The Research For Surrounding Rock Stability Of Construction Excavation Based On Underground Laboratory For Disposal Of High-Level Radioactive Waste

Nowadays,more and more attention has been focused on environmental protection and climate change.As a result,nuclear energy,because of its clean and efficient advantages,attracts increasing attention from all over the world,and has become an important energy for human use.However,with the rapid development of China's nuclear industry,there was a certain amount of accumulated high-level waste.So whether the high-level waste can be disposed of safely or not has become the strategic issues of China's nuclear industry sustainable development and environmental protection.At present,deep geological disposal is internationally accepted as a safe measure.The high-level radioactive waste disposal project has the characteristics of complex construction conditions,high safety grade and long service period(tens of thousands of years),which determines that the process of site selection,construction and safety evaluation is extremely complicated and difficult.Meanwhile,there was a lack of practical engineering experience because nobody has experience of the whole disposal process predecessors.As a result,in many countries,establishing one or several underground laboratories for high-level radioactive waste disposal is explicitly required in high-level radioactive waste disposal plan.The underground laboratories can be used to understand the deep geological environment and geostress status,provide access to deep rock and water samples,and test the long-term performance of the barrier in the real deep geological environment.In the process of constructing underground laboratories,stability analysis of the cave is quietly essential to ensure that the project is reasonable,safe and stable.Therefore,this paper takes the construction of underground laboratory of a high level radioactive waste disposal in China as the engineering background,uses theoretical analysis,experimental research and numerical simulation to carry out research on the stability of underground caverns and obtain some results,in order to,come up with some reasonable advice for the underground laboratory design and construction.The results of this paper are as follow:Firsty,according to the geological prospecting data of the pre-selected laboratory,the BQ method,RMR method,Q system method and GSI method are used to classify the rock mass of the underground laboratory pre-selection area respectively.Based on the comprehensive analysis,it is concluded that the quality of the pre-selected rock mass is better,and the ?-type rock mass is the main.Secondly,based on the Hoek-Brown criterion,combined with the geological strength index(GSI)rock mass grading system,the sensitivity analysis of the influence of mechanical parameters on the stability of the underground laboratory chamber was carried out,and the sensitivity of the Hoek-Brown criterion mechanical parameters was calculated(GSI),among which rock mass disturbance parameters(D)are the most sensitive.Thirdly,based on the Hoek-Brown criterion and the GSI rock mass grading method,the strength of the pre-selected rock mass is calculated according to the results of the rock mass quality grading of the pre-selected laboratory,and the mechanical parameters of the pre-selected rock mass are determined.Fourthly,through the numerical calculation method,the research on the influence of different excavation methods on the stability of the caverns is put forward,and reasonable suggestions are put forward for the construction of underground laboratory.Fifthly,through the numerical calculation method,the research on the influence of different geostress field characteristics on the stability of the caverns is put forward,and reasonable suggestions are put forward for the construction of underground laboratory.Sixthly,through the numerical analysis method,the numerical simulation analysis of the whole excavation of the cavern group is carried out,and the distribution law of the displacement chamber,the secondary stress field and the plastic zone of the underground laboratory chamber are obtained,which makes a reasonable basis for the overall construction of the underground laboratory.which in the meantime provides reference and guidance for the development of the verification test of the geologic model of the underground laboratory excavation.