Stability Evaluation of an Age-Old Landslide By Numerical Method

摘要

Xietan landslide is located in Zigui County, Hubei Province, China. It is an age-old landslide at the northern bank of the Yangtze River in the Three Gorges Reservoir areas. The landslide is mainly composed of sliding mass, slip band and bedrock. Considering that the age-old landslide may reactivate due to the impoundment of the Three Gorges Reservoir, it is necessary to evaluate the stability of the age-old landslide. Numerical simulation results by the shear strength reduction method have shown that with the increase of the shear strength reduction factor, elements of the slip band yield gradually to form a connected plastic zone, which provides a slip path or slip surface for reactivation of the age-old landslide. In view of the plastic resistance of the soils, formation of the connected plastic zone does unnecessarily indicate that the age-old landslide is about to fail. Other auxiliary criterion is necessary to predict whether the landslide is in a critical state. Here, incremental percent of the horizontal displacement of the slip band node at the outcrop, which is changeable with increase of the shear strength reduction factor, is regarded as an auxiliary condition to distinguish the critical state of the landslide. With the above idea, stability of the age-old landslide has been evaluated for the initial and the long term reservoir water level conditions. Factors of safety of the numerical simulations have been compared with that of the limit equilibrium method, which indicates that the method used in the paper for evaluating stability of the age-old landslide is feasible. Because numerical method has more advantages over the limit equilibrium method, the idea for evaluating stability of the landslide can be applied to three-dimensional or more complicated landslides further.