DamsDesign standards for dams are effective for earthquakes: study
There has long been a concern among civil engineers that dams could fail days or weeks after an earthquake, even if no immediate evidence of a problem surfaced. Their concern has focused on possible cracks at the interface between the concrete section of a dam and the soil embankments at the dam’s sides, and on how the soil filters nestled amidst the embankments would fare. Soil filters consist of coarser grain soils than the soil used in the dam’s impervious core, and their purpose in the event of a crack in the soil, is to prevent the finer core soil particles from rapidly eroding and flushing through the filter. Since soil filters were instituted, their design standards have been based on experimental studies without detailed and validated computer modeling of the soil grains — until now.
There has long been a concern among civil engineers that dams could fail days or weeks after an earthquake, even if no immediate evidence of a problem surfaced. Their concern has focused on possible cracks at the interface between the concrete section of a dam and the soil embankments at the dam’s sides, and on how the soil filters nestled amidst the embankments would fare.
Soil filters consist of coarser grain soils than the soil used in the dam’s impervious core, and their purpose in the event of a crack in the soil, is to prevent the finer core soil particles from rapidly eroding and flushing through the filter. This helps reduce the flow of water, preventing the dam’s catastrophic failure. Soil filters have been incorporated into dams for more than five decades.
Since soil filters were instituted, their design standards have been based on experimental studies without detailed and validated computer modeling of the soil grains — until now.
An LLNL release reports that for the first time, under a collaboration between Lawrence Livermore National Laboratory (LLNL) and the U.S. Army Corps of Engineers’ Engineer Research and Development Center (ERDC), researchers have completed a study demonstrating the effectiveness of soil filters at the soil grain scale.
Their work involved conducting three-dimensional modeling of soil filters at the grain level and then bridging the interaction of soil erosion to the behavior of the dam itself, said LLNL mechanical engineer Lee Glascoe.
“Researchers in the past have looked at dam-scale models using experiment-based assumptions about grain-scale behavior,” Glascoe said. “We modeled the grain scale and pushed our assumptions back to first principles.
“We believe we have helped to put to rest one of the major concerns among dam engineers — are the soil filter standards that have been the design criteria for dams valid for earthquakes? The answer is ‘yes,’ if they are consistent with the current design standards,” Glascoe explained.
While Glascoe headed the Livermore team, the researchers from the ERDC team in Vicksburg, Mississippi were led by structural engineers Stan Woodson and Robert Hall.
Funded by the Department of Homeland Security’s (DHS) Science and Technology Directorate, the project focused on validating LLNL’s advanced high performance computer simulations of soil erosion and transport to detailed experimental centrifuge and soil erosion tests by the ERDC.
