and control rockburst. The research results can provide an effective basis for identification of rockburst hazard area and establishment of prevention and control measures in deep engineering.