Analysis & Study On Stability Of NO.2 Landslide For Lijiaxia Hydropower Station On Yellow River

No. 2 landslide located at the upstream of dam of Lijiaxia hydropower station belongs to ancient landslide accompanied with creep activities, which volume is 18.45 x 106 m3. The dam protected height is determined as 15m higher above reservoir water level during initial reservoir impounding period in order to preventing surge damage caused by landslide. This article deals with the analysis carried out in association with measured creep process before and after initial dam impoundment when landslide occurs, which suggests that the landslide undergoes both acceleration and deceleration procedures as the water level increases and ends up with retarded creep state after the water level is in stabilized status. The shear and rheologic tests related to sliding soil within landslide zones are conducted and long-term strength as well as critical strength of acceleration creep are obtained accordingly. The study on retarded creep behavior using creep theory under condition of reservoir water lever in stabilized status for one and a half year demonstrates that the viscous coefficient of sliding soil shall increase as creep procedure continues, meanwhile, the displacement process of landslide surface area fitted by logarithmic curve matches closely with measured values. The condition regarding transformation from creep into intensive sliding of reservoir landslide has been elaborated taking the examples of landslide taken place in Wayiong reservoir and Jepachi reservoir into consideration, while the landslide of Lijiaxia hydropower station has no such condition. The rigid limit equilibrium computation and finite element computation have been performed which concluded that the integral stability coefficient of No. 2 landslide shall be the minimum value when water level is 2145m a.s.l., then the coefficient increases slightly as the reservoir water level rises up, there exists, however, a fact that the stability coefficient of local section may tend to decrease continuously along with the rise of reservoir water level. Because the location of landside is too close to the dam which presents risks to some extent, the treatment methodology involved in local excavation and local slide promotion for No. 2 landslide has been proposed.