Study On Creep Of Time-dependent Deformation And Acoustic Emission Characteristics Of Sandstone Under Uniaxial Compression

The creep acoustic emission of the sandstone under the condition of single-stage loading is based on the uniaxial compression condition,which is caused by the long-term creep eventually lead to unstable failure of the underground structure under the condition of constant load;Research on the creep process characteristics during the variation of axial,lateral and volumetric deformation,then,study on the relationship between the creep stress and the expansion point stress ratio(β-value)with the creep failure time.Lastly,the variation of acoustic emission signals at different creep stages were analyzed by acoustic emission technique.The main conclusions are as follows:(1)The creep time and deformation of the lateral creep in the creep process of the sandstone are higher than the axial creep,and the volumetric deformation expansion effect is significant.Rock’s particle size is smaller and more homogeneity,the sandstone is less prone to creep deformation.The sandstone damages mainly occur in the deceleration and acceleration creep stages.The average expansion point stress obtained by uniaxial compression test can be used as the basis for the preliminary development of creep stress level.(2)The relationship between the creep stress and the expansion point stress ratio(β-value)with the creep failure time is as follows: the creep failure time decreases with the increase of the β-value.(3)The acoustic emission signal exhibits proportional relationship with the creep rate,in the deceleration creep stage,the acoustic emission signal is gradually smaller with the time;In the steady creep stage,the acoustic emission signal is roughly,the frequency and amplitude is small;at the junction of the steady and accelerating creep process,the acoustic emission parameter signal appears "abrupt" rise and suddenly stabilizes,but it’s frequency and amplitude are higher than the other two process;during the sandstone creep failure process,the acoustic emission signal is large,cluster-like growth.The acoustic emission ∑N/∑E(referred to acoustic emission r-value)of the decelerated creep process is generally higher than steady creep process,and in the steady creep stage,the acoustic emission r-value is more stable.In the accelerated creep process,the acoustic emission r-value is significantly reduced,and it’s reduced to the lowest level during the sandstone creep failure process.Combining with the characteristics of acoustic emission parameters and acoustic emission r-value at different creep process,to some extent,it can be forecasted the sandstone creep failure.(4)The axial strain curve in the deceleration and steady creep stages have the "mutation" phenomenon,these "mutations" after a brief adjustment,can still restore the stable state,and in this time the acoustic emission signal appears " abrupt " phenomenon,which indicates that the rock material strength of the lower part of the rupture,but the sample did not constitute a significant damage,the acoustic emission r-value of the smaller reduction is also illustrates this phenomenon.Therefore,the acoustic emission signal and r-value describe the deformation and damage evolution character of sandstone.