Abstract
Standard penetration test is often used as an index for prediction of geomaterial elastic and strength properties. It consists of releasing a 63.5 kg hammer from a specified distance of 762 mm on a series of connected drill rods. The N-value is defined after a total 457 mm of penetration is achieved by counting the below counts for the last 300 mm of penetration. This required penetration is not often achieved in weak rocks due to their relatively large compressive strength. To eliminate the need for achieving a total required 457 mm of penetration, a novel approach is introduced where the rate of penetration of the split spoon sampler is used for the characterization of the engineering properties of the weak argillaceous rocks. The rate of penetration is defined as the slope of the final segment of the blow count versus penetration plot. The test results show that the average penetration rate at each test depth approaches a relatively constant value as the penetration increases. It is found that penetration rate is affected by the unconfined compressive strength, deformation modulus, and water content of the rock mass as well as the mean effective stress at the elevation of each test. Using in situ tests from 21 weak rock sites in Illinois, United States, models are proposed for the prediction of deformation modulus and unconfined compressive strength based on the penetration rate. The models account for the influence of mean effective stresses and the in situ water content of rock.
Original language | English (US) |
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Article number | 104397 |
Journal | International Journal of Rock Mechanics and Mining Sciences |
Volume | 133 |
DOIs | |
State | Published - Sep 2020 |
Externally published | Yes |
Bibliographical note
Funding Information:The Author would like to thank and acknowledge the University of Illinois at Urbana-Champaign and the University of Minnesota for providing access to the technical and computational resources that were required for completion of this work. The Author acknowledges the contributions of Professor Emeritus James H. Long to this manuscript. All data in this manuscript and the enclosed Supplemental Data section are from published work by Stark et al. (2013), 36 Stark et al. (2017) 37 and Baghdady (2018) 38; interested reader may refer to these publications for the original data. Some of the data reported in this manuscript are based on tests conducted by Mr. Joseph Gamez of the University of Illinois; his contributions are acknowledged.
Publisher Copyright:
© 2020 Elsevier Ltd
Keywords
- Deformation modulus
- Standard penetration test
- Statistical analysis
- Uniaxial compressive strength
- Weak argillaceous rock