The stability evaluation and control design of a deformable rockmass body was one of the most challenging problems encountered during the construction of the Three Gorge Reservoir in China. Part of the rockmass body appeared to be deforming where as the whole rockmass remained stable. The evaluation and improvement of the stability of a landslide appeared to be different for each location. This paper will aim to introduce the research methodology followed in order to control the design on a deformable body. Three key factors were identified and are introduced below:
- The determination of the most dangerous sliding surface: for the consequent bankslope, it should be decided according to the rear edge deformation and the bedding plane; as for the not consequent bankslope, it
should be confirmed considering the preponderant joint combination angle, the tensile cracks, FSK method and the structural plane network simulation results.
- The arrangement of reasonable position of the anti-slide piles: when the deformation is serious, the piles should be placed in the descendant section of the pushing force diagram and above 175m water level; when it isn't, they should be placed in the rear part of the deformable body where there is no deformation.
- The determination of the design pushing force: not considering the resistance of the rock and soil mass before the piles, it is the maximum value under different conditions; concerning resistance, it can be the maximum value at the shearing-out point under different conditions or the difference between the maximum value of the design and checkout condition and value under natural condition.
To summarise taking the example of the Archives Office deformable body, which lies in the Three Gorge reservoir area, with the above method, first the sliding surface is determined, then the stability is evaluated with the residual pushing force method, and the positions of the piles and design pushing force are decided.