Abstract
An collapsing accident involving continuous-fiber reinforced soil on steep slope occurred. The accident cause may be drainage capacity degradation by clogging by ferric hydroxide gel. Ferric hydroxide gel is formed by chemical processes depending on groundwater environment and exposure time. So, we investigated the chemical background condition of the accident and measured water permeability variations of clogging geosynthetics with time. Then we found that ferrous ion rich groundwater which produces ferric hydroxide gel by oxidation abundantly flowed out at the accident site. And the drainage capacities of geosynthetics are rapidly degraded by clogging of ferric hydroxide gel.
