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Levees and dams constructed across active faults face a risk of failure due to the formation of transverse cracks induced by a vertical offset in the foundation and the subsequent initiation and progression of concentrated leak erosion (CLE). The present understanding of crack formation, developed from a limited set of case histories and numerical simulations, includes large uncertainties, and the empirical methods used to estimate crack potential and extent are based on simplified geometries and limited data. A research program was undertaken to better understand mechanisms of crack formation and propagation using the 9m radius centrifuge at the University of California at Davis. A model test was performed at 40g to simulate a levee/dam with a height of 10 m and side slopes of 1.5:1. The homogenous embankment was constructed using a low plasticity clay (locally sourced Yolo loam) prepared to a relative compaction of 96%, based on the standard Proctor test, and a water content of 17.2% (dry of optimum). A vertical offset in the foundation was incrementally induced using a hydraulically actuated table with a maximum offset equal to 10% of the levee/dam height. Cameras and digital image tracking algorithms were used to measure deformation through 3D tracking markers embedded on the downslope surface. At low offset displacements, a rigid block rotation mechanism caused tensile cracks in the upthrown side which first initiated at the crest and was followed by a complimentary crack originating at the base of the embankment. At higher offset displacements, a third shear-induced crack was observed adjacent to the downthrown side. Following testing the model was dissected and the geometry of the transverse and shear cracks were mapped. Comparison of the results against the simplified geometries routinely used in engineering practice methods reveal notable differences. 

A centrifuge test (ODA01) was used as a proof-of-concept test to investigate the effect of vertical differential settlement on crack formation in a model levee. The Yolo loam embankment levee and its foundation were 250 mm and 62.5 mm high in prototype scale, respectively. Viscous pore fluid was used to simulate water behind the levee at a height of 225 mm and the test was conducted at 40g. The foundation of the levee included a moving part (a hydraulic table) and a non-moving part (a jointed wood table). The hydraulic actuators were extended to a maximum height of 25 mm before the start of the test. In the centrifuge, the hydraulic table was lowered to a maximum settlement of 25 mm to simulate the differential settlement of the levee. Hairline, transverse and longitudinal cracks were effectively induced in the levee through this vertical differential settlement. Furthermore, seepage flow was initiated through the cracks. The seepage flow stopped after some time without significant erosion, likely due to swelling of the soil around the crack and lowering of the upstream water level. 

Biogeotechnics, specifically bio-mediated and bio-inspired geotechnical engineering, has matured rapidly over the past two decades, becoming one of the fastest growing subdisciplines within geotechnical engineering. As typical in most science and engineering fields, biogeotechnics relies on data from physical experiments and field observations to advance technology. Obtaining field data to drive advancement can pose unique challenges, and in many cases may be cost or logistically prohibitive. Physical experiments or models are often preferable and may offer the sole feasible pathway for technology development and upscaling. Hypergravity scaled modeling using centrifuges has been instrumental in biogeotechnics development to support the building of basic science knowledge, the validation of computational and theoretical models, and the advancement of emerging technologies towards field implementation. 

This paper investigates and presents the numerical modeling and validation of the response of a uniform clean sand using monotonic and cyclic laboratory tests as well as a centrifuge model test comprised of a submerged slope. The dynamic response of the sand is modeled using a critical state compatible, stress ratio-based, bounding surface plasticity constitutive model (PM4Sand), implemented in the commercial finite-difference platform FLAC, and PM4Sand’s performance is evaluated against a comprehensive testing program comprised of laboratory data and a well-instrumented centrifuge model test. Three different calibrations informed by the lab and centrifuge data are performed and the goodness of the predictions is discussed. Conclusions are drawn with regards to the performance of the simulations against the laboratory and centrifuge data, and recommendations about the calibration of the model are provided.