The Study On The Settlement Law And Prediction Of The High-filled Loess Embankment

Nowadays,with the rapid development of economy in China,the mileage and density of the highway have been greatly improved.The structure of high embankment is very common in building road in the mountains with complex terrain.Loess is regarded as the main filler in the area covered with loess widely in order to attain save the cost of embankment filling.Therefore,it is necessary to study the settlement law and prediction of loess high-filled embankment on the basis of understanding the physical and mechanical properties of loess filler.The author adopts the project of Yan Jia Feng Road belonging to Taihang Road in Taiyuan as the subject.First,the monitoring for settlement after construction of high-filled embankment lasted for a year.As the same time,the indoor test for compacted samples with different depths was carried out.Then study the settlement of the loess high-filled embankment on the based of the test data obtained from indoor test and outdoor test.The main research contents and conclusions are described as follows.1.The physical and mechanical characteristics of Loess.It studied the soil samples of compaction soils with different depths obtained at different depths of Dongshan in Taiyuan.The research contents mainly include the particle diameter of loess,the liquid and plastic limit,the optimal moisture content of the maximum dry density and the compression properties.The test conclusions are:?1?The void ratio changes in cycle with the depth of embankment and the cycle is 1/4 sine wave.The void ratio is the least at the interface of the hammer.?2?The high-filled embankment has been significantly reduced because of lateral rolling and heavy tamping,and all of them become medium and low compression soil.?3?Loess has a hardening characteristic.With the improvement of stress level,loess stiffness will become larger.2.The settlement monitoring results of the high-filled Loess embankment.Five sections were selected from the high-filled Loess embankment to monitor longitudinally.The settlement monitoring results show that:?1?According to the position of the settlement magnetic ring in the settlement hole,the high embankment is divided into four layers.The sedimentation rates of the second and third layers change faster and the compression is larger.However,the settling rates of the first and fourth layers are relatively stable and the compression is smaller.?2?The high-filled Loess embankment has a faster settling rate in about nine months of pre-settling,followed by a slow settling rate,and the final settling rate tends to zero.?3?The settlement value of the high-filled Loess embankment is largely affected by the height of the filling and the terrain.The lower the embankment height is and the greater foundation constraintion on embankments is,the smaller the settlement value of the embankment is.The settlement of the original foundation is about 10% of the total settlement of the embankment.The linear fitting relation is 's=1.109h-3.3889 between the settlement value and the filling height of the high-filled embankment.3.The settlement prediction for the high-filled loess embankment.If the law of change about the settlement value over time is considered as a system,because of the less obtained data about the high embankment settlement monitoring,the system can be called as a gray system with the poor information and a small sample.It will be more effective to study the gray system by using the gray system theory.Based on the GM?1,1?a model proposed by Professor Deng Julong in 1982,this paper uses the cubic spline interpolation function to generate the gray sequence needed by the model.The results are gained by the model calculation during the early and later settlement of the high-filled embankment.The relationship between s and t is ???⁰?t?= 7.980)0.216?-1?and ???⁰?t?= 26.760)0.009?-1?.in these two periods,the gray proximity correlative values of the original and predicted sequences are 0.65 and 0.998.The proximity correlations of the later settlement are higher than that of the early settlement.The Average absolute percentage error values of the original and predicted sequences are 7.65 and 0.61.The Average absolute percentage error of the later settlement is lower than that of the early settlement.Gray model is used to the later settlement of the embankment,and the accuracy of the prediction result will be higher.4.The finite element supplement analysis of settlement of the high-filled Loess embankment.According to the actual and simplified engineering overview,finite element analysis model is obtained.The Mises stress contour plots,vertical displacement contour plots and horizontal displacement contour plots are summarized by analyzing using the finite element ANSYS software.By contour plots,it was found that:?1?The embankment of the high embankment has a small settlement after the embankment packing has been treated by stratified rolling and heavy hammer.?2?The horizontal displacement of the high embankment in foot is too large,and the compaction of the soil in this area should be strengthened.