Three-dimensional finite element simulation and reconstruction of jointed rock models using CT scanning and photogrammetry

Abstract

The geometry of joints has a significant influence on the mechanical properties of rocks. To simplify the curved joint shapes in rocks, the joint shape is usually treated as straight lines or planes in most laboratory experiments and numerical simulations. In this study, the computerized tomography (CT) scanning and photogrammetry were employed to obtain the internal and surface joint structures of a limestone sample, respectively. To describe the joint geometry, the edge detection algorithms and a three-dimensional (3D) matrix mapping method were applied to reconstruct CT-based and photogrammetry-based jointed rock models. For comparison tests, the numerical uniaxial compression tests were conducted on an intact rock sample and a sample with a joint simplified to a plane using the parallel computing method. The results indicate that the mechanical characteristics and failure process of jointed rocks are significantly affected by the geometry of joints. The presence of joints reduces the uniaxial compressive strength (UCS), elastic modulus, and released acoustic emission (AE) energy of rocks by 37%–67%, 21%–24%, and 52%–90%, respectively. Compared to the simplified joint sample, the proposed photogrammetry-based numerical model makes the most of the limited geometry information of joints. The UCS, accumulative released AE energy, and elastic modulus of the photogrammetry-based sample were found to be very close to those of the CT-based sample. The UCS value of the simplified joint sample (i.e. 38.5 MPa) is much lower than that of the CT-based sample (i.e. 72.3 MPa). Additionally, the accumulative released AE energy observed in the simplified joint sample is 3.899 times lower than that observed in the CT-based sample. CT scanning provides a reliable means to visualize the joints in rocks, which can be used to verify the reliability of photogrammetry techniques. The application of the photogrammetry-based sample enables detailed analysis for estimating the mechanical properties of jointed rocks.