Labor accidents due to slope failure and rock fall are topics of high concern in occupational safety governance; such accidents usually occur during excavation works carried out on slopes. Excavation works on rock slopes are difficult and hazardous because the slopes have varying geological and physical properties, different types of stratification, and a complex geometry. Therefore, many accidents occur during such excavation works on rock slopes.

In this study, we present a case history of a real-life labor accident due to slope failure on soft rock. We then extract the hazards and risks from the example and suggest preventive measures against the risks involved. The height of the slope, slope angle, ground water level inside the slope, and the boundary between the strata of the slope were considered especially as factors of hazards. For proposing preventive measures against accidents, we must consider carrying out a ground survey, create a design for excavation based on the survey, conduct inspection of the slope, and follow the observational procedure in construction project.

Risk Assessment (hereafter referred to RA) is recommended as an effective measure to prevent accidents that occur in the workplace and its implementation is increasing. Nevertheless, accidents in the workplace continue to occur. In order to establish RA as an effective measure to prevent accidents in the workplace, an important process is to detect issues in the contents of RA executed in workplaces where accidents have occurred and to improve these issues. In this study, I surveyed the contents of RA described in the “Report concerning the Conditions of Health and Safety Management ”, which requested submissions from around 3,200 workplaces with more than 50 workers, to the Health and Safety Division of the Labour Standards Department in the Ibaraki Labour Bureau of the Ministry of Health, Labour and Welfare from FY2013—2015 and FY2017. I compared the contents of RA for the workplace in which accidents had occurred with the contents of RA for the workplace in which no accidents had occurred. Based on this comparison, I identified the issues with quantitative reasoning of contents of RA in workplaces in which accidents had occurred.
All workplaces in Ibaraki Prefecture, not only workplaces in which accidents have occurred, but also those in which no accidents have occurred should be able to improve the contents of RA by applying the issues identified in this study as more effective measures to prevent accidents in the workplace.

This study experimentally investigated the dust-proof performance of a bipolar electrostatic ionizer. A circulating-type dust testing apparatus and talcum powder with a middle particle diameter of 6 µm were used in this study. Compressed air was supplied to the bipolar ionizer, with pressure in the range of 0.01 to 0.05 MPa. The test time for each test was 1800 s. The results show that talcum powder did not enter the inner parts of the ionizer under all test conditions. It was also confirmed that the ion-generating ability was the same before and after testing the dust-proof performance.

We investigated the effect of humidification to prevent human body from becoming charged where footwear and flooring made of synthetic polymeric materials low in hygroscopicity are used. The human body potential during walking, the leakage resistance between the human body and the earth, and the surface and volume resistivity of the flooring materials measured showed no remarkable changes in these values due to relative humidity variation (10% 60%). The results indicated that humidification is not always effective to reduce the leakage resistance yielding charge relaxation when low hygroscopic materials are used. It is necessary to recognize that humidification is an auxiliary antistatic countermeasure and to take the essential antistatic countermeasures (use of conducive or charge dissipative materials to lower leakage resistance).