Study On Long-term Stability Mechanism Of Mined-out Area Influenced By Dynamic Disturbance Considering The Role Of Water In Gypsum Mine

The stability of mined-out area is always the important research field of mine safety.As the role of supporting the stability of mined-out area,the rock is influenced by many factors of rheological,blasting disturbance,groundwater;damage increases constantly,mechanics properties have been weaken;the stability of mined-out area changes as time goes on.To study the long-term stability of mined-out area,it is necessary to study and analyze the stability evolution mechanism of mined-out area influenced by the effect of water-rock and dynamic disturbance,the mined-out area is constituted of the continuous deterioration rock.Combining with the field measurement,laboratory similar simulation experiment and theoretical analysis,numerical simulation and other means;the mined-out area was inspected in gypsum mine of Yicheng district,the damage of mined-out area pillar was measured which was influenced by the blasting disturbance in gypsum mine;by rock rheological instrument with ordinary triaxial,perturbation loading devices and blasting disturbance precision analog device,the experiments of rheological and the coupling effects experiments of rheological,disturbance of gypsum ore were made,the experiments of rheological and the coupling effects experiments of rheological,disturbance were explored under different stress levels and different moisture content of gypsum ore;based on the deteriorating regular study of rock mechanics parameters influenced by the multi-factor coupling of water rock-dynamic disturbance-rheological,the numerical simulations of the stability of mined-out area were made and analyzed;finally by dynamic simulation module and fluid-solid coupling module of FLAC3D,the impact on the stability of mined-out area from groundwater and blasting disturbance was analyzed in gypsum mine.The main research results are as follows:(1)According to the blasting characteristics of field testing,the Sadove's vibration formula of test mining is established;according to the acoustic velocity measurements of pillar rock,rock damage evolution law of pillar rock is obtained.(2)Respectively under the stress levels that 20%,35%,40%,60%,75%and 80%of uniaxial compressive strength of gypsum ore,rock compression rheological experiments were made,the experiments results are found that:when the 40%stress level and below,slow rheological stage only exist,and finally tends to be stable;only when the 80%high stress level,the accelerated rheological of rock appears.(3)Under three kinds of stress level that 40%,60%,80%of the uniaxial compressive strength of gypsum ore,the coupling experiments of rheological and disturbance under different disturbance intensity were made;by using sonic detector,the sound velocity changes were measured and the amount of corresponding damage were obtained,then the dates were dealt and analyzed by using the Matlab software.Under the condition of low load disturbance,only when reached the creep stress that the long-term strength of gypsum,continuously exerting disturbance for a long time,the major damage of the gypsum can be produced even destroyed.Under the condition of high load disturbance,the process of gypsum accelerated creep is accelerated,when it closes to the stress level of intensity for a long time,the gypsum ore may be damaged only under a short time.The amount of gypsum damage after disturbance is increasing as the amount of disturbance.Actually it is the process that the integrity of gypsum is degraded constantly and the damage is intensified.(4)In order to analyze the influence on the stability of mined-out area from water-rock,disturbance coupling;the rheological and rheological disturbance experiment of gypsum under different moisture content were made.The result is that no matter the rheological curve and the rheological disturbance curve of gypsum specimen,the more moisture content of gypsum specimen,the more obvious characteristics of gypsum weakening,and the constant disturbance impact accelerates the gypsum specimen to be damaged,deformation modulus of the initial moment of creep,viscosity coefficient of creep and the parameters of the model decrease with the increase of moisture content,limiting creep deformation modulus tends to increase significantly.(5)Based on the coupling experiments of rheological and disturbance under different moisture content,the changes of rock mechanics parameter were got,the long-term stability of goaf was analyzed by using numerical simulation software FLAC3D;the vertical stress distribution of goaf roof,displacement change value of goaf roof,the change of the plastic zone of goof were simulated;the results show that the vertical stress values,displacement of roof and floor,the plastic zone range increase significantly.(6)Using the dynamic simulation module and fluid-solid coupling module of FLAC3D to simulate the impact on the stability of mined-out area from groundwater and blasting disturbance in gypsum mine,it is found that:after the dry mined-out area was excavated and the mined-out area was applied blasting disturbance under hydrostatic pressure,the stress of surrounding rock is redistributed;And the maximum vertical stress increases more obviously caused by the later,the maximum displacement also increases obviously,the distributions scope and form of displacement change obviously;after the large range,connected,irregular shape of mined-out area was excavated,the range of plastic zone is larger;After applying the blasting dynamic load,the range of plastic zone expands obviously,even extends to the roof,and the expanding range increases as the dynamic load amplitude increases.