2010 Volume 52 Issue 2 Pages 49-55
In order to clarify the effect of the slope angle on the maximum moment of resistance against uprooting, we performed the tree-pulling experiments of Cryptomeria japonica (14 years) at inclined slopes which have four different angles. To examine the relationship between the tree-pulling experiments and root distributions, we also measured root distribution areas, weights and total areas of cross section of roots per 10cm from center of the stump. As the slope was steep, the maximum moment of resistance against uprooting showed to increase in the case of pulling downward compared with upward, and root distribution areas were more extended to upward and sideward than downward. When the slope was steep, weights and total areas of cross section of roots which distributed to upward increased compared with downward. These results showed that the thick roots tended to distribute to upward compared with downward, as the slope was steep. By examining the relationship between the tree-pulling experiments and root distributions, we found that the larger thick roots which distributed to upward, the higher the maximum moment of resistance against uprooting in the case of pulling downward. These results suggest that the partial root distributions at inclined slopes contribute to the results of the tree-pulling experiments, and the maximum moments of resistance against uprooting are different by the slope angle and the direction of pulling.
