Research On Permeation Characteristics And Settlement Prediction Of Subgrade Filled With Clayey Sand

Because of its high strength,clayey sand is often used as filling material for highway subgrade.The content of clay has a great influence on its permeability and strength,which directly determines the filling quality.Based on the project of majang high-speed filling section of sandy soil containing clayey particles,compaction tests and permeability tests were carried out on sandy soil with different red clay content,and the permeability and compaction properties of sandy soil containing clayey particles were studied from the aspects of different clayey particle content and different degree of compaction.On this basis,the following settlement observation and settlement prediction of the embankment are studied.The main work is as follows:Firstly,in view of the settlement damage caused by scouring after rain,a certain amount of red clay is added to the sandy soil to improve the sandy soil subgrade.The permeability coefficient of sand with different clayey content was obtained by the improved permeability test,and it was found that the permeability coefficient decreased with the increase of clayey content.Secondly,through compaction test,the influence of different compaction degree on the subgrade containing clayey sand is studied.The results show that the permeability coefficient of sand with the same clayey content decreases with the increase of the compactness,and the permeability coefficient of sand with the same compactness decreases with the increase of the clayey content.Then,three typical sections,namely,K147+510 of preloading treatment,K149+650 of sand cushion treatment and K151+120 of cement mixing pile treatment,were selected to conduct settlement observation tracking for 288 days.The settlement observation results show that the final settlement of section K147+510 is 416 mm,that of section K149+650 is 445 mm,and that of section K151+120 is 494 mm.Sedimentation variation law of three typical sections are as follows: as the growth of the settling time,subgrade top load increasing,soil consolidation speed is accelerated,sedimentation rate increased gradually,and then to design level,filling the upper does not continue to increase the load,the soil consolidation began to stabilize,sedimentation rate gradually decreases,and reach the final settlement.Finally,an isochronic grey GM(1,1)model is established to predict the settlement of K150+480 section by MATLAB programming.By comparing and analyzing the prediction results of the isochronous grey GM(1,1)model with those of the hyperbolic method and the three-point method,it is found that the accuracy of the model prediction results will be more reliable with more sets of measured settlement data and greater time interval.The isochronous gray GM(1,1)model is more suitable than other prediction methods for the settlement prediction of the high-speed section of mayang sand filled with clay.