Abstract: The ancient and old landslides of terrace type are often greatly influenced by external geological processes and human activities, and the morphological characteristics of landslides are seriously damaged or even disappeared;Therefore,it is difficult to determine their existence by remote sensing technology and general engineering geological mapping;However,they are potential hazards in constructions and operations. In order to identify the ancient and old landslides with unclear shape, the typical material structure caused by the shear failure of the terrace can be traced back from the evolution of the terrace material structure. For example, the broken stratigraphic structure, abnormal directional gravel alignment, augen structure of friction mirror and mud coated particles can be used as the basis to precisely identify the landslides. The criss-crossing tracking method of an engineering geological mapping along gully is used to determine the longitudinal range and sliding surface shape of landslide body, and then the plane range and distribution of landslides at each level and block are deduced according to the geomorphological features. Finally, the conclusion is verified and corrected by point exploration engineering. This terrace landslide identification procedure can be summarized as "recognizing geomorphological anomaly, tracking along the gully, surface inference,and point verification". Combined with the characteristics of each stage of the linear engineering investigation and design, the identification steps of terrace landslide during the preliminary work of linear engineering were put forward and applied successfully in the construction project of Lin-Wei expressway.

Key words: ancient and old landslide, landslide identification, identification mark, identification method, identification procedure