Masatomo Ichinose

Geochemistry of waste rock at dumping area

Geochemical characteristics and the increase in the total reactive surface area of the sulphide-bearing rock due to weathering processes at dumping area, are expected to enhance the oxidation of sulphides, leading to the generation of acid mine drainage (AMD). The study of the changes of geochemical characteristics of sulphide-bearing rocks showed that the oxidation uniformly occurred at the surface layer of 2- and 10-year-old waste rock dumps. The changes of mineralogical composition were also investigated, particularly for the cases where significant formation of clay minerals occurred. The study showed that the formation of clay minerals after the weathering processes took place at the dumping area, suggested that the generation of AMD would be minimised because the interior of the waste rock dump provided a barrier to oxygen and water.

Estimation of Impact Hardness of Rocks by Means of Drop Hammer Test.

The impact hardness of rock is normally determined by using a ‘Protodyakonov’ type drop hammer. However, this test cannot be applied to a wide range of rocks. Therefore, standardized impact hardness test using the ‘Protodyakonov’ type drop hammer was carried out and the correlati ons of the resulting values of impact hardness with the mechanical properties obtained from usual laboratory tests were investigated.The results show that the impact hardness has, a generally good correlation with the tensile or the compressive strength of rocks. Therefore, the impact hardness can be used as a strength index in the estimation of rock properties. Moreover, the performance of rock drilling or machine roadway drivage can be predicted using the impact hardness of rock.

Study of maintenance of gate roadways in coal mine. (2nd Report). Comparison of deformational behaviours of roadway driven by shotfiring with those by machine cutting.

In an attempt to clarify the effectiveness of machine drivage on roadway deformation, field measurements of vertical closure were carried out both in the roadway driven with a roadheader and with drill and blast. A theoretical discussion considering the interaction between support and rock mass was also made.The results show that there is no significant difference in the deformational behaviour of roadway driven by each method. This is related to the deterioration of the surrounding strata by the presence of water and the setting conditions of the support. A suitable support system to the strata conditions should be used to obtain the effectiveness of machine drivage on roadway deformation. However, if the magnitude of deformation of the roadway driven with machine and supported with the traditional system is within an allowable limit, the validity of using machine cutting can be found in the rapid drivage rate leading to the total cost reduction in formation and maintenance of roadway.