Abstract of Special Research Report (SRR-No.25)
National Institute of Occupational Safety and Health, Japan
Specific Research on Preventional Countermeasures of Labor Accidents due to Debris Flow
Introduction
SRR-No.25-1 |
Noriyuki HORII |
: Since Japan has a lot of steep terrain, local heavy rainfalls may sometimes produce dangerous debris flows. In December 1996, a large debris flow occurred at Gamaharazawa located at the border between Nagano and Niigata prefectures. The debris flow, which involved construction workers working in the drainage basin, resulted in a serious disaster with 14 persons dead and 9 persons injured. In this case, once a debris flow occurs not only many workers in the basin but also nearby residents might be involved and then the disaster becomes expanded widely.
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Questionnaire Survey regarding On-site Construction Management of Debris Flow
SRR-No.25-2 |
Yasuo TOYOSAWA and Noriyuki HORII |
: In order to establish countermeasures against accidents due to debris flow in construction work sites, a questionnaire survey of construction sites was carried out. To identify the factors concerning accidents in construction work sites, the questionnaire focused on the followings: the contents and scale of construction, site conditions, alarm and evacuation equipment, and evacuation procedure at the time of debris flow, etc. Statistical analyses were made on 226 responses to this questionnaire survey.
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An Experimental Study on the Flow Characteristics of a Debris Flow --Influence of Particle Size and Structure Rigidity on Impact Stress in Model Debris Flow--
SRR-No.25-3 |
Noriyuki HORII, Yasuo TOYOSAWA, Satoshi TAMATE and Hideo HASHIZUME |
: Since Japan has a lot of steep terrain, local heavy rainfalls may sometimes produce dangerous debris flows. In December 1996, a large debris flow occurred at Gamaharazawa located a the border between Nagano and Niigata prefectures. The debris flow, which involved construction workers working in the drainage basin, resulted in a serious disaster with 14 persons dead and 9 persons injured.
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Evaluation of Evacuation Time from Debris Flow by On-site Experiments
SRR-No.25-4 |
Yasuo TOYOSAWA and Noriyuki HORII |
: It is important to predict the time required to evacuate from a debris flow at the planning stage to take effective countermeasures against debris flow such as installing a detection system consisting of monitors, alarms, etc. To prevent accidents caused by debris flow, the evacuation time should be shorter than that of taken from when an alarm sounds until the debris flow hits the construction site. The evacuation time depend on several factors such as the evacuation route, composition of workers, and geographical conditions of the site. Therefore, on-site evacuation experiments were carried out to evaluate the influence of those factors on the evacuation time.
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Detection Method for Debris Flow using Visual Information
SRR-No.25-5 |
Kyoko HAMAJIMA, Noriyuki HORII, Yasuo TOYOSAWA and Satoshi TAMATE |
: There is an extremely high possibility of encountering a landslide due to debris flow in erosion control work and disaster relief work conducted on site where the ground may essentially collapse with a high degree of danger. Due to its large destructive force in particular, there is a large possibility that the landslide may develop into a labor accident with many deaths or injuries. To avoid a disaster due to this sudden debris flow, the key points are how quickly the occurrence is detected and whether it is possible to flee to safe shelter before the debris flow arrives. To achieve these goals, a system must be developed at the work site with placing observers or detection systems to ensure detection of the debris flow, an evacuation alarm that is certain to reach workers, and shelter that workers can move to within a short amount of time. Wire sensors that are frequently used as a detection system because of their highly reliable detection, have several problems: (1) workers must enter areas where there is a danger of debris flow during placement of the system, and (2) continual detection is not possible. Therefore, supplementary measures are needed to ensure further safety. Currently, an image detection sensor has been a focus of constant attention for its use as a detection system to compensate for these problems. The characteristics of this image detection sensor are: (i) easy placement of the system with no need for workers to enter dangerous areas and (ii) there is no system damage due to the debris flow and continual detection is possible. Thus, improvement of the system's detection capability as a whole is possible if it is used in combination with existing detection systems. However, there are few image detection sensors among those currently being developed that are designed to take safety theories into consideration. In order to create a safe work site, a system must ensure and maintain safety. There are theories for safety that are defined by ISO and the like in the field of mechanical safety. |
Developmeny of Monitoring and Alarm System for Debris Flow
SRR-No.25-6 |
asuo TOYOSAWA, Shigeo UMEZAKI and Noriyuki HORII |
:Various measures, such as weather forecasting, prediction of debris flows, evacuation drills, etc. were taken to avert accidents at construction site caused by debris flow. In doing so, factors found indispensable to preclude debris flow accidents are as follows; (1) Detecting a flow without fail, (2) Issuing evacuation warnings, and (3) Safe evacuation.
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Construction of a Support System for Optimum Arrangment of Debris Flow Detection Sensors
SRR-No.25-7 |
Noriyuki HORII, Yasuo TOYOSAWA, Satoshi TAMATE and Kyoko HAMAJIMA |
: In December 1996, a large debris flow occurred at Gamaharazawa located at the border between Nagano and Niigata prefectures. The debris flow, which involved construction workers working in the drainage basin, resulted in a serious disaster with 14 persons dead and 9 persons injured. In this case, once a debris flow occurs not only many workers were in the basin but also nearby residents were involved and then the disaster becomes expanded. For this reason, "the guideline for the prevention of industrial accidents due to the debris flow" is published in accordance with the revision of a regulation of Occupational safety and health at Ministry of Labor.
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