Abstract：Research purposes: The analysis and research were done on the structural dynamics of the subgrade of Qinghai-Tibet Railway in permafrost region under the load of train for the purpose of providing the basis for design of subgrade in permafrost region and making analysis of railway operation.
Research methods: Taking the subgrade structure in test section of Qinghai-Tibet Railway in Qingshuihe permafrost region as object，the finite element time-histories reactive analysis was done by using the excited curves of roadbed bottom under train load obtained from two dimensional dynamic model，and the exploration was made on the subgrade effects to the train vibration load under freeze-thawing condition.
Research conclusions: No matter whether under the thawing condition in warm season or under freezing condition in cold season，the pressure stress of soil body caused by train vibration load is much higher than that under static load and the stress of soil body influences the train speed obviously. Under freezing condition，the soil body in middle and bottom parts of subgrade has a larger dynamic effect，but under thawing condition in warm season，the soil body on the subgrade has obvious amplification effect to dynamic stress. Therefore，the structure should be reinforced correspondently in engineering design and maintenance
2007, Vol. 24 
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