Analysis of Borehole Inclusion Stress Measurement Concepts Proposed for Use in the Waste Isolation Pilot Plant in Situ Testing Program

摘要

Various borehole inclusion stressmeters are analyzed to determine how the creep behavior of salt affects their performance. The analysis is based on a series of calculations in which gage responses are computed for representative laboratory and in situ stress fields. Results are presented for the strain gaged stressmeter (SGS) which is being considered for use in the in situ testing program at the Waste Isolation Pilot Plant. In addition, results are presented for three general inclusions: a stiff inclusion, a matching inclusion and a soft inclusion. The adjectives stiff, matching, and soft describe the elastic modulus of the inclusion relative to the modulus of the host rocksalt. These results are useful in determining the importance of inclusion stiffness to gage performance. The results for the SGS indicate that the gage's performance is noticably distorted by creep. Nevertheless, the SGS still responds to even small in situ stress changes. Of the general inclusions, only the matching stressmeter performs without distortion due to creep. Soft inclusion response is severely distorted by creep, and the stiff inclusion performance is slightly distorted by localized stress relaxation in the salt around the borehole. (ERA citation 07:055301)