音響トモグラフィーによる戦災樹木の非破壊的腐朽診断

Abstract

In the 77th year of the end of the war, “war-damaged trees” are the solution how can we pass on the memories of the war to future generations. Externally, war-damaged trees are characterized by damages, such as burning, hollowing, and leaning. However, there is still no information on the extent of how these damages affect the health of the trees and how to treat them. Therefore, the internal decay state and effects of damages specific to war-damaged trees were investigated using sonic tomography on 11 remaining war-damaged ginkgo trees (35 cross-sections) at Tobiki Inari Shrine in Sumida-ku, Tokyo. The decay and hollowing rate in 10 sections were calculated. By looking at the characteristics of the cross-sections only and not the whole tree, the cross-sections at each measurement height were classified into five types. This survey made it possible to capture the condition of the war-damaged trees’ cross-sections in images. Results showed that war-damaged trees that have lived for more than 77 years after the war have been strengthened by the self-recovery growth of the tree body. In relatively young trees, it was confirmed that almost 100% of damaged areas were covered, and the restoration process was complete due to wrapping by self-recovery growth.