| The effect of supercritical carbon dioxide on fracture toughness of sandstone is studied.three-point bending test method are used to determine conventional type I fracture toughness of sandstone and the different effect of temperature and pressure conditions of supercritical carbon dioxide treatment on sandstone are investigated.The influence mechanism of supercritical carbon dioxide on fracture toughness of sandstone was analyzed by acoustic emission technique,component analysis and electron microscope.the conclusions are as follows:(1)The fracture toughness KIC of the treated sandstone is lower than that of untreated sandstone.The fracture toughness KIC of treated sandstone decreases with the temperature and pressure increasing.(2)Based on the acoustic emission signal in the test process,the AE released energy is analyzed in sandstone during fracture.The energy released by the treated sandstone is lower than the energy released by the untreated sandstone during the fracture.The supercritical carbon dioxide can reduce the resistance of fracture propagation in crack tip of sandstone.(3)The compositions of sandstone are studied before and after treatment.The sandstone contains feldspar minerals that react with carbon dioxide mostly.(4)The microstructures are contrasted before and after treatment.The cracks induced by supercritical carbon dioxide were higher than that of untreated samples.Primary pores and microcracks are eroded,and the microstructure of sandstone is changed to a new pore structure. |
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