Papers in the Proceedings of the 29th U.S. Symposium on Rock Mechanics were solicited to address the symposium theme of Key Questions in Rock Mechanics. The proceedings include the text for the symposium keynote address, and two keynote papers in the areas of 'design and construction in rock mechanics', and 'conceptual, analytical and numerical modeling'. Seventy-five technical papers are presented in sessions on numerical modeling, laboratory experimentation, field investigation and design, classification statistics. Abstracts of sixteen poster papers at the symposium are also inluded. The proceedings reflect the most active areas of rock mechanics and should be of great value to both researchers and practitioners in rock mechanics and related fields.