Nicholas Sitar

Geotechnical earthquake engineering, characterization and behavior of weakly cemented soils, static and seismic slope stability, ground improvement, seismic stability of mechanically stabilized slopes and embankments, stability of rock slopes and rock masses, application of stochastic methods in Geoengineering, applications of ubiquitous wireless sensor networks in environmental and seismic monitoring.

Application of Wireless Sensor Technology to Environmental Monitoring

Ubiquitous wireless sensor networks have numerous potential applications in many areas.  The main objective of this research is to develop affordable, reliable wireless instrumentation for a variety of applications such as wild fire monitoring, landslide and rock fall monitoring, and monitoring on underground space.

Monitoring of Rock Mass Response to Environmental Loading

Rock masses deform in response to changes in atmospheric pressure and temperature. These deformations can be monitored using a variety of sensors. In this effort acoustic emissions are being tracked at a site in Yosemite in order to establish correlation between the intensity of acoustic emissions and the expansion and contraction of rock blocks. In a related effort, seismic monitoring has been successfully used to monitor rock falls and rock fall impacts.  The ultimate goal is to develop rock fall hazard warning system for high rock walls.

Application of Reliability Methods to Probabilistic Slope Stability Analysis 

It is well recognized that the natural heterogeneity of the subsurface environment introduces a significant level of uncertainty in making predictions of the expected contaminant pathways and concentration levels. The approach taken in this work is to use reliability methods developed primarily in structural engineering and to apply them to slope stability analyses in soil and rock. These techniques appear to offer considerable computational advantage in the analysis of events with a very low probability of occurrence. The current emphasis is on development of new applications. 

Earthquake Engineering 

Evaluation of Seismically Induced Earth Pressures on Retaining Structures – It is generally accepted that retaining structures are subject to increased loads due to seismic loading.  However, observations in a number of recent earthquakes suggest that well designed retaining structures perform quite well even if they are not particularly designed for seismic loading.  Most recent results from dynamic centrifuge experiments show that the magnitude of the dynamic pressure is significantly lower than has been assumed previously.  The current effort is concentrating on the evaluation of basement and underground structures and numerical modeling.

Seismic Response of Improved Ground

Ground improvement using different techniques is extensively used to mitigate the seismically induced liquefaction hazard.  In this project, dynamic centrifuge tests were being used to evaluate the influence of the geometry of the improved zone on the expected performance of the improved ground.