Stability Analysis of Unfavourable Geological Bodies in a Post-Earthquake Area: A Case Study in Gengda Township China

Abstract

On 12 May 2008, a devastating mega-earthquake of magnitude 8.0 struck the Wenchuan area, northwestern Sichuan Province, China. Following this earthquake event, many areas in the affected areas were susceptible to geological disasters, such as debris flows, landslides and other secondary disasters. To better understand the mechanism of the formation processes of geological disasters, and to reduce the economic loss caused by the disasters, a comprehensive analysis is required. With the aim of obtaining the characteristics of unfavourable geological bodies, and analysing their stability, we choose the Gengda Township as an example (there are many unfavourable geological bodies distributed in this area, including landslides and deformation bodies). Field investigations and computational models are employed to analyse the stability of the unfavourable geological bodies. Through preliminary analysis and model calculation, the following conclusions can be drawn: under natural conditions, the stability factor of the landslide ranges from about 1.02-1.03, which means that the landslide is in a basically stable or less stable condition. Under the effect of continuous heavy rainfall, the stability factor of the landslide will be significantly reduced, and the corresponding value ranges from 0.9-0.96, which signifies that the landslide is in an unstable condition. For No 1 and No 2 deformation bodies (named by local inhabitants), the stability varied from less stable to unstable, and basically stable to unstable, respectively. On the basis of the results of the calculation, some countermeasures are proposed to mitigate the effects of these disasters probably caused by geological bodies.