Study On Acoustic-seismic Characteristics Of Freeze-thaw Damage Process Of Rock

China’s cold areas are vast.With the implementation of the“Belt and Road”,the implementation of the western development strategy and the vigorous construction of railways and highways in the cold areas,the scale of infrastructure construction in the cold areas has also been greatly increased year by year.At present,the research on freeze-thaw cycle damage of rock is not enough.Therefore,based on the characteristics of acoustic emission and microseismic signals,p Hysical,mechanical and acoustic parameters,the damage mechanism of frozen-thawed rock under the action of four different influencing factors,such as freezing-thawing times,temperature change rate,salt concentration of solution and p H value,is studied in this paper.The main work and achievements of this paper are as follows:1.The relationships among the p Hysical acoustic parameters,mechanical properties,acoustic-seismic properties,damage variables and temperature change rate of rock subjected to freeze-thaw damage are investigated:(1)with the increase of temperature change rate,the elastic modulus E,peak stress intensity σ_c,p-wave Velocity V_P and S-wave velocity V_s of sandstone all decrease,while the porosity change value(35)N,mass loss rate M and Siméon Denis Poisson ratiomincrease,the failure mode gradually changes from brittleness to plasticity.(2)the high amplitude of AE Energy gradually changed from only appearing in the middle and late stage of failure to appearing in the compaction stage and the elastic stage,and finally to appearing in the whole process of loading;The cumulative ring number-time curve of AE tends to increase linearly with the increase of temperature change rate.(3)when the temperature change rate is low,the high amplitude of microseismic energy changes gradually from a small area just before the stress drop to a uniform distribution during the loading stage;The cumulative ringing number-time curve of microseism shows obvious variable speed increase without freezing-thawing and temperature change rate is small,the amplitude of ringing number before and after speed change point is very different,and with the increase of temperature change rate,speed change point keeps approaching to the failure point,the amplitude difference of ringing number before and after the change speed point is gradually reduced,and the time proportion and the average speed are gradually increased in the period of constant speed growth.When the temperature change rate is 3°C/min,the time of uniform growth stage is 90%,and the average rate is 3.25 times of that before freezing and thawing.(4)the relationship between the damage parameters and the temperature change rate is exponential increasing,and the correlation is high,but the increase of the damage parameters from 0.1°C/min to 1°C/min is much lower than that from 1°C/min to 3°C/min,it is considered that the critical value of temperature change rate is1°C/min.When the temperature change rate is higher than 1°C/min,the initial damage degree of freeze-thaw rock rises sharply.2.To explore the relationship between the p Hysical acoustic parameters,mechanical properties,acoustic vibration properties,damage variables and the concentration of salt in the solution of freeze-thaw damaged rocks:(1)with the increase of salt concentration in solution,E,V_P,V_s of sandstone decrease,(35)N,M,mincrease,and plastic failure occurs gradually during mechanical loading.(2)when the concentration of salt solution is low,the AE energy fluctuates in high amplitude only in the middle and late stages of the failure stage,and increases only slightly in the compaction stage.With the increase of salt concentration,the range of high amplitude appears in the compaction stage and the elastic stage,and the level of the whole amplitude increases When the concentration of salt solution is low,the cumulative ringing number-time curve of acoustic emission(ae)shows an obvious three-stage ladder-like increase.When the concentration of salt solution reaches1.5mol/l,the ladder-like increase trend becomes less and less obvious,the cumulative ringing number-time curve increases linearly.(3)with the increase of salt concentration,the high amplitude of microseism energy changes gradually from a small area only before stress drop to the whole process of loading The cumulative ringing number-time curve of microseism shows obvious variable speed increase when the concentration of salt in solution is low,both the time share and the average growth rate in the constant velocity p Hase increase gradually.When the concentration of salt in the solution is 2mol/l,the curve becomes linear,and the average growth rate tends to be the same in the constant p Hase and the destruction p Hase.(4)the relationship between the damage parameters and the concentration of salt solution increases exponentially.3.Based on the study of the damage parameters of AE and microseism,the damage parameters of AE and microseism are taken as independent variables,and the damage parameters are taken as dependent variables.