In-situ test and bolt-grouting design evaluation method of underground engineering based on digital drilling

The reasonable design and in-time optimisation of the supporting scheme is very important for ensuring the safe control of the surrounding rock. The key steps are to conduct in-situ real-time tests and quantitative evaluation of the surrounding rock before and after being supported. In order to solve the difficult problem of in-situ testing the surrounding rock, the surrounding rock digital drilling test system (SDT system) of underground engineering is developed, and the in-situ test and bolt-grouting design evaluation method of surrounding rock in underground engineering based on digital drilling is proposed. The systematic test studies including digital drilling test, borehole inspection and coring test are conducted on typical surrounding rock of chamber in the high stress mine of China. The effectiveness of SDT system and the prediction model of rock equivalent strength based on drilling applied to on-site engineering are validated. The zoning of surrounding rock of deep chamber based on equivalent strength is obtained, which are the strength deterioration zone, strength recovery zone and original rock strength zone, respectively. Based on the results of the in-situ digital drilling test of surrounding rock, the bolt-grouting support scheme to reinforce the surrounding rock is designed and evaluated. The average equivalent strength increase rate of the fractured regions of chamber surrounding rock reinforced by bolt-grouting is 61.6%. The bolt-grouting support can effectively enhance the strength of the fractured surrounding rock and reinforce the fractured rock mass. This study provides an effective means for classifying surrounding rock based on their strengths and design optimisation of the support system.