Volume 14 (2015) Pages 60-72
High-density road networks, including established operation-roads, are necessary for mechanized forestry. However, operation-roads and forest roads are typically constructed using different methods. For example, surface processing and the creation of retaining walls are often omitted from the construction of operation-roads to keep costs low, even though such omissions can increase the risk of collapse due to heavy rainfall. Previous studies have clarified the factors that can cause the collapse of forest roads; however, these risks factors remain unknown for operation-roads. To address this, we attempted to extract estimates of the collapse risk for operation-roads with reference to previous studies regarding forest roads. In particular, we extracted the factors resulting in high risk of collapse (i.e., terrain conditions, the geometric structure of the collapse point) based on the operation-road patrol record. Numeric values in the range 0–1 were used to express the determined collapse risk based on the concept of fuzzy theory. Finally, a comparison of the importance of the various contributing factors was conducted using mathematical quantification type II. The results demonstrate that the geometric structure of the collapse point is the dominant factor controlling the collapse risk of operation-roads, in contrast to forest road collapse, which is induced primarily by unfavorable terrain conditions.