The soil in sliding zone is an essential part of landslides, and closely related to the evolutionary development and landslide stability evaluation. The study of sliding zone soil has been concerned recently and gradually turned to a hotspot because the study is the fundamental content of landslide in engineering geology. However, most of the study of sliding zone soil, at present, mainly has concentrated on physical and mechanical property, lacked of discussing the essential factors which affect the strength of sliding zone soil. Based on the work that have been done, in this paper, we briefly summarize the recognition and the classification of sliding zone, and the current study situation of the strength characteristics of sliding zone soil, and then emphatically give a summary and analysis according to the microstructure, mineral composition, geochemical characteristics and formation mechanism of sliding zone soil, especially the discussion of the effect of these characteristics on the strength of sliding zone soil. The study results suggest that: ①the recognition of sliding zone, the classification of sliding zone soil and the analysis of the strength of sliding zone soil need to be further studied, and we ought to do some work to broaden steadily research scopes of sliding zone soil and improve the understanding of the essential factors of affecting its strength; ②the research of sliding zone soil should be emphasized on the change of strength with its mineral composition, water, density, grain-size, geochemical characteristics, microorganisms, and the variation laws of microstructure under different conditions, and the effect of water-rock(soil) interaction, permeability and water chemical action on sliding zone soil; ③the systematical research of sliding zone soil formation process should be based on the evolutionary viewpoint. More information  about sliding zone soil  landslide evolutionary progress and environment change should be sought in future.

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