Study on Mining Effect Caused by Normal Fault and the Inducing Mechanism of Rock Burst
Supervisor:jiang jin quan
In China,coal is the basic energy and the shallow resource has been dried up currently.With the demand increasing of coal,the depth and intensity of coal mining aggravate which lead to the geological and mining conditions complex.Field observations show strong dynamic disasters,such as rock burst,shock bump,coal and gas outburst and so on,are easy to occur affected by fault,bend or coal seam dip angle.Among them,fault is the most common cause and have larger influenced geological structure due to its cutting effect and blocking effect.The mining effect shows notable which can result in a serious threat to the safety of mine production.Hence,the study on mining effect caused by normal fault and inducing mechanism of rock bursts has become an urgent problem at present.In this paper,the mining effect caused by normal fault is studied using physical simulation test,numerical simulation and theory analysis.Then,the classifications and inducing mechanisms of rock bursts in the vicinity of fault are revealed.Finally,the study results are verified via the filed observations.The main study results are as follows:(1)By using the simulation of uniaxial loading,the characteristics of macroscopic fracture,stress response,acoustic emission(AE)response of rock mass with different dip angle structure plane are analyzed.Then,the notable effect of strength weakening and interface slipping are revealed.Moreover,the failure forms and the bursting liability of rock bursts for rock mass with different dip angle structure plane are compared.(2)The mining effect caused by normal fault with different mining directions are studied using physical simulation test.And then,the different responses of fault activation-slipping to the mining disturbance are revealed.Moreover,the movement of overlying strata is more intense when the footwall face passes through the fault compare to that of hanging wall.(3)Considering the mechanical characteristics and the dip of normal fault,the mining effect with the conditions of residual fault coal-pillar,fault dip angle and mining direction are studied;and then the inducing mechanisms of rock bursts are revealed.(4)Mining effect with a working face,which is under a hard and thick stratum,advancing towards a normal fault are studied by numerical simulation.The different of structural morphology and movement characteristics for the hard thick stratum on the two fault walls are obtained.Then,the potential hazard zone and risk of rock burst on two fault walls are analyzed.Finally,the induced modes and these leading factors of rock bursts with different mining directions are summarized.(5)A rheological model of rock burst induced by the instability of coal and rock masses with a fault occurrence is established.According to the failure of different branches or different parts in this model,two different classifications of rock burst,including strain burst affected by high strain energy and fault-slip burst affected by fault activation-slipping,are obtained and the inducing mechanisms of rock bursts are explained further.