Stability and treatment of Zhenggang landslide accumulation mass

The volume of Zhenggang landslide accumulation mass in Gushui Hydropower Station is more than 47500000 m3, which is one of the rarely largest landslide accumulation bodies in the world. According to the speciality of the geological engineering conditions of the accumulation body, the formation mechanism and instability mode in the future of the landslide is studied. When the slip surface on the bottom is determined, a section random combination method in back analysis towards the unstable failure process of the deformation regions after raining is proposed. The analytic results are compared with those of site investigation, laboratory experiment and other similar projects so as to find out reasonable calculation parameters. The stable analysis of the accumulation mass is conducted, and it shows that the accumulation mass is in the state of creep deformation under the normal conditons and possibly slumps under any conditon, so the treatment such as excavation and reinforcement is needed. Due to the differences among the unstable failure modes of side slopes, Zhenggang landslide accumulation mass is divided into Region I and Region Ⅱ. Various treatment schemes are proposed, and a safety factor formula of slip surface under anti-slide piles is deduced. After comparison and optimization, the best economic and reasonable treatment scheme is chosen. It shows that the treatment of the accumulation mass can increase local stability and ensure the whole stability.