Abstract: Deformation types of landslides generally include retrogressive landslide, load-caused landslide and complex landslide, which present regressive progressive failure mode, advancing progressive failure mode and composite progressive failure mode, respectively based on the development form of sliding zone. Based on the strain-softening behavior of sliding zone, the nature of progressive failure of landslide is weakening process of mechanical parameters of sliding zone which is revealed from the mechanical point. The movement and mechanical characteristics of three types of landslides in the process of progressive failure are determined preliminarily; and evolution process of different types of landslides are revealed. The distinguish criterion of sliding block of critical state is proposed based on the unbalanced thrust method and progressive evolution process. The calculation model and calculation formula of stability of progressive failure of landslides are established and the parameter value method of sliding zone is proposed, and the process to achieve stability calculation of the progressive failure is described. The method shows a complementary relationship in solving the stability problem of strain-softening landslides. Moreover, the progressive failure and stability variation for three typical examples of landslides are analyzed. The results show that the law of reducing speed of retrogressive landslide and complex landslide is from large to small to large; and the law of reducing speed of load-caused landslide is from small to large. In addition, the different part of landslide plays a different role on stability in the progressive failure process of three types of landslides; and the deformation regularity of different types of landslides is verified. The research results can predict the development of stability for different types of landslides preliminarily and provide guidance for landslide control.

Key words: retrogressive landslide, load-caused landslide, complex landslide, progressive failure, stability