Effect of liquid nitrogen freezing-thawing on the mechanical properties of saturated coal
A new high confining pressure triaxial visual measurement system based on image measure-ment technology was used to conduct triaxial loading and unloading experiments on coal samples under different pre-treatment and confining pressures.The research results show that under confining pressures of 3,6,and 9 MPa,the compressive strength of liquid nitrogen freeze-thaw coal samples decreased by 0.29％,25.34％,and 47.67％compared to dry coal samples,respectively.The internal structural damage of coal samples treated with water and then liquid nitrogen freeze-thaw was more serious,and the brittleness was increased.The axial,radial and bulk strain values of liquid nitrogen freeze-thaw coal samples were smaller than those of dry coal samples,and the strain of confining pressure unloading test body larger than that of axial pressure loading test.After water saturation,liquid nitrogen freeze-thaw treatment and confining pressure unloading test had a better cracking and reflection improvement effect on coal samples.After the liquid nitrogen freeze-thaw treatment,the maximum crack width of coal sam-ple end face increased by 220.83％,and the box dimension increased by 43.9％.After the experiment,the original shape could not be maintained,and the coal sample showed a massive and powdered combina-tion.After the liquid nitrogen freeze-thaw treatment,cracks developed and the internal structure was seri-ously damaged.
liquid nitrogen freeze-thawaxial compression loadingconfining pressure unloadingdam-age to structure
万方数据
维普
