Simpson Gumpertz & Heger (SGH) staff member Riccardo Cappa recently published an article in the September 2017 issue of the American Society of Civil Engineers’ (ASCE) Journal of Geotechnical and Geoenvironmental Engineering (JGGE). In the study, “Strains and Pore Pressures Generated during Cyclic Loading of Embankments on Organic Soil,” Riccardo and coauthors Scott Brandenberg of the University of California, Los Angeles, and Anne Lemnitzer of the University of California, Irvine, examined the seismic response of a stiff levee structure placed on a soft organic soil (peat) foundation, similar to those found in the Sacramento-San Joaquin Delta in California.
The authors conducted a series of centrifuge tests and compared the results to simple shear strength tests. “The stress path mobilized during the centrifuge tests were more complicated than a simple shear stress path because of vertical strains induced by levee rocking; therefore a one-dimensional interpretation of shear strain is inappropriate for this two-dimensional problem,” the authors conclude. “This is an important finding because procedures used to solve geotechnical earthquake engineering problems often inherently assume one-dimensional wave propagation,” (e.g., liquefaction triggering). In the article, the authors postulate a more robust direct-simple-shear strain invariant capable of accounting for the contributions of in-plane shear, vertical, and horizontal strains. This strain invariant is then used to develop a mobilized-strain vs. excess-pore-water-pressure ratio curve for peat, similar to those already available for sands and clays.
The journal featured the article as its “Editor’s Choice” and also recognized it as one of the most downloaded studies for the month of September. In addition, the journal recognized Riccardo as a 2016 Outstanding Reviewer for his contributions to JGGE.
Read the abstract and learn more about the issue.