DEM simulation of crack evolution in cement-based materials under inclined shear test

Abstract

The study aimed to investigate the initiation and propagation of cracks in cement-based materials subjected to shear stresses via discrete element method (DEM) simulations. It carried out numerical simulations and calibration of confinement stress-dependent bond parameters in inclined shear tests (IST), coupled with acoustic emission (AE) technique, on cement-based samples. Without modification, the default bonded models (DBM) in existing DEM software cannot consider the effect of confinement, which is critical for the strength and crack behavior of cemented materials. The study put forth a set of linear equations for determining confinement-dependent bond parameters, which are related to shear angle and confinement stress. The DEM simulation showed that the peak shear stresses were 6.26, 17.78 and 24.43 MPa at shear angles of 80°, 70° and, 65° respectively and corresponds to those results obtained from the tests. The broken bonds initiation (crack initiation) position was located around the center of the sample and subsequent crack propagation behavior was affected by the shear angle which agrees with the experimental results of AE evolution. Broken bonds proved to be a useful tool in studying micro-crack behavior. The proposed model is simple and yields results close to the test.