New England Chapter Webinar: Determination of Undrained Strength for Contractive Coal Combustion Residuals for Seismic Assessment

Wednesday, October 20, 2021, 1:00–2:00 PM, Eastern Time

Cost: Free

The EERI New England Chapter held a free webinar on the evaluation of slope stability for Coal Combustion Residuals (CCR) impoundments. Such evaluation is becoming increasingly important as multiple failures involving undrained behavior of granular materials have recently occurred. Seismic loading is a load case where undrained behavior can be triggered that causes a rapid increase in mobilized shear stress or a rapid decrease in effective stress if contractive saturated materials are present. This rapid loading can trigger liquefaction within a CCR layer which would require considering the residual shear strength for the CCR material. The speakers summarized a study to improve understanding of the shear strength of CCR materials, discussing the approaches used to apply best applicable practices to make a reliable determination of peak and residual undrained shear strength of CCR materials, and provide recommendations on improving available methods to determine undrained shear strength of contractive materials.


  • Dr. Seda Gokyer Erbis is a Project Engineer/Assistant Project Manager for Geocomp Corporation—Massachusetts Consulting Group.
  • Ryan Lavorati is a Project Engineer at Geocomp Corporation—Massachusetts Consulting Group.