| Today, numerical simulation analysis is more and more important in the engineering geology research field, especially in the quantitative evaluation. Relating closely to the main problem of the high sidewall and wide span underground cavities excavation stability of Xiluodu hydroelectric project, the evolution characters of geo-stress field in deep-cutting gorge and the whole features of the stress field, strain field and plastic failure zone around the underground chambers after excavation are studied systematically in the dissertation, based on a great deal of data gathered in field investigation and taking the FLAC3D V2.0 software as basic computation tools. Meanwhile, In the course of research, the new methods of dynamic numerical simulation are summarized and applied. Furthermore, the effects of Rock Mass Qualities, initial geo-stress field and Excavation Procedure on Surrounding Rock Mass Stability are discussed. The main achievement in the paper can be drawn as follows:(1) As a most important achievement, the concepts of numerical simulation are expanded. Three composition parts of dynamic numerical simulation are put forward clearly e.g., building the dynamic numerical simulation model, designing the simulation process and the output controls of the simulation computation results. Each part should connect tightly with the study results of engineering geological condition and the deformation and failure of rock mass in the investigated area. The dynamic numerical simulation should replay both the whole course of geological process and real human activity. It is an interactive dynamic analysis course that the computation results are coincident to the new engineering geological messages and changeable features of the rock mass deformation and failure.(2) As an important outcome in the paper, the author developed the FLAC3D Pre-processing package in the basis of the 12 primitive meshes provided by FLAC3D, which can construct the calculating model containing the actual topographic and geological features of the investigated area automatically. Thus, it can not only improve the calculating precision, but also decrease time consuming greatly. And the design method of the program is a good help to the same kind of programs.(3) According to the new methods of dynamic numerical simulation analysis, the computation model of the deep cutting gorge is contracted with FLAG30 software and FLAG30 Pre-processing package, the reasonable simulation course is designed and the calculating results is controlled effectively. Finally, the forming process and the evolution features of the 4 stages geo-stress field evolution in Xiluodu gorge are displayed in the paper, from which the variable regulations are analyzed and summarized systematically. These achievements can be regarded as creditable evidences for technocrats to solve some problems of geo-stress field in Xiluodu area.(4) According to the new methods of dynamic numerical simulation analysis and resting on the engineering geological conditions of surrounding rock mass and the project design, the threenumerical simulation results are obtained, from which the author analyze systematically the distribution features of stress field, strain field and plastic zone in the surrounding rock mass of the underground cavities after the excavation and also the variable features of stress field, strain field and plastic failure zones in the surrounding rock mass of the underground cavities in the course of excavation. And that, the variable regulations of stress field, strain field and plastic failure zones in the surrounding rock mass of the underground cavities are summarized for the right and the left bank of underground chambers. The main results can be taken as the basic data and the theoretical proofs to evaluate cavities stability and guide the correct excavation.(5) Relating closely to the engineering geological condition and the project design of the underground cavities in the right side bank of Xiluodu, the effects of Rock Mass Qualities, initial ge...
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