FAILURE MODE AND MESOSCALE FAILURE PROCESS OF JOINT LIMESTONE WITH DIFFERENT DIP ANGLES BASED ON DIGITAL IMAGE¹⁾

In order to study the influence of the joint digital image processing (DIP) angle on the fracture mode and the fracture process of limestone, digital images are used to characterize the microscopic non-uniformity caused by the shape, the size and the distribution of the calcite in limestone. RFPA2D-DIP is used to simulate the fracture process and the failure mode of the jointed limestone with different dip angles. The results show that the meso structure has an important influence on the mechanical properties and the ultimate failure mode of the jointed specimens. The elastic modulus and the compressive strength of the jointed limestone have obvious anisotropy, and show shaped changes with the increase of the jointed dip angle. Under the action of the uniaxial compression, the jointed limestone is mainly subjected to the tensile failure accompanied with a small amount of shear failure on the mesoscale. The ultimate failure modes of the jointed limestone are shown in six forms depending on the jointed dip angle: the linear shape (\alpha =45^\circ, \alpha =75^\circ), the N shape (\alpha=60^\circ), the oblique Z shape (\alpha =0^\circ), the oblique N shape (\alpha =90^\circ), the M shape (\alpha =15^\circ), and the V shape (\alpha =30^\circ).