Study On Settlement And Deformation Law And Prediction Of Loess High-Filled Roadbed In Northwest Hebei

The northwestern Hebei region is surrounded by mountains,ravines and ravines,and there is a wide range of collapsible loess.There are many loess high-filled roadbed engineering problems in the highway construction in this area.The settlement and deformation of loess high-filled roadbed is a difficult problem in roadbed engineering.Its uneven settlement and excessive settlement will cause settlement and cracking of the road surface,which will affect the normal operation of the road.Research on the law and prediction of settlement and deformation of loess high-filled roadbed is beneficial to ensure the safe use of loess high-filled roadbed and reduce the cost and difficulty of later road maintenance.The article combines the subject of "Key Technology Research on the Stability of Collapsible Loess High-filled Roadbed in Northwest Hebei",and takes the loess high-filled roadbed of the Hebei section of Yan-Chong Expressway as the supporting project.Through indoor physical and mechanical tests of loess in northwestern Hebei,on-site loess high-filled roadbed settlement monitoring,settlement monitoring data processing analysis and numerical simulation methods,the settlement deformation of loess high-filled roadbed is studied.The main research contents and results are as follows:1.Through indoor physical and mechanical experiments,basic parameters such as particle size distribution,liquid-plastic limit,optimal moisture content,maximum dry density,and loadbearing ratio of loess in northwestern Hebei were obtained,which were evaluated as roadbed filling soil indicators.Consolidation test and triaxial test were used to analyze its compression characteristics and shear strength characteristics,and the compressive modulus and shear parameters under different compaction degrees and moisture contents were obtained,which provided references for later numerical simulations.2.By analyzing the monitoring data of pavement settlement and layered settlement of filling body,it can be concluded that the settlement of shoulder position is greater than that of roadbed center,loess high-filled roadbed is susceptible to the freezing and thawing of the filling caused by the replacement of winter and spring,resulting in a short-term increase in settlement rate.Due to the influence of filling time and soil load on settlement and consolidation of different soil layers,the settlement of the second and third layers in the middle is greater than that of the first and fourth layers,and the settlement of the third layer is the largest.The settlement of the original foundation accounts for about 23% of the total post-construction settlement of the loess high-filled roadbed.3.Based on the measured data,four settlement prediction models are established,and the characteristics and prediction accuracy of each model are analyzed.The results show that the four models can predict the short-term settlement well,but can not predict the final settlement of roadbed.A hyperbolic-Gompertz combined prediction model was established by variable weight recombination method,which can complement each others advantages with a minimum prediction accuracy of 27%,and can predict the final settlement of loess high-filled roadbed more accurately.4.Using the numerical simulation method to study the settlement and deformation of loess high-fill roadbed in the process of layered filling,it is obtained that the maximum settlement occurred at 1/6～1/2 from the original foundation during the filling process.At the same height,the settlement in the center of the deformation roadbed is greater than that at the edge of the roadbed,showing a "U" shaped distribution.With the increase of the filling height,the horizontal displacement and deformation area gradually increase,and expand to the roadbed filling body.5.Analyze the influence of compaction,moisture content and filling height on the settlement and deformation of loess high-filled roadbed with the help of numerical modeling.It is obtained that the roadbed settlement has a quadratic function relationship with the degree of compaction,a linear positive correlation with the water content,and a positive correlation with the fill height.When the water content increases by one percentage,the settlement increases by about 4%～8%.When the degree of compaction reaches 96%,the effect of increasing the degree of compaction on settlement is not obvious.