伐倒作業の死亡災害分析

Abstract

A total of 414 fatal accidents in felling operations were investigated, with the following results:1) The source of many accidents was the misdirection of falling trees causes included mistaken cutting angle (“undercutting” or “backcutting”), the lodged tree of windfall, and trees that were entangled with climbing plants. Trees falling in the wrong direction caused “flying branch” accidents by striking against standing trees, and “pulling down” accidents by lodging against a standing tree. There were also many cases of being “struck by the butt-end of a fallen tree” caused when a tree being felled suddenly broke during backcutting.2) Safety education, KYT (a system to heighten workers' ability to determine whether or not conditions are safe) were judged to be important measures for preventing accidents from the perspective of safety management. The most common types of unsafe acts of fellers included entering danger zones, failure to confirm the safety of the work environment.3) The accident conditions were classified into two modes, slightly reduced alertness (Phase II) and further reduced alertness (Phase I).4) Errors in undercutting or backcutting resulted from fellers' uncertainly or presumptions without confirmation. Errors in walking resulted from fellers' uncertain operation, and in limbing or bucking, from their presumptive operation without confirmation. Errors in the handling of lodged trees resulted from fellers' improper sequence of operations. Therefore, the most effective felling accident prevention measures are considered to be a combination of safety education, KYT and having fellers point out dangerous situations with gestures and words.