Dynamic failure process and strain-damage evolution law of sandstone based on SHPB experiments

Abstract

In order to study the failure characteristics and damage evolution law of sandstone type uranium ore by blasting, the SHPB experimental system with strain control loop is used to conduct dynamic impact experiment on sandstone samples under controlled strain conditions. Combined with the wave velocity experiment and CT scanning experiments, the whole failure process, crack distribution and strain damage evolution law of sandstone samples are analyzed and studied. The experimental results show that the sandstone sample will suddenly appear obvious overall failure when the strain value exceeds 0.008 3 under impact load, and that the overall failure form is approximately biconical and its failure mode is shear-tension mixed failure. With the increase of strain, the generation and propagation of cracks can be roughly divided into crack free stage (0−0.003 3), microcrack initiation stage (0.003 3−0.008 3) and crack through stage (0.008 3−0.009 9). The quantitative relationship between strain and damage is established from macroscopic and microscopic aspects. The growth trend of damage variable with strain can be roughly divided into two stages, i.e. the smooth development area (0−0.008 3) and the rapid growth area (0.008 3−0.011 5). The damage variable does not increase linearly with the increase of strain, but the damage degree increases sharply when the strain value exceeds the strain damage threshold (0.008 3).