Study On Mechanical Properties And Fracture Behavior Of Marble Under And After Creep Loading

Creep is a widespread scientific phenomenon in rock engineering.The strength,deformation and failure characteristics of rock mass in the process of creep will directly affect the difficulty of the engineering.In order to study the time delay failure mechanism of rock under the action of high stress creep and the mechanical properties and fracture behavior of rock after creep action,laboratory experiments of marble were carried out in this paper.(1)The deformation characteristics,energy consumption characteristics and acoustic emission characteristics of rock with time-delay failure under different conditions are analyzed.The results show that: The lag time of failure decreases with the increase of creep stress ratio,and increases with the increase of confining pressure.In the process of time-delay failure,the development of the cyclic variation is more sufficient than the axis variation,which is generally greater than that of the conventional compression test.The regularity of the body transmission rate and the number of acoustic emission energy is more consistent.With the increase of the stress ratio,the attenuation creep stage gradually disappears and the acoustic emission manifests in the decline phenomenon.The average rate of creep,the steady creep rate and the number of acoustic emission energy decrease with the increase of the confining pressure,and increase with the increase of the stress ratio.The total energy absorbed and dissipated energy of rock during failure are related to confining pressure,which may not be related to the creep stress ratio.The elastic energy increases linearly with the increase of confining pressure and increases slightly with the increase of creep stress ratio.With the increase of stress,the type of rock specimen failure is transferred from shear and splitting type to shear type,and the single axis delay leading failure type is split type,rock sample is not formed,and the degree of fracture is high.With the increase of confining pressure,the shear surface begins to appear,and the rock sample is formed.(2)The strength characteristics,deformation and fracture behavior of marble after different degrees of dead load are analyzed,and a new way to divide thedeformation by using the rate of strain is found.The results show that: The structure property of marble is enhanced by constant load under the lower stress characteristic value.The longer the creep,the higher the enhancement level,and higher in the linear stage than in the compaction stage.However,after constant load at high stress characteristic values,the structural properties of marble tend to deteriorate.The longer the creep is,the easier the deterioration level is.Based on the rate of change,3stages of marble are divided into equal speed,acceleration and deceleration.Compared with untreated marble,the maximum value of uniaxial compression expansion rate of rock is reduced after constant load in the first two stages,the longer the creep,the larger the decrease,but less overall reduction,and the decrease of the linear stage is less than that of the crack compression stage,and the expansion rate is the most in the later stage of higher stress characteristic value.The larger the value is,the higher the amplitude is.The longer the creep,the higher the increase.0 after H creep,the rock failure pattern is basically the same as that of untreated rock samples,that is,single shear failure.The longer the creep,the marble shows a transition from shear to splitting failure in the first two stages under low stress,and the cleavage and shear combination type is more likely to occur in the leading fissure under the high stress,with a large number of fissures,and the formation degree is very poor.