Adoption of Astm A956-06 Leeb Hardness Testing Standard to Rock Engineering Applications


The Leeb dynamic hardness test was originally developed for metallic materials and is now widely used in rock engineering and engineering geology. This study aims to fundamentally investigate the application conditions of the Leeb hardness test in rock engineering because it is a high-precision, fast, nondestructive, and portable method. Therefore, four main limitations of the Leeb method mentioned in ASTM A956-06 have been further analyzed. The important challenges, including scale effect, temperature effect, surface roughness effect, and the effect of physical properties on the Leeb method, have been studied. For this purpose, 33 rock samples with a wide range of hardness and different geology origins were used. Based on the results, the minimum thickness of the block samples of 5 cm (or volume of 500 cm3) and the length-to-diameter ratio of 1.6 on core samples were suggested. Moreover, block samples were exposed to various temperatures, including −30, 0, 20, 50, 100, and 150 °C. The results indicated that with increasing the temperature, the Leeb hardness decreased, but the trend of the Leeb hardness variations is unnoticeable. The roughness analyses using a laser profilometer indicate that the Leeb hardness of rough samples can easily be determined with high reliability using the Leeb hardness of polished samples. Also, the Leeb hardness test for rough surfaces with JRC <4 (classes 1 and 2) can be used properly and performed locally in classes 3 to 10. Finally, the statistical analyses showed that the density and porosity have reasonable effects on Leeb's hardness.


Mining Engineering

Keywords and Phrases

Astm A956-06; Leeb Dynamic Hardness; Physical Properties; Scale Effect; Surface Roughness; Temperature

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Article - Journal

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© 2023 Elsevier, All rights reserved.

Publication Date

18 Jan 2023

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