Application Of Two-Factors Model In Prediction Of High Filled Settlement In Loess

With the steady development of China's western development strategy and the plan for the rise of the new central region,the state's investment in infrastructure along the route has gradually increased,and the construction of road engineering is an important part of it.The provinces in the central and western regions of China,such as Gansu,Shaanxi,Shanxi,Inner Mongolia etc.are areas of the Loess Plateau.When constructing roads in these widely distributed areas of loess,they are subject to various geological and topographical conditions.In order to solve the special terrain such as deep ditch encountered in the construction of loess area,the construction method of loess high fill embankment came into being.The loess high fill embankment is a unique subgrade treatment method in the loess distribution area.It has the advantages of convenient and quick construction,reasonable construction cost and close access to the filling materials.Since the previous research on high-fill embankment was mainly concentrated in the soft soil category,the theoretical research on the loess high-fill embankment was scarce.A series of problems affecting the safety and stability of the embankment caused by the difference in settlement in the embankment construction project and the large settlement during the use of the work.Therefore,it is of great significance to use the reasonable method to detect and predict the settlement of loess high fill embankment for the normal use of high-grade highways.The main purpose of this paper is to use the new settlement prediction model to predict the settlement of the loess high fill embankment treated by the specific pressure implementation method to ensure the normal use of the road.Based on the study of the loess high filling project of the Yanjiafeng section of Taihang Road,this paper investigates the settlement data of pavement,embankment and original soil foundation of loess high filling section,and summarizes their settlement laws.By looking up the literature,we can find a new settlement prediction model suitable for loess high fill embankment under the condition of heavy hammer compensation construction method(compaction degree is 0.93-0.95).The conclusions are as follows:1.Conclusions from in-situ settlement monitoring test of loess high filling section(1)Analysis of the settlement curves of the east-west road surface is available.They all have a faster settlement rate within 0-100 days,a larger settlement,and reach the maximum settlement value in the same period.After a period of fluctuation in the sedimentation curve within 100-200 days,the sedimentation curve is transiently stable.The sedimentation rate increases within 200-350 days,and the sedimentation value continues to decrease,gradually reaching stability.(2)The monitoring results of the settlement of the filling body show that due to the influence of terrain conditions and other factors,the settlement on the west side of the filling body is the largest,the middle part is the second,and the east side is the smallest.(3)The main component of road surface settlement is the settlement of high-fill embankment,which accounts for about 90%of the total settlement of the road surface,and the settlement of the original land base accounts for 10%of the total settlement.2.Conclusions from the prediction model of loess high fill embankment settlement(1)The two-factor settlement prediction model consists of a final settlement control function and a process control function.The final settlement control function only affects the final settlement of the fill.The process control function is responsible for controlling the development trend of the settlement of the fill.It has an important influence on the settlement of the fill at a certain moment.(2)Analysis of the two-factor settlement prediction models at the east,middle and west sides of the high-fill embankment shows that the final settlement control functions in their settlement prediction models are linear functions.The settlement control function of the east side embankment is an exponential function,and the control function of the settlement process in the middle and west is a hyperbolic function.Their MAPE values are distributed between 1.5 and 3.1,and the prediction accuracy is higher than other high-fill embankment settlement prediction models.The two-factor settlement prediction model can be considered in similar projects in the future.(3)By summarizing the previous research results,it is found that the optional types of parameters in the settlement process control function are:linear function,polynomial function,exponential function.The type of parameter aH in the settlement process control function of the east-west embankment prediction model is a polynomial function,and the type of parameter aH in the control function of the intermediate embankment prediction model is a linear function.In the engineering application,the aH function type with higher fitting degree should be selected according to the actual situation.