Discontinuous Deformation Analysis (DDA) is a novel method used to analyze the motional law for discontinuous, jointed rock masses. This method has been widely used in engineering practice. However, there are still some limitations in both its theory and practical application. A modified DDA code was compiled and applied in several projects. A selection of three DDA applications are presented in the form of case studies. Some good results were obtained and played a significant role in designing the systems of support stabilization and the sequence of work. All of the results are presented in this paper.
Rock masses are always dissected by joints, faults and other discontinuities which control the failure and sliding of the masses. The discontinuous deformation model provides the most rational and effective way to analyze such geotechnical problems. The commonly used discontinuous numerical methods include: Discrete Element Method (DEM), Rigid- Block Spring Method (RBSM), Fast Lagrangian Analysis of Continua (FLAC), Contact -Spring Model and Discontinuous Deformation Analysis (DDA). The DDA method provides the theoretical basis for a forward numerical model of rock block systems, and also provides a more accurate and convenient approach in numerical analyses. This method was developed to compute stress, strain, sliding and opening of rock blocks; rigid body movement and deformation occurred simultaneously. Input data consist of block geometry, loading forces, the deformability constants Young''s modulus E and Poisson ration, and the restraint or boundary conditions of the block system. The output of such analyses include the movements, deformations, stresses and strains of each block, and the sliding and detachment, or rejoining of blocks.
The ship lock of Three Gorges Project in China is under construction and has been excavated in high mountains.
