SCEC Award Number 21058 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Impact of Contact and Interface Modeling on Precarious Rock Fragilities – Phase 3: Material Properties and Soil
Investigator(s)
Name Organization
Christine Wittich University of Nebraska, Lincoln
Other Participants 1 Ph.D. Student, TBD
1 Undergraduate Student, TBD
SCEC Priorities 5b, 5c, 4b SCEC Groups Geology, SAFS, FARM
Report Due Date 03/15/2022 Date Report Submitted 03/11/2024
Project Abstract
 Given their age and formation, PBRs provide a unique opportunity to gauge maximum ground motion over extended periods. This project aims to explore how variations in the material and interface conditions of these rocks influence their stability and response to seismic activities. The methodology incorporated a blend of experimental shake table tests and advanced three-dimensional numerical modeling using the Distinct Element Method (DEM). The experimental phase involved shake table tests on two limestone rock specimens, one of which was chiseled to modify its interface, with each specimen subjected to 1164 earthquake simulations. The results of which are compared to tests on granite rock specimens (SCEC Award 20106). High-resolution LiDAR was utilized for precise geometric data acquisition. The numerical phase leveraged the DEM platform 3DEC, employing volumetric meshes from LiDAR-derived point clouds to simulate complex failure modes like rocking, sliding, and overturning. This research is significant in enhancing the understanding of PBRs' seismic behavior, highlighting the influence of subtle interface changes and rock material properties on their stability and overturning probabilities. It provides crucial insights for seismic hazard assessments and forms a foundation for further studies to deepen our understanding of PBRs' behavior under seismic influence.
Intellectual Merit The proposed project closely aligns with the objectives and priorities of the Earthquake Geology disciplinary committee, which aims in part to foster research in outstanding seismic hazard issues and in the earthquake history of southern California. To this end, the analysis of precarious rocks and fragile geologic features has been identified as a particular strategy to evaluate ground motion hazard and inform seismic hazard methodologies. While precarious rocks are recognized as a means to evaluate hazard, it is also understood that existing analysis techniques carry potentially significant uncertainty and the development of analysis techniques is a noted research priority of this particular disciplinary committee. This project directly addresses this research priority through the analysis and quantification of epistemic uncertainty associated with interface geometry and material of precarious rocks and the impact that this may have on subsequent fragility analyses.
Broader Impacts This project directly contributed to the dissertation of 1 PhD student. In addition, 2 undergraduate students directly participated in the shake table testing, including 1 from an underrepresented group. Shake table testing was also used during outreach events visiting UNL's College of Engineering, where the events were directed to encourage participation in STEM for young women and other underrepresented groups.
Exemplary Figure Figure 3: Steps involved in geometric modeling