[H-DS09] Landslides and related phenomena

[HDS09-10] A field example of flexural toppling at Song-Mao Village in central Taiwan

*鄒 青穎¹、横山 修²、今泉 文寿³、Lin Hsi-Hung⁴、Hsieh Yu-Chung⁴、Chen Mien-Ming⁴、千木良 雅弘⁵、Wu Chun-Yi⁶、Chen Su-Chin⁶ (1.弘前大学農学生命科学部、2.国土防災（株）、3.静岡大学農学部、4.台湾中央地質調査所、5.京都大学防災研究所、6.国立中興大学農業自然資源学部)

キーワード：トップ リング、重力変形斜面、台湾

Landslides can pose a serious risk to the urban environment and to line infrastructures in many humid, tectonically active regions. In this study, geological and geomorphological surveys were conducted at Song-Mao Village in central Taiwan, whereas the area has been affected by deep-seated gravitational slope deformation in the long-term. Aligned at the similar elevations at 1600 m a.s.l. along both sides of the Dajia River, a series of the flat ledge is distributed and ledges on opposite sides of the river sometimes interlock, suggesting that they are the remnants of ridges above slip-off slopes of an old meandering river. The study area is located at one of the flat ledges with two free surfaces (NE-facing and W-facing) along the Dajia River. The bedrock on the upper slope consists of slate striking NE-SW with steeply dipping cleavage at 85° to SE and the lower slope consists of alternating beds of sandstone and slate striking NE-SW and dipping 70° to 85° to SE. The beds show flexural toppling at NE-facing and W-facing slopes, totally cover an area of 0.25 km². Flexural toppling has led to the formation of ridge-top depression and bulging slope at the middle slope. Active unit of the slope deformation appears at the lower slope of W-facing slopes indicated by a slope failure and its debris deposit that looked quite fresh, suggesting they probably formed recently.