Bayesian partial pooling to reduce uncertainty in overcoring rock stress estimation

Feng，Yu1; Gao，Ke2; Lacasse，Suzanne1

2023

10.1016/j.jrmge.2023.05.003

Journal of Rock Mechanics and Geotechnical Engineering   Impact Factor & Quartile

1674-7755

The state of in situ stress is a crucial parameter in subsurface engineering, especially for critical projects like nuclear waste repository. As one of the two ISRM suggested methods, the overcoring (OC) method is widely used to estimate the full stress tensors in rocks by independent regression analysis of the data from each OC test. However, such customary independent analysis of individual OC tests, known as no pooling, is liable to yield unreliable test-specific stress estimates due to various uncertainty sources involved in the OC method. To address this problem, a practical and no-cost solution is considered by incorporating into OC data analysis additional information implied within adjacent OC tests, which are usually available in OC measurement campaigns. Hence, this paper presents a Bayesian partial pooling (hierarchical) model for combined analysis of adjacent OC tests. We performed five case studies using OC test data made at a nuclear waste repository research site of Sweden. The results demonstrate that partial pooling of adjacent OC tests indeed allows borrowing of information across adjacent tests, and yields improved stress tensor estimates with reduced uncertainties simultaneously for all individual tests than they are independently analysed as no pooling, particularly for those unreliable no pooling stress estimates. A further model comparison shows that the partial pooling model also gives better predictive performance, and thus confirms that the information borrowed across adjacent OC tests is relevant and effective.

Bayesian hierarchical model Nuclear waste repository Overcoring stress measurement Partial pooling Uncertainty reduction

English

Corresponding

Basic and Applied Basic Research Foundation of Guangdong Province[2023A1515011244];

2-s2.0-85164515493

Scopus

1.Norwegian Geotechnical Institute,Oslo,Norway
2.Department of Earth and Space Sciences,Southern University of Science and Technology,Shenzhen,China

Feng，Yu,Gao，Ke,Lacasse，Suzanne. Bayesian partial pooling to reduce uncertainty in overcoring rock stress estimation[J]. Journal of Rock Mechanics and Geotechnical Engineering,2023.

Feng，Yu,Gao，Ke,&Lacasse，Suzanne.(2023).Bayesian partial pooling to reduce uncertainty in overcoring rock stress estimation.Journal of Rock Mechanics and Geotechnical Engineering.

Feng，Yu,et al."Bayesian partial pooling to reduce uncertainty in overcoring rock stress estimation".Journal of Rock Mechanics and Geotechnical Engineering (2023).