Appraisal Of Improvement Effect Of Soft Soil And Analysis On Dynamic Response Of Subgrade Of High-Speed Railway

With the rapid development of our national economic,traditional railway hasn't satified the great need of modern people. As a new transportaion vehicle,the high-speed railway has the advantage of fast,comfortable and high efficiency,which is being accepted by the public.The high-speed running of train needs a extremely smooth and stable foundation.The subgrade which is the foundation of track system must maintain the designing parameters of track within a standard under the operating condition.《Design Temporary Code for Jing-Hu High Speed Railway》tells:The value of the post-construction settlement of the subgrade is no more than 5cm.The settlement value of per year is less than 2cm in the early stage after the construction is completed.The total length of the soft soil in Xia-Shen line is 142.7km.Therefore,the effective controlling of post-construction settlement and elastic deformation pruduced by temporary high-speed train load become key point of designing and construction of high speed railway subgrade.The post-construction settlement of soft soil subgrade includes the fill compression,the plastic deformation provoked by running of train and the post-construction settlement generated by soft soil.Among them,controlling the post-construction settlement generated by soft soil is the chief task.In order to guarantee the post-construction settlement of subgrade to satisfy the standard of high speed railway,a trial subgrade was acted over soft soil,the methods of ground improvement were plastic drainage board combined with vacuum and plastic drainage board combined with surcharge preloading. The properties of settlement and interstitial water pressure were studied,meanwhile,gave appraisal of controlling effect of post-construction settlement between the two methods described above.According to the deformation and vibration characteristics of all the parts of track-subgrade system,meanwhile combining with Xia-Shen high-speed railway,the subgrade analysis system model is established,meanwhile,the current finite element software ANSYS has been to doing dynamic analysis of subgrade in this paper.The track is modelde as beam element on discrete pad-tie support,the sleeper,ballast,subgrade and foundation are discretized into eight-node solid elements,the non-linear factors about materials which are underneath the sleeper are also taken into account. As can be seen from the results,the modulus of elasticity of top layer of bedding have large effect on acceleration of the top surface of subgrade,yet,the modulus of elasticity of soft soil has large effect on displacement of top subgrade.