SQUISHLAB (2022- 2024)

This project is a collaboration between Squishlab (headed by Dr. Ted Brzinski) at Haverford College, DanielsLab (headed by Dr. Karen Daniels) at NCSU and Scripps Tectonorockphysics Lab (headed by Dr. Vashan Wright) at UCSD. The object of this research is to measure the Density of Modes (DoM) of granular materials and find a way to use the results to predict failure in geophysical systems. The density of modes tells us about the number of modes per unit frequency. In previous experiments, we have noticed an anomalous excess of low frequency modes (compared to Debye scaling) beyond some characteristic frequency ω*. We are very interested in how ω* changes as a system approaches failure. For example, if our system is being put under increasing pressure, ω* continues to increase until things fail. On the other hand, if a system is slowly losing structure as if it is turning to sludge, ω* slowly decreases. So, we hope the density of modes can help us predict some kinds of failure events in soil. My work at Squishlab involves designing and prototyping systems and techniques to measure the Density of Modes. The plan is to disturb granular materials by supplying a driving frequency using a vibrating shaker or a stack of piezoelectric cells, and then measure the response using a piezoelectric ceramic sensor. A piezoelectric ceramic provides us with a charge proportional to the force applied to it, so I worked to design a circuit and some code that converts this miniscule charge output into a reading of the Density of Modes of the material. Once we finalized the circuit design, I worked to convert the circuit into a working prototype (with a functional PCB). I also helped design a device that can collect granular samples without disturbing them, so they can be easily attached to a vibration system and a piezoelectric ceramic in the field to measure the Density of Modes on the fly.