Dynamic Response Of Warm Permafrost Subgrade Under Train-induced Dynamic Loads

Along with advance of China’s Western Development, the subgrade construction incold and arid region also boosts steadily and systematically. There are numerousengineering problems and challenges for lifeline systems built in permafrost zone,including roads, railways, pipelines and etc. Especially those in warm permafrost haveto guarantee heat stability of subgrade under permafrost, and keep long-time dynamicstability of it. This is why researchers in the field of subgrade engineering focus on it.In-situ results in Qinghai-Tibet railway indicate that degradation of permafrost regionsand increase of mean annual temperature also appear in warm permafrost regions.Temperature rise in cold and arid region will affect working environment ofQinghai-Tibet railway. For in-service building, such affection would be worse.Hence on the basis of materials summarizing of ordinary and warm permafrost,research on train vertical load pattern model by means of exciting force, this paperestablish two-dimensional numerical subgrade model by ABAQUS, and analyzedynamic responses of subgrade under warm permafrost for different motor speed.Details are as follows:Firstly summarize characters of train load pattern on the subgrade, includingcombined pattern of train-track coupled system, simplified calculation method ofdynamic stress on the subgrade given by codes, and train load model by means ofexciting force.Secondly, distribution laws of vertical dynamic stress of points along depth ofcenter line of subgrade section and vertical lines beneath the tracks, and subgradesurface, have been found and made comparisons with those of geostress. Furthermoredistribution law of dynamic stress along depth of center line of subgrade section is quitedifferent from that along depth of vertical lines beneath the tracks. This paper takesmodel under train speed of60m/s as example, analyzesattenuation of subgrade verticaldynamic stress along depth and distribution law of that on the subgrade horizon bynumerical simulation, and concludes attenuation ratio along depth of subgrade. Itapproaches data measured actually and theoretical calculated values by Japan railwaycode very well.Finally,taking contrasts of distribution laws of subgrade vertical dynamic stressunder different speed and results indicate that obtained amplitude curves of those aresimilar and main difference is values of amplitude. However calculation values of it onthe shoulder region approach well.