Early-warning method of rock collapse and its experimental verification

Early warning of rock collapse has been one of the frontier problems in the study of geological hazards for many years. The traditional monitoring methods pay more attention to failure phase,and it is difficult to realize the ear- ly warning of brittle failure such as rock collapse. In fact,the collapse generally undergoes two phases,which are sepa- ration phase and failure phase. Focusing on the precursory events of the separation phase can quickly alert the public in time to seek shelter before a devastating rock collapse. Based on the Laser Doppler vibration testing technology and new physical model experiment,the study focused on the identification of failure precursors of unstable rock in the sep- aration phase. In this experiment,a new freezing experiment method was adopted to simulate the continuous decrease of the bond strength of rock block,and the stability of the block continued to decrease as time went by,and finally broke down at 117 s. The monitoring results showed that the separation precursor occurred at 50 s and the accelerated failure precursor occurred at 115 s,respectively. The early warning based on the identification of failure precursor in the sepa- ration phase was triggered 67 seconds before the destruction,while the early warning based on the identification of fail- ure precursor in the accelerated failure phase was 2 seconds. Compared with the traditional early-warning idea based on the recognition of failure precursor,the early-warning method based on the separation failure precursor used for ear- ly warning of rock block collapse created 65 s in advance,which has better timeliness and can effectively be used as “golden period” of early warning to buy time for better coping with collapse disasters in the projects. The idea of early warning of rock mass collapse disaster based on separation failure precursor recognition is the development direction of emergency prevention of brittle failure disasters such as rock mass collapse of high and steep slopes in mines.