Analysis and evaluation of stability for the reactivated landslide along deep-seated weakness zones

Abstract

In areas where landslides have occurred in the past, it is prone to additional landslides because of similar geological and geographical characteristics. A slope sliding by a reactivated landslide can result in accidents, extra cost and delayed construction schedule. Hence, it is important to identify evidence of past landslides during the design and construction phases in these areas. In the study area presented in this paper, tension cracks were found during clearing and grubbing work prior to the construction of cut slopes at a tunnel portal, implying that landslides had occurred in the past. To mitigate risk, slope gradient was decreased to 1:1.3 with removal of tension cracks, however, 90 m-long tension cracks occurred subsequently. Therefore, detailed geotechnical investigations and analysis were carried out. This paper aims to present procedures and results of analysis to clarify causes of landslides, including selection of the optimum countermeasures for stabilization of the cut slope. We hope that this case study will provide useful information to other engineers and contribute to the prevention of disaster caused by landslide.