Post-Failure Strength of Gypsum Silica-Sand Aggregate Stemming Material

摘要

Post-failure stress-strain tests were performed on a mixture of gypsum cement and silica-sand aggregate used as stemming material for emplacement holes in underground nuclear testing. The purpose of these tests was to evaluate the remaining strength of the stemming material after it underwent initial failure at confining pressures typical of those found near the working point of the explosion. The failure data can also provide consitutive parameters that can be incorporated into future numerical calculations of the residual stress field of the stemming material. Individual samples were loaded to failure at a single elevated confining pressure. The experiments spanned a range of confining pressures from 10 to 300 MPa. For a set of samples experiencing failure at a given confinging pressure, each sample was subjected to a different amount of strain (up to 15%) subsequent to failure. After this procedure, each sample of failed material was then reloaded to failure again, but without confining pressure. Results indicate that the unconfined post-failure compressive strength of the material decrease as a function of increasing initial post-failure strain under confining pressure. Also, the samples that have experienced more than 15% initial post-failure strain under confining pressure have a complete loss of strength upon reloading without confining pressure. 4 figs., 1 tab. (ERA citation 13:034421)