Infrasound induced by blasting in a limestone mine propagates to the houses in a neighboring village and vibrates their windows, doors, furniture and so on. This infrasound causing vibration becomes an apparent problem for the limestone mine near a village. The most effective way to reduce the vibration is to reduce the blasting scale, but this cannot be performed because of low efficiency for mining. Another effective way is to shift and reduce the dominant frequency of infrasound by changing the delay time of blasting caps so that it may not overlap the resonance frequencies of vibrated objects, but the necessary conditions to do so have not been shown.In this paper, in order to propose the necessary conditions for setting an optimal delay time of blasting caps to reduce the vibration, the infrasound of many patterns of blasting was measured in the face of Ube-Isa Limestone Mine and at a neighboring house of the mine. At the neighboring house, the windows vibration was also measured. From the analyses of these measured data, it was found that the longer delay time of blasting caps is necessary to reduce the lower frequency component causing a large vibration, and shorter one is necessary to shorten the duration of blasting and reduce the resonant vibration. Then, in order to satisfy these conflicting conditions, a varied delay time of blasting caps was proposed and tested. As a result, the windows vibration was reduced 60% in total energy and 24% in maximum displacement compare to the minimum vibration of usual blasting using a fixed delay time of blasting caps.
In snowy areas, slope failure triggered by snowmelt water (hereinafter referred to as snowmelt disasters) have occasionally occurred. In this paper, we analyzed 45 cases of snowmelt disasters that occurred along the railway slope. In embankment cases, there was a tendency to cause snowmelt disasters frequently in expanded or embankments under cutting slope with the height of about 3m or more, and in cutting slope of terrace cliff. In addition, as an extracting method of the dangerous location concerning snowmelt disasters, we focus on the risk assessment criteria of rainfall for the slope failure that is used in Japanese railway and compared the evaluation points of that criteria between the snowmelt disaster cases and the no-disaster cases. As the result of comparison, the tendency of the evaluation point of disaster cases to be lowered and it is confirmed that the proposed extracting method of dangerous location can be effective.
The recent rise in short, localized high-intensity torrential rainfall events leading to flooding from rivers, has generated a growing number of disasters affecting urban areas. Japan's railways restrict train operations according to precipitation and river water levels, however, these traffic control methods have not yet been adapted to cope with such short, intense downpours. A real-time rainfall runoff-flooding simulation method, which takes into account predicted rainfall therefore needs to be developed. This paper reports on evaluation results obtained to validate a simulation method.
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