Study On Dynamic Response Of Ballastless Track Subgrade Under Traffic Load

The CRTS Ⅲ slab ballastless track,thoroughly and undoubtedly pioneered by China,due to its superior and remarkable performance,has been used and promoted exceedingly and literally over these years.The subgrade has been put forward more stringent requirements,which primarily plays the role of track foundation.Besides,it is predictably pivotal and notable that dynamic load is accurately calculated in the process of studying the dynamic response of subgrade.Hence,inevitably and spontaneously,how to deal with the train load and research on dynamic response of the ballastless track subgrade has become a momentous node.On the basis of summarizing the relevant research,the dynamic response of subgrade concerning CRTS III slab ballastless track was studied by means of theoretical analysis and numerical simulation.The main research contents are as follows:(1)Considering the dynamic characteristics of vehicle,wheel rail contact relationship and random irregularity,the vertical coupling model of train-track was established exceedingly.On this basis,the safety stability indexes,such as wheel-rail excitation load,derailment coefficient,wheel weight reduction rate,lateral and vertical vibration acceleration and Sperling coefficient,were obtained at four speeds of 200km/h,250km/h,300km/h and 350km/h respectively.By comparing with the current standard limit of high-speed railway,it is considerably reasonable that the model adopted in this paper is literally superior and meets the specification requirements.Moreover,there is a notably positive correlation between safety and stability index results and vehicle speed.(2)The finite element model,concerning ballastless track-subgrade-natural foundation,was adequately and completely used to study the time history,transverse and vertical distribution of subgrade.Besides,the effect of material properties and vehicle speed on response of subgrade was analyzed,which supply an unexceptionable basis with optimization of subgrade dynamics.It can be concluded that subgrade has an extremely crucial effect on absorbing,dispersing and buffering the dynamic effect,and there is a damage between the edge of concrete base and subgrade,notably and easily.Enough attention should be paid to the design,construction and operation maintenance.(3)The double line finite element model,concerning ballastless track-subgrade-natural foundation,was adequately and completely used to study the response of subgrade under single line and double line.It can be inevitably concluded that the dynamic response of subgrade under double line will be more even.However,due to the existence of the superposition effect,the dynamic response under double-line opposite operation is exceedingly greater than that under single-line operation.Furthermore,there is a remarkably positive correlation between the depth of subgrade and superposition effect.Compared with the single-line train operation,it is extremely obvious that the double-line opposite operation will undoubtedly aggravate the dynamic action in the subgrade and cause greater damage to the subgrade.