Engineering Performance Analysis Of Roadbed Construction With Lateritic Gravels In Senegal

The subgrade engineering is of great quantity of earthwork.The basic principle of Subgrade Earthwork is according to local conditions from the local areas and materials.In Senegal,the infrastructure construction of roads and railways is following European norms,among them French norm is an important part.There are great differences between subgrade soil materials,humid conditions and service conditions in Senegal area and France norm.Lack of sufficient test data to support and neglect the road performance of special soil materials,and the hard cover of French soil classification method will cause great deviation from the actual engineering and cause more engineering waste.Firstly,this article studies the materials in Senegal,and selects 18 materials for research.The research on particle composition,mineral composition,engineering properties and mechanical properties will study the physical,chemical and mechanical properties of laterite aggregates in Senegal.According to the French norm "types of materials available for road bedding and embankment construction"(NFP11-300)require soil classification.Secondly,the application technology of Senegal local materials in the lower part of subgrade,PST layer at the upper part of subgrade and CDF layer of subgrade improvement layer are put forward.The lower part of the soil foundation can be filled by the "sand core" method with red soil particles as the edge and sand as the filling material.In the saline land area,a certain thickness of low plasticity index and non saline sand shall be laid,and the sand with 30 cm mixed with a small amount of red soil particles shall be laid on it,and then PST layer shall be laid.The PST layer is preferred to fill with red soil granular materials.When natural sand is more abundant,red soil aggregate and sand are used for filling.The proportion of sand mixing needs to be determined by CBR on site,and the maximum mixing amount can reach 40%.The sand can also be treated with low cement dosage.The CDF layer shall be considered comprehensively in combination with the overall structure of pavement,and can be filled with cement stabilized sand,cement stabilized red soil gravel or cement stabilized red soil gravel,and the cement dosage can be medium and low dose.Finally,relying on the construction of the Tes-Tuba Expressway in Senegal,it was proposed to use centralized plant mixing to realize the continuity of material supply,and to use a grader equipped with a GPS elevation system to realize the paving operation of large-thickness cement to treat the laterite pellets.The use of road rollers and the reasonable process combination of the grader realizes the rolling of the large-thickness structural layer,which successfully guides the large-scale construction of the highway subgrade improvement layer,and provides theoretical support for the later widespread application.