Cyclic Triaxial Testing of Water-Pluviated Fly Ash Specimens

摘要

Liquefaction resistance of soils during earthquake shaking can be quantified in terms of the cyclic resistance ratio (CRR). The CRR can be estimated based on field and/or laboratory methods. However, field data correlations are typically based on behavior of natural soils (sands, silty sands, etc.) and may not be directly applicable to unique materials such as Class F fly ash. In these cases, cyclic testing in the laboratory may provide more definitive results. As part of the closure design process for the Class F fly ash pond at American Electric Power’s (AEP) John E. Amos Plant, cyclic triaxial testing was performed to estimate CRR. Because it is difficult to obtain undisturbed samples of the soft, sluiced fly ash from the pond, specimens were reconstituted via water- pluviation methods in the lab. For the confining stresses that were considered, the behavior of the fly ash was shown to be dilative, which was consistent with the material response during conventional triaxial compression testing. Dilative behavior during an earthquake is associated with “cyclic mobility”, as opposed to “flow failure”. Cyclic mobility is associated with relatively low deformations, while flow failure is associated with relatively large deformations. The results of the testing were combined with testing by others (using the same material) to evaluate trends in CRR versus number of loading cycles (N_(liq)) that causes liquefaction. These trends were then compared to anticipated earthquake loading from a design event, which showed that liquefaction was unlikely to occur.