| At present, the traditional mechanical method used for evaluating the abilities of the concrete dam's resistance for earthquake and explosion is unable to carry out the exact destruction condition under the earthquake load as well as the blast-impact load, because it is not involved the influence of dynamics performance of materials caused by the "material dynamic deterioration" due to the generation and development of micro cracks in materials. Therefore, the stress analysis is based on the linear elastic theory and the nonlinear response, such as the damage development in dam is neglected. This paper presents a basis of the theory of anisotropic brittle damage mechanics, develops a general three dimensional anisotropic brittle dynamic damage finite element model with the associated 3-D numerical analysis program, and applies the developed model and the program into simulation of 3-D anisotropic brittle dynamic damage problem for the concrete gravity dam and the rock foundation as well as the arch dam and rock foundation under the blast-impact load and the earthquake load. The principal works of this paper can be summarized as follows:1. The developed 3-D anisotropic brittle damage stress-strain constitutive model, the 3-D anisotropic brittle damage evolution equations of rock like material and the 3-D anisotropic brittle dynamic damage finite element equations for the rock like structures have been taken into account of virtual work principle to develop the integral form of weak solution of 3-D anisotropic brittle dynamic damage mechanics problems. According to these theories, the independent 3-D anisotropic brittle dynamic damage finite element analysis program (3DADDFEP) has been designed and developed based on the FEPG system.2. Using the developed 3DADDFEP system, the 3-D dynamic damage response and the 3-D anisotropic brittle damage process in the concrete gravity dam and archdam as well as in rock foundations have been numerically simulated under the blast-impact load and the earthquake load. There are some conclusions from this numerical analysis:(1) The serious damage appears at the position of the dam back near the load range where the dam surface is much easer to damage. The peak value and the duration time of the blast-impact load have an important influence to damage growth and damage propagation. When the dynamic stress due to the impact load is higher than that of the threshold value of damage developing in the material, the damage in the material would be sharply grow, that may extremely adverse to the safety of structure. Because the duration period of the blast-impact load lasted very short, the localization of the damage is quite obviously.(2) Under the earthquake load, the top of arch dam, especially the union spot of dam body and dam shoulder, is damaged more easily. In the union spot of dam and its foundation, the damage growth is quite obvious. The deformational tendency of the dam and foundation basically follows the step of the earthquake acceleration, if the phase difference between the response of dam and foundation and the acceleration of the earthquake is neglected, but has some delays due to damage growth in the dam and foundation.(3) The damage growth and develop in these concrete dams and foundation system affected strongly by the load, the boundary condition and the material properties show anisotropy obviously under dynamic load. There are more differences presented in different results which are obtained by using the different damage evolution models. Therefore, development of new damage evolution model in order to better express dynamic damage behaviors and physical properties of materials is one of very important research direction of continuum damage mechanics. |
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