Research On Dynamic Characteristics Of High-speed Expressway Low Embankment In Riverine Plain Area

Highway low embankment design is to save the land resources, saving investment, construction is convenient, safety, landscape coordination, less roadbed disease etc. But reduce the embankment height also has its new problems, mainly including:low embankment vulnerable to surface water erosion and groundwater seepage, thus reduce the bearing capacity of the subgrade; Due to the low embankment height, the traffic load in embankment can’t fully diffusion and transfer to the foundation, thus increased the foundation settlement and deformation. In addition, the traffic load caused by the vibration is also easy to cause the foundation soil uneven settlement. These problems can be attributed to water, the traffic load of the role of the subgrade. Therefore, it is a key technical problems how to analyse the affact of traffic load on low embankment subgrade. Based on this starting point, this study focus on the following several aspects to study the traffic load of roadbed under the action of dynamic response to the subgrade state influence:(1) based on the information at home and abroad research, master the traffic moving load and water on the major effect of the roadbed and its mechanism, clear up this kind of influence the means and methods, and based on this, puts forward low embankment subgrade research existing main shortage and improvement methods.(2) puts forward traffic load on low embankment influence field test method. The method adopted the in situ test technology, based on the actual through the vehicle for vibration source, test content including surface vibration, roadbed internal structure dynamic response, etc., and introduced the test element embedded plan, plan including test position selection, applicable element performance, embedded technology, can be used as the reference for the other similar.(3) the field test for different vehicle load caused by the road of the pavement structure layer, road bed and road surface dynamic stress and dynamic strain, vibration acceleration and dynamic displacement and vibration data, analyze think, subgrade top surface dynamic stress along the depth direction attenuation, is apart from the pavement top0.7m place dynamic stress decay60%; Various structural layers in the highway traffic load dynamic stress with the increase of the linear increase, Pavement dynamic deflection of the time domain waveform is mainly composed of low frequency component, and is mainly affected by vehicle load effect. Pavement structure layer dynamic response with the speed of increase and decrease, and stress change along with the increase of the load.,(4) according to the testing data to establish the finite element calculation model, to supplement the test test unable to get the dynamic response of roadbed state. It is found that when using standard120kn amplitude loading, transportation influence dynamic load at a depth of2.5m scope is quite obvious, vibration acceleration sphere of influence in less than5.5m; Along with the load amplitude increase dynamic stress increases; The traffic load the same condition, the embankment height, significant decrease with height embankment settlement increase obviously; But pavement modulus increase the settlement is less affected.