Study Of Damage And Acoustic Emission Characteristics Of Marble Under Step-cyclic Loading And Unloading

In the metal underground mining process, underground rock mass stress state is not stable. Due to the influence of ground pressure activities and artificial disturbance, rock mass is in frequent loading and unloading state. In order to fully understand the damage and acoustic emission characteristics of marble under cyclic loading and unloading. In this paper, based on the field and laboratory experiments to explore the dissipated energy and acoustic emission method to characterize the suitability and differences of marble damage; introducing LURR theory, based on acoustic emission method to analyze LURR features of marble at different stages of stress and suitability of different parameters characterize LURR; combined with in-situ stress values to study LURR features of marble at in-situ stress points. According to the above research, the main conclusions of this paper are as follows:(1)Characterizing the damage of marble based on dissipated energy method, the damage evolution curve of marble was "concave" shape as a whole, and damage variable of marble increases very significantly. The results show that damage of marble mainly in the non-steady stage of development of crack, namely in the stage near the peak stress.(2)Characterizing the damage of marble based on acoustic emission method, marble damage is taken into account during Loading and unloading period, the damage evolution curve of marble perform " bent upward ", the curve become more smooth and show the signs of nonlinear growth.(3)Both dissipated energy and acoustic emission method are suitable for characterizing the damage evolution process of marble. In terms of acoustic emission than dissipated energy method, the advantage of acoustic emission method can reflect the status of the marble damage during the unloading period, on the other hand although dissipated energy method can not characterize the damage of marble during unloading period, it can avoid the impact of acoustic emission quiet period.(4)The LURR of marble show a high consistency rule by characterization of acoustic emission impact counts, ringing counts, energy, Benioff strain. The ringing counts, energy, Benioff strain are superior to impact counts to characterize LURR of marble, the changes in the magnitude of LURR of marble by characterization of acoustic emission energy is more obvious and more sensitive on the numerical value with the increase of stress.(5)As the stress increase, the LURR of marble perform “decline-steady-rise” as a whole. The LURR of marble at a high level in initial compression phase, and it fluctuates around 1 in elastic deformation stage and steady stage of development of crack, the LURR of marble significant increase in non-steady stage of development of crack. The feature of marble LURR which can identify stress state and provide a basis for determining the stability of the rock mass.(6)The LURR of marble at in-situ stress points at high levels and significantly greater than 1, and perform “decline-steady”, which is different from the LURR in elastic deformation stage and steady stage of development of crack, The feature of marble LURR which can provide a basis for recognition of the Kaiser effect point.