Predicting the sliding behavior of rotational landslides based on the tilting measurement of the slope surface

The surface displacements of slopes have been considered as a significant indicator in landslide investigations in last several decades, while in recent years the tilting of slope surfaces is also being recognized as an important index in landslide monitoring. However, the slope surface tilting has been rarely examined so far, and requires detailed investigations. In this paper, a series of laboratory tests and a field test were performed to investigate the surface tilting in rotational landslides, as well as the correlation between tilt angles and displacements of slope surfaces. In the laboratory tests, slope models were constructed with different shapes of pre-designed slip surfaces, and tested under varying test conditions. The tilting behavior of the slope surfaces in laboratory tests was measured using tilt sensors embedded into the slopes, while the surface displacement was obtained by tracing the movement of marked points set on the slope surfaces near to the tilt sensors. The test results revealed a linear relationship between the tilt angles and displacements of slope surfaces in the process of slope failure, and this linear relationship was validated by a field test in which the slope failure was triggered by artificial rainfall. The test results also indicated that the coefficient of the linear relation is consistent with the value of real distance between the locations of tilt sensors and the centers of slip surfaces. An equation that relates the slope surface tilting and displacements was proposed in this study. Furthermore, a method to estimate the geometry of the slip surface was also developed, which was deduced from the observation that the path of the sliding masses was parallel to the slip surface according to the results of laboratory tests. Additionally, an acceleration stage of surface tilting was observed in slope failure induced by artificial rainfall, which implies that the surface tilting measurement can be used to predict the potential development of a rotational landslide or its reactivation. •A linear relationship between the tilt angles and displacements of the slope surface was documented via laboratory and field tests, and a specific equation proposed for this relation.•A simplified method to estimate the geometry of slip surface at depth was proposed, and validated by the tests in this study.•Slope surface tilting data can be effectively used to predict the pre-failure behavior of rotational landslides induced by rainfall.