AEG/EERI/GI Virtual October Meeting: Renmin Pretell 

Please join us on Tuesday, October 27, 2020 for the AEG Sacto/EERI/GI virtual monthly meeting through Zoom! We will be hosting Renmin Pretell from UC Davis, who will be giving a presentation on liquefaction and cyclic softening at Balboa Boulevard during the 1994 Northridge earthquake. There will be no cost to attend this virtual meeting.

Register Now! Note: Zoom link will be provided in the confirmation email after registerring.

Liquefaction and Cyclic Softening at Balboa Boulevard LDuring the 1994 Northridge Earthquake

Renmin Pretell

 UC Davis, Graduate Student Researcher

rpretell@ucdavis.edu

Abstract and Bio

The seismic performance of the Balboa Blvd. during the 1994 M_W 6.7 Northridge Earthquake was examined through nonlinear deformation analyses (NDAs) using stateoftheart tools to (1) evaluate the accuracy of the adopted modeling protocols and engineering procedures to capture ground deformation patterns and displacement magnitudes; and (2) investigate the failure mechanisms and key factors leading to ground deformations at this site. 1D liquefaction vulnerability indexes (LVIs) and permanent displacements using Newmark sliding block analyses were also estimated and compared against ground deformations observed after the earthquake. The geotechnical characterization of Balboa Blvd. was assessed based on field and laboratory data obtained from two investigation campaigns. Transitional probability geostatistics were used to develop stratigraphic models that capture the heterogeneity and the spatial variability patterns of sandlike and claylike soils present at this site. The stratigraphic models were implemented in the finite different software FLAC and the behavior of sandlike and claylike soils simulated using the PM4Sand v3.1 and PM4Silt v1.0 constitutive models (Boulanger and Ziotopoulou 2017, 2018). A series of sensitivity analyses were performed to address uncertainties associated to the spatial variability of soils, input ground motions, the I_c cutoff parameter to differentiate between sandlike and claylike soils, relative density (D_R) of sandlike soils, and undrained strength (s_u) of claylike soils, amongst others. Results from NDAs suggest that a compounded effect of both liquefaction of sandlike soils and cyclic softening of clay­like soils led to the excessive ground deformations at Balboa Blvd. This study sheds light on the importance of using appropriate engineering procedures and numerical modeling protocols in the prediction of deformation patterns, the selection of key input parameters, as well as the applicability of LVIs in complex sites.

Renmin earned his B.Sc. in civil engineering from the National University of Engineering (UNI) in Peru (2012). From 2013 to 2017, Renmin worked for Golder Associates in the Lima (Peru) and Denver (CO) offices, mainly focused on geotechnics applied to mining projects. Renmin joined the University of California, Davis, in 2017 received his M.Sc. in 2019, and is currently pursuing his Ph.D. degree. Renmin’s research interests include liquefaction, site response, ground motions, and geostatistics.