Mutation mechanism analysis and nonlinear dynamic characteristics on geological hazards triggered by external disturbance

According to the water burst type and its mode,the concept of key mass for water preventing was put forward,based on solid rock structure and its size difference,the mechanical model of key block and key strata was established.Based on the external disturbance form of harmonic wave,the catastrophic model of double cusp for instability of the critical rock layer for water bursting induced by dynamic disturbances was established,and its condition of instability is worked out.The instability criterion and minimum critical rock layer was confirmed according to the instability condition,which are effected not only by the geometry size,material properties and water pressure of key stratum,but also the amplitude and frequency of external force disturbance.The influence of amplitude,frequency of dynamic disturbances on critical rock layer was studied by numerical analysis,and the mechanism of small footage and weak blast to lessen rock damage is put forward.