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NEESR-II: Advanced Site Monitoring and Effective Characterization of Site Nonlinear Dynamic Properties and Model Calibration

Principal Investigator: Mourad Zeghal, Rensselaer Polytechnic Institute (RPI)

Earthquake induced site liquefaction and lateral spreading are often associated with very costly damage to civil systems such as port facilities, bridges, dams, buried pipes, and buildings of all types. However, realtime field measurements of soil permanent deformation have eluded researcher and practitioners until recently, and hindered the development of reliable tools to predict phenomena such as site lateral spreading and failure. Some practitioners remain rightly skeptical about lateral spreading predictions provided by computational models for the obvious reason that these models could not be properly calibrated due to a lack of appropriate measurements of field performance.

This project proposes a research program to develop a capability to characterize and estimate (low and large strain) three-dimensional in situ dynamic properties of sites and other soil systems for strata ranging from ground surface to a depth of about 30 m. A number of wireless shape-acceleration arrays (WSSA) will be installed permanently with an optimized configuration at the NEES Wildlife Refuge site to monitor low-strain response as well as earthquake induced liquefaction, permanent deformation and lateral spreading. It is highly anticipated that a near-future earthquake will induce large deformation and lateral spreading at this site. The installed arrays would then provide for the first time measurement of the time history of the whole site lateral spreading profile. The shape-acceleration array has capabilities that go beyond those of current state-of-the-art arrays used in monitoring the response of soil-systems. This array provides accurate remote realtime measurements of permanent three-dimensional displacements along with three-dimensional accelerations. Optimal spacial instrument configurations (i.e., topology) will be developed for the WSAA to ensure adequate measurements. Innovative data reduction and identification techniques will be developed for systematic site characterization and model calibration.

Specifically, this project comprises the following tasks: (1) development and validation of optimized array configurations using centrifuge model tests and computational analyses, (2) permanent installation of a number of wireless shape-acceleration arrays with an optimized configuration at the NEES Wildlife refuge site, (3) excitation of the site using the nees@UTexas T-Rex vibroseis, and (4) development of innovative data reduction and identification tools to estimate the 3-dimensional (small and large strain) mechanical properties and response mechanisms of the Wildlife site as well as other field ites that may be instrumented in the future.