Experimental Study On Phase Evolution And Deformation And Failure Characteristics Of Frozen Aquifer Frozen Body

As a typical geological condition in the northwestern region,loose aquifers are widely distributed,especially affected by the alpine climate in the region,often in the state of permafrost and seasonal frozen soil,which poses great challenges to engineering construction,resource exploitation and environmental protection in the northwest region..Based on the geological conditions in the northwest alpine region,the evolution characteristics and mining dynamics of frozen aquifers were studied.The physical properties of loose aquifers under different freezing temperatures were studied by NMR.The MTS-810 low temperature triaxial experiment was carried out.The machine studied the influence of initial water content and freezing temperature on the strength characteristics of frozen loose aquifer and the deformation and failure law of frozen loose aquifer under mining stress path,and obtained the following results:(1)The unfrozen water measurement test was carried out by using nuclear magnetic resonance equipment,and the freezing characteristic curve of the frozen aquifer frozen body,the relationship between temperature and unfrozen water content and the mathematical relationship were obtained.The frozen body was developed by the thermal constant analyzer.Thermal conductivity measurement test,research shows that: at positive temperature,the thermal conductivity of the sample increases with the increase of water content,but is less affected by temperature;0 °C ~-5 °C,the thermal conductivity of the frozen body increases with the decrease of temperature and the water content The higher the rate becomes faster;from-10 ° C to-5 ° C,the thermal conductivity of the frozen body of each moisture content remains basically unchanged.(2)The full stress-strain mechanics test of the frozen body during triaxial compression is carried out.The test shows that the frozen body undergoes elastic,plastic and softening processes;under low confining pressure,the sample undergoes three stages of volume compression,constant and expansion.Under high confining pressure,the sample only undergoes volumetric compression process;the same water content,The lower the freezing temperature,the lower the unfrozen water content inside the sample,the stronger the cohesive force;the same freezing temperature,the higher the water content,the greater the strength of the sample;the sensitivity factor analysis shows the factors affecting the strength of the frozen body: Confining pressure>temperature>water content.(3)The mechanical test under the frozen body mining stress path was carried out.The results show that the samples undergo elastic and plastic softening stages under different water content and freezing temperature conditions.With the increase of water content and freezing temperature,the peak stress of the sample increases,and the stress loss in the post-peak stage is larger.The amount increases and the Poisson’s ratio decreases.-4~-8°C,the elastic modulus of samples with different water content decreases with temperature,the average increase is 84.23%;within the range of 5%~15% moisture content,the elastic modulus of samples increases with water content at different temperatures.The average increase was 166.77%.