Norio Yagi

Influence of Rainfall on Movement of Fractured Zone Landslide

The relationship of displacement of fractured zone landslide and rainfall is investigated on basis of the observational data. In the majority of cases, the displacement increased in proportion to rainfall. In Nuta and Honmura landslide, the displacement is correlated to the change of ground water level. This fact means that the decrease of effective stress is a primary factor of the char ge of displacement. As the landslide movement has an immediate connection with rainfall or ground water level, the prediction of landslide displacement is possible by the measurement of rainfall of ground water level.

Consideration on Critical Rainfall for Prediction of Occuring Time of Slope Failure

In order to develop a prediciion method for the occurring time of a slope failure based on the critical rainfall, the following studies were carried out. Conditions which has influence on the critical rainfall were discussed. Then, the change of pressure head in natural condition were investigated. Finally, the pore pressure distribution in a slope and the stability of slope were analysed numerically.Consequently, the following results are obtained:(1) The critical rainfall curve which is the relation between rainfall per a week and rainfall per a day of the failed slopes can be obtained numerically.(2) The seepage characteristic and the thickness of permeable layer have a great influence on the total rainfall till the slope failure.(3) The quantity of successive rainfall for the slope failure can be accurately estimated by numerical analysis if the initial pore pressure distribution in the slope is known.