Study On Load Reduction Of EPS Plate Of High Fill Culvert With Laterite Gravel

With the extension of The Belt And Road initiative implemented,China’s overseas infrastructure projects are increasing day by day.In the process of transportation construction in Africa,due to the fact that part of the line needs to cut across primeval forest and the terrain fluctuates greatly.In order to ensure the development of transportation and inter-city connection,high-fill and high-excavation sections appears in the line design.High fill sections with culverts are prone to Marston effect,which has obvious influence on the safety of culvert structure.In addition,the special laterite gravel material in Africa is often used for replacement in the project,which has a unique impact on the culvert.Laying EPS plate on the top of culvert can effectively reduce the additional stress caused by high fill subgrade to culvert.Therefore,it has theoretical value and engineering significance to study Marston effect of culvert under high fill laterite gravel and influence factors of load reduction of high fill culvert under laterite gravel with EPS plate.Based on Cameroon Yaoundé-Douala Expressway construction project,this paper studies the load reduction effect of EPS plate of high fill culvert with laterite gravel.The main research work is as follows:(1)The mechanical analysis of laterite gravel of Cameroon Yaoundé-Douala Expressway is carried out,and the Marston effect of high fill culvert and the load reduction effect of EPS plate are studied through in-situ test;(2)The stress-strain characteristics of EPS material under 40% strain were studied by uniaxial compression test and finite element simulation analysis;(3)The load reduction effect of EPS plate with different density and thickness on Marston effect of culvert was studied by indoor scale model test.(4)Through numerical simulation,the influence of density,thickness and laying height of EPS plate on the effect of culvert Marston effect were analyzed.The results show that:(1)Laterite gravel has the characteristics of high liquid limit,high friction angle,loose structure,low cohesion and good grading,which is a kind of filler in line with the road standard.Marston effect will produce more obvious additional stress on culvert roof.Laying EPS plate can effectively reduce the Marston effect.(2)When the strain of EPS material is less than 40%,its stress-strain shows obvious elastic stage and plastic stage,and the elastic modulus of EPS material has a certain linear relationship with material density.The Crushable Foam model can simulate EPS materials with high precision.(3)Vertical earth pressure on culvert roof is sensitive to the density change of EPS plate in the load reduction effect of culvert roof,generally sensitive to thickness change.The lower the density of EPS plate is,the thicker it is,the better the load reduction is.In the study of the horizontal earth pressure of culvert sidewall,the density and thickness variation of EPS plate had no obvious effect on the horizontal earth pressure.(4)The sensitivity order of the influence of related parameter of EPS plate on its load reduction effect is: density > thickness > laying height.The lower the density of the EPS plate is or the thicker it is,the better the effect of load reduction on culvert roof pressure is,and the greater the additional stress on horizontal earth pressure on culvert side is,but the difference is limited,less than 5% approximately.Laying height of EPS plate has little influence on the culvert roof and culvert side earth pressure.