Evaluation of different surface characteristics and mineral grain size in the estimation of rock strength using the Schmidt Hammer


Karaman K.

JOURNAL OF THE SOUTHERN AFRICAN INSTITUTE OF MINING AND METALLURGY, vol.124, no.4, pp.173-184, 2024 (SCI-Expanded)

  • Publication Type: Article / Article
  • Volume: 124 Issue: 4
  • Publication Date: 2024
  • Doi Number: 10.17159/2411-9717/2325/2024
  • Journal Name: JOURNAL OF THE SOUTHERN AFRICAN INSTITUTE OF MINING AND METALLURGY
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Aerospace Database, Communication Abstracts, Compendex, Metadex, Directory of Open Access Journals, Civil Engineering Abstracts
  • Page Numbers: pp.173-184
  • Karadeniz Technical University Affiliated: Yes

Abstract

This study aims to investigate the effect of surface roughness on Schmidt Rebound Hardness (RL). Accordingly, four different testing surfaces of natural, ground, cut surfaces, and core samples were studied on rock samples. There was a momentous variability of standard deviation based on the RL on the natural surface which indicates great roughness of the rock surface, whereas surface polishing caused a significant decrease in standard deviation. ISRM and ASTM methods were compared to estimate Uniaxial Compressive Strength (UCS) for different testing surfaces. RL obtained from the cut surface was found to be more reliable than those obtained from other testing surfaces for the prediction of UCS. However, regression and ANOVA analyses revealed that the ISRM method gave a more accurate UCS estimation of rocks with highly rough surfaces. It was also shown that RL values obtained from the cut surface were significantly higher than those obtained from core samples. Therefore, a comparison between RL values obtained from core samples and cut surfaces was made based on the previous studies. The present study statistically showed that estimated UCS values ​​were not statistically significant if Schmidt Rebound Tests were not performed on similar surfaces. In addition, the mineral grain sizes of the studied rocks, different testing surfaces from the literature, and standard deviation from the RL were evaluated and discussed. The Schmidt Hammer Technique is a rapid, inexpensive, and straightforward technique for estimating UCS for preliminary assessment.  However, the roughness of the surface where the Schmidt Hammer Technique is applied should be eliminated if variations are shown in the surface rebound hardness.  


Keywords: Schmidt Hammer Technique, UCS estimation, Surface roughness, Mineral grain size