Development of a Needle Penetrometer Device and Evaluation of its Performance

Abstract

Mining and excavation activities involve dealing with earth materials typically rock mass of varying properties. The mechanical properties of rocks play major in successful excavation process. However the determination of correct strength values is a challenge as rock properties vary widely. Obtaining the right sizes for strength test are very difficult due to structural variation. Innumerable attempts have been made to predict rock properties. Needle penetrometer is one such unit developed to predict compressive strength of rock from the surface testing. It measures the surface behavior and correleate the same with the compressive strength parameter. In this investigation a needle penetrometer using mild steel material has been developed as per the ISRM (2014) suggested guidelines. Different parts were fabricated and one unit was prepared. Five different coal samples collected from varying depth from 480 m to 580m and their behavior were measured. Both th unconfined compressive strength and needle penetration index values of these sample were determined. Six established approaches Ulusay and Erguler (2012), Aydan (2012), Uchida et al. (2004), Okada et al. (1985) and Takahashi et al. (1988) and Yamaguchi et al. (1997) were compared with the measured results. It was observed that the measured values compared favourably with that of Okada et al. (1985)