Failure of high arch dam subjected to excessive flooding: Insights from model test combined with distributed fibre optic strain sensing and 3D-DIC technologies

Physical scaled model test of high arch dam is effective to intuitively uncover its failure process in the case of excessive flooding. Nevertheless, the model test research combined with the automated visualization of deformation and cracks in full field is still blanking. Thus, the present work conducted a hydraulic jacks-based arch dam physical model overloading test for one actual dam. The distributed fibre optic strain sensing (DFOSS) and 3D-digital image correlation (DIC) technologies monitored the deformation on dam model surface in full field. A novel DFOSS-greyscale image processing-interpolation method was established. It integrated with 3D-DIC, achieved the automatic visualization of the deformation and cracks in full field. The outcomes stated the dam model subsequently failed owing to upstream cracks adjacent to dam-abutment interface including those on dam heel; downstream cracks on crown arch cantilever. Based on the visualized and quantified full-field deformation and cracks, the failure mechanism was well explained by the theoretical and numerical analysis of buckling, fracture, deformation energy, and the mechanical interactions between arch rings and arch cantilevers. The state of the arch dam experienced the phases of the quasi-elastic, nonlinear, arching action and ultimate failure, with respective overloading factor K and failure modes: 2.0 since crack initiated on dam heel; 6.0 when dam toe destructed; 10.0 as arches played the significant role; and 14.0 when failed. The achievement of this study bears significance for failure mechanism investigation, and improving test and analysis method of high arch dams.