The needle penetration test provides a laboratory strength index. The test method is covered by the ISRM suggested methods for rock characterization. Presented project experience draws from more than 1000 needle penetration tests, point load strength index tests and unconfined compression tests. The results show that common correlations between needle point resistance (NPR) and uni-axial compressive strength can reliably be adopted for chalk.
Proceedings of the XVII European Conference on Soil Mechanics and Geotechnical Engineering - ECSMGE 2019: Geotechnical Engineering Foundation of the Future