MRI: Acquisition of a Confined Bi-Directional Cyclic Shear Apparatus for Research and Education on Earthquake-Resilient Infrastructure

Liquefaction is one of the major causes of extensive wide-spread damage during major seismic events, threatening the integrity of foundation systems for buildings, infrastructure and lifelines such as water and gas pipes, dams, and port facilities. This Major Research Instrumentation (MRI) award supports the acquisition of a confined bi-directional simple shear apparatus to simulate conditions that represent the actual soil stress state in the field-- allowing more effective design of structures to mitigate earthquake hazards.

The PI will also develop a unique add-on system to control saturation drainage of the soil specimen enabling, for the first-time, laboratory research with realistic boundary and loading conditions on the effect of partial drainage on the response of sands. The device will promote research collaborations between faculty at Cal State LA and their partners in academia and industry.

The instrument will also provide training opportunities for underrepresented minority students in Southern California who otherwise would not be exposed to advanced hands-on laboratory research.

Although much research has been carried out on the cyclic response of sands to understand the phenomenon of liquefaction, a number of fundamental questions remain unanswered, especially in relating laboratory results to field performance. The researched testing program can identify factors that explain the discrepancies between lab and site, allowing the development of more robust prediction tools to complement empirical relationships to assess whether the ground will liquefy during the expected seismic excitation, thus enabling more effective design of structures and mitigation of the hazard.

The instrument will enable researchers to characterize soil response subjected to unique stress paths and partial drainage conditions. The data will be used to investigate the feasibility of using boundary-control tests to simulate soil partial drainage tests. The new apparatus will also support investigations on soil responses in ground slope as well as the pile drift phenomenon.

The test results will be used to advance understandings in post-cyclic clay reconsolidation and stress-strain behavior, and soil-pile interaction under lateral loading with varying shearing directions. Studies using the instrument will generate valuable data sets for numerical modelers when calibrating and validating their constitutive models.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.