Stability Evolution of a Large Rock Block Revealed in the Excavation Process of the Left Slope of Jinping-I Hydropower Station Based on the Proposed Sarma's Method

Abstract

Abstract. There is a latent large block near the dam abutment of Jinping-I hydropower station, the stability of which is very important in the excavation process. As we know, Sarma's method is able to evaluate the stability of rock slopes with complex structural planes, because it takes into account the mobilization of internal strength of potential landslides. In the presence of multiple rock layers, however, no unified way is available to calculate the total strength on the slice interface, although in most cases the equivalent strength parameters are taken as the weighted averages of strength parameters of all layers. From the assumption that the normal pressure along the slice interface takes on a triangular distribution, we derive the equivalent strength parameters of the slice interface. Moreover, we discuss the influence of different selections of equivalent strength parameters of the slice interface on the factor of safety of a rock slope from a hydropower station in construction, with the conclusion that the difference might be appreciable. At last, based on the proposed procedure the stability evolution of the large rock block in excavation process is discussed. Its stability is increased before elevation 1840 m is reached because the upper portions of the blocks are removed, which help slide. After that, however, the stability is decreased gradually because the lower anti-sliding portions are removed little by little, which help stabilize the slip bodies. After the sliding body is wholly revealed, the factor of safety is 2.83, which is higher than that of sliding body corresponds to the dam crest and lower than that of the maximum in excavation process.