Dynamic Response Of Collapsible Loess Sections Of High-speed Trains To Run Under The Roadbed Lime Soil Compaction Pile

Combining engineering background of yangling northern station on Seebio passengerline, the segement observations on soil Compaction Pile Composite Foundation Settlementhas been collected. Using of complex modulus method, layered summation method and thetranslation soil column method to do theoretical calculations. Using finite element softwareABAQUS to establish preload static load models and non-ballasted track model consistentedwith field sizes. Using artificia excitation method to imitate train dynamic load. On this basis,Train loads effecting on soil compaction pile composite foundation settlement characteristicsand power attenuation characteristics has been conducted a correlation analysis. The mainfindings are as follows:1.Both displacement settlement law of the subgrade and dynamic load attenuation lawwere not changed for the the changing of speed, cutting thickness, pile length, pile diameterand pile spacing.They diminishing in non-ballasted track as the center, along the the depthand horizontal direction.2. The center is the main position High-speed Rail load transmission, compositefoundation settlement displacement is butterfly The maximum displacement of settlement ofthe whole composite Foundation lot appeared at the bottom of the non-ballasted track. Themaximum vertical velocity, size is about4.76mm/s, appeared in the upper half ofnon-ballasted track and cutting. Decay rate of Train load In the cutting section of road lessthan composite foundation segment.3.Changes of train speed showed a critical speed existed. When the train speed is lessthan the critical speed, the speed increases and subgrade settlement larger; When the trainspeed is greater than the critical speed, the speed increases, and subgrade settlement reduced. When lots in loess, the critical speed of lime-soil compaction pile composite foundationshould be between300km/h and350km/h. Upgrading train speed lead to the scope ofdissemination of Train load Expanded in the subgrade and train load decay rate decreases. theprocess of train speed increased from300km/h to350km/h, amplitude attenuation of verticalspeed is significantly greater than the process of train speed increased from200km/h to300km/h.4.As cutting thickness is not the same and at constant speed (300km/h), results are asfollows.Cutting thickness increases, Train load distribution is more uniform in the Cut, therelative displacement reduced between the pile and the soil pile, Train load spread expandedin the subgrade, train moving loads smaller in the following of cut the top surface, anddynamic load decay rate in the depth direction becomes large.5.As Pile length is not the same and at constant speed (300km/h), results are asfollows.Pile length increases，between the pile and the pile of soil subsidence, displacement ofthe entire embankment subsidence decreases, but to reduce the magnitude is not large.Therefore, when the composite railroad roadbed construction, do not blindly increase thelength of the pile to reduce the subgrade settlement.6.As Pile diameter and pile spacing is not the same and at constant speed (300km/h),results are as follows. When pile diameter and pile spacing becomes smaller, settlement valuedifference between the top of the pile and the pile of soil decreases. When the pile spacingunchanged, with the pile diameter increases, sedimentation of the top surface of the compositefoundation and entire roadbed reduces. Compaction effect a small number of big pile diameterpile is smaller than a large number of Small pile pile diameter. With the cutting section isreduced, pile diameter and pile spacing decreases can effectively reduce the dynamic responseof train load. In paragraph composite foundation, it has little effect on dynamic response oftrain load.