2017 Volume 58 Issue 3 Pages 166-177
Bhutan is located between China and India along the Himalayan Mountains and almost entirely mountainous country with nearly 95 percent of the country being above 600 meters altitude. Roads are major means of travel and transportation in Bhutan, and development of an efficient and safe road network is essential for Bhutan's social and economic development.
However, large parts of the country consist of steep slopes and cliffs, and there are few roads with sufficient road slope disaster countermeasures in place. Consequently, slope failures and landslides frequently occur and isolate areas from the capital or other areas of the country, disrupting travel and the transport of agricultural crops.
Therefore the authors have implemented a slope disaster inspection on roads in the National Road 1 and 4 as an activity of the development of a road slope management master plan. To prepare the inspection sheet in Bhutan where there are few engineers who have experience on slope disaster inspection, the authors have discussed the factors and their contributions that affect on each disaster and decided the item in the list on the slope disaster inspection sheet in Bhutan using multivariate statistical analysis, namely quantification theory.
Through the multivariate statistical analysis in this study, the following was observed: “collapsed factors on topography”,“topsoil and detached rock on surface” and “dip on profile” have greatly affected the hazard on rock slope failure; “dip slope of bedding plane on geology” and “dip on profile” have greatly affected the hazard on debris slope failure; and “surface anomalies on topography” have greatly affected the hazard on landslide in Bhutan. Based on the analysis, new evaluation sheets are proposed for the slope inspection on roads for each slope disaster, which are suitable to the conditions of geology and topography in Bhutan.
The analysis and discussion in this study help the Bhutanese Government understand which feature and condition they should pay attention to identify accurately the hazard on slope disasters in Bhutan.
The Bhutanese Government has to keep fighting slope disasters like the Japanese Government does. Data accumulation of the evaluation sheets is important for the continuous inspection to improve the accuracy of hazard evaluation on each slope disaster.
