| The impact force of rockfall has an important influence on the design and safety of the passive protection structure like tunnels, however, it cannot be calculated accurately because of many influencing factors, and its influence is not considered by reliability design method of passive protection structure like tunnels at present. In this paper, calculation method and the impact effect are studied. The main research contents and results are as follows:(1) Assessment of rockfall impact forceModeling, calculation and analysis were done using particle flow code based on the discrete element method. The influence of height, weight of the rock, the gradient of the mountain slope and thickness of backfill soil to impact force of rockfall was studied and focus of the study was the influence of the thickness of backfill soil to rockfall impact force of passive protection structure like tunnels.Comparison and analysis of calculation results of different methods at home and abroad were done, the principles of various calculation methods were learned, and the rationality of the results of rockfall impact force was analyzed. Then, a recommended value of thickness of backfill soil was provided.By reading the relevant literature and projects information at home and abroad, the principles of various calculation methods and factors considered were learned. Formula of rockfall impact force was derived using methods of data fitting and multiple linear regression based on the calculation results.(2) Study on impact effects of rockfallAn anti-rockfall shed tunnel structure model was established using particle flow code based on the discrete element method and data of stress from different parts of the shed tunnel like roof, stringers, columns and bases were recorded and extracted and finally curves of stress-time and were drawn. After that, the dynamic response of the rockfall impaction on shed tunnel was analyzed and the conclusion can provide a theoretical design basis for design of sheds tunnel. |
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