CAREER: Stress Redistribution Imaging for Rock Failure Prediction

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

CMS-0134034 PI: Erik Westman Institution: Virginia Polytechnic Institute and State University Title: "CAREER: Stress Redistribution Imaging for Rock Failure Prediction" This Faculty Early Career Development (CAREER) research and education project uses high-resolution, three-dimensional tomographic imaging to better understand and communicate the process of failure in rock. Accomplishing the ultimate goal of predicting rock mass failure will result in significantly reduced fatalities, lowered construction costs, and increased environmental protection. Failure prediction extends to all aspects of rock mechanics including tunnels, mines, rock slopes, earthquakes, waste repositories, and bridge and dam abutments. To predict rock failure, it is quite helpful to monitor the redistribution of stresses within the rock. Recent advances in computational power have allowed this to be done using acoustic waves and tomographic imaging. The basic principal behind monitoring the redistribution of stresses is that microfractures within the rock are closed under increased loading, allowing the acoustic wave to travel at a greater velocity and with less attenuation. This method has been used successfully in the laboratory and has had growing, but poorly founded, application in the field. This project will put the technique of imaging stress redistribution in rock on a sound theoretical and practical foundation by 1) standardizing methods and 2) extending results of prior studies into the gap between laboratory- and field-scale studies. Educational efforts related to rock failure prediction will also be enhanced. Specific tasks associated with both education and research include 1) generating three-dimensional tomographic images to observe relevant alterations to the fabric of rock samples loaded to failure, and 2) using those images to calibrate numerical modeling results. By collecting data as rock samples are loaded, time-lapse animations will be developed which will assist in the communication of stress-analysis to undergraduates. Additional educational efforts focus on transitioning from a presentational teaching method to a constructivist model for two of the proposer's undergraduate courses and developing a graduate-level course for understanding failure through coupled analysis of imaging and numerical modeling results.