Abstract:In order to discuss the microstructural mechanism of strength property of red sandstones,the microstructural changes of red sandstone under load are tracked by using optical testing systems;the unconfined compressive strength of corresponding rock specimen is measured and the comparable quantitative parameters are extracted. By using multilinear regression method,the correlations between unconfined compressive strength and microstructural parameters are analyzed. Then the microstructural elements closely linked with unconfined compressive strength of red sandstone are filtered and the evolutionary characteristics of prominent microstructural elements are analyzed. The findings indicate that under uniaxial compression,the red sandstones at first experience structural intensification and then structural degradation until they are failed;the unconfined compressive strength of red sandstone is mainly related with compaction rate,pore distribution and connecting condition of mineral grains;and the above factors have a more notable impact on the unconfined compressive strength of red sandstone with the increase of weathering;with the increase of load,the grains area ratio and Euler number decrease,the pore develops towards centralization or collectivization,and the red sandstones gradually lose their resistance to deformation.