3D Experimental Measurement of Lattice Strain and Fracture Behavior of Sand Particles Using Synchrotron X-Ray Diffraction and Tomography

Three-dimensional synchrotron X-ray diffraction (3DXRD) and synchrotron microcomputed tomography (SMT) techniques were used to measure and monitor the lattice strain evolution and fracture behavior of natural Ottawa sand particles subjected to one-dimensional (1D) compression loading. The average particle-averaged lattice strain within each sand particle was measured using 3DXRD and then was used to calculate the corresponding lattice stress tensor. In addition, the evolution and mode of fracture of sand particles was investigated using high-resolution three-dimensional (3D) SMT images. The results of diffraction data analyses revealed that the major principal component of the lattice strain or stress tensor increased in most of the particles as the global applied compressive load increased until the onset of fracture. Particle fracture and subsequent rearrangements caused significant variation and fluctuations in measured lattice stress-strain values from one particle to another and from one load stage to the next load stage. SMT image analysis at the particle scale showed that cracks in fractured sand particles generally initiated and propagated along the plane that connects the two contact points. Fractured particles initially split into two or three major fragments, which in some cases was followed by disintegration into multiple smaller fragments. Microscale analysis of fractured particles showed that particle position, morphology, and the number and location of contact points played a major role in the occurrence of particle fracture in confined comminution of the sand assembly. (C) 2017 American Society of Civil Engineers.