Study On Physico-mechanical Properties And Acoustic Parameters Of Saturated Salty Artificial Frozen Silt

The acoustic wave propagates in geotechnical media,and its acoustic characteristics are closely related to the physico-mechanical properties of rock and soil.Understanding the acoustic characteristics of salt-containing artificial frozen soil in artificial ground freezing engineering and establishing the relationship between acoustic parameters and physico-mechanical properties of salt-containing artificial frozen soil can provide the necessary basis for acoustic detection of salt-impregnated frozen wall anomalies.Therefore,in this thesis,the correlation between physico-mechanical properties and acoustic parameters of saturated salty artificial frozen silt is studied by means of laboratory test and numerical simulation,considering factors such as temperature,confining pressure and salt content.The freezing temperature,unfrozen water content and creep characteristics of saturated salty artificial frozen silt were obtained through this study.Sound velocity and attenuation characteristics under different temperature,salt content and confining pressure conditions;the relationship between its physico-mechanical indexes and acoustic parameters is analyzed.The main conclusions are as follows:（1）Saturated silt with salt content of 0%～3%,freezing temperature is-0.1～-9.7°C.There is an approximate linear relationship between freezing temperature and salt content.For every 1%increase in salt content,the freezing temperature decreases by3.23°C.（2）The water in the pores of salty silt is mainly free water and capillary water.The unfrozen water content decreases in a power function with the decrease of temperature,and the increase of salt makes the unfrozen water content increase under the same temperature conditions.（3）It is found that under the condition of-20°C temperature and maximum creep stress of 2.3 MPa,the frozen silt with salt content less than 3%is attenuated creep,and the frozen silt with salt content of 3%is non-attenuated creep.When the salt content increased from 0%to 3%,the average creep rate increased from 0.02 h^-1 to 0.20 h^-1,which increased by about 100 times.（4）After freezing,the wave velocity increases logarithmically with the decrease of temperature,and increases exponentially with the decrease of unfrozen water content,and the change with pressure is relatively small.（5）The attenuation coefficient of P wave amplitude increases with the increase of salt content,decreases with the decrease of temperature,and decreases with the increase of confining pressure.The wave velocity ratio increases obviously with the increase of confining pressure,and the wave velocity ratio increases with the increase of salt content.When there is no confining pressure,the wave velocity ratio varies from 1.82to 2.41 with salt content.（6）The numerical simulation results show that the saturated salt-containing frozen silt has a selective absorption effect on the S-wave.The high-frequency part of the S-wave receiving signal spectrum of the salt-containing 0%～2%frozen silt accounts for a high proportion,while the salt-containing 3%frozen silt only has a low-frequency part that is not easy to attenuate.（7）The maximum axial strain and radial strain of saturated saline frozen silt in the attenuation stage are negatively correlated with the wave velocity ratio and positively correlated with the attenuation coefficient.The axial and radial average creep rates decrease nonlinearly with the increase of wave velocity ratio,and increase linearly with the increase of attenuation coefficient.There are 105 figures,18 tables,and 139 references in this thesis.