Failure Mechanism of Layered Salt Rock in Three-Point Bending Test
Sample of layered rock salt was subjected to three-point bending test with SHIMADZU SEM (Scanning Electron Microscope) system monitoring. Initiation and propagation of crack in both salt rock and mudstone impurity were recorded, so was the micro-structure in the interface between rock salt and mudstone impurity. By analyzing the SEM photos of failed sample, it is found that crack initially comes out in salt rock or mudstone impurity rather than the interface. Three-point bending test was numerically calculated based on bridging model. Calculation results show that the interface is not weak plane, and that the failure mode of salt rock and mudstone impurity is closely correlated with the dip angle of the infinitesimal element of the interface. When the dip is larger than 70°, tensile failure firstly occurs in mudstone impurity. When the dip is smaller than 70° , tensile failure initiates in salt rock.