The Study On The Influence Of Ultra-low Temperature On The Mechanical Properties Of Sandstone

As a new green and environment-friendly non-water fracturing technology,liquid nitrogen fracturing may be of great significance in alleviating energy pressure and protecting ecological environment in China.In order to promote the application of liquid nitrogen fracturing as a non-water fracturing technique,it is necessary to clarify the Change Law of mechanical properties of Sandstone under the action of ultra-low temperature of liquid nitrogen and explore the damage and failure mechanism of rock under the action of ultra-low temperature of liquid nitrogen.In this paper,uniaxial compression test,Brazilian crack test,acoustic emission test,DIC test,SEM test,the change rule of mechanical properties and the reason behind the change of mechanical properties of Sandstone after the action of room temperature and ultra-low temperature of liquid nitrogen are studied,the compressive strength,elastic modulus and tensile strength of sandstone samples increase slowly at first and then increase and then decrease with the increase of water saturation of sandstone,while Poisson's ratio increases first and then decreases and then increases The analysis of Acoustic emission characteristic parameters shows that the damage decreases firstly and then increases with the increase of water saturation The results of digital image correlation and scanning electron microscope(SEM)show that the effect of ultra-low temperature of liquid nitrogen on the structure damage and microstructure damage of sandstone samples under different waterbearing conditions,the irrecoverable damage deformation and microstructure damage are the largest at 80% water saturation,followed by the dry sandstone specimen.The damage deformation and microstructure damage are the smallest at 40% water saturation.