The Values And Validation Of The Controlling Parameters With The Discontinuous Deformation Analysis Method

Discontinuous deformation analysis method is developed by Dr Shi in the late1980s, whichis a new type of numerical analysis method. The rock body system of DDA is formed by thediscontinuous surface exited in nature rock body. Based on the assumption of the displacementfunction, the global equilibrium equations of the block system are established according tominimum potential energy. In the solving process, the penalty spring of the interfaces is added orremoved based on the penalty function method. Thus, no penetration and no tension can berealized. Through the open-close iteration of block system, the blance requirement of the forcesystem is satisfied. Based on the introduction of inertial force, the convergence of dynamicsolution is realized. Then the genuine solution of force and deformation of the block system canbe obtained. DDA contains the complete kinematics theory, the strict equilibrium assumption, thecorrect energy consumption, and it can simulate the translation, rotation, open and closed of thestructural surface, as with the large body and large displacement of the block system. Accordingto the deformation and movement characteristics of block system, the damaged range and degreeof the rock mass can be estimated, so the overall and local stability of rock mass can beanalysized.Since DDA is proposed, it has been paid great attention worldly-wide in therock and soilmechanics numerical analysis field. It has great potential in simulating discontinuous and largedeformation of the structure, rock and soil mass. To2013, it has successively held11sessions ofDDA international conference, and the development, application, validation of DDA method arestill the current important research topics of this method. Based on the DDA theory, the problemsconcerning the controlling parameter have been studied. At the same time, the DDA program hasbeen improved, and it has got good results in solving underground caverns and landslideengineering problems. The research results mainly contain?(1) It introduces the basic theory of two-dimensional DDA, including the displacement anddeformation of block, the formation of each matrix, and the block contact theory, etc. Especially,the latest block contact theory.(2) It introduces the computational program of DDA, and the realization of the block contact theory and the non-zero sparse storage have been introduced in detail, which contain theexplanation of geometric figures and specification of the instances.(3) The controlling parameters of DDA method are studied in detail. Firstly, the relationshipbetween the contact displacement and the controlling parametes is studied theoretically, and theanalytical formula of the contact displacement can be obtained based on the simplifiedmechanical analytical model, which reveals that introducing inertia to the contact convergence isto realize that blocks on the contact interfaces have no embedding and no tension with adjustingthe time step. Then, based on the simple model, the joint effect of the time step and the springstiffness with the reasonable value considering regional characteristics are studied. The resultsshow that the proper value range of the time step and the spring stiffness constitutes asimply-connected domain, when the values of the time step and the spring stiffness are bothwithin the proposed domain, the results of DDA method is then reasonable. This study of solvingthe value problems of the time step and the spring stiffness has made the positive exploration,which has a significant meaning for the development and application of DDA.(4) According to the needs of actual engineercal calculation, some computational programshave been improved, so it can calculate the initial stress of the underground cavern according tothe different buried depth, which is easy to study the effect of the initial stress to the stabilityproblems of underground cavern.(5) Based on the results of the DDA theory and parameters, the improved DDA programshave been used in a underground powerhouse and the landslide of Taziping. The results showthat DDA has a good applicability on studying the deformation and damage of the surroundingrock of underground cavern and the evaluation of the stability of the landslide.