Research On Dynamic Failure Test And Reliability Of Concrete Gravity Dam

With implementing of the West Grand Development Strategy, one batch of high concrete dam is building or will be constructed in southwest in China. The reservoir capacities of these projects reach several billion cubic meters, and most of these projects build in strong earthquake region. Once the dams are failure, society and people will suffer from the disaster to economy development, people's life and property. In order to study the dynamic destruction mechanism of concrete gravity dam in earthquake, the dynamic shaking table model experiments and FEM-based numerical calculations were adopted to research the whole process of concrete gravity dam from damage to failure in this paper. The failure mode and reliability of gravity dam was also discussed. The results offer important reference to engineering designers and. anti-seismic design. The major contributions are summarized as follows:In large scale model shaking table test of concrete gravity dam, How to develop a type of similar model material to meet the similar requirements have been a noticeable focus. In order to obtain a ideal material for large scale model test, this dissertation investigated the features of low strengthen-emulation concrete materials including their uniaxial proportions in tensile and compressive loadings, dynamic natures. The deformation and relationship of concrete under tensive and compressive loading were researched referring to mechanical properties of common concrete. Test on shear strength and fracture behavior of emulation concrete were also performed. The effect of strain rate on emulation concrete tension and compressive properties was examined and the failure mechanism of emulation concrete under dynamic load was analyzed.Similarity theory is the premise of the large scale model experiments. The basic requirements and similarity criteria of dynamic model test were derived in detail based on the equations analysis methods. The prerequisites and relationship of each similarity rules were researched. On this basis, similarity conditions of seismic rupture model test were discussed. On the condition of relaxing strain scale, the similarity theory of nonlinear dynamic model test was derived.The failure process and failure mode of concrete gravity dam were studied using seismic rupture model test and simulation calculation and the failure mechanism of gravity dam was discussed. Emulation concrete material was used to study the gravity dam failure process and nonlinear dynamic response in earthquake by shaking table tests. The factors influencing the damage of dam were analyzed through simulation on the failure process of concrete gravity dam by using elasto-plastic damage constitutive relations model for concrete. Aiming at how to simulate the uplift pressure of the interface between dam and foundation in the stress and stability analysis of dam with Finite Element Method, different numerical simulation methods of imposing uplift pressure were analyzed. By comparing the influences on the deformation, stress distribution and stability of dam foundation rock, their applied range and limitation of are indicated respectively for specific application purpose. At same time, the influences of dam seepage fields on the dam deformation were discussed based on spatial seepage flow theory. Detailed formula for the soil-structure dynamic interaction analysis is derived, the concept and the application criteria of mass-less base model for soil-structure dynamic interaction analysis is clarified. A simplified method was presented on engineering design for analysis of dynamic soil-structure interaction.Taking the variability of material parameters and earthquake into account, a quadratic polynomial fitted by using response surface method was used to simulate the limit state equation of concrete gravity dam. The reliability index was calculated by a finite iteration step method. The distribution of effective earthquake forces was ameliorated according to adaptive spectra-based Push-over procedure and used in calculating the gravity dam's probability. The influence of different failure path on the reliability of concrete gravity dam was studied by analyzing the dam's ultimate load bearing capacity. Probable seismic failure paths and failure modes corresponding to limit load state and normal operation state were analyzed. The failure probabilities for the different failure modes corresponding to dam, rock, sliding of roller compacted layer and floor were further analyzed. And based on system reliability theory, the dynamic system failure probability and reliability index of concrete gravity dam were obtained in terms of the correlated and non-correlated failure modes. The results indicate that the reliability levels have relation to various failure paths. The corporate influence of the different failure path on system's reliability of pile foundations should be considered.