Forecasting of landslide failure is a significant topic in the field of geological engineering; but it is difficult to accurately determine the model parameters in the practical application. The ladder-shaped displacement curves are generally observed in actual landslide monitoring; and the changing points on the curve represent the mutation points of landslide deformation. To investigate the deformation characteristics at the mutation points in landslide

a series of rheological tests is carried out on natural samples under different loading levels and on immersion samples under different loading levels and with different water contents. The curves of accumulative deformation vs. time and deformation velocity vs. time are obtained. Based on the Qin's locking section theory and the landslide early warning model with inverse-velocity method

the experimental results are analyzed. The results show that the model parameters are independent of the loading level and water content

and are the functions of material properties. The deformation characteristics of mutation points in deformation process are similar to those at failure

and the model parameters of the landslide early warning model based on the inverse-velocity method at mutation point are identical to those at failure point. Hence the model parameters determined by the early mutation point in landslide monitoring curve can be utilized in the early warning for landslide failures.