Geotechnical characteristics of the collapsed $\bigcirc\bigcirc$tunnel slope in Yeosu-Suncheon area

여수-순천 도로확장공사 구간 $\bigcirc\bigcirc$터널 붕괴사면 지반특성

In September 2007, the collapses of slopes and landslides are happened at Jeonlanamdo due to heavy rains accompanied with Typoon "Nari". The study area is the tunnel portal slope in new road construction site. This slope consists of pyroclastic rocks and has lots of faults. Particularly, the residual soils of the slope is deteriorated with yellowish mudstone layer as a results of chemical and physical weathering. This has a variety of swelling clay minerals and might be moved easily down at the gentle terrain. The inner factor of $\bigcirc\bigcirc$tunnel portal slope's collapse is the geological weak zone, the convergent topography, the inferiority of drainage and the heavy rain act on the failure as direct trigger.