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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.
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This content will become publicly available on May 5, 2027
Centrifuge modeling of cracking and internal erosion in embankment dams and levees
There is a need in dam engineering to better understand certain failure mechanisms, including embankment cracking and concentrated leak erosion (CLE). This is especially pertinent for Potential Failure Mode Analysis. The present understanding of these mechanisms has been developed from limited case histories, numerical simulations, and bench-scale testing. Centrifuge tests were performed to investigate embankment crack propagation and CLE using the 9 m radius centrifuge at the University of California, Davis. Tests have been performed at 40g to simulate a levee/dam with a height of 10 m and 1.5H:1V slopes. The homogeneous embankments were constructed using a low plasticity clay compacted above 95% standard Proctor maximum dry density. Tests lowered one side of the foundation using a hydraulically actuated table to induce transverse cracking under unsaturated and saturated embankment conditions. Crack propagation was tracked as the hydraulic table was lowered using markers and digital image tracking on the downstream slope. An upstream reservoir was maintained, allowing for flow through the cracks and for CLE to initiate. After testing the final crack geometries were carefully recorded as the model was dissected. These tests provide system-level experimental data under in-situ stress conditions against which current empirically- and numerically-based analysis methods can be evaluated.
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- Award ID(s):
- 2047402
- PAR ID:
- 10701467
- Publisher / Repository:
- United States Society on Dams
- Date Published:
- Format(s):
- Medium: X
- Location:
- Austin, Texas
- Sponsoring Org:
- National Science Foundation
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