Abstract: Rainfall is the most important factor in triggering the landslide. To reduce the loss of life and property caused by the landslide disaster, the early warning system against landslides becomes one of the best choices. Based on the principle of elastic wave propagation and the characteristics of deformation and failure of rainfall-induced landslides, this paper proposes to use the elastic wave velocity to detect the changes in soil moisture content and displacement on slope surface. The bender elements and ceramic disk, incorporated in a triaxial apparatus, are used to measure the S-wave and P-wave velocities in soils subjected to water infiltration. The device allows water to infiltrate into the soil from the pedestal to simulate the process of rainfall infiltration into the soil. The moisture content, deformation and elastic wave velocity are simultaneously measured during the tests. Besides, the rainfall model tests are carried out. Based on the triaxial model tests, this study reveals the process of rainfall-induced landslides, the evolution of elastic wave velocity, and the coupling relationship among the wave velocity, water content and deformation. The results show that the elastic wave velocity decreases slowly with the increase of water content, but decreases sharply with the increase of deformation, indicating the initiation of the instability. We also interpret possible mechanisms of the reduction of elastic wave velocity caused by water content and deformation. This paper provides a new method and reliable basis for an early warning system for rainfall-induced landslides and slope failures.

Key words: slope failure, early warning, rainfall, elastic wave velocity, triaxial test, slope model test