Productivity, safety and its improvement is also an integral part of a good mining operation. In recent times, due to constraints on time and cost, it has become increasingly harder to conduct training and safety inductions at mine sites. For the purpose of overcoming these limitations, the use of virtual reality (VR) is proposed for mining education and training. VR has already been introduced in the education and training of miners overseas, and quantitative studies on the effects of using VR for miner's education and training have been made. However, Japan has only one such application of VR for mining education, namely, “Virtual Mining Practice System” which was produced by Akita University, and there are relatively few cases where VR has been introduced in the Japanese mining industry. Furthermore, there has been no quantitative study to date on the effects of education using VR for mining education. Therefore, the objective of this study is to investigate the effects of a class that utilizes a VR application developed for mining education (Mining VR), as well as evaluate its learning outcomes. In this study, a method called randomized controlled trial (RCT) is used for evaluating Mining VR's effectiveness. Study participants are divided two groups randomly where one class makes use of Mining VR and another class using other non-VR material. After the classes are completed, a test is conducted and the average results of each group are compared by T-test. The results of this experiment showed that there were no statistically significant differences in skill of “understanding” and “knowledge retention” comparing two groups. On the other hand, results suggested that Mining VR has improved students'“ motivation” for class when using Mining VR.

The mud flow between the borehole and the drill pipe in well drilling can be regarded as the flow of nonNewtonian fluids through a concentric annulus. In recent years, the Herschel-Bulkley rheological model is recommended as a general fluid model of drilling mud because it encompasses the power law model and the Bingham plastic model. Also, in the field of well drilling, the flow through a concentric annulus is conventionally approximated by the flow between two parallel plates. However, its applicability does not seem to be examined because it is not easy to perform analysis of non-Newtonian fluid flow through a concentric annulus. For studies on laminar flow of viscoplastic fluids (fluids with yield stress) through concentric annuli, there are researches on Bingham fluid by Fredrickson & Bird and on Herschel-Bulkley fluid by Hanks. Since the equation of motion in viscoplastic fluid flow through a concentric annulus cannot be analytically solved in all of them, in their researches numerical calculations are presented by charts. However, it is not simple as a method to estimate the frictional pressure loss, because multiple charts are related. In this research, based on the results of previous authors' research^{7, 8)}, we investigate a method that can easily calculate the average wall shear-stress in laminar flows of viscoplastic fluids through concentric annuli. That is, using the results of circular pipe and parallel-plate, an approximate expression of viscosity factor in viscoplastic fluid flow through concentric annuli is derived and the error of the average wall shear-stress represented by the approximate equation is evaluated. Furthermore, a simpler approximate formula which can be calculated directly without numerical calculation is derived and its error is also evaluated. In addition, error assessment is performed to confirm the applicability of approximation by the flow in the parallel-plate for the flow in a concentric annulus, which has been conventionally done in the field of well drilling.