Research On Dynamic Response And Settlement Prediction Of Low Embankment Of Soft-foundation Highways

The highway low embankment scheme is used in soft soil areas because of its features such as reduced land occupation,reduced engineering volume,safe and comfortable driving,low post-construction settlement（static load）,and easy control of construction quality.There are many hills in the Fujian-Zhejiang area,and it is convenient to use the slag to fill the roadbed.In addition,the strength of the subgrade filled by the slag is very high,and it also has a certain degree of water permeability,so it is very suitable for the construction of high-grade and low embankment roads.However,due to the low filling height and low rigidity,the increasing traffic volume,the increase in vehicle speed,and the substantial increase in vehicle load,the low embankment under the action of the traffic cycle load appears loose roadbed slag filling and excessive permanent deformation and foundation The dynamic stress affects the depth expansion and causes the phenomenon of excessive settlement and deformation.This greatly reduces the service life of the road and seriously affects the comfort and safety of driving.At present,whether it is scientific research or engineering practice,there is still insufficient attention to the research on the stress and deformation characteristics of low embankment in soft soil area under traffic load,especially the low slag embankment.Therefore,the operation status of subgrade projects represented by low slag embankments has a short-term effect on maintaining the long-term safe and stable operation of road projects in soft soil areas in our country,and restricts the overall situation.Therefore,in view of the above problems,obtaining the stress and deformation characteristics of the slag&soft-soil structure system under traffic load is the basis for solving the problem of restricting the promotion of low slag embankment in soft soil areas.The article uses numerical simulation and field test as the main research methods,supplemented by theoretical analysis,and carries out the following research:（1）Developing subroutines by the PFC5.0^2Dplatform,a two-dimensional discrete element model of the slag roadbed was established,and cyclic moving harmonic loads of different properties were applied.In this thesis,a standard truck driving test on site was carried out,and the combined working conditions of different loads and different speeds were set.Combined with the pavement-elastic layer-saturated porous half-space dynamic response analytical model,the dynamic response law of“asphalt pavement-low slag embankment-soft soil foundation”is discussed.And reasonably determine the depth of the roadbed work area through the attenuation state of the dynamic parameters of each structure layer.Provide reasonable suggestions for the promotion of low slag embankment.（2）The mesoscopic mechanism of slag particle breakage evolution and cumulative plastic deformation were discussed through the PFC5.0^3Dsimulated slag failure triaxial test,and the cumulative plastic deformation mechanics-empirical model was established according to the slag stress-strain curve.The on-site vibration test was carried out through the SBZ30 variable frequency torque converter vibrator independently developed by the Chinese Academy of Railway Sciences to simulate the1.5-year operating life of the road and obtain the long-term settlement development trend of the dynamic load of the slag subgrade,and compared it with the calculation result of the model to test the scientificity of the model.（3）On the basis of summarizing the dynamic triaxial tests of two typical saturated soft clays in the Shanghai area,the coupling effect of dynamic and static deviatoric stresses is fully measured,the coupling stress level is defined,and the strength attenuation model of soft soils under the influence of cyclic loading is revised.The limit value of softening index is added,the concept of modified coupling stress level is proposed,and the cumulative plastic deformation of soft soil is established that comprehensively reflects the coupling effect of dynamic and static deviator stress,confining pressure,soil structure,strength weakening,and loading times.The model is used to calculate the long-term settlement of soft foundations,and the rationality of the model is tested with the example of Shenjiahu Expressway.In this thesis,the dynamic influence depth range and dynamic parameter law are obtained through the dynamic response research,and the long-term settlement calculation of the traffic load is carried out in（foundation）mechanics-empirical models.This research provides scientific guidance and theoretical basis for the promotion of low-slag embankment road forms in soft soil areas.104 figures,31 tables,and 117 references...